West Sacramento Levee Improvement Program Alternatives Analysis Draft

ALTERNATIVES ANALYSIS

WEST SACRAMENTO AREA FLOOD CONTROL AGENCY LEVEE IMPROVEMENT PROGRAM

YOLO COUNTY, CA

13 November 2009

2365 Iron Point Road, Suite 300 Folsom, CA 95630

Table of Contents

WEST SACRAMENTO LEVEE IMPROVEMENT PROGRAM ALTERNATIVES ANALYSIS

1.0 Authority ...... 1 2.0 Purpose And Scope ...... 1 3.0 Prior Studies, Reports And Existing Water Projects ...... 1 4.0 Plan Formulation ...... 4 4.1 Assessment of Water and Related Land Resources Problems and Opportunities4 4.1.1 National Objectives ...... 4 4.1.2 Public Involvement and Concerns ...... 5 4.1.3 Existing Conditions ...... 6 4.1.4 Future Without Project Conditions ...... 8 4.1.5 Problems and Opportunities ...... 10 4.1.6 Planning Objectives ...... 15 4.2 Alternative Plans ...... 15 4.2.1 Single Deficiency Mitigation Measures ...... 16 4.2.2 Levee Deficiency Groups ...... 22 4.2.3 Combinations of Mitigation Measures for Levee Deficiency Groups ...... 22 4.2.4 Mitigation Alternative Selection Process ...... 22 4.2.5 Mitigation Alternatives Selected for Further Consideration ...... 24 4.2.6 Mitigation Alternative Evaluation ...... 24 5.0 Plan Selection ...... 26 6.0 Plan Uncertainty ...... 26 7.0 Description of the Selected Plan ...... 26 8.0 Implementation Requirements ...... 27 9.0 Recommendations ...... 28 10.0 References ...... 29

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List of Figures Figure 1 – Study Area Figure 2 – Land Use and Structure Distribution in West Sacramento Figure 3 – West Sacramento Basin Levee Reaches Figure 4 – Through-Seepage Deficiencies (Graphical Approximation) Figure 5 – Slope Stability Deficiencies (Graphical Approximation) Figure 6 – Preliminary Seismic Vulnerabilities (Graphical Approximation) Figure 7 – Erosion Deficiencies (Graphical Approximation) Figure 8 – Freeboard Deficiencies (200-Year WSEl) (Graphical Approximation) Figure 9 – Geometry Deficiencies (Graphical Approximation) Figure 10.1 – Utility Levee Encroachments Figure 10.2 – Utility Levee Encroachments Figure 11 –Levee Deficiencies (Graphical Approximation) Figure 12 – Levee Deficiency Groups (Graphical Approximation) Figure 13 – Sacramento River West North Levee – Alternative 1 Figure 14 – Sacramento River West North Levee – Alternative 2 Figure 15 – Sacramento Bypass – Alternative 1 Figure 16 – Sacramento Bypass – Alternative 2 Figure 17 – Sacramento Bypass – Alternative 3 Figure 18 – Yolo Bypass – Alternative 1 Figure 19 – Yolo Bypass – Alternative 2 Figure 20 – Yolo Bypass – Alternative 3 Figure 21 – Port North Levee – Alternative 1 Figure 22 – Port South Levee – Alternative 1 Figure 23 – Port South Levee – Alternative 2 Figure 24 – DWSC West – Alternative 1 Figure 25 – DWSC West – Alternative 2 Figure 26 – DWSC West – Alternative 3 Figure 27 – DWSC West – Alternative 4 Figure 28 – DWSC East – Alternative 1 Figure 29 – DWSC East – Alternative 2 Figure 30 – DWSC East – Alternative 3 Figure 31 – Sacramento River West South Levee – Alternative 1 Figure 32 – Sacramento River West South Levee – Alternative 2 Figure 33 – Sacramento River West South Levee – Alternative 3 Figure 34 – South Cross Levee – Alternative 1 Figure 35 – South Cross Levee – Alternative 2 Figure 36 – South Cross Levee – Alternative 3 Figure 37 – South Cross Levee – Alternative 4

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List of Tables Table 1 – Summary of Existing Social-Economic Resources and Relevant Indices Table 2 - Summary of Levee Deficiencies and Measures Table 3 – Reach Summary Table 4 – Single Deficiency Mitigation Alternatives Table 5 – Deficiency Groups (200-Year Water Surface Elevation) Table 6 – Deficiency Group Mitigation Alternatives Table 7 – Selected Alternatives Summary Table 8 – Alternatives Evaluation

Appendices Appendix A – Public Comments Appendix B – Alternative Cost Opinions

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WEST SACRAMENTO LEVEE IMPROVEMENT PROGRAM ALTERNATIVES ANALYSIS

1.0 Authority This draft report was prepared as an interim response to the study authorization contained in the contract awarded to HDR Engineering, Inc. on 19 July 2006, and amended 27 October 2006, by the City of West Sacramento to provide engineering services for the West Sacramento Levee System – Problem Identification and Alternatives Analysis. In response to the study authority the reconnaissance phase of the study was initiated in July 2006. A draft problem identification report was transmitted to the California State Department of Water Resources (DWR), the United States Army Corps of Engineers Sacramento District (Corps) and the West Sacramento Area Flood Control Agency (WSAFCA) in May 2008. That phase of the study resulted in the finding that there are deficiencies in the existing levee system that make it inadequate for protecting the City of West Sacramento from flooding caused by a 100-yr or 200-yr event, and that an alternatives analysis for upgrading the system to provide protection from the 200-yr event is needed. The City of West Sacramento (The City, hereafter), on behalf of the West Sacramento Area Flood Control Agency (WSAFCA), initiated this phase of the study (alternatives analysis, hereafter) in July 2007. The total cost of the alternatives analysis is being paid by the City.

2.0 Purpose And Scope The purpose of this report is to present the findings of an alternatives analysis for upgrading the West Sacramento levee system to a level that provides protection from the 200-yr flood event. This report analyzes the system problems and opportunities and expresses desired outcomes as planning objectives. Alternatives are then developed to address these objectives. These alternatives include a plan of no action and various combinations of levee upgrade measures. The economic, social, and environmental impacts of the alternatives are then evaluated and a levee system upgrade plan is recommended. This document develops a rationale for adopting the recommended plan but does not address all implementation requirements, including adherence to a design process and set of standards recognized as valid by the relevant state and federal authorities.

3.0 Prior Studies, Reports And Existing Water Projects The following reports are being reviewed as directed in the study authorization:

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Prior Studies and Reports

1. Sacramento River Flood Control Project: Sacramento Urban Area Levee Reconstruction Basis of Design – USACE (November 1989).

The United States Army Corps of Engineers has developed a basis of design (BOD) document to present the results of engineering studies and investigations prior to preparing plans and specification for remedial construction of select levees in the cities of Sacramento and West Sacramento. The BOD includes discussion of previous studies, geology of the region, discussion of subsurface characteristics, design considerations, alternative comparisons and cost estimates.

2. Sacramento Metropolitan Area, California: Feasibility Report, Environmental Impact Statement/Environmental Impact Report – USACE (February 1992).

The Corps has performed a feasibility study to assess the need for additional flood protection, to identify potential alternatives to increase flood protection and to determine Federal interest in the proposed alternatives. The study determined that there was a need for additional flood protection and then provided several potential alternatives which would provide varying levels of flood protection. The alternative which was selected would raise the south bank of the Sacramento Bypass and the east bank of the Yolo Bypass from the Sacramento Bypass south to the Navigation Levee. The proposed alternative would provide 400- year flood protection assuming the proposed dam in Auburn was constructed; however since the Auburn dam was never constructed the alternative only provides 150-year flood protection.

3. West Sacramento Project, West Sacramento, California: Design Memorandum and Environmental Assessment/Initial Study – USACE (May 1995).

The Corps prepared a design memorandum for the flood protection improvements suggested in a previous document titled Sacramento Metropolitan Area, California: Feasibility Report, Environmental Impact Statement/Environmental Impact Report (USACE 1992). The memorandum addressed revisions done to the Sacramento Metropolitan Area, California: Feasibility Report, Environmental Impact Statement/Environmental Impact Report (USACE 1992). It noted that the Auburn Dam was not constructed and, as a result, the final design elevation of the levee was altered. The memorandum presented and described the process for construction and mitigation as well as associated costs.

4. Sacramento and San Joaquin River Basins, California Comprehensive Study: Interim Report – USACE (December 2002).

The Corps prepared a Technical Study Documentation discussing State and Federal legislation comprehensive plans for flood damage reduction and ecosystem restoration along the Sacramento and San

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Joaquin rivers following the floods that occurred in January 1997. This report also reflects that the public’s safety and economic prosperity should not conflict with conserving natural systems. This report goes into more detail on developing a comprehensive and effective plan for flood management, how the system functions, and how it can be improved. The major undertaking of the study was developing the necessary analytical tools to evaluate how changes to the system affected the performance of the system as a whole with respect to reducing flood damages, protecting public safety, and restoring degraded ecosystem. It was intended that the study would ultimately recommend a “Master Plan” for development of integrated flood damage reduction and ecosystem restoration projects throughout the Central Valley. A final study has not been prepared.

5. City of West Sacramento Flood Emergency Preparedness Mapping – Wood Rogers (November 2006).

Wood Rogers prepared an analysis of two hypothetical Sacramento River levee failures: one in the northern area at station 54+00 of Sacramento River North West levee (Figure 3), and one in the southern area at station 287+00 of the Sacramento River West South levee (Figure 3). The analysis determined the rate and depth at which water will flood the City of West Sacramento if a levee failure occurred in these reaches. This analysis can be used to determine an evacuation plan, the extent of property damage and the economic impact of having such a flood.

Existing Water Projects

This study incorporates findings from two studies authorized by the DWR, in partnership with WSAFCA, as part of the Urban Levee Evaluation Program: the Preliminary Geotechnical Data Report (URS, 2007) and the Phase 1 Geotechnical Evaluation Report. These documents characterized stability, seepage, and seismic deficiencies in the levee surrounding the north basin in West Sacramento – that bounded on the north by the Sacramento Bypass, the west by the Yolo Bypass, the south by the barge canal and the east by the Sacramento River.

Some recommendations contained in this alternatives analysis, if implemented, would constitute extensions of recent Corps project work along the Yolo and Sacramento Bypass levees as developed through design efforts documented in the Corps’ 1992 feasibility study and 1995 design memorandum described above. Specifically, Corps levee improvement work associated with the West Sacramento project Contracts A (Reach: Deep Water Ship Channel West station 00+00 to 12+00 and Reach: Yolo Bypass Station 00+00 to 134+00, Figure 3) would be upgraded to correct continuing seepage deficiencies along the Yolo Bypass. Proposed improvements along the Sacramento Bypass would upgrade and extend the Contract B improvements (Reach: Sacramento Bypass stations 00+00 to 60+00) east to Harbor Boulevard. In addition,

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recommendations are made in this document that would extend levee upgrades planned at RM 57.5 by the Corps under the Sacramento River Bank Protection Program. Specifically, bank erosion mitigation planned near station 310+00 of Sacramento River South West (Figure 3) levee would be augmented by upgrades recommended in this document for levee reaches extending west along the barge canal and deep water ship channel and south along the Sacramento River.

4.0 Plan Formulation 4.1 Assessment of Water and Related Land Resources Problems and Opportunities Studies indicate that the existing levee system surrounding the City of West Sacramento is deficient and that the consequences of levee failure during a major flood event would be significant. Data collected as part of the City’s ongoing levee evaluation program show with reasonable certainty that much of the existing levee system will not contain the 1% annual chance exceedance flood – the general basis for levee certification and accreditation in the National Flood Insurance Program (NFIP). The low level of flood protection provided by the existing system combined with the findings of the Wood Rodger’s inundation study, which predicted flooding depths up to and over 10 ft associated with the 100-yr event, show that improvements to the existing system are needed to reduce the current level of risk to human health and safety, and the adverse economic impact that these flood scenarios would cause. The finding that the existing system should be improved is consistent with that reported in the Sacramento Metropolitan Area, California: Feasibility Report, Environmental Impact Statement/Environmental Impact Report – USACE (February 1992).

The primary challenges that must be faced to improve the existing levee system are minimizing the impact to local communities, and environmental and cultural resources within the system footprint. Although disruptive, property acquisition and resident re-location are sometimes necessary as part of levee improvements. In several portions of the system it appears feasible to couple levee system upgrades with environmental restoration and enhancements, and to improve public recreation opportunities in areas adjacent to the Sacramento River.

4.1.1 National Objectives The U.S. Army Corps of Engineers planning process is grounded in the Principles and Guidelines promulgated in 1983 as set forth in the two documents titled, Economic and Environmental Principles for Water and Related Land Resource Implementation Studies and the Economic and Environmental Guidelines for Water and Related Land Resource Implementation Studies. Together, these guidelines establish a framework for the Corps to balance economic development and environmental needs while developing water resource planning studies.

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The Principles and Guidelines require that Federal water and related land resources projects directly contribute to National Economic Development (NED) in a manner consistent with protecting the Nation’s environment. Contributions to NED are achieved by increasing the net value of the Nation’s output of goods and services, expressed in monetary units. NED contributions must also consider environmental quality as pertaining to the effects of proposed changes on ecological, cultural, and aesthetic attributes of significant natural and cultural resources.

Federal projects associated with ecosystem restoration must directly contribute to the National Ecosystem Restoration (NER) outputs by restoring degraded ecosystem structure, function, and dynamic processes to a less degraded, more natural condition. Contributions to NER are increases in ecosystem value and productivity, and are measured in non-monetary units such as average annual habitat units or acres.

4.1.2 Public Involvement and Concerns WSAFCA and the City have made reducing flood risk in their community a priority. In order to generate revenue for the evaluation and improvement of their levees, WSAFCA held a Proposition 218 election. Proposition 218 authorizes a government agency to fund public improvements by levying an assessment on the properties that would receive a special benefit from the improvements. Between March and June of 2007, WSAFCA hosted a series of four public workshops to inform the public of the known flood risks facing the community and the benefit of the assessment. On 16 July 2007, WSAFCA announced that property owners in West Sacramento approved the annual flood protection assessment.

The City Council for West Sacramento reaffirmed its General Plan policy of achieving a minimum level of 200 year protection for the City during this same timeframe by adopting Ordinance 07-11 during a City Council Meeting on 2 May 2007. The Council also established an in lieu fee on future development to provide additional resources for levee improvements.

In association with these actions, WSAFCA and the City have initiated programmatic investigations of the levees protecting the City in order to characterize the existing conditions and establish the program of improvements necessary to provide protection against the 200 year flood event. One of the studies initiated was a Programmatic Environmental Impact Report (PgEIR) for the levee improvement program. A public scoping workshop was held in association with this study on 13 November 2007.

A transcript of recorded concerns, including details about the origin of the comments can be found in Appendix A. A summary of concerns expressed by the public about the levee improvement program is included below.

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Summary Comments

 Corps certification and FEMA accreditation should be considered in relation to proposed alternatives  Address in detail how seepage and stability will be addressed  Address growth inducing impacts  Address how project spoils and fill will be evaluated  Address how modification of flood control structures will accommodate intake structures  The South River Road Pump Station, located south of the South Cross levee and, thus outside of the City’s levee system, provides service to the City of West Sacramento and should be included in levee system evaluation  The City’s flood control plans should be coordinated with Yolo County’s Integrated Regional Water Management Plan  Levee system evaluation should include assessing potential impacts to the Lower Northwest Interceptor  What impact proposed upgrade alternatives may have on wetland habitat and growth inducement should be evaluated  Wetland mitigation should be evaluated as off-site mitigation

 The area known as the ‘Notch’ should be considered for protection by an expanded levee system

4.1.3 Existing Conditions General Description

The City of West Sacramento is located along the shores of the Sacramento River within the central region of the Sacramento River Valley. It is located directly across the river from the City of Sacramento, the state’s capitol. The Sacramento River is the main drainage for the area and flows generally north to southeast from the Klamath mountains to the San Francisco Bay Area.

The West Sacramento basin is bounded by the Sacramento Bypass on the north, the Sacramento River on the east, the Yolo Bypass and the Sacramento Deep Water Ship Channel (DWSC) on the west and the South Cross levee on the south (Figure 1 and Figure 3). The levee system is a part of the Sacramento River Flood Control Project (SRFCP) and includes over 50 miles of levees in Reclamation District (RD) 900, RD 537, Maintenance Area 4, and the DWSC.

The basin is divided into the north and south basins. The north basin is a ring levee bounded by the Sacramento Bypass levee on the north, the Port North levee on the south, the Yolo Bypass levee on the west

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and the Sacramento River West North levee on the east. The south basin is an ‘open’ ring levee that is bounded on the north by the Port South levee, the east by the Sacramento River West South levee. The South Cross levee and the Deep Water Ship Channel West levee provide some flood protection to the basin, but the Deep Water Ship Channel, which converges with the Yolo Bypass approximately 18 miles south of the South Cross levee, provides a hydraulic pathway for floodwaters to encroach into the south basin via backwatering during high stage events in the Yolo Bypass.

Geology and Morphology

The primary geological features in the region are the Sierra Nevada mountain range to the east, the Coastal range to the west, and the north Central Valley between. The geomorphology of the north Central Valley was created primarily by the drainage and erosive action of waters discharging from these flanking mountain ranges and the associated transport and deposition of sediments into the lower valley. The Sacramento River is the primary conveyance for these sediments and sea level fluctuations over geologic time have modified the relative rates of sediment scour and deposition in the system. These mechanisms have filled the Central Valley with interbedded sequences of alluvial, basin, and delta sediments extending to a depth of about 8000 feet. The West Sacramento basin is underlain by quaternary alluvial deposits that are partly covered by Holocene crevasse splays and overbank deposits.

Hydrology and Hydraulics

The hydrology and hydraulics of the Sacramento River and its tributaries control the water surface elevations of importance to the West Sacramento levee system. Flood stage flows in two bypasses – the Sacramento bypass and the Yolo bypass – also impact the system.

Water surface elevations used for this study were obtained from the Hydraulics Report for the City of West Sacramento Levee Alternatives Analysis (MBK, 2007). The MBK version of the Sacramento and San Joaquin River Basin Comprehensive Study (Comp Study) Sacramento UNET model adopted for the Natomas Levee Evaluation was used for this analysis. UNET is a one-dimensional unsteady open-channel flow model with the ability to simulate exchange of flow over levees with storage areas. The software was developed by and is supported by the Corps’ Hydrologic Engineering Center.

The Corps previously developed inflows to the Sacramento river system by modeling runoff from storms centered at various points within the larger drainage basin. Inflows for this study were based on two storm centerings that created the peak system inflows: one centered over Sacramento and one over the Feather River at Shanghai Bend.

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Key model assumptions included the following: 1) American River inflows (145,000 cfs for the 100-yr event and 160,000 cfs for the 200-yr event) and 2) levee overtopping permitted, but not subsequent levee failure.

4.1.4 Future Without Project Conditions The City of West Sacramento is comprised of a network of environmental, cultural, and socio-economic resources. Together, these resources represent an important part of the larger regional community. This section provides a summary of existing resources in the West Sacramento community and projections of the future nature of these resources. Access to and the functionality of the resources and systems described in the following sections could potentially be jeopardized as a result of a failure in the flood protection system.

Social-Economic Resources

The West Sacramento study area accommodates a diverse business and industrial culture, employs thousands, and is home to over forty-thousand residents (Figure 2). A summary of existing social-economic resources and relevant indices are provided in Table 1.

Table 1 – Summary of Existing Social-Economic Resources & Relevant Indices Category Value Population 44,162 (Year: 2007)* Employed (as 2000) 34,205 Jobs*** in West Sacramento Income Median Household (2007)*: $38,609 Per Capita (2007)*: $17,709 Number of Housing Units 12,677* Median Home Price $99,900** Transportation Infrastructure Interstates: I-80, I-5, Business 80 Highways: US 99, US 50, State 84 and 275 Commercial and Industrial Structures 734*** Public Structures 46*** Public Parks 145 acres (27 facilities)**** Source: City of West Sacramento Website. *Source: Sperling’s Best Places **Source: 2000 Census ***Sacramento Area Council of Governments ****City of West Sacramento Parks Website

The study area includes several categories of critical infrastructure including several facilities unique to the City of West Sacramento. A list of critical and unique infrastructure facilities follows:

 Emergency Services – The study area includes 5 fire departments and 2 police facilities. One facility houses the City of West Sacramento Police Department; while, the second facility is the primary training facility for the California Highway Patrol. Since 1974, the CHP Academy has been located on a 457-acre site in Yolo County. The present facility is one of the most modern and complete law enforcement training academies in the United States. The Academy will accommodate

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280 students in dormitory rooms and includes a dining facility designed to seat 400 persons. There are seven classrooms designed to accommodate a total of 362 students.

 Water Infrastructure – The City’s potable water supply is generated by the Bryte Bend Water Treatment Plant along the Sacramento River. This facility is located within the Sacramento River West North Levee reach and has a capacity of 58 MGD. The City’s wastewater treatment needs are served through the Lower Northwest Interceptor which conveys wastewater from Natomas through West Sacramento to a treatment plant in Elk Grove. The interceptor has a capacity of 221 MGD and is owned and operated by the Sacramento County Regional Sanitation District.

 Schools – The study area includes 12 schools.

 Rail Commerce - According to the Sacramento Area Council of Governments (SACOG), approximately 9.3 million tons of rail freight valued at approximately $5 billion travels through West Sacramento annually. Currently, no viable alternate east-west rail alignment connects the San Francisco Bay Area and the Port of Oakland to the rest of the country.

 Truck Traffic - The SACOG study also indicates that trucks on I-80 and US-50 carry more than 20 million tons of cargo valued at over $63 billion through West Sacramento annually.

 Water-Borne Commerce - The Port of Sacramento is expected to process 1.3 million tons of cargo in State FY 2008/2009.

 US Postal Service – West Sacramento is the home of a Regional Distribution Center for the US Postal Service. This Center employs 1,300 individuals who process up to 900,000 pieces of mail per day for the Sacramento region.

 Major Firms  United Parcel Service  Cal Fed Bank  Raley's / Bel Air  Viking Freight System, Inc.  Dade MicroScan  Fleming Foods  First Health Corporation  City of West Sacramento  Farmer's Rice Cooperative  Treasure Chest Advertising Co.  Roadway Express, Inc.  Clark Pacific  MTS Inc./Tower Records  Nor-Cal Beverages

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 Tony's Fine Foods  Idexx Veterinary Services, Inc./CVD  McKesson Drug Co.  Flowmaster  KOVR-13  Rex Moore Electrical  Crum & Crum  Williams Communication

Future Conditions

Residential, commercial, and industrial growth is expected to continue in the study area. In 2002, the Sacramento Area Council of Governments (SACOG) framed a discussion about long-range regional development scenarios. According to SACOG projections, West Sacramento will grow at a steady rate over the next 50 years, adding 20,000 residential units by 2030 and 33,000 by 2050. SACOG also forecasts growth in job opportunities by adding 30,000 new jobs by 2030 and 41,000 new by 2050.

This prognostication highlights the important role the City of West Sacramento will continue to play in the regional economy and in the quality of life this portion of the Central Valley offers to many. The preservation of what the City provides, and the likelihood that it will realize the positive changes predicted, are dependent on community stability and the perception within the business sector that investments here are sustainable. The confidence and sense of security that current and future residents have, both of which are key to realizing these ends, are in turn dependent on the City having a robust flood protection system. Anything less will jeopardize the citizens, resources, and viability the City currently provides to the region, and what it is able to in the future.

4.1.5 Problems and Opportunities The City of West Sacramento (City) has embarked upon a comprehensive evaluation of the levees that protect the City and the surrounding areas. As part of this evaluation, the City has hired HDR to perform a comprehensive levee evaluation by identifying the existing levee deficiencies and potential mitigation alternatives. While identifying potential mitigation alternatives, HDR has noted where opportunities may exist for enhancing riverside recreation and/or restoring riparian habitat in conjunction with potential future upgrades to the levee system.

HDR has assembled a number of sub-consultants with expertise in specific fields of study to assist in these evaluations. HDR and the team of sub-consultants have sought to identify six (6) different types of deficiencies. The types of deficiencies that were evaluated include: seepage (through- and underseepage), stability (steady-state and rapid drawdown), seismic vulnerability, erosion, freeboard and geometry. In

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addition, an inventory of existing levee system encroachments was compiled for use in existing levee upgrade cost opinions.

For purposes of the problem identification and this alternatives analysis the system has been divided into nine reaches as shown on Figure 3: the Yolo Bypass, Sacramento Bypass, Sacramento River West North, and Port North levees; and the Port South, Deep Water Ship Channel East and West, Sacramento River West South and the South Cross levees in the south. With one exception, all levee system deficiencies summarized in the following sections were taken from the West Sacramento Levee Evaluation Project Draft Problem Identification Report, (HDR, 2008). A more detailed analysis of geometry deficiencies was completed for the administrative draft alternatives analysis than was completed in the problem identification study.

Seepage

The levee system was evaluated for seepage deficiencies by using the Corps guideline (ETL 1110-2-569) requiring underseepage to have a vertical gradient less than 0.5. Through-seepage was determined by using computer modeling and visual observations to see if the water surface exits the levee face. That condition combined with an associated stability deficiency is the definition of a through-seepage deficiency. The data are summarized in Table 3 and Figure 4. They show that the Sacramento River West North, and Sacramento River West South, and the Deep Water Ship Channel West levees have a significant amount of underseepage, whereas the other reaches have much less extensive underseepage problems. Through- seepage is prevalent through the Sacramento River West North and Sacramento River West South levees, as well as the Yolo Bypass, Sacramento Bypass and South Cross levees. The other reaches have limited through-seepage problems.

Stability

The levee system has been evaluated for slope stability deficiencies using the Corps guidelines (EM 1110-2- 1913) requiring steady state stability to have a factor of safety above 1.4 and rapid drawdown to have a factor of safety of 1.2. The data are summarized in Table 3 and Figure 5. They show significant extents of the Sacramento River West North and South levees, as well as the Sacramento and Yolo Bypass levees have steady state stability deficiencies; whereas as the other reaches have less or none. Rapid drawdown stability appears to only be a significant problem along the Sacramento River West South levee; however no 200- year rapid drawdown analysis was completed at the time of publication of this document at the following reaches: Sacramento River West North, Sacramento Bypass, Yolo Bypass and South Cross.

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Seismic Vulnerability

Seismic vulnerability has been evaluated for the levee system, but the assessment is not complete as of the publication of this document. Currently, there is not a set of federal standards for evaluating levee seismic vulnerability, and the state standards that exist are in draft form. Moreover, seismic evaluation of the north and south basins in West Sacramento was performed by two geotechnical engineering firms and their methods, including selection of ground motion return period and assumed design water surface elevations, differed. Table 3 and Figure 6 summarize the results of the seismic vulnerability analysis to date. The majority of reaches in the north basin that have been analyzed show some degree of seismic vulnerability; however, over half of the Sacramento River West North levee has not yet been evaluated. The only reach that has been evaluated in the south basin, the South Sacramento River West levee, shows some degree of seismic vulnerability throughout, with the exception of the northern-most stretch along the barge canal.

Erosion

An inventory of current erosion sites has been performed to identify sections of the levee which might incur future stability or seepage problems owing to erosion. The erosion sites have been identified by visual inspection for the whole levee system. Figure 7 summarize the results of this evaluation. The sites have been prioritized based on significance of repairs needed for FEMA certification. High priority sites are those where erosion conditions are likely to compromise the integrity of the existing flood protection structure, and must be repaired for certification. Moderate priority sites must be considered on a case by case basis as to whether repairs are needed for certification. The Sacramento River West North levee has three high priority sites totaling a little over 1100 ft. With the exception of one other long reach along the Yolo Bypass (over 7000 ft long) there were no other high priority sites located in the north basin. Over 4000 ft of the Sacramento River West South levee was identified as having high priority erosion sites and another 1000 ft was identified as having moderate priority erosion sites. The Deep Water Ship Channel East has two moderate erosion sites, one each near the two pump stations. By far the Deep Water Ship Channel West levee has the most significant degree of erosion with 60,000 ft of high priority erosion sites.

Freeboard

A survey of elevations taken at 100 ft. intervals has been completed along the levee crown of the entire levee system. These elevations obtained from the survey have been compared to predicted water surface elevations from a 200-year event to determine the amount of freeboard present. A minimum of 3 ft. of freeboard above the 200-year water surface elevation was the basis of this comparison per guidance provided in the California Department of Water Resources Propose Interim Levee Design Criteria, May 2009. An exception to this rule was made for the Yolo Bypass, for which a 5 ft freeboard criterion was

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applied – the apparent project freeboard design criterion originally applied to that system component. Figure 8 shows the approximate locations of freeboard deficiencies along the levee system. Deficiencies extend in the north basin from the I Street Bridge south to the barge canal (See Figure 3 for barge canal reference), and west to the Deep Water Ship Channel. The deficiencies are discontinuous along this stretch. With a few exceptions, the Port South, South Cross, and Deep Water Ship Channel West levees have freeboard deficiencies throughout.

Geometry

The City has opted to use a modified version of the Corps levee template which requires both landside and waterside slopes to have a 3 (horizontal) to 1 (vertical) side slopes and a minimum crown width of 20 ft. This template is slightly flatter than what the Corps uses as a standard which requires a 3H:1V waterside slope and 2H:1V landside slope, but is consistent with guidance provided by the Corps Sacramento District (REFP10l0, Geotechnical Levee Practice, 4 April 2008). Figure 9 shows the approximate locations where a geometry deficiency has been identified. Most of the levees in the system, with the exceptions of the Port South and Deep Water Ship Channel East levees, have a geometry deficiency and, typically, it is an over- steepened waterside slope that is the problem.

Utilities and Other Encroachments

Utilities and other encroachments represent potential ‘weak links’ in a flood protection system because of potentially flawed boundary conditions where they join with adjacent flood control structures. In addition, their breach can provide a hydraulic conduit through a flood protection system. Finally, many times their integrity is dependent upon routine inspection and maintenance, which may be inadequate due to fluctuations in available resources, human error or negligence. Two steps were taken to characterize the number and type of levee encroachments in the West Sacramento system: cataloguing of all Central Valley Flood Protection Board encroachment permits and completion of a documented field survey of the entire 50- plus mile system. Data collected during the foot survey was compiled using Global Information System (GIS) software and is included in Figures 10.1 and 10.2.

In addition to utility encroachments, a number of critical infrastructure related encroachments are present in the West Sacramento levee system. These include, but are not limited to, the following:

 Union Pacific Railroad Crossing - Yolo Bypass  Jefferson Avenue Bridge – North and South Port Levees  Pioneer Bridge, Tower Bridge, and I Street Bridge – Sacramento River West North levee  Waterside residential homes – Sacramento River West North levee  I-80 Bridge – Sacramento River West North levee

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U.S.A.C.E. Engineering Technical Letter (ETL 1110-2-571) Guidelines for Landscape Planting and Vegetation Management at Levees, Floodwalls, Embankment Dams, and Appurtent Structures, April 3, 2008.

This ETL provides guidelines to assure that landscape planting and vegetation management provide aesthetic and environmental benefits without compromising the reliability of levees, floodwalls, embankment dams, and appurtenant structures. The ETL presents a challenge and an opportunity to WSAFCA. The guidelines provide a set of design criteria that, if applied throughout the flood protection system, will provide a pathway to certification with respect to this particular system component; however, attaining public and agency approval for implementing these design guidelines will be a significant challenge. Recent coordination with the Corps on levee projects in the Central Valley area indicates that the Corps intends to approve levee system modifications that conform with the requirements therein.

Because the ETL was in the draft stage when the analyses for this study were completed, the West Sacramento levees were not evaluated for conformance to the Corps’ ETL. Instead, it was assumed for the purposes of this study that all existing levees were out of compliance with the requirements of the draft ETL. Cost opinions developed as a part of mitigation alternative evaluation include costs for levee clearing and revegetation in conformance with the draft ETL. This approach allows for WSAFCA to plan for levee system upgrades that would meet levee vegetation certification requirements assuming the draft ETL will provide the basis for certification. A review of the final ETL indicates that this planning goal holds for the final ETL as well. It should be noted that a refined evaluation, based on a more comprehensive vegetation data base than was available a the time of this study and a more narrow interpretation of the extents of the levee template, may result in a reduction in the amount of vegetation deficiency defined in the system and associated mitigation costs.

Opportunities

Although the City has a formidable task ahead with regard to finalizing the identification of system deficiencies, assessing potential mitigation alternatives, marshalling necessary funding resources, and constructing system upgrades, it recognizes that these challenges present a number of opportunities to improve community life while increasing the level of protection provided by the flood protection system. The City has identified waterfront recreation and waterfront habitat restoration as two opportunities to be sought in conjunction with improvement of the flood protection system. The Sacramento River West South levee, where a setback levee for much of the reach is included in the recommended alternative, is a good example of where improvement of the flood protection system may provide these additional opportunities.

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The City is actively integrating its understanding of best practices in flood control management with its long-term redevelopment plans for the waterfront, which include mixed use, residential and recreational facilities. In short, certification standards for levee systems are being advanced as a set of general requirements that development interests must conform to – a good example of a community attempting to proactively coordinate flood control management with riverfront development and associated recreation. The City’s flood protection staff routinely meets with potential developers to review conceptual development plans and to provide constructive criticism of these plans with regard to maintenance of an encroachment-free, easily accessible corridor along the flood protection system.

The City recognizes that many times levee system upgrades require mitigation for associated environmental impacts and sees on-site mitigation, or enhancement of nearby riparian habitat as a means of meeting this requirement while preserving the integrity and beauty of the City’s natural shoreline environs.

4.1.6 Planning Objectives Deficiencies identified in the existing flood protection system point to one major planning objective: improving the current level of protection the system provides. That objective is expressed explicitly in two forms: 1) City Ordinance 07-11, An Ordinance the City Council of The City of West Sacramento Enacting Chapter 15.50 Related to 200 Year Flood Protection, which requires the City to establish a flood management program designed to provide a minimum 200-yr flood protection, and 2) the City’s goal of having all reaches of the flood protection system certified under 44 CFR 65.10 and accredited in the Federal Emergency Management Agency’s (FEMA) Flood Insurance Program as providing protection from the 100- yr flood event. Because these objectives relate directly to the health and safety of the community, they are first priority planning objectives of this study.

Two secondary planning objectives of importance to the community are waterfront recreation opportunities and restoration of waterfront habitat. The City is committed to a balance between these three general objectives on a system-wide basis, using a model that has improved flood protection as the objective with first priority and waterfront recreation and habitat restoration alternating as the second priority, depending on the particular location within the system and associated site-specific opportunities.

4.2 Alternative Plans The West Sacramento levee system has a range of deficiencies throughout. For example, some sections have geometry and stability deficiencies, while others have stability, seepage and freeboard deficiencies. There are numerous combinations of deficiencies throughout the system. For each individual type of deficiency there is a range of mitigation alternatives. Similarly, for each levee reach with a set of deficiencies (referred to as a ‘deficiency group’, hereafter) there are a range of mitigation alternatives. This

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section of the report describes the alternatives considered in this study for mitigating the deficiencies identified to date in the West Sacramento levee system, the mitigation alternative selection process, and recommended mitigation alternatives. The section is organized as follows:

1. Single Deficiency Mitigation Measures; 2. Levee Deficiency Groups; 3. Combinations of Mitigation Measures for Levee Deficiency Groups; 4. Mitigation Alternatives Selection Process; 5. Mitigation Alternatives Selected for Further Consideration; and 6. Mitigation Alternative Evaluation.

4.2.1 Single Deficiency Mitigation Measures The levee system protecting the City has been analyzed and the existing deficiencies have been identified. Each type of deficiency has a number of potential mitigation measures that will correct the deficiency. The conventional set of mitigation measures implemented to correct levee deficiencies are summarized on Table 4.

Site-specific characteristics, such as the landside proximity of existing structures, sensitive environmental and cultural resources, and existing improved levee segments all ultimately would affect what mitigation measure were selected for a given deficiency. Our situation is more complex, though. And a second set of measures were applied to inform the identification of mitigation alternatives for reaches with multiple levee deficiencies: the definition of deficiency groups and associated combinations of mitigation measures.

A broad array of flood risk reduction measures was considered during the planning and design of levee improvements within the study area. Each levee improvement measure is best suited to remedy one particular type of levee deficiency. In areas where multiple levee deficiencies have been identified, levee improvement measures will be combined to create an adequate levee improvement alternative. Table 2 compares various levee improvement measures to the type of levee deficiency they are best suited to correct.

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Table 2 - Summary of Levee Deficiencies and Measures Through Slope Excess Measure Freeboard Underseepage Erosion Geometry -Seepage Stability Vegetation In-Place Yes No No Yes No Yes No Levee Raise Adjacent Yes Yes No Yes Yes Yes No Levee Raise Floodwall Yes No No No No No No

Cutoff Wall No Yes Yes No No No No

Jet Grouting No Yes Yes No No No No

Sheet Pile Walls No Yes Yes No No No No

Seepage Berm No No Yes No No No No

Stability Berm No Yes No Yes No No No

Relief Wells No No Yes No No No No

Slope Flattening No Yes No Yes No Yes No

Interior Drain No Yes No Yes No No No

Setback Levee Yes Yes No Yes Yes Yes Yes

Vegetation No No No No Yes No Yes Removal

The following sections describe each of the measures discussed in the previous table.

In Place Levee Raise

To address deficiencies found in the required levee freeboard (i.e., a minimum of 3 feet of freeboard above the 200-year water surface elevation), various methods of raising the existing levee crown elevation could be implemented. The two most likely alternatives include a crown-only raise and a full levee raise. A crown- only levee raise assumes that the levee crown is currently wide enough to support the placement of additional embankment material while maintaining the minimum allowable crown width upon the completion of the raise. A full levee raise includes an embankment raise from the waterside crown hinge point upward at a 3H:1V slope, establishing a new crown width, and then down the landside at a new 3H:1V

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slope). A mirrored version of this approach can likewise be implemented up from the landside crown hinge point, across the levee crown, and down the waterside slope.

Adjacent Levee Raise

The adjacent levee raise involves the construction of a new embankment adjacent to the existing levee. There will be a 5 foot shoulder from the landside hinge point of the levee. A 3H:1V slope will lead to the design crown elevation. There will be a 20 foot crown covered with an aggregate base patrol road. A 3H:1V landside slope will extend to existing ground. The adjacent levee raise will be constructed of compacted embankment fill material from a nearby borrow source.

Floodwall

Floodwalls are an efficient, space-conserving method for containing unusually high water surface elevations. They are often used in highly developed areas, where space is limited. They are primarily constructed from pre-fabricated materials, although they may be cast or constructed in place, and are constructed almost completely upright. Floodwalls mostly consist of relatively short elements, making their connections very important to their stability. Floodwalls are typically located along a levee hinge point to allow vehicular access along the crown. The drawback is that floodwalls prohibit access to or from the slopes, and may prevent visual inspection of the slope and toe areas from the crown if the wall is of sufficient height.

Cutoff Wall

Conventional slurry cutoff walls are used to mitigate through and underseepage. Cutoff walls are constructed using an excavator with a long-stick boom capable of digging a trench to a maximum depth of approximately 80 feet. Bentonite slurry is placed in the trench as it is excavated to prevent caving as the backfill material is mixed. Excavated soil is mixed with bentonite (SB Wall) or cement and bentonite (SCB Wall) to achieve the required cutoff barrier strength and permeability, and then backfilled into the trench. This method typically requires that the levee is degraded roughly 1/3 of the levee height to prevent hydraulic fracturing.

Deep Soil Mix (DSM) cutoff walls are constructed using a crane-supported set of two to four mixing augers set side by side. These augers are drilled through the levee crown and foundation to the required depth (capable of a maximum depth of about 200 feet). As the augers are inserted and withdrawn, a cement- bentonite grout is injected through the augers and mixed with the native soil. An overlapping series of mixed columns is drilled to create a continuous seepage cutoff wall panel. An approximately thirty foot wide working area along the top of levee is required for the equipment to operate, usually resulting in a slight degrade of the levee (on the order of 2 feet).

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Jet Grouting

Jet grouting is a term used to describe several construction techniques where fluids or binders are injected into the soil at very high pressures and velocities. The injected fluid could be grout, grout and air, or grout, air and water. Jet grouting breaks up soil and, with the aid of a binder, forms a homogenous mass that solidifies over time to create material of low permeability.

Sheet Pile Walls

Interlocking steel sheet piles are driven into the ground by a hydraulic or pneumatically-operated pile driving head attached to a crane. Pre-drilling may be need in earth that is particularly solid. The conditions of the site and the life of the project determine the thickness and configuration of the sheet piles. Additional thickness should be added to account for corrosion over the design life of the project.

Seepage Berms

Seepage berms are wide embankment structures that extend outward from the landside levee toe. The berms extend the underseepage path and control exit gradients near the landside toe of the levee. There are two types of berms examined in this report; hybrid and semi-pervious berms.

Hybrid berms (i.e., berms with drain layers) can vary in width between four times the levee height or 100 feet (minimum) and 300 feet (maximum). A typical 100-foot wide berm has a height of 5 feet at the landside levee toe tapering off to 3 feet at the end of the berm. A typical 300-foot wide berm will taper from 7.5 feet at the levee landside toe to 3 feet at the end. Each berm will be constructed of random fill over a one-foot thick layer of drain rock that allows drainage of seepage to the berm toe. The seepage water will then be collected in a v-ditch or similar drainage structure and eventually pumped back into the river. The random fill can be locally excavated materials available along these improvement reaches due to excavation for a drainage canal near the berm toe. This locally available material is anticipated to provide significant cost savings during construction.

As an option to the drained hybrid berm, semi-pervious berms that do not contain a drain layer may be utilized. To utilize locally excavated random fill however, the configuration of the berm must be adjusted when a drainage layer is not included. Semi-pervious berms will vary from 150 feet to 400 feet in width. At the levee landside toe the berm thickness will be 9 feet and will taper to 4 feet at the berm toe, regardless of the berm width.

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Stability Berm

A stability berm would be constructed against the landside slope of the existing levee with the purpose of supplying support as a buttress. The height of the stability berm is generally 2/3 of the height of the levee and extends for a distance determined by the structural needs of the levee along that reach.

Relief Wells

Relief wells are passive systems that are constructed near the levee landside toe to provide relief of pressure beneath surficial fine-grained soils (the clay or silt "blankets"). Relief wells are constructed using soil boring equipment to bore a hole vertically through the fine-grained blanket layer and into the coarse grained aquifer layer beneath. Pipe casings and gravel/sand filters are installed to allow the pressurized water to flow to the ground surface, relieving the pressures beneath the clay blanket while not transporting fine materials to the surface. The water will then be collected in a v-ditch or similar drainage structure and eventually pumped back into the river. Relief wells require a clearly defined fine-grain blanket layer and underlying coarse grained aquifer to ensure proper operation, making them unsuitable in some areas.

It is often assumed that the existing internal drainage infrastructure has enough capacity to handle the water generated from the relief wells. However, additional infrastructure and pumping costs could be estimated as part of the annual operational costs considering preliminary estimates of flow rates. A significant issue with relief wells is their dependence on regular maintenance to ensure proper operation. Piezometers, also called monitoring wells, could also be installed between each relief well to allow monitoring of ground water levels to ensure the wells are relieving the pressure within the aquifer.

Slope Flattening

Although also a requirement of current levee design guidance established by the Corps, slope flattening is a mechanical method to repair slope that may not have stable slopes. Both the waterside and landside slopes can be graded using construction equipment to meet the project design goal of 3H:1V slopes. In most cases, this process requires the removal of all vegetation and encroachments from the levee slope being flattened.

Internal Drain

Internal drains are layers of drain rock encased in filter fabric or filter sand that are placed on the landside 1/3 of the levee to collect through-seepage. This may require the partial excavation of the levee if the drain is not installed during original construction. A 1.5 foot thick layer of drain rock is placed at the levee toe and extended roughly 15 feet into the levee foundation. An additional drain layer, approximately 1.5 feet thick, runs up into the core of the levee at a 2H:1V slope from the end of the base layer to the approximate elevation of the design flood. Import material is then placed above the drain rock to rebuild the levee. The

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purpose of internal drainage layers is to capture any through-seepage and direct it away from the face of the levee. A drainage canal is excavated at the landside levee toe to capture the water and direct it to an existing pump station or detention basin.

Setback Levee

A setback levee consists of a full levee section, set back a given distance on the landside of the existing levee. The setback levee would act as the new project levee. The levee section would be constructed to a height to meet freeboard requirements, with landside and waterside slopes at 3H:1V. The existing levee would remain in place or be removed, per project and regulatory requirements.

The existing levee can be excavated and used as fill for the setback, depending on the quality of the material. Some grading may need to be completed in the setback area in order to ensure proper drainage and minimize negative impacts to wildlife habitat or refuge.

Vegetation Removal

Corps levee guidance requires the removal of certain types of vegetation on the levee slopes. For the raise in place alternative, the levee vegetation free zone extends from 1/3 of the levee height down from the waterside hinge point to the landside toe. For the adjacent levee raise, the vegetation free zone will only extend from the waterside hinge point to the entire landside slope. A 15-foot zone landward of both the raise in place and the adjacent levee landside toe will also be cleared of vegetation. Conforming to the Corps’s vegetation policy is typically required in order to attain 408 approval for levee modifications.

Closure Structure

The City of West Sacramento has considered installation of a closure structure in the Deep Water Ship Channel as a potential modification to the City’s flood protection system; however, this consideration has not been to the same level of detail as the other flood protection improvement alternatives described within this report. A conceptual design and cost opinion for installing a closure structure in the Deep Water Ship Channel was developed as part of the report titled, Lower Sacramento River Regional Projects Conceptual Design and Cost Estimates, PB, June 2008. The proposed location of the structure is unclear as is the time period through which the cost opinion was intended to apply. Installation of a closure structure would likely be accompanied by a redefinition of the extents of the West Sacramento flood protection system – a prospect not evaluated in this study and not considered when identifying corrective measures and levee improvement alternatives. As a result, a closure structure was not evaluated with respect to correcting levee deficiencies in the system and is not included in the study cost analysis.

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4.2.2 Levee Deficiency Groups Preliminary investigations indicate that the existing deficiencies in the West Sacramento levee system are numerous. A summary of the spatial distribution of levee deficiencies identified in the West Sacramento levee system can be found in Figure 11. A set of deficiency groups were defined so that each reach could be reviewed with respect to all deficiencies identified for various station ranges within a given reach. That information was used to inform the process of identifying potential mitigation alternatives for each levee system reach. The deficiencies groups defined for the West Sacramento levee system a summarized in Table 5, and their spatial distribution along each reach is shown in Figure 11.

4.2.3 Combinations of Mitigation Measures for Levee Deficiency Groups The next step in the development of mitigation alternatives was to identify the range of potential solutions to deficiencies found in each levee reach. Toward this end, information in the single mitigation deficiency table was combined with each deficiency group to identify combinations of mitigation measures for each levee deficiency group. Table 6 provides the results of this cross-correlation. For example, deficiency group 5 applies to a section of levee with freeboard and geometry deficiencies. Table 6 shows that an in- place levee raise, an adjacent levee raise, slope flattening, or a setback levee can be employed to correct geometry deficiencies, depending on their nature and factors specific to location. Additionally, the table shows that the freeboard deficiency can be mitigated with an in-place or adjacent levee raise, or a setback levee. Hence, three of the five mitigations listed for geometry also will mitigate a freeboard deficiency. This exercise is intended to illustrate how the deficiency group mitigation table was utilized to help identify mitigation alternatives for further consideration.

4.2.4 Mitigation Alternative Selection Process A number of factors are considered when identifying the recommended mitigation alternative for deficient levee section. Evaluation criteria include the following:

1. System continuity; 2. Community impact; 3. Environmental impact; 4. Operation and Maintenance Cost; and 5. Construction Cost

System Continuity

The primary goal for levee upgrade of a given deficient reach is to enhance the overall performance of the flood protection system. System discontinuities –whether transitions from one type of seepage barrier to

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another (cutoff wall embedded in earthen embankment to a seepage berm) or from an unencroached levee section to an encroached section (i.e. levee transition to a bridge structure) – represent potential system vulnerabilities because they require a third type of design component to achieve transition while maintaining system function. It is, therefore, desirable to limit system discontinuities whenever possible and, by implication, system vulnerabilities.

This alternatives analysis gives priority to system continuity. Therefore, if two adjacent deficient levee reaches can be mitigated with the same alternative that will likely be the recommended alternative, even if the alternative is less favorable as regards other evaluation criteria.

Community Impact

Mitigation alternatives that preserve existing or planned land use designations are preferred over those that change those designations. Temporary construction-related impacts are considered as well. Levee system upgrades that can be implemented within existing levee easements are preferable to those that require acquisition of residential, commercial, industrial, recreational or cultural resource property. Such acquisitions can be disruptive to a community’s social and economic well being and, therefore, are not preferable.

Environmental Impact

Mitigation alternatives that have a ‘light’ environmental footprint are preferred over those with a ‘heavy’ footprint. A setback levee, with enhanced shoreline habitat may be preferable to stone revetment along the same shoreline – even though both may stabilize the shoreline from erosion and associated instabilities. In addition, although compensatory habitat mitigation plans are legally required, they do not necessarily include habitat construction or enhancement at the same geographic location. So there is a local environmental impact as regards natural habitat within a specific community.

Operation and Maintenance Reliability

‘Passive’ systems, requiring monitoring and occasional repair as the primary forms of operation, are preferred to those that require more active operation personnel and equipment-based operation. A seepage cutoff wall is a more passive system than a relief well system, and many times is the preferred alternative for underseepage, because the latter requires monitoring, well maintenance, and water management.

Construction Cost

Levee system upgrades are expensive, and communities generally have limited means for raising local funds to contribute to the cause – many times a requirement for qualifying for state or federal assistance.

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Therefore, less expensive options are preferred to more expensive ones, assuming equal or comparable functionality.

4.2.5 Mitigation Alternatives Selected for Further Consideration All alternatives considered in this study carry a prerequisite requirement that, if properly designed and constructed, they would mitigate for the deficiencies identified in this study. The list of alternatives considered in this study, however, is not comprehensive, but is intended to engage a range of potential solutions to the levee deficiencies identified to this point as part of the levee evaluation program. Professional judgment and a review of qualitative factors making one alternative more favorable than another were considered when selecting what alternatives would be evaluated.

The deficiency group mitigation alternatives were reviewed with aerial photographs as a visual aid to bring site-specific factors into focus as part of the alternatives selection process. This ‘high level’ review was completed to identify obvious flaws associated with implementing a given mitigation alternative that may appear on the deficiency group mitigation table. A primary factor that guided this review was the space available for mitigation implementation.

A key question this review sought to answer was to what degree, qualitatively speaking, shifting the levee template landward during mitigation would impact existing land uses and environmental resources. Potentially significant impacts associated with landward shifts were avoided when selecting alternatives for further consideration. Applying that principle as a guiding tenet for alternative selection, additional, general criteria, including system continuity (more being better) and level of maintenance (less being better) were brought into the selection process. In one case – that of installing a closure structure in the Deep Water Ship Channel – an alternative proposed as part of a previous study, was selected for consideration outright.

The alternatives selected for further consideration in this study are summarized, by reach, on Table 7. A minimum of two alternatives were considered for each reach. It should be noted that the most accurate deficiency information is contained on Figure 4 through Figure 9. The station range/deficiency information presented on Table 7 indicates the presence of a given deficiency in that station range, but not necessarily the presence of each deficiency throughout the entire station range.

4.2.6 Mitigation Alternative Evaluation The alternatives selected for further consideration were evaluated using the five evaluation criteria defined in section 4.2.4 and listed below for convenience. A brief explanation of how each criterion was assessed is included.

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1. System continuity – Based on the number and nature of transitions from one type of mitigation method to another; 2. Community impact – Based on amount of residential and business relocation and real estate purchase; 3. Environmental impact – Based on riparian and non-riparian habitat mitigation requirements; 4. Operation and Maintenance Reliability – Based on qualitative assessment regarding site inspection requirements and perceived equipment maintenance requirements; and 5. Construction Cost – Based on cost opinion developed from mitigation alternative quantities and unit rates for 2009 construction adopted from Sacramento Area Flood Control Agency (SAFCA) Natomas Project. Cost opinions include approximate quantities of riparian and non-riparian habitat mitigation, real estate purchase, and residential and business re-location, as well as traditional construction quantity components for upgrading the levees. Quantities used for these cost opinions were based on levee deficiencies shown on Figure 4 through Figure 9. A detailed cost opinion for each alternative considered in this study is included in Appendix B. Summary cost opinions are included on Table 7.

A final evaluation of each mitigation alternative was completed by assigning values of ‘positive’, ‘negative’, or ‘average’ for each of the five evaluation criteria. ‘Positive’ ratings were assigned for alternative criteria that were considered favorable to final selection, ‘Average’ to those considered of have neutral value, and ‘Negative’ to those considered to be less favorable to final selection. The ratings were assigned based on a comparison between alternatives considered for a given reach. So, a ‘positive’ criterion rating for one alternative should be viewed as positive relative to the other alternatives considered for that reach.

For example, a large environmental impact relative to other alternatives considered – i.e. a large requirement for habitat mitigation – would be given a ‘Negative’ rating for that criterion. A low construction cost relative to other alternatives considered would be given a ‘Positive’ rating for that criterion.

Final alternative selection for each reach was based on the assumption of equal weighting to all five criteria, a numerical scheme that assigns a -1 value for a ‘Negative’ rating, 0 for ‘Average’, and 1 for ‘Positive’, and a simple arithmetic sum of criteria values to identify the recommended alternative. The results of this evaluation, including the recommended mitigation alternatives for each reach are summarized in Table 8. The recommended alternatives are also identified on Table 7. In one case, the South Cross levee, the highest evaluation score was calculated for two alternatives. In addition, the ratings for each criterion for those alternatives were the same. Although close in cost, there was a small difference between the two and the alternative with the lower cost was recommended.

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5.0 Plan Selection The levee system plan selected based on this alternatives analysis includes upgrading each levee reach with the recommended alternative identified in Table 8.

6.0 Plan Uncertainty The selected plan, and all characterization on the extents of the seepage, stability and seismic deficiencies identified in the problem identification report, and reiterated in this document, are based on preliminary geotechnical investigations. The potential difference between those assessments and what design-level investigation, consistent with U.S. Army Corps of Engineers guidance, would produce represent the main uncertainty associated with the findings of this study.

7.0 Description of the Selected Plan The selected plan includes mitigation of all levee system deficiencies identified in this study. The total construction cost for implementing the selected plan is estimated at approximately $545 million in 2009 dollars. This section provides a narrative description of the plan components by reach, with special features specific to each reach noted. The recommended alternatives summarized in Table 7, in combination with Figures 13 – 37, provide a breakdown by station range of each set of mitigation measures proposed in the selected plan.

In the north basin, the Sacramento Bypass levee would be upgraded with an Alternative 3, cutoff wall (Figure 17). It was assumed for this study that the concrete-lined, waterside slope, with a side slope slightly less than 3:1, would prove stable via final design analysis and allowed to stay in place without slope flattening.

The Sacramento River West North levee would be upgraded with Alternative 1 – a combination of cutoff walls (conventional and deep soil mixed) and raised levees, with waterside slope flattening throughout (Figure 13). This alternative also requires jet-grouting beneath the I Street Bridge and a closure structure for the Union Pacific Rail Road portion of the bridge.

The Yolo Bypass would be improved with Alternative 3 - a stability berm throughout, and a cutoff wall over one 2-mile stretch (Figure 20). This alternative assumes, based on levee performance during 1997 and 1998 high water events, that the Corps’ Contract B improvements at the north end of the levee are effective and require minimal future upgrades. Ongoing maintenance for this levee section will be required. Additionally, a closure structure would be required for the I-80 crossing.

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The Port North levee would be upgraded with Alternative 1 - a floodwall approximately oriented at an offset, internally, to the property line of the Port (Figure 21). That alignment would maintain a minimum 25-ft offset from local railways and would require two closure structures at the east end of the property.

The south basin upgrades would include a lengthy (~3 mile) setback levee throughout the middle portion of the Sacramento River West South Levee, shoreline vegetation stabilization and habitat enhancement; slope flattening, relief wells, and an adjacent levee at the far north end, and slope flattening and relief wells along the south end of the reach (Alternative 2, Figure 32). Although more costly than Alternative 3, The habitat and floodplain restoration features of Alternative 2 are a positive aspect of the overall plan that addresses one the secondary planning objectives: waterfront habitat restoration. In addition, Alternative 2 eliminates the extensive amount of shoreline rip rap and associated environmental mitigation and maintenance requirements that would be part of implementing Alternative 3. Financial benefits associated with Alternative 2 – including a potential increase in state cost sharing – were not included in this study.

The South Cross levee would be upgraded with Alternative 1 - a combination of slope flattening, a short cutoff wall, and an adjacent levee raise with an interior drainage system (Figure 34). The Port South levee would be upgraded with Alternative 1 - slope flattening, a section of flood wall, and a section of cutoff wall (Figure 22).

The Deep Water Ship Channel East levee would be upgraded at each existing pump station (Alternative 1, Figure 28). Mitigation measures at both locations would include slope flattening, installation of a cutoff wall, and stabilization with revetment.

The Deep Water Ship Channel West levee would be upgraded with Alternative 1 - slope flattening, a levee raise and over 11 miles of rip rap revetment (Figure 24). Mitigation of freeboard deficiency along this reach was based on establishing a crest elevation 5 ft above the 200-yr water surface elevation (5 feet of freeboard, rather than 3 ft). This assumption appears to be consistent with the original levee design.

8.0 Implementation Requirements Implementation of the selected plan will require the following steps:

1. Final investigation and design of the levee upgrades; 2. Completion of required state (CEQA) and federal (NEPA) environmental analyses and associated permits and approvals, including mitigation for 120 acres of riparian habitat and 740 acres of non- riparian habitat (See Appendix B), 3. Establishment of approximately 206 acres expanded levee right-of-way through land purchase and easement attainment and, in some cases, potential home relocation (11 homes),

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4. Attainment of encroachment permits from the CVFPB for all levee upgrades, 5. 408 approval from the Corps for all levee upgrades, 6. A prioritization of levee system reach upgrades, and 7. Establishing the partnerships necessary to marshal the required funding for levee improvement construction (~ $460 million).

9.0 Recommendations A number of recommendations can be made from this study, both short-term and long-term, some directly related to the selected plan, and others more generally related to improving flood protection in the City. Recommendations to the City are the following:

1. The deficiencies derived from the system problem identification report should be confirmed through further geotechnical investigation. Those investigations should be conducted at a spatial frequency consistent with Corps requirements, or at least designed to eventually reach that threshold during the final design phase;

2. Continue to develop preliminary design plans for system upgrade and to initiate associated environmental impact assessment to pre-position for possible funding opportunities;

3. Continue to seek uniformity in technical approach to assessing seismic vulnerability and to seek clarification from the Corps and DWR as to what mitigation for seismic vulnerability are acceptable; 4. Develop a levee reach upgrade prioritization plan based on the following factors: safety enhancement, certification cost/benefit, imminent threat, poor performance, emergency response, and investment optimization;

5. Continue to investigate re-use of dredged material as upgrade levee fill or emergency levee fill;

6. Develop a flood-fighting plan based on the California Department of Water Resources Interim Levee Design Guidelines;

7. Expand alternatives analysis to identify recommended plans for 100-yr design water surface elevation;

8. Develop for potential adoption and implementation a portfolio of risk reduction measures to mitigate short-term exposure.

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10.0 References

 DWR (2007), Preliminary Geotechnical Data Report, West Sacramento. September 2007. Prepared by URS.  DWR (2007), Phase 1 Geotechnical Evaluation Report (P1GER), West Sacramento Region. November 2007. Prepared by URS.  HDR Engineering (2008), West Sacramento Levee Evaluation Project Draft Problem Identification Report. April 2008.  MBK Engineers et. al. (2007) Hydraulics Report for the City of West Sacramento Levee Alternatives Analysis. March 2007.  U.S. Army Corps of Engineers (1992), Sacramento Metropolitan Area, California: Feasibility Report, Environmental Impact Statement/Environmental Impact Report. February 1992.  U.S. Army Corps of Engineers (2000), Engineering Manual (EM 1100-2-1913) Engineering and Design: Design and Construction of Levees. April 30, 2000.  U.S. Army Corps of Engineers (2005), Engineering Technical Letter (ETL 1100-2-569) Engineering and Design: Design Guidance for Levee Underseepage. May 1, 2005.  U.S. Army Corps of Engineers (2007), Request for Federal Assistance in Repairing Flood Damages for Public Law (P.L.) 84-99 Sites, Reclamation District 900, Yolo County, California – Order 3 Site. (Final). April 2007.  U.S. Army Corps of Engineers (2008), REFP10L0 Geotechnical Levee Practice. April 4, 2008.  33 U.S.C Section 408

City of West Sacramento 29 Levee Improvement Program HDR Project # 007436-44683-141 November 12, 2009

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