CITY OF CHANHASSEN, MN

Local Water Management Plan January 2018 Review Draft

City of Chanhassen 7700 Market Boulevard P.O. Box 147 Chanhassen, MN 55317 www.ci.chanhassen.mn.us

City of Chanhassen, Minnesota Local Stormwater Management Plan Adopted xxxxxxxxxxx, 2018

COUNCIL:

Mayor Denny Laufenburger Bethany Tjornhom Jerry McDonald Elise Ryan Dan Campion

STAFF:

Vanessa Strong Paul Oehme Terry Jeffery

Photos: City of Chanhassen Wenck Associates, Inc.

WENCK ASSOCIATES, INC.: Prepared by: Diane Spector WENCK Associates, Inc. 1800 Pioneer Creek Center Erik Megow Maple Plain, MN 55359 Todd Shoemaker, P.E. Phone: 763-479-4200 Fax: 763-479-4242 File 1481-0013

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Table of Contents

1.0 INTRODUCTION AND PURPOSE ...... 1-1 1.1 Purpose of Plan ...... 1-1 1.2 Relationship to Other City Plans ...... 1-1 1.2.1 Comprehensive Plan...... 1-1 1.2.2 Storm Water Pollution Prevention Program ...... 1-1 1.2.3 Wellhead Protection Plan ...... 1-2 1.2.4 Bluff Creek Natural Resources Management Plan ...... 1-2 1.3 Relationship to Other Plans ...... 1-3 1.3.1 Metropolitan Council Water Resources Policy Plan...... 1-3 1.3.2 Minnesota River Basin Plan ...... 1-3 1.4 Relationship to Other Regulatory Agencies ...... 1-3

2.0 REGULATORY FRAMEWORK ...... 2-1 2.1 Chanhassen Ordinances and Policies ...... 2-1 2.2 State Agency Regulatory Framework ...... 2-1 2.2.1 Metropolitan Council ...... 2-2 2.2.2 Minnesota Pollution Control Agency ...... 2-2 2.2.3 Minnesota Department of Natural Resources ...... 2-2 2.2.4 Minnesota Department of Health ...... 2-3 2.2.5 Carver County and Carver SWCD ...... 2-3 2.2.6 Watershed Districts and WMOs ...... 2-4 2.3 Wetland Conservation Act ...... 2-6 2.4 Relationship to NPDES Stormwater Permit ...... 2-6 2.5 Water Resource Related Agreements ...... 2-6

3.0 ASSESSMENT OF PROBLEMS ...... 3-1 3.1 Hydrologic Modeling ...... 3-1 3.1.1 Areas of Known Flooding ...... 3-1 3.2 Impaired Waters ...... 3-1 3.3 TMDLs and UAAs ...... 3-2 3.3.1 Total Maximum Daily Load (TMDL) Studies ...... 3-2 3.3.2 UAAs ...... 3-3 3.4 Problems and Issues ...... 3-4

4.0 GOALS AND POLICIES ...... 4-1 4.1 Goals and Policies ...... 4-1

5.0 IMPLEMENTATION PLAN ...... 5-1 5.1 Permitting and Enforcement ...... 5-1 5.1.1 Current Ordinances and Potential Revisions ...... 5-1 5.1.2 NPDES Permit Implementation Requirements ...... 5-5 5.2 Implementation Programs and Projects ...... 5-5 5.2.1 Education and Outreach Program ...... 5-5 5.2.2 Monitoring Program ...... 5-6 5.2.3 Operations and Maintenance ...... 5-7 5.2.4 Capital Improvement Program ...... 5-8

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Table of Contents

5.3 Implementation Plan Funding ...... 5-8 5.4 Addressing Identified Problems and Issues ...... 5-11

6.0 AMENDMENTS TO THE PLAN ...... 6-1 6.1.1 WMO Plan Amendments...... 6-1 6.1.2 Major Plan Amendments ...... 6-1 6.1.3 Routine Updates ...... 6-1

7.0 REFERENCES ...... 7-1

TABLES Table 3.1. Impaired Waters in Chanhassen...... 3-1 Table 3.2. Problems, issues, and opportunities...... 3-4 Table 4.1. Water resources management goals...... 4-1 Table 4.2. Comparison of TP-40 to Atlas 14 event depths...... 4-2 Table 4.3. Agencies with regulatory authority...... 4-6 Table 5.1. Regulatory requirements of various agencies compared to Chanhassen current ordinances. 5-2 Table 5.2. Chanhassen LWMP Implementation Plan 2018-2027...... 5-9 Table 5.3. Chanhassen LWMP Implementation Plan 2018-2027 by year...... 5-10 Table 5.4. Implementation actions addressing identified problems and issues...... 5-11

FIGURES Figure 1.1. City of Chanhassen in located in the Twin Cities Metro Area, Minnesota...... vii Figure 2.1. Watershed Management Organizations in Chanhassen...... 2-5

APPENDICES

Appendix A: Land and Water Resources Inventory Appendix B: Hydrologic Modeling Update

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Acronyms

AIS Aquatic Invasive Species BMP Best Management Practice BWSR Board of Water and Soil Resources cfs cubic feet per second cfu colony-forming unit Chl-a Chlorophyll-a CIP Capital Improvement Program DNR Department of Natural Resources DO Dissolved Oxygen EPA or USEPA US Environmental Protection Agency F-IBI Index of Biotic Integrity for Fish LA Load Allocation LWMP Local Water Management Plan Met Council Metropolitan Council mg/L milligrams per liter M-IBI Index of Biotic Integrity for Macroinvertebrates MPCA Minnesota Pollution Control Agency MS4 Municipal Separate Storm Sewer Systems NPDES National Pollutant Discharge Elimination System NWI National Wetland Inventory SD Secchi depth SWCD Soil and Water Conservation District SWPPP Storm Water Pollution Prevention Program TMDL Total Maximum Daily Load TP Total phosphorus TSS Total suspended solids µg/L microgram per liter WLA Wasteload Allocation WD Watershed District WMO Watershed Management Organization

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Executive Summary

The City of Chanhassen, Minnesota is located in northeastern Carver County (see Figure 1.1), except for one small area in Hennepin County. It is bordered on the east by the City of Eden Prairie; on the north by Shorewood; and on the west by Victoria and Chaska. Its southern border is the Minnesota River. The City has land in four watersheds: the Carver WMO, Riley-Purgatory-Bluff Creek, Minnehaha Creek, and the Lower Minnesota River Watershed Districts.

This Local Water Management Plan (LWMP) was prepared in conformance with Minnesota Statutes 103B.235 and Minnesota Rules 8410. This plan is intended to provide the City of Chanhassen with information and direction in the administration and implementation of water resource management activities within the City during the period 2018-2027. It serves as a guide to projects, provides for effective allocation of resources, and sets forth a funding plan for projects and programs over the next 5 to 10 years.

A number of water resources-related problems, issues and requirements were identified in this planning process. These include:

• The reissue of the State of Minnesota’s NPDES General Stormwater Permit in 2013 requires local governments such as Chanhassen to adopt and enforce standards and ordinances for development and redevelopment which limits stormwater runoff from sites over one acre in size. • New or expanded maintenance and administrative responsibilities are required in the NPDES permit to control runoff and protect and improve water quality from City owned or maintained land. • All 4 WMO’s are updating their 10 year Comprehensive Plans. The City is required to amend their LWMP to be consistent with each WMO • In order to maintain and/or obtain primary responsibility for managing local water resources additional ordinance revisions are required. The alternative is to defer the authority to the local WMO • Some of the lakes and streams in the City do not meet the state’s water quality standards for recreation and aquatic life. • Stream gullies and escarpments are contributing excess sediment into Bluff Creek and the Minnesota River.

The LWMP updates the City’s goals and related policies to address the problems and issues that were evaluated for the updated LWMP. The goals are as follows:

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Executive Summary

Goal 1. Promote abstraction through infiltration, reuse and other methods where practicable to do so to provide flood protection, ground water recharge and improved water quality. Goal 2. Achieve water quality standards in lakes, streams, and wetlands consistent with their designated uses and established classifications. Goal 3. Protect and rehabilitate wetlands to maintain or improve their function and value. Goal 4. Prevent contamination of the aquifers and promote groundwater recharge to maintain base flows in streams and wetlands. Goal 5. Maintain primary responsibility for managing water resources at the local level where efficient to do so but continue coordination and cooperation with other agencies and organizations. Goal 6. Cultivate an environmentally literate public to promote an active community role in sustainable management of water resources.

Implementation

This LWMP includes an Implementation Plan to help achieve those goals through capital projects, management programs, and operations and maintenance activities.

Capital Projects. The Riley-Purgatory-Bluff Creek WD has completed Use Attainability Assessments (UAAs) and/or Total Maximum Daily Load (TMDL) studies for some of the waterbodies in the City. These studies have identified potential actions that could help protect or improve water quality. The City evaluates partnership opportunities with the Districts to undertake priority projects as project plans develop. In addition, the City has been systematically surveying the condition of storm drainage system features. These condition assessments have identified a number of potential improvement projects, and priority actions are included in the Implementation Plan. The Implementation Plan also includes projects to install water quality Best Management Practices (BMPs) with street or other construction projects.

Management Programs. The City operates several programs that directly or indirectly affect water resources, including a Public Education and Outreach program. A variety of social and traditional media are also used to inform and educate citizens. City and partnership events, workshops and festivals provide additional opportunities for education.

The City of Chanhassen collaborates with the Metropolitan Council to participate in its Citizen Assisted Monitoring Program (CAMP). Volunteer residents take samples from the following lakes: Lake Lucy, Lake Minnewashta, Lake Riley, Lake St. Joe, Lake Susan, and Lotus Lake. Aquatic Invasive Species management is implemented through a partnership with Carver County WMO, Riley Purgatory Bluff Creek Watershed District, and local Lake Associations.

Operations and Maintenance Activities. The City undertakes a variety of operations and maintenance actions, including actions required by its NPDES MS4 Permit. These include ongoing water body inventory and condition assessments, erosion control monitoring, street sweeping, stormwater system inspection, maintenance and repairs, road salt management, and a general education and outreach program.

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Executive Summary

Plan Updates

Section 6 of this Plan sets forth a process to update the LWMP in response to city operations, budget planning, work requirements or WMO plan revisions. The Implementation Plan and Capital Improvement Program (CIP) will be reviewed and updated periodically by the City as needed based on new information or as new opportunities and requirements arise. At a minimum, the CIP will be updated biannually. Major issues that result in potential significant revisions to the LWMP will be forwarded to the Watershed Districts and WMO for discussion and review to determine if the LWMP will require a formal update.

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Figure 1.1. City of Chanhassen in located in the Twin Cities Metro Area, Minnesota.

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1.0 Introduction and Purpose

1.1 PURPOSE OF PLAN

The City of Chanhassen is located in Carver County within the Twin Cities Metropolitan Area (Figure 1.1). This Local Water Management Plan (LWMP) describes how the City of Chanhassen will fulfill the requirements of Minnesota Statutes 103B.235 and Minnesota Rules 8410 in the management of the water resources within the city during the period 2018-2027. It is a summary of the city’s management goals and policies, and strategies, including a capital improvement program and review of local policies and ordinances.

Minnesota Statutes 103B.231 establishes the purposes of water management planning in the Twin Cities Metropolitan Area as to:

1. Protect, preserve, and use natural surface and groundwater storage and retention systems 2. Minimize public capital expenditures needed to correct flooding and water quality problems 3. Identify and plan for means to effectively protect and improve surface and groundwater quality 4. Establish more uniform local policies and official controls for surface and groundwater management 5. Prevent erosion of soil into surface water systems 6. Promote groundwater recharge 7. Protect and enhance fish and wildlife habitat and water recreational facilities 8. Secure the other benefits associated with the proper management of surface and ground water

Minnesota statutes and administrative rules also require that City management of its water resources be consistent with the requirements of the four watershed districts having land within its borders: Riley- Purgatory-Bluff Creek Watershed District; Minnehaha Creek Watershed District; Carver County WMO; and the Lower Minnesota River Watershed Management District.

1.2 RELATIONSHIP TO OTHER CITY PLANS

This LWMP is intended to address surface water management; ground water supply and wellhead protection planning are separate from this Plan except as surface water management influences groundwater.

1.2.1 Comprehensive Plan

The Comprehensive Plan is a blueprint for how the City manages its land use. The Metropolitan Council in accordance with the Metropolitan Land Planning Act develops and updates regional planning policies and requires that all cities periodically update their Comprehensive Plans to be consistent with those policy plans. Thrive MSP 2040 and the 2040 Water Resources Policy Plan identify certain required elements of local water resources planning. This Local Water Management Plan Update meets those requirements.

1.2.2 Storm Water Pollution Prevention Program

Chanhassen is regulated by the State of Minnesota’s National Pollutant Discharge Elimination System (NPDES) General Stormwater Permit as a Municipal Separate Storm Sewer System (MS4). In accordance

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with that permit, the City developed a Storm Water Pollution Prevention Program (SWPPP) comprised of a series of Best Management Practices (BMPs) in six Minimum Control Measure (MCM) areas to prevent pollution and to manage and treat runoff discharged from the city into state waters. An annual report documents the specific actions taken in the previous year, which is presented to the public for review, approved by the City Council, and submitted to the Minnesota Pollution Control Agency (MPCA) for approval.

In 2006 the City was one of 30 cities statewide selected by the MPCA to undertake a special Nondegradation Assessment as part of its NPDES permit. The purpose of the study was to assess changes in stormwater runoff volume, total suspended solids (TSS) and total phosphorus (TP) loading since 1988, and to predict how land change expected to 2020 would impact those parameters. The study found that while runoff volumes had increased, pollutant loading had decreased as a result of City and watershed district water quality treatment requirements.

A new General Permit became effective August 1, 2013, and the City and other MS4s were required to prepare a new SWPPP and submit obtain renewal of coverage under the permit. Many of those BMPs are incorporated into this LWMP.

1.2.3 Wellhead Protection Plan

Minnesota state statutes require the owners and operators of public drinking water systems to prevent contamination of public water supply wells by effectively managing potential contaminant sources in the area which contributes water to those wells. They must prepare a wellhead protection plan which includes: a map showing the boundaries of the delineated wellhead protection area, a vulnerability assessment of the well and the wellhead protection area, an inventory of potential sources of contamination within the wellhead protection area, a plan to manage and monitor existing and proposed potential sources of contamination, and a contingency strategy for an alternate water supply should the water supply be disrupted by contamination or mechanical failure.

The City’s Wellhead Protection Plan (WHPP) addresses the ten municipal supply wells used by the City. Initially completed in 2002, it was updated in 2011 to include new wells and additional analysis. The WHPP includes an identification of a Wellhead Protection Area and an assessment of the vulnerability of the wells to contamination. One well, an emergency backup well, was identified as vulnerable to surface contamination, while the other wells were classified as not vulnerable. The uppermost source water aquifer within the Drinking Water Supply Management Area (DWSMA) was identified as having mostly low vulnerability to surface contamination.

Infiltration of stormwater is not desirable where the DWSMA indicates the aquifer is vulnerable to contamination from the surface, and other stormwater BMPs are recommended. DWSMA vulnerability is further described at the subwatershed level in Appendix A of this Plan.

1.2.4 Bluff Creek Natural Resources Management Plan

The Bluff Creek Natural Resources Management Plan was completed in 1996. The Management Plan identified high-quality natural features for preservation as well as potential restoration projects. To protect this area, several zoning and land use recommendations were intended to minimize new impervious surface, control and limit stormwater runoff and pollutant loading, and protect or enhance wildlife corridors and connectivity. Many of these recommendations were incorporated into the Bluff Creek Overlay District zoning ordinance enacted in 1998. Maintaining and enforcing stormwater

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management requirements through this Plan and the Riley-Purgatory-Bluff Creek Watershed District are integral to achieving the goals of the Bluff Creek Plan.

1.3 RELATIONSHIP TO OTHER PLANS

Several agencies manage programs or regulate activities for local stormwater or water resource management. The following sections summarize those relevant to local water management planning.

1.3.1 Metropolitan Council Water Resources Policy Plan

The Metropolitan Council’s Water Resources Management Policy Plan is a framework to integrate water resources management and protection with planning for the Metro region’s growth. In 1995, the Metropolitan Land Planning Act was amended to require that each city and township's comprehensive plan include a local water management plan. These local plans need to be consistent with Minnesota Statutes 103B and Metropolitan Land Planning Act requirements. Local water management plans are reviewed by the Met Council as part of the local comprehensive planning process prior to their approval by the WMO and adoption by the city or township.

In addition to the local stormwater plan elements required in statute and administrative rule, the Policy Plan expects communities to show that they are committed to the Met Council’s goal of no adverse impact (nondegradation) for area water resources. Local plans should include actions such as ordinances requiring runoff water quality treatment and limiting the rates and volumes of runoff; adopting Best Management Practices for development and redevelopment; and wetland management planning. The Policy Plan places a special emphasis on nondegradation of lakes identified as Priority Lakes. The Met Council defines Priority Lakes as lakes of high regional recreational value that are at least 100 acres in size; supply drinking water; have very good water quality; or have exceptional significance for wildlife habitat. Lakes in Chanhassen that have been designated as Metro Priority Lakes are: Minnewashta, Ann, Lotus, and Riley.

1.3.2 Minnesota River Basin Plan

The Minnesota River flows southeast from its source at Big Stone Lake on the South Dakota border to Mankato then northeast to join the Mississippi River at Fort Snelling (about 335 total miles). It covers approximately 16,770 square miles, roughly 10 million acres. Thirteen major watersheds in Minnesota drain into the basin, which touches 37 counties. Most of Chanhassen is located in the Lower Minnesota River subbasin. The 2001 Minnesota River Basin Plan (MPCA 2001) lays out a broad framework for directing environmental programs toward improving water quality in the Minnesota River, its tributaries and other water bodies. Priority actions include reducing nutrient, sediment, and bacteria inputs to the River and improving the health of biologic communities.

1.4 RELATIONSHIP TO OTHER REGULATORY AGENCIES

The LWMP is intended to meet requirements outlined in Minnesota Rules 8410 and Minnesota Statutes 103B as well as provide a user-friendly tool for day-to-day management of the City’s water resources. The LWMP provides the following information, as required in the Minn. Statutes 103B.235.

• Existing and proposed physical environment and land use within the City • Drainage areas and the volumes, rates, and paths of stormwater runoff • Identification of stormwater storage areas

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• Performance standards for water quality and water quantity protection • Implementation program • Capital improvement program

The Plan was also written with consideration of the needs, requirements and direction outlined in the following:

• Local Water Management Rules – Minn. Rules 8410 • Wetland Conservation Act – Minn. Rules 8420 • Minnesota Pollution Control Agency Water Quality Standards – Minn. Rules 7050 • U.S. Army Corps of Engineers Section 404 Clean Water Act • Metropolitan Council Water Resources Policy Plan May 2005 • Riley-Purgatory-Bluff Creek Watershed District Water Management Plan - January 2011 • Minnehaha Creek Watershed District Comprehensive Water Resources Management Plan – April 2007/ January 2018 • Carver County WMO Comprehensive Water Resources Management Plan – October 2010 • Lower Minnesota River Watershed District Water Management Plan - December 2011 • Metropolitan Surface Water Management Act (Chapter 601, Laws of 1990) • Use Attainability Analyses (UAAs) for lakes and streams in the city • The approved TMDLs for turbidity and fish biotic impairments in Bluff Creek

The watershed organizations and their respective jurisdictions within the City are shown on Figure 2.1. The LWMP is intended to satisfy the rules set forth in the current watershed management plans. The City will participate in upcoming revisions, evaluate any future watershed management plan amendments in relation to the LWMP and incorporate items as needed.

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2.0 Regulatory Framework

2.1 CHANHASSEN ORDINANCES AND POLICIES

The City has enacted several ordinances to protect and manage its water resources.

Chapter 19 of Chanhassen City code addresses design standards and requirements for water and sewers. Article V addresses illicit discharge detection and elimination within Chanhassen storm sewer systems. Article VII spells out development standards and design elements intended to implement the standards and achieve the goals set forth in this plan in order to preserve, protect and improve the city’s surface water resources. Specific elements within Article VII include erosion prevention and sediment control requirements, hydrologic and hydraulic design elements, water quality, rate control and volume reduction requirements. Those design standards include more stringent requirements for developments that discharge into Assumption Creek. That Article also establishes a Surface Water Management Utility and associated fees for operation of this utility.

Chapter 20 is the City’s Zoning Code. Article VI establishes wetland management classifications and standards for managing and protecting wetlands in the city. The City of Chanhassen is the responsible Local Government Unit (LGU) for the administration of the Wetland Conservation Act (WCA) in all areas of the city. This article includes standards for setbacks and for establishing and maintaining buffer strips adjacent to wetlands, and policies and procedures for altering wetlands and mitigating impacts to wetland functions and values.

Article V establishes the City’s Floodplain Overlay District and floodplain management standards. The ordinance establishes the regulatory flood protection elevation as no lower than two feet above the elevation of the regional flood. The ordinance also establishes what land uses may occur within the Overlay District under what conditions.

Article VII sets forth the City’s Shoreland Management District ordinances. The lakes and streams within the city that are regulated under this ordinance are established by management classification. The article includes minimum lot size and width requirements, structure and onsite sewage system setbacks, and limitations on altering and clearing vegetation and adding impervious surface. Article XXVIII establishes bluff protection standards in general.

Article XXXI establishes the Bluff Creek Overlay District and standards for protecting the quality and extent of the natural features within the District, which is centered on Bluff Creek. The Overlay District defines a Primary Zone, which is intended to be Open Space, and a Secondary Zone, in which regulated development may occur. Within this Secondary Zone, the ordinance requires a more stringent bluff setback; limits the amount of impervious surface allowed based on bluff slope; encourages terrain- adaptive architecture and density clustering; and requires preservation of natural habitat or, within the Secondary Zone, mitigation of any unavoidable impacts.

2.2 STATE AGENCY REGULATORY FRAMEWORK

Many agencies manage programs or regulate activities for local stormwater or water resource management. The following sections summarize those of primary relevance to urban local water management planning.

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2.2.1 Metropolitan Council

The Metropolitan Council’s Water Resources Management Policy Plan includes a range of programs administered by various governmental and private agencies for management of water resources in the Metro area. Several of Met Council’s programs of interest to cities include the following:

• Development of targeted watershed pollutant loads • Review of watershed and local water plans and comprehensive plans for consistency with metropolitan goals and objectives • Watershed Outlet Monitoring Program (WOMP) • Citizens’ Assisted Lake Monitoring Program (CAMP) • Environmental Information Management System • Regional Water Supply Plan for the Metropolitan Area

2.2.2 Minnesota Pollution Control Agency

The MPCA administers several programs applicable to local storm water management planning. The MPCA monitors water quality, sets standards, and implements various controls. Following are two programs related to water quality.

• The MPCA manages the National Pollutant Discharge Elimination System (NPDES) Phase II permitting for small municipal separate storm sewer systems (MS4s) and construction and industrial discharge permitting • The MPCA implements the Clean Water Act, which requires that states adopt water quality standards to protect waters of the state. The EPA and MPCA require preparation of Total Maximum Daily Load (TMDL) studies to identify the source of pollutants and plans for bringing the water resources into compliance. Lake Susan, Riley Lake, and Lotus Lake are impaired by excess nutrients; Bluff Creek is impaired by excess turbidity and does not meet state fish biology standards; and the Minnesota River does not meet turbidity standards. Several lakes and the Minnesota River do not meet mercury or PCB standards and have been listed on the MPCA’s 303(d) list of impaired waters. Section 3.2 discusses impaired waters in more detail.

2.2.3 Minnesota Department of Natural Resources

The DNR manages and protects the state’s natural resources and operates numerous programs. The department provides technical assistance and information regarding best management practices, natural resource management, incorporating natural resource conservation in land use planning, and lakescaping.

The Fisheries Division monitors and improves fisheries within the state. It also promotes fishing opportunities and provides grants to assist in the construction of fishing piers. The Ecological and Water Resources (EWR) Division focuses on an overarching vision of “Healthy Watersheds throughout Minnesota.” The EWR Division also provides the following services:

• Maintains an inventory of public waters and operates permit programs for working in public waters or for appropriating public waters; • Oversees the state’s floodplain management program; • Provides local stewardship by coordinating the Mississippi River Critical Area and MNRAA programs and the Shoreland Management program;

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• Collects, analyzes, and provides ecological information, including: ▪ Location and management of rare resources (endangered and threatened species, critical habitats, high quality natural communities); ▪ Management of harmful exotic species, fish and wildlife diseases, and negative environmental impacts of human development; ▪ Management and restoration of important ecological processes in river systems and key natural areas; and ▪ Development of information about Minnesota's ecosystems and their significance to a sustainable quality of life.

The DNR’s webpage at http://www.dnr.state.mn.us/lakefind/index.html is LakeFinder, a DNR supported tool that combines information from various DNR Divisions, as well as other state agencies, such as Minnesota Pollution Control Agency (water quality) and Minnesota Department of Health (fish consumption). This tool contains data for more than 4,500 lakes and rivers throughout Minnesota. The DNR also provides a variety of specialized programs oriented to property owners or neighborhood groups, such as the Aquatic Plant Management, Urban Fisheries and Fishing in the Neighborhood, Neighborhood Wilds, and Metro Greenways programs.

2.2.4 Minnesota Department of Health

The Environmental Health Division of the MDH administers numerous programs of interest to local water management planning, including the following.

• Drinking water protection • Wellhead protection • Lake and fish monitoring (in partnership with DNR/MPCA) • Environmental Health Services • Health risk assessment, site assessment, and consultation • Well management

The City worked with the MDH to develop a Wellhead Protection Plan (WHPP).

2.2.5 Carver County and Carver SWCD

Carver County provides a variety of programs throughout the county that relate to water resources management. County staff manage feedlot and septic system programs, and undertake lake and stream monitoring for water quality where that is not undertaken by a WMO. The County also provides Aquatic Invasive Species (AIS) monitoring and works to stop their spread. Common carp, curlyleaf pondweed, Eurasian water milfoil, and zebra mussels have been found in some of the lakes in Chanhassen. The County has in place an approved groundwater plan, and offers financial assistance to property owners to properly seal unused or abandoned wells.

The Carver Soil and Water Conservation District (SWCD) provides outreach and assistance to both urban and agricultural land owners to help them protect and improve lakes, streams, and wetlands in the county. The SWCD promotes environmentally-friendly landscaping, offers financial assistance for shoreline restorations and other Best Management Practices (BMPs), and sponsors student and adult education programming.

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2.2.6 Watershed Districts and WMOs

Watershed Management Organizations (WMOs) in the Metro area are required by statute to prepare and administer water management plans that establish watershed-wide goals, policies, and regulations. Local governments are also required by statute to prepare and administer local water management plans that establish local goals, policies, and regulations regarding those water resources management areas that are consistent with the watershed plans. Chanhassen has land within the boundaries of three watershed districts and one county WMO (see Figure 2.1):

• Riley-Purgatory-Bluff Creek Watershed District • Minnehaha Creek Watershed District • Lower Minnesota River Watershed District • Carver County WMO

Minnehaha Creek WD Local Plan Requirements. The MCWD updated its Watershed Management Plan in 2017. The City of Chanhassen has land in the Lake Virginia, Christmas Lake and Lake Minnetonka subwatersheds. In addition to the general requirements for Local Management Plans set forth in Minnesota Rules 8410, additional items must be addressed in the city’s Local Plan.

One focus of the MCWD plan is fostering collaboration between the District and the cities to achieve mutual water and natural resource management goals. To that end the local plan should include:

• Locations of publicly-owned lands such as parkland, right of way, or public facilities that may provide opportunities for collaborative stormwater management BMPs. • Lands that may potentially develop or redevelop within the planning timeframe. • Planned Infrastructure improvements or parks or open space acquisitions. • Potential to use development and redevelopment regulation to create incentives to protect water and other natural resources, including controls on removing mature trees. • Ways in which the city’s development review process encourages low impact development, and how the City ensures BMPs are adequately maintained post-construction. • A description of how the City will proactively and at least annually communicate and coordinate with the District on implementation efforts and opportunities for collaboration.

Riley-Purgatory-Bluff Creek WD Requirements. The Riley-Purgatory-Bluff Creek Water Management Plan requires Local Water Plans (LWP) to meet the standards set forth in Minnesota Rules 8410. In addition, cities must submit an annual compliance report describing its annual achievements and progress towards meeting its goals. The LWP should also describe the self-evaluation process the city will use to assess whether those goals and actions should be revised.

Lower Minnesota River WD Requirements. The Lower Minnesota River Third Water Management Plan requires Local Water Plans (LWP) to meet the standards set forth in Minnesota Rules 8410. The District will spot-check projects and programs for continued compliance with the approved LWP.

Carver County WMO Requirements. The Carver County WMO Comprehensive Water Management Plan requires Local Water Plans (LWP) to meet the standards set forth in Minnesota Rules 8410. In addition, if the City desires to take on regulatory responsibility, the Plan should state so, and describe the local controls, policies, and procedures it will use to administer the permitting program, and demonstrate it has the technical capacity to do so.

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Figure 2.1. Watershed Management Organizations in Chanhassen. Source: Minnesota Board of Water and Soil Districts.

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2.3 WETLAND CONSERVATION ACT

The primary permitting responsibilities for the Wetland Conservation Act of 1991 (WCA) will continue to rest with the City. Wetland LGU responsibilities include:

• Review and approve wetland delineations and determinations • Review and approve wetland exemption / no-loss applications • Review and approve wetland replacement plan applications • Coordinate Technical Evaluation Panel (TEP) meetings • Send Notices of Application and Decision to the TEP • Enforce wetland replacement monitoring requirements, review monitoring reports and certify replacement wetlands • Work with DNR and Carver County to enforce WCA violations

2.4 RELATIONSHIP TO NPDES STORMWATER PERMIT

The City holds a permit from the MPCA to discharge stormwater into waters of the state through the MPCA’s NPDES General Stormwater Permit. The permit specifies that the City must develop, receive MPCA approval of, and implement a Stormwater Pollution Prevention Plan (SWPPP) that addresses a series of Best Management Practices (BMPs) for the following six minimum control measures established by the EPA:

1. Public education and outreach 2. Public participation/involvement 3. Illicit discharge detection and elimination 4. Construction site runoff control 5. Post-construction runoff control 6. Pollution prevention/good housekeeping during municipal operations

The City’s previous SWPPP was approved in 2003 and amended in 2006. The State of Minnesota adopted a new NPDES General Stormwater Permit effective August 1, 2013, and the City submitted a permit reapplication in December 2013. Approval of the new permit and SWPPP was received in 2014.

Activities and policies to be included in the SWPPP are prescribed in the General Permit, and include many of the actions and policies set forth in this LWMP.

2.5 WATER RESOURCE RELATED AGREEMENTS

Water resource-related agreements, including Joint Powers Agreements, are typically struck between agencies or entities with overlapping regulatory interests or geographic similarities. The City has the following agreements:

• Memorandum of Agreement Between Carver County Land and Water Services and the City of Chanhassen Regarding Water Quality Education (MS4 Requirements), AIS and Targeted Monitoring Within City Boundaries. • Agreement Between the Carver Soil and Water Conservation District and the City of Chanhassen Relating to Urban Development Review and Site Inspection Services; Wetland Conservation Act; Individual Homeowner Natural Resource Issues.

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3.0 Assessment of Problems

3.1 HYDROLOGIC MODELING

As part of this Plan, the HydroCAD hydrologic and hydraulic models for the city were updated to include the most recent watershed and basin information. There are fifteen individual HydroCAD models for the City. Issues raised by these models are discussed in Appendix A in the Subwatershed Summaries. The purpose of performing this modeling is for planning level assessments. The models were not calibrated to actual runoff and flows, and are not intended to be flood studies. The models were executed for the 100-year Atlas 14 precipitation event. Model output is quite lengthy and is available electronically. The output files are incorporated into this Plan as Appendix B.

3.1.1 Areas of Known Flooding

On June 19, 2014, 4.98 inches of rain fell in less than 24 hours at the National Weather Service monitoring site in Chanhassen, a nearly 25-year return interval event. Almost 4.5 inches of rain had fallen in the weeks preceding this storm event, and the ground was saturated and ponds and wetlands were still full. Localized flooding occurred at a number of locations. These included both ongoing problem areas as well as locations where no or minimal flooding had been observed before:

• Market Boulevard north of MN T.H. 5 • Pipewood Curve • Kerber Boulevard between Saddlebrook Curve and Sierra Trail • Lake Riley Boulevard at Lyman Boulevard

3.2 IMPAIRED WATERS

Waters that do not meet state water quality standards are listed as “Impaired” by the State of Minnesota will require additional analysis in the form of a Total Maximum Daily Load (TMDL) study. A TMDL is the maximum amount of a pollutant a waterbody can receive and still meet water quality standards. The TMDL study identifies the sources and magnitude of pollutant loading and establishes a numeric load reduction that must be made for each source.

Table 3.1. Impaired Waters in Chanhassen. DNR Lake # Lake/Stream Affected Use Pollutant /Reach # Minnewashta 10-0009 Aquatic consumption Mercury FT1 Lucy 10-0007 Aquatic consumption Mercury FT1 Ann 10-0012 Aquatic consumption Mercury FT1 Susan 10-0013 Aquatic consumption/Aquatic recreation Mercury FT1 and Excess Nutrients Christmas 27-0137 Aquatic consumption Mercury FT1 Lotus 10-0006 Aquatic consumption/Aquatic recreation Mercury FT1 and Excess Nutrients Riley 10-0002 Aquatic consumption/Aquatic recreation Mercury FT1 and Excess Nutrients Bluff Creek 07020012-710 Aquatic life Fish IBI2, Turbidity Minnesota Mercury FT1, Mercury WC1, PCB 07020012-506 Aquatic consumption/Aquatic life River FT1, Turbidity 1 "FT" means mercury or PCBs in fish tissue while “WC” means in the water column. 2 Index of Biotic Integrity. A measure of the quantity and quality of aquatic life. Source: MPCA 2016 draft 303(d) list of impaired waters.

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3.3 TMDLS AND UAAS

A TMDL was completed and approved in 2013 for the Bluff Creek biotic integrity and turbidity impairments. A statewide TMDL has been completed for the mercury impairments. The Riley-Purgatory- Bluff Creek Watershed District has completed Use Attainability Analyses (UAAs) for Lake Susan, Lake Lucy, and Lake Ann. The UAAs are scientific assessments of a water body’s physical, chemical, and biological condition. The studies include water quality assessments and recommendations for protective and/or remedial measures for the studied lakes and their directly tributary watersheds. The results of these UAAs provide the City guidelines for water resource improvement projects for these water bodies. Although the UAAs provide some background data that may be used towards preparation of a TMDL they do not meet MPCA criteria for a TMDL document.

3.3.1 Total Maximum Daily Load (TMDL) Studies

Bluff Creek Turbidity and Fish Biota TMDL. Bluff Creek is listed by the Minnesota Pollution Control Agency (MPCA) as impaired for aquatic life use due to excess turbidity levels and low fish biota scores. The Turbidity and Fish Biota TMDL was approved in 2013. The Bluff Creek TMDL Biological Stressor Identification Report identified sediment, metals, habitat fragmentation, and flow as stressors to fish biota. Although the TMDL Report discusses all of these stressors, Wasteload Allocations (WLAs) were made only for total suspended solids (TSS), which represents a surrogate for both turbidity and fish biota.

Chanhassen’s TSS Wasteload Allocation requires an 88 percent reduction in TSS contributed to the stream. Primary sources of sediment are stream bank and bluff erosion, as well as poorly vegetated ravines and gullies. An inventory and assessment of the Bluff Creek lower valley was completed to identify sites contributing excessive amounts of sediment to Bluff Creek and to determine feasible options for addressing sources of excess sediment delivery to the stream.

Five sites were classified as Severe and are highest priority for stabilization and restoration, as was the stream just below the Hennepin County Regional Trail Corridor culvert crossing. The stream channel has downcut significantly below that culvert, and the culvert is being undermined, which could lead to future failure. This large drop also disrupts the connectivity of the creek, fragmenting habitat. Fish and other aquatic organisms are not able to migrate upstream of the culvert. Correction of the severe erosion and addition of a fish passage to reconnect the creek above and below the culvert were identified as priority implementation projects.

South Metro Mississippi Total Suspended Solids TMDL. The South Metro Mississippi TSS TMDL was approved in 2016. This TMDL would require a 25 percent reduction in TSS load from MS4 communities such as Chanhassen. MS4s can demonstrate they meet this reduction by implementing a suite of BMPs that the MPCA will develop, or by showing that pollutant loads from their community meet or are less than the target load of 154 lbs/acre/year. This proof can be accomplished through water quality monitoring or modeling.

Twin Cities Metropolitan Chloride TMDL. This study includes TMDLs for 37 of the 39 lakes and streams in the Metro Area that are impaired by excess chloride levels. The report also identifies high-risk waterbodies where monitoring data indicates that resource is approaching the impairment threshold. There are no chloride-impaired waters in Chanhassen, but the City is located within the tributary area of Minnehaha Creek, which is impaired by excess chloride. In addition, Bluff Creek has been classified as a high-risk waterbody. No specific load reductions were identified for Bluff Creek or any other waterbody

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in Chanhassen, but the TMDL suggests that all cities where high-risk resources are located consider developing a chloride management plan for those lakes and streams. In general, the TMDL suggests that regardless of whether or not runoff drains to an impaired or high-risk waterbody road authorities and other regulated entities take proactive steps to reduce the application of road salt for winter ice control as much as possible without compromising public safety.

3.3.2 UAAs

The three UAAs were updated in 2013. Short descriptions of findings are provided below. More detail can be found in the Lake Susan Use Attainability Assessment Update (Wenck 2013) and the Lake Lucy and Lake Ann Use Attainability Assessment Update (Barr 2013) available from the Watershed District (http://www.rpbcwd.org/resources/).

Lake Susan. Lake Susan is a shallow, 88 acre lake. Nearly all the surface area is less than 15 feet deep, shallow enough to be almost entirely dominated by rooted aquatic vegetation. Water quality is variable, some years approaching state water quality standards for shallow lakes and some years worse, but on average, the lake does not meet those standards. The Riley-Purgatory-Bluff Creek Management Plan classified Lake Susan as a deep lake, and water quality falls short of deep lake goals.

Invasive aquatic vegetation has been an issue in Lake Susan for many years. Curly-leaf pondweed and Eurasian watermilfoil present the greatest threat to the lake. The University of Minnesota has been working to manage the rough fish population in the lake while also trying to reestablish native aquatic vegetation.

Modeling completed for the UAA update estimated the amount of nutrient loading from the watershed and from internal and other sources. The North subwatershed, where there are developed areas with little or no water quality treatment, is the largest source of load to the lake. In the South subwatershed, a large wetland in Lake Susan Hills West Park is a likely exporter of phosphorus. Lake Susan also experiences high sediment loading.

Total Phosphorus (TP) load to Lake Susan needs to be reduced by 182 pounds per year, or about 25 percent, to meet the shallow lake standard. The UAA identified some pond enhancements and a restoration of the identified wetland in Lake Susan Hills Park followed by a lake alum treatment to seal bottom sediments as potential actions to achieve that goal.

Lake Lucy and Lake Ann. Water quality in Lake Lucy and Lake Ann has been fairly stable—neither degrading nor improving—in recent years. Lake Lucy currently meets the MPCA shallow lake water quality standards; however, excess phosphorus results in algal blooms and reduced water clarity that does not meet the RPBCWD’s goals. The annual phosphorus loading to Lake Lucy, based on the 2012 water year, indicates nearly half of the phosphorus load to the lake is from watershed runoff. Since the watershed to Lake Lucy has many ponds and wetlands that settle out particulates, much of the phosphorus that reaches Lake Lucy is in the soluble, or non-settleable, form that is readily available for algal uptake. The other primary contributions of phosphorus are internal sources, including release from the bottom sediments and from the dieback of Curlyleaf pondweed.

While Lake Ann is currently meeting both the RPBCWD and MPCA water quality goals, the release of phosphorus from the lake sediments appears to lead to periodic blue-green algal blooms suspended below the water surface. During the 2012 water year, more than half of the phosphorus load to Lake Ann came from internal sources, primarily the release from the bottom sediments. Approximately

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30 percent of the phosphorus load was from the Lake Ann watershed and discharge from Lake Lucy.

Because the lakes currently meet state water quality standards, no specific phosphorus load reductions have been identified. However, to meet Watershed District goals, improve water clarity, and reduce the incidence and severity of algal blooming, the UAA identified a number of management actions. These include: implementing stormwater volume abstraction rules as portions of the watershed develop or redevelop; maximizing the treatment of watershed runoff such as iron-enhanced sand filter pond benches or the use of spent lime treatments to remove soluble phosphorus; and curly-leaf pondweed treatment in Lake Lucy and a whole-lake alum treatment in Lake Ann to help control internal phosphorus load.

3.4 PROBLEMS AND ISSUES

Local water management problems, issues, and opportunities were identified by reviewing: • Statutory requirements for Local Water Management Plans • Lake inventory data • Lake UAAs and stream TMDLs • Input solicited from the public, the Environmental Commission, City staff, and state and local agency staff

Once the problems and issues were identified staff identified and prioritized potential solutions to help the City of Chanhassen accomplish the goals of this Plan. This section presents those items evaluated to develop the proposed improvements and management studies summarized in the Implementation Plan.

Table 3.2. Problems, issues, and opportunities. Water Quality • Lakes and streams are listed on the Clean Water Act Section 303(d) TMDL List of Conditions Impaired Waters. • Nonpoint source pollution reduction is necessary through maintenance practices such as street sweeping, sump manhole cleaning, and pond inspections. Drainage and • Near stream gullies and escarpments should be addressed to control sediment Flooding deposition into surface waters and to protect property and infrastructure. • Subsurface drainage causing icing on public streets and pedestrian pathways. Regulatory • Atlas 14 updated precipitation frequency data is available for adoption. Requirements and • Approaches such as Minimal Impact Development and Integrated Management Operational Policies Practices are available to reduce the public expenditures necessary to control runoff and protect and improve water quality. • The City’s approved NPDES permit and SWPPP requires ordinance revisions and operating program enhancements. • City goals, policies and ordinances to help protect natural resources may need review and refinement. Water-Based • Water quality should be protected and improved to protect and enhance Recreation Needs recreational opportunities. • Control of aquatic invasive species (AIS) is of growing concern. Maintenance • BMP maintenance and repair requirements have been identified during NPDES Requirements inspections, including restoration of storage capacity, repair of erosion, and prevention of future problems. • Street sweeping, sump manhole cleaning, and BMP inspections are necessary on an ongoing basis to help reduce nonpoint source pollutant loads.

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Education and • Education and outreach efforts could be expanded with a focus on targeted groups Outreach with new and expanded educational opportunities. Financial Resources • Financial resources are limited, requiring that projects be prioritized. Groundwater • The LWMP should be coordinated with the Wellhead Protection Program so that Protection policies that encourage infiltration and groundwater recharge are consistent with the policies to protect sensitive areas and groundwater supply recharge areas. • Seminary Fen is a rare calcareous fen and Assumption Creek is a trout stream, both of which are dependent on groundwater. Collaboration • There are opportunities for collaboration with other agencies such as the WMOs, Opportunities the county, and state agencies to leverage expertise and resources to finance and construct improvements.

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4.0 Goals and Policies

This section of the Plan outlines goals and policies guiding surface water management in the City of Chanhassen. A goal is a desired end toward which surface water management efforts are directed. Each goal has several corresponding policies that form the governing principals that will be followed to achieve the goals. Table 4.1 summarizes the six water resources management goals. The six goals and the corresponding policies are presented and discussed in more detail in the following pages.

Table 4.1. Water resources management goals. Goal Goal Area Goal Statement Number

1 Water Quantity Promote abstraction through infiltration, reuse and other methods where practicable to do so to provide flood protection, ground water recharge and improved water quality.

2 Water Quality Achieve water quality standards in lakes, streams, and wetlands consistent with their designated uses and established classifications.

3 Wetlands Protect and rehabilitate wetlands to maintain or improve their function and value.

4 Groundwater Prevent contamination of the aquifers and promote groundwater recharge to maintain base flows in streams and wetlands.

5 Regulatory Maintain primary responsibility for managing water resources at the Responsibility local level where efficient to do so but continue coordination and cooperation with other agencies and organizations.

6 Public Education and Cultivate an environmentally literate public to promote an active Participation community role in sustainable management of water resources.

4.1 GOALS AND POLICIES

Water Quantity

Development and changes in land use that result in additional impervious surface will result in a corresponding increase in stormwater runoff rates and volumes. This increase can cause flooding and erosion issues in the downstream system. It is important to control these increased runoff rates and volumes in order to ensure reduction of flooding in the downstream system and to control the potential effects of erosive flows on streams and waterways.

Storm sewer design within the City of Chanhassen has been largely based upon the precipitation frequency estimates published in the Weather Bureau’s Technical Paper Number 40 (“TP 40”), Rainfall Frequency Atlas of the United States for Durations from 30 Minutes to 24 Hours and Return Periods from 1 to 100 years (Hershfield 1961). In April 2013 the National Oceanic and Atmospheric Administration (NOAA) published Atlas 14, Precipitation – Frequency Atlas of the United States, Volume 8 Version 2.0 to replace TP40. Atlas 14 used a much more robust data set over a much longer time span then was used for TP 40. While the 2-year average return interval and the 10-year average return interval remained relatively unchanged, the 100-year amount increased by 1.38 inches or 23% over the previous estimate

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(Table 4.2). The longer period of record used in developing Atlas 40 allowed for a more statistically accurate estimate of the less frequent events.

Table 4.2. Comparison of TP-40 to Atlas 14 event depths. Publication 2-Year, 24 Hour 10-Year, 24 Hour 100-Year, 24 Hour TP 40 2.8” 4.2” 6.0” Atlas 14 2.87” 4.27” 7.38”

Even though we now know to design to greater depths for certain events the City’s infrastructure has generally performed very well. However, there have been a few instances where the existing infrastructure was inadequate to accommodate the runoff volumes and/or rates. The City experienced large storm events in 2005, 2009, and 2014. The first 2005 large event occurred on September 3 and 4 and totaled approximately 5.55 inches of rainfall. The second occurred on October 4 and 5, 2005, and totaled approximately 4.61 inches of rainfall. From June 19 through June 20, 2014 the Chanhassen area received approximately 6.23 inches of rainfall. That June Chanhassen received 12.79 inches of rainfall after a wetter than average April and May.

While significant damages did not occur from these events, a few areas were subject to high water levels and short-term flooding of streets. Lotus Lake, Lake Riley and Lake Minnewashta all experienced extended high water levels. Residents on these lakes experienced submerged docks and some shoreline erosion damage. Users were subject to the City’s emergency slow/no-wake restrictions for a period of about 15 days. Looking at opportunities to reduce the extent and/or duration of these high water levels is one of the key water quantity issues for the City. Because the lake discharges to Purgatory Creek, the solution is not a simple one. Coordination with RPBCWD, Lotus Lake area residents and the potentially impacted property owners downstream will be a critical step in developing a long term solution that does not push the problem downstream.

Another issue that was discovered during the large event of 2005 is the lack of emergency overflows and flow paths in some areas of the City. Ultimately, the City’s focus is to operate and maintain the system so that it continues to function in the way it is intended, and provides flood protection for adjacent properties. During review of storm water management plans it is important for City staff to review the location of emergency overflow paths for storm water infrastructure in new developments.

In recent years there has been a paradigm shift in water quantity management. The strategy today is to where possible manage stormwater where it falls, as exemplified by the State of Minnesota’s Minimal Impact Design Standards (MIDS). The emphasis is on reducing the volume of runoff discharged to downstream resources through abstraction, or the permanent retention of runoff on a site through structures and practices such as infiltration, evapotranspiration and capture and reuse. This abstraction can help mitigate the effects of larger storm events. Abstraction has other benefits as well, including minimizing and reducing the amount of pollution reaching our lakes, rivers and streams and recharging groundwater resources.

A Flood Hazard Boundary Map dated January 1979 was completed for the City of Chanhassen, which identifies the entire City as a No Special Flood Hazard Area or Zone C. The Flood Insurance Study for Carver County is being updated as part of the FEMA Map Modernization Program. Updated maps are expected to be published in 2018. Maps are available from the FEMA website, www.fema.gov, available at City Hall or from the respective WMO.

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Goal 1. Promote abstraction through infiltration, reuse and other methods where practicable to do so to provide flood protection, ground water recharge and improved water quality.

Policy 1.1. Require all developments to construct stormwater best management practices, improve existing practices, and/or contribute to the construction or improvement of a regional facility for the purpose of reducing peak flows and runoff volume generated by the subject development. Policy 1.2. Require all development and redevelopment projects to demonstrate no net increase in the annual runoff water volume discharged from the site compared to pre-development conditions. Policy 1.3. Creative and innovative site design and Best Management Practices, including infiltration systems and stormwater reuse, will be the preferred practice unless site limitations such as soil conditions, depth to groundwater, and safety preclude the use of these practices. Policy 1.4. Continue to stringently enforce impervious surface requirements set forth in City Code and development contracts. Policy 1.5. Establish and maintain overflow routes for ponds and low areas to provide relief during storm conditions that exceed design conditions. Policy 1.6. Where volume reduction is infeasible and detention ponds are necessary, regional ponding areas, as opposed to individual on-site ponds, should be used to reduce flooding, to control discharge rates, and to provide necessary storage volumes as indicated in this Plan. Policy 1.7. When areas are developed, redeveloped, and as infrastructure is replaced, stormwater facilities should be built and/or upgraded to provide or improve flood management and water quality. Policy 1.8. Encourage the development of new and improvement of existing ponds located upstream of priority water bodies. Policy 1.9. Permanently protect surface water impoundments and drainage systems by requiring the dedication of land and/or protective easements as required. Policy 1.10. Design, operate and maintain newly constructed storm water facilities in accordance with this Plan. Policy 1.11. Manage floodplain activities in accordance with all City, state, and federal regulations. Policy 1.12. Require building elevations to provide at least 3 feet of freeboard adjacent to ponding areas and floodplains as an area develops or when drainage facilities are constructed for an area. Policy 1.13. Preserve existing water storage below 100-year flood elevations. Policy 1.14. Continue management and development of public and private stormwater infrastructure as separate systems. Policy 1.15. Require development and redevelopment stormwater management incorporate the protection of existing and native plant and forest communities to meet regulatory requirements.

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The City of Chanhassen seeks to maintain and improve the water quality in its lakes, streams and wetlands to meet or better the State of Minnesota surface water quality standards for lakes and streams. There are many potential sources of water pollution that can negatively impact public safety and the enjoyment of these resources. Stormwater runoff can convey phosphorus, chloride, sediment, oils, debris, and bacteria to downstream waters, increasing algal blooms, reducing water clarity, and impacting fish and other aquatic communities. Excessive volumes and rates of stormwater runoff discharged into channels and streams can erode streambanks, causing additional water quality impacts.

One of the City’s chief strategies for achieving its water quality goals is to require development and redevelopment to provide stormwater quality treatment through abstraction of 1.1 inch of runoff from impervious surfaces, or if that is infeasible, to provide treatment by some other means. Other strategies include better management of construction site erosion control measures, reducing the level of impervious cover, reducing the extent of managed lawn areas and replacing them with native vegetation, reducing stream bank erosion, and practicing good housekeeping practices, such as removing leaves from streets and storm drains and limiting the use of phosphorus fertilizers.

Goal 2. Achieve water quality standards in lakes, streams, and wetlands consistent with their designated uses and established classifications.

Policy 2.1. Manage each water body in the City’s surface water system to meet state, local, and federal water quality standards. Policy 2.2. Require that development and redevelopment projects demonstrate no net increase in the annual mass of total suspended solids (TSS), total phosphorous (TP) from the site compared to pre-development conditions. Policy 2.3. Require owners of development or redevelopment projects to provide on-site volume reduction or treatment or, where volume reduction is infeasible, contribute to the construction or improvement of a regional facility. Policy 2.4. Establish and implement on-going programs for property owners, local leaders, and those who live, work and play in the city designed to promote active stewardship of water resources. Develop and maintain a public education program to promote reduction of nutrient and sediment loading to water bodies. Policy 2.5. Continue to monitor long-term water quality trends on prioritized water bodies. Policy 2.6. Develop and implement a priority ranking scheme to focus management activities and capital improvements. Update priorities annually with a 5 year horizon. Policy 2.7. Evaluate the progress of the surface water management program on an annual basis in conjunction with the NPDES MS4 annual report. Policy 2.8. The City may require higher water quality standards in areas draining to an Impaired or Special Water. Policy 2.9. The City will lead by example by following the standards of this Plan and implementing BMPs to provide pollution prevention and water quality treatment on City-initiated projects. Policy 2.10 Require the use of low impact design techniques such as Mimimal Impact Design Standards (MIDS) during development review to meet infiltration and reduce pollutant and nutrient loading to water resources where feasible.

Page | 4-4 REVIEW DRAFT Local Stormwater Management Plan, January 2018 Policy 2.10. Prohibit the discharge of foreign material into the storm water system. Such material should include, but not be limited to, waste oil, paint, grass clippings, leaves, commercial fertilizers, trash, construction debris, and miscellaneous chemicals. Policy 2.11. Continue implementing a spill response program for the City personnel to prevent discharge of spilled materials into the storm sewer system. Policy 2.12. Continue to implement the erosion and sediment control policies and the construction site inspection program to ensure reduction of water quality impacts from lack of erosion and sediment control.

Wetlands

The City of Chanhassen serves as the Local Government Unit (LGU) for the purposes of administering the State of Minnesota’s Wetland Conservation Act (WCA). The City’s Wetland Protection Ordinance sets forth standards for the protection of wetlands, including wetland buffers, setbacks, and mitigation of unavoidable impacts. The policies and strategies set forth in this Plan will apply to new development and redevelopment projects proposed within the City. Any wetland habitat on property to be developed will be subject to these management policies, as well as the rules and requirements of the Wetland Conservation Act.

Goal 3. Protect and rehabilitate wetlands to maintain or improve their function and value.

Policy 3.1. Continue to act as the responsible Local Government Unit (LGU) for administration of the Minnesota Wetland Conservation Act (WCA) for wetland impacts in the City. Policy 3.2. Maintain an official wetlands map that classifies wetlands by function and value and periodically update the wetland inventory data and the wetland management classifications. Policy 3.3. Update the City’s Wetland Protection Ordinance as necessary to maintain consistency with state and watershed district requirements. Policy 3.4. Promote stewardship of wetlands on private property Policy 3.5. Improve historic wetlands through pre-treatment and restoration activates when practical to do so, and in conjunction with street improvement and redevelopment projects

Groundwater

The City’s role in managing groundwater resources is limited in scope. There are actions the City can take to prevent or minimize impacts to groundwater quality. Groundwater and surface waters interact, and streams and wetlands and to a lesser extent lakes are reliant on groundwater contributions to maintain stream baseflow and wetland hydrology. The City’s primary strategies in groundwater management are to encourage infiltration of stormwater to help recharge surficial groundwater and to encourage water reuse and conservation to reduce consumption and protect the water supply.

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Goal 4. Prevent contamination of the aquifers and promote groundwater recharge to maintain base flows in streams and wetlands.

Policy 4.1. Continue implementation of the City of Chanhassen Wellhead Protection Plan. Policy 4.2. Cooperate with the Minnesota Department of Health (MDH), Carver County, the Department of Natural Resources, and other agencies to periodically assess the vulnerability of groundwater used for drinking water supplies. Policy 4.3. Promote infiltration of stormwater and resulting groundwater recharge where it is feasible and does not pose a threat to groundwater quality, in accordance with the Minnesota Department of Health’s Evaluating Proposed Storm Water Infiltration Projects in Vulnerable Wellhead Protection Areas. Policy 4.4. Promote proper well abandonment.

Regulatory Responsibility

The City assumes the role of permitting all land alteration activities summarized in table 4.3 and enforcing the standards and policies set forth by the Plan. Riley Purgatory Bluff Creek Watershed District (RPBCWD) also reviews and permits on any proposed land alteration under their rules within the RPBCWD. Minnehaha Creek Watershed District (MCWD) permits for projects that include land alteration, floodplain alteration, dredging, shoreline and streambank improvement, and stream and lake crossings. Lower Minnesota River Watershed District reviews alterations to land within the Minnesota River valley. Carver County Water Management Organization reviews land altering projects in the WMO. The City is the LGU for the Wetland Conservation Act, and assumes the role of permitting all wetland impacts.

The Minnesota Department of Natural Resources has authority over issues relating to water and wetlands designated as State Protected Wetlands and Waters. The U.S. Army Corps of Engineers has authority relating to all wetlands identified by the U.S. Fish and Wildlife Service’s National Wetland Inventory.

Carver County and the Minnesota Department of Health have regulatory authority over groundwater issues within the City. Erosion control falls under several jurisdictions including the City, the watershed districts, and the MPCA. The MPCA also has regulatory authority over individual septic systems within the City limits.

Table 4.3. Agencies with regulatory authority. Rule Chanhassen CCWMO LMnRWD MCWD RPBCWD Dredging And Sediment Removal No No NA Yes Yes Erosion Prevention & Sediment Yes MOU NA MOU Yes Control Floodplain Management Yes MOU NA Yes Yes Shoreline & Streambank Stabilization No No NA Yes Yes Stormwater Management Yes MOU NA MOU Yes Water Appropriations No No NA No Yes Waterbody Crossings No No NA Yes Yes Wetland & Stream Buffers Yes Yes NA MOU Yes MOU = Memorandum of Understanding

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Goal 5. Maintain primary responsibility for managing water resources at the local level where efficient to do so but continue coordination and cooperation with other agencies and organizations.

Policy 5.1. Adopt policies consistent with the most stringent local watershed authorities’ management plans to the extent practicable. Policy 5.2. Enter into memorandum of understanding where maintaining consistency with local watershed authorities’ plans would otherwise be counter to City’s overall goals. Policy 5.3. This plan and all subsequent amendments will be consistent with the plans of regulatory agencies. Policy 5.4. This plan will be amended as necessary to remain current. Policy 5.5. Coordinate projects and information with government agencies; i.e. MnDOT, Carver and Hennepin Counties, Department of Natural Resources, Watershed Districts, and Water Management Organizations.

Public Education and Participation

The public education and participation goals and policies recognize that people want to be involved in decisions that affect the water resources in their community. The City seeks to create opportunities for the public to participate in information gathering and decision-making. Public education and participation activities are also requirements of the National Pollutant Discharge Elimination System (NPDES) Permit.

Goal 6. Cultivate an environmentally literate public to promote an active community role in sustainable management of water resources.

Policy 6.1. The City will continue to provide opportunities for public involvement (e.g., neighborhood meetings, public hearings, mailed notices, etc.) for significant water resource decisions or projects. Policy 6.2. The City will coordinate and consult with appropriate City commissions and committees on surface water issues. Policy 6.3. The City will communicate with lake associations and other appropriate civic and citizen groups. Policy 6.4. The City will actively implement the current educational programs and work to develop and implement new education programs and activities related to water resources. Policy 6.5. The City will cooperate with other agencies and encourage establishment of model interpretative sites for public education like the stormwater practices at the Landscape Arboretum. Policy 6.6. Continue to remain in compliance with the NPDES Phase II MS4 permit with respect to public education and involvement.

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5.0 Implementation Plan

The City of Chanhassen will implement both management programs and capital projects to achieve the goals and policies set forth in this Plan. These actions address the problems and issues identified here as well as NPDES and TMDL requirements and agency and watershed expectations. The following sections describe those actions, which as summarized in Tables 5.2 and 5.3. Each year the City will review progress and resources, and these implementation actions may be reviewed and updated based on changing conditions or requirements. If necessary, this Plan may be amended in accordance with the procedure set forth in Section 6.0.

5.1 PERMITTING AND ENFORCEMENT

Numerous local, state, and federal agencies regulate water resources. However, the primary regulators are the City of Chanhassen; the four watershed management organizations within Chanhassen; the Minnesota Department of Natural Resources (MDNR); and the Minnesota Pollution Control Agency (MPCA). These regulations are discussed in Section 2.0 Regulatory Framework.

5.1.1 Current Ordinances and Potential Revisions

The City of Chanhassen has enacted numerous policies and ordinances regulating and managing water resources. These are described in Section 2.1 above. In its NPDES stormwater permit application, the City agreed to within one year or permit approval adopt ordinance revisions as necessary to meet permit requirements. Additional regulatory revisions are necessary to bring the ordinances into conformance with the requirements of the watershed district in the city (Table 5.1). The city will undertake these ordinance revisions within six months after adoption of this Plan. It is expected that where the requirements of the individual watershed distracts differ, the City will adopt the most stringent of the requirements for application citywide. The most stringent requirements the City will adopt are highlighted in Table 5.1. In 2018 the City will implement a new water resource permit and process for development and redevelopment to administer permit requirements.

The City intends to continue to permit development and redevelopment projects requiring stormwater, wetland, floodplain, or erosion control review and approval, and will work with the WMOs to modify the existing Memoranda of Understanding or adopt a new MOU. The city will also work with the WMOs as it considers regulatory revisions to ensure that they are consistent with WMO requirements. It is the City’s desire to reduce administrative and regulatory burden while staying protective of our water and natural resources.

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Table 5.1. Regulatory requirements of various agencies compared to Chanhassen current ordinances. Note: Highlight indicates the standards the City expects to adopt following approval of the Plan. Lower Minnesota River WD Carver County WMO Riley- Purgatory –Bluff Cr WD Minnehaha Creek WD Plan: December 14, 2011 Standard Chanhassen NPDES General Permit NPDES Construction Permit Plan: October 26, 2010 Plan: January 26, 2011 Plan: July 5, 2007 Rules: Cities; new standards Rules: 10/15/16 Rules: Effective 1/1/15 Rules: 6/6/14 pending 9/17 Threshold: single family N/A Disturb >1 acre of land, or Disturb >1 acre of land, or Create 1> impervious or a. Land-disturbing activities Disturb >1 acre of land ≥1 acre where more than 20% residential new development part of common development part of common development >10,000 sf in sensitive areas that will disturb 50 cubic yards Pending Draft: within the of site is or will be impervious >1 acre >1 acre or more of earth; HVRA Overlay, create >10,000 b. Land-disturbing activities sq ft new impervious area that will disturb 5,000 square feet or more of surface area or vegetation; or c. Subdivision of a parcel into three or more residential lots. Threshold: non-residential N/A Disturb >1 acre of land, or Disturb >1 acre of land, or Create 1> impervious or a. Land-disturbing activities Disturb >1 acre of land ≥1 acre where more than 20% new development part of common development part of common development >10,000 sf in sensitive areas that will disturb 50 cubic yards Pending Draft: within the of site is or will be impervious >1 acre >1 acre or more of earth; HVRA Overlay, create >10,000 b. Land-disturbing activities sq ft new impervious area that will disturb 5,000 square feet or more of surface area or vegetation Threshold: single family N/A Disturb >1 acre of land, or Disturb >1 acre of land, or Additions: Create >1 acre Same as above, except where Disturb >1 acre of land ≤1 acre; requirements vary by residential redevelopment part of common development part of common development impervious or >10,000 sf in redevelopment of more than Pending Draft: within the size, change in >1 acre >1 acre sensitive areas, for new 50% of site or that increases HVRA Overlay, create >10,000 imperviousness, and % impervious impervious by more than 50%, sq ft new impervious area disturbance Tear downs: Create >1 acre applies to entire site; less than impervious or >10,000 sf in 50% of site, applies only to sensitive areas, for all disturbed area/new impervious created by project; impervious

Redevelopments that reduce imperviousness by 10% are exempt from rate, volume, and WQ reqs Threshold: non-residential N/A Disturb >1 acre of land, or Disturb >1 acre of land, or Additions: Create >1 acre Same as above, except where Disturb >1 acre of land >1 acre; requirements vary of redevelopment part of common development part of common development impervious or >10,000 sf in redevelopment of more than Pending Draft: within the < or > 40% site disturbance >1 acre >1 acre sensitive areas, for new 50% of site or that increases HVRA Overlay, create >10,000 impervious impervious by more than 50%, sq ft new impervious area Tear downs: Create >1 acre applies to entire site; less than impervious or >10,000 sf in 50% of site, applies only to sensitive areas, for all disturbed area/new impervious created by project; impervious

Redevelopments that reduce imperviousness by 10% are exempt from rate, volume, and WQ reqs

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Lower Minnesota River WD Carver County WMO Riley- Purgatory –Bluff Cr WD Minnehaha Creek WD Plan: December 14, 2011 Standard Chanhassen NPDES General Permit NPDES Construction Permit Plan: October 26, 2010 Plan: January 26, 2011 Plan: July 5, 2007 Rules: Cities; new standards Rules: 10/15/16 Rules: Effective 1/1/15 Rules: 6/6/14 pending 9/17 Threshold: grading and erosion Disturb>5,000 sf, excavate or Disturb >1 acre of land, or Disturb >1 acre of land, or >1 acre construction activity; a. Land-disturbing activities As required by the General All land disturbing activity control place >50 cy fill, any part of common development part of common development <1 acres in sensitive areas or that will disturb 50 cubic yards Permit for Construction except agriculture and disturbance on “highly >1 acre >1 acre part of common development or more of earth, Pending Draft: Disturb >1 acre disturbances of less than erodible” land or land in the b. Land-disturbing activities of land, or within the HVRA 5,000 sq ft moving less than Bluff Creek Overlay District, or that will disturb 5,000 square Overlay District, disturb more 50 cu yd with any earthwork permit feet or more of surface area than 5,000 sq feet or disturb or vegetation 50 cubic yards or more of earth, Water quality: new Whichever is most restrictive: No net increase in TP or TSS Wet pond with 1,800 cu ft 90% removal of TP and TSS Provide for at least 60% Treatment as required by the No net increase in TP, except development meet NPDES construction annual load dead storage per contributing from the 1.05” event removal of TP and 90% General Permit for where land use was row permit; NURP criteria (90% acre and live storage of 1” of removal of TSS from all runoff Construction; NURP pond crop/feedlot, must be TSS and 60% TP; or special runoff from new impervious from site designs apply modeled as if meadow requirements for discharges surface Draft pending: No net to “Preserve” waters increase in TP or TSS. Within HVRA 60% decrease in TP and 80% TSS from predevelopment condition Water quality: redevelopment Whichever is most restrictive: Decrease in TP and TSS annual Wet pond with 1,800 cu ft 90% removal of TP and TSS Provide for at least 60% Treatment as required by the Varies based on size and meet NPDES construction load dead storage per contributing from the 1.0” event removal of TP and 90% General Permit for whether impervious is permit; NURP criteria (90% acre and live storage of 1” of removal of TSS from all runoff Construction; NURP pond increased or decreased TSS and 60% TP; or special runoff from new impervious from site designs apply requirements for discharges surface Draft pending: No net to “Preserve” waters increase in TP or TSS. Within HVRA decrease in TP and TSS from predevelopment condition Rate control No increase over 1- or 2-, 10-, No specific requirement No more than 5.66 cfs per No increase over 2-, 10-, and No increase over 2-, 10-, and No increase over 1-or 2-, 10-, No increase over 1-, 10-, and and 100-year rates acre pond surface area 100-year rates and 10-day 100-year Atlas 14 Nested or 100-year rates Pending 100-year rates, except where snowmelt; Distribution rates draft: using Atlas 14 Nested land use was row Extended detention for sites Distribution rates crop/feedlot, must be discharging directly to modeled as if meadow streams: 50% reduction of 2- year discharge from existing Infiltration: new development Discharging to special waters: No net increase in annual If more than 1 acre of new Abstraction of 1.0” runoff 1.1” abstraction from all 0.5” runoff from new 1” from impervious surface. Infiltration of excess volume runoff volume impervious, infiltrate/abstract from impervious surface impervious surface impervious surface Where 1” infeasible, must do over pre-development 1” from new impervious Pending Draft: sites that at least 0.5” plus additional TP volume, up to 2-yr, 24-hour surface create >1 acre new reduction event impervious abstract 1” from Any grading permit: Soil all impervious. Within HVRA, amendment ripped into sites that create >10,000 sf existing soil materials to a new impervious abstract 1.1” depth of ten inches on the site

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Lower Minnesota River WD Carver County WMO Riley- Purgatory –Bluff Cr WD Minnehaha Creek WD Plan: December 14, 2011 Standard Chanhassen NPDES General Permit NPDES Construction Permit Plan: October 26, 2010 Plan: January 26, 2011 Plan: July 5, 2007 Rules: Cities; new standards Rules: 10/15/16 Rules: Effective 1/1/15 Rules: 6/6/14 pending 9/17 Infiltration: redevelopment Discharging to special waters: Decrease in annual runoff If more than 1 acre of new Abstraction of 1” runoff from 1.1” abstraction from all 0.5” runoff from new 1” from impervious surface. Infiltration of excess volume volume impervious, infiltrate/abstract impervious surface impervious surface impervious surface Where 1” infeasible, must do over pre-development 1” from new impervious Pending Draft: sites that at least 0.5” plus additional TP volume, up to 2-yr, 24-hour surface create >1 acre new reduction event impervious abstract 1” from Any grading permit: Soil all impervious. Within HVRA, amendment ripped into sites that create >10,000 sf existing soil materials to a new impervious abstract 1.1” depth of ten inches on the site Wetland buffer ** 16.5 to 50 feet from wetlands No specific requirement 100 feet from a special water Minimum 20 feet, adjusted Avg width 20 to 80 feet from a. <2 acres, 25’ minimum; 16 to 75 feet, depending on depending on mgmt. class; based on slope, whether wetlands, depending on b. .2 acres, 25’ minimum, wetland mgmt class 100 feet from special water runoff s directed to the buffer mgmt. class; 50 feet from a average 50’ or if the wetland is ranked water basin; 50 feet from the “high,” to a maximum 50 feet thalweg of any watercourse in a High Risk Erosion Area, 50 feet from the centerline of a public waters watercourse Linear projects No specific requirement Disturb >1 acre of land; may Disturb >1 acre of land Projects adding 1 acre or If project constructs more No specific requirement Projects creating >10,000 sq ft be excepted from some or all more of impervious (10,000 sf than 5,000 square feet of new impervious surface infiltration requirement if lack in sensitive areas), for new impervious, and creates ≥1 sufficient right of way impervious created by project. acre new or fully Reconstructs that reduce reconstructed impervious imperviousness by 10% are surface. Applies only to all exempt from rate, volume, new and reconstructed and WQ reqs impervious surface. Bluff requirements No removal of vegetation and No specific requirement No specific requirement Unknown Unknown No removal of vegetation in No specific requirement no new impervious in the the Bluff Impact Zone and Bluff Impact Zone (20’ from Bluff Face; new structure top of bluff); new structure setback 30 ft top of bluff, SSTS setback 30 ft top of bluff, SSTS setback 50 ft. Pending Draft: setback 50 ft establishes High Value Resources Area (HVRA) Overlay District TP-40 or Atlas 14 TP-40 No specific requirement No specific requirement Atlas 14 Atlas 14 Cities Will adopt Atlas 14 as part of Pending Draft: Atlas 14 current rule revision

** No single WMO had the most stringent wetland buffers. The City will adopt the most stringent buffers across all WMOs as follows: Preserve management class = 80’ base buffer width and 67’ minimum, Manage 1 = 60’ base buffer width and 34’ minimum, Manage 2 = 40’ base buffer width and 24’ minimum, Manage 3 = 20’ base buffer width and 16’ minimum. Seminary Fen = 100’ base buffer width and 50’ minimum. Base buffer widths will be an average for all management classes. Principal structure setback will be 20’ for all management classes.

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5.1.2 NPDES Permit Implementation Requirements

Under the requirements of NPDES Phase II, the City has implemented a Storm Water Pollution Prevention Program (SWPPP). Best Management Practices (BMPs) identified in the MPCA-approved SWPPP are implemented on an ongoing basis. Annual activities are detailed in the city’s Annual Report and reviewed at an annual public meeting prior to submittal of the annual report to the MPCA. More information about the SWPPP can be found in the Surface Water Resources Section of the City’s website (http://www.ci.chanhassen.mn.us/index.aspx?nid=1085.)

The City’s Engineering/GIS Department maintains databases and GIS mapping of stormwater and wetland information for both public and private systems. These sources summarize pertinent management information about BMPs, wetlands, and other water resources in the city. The information provided for stormwater ponding systems includes physical condition, maintenance histories, pond elevations, watershed acreages, basin sizes, and other as-built information where available. This information is being collected, updated, and integrated into asset management software on an ongoing basis as part of the NPDES Phase II permit requirements.

The State’s General Permit was reissued effective August 1, 2013, and the City has been issued a reauthorized permit. The City’s SWPPP application identified a number of BMPs that the City needs to initiate or update, such as developing certain programs, expanding record keeping, and establishing new or modified policies. The new permit also requires revisions to the city’s ordinances requiring stormwater management, namely adopting more stringent standards to reduce phosphorus and total suspended sediment in stormwater runoff, limiting new volumes of stormwater runoff, public education and staff training, illicit discharge, BMP inspection and maintenance for both public and private stormwater BMPs.

5.2 IMPLEMENTATION PROGRAMS AND PROJECTS

5.2.1 Education and Outreach Program

The City recognizes that a critical element in reaching the long-term goals developed for this LWMP is public education. An education and outreach plan will be developed to achieve these goals and meet requirements of the NPDES permit. The City also uses various media outlets such as local news articles, City newsletters, Facebook, and the City of Chanhassen website to educate citizens on the basics of our stormwater system, provide updates on current actions the City is taking to monitor or improve stormwater systems, and inform residents about opportunities to improve local water bodies through workshops, volunteer opportunities, or rebates. City events and festivals provide additional opportunities for education. High priority topics are periodically identified for emphasis, including topics such as:

• Water resource management • Pollinators and Wildlife habitat • Groundwater protection • Low impact and green design such as pervious pavers • Wetlands • Pet waste control • Native plant establishment • Leaf and grass clipping management • Wetland, lake and pond buffers • Lawn chemical and phosphorus fertilizer usage

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Adults and youth can also participate in outreach activities such as: the storm drain labelling program; Wetland Health Evaluation Program (WHEP); park cleanup events; Citizen Assisted Lake Monitoring program (CAMP). The City Council relies on a Planning Commission and Environmental Commission to provide recommendations and direction on water resource topics.

The City recognizes the important value of coordination and collaboration with other agencies, and will continue to find opportunities to improve these relationships and will utilize collaborative resources such as WaterShed Partners, Blue Thumb, Let’s Keep it Clean, and the Minnesota Stormwater Coalition to maximize resources and message impacts. Education programming includes training for City staff on various water resources management topics.

5.2.2 Monitoring Program

Citizen Assisted Monitoring Program (CAMP). The City of Chanhassen partners with the Metropolitan Council to participate in its Citizen Assisted Monitoring Program (CAMP). Volunteers collect surface water samples from Chanhassen lakes. The samples are then sent to the Metropolitan Council to be analyzed for the following:

• Total phosphorus (TP) • Total Kjeldahl nitrogen (TKN) • Chlorophyll-a (CLA)

Volunteers also gather the following information:

• Measure surface water transparency using a Secchi disc • Record water temperature • Record perceptions such as weather conditions

Samples are taken bi-weekly from April through October (14 sampling dates) and are sampled at the lake's deepest open-water location. The CAMP currently monitors the following lakes:

• Lake Lucy • Lake Minnewashta • Lake Riley • Lake St. Joe • Lake Susan • Lotus Lake

Stream Health Evaluation Program (SHEP). This program gives citizens professional training on how to evaluate a stream health based on physical assessments and bio-monitoring. Citizens evaluate physical characteristics of stream sites, collect and identify macro-invertebrates. Citizens get hands on opportunities to learn about stream ecosystems and assist Carver County in water quality monitoring.

Aquatic Invasive Species (AIS). AIS monitoring is coordinated through a partnership program with CCWMO, RPBCWD, and local lake associations

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5.2.3 Operations and Maintenance

The City of Chanhassen follows Best Management Practices (BMPs) in operating and maintaining its infrastructure and facilities, consistent with its NPDES permit and this Plan. City staff and projects serve as a model for good housekeeping practices. Some specific Best Management Practices integrated into daily activities include:

Street Sweeping. The City sweeps all streets at least annually, and sweeps more frequently in certain key areas. Staff continuously reviews street sweeping practices to assure they are consistent with the latest management recommendations. Some TMDLs and UAAs have identified key areas where enhanced sweeping can provide additional nutrient and sediment removal to protect or improve lake and stream water quality.

Snow and Ice Control. Street maintenance staff use the recently-developed Winter Maintenance Assessment Tool from the MPCA to evaluate and enhance snow and ice control practices optimizing the application of road salt - sodium chloride – to limit chloride loading to surface waters.

BMP Inspections and Maintenance. In accordance with its NPDES permit, stormwater ponds are inspected at least every five years for sediment accumulation and maintenance needs. The City’s BMP Inspection and Maintenance Program ensures public and private stormwater infrastructure is inspected and maintained to meet regulatory requirements. Private stormwater BMPs on sites over an acre that discharge into the City’s system submit annual inspection reports, and are inspected by City staff once every three years. The City utilizes design standard details setting forth the City’s BMP and infrastructure design and maintenance requirements. The City is developing its Stormwater Inventory Inspection and Maintenance Plan. This Plan includes both activities necessary to meet NPDES Phase II permit obligations as well as general operations and maintenance activities. These include:

• BMP operation and maintenance plans • Vegetation Management Plan • Facilities Maintenance Plans • Street and parking lot sweeping • Chloride management • Catch basin and sump inspection, cleaning, and repair. • Sump catch basin inspection, cleaning, and repair. • Sediment removal schedules. • Televising, jetting, and repair of storm sewers and culverts. • Treatment effectiveness evaluation. • Illicit discharge detection and elimination plan

As a requirement of its NPDES permit, the City must establish Enforcement Response Procedures and Plan Review Checklists which will be added as Appendix D and E within 6 months of Plan adoption. The City of Chanhassen also maintains up to date GIS shapefiles containing information about water bodies, stormwater facilities, and stormwater infrastructure.

Opportunistic BMPs. Where possible, Chanhassen will incorporate BMPs into its street and utility infrastructure to protect and preserve its water and natural resources.

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5.2.4 Capital Improvement Program

The Implementation Plan in Tables 5.2 and 5.3 details a Capital Improvement Program (CIP) of projects. The Use Attainability Analyses (UAAs) and Total Maximum Daily Load (TMDL) studies have identified potential actions that could help protect and improve the water quality in and enjoyment of studied waterbodies. Maintenance and condition assessments have identified a number of pond maintenance and other projects such as dredging to restore or enhance the effectiveness of those features, and priority actions have been included in the CIP.

The CIP also includes projects to install water quality BMPs as part of routine street or other construction projects. These projects are intended to maximize the amount of nutrient and sediment removal from stormwater prior to being discharged into the lakes, streams, and wetlands in the community.

The CIP also includes collaborative projects with the watershed districts. The City is open to working together with the districts to identify additional projects or opportunities, including working with the Minnehaha Creek district in advancing its Balanced Urban Ecology policy.

This CIP is periodically reviewed and updated, and additional projects may be added as more or better information is available or as opportunities arise.

5.3 IMPLEMENTATION PLAN FUNDING

The City will fund the Implementation Program (IP) through a combination of sources. The primary source of funds will be Stormwater Utility Fees. The types of activities included in the IP can be categorized as operations and maintenance; programs and special studies; and capital projects. Operations and maintenance and most of the proposed programs and special studies would be funded by the Stormwater Utility, the General Fund, or the Water Surcharge Fund. For capital projects, other sources of funding may be available to supplement Stormwater Utility Funds: matching funds from the watershed districts, contributions from other agencies for cooperative projects, or grant funds.

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Table 5.2. Chanhassen LWMP Implementation Plan 2018-2027. Program/Project Description Cost Year Funding Source* PROGRAMS AND ADMINISTRATION Administration Maintain and update modeling tools Update the city’s integrated stormwater management models and tools and develop new tools and linkages as $30,000 As needed SWUF, GF necessary to manage stormwater and water quality. Implement SWPPP Undertake operations and maintenance activities in accordance with the City’s approved SWPPP and NPDES permit $430,000 Annual SWUF including Vegetation Management, BMP Inspection and Maintenance, and IDDE programs Implement ordinances Implement stormwater management, shoreland, floodplain, and wetland management ordinances. Implement permit $95,000 Annual SWUF, permit fees program to administer standards and ordinances Revise and update ordinances Update ordinances as necessary, based on new MOU, WMO or NPDES permit requirements, evolving standards and $5,000 As needed SWUF new best management practices. CIP Updates Update the CIP annually $5,000 Annual SWUF WCA Administration Continue to act as LGU for administration of WCA for wetlands in the city. $40,000 Annual Permit fees Education and Outreach General education and outreach programming Both individually and with the city’s partners and using a variety of delivery mechanisms to cultivate an $30,000 Annual SWUF, WMO, CWF environmentally literate public to promote an active community role in sustainable management of water resources. Education and Outreach Plan Complete the Education and Outreach Plan to assist with targeting educational needs, audience, funding priorities, $5,000 2020 SWUF partnership opportunities and annual program assessment Monitoring Water quality and AIS monitoring Continue CAMP and AIS support partnership monitoring programs. Develop additional citizen monitoring $20,000 Annual SWUF, WMO, CWF opportunities that prioritize resident and water resource concerns or fill gaps in existing programs. TOTAL: Programs and Administration $660,000 CAPITAL IMPROVEMENT PROJECTS Improvement Projects Downtown Water Reuse Project Integrate reuse irrigation from Hwy 5 storm ponds into downtown vision and update project $350,000 2020 SWUF Partner with RPBCWD to install pump and treatment device to withdraw water from Lake Susan Pond to irrigate Lake $333,000 2018 WMO, CWF, SWUF Lake Susan Park Water Re-use Project Susan Park. Partner with RPBCWD to install pump and treatment device to withdraw water from a pond on the property to $350,000 2018 WMO, CWF, SWUF Chanhassen HS Water Re-use Project irrigate ballfields and other green space at the high school. W Central Lotus Lake Channel Restoration Phase II Stabilization of 1,540 lineal feet of deeply incised channel draining 347 acres to Lotus Lake $275,000 2021 WMO, SWUF Volume reduction and rate control in the Bluff Creek drainage are to reduce channel and gully erosion and $1,450,000 2018-2022 WMO, SWUF Lower Bluff Creek TMDL Implementation sedimentation into the Creek. Stabilization of in- and near-stream bank undercutting, escarpment and gully erosion in Riley Creek adjacent to the $132,000 2021 WMO, SWUF Upper Riley Creek Channel Stabilization Public Works Facility. Rice Marsh Lake Iron Enhanced Sand Filter Installation of an iron-enhanced sand filter within Rice Marsh Lake Park. $300,000 2019 WMO, SWUF Maintenance/Protection Projects Street Sweeper Purchase a Vactor street sweeper. The City currently has only one street sweeper $239,000 2019 SWUF, GF, WMO Stormwater Infrastructure Maintenance/ Replacement Annual repair or replacement of public stormwater infrastructure costing less than $25,000. $450,000 Annual SWUF Stormwater Pond Improvements Inspection, repair, and cleaning of stormwater ponds $760,000 Annual SWUF Stormwater Management Component of Street Projects Infrastructure construction or expansion associated with street improvement projects $2,985,000 Annual SWUF, WMO, CWF Lake Lucy Lane Culvert Replacement Culvert replacement and stormwater improvements between wetlands North and South side of Lake Lucy Ln $30,000 2018 SWUF Pioneer Trail Flood Mitigation Reduce flood potential to residential structures by improving failing and deficient infrastructure $150,000 2019 SWUF Strategic Property Acquisition Strategic property acquisition $800,000 Periodic SWUF, WMO TOTAL: Capital Improvement Projects $8,365,000 • GF = General Fund; SWUF = Storm Water Utility Fund; WMO = local Watershed Management Organization; CWF = Clean Water Fund or similar grant funding

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Table 5.3. Chanhassen LWMP Implementation Plan 2018-2027 by year. Program/Project 2018 2019* 2020* 2021* 2022* 2023* 2024* 2025* 2026* 2027* Administration Maintain and update modeling tools $30,000 $31,200 $32,448 $33,746 $35,096 $36,500 $37,960 $39,478 $41,057 $42,699 Implement SWPPP $430,000 $447,200 $465,000 $483,691 $503,000 $523,120 $544,045 $565,807 $588,439 $611,977 Implement ordinances $95,000 $98,800 $102,752 $106,862 $111,136 $115,581 $120,204 $125,012 $130,012 $135,212 Revise and update ordinances $5,000 $5,200 $5,408 $5,624 $5,850 $6,084 $6,327 $6,580 $6,843 $7,117 CIP Updates $5,000 $5,200 $5,408 $5,624 $5,850 $6,084 $6,327 $6,580 $6,843 $7,117 WCA Administration $40,000 $41,600 $43,264 $44,995 $46,794 $48,666 $50,613 $52,638 $54,744 $56,934 Education and Outreach General education and outreach programming $30,000 $31,200 $32,448 $33,746 $35,096 $36,500 $37,960 $39,478 $41,057 $42,699 Education and Outreach Plan $5,000 $5,200 $5,408 $5,624 $5,850 $6,084 $6,327 $6,580 $6,843 $7,117 Monitoring Water quality and AIS monitoring $20,000 $20,800 $21,632 $22,497 $23,397 $24,333 $25,306 $26,318 $27,371 $28,466

CAPITAL IMPROVEMENT PROJECTS * * *To Be Determined In Future Annual CIP Updates * * * TMDL/Resource Improvements Downtown Water Reuse Project $350,000 Lake Susan Park Water Re-use Project $50,000 Chanhassen HS Water Re-use Project $100,000 W Central Lotus Lake Channel Restoration Phase II $250,000 Lower Bluff Creek TMDL Implementation $250,000 $175,000 Upper Riley Creek Channel Stabilization $132,000 $25,000 $75,000 Rice Marsh Lk Iron Enhanced Sand Filter $300,000

Maintenance/Protection Projects Street Sweeper $239,000 Stormwater Infrastructure Maintenance/ Replacement $50,000 $50,000 $50,000 $50,000 $50,000 Stormwater Pond Improvements $80,000 $80,000 $80,000 $80,000 $80,000 Stormwater Management Component of Street Projects $360,000 $250,000 $100,000 $250,000 Lake Lucy Lane Culvert Replacement $30,000 Pioneer Trail Flood Mitigation $150,000 Strategic Property Acquisition $300,000 $75,000 $75,000 $75,000 $75,000 TOTAL, IMPLEMENTATION PROGRAMS AND PROJECTS $1,891,000 $1,576,400 $1,518,768 $1,322,409 $1,602,069 $802,952 $835,070 $868,473 $903,212 $939,340 *Assumes an annual 4% budget increase; actual increase may differ.

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5.4 ADDRESSING IDENTIFIED PROBLEMS AND ISSUES

As noted earlier in Table 3.2 of this Plan, the planning process revealed a number of problems and issues. Table 5.4 repeats those by category, and describes how each was addressed in this Plan.

Table 5.4. Implementation actions addressing identified problems and issues. Category Identified Problems and Issues Identified Solutions Water Quality Lakes and streams are listed on the Clean The CIP includes, and will periodically be Conditions Water Act Section 303(d) TMDL List of updated to include, projects to achieve Impaired Waters. pollutant load and runoff volume reductions to address listed impairments and NPDES permit requirements. Nonpoint source pollution reduction is The City has an ongoing program of routine necessary through maintenance practices and targeted street sweeping and sump such as street sweeping, sump manhole manhole cleaning. Public BMPs will continue cleaning, and BMP inspections. to be systematically inspected. Maintenance activities and projects programmed into the CIP. Drainage and Near stream gullies and escarpments The City will continue to work with WMOs to Flooding should be addressed to control sediment protect existing and improve flood storage deposition into surface waters and to capacity through targeted BMPs and increased protect property and infrastructure. street sweeping. The City will prioritize BMPs that protect or repair highly erodible and sensitive soil areas in the Bluff Creek Overlay District. Regulatory Atlas 14 updated precipitation frequency The City will require stormwater modeling Requirements data is available for adoption. work to use Atlas 14 precipitation depths and and Operational nested distributions. Policies Approaches such as Minimal Impact The City will continue to work with developers Development and Integrated Management to incorporate standards into new Practices are available to reduce the public development and redevelopment. expenditures necessary to control runoff and protect and improve water quality. The City’s approved NPDES permit and City Code will be revised within 12 months to SWPPP requires ordinance revisions and incorporate volume management and water operating program enhancements. quality requirements. City goals, policies and ordinances to help The City currently has ordinances in place protect natural resources may need review protecting steep slopes and bluffs, shorelands, and refinement. wetlands, and the Bluff Creek Overlay District Water-Based Water quality should be protected and This Plan includes a number of capital projects Recreation improved to protect and enhance and maintenance programs intended to Needs recreational opportunities. improve water quality to better support fishing, swimming and boating.

Control of aquatic invasive species (AIS) The City will continue to work with CCWMO, continues to be an important concern watershed districts, lake associations, and DNR to undertake AIS program activities such as watercraft inspections, biocontrol, fish restocking, or other similar activities. Maintenance BMP maintenance and repair requirements The City will continue to systematically assess Requirements have been identified during NPDES the condition of public BMPs. The CIP includes

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Category Identified Problems and Issues Identified Solutions inspections, including restoration of and will periodically be updated to include storage capacity, repair of erosion, and projects identified in the pond inventory and prevention of future problems. inspections. Street sweeping, sump manhole cleaning, The maintenance program includes provisions and BMP inspections are necessary on an for regular and special street sweeping; ongoing basis to help reduce nonpoint inspection and maintenance of sump source pollutant loads. manholes and catch basins; basin inspections and repairs; illicit discharge detection; and erosion control. Education and Education and outreach efforts could be Education and outreach efforts will be Outreach expanded with a focus on targeted groups continued including written and electronic with new and expanded educational communications, and opportunities for opportunities. participation by citizen volunteers such as the Wetland Health Evaluation Program (WHEP) and the Citizen Assisted Monitoring Program (CAMP) for lakes. Financial Financial resources are limited, requiring The budget in this Plan prioritizes operating Resources that projects be prioritized. programs and projects to address both regulatory and operational needs and water resource improvements. The City will continue to leverage available funding by collaborating with partners and seeking grant funding. Groundwater The LWMP should be coordinated with the Infiltration requirements are integrated with Protection Wellhead Protection Program so that Wellhead Protection requirements to protect policies that encourage infiltration and groundwater quality. groundwater recharge are consistent with the policies to protect sensitive groundwater recharge areas Seminary Fen is a rare calcareous fen and The City participates in the Met Council’s Assumption Creek is a trout stream, both Seminary Fen Work Group to study the effects of which are dependent on groundwater. of groundwater pumping on Seminary Fen. City ordinance imposes stringent standards on development and redevelopment in the Assumption Creek drainage area. Collaboration There are opportunities for collaboration The City will continue to collaborate with the Opportunities with other agencies such as the watershed watershed districts to identify and complete districts, the Three Rivers Regional Park capital projects and pursue opportunities with District, and state agencies to leverage development and redevelopment projects. expertise and resources to finance and construct improvements.

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6.0 Amendments to the Plan

The Chanhassen Local Water Management Plan extends from 2018 to 2027. However, this document is intended to be a planning tool that will change as the City’s needs change and may be amended as necessary to meet the City’s goals. The Implementation Plan will be reviewed and updated annually.

6.1.1 WMO Plan Amendments

Revisions to this Plan required by Watershed Management Organization (WMO) Plan Amendments will be addressed in accordance with Minn. Stat. 103B.235 and Minn. Rules 8410.0160 Subp.6.

6.1.2 Major Plan Amendments

Major Plan Amendments to this Plan, such as adoption of significant revisions to official controls or actions that would change the Goals of the Plan will be reviewed by the City Council and submitted to the appropriate WMO for comment and approval and to the Metropolitan Council for comment as set forth in Minn. Stat. 103B.235 and Minn. Rules 8410.160 Subp. 6.

6.1.3 Routine Updates

The Implementation Plan will be reviewed and updated as needed as the City’s annual NPDES, operating programs, and CIP and project needs are evaluated and completed. The City may make routine updates including budget and CIP changes, changes in education and outreach programming, revisions in operations and maintenance practices and other programming changes that are consistent with the Goals and policies set forth in this Plan without making formal revisions to this document.

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7.0 References

Barr, 2010. Bluff Creek TMDL Biological Stressor Identification.

Barr, 2013a. Bluff Creek Watershed Total Maximum Daily Load Report: Turbidity and Fish Bioassessment Impairments.

Barr, 2013b. Lake Lucy and Lake Ann Use Attainability Analysis Update.

Bonestroo, 1996. Bluff Creek Watershed Natural Resources Management Plan.

MPCA, 2001. Minnesota River Basin Plan.

Wenck, 2013. Lake Susan Use Attainability Assessment (UAA) Update.

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Appendix A

Land and Water Resources Inventory

(This page is intentionally blank.) Table of Contents 1.0 PHYSICAL INVENTORY ...... 1-1 1.1 Physical Environment ...... 1-1 1.1.1 Climate and Precipitation...... 1-1 1.1.2 Geology, Topography and Drainage...... 1-1 1.1.3 Soils ...... 1-3 1.2 Biological Environment ...... 1-5 1.2.1 Vegetation ...... 1-5 1.2.2 Fish ...... 1-5 1.2.3 Unique Features and Scenic Areas ...... 1-6 1.3 Human Environment ...... 1-8 1.3.1 Land Use ...... 1-8 1.3.2 Future Land Use ...... 1-8 1.3.3 Parks, Open Space, Recreational Facilities ...... 1-11 1.3.4 Pollutant Sources ...... 1-11 2.0 WATER RESOURCES INVENTORY ...... 2-1 2.1.1 Watersheds ...... 2-1 2.1.2 Lakes ...... 2-3 2.1.3 Streams ...... 2-3 2.1.4 Wetlands ...... 2-5 2.1.5 Public Waters ...... 2-6 2.1.6 Special Waters ...... 2-6 2.1.7 Groundwater ...... 2-9 2.1.8 Floodplain ...... 2-9 3.0 SUBWATERSHED SUMMARIES ...... 3-1 3.1 Lotus Lake Subwatershed ...... 3-3 3.1.1 Subwatershed Characteristics ...... 3-3 3.1.2 Issues & Opportunities ...... 3-4 3.2 Lake Minnewashta Subwatershed ...... 3-5 3.2.1 Subwatershed Characteristics ...... 3-5 3.2.2 Issues & Opportunities ...... 3-5 3.3 Lake Lucy Subwatershed ...... 3-7 3.3.1 Subwatershed Characteristics ...... 3-7 3.3.2 Issues & Opportunities ...... 3-8 3.4 Lake Ann Subwatershed ...... 3-9 3.4.1 Subwatershed Characteristics ...... 3-9 3.4.2 Issues & Opportunities ...... 3-10

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3.5 Lake Susan Subwatershed ...... 3-11 3.5.1 Subwatershed Characteristics ...... 3-11 3.5.2 Issues & Opportunities ...... 3-11 3.6 Rice Marsh Lake Subwatershed ...... 3-13 3.6.1 Subwatershed Characteristics ...... 3-13 3.6.2 Issues & Opportunities ...... 3-13 3.7 Lake Riley Subwatershed ...... 3-15 3.7.1 Subwatershed Characteristics ...... 3-15 3.7.2 Issues & Opportunities ...... 3-15 3.8 Bluff Creek Subwatershed ...... 3-17 3.8.1 Subwatershed Characteristics ...... 3-17 3.8.2 Issues & Opportunities ...... 3-17 3.9 Lower Minnesota Subwatershed ...... 3-19 3.9.1 Subwatershed Characteristics ...... 3-19 3.9.2 Issues & Opportunities ...... 3-20 3.10 Drainage to Neighboring Communities ...... 3-21 3.10.1 Subwatershed Characteristics ...... 3-21 3.10.2 Issues & Opportunities ...... 3-22 4.0 REFERENCES ...... 4-1

Figures Figure 1.1. City of Chanhassen location map...... 1-2 Figure 1.2. Hydrologic Soil Groups (HSG) in Chanhassen...... 1-4 Figure 1.3. Unique features in Chanhassen...... 1-7 Figure 1.4. Chanhassen 2016 land use and 2020 MUSA limits...... 1-9 Figure 1.5. City of Chanhassen 2040 land use...... 1-10 Figure 2.1. Watershed Management Organizations in Chanhassen...... 2-2 Figure 2.2. Lakes and streams in Chanhassen...... 2-4 Figure 2.3. Chanhassen wetlands on the National Wetlands Inventory...... 2-7 Figure 2.5. Chanhassen lakes and streams on the DNR Public Waters Inventory...... 2-8 Figure 2.6. FEMA floodplain in Chanhassen...... 2-10 Figure 3.1. Chanhassen modeled subwatersheds...... 3-2 Figure 3.2. The Lotus Lake subwatershed...... 3-3 Figure 3.3. Lake Minnewashta subwatershed...... 3-6 Figure 3.4. Lake Lucy subwatershed...... 3-7 Figure 3.5. Lake Ann subwatershed...... 3-9 Figure 3.6. Lake Susan subwatershed...... 3-12 Figure 3.7. Rice Marsh Lake subwatershed...... 3-14 Figure 3.8. Lake Riley subwatershed...... 3-16 Figure 3.9. Bluff Creek subwatershed...... 3-18 Figure 3.10. Lower Minnesota River subwatershed...... 3-19 Figure 3.11. Drainage to neighboring communities...... 3-21

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Tables Table 1.1. Climate and precipitation data at Chanhassen, 1981-2010...... 1-1 Table 1.2. 2016 land use in the City of Chanhassen...... 1-8 Table 2.1. Watershed Management Organizations within Chanhassen...... 2-1 Table 2.2. Water quality standards for lakes in the North Central Hardwood Forest Ecoregion...... 2-3 Table 2.3. Characteristics of lakes in Chanhassen, 2007-2016...... 2-3 Table 2.4. Characteristics of streams in the City of Chanhassen...... 2-3 Table 2.5. NWI wetland area by type in the City of Chanhassen...... 2-5 Table 3.1. Chanhassen modeled subwatersheds...... 3-1 Table 3.2. Lotus Lake subwatershed 2010 land use...... 3-4 Table 3.3. Lake Minnewashta subwatershed 2010 land use...... 3-5 Table 3.4. Lake Lucy subwatershed 2010 land use...... 3-8 Table 3.5. Lake Ann subwatershed 2010 land use...... 3-9 Table 3.6. Lake Susan subwatershed 2010 land use...... 3-11 Table 3.7. Rice Marsh Lake subwatershed 2010 land use...... 3-13 Table 3.8. Lake Riley subwatershed 2010 land use...... 3-15 Table 3.9. Bluff Creek subwatershed 2010 land use...... 3-17 Table 3.10. Lower Minnesota River subwatershed 2010 land use...... 3-20

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1.0 Physical Inventory

1.1 PHYSICAL ENVIRONMENT

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The City of Chanhassen lies in the northeastern corner of Carver County (Figure 1.1

), within the Minneapolis-St. Paul Metropolitan Area. The city encompasses 22.9 square miles and is

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bordered by Chaska to the west, Shorewood to the north, Eden Prairie to the east, and the Minnesota River to the south. A small part of the City extends into Hennepin County.

1.1.1 Climate and Precipitation

The climate is humid continental with moderate precipitation, wide daily temperature variations, warm humid summers, and cold winters. The total average annual precipitation is approximately 31.2 inches (Table 1.1) while the annual snowfall average is approximately 54 inches, equivalent to approximately 5.4 inches of water precipitation.

Table 1.1. Climate and precipitation data at Chanhassen, 1981-2010. Average Average Average Precipitation Snowfall Month Temperature (F) (inches) (inches) January 14.3 0.87 10.3 February 19.1 0.94 9.7 March 31.3 1.78 10.8 April 46.5 3.00 3.4 May 58.0 3.66 0.0 June 67.6 4.02 0.0 July 72.0 3.59 0.0 August 69.9 4.14 0.0 September 60.7 3.43 0.0 October 47.8 2.51 0.4 November 32.7 1.97 5.4 December 18.1 1.25 13.9 Annual Average 44.8 31.16 53.9 Source: NOAA National Climatic Data Center.

1.1.2 Geology, Topography and Drainage

The landscape of Chanhassen was shaped by the Des Moines lobe of the Wisconsin glaciation. The bedrock underlying Chanhassen is primarily Prairie du Chien Group dolostone, with Jordan sandstone underlying a bedrock valley along the western side of the city and Lone Rock Formation in the Minnesota River Valley (Mossler and Chandler 2009). The surficial geology is primarily glacial till - pebbly, unsorted, with scattered cobbles and rare boulders – with scattered deposits of organic debris and marl. Outwash and floodplain alluvium is found in the River valley. Refer to the Carver County Geologic Atlas for more information.

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Figure 1.1. City of Chanhassen location map. Source: Minnesota DNR, World Street Map

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The landscape is characterized by four geomorphic units. The central part of the city is located within the Prior Lake Moraine unit, which consists of irregular ground, end and terminal moraines, and ice disintegration features of loamy texture. The dominant landform is rolling hills and irregularly placed knolls with relief ranging from 20 to 100 feet above the base, with wetlands in deeply inset depressions. The northwest area of the city, west of Lakes Ann and Lucy and including Lake Minnewashta and the Arboretum is within the Emmons-Faribault Moraine, and the topography is typical of that region – gentle rolling hills with an abundance of lakes and ponds.

The northeast portion of the city, including the areas around Lotus Lake and Rice Marsh Lake, are within the Twin Cities Formation geomorphic unit. The landscape of the Twin Cities Formation is similar to the Prior Lake Moraine unit – steeply and irregularly rolling – but it is underlain with a silty, clayey, glacial till. In the southern part of the city, the Minnesota Valley Outwash Plain is nearly level with low terraces, and comprised of areas of sand and gravel.

1.1.3 Soils

The soils in Chanhassen are generally moderate to well drained Lester and Kilkenny clay loams with pockets of moderately to poorly drained soils. In the Minnesota River Valley, floodplain soils are generally muck or silt loams and range from moderately to very poorly drained. Refer to the Carver County Soil Survey for more information.

Soils are classified by the Natural Resources Conservation Service (NRCS) into hydrologic soil groups (HSGs) to indicate the minimum rate of infiltration obtained for bare soil after prolonged wetting. The HSGs are A, B, C and D. Figure displays the hydrologic characteristics of soils in Chanhassen. Type B soils predominate, but there are many pockets of B/D and C/D soils. These dual-designation soils tend to follow the terrain and characterize the lower areas.

A Sandy soils with low runoff potential. These soils have a high rate of infiltration even when thoroughly wet. They are deep, well to excessively drained sands or gravels. B Loamy soils with a moderate infiltration and transmission rate when thoroughly wetted and with moderately fine to moderately coarse textures. Water movement through these soils is moderately rapid. C Sandy clay loam soils with a slow rate of infiltration rate when thoroughly wet. Water movement through these soils is moderate or moderately slow and they generally have a restrictive layer that impedes the downward movement of water. D Clayey soils with very slow infiltration rates because of clay content, high water table, or claypan or clay layer at or near the surface. These soils have a very slow rate of water transmission. A/D Dual hydrologic soil groups are given for certain wet soils that could be adequately drained. The B/D first letter applies to the drained and the second to the undrained condition. Soils are assigned to C/D dual groups if the depth to a permanent water table is the sole criteria for assigning a soil to hydrologic group D.

Source: Natural Resources Conservation Service.

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Figure 1.2. Hydrologic Soil Groups (HSG) in Chanhassen. Source: NRCS, SSURGO.

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1.2 BIOLOGICAL ENVIRONMENT

1.2.1 Vegetation

The City’s landscape has gone through many changes due to human activity. Prior to European settlement the landscape across much of the central part of the city was “oak openings.” Today oak openings are called oak savanna, a now-rare in Minnesota landscape that is transitional between prairie and forest. Savannas are grasslands with scattered trees providing between 30 percent and 70 percent canopy cover, and are maintained by fire. Bur oaks and a few other tree species typical of oak savannas are fire resistant. When a fire swept through a savanna area, the maples, basswood, and other fire- susceptible species burned but the oaks remained and the prairie species were rejuvenated. Most of the rest of the city was Big Woods, where oak woodland and maple-basswood forests were the dominant vegetation types. Upon settlement, much of the landscape was converted to agriculture and eventually suburban development.

However, there are remnants of the original landscape, as well as patches of only moderately impacted lands that retain some higher ecological values. The Minnesota County Biological Survey (MBS) has identified those locations in the Metro area with intact native plant communities, and those with biodiversity significance. The ecological value of these Regionally Significant Terrestrial and Wetland Ecological Areas is determined by examining attributes of the patches including size, shape, cover type diversity, and adjacent land use. Three areas of outstanding ecological value have been identified in Chanhassen: Seminary Fen; Rice Marsh Lake and its riparian wetland; and the Minnesota River corridor. The Minnesota River Valley is home to significant natural communities, including remnants of the Big Woods, river bluffs, and wetland areas. Additional areas identified as having high ecological value include patches within the Landscape Arboretum; the Lower Bluff Creek corridor; and patches in Lake Minnewashta Regional Park. Other small patches around Lake St. Joe and Lake Ann and in the Arboretum were classified as moderate ecological value. Most of the significant natural communities identified in the Carver County Biological Survey are in areas under public ownership and have been preserved as park or managed conservation areas.

1.2.2 Fish

Two boat launches on Lake Minnewashta provide public access to the lake for fishing and boating. There is also a fishing pier at Roundhouse Park, which is extended to reach beyond the aquatic plant edge. The most recent fish survey, completed in 2011, found abundant northern pike and largemouth bass, and six species of panfish. Rough fish are present but in low numbers. The DNR has imposed a catch and release limitation on largemouth bass.

A fishing pier and boat launch are available on Lake Ann at Lake Ann Community Park. Each year on the first Saturday in February, the City hosts February Festival on Lake Ann. One of the highlights of this community event is an ice fishing contest.

The Minnesota DNR completed a detailed fish survey and assessment on Lake Ann in 2012. The DNR is actively managing the fishery, having imposed both a catch and release limitation on largemouth bass and a size restriction on northern pike. The survey found that these regulations appear to be helping to restore the size structure for those communities. The 2012 assessment also included an evaluation of fish in the shallow, nearshore habitats to calculate an Index of Biotic Integrity score. Sensitive species such as minnows and darters were mostly absent, contributing to a low IBI score. In August 2012, Ann

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Lake scored 74.6 out of a maximum of 160, indicating possible water quality and habitat impairment. In September 2012, the nearshore survey was replicated and the second score was 76.4, very similar to the first. There are special regulations limiting human consumption of fish from Lake Ann.

A fishing pier and boat launch are available on Lake Susan at Lake Susan Community Park. The 2009 Lake Susan DNR fish survey found that fish abundances were low, as historically been the case. There are special regulations limiting human consumption of fish from Lake Susan. The University of Minnesota is conducting research on common carp in Lake Susan. The goal of carp research in Lake Susan is to determine the relationship between carp abundance (biomass) and 'lake health' measured as water quality, vegetation density and native fish. To do so, specific numbers of carp are removed from each lake while improvements in water quality, vegetation, and native fish are monitored. In 2009, carp biomass in the lake was reduced from about 300 lbs/acre to about 60 lbs/acre. After the carp were removed, aquatic vegetation coverage increased from 5 percent of the lake to 45 percent. Spring water clarity was greatly increased, but there appears to be minimal impact on summer clarity and total phosphorus concentration.

Lotus is primarily managed for walleye and largemouth bass, with walleye fingerling and adult fish stocking every other year. There are special regulations limiting human consumption of fish from Lotus Lake.

1.2.3 Unique Features and Scenic Areas

Seminary Fen, a DNR Scientific and Natural Area (SNA), lies to the north of Flying Cloud Drive, west of Bluff Creek Drive (Figure 1.3). Named for an old seminary that was once on the site, Seminary Fen contains one of the rarest types of wetland in the United States, a calcareous fen. Calcareous fens are a special type of wetland that can occur only at the base of slopes or bluffs, where cool, mineral-rich groundwater appears as springs. Water charged with minerals comes to the surface, then saturates and helps maintain thick layers of peat created by the decomposition of the plants that grow in the oxygen- poor water. Fewer than five hundred calcareous fens survive in the world. It is home to many threatened and endangered plant species. Calcareous fens have special protection under Minnesota state law and may not be drained, filled or otherwise altered or degraded. A history of Seminary Fen may be found at mnopedia.org/place/seminary-fen-scientific-and-natural-area.

Seminary Fen's groundwater drains into Assumption Creek, one of the few trout streams in the Metro Area. South of Flying Cloud Drive and west of TH 101, in the floodplain of the Minnesota is the DNR’s Raguet Wildlife Management Area (WMA). Wildlife viewing and hunting are allowed in this WMA. Portions of the city south of Flying Cloud Drive are located in the Minnesota River Valley National Wildlife Refuge.

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Figure 1.3. Unique features in Chanhassen. Source: MnDNR.

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1.3 HUMAN ENVIRONMENT

1.3.1 Land Use

Figure 1.4 shows 2016 land use within Chanhassen. The city is over 80% developed, and has a commercial and industrial core centered on TH 5, surrounded by residential uses of various densities. According to the City’s Available Land inventory, only about 3% of vacant land in the city is developable. Regional and local parks and open space, including Lake Minnewashta Regional Park, the University of Minnesota Landscape Arboretum, encompassing over one-fifth of the city’s area. Only the Minnesota Valley Wildlife Refuge and areas within the Minnesota River Bluffs in the southern part of the city are outside the Metropolitan Urban Services Area (MUSA).

Table 1.2. 2016 land use in the City of Chanhassen. Area Area Land Use (acres) (%) Single Family 4,225.0 28.8% Parks and Recreation 2,999.1 20.5% Undeveloped 2,872.1 19.6% Water 1,712.8 11.7% Agricultural 845.9 5.8% Industrial 453.9 3.1% Commercial 435.8 3.0% Multi Family 398.6 2.7% Highway 370.2 2.5% Institutional 280.9 1.9% Extractive 43.8 0.3% Mixed Use 21.1 0.1% 14,659.3 Source: Metropolitan Council from city comprehensive plan and air photos.

1.3.2 Future Land Use

Planned 2040 land use from the 2040 Comprehensive Guide Plan is shown in Figure 1.5. The southernmost part of the City south to Flying Cloud Drive is within the MUSA 2020 boundary, and is expected to be in development by that time. Some large-lot residential development relies on individual subsurface sewage treatment systems, and will continue to do so until the majority of residents in an area desire to hook up to city sewer and water. The area south of Flying Cloud Drive to the Minnesota River is currently unsewered, and there are no plans to extend urban services to that zone.

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Figure 1.4. Chanhassen 2016 land use and 2020 MUSA limits. Source: Metropolitan Council, from city Comprehensive Plans and air photo interpretation

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Figure 1.5. City of Chanhassen 2040 land use. Source: City of Chanhassen 2030 Comprehensive Plan

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1.3.3 Parks, Open Space, Recreational Facilities

Three regional parks and recreation facilities are located in Chanhassen: Carver County’s Lake Minnewashta Regional Park, the Minnesota Landscape Arboretum, operated by the University of Minnesota, and the Three Rivers Park District Minnesota River Bluffs LRT Regional Trail, which passes through southern Chanhassen, crossing Bluff Creek and running north of Seminary Fen.

Swimming beaches are available Lake Minnewashta Regional Park, and city parks Lake Ann Park, Carver Beach on Lotus Lake, and Roundhouse Park on Lake Minnewashta.

1.3.4 Pollutant Sources

The Wellhead Protection Plan (WHPP) completed in 2004 evaluated and included recommendations for monitoring or remediating potential pollutant sources such as dumpsites, leaking underground storage tank sites, Voluntary Investigation and Cleanup sites and others. The WHPP was updated in 2011 to incorporate new information and new wells and updated groundwater modeling. A new WHPA and DWSMA were delineated and well and aquifer vulnerabilities were also reassessed and updated.

Subsurface sewage treatment systems (SSTS), or septic systems, and operating or abandoned wells can also be a source of pollution. Chanhassen had an estimated 388 septic systems. The MDH regulates new and abandoned wells and maintains a comprehensive list of the status of each. A plan for management of private wells and septic systems is also included in the City’s WHPP.

Information on other potential pollutant sources can be found by contacting the Minnesota Pollution Control Agency or the Environmental Protection Agency, or visiting the EPA’s EnviroMapper website at www.epa.gov.

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2.0 Water Resources Inventory

2.1.1 Watersheds

The Twin Cities Metropolitan Area is subdivided into about 34 watersheds, each managed by a Watershed Management Organization (WMO). WMOs may be either Joint Powers consortia of cities or Watershed Districts, which are special units of government. Chanhassen is located in four watersheds (Table 2.1 and Figure 2.1), three of which are Watershed Districts, and one a Joint Powers Organization.

Table 2.1. Watershed Management Organizations within Chanhassen. Area in Total Area Percent of Watershed Chanhassen (sq. miles) Chanhassen (sq. miles) Riley-Purgatory-Bluff Creek WD 47.1 14.0 61.3% Minnehaha Creek WD 180.1 5.2 22.8 Lower Minnesota River WD 75.9 2.9 12.7 Carver County WMO 320.2 0.75 3.2 TOTAL 22.85 100%

2.1.1.1 Riley-Purgatory-Bluff Creek Watershed District

The RPBCWD covers approximately 32.8 square miles in Hennepin County and approximately 14.3 square miles in Carver County. Nearly two-thirds of Chanhassen is within the RPBCWD, including six lakes – Lucy, Ann, Susan, Lotus, and part of Riley and Rice Marsh. Bluff Creek drains the central area of the city south to Rice Lake. Riley Creek is formed at the outlet of Lake Ann and flows to Rice Marsh Lake and into Eden Prairie. The northeast corner of the city flows to Lotus Lake, which outlets east into Eden Prairie and Purgatory Creek.

2.1.1.2 Minnehaha Creek Watershed District

The Minnehaha Creek Watershed District (MCWD) encompasses 181 square miles in Hennepin and Carver Counties. Almost one-quarter of the city is within the MCWD, including the area west of Hazeltine Boulevard draining to Lake Minnewashta, and an area along the northern border, part of which drains to Christmas Lake and part into Lake Galpin to the north. Lake Minnewashta and Lake St. Joe are in this drainage area, as is a southern bay of Christmas Lake.

2.1.1.3 Lower Minnesota River Watershed District

The LMRWD is located in the far southern part of Chanhassen and includes the Flying Could Drive corridor and floodplain to the Minnesota River, and the area east of TH 101 and south of Pioneer Trail to the river. The overall District boundaries encompass an area of 64 square miles of Carver, Hennepin, Dakota, Scott, and Ramsey Counties, including bluffs on both sides of the Minnesota River. The LMRWD includes Rice Lake, Assumption Creek, and Seminary Fen.

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2.1.1.4 Carver County WMO

A few small areas of Chanhassen are within the Carver WMO. In southwestern Chanhassen, the area west of Bluff Creek Drive, north of Seminary Fen, and south of TH 212 is in the Carver WMO and drains into Chaska. A small corner of Chanhassen west and south of Lyman Boulevard and Galpin Boulevard drains to Lake Hazeltine in Chaska.

Figure 2.1. Watershed Management Organizations in Chanhassen. Source: Board of Water and Soil Resources.

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2.1.2 Lakes

There are 9 major lakes in Chanhassen, which are shown on Figure 2.2. Minnesota’s standards for lake water quality vary depending on the depth classification of the lake (Table 2.2). Shallow lakes are 15 feet deep or less, or 80% or more of the lake area is shallow enough to support rooted aquatic plants. The lake number and shoreland classification, lake morphometry, and water quality data are shown in Table 2.3. More information about the lakes can be found online at the DNR’s LakeFinder website: dnr.state.mn.us/lakefind/index.html.

Table 2.2. Water quality standards for lakes in the North Central Hardwood Forest Ecoregion. Parameters Shallow Lakes Deep Lakes Total Phosphorus (TP) (g/L) ≤60 ≤40 Chlorophyll-a (chl-a) (g/L) ≤20 ≤14 Secchi Depth transparency (SD) (meters) ≥1.0 ≥1.4 Source: MPCA.

Table 2.3. Characteristics of lakes in Chanhassen, 2007-2016. Surface Max Summer Average DNR Depth DNR Lake Area Depth TP Chl-a SD ID# Class Class* (ac) (ft) (µg/L) (µg/L) (m) Ann 10-0012 116 42 Deep RD 23 9 3 Christmas 27-0137 257 87 Deep RD 13 2 6 Harrison 10-0008 6 Na Shallow NE NA NA NA Lotus 10-0006 246 29 Deep RD 54 36 1 Lucy 10-0007 92 18 Shallow RD 67 21 1 Minnewashta 10-0009 738 70 Deep RD 24 9 2 Rice Marsh 10-0001 79 11 Shallow NE 120 2 2 Rice 27-0132 238 Na Shallow NE NA NA NA Riley 10-0002 297 49 Deep RD 41 21 2 Susan 10-0013 93 17 Shallow RD 119 40 1 St. Joe 10-0011 14 52 Deep NE 25 5 3 Sources: Minnesota DNR, MPCA EQuIS. *NE = Natural Environment; RD = Recreational Development (Shoreland Management Classification)

2.1.3 Streams

Bluff Creek is the longest stream in the City (Table 2.4, Figure 2.4), rising from a wetland complex in the northwest quadrant of Highway 5 and Galpin Boulevard, then flowing just over 7 miles southeast to Rice Lake in the Minnesota River floodplain. The headwaters of Riley Creek is Lake Ann. From the lake’s outlet Riley Creek flows southeast to Lake Susan, and then outlets Lake Susan to Rice Marsh Lake. On the Eden Prairie side of the lake, the Creek flows out of that lake south to Riley Lake, then outlets that lake and flows to the Minnesota River. Assumption Creek is a DNR-designated trout stream. Table 2.4. Characteristics of streams in the City of Chanhassen. Stream Length (mi) Bluff Creek 7.1 Riley Creek 2.5 Assumption Creek 2.8 Source: MnDNR.

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Figure 2.2. Lakes and streams in Chanhassen. Source: Minnesota DNR.

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The Bluff Creek Turbidity and Fish Biota TMDL and its associated Biological Stressor Identification Study assessed water quality conditions in Bluff Creek to determine the potential cause or causes of impairment of its fish community. Monitoring data from 1991 through 2008 were reviewed. Dissolved oxygen concentrations were adequate to support aquatic life. High nutrient and sediment concentrations and loads in the Creek were mostly associated with storm events, washed off from the watershed. The Creek does not meet state standards for turbidity as measured by Total Suspended Solids (TSS) concentration. The TMDL found that the source of the excess TSS was both watershed load and also sediment contributed from streambank and gully erosion.

No water quality data is available for Riley Creek in Chanhassen, or for Assumption Creek.

2.1.4 Wetlands

The US Fish and Wildlife Service compiled wetland maps from aerial photo interpretation as part of the National Wetland Inventory (NWI). Wetland scientists use two common classification schemes to identify wetland type – the US Fish and Wildlife Service’s “Circular 39” system, and a replacement classification system developed by Cowardin et al. for the Fish and Wildlife Service, commonly referred to as the Cowardin system. The Circular 39 system was originally developed as a means for classifying wetlands for waterfowl habitat purposes. Nine of the Circular 39 freshwater wetland types are found in Minnesota. The Cowardin scheme is a hierarchical classification based on landscape position, substrate, flooding regime, and vegetation. While the Cowardin scheme has been officially adopted by the Fish and Wildlife Service and other agencies, the Circular 39 system is still commonly used because of its simplicity and ease of use.

The original NWI was developed in the 1980s from aerial photography. The DNR is updating the NWI statewide using remote sensing imagery; the East-Central region of Minnesota, including Carver County, was reevaluated using 2010 and 2011 imagery. According to the updated NWI (Figure 2.3 and Table 2.5, wetlands, including lakes, cover approximately 27.3 percent of the city’s surface. The NWI map is not considered definitive. A delineation of wetland boundaries is required to be completed any time development or other impacts may occur near or in a wetland.

Table 2.5. NWI wetland area by type in the City of Chanhassen. Circular 39 Type Acres Percent Cowardin Type Acres Percent

1 - Seasonally Flooded 1,077.78 7.4% Emergent (EM) 1,619.9 11.1%

2 - Wet Meadow 4.05 0.0% Unconsolidated Bottom (UB) 1,483.8 10.1%

3 - Shallow Marsh 906.68 6.2% Forested (FO) 387.6 2.6%

4 - Deep Marsh 123.87 0.8% Aquatic Bed (AB) 310.0 2.1%

5 - Shallow Open Water 1,638.66 11.2% Upland Scrub-shrub (SS) 198.6 1.4%

6 - Shrub Swamp 198.60 1.4% Unconsolidated Shore (US) 2.8 0.0% 7 - Wooded Swamp 1.70 0.0% Upland 10,656.6 72.7%

80 - Mun. and Indus. Activities 12.36 0.1% Grand Total 14,659.3

90 - Riverine 39.02 0.3%

98 - Uplands 10,656.58 72.7%

Grand Total 14,659.3 Source: Minnesota DNR, 2013 NWI Update East-Central Minnesota.

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The City has also completed its own wetland inventory and functions and values assessment. A functions and values assessment uses a structured methodology to evaluate the condition of the wetland and its function as part of the overall ecosystem. Examples of the features assessed include vegetative quality and diversity, habitat diversity, flood attenuation, human disturbance, etc. Each wetland is assigned to one of five classifications based on its weighted score: Outstanding, Preserve, Manage 1, Manage 2, or Manage 3. The City’s Wetland Protection ordinance (Section 20.401 – 20.421) regulates requirements for structure setbacks and wetland buffer widths based on each wetland’s management classification. The City maintains an Official Map of wetlands by classification that is continuously updated.

2.1.5 Public Waters

State Statutes classify certain waterbodies as Waters of the State and the DNR maintains maps and lists on the Public Waters Inventory (PWI). Public Waters wetlands include all type 3, type 4, and type 5 wetlands (as defined in U.S. Fish and Wildlife Service Circular No. 39, 1971) that are 10 acres or more in size in unincorporated areas or 2.5 acres or more in size in incorporated areas. There are 12 public waters basins (lakes) and 21 public waters wetlands in Chanhassen. Public watercourses are defined as natural and altered watercourses with a total drainage area greater than two square miles or natural and altered watercourses designated by the DNR commissioner as trout streams. Public watercourses in Chanhassen include Bluff, Riley, and Assumption Creeks, the outlet of Lotus Lake (Purgatory Creek), and the outlet of Lake Minnewashta that flows to Lake Virginia.

Work within waterbodies designated on the PWI is regulated by the DNR. Public waters wetlands and watercourses are shown on Figure 2.4.

2.1.6 Special Waters

As noted above, two Outstanding Resource Value Waters are located within Chanhassen: Seminary Fen, a calcareous fen, and Assumption Creek, a trout stream. These are shown on Figure 1.3 above.

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Figure 2.3. Chanhassen wetlands on the National Wetlands Inventory. Source: Minnesota DNR.

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Figure 2.4. Chanhassen lakes and streams on the DNR Public Waters Inventory. Source: Minnesota DNR.

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2.1.7 Groundwater

Chanhassen relies on groundwater for its municipal water system, operating ten wells drawing water from the Prairie du Chien-Jordan and Prairie du Chien-Wonewoc aquifers. The City manages groundwater principally through its Wellhead Protection Plan (WHPP), which was updated in 2012. This plan provides comprehensive guidance to protect wellhead areas from contamination while meeting the requirements of the Federal Safe Drinking Water Act and the Minnesota Groundwater Protection Act. The purpose of the WHPP is to provide measures needed to protect the groundwater entering and flowing through this area in order to protect our drinking water supply from contamination.

The following items are included in the WHPP: • Delineation of the Wellhead Protection Area (WHPA) and Drinking Water Supply Management Area (DWSMA) for the public water supply system • Identification of potential sources of contamination to the DWSMA as well as the degrees of risk of land uses within this area • Definition of goals and objectives and set priorities to manage the risk and/or potential contaminant sources to minimize impacts to the DWSMA • Identification of monitoring methods to track the effectiveness of the goals and objectives • Planning contingency measures to address potential interruption of public water supply if contaminants are identified within the DWSMA

The Carver County Groundwater Plan was updated in 2016 and contains goals, objectives, and strategies for protecting groundwater resources. It is focused on preventing groundwater contamination, ensuring the continued groundwater supply, and protecting groundwater dependent natural resources like the Seminary Fen and Assumption Creek from the impacts of groundwater withdrawals and groundwater contamination

2.1.8 Floodplain

As a part of the FEMA Map Modernization Program, the Federal Flood Insurance Program has delineated the floodplain in Chanhassen and includes floodway and flood fringe areas inundated as a result of the 1-percent annual chance (100-year) flood. The 1-percent annual chance (100-year) floodplain, as defined by the Flood Insurance Program for flood insurance purposes, was detailed by a Flood Insurance Study. The resultant maps are expected to be adopted in 2017-2018 and will be on file at City Hall and with the DNR and the Federal Emergency Management Agency (FEMA).

Land use regulations define the floodplain as the area covered by the flood that has a one percent chance of occurring each year, also known as the 100-year flood. The floodplain is divided into two zoning districts: the floodway and flood fringe. The floodway includes the river channel and nearby land areas which must remain open to discharge the 100-year flood. The flood fringe, while in the flood plain, lies outside the floodway. Regulations usually allow development in the flood fringe but require flood-proofing or raising to the legal flood protection elevation.

The City has a floodplain overlay district ordinance in effect that establishes allowable uses and in the floodplain, floodway, and flood fringe. That ordinance requires that fill or excavation within the floodplain is subject to a conditional use permit.

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Figure 2.5. FEMA floodplain in Chanhassen. Source: DNR Preliminary Map Modernization Data.

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3.0 Subwatershed Summaries

As part of this Plan, the HydroCAD hydrologic and hydraulic models for the City were updated to include the most recent watershed and basin information and the newly-redefined 100-year Atlas 14 precipitation event. In 2014, the National Weather Service Hydrometeorological Design Studies Center released NOAA Atlas 14, Volume 8, detailing updated precipitation frequency estimates. The new estimates are based on improvements in three primary areas: denser precipitation data networks with a longer period of record, advanced statistical techniques, and new techniques for spatial interpolation and mapping. Atlas 14 improves the accuracy of the precipitation frequency estimates, and supersedes older references, including the commonly-used Technical Paper 40, which was published in 1961.

Nine major subwatersheds were modeled (Table 3.1 and Figure 3.1), along with several small areas designed under the classification “Drainage to Other Communities.” The purpose of performing this modeling is for planning-level assessments. The models were not calibrated to actual runoff and flows, and are not intended to be flood studies.

Model output is quite lengthy and is available electronically. The models and output files are incorporated into this Plan as Appendix B.

The following sections briefly describe each of the subwatersheds and their features and issues and opportunities where available.

Table 3.1. Chanhassen modeled subwatersheds. Area Area Subwatershed % of Total (acres) (sq mi) Lotus Lake 1,318.0 2.06 9.0 Lake Minnewashta 2,538.4 3.97 17.3 Lake Lucy 949.9 1.48 6.5 Lake Ann 257.2 0.40 1.8 Lake Susan 1,250.9 1.95 8.5 Rice Marsh Lake 718.7 1.12 4.9 Lake Riley 928.0 1.45 6.3 Bluff Creek 4,164.6 6.51 28.4 Lower Minnesota 1,334.9 2.09 9.1 To Neighboring Communities 1,199.2 1.87 8.2 TOTAL 14,659.7 22.91

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Figure 3.1. Chanhassen modeled subwatersheds.

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3.1 LOTUS LAKE SUBWATERSHED

3.1.1 Subwatershed Characteristics

The Lotus Lake subwatershed (Figure 3.2) is over 1,000 acres in size, with a majority of the land cover in single-family residential (Table 3.2). There is a substantial (50-90 foot) drop from the highlands on the west side of the lake to the lake. A large ravine originates in LL 1-7 and LL 1-6 and flows through pond LL 1-5 to Lotus Lake. Lotus Lake discharges into and is the headwaters of Purgatory Creek. Another ravine flows from Kerber Pond in LL 5-1 to the lake, and another from LL 6-2 to the lake. Numerous ponds and wetlands dot the subwatershed.

Figure 3.2. The Lotus Lake subwatershed.

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Table 3.2. Lotus Lake subwatershed 2010 land use. Land Use Area (ac) Percent Residential Low Density 734.2 69% Right Of Way 157.1 15% Parks Open Space 101.6 10% Public Semi Public 50.4 5% Residential Medium Density 20.7 2% Residential High Density 4.1 <1% 1,068.1 100%

3.1.2 Issues & Opportunities

Lotus Lake Water Quality. Lotus Lake is classified as a deep lake, with a surface area of 246 acres and a maximum depth of nearly 30 feet. Water quality in the lake does not meet State of Minnesota standards, with excessive nutrient and chlorophyll-a concentrations and poor water clarity. In 2015, the DNR conducted a survey of the quality and ecologic integrity of the fish community in the lake using a tool called the Fish Index of Biotic Integrity (F-IBI). That analysis indicated that the fish community is impaired compared to similar lakes, with some pollution-tolerant species and no pollution-intolerant species present, a lack of vegetation-dwelling fish and a low biomass of top carnivores. Common carp are present in the lake, and efforts to reduce the population and biomass appear at this time to be successful. An aquatic vegetation survey found mostly native vegetation with the invasive Eurasian watermilfoil and curly-leaf pondweed at low abundance.

A Use Attainability Analysis (UAA), which is a diagnostic study similar to a Total Maximum Daily Load (TMDL) study, was completed in 2016 (Barr 2016). This analysis estimated that just under 30 percent of the nutrient load to the lake came from watershed sources. Ponds and wetlands in the Lotus Lake subwatershed provide filtering and settling of the particulate matter in stormwater, removing a significant amount of total phosphorus (TP). However, these types of practices do little to remove dissolved phosphorus. Over two-thirds of the load to the lake comes from internal sources, mostly release from the sediments during extended periods of low-oxygen conditions at the lakebed. To improve water quality to meet state water quality standards and enhance conditions for fish, phosphorus from watershed and internal sources needs to be reduced by 37 percent from the existing condition.

The UAA identified several potential Best Management Practices (BMPs) that could be considered in this subwatershed. Treatment practices that can remove dissolved TP such as infiltration and enhanced filtration practices in addition to practices in currently untreated areas could help reduce nutrients conveyed from the watershed. An internal load project such as an alum treatment could significantly reduce internal load form sediment release.

Ravine Stabilization. A project to stabilize 1,540 lineal feet of deeply incised channel between Carver Beach Road and Lotus Lake is included in the CIP and Implementation Plan in 2018.

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3.2 LAKE MINNEWASHTA SUBWATERSHED

3.2.1 Subwatershed Characteristics

The Lake Minnewashta subwatershed (Figure 3.3) is the second largest in the city, and is dominated by the 738 acre Lake Minnewashta (Table 3.3). Parks and Open Space are also a defining feature, as the subwatershed includes Lake Minnewashta Regional Park Large, portions of the University of Minnesota Landscape Arboretum and Horticultural Research Center, and Camp Fire MN’s Camp Tanadoona. There are a number of mostly small, direct drainage subwatersheds. Lake St. Joe, a small but deep lake surrounded by wetlands, discharges through storm sewer to Lake Minnewashta. Lake Minnewashta outlets through a channel to Lake Virginia in the city of Victoria and ultimately to Lake Minnetonka.

Table 3.3. Lake Minnewashta subwatershed 2010 land use. Land Use Area (ac) Percent Public Semi Public 716.4 40% Residential Low Density 523.6 29% Parks Open Space 370.9 21% Right Of Way 137.1 8% Residential Large Lot 27.1 2% Residential Medium Density 8.7 <1% Commercial 7.5 <1% Office 2.2 <1% 1,793.5 100%

3.2.2 Issues & Opportunities

Lake Water Quality. Both Lake Minnewashta and Lake St. Joe are deep lakes with good water quality. The City will continue to undertake BMPs as opportunities arise and will work with residents and other stakeholders to undertake improvements to help preserve this water quality.

Aquatic Invasive Species. Lake Minnewashta has been infested with Eurasian watermilfoil, curlyleaf pondweed and zebra mussels. There are partnership opportunities with the Minnehaha Creek Watershed District and the Lake Minnewashta Preservation Association continue to monitor any impacts or trends related to the zebra mussel infestation and other invasive species.

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Figure 3.3. Lake Minnewashta subwatershed.

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3.3 LAKE LUCY SUBWATERSHED

3.3.1 Subwatershed Characteristics

The Lake Lucy subwatershed (Figure 3.4) is located in the north-central part of the city. Land use in the subwatershed (Table 3.4) consists almost entirely of single family residential parcels and associated road right of way. Some large-lot residential is present. Pheasant Hills Park is the largest park in the subwatershed. Runoff from the upper subwatershed is collected in a series of ponds and flows through storm sewer along Lake Lucy Road to Lake Lucy. The upper watershed has two main collection systems, south along Galpin and east along Lake Lucy Road, the other flows from 63rd street to the wetland system south of Lake Lucy Lane. Wetlands and open space dominate the lower subwatershed. Lake Lucy outlets into Lake Ann by a short channel.

Figure 3.4. Lake Lucy subwatershed.

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Table 3.4. Lake Lucy subwatershed 2010 land use. Land Use Area (ac) Percent Residential Low Density 625.9 73% Right Of Way 88.2 10% Residential Large Lot 74.2 9% Parks Open Space 60.5 7% Public Semi Public 6.8 1% Residential Medium Density 2.6 <1% 858.2 100%

3.3.2 Issues & Opportunities

Potential Street Flooding. Modeling suggested a possibility of pond P-LU 3-4 overtopping Manchester Drive during a 100-year event. However, during the June 2014 wet period no flooding was observed. This location will continue to be monitored during large rain events.

Lake Water Quality. Lake Lucy is considered to be a shallow lake and its water quality hovers near the state’s shallow lake standards for nutrient concentration. Section 3.3.2 of the Plan describes the findings of a UAA for Lake Lucy and Lake Ann. Several potential actions were identified to improve water quality in Lake Lucy, including potential phosphorus load reductions in the watershed, a potential alum treatment to reduce nutrient loading from the sediments, and management of invasive aquatic vegetation in the lake.

The City will continue to work with the RPBCWD to partner on potential improvement projects and will continue to undertake BMPs as opportunities arise.

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3.4 LAKE ANN SUBWATERSHED

3.4.1 Subwatershed Characteristics

The Lake Ann direct subwatershed (Figure 3.5) is a small drainage area that flows overland directly to the lake. Lake Lucy flows into Lake Ann through a small channel on the north side of the lake. Land use is primarily parks and open space and public/semi-public uses (Table 3.5). The Temple of Eck owns a substantial amount of open space. The outlet of Lake Ann is the headwaters of Riley Creek.

Figure 3.5. Lake Ann subwatershed.

Table 3.5. Lake Ann subwatershed 2010 land use. Land Use Area (ac) Percent Public Semi Public 40.5 30% Residential Low Density 38.0 28% Parks Open Space 36.2 27% Residential Medium Density 17.8 13% Residential High Density 1.1 1% Right Of Way 0.9 1% 134.6 100%

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3.4.2 Issues & Opportunities

Lake Water Quality. The water quality in Lake Ann currently is better than the state’s standard. However, the lake does experience occasional blue-green algal blooms, Section 3.3.2 of the Plan describes the findings of a UAA for Lake Lucy and Lake Ann. As the water quality in outflow from Lake Lucy can affect water quality in Lake Ann, improvements to Lake Lucy will help to protect Lake Ann.

The City will continue to work with the RPBCWD to partner on potential improvement projects and will continue to undertake BMPs as opportunities arise.

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3.5 LAKE SUSAN SUBWATERSHED

3.5.1 Subwatershed Characteristics

The Lake Susan subwatershed includes part of the City’s commercial/industrial core (Table 3.6) as well as parks and open space. There are five major subdrainage systems in the subwatershed (Figure 3.6). Riley Creek drains the upper subwatershed. The area west of Karber Boulevard and north of Santa Vera Drive flows through wetlands and channels southeast to Riley Creek. Drainage from the area south of Highway 5 is collected in storm sewer and ponds which are routed into Riley Creek. The southern part of the subwatershed flows into a large wetland complex in the Lake Susan Preserve (LS 2-3), which flows to Lake Susan. Commercial and industrial land uses in the vicinity of Highway 5 and Highway 101 are routed to a large pond (LS 3-1) west of Lake Susan Park. Residential development around the lake flows overland to the lake. Lake Susan outlets into Riley Creek, which then flows to Rice Marsh Lake.

Table 3.6. Lake Susan subwatershed 2010 land use. Land Use Area (ac) Percent Office Industrial 270.0 21% Right Of Way 219.5 17% Parks Open Space 197.2 15% Residential Low Density 196.6 15% Commercial 138.3 11% Public Semi Public 82.0 6% Residential High Density 62.7 5% Office 38.1 3% Residential Medium Density 37.7 3% Agriculture 26.6 2% Residential Large Lot 20.7 2% Mixed 6.2 <1% 1,295.5 100%

3.5.2 Issues & Opportunities

Lake Water Quality. Lake Susan is a shallow lake that has poor water quality. Water clarity has improved in the past several years, possibly in response to the reduction of a large population of carp to more manageable levels, and to treatment of the invasive curly-leaf pondweed. A Use Attainability Assessment completed in 2013 reviewed potential options for improving water quality. In 2016 the RPBCWD and City partnered to contract a spent lime treatment system to treat discharge from the wetland complex in the Lake Susan Preserve. The RPBCWD is currently evaluating the feasibility of a whole-lake alum treatment for Susan as well as other BMPs identified in the UAA.

A partnership project with RPBCWD to install pump and treatment device to withdraw water from Lake Susan Pond to irrigate Lake Susan Park is included in the CIP and Implementation Plan in 2017. The City will continue to work with the RPBCWD to partner on potential improvement projects and will continue to undertake BMPs as opportunities arise.

A project to stabilize a segment of Riley Creek adjacent to the City’s Public Works Faciality is in the CIP and Implementation Plan in 2019. This project will reduce sediment and nutrient load in the creek and conveyed to Lake Susan.

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Figure 3.6. Lake Susan subwatershed. Page | 3-12 REVIEW DRAFT Appendix A Land and Water Resources Inventory

3.6 RICE MARSH LAKE SUBWATERSHED

3.6.1 Subwatershed Characteristics

Rice Marsh Lake straddles the boundary of Chanhassen and Eden Prairie, and its lakeshed encompasses land in both cities. Within Chanhassen the Rice Marsh Lake subwatershed (Figure 3.7) has two distinct land uses. North of Highway 5 and at the southeast quadrant of Highway 5 and Great Plains Boulevard is highly impervious commercial property (Table 3.7). Single-family and medium density residential lies between Highway 5 and Highway 212. Wide riparian wetlands and wooded areas surround Rice Marsh Lake Park, which extends into Eden Prairie.

Lake Susan to the west outlets into Rice Marsh Lake via Riley Creek. Rice Marsh outlets via Riley Creek in Eden Prairie, where it flows into Lake Riley. A winter aeration system is operated on the lake to support the bluegill population that keep invasive carp in check.

Table 3.7. Rice Marsh Lake subwatershed 2010 land use. Land Use Area (ac) Percent Residential Low Density 190.8 27% Right Of Way 139.4 19% Parks Open Space 101.2 14% Commercial 96.3 13% Mixed 58.8 8% Residential Medium Density 51.7 7% Public Semi Public 38.2 5% Residential High Density 20.1 3% Office Industrial 18.5 3% 715.0 100%

3.6.2 Issues & Opportunities

Potential Flooding. Modeling identifies potential flooding issues in RM 3-3. Private ponds have the potential to overflow onto private property.

Lake Water Quality. Water quality and clarity has improved in Rich Marsh Lake since the 1970s, when wastewater treatment plant effluent was discharged into the lake. However, it is still classified as an Impaired Water and does not meet nutrient standards for a shallow lake. At an average depth of only five feet, sediment cores suggest that it has always been a eutrophic lake

A UAA was completed in 2016 to evaluate conditions and identify options for improvement. Modeling suggests that excess nutrients in Rice Marsh Lake are contributed from the watershed, from outflow of Lake Susan conveyed by Riley Creek, and from internal sediment release. Recommended strategies include increasing water quality treatment in the watershed, improving water quality in Lake Susan, and applying alum to the lake to seal sediments and reduce phosphorus release.

A partnership project with RPBCWD to install an iron-enhanced sand filter within Rice Marsh Park is included in the CIP and Implementation Plan in 2019. The City will continue to work with the RPBCWD to partner on potential improvement projects and will continue to undertake BMPs as opportunities arise.

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Figure 3.7. Rice Marsh Lake subwatershed.

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3.7 LAKE RILEY SUBWATERSHED

3.7.1 Subwatershed Characteristics

Lake Riley straddles the Chanhassen/Eden Prairie border and its lakeshed encompasses land in both cities. Rice Marsh Lake to the north outlets into Lake Riley through Riley Creek in Eden Prairie. Within Chanhassen the Lake Riley subwatershed (Figure 3.8) is comprised of mainly large-lot and low density residential uses (Table 3.8), with a significant amount of Highway 212 right of way. The outlet of Lake Riley, which is in the city of Eden Prairie, is Riley Creek, which flows down the Minnesota River bluff to Grass Lake and then to the river.

Table 3.8. Lake Riley subwatershed 2010 land use. Land Use Area (ac) Percent Residential Low Density 363.5 44% Residential Large Lot 189.7 23% Right Of Way 141.2 17% Residential High Density 49.6 6% Mixed 41.8 5% Parks Open Space 41.7 5% Residential Medium Density 0.2 <1% 827.6 100%

3.7.2 Issues & Opportunities

Potential Flooding. Modeling identifies potential flooding issues. Modeling predicts an overtopping possibility for a pond in LR 3-2 at Lake Riley Boulevard and Lyman Boulevard. This is a location that is known to experience street flooding during large rain events. Street flooding was observed during the October 2014 25-year rain event. City staff regularly check this location during rain events. Modeling also predicts that a wetland just to the north of Lyman Boulevard could possibly overtop. This location is checked periodically by City staff as well.

Lake Water Quality. Water quality in Lake Riley hovers around the deep lake standards for recreation in Minnesota. A UAA was completed in 2016 to evaluate conditions and identify options for improvement. Recommended strategies include increasing water quality treatment in the watershed, improving water quality in upstream Lake Susan and Rice Marsh Lake, and applying alum to the lake to seal sediments and reduce phosphorus release.

The RPBCWD applied an alum treatment to Lake Riley in 2016, which brought an immediate improvement in lake water quality and clarity as well as an improvement in native aquatic vegetation abundance. The lake has also been treated for invasive curly-leaf pondweed and Eurasian watermilfoil and will continue to be spot treated as necessary.

The City will continue to work with the RPBCWD to partner on potential improvement projects and will continue to undertake BMPs as opportunities arise.

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Figure 3.8. Lake Riley subwatershed.

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3.8 BLUFF CREEK SUBWATERSHED

3.8.1 Subwatershed Characteristics

The Bluff Creek subwatershed is the largest in Chanhassen, draining almost 4,200 acres. The Creek rises in a large wetland complex in subwatershed BC 2-1. In general, stormwater from the central core of the city is collected in a series of storm sewers and ponds which are discharged in the Creek. The lower subwatershed is less developed than the upper subwatershed. Below Highway 212, runoff is conveyed down the bluff through a series of ravines.

Table 3.9. Bluff Creek subwatershed 2010 land use. Land Use Area (ac) Percent Residential Low Density 1,370.3 33% Right Of Way 632.7 15% Parks Open Space 446.7 11% Office Industrial 427.5 10% Residential Large Lot 319.0 8% Residential Medium Density 274.0 7% Agriculture 213.7 5% Public Semi Public 169.0 4% Office 145.6 3% Residential High Density 94.9 2% Commercial 86.0 2% Mixed 9.0 <1% Total 4,188.5 100%

3.8.2 Issues & Opportunities

Water Quality and Biotic Integrity TMDL. As discussed in Section 2.1.3 of this Plan, a turbidity and fish biota TMDL was completed in 2013 to diagnose pollutant sources and biotic stressors and identify implementation actions. The TMDL found that the source of excess TSS was both watershed load and also sediment contributed from streambank and gully erosion, especially downstream of Pioneer Trail, during high flow events. Excess turbidity from TSS load was also identified as one of the primary stressors to the fish community. A stream and gully assessment downstream of Pioneer Trail evaluated conditions rated the severity of erosion. In 2014 the City completed the stabilization of Ravine 2.

Habitat fragmentation was also identified as a stressor, singling out the large drop at the regional trail crossing culvert. A project to stabilize the stream at this location and create a fish passage was proposed for 2017, but the City and RPBCWD were unable to secure a required easement form the landowner. An additional project is included in the City’s CIP and Implementation plan for 2019 to add volume reduction and rate control BMPs in the subwatershed.

Stream Condition. In 2017 the RPBCWD developed its Creek Restoration Action Strategy (CRAS) to help guide future actions to protect and improve Bluff Creek as well as other major streams in that watershed. The CRAS combines stream physical condition and stability, water quality, and other attributes into a classification and prioritization system. Four segments on Bluff Creek and one on a tributary were rated as “severe,” with poor water quality, unstable banks experiencing erosion and mass wasting, and limited habitat.

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Figure 3.9. Bluff Creek subwatershed.

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3.9 LOWER MINNESOTA SUBWATERSHED

3.9.1 Subwatershed Characteristics

The Lower Minnesota subwatershed (Figure 3.10) is low-density, with grasslands, wetlands, some agriculture, and large-lot residential development (Table 3.10). This subwatershed includes Assumption Creek, a designated trout stream, and Seminary Fen and the Seminary Fen Scientific and Natural Area.

Figure 3.10. Lower Minnesota River subwatershed.

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Table 3.10. Lower Minnesota River subwatershed 2010 land use. Land Use Area (ac) Percent Agriculture 655.0 51% Residential Large Lot 340.4 27% Office 153.5 12% Right Of Way 88.6 7% Office Industrial 38.0 3% Residential Low Density 5.9 0% Total 1,281.5 100%

3.9.2 Issues & Opportunities

Seminary Fen. The City participates in the Seminary Fen Work Group with Chaska and the Met Council, which meets periodically to discuss the impacts of groundwater pumping on this rare, protected resource.

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3.10 DRAINAGE TO NEIGHBORING COMMUNITIES

3.10.1 Subwatershed Characteristics

There are a number of small subwatersheds that flow to receiving waters in adjacent cities. Within the Minnehaha Creek Watershed District, portions of Chanhassen discharge to Lake Virginia, Lake Galpin, and Christmas Lake. Land use in those subwatersheds is almost entirely single-family residential, wetland, or park. Within the RPBCWD, portions of residential areas in Chanhassen are tributary to Silver Lake or Purgatory Creek. The commercial/industrial district at Highway 5 west of Dell Road is tributary to Mitchell Lake in Eden Prairie. Some areas within the Landscape Arboretum and a mixed-use area in the vicinity of Galpin and Lyman Boulevards drain to Lake Hazeltine in the Carver WMO.

Figure 3.11. Drainage to neighboring communities.

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3.10.2 Issues & Opportunities

Lake Virginia Tributary Area. The outlet of Lake Minnewashta, a channel to Lake Virginia, flows under several driveways that are undersized for large events. No information is available regarding potential flooding or other issues that may arise.

Purgatory Creek Tributary Area. A ravine north of Fox Hollow Drive, west of Fox Drive in PC 2-2 that discharges into the pond at Fox Hollow Drive and Highway 101 needs stabilization.

Christmas Lake. The headwaters of Christmas Creek are in Curry Farms Park. The park did experience some flooding in June 2014. Christmas Creek downstream of Powers Boulevard is in need of stabilization.

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4.0 References

Barr. 2010. Bluff Creek TMDL Biological Stressor Identification. pca.state.mn.us/index.php/view- document.html?gid=13751. Barr. 2013a. Bluff Creek Watershed Total Maximum Daily Load Report: Turbidity and Fish Bioassessment Impairments. pca.state.mn.us/index.php/view-document.html?gid=19684. Barr. 2013b. Lake Lucy and Lake Ann Use Attainability Analysis Update. rpbcwd.org/files/7213/8426/4821/LakeLucy_LakeAnn_UAAUpdate_September2013_FINAL.pdf. Bass. 2013c. Lake Susan Use Attainability Analysis Update. rpbcwd.org/index.php/download_file/128/209/ Barr. 2016. Rice Marsh Lake and Lake Riley: Use Attainability Analysis Update. rpbcwd.org/index.php/download_file/714/209/ Barr. 2017. Creek Restoration Action Strategy (CRAS) 2017 Report. rpbcwd.org/index.php/download_file/1020/197/. Barr. 2017. Lotus, Silver, Duck, Round, Mitchell, Red Rock Use Attainability Analysis Update; Lake Idlewild and Staring Lake Use Attainability Analysis; and Lower Purgatory Creek Stabilization Study. rpbcwd.org/index.php/download_file/952/200/ Lusardi, B. 2009. Plate 3 - Surficial Geology. Minnesota Geological Survey, County Atlas Series, Atlas C- 21, Part A. Minnesota DNR. 2017. Lake Finder. dnr.state.mn.us/lakefind/index.html Minnesota DNR. 2017. Minnesota Biological Survey Native Plant Community and Rare Species County Maps. dnr.state.mn.us/eco/mcbs/maps.html Minnesota Geospatial Commons. 2017. gisdata.mn.gov/ Minnesota Pollution Control Agency. 2017. Environmental Data Application. pca.state.mn.us/data/surface-water-and-stormwater-data Mossler, and V.W. Chandler. 2009. Plate 2 - Bedrock Geology. Minnesota Geological Survey, County Atlas Series, Atlas C-21, Part A. dnr.state.mn.us/waters/programs/gw_section/mapping/platesum/carvcga.html NOAA National Climatic Data Center. 2014. 1981-2010 Normals Data Access. www.ncdc.noaa.gov/land- based-station-data/climate-normals/1981-2010-normals-data Ramstack Hobbs, J.M. and M.B. Edlund. 2014. Historical water quality and ecological change in Rice Marsh Lake. Final report submitted to Riley Purgatory Bluff Creek Watershed District. St. Croix Watershed Research Station, Science Museum of Minnesota, Marine on St. Croix, Minnesota, 55047. rpbcwd.org/index.php/download_file/418/209/ USDA NRCS. 2016. Soil Survey Geographic (SSURGO) Data Base. www.lib.ncsu.edu/gis/nrcs.html

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Appendix B

HydroCAD Modelling Results This technical document is available separately

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