INTEGRATED AQUATIC PLANT CONTROL PLAN

Lake Stevens

Prepared for

City of Lake Stevens

Photo Courtesy of Gene Williams: Snohomish County Surface Water Management

January 2011 Note: Some pages in this document have been purposefully skipped or blank pages inserted so that this document will copy correctly when duplexed.

Contents

Project Overview ...... 1 Lake and Watershed Characteristics ...... 1 Physical Characteristics ...... 1 Geology ...... 2 Wetlands ...... 2 Land Use ...... 2 Water Quality ...... 3 Water Rights ...... 3 Fish and Wildlife Community ...... 3 Beneficial Use ...... 4 Aquatic Plant Community ...... 4 Development of the Plan ...... 7 Public Involvement ...... 7 Aquatic Plant Management Goals ...... 8 Problem Statement ...... 8 Potential Plant Control Scenarios ...... 9 Scenario 1: Harvesting ...... 9 Scenario 2: Fluridone ...... 10 Scenario 3: Triclopyr ...... 10 General Information for Selected Strategies ...... 10 Triclopyr ...... 10 Hand Pulling ...... 12 Bottom Barrier ...... 12 Other ...... 12 Recommended Plant Control Plan ...... 12 Year 1 ...... 13 Year 2 ...... 14 Years 3-10 ...... 14 Other Considerations ...... 15 Sensitive Species Assessment ...... 16 Plant Control Advisory Committee ...... 17 General Considerations and Permitting ...... 18 Funding ...... 18 Public Education Program ...... 18 Invasive Plant Prevention and Detection Program ...... 18 Volunteer Patrols ...... 19

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Lakeside Stewardship Education ...... 20 Plan Elements, Costs, and Funding...... 21 Implementation and Evaluation ...... 22 References ...... 25

Appendix A Public Meeting Announcements and Sign in Sheets Appendix B Summary of Ecology Approved Plant Control Strategies and Their Appropriateness for Lake Stevens Appendix C Detailed Control Strategies Presented at Steering Committee Meeting 2 Appendix D Pesticide Labels and Toxicity Information for Triclopyr, Fluridone, and Glyphosate Appendix E Letter from WDNR Natural Heritage Program

Tables

Table 1. Physical Characteristics of Lake Stevens and its Watershed...... 2 Table 2. Lake Stevens IAVMP Estimated 10-Year Budget...... 21

Figures

Figure 1. Lake Stevens Eurasian Watermilfoil Location and Density...... 5 Figure 2. Beneficial Use Areas in Lake Stevens...... 6

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PROJECT OVERVIEW

Lake Stevens is the largest and deepest lake in Snohomish County. Approximately 200 acres of this 1,040-acre lake is littoral zone (the area between the shore edge and a depth of about 20 feet). Eurasian watermilfoil (Myriophyllum spicatum, or milfoil) was first observed in the Lake Stevens in the early 1980s (Gene Williams, Snohomish County Surface Water Management. personal communication). It did not reach problematic levels until 2006, when its colonization expanded from a few isolated plants to aggressive growth throughout much of the littoral zone. An aquatic plant survey in July 2010 indicated that dense milfoil covered approximately 135 acres of the lake. Now, milfoil growth severely limits many of the beneficial uses of the lakes for both people and animals. The City of Lake Stevens applied for a planning grant from the Washington State Department of Ecology (Ecology) to develop an Integrated Aquatic Vegetation Management Plan (IAVMP) to address the current milfoil problem and future aquatic plant management needs. The planning process included a series of public and steering committee meetings, ending with final agreement on the recommended plan. This report describes the IAVMP (referred to in this report as the Aquatic Plant Plan) developed for Lake Stevens. The goal of this plan is to eradicate milfoil from Lake Stevens. The following are the basic recommendations for aquatic plant control in the lake:

 Apply one large scale triclopyr treatment to eliminate the majority of milfoil from the lake  Make targeted, small-scale applications of triclopyr to manage small patches of milfoil