Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Des Moines River, Saylorville Lake, & Lake Red Rock
June 2018
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Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Des Moines River, Saylorville Lake, & Lake Red Rock
EXECUTIVE SUMMARY
The U.S. Army Corps of Engineers (Corps), Rock Island District (District) impounded the Des Moines River by two congressionally authorized Civil Works projects, Red Rock Dam (authorized in 1938) and Saylorville Dam (authorized in 1958) (Figure ES-1), creating Lake Red Rock and Saylorville Lake. The projects’ authorized purposes included flood risk management (FRM) for the Des Moines and Mississippi Rivers, low flow augmentation for downstream water supply and water quality, fish and wildlife management, and recreation.
The current Des Moines River Basin Master Reservoir Regulation Manual was approved in 1992. Reservoir Regulation manuals consist of operational parameters defining how, and when, water is stored and released. These include a schedule of releases, conservation pool levels to be maintained during non- flood or drought conditions, and downstream water level constraints.
The following key issues inform the primary purpose and need of the Des Moines River Basin Master Reservoir Regulation Manual update and are individually discussed in subsequent paragraphs: 1. The Des Moines River has experienced a significant increase in the magnitude and frequency of flooding. 2. Sedimentation has negatively impacted water supply capacity. 3. Approved water control deviations have confirmed the need to update the water control plans for each of these reservoirs.
The Des Moines River Basin has experienced significant land use changes. These changes influence runoff rates into tributaries of, and the main stem Des Moines River resulting in increased flood risk within the Des Moines River Basin. Following the 2008 Des Moines River flood, the District re- evaluated regulated flow frequencies on the Des Moines River. The Regulated Flow Frequency Study, completed in early 2010, concluded the frequency of flooding on the Des Moines River increased and indicated flood events like 1993 and 2008 are more likely to occur in the future.
The water supply contract with the State of Iowa and the U.S. Government allots 18.86% of the usable storage between elevations 812 feet and 836 feet (NGVD29) for water supply storage. Potential changes to the water control plan at Saylorville Lake could improve the availability of water during drought conditions.
ES-I
During portions of 2016-2018, the District requested and obtained three temporary deviations from normal operating protocols. These deviations provided opportunities to determine the impact of potential changes to the water control plans for Saylorville Lake and Lake Red Rock.
The purpose of the study is to update the Des Moines River Basin Master Reservoir Regulation Manual to better meet mission objectives based on changes in flood frequencies, land use, and reservoir sedimentation. The recommended plan would result in a revised Des Moines River Basin Master Reservoir Regulation Manual and updates to the Saylorville Lake and Lake Red Rock Water Control Plans. The District drafted this feasibility report with an integrated environmental assessment to present a detailed account of the planning, regulatory, and environmental considerations resulting in the Recommended Plan.
Figure ES-1. Des Moines River Basin
The final array of alternatives, 5A and 6, met all project goals and objectives with the exception of Goal 5 Objectives 5.a. Making improvements to the conditions for Red Rock and Ottumwa hydropower operations. Finally criteria used to select the recommended plan was based on which alternative reduced flood damages the most. Tables EA-20 and EA-21 in VI.B. Process for Selection of a Recommended Plan present the final comparison of alternative 5A and 6.
Based on the environmental assessment and the resulting damage summary, Alternative 6 is the preferred alternative and is recommended for replacing the current Des Moines River Basin Master Reservoir Regulation Manual. The recommended plan is not anticipated to be controversial in nature as local emergency managers, Iowa Department of Natural Resources, city and county governments, and NGO’s
ES-II
have been active project partners through the National Environmental Policy Act (NEPA) process. Additionally, the recommended plan requires no construction and no additional implementation or operational costs.
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Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Des Moines River, Saylorville Lake, & Lake Red Rock
EXECUTIVE SUMMARY ...... ES-I
LIST OF ACRONYMS ...... EA-v
CHAPTER I: PURPOSE AND NEED FOR FEDERAL ACTION ...... EA-1
A. INTRODUCTION B. PURPOSE AND NEED C. DECISION D. AUTHORITY E. SCOPING AND SIGNIFICANT ISSUES F. PROBLEMS AND OPPORTUNITIES G. GOALS AND OBJECTIVES H. RELATED NEPA DOCUMENTATION AND OTHER STUDIES
CHAPTER II: INVENTORY AND FORECASTED CONDITIONS ...... EA-13
A. INTRODUCTION B. GENERAL SETTING C. FLOODPLAIN RESOURCES D. LAND USE E. AQUATIC WILDLIFE RESOURCES F. ENDANGERED, THREATENED, & CANDIDATE SPECIES G. INVASIVE SPECIES H. VEGETATION I. RIVERS AND STREAMS, WATER QUALITY, WETLANDS J. HYDROLOGY AND HYDRAULICS K. STATE PARKS, CONSERVATION AREAS, AND OTHER AREAS OF RECREATIONAL, ECOLOGICAL, SCENIC, OR AESTHETIC IMPORTANCE L. HISTORICAL & CULTURAL RESOURCES M. SOCIOECONOMIC RESOURCES
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N. HUMAN HEALTH & SAFETY O. SUSTAINABILITY, GREENING AND CLIMATE CHANGE P. CONSTRUCTED RESOURCES-PUBLIC STRUCTURES, UTILITIES, TRANSPORTATION, OTHER Q. RECREATION R. SEDIMENTATION/SOILS/PRIME AND UNIQUE FARMLAND S. HAZARDOUS, TOXIC, AND RADIOACTIVE WASTE (HTRW)
CHAPTER III: FORMULATION OF ALTERNATIVES ...... EA-58
A. ALTERNATIVE FORMULATION STRATEGIES FINAL ARRAY OF ALTERNATIVES B. ALTERNATIVES CONSIDERED BUT NOT CARRIED FORWARD FOR DETAILED ANALYSIS C. ALTERNATIVES CARRIED FORWARD FOR DETAILED ANALYSIS NO ACTION ALTERNATIVE 5a ALTERNATIVE 6
CHAPTER IV: EVALUATION OF ALTERNATIVE PLANS ...... EA-67
A. INTRODUCTION B. STEP 1: HYDRAULIC EVALUATION C. STEP 2: ECONOMIC EVALUATION
CHAPTER V: THE ACTION ALTERNATIVES’ ENVIRONMENTAL CONSEQUENCES . EA-72
A. INTRODUCTION B. COMPARING FINAL ARRAY C. FLOODPLAIN RESOURCES D. LAND USE E. AQUATIC WILDLIFE RESOURCES F. ENDANGERED, THREATENED, & CANDIDATE SPECIES G. INVASIVE SPECIES H. VEGETATION I. RIVERS AND STREAMS, WATER QUALITY, WETLANDS J. HYDROLOGY AND HYDRAULICS K. STATE PARKS, CONSERVATION AREAS, AND OTHER AREAS OF RECREATIONAL, ECOLOGICAL, SCENIC, OR AESTHETIC IMPORTANCE L. HISTORICAL & CULTURAL RESOURCES M. SOCIOECONOMIC RESOURCES N. HUMAN HEALTH & SAFETY O. SUSTAINABILITY, GREENING AND CLIMATE CHANGE P. CONSTRUCTED RESOURCES-PUBLIC STRUCTURES, UTILITIES, TRANSPORTATION, OTHER Q. RECREATION R. SEDIMENTATION/SOILS/PRIME AND UNIQUE FARMLAND
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S. HAZARDOUS, TOXIC, AND RADIOACTIVE WASTE (HTRW)
CHAPTER VI: SELECTED PLAN ...... EA-80
A. ENVIRONMENTAL OPERATING PRINCIPLES AND CAMPAIGN PLAN GOALS B. PROCESS FOR SELECTION OF A RECOMMENDED PLAN C. DISCUSSION OF RECOMMENDED PLAN D. PARTNER COORDINATION E. ENVIRONMENTAL COMPLIANCE F. RELATIONSHIP BETWEEN SHORT-TERM USE AND LONG-TERM PRODUCTIVITY G. RELATIONSHIP TO LAND USE PLANS H. IRREVERSIBLE AND IRRETRIEVABLE COMMITMENT OF RESOURCES I. INDIRECT EFFECTS J. CUMULATIVE IMPACTS K. ADAPTIVE MANAGEMENT AND MONITORING PLAN L. RISK AND UNCERTAINTY M. CONCLUSIONS
VII. LITERATURE CITED ...... EA-95
FIGURES Figure EA-1 Project Vicinity ...... EA-2 Figure EA-2 Des Moines River Basin ...... EA-15 Figure EA-3 Land Use Land Cover Class ...... EA-17 Figure EA-4 Prairie Management at Lake Red Rock ...... EA-22 Figure EA-5 Major Rivers and Streams in the Des Moines River Watershed ...... EA-30 Figure EA-6 Des Moines River Basin Impaired Water Bodies ...... EA-32 Figure EA-7 Des Moines River Wetland Area (ha) ...... EA-34 Figure EA-8 Statewide and Individual Gage Precipitation Records ...... EA-35 Figure EA-9 High Trestle Bridge Over the Des Moines River in Boone County ...... EA-40 Figure EA-10 Des Moines, Iowa Percent Minority by Census Block Groups ...... EA-47 Figure EA-11 Des Moines, Iowa - Percent Below Poverty by Census Block Groups ...... EA-48 Figure EA-12 Temperatures Rising in the Midwest ...... EA-50 Figure EA-13 Iowa Annual State-wide Precipitation in Inches from 1873-2008 ...... EA-51 Figure EA-14 Ongoing Construction Adding a Two-unit, 36.4-MW Powerhouse at the Existing Red Rock Dam, 2016 ...... EA-52 Figure EA-15 Paddler at Lake Red Rock ...... EA-54 Figure EA-16 Soil Farm Class from Fraser, Iowa, to the Mississippi River ...... EA-57
TABLES Table EA-1 Floodplain Terminology ...... EA-16 Table EA-2 Land Cover Type ...... EA-16 Table EA-3 Migratory Birds of Conservation Concern ...... EA-21 Table EA-4 Threatened and Endangered Species for the Project Area ...... EA-24 Table EA-5 Other Species Considered ...... EA-27 Table EA-6 Major Rivers and Streams in the Des Moines River Watershed ...... EA-29 Table EA-7 Causes for Iowa Impaired Water Bodies ...... EA-32
EA-iii Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Table EA-8 Summary of NWI-Indicated Wetlands (ha) within the 500-year Floodplain ...... EA-34 Table EA-9 Population and Housing, 2000-2016, Des Moines River Project Area ...... EA-41 Table EA-10 Racial Composition in Study Area ...... EA-42 Table EA-11 Median Income of Study Area ...... EA-42 Table EA-12 Employment in Study Area ...... EA-43 Table EA-13 Education Level in Study Area ...... EA-44 Table EA-14 Percentage of Minority Population in Study Area ...... EA-46 Table EA-15 Low Income Population in Study Area ...... EA-46 Table EA-16 Soil Farm Class from Fraser, Iowa, to Lake Red Rock Dam ...... EA-57 Table EA-17 Comparison of No Action to Alternatives 2 - 3C ...... EA-69 Table EA-18 Comparison of No Action with Alternatives 4 - 6 ...... EA-70 Table EA-19 Summary of Environmental Impacts ...... EA-72 Table EA-20 Average Annual Damages (AAD) Saylorville Lake Tailwater - Lake Red Rock Pool . EA-83 Table EA-21 Average Annual Damages Lake Red Rock Tailwater - Keosauqua Reach ...... EA-84 Table EA-22 Public Meeting Locations ...... EA-85 Table EA-23 Rivers and Harbors Act – 17 Points ...... EA-90 Table EA-24 ER 1105-2-100 Resources ...... EA-90
FINDING OF NO SIGNIFICANT IMPACT
APPENDICES
APPENDIX A – CORRESPONDENCE AND PUBLIC COMMENT APPENDIX B – ENVIRONMENTAL RESOURCES APPENDIX C – SUSTAINABLE RIVERS PROJECT REPORT APPENDIX D – HYDROLOGY AND HYDRAULICS APPENDIX E – ECONOMICS APPENDIX F – CLIMATE CHANGE IMPACT ASSESSMENT APPENDIX G – DISTRIBUTION LIST
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LIST OF ACRONYMS
Acronym Definition AAD Average Annual Damages ACE Annual Chance Exceedance ACS American Community Survey APE Area of Potential Effect BCSD Bias Corrected Spatial Downscaling BG Block Group BLH Bottomland Hardwoods CEQ Council of Environmental Quality CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations cfs cubic feet per second CLOMR Conditional Letter of Map Revision
CO2 Carbon Dioxide CONUS Contiguous United States CWA Clean Water Act CWMS Corps Water Management System dbh diameter at breast height DMRWQN Des Moines River Water Quality Network DNR Department of Natural Resources DO Dissolved Oxygen EA Environmental Assessment ECB Engineering and Construction Bulletin EO Executive Order EPA Environmental Protection Agency ER Engineering Regulation ESA Environmentally Sensitive Area ETL Engineering Technical Letter EW Emergent Wetlands FAA Federal Aviation Administration FEMA Federal Emergency Management Agency FERC Federal Energy Regulatory Commission FFS Flood Frequency Study FIRM Flood Insurance Rate Map FRM Flood Risk Management FSST Flandreau Santee Sioux Tribe FWCA Fish and Wildlife Coordination Act FWS Fish and Wildlife Services FY Fiscal Year GCM Global Climate Model
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Acronym Definition GHG Greenhouse Gas GPG Gosport-Pershing-Gara gSSURGO Gridded Soil Survey Geographic Database HA Hydrologic Alteration HAZUS Hazards United States HEC Hydrologic Engineering Center HEC-FIA Flood Impact Analysis Software HEC-RAS River Analysis System Software HEC-ResSim Reservoir Simulator Software HEC-RPT Regime Prescription Tool Software HEC-SSP Statistical Software Package Software HH Human Health HPMP Historic Property Management Plan HTRW Hazardous Toxic and Radioactive Waste HUC Hydrologic Unit Code IBA Important Bird and Biodiversity Area IDALS Iowa Department of Agriculture and Land Stewardship IDNR Iowa Department of Natural Resources IIHR Iowa Institute of Hydraulic Research IPaC Information, Planning, and Conservation ISU Iowa State University IWR Institute for Water Resources LCO Ladoga-Clinton-Otley LiDAR Light Detection and Ranging LSC Ladoga-Sharpsburg-Clinton MBTA Migratory Bird Treaty Act MF Mudflats MMC Mapping, Modeling, and Consequences MOA Memorandum of Agreement MoDNR Missouri Department of Natural Resources MRES Missouri River Energy Services MSA Metropolitan Statistical Area MSIM Multiple Species Inventory Monitoring MVD Mississippi Valley Division MVR Mississippi Valley, Rock Island District NASS National Agricultural Statistics Service NATA National-Scale Air Toxics Assessment NCSS National Cooperative Soil Survey NEPA National Environmental Policy Act NFHL National Flood Hazard Layer NGO Non-governmental organization
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Acronym Definition NGVD National Geodetic Vertical Datum NHPA National Historic Preservation Act NLCD National Land Cover Database NRCS National Resources Conservation Service NRHP National Register of Historic Places NRI National Rivers Inventory NSI National Structure Inventory NWI National Wetlands Inventory O&M Operation and Maintenance OMP Operational Management Plan orgs Organisms OSA Office of the State Archaeologist OW Open Water P Prairie (USFWS) PCB Polychlorinated biohenyl RCRA Resource Conservation and Recovery Act RID Rock Island District RMC Risk Management Center RPEDN Regional Planning and Environmental Division North SHPO State Historic Preservation Office SRP Sustainable Rivers Project SS Shrub/Scrub THPO Tribal Historic Preservation Officer TNC The Nature Conservancy TNDL Total Maximum Daily Load TSP Tentatively Selected Plan UE Upland edge UG Upland Hardwoods UI University of Iowa USACE U.S. Army Corps of Engineers USFWS U.S. Fish and Wildlife Service USGS U.S. Geological Survey VDF Volume-Duration-Frequency WOWA Weighted Order Weighted Average WSR Wild and Scenic Rivers WW Warm Water
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Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Des Moines River, Saylorville Lake, & Lake Red Rock
CHAPTER I: PURPOSE AND NEED FOR FEDERAL ACTION
A. INTRODUCTION
The Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment study area encompasses the Des Moines River watershed, a tributary of the Mississippi River. The Des Moines River Watershed basin is 14,470 square miles and begins in southwestern Minnesota and extends south/southeast across central and southeastern Iowa. The Des Moines River is approximately 525 miles long and joins the Mississippi River at Keokuk, Iowa (Figure EA-1) The U.S. Army Corps of Engineers (Corps), Rock Island District (District) impounded the Des Moines River by two congressionally authorized Civil Works projects, Red Rock Dam (authorized in 1938) and Saylorville Dam (authorized in 1958). The authorized purposes included flood risk management for the Des Moines and Mississippi Rivers, low flow augmentation for downstream water supply and water quality, fish and wildlife management, and recreation. Downstream of these projects lie thousands of acres of agricultural land, wildlife habitat, and a number of cities and small towns.
The current study effort is a re-evaluation and update to the Des Moines River Basin Master Reservoir Regulation Manual for the multi-purpose reservoir projects. The Manual consists of operational parameters defining how and when water is stored and released. These include a schedule of releases, conservation pool levels to be maintained during non-flood or drought conditions, and downstream water level constraints. This study does not involve any modifications to the dam structures themselves, but rather is evaluating how to best manage water using the existing projects. As such, the study does not involve any new construction or modification of the dam and levee structures (including the remedial works) constructed as part of the original project.
This feasibility report with an integrated environmental assessment documents the study process and results including an account of the planning, regulatory, and environmental considerations that could result in a new Plan Recommendation or Tentatively Selected Plan (TSP).
The study effort began in 2015, when the District conducted an initial assessment of preliminary alternatives to the current Saylorville Lake and Lake Red Rock water control plans. The purpose of the study is to update the Des Moines River Basin Master Reservoir Regulation Manual to better meet mission objectives based on changes in flood frequencies, land use and reservoir sedimentation. The Manual consists of two District flood risk management (FRM) projects, Saylorville Lake and Lake Red Rock, and how the District operates the projects to manage flood risk.
EA-1 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Figure EA-1. Project Vicinity
B. PURPOSE AND NEED
The Des Moines River Basin has experienced significant land use changes in the last century, from a prairie and forested landscape, to predominately agricultural land-use, to its current trend toward urbanization. These changes influence runoff rates into tributaries of, and the main stem Des Moines River resulting in increased flood risk within the Des Moines River Basin.
Changing weather patterns have also increased the susceptibility of the environment and flood risk along the Des Moines River. These factors resulted in a changed environment from which the District must try to manage water levels along the Des Moines River for the stated purposes of FRM, low flow augmentation, fish and wildlife management, and recreation.
Following the 2008 Des Moines River flood, the District received funding to re-evaluate regulated flow frequencies on the Des Moines River to improve the characterization of flood risk, update the reservoir pool-frequency relationships and update the flow frequency values downstream of the District reservoirs, henceforth referred to as the Regulated Flow Frequency Study.
The Regulated Flow Frequency Study, completed in early 2010, concluded the frequency of flooding on the Des Moines River increased and indicated flood events like 1993 and 2008 are more likely to occur in the future than previously estimated. While there may be many underlying reasons why river flows and flooding have increased (e.g., changes in land use, increased precipitation,), the study was
EA-2 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment not designed or conducted to define the cause(s). The scope of the study was to examine river and reservoir data and project future flood probabilities. The study findings clearly indicate flooding is more frequent than previously estimated. Thus, floodplains adjacent to the Des Moines River and some areas once thought to be outside of the floodplain or protected by flood-risk-management projects have a greater risk of flooding than was previously estimated.
Considering the results of the Regulated Flow Frequency Study, in July of 2010 a FRM study of Saylorville Lake and Lake Red Rock was proposed. The study would analyze and evaluate alternatives to the existing Des Moines River Basin Master Reservoir Regulation Manual. The District recognized the need to comprehensively study FRM alternatives for the Des Moines River related to management of the reservoir system, infrastructure improvements in the City of Des Moines, and other existing Federal and non-Federal FRM projects.
Some of the alternatives that were considered included modifying downstream constraints, modifying the seasonal release schedules, and adopting seasonal variations in pool levels to increase flood storage. It is the District’s priority to develop feasible alternatives to reduce the risk of flooding along the Des Moines River.
C. DECISION
The District proposes to update the water control manuals for Saylorville Lake and Lake Red Rock, and the Des Moines River Basin Master Reservoir Regulation Manual. The District will identify alternative water control strategies that improve the projects’ ability to meet the congressionally authorized purposes, including reducing future flood risk and maintaining public safety. While it is impossible to eliminate all flood risk, the goal of this study is to modify the Des Moines River Basin Master Reservoir Regulation Manual to better manage the system resulting from changed hydrologic conditions. As discussed above, the project involves no new project design or construction.
D. AUTHORITY
Saylorville Lake was authorized for flood control and conservation by Congress in the Flood Control Act of 3 July 1958. Recreation facility authorization started with Section 4 of the Flood Control Act of 22 December 1944 and continued under Section 111 of the Water Resources Development Act of 1976. Management for fish and wildlife was authorized as part of the 1958 Fish and Wildlife Coordination Act (Public Law No. 624, 85th Congress). Establishment of a 1982 contract between the United States of America and the State of Iowa for water supply storage within Saylorville Lake was under the discretional authority (pursuant to the Flood Control Act of 1944, Public Law No. 534, 78th Congress) of the Chief of Engineers (for municipal and industrial water supply). The Des Moines and Mississippi Rivers primary authorized purpose was originally flood control, but was semantically changed to FRM. Other purposes included low flow augmentation for downstream municipal and industrial water supply and water quality, fish and wildlife management, and recreation.
Lake Red Rock was authorized for flood control (again, FRM) in Public Law 761, 75th Congress, 3rd Session, 28 June 1938. Recreation facilities were subsequently authorized in Public Law 534, 78th Congress, 22 December 1944, and Section 3 of the Water Resources Development Act of 1976. Management for fish and wildlife was authorized as part of the 1958 Fish and Wildlife Coordination Act (Public Law No. 624, 85th Congress).
Engineering Regulation (ER) 1110-2-240 requires reservoirs and inter-related water resources systems to have an up-to-date Water Control Manual. The water control plans contained in the manuals must
EA-3 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment be prepared giving appropriate consideration to all applicable Congressional Acts relating to operation of Federal facilities, i.e., Fish and Wildlife Coordination Act (FWCA), National Environmental Policy Act (NEPA), the Clean Water Act (CWA).
Policy Guidance Letter dated 2 July 2013 states updates to Water Control Manuals would generally be categorized as “other work products” and requires compliance with Engineering Circular 1165-2-217 Civil Works Review Policy.
Engineering Regulation (ER) 1110-2-8156, Engineering and Design Safety of Dams – Policy and Procedures, provides guidance on the content and format of Water Control Manuals with additional guidance in Engineering Manual 1110-2-3600, Management of Water Control Systems. Additional guidance on water control plan development can be found in ER 1105-2-100, Planning Guidance Notebook and in ER 1165-2-119, Modifications to Completed Projects.
E. SCOPING AND SIGNIFICANT ISSUES
The District solicited input from the public, local emergency management, state, county and Federal agencies, and tribal nations for the Des Moines River Basin Master Reservoir Regulation Manual Study. Eight public meetings and multiple agency meetings were held to gather input. The following points were developed through categorizing public comments:
Category Number of related comments Silt impeding hunting activity 4 Increase flow for waterfowl hunters 2 Rowing club requirements 1 Increase outflows for power-municipal water supply purposes 1 High water affecting commercial navigation and agriculture 1 Current conditions adversely affecting agriculture 4 High water affecting recreation-related business 1 High water affecting private property (non-farm) 1
Both physical and regulatory constraints exist for each project and are discussed below.
Saylorville Lake and Dam. Under certain reservoir conditions, the maximum release at the outlet is limited by the dimensions of the outlet conduit. In order to pass the normal maximum allowable release of 16,000 cfs, the pool must be above elevation 850 feet NGVD. Regulation of the conservation pool for low-flow augmentation has priority over recreation, and water supply has priority over both recreation and water quality.
The authorized plan of regulation considers several other constraints regarding downstream channel capacity. These include: • flooding near the City of Des Moines, • approximate flood control storage balancing between Lake Red Rock and Saylorville Lake, • major flooding reservoir level, • water supply requirements and minimum low-flow requirements.
Lake Red Rock and Dam. The authorized water control plan considers several regulatory constraints regarding the operation of Lake Red Rock Dam. Regulation of the conservation pool for FRM and low flow augmentation has priority over recreational needs. Regulation constraints include:
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• downstream channel capacity, • discharge and flood stage on the Des Moines River at Ottumwa and Keosauqua, • flood stage on the Mississippi River at Burlington, IA, and Quincy, IL, • major flood reservoir levels, and minimum low flow requirements.
F. PROBLEMS AND OPPORTUNITIES
Land-use changes and climate variations have altered the landscape within the Des Moines River Basin over the past few centuries and resulted in changes to the hydrologic regime (hydrology) of the basin. As the basin environment responded to and changed over time through both natural and man- made forces, floods increased in frequency and magnitude. Consequently water level management has become increasingly challenging. Increased flood risk, significant changes in land use, sedimentation, and ecosystem degradation are all factors that impact the hydrology within the Des Moines River Basin.
Problem 1. Flood Risk Management. Over time, changes in precipitation and runoff in the Des Moines River Basin led to changes in the magnitude and frequency of flooding. Historic flooding in 1993, 2008, and 2010 resulted in widespread flood damages along the Des Moines and Upper Mississippi Rivers. Additionally, as a result of the changes in precipitation and runoff, inundation of easement lands in Lake Red Rock’s flood pool originally predicted to occur infrequently has been occurring every 2 to 3 years.
Opportunity 1.1. Reduce future flood risk along the Des Moines and Upper Mississippi River corridors. Land use changes throughout the Des Moines River Basin have resulted in significantly increased flood frequencies. Operational efficiencies of Saylorville Lake and Lake Red Rock dams can be implemented to reduce risks to life, health, and safety of residents, critical infrastructure, commercial, residential, and agricultural areas from flooding events along the Des Moines and Upper Mississippi Rivers.
Opportunity 1.2. Seek opportunities to improve recreational activities consistent with reservoir operating objectives of flood risk management, low-flow augmentation and fish and wildlife management. The reservoirs’ primary operational authorities are flood risk management, low flow augmentation, and fish and wildlife management, however recreation is also an authorized purpose providing recreational benefits. Flood events result in inundation of recreational areas. By more effectively managing flows and storage at the two reservoirs, the District potentially could reduce flooding impacts to recreational facilities.
Opportunity 1.3. Manage reservoir storage to facilitate the functioning of the Lake Red Rock Hydroelectric Project in the future. While generation of hydroelectric power at Lake Red Rock is not an authorized project purpose, the District works in partnership with Missouri River Energy Services (MRES) to provide a reliable water supply for energy production. The MRES project strives to sustain power to support 18,000 homes annually.
Problem 2. Land Use. Changes in land use have increased runoff rates into the Des Moines River. Land use changes include loss of native ground cover (prairies and woodland habitat), increased urbanization, and changes in agricultural practices and tiling.
Opportunity 2.1. Coordinate with local urban entities to ensure maximum flood risk mitigation and minimal contribution to degraded hydrological conditions. The Des Moines
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Metropolitan Statistical Area (MSA) is projecting future growth, and will likely result in additional land use changes. The District has the opportunity to continue coordination with municipalities in the Des Moines River system and ensure municipalities are integrating changing hydrologic conditions and flood risk into infrastructure plans and improvements. This would facilitate greater protection of life and property.
Problem 3. Sedimentation. Sedimentation was anticipated and included in the development of the water control plans for the reservoir projects. Landscape and hydrologic changes within the watershed have increased the delivery rate of sediment to the reservoirs. Sedimentation in the conservation pool at Saylorville Lake has affected the availability of water required under the State of Iowa’s water supply contract. The contract allots a percentage of the reservoir’s remaining conservation storage for consumptive water use. In addition, sedimentation affects recreational activities including hunting access and operation of motorized watercraft in the upper reaches of Saylorville Lake and Lake Red Rock.
Opportunity 3.1. Re-establish water supply capacity in the system through potential changes to reservoir water control plans. Currently, the State of Iowa and the federal government have an agreement which allots a percentage of the total conservation storage capacity of Saylorville Lake for the purpose of water supply. Potential changes to the water control plan at Saylorville Lake could help meet downstream municipal and industrial water supply demand.
Problem 4. Ecosystem Degradation. Ecosystem degradation is a major concern regarding the reservoir system. Increased precipitation runoff results in various ancillary effects including: • Increased runoff rates, increased water temperatures at junctures where runoff does not naturally infiltrate the river system, and unfiltered introduction of runoff contaminants into the system are the end result of such changes. • Sediment deposition and increased flow rates are altering the morphology of the river system, and changing the aquatic environment in which various aquatic species reside and thrive. Alteration of the riverine morphology can also change the adjacent terrestrial morphology. This impacts the flora and fauna found in the river’s floodplain. • Under certain flow rates coming into and leaving the Red Rock Dam, fish may be affected by gas bubble disease. This phenomena occurs directly below the dam when cascading water creates supersaturated oxygenated water. The fish breathe in too much oxygen affecting their mobility plus sight and encourages blood vessel ruptures which may result in mortality. • Sedimentation, invasive species, poor water quality and stream modifications in the Des Moines River are leading to a decline in freshwater mussels communities. Low flows, done for periodic maintenance exposes freshwater mussels to air and extreme temperatures resulting in mortality and elevated predation rates.
Opportunity 4.1. Manage reservoir release rates along the Des Moines River encouraging preservation and connectivity of aquatic and terrestrial habitats for flora and fauna during migration periods. Rapid changes in reservoir release rates can alter shoreline habitat and degrade the environmental quality and quantity of the aquatic habitat, as well as isolate terrestrial habitat and disrupt natural corridors for plants and animals. By limiting the magnitude of changes in release rates, current natural corridors may maintain or improve their connectivity thereby promoting a flourishing environment for terrestrial flora and fauna.
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G. GOALS AND OBJECTIVES
The District, with input from the public, emergency management, state, county and Federal agencies, and tribal nations, developed the following project goals and objectives:
Goal 1: Reduce Future Flood Risk
Objective 1.a. Reduce risks to life, health, and safety of residents due to flooding events along the Des Moines and Upper Mississippi Rivers.
Objective 1.b. Reduce future flood risk to critical infrastructure, commercial, residential, and agricultural areas along the Des Moines and Upper Mississippi Rivers.
Objective 1.c. Improve communication mechanisms to ensure populations at risk have access to timely and relevant information on impending water levels.
Goal 2: Increase and Reestablish Water Supply Reliability
Objective 2.a. Improve reliability intended in the water supply contract for Saylorville Lake.
Objective 2.b. Ensure conservation flows meet ecological and water supply needs downstream.
Goal 3: Promote Fish and Wildlife Sustainability
Objective 3.a. Implement practices which reduce nitrate levels and /or improve water quality.
Objective 3.b. Implement practices that may reduce mussel mortality.
Objective 3.c. Implement practices that may reduce sturgeon mortality.
Objective 3.d. Implement practices that may reduce gas bubble trauma in fish below the dam.
Objective 3.e. Implement practices that may improve conditions for migrating waterfowl and shorebirds.
Objective 3.f. Implement practices that improve conditions for reptiles and amphibians.
Goal 4: Promote Enhancement of Recreational Features
Objective 4.a. Improve the availability of water based recreational features at Saylorville Lake and Lake Red Rock through improved water level management.
Objective 4.b. Reduce the potential of financial impacts to recreational interests as a result of water level fluctuations.
Goal 5: Accommodate Other Stakeholder Interests
Objective 5.a. When possible, improve the conditions for Red Rock and Ottumwa hydropower operations.
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Objective 5.b. When possible, augment navigation flows on the Mississippi River.
H. RELATED NEPA DOCUMENTATION AND OTHER STUDIES
Many reports and studies have been published about Saylorville Lake, Lake Red Rock, and the Des Moines River. Those most relevant to this study are listed in the following paragraphs.
Pool Raise and Release Rate Studies
Saylorville Lake
Proposed Project Modifications, Saylorville Lake, Des Moines River, Iowa, May 1974. U.S. Army Corps of Engineers, Rock Island District.
Effects of Alternate Release Rates from Saylorville Dam, Des Moines River, Iowa, Mar 1975. U.S. Army Corps of Engineers, Rock Island District.
Saylorville Dam, Spillway Chute Analysis, June 1979. U.S. Army Corps of Engineers, North Central Division Water Control Center.
Re-allocation of Reservoir Storage in Saylorville Lake for Municipal and Industrial Water Supply, Des Moines River Basin, Iowa, Apr 1982. U.S. Army Corps of Engineers, Rock Island District.
Spillway Design Analysis Report, Preliminary Draft, Saylorville Lake, Des Moines River, Iowa, 1989. U.S. Army Corps of Engineers, Rock Island District.
Spillway Improvement Design Analysis Report, Saylorville Lake, Des Moines River, Iowa, 1991. U.S. Army Corps of Engineers, Rock Island District.
Spillway Channel Repair Design Analysis Report, Saylorville Lake, Des Moines River, Iowa, 1996. U.S. Army Corps of Engineers, Rock Island District.
Lake Red Rock
Lake Level Re-evaluation Study, Technical Report, Lake Red Rock, Des Moines River, Iowa, Nov 1972. U.S. Army Corps of Engineers, Rock Island District.
Alternatives to the Regulation of Lake Red Rock, Des Moines, River, Iowa, Mar 1985. U.S. Army Corps of Engineers, Rock Island District.
Other
Supplement No. 1, Conservation Storage in Red Rock and Saylorville Reservoirs on Design Memorandum No. 3, Conservation Storage, Red Rock Reservoir, Howell Dam Site, Des Moines River, Iowa, Oct 1961. U.S. Army Corps of Engineers, Rock Island District.
Water Demand and Availability, Phase I, Technical Report, Des Moines River Basin, Jul 1978. U.S. Army Corps of Engineers, Rock Island District.
EA-8 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Inventory of Reservoir Sites, Des Moines River Basin, Iowa, Jan 1981. U.S. Army Corps of Engineers, Rock Island District.
Re-allocation of Reservoir Storage, Lake Red Rock and Saylorville Lake, Phase II, Technical Report, Des Moines River Basin, Iowa, Dec 1981. U.S. Army Corps of Engineers, Rock Island District.
Water Demand and Availability Study, Des Moines River Basin, Saylorville and Red Rock Reservoirs, Sep 1994. U.S. Army Corps of Engineers, Rock Island District.
Regulated Flow Frequency Study
Des Moines River Regulated Flow Frequency Study, 2010. U.S. Army Corps of Engineers, Rock Island District.
Original Design Documentation
Saylorville Lake
Design Memorandum No. 1, Hydrology and Hydraulic Analysis, Saylorville Reservoir, Des Moines River, Iowa, 1960. U.S. Army Corps of Engineers, Rock Island District.
Design Memorandum No. 3, General Design Memorandum, Saylorville Reservoir, Des Moines River, Iowa, 1960. U.S. Army Corps of Engineers, Rock Island District.
Design Memorandum No.10, Spillway, Saylorville Reservoir, Des Moines River, Iowa, 1962. U.S. Army Corps of Engineers, Rock Island District.
Design Memorandum No. 1, General Design Memorandum, Des Moines River at Des Moines, Iowa, Local Flood Protection, 1963. U.S. Army Corps of Engineers, Rock Island District.
Design Memorandum No. 9, Dam Outlet Works, Saylorville Reservoir, Des Moines River, Iowa, 1964. U.S. Army Corps of Engineers, Rock Island District.
Real Estate – Reservoir Area, Saylorville Lake Project, 1964. U.S. Army Corps of Engineers, Rock Island District.
Real Estate – Modification of Design Flood Control Level, Saylorville Lake Project, 1966. U.S. Army Corps of Engineers, Rock Island District. Review of Reports for Flood Control and Related Purposes on the Des Moines River, Iowa and Minnesota, 1970. U.S. Army Corps of Engineers, Rock Island District.
Proposed Project Modifications, Saylorville Lake, 1975. U.S. Army Corps of Engineers, Rock Island District.
Real Estate – Saylorville Corridor, Saylorville Lake Project, 1976. U.S. Army Corps of Engineers, Rock Island District.
Master Plan Design Memorandum 6B, Saylorville Lake, 1984. U.S. Army Corps of Engineers, Rock Island District.
EA-9 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Lake Red Rock
Design Memorandum No. 1, Hydrology and Hydraulic Analysis, Red Rock Reservoir, Howell Dam Site, Des Moines River, Iowa, 1956. U.S. Army Corps of Engineers, Rock Island District.
Design Memorandum No. 3, Conservation Storage, Red Rock Reservoir, Howell Dam Site, Des Moines River, Iowa, 1957. U.S. Army Corps of Engineers, Rock Island District.
Design Memorandum No. 4, General Design Memorandum, Red Rock Reservoir, Howell Dam Site, Des Moines River, Iowa, 1958. U.S. Army Corps of Engineers, Rock Island District.
Resource Master Plan, Preliminary Master Plan, Lake Red Rock, 1959. U.S. Army Corps of Engineers, Rock Island District.
Real Estate Memoranda 5B., Lower Portion of Reservoir Area, 1960. U.S. Army Corps of Engineers, Rock Island District.
Real Estate Memoranda 5C, Upper Portion of Reservoir Area, 1960. U.S. Army Corps of Engineers, Rock Island District.
Design Memorandum No. 9, Dam – Overflow and Concrete Non-Overflow Sections, Exhibit 1, Hydraulic Design, Red Rock Reservoir, Howell Dam Site, Des Moines River, Iowa, 1960. U.S. Army Corps of Engineers, Rock Island District.
Spillway and Sluices, Red Rock Dam, Des Moines River, Iowa, Hydraulic Model Investigation, 1965. Sponsor: U.S. Army Corps of Engineers, Rock Island District. Conducted by: U.S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi.
Environmental Assessment for Red Rock Flowage Easement Land Acquisition, Lake Red Rock, Marion County, Iowa, June 1989. U.S. Army Corps of Engineers, Rock Island District.
Other
Des Moines LFP Chief’s Report, Des Moines River Iowa, 1941.
Supplement 1 - Conservation Storage in Red Rock and Saylorville Reservoirs, 1961. U.S. Army Corps of Engineers, Rock Island District.
Historical Regulation and Operation & Maintenance Manuals
Saylorville Lake
Master Reservoir Regulation Manual Appendix B, 1 Aug 76 - Saylorville Lake. U.S. Army Corps of Engineers, Rock Island District.
Master Reservoir Regulation Manual, Interim Plan, Saylorville Lake. U.S. Army Corps of Engineers. Jan 1977. U.S. Army Corps of Engineers, Rock Island District.
Master Reservoir Regulation Manual, Saylorville Lake. U.S. Army Corps of Engineers. Revised March, 1983. U.S. Army Corps of Engineers, Rock Island District.
EA-10 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Appendix B of the Des Moines River Master Reservoir Regulation Manual, Water Control Manual, Saylorville Lake, Des Moines River Basin, Sep 1983, U.S. Army Corps of Engineers, Rock Island District.
Operation and Maintenance Manual, Saylorville Lake, Des Moines River, Iowa, 1984. U.S. Army Corps of Engineers, Rock Island District.
Appendix B of the Des Moines River Master Reservoir Regulation Manual, Water Control Manual, Saylorville Lake, Des Moines River Basin, 3rd Revision, 2001, U.S. Army Corps of Engineers, Rock Island District.
Lake Red Rock
Master Reservoir Regulation Manual, Appendix A, Red Rock (Preliminary). US Army Corps of Engineers. Dated 26 June 1968.
Operation and Maintenance Manual, Red Rock Dam and Lake Red Rock, Des Moines River, Iowa, 1976. U.S. Army Corps of Engineers, Rock Island District.
Operation and Maintenance Manual, Red Rock Dam and Lake Red Rock, Des Moines River, Iowa, 1977. U.S. Army Corps of Engineers, Rock Island District.
Operation and Maintenance Manual, Lake Red Rock, Des Moines River, Iowa, Jan 1983. U.S. Army Corps of Engineers, Rock Island District.
Water Control Plan with Final Environmental Impact Statement Supplement, May 1988. U.S. Army Corps of Engineers, Rock Island District.
Des Moines River Basin Master Regulation Manual and Appendix A, Lake Red Rock, June 1988. U.S. Army Corps of Engineers, Rock Island District. Water Control Plan with Supplemental Master Plan and Final Environmental Impact Statement Supplement II, May 1990. U.S. Army Corps of Engineers, Rock Island District.
Appendix A of the Des Moines River Master Reservoir Regulation Manual, Water Control Manual, Lake Red Rock, Des Moines River Basin, 2nd Revision, 2003, U.S. Army Corps of Engineers, Rock Island District.
Other
Upper Mississippi River Basin, Des Moines River Basin, Iowa and Minnesota, Master Regulation Manual, 1968. U.S. Army Corps of Engineers, Rock Island District.
Upper Mississippi River Basin, Des Moines River Basin, Iowa and Minnesota, Master Regulation Manual, 1989. U.S. Army Corps of Engineers, Rock Island District.
Appendix C Master Reservoir Regulation Manual, Drought Contingency Plan for Lake Red Rock and Saylorville Lake, 1992. U.S. Army Corps of Engineers, Rock Island District.
Sedimentation Surveys
EA-11 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Saylorville Lake
Saylorville Lake Report of Sedimentation, 2014. U.S. Army Corps of Engineers, Rock Island District.
Lake Red Rock
Lake Red Rock Report of Sedimentation, 2011. U.S. Army Corps of Engineers, Rock Island District.
Flood Damage Reduction Studies
Feasibility Report, Flood Damage Reduction for Des Moines and Raccoon Rivers Project, Des Moines, Iowa (with integrated Environmental Assessment), Volume 1, 2005. U.S. Army Corps of Engineers, Rock Island District.
Other Studies and Reports
Saylorville Lake
Saylorville – Backwater Effects, Backwater Envelope Curves, Saylorville Lake, 1986. U.S. Army Corps of Engineers, Rock Island District.
Implementation of HMR52 Procedures for Probable Maximum Precipitation and Flood (PMP/PMF) Estimates, 1990. Memorandum for Commander, U.S. Army Engineer Division, North Central.
Saylorville Water Supply Contract Summary, 2006. U.S. Army Corps of Engineers, Rock Island District.
Emergency Action Plan, Saylorville Dam and Big Creek Remedial Works, Des Moines, Iowa, 2011. U.S. Army Corps of Engineers, Rock Island District.
Saylorville Dam Semi-Quantitative Risk Assessment, Des Moines River, Embankment and Spillway, DQC Review 2015. U.S. Army Corps of Engineers, Rock Island District.
Lake Red Rock
Emergency Action Plan, Red Rock Dam and Lake, Des Moines, Iowa, 2012. U.S. Army Corps of Engineers, Rock Island District.
Other
Survey Report for Flood Control, Binder 1, Main Report and Appendix VII (Detailed Cost Estimates), Des Moines River, Iowa, Aug 1941. U.S. Army Corps of Engineers.
Survey Report for Flood Control, Binder 3, Des Moines River, Iowa, Aug 1941. U.S. Army Corps of Engineers.
EA-12 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
CHAPTER II: INVENTORY AND FORECASTED CONDITIONS
A. INTRODUCTION
The District inventoried the applicable social, economic, and environmental factors for the study area within the Des Moines River floodplain corridor. The floodplain corridor includes federally-managed lands upstream of Saylorville Lake Dam near Fraser, Iowa, to the confluence with the Mississippi River (River Mile 361.5). The District used applicable social, economic, and environmental factors as the foundation of the analysis, to evaluate and compare alternatives and select the District’s Recommended Plan. These factors establish a baseline to measure the project’s impacts.
The floodplain corridor includes the following parameters: • the river and adjacent lands (agriculture, urban, and wildlife habitat); • constructed facilities adjacent to the river; • areas receiving flood inundation as a result of Saylorville Lake and Lake Red Rock water releases; and • area of influence varies based on the resource and was tailored to capture the measureable impacts
The District focused on information gathered from this project area, or area of influence. If the District used data from outside this area in their analysis, rationale is provided in resource section below.
Resources Not Evaluated in Detail. The District considered all possible environmental factors potentially influenced by the project alternatives and eliminated resources from further evaluation not in the area of potential affect, or that would not be impacted by any of the alternatives. These resources include: • Geology, Topography • Wild and Scenic Rivers • Mineral and Energy Resources • Noise • Air quality
Relevant Resources Found in the Planning Area. The District focused their evaluation on those resources potentially affected by any of the alternatives. These resources are described within this chapter and include: • Floodplain Resources • Land Use • Aquatic & Wildlife Resources (Fish and Mussels, Mammals, Migratory Birds) • Threatened and Endangered Species • Invasive Species • Vegetation • Water Quality, Wetlands, Rivers, and Streams • Hydrology and Hydraulics • State Parks, Conservation Areas, and Other Areas of Recreational, Ecological, Scenic, or Aesthetic Importance • Cultural and Historic Resources
EA-13 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
• Socioeconomics Resources • Minority and Low-Income Populations • Human Health and Safety • Sustainability, Greening and Climate Change • Constructed Resources (Utilities, Infrastructure, Transportation, Among Others) • Recreation • Sedimentation/Soils/Prime and Unique Farmland • Hazardous Substances/Petroleum Products
Each resource section described in this chapter also includes a description of the future without project conditions, or the No Action Alternative. The No Action Alternative is the condition the PDT used to compare the effects of the action alternatives.
B. GENERAL SETTING
The Des Moines River Basin (Figure EA-2) begins in Southwestern Minnesota and extends southerly across central Iowa to Southeastern Iowa. The Des Moines River joins the Mississippi River in Keokuk, Iowa.
The Des Moines River Basin drains 14,802 square miles. The basin contains 9.4 million acres of land and 42,000 acres of water surface. Des Moines, Ottumwa, and Fort Dodge are the largest population centers within the basin. Population growth and economic development in the three population centers are basic factors in determining future resource needs. Urbanization within the Greater Des Moines area continues at a faster rate as compared to the rest of the state. In a five-year period from 2006 to 2011, approximately 14,000 acres were urbanized. Population of the project area in 2016 was 513,985, an increase of 17.5 percent from year 2000 (U.S. Census ACS 2011-2016, Table EA-9). Water resources development in the basin includes Saylorville Lake, Lake Red Rock, several local flood protection levee systems and facilities, and agricultural levees.
Saylorville Lake is located in Polk County on the Des Moines River in central Iowa, approximately 214 miles upstream from the confluence with the Mississippi River. The conservation pool impounded by the dam is within Polk County. The flood pool extends into Dallas and Boone Counties. The City of Des Moines is 10 miles to the south of Saylorville Lake. The lake is surrounded by the growing communities of Ankeny, Johnston, and Polk City.
Lake Red Rock and the Red Rock Dam are located in Marion County on the Des Moines River in south-central Iowa, approximately 142.9 miles upstream from the Mississippi River confluence. The conservation pool impounded by the dam is within Marion County. The flood pool extends into Jasper, Warren, and Polk Counties. Major communities near Lake Red Rock include: Des Moines, Pella, and Knoxville.
EA-14 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Figure EA-2. Des Moines River Basin
C. FLOODPLAIN RESOURCES
There are two descriptions for floodplains, natural and regulatory.
Natural Floodplain. By their very nature, floodplains are the low, flat, periodically flooded lands adjacent to rivers and are subject to the land-shaping and water flow processes. As distinguished from the floodplain, a river' floodway is the dry zone typically between levees, which is designed to convey flood waters. It is only during and after major flood events the connections between a river, its floodway and its floodplain become more apparent. These areas form a complex physical and biological system that not only supports a variety of natural resources but also provides natural flood and erosion control. In addition, the floodplain represents a natural filtering system, with water percolating back into the ground and replenishing groundwater.
Regulatory Floodplain. The regulatory floodplain is defined by areas inundated by a 100-year or 500-year rainfall event. A 100-year flood is defined as a flood event having a one percent chance of occurring in any given year. For land use planning purposes, the regulatory floodplain is usually viewed as all lands within reach of a 100 year flood. The Federal Emergency Management Agency (FEMA) produces floodplain maps, defining what’s in and out of the 100-year (or “regulatory”) floodplain in order to implement the National Flood Insurance Program. Flood Insurance Rate Map Zones (FIRM) are depicted in the floodplain terminology Table EA-1.
EA-15 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Table EA-1. Floodplain Terminology
Terms Measured Flood Event Common Name FIRM Zones Base Flood 1% chance flood 100-year flood Zone AE, A 0.2% chance flood 500-year flood Zone X 0.1% chance flood 1000-year flood Zone X Floodway Zone AEF
A common misconception about the 100-year flood is that it represents the peak flow from historical records, or it will occur once every 100 years. In fact, a 100-year flood has a 26 percent chance of occurring during a 30-year period, the length of many home mortgages. The 100-year flood is a statistically derived regulatory standard used by Federal agencies, and most states, to administer floodplain management programs.
For this project, the District assumed the area of influence would be approximate to the 500-year floodplain. The current (baseline) water control plan and the possible revised plan alternatives do not exceed the 500-year floodplain standards under normal operating conditions (low flow augmentation to maximum controlled releases). Appendix B contains maps of the project area and its resources. The 500-year flood boundaries are delineated on each map.
Future Condition: The FEMA may change the regulatory floodplains based on future precipitation trends and changes in flood frequency. If a change occurs, the District would consider if any additional changes in the Des Moines River Basin Master Reservoir Regulation Manual are warranted.
D. LAND USE
The 2011 National Land Cover Database (NLCD) Data includes the most up-to-date data concerning the project area (Appendix B). Table EA-2 and Figure EA-3 depict the project area’s various land uses. Table EA-2. Land Cover Type
Land Cover Type Area (ha) Open Water 11,340 Developed, Open Space 900 Developed, Low Intensity 447 Developed, Medium Intensity 129 Developed, High Intensity 44 Barren Land 300 Deciduous Forest 4,595 Evergreen Forest 4 Mixed Forest 7 Shrub/Scrub 78 Grassland/Herbaceous 1,645 Pasture/Hay 1,889 Cultivated Crops 12,814 Woody Wetlands 3,072 Emergent Herbaceous 3,388 Wl d National Land Cover Dataset, 2011
EA-16 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Figure EA-3. Land Use Land Cover Class (Source: National Land Cover Dataset, 2011)
According to the NLCD database, the Des Moines area had a slight increase in developed impervious surfaces between 2006 and 2011. This is noteworthy as increases in impervious surfaces can lead to lower water quality, higher nutrient loads, and increased stormwater runoff. Still, 96 percent of soils overall, saw a loss of less than 1percent of impervious soils in the Des Moines area. In the planning area outside Des Moines, there were increases in impervious soils, but at a slower rate.
Land Use Plans. Corps reservoirs master plans are management plans for environmental stewardship of the land and recreational opportunities. Master plans do not address the specifics of regional water quality or water level management for FRM.
Master plans present an inventory of land resources; land classifications; and three main focus areas— Sustainable Environment, A Natural Place to Play, and Connections. The focus areas provide management concepts for environmental stewardship of environmentally sensitive areas and other lands; existing and expanded recreational facilities; and connections between people and nature. All actions by the District, partnering agencies, and individual granted leases use District-managed lands (out-grantees) must be consistent with the master plans.
Master plans are based on responses to regional and local needs, resource capabilities and suitability and expressed public interests consistent with authorized project purposes and pertinent legislation and regulations. They provide a District-level policy consistent with national objectives and other State and regional goals and programs. The plans are distinct from the project-level implementation emphasis of the Operational Management Plan (OMP). Policies in the master plan are guidelines
EA-17 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment implemented through provisions of the OMP, specific design memorandums, and the annual management plans. Saylorville Lake and Lake Red Rock staff updated and approved their master plans in 2015.
While the Iowa DNR manages a large share of federally-managed lands at Saylorville Lake and Lake Red Rock for wildlife management purposes, it does not have an established planning document, other than the original lease agreements. The District reviews and approves the Iowa DNR’s annual work plan at each site.
Future Condition: The Des Moines River Basin should continue to be predominately agricultural landuse; however, urbanization and non-permeable surfaces should continue to expand at their current rate. This may increase flash flooding and increased run-off. Local FRM measures may result from the urban growth near the river. Land under current county, state, and Federal management should continue as public lands. These lands’ missions should remain as FRM, water supply, fish and wildlife management, and recreation.
E. AQUATIC WILDLIFE RESOURCES
Fisheries and Mussels and Their Habitats. Fisheries and other aquatic resources are managed by the Iowa DNR Fisheries Bureau for Saylorville Lake and Lake Red Rock. Work is primarily aimed at maintaining a sport fishery for anglers. Primary management species in the Des Moines River include walleye, wiper and northern pike, which require stocking due to limited or no reproduction. Largemouth bass, channel and flathead catfish, white bass, crappie and other pan fish reproduce naturally and only require supplemental stocking when necessary. River fish below the dams include species such as catfish, suckers, minnows, walleye, catfish, and gar. Rarer species like American eel and sturgeon also inhabit the Des Moines River at certain times of the year.
Shoreline development, bridges, and dams limit the river’s natural setting in many places. Still, the project area supports a good fishery near dams, snags, and other places where flow and structure are diverse. The Saylorville, Red Rock, and Ottumwa dams limit upstream movement of fish. Yet many species are flushed out of the lakes such as striped bass, muskellunge, and other game fish.
The Des Moines River was historically inhabited by more than 36 species of mussels. Unfortunately, a substantial loss in (>50 percent) species diversity has occurred below Lake Red Rock (Gritters, 2003). However, this is not surprising, as a loss in species diversity and range size has been a statewide trend in Iowa (Poole and Downing, 2004). Recent mussel surveys in the Des Moines River found 19 species.
Two major contributors to fish mortality events as well as less well-documented and potentially chronic drivers of fish mortality are: • Gas bubble trauma associated with supersaturated conditions downstream of Red Rock Dam. • Thermal conditions in the Des Moines downstream of Red Rock and Ottumwa that periodically exceed lethal tolerance limits for fish and other aquatic taxa. Mortality concerns relate primarily to shovelnose sturgeon.
Based on the literature review and first-hand knowledge, gas bubble trauma induced fish kills are linked to periods when there is a rapid step down in flow through the dam at Lake Red Rock. Operators at Lake Red Rock have already begun working with fisheries managers to try to reduce the
EA-18 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment rate of change during step down to reduce the incidence of gas bubble trauma; however, more scientific studies are needed. Gas bubble disease appears to be related to a combination of gas super- saturation combined with a lack of habitat of sufficient depth where fish can move to re-equalize pressure. Therefore, the problem is compounded during low flow periods, when fish have less access to deeper habitats. However, it can also occur at high flows, because gas super-saturation is typically higher when the tainter gates are in operation.
Wildlife and Their Habitat. The project area is a mosaic of habitat types closely associated with the riverine environment. Agriculture, urbanization, recreation, dams, and other infrastructure such as utility and transportation corridors contribute to habitat fragmentation and other stressors to wildlife.
The Des Moines River basin provides a significant fish and wildlife resource both for the state of Iowa and regionally for the Midwest. Constructed on Iowa’s largest interior stream, Saylorville Lake represents the only major extension of timber (forest) into North Central Iowa. Lake Red Rock extends this federally-managed and protected land into southern Iowa. Well known for its importance as a migratory corridor, Saylorville was deemed globally significant by the American Bird Conservancy in 1998. Iowa ranks 49th in public land ownership and significant tracts of wildlife habitat are uncommon. The 26,000 acres of the Saylorville Lake include 7,000 acres of water, 15,000 acres of forest cover and approximately 4,000 acres in grasslands, crop fields and other open habitat.
For the Lake Red Rock project, the District manages approximately 53,000 acres of land and water, which includes 23,054 acres managed by Iowa DNR and 1,788 acres managed by the Marion County Conservation Board. Large habitat complexes like Saylorville and Red Rock allow for the successful reintroduction of once-extirpated species from Central Iowa such as river otter, bobcat, osprey and bald eagle. All of these species now have reproducing populations and stable or growing numbers of individuals. While 12,807 acres of project lands are out granted to the Iowa DNR for wildlife management, almost all remaindering lands have high wildlife value.
Iowa State University and the Iowa DNR’s Iowa Multiple Species Inventory Monitoring Program (MSIM) final report tallied 19 species of mammals, 177 species of birds, 20 species of herptiles, 34 species of butterflies, 43 species of dragonfly, and 17 species of mussels during the survey period (2013). Many Species of Greatest Conservation Need (Iowa Action Plan 2006) were identified during the MSIM study, they include: 3 mammals, 43 birds, 3 herptiles, and 1 dragonfly (Harms et al., 2013). Some species not recorded (absent) have suffered significant decline in the last two decades. Three mammals including Franklins Ground Squirrel, Grey Fox, and Southern Flying Squirrels have scant records of late but were common occurring mammals in the 1970s.
In urban areas, wildlife and their habitat is limited in the planning area. Levees (agriculture and urban) are void of trees and are mowed regularly. In many areas, pedestrians and bicyclists utilize a paved trail on top of the levee. Beyond the existing levee toe, there are areas with mature bottomland trees. There are several large tracts of timber, however the majority of adjacent property is residential or industrial areas. Despite the human disturbances such as traffic, recreation, noise, and lights, the river corridor has suitable habitat for those species accustomed to an urban setting. Common residents are white-tailed deer, bats, squirrels, cottontail rabbits, raccoons, and year round resident birds such as owls, and songbirds. Mammals such as muskrat, mink, raccoons, and beaver may use the river side habitat.
Existing rip rap mainly near the dams’ outlets and along urban levees, may make traversing these area more difficult for wildlife species, however species such as mink will regularly hunt these areas for small mammals and fish.
EA-19 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Migratory Birds. Well known for its importance as a migratory corridor, Saylorville Lake and Lake Red Rock were deemed globally significant by the American Bird Conservancy in 1998. The project area includes two Important Bird and Biodiversity Area (IBA) located above both the Saylorville Lake Dam and Lake Red Rock Dam. An IBA is an area identified using an internationally agreed set of criteria as being globally important for the conservation of bird populations. An IBA supports: • species of conservation concern (e.g. threatened and endangered species); • range-restricted species (species vulnerable because they are not widely distributed); • species that are vulnerable because their populations are concentrated in one general habitat type or biome; and, • species, or groups of similar species (such as waterfowl or shorebirds), that are vulnerable because they occur at high densities due to their congregatory behavior (National Audubon Society, 2016).
Migrating birds such as warblers, waterfowl, and song birds migrate and nest through the river corridors in the planning area. In one Saylorville Lake survey, there were over 170 birds utilizing a variety of habitats near the lake (Harms, et al., 2013). Bird nesting occurs along the mud flats in the upper reaches of each lake as well as the woodlands and prairies near the lake and the downstream study areas. The Des Moines River corridor supports peregrine falcons, red-tailed hawks, American kestrels and other predatory birds during their nesting and migration seasons.
Lake Red Rock is a premier waterfowl management area. Every year, 125 to 150,000 migrating waterfowl use the lake along with large proportions of the nation’s water birds such as gulls, terns, and pelicans. Open water in the tailwaters of the dam also attracts hundreds of bald eagles each winter (USACE, 2015).
The US Fish and Wildlife Service’s (USFWS) website, Information for Planning and Conservation (IPAC), (USFWS, 2018, Appendix A) listed 25 migratory bird species of conservation concern and has the highest priority for conservation that may use the project area sometime during their nesting or migration seasons (Table EA-3).
EA-20 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Table EA-3. Migratory Birds of Conservation Concern
Species Scientific Name Season Habitat1 Acadian Flycatcher Empidonax virescens Breeding BLH American Bittern Botaurus lentiginosus Breeding EW American Golden-plover Pluvialis dominica Migration EW Bald Eagle Haliaeetus leucocephalus Year-round BLH/OW Black Tern Chlidonias niger Breeding OW/MF Black-billed Cuckoo Coccyzus erythropthalmus Breeding UH Bobolink Dolichonyx oryzivorus Breeding P Buff-breasted Sandpiper Calidris subruficollis Migration EW/OW Cerulean Warbler Dendroica cerulea Breeding UH Dunlin Calidris alpina arcticola Migration EW/MF Franklin's Gull Leucophaeus pipixcan Breeding OW/MF Golden Eagle Aquila chrysaetos Wintering OW/BLH Henslow’s Sparrow Ammodramus henslowii Breeding P Hudsonian Godwit Limosa haemastica Migration MF Least Bittern Ixobrychus exilis Breeding EW Lesser Yellowlegs Tringa flavipes Migration EW/MF Marbled Godwit Limosa fedoa Migration EW/MF Nelson's Sparrow Ammodramus nelsoni Breeding P Prothonotary Warbler Protonotaria citrea Breeding BLH Red-headed Woodpecker Melanerpes erythrocephalus Year-round UH Ruddy Turnstone Arenaria interpres morinella Migration MF Rusty Blackbird Euphagus carolinus Wintering EW Short-billed Dowitcher Limnodromus griseus Migration MF Willet Tringa semipalmata Breeding P/EW Wood Thrush Hylocichla mustelina Breeding UH 1BLH=bottomland hardwoods, UH=upland hardwoods, SS=shrub/scrub, P=prairie, EW=emergent wetlands, UE-upland edge, OW=open water, MF=mudflats (USFWS, 2018)
Fish and Wildlife Management. The Saylorville Lake and Lake Red Rock Projects encompass 100,000+ acres of land and water along the Des Moines River corridor. This land is collectively managed with multiple state agencies including the Iowa DNR, Polk County Conservation, and Marion County Conservation. Through cooperative efforts each project’s natural resource team and their partners have restored and maintained this public land for multiple user groups to enjoy now and in the future (Figure EA-4).
EA-21 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Figure EA-4. Prairie Management at Lake Red Rock
EA-22 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
F. ENDANGERED, THREATENED, AND CANDIDATE SPECIES
The District conducted a preliminary review of federally-listed threatened and endangered species in the project area using the IPAC website (USFWS, 2018a) (letters both dated May 3, 2018, Appendix A, Correspondence). The website lists 12 species (Table EA-4). This means the project area may have potential habitat suitable for one, or all of the species’ life requisites.
The Indiana bat and Northern long-eared bat may inhabit the wooded areas near the proposed project. Several surveys at Lake Red Rock and near Des Moines Iowa, detected both species. Both bats utilize mature or dead trees with flaky bark as their summer maternity sites and may forage in areas near the river.
Prairie bush clover (Lespedeza leptostachya) is a federally-threatened prairie plant found only in the tallgrass prairie region of four Midwestern states. At the beginning of the 19th century, native prairie covered almost all of Illinois and Iowa, a third of Minnesota and 6 percent of Wisconsin. Prairie with moderately damp-to-dry soils favored by prairie bush clover was also prime cropland; today only scattered remnants of prairie can be found in the four states. Many of today's prairie bush clover populations occur in sites that were too steep or rocky for the plow.
The western prairie fringed orchid (Platanthera praeclara) is restricted to west of the Mississippi River and currently occurs in Iowa, Kansas, Minnesota, Nebraska, North Dakota, and in Manitoba, Canada. This orchid occurs most often in mesic-to-wet unplowed tallgrass prairies and meadows, but has been found in old fields and roadside ditches.
Mead’s milkweed is a perennial plant of the tallgrass prairies. It was listed as threatened in 1988. This milkweed formerly occurred throughout the eastern tallgrass prairie region of the central United States, from Kansas through Missouri and Illinois and north to southern Iowa and northwest Indiana. It currently is known from 171 sites in 34 counties in eastern Kansas, Missouri, south-central Iowa, and southern Illinois.
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Table EA-4. Threatened and Endangered Species for the Project Area
Common Name Classification Habitat Indiana bat Caves, mines (hibernacula); small stream corridors with well-developed riparian Myotis sodalis Endangered woods; upland forests (foraging) Northern long-eared bat Hibernates in caves and mines - swarming in surrounding wooded areas in autumn. Myotis septentrionalis Threatened Roosts and forages in upland forests during late spring and summer. Mesic to wet unplowed tallgrass prairies and meadows but have been found in old Eastern Prairie Fringed Orchid fields and roadside ditches. The eastern prairie fringed orchid also occurs in bogs, Platanthera leucophaea Threatened fens, and sedge meadows Mead's Milkweed Asclepias meadii Threatened Tallgrass prairies Prairie Bush-clover Lespedeza leptostachya Threatened Tallgrass prairies Western Prairie Fringed Orchid Mesic to wet unplowed tallgrass prairies and meadows but have been found in old Platanthera praeclara Threatened fields and roadside ditches. Least tern Sterna antillarum Endangered Bare alluvial sand bars and dredged material islands Topeka Shiner Endangered Notropis topeka and Critical Prairie streams and rivers. Pallid Sturgeon Floodplains, backwaters, chutes, sloughs, islands, sandbars, and main channel waters Scaphirhynchus albus Endangered formed in a large-river ecosystem Higgins Eye (pearlymussel) Larger rivers where it is usually found in deep water with moderate currents. Sand Lampsilis higginsii Endangered and gravel substrate. Sheepnose Mussel Larger rivers where it is usually found in deep water with moderate currents. Sand Plethobasus cyphyus Endangered and gravel substrate. Spectaclecase (mussel) Larger rivers where it is usually found in deep water with moderate currents. Rocky Cumberlandia monodonta Endangered substrate. Ref: US Fish and Wildlife Service webpage: http://www.fws.gov/midwest/Endangered/lists/iowa_cty.html (updated May 3, 2018)
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Prairie bush clover's rarity is probably best explained by the loss of its tallgrass prairie habitat. At the beginning of the 19th century, native prairie covered almost all of Illinois and Iowa, a third of Minnesota and 6 percent of Wisconsin. Prairie with moderately damp to dry soils favored by prairie bush clover was also prime cropland; today only scattered remnants of prairie can be found in the four states. Many of today's prairie bush clover populations occur in sites that escaped the plow because they were too steep or rocky.
The least tern (Sterna antillarum) is listed as endangered in Polk County, Iowa. Historically, terns nested on sparsely-vegetated sandbars along major rivers in the Central United States. Much of their natural habitat has been lost because of broad-scale changes to our natural river systems that include invasive plants, dams and reservoirs, river channelization, bank stabilization, hydropower generation, and water diversion. In June 2006 a pair of least terns nested with 2 eggs on a large mudflat on the upper end of the reservoir. Unfortunately the pair failed to fledge young birds as an increase in water levels submerged the nest. This was the first recorded nest on an interior stream in the State of Iowa.
The Topeka shiner occurs primarily in small prairie (or former prairie) streams in pools containing clear, clean water. Most Topeka shiner streams are perennial (flow year-round), but some are small enough to stop flowing during dry summer months. In these circumstances, water levels must be maintained by groundwater seepage for the fish to survive. Topeka shiner streams generally have clean gravel, rock, or sand bottoms. The USFWS listed the species for portions of Webster, Boone, and Dallas County (Appendix B). Since Topeka shiners prefer small streams and seasonally flooded oxbows, their presence in the planning area (500-year flood plain of the Des Moines River) is low.
Pallid sturgeon are a bottom-oriented, large river obligate fish inhabiting the Missouri and Mississippi rivers and some tributaries from Montana to Louisiana (Kallemeyn 1983). Pallid sturgeon evolved in the diverse environments of the Missouri and Mississippi river systems. Floodplains, backwaters, chutes, sloughs, islands, sandbars, and main channel waters formed the large-river ecosystem that met the habitat and life history requirements of pallid sturgeon and other native large-river fishes. Pallid sturgeon have been documented over a variety of available substrates, but are often associated with sandy and fine bottom materials
Higgins eye depend on deep, free-flowing rivers with clean water. Much of their historic habitat has been changed from free-flowing river systems to impounded river systems. Impoundments changed water flow patterns, substrate characteristics, and host fish habitat which, in turn, affect how Higgins eye feed, live, and reproduce. Municipal, industrial, and farm run-off degrade water quality. As filter- feeders, mussels concentrate chemicals and toxic metals in body tissues and can be poisoned by chemicals in their water. Dredging and waterway traffic produce siltation which can cover river substrate and mussel beds. The Higgins eye pearly mussel is considered extirpated from Central Iowa.
The Sheepnose is a freshwater mussel found across the Midwest and Southeast. However, it has been eliminated from two-thirds of the total number of streams from which it was historically known. The Sheepnose is a medium-sized mussel that grows to about 5 inches in length. It lives in larger rivers and streams where it is usually found in shallow areas with moderate to swift currents flowing over coarse sand and gravel. Most populations of Sheepnose are small and geographically isolated. These small populations, which live in short sections of rivers, are susceptible to extirpation from single catastrophic events, such as toxic spills. Also, isolation makes natural repopulation impossible without human assistance.
Historically, the Spectacle case was found in at least 44 streams of the Mississippi, Ohio and Missouri River basins in 14 states. It has been extirpated from 3 states and today is found in only 20 streams. The Spectaclecase’s current range includes Alabama, Arkansas, Illinois, Iowa, Kentucky, Minnesota,
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Missouri, Tennessee, Virginia, West Virginia, and Wisconsin. With few exceptions, Spectaclecase populations are fragmented and restricted to short stream reaches. No recent surveys have found Spectaclecase in the Des Moines River.
While the bald eagle is no longer listed as endangered, they are protected by the Bald and Golden Eagle Protection Act. Despite the project’s urban setting and presence of human activity, many eagles forage, roost, and nest in the Des Moines River corridor. Warm water from the Saylorville Lake and Lake Red Rock Dams prevents the river from freezing completely, allowing the eagles to forage for fish throughout the winter. The areas and the lands below each dam have large cottonwood and maples. Bald eagles are beginning to nest in the Des Moines River Valley.
While not officially listed within the project area, there are several animals the USFWS has or is considering to add to the endangered species list. Table EA-5 lists these species.
The Des Moines River Valley is home to 150+ state listed species. These include mussels, amphibians, reptiles, birds, mammals, and plants. For county specific information, see, the Iowa DNR’s Natural Areas Inventory webpage for up to date information on state listed species (https://programs.iowadnr.gov/naturalareasinventory/pages/Query.aspx.
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Table EA-5. Other Species Considered Common Name Classification Habitat Future Concern This species is listed in several counties in Eastern Rusty patch Bumblebee Grasslands and tallgrass prairies of the Upper Midwest Iowa. As more range information is studied, the Endangered Bombus affinis and Northeast USFWS may expand the bee’s range to include central Iowa. On Dec 20, 2017, the USFWS announced a 90-day Open woods near the edges of water, as well as over findings to petition to list the species. The USFWS water. They are not usually found in open fields or deep Tricolored bat requested any information relevant to whether the Threatened forests. They roost in rock crevices, caves, buildings, and Perimyotis subflavus species falls within the definition of either tree foliage in the summer. During the winter, caves, ‘‘endangered species’’ or ‘‘threatened species.’’ mines, and deep crevices serve as hibernaculum. No decision has been made at this time. Wet areas including wet prairies, marshes and low areas along rivers and lakes. In many areas, massasaugas also Eastern massasauga This species is listed in several counties in Eastern Threatened use adjacent uplands during part of the year. They often Sistrurus catenatus Iowa, but not listed in the planning area. hibernate in crayfish burrows but may also be found under logs and tree roots or in small mammal burrows.
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Future Condition: Fish and wildlife species (common to rare), will continue to inhabit the riverine and urban areas along the river and lakes. As urbanization increases, introduction of invasive species, or other habitat threats, animal species may shift from specific niche species to generalists who can adapt to future habitat changes or declines.
G. INVASIVE SPECIES
In urban settings the potential for exotic and invasive plants is always prevalent. “Escaped” plants and seeds from home gardens are a constant percent of the overall vegetation. More persistent species such as Tree of heaven prefer wet fields, roadsides, fencerows, woodland edges and forest openings. Several plants like Exotic bush honeysuckle, and Garlic mustard prefers shaded or semi-shaded areas (upland and floodplain forests, shrublands, and shaded yards). Phragmites is a very persistent wetland invasive plant found in the project area. A few species including Serecea Lespedeza, Autumn olive and Crown vetch cause serious threats and expensive control measures on an annual basis. All of these species have the ability to significantly alter native ecosystems.
Aquatic invasive species include zebra mussels, quagga mussels, rusty crayfish, big head carp, grass carp, and silver carp in the river. Barriers such as the Ottumwa Dam and Red Rock Dam have helped to curb these species upstream migration.
Aquatic plants have difficulty establishing in the reservoirs and pose a smaller threat, however, if zebra mussels, big head carp or silver carp were introduced, they would negatively affect the overall fishery of Saylorville Lake and Lake Red Rock.
Invasive species pose a significant threat to the Saylorville Lake and Lake Red Rock landscape. The vegetative management program spends over $60,000 annually on invasive species management. Now and in the future, the Emerald ash borer will have tremendous consequences, both in actual costs to manage and the overall dynamic change that will occur within forests. Trees are also very susceptible to invasive species, as evidenced by the Emerald ash borer, Gypsy moth (oak) and Thousand cankers disease (walnut), to name a few. Forty-seven invasive species have been identified on project lands; all pose threats to different plant communities.
Future Condition: The success of an invasive species is in large part due to favorable conditions resulting from the complex interactions among natural and anthropogenic factors such as native and nonnative pests, fires, droughts, hurricanes, wind storms, ice storms, climate warming, management practices, human travel, and trade (Dix, et al., 2009). One consequence of globalization is in addition to people and products moving across the globe, wildlife has been transported as well. These trends should continue in the future but knowing the consequences of invasive species, perhaps the impact of invasives will be abated. Many strategies have been developed to stop the damage caused by invasive species and to prevention future invasions. An important component is educating people about the dangers of transporting wildlife to new areas. Many laws and regulations have also been passed to combat the future spread of invasives.
H. VEGETATION
The existing upland and wetland forests on and adjacent to the river have structural diversity such as snags, an overstory and understory, and downed logs, which is indicative of habitat for a variety of species.
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In 2013, the City of Des Moines contracted for a natural resources inventory in all of its parks’ open spaces, and natural areas (see section Park and Natural Areas, below). The 3,800 acres of the City's park lands and open space netted 651 plant species, one-third of all species found in Iowa. Of those, 459 species are native to central Iowa and 8 have been identified as endangered, threatened or of special concern (Rosburg, 2013)
Among these natural plant associations, 21 are herbaceous/grassland types, 4 are shrubland types, 2 are savanna types, 11 are woodland types, 23 are forest types and 19 are wetland types. Among the natural/semi-natural associations, forest associations account for the greatest area (64.6 percent), followed by herbaceous associations (22.8 percent), woodlands (6.0 percent) and wetlands (5.8 percent).
Future Condition: The current vegetation types and quantity should experience slight declines based on urbanization and the spread of invasive plant species.
I. RIVERS AND STREAMS, WATER QUALITY, WETLANDS
Rivers and Streams. Within the study area, the Des Moines River has several tributaries. The District monitors 26 streams which contribute to Saylorville Lake and Lake Red Rock’s water sources. These rivers and streams are like other Iowa streams as far as their benefits to drinking water, fish, wildlife, and humans. There are other small intermittent streams and drainages throughout the planning area. Levees and small head dams have heavily constrained some of the streams in certain segments through the planning area.
Table EA-6 and Figure EA-5 identify the major rivers and streams along the Des Moines River.
Table EA-6. Major Rivers and Streams in the Des Moines River Watershed Length Length ID Name (km) (miles) 1 Des Moines River 44.04 27.36 2 East Fork Des Moines River 272.16 169.11 3 Des Moines River 34.53 21.46 4 Allen Creek 11.13 6.91 5 Boone River 98.58 61.26 6 Big Creek 14.73 9.16 7 Beaver Creek 77.25 48.00 8 Four Mile Creek 26.67 16.57 9 North Raccoon River 313.36 194.71 10 Raccoon River 359.64 223.47 11 Middle Raccoon River 148.38 92.20 12 South Raccoon River 115.93 72.04 13 North River 98.54 61.23 14 Cedar Creek 25.41 15.79 15 Middle River 95.78 59.51 16 South River 83.46 51.86 17 White Breast Creek 72.20 44.86 18 English Creek 44.53 27.67
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19 Cedar Creek 40.96 25.45 20 North Cedar Creek 24.73 15.37 21 Des Moines River 689.60 428.49 22 Rock Creek 6.69 4.16
Figure EA-5. Major Rivers and Streams in the Des Moines River Watershed
Water Quality. The Iowa DNR manages water quality through the implementation of the state's Water Quality Standards. Lakes and stretches of streams and rivers in Iowa each have specific designations, based on what they are used for—recreation such as swimming or fishing; drinking water; or maintaining a healthy population of fish and other aquatic life.
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There are five categories or designations for Iowa’s water quality:
Category 1: All designated uses (e.g., for water contact recreation, aquatic life, and/or drinking water) are met.
Category 2: Some of the designated uses are met but insufficient information exists to determine whether the remaining uses are met.
Category 3: Insufficient information exists to determine whether any uses are met.
Category 4: The waterbody is impaired but a total maximum daily load (TMDL) is not required.
Category 5: The waterbody is impaired and a TMDL is required, designated as a CWA, Section 303(d) Impaired Water Body.
If the water quality in the stream or lake does not meet its designated use, it does not meet Iowa's water quality standards and is considered "impaired” http://www.iowadnr.gov/Environmental- Protection/Water-Quality/Water-Quality-Standards . Water quality improvement plans investigate streams and lakes on Iowa's impaired waters list. The ultimate goal is to improve water quality and remove streams and lakes from the impaired list. The plans, developed by the Iowa DNR, use research results and the public's input to help reduce the amount of pollutants reaching our water.
In Iowa, there were 813 impairments of 605 stream/river segments and 283 impairments of 145 lakes, reservoirs, and wetlands (Iowa DNR, 2016). There are several rivers and streams in the planning area with water quality concerns including a designation 303(d) status (Figure EA-6). Table EA-7 identifies the reasons for poor water quality.
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Figure EA-6. Des Moines River Basin Impaired Water Bodies
Saylorville Lake (turbidity and beach bacteria (E. coli)) and Lake Red Rock (beach bacteria) are on the Iowa Eutrophic Lakes on Category 5a. Both lakes are on the State wide Beach Bacteria TMDL list – 2016 Impaired Waters List. Bacteria sources are unknown. Turbidity results from sediment suspension.
Table EA-7. Causes for Iowa Impaired Water Bodies
Bacteria Temperature Aesthetics Biological Metals Algal Growth Fish Kill Nutrients Dissolved Solids Fish Consumption Advisory Other Cause Pesticides Organic Enrichment Habitat Alterations Sediment pH Toxic Inorganics Turbidity Flow Alteration
The Des Moines River Water Quality Network (DMRWQN), a collaborative effort between the Rock Island District and Iowa State University, conducts water quality observations and data collection at locations along the Des Moines River and the Raccoon River from above Saylorville Lake to below Lake Red Rock. The year 2018 marks the 50th year of Des Moines River water quality sampling.
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There are 23 river/reservoir locations (of which six are currently active with one additional as needed for high water events and seven beach-only sampling locations. The DMRWQN publishes annual reports covering over 50 water quality parameters as well as fish tissue sampling for mercury and select pesticides (Green, et al., 2018). A full summary of water quality data for each reservoir is provided in Appendix B.
Elevated bacteria levels require the District to close the reservoirs’ beaches periodically.
While the exact sources of the bacteria is not known, fecal contamination of beach water commonly occurs due to: improperly constructed and operated septic systems and sewage treatment plants, manure spills, storm water runoff from lands with wildlife and pet droppings, or direct contamination from waterfowl, livestock, or small children in the water. In Iowa, precipitation run-off appears to be one of the most important factors in generating high levels of bacteria. Surface runoff after a heavy rainfall may transport high levels of fecal bacteria to the water at the beach. The rain also increases the sediment in the water causing it to be murky. Since bacteria are destroyed by sunlight, murky water aids in their survival.
In recent years blue-green algae (cyanobacteria) have been observed and monitored at both Saylorville Lake and Lake Red Rock. In 2009 testing revealed elevated microcystin levels at Saylorville Lake, prompting the District to posted health advisories at all public access points. Since then seasonal monitoring of microcystin levels has been conducted at both reservoirs. According to the IADNR, factors that influence cyanobacterial bloom formation and persistence include:
• Light intensity and total sunlight duration: stronger light and longer duration • Nutrient availability (both nitrogen and phosphorus) • Water temperature: warmer temperatures, in the range of 60°F – 80°F
Downstream water quality objectives are also part of the authorized project purposes (low flow augmentation) at Saylorville Lake and Lake Red Rock. The District’s water quality releases from the reservoirs are intended to be met at least 90 percent of the time. The objectives are met by maintaining a minimum flow of 200 cfs from Saylorville Dam to the confluence with the Raccoon River, 270 cfs from the confluence to the sewage treatment plant (Des Moines river mile 199), and 300 cfs below that point to Ottumwa. Low-flow releases from Saylorville Lake need to be adjusted such that minimum low-flow requirements in the specified reaches are satisfied until Saylorville Lake falls to elevation 827 feet NGVD at which time water rationing begins. The conservation storage in Lake Red Rock is then utilized to satisfy the Ottumwa minimum constraint of 300 cfs until Lake Red Rock falls to elevation 734 NGVD at which time water rationing begins.
Wetlands. The District reviewed the USFWS National Wetlands Inventory (NWI) data to identify areas of potential wetland within the project area. Table EA-8 and Figure EA-7 provides a summary of NWI-indicated wetland currently mapped along each levee system within the project area. Appendix B includes the NWI–indicated wetlands.
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Table EA-8. Summary of NWI-Indicated Wetlands (ha) within the 500-year Floodplain
Wetland Type Area (ha) Freshwater Emergent Wetland 3,034.59 Freshwater Forested/Shrub Wetland 4,159.19 Freshwater Pond 702.99 Lake 7,374.99 Riverine 5,591.25
Figure EA-7. Des Moines River Wetland Area (ha)
Future Conditions: The study area’s rivers and streams should not change in the foreseeable future. Climate change (increased precipitation) and urbanization (increased impermeable surfaces) may promote flash flooding more often.
Urbanization increases flood volume, frequency, and peak flood value because it brings with it more impervious surfaces, such as roads and large paved areas. This causes increased runoff that would occur more rapidly and with a greater peak flows than under rural conditions. Urbanization would tend to increase flash flooding, turbidity, pollutant loads, and bank erosion. Increases in dissolved solutes (conductivity), suspended solids (turbidity), fecal bacteria, nitrogen and phosphates, dissolved oxygen, and/or toxics (e.g. metals, pesticides, pharmaceuticals, other organic pollutants) would tend to increase. Additionally, chloride, sulfates, ammonia, and bacteria by infiltration from surface water polluted by municipal and industrial wastes and/or from leaking sewer lines could contaminate the groundwater.
To address the potential for an increase in contaminants entering water sources, the Iowa DNR and EPA would continue to update and enforce regulations addressing and minimizing the pollutant effects on water quality.
Wetland conditions should remain at risk of invasive plants and development.
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J. HYDROLOGY AND HYDRAULICS
The major sub-basins of the Des Moines River Basin are long and narrow. Streams flow generally from the northwest to southeast. Average slope of the Des Moines River ranges from two to three feet per mile upstream of Red Rock Dam and 1.3 to 1.6 feet per mile downstream of the dam. Bottom widths vary from about 200 to 300 feet below Saylorville Dam and from about 300 to 500 feet below Red Rock Dam.
The current water control plans for Lake Red Rock and Saylorville Lake were developed based on the hydrologic record available at the time (1917 to 1961). Since the projects were constructed, significant changes in rainfall and resulting inflow to the reservoir projects have been observed. Statewide and individual gage precipitation records show significant upward trends in annual precipitation over the 20th and early 21st centuries (Figure EA-8). This observed trend of increased annual precipitation has resulted in increased inflow volumes into Saylorville Lake and Lake Red Rock.
Iowa Annual Precipitation (inches) 50
45
40
35
30
25
Source: National Climatic Data Center http://www.ncdc.noaa.gov/oa/climate/research/cag3/ia.html 20 1917 1927 1937 1947 1957 1967 1977 1987 1997 2007
Figure EA-8. Statewide and Individual Gage Precipitation Records
Due to the use of reservoir storage to manage flood flows, peak annual reservoir elevations and downstream flood flows are driven by overall flood volumes rather than peak daily inflows. Based on the results of the 2010 Regulated Flow Frequency Study, the peak 30-day inflow volume is the best predictor of ultimate peak reservoir releases. Comparison of the peak annual 30-day inflow volumes into Lake Red Rock for the period of record used in the original design of the project (1917 to 1961)
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and the period of record since the project was placed into operation (1969 to 2014), shows a 45 percent increase in the average annual peak 30-day inflow volume as well as a 43 percent increase in the standard deviation of peak annual 30-day inflow volume; reflecting higher and more extreme flood events in the later period.
Saylorville Lake
The Saylorville Lake project, is situated on the Des Moines River, approximately 213.7 miles above the confluence with the Mississippi River, 2.5 miles upstream of the town of Saylorville, and 9 miles upstream of Des Moines, Iowa. The dam is 360 river miles downstream of the basin divide; over this distance basin relief changes from elevation 1,700 feet to elevation 800 feet. The lake provides a permanent conservation pool at elevation 836 feet that supports low flow augmentation, water supply, fish and wildlife habitat and recreation. Between elevations 836 and 890 feet, 559,100 acre-feet of storage is available for FRM, the primary purpose of the project. In the fall during the months of September through November, the conservation pool may be gradually increased by as much as 4 feet from the normal conservation level of 836, to elevation 840 feet. The timing of the pool raise greatly enhances the waterfowl food supply along the shoreline of the reservoir.
Saylorville Dam has a drainage area of 5,823 square miles. Large tributaries above the dam include: the West Fork of the Des Moines River (2,308 square miles), East Fork of the Des Moines River (1,315 square miles), the Boone River (906 square miles), and Lizard Creek (437 square miles). The structure and its operation provide flood damage reduction for the downstream Des Moines River corridor, which includes the communities of Des Moines, as well as significant rural areas. The corridor downstream of Saylorville Dam starts at the dam (river mile 213.7) and ends at the 6th Avenue Bridge in the City of Des Moines (river mile 204.28). The Saylorville Lake and Dam study area is located primarily in Polk County, Iowa, with portions covering Dallas and Boone Counties.
Channel capacity below Saylorville Dam is about 16,000 cfs. In the reach of the Des Moines Local Flood Protection project, the design flood is 40,000 cfs and 100,000 cfs above and below the confluence with the Raccoon River, respectively. Bank-full stage at the S.E. 6th Street gage corresponds to a stage of approximately 24 feet with a discharge of 30,000 cfs. Most of the local flow below the dam and above the Local Protection Works at Des Moines is contributed by Beaver Creek. Beaver Creek has a drainage area of 358 square miles at the gaging station at Grimes, located six miles upstream from its confluence with the Des Moines River. The entire drainage area below Saylorville Dam and above the S.E. 6th Street gage is 4,056 square miles.
The District developed the current Des Moines River Basin Master Reservoir Regulation Manual with the objective of reducing the discharge at the downstream control station during runoff events when there is less utilization of flood control storage. As more storage capacity is utilized, the degree of downstream protection is reduced. For reduction of flooding at the City of Des Moines, about 62 percent of the reservoir flood control capacity is utilized prior to the reservoir reaching the intermediate/large magnitude flood level of 875 feet NGVD.
Saylorville Lake is operated by considering the river level at the SE 6th Street gage at Des Moines while keeping the storage in balance with Lake Red Rock for seasonal conservation pool levels between (836/840 feet NGVD) and 860 feet NGVD.
Flood stage at the SE 6th Street gage is 24 feet. If the lake level is between conservation pool 836/840 feet NGVD, and 875 feet NGVD, regulation adjustments are made to keep the discharge at the control point below 30,000 cfs. Inflows are released up to a maximum outflow of 12,000 cfs (16,000 cfs if the
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Lake Red Rock pool level is less than elevation 758 NGVD) in the growing season (21 April to 15 December) or a maximum outflow of 16,000 cfs in the non-growing season (16 December to 20 April). Minimum release during flood events is 2,000 cfs. This corresponds to a downstream channel depth of 2 to 3 feet. In complying with these constraints, the maximum change of daily outflow rates are limited to 3,000 cfs, except when pool levels dictate following either the Intermediate or Large Magnitude Flood operation schedules (elevation 875 feet NGVD).
Normal flood control operation is accomplished by regulation of releases through operation of three inlet gates. The basic objective is to release the maximum permissible outflow as limited by the conduit capacity and other constraints outlined above.
The Intermediate Magnitude Flood operation schedule of the water control plan takes effect when the pool level is at or forecast to be between elevations 875 and 884 feet NGVD. Above this level, the Large Magnitude Flood Operation Schedule is followed, and all other constraints are disregarded.
During floods in which the flood volume exceeds the flood control capacity of the reservoir at elevation 890 feet NGVD, release rates are limited only by the capacity of the outlet conduit. When floods of sufficient volume and magnitude are at or forecast to exceed elevation 884 feet NGVD, pneumatic crest gates along the emergency spillway are raised. The pneumatic crest gates prohibit spillway flow until pool elevation 890 NGVD is exceeded.
• Reservoir Flood Pool Rising. Intermediate/large magnitude flood release rates from 12,000/16,000 cfs at 875 feet to 21,000 cfs at elevation 884 feet NGVD are accomplished by operation of the conduit as specified in the current Des Moines River Basin Master Reservoir Regulation Manual. The release rate above 884 feet NGVD is held at 21,000 cfs (fully open conduit) until pool elevation 889 feet NGVD is reached. At 889 feet NGVD, if the pool is forecast to exceed elevation 890 feet NGVD, the pneumatic crest gates are gradually lowered, as necessary, so that the combined outflow from the fully open conduit and the spillway is 42,000 cfs at elevation 890 feet.
• Reservoir Flood Pool Falling. Above 890 feet NGVD, no further regulation is attempted. After the reservoir level has crested and the lake level falls below elevation 890.0 feet NGVD, the sluice gates controlling flow through the conduit are adjusted to reduce the combined spillway/conduit discharge from 42,000 cfs at elevation 890.0 feet NGVD to 21,000 cfs at elevation 889.0 feet NGVD. Between elevation 890 and 889 feet, outflow release rates will be no less than the inflow to the reservoir. Between elevation 889.0 feet and 884.0 feet the conduit discharge is adjusted to maintain a combined spillway/conduit discharge of 21,000 cfs. At the spillway crest elevation 884.0 feet, full conduit flow of 21,000 cfs is maintained to elevation 875.0 feet NGVD. At elevation 875.0 feet NGVD, release rates are adjusted to revert to normal flood control operation.
Lake Red Rock
The Lake Red Rock project is situated on the Des Moines River, approximately 142.9 miles above the confluence with the Mississippi River, approximately 60 miles downstream of the City of Des Moines and about 70.8 miles downstream of Saylorville Lake. The Des Moines River flows generally southeastward 143 miles from Red Rock Dam to the mouth. The basin relief above Lake Red Rock Dam changes from elevation 1,700 feet to elevation 654 feet.
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Lake Red Rock Dam has a drainage area of 12,323 square miles. Major tributaries above the dam between Saylorville Lake and Lake Red Rock include: the Raccoon River (3,625 square miles), North River (400 square miles), Middle River (558 square miles), South River (590 square miles), and White Breast Creek (430 square miles).
The dam structure and its operation provide flood risk reduction downstream along the Des Moines River corridor, which includes the communities of Eddyville, Ottumwa, Eldon, Keosauqua, Farmington, and Bonaparte, Iowa, as well as several other communities and significant agricultural land. Regulated flows of the Des Moines River from the reservoir also provide varying degrees of protection along the Mississippi River downstream of the mouth of the Des Moines River. Between elevations 742 and 780 feet, 1,463,100 acre-feet of reservoir storage is provided for flood risk reduction.
Lake Red Rock provides a permanent conservation pool at elevation 742 feet supporting low flow augmentation, fish and wildlife habitat and recreation. In the fall during the months of September through November, the conservation pool may be gradually increased by as much a 2-feet from the normal conservation level of 742, to elevation 744 feet. The timing of the pool raise greatly enhances the waterfowl food supply along the reservoir’s shoreline.
The drainage area below the S.E. 6th Street gage and above Red Rock Dam is 2,444 square miles. The majority of the drainage area (1,654 square miles) is contributed by the North, Middle, and South Rivers and Whitebreast Creek. Quick, large-volume rainfall events in these areas can cause significant effects on the pool elevation of Lake Red Rock and corresponding release rates of Lake Red Rock Dam.
Under the current Des Moines River Basin Master Reservoir Regulation Manual, (1992), normal flood control operation is accomplished by regulation of releases through operation of 14 conduits controlled by sluice gates. The basic objective is to release the maximum permissible outflow as limited by the downstream control stations. Maximum reduction in discharge at downstream control stations is provided during periods when there is less utilization of flood control storage. A minimum flow release of 5,000 cfs is made when operating for control points. As more storage capacity is utilized, the degree of downstream protection is reduced. For reduction of flooding along Des Moines River during the growing and non-growing seasons approximately 80 percent of the reservoir flood control capacity is utilized prior to the large magnitude flood level of 775 feet.
In the reach of the Des Moines River from Red Rock Dam to the confluence of the Mississippi, growing season discharges (01 May through 15 December) are limited to 18,000 cfs and 22,000 cfs as registered on the Ottumwa and Keosauqua gages, respectively. These discharges provide a freeboard at the gages of three feet and provide a small margin of bank freeboard in the reach to minimize saturation damage associated with prolonged periods of bank-full flow. The regulated release rates from Red Rock Dam, adjusted for downstream local inflow, are keyed to these flows.
In addition to flood damage reduction along the Des Moines River, downstream control points at Burlington, Iowa, and Quincy, Illinois, are considered in the operation of Lake Red Rock to reduce Mississippi River flooding. Mississippi River flooding begins when the stage is at, or forecasted to be at or exceed 18.5 feet, for Burlington, Iowa, or 20.0 feet at Quincy, Illinois. Reductions in reservoir releases for flooding along the Mississippi River will not be in excess of that required to limit the Quincy stage to 20.0 feet. The release is determined as the maximum allowable considering all constraints.
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During the non-growing season (16 December through 01 May), larger discharges up to a maximum of 30,000 cfs can be tolerated without causing significant impacts.
Large magnitude flood operation takes effect when the pool level is at or forecast to exceed 775 feet NGVD. Releases as specified in the Regulation Schedule are made through the outlet conduits until the required release rate exceeds the gated conduit capacity. At this point the outflow is transitioned to the spillway. Outflow rates are increased as the pool continues to rise in accordance with the schedule. At pool elevation 785 feet NGVD the spillway tainter gates are opened sufficiently to maintain the pool at 785 until unrestricted discharge prevails.
K. STATE PARKS, CONSERVATION AREAS, AND OTHER AREAS OF RECREATIONAL, ECOLOGICAL, SCENIC, OR AESTHETIC IMPORTANCE
Parks, conservation areas, and wildlife management areas in or near the planning area are listed in Appendix B. An example of a popular recreational area is the bike trail pictured in Figure EA-9. These areas are free of housing developments or other buildings and provide simple pleasures such as relaxing, exercising, hunting, fishing, and nature watching. Some of these areas provide protection to sensitive plants and wildlife. Appendix B lists conservation easement information as well as maps showing many of the public areas.
During high water events on the river or in the reservoirs, many recreation facilities go out of service. The District designed many of the recreation facilities along the reservoirs’ shorelines to accommodate low water and high water conditions. Their design maximizes recreation opportunities as well as keep maintenance costs low.
Future Conditions: Public lands should not change in the future. They will continue to play an important role for people’s enjoyment and education, as well as important wildlife areas. Because these areas are in public ownership, their popularity should increase as other non-public lands become more urbanized. Conservation easements should continue but may depend on state and Federal funding. These areas are generally low in agriculture value, so there should be incentive to the landowners to continue setting aside flood prone lands for wildlife if there is a financial incentive.
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Photo Credit: Boone County Conservation Figure EA-9. High Trestle Bridge Over the Des Moines River in Boone County
L. HISTORICAL & CULTURAL RESOURCES
The Saylorville and Lake Red Rock Master Plans summarize the area’s 13,000-year-long culture history from the Paleo-Indian Period through the historic era. Cultural resources are a broad pattern of material and non-material sites or objects that represent contemporary, historic, and pre-historic human life, ways, or practices. Cultural resources include historic properties, archeological resources, and Native American resources including sacred sites and traditional cultural properties. The study area contains a variety of cultural resource types spanning from the earliest Native American inhabitants of North America to the present. Common historic properties within the study area include prehistoric and historic archeological sites, buildings, objects, structures, and historic districts.
Each master plan classifies significant archeological sites, along with areas of other scientific, ecological, or aesthetic importance, as Environmentally Sensitive Areas (ESA). Development of public use on an ESA is generally prohibited. Respectively, there are 1,967 and 11,124 acres classified as ESA at Lake Red Rock and Saylorville. There is one archeological ESA in the planning area, the Christensen Oneota Site (13PK407), situated along Saylorville’s downstream corridor.
Several dozen cultural resource surveys occurred in concert with both project’s original construction and subsequent developments. Surveys and sites information is generally summarized in Lake Red Rock (1999) and Saylorville’s (1993) Historic Property Management Plans (HPMP).
Future Conditions: Cultural and historical resources management will continued in the planning area. As constructed buildings and structures age, they may become important for their historic value to the local community as well as the nation. If cultural resources are found on federally-managed lands, the responsible Federal agency would consult in a timely manner with the State Historic Preservation Office (SHPO), tribes, and all interested parties in adherence to Section 106 of the National Historic Preservation Act (NHPA).
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M. SOCIOECONOMIC RESOURCES
The District queried the 2000 U.S. Census and the five-year average (2011-2016) from the American Community Survey (ACS) to obtain relevant socioeconomic data for this analysis. Socioeconomic data is presented for 364 block groups comprising the Des Moines River and tributaries intersecting the 500-year floodplain.
Population 2000-2016. Population of the project area in 2016 was 513,985, an increase of 17.5 percent from year 2000 (U.S. Census ACS 2011-2016, Table EA-9). A majority of the project area’s population resides in Polk County (75 percent), encompassing the City of Des Moines. A substantial amount of the population growth within the 500-year floodplain also took place in Polk County communities. Dallas County population increased 60 percent or an additional 10,000 people over 16 years. In Mahaska County, four block groups in the 500-year floodplain declined nearly 74 percent of their population between 2000 and 2016.
Table EA-9. Population and Housing, 2000-2016, Des Moines River Project Area County No. of Population Housing Units Households Block 2000 2016 Change 2000 2016 2000 2016 Change Groups Boone 14 17,397 18,861 8.42% 7,084 7,954 6,710 7,482 11.51% Clark 2 1,277 2,833 121.85% 570 1,298 490 1,091 122.65% Dallas 7 9,988 16,002 60.21% 3,891 5,677 3,649 5,530 51.55% Davis 1 611 569 -6.87% 269 244 239 244 2.09% Jasper 1 946 769 -18.71% 387 361 354 361 1.98% Jefferson 1 1,169 1,197 2.40% 454 539 437 498 13.96% Lee 14 13,867 13,514 2.55% 6,181 6,009 5,598 5,318 5.00% Mahaska 4 16,593 4,347 -73.80% 7,291 1,841 6,628 1,686 -74.56% Marion 14 17,221 19,155 11.23% 6,728 7,809 6,386 7,257 13.64% Monroe 1 935 855 -5.35% 409 391 372 304 -18.28% Polk 257 304,491 384,632 26.32% 12,699 159,921 120,826 149,187 23.47% Van 8 6,955 6,460 -7.12% 3,241 3,309 2875 2635 -8.35% Buren Wapello 32 32,207 31,501 -2.19% 14,274 14,340 13,316 12,927 -2.92% Warren 7 12,966 12,256 -5.48% 4,848 4,980 4692 4,772 1.71% Webster 1 820 1004 22.44% 342 425 317 351 10.73% Total 364 437,443 513,985 17.50% 182,960 215,098 172,889 199,643 15.47%
Project area consists of 364 Block Groups within or intersecting the 500-year floodplain. Data is from Block Groups within or intersecting the 500-year floodplain. Source: U.S. Census 2000 and ACS 2011-2016.
Housing Units. In 2016, 215,098 housing units were present in the project area, an increase from a recorded 182,960. The percent vacant increased, from 5.5 percent (2000) to 7.2 percent vacant (2016). The project area experienced a slight increase in the average household size rising from 2.5 people per household (2000) to 2.6 (2016).
Race/Ethnic Diversity: Ethnic diversity in the project area is lower than state and national levels, a slight upward trend in the ratio of minority residents to white residents. Between 2000 and 2016, an increase in the percentage of minority persons from 10 to 13 percent. The largest three races represented by proportion are White (86.6 percent), Black or African American (5.6 percent), and
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Asian, (3.3 percent). All of the counties in the project area have a majority white population (Table EA-10).
Table EA-10. Racial Composition in Study Area County No. of Total White Black Native Asian Hawaiian Other Two Block Populaion America Race Plus Groups 2016 n Races Boone 14 18,861 18,333 140 60 36 27 254 Clark 2 2,833 2,746 11 5 71 Dallas 7 16,002 14,384 137 1 947 96 437 Davis 1 569 543 26 Jasper 1 769 749 Jefferson 1 1,197 1,194 2 1 Lee 14 13,514 12,262 542 47 7 90 566 Mahaska 4 4,347 4,294 11 10 32 Marion 14 19,155 18,641 102 68 80 1 263 Monroe 1 855 885 Polk 257 384,632 32,3863 26,838 1,125 15,717 6,073 10,650 Van 8 6,460 6,355 15 7 3 6 74 Buren Wapello 32 31,501 28,347 794 36 313 1,446 470 Warren 7 12,256 11,787 97 24 109 4 235 Webster 1 1004 1,000 4 Total 364 513,985 44,5383 28,678 1,373 17,223 7,753 13,083 Percent 86.65% 5.58% 0.27% 3.35% 0.00% 1.51% 2.55%
Project area consists of 364 Block Groups within or intersecting the 500-year floodplain. Data is for Block Groups within or intersecting the 500-year floodplain. Source: U.S. Census 2000 and ACS 2011-2016.
Income. Median incomes within the project area are presented in Table EA-11 range from $42,494 in Wapello to $78,918 in Warren County (2016).
Table EA-11. Median Income of Study Area County Median Income County** Median Income Webster $42,196 Polk $61,684 Jefferson $45,257 Davis $49,696 Warren $67,090 Boone $54,513 Dallas $78,918 Jasper $55,503 Marion $57,412 Lee $44,568 Mahaska $49,599 Wapello $42,494 Van Buren $46,769 Monroe $47,515 Clark $45,169 Project area consists of 364 Block Groups within or intersecting the 500-year floodplain. Data is for Block Groups within or intersecting the 500-year floodplain. Source: U.S. Census 2000 and ACS 2011-2016.
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Employment. The largest employment sector within the project area is Wholesale and Retail Trade employing with approximately 38,000 people. Finance and Real Estate and the Health Care sectors employ approximately 35,000 people each. The largest city in Iowa, Des Moines, is located in Polk County. Polk County provides a majority of jobs in the project area, having approximately 78 percent of the jobs (Table EA- 12). Table EA-12. Employment in Study Area County Ag and Constr Mfg. Wholesale Trans/ Finance Prof Educ Health- Hotel/ Art and Total Mines and Retail Utility & R.E. Mgt and care Food Other Trade Info and Public Serv Admin Admin
Boone 493 650 1,017 1,685 767 511 794 1,429 1,400 531 541 14,511 Clark 127 89 242 197 109 12 61 154 135 41 68 16,41 Dallas 166 449 475 868 512 2,159 1,056 850 987 294 319 13,414 Davis 59 17 37 26 9 18 10 46 24 0 27 323 Jasper 18 14 36 98 0 66 0 84 41 0 74 661 Jefferson 34 30 77 154 60 53 17 38 88 4 86 929 Lee 208 343 1,476 699 339 140 379 712 813 450 286 7,906 Mahaska 179 135 509 218 126 76 104 308 230 107 145 2,790 Marion 450 436 2,541 1,135 481 445 522 1,405 1,134 576 548 13,211 Monroe 50 16 143 50 25 14 10 29 77 19 0 511 Polk 2,326 13,077 19,011 29,509 12,889 30,177 20,473 23,809 26,251 13,342 12,165 317,560
Van Buren 164 293 629 361 162 209 158 266 478 112 155 3,979 Wapello 231 1105 3542 2052 726 699 719 1628 2319 880 777 20,271 Warren 59 499 426 882 477 907 770 931 774 267 311 10,211 Webster 60 61 23 65 43 6 0 36 88 14 0 486
Total 4624 17,214 30,184 37,999 16,725 35,492 25,073 31,725 34,839 16,637 15,502 408,404
**Project area consists of 364 Block Groups within or intersecting the 500-year floodplain. Data is for Block Groups within or intersecting the 500-year floodplain. Source: U.S. Census 2000 and ACS 2011-2016.
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Education Level. The project area has a range in education level for the Block Groups (Table EA- 13). Block groups vary greatly on education level but generally track are higher around the Greater Des Moines and Polk County. Approximately, 60 percent of the population have an Associate, Bachelor, Master’s or PhD degree.
Table EA-13. Education Level in Study Area County No HS Degree Schoo Diplom Associat Bachelo Maste Professiona Doctorat Total l a e r r l e Boone 131 4568 1,786 2,013 613 140 198 9,449 Clark 18 849 110 134 52 16 1,179 Dallas 52 1434 1,153 4,108 1,160 334 88 8,329 Davis 0 270 41 56 9 0 0 376 Jasper 0 221 48 169 20 0 12 470 Jefferso 14 400 70 80 32 2 598 n Lee 37 4123 871 948 279 45 22 6,325 Mahask 32 1469 257 481 206 0 8 2,453 a Marion 44 4710 1,470 2,229 810 88 88 9439 Monroe 0 349 58 38 9 0 0 454 Polk 3,050 65451 26,010 59,193 17,395 5,374 2,575 179,04 8 Van 7 1975 565 462 166 2 4 3,181 Buren Wapello 371 7759 2,247 2,497 904 254 97 14,129 Warren 49 2899 974 1,774 436 153 38 6,323 Webster 0 132 166 89 14 0 7 408 Total 3,805 96609 35,826 74,271 22,105 6,408 3,137 242,16 1 Percent 2% 40% 15% 31% 9% 3% 1% 100%
Project area consists of 364 Block Groups within or intersecting the 500-year floodplain. Data is for Block Groups within or intersecting the 500-year floodplain. Source: U.S. Census 2000 and ACS 2011-2016.
Agricultural Land. Approximately, 1.5 million acres of agricultural cropland was located in the Project area in 2016 which is about the same amount as in 2000 (National Land Cover Dataset 2011). Boone contains the largest number of crop acres located in the 500-year floodplain, about 289,400 acres in 2016 or 19 percent of all crop acres in the floodplain. Marion, Polk and Van Buren Counties have close to 200,000 acres each.
Future Conditions: The future conditions, or No Action Alternative, includes the current operating scenarios at Saylorville Lake and Lake Red Rock and therefore, conditions occurring today are likely to exist in the future. According to the Des Moines Area Metropolitan Planning Organization 2015, it is anticipated the Des Moines metro population, where most of the project area population resides, will grow from 480,000 to 750,000 by 2050, an increase of approximately 56 percent. This growth and development pattern may exacerbate impacts to the socioeconomic resources and contribute to continued resource decline in the rivers vicinity. The City of Des Moines developed The Tomorrow Plan, a regional development plan which identifies projected regional growth, community planning
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concepts, and goals to sustain future development. This proactive plan may help the City of Des Moines to enhance socioeconomic resource benefits in the project area. Therefore, impacts to socioeconomic resources, including current population, housing, businesses and employment trends are expected to occur in the future.
Minority and Low-income Populations (Environmental Justice). Environmental justice is defined as the fair treatment and meaningful involvement of all people, the final decision should be whether the project area is likely to, or is already, impacted by greater adverse effects than a demographically similar reference community. As with socioeconomic data, the five-year average (2011-2016) American Community Survey (ACS) data was queried to obtain relevant information associated with environmental justice. This ACS data is tabulated by the U.S. Census Bureau and was procured from the national, state, county and local perspective in order to provide a multi-level geographical analysis.
In order to identify whether the potential alternatives may disproportionately affect minorities or impoverished citizens, an analysis was conducted utilizing census block groups obtained from ACS. Detailed block group data was compiled using ACS 2011-2016 data. The following information was collected from specific census block groups in the study area. Appendix B contains Environmental Justice data including environmental indicators for the project area.
• Racial and Ethnic Characteristics. Race and ethnic populations in each census block of the project area were characterized using the following racial categories: Hispanic White Black or African American, American Indian and Alaska Native, Asian, Native Hawaiian and Other Pacific Islander, Persons of Hispanic Origin, and Other. These categories are consistent with the affected populations requiring study under Executive Order (EO) 12898. Table EA-15 lists race and ethnic characteristics per County in the Project area.
• Percentage of Minority Population. As defined by the U.S. Census Bureau, the minority population includes all non-Whites and White-Hispanic persons. According to Council of Environmental Quality (CEQ) guidelines, “Minority populations should be identified where either: (a) the minority population of the affected area exceeds 50 percent or (b) the minority population percentage of the affected area is meaningfully greater than the minority population percentage in the general population or other appropriate unit of geographic analysis.” The map following this sections displays the block group locations in relation to the Project area.
• Low-Income Population. The percentage of persons living below the poverty level, as defined in the 2011-2016 ACS, was one of the indicators used to determine the low-income population in a given census block or tract. Low-income population is defined as a Census block group with 20 percent or more of its residents below the poverty threshold. There are 137 block groups in the project area having at least 20 percent of population below the poverty level with a vast majority being in Polk County.
Minority and population below poverty level percentages are shown in Table EA-14 and illustrated in Figures EA-10 and EA-11 for the block groups comprising the project area. Only 15 of the 364 block groups within or intersect the floodplain have a majority minority population (or at least 50 percent of population non-white). All 15 are located in Polk County (FP153 in Table EA-14). Low-income populations spread throughout the project area. In total, there are 137 block groups in seven counties within or intersecting the floodplain that have 20 percent or higher of residents living below the
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poverty threshold. Low-income communities (as identified by Block Group data) are located in all 15 Counties within the Project area, half being in Polk County (Table EA-15).
Table EA-14. Percentage of Minority Population in Study Area
County FP Census Tract Block Group BG with over 50% Minority 153 1000 1 55% 153 3901 2 52% 153 1100 2 57% 153 701 1 71% 153 1100 3 51% 153 1200 1 56% 153 1200 2 72% 153 1200 3 68% 153 1700 1 55% 153 1700 2 63% 153 3902 1 52% 153 5000 2 85% 153 5000 4 74% 153 5100 1 61% 153 5100 2 59%
Project area consists of 364 Block Groups within or intersecting the 500-year floodplain. Data is for Block Groups within or intersecting the 500-year floodplain. Source: U.S. Census 2000 and ACS 2011-2016.
Table EA-15. Low Income Population in Study Area County Poverty BGs Boone 1 Dallas 4 Davis 2 Jasper 3 Jefferson 4 Lee 8 Mahaska 5 Marion 4 Monroe 1 Polk 76 Van Buren 2 Wapello 12 Warren 1 Webster 14 Total 137
Project area consists of 364 Block Groups within or intersecting the 500-year floodplain. Data is for Block Groups within or intersecting the 500-year floodplain. Source: U.S. Census 2000 and ACS 2011-2016.
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Figure EA-10. Des Moines, Iowa Percent Minority by Census Block Groups (U.S. Census data)
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Figure EA-11. Des Moines, Iowa - Percent Below Poverty by Census Block Groups (U.S. Census data)
Future Conditions: The future conditions include the current operating scenarios at Saylorville Lake and Lake Red Rock. Conditions occurring today are likely to exist in the future. Therefore, impacts to Environmental Justice resources, including minority and low-income population, taking place today are expected to occur in the future. These impacts are anticipated to be positive such as FRM and recreation opportunities.
N. HUMAN HEALTH & SAFETY
The Saylorville Lake and Lake Red Rock projects offer FRM for people living downstream. The purpose of the District’s FRM mission is to reduce the threat to life and reduce property damages from riverine flooding. The District’s flood damage reduction projects include structural and non-structural measures. The District is an integral part of Nation’s efforts to manage flood plains and maintain and operate aging water resources infrastructure. Execution of the FRM program serves to integrate and synchronize programs and activities within the Corps and with counterpart activities of the Department of Homeland Security, FEMA, other Federal agencies, state organizations, and regional and local agencies.
Saylorville Lake’s FRM structures include the main dam, spillway, and Big Creek Remedial Works (consisting of a diversion dam, diversion channel, terminal spillway, barrier dam and pump station).
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Lake Red Rock’s FRM structures include the Red Rock Dam; Remedial Levee Works at Avon, Carlisle and Southeast Des Moines/Southwest Pleasant Hill; and Robert’s Creek Sub-impoundment.
The Corps provides water supply storage space in its multi-purpose reservoirs for many years. Based on current data, approximately 9.8 million acre feet of municipal and industrial water supply storage space are included in 135 reservoir projects in 25 states. As one of the nation’s largest water management agencies, the Corps plays an important role in ensuring that Americans have enough water to meet their needs. The Water Supply Program currently is capable of providing about 6.5 billion gallons of water per day to allow state and local interests to supply cost effective water to homes, municipalities and businesses nationwide. A water-supply contract with the State of Iowa has been in place at Saylorville Lake since 1982. This contract allows the State of Iowa to utilize 18.86 percent of the usable storage space (estimated to be 11,940 acre feet) in the lake between elevations 812 National Geodetic Vertical Datum (NGVD) and 836 NGVD. The state has sub-allocated that water to the Des Moines Water Works and Iowa Southern Utilities (Alliant Energy). There are no direct water intake structures in Saylorville Lake, but water is withdrawn downstream from releases made through the Saylorville Dam.
In addition to the FRM health and human safety component, recreation safety is a high priority at each reservoir. Reservoir staff fosters public and employee safety through education, research, and proactive visitor assistance activities, such as personal visitor contact, water safety patrols, and timely maintenance of signs and public use facilities.
Lastly, as noted in section I. Rivers and Streams, Water Quality, Wetlands, moderately large population of cyanobacteria, also known as blue-green algae, exists at Lake Red Rock (Iowa State University data), but it is not necessarily an impairment. Cyanobacteria are capable of producing toxins hazardous to health, but they do not always produce toxins. Occasionally blooms of blue green algae form on the lake, and can give an eerie bluish cast to the water.
Future Conditions: The area populations would continue to increase and, concurrently, development would also continue to increase. Water use and current water borne issues should continue into the future.
O. SUSTAINABILITY, GREENING AND CLIMATE CHANGE
Executive Order 13423, Strengthening Federal Environmental, Energy, and Transportation Management (January 24, 2007), directs Federal agencies to conduct their environmental, transportation and energy-related activities in an environmentally, economically and fiscally sound and sustainable manner. The District strives to protect, sustain, and improve the natural and man- made environment of the Nation, and is committed to compliance with applicable environmental and energy statutes, regulations, and EOs. Sustainability is an overarching concept encompasses energy, climate change, and the environment to ensure Federal activities do not negatively impact resources for future generations. Proposed alternative plans must provide for sustainable solutions addressing both short- and long-term environmental as well as social and economic considerations.
Greenhouse gases (GHGs) are components of the atmosphere that trap heat relatively near the surface of the earth and contribute to the greenhouse effect (or heat-trapping) and climate change. Most GHGs occur naturally in the atmosphere from natural processes and events, but increases in their concentration result from human activities such as burning fossil fuels. Global temperatures are expected to continue to rise as human activities continue to add carbon dioxide (CO2), methane,
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nitrous oxides, and other GHGs to the atmosphere. Whether rainfall increases or decreases remains difficult to project for specific regions. In 2010, the CEQ released draft guidance on when and how Federal agencies should consider GHG emissions and climate change in NEPA analyses. This draft guidance includes a presumptive effects threshold of 27,563 tons of CO2 equivalent emissions from a Federal action annually (CEQ, 2010).
Climate change impacts within the study area would likely involve increased temperatures (Figure EA-12) and increased precipitation leading to further altered (flashier) hydrologic conditions (Figure EA-13). Any changes in hydrologic conditions occurring within the basin would likely result from less frequent but more intense warm-weather precipitation events, moderately to severely reduced summer flow conditions and degraded water quality, less winter ice cover and more cold-weather erosion events. The character of riparian habitats may also change and invasive species may move into the area with changing climate (Pryor et al., 2014). Extreme rainfall events and flooding have increased during the last century and these trends are expected to continue, causing erosion, declining water quality, and negative impacts on transportation, agriculture, human health, and infrastructure. The range and distribution of fish and other aquatic species will likely change, and an increase in invasive species would also likely occur (Pryor et al., 2014).
Figure EA-12. Temperatures Rising in the Midwest Annual average temperatures (red line) across the Midwest show a trend towards increasing temperature. The trend (heavy black line) calculated over the period 1895-2012 is equal to an increase of 1.5°F. (Source: updated from Kunkel et al. 2013).
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Figure EA-13. Iowa Annual State-wide Precipitation in Inches from 1873-2008 Note the State has had an 8 percent increase in annual precipitation over this 136-year period (Iowa Climatology Bureau, 2010. (http://www.iowadnr.gov/Conservation/Climate-Change)
In the next few decades, it is expected longer growing seasons and rising CO2 levels would increase yields of some crops, though such benefits will be progressively offset by extreme weather events. Though adaptation options can reduce some of the detrimental effects, in the long-term, the combined stresses associated with climate change are expected to decrease agricultural productivity (Pryor et al., 2014).
The climate change assessment tools, utilized in the study are consistent with USACE Engineering and Construction Bulletin (ECB) 2016-25, Guidance for Incorporating Climate Chance Impacts to Inland Hydrology in Civil Works Studies, Designs, and Projects to provide an indication of the potential for non-stationarity and impact to flood risk. Additional discussion on this topic is found in Appendix G, Climate Change Impact Assessment.
Future Conditions: District projects, programs, missions, and operations have generally proven to be robust enough to accommodate the range of natural climate variability over their operating life spans. However, recent scientific evidence shows in some places and for some impacts relevant to District operations, climate change is shifting the climatological baseline about which natural climate variability occurs, and may be changing the range of variability as well. This is relevant to the District because the assumptions of stationary climatic baselines and fixed range of natural variability, as captured in the historic hydrologic record may no longer be appropriate for long-term projections of flood risk.
The District considered climate change impacts on the hydrology of the Des Moines River Basin in accordance with ECB 2016-25, Guidance for Incorporating Climate Change Impacts to Inland Hydrology in Civil Works Studies, Designs and Projects, as well as USACE Engineering Technical Letter (ETL) 1100-2-3, Guidance for Detection of Nonstationarities in Annual Maximum Discharges.
The flow records within the Des Moines River Basin indicate one nonstationary change point from six analyzed gages. This same gage (Raccoon River at Van Meter, IA) shows a statistically significant increasing trend in annual maximum flood peaks from 1915-2014, while the other five analyzed gages
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show no statistically significant trends or indeterminate trends. The literature agrees that projected temperatures and precipitation will increase, while there is little consensus on projected streamflow.
According to the Vulnerability Assessment, the Des Moines River basin is more vulnerable to climate change impacts on flood risk management than neighboring watersheds in the District and all watersheds in the continental United States. This indicates that there is more uncertainty regarding flood risk management in the Des Moines River watershed because of future climate change. Available literature and USACE Climate Assessment tools do not reach a consensus on observed and projected streamflow throughout the Des Moines River Basin due to long-term persistent climate trends or anthropogenic climate change. There is some agreement that streamflow variability will increase and extreme events will occur more frequently.
P. CONSTRUCTED RESOURCES-PUBLIC STRUCTURES, UTILITIES, TRANSPORTATION, OTHER
There are many critical structures such as hospitals, schools, fire stations, police stations, pump stations, electrical sub stations, waste water treatment and drinking water facilities in the project area. Within the project area there are two FRM dams (Saylorville and Red Rock), two remedial works dams that are part of the Saylorville project (Big Creek Barrier Dam and Big Creek Diversion Dam), two hydroelectric dams (Red Rock, under construction, and Ottumwa), and two low head dams (Center Street and Scott Street dams in Des Moines). Figure EA-14 shows the ongoing construction of the hydroelectric facilities at Lake Red Rock.
Figure EA-14. Ongoing Construction Adding a Two-unit, 36.4-MW Powerhouse at the Existing Red Rock Dam, 2016 (photo courtesy Missouri River Energy Services)
There are over 65 river crossings including interstate, state, county, and local highways as well as railroad and bicycle trails. There are county roads at Lake Red Rock that are impacted by lake levels
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if the lake rises to elevation 748 and higher (6 feet over normal level.). There are also utility crossings such as overhead transmission lines or underground pipes.
Future Conditions: Infrastructure in and near the river will remain an integral part of the Des Moines River. These structures will require maintenance, upgrades, and replacement. Additional constructed structures would reduce the river’s meander into a stable channel.
Q. RECREATION
Recreation at Saylorville and Red Rock falls within two categories and can be identified as either land or water-based recreation. Management objectives for each type vary depending on the location, safety hazards, and the intensity of use. At each reservoir, the operations project managers use their Master Plan to guide their work necessary to meet the public’s needs for land and/or water-based recreation, while maintaining stewardship to the resource. Land-based recreation activities include camping, picnicking, biking, hiking, disc golf, shore fishing, hunting, bird and wildlife watching, cross country skiing, sledding, snowmobiling, horseback riding, geo-caching, sightseeing, etc. on or adjacent to Corps-managed land.
Facility types typically found within recreation areas within the Des Moines River Valley include campsites, picnic shelters, picnic sites, playgrounds, disc golf courses, equestrian trails, sand volleyball courts, horseshoe pits, ball fields, hunting areas, and hard and soft trails. These recreation areas are managed by several entities, which include the District, the Iowa DNR, the Missouri DNR, the Missouri Department of Conservation, county conservation boards, and city governments. Land- based recreation includes modernizing and rehabilitating existing recreation areas and providing a justified level of service.
Water-based recreation activities occurring within the planning area’s water managed areas include pleasure boating, fishing, waterfowl hunting, sailing, swimming, paddle boarding, kayaking, water skiing and tubing, wind surfing, parasailing, and canoeing (Figure EA-15). The majority of water- based recreation is managed by the District with assistance from the Iowa DNR and Coast Guard Auxiliary. The management objective is to ensure public safety, while providing recreation opportunities on the water. This involves promoting water safety, studying recreation carrying capacity vs. current use patterns, zoning requirements for no-wake or restricted areas, and areas to remain open for public recreation.
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Figure EA-15. Paddler at Lake Red Rock
Future Conditions: The parks, wildlife, historical, and recreation areas would remain an important part of the community. Because these areas are in public ownership, their popularity should increase as other non-public lands become more urbanized.
R. SEDIMENTATION/SOILS/PRIME AND UNIQUE FARMLAND
Reservoir Sedimentation: Reservoir sedimentation is an important issue with regard to meeting authorized purposes and reservoir life. The rate of sedimentation varies based on watershed characteristics. As sediment deposition occurs, reservoir storage capacity for both water conservation and FRM is reduced.
Saylorville Lake: During the planning phase of Lake Red Rock, conservation storage was shifted from Lake Red Rock to Saylorville Lake and increased from 50,000 to 75,000 acre-feet. The primary reason for the shift was the high sedimentation rates anticipated for Lake Red Rock. Before the 1977 sedimentation report was written, the calculated capacity from the survey data for elevation increment 885 feet to 890 feet was approximately 80,000 acre feet and the total capacity for elevation 890 feet and below was 666,000 acre feet. Big Creek Lake reduces the area that contributes sediment to Saylorville Reservoir to only 5,797 square miles.
Based on results from the 2014 re-survey, the amount of deposition between elevations 836 feet and 890 feet (flood control pool) amounted to 13,185 acre feet since operation of the reservoir began in April 1977. This equates to about 335 acre feet of flood control storage loss per year. Storage at elevation 890 feet and below decreased by 39,535 acre feet or approximately 6 percent over the 37 year life of the project. The rate of deposition within the reservoir is 1,066 acre feet per year, which is higher than the predicted rate from 1979 of 800 acre feet per year and lower than the 1998-1999 re- survey’s calculated rate of 1,135 acre feet per year. The amount of sediment deposition below elevation 836 feet (conservation pool level) amounted to 67 percent of the total deposition in the reservoir (elevation 890 feet and below) since April 1977. With a capacity reduction of 31 percent for the elevation increment of 835 feet to 836 feet NGVD, this 1 foot increment has been one of the highest rates of filling since project inception, which is expected due to the amount of time the
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reservoir water surface elevation is within that range. Wave action and erosion along the shoreline followed by deposition in low flow areas with shallow depths, such as, coves and slack water areas, could also help explain the amount of deposition.
Suspended sediment trap efficiency for Saylorville Lake is approximately 85 percent. Over the time of reservoir operation, this rate holds true for most suspended sediment loading except when inflows and suspended sediment values are low. The volume of suspended sediment loading at Saylorville Lake does not always directly correlate to high water events. The 5 highest stages (listed in descending order of magnitude) recorded upstream of the reservoir at the Stratford gage were in June 2010, June 2008, April and July 1993, and March of 2010 according to the National Weather Service. The 5 highest suspended sediment loadings (listed in descending order of magnitude) occurred in June 1984, June 1991, March 1979, June 1984, and April of 1998. Although peak flows don’t associate with peak suspended sediment loadings every time, monitoring results indicate that higher inflows typically lead to higher suspended sediment loading and sediment trap efficiency at Saylorville Lake.
The State of Iowa has a contract with the U.S. Government for water supply storage space in Saylorville Lake. Under the contract, the state has the right to utilize 18.86 percent of the usable storage between elevations 812 feet and 836 feet NGVD (with reduction for 25 years of sediment deposits considered). The 2014 re-survey indicates there is currently 11,940 ac-ft of usable storage available for water supply.
Due to the ongoing effects of sedimentation in the reservoir, the volume of conservation storage available below a given elevation has continually decreased, prompting a potential pool raise to offset these effects and recoup lost storage. However, reliability still meets the 99% requirement per the contract.
Lake Red Rock: As mentioned above, in 1948, conservation storage was shifted from Lake Red Rock to Saylorville Lake and increased from 50,000 to 75,000 acre-feet. The primary reason for the shift was the high sedimentation rates anticipated for Lake Red Rock with a large permanent pool. Although it was acknowledged that substantial sedimentation would occur at Lake Red Rock, specific sedimentation reserve was not provided. It was recognized that sedimentation would fill in the conservation pool over time.
In 1961, a conservation pool design elevation of 725 feet was established, which would provide approximately 90,000 acre-feet for conservation and sediment storage and would enable operation of the two reservoirs to achieve the desired low flows at City of Des Moines and Ottumwa Iowa.
The shift from elevation 725 feet to elevation 728 feet was initiated in 1979 to regain the 90,000 acre- feet of conservation storage. This raise was prompted by the drought of 1977 and the loss of adequate storage for low-flow releases due to sedimentation. Following the 1979 pool raise, the District began investigations to further refine sedimentation rate estimates and to develop a plan for dealing with the sediment accumulation. As a result of ongoing reservoir sedimentation and public request, the conservation pool was raised to elevation 734 feet on October 28, 1988. That raise was made with the understanding that a future raise to 742 feet would be necessary. Following the pool raise to 734, an analysis was conducted to determine the effect of a 742 conservation pool. Upon completion of an Environmental Impact Statement and at the urging of the Governor of the State of Iowa, a decision was made to raise the pool to elevation 742 feet. The pool raise was completed in February 1992.
From results of the 2011 re-survey, the amount of deposition below elevation 780 (flood control pool elevation) amounted to 181,300 acre feet since operation of the reservoir began in March of 1969.
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This equates to about 4,250 acre feet of storage loss per year. Based on the 2011 re-survey, the amount of sediment deposition below the historic conservation pool elevation of 725 amounted to 60 percent of the total deposition in the reservoir since commencing operation. With the latest Red Rock Reservoir Regulation Schedule change in 1992, the conservation pool elevation was raised to 742, thus the flood pool now consists of capacity between elevations 742 and 780. Comparing the current conservation pool capacity to the estimated 1969 capacity, the conservation pool has lost 147,850 acre feet or 44 percent. At the new regulated elevations, the 2011 re-survey shows Red Rock Reservoir flood pool capacity at 1,463,250 ac ft. The flood pool capacity between 1969 and 2011 has decreased by 34,120 ac feet or 2.3 percent.
The elevation increment 720 to 725 had a higher rate of sediment deposition than the adjacent elevation increments. The sedimentation rate in this increment could be due to its proximity to the historical conservation pool elevation of 725, as the conservation pool is the most frequent elevation. During the 10 years of operation at this elevation, wave action and erosion likely occurred along the shoreline and deposition followed in low flow areas with shallow depths, particularly areas at the elevation near the conservation pool elevation, such as, coves, slack water areas adjacent to bridge embankments, and the regions near shorelines. At boat ramps, the primary difficulties arising are due to ongoing sediment deposition.
Sediment range cross sections illustrate the sedimentation rate in the channel thalweg has been extremely high and much higher than in the other portions of the reservoir. In many cases, the thalweg have been completely filled. For any cross section, the location in the pool, proximity to tributaries, and hydraulic properties such as, cross-sectional area and slope all may be interrelated and affect sedimentation patterns in the reservoir.
Due to the ongoing effects of sedimentation in the reservoir, the volume of conservation storage available below a given elevation has continually decreased, prompting a series of pool raises to offset these effects and recoup lost storage. Since Saylorville storage became available to augment Des Moines River flows and the pool levels at Lake Red Rock have been raised, the Lake Red Rock pool has not decreased below the established conservation elevation. Thus, it is not known how low the pool can drop before the accumulated sediment renders various facilities inoperable.
Soils & Prime and Unique Farmland: There are three major soil associations within the Saylorville Lake (Polk County) vicinity – the Clarion-Nicollet-Webster Association; the Hayden-Lester Association; and the Waukegan-Dickinson-Dorchester Association.
Lake Red Rock is located in the Southern Iowa Driftplain landform. The topography of the area is steeply rolling hills interspersed with areas of uniformly level upland divides and level alluvial lowlands. This terrain was developed in Pre-Illinoisan glacial drift with a well-developed Yarmouth- Sangamon paleosol and topped with moderately thick Peoria Loess.
Primary soil associations at Lake Red Rock (Marion County) include Ladoga-Clinton-Otley [LCO (16 percent)], Ladoga-Sharpsburg-Clinton [LSC (29 percent)], and the Gosport-Pershing-Gara association [GPG (27 percent)]. Together these three associations comprise roughly 72 percent of all soil associations in the county. All were formed on convex ridge tops and moderate to steep side slopes and developed under native prairie or mixture of native prairie and trees. The surface layer is typically dark brown or grayish brown silty clay loams or silt loams of 6-20 inches in depth.
Soil mapping is available showing the various soil types, parent material, slope, drainage and fertility characteristics. This information is used to determine resource protection needs, historic biotic
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occurrence, stability, fertility and drainage characteristics for various uses. The Gridded Soil Survey Geographic (gSSURGO) Database was developed by the National Cooperative Soil Survey (NCSS), Natural Resources Conservation Service (NRCS), U.S. Department of Agriculture (Soil Science Division Staff, 2017). Appendix B includes planning area maps of farmland soils. Figure EA-16 and Table EA-16 summarize the planning area’s soil information.
Figure EA-16. Soil Farm Class from Fraser, Iowa, to the Mississippi River
Table EA-16. Soil Farm Class from Fraser, Iowa, to Lake Red Rock Dam
Soil Farm Class Area (ha) Farmland of Statewide Importance 4,195.54 All Areas Are Prime Farmland 12,799.05 Prime Farmland if Drained 6,828.38 Prime Farmland if Protected From Flooding or Not Frequently Flooded During the Growing Season 364.54 Not Prime Farmland 16,465.46
Future Conditions: The geologic character of the study area should remain relatively unchanged. However, soils should continue moving throughout the system and silting-in the reservoirs. The topography of the study area would change with accretion and erosion activities throughout the riverine system in the study area.
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S. HAZARDOUS, TOXIC, AND RADIOACTIVE WASTE (HTRW)
Per Corps Engineering Regulation 1165-2-132, Hazardous Toxic and Radioactive Waste HTRW Guidance for Civil Works Projects, HTRW includes any material listed as a “hazardous substance” under the Comprehensive Environmental Response, Compensation and Liability Act, 42 U.S.C. 9601 et seq (CERCLA). [See 42 U.S.C. 9601(14].) Hazardous substances regulated under CERCLA include "hazardous wastes" under Sec. 3001 of the Resource Conservation and Recovery Act, 42 U.S.C. 6921 et seq; "hazardous substances" identified under Section 311 of the Clean Air Act, 33 U.S.C. 1321, "toxic pollutants" designated under Section 307 of the CWA, 33 U.S.C. 1317, "hazardous air pollutants" designated under Section 112 of the Clean Air Act, 42 U.S.C. 7412; and "imminently hazardous chemical substances or mixtures" on which EPA has taken action under Section 7 of the Toxic Substance Control Act, 15 U.S.C. 2606; these do not include petroleum or natural gas unless already included in the above categories.
There are numerous structures and properties within the District boundaries that have the potential to contain HTRW.
The EPA’s Envirofacts Web site lists 162 EPA-regulated facilities within close proximity to the planning area (EPA, 2018). Given the level of ongoing development in the region surrounding Saylorville Lake, it is difficult to accurately identify all of the potential hazardous materials that may exist within or adjacent to the project boundary. Federal law requires site-specific due diligence on a case-by-case basis before development can take place.
Previous studies with integrated environmental assessments have been conducted in both the Saylorville Lake and Lake Red Rock Areas. Since this study will not involve the acquisition of real estate outside of that already under the control of USACE nor the construction of new engineering measures, it is deemed unnecessary to conduct an HTRW assessment at this time. Should conditions change, the District would conduct a HTRW assessment, as needed.
Future Conditions: There is no anticipated change to HTRW risks.
CHAPTER III: FORMULATION OF ALTERNATIVES
A. ALTERNATIVE FORMULATION STRATEGIES FINAL ARRAY OF ALTERNATIVES
Based on the study goals, objectives and planning constraints, an initial array of alternatives was developed. Six major alternatives were formulated for consideration with an additional six alternatives that are minor variations of Alternatives 3 and 5. This initial set of alternatives focused on FRM and low flow augmentation as these are the primary authorizations for the project. Details of each alternative are presented in Section B, Alternatives Considered But Not Carried Forward for Detailed Analysis, below.
There are a few regulation rules for each reservoir that are common to all of the alternatives (including the no action alternative) but which are omitted or ambiguous in the current regulation manual.
For Saylorville Lake these are: • Maximum allowable changes in release rates refer to outflow reductions rather than increases in outflows unless specifically noted. Limiting the magnitude of reductions in outflow are important as rapid reductions in water levels can lead to downstream bank erosion. However,
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unexpected large magnitude increases in outflow can also create problems by limiting response time for closing roads, etc. • Once the reservoir has peaked and storage is being evacuated, the maximum daily reduction in outflow should be maintained so as not to exceed a recession rate in the pool of more than 1.0 foot per day in order to limit erosion around the rim of the reservoir. • As the reservoir recedes following a large magnitude flood, the maximum release rate is to be maintained until elevation 875 is reached and then gradually reduced to follow the normal flood control operation schedule.
For Lake Red Rock these are: • Once the reservoir has peaked and storage is being evacuated, the maximum daily reduction in outflow should be maintained so as not to exceed a recession rate in the pool of more 1.0 foot per day in order to limit erosion around the rim of the reservoir. • The maximum reduction in release per gate change is limited to 5,000 cfs in order limit downstream bank erosion. • During periods of Mississippi River flooding the reservoir release is set to reduce flooding to the extent possible (variable minimum release based on reservoir elevation) during the 7 days corresponding to peak flow along the Mississippi River with due allowance for travel time. • After the reservoir has peaked and begins to recede, maintain the maximum release reached during the event, gradually reducing the outflow to maintain a rate of fall not to exceed the max reduction in pool level (1.0 ft/day) and outflow (5,000 cfs/ gate change) as specified in the normal flood control operation schedule of the water control plan.
B. ALTERNATIVES CONSIDERED BUT NOT CARRIED FORWARD FOR DETAILED ANALYSIS
Alternative 2: This alternative represents the regulation strategy utilized during the 2016, 2017, and 2018 growing seasons (conducted as planned deviations to the existing water control plans).
This alternative would implement on a permanent basis the deviations to the currently authorized water control plans utilized in the 2016, 2017 and 2018 growing seasons. It is essentially the baseline plan plus the currently approved deviations. These modifications were conceived following completion of an initial assessment to investigate changes to the current water control plan that would conserve reservoir storage through earlier releases of water during a flood event to reduce flood risk during long duration, large magnitude flood events resulting from multiple storms. These modifications are: • Operating Saylorville Lake to control for a stage of 26.5 feet at the S.E. 6th Street Gage in Des Moines which is an increase of 2.5 feet above the current authorized control stage of 24 feet. Discussions with City of Des Moines, county Emergency Management officials and public works staffs, there was consensus that only very minor impacts occur at a stage of 26.5 feet as many local infrastructure improvements have reduced the impact of water levels less than 26.5 feet. The higher control stage reduces the frequency of having to reduce releases, thereby conserving reservoir storage. • Increasing the maximum growing season release at Saylorville Lake from 12,000 cfs to 16,000 cfs thus matching the non-growing season release and the growing season release when Lake
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Red Rock is below elevation 758 feet. Following discussions with City of Des Moines and county Emergency Management officials and public works staff, there was consensus that downstream impacts are minimal below a discharge of 16,000 cfs and that it is more important to preserve flood storage to reduce the possibility of future higher releases. • Eliminate the balancing of flood storage between Saylorville Lake and Lake Red Rock when Saylorville Lake is below elevation 860 feet. While storage balancing has the potential to reduce the frequency of flooding of easement land at Lake Red Rock, by holding water back in Saylorville Lake, this strategy has the is potential to increase the duration of high releases. Elimination of storage balancing allows flood waters to be moved through the system quicker resulting in an earlier return to normal flows. • Add a 21.0 foot constraint at the 2nd Avenue gage in the City of Des Moines representing when impacts begin above the confluence with the Raccoon River. • Increase the maximum growing season release from 18,000 cfs to 22,000 cfs at Lake Red Rock to offset increased releases from Saylorville Lake. Release rates of 18,000 and 22,000 are both within bank flows. Previous water control strategies constrained to 18,000to prevent drainage issues on marginal agricultural land adjacent to the river bank, this strategy will enhance the a maximum release rate of 22,000 cfs to provide a faster transitioning to lower flows much sooner. Alternatives 2 reduced the reliability of meeting minimum conservation releases at Saylorville by reducing the number of years Saylorville Lake fell below elevation 827, from 5 years to only 2 years by allowing a proactive increase in Saylorville’s conservation pool to 838 during declared droughts between July 1 and March 1.Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
Alternative 3: Reduce the frequency and magnitude of reservoir balancing while concurrently allowing for earlier increases in outflow from Lake Red Rock to preserve flood storage.
For Saylorville Lake, Alternative 3 includes many of the changes incorporated within Alternative 2, but reduces, rather than eliminates, the frequency and magnitude of storage balancing. Additionally, Alternative 3 allows for a faster rate of opening at Saylorville Lake to better respond to a rapidly rising inflow hydrograph (the maximum rate of daily flow reductions remains unchanged). To allow for additional conservation storage during years in which there is a declared drought (to improve the reliability in meeting downstream conservation flows) this alternative also incorporates a drought contingency pool at Saylorville Lake beginning July 1.
For Lake Red Rock, Alternative 3 allows for earlier increases in outflow to preserve flood storage, while not increasing growing season releases during years when the reservoir remains below elevation 750. In addition, this alternative allows for a higher fall pool raise that can be held through the winter (current plan allows for holding until December 15).
A summary of the modifications for each of the respective reservoirs are:
Saylorville Lake • Allowing for a 16,000 cfs year-round maximum discharge with no correlation to Lake ed Rock Pool elevation levels. As noted in Alternative 2, downstream impacts are minimal for releases below 16,000 cfs and that it is more important to conserve reservoir storage to reduce the possibility of future higher releases
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• Reducing the range of balancing operations to when Lake Red Rock is above elevation 750 feet and Saylorville Lake is below elevation 860 feet. Limit the degree of balancing to setting the maximum outflow from Saylorville Lake as the lesser of inflow or 16,000 cfs when Lake Red Rock is between elevations 750 feet and 760 feet or 2,000 cfs when Lake Red Rock is above elevation 760 feet. • Modifying the daily maximum flow change per day of 3,000 cfs to a maximum change of 3,000 per gate setting (maximum 6,000 cfs per day) for flow increases with no changes for decreasing flows. • Establish a drought contingency conservation pool of elevation 838 feet during declared drought periods from July 1 until March 1 to improve the reliability of meeting downstream flow targets. • Modified SE 6th constraint maximum allowable level of 26.5 feet • Addition of a 2nd Avenue constraint maximum allowable level of 21.0 feet
Lake Red Rock • Modified maximum growing season releases: o Below elevation 750 feet constitutes a release rate of 18,000 cfs. o Lake levels between elevations 750 feet and 770 feet allow for a release rate of 22,000 cfs offset the effects of increased releases from Saylorville Lake. o Lake levels above elevation 770 feet permit a release rate of 30,000 cfs thus initiating an earlier start elevation for large magnitude flood operations. • Increasing the maximum fall pool raise to 746 feet and allow for holding until March 1. Alternative 3C, which allowed for a 30,000 cfs year around release at Red Rock, significantly reduced the frequency and duration of flooding of easement lands. However, since limited balancing was included in this alternative there were three spillway overtopping events at Saylorville versus two events when balancing was eliminated entirely. In addition, an allowable release of 30,000 cfs would be very difficult to maintain without the potential for frequently impacting downstream agricultural lands and secondary roads, since impacts begin to occur above 30,000 cfs. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
Alternative 3.A: Sustain all of the modifications implemented in Alternative 3, with the only modification being a transition period between growing season and non-growing season maximum releases when Lake Red Rock is above elevation 750 feet on May 1.
As stated, this alternative would carry with it the measures stated above in Alternative 3 with the addition of a transitional period between the two designated seasonal periods. It would be accomplished as such: o If Lake Red Rock is above elevation 750 feet on May 1 maintain the release rate at a maximum of 30,000 cfs, then allow to recede below elevation 750 feet at the maximum rate of Red Rock inflow or 18,000 cfs. This would allow the reservoir to complete operations for the flood event occurring on May 1 before transitioning to lower releases.
While slightly better than the current water control plan with only four associated overtopping events, Alternatives 3A, 3Ai, 3B, 5 and 5B were not as effective as Alternatives 2, 5A and 6 which reduced the number of overtopping events to 2. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
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Alternative 3.A.I: Sustain the measures implemented in Alternatives 3 and 3.A. above, with the only modification being to Lake Red Rock Major Flood Operations.
As stated this alternative would simply encompass the measures discussed above in Alternatives 3 and 3.A. Additionally, it modifies the major flood operations at Lake Red Rock to allow for an earlier increase in releases, allowing more water to be evacuated from the reservoir at lower reservoir elevations. As such it would not directly modify any measures related to operations at Saylorville Lake. This alternative establishes a Lake Red Rock maximum release rate above elevation 770 feet to reduce the frequency of flows exceeding 60,000 cfs. Releases in excess of 60,000 cfs produce water levels downstream of Lake Red Rock that result in flooding within small, unprotected towns (Bellefontaine, Keosauqua, Bentonsport, Bonaparte, and Farmington as well as basement flooding in Ottumwa). It also creates an impediment to highway access to Eddyville and can create sewer backup issues and additional negative impacts to a trailer court near Ottumwa.
• At elevation 770 feet the release rate would be 30,000 cfs. • At elevation 775 feet the release rate would be 50,000 cfs. At elevation 780 feet the release rate would be 60,000 cfs.
While slightly better than the current water control plan with only four associated overtopping events, Alternatives 3A, 3Ai, 3B, 5 and 5B were not as effective as Alternatives 2, 5A and 6 which reduced the number of overtopping events to 2. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
Alternative 3.B: Sustain the measures implemented in Alternative 3 above, with the only modification being to increase the maximum Red Rock growing season release to 25,000 cfs when Lake Red Rock is between elevation 750 and 770 feet (below elevation 750 feet, release rate remains 18,000 cfs).
While slightly better than the current water control plan with only four associated overtopping events, Alternatives 3A, 3Ai, 3B, 5 and 5B were not as effective as Alternatives 2, 5A and 6 which reduced the number of overtopping events to 2. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
Alternative 3.C: Sustain the measures implemented in Alternative 3 above, with the only modification being the implementation of a 30,000 cfs year round maximum release rate at Lake Red Rock matching the non-growing season release.
Lake Red Rock • Modified maximum growing season releases: o Below pool elevation 775 feet would warrant a maximum release rate of 30,000 cfs. • Increase the maximum fall pool raise to elevation 746 feet and allow for holding until March 1.
Alternative 4: Modification of only the Lake Red Rock Water Control Plan to facilitate maximization of hydropower operations at Lake Red Rock by the Missouri River Energy Service Corporation.
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This alternative is a stakeholder preferred alternative which was derived from input given by the hydropower development company at Lake Red Rock in regards to their water level and flow needs. This alternative seeks to increase power generation opportunities by reducing maximum releases when Lake Red Rock is below elevation 765 feet in order to pass as much of the dam releases through the hydroturbines as possible. As such this alternative does not include modification of Saylorville Lake’s water control plan. This alternative would be accomplished by implementing the following at Lake Red Rock:
Conservation Pool: • April 1 – October 31 o Pool level is maintained between 744 feet to 746 feet. o A maximum release rate of 10,000 cfs when the pool level falls below an elevation of 746 feet. o The maximum release rate below elevation 744 feet is the reservoir inflow. • November 1 – March 31 o Pool is maintained between elevation 742 feet and 744 feet. o Maximum release rates are same as April 1 to October 31 period
Normal Flood Control Operations: • When the reservoir is between elevation746 feet and 765 feet, the release rate is limited to 110 percent of the inflow rate. • From May 1 to December 15 if the pool level is below elevation 765 feet, the maximum outflow will be 18,000 cfs. • If the 10-day forecast indicates significant precipitation would raise the lake level above elevation 765 feet increase the release as necessary to accommodate anticipated runoff.
Alternative 4, resulted in negative impacts on all FRM metrics and resulted 6 overtopping events along with increasing both the frequency and duration of flooding of easement land at Red Rock. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
Alternative 5: Utilization of the reservoir elevations on May 1as a trigger for following either a “wet” or “dry” schedule of maximum releases during the growing season.
Alternative 5 incorporates the concept of a decision point, on 1 May, that would determine whether a “wet” or “dry” release schedule were to be followed that year. The alternative utilizes the lake elevations on May 1 to make the determination. If Saylorville Lake is above elevation 855 feet, or Lake Red Rock is above elevation 750 feet, the “wet” schedule would be followed; if neither is exceeded, the “dry” schedule would be followed. Under the current water control plan, the start of the growing season at Saylorville Lake is 21 April. For Alternative 5, the start of the growing season would be changed to May 1 to align with Lake Red Rock and the proposed decision point.
For Saylorville Lake, under either the “wet” or “dry” schedule, Alternative 5 incorporates the changes from Alternative 3 to the SE 6th gage constraint, the new 2nd Avenue constraint, the increase in maximum daily rate of flow change during a rising river, the contingent drought conservation pool, and the modified balancing operations. The “wet” or “dry” schedule would determine the maximum growing season release from Saylorville Lake—16,000 cfs during a “wet” year, and 12,000 cfs or 16,000 cfs during a “dry” year depending upon Lake Red Rock’s elevation.
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For Lake Red Rock, under the “dry” schedule the existing (Alternative 1) water control plan would be followed. During a “wet” year Lake Red Rock would follow a more aggressive release schedule that is a combination of the changes for Lake Red Rock found in Alternatives 3A and 3B.
Alternative 5 implements the following measures relative to each respective reservoir:
Saylorville Lake • Changes the start of the growing season to May 1to match Lake Red Rock’s schedule to allow for a consistent decision point. • Operating Saylorville Lake to control for a stage of 26.5 feet at the S.E. 6th Street Gage in Des Moines which is an increase of 2.5 feet above the current authorized control stage of 24 feet. • Addition of a 21 foot maximum stage constraint for 2nd Avenue which represents when impacts begin above the confluence of the Des Moines and Raccoon Rivers. • Modified daily maximum flow change per day of 3,000 cfs to a maximum change per gate setting for increasing flows (maximum 6,000 cfs per day) with no change for falling flows. • Establish a drought contingency conservation pool of elevation 838 feet during declared drought periods from July 1until March 1. • Reduce range of balancing operations to situations in which Lake Red Rock is above elevation 750 feet and Saylorville Lake is below elevation 760 feet. Limit the degree of balancing to setting maximum outflow from Saylorville as the lesser of inflow or 16,000 cfs when Lake Red Rock is between elevation 750 feet and 760 feet or 2,000 cfs when Lake Red Rock is above elevation 760 feet. • If Saylorville Lake is above elevation 855 feet on May 1(wet year) , which has occurred 26% of the time between the years 1977-2015, then: o Establish a growing season maximum release rate of 16,000 cfs. o Initiate earlier opening of the conduit, with the outflow rate controlled only by downstream constraints and the conduit capacity (release of 16,000 cfs cannot be achieved until the lake level is approximately elevation 850 feet. • If Saylorville Lake pool level is below elevation 855 feet on May 1 (dry year) then: o Establish a growing season maximum release rate of 12,000/16,000 cfs depending upon the Lake Red Rock pool elevation level. (Consistent with No Action Alternative.) Lake Red Rock • If Lake Red Rock is above elevation 750 feet on May 1(wet year) , which has occurred 30% of the time between 1969 and 2015, then: o Maintain release at a maximum rate of 30,000 cfs then allow to recede below elevation 750 feet and release a maximum of Red Rock inflow or 18,000 cfs. o Once the lake elevation recedes below elevation 750 feet: o For reservoir levels below elevation 750 feet release up to 18,000 cfs. o For reservoir levels between elevation 750 feet and 770 feet release up to 22,000 cfs. o For reservoir levels above elevation 770 feet release up to 30,000 cfs thus facilitating an earlier start elevation for large magnitude flood operations. • If the Lake Red Rock level is below elevation 750 feet on May 1utilize the current maximum growing season limits (No Action Alternative).
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• Increase the maximum fall pool raise to elevation 746 feet and allow for holding until March 1.
While slightly better than the current water control plan with only four associated overtopping events, Alternatives 3A, 3Ai, 3B, 5 and 5B were not as effective as Alternatives 2, 5A and 6 which reduced the number of overtopping events to 2. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
Alternative 5.B: Sustains all of the measures implemented by Alternative 5a, with the only modification being to Lake Red Rock Major Flood Operations.
Establish a Lake Red Rock maximum release above elevation 770 feet to reduce the frequency of releases above 60,000 cfs. Releases in excess of 60,000 cfs produce water levels downstream of Lake Red Rock that result in flooding within small, unprotected towns (Bellefontaine, Keosauqua, Bentonsport, Bonaparte, and Farmington as well as basement flooding in Ottumwa). It also creates an impediment to highway access to Eddyville and can create sewer backup issues and additional negative impacts to a trailer court near Ottumwa. • At elevation 770 feet the release rate would be 30,000 cfs. • At elevation 775 feet the release rate would be 50,000 cfs. • At elevation 780 feet the release rate would be 60,000 cfs.
While slightly better than the current water control plan with only four associated overtopping events, Alternatives 3A, 3Ai, 3B, 5 and 5B were not as effective as Alternatives 2, 5A and 6 which reduced the number of overtopping events to 2. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
C. ALTERNATIVES CARRIED FORWARD FOR DETAILED ANALYSIS
Alternative 1- No Action- Maintains the current plan and facilitates no changes towards the current Des Moines River Basin Master Reservoir Regulation Manual for Saylorville Lake or Lake Red Rock.
Under this baseline alternative the reservoirs would continue to be operated under the current water control plans.
For Saylorville Lake this would mean: • Maintain the normal conservation pool level of 836.0 feet. • Normal flood control operations, which occur between elevations 836 feet and 860 feet, would allow for a maximum release of 12,000 to 16,000 cfs during the growing season and 16,000 cfs during the non-growing season. This range of operations also allows for balancing of storage with Lake Red Rock when Saylorville is below elevation 860 feet. During periods of runoff downstream, releases are reduced to maintain the stage at SE 6th street in the City ofDes Moines below 24 feet. • Large magnitude flood operations would begin at elevation 875 feet with 62 percent of flood storage capacity being utilized and full flood control pool being reached at elevation 890 feet.
EA-65 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
• Above elevation 890 feet the conduit is fully opened and the spillway is utilized.
For Lake Red Rock this would mean: • Maintain the normal conservation pool level at 742.0 feet. • Normal flood control operations, which are conducted between elevations 742 feet and 760 feet, would allow for a maximum release of 18,000 cfs if the pool level is below elevation 760 feet or 22,000 cfs if the pool level is above elevation 760 feet during the growing season and 30,000 cfs during the non-growing season. Control stages at Ottumwa and Keosauqua, Iowa are maintained to reduce downstream flooding based on season and lake levels. • Any date the Mississippi River is forecast to exceed a stage of 20 feet at Quincy, Illinois, the maximum allowable outflow is released (variable minimum release based on reservoir elevation) considering all constraints to reduce flooding during the peak 7-days of the Mississippi River crest. • Large magnitude flood operations begin at elevation 775 feet with 79 percent of flood storage capacity being utilized and full flood control pool being engaged reached at elevation 780 feet. Releases are subsequently released increased in an incremental incrementally nature following the large magnitude flood operation schedule mandated. • Above elevation 785 feet the spillway gates are opened as necessary to maintain the pool utilizing an uncontrolled spillway release
Alternative 5.A: Sustain the measures implemented in Alternative 5 (alternative considered but not carried forward), with the only modification being the removal of reservoir balancing during declared “wet years”.
• Summary of modifications to the existing Saylorville Lake Regulation Plan o Implements the changes listed in Alternative 5, except o If Saylorville Lake is above elevation 855 feet on May 1 (“wet” year), eliminate reservoir balancing and establish a growing season release rate of 16,000 cfs. If the reservoir elevation is below 855 feet on May 1(“dry” year), maintain reservoir balancing and the same release schedule as the No Action Alternative • Summary of modifications to the existing Lake Red Rock Regulation Plan o Implements the changes listed in Alternative 5
Alternatives 5A reduced the number of overtopping events to 2. This was in large part due to the elimination of the storage balancing rule in these three alternatives. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
Alternative 6: Minor modification of Alternative 2 as applicable to Saylorville and Alternative 3B as applicable to Lake Red Rock.
This alternative is a hybrid of Alternative 2 in regards to Saylorville operations and Alternative 3Ai and 3B in regards to operations at Lake Red Rock. This alternative provides for higher, earlier releases from Saylorville and Red Rock Dams to preserve flood storage and thereby reduce the likelihood of higher reservoir releases during moderate to major flood years.
For Saylorville:
EA-66 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
• Operating to control releases from Saylorville Lake for a maximum stage of 26.5 feet at the Southeast 6th Street Gage in the City of Des Moines, which is an increase of 2.5 feet above the current authorized control stage of 24 feet • The addition of a 21.0 feet stage constraint at the 2nd Avenue Gage in the City of Des Moines, which represents when impacts begin above the confluence of the Des Moines and Raccoon Rivers • Increasing the maximum growing season release from 12,000 cfs to 16,000 cfs, matching the non-growing season constraint and the constraint during the growing season when Lake Red Rock is below elevation 758 feet • Elimination of balancing of flood storage between Saylorville Lake and Lake Red Rock when the elevation within Saylorville Lake is below 860 feet • Modifying the maximum release change per day to 3,000 cfs per gate setting (for a maximum of 6,000 cfs per day), with no changes to receding flows • Creation of a drought contingency conservation pool at elevation 838 feet during declared drought periods from July 1 – March 1.
For Red Rock:
This alternative increases the maximum releases allowed during the growing season for lake levels between elevations 750 and 770. It allows for a Lake Red Rock maximum release rate above elevation 770 feet to reduce the frequency of flows exceeding 60,000 cfs. Releases in excess of 60,000 cfs produce water levels downstream of Lake Red Rock that result in flooding within small, unprotected towns (Bellefontaine, Keosauqua, Bentonsport, Bonaparte, and Farmington as well as basement flooding in Ottumwa). It also creates an impediment to highway access to Eddyville and can create sewer backup issues and additional negative impacts to a trailer court near Ottumwa.
• 22,000 cfs maximum release when pool level is below elevation 750 • 25,000 cfs maximum release when pool level is between elevation 750 and 770 • Earlier 30,000 cfs release for the growing season when the pool level reaches elevation 770. Alternatives 5A reduced the number of overtopping events to 2. This was in large part due to the elimination of the storage balancing rule in these three alternatives. Additional rationale for dismissal of this alternative can be found in Chapter IV: Evaluation of Alternative Plans.
CHAPTER IV: EVALUATION OF ALTERNATIVE PLANS
A. INTRODUCTION
Potential alternatives were evaluated on the basis of whether the alternatives enhanced, maintained or reduced the ability to meet project goals and objectives. Screening criteria included FRM (primary project authorization), water supply dependability (Saylorville Lake) and low flow augmentation, fish and wildlife, recreation and other stakeholder interests such as hydropower and navigation. The screening of alternatives compared performance across metrics based on acceptability, efficiency, effectiveness and completeness. Following the completion of the qualitative screening process, the alternatives were analyzed quantitatively using the reservoir simulation model HEC-RESSIM to further evaluate each alternatives effectiveness, primarily focusing on FRM and to a lesser extent water conservation and hydropower production (non-authorized purpose).
EA-67 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
The District modified an existing RESSIM model of the Des Moines River Basin using project and tributary flow data spanning the years from 1917 through 2016 as primary inputs to the model. Model results are provided as daily flows and reservoir elevations throughout the system. Each alternative plan was modeled and results were evaluated and compared based on estimating frequency and duration of a series of metrics related to key flows and reservoir levels.
B. STEP 1: HYDRAULIC EVALUATION
Results from the RESSIM model are presented in Tables EA-17 and EA-18 which provide a comparison of reservoir simulation results for each alternative plan, organized by river reach and associated concerns and metrics. Results related to each metric are presented in terms of exceedance probability, duration or other pertinent measures as shown in the tables. The highlighted results shown in green in the table under each alternative indicate that the frequency, duration or other pertinent measure improved for that alternative when compared to Alternative 1 (no action alternative). Similarly, highlighted results shown in red in the table under each alternative indicate that the frequency, duration or other pertinent measure were worse for that alternative when compared to Alternative 1 (no action alternative). Non- highlighted results in the tables indicated that in implementing that alternative, conditions remained the same as in the no action alternative.
EA-68 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Table EA-17. Comparison of No Action to Alternatives 2 - 3C No Action River Reach Concern Metric (Alt 1) Alt 2 Alt 3 Alt 3A Alt 3Ai Alt 3B Alt 3C Exceedance of 26.5 Foot Stage at Probability of Exceeding 37k cfs at 0.19 0.14 0.19 0.21 0.21 0.21 0.2 SE 6th Street in Des Moines SE 6th Street, Des Moines Large Magnitude Flood Releases Probability of Exceeding 16k cfs Des Moines 0.09 0.08 0.08 0.09 0.09 0.08 0.08 River from Saylorville Release from Saylorville Below Probability of Exceeding 21k cfs Spillway Release from Saylorville 0.05 0.02 0.04 0.04 0.04 0.04 0.03 Saylorville Dam Release from Saylorville Number of Spillway Events at Spillway Release from Saylorville 5 2 4 4 4 4 3 Saylorville Lake Start of Flooding of Secondary Probability of Exceeding 30k cfs Roads and Significant Ag Areas 0.08 0.07 0.05 0.05 0.06 0.05 0.04 Release from Red Rock Below Red Rock Dam Des Moines Impacts Begin in Small, River Below Red Probability of Exceeding 60k cfs Unprotected Towns Below Red 0.02 0.02 0.02 0.02 0.02 0.02 0.02 Rock Dam Release from Red Rock Rock Dam Flood Waters Approaching Top of Probability of 100k cfs or Greater 0.02 0.02 0.02 0.02 0.01 0.02 0.02 Eddyville and Ottumwa Levees Release from Red Rock Flooding of Flowage Easement Probability of Exceeding Red Rock 0.3 0.29 0.31 0.31 0.31 0.27 0.22 Lands Within Red Rock Lake Level of 760 feet Duration of Flooding of Flowage Duration of Exceeding Red Rock Lake Red Rock 4.30% 4.40% 4.00% 3.50% 3.40% 3.30% 2.30% Easement Lands Within Red Rock Lake Level of 760 feet Pool Duration of Flooding of Flowage Duration of Exceeding Red Rock Easement Lands Within Red Rock - Lake Level of 760 feet Between May 9.00% 9.10% 8.10% 7.00% 6.70% 6.60% 4.40% Growing Season 1 and September 30 UMR Below Average Flow Reduction at Peak for Reduction of Mississippi River Confluence with Events Exceeding Quincy Constraint 21,000 21,000 21,000 21,000 21,000 21,000 21,000 Flooding Des Moines (cfs)
Low Flow Augmentation/Conservation Reliability in Meeting Minimum Number of Years Saylorville Lake Des Moines Conservation Releases From Fell Below Elev 827 resulting in 5 5 2 2 2 2 2 River Saylorville Lake reduced conservation releases
EA-69 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Table EA-18. Comparison of No Action with Alternatives 4 - 6 No Action River Reach Concern Metric (Alt 1) Alt 4 Alt 5 Alt 5A Alt5B Alt 6 Exceedance of 26.5 Foot Stage Probability of Exceeding 37k cfs at SE 0.19 0.16 0.21 0.16 0.21 0.14 at SE 6th Street in Des Moines 6th Street, Des Moines Large Magnitude Flood Probability of Exceeding 16k cfs 0.09 0.13 0.08 0.08 0.08 0.08 Des Moines River Releases from Saylorville Release from Saylorville Below Saylorville Spillway Release from Probability of Exceeding 21k cfs Dam 0.05 0.06 0.04 0.02 0.04 0.02 Saylorville Release from Saylorville Spillway Release from Number of Spillway Events at 5 6 4 2 4 2 Saylorville Saylorville Lake Start of Flooding of Secondary Probability of Exceeding 30k cfs Roads and Significant Ag Areas 0.08 0.08 0.05 0.05 0.07 0.04 Release from Red Rock Below Red Rock Dam Des Moines River Impacts Begin in Small, Probability of Exceeding 60k cfs Below Red Rock Unprotected Towns Below Red 0.02 0.02 0.02 0.02 0.02 0.02 Release from Red Rock Dam Rock Dam Flood Waters Approaching Top Probability of 100k cfs or Greater of Eddyville and Ottumwa 0.02 0.02 0.02 0.01 0.01 0.01 Release from Red Rock Levees Flooding of Flowage Easement Probability of Exceeding Red Rock 0.3 0.35 0.32 0.3 0.32 0.26 Lands Within Red Rock Lake Level of 760 feet Duration of Flooding of Duration of Exceeding Red Rock Lake Flowage Easement Lands 4.30% 8.30% 3.70% 3.80% 3.50% 3.70% Level of 760 feet Lake Red Rock Pool Within Red Rock Duration of Flooding of Duration of Exceeding Red Rock Lake Flowage Easement Lands Level of 760 feet Between May 1 and 9.00% 16.50% 7.40% 7.60% 7.00% 7.40% Within Red Rock - Growing September 30 Season Average Flow Reduction at Peak for UMR Below Reduction of Mississippi River Events Exceeding Quincy Constraint 21,000 21,000 21,000 21,000 21,000 22,000 Confluence with Des Flooding Moines River (cfs) Low Flow Augmentation/Conservation Reliability in Meeting Minimum Number of Years Saylorville Lake Fell Des Moines River Conservation Releases From Below Elev 827 resulting in reduced 5 5 2 2 2 2 Saylorville Lake conservation releases
EA-70 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
In order to eliminate alternatives less effective at meeting project objectives, metrics were ranked based on the importance of the metric with regard to reducing flood risk and the operational feasibility and effectiveness. Reducing the number of spillway events at Saylorville Lake (releases in excess of 21,000 cfs) along with avoiding releases in excess of 100,000 cfs at lake Red Rock were considered to be two of the most important metrics due to damage to infrastructure at Saylorville Lake occurring when the spillway is overtopped and water levels nearing the top of levees at Ottumwa and Eddyville when releases from Lake Red Rock exceed 100,000 cfs. Any alternative that would flood easement land in Red Rock’s pool more frequently (i.e. pool elevations above 760) or increased the duration of flooding was also excluded as worsening of flooding of easement lands could result in the need to acquire additional real estate interests.
In accordance with the above criteria and simulation results, Alternatives 2, 3A, 3Ai, 3B, 3C, 4, 5 and 5B could be eliminated as viable alternatives. Alternative 1, the No Action Alternative, resulted in five overtopping events at Saylorville which causes significant erosion in the overflow spillway channel downstream of the dam and results in a considerable increase (21,000 cfs to 42,000 cfs) in downstream flows through the City of Des Moines. Alternative 4, a stakeholder preferred alternative provided by the Missouri River Energy Service Corporation to maximize hydropower production at Lake Red Rock, performed worse than the current plan in all FRM metrics and resulted in and increase to 6 overtopping events and increased both the frequency and duration of flooding of easement land at Lake Red Rock. While slightly better than the current water control plan with only four associated overtopping events, Alternatives 3A, 3Ai, 3B, 5 and 5B were not as effective as Alternatives 2, 5A and 6 at reducing the number of overtopping events. This was in large part due to the elimination of the storage balancing rule in these three alternatives. Alternative 3C, which allowed for a 30,000 cfs year round release at Lake Red Rock, significantly reduced the frequency and duration of flooding of easement lands. However, since limited balancing was included in this alternative there were three spillway overtopping events at Saylorville Lake versus two events when balancing was eliminated entirely. In addition, an allowable release of 30,000 cfs would be very difficult to maintain without the potential for frequently impacting downstream agricultural lands and secondary roads as these impacts begin to occur above 30,000 cfs. All of the plans performed equally well at reducing Mississippi River flood peaks for events exceeding the Quincy, Illinois, constraint of 20 feet. With the exception of Alternatives 1, 2 and 4, all of the other alternatives improved the reliability of meeting minimum conservation releases at Saylorville Lake by reducing the number of years Saylorville Lake fell below elevation 827, from 5 years to 2 years by allowing a proactive increase in Lake Saylorville’s conservation pool to 838 during declared droughts between July 1 and March 1.
With the intent of selecting a Recommended Plan, Alternative 5A (“wet” or “dry” year alternative schedules) and Alternative 6 (hybrid of alternatives 2, 3A and 3Ai) were selected for detailed economic analysis as both plans provide similar and superior flood risk reduction when compared to the other alternatives. Additionally, detailed economic analysis of Alternative 1 (current water control plan-no action) is required for comparison purposes in all Corps of Engineer studies as the baseline alternative.
C. STEP 2: ECONOMIC EVALUATION
Economic assessments were completed on alternatives carried forward for detailed analysis, No Action (Alternative 1), Alternative 5a, and Alternative 6, using HEC-FIA. The HEC-FIA uses a structure inventory from nationwide National Structure Inventory (NSI). Hydraulic stage data were used to determine the flood depths at each structure, and structure depth-damage curves are used to estimate damages. The economic model was split into the following six reaches:
EA-71 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
1. Red Rock Tailwater Reach 2. Ottumwa Reach 3. Keosauqua Reach 4. Saylorville Tailwater to Raccoon River Confluence Reach 5. Raccoon River to Red Rock Pool Reach 6. Red Rock Pool Reach
Each reach was analyzed using depth, duration, and arrival grids. The change in benefits, or damages avoided, for each alternative was determined through the hydraulic frequency of each of the flows or stages occurring. Results of this analysis are summarized in Chapter 6: Selected Plan, Section B, Process for selection of a Recommended Plan and the detailed assessment is provided in Appendix E.
The final array of alternatives, 5A and 6, met all project goals and objectives with the exception of Goal 5 Objectives 5.a. Making improvements to the conditions for Red Rock and Ottumwa hydropower operations. Finally criteria used to select the recommended plan was based on which alternative reduced flood damages the most. Tables EA-20 and EA-21 in VI.B. Process For Selection Of A Recommended Plan present the final comparison of alternative 5A and 6.
CHAPTER V: THE ACTION ALTERNATIVES’ ENVIRONMENTAL CONSEQUENCES
A. INTRODUCTION
With-Project Conditions Environment Summary. Along with FRM improvements, the District considered environmental impacts and environmental compliance to verify the preferred alternative. An environmental impact, or effect, may be described in terms of significance, duration, frequency, location, magnitude, or other characteristics, such as reversibility, retrievability, and the relationships to long-term productivity.
B. COMPARING FINAL ARRAY
Chapter 2 describes in detail the No Action Alternative. Table EA-19 summarizes environmental impacts in a qualitative assessment if the District were to select Alternative 5a or 6. Impacts to environmental resources were considered to be similar in nature across the range of with-project alternatives. However, the magnitude of adverse and beneficial impacts to resources for the with-project alternatives were considered to be proportional to the size of each restoration alternative.
Table EA-19. Summary of Environmental Impacts
Alternatives Public Interest Category/Measure No Action 5A 6 Floodplain Resources - ++ ++ Land Use o o o Aquatic & Wildlife Resources o ++ ++ Threatened & Endangered Species o + + Invasive Species o o o Vegetation o ++ ++ Water Quality, Wetlands, Rivers, and Streams o + +
EA-72 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Hydrology and Hydraulics - + + State Parks, and Other Aesthetic Resources o + + Cultural and Historic Resources o o o Socioeconomics o ++ ++ Minority and Low-Income Populations o o o Human Health & Safety o + + Sustainability, Greening & Climate Change o o o Constructed Resources o + + Recreation o o o Sedimentation/Soils/Prime And Unique Farmland o o o Hazardous Substances, Toxic, Radioactive Waste (HTRW) o o o ++ Expected major long-term environmental or social benefit as a result of alternative implementation. + Expected moderate long-term environmental or social benefit as a result of alternative implementation. o No or minor expected long-term environmental or social benefit or impact as a result of alternative implementation. - Expected moderate long-term environmental or social impact as a result of alternative -- Expected major long-term environmental or social impact as a result of alternative implementation.
Significance. Resource significance is determined by the importance and non-monetary value of the resource based on institutional, public, and technical recognition in the study area. The potential significant impacts of the project were taken into account in compliance with the Council of Environmental Quality (CEQ) NEPA regulations (40 Code of Federal Regulations (CFR) 1500.1(b), 1501.7(a)(2) and (3), and 1502.2(b)). "Significant" is defined as, "likely to have a material bearing on the decision-making process” (Apogee Research, Inc., 1995).
Engineering Regulation 1105-2-100, Corps’ Planning Guidance Notebook, defines these significance criteria as:
• Institutional Recognition: Institutional recognition means that the importance of a resource is acknowledged in the laws, adopted plans, and other policy statements of public agencies, tribes, or private groups. Sources of institutional recognition include public laws, executive orders, rules and regulations, treaties, and other policy statements of the Federal Government; plans, laws, resolutions, and other policy statements of states with jurisdiction in the planning area; laws, plans, codes, ordinances, and other policy statements of regional and local public entities with jurisdiction in the planning area; and charters, bylaws, and other policy statements of private groups.
• Public Recognition: Public recognition means that some segment of the general public recognizes the importance of a resource, as evidenced by people engaged in activities that reflect an interest or concern for that particular resource. Such activities may involve membership in an organization, financial contributions to resource-related efforts, and providing volunteer labor and correspondence regarding the importance of a resource.
• Technical Recognition: Technical recognition means that the resource qualifies as significant based on its technical merits, which are based on scientific knowledge or judgment of critical resource characteristics. Whether a resource is determined to be significant may of course vary based on differences across geographical areas and spatial scale. While technical significance of a resource may depend on whether a local, regional, or national perspective is undertaken,
EA-73 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
typically a watershed or larger (e.g. ecosystem, landscape, or ecoregion) context should be considered.
This section outlines the possible environmental impacts associated with the alternatives carried forward for detailed analysis (Alternatives 5a and 6). The District compared the No Action Alternative to these alternatives for operational differences in Section III, Alternatives. The following section compares the action alternatives’ environmental consequences with the No Action alternative (profiled in Section II, Affected Environment).
The District determined the environmental consequences would be very similar among the two action alternatives. Therefore in the sections below consequences are described individually where consequences differ between Alternatives 5a and 6 or described as the “action alternatives” in sections where consequences are expected to be similar across 5a and 6.
C. FLOODPLAIN RESOURCES
Since Alternative 5A and Alternative 6 operate similarly to the No Action Alternative during low flow and high flows no additional impacts to floodplain natural and constructed resources are expected. The alternatives would not result in a decrease in floodplain capacity or an increase in flood risk. The proposed action would be in compliance with EO 11988.
D. LAND USE
The action alternatives are consistent with current land uses and would enhance the existing public use areas and general quality of life for local residents. The alternatives would not alter existing land uses or transportation facilities within the project area. None of the action alternatives would negatively impact the community state parks, conservation areas, and other areas of recreational, ecological, scenic, or aesthetic importance (per 40 CFR 1508.27(b)(3)).
Operating the dams under non-flood periods for natural resource management would contribute to the Master Plan goals at each reservoir.
E. AQUATIC WILDLIFE RESOURCES
Under normal operating conditions, the District could manage for aquatic, wetland, and migrating species within the operating conservation bands. This would benefit important mussel, fish, herptiles, and birds during important life stages and seasons. Appendix C outlines the Des Moines Sustainable Rivers Study conducted by the District and TNC. It outlines the possible scenarios the District can manage lake levels and outflows to benefit these animals and the ecosystem.
For either action alternative selected, the District would impose strict guidelines for operation or maintenance induced low flow periods during cold temperatures (40 degrees F or below for water and or air temp). If the District or other entity requests the flows out of either dam be reduced for dam inspections, maintenance, or any other activity, the District would follow these guidelines:
1. If possible (not under emergency conditions), the District would notify the resource agencies concerning the proposed drawdown at least 60 days in advance. During an emergency, the District would notify the agencies as soon as possible.
2. The District would obtain all required permits prior to commencing a drawdown.
EA-74 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
3. Graduated drawdowns over 5 days prior to the outflow goal thereby reducing the outflows by no more than 20 percent per day.
4. Outflow reductions should coincide with fall-pool raises, normally during the first 2 weeks in September. This would prevent freezing or peak summer heat.
5. Outflows will not fall below the minimal low flow augmentation levels (Saylorville Lake – 200 cfs; Lake Red Rock – 300cfs) range during each day of the drawdown.
6. The outflows would be raised each night to at least normal or near normal operating levels up to a maximum of 3,000 cfs.
Although current operating rules restrict the rate of drawdown at Saylorville Lake to a maximum of 3000 cfs per day, there are no such restrictions at Lake Red Rock. The Sustainable Rivers Project (SRP) report (Appendix C) suggests placing a restriction on the maximum rate of change, both increasing (rise rate) and decreasing (fall rate). Several values were proposed as hypotheses, ranging from 3,000 to 5,000 cfs maximum change per day. The SRP also discussed if restrictions on the rate of change should be flow dependent, i.e., smaller maximum rate of change allowed at low flow than during average or high flow conditions. The SRP Report concluded research is needed to determine rate of acclimation needed for fish to prevent gas bubble trauma, and the need to understand how the future operation of hydropower turbines may impact the problem.
In cooperation with the resource agencies, the District would, if possible, manage flows to offset gas bubble trauma and stressful thermal conditions downstream of Lake Red Rock.
F. ENDANGERED, THREATENED, & CANDIDATE SPECIES
The District determined the action alternatives would have No Effect on any listed species or species being considered by the FWS for listing. The District concludes neither action alternative would change hydraulic scenarios to cause negative impacts to listed species. Updates to the Des Moines River Master Water Control Plan, cold weather guidelines mentioned in the previous section would ensure protection of listed mussel occupying the areas near the dam outlets under either 5A or 6 alternatives.
Within the conservation operation band during normal or dry conditions, the District could create improved least tern nesting conditions at either lake. The District would coordinate this water management with the resource agencies before and after the nesting season.
G. INVASIVE SPECIES
Implementation of either the No Action or Preferred Alternative would not have a negative effect on invasive species introduction, spread, or management. The District would continue to implement best management practices with regards to invasive species management at Saylorville Lake and Lake Red Rock. Following District policy and using adaptive and best management practices in prevention, education, early detection, rapid response, and containment in trying to control invasive species will aid in cost effective and environmentally sound invasive species management regardless of the selected plan.
EA-75 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
H. VEGETATION
Alternative 5a or 6, could operate lake and river levels during normal operations for more flexible natural resources management. This may result in improved vegetation communities. The District would be able to focus on habitat management problems and opportunities to promote aquatic and wetland plant growth.
For instance, maintaining the lakes a foot or two higher than normal and then dropping them to flat pool during the growing season would promote plant growth on the exposed mudflats in the upper reaches of each lake.
Under the No Action Alternative, the District is required to operate the lake at flat pool with no ability to fluctuate the levels for habitat management except in the fall for migrating bird benefits. A fall pool raise would still be a wildlife management option under Alternative 5a or 6.
I. RIVERS AND STREAMS, WATER QUALITY, WETLANDS
Alternative 5a or 6 would not negatively impact Des Moines River, Saylorville Lake or Lake Red Rock water quality. The District would continue low flow augmentation practices to ensure adequate water volume at downstream water intakes and outfalls.
Water Residence times in each lake was compared for Alternatives 1 and 6 at both reservoirs for growing season (1May-15Oct) when the pool is at conservation elevation.
For the period of record analysis at Saylorville (1977-2016), the change in residence time during the growing season, when the pool is at conservation elevation, was -4.24 days (15.33 to 11.09 days).
For the period of record analysis at Red Rock (1968-2016), the change in residence time during the growing season, when the pool is at conservation elevation, was -1.60 days (17.55 to 15.95 days).
Therefore, the proposed action alternatives would not significantly change the water retention time at either reservoir to substantially alter water quality positively or negatively.
Since the District proposes no construction or would have no discharge into the Waters of the United States, a CWA, Section 401 Water Quality Certification is not required.
Without watershed improvements, under the No Action alternative or either action alternatives, the threat of water quality impairment would continue its current trend.
Annual wetland management may or may not be an achievable goal due to other habitat management objectives in the Master Plans and SRP program for any given year. Flood risk management takes priority over wetland management. Still, wetlands at each reservoir would improve under either action alternative given the added flexibility of water level management during normal (non-flood) years.
The action alternatives would not have additional (positive or negative) impact to the rivers and stream in the project area. The change in operation would mimic historic “run of the river” conditions up to a certain point when flood risk protocols would limit releases from both dams.
The proposed action alternatives would not impact any waterbodies designated as a wild or scenic waterway, in accordance with the Wild and Scenic Rivers Act.
EA-76 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
The District would continue their robust water quality monitoring program under any of the alternatives. Based on the results of water quality monitoring, the Iowa DNR or the District may impose beach closures, or other precautionary steps. If possible, the District would attempt to offset water quality problems while operating the reservoirs within in their conservation bands.
J. HYDROLOGY AND HYDRAULICS
The action alternatives carried forward have positive impacts on the hydrology/hydraulics of the system by conserving reservoir storage through earlier releases of water during small scale flood events, thereby reducing flood risk during long duration, large magnitude flood events resulting from multiple storms. While higher non-damaging, within bank flows, would be observed more frequently in order to conserve flood storage, the frequency and duration of flows exceeding the channel capacity downstream of the reservoirs will be reduced in most cases. At Saylorville Lake, the addition of drought contingency pool during declared droughts will have the beneficial effect of improving the reliability of meeting downstream water supply and water quality targets during droughts. In addition, flexible conservation pool operating bands as proposed as part of the SRP (Chapter VI and Appendix 6) would have potential environmental benefits without impacting other project purposes.
With regard to updates of the Des Moines River Basin Master Reservoir Regulation Manual and Saylorville Lake and Lake Red Rock Control Plans, it is suggested that opportunities for increased flexibility in project operations be built into the regulation schedules. This will allow water managers to more easily adapt project regulation for each event based on information available at the time of the event. Overall, this flexibility would help to account for the uncertainty in projected climate changes impacts in the Des Moines River watershed and will help to reduce future risk.
K. STATE PARKS, CONSERVATION AREAS, AND OTHER AREAS OF RECREATIONAL, ECOLOGICAL, SCENIC, OR AESTHETIC IMPORTANCE
The action alternatives do not require construction so there would be no impacts from construction lighting, noise, dust or other disturbances to the planning area. Long-term beneficial impacts would include restoration of natural resource areas.
The activities within the action alternatives are consistent with current land uses and potentially would improve habitat and wildlife viewing, thereby enhancing the general quality of life for local residents.
Several public areas are adjacent or in the planning area ranging from city parks to preserves. None of the alternatives would negatively impact the community, state parks, conservation areas, and other areas of recreational, ecological, scenic, or aesthetic importance (per 40 CFR 1508.27(b)(3)).
L. HISTORICAL AND CULTURAL RESOURCES
The District coordinated the, “Saylorville Regulation Plan Modification, Saylorville Reservoir, Polk County, Iowa,” dated April 2001, through SHPO and 27 federally-recognized tribes. A portion of the Downstream (Des Moines River) Corridor required Phase I archeological survey in association with the 2001 plan alterations. The 2001 plan alterations were anticipated to have an adverse effect to one historic property: increased erosion to the Christensen Oneota Site (13PK407). In a letter dated February 7, 2001, the Iowa SHPO concurred with the District’s finding of Adverse Effect, which was resolved through data recovery excavations.
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Prior to finalization of Lake Red Rock’s May, 1990, water control plan modification, entitled, “Water Control Plan with Supplemental Master Plan and Final Environmental Impact Statement Supplement II” associated archeological survey occurred, with 11 National Register of Historic Places (NRHP)-eligible properties identified and subjected to data recovery excavations. As a result, the SHPO concurred in letters dated May 16, and October 25, 1989, with the District’s determination the proposed 1990 alterations would have No Adverse Effect to Historic Properties, conditional upon completion of the data recovery mitigation measures.
Action Alternatives 5A or 6 operate similarly to the No Action Alternative at high and low flows. Their implementation would not significantly change the water retention time at either reservoir to substantially alter flows, flood elevations, or shoreline erosion rates from those presently experienced under the No Action alternative. Consequently, implementation of Action Alternatives 5A or 6 would have no foreseeable negative impact to the project’s cultural and historic resources as compared to the presently utilized Water Control Plans, which have previously been coordinated through the SHPO and tribes.
The District initiated consultation with SHPO and tribes on the present project in a letter dated June 20, 2017, inviting them to identify cultural and historic preservation issues early in the plan formulation process. The District received no responses pertaining to project concerns. One historic property, the aforementioned Christensen Oneota Site, is situated in the project area. Implementation of the action alternatives will result in no new adverse effects on the site. Prior Water Control Plan-related adverse effects to the site were resolved through 2001 data recovery excavations. Neither action alternative would change any hydraulic scenario to cause effects to historic properties. The District determined implementation of the action alternatives would result in No Adverse Effects. The District has invited the Iowa SHPO, federally-recognized tribes, and other interested parties to comment on this finding and ascertain if additional concerns exist.
M. SOCIOECONOMIC RESOURCES
Alternatives 5a and 6 are expected to reduce the number of extreme floods. With improved flexibility under the normal non-flood operations that manipulate lake and river levels, socioeconomic resources are expected to be improved. Socioeconomic resources would be positively impacted as flooding frequency could be reduced in developed areas.
All six economic reaches, including Red Rock Tailwater, Ottumwa, Keosauqua, Saylorville Tailwater to Raccoon River, Raccoon River to Red Rock Pool and Red Rock Pool are expected to see a reduction in damages from flood events, mainly due to a lower frequency of floods. Population, housing, businesses and agriculture will realize positive benefits from both Alternatives 5a and 6 in terms of FRM. Alternative 6 provides a higher level of risk reduction than Alternative 5a, compared to the No Action Plan, Alternative 1. Alternative 6, would provide the largest percent reduction in average annual damages takes place in the Keosauqua Reach closely followed by Ottumwa Reach. The Alternative 6 annual damage reductions would have a positive impact on all socioeconomic resources in the project area. A vast majority of the flood damage reduction benefits are from reduced flooding of structures. See the Appendix E, Economics.
Environmental Justice: Impacts associated with the action alternatives are expected to have positive benefits for people in the study area, including minority and low income residents throughout the WCP study area. Environmental Justice communities are spread throughout the WCP study area, with most of the Environmental Justice communities (as identified using block group data) located in Polk County.
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There would be no direct/indirect/cumulative high adverse impacts on minority and/or low-income communities within the study area as per 2016 U.S. Census information and requirements of E.O. 12898.
N. HUMAN HEALTH & SAFETY
The proposed action would not impact human health and safety.
O. SUSTAINABILITY, GREENING & CLIMATE CHANGE
Corps of Engineers projects, programs, missions, and operations have generally proven to be robust enough to accommodate the range of natural climate variability over their operating life spans. However, recent scientific evidence shows in some places and for some impacts relevant to Corps operations, climate change is shifting the climatological baseline about which that natural climate variability occurs, and may be changing the range of that variability as well. This is relevant to the Corps because the assumptions of stationary climatic baselines and fixed range of natural variability, as captured in the historic hydrologic record may no longer be appropriate for long-term projections of flood risk.
The District considered climate change impacts on the hydrology of the Des Moines River Basin in accordance with ECB 2016-25, Guidance for Incorporating Climate Change Impacts to Inland Hydrology in Civil Works Studies, Designs and Projects as well as ETL 1100-2-3, Guidance for Detection of Nonstationarities in Annual Maximum Discharges.
The flow records within the Des Moines River Basin only indicate one nonstationary changepoint from six analyzed gages. This same gage (Raccoon River at Van Meter, IA) shows a statistically significant increasing trend in annual maximum flood peaks from 1915-2014, while the other five analyzed gages show no statistically significant trends or indeterminate trends. The literature agrees that projected temperatures and precipitation will increase, while there is little consensus on projected streamflow.
The vulnerability assessment of the Des Moines River Basin regarding FRM using projected future hydrology, shows that the basin is a particularly vulnerable basin when compared to the other watersheds in the United States and that there is more uncertainty regarding flood risk management in the Des Moines River watershed because of future climate change. The available literature and USACE Climate Assessment tools do not reach a consensus on observed and projected streamflow throughout the Des Moines River Basin due to long-term persistent climate trends or anthropogenic climate change. However, there is some agreement that streamflow variability would increase and extreme events will occur more frequently.
P. CONSTRUCTED RESOURCES-PUBLIC STRUCTURES, UTILITIES, TRANSPORTATION, OTHER
The action alternatives would not have negative impacts to constructed resources. The alternatives would not alter existing land uses or transportation facilities within the study. Further, the action alternatives would not impact surrounding facilities such as police stations, fire stations, schools, hospitals and post offices.
Q. RECREATION
The action alternatives would not have any impacts to lake or river recreation. With improved natural resource management, there may be additional eco-recreation opportunities.
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Based on the proposed higher, earlier releases to preserve flood storage and thereby reduce the likelihood of higher reservoir releases during moderate to major flood years, Alternatives 5a or 6 would improve the availability of water based recreational features at Saylorville Lake and Lake Red Rock (Goal 4.a).
R. SEDIMENTATION/SOILS/PRIME AND UNIQUE FARMLAND
The action alternatives would not have any additional impacts to prime or unique farmland.
S. HAZARDOUS, TOXIC, AND RADIOACTIVE WASTE (HTRW)
None of the alternatives would be expected to affect HTRW sites within the planning area. The lands affected by any of the action alternatives would not be expanded beyond what already exists, so known HTRW sites would not change.
CHAPTER VI: SELECTED PLAN
A. ENVIRONMENTAL OPERATING PRINCIPLES AND CAMPAIGN PLAN GOALS
The Des Moines Basin Master Reservoir Regulation Manual update would incorporate environmental sustainability by integrating environmental flows into the day to day water control operations. During non-flood periods, the District could operate within various reservoir heights and releases geared toward environmental benefits. Operating the reservoirs with a band of lake elevations for conservation was a result of close planning with The Nature Conservancy (TNC), Iowa DNR, USFWS, and academics through a SRP partnership with the TNC. The Des Moines River Sustainable Rivers project helped identify environmental flow requirements for the Des Moines River, and develop hypotheses for alternative flow releases from the Red Rock and Saylorville dams that might establish more natural flow regimes and/or enhance multiple benefits within the project area. The goal of the project is to explore whether it is possible to modify the District’s dam operations to manage for a more “naturalized” flow regime benefiting fish and wildlife populations, ecosystem function, river and floodplain habitat, and water quality.
Implementing a conservation band would allow the reservoirs to operate within a range of elevations during both the “summer” and “winter” seasons.
The District and TNC determined those bands to be the following: • September 1 – March 1 (“winter” season) o Saylorville Lake: Elevations 836 – 840 feet o Lake Red Rock: Elevations 741.5 – 747 feet
• March 1 – September 1 (“summer” season) o Saylorville Lake – Elevations 836 – 838 feet o Lake Red Rock: Elevations 741.5 – 743 feet
Model Simulations were run for the No Action Alternative (Alternative 1) to evaluate the effects of operating the reservoirs under the band concept. The results of the simulations showed little to no effect on peak reservoir elevations at either the low or high ends of the proposed operating bands. A more detailed discussion of these results is available in Appendix D, Hydrology and Hydraulics.
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Restoring at least some aspects of the natural flow regime would be expected to benefit numerous species, including several ancient river fishes, such as paddlefish, shovelnose and lake sturgeon, as well as floodplain plant communities and terrestrial wildlife. The Des Moines SRP flow restoration project may also be linked to a larger Des Moines River watershed project. The project involves development of a literature review and initial hypothesized recommendations for environmental flow adjustments. The project would also identify whether proposed modifications are within current guidelines allowed by the Des Moines River Master Water Control Plan, or might require adjustments to the operations regulations in the course of updates to the water regulation manuals scheduled over the next several years.
The significance of the Des Moines River’s contribution to the health of aquatic, terrestrial, and migrating birds ecosystems are of national importance. Preserving the opportunity to restore additional habitat in the future is supported by the Corps Environmental Operating Principles and Campaign Plan goals. The principles are: 1. Foster sustainability as a way of life throughout the organization. 2. Proactively consider environmental consequences of all Corps activities and act accordingly. 3. Create mutually supporting economic and environmentally sustainable solutions. 4. Continue to meet our corporate responsibility and accountability under the law for activities undertaken by the Corps, which may impact human and natural environments. 5. Consider the environment in employing a risk management and systems approach throughout the life cycles of projects and programs. 6. Leverage scientific, economic and social knowledge to understand the environmental context and effects of Corps actions in a collaborative manner. 7. Employ an open, transparent process that respects views of individuals and groups interested in Corps activities.
The Recommended Plan would address these principle in the following ways: 1. The Recommended Plan would incorporate environmental sustainability by operating the Saylorville Lake and Lake Red Rock outflows in conservation bands when flooding is not a concern. This would create a naturally functioning wetland, lake, and river ecosystem. 2. Coordination with resource agencies and stakeholders through development of the study identified and resolved or reduced the risk of environmental consequences of implementation of the Recommended Plan. 3. The Recommended Plan would create aquatic and riparian habitat conditions required by numerous fish and wildlife species living in or migrating through the system. The economic benefits were not quantified, but would tend to invigorate the existing ecotourism economy associated with the resource. Implementation would not impact flood risk or floodplain development and would not cause negative environmental impacts. 4. The project has been reviewed and found to be consistent with all applicable laws and policies, including those related to potential impacts to human and natural environments. The District would meet their corporate responsibility and accountability for the project in accordance with those laws and policies. 5. The project would balance ecosystem restoration by restoring habitat without increasing the existing flood risk. Cost and schedule risk assessment was considered for project implementation to assure costs and construction schedules were achievable. Risk management was also applied
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in the development of the adaptive management and monitoring plan to assure restoration plans realized forecast environmental outputs. 6. The District has operated the Lake Red Rock since 1969 and Saylorville Lake since 1977. The knowledge of resource agency subject matter experts and long standing partnership with the resource agencies was leveraged in the collection of field data and to develop the possible conservation band management for environmental management. 7. The study process involved coordination with and the participation of numerous agencies and interested resource partners. Both the local sponsor and the District met with the public to seek input at the beginning and during the study.
Appropriate ways and means were used to assess cumulative impacts to the environment through the NEPA and use of engineering models, environmental surveys, and coordination with natural resource agencies. Because of employing a risk management and systems approach throughout the life cycle of the project, the project design evolved to address as many concerns as possible with no mitigation required to address adverse impacts.
The Corps Campaign Plan a strategic change decision document. It drives and aligns strategic change; anticipates and shapes future operating and fiscal environments; unites all of the Corps with a common vision, purpose, and direction; and responsively adapts to mission and “battle space” changes. The plan is composed of four goals: Support National Security, Deliver Integrated Water Resource Solutions, Reduce Disaster Risk, and Prepare for Tomorrow. The Recommended Plan relates to the second goal. The second goal reflects an effort to operationalize the civil works strategic plan by focusing on holistic integrated water resource management. The goal has four objectives: deliver quality water resources solutions and services, deliver the civil works program using innovative solutions, develop the civil works program to meet the future water resources needs of the Nation, and manage the life-cycle of water resources infrastructure systems to consistently deliver reliable and sustainable performance. Each objective has three action items. Of the twelve items, those to which the Recommended Plan relates are listed below: The applicable Campaign Plan goal is Goal 2 – Deliver Integrated Water Resource Solutions. The goal has four objectives: 1. Deliver Quality Water Resource Solutions and Services 2. Deliver the Civil Works Program and innovative solutions 3. Develop the Civil Works Program to meet the future needs of the Nation 4. Manage the life-cycle of water resources infrastructure systems to consistently deliver reliable and sustainable performance.
The preserved study opportunity would apply to the Campaign Plan goal’s objectives one and three by maintaining the ability to initiate a restoration study in the timeliest manner in the future. The significance of the FRM and natural resources value to the surrounding ecosystem are of national importance.
Appropriate ways and means were used to assess cumulative impacts to the environment through the NEPA and use of engineering models, environmental surveys, and coordination with natural resource agencies. Because of employing a risk management and systems approach throughout the life cycle of the project, the project design evolved to address as many concerns as possible with no mitigation required to address adverse impacts.
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B. PROCESS FOR SELECTION OF A RECOMMENDED PLAN
Selection of a Recommended Plan was accomplished by developing analytic frequency curves for each of the of the 3 alternatives carried forward by following the procedures used in developing the regulated flow frequency relationships used in the 2010 Des Moines River Regulated Flow Frequency Study. The procedures generally consisted of: • Developing an unregulated period of flow record based upon the HEC-ResSim simulation using historical inflows. • Developing volume-duration-frequency curves for reservoir inflow volumes using the simulated unregulated flow record. • Estimating the critical duration for flood inflows. • Developing a relationship between the regulated peak reservoir outflow and the unregulated inflow volume for the identified critical duration. • Combining the volume-duration-frequency curve for the critical duration with the regulated versus unregulated relationship to obtain the regulated frequency curve. The resulting flow frequency values were then provided as input to the Hydrologic Engineering Center’s model, HEC-RAS, used for computing water surface profiles and inundation mapping for each flow frequency value. The area inundated versus discharge for each damage reach was then provided as input to develop stage-damage relationships for each alternative using the flood impact analysis program, HEC- FIA. Tables EA-20 and EA-21 provide a summary of computed average annual damages and associated reductions in damage for each alternative (5A and 6) from Alternative 1 presented in terms of dollars and percent reduction in damages.
Table EA-20. Average Annual Damages (AAD) Saylorville Lake Tailwater - Lake Red Rock Pool Saylorville Tailwater to Raccoon River to Raccoon River Confluence Red Rock Pool Red Rock Pool AAD AAD AAD Alternative 1 992,536 224,489 321,945 Alternative 5A 813,933 179,474 283,891 Alternative 6 813,933 179,833 228,825
Saylorville Tailwater to Raccoon River to Raccoon River Confluence Red Rock Pool Red Rock Pool AAD Reduced AAD Reduced AAD Reduced (From Alt 1) (From Alt 1) (From Alt 1) Alternative 1 0 0 0 Alternative 5A 178,602 45,015 38,054 Alternative 6 178,602 44,656 93,120
Saylorville Tailwater to Raccoon River to Raccoon River Confluence Red Rock Pool Red Rock Pool % AAD Reduced % AAD Reduced % AAD Reduced (From Alt 1) (From Alt 1) (From Alt 1) Alternative 1 0 0 0 Alternative 5A -18% -20% -12% Alternative 6 -18% -20% -29%
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Table EA-21. Average Annual Damages Lake Red Rock Tailwater - Keosauqua Reach
Red Rock Tailwater Reach Ottumwa Reach Keosauqua Reach AAD AAD AAD Alternative 1 48,949 1,064,050 151,819 Alternative 5A 36,946 799,142 106,434 Alternative 6 33,611 677,936 94,593
Red Rock Tailwater Reach Ottumwa Reach Keosauqua Reach AAD Reduced AAD Reduced AAD Reduced (From Alt 1) (From Alt 1) (From Alt 1) Alternative 1 0 0 0 Alternative 5A 12,003 264,908 45,385 Alternative 6 15,338 386,114 57,226
Red Rock Tailwater Reach Ottumwa Reach Keosauqua Reach % AAD Reduced % AAD Reduced % AAD Reduced (From Alt 1) (From Alt 1) (From Alt 1) Alternative 1 0 0 0 Alternative 5A -25% -25% -30% Alternative 6 -31% -36% -38%
C. DISCUSSION OF RECOMMENDED PLAN
Based on the above analysis and the resulting damage summary, Alternative 6 is the preferred alternative and is recommended for replacing the current Des Moines River Basin Master Reservoir Regulation Manual. While both Alternatives 5A and 6 reduced average annual damages as compared to the No Action- Alternative 1 for each of the reaches studied. Alternative 6 reduced damages to a greater extent than Alternative 5A. Detailed information related to this analysis can be found in Appendix D, Hydrology and Hydraulics, and Appendix E, Economics.
D. PARTNER COORDINATION
Public Involvement. The District held eight open house style public meetings between 31 January 2017 and 3 February 2017 (Table EA-22). The District conducted the meetings to attain public input at the beginning phase of the feasibility plan to ensure agency perspectives aligned to the extent allowable under law and policy with public needs. District representatives including reservoirs staff, were available to answer any questions from the public or other agency representatives. The meetings consisted of an approximately 30 minute meeting followed by a lengthy question and answer session.
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Table EA-22. Public Meeting Locations
Date Location Time Tuesday, January 31, 2017 Johnston, IA, Public Library 2:00-4:00 pm & 6:00–8:00pm Wednesday, February 1, 2017 Central College, Pella, IA 2:00-4:00 pm & 6:00–8:00pm Thursday, February 2, 2017 Bridge View Church, Ottumwa, IA 2:00-4:00 pm & 6:00–8:00pm Friday, February 3, 2017 Town & Country Inn and Suites, Quincy, IL 2:00-4:00 pm & 6:00–8:00pm
The following is a brief synopsis of the public input.
Johnston Meetings • Multiple individuals indicated reduced recreational opportunities due to sedimentation within the conservation pool. Desire for greater increase in fall pool raise.
Pella Meetings • Easement land owners expressed concern about how meeting info was communicated. • Easement land owners want more consideration that flooding of their fields is just as damaging as flooding of fields downstream of Lake Red Rock. • Similar to Des Moines meetings, multiple individuals indicated reduced recreational opportunities due to sedimentation within conservation pool. Desire for greater increase in fall pool raise. Within Lake Red Rock, specific areas mentioned included the upper end of the conservation pool and the areas along Whitebreast Creek. • River users immediately downstream of the reservoir are impacted by unexpected changes in releases (those not shown in initial daily forecast). Would like us to stick to our initial forecast or have some way of pushing out notification of changes in planned releases. • Flooding of crops for more than ~3 days results in loss. • Complaints of incision occurring along small streams directly entering Lake Red Rock. • Complaint that DNR plantings were causing invasive plants to be brought into adjacent fields by deer.
Ottumwa Meetings • The Ottumwa hydropower dam shuts down (produces no power) at flows above 18,000 cfs. Primary purpose of the dam is to create the pool for potable water supply, hydropower is added benefit. Ideally, they would like us to pass higher flows if going to go over 18,000 cfs, as they are shut down anyway. Once flows drop off, it would help them make up some of the lost power production if we would more quickly drop to 15,000 cfs (instead of holding at 22,000 or 30,000 cfs) then hold at that flow to vacate the remaining flood storage.
• One individual commented that flows in excess of 18,000 cfs resulted in impacts to the lowest areas of his fields. It is unclear if this is actual direct flooding or the result of higher river levels resulting in “wet spots” further in from the bank in low areas of the field.
• One individual expressed concerns over bank instability along his agricultural field. His perception is that the channel has become wider and deeper over time as a result of erosion. When asked, he could not say for certain whether the river had overall widened or migrated towards his field. He further indicated that after prolonged periods of high flows (e.g., 18,000+ cfs) he doesn’t feel safe operating his equipment up to the banks of the Des Moines River due to fear of bank sloughing due to the saturated condition.
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Quincy Meetings • One individual expressed concerns over the potential for Des Moines River Basin Master Reservoir Regulation Manual changes to affect continuous fluctuations in water level between lock 20 and 21 on the Mississippi River. The individual would like to see a more stable or controlled water level to assist with the local economy and boating community.
• One individual advocated for changes to the downstream triggers which would allow for water to be held back to lower the peak levels on the Mississippi River. He suggested the current conservation pool is too high, perhaps a conservation pool that would vary depending on the time of the year and the prediction of wet or dry conditions. He supported the reservoir primary authorization remaining flood control but stated commercial navigation and low land flooding should be added as part of the operational control.
Agency Coordination. The USFWS, the Iowa DNR, and TNC support the Recommended Plan. The plan fulfills a number of missions and objectives common to these organizations. The organizations provided input throughout the study and were involved in plan formulation, and data collection (Appendix A). The District integrated their comments into this planning document. The Iowa SHPO, federally recognized tribes, and other interested parties have been invited to comment on the District’s No Historic Properties Affected finding for this project.
The following agencies and tribes provided input to this project: • US Environmental Protection Agency • Iowa Department Of Natural Resources • US Fish and Wildlife Service • Santee Sioux Nation • Flandreau Santee Sioux • Office of the State Archaeologist
Des Moines River Sustainable Rivers Program. The Des Moines River Sustainable Rivers Project environmental flows workshop was held 25-26 October at Central College in Pella, Iowa, with the purpose of exploring whether management changes related to flow could improve the long-term ecological health of the Des Moines River. The workshop was co-organized and sponsored by The Nature Conservancy in Iowa and the U.S. Army Corps of Engineers, Rock Island District and Lake Red Rock, and was attended by over fifty scientists, fisheries, water and natural resource managers from government agencies, universities and non-government organizations. Appendix C contains the workshop agenda and meeting minutes. The resulting report is also in Appendix C.
Stakeholder Input.
District staff has met with Missouri River Energy Services, the company developing a new 36.4 megawatt hydroelectric facility at Lake Red Rock. As a result of these meetings an additional alternative was created to assess the impacts to FRM metrics if operations for power generation were maximized. This alternative was not carried forward for final analysis because it performed negatively in all FRM metrics as compared to the current Des Moines River Basin Master Reservoir Regulation Manual and Lake Red Rock control plans. The recommended plan has minimal impact to power generation at the hydroelectric facility.
State and Local Governments including Emergency management organizations
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Public Review. The District will circulate this feasibility report to a wide distribution list (Appendix D) to solicit public input as part of the decision-making process. The District will also post the report on the District’s website’s Public Notice link (http://www.mvr.usace.army.mil/About/Offices/Programs-and- Project-Management/Civil-Works-Public-Notices/). During the 30-day public review, the District will hold public meetings/open houses similar to the earlier scoping meetings. The purpose of these meetings is to solicit input on this report and the recommended plan. At the conclusion of the 30-day period, the District will integrate all comments into their decision making process.
E. ENVIRONMENTAL COMPLIANCE
The District prepared this integrated report to satisfy the requirements of all applicable environmental laws and regulations. The District efforts comply with the Council on Environmental Quality (CEQ) NEPA regulations (40 CFR Part 1500–1508) and the District’s implementing NEPA regulation ER 200-2- 2 - Environmental Quality: Policy and Procedures for Implementing NEPA, 33 CFR 230. In implementing the Recommended Plan, the District would follow provisions of all applicable laws, regulations, and policies related to the proposed actions. The following sections present brief summaries of Federal environmental laws, regulations, and coordination requirements applicable to this project.
Clean Water Act. The CWA was enacted to restore and maintain the integrity of the nation’s waters. There are two fundamental goals: to eliminate the discharge of pollutants into the nation’s waters, and to achieve water quality levels that are fishable and swimmable. Two sections of the Act are discussed below.
Section 404(b)1. The Corps, under the direction of Congress, regulates the discharge of dredged and fill materials into all waters of the United States, including wetlands. Although the Corps does not issue itself permits for construction activities affecting waters of the U.S., it must meet the legal requirement of the Act. Since the action alternatives do not require any fill activities, the District did not complete a CWA, Section a 404(b)(1) analysis.
Section 402. Since there is no construction activities associated with this project, none of the action alternatives would require National Pollutant Discharge Elimination System requirements of the CWA Section 402(p).
Clean Air Act of 1970. Federal agencies are required by this Act to review all air emissions resulting from federally-funded projects or permits to insure conformity with the State Implemented Plans in non- attainment areas. Neither the Saylorville Lake project nor Lake Red Rock project is in a metropolitan area currently in attainment for all air emissions. The Recommended Plan would be in accordance with the Clean Air Act.
Endangered Species Act (ESA). The Recommended Plan would have “no effect” on any federally- listed endangered or threatened species. “No effect” means the proposed project would not affect, directly or indirectly any ESA-listed species or critical habitat. Generally, this means no ESA-listed species or critical habitat would be exposed to any potentially harmful/beneficial elements of the action. While the project may have beneficial impacts on listed species, additional documentation is not required under this Act for consultation with the USFWS. The “no effect” determination, fulfilled the District’s ESA, Section 7(a)2 consultation requirements.
Executive Order 13112, Invasive Species. EO 13112 recognizes the significant contribution native species make to the well-being of the nation’s natural environment and directs Federal agencies to take preventative and responsive action to the threat of the invasion of non-native plants and wildlife species in
EA-87 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment the United States. This EO establishes processes to deal with invasive species and among other items establishes that Federal agencies “will not authorize, fund, or carry out actions that it believes are likely to cause or promote the introduction or spread of invasive species in the United States or elsewhere unless, pursuant to guidelines that it has prescribed, the agency has determined and made public its determination that the benefits of such actions clearly outweigh the potential harm caused by invasive species; and that all feasible and prudent measures to minimize risk of harm will be taken in conjunction with the actions.”
The proposed action would be in compliance with EO 13112 since the action alternatives are within the existing project operation of each reservoir.
Executive Order 11988, Floodplain Management. The EO 11988 was enacted May 24, 1977, in furtherance of the National Environmental Policy Act of 1969, as amended (42 U.S.C. 4321 et seq.), the National Flood Insurance Act of 1968, as amended (42 U.S.C. 4001 et seq.), and the Flood Disaster Protection Act of 1973 (Public Law 93-234, 87 Star.975). The purpose of the EO was to avoid to the extent possible the long and short-term adverse impacts associated with the occupancy and modification of floodplains and to avoid direct or indirect support of floodplain development wherever there is a practicable alternative.
The order states each agency shall provide and shall take action to reduce the risk of the flood loss, to minimize the impacts of floods on human safety, health, and welfare, and to restore and preserve the natural and beneficial values served by floodplains in carrying out its responsibilities for (1) acquiring, managing, and disposing of Federal lands and facilities; (2) providing federally-undertaken, financed, or assisted construction and improvements; and (3) conducting Federal activities and programs affecting land use, including but not limited to water and related land resources planning, regulating, and licensing activities.
The FEMA digital flood insurance rate maps of the study area were analyzed to establish the locations of the 100-year and 500-year flood zones. All alternatives were designed to ensure that the proposed alternatives would not result in a decrease in the floodplain capacity and an increase in flood risk to the study area. The proposed action would be compliance with EO 11988 since the Des Moines River floodplain would not be impacted.
The alternatives would be implemented within the 500-year floodplain, but there would be no direct or indirect impact to the floodplain or related to floodplain development. It was not necessary to apply the eight-step process required by the Water Resources Council, Floodplain Management Guidelines for Implementing E.O. 11988, February 10, 1978.
Migratory Bird Treaty Act, Migratory Bird Conservation Act, and Executive Order 13186, Migratory Birds. The importance of migratory non-game birds to the nation is embodied in numerous laws, executive orders, and partnerships. The Fish and Wildlife Conservation Act of the Army for Civil Works demonstrates the Federal commitment to conservation of non-game species. Amendments to the Act adopted in 1988 and 1989 direct the Secretary to undertake activities to research and conserve migratory non-game birds. The EO 13186 directs Federal agencies to promote the conservation of migratory bird populations, including restoring and enhancing habitat. Migratory Non-Game Birds of Management Concern is a list maintained by the USFWS. The list helps fulfill the primary goal of the USFWS to conserve avian diversity in North America. The USFWS Migratory Bird Plan is a draft strategic plan to strengthen and guide the agency’s Migratory Bird Program. The proposed natural resource management abilities would contribute directly to the USFWS Migratory Bird Program goals to protect, conserve, and restore migratory bird habitats to ensure long-term sustainability of all migratory bird populations.
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Executive Order 12898, Environmental Justice. EO 12898 “Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations” dated February 11, 1994, requires all Federal agencies to identify and address disproportionately high and adverse effects of its programs, policies, and activities on minority and low-income populations. Data was compiled to assess the potential impacts to minority and low-income populations within the study area.
Environmental justice is the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies. Even though minorities account for a large portion of the local population in Des Moines, implementation of any of the action alternatives would not have a disproportionately high or adverse effect on these populations. The proposed action would be consistent with EO 12898.
Executive Order 13045, Protection of Children. EO 13045 “Protection of Children from Environmental Health Risks” dated April 21, 1997 requires Federal agencies to identify and address the potential to generate disproportionately high environmental health and safety risks to children. This EO was prompted by the recognition that children, still undergoing physiological growth and development, are more sensitive to adverse environmental health and safety risks than adults.
The project would cause no short-term impacts on the protection of children. Since no construction or project altering activities would take place, there is no risk to children or their neighborhoods. Further, green space and public parks where children thrive, would be diminished or lost if the proposed project is implemented.
Farmland Protection Policy Act of 1981. The action alternative s would not affect downstream farmland since the action alternatives do not significantly alter downstream flows.
Rivers and Harbors Act
Section 10 (30 Stat. 1151; 33 U.S.C 403, 1899). The proposed -plan would not place any permanent obstruction across navigable water nor would it place obstructions to navigation outside established Federal lines.
Section 122 (PL 91-6110, 1970) 17 Points. This Act assures the District will consider all possible adverse economic, social and environmental effects relating to any proposed project have been fully considered in developing such project. The final decisions on the project are made in the best overall public interest taking into consideration the need for FRM, navigation, and associated purposes, and the cost of eliminating or minimizing such adverse effects. The Act referred to specific resources all projects need to take into account during the planning process. Table EA-23 outlines each of these resources and the project’s possible impacts. These resources are commonly called the 17 Points.
EA-89 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Table EA-23. Rivers and Harbors Act – 17 Points1 Possible Resource Project Effects1 Air No Impacts Noise No Impacts Water Pollution No Impacts Man-made Resources No Impacts Natural Resources Positive Impacts Aesthetic Values No Impacts Community Cohesion No Impacts Availability of Public Facilities and Services No Impacts Availability of Public Services No Impacts Employment No Impacts Tax Income Value Losses No Impacts Property Value Losses No Impacts Displacement of People No Impacts Business and Industrial Growth No Impacts Farms No Impacts Community Growth No Impacts Regional Growth No Impacts
1 All 17 points – Reason for Possible Project Effects: No construction activity or change in long-term O&M.
Engineer Regulation 1105-2-100. In addition to the resources listed in Table EA-23, the Corps planning guidance (ER 1105-2-100, 1983) identifies other resources needed to take in to account in their project planning in Table EA-24.
Table EA-24. ER 1105-2-100 Resources
Resource Possible Project Effects Reasons Life Positive Effect Added FRM Health Positive Effect Added FRM Safety Positive Effect Added FRM Long Term Productivity Positive Effect Added Natural Resource Benefit Energy Requirements No Effect Energy Conservation No Effect
Executive Order 11990 Protection of Wetlands. This EO states each Federal agency shall avoid undertaking new construction located in wetlands unless there is no practicable alternative to such construction, and the proposed action includes all practicable measures to minimize harm to wetlands. This water regulation plan update would not initiate or alter water management to change any existing wetland impacts. The proposed project is in full compliance with the EO.
Wild and Scenic Rivers Act of 1968, as amended. The Des Moines River and its tributaries are not listed in the National Rivers Inventory (NRI). The NRI is used to identify rivers that may be designated by Congress to be Component Rivers in the National Wild and Scenic Rivers System.
EA-90 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Federal Water Project Recreational Act of 1966. The Act states, “it is the policy of Congress and the intent of this Act that in investigating and planning any Federal navigation, flood control, reclamation, hydroelectric, or multipurpose water resource project that consideration shall be given to the opportunities, if any, which the project affords for outdoor and for fish and wildlife enhancement ...” The District considered recreation impacts in project planning, but concluded none of the action alternatives would significantly alter recreation opportunities at each lake.
National Historic Preservation Act of 1966. Federal agencies are required under Section 106 of the NHPA of 1966, as amended, to “take into account the effects of their undertakings on historic properties” and consider alternatives “to avoid, minimize or mitigate the undertaking’s adverse effects on historic properties” [(36 CFR 800.1(a-c)] in consultation with the SHPO officer and appropriate federally-recognized Indian Tribes (Tribal Historic Preservation Officers - THPO) [(36 CFR 800.2(c)].
Other applicable cultural resources laws, rules, and regulations will inform how investigations and evaluations will proceed throughout the study and implementation phases (e.g., Archeological and Historic Preservation Act of 1974, National Environmental Policy Act of 1969, Native American Graves Protection and Repatriation Act, Engineer Regulation 1105-2-100).
The District initiated consultation with SHPO and tribes in a letter dated June 20, 2017, inviting them to identify cultural and historic preservation issues early in the plan formulation process. The District received no responses pertaining to project concerns. In accordance with Section 106 of the NHPA, the District is consulting with the Iowa SHPO, as well as 33 federally-recognized Native American Tribes with an interest in the project area, regarding the project’s potential to impact historic properties (Appendix A). Based on background research and correspondence with the SHPO, the District proposed a finding of No Adverse Effects in a letter dated June 29, 2018. This District awaits responses to this proposed finding
Archaeological and Historic Preservation Act. The Archaeological and Historic Preservation Act of 1974 amends the 1960 Reservoir Salvage Act by providing for the preservation of significant scientific, prehistoric, historic and archaeological materials and data that might be lost or destroyed as a result of flooding, the construction of access roads, relocation of railroads and highways, or any other federally- funded activity associated with the construction of a dam or reservoir. The Recommended Plan would not create any new dams, raise water levels beyond the existing conditions, or increase flooding. No impact to any project significant scientific, prehistoric, historic, and archaeological materials and data is anticipated.
Fish and Wildlife Coordination Act. The FWCA requires Federal agencies that are impounding, diverting, channelizing, controlling, or modifying the waters of any stream or other water body to consult with the USFWS and appropriate state fish and game agency to ensure wildlife conservation receives equal consideration in the development of such projects. The USFWS and the Iowa DNR have been involved in the planning process of this study since the initial stages participating in the planning process, data collection efforts, providing input and comment throughout the process. By email, dated May 11, 2018, Kraig McPeek, Field Supervisor, Illinois and Iowa ES Field Office, USFWS, stated a FWCA Coordination Act Report was not required for this project. Therefore, this project is in full compliance with the FWCA.
Advisory Circular 150/5200-33A – Hazardous Wildlife Attractants on Near Airports. The advisory circular provides guidance on locating certain land uses having the potential to attract hazardous wildlife to or in the vicinity of public-use airports. The circular provides guidance on wetlands in and around
EA-91 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment airports and establishes notification procedures if reasonably foreseeable projects either attract or may attract wildlife.
In response to the advisory circular, the U.S. Army as well as other Federal agencies, signed a Memorandum of Agreement (MOA) with the Federal Aviation Administration (FAA) to address aircraft- wildlife strikes. The MOA establishes procedures necessary to coordinate their missions to more effectively address existing and future environmental conditions contributing to aircraft-wildlife strikes throughout the U.S.
The Red Rock Dam is located 1.85 miles from the Pella Municipal Airport and 8 miles from the Knoxville airport. The Saylorville Dam is located 10.88 mile from the Des Moines International Airport. In accordance with the advisory circular, the District will provide the FAA a copy of this EA to address potential hazardous wildlife attractants near the airports with respect to the proposed action. Because the proposed project would not be actively managing wetland habitat in the airports’ runway zones, the District determined there would be no adverse impacts or increased likelihood of bird/airplane accidents.
F. RELATIONSHIP BETWEEN SHORT-TERM USE AND LONG-TERM PRODUCTIVITY
There would be no short-term use issues with this project. The District anticipates long-term FRM benefits as well as long-term productivity for natural resource management. Long-term productivity would be enhanced through improved natural resource inspired lake and river levels during non-flood periods.
G. RELATIONSHIP TO LAND USE PLANS
The current land use plans at each reservoir would not change because the project is compatible with all existing land use plans within the project area. The land use remains the same because the project would not add or remove any mission elements.
This project is compatible with and supports the Red Rock Mater Plan (2015) and the Saylorville Lake Master Plan (2016).
A Real Estate review of easements and other lands within the study area determined that existing easements are sufficient to meet the needs of the recommended plan and that no additional real estate interests are needed for Alternative 6.
H. IRREVERSIBLE AND IRRETRIEVABLE COMMITMENT OF RESOURCES
The Recommended Plan would not entail significant irretrievable or irreversible commitments of resources. Long-term sustainability actions were included for the benefit of environmental resources.
I. INDIRECT EFFECTS
Indirect effects, as defined by the CEQ regulations, are “caused by the proposed action and occur later in time or farther removed in distance, but are still reasonably foreseeable. Indirect effects may include growth inducing effects and other effects related to induced changes in the pattern of land use, population density, or growth rate, and related effects on air and water and other natural systems, including ecosystem” (40 CFR 1508.8). Indirect effects differ from direct impacts associated with the construction and operation of the proposed project and are caused by an action or actions having an established
EA-92 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment relationship or connection to the proposed project. Indirect effects can be linked to direct effects in a causal chain, which can be extended as indirect effects producing further consequences.
As previously discussed, implementation of the proposed action would directly result in a net beneficial impact to FRM and natural resources along the Des Moines River. In addition, the proposed project’s ecosystem measures may result in benefits extending farther outside the study area for several notable environmental resources such as migrating birds.
J. CUMULATIVE IMPACTS
The CEQ regulations define a cumulative impact as an effect which results from the incremental impact of the action when added to other past, present, and reasonably foreseeable future actions regardless of what agency (Federal or non-Federal) or person undertakes such other actions (40 CFR Section 1508.7). Relatively minor individual impacts may collectively result in significant cumulative impacts. Project- related direct and indirect impacts must be analyzed in the context of non-project-related impacts affecting the same resources. Cumulative impacts are the incremental impacts the project has, directly or indirectly, on a resource in the context of other past, present, and future effects on the resource from related or unrelated activities. Unlike direct impacts, quantifying cumulative impacts may be difficult since a large part of the analysis requires forecasting future trends of resources in the study area and future projects that may impact these resources.
The initial step of the cumulative impacts analysis uses information from the evaluation of direct and indirect impacts in the selection of environmental resources that should be evaluated for cumulative impacts. The proposed action would not contribute to a cumulative impact if it would not have a direct or indirect effect on the resource. Similarly, CEQ guidance recommends narrowing the focus of cumulative impacts analysis to important issues of national, regional, or local significance. Therefore, the cumulative impact analysis for the Recommended Plan focused on those resources substantially directly or indirectly impacted by the study and resource at risk or in declining health even if the direct/indirect impacts were insignificant.
The cumulative impacts analysis included the resources discussed in this report that may have an impact on the preferred alternative or, the preferred alternative may have on the resource.
Past Actions. Past actions include the construction and operation of the reservoir, the recreation sites surrounding the reservoir, as well as residential, commercial, and industrial facilities throughout the region. All of these developments have had varying levels of adverse impacts on the physical and natural resources in the region. Many of these developments, however, have had beneficial impacts on the region’s socioeconomic resources. In addition, many of the historic impacts have been offset throughout the years by the resource stewardship efforts of the District, the Iowa DNR, and other management partners.
The most significant past action was the construction and development of the Saylorville Lake and Red Rock Reservoirs. This change created new natural and physical conditions, which, through careful management by the District, the Iowa DNR, and other management partners, have created new and successful habitats and other natural resource conditions. The construction of the project also had an impact on cultural resources. Impacts to cultural resources were coordinated with the Iowa SHPO. This coordination included appropriate research and documentation of cultural resources. Since that time, the District, the Iowa DNR, and other management partners have worked to preserve, protect, and document cultural resources within the project boundary. The District and the other management partners have also brought a wide variety of high-quality recreational opportunities to the reservoir.
EA-93 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Present Actions. Existing and future actions also contribute to the cumulative impacts in and around the reservoir. Existing and future actions include the operation of project facilities, upgrades and maintenance of recreation sites, as well as residential, commercial, and industrial development throughout the region. Continued project operations would result in the sustained maintenance and development of recreational facilities. These facilities would enhance the recreational offerings made by the District and other management partners. Such improvements would result in varying levels of impacts to the surrounding resources. Similarly, surrounding residential, commercial, and industrial development could result in varying levels of adverse impacts to many resources. Within the project boundary, adverse impacts would be offset through resource stewardship efforts.
Currently the Missouri River Energy Services is developing a new 36.4 megawatt hydroelectric facility at Lake Red Rock.
Future Actions. The Preferred Alternative would provide updated FRM and improved natural resource management capabilities to the region. Other actions in the region would be climate change, improved infrastructure, regional growth, and urbanization. All of these actions are speculative. The District’s FRM mission will be challenging, but flexible to accommodate system wide changes in the future.
The programmatic approach to project management, would allow for future development plans and mitigation responses to be adapted to address any adverse actions. This would allow the District and other management partners at Saylorville Lake to continue to reduce the contribution of its activities to regional cumulative impacts through proactive actions and adaptive resource management strategies.
K. ADAPTIVE MANAGEMENT AND MONITORING PLAN
A fully vetted monitoring and adaptive management is not required for this water regulation plan update. If the FRM efforts need modification, there is a formalized procedure to request a deviation from the Corps’ Mississippi Valley Division for the approved plan.
For the natural resource management aspect of operating within the conservation bands, the District would continue its existing practice of meeting with its resource partners on an annual basis. During this meeting the District and agencies discuss the current year’s desired outcomes based on the ability to manage with a drier or wetter than normal conditions. They also discuss the next year’s management goals. If conditions are right, the District would operate the dams to the best of their ability to meet these goals. Appendix C contains the final report from the Des Moines Sustainable Rivers Program. This report offers management scenarios fitting with the proposed conservation operating bands. The District would also implement other operating scenarios within the conservation bands not in the plan if there is a potential for natural resource benefit.
L. RISK AND UNCERTAINTY
Risk is defined as the probability or likelihood for an outcome. Uncertainty refers to the likelihood an outcome results from a lack of knowledge about critical elements or processes contributing to risk or natural variability in the same elements or processes. Throughout project planning, risk and uncertainty were identified. Risk informed decisions were made regarding the reliability of estimated benefits and the costs of alternative plans.
Measures were developed to manage risk, expanding on and referencing successful similar work completed by previous water regulation manual updates nationwide. Experience from previous projects
EA-94 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment helped in the identification of possible risks and decrease uncertainty in plan formulation. No measure or alternative in the Recommended Plan is burdened by significant risk or uncertainty regarding its eventual success. Significant risks were avoided by using proper design, appropriate selection, and correct seasonal timing of applications. Risks were also managed through extensive coordination with other agencies and District experts.
The District has conducted 3 years of planned deviations to the water control plans to test their acceptability and effectiveness. These deviations helped the District with their alternative formulation as well as strengthened the hydraulic modelling in the alternative evaluation. Future climate and precipitation amounts are the principal sources of uncertainty.
M. CONCLUSIONS
The Recommend Plan selected for the Des Moines River Master Water Control Study is Alternative 6 which is designed to meet the Project’s goals of strengthen the flood risk management measures by reducing risks to life, health, and safety of residents due to flooding events along the Des Moines River. Additionally, a reduction in future flood risk to critical infrastructure, commercial, residential and agricultural areas along the Des Moines River.
The Recommended Plan has positive impacts on the hydrology/hydraulics of the system by conserving reservoir storage through earlier releases of water during small scale flood events, thereby reducing flood risk during long duration, large magnitude flood events resulting from multiple storms.
The Recommended Plan would incorporate environmental sustainability by operating the Saylorville and Red Rock outflows in conservation bands when flooding is not a concern, creating a naturally functioning wetland, lake, and river ecosystem. Further the recommended plan would create aquatic and riparian habitat conditions required by numerous fish and wildlife species living in or migrating through the system. Implementation would not impact flood risk or floodplain development and would not cause negative environmental impacts.
The Recommended Plan has positive impacts on recreational areas as they are projected to be inundated less frequently potentially reducing operational costs.
Further, this Project is consistent with and fully supports the authorized purposes of Saylorville Lake and Lake Red Rock.
VII. LITERATURE CITED
Apogee Research, Inc & U.S. Army Engineer Institute for Water Resources. 1995. Resource significance in environmental project planning. U.S. Army Corps of Engineers, Water Resources Support Center, Institute for Water Resources; Springfield, VA. National Technical Information Service, distributor, Alexandria, VA. 58pp.
Braatz, D. T., Halquist, J. B., Warvin, R. J., Ingram, J., Feldt, J. J., & Longnecker, M. S. (1997). Moving From the Traditional to the Technically Advanced. In NWS Hydrologic Products & Services. N.p.: NOAA. Retrieved from http://www.nws.noaa.gov/oh/hrl/papers/ams/amspaper.htm
Dix, Mary Ellen, Marilyn Buford, Jim Slavicek, Allen M. Solomon, and Susan G. Conard. 2009. Invasive Species and Disturbances: Current and Future Roles of Forest Service Research and
EA-95 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
Development. A Dynamic Invasive Species Research Vision: Opportunities and Priorities 2009– 29. pp 91-102.
Ecological Specialists, Inc. 2015. Downtown Des Moines, Iowa Unionid Survey, Des Moines and Raccoon Rivers, Prepared for: City of Des Moines Des Moines, IA, Ecological Specialists, Inc. is located in O’Fallon, Missouri. 35pp.
Green, David I.S., Benjamin Noack, Grace M. Wilkinson, William G. Crumpton, Chris R. Rehmann. 2018. Des Moines River Water Quality Monitoring Network Annual Report – 2017. Iowa State University Department of Ecology, Evolution, and Organismal Biology and Department of Civil, Construction and Environmental Engineering. 125 pp.
Harms, Tyler, Dinsmore, S.J., Kinkead, K.E. 2013. Evaluate Indicators of Environmental Sensitivity with Respect to Native Flora and Fauna – Saylorville Lake Project, Iowa. Final Report. Iowa State University. 18pp.
Iowa Climatology Bureau. 2010. (http://www.iowaagriculture.gov/climatology.asp) in the Iowa Climate Change Impacts Committee. 2010. Climate change impacts on Iowa. January 1, 2011 Report to the Governor and the Iowa General Assembly. http://www.iowadnr.gov/Conservation/Climate- Change.
Iowa Department of Natural Resources. 2016. Iowa’s Section 303(d) Impaired Waters Listings. http://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Monitoring/Impaired- Waters. 2016 305(b) Assessment Summary. 2016 Impaired Waters List: Approved by U.S. EPA January 16, 2018
2015. .Long-Term Vision for Assessment, Restoration, and Protection under the Clean Water Act Section 303(d) Program. Updated October, 2015
Iowa State University, Department of Natural Resource Ecology and Management and Iowa Department of Natural Resources. 2013. Multiple Species Inventory and Monitoring Final Report (MSIM) – Evaluate Indicators of Environmental Sensitivity with Respect to Native Flora and Fauna – Saylorville Project, Iowa.
Kallemeyn, Larry. 1983. Status of the Pallid Sturgeon: Scaphirhynchus albus. Fisheries, Vol 8, Issue 1. 9pp.
Kunkel, K. E. Stevens, L. E. Stevens, S. E. Sun, L. Janssen, E. Wuebbles, D. Hilberg, S.D. Timlin, M.S. Stoecker, L. Westcott, N.E. Dobson, J.G. 2013. Regional Climate Trends and Scenarios for the U.S. National Climate Assessment: Part 3. Climate of the Midwest U.S. NOAA Technical Report NESDIS 142-3. Regional Climate Trends and Scenarios for the U.S. National Climate Assessment: Part 3. Climate of the Midwest U.S. NOAA Technical Report NESDIS 142-3. 103pp.
National Audubon Society. 2016. Important Bird Areas Program A Global Currency for Bird Conservation. https://www.audubon.org/
Pryor, S. C., D. Scavia, C. Downer, M. Gaden, L. Iverson, R. Nordstrom, J. Patz, and G. P. Robertson. 2014. Chapter 18: Midwest. Pages 418-440 in J. M. Melillo, T. C. Richmond, and G. W. Yohe,
EA-96 Des Moines River Basin Master Reservoir Regulation Manual Feasibility Report with Integrated Environmental Assessment
eds. Climate change impacts in the United States: The Third National Climate Assessment. U.S. Global Change Research Program, doi:10.7930/J0J1012N.
Poole, K. Elizabeth and John A. Downing. 2004. Relationship of declining mussel biodiversity to stream-reach and watershed characteristics in an agricultural landscape. J.N. Am. Benthol. Soc. 23(1):114-125. 12pp.
Rosburg, Thomas. 2013. Natural Resources Inventory Of The City Of Des Moines Parks And Conservation Land Report to: City of Des Moines Parks and Recreation Department 3226 University Avenue, Des Moines, IA 50311. https://www.dmgov.org/Departments/Parks/Pages/NaturalResourcesandWildlife.aspx
Soil Science Division Staff. 2017. Soil survey manual. C. Ditzler, K. Scheffe, and H.C. Monger (eds.). USDA Handbook 18. Government Printing Office, Washington, D.C.
U.S. Army Corps of Engineers. 2015. Lake Red Rock Project Master Plan. Rock Island, IL. 246 pp.
U.S. Environmental Protection Agency. 2018. US Environmental Protection Agency’s Envirofacts website. http://www.epa.gov/enviro/
U.S. Environmental Protection Agency.2017. EJSCREEN EPA’s Environmental Justice Screening and Mapping Tool (Version 2017). https://ejscreen.epa.gov/mapper/
U.S. Fish and Wildlife Service. 2018. Information for planning and consultation webpage. https://ecos.fws.gov/ipac/
U.S. Geological Survey. 2011. National Land Cover Database (NLCD) Land Cover Collection. https://catalog.data.gov/dataset/national-land-cover-database-nlcd-land-cover-collection
United States Census Bureau. 2018. American FactFinder web application. Accessed online at http://factfinder2.census.gov/faces/nav/jsf/pages/searchresults.xhtml?refresh in May, 2018.
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Des Moines River, Saylorville Lake, & Lake Red Rock
DRAFT FINDING OF NO SIGNIFICANT IMPACT
The U.S. Army Corps of Engineers, Rock Island District proposes to upgrade the Des Moines River Basin Master Reservoir Regulation Manual (Project).
The District determined the proposed Project meets the objectives of providing sound flood risk management and natural resources management at Saylorville Lake, Polk County, Iowa and Lake Red Rock, Marion County, Iowa. The other alternatives do not meet the objectives of a revised plan or would not be as effective as the current water regulation plan.
I have reviewed the information provided in the accompanying environmental assessment, along with data obtained from cooperating Federal, state, and local agencies, and from the interested public. Based on this review, I find the proposed Project would not significantly affect the quality of the human environment. Therefore, it is my determination that an Environmental Impact Statement is not required. The District would re-evaluate this determination if warranted by later developments.
Alternatives considered along with the preferred action were:
• Alternative 1 – No Federal Action • Alternative 2 – This alternative represents the regulation strategy utilized during the 2016, 2017, and 2018 growing seasons (conducted as planned deviations to the existing water control plans). • Alternative 3 – Reduce the frequency and magnitude of reservoir balancing while concurrently allowing for earlier increases in outflow from Lake Red Rock to preserve flood storage. • Alternative 3a – Sustain all of the modifications implemented in Alternative 3, with the only modification being a transition period between growing season and non-growing season maximum releases when Lake Red Rock is above elevation 750 feet on May 1. • Alternative 3ai – Sustain the measures implemented in Alternatives 3 and 3.A. above, with the only modification being to Lake Red Rock Major Flood Operations. • Alternative 3b - Sustain the measures implemented in Alternative 3 above, with the only modification being to increase the maximum Red Rock growing season release to 25,000 cfs when Lake Red Rock is between elevation 750 and 770 feet (below elevation 750 feet, release rate remains 18,000 cfs). • Alternative 3c - Sustain the measures implemented in Alternative 3 above, with the only modification being the implementation of a 30,000 cfs year round maximum release rate at Lake Red Rock matching the non-growing season release.
• Alternative 4 – Modification of only the Lake Red Rock Water Control Plan to facilitate maximization of hydropower operations at Lake Red Rock by the Missouri River Energy Service Corporation. • Alternative 5. – Utilization of the reservoir elevations on May 1 as a trigger for following either a “wet” or “dry” schedule of maximum releases during the growing season. • Alternative 5a - Utilization of the reservoir elevations on May 1 as a trigger for following either a “wet” or “dry” schedule of maximum releases during the growing season. • Alternative 5b - Sustains all of the measures implemented by Alternative 5a, with the only modification being to Lake Red Rock Major Flood Operations. • Alternative 6 – Minor modification of Alternative 2 as applicable to Saylorville and Alternative 3B as applicable to Lake Red Rock.
Factors considered in determining an Environmental Impact Statement is not required are:
• The Project would improve flood risk management and natural resource management capabilities at Saylorville Lake and Lake Red Rock.
• The Project meets the goal of providing, life, healthy, and safety conditions at both reservoirs.
• The District does not anticipate any significant social, economic, or environmental impacts as a result of this action.
• The Project was reviewed for known and unknown cultural resources. Based on investigation results, the Project will result in No Adverse Effects. A letter making this historic properties determination has been submitted to the State Historic Preservation Officer, Tribal Historic Preservation Officer or other representatives of 33 Native American tribes with an interest in this area, and other stakeholders for review and comment prior to the Project’s implementation.
______Date Steven M. Sattinger Colonel, US Army Commander & District Engineer