Western Lake Superior Sanitary District Comprehensive Wastewater Services Plan May 2010 Western Lake Superior Sanitary District 2626 Courtland Street Duluth, MN 55806 (218) 722-3336 Western Lake Superior Sanitary District Comprehensive Plan May 2010 WLSSD Board of Directors Deb Hill (Chair) Dave Manderfeld (Vice Chair) Albert Katz (Secretary) Guy Unertl (Treasurer) Rob Prusak Bill Majewski Paul Heller Ruth Janke Jim Aird WLSSD Executive Director Marianne Bohren Project Consultants Brown and Caldwell Camp Dresser & McKee, Inc Cover Photography Michael K. Anderson Date of WLSSD Board Adoption May 24, 2010 Western Lake Superior Sanitary District COMPREHENSIVE WASTEWATER SERVICES PLAN Western Lake Superior Sanitary District Comprehensive Wastewater Services Plan MAY 2010 Table of Contents EXECUTIVE SUMMARY .............................................................................................5 INTRODUCTION...........................................................................................................9 PLAN GOALS..............................................................................................................17 ENVIRONMENTAL CHARACTERISTICS ................................................................ 23 LAND USE AND DEMOGRAPHICS .......................................................................... 37 SUBSURFACE SEWAGE TREATMENT SYSTEMS (SSTS) ..................................... 55 PROCESS AND FACILITY ANALYSIS ..................................................................... 63 PLAN RECOMMENDATIONS.................................................................................. 105 PLAN ADMINISTRATION ....................................................................................... 109 LITERATURE REVIEW............................................................................................ 111 List of Tables Table 1, WLSSD Population Trends (1980-2010).......................................................... 47 Table 2, WLSSD Population and Estimated Sewered Services ...................................... 57 Table 3, Maximum Month Flows and Loads.................................................................. 67 Table 4, Planning Period Flows and Loadings (2000-2020) ........................................... 68 Table 5, Summary of WLSSD Capacity and Design Requirements................................ 71 Table 6, Average Dry Weather Flow, Level of Service, and Peak Flow by Metering Location......................................................................................................78-79 Table 7, Pump Station Capacity and Model Predicted Results for Existing and Future Conditions During a 10-year Flow Event.......................................................... 90 Table 8, Pump Station Capacities and Capacity Ratios .................................................. 92 Table 9, Pump Station Capacities and Capacity Ratios – Future Conditions................... 93 Table 10, Model Predicted Overflow Points and Volumes for Points in the Consent Decree................................................................................................95 Table 11, Model Predicted Overflow Points and Volumes for Points NOT in the Consent Decree...........................................................................................................96 Table 12, WLSSD Pump Stations.................................................................................. 99 Table 13, 10-year Capital Improvement Plan for Pump Stations .................................. 102 Table 14, 10-year Capital Improvement Plan for Gravity Interceptors ......................... 103 1 Western Lake Superior Sanitary District COMPREHENSIVE WASTEWATER SERVICES PLAN List of Figures Figure 1, Location Map ...................................................................................................9 Figure 2, Statutory Limits..............................................................................................10 Figure 3, Soil Classification Map...................................................................................25 Figure 4, Regional Watershed Map................................................................................ 29 Figure 5, Winter Precipitation........................................................................................35 Figure 6, Spring Precipitation........................................................................................35 Figure 7, Summer Precipitation ..................................................................................... 35 Figure 8, Fall Precipitation ............................................................................................35 Figure 9, Land Use/Cover Map...................................................................................... 38 Figure 10a, Population Density by Census Block........................................................... 48 Figure 10b, Population Density by Minor Civil Division ............................................... 49 Figure 10c, Projected Growth........................................................................................ 50 Figure 11, Existing WLSSD Collection System............................................................. 51 Figure 12, Urban Services Boundary Map ..................................................................... 54 Figure 13, WLSSD Existing Facilities Schematic .......................................................... 65 Figure 14, WLSSD Interceptor System.......................................................................... 73 Figure 15, WLSSD Municipal Peak Flow Standards...................................................... 76 Figure 16, Pipe Capacity – 10 Year Design Flow Event (Pump Side) ............................ 80 Figure 16a, Pipe Capacity – 10 Year Design Flow Event (Gravity Side)........................ 80 Figure 17, Pipe Surcharging – 10 Year Design Flow Event (Pump Side) ....................... 81 Figure 17a, Pipe Surcharging – 10 Year Design Flow Event (Gravity Side)................... 81 Figure 18, Pipe and Pump Station Capacity Ratios (Pump Side) .................................... 83 Figure 18a, Pipe and Pump Station Capacity Ratios (Gravity Side)................................ 83 Figure 19, Modeled Service Basins................................................................................ 85 Figure 20, Future Conditions Pipe Capacity – 10 Year Design Flow Event (Pump Side) ..................................................................................................86 Figure 20a, Future Conditions Pipe Capacity – 10 Year Design Flow Event (Gravity Side)...........................................................................................................86 Figure 21 Future Conditions Pipe Surcharging – 10 Year Design Flow Event (Pump Side) .............................................................................................................87 Figure 21a, Future Conditions Pipe Surcharging – 10 Year Design Flow Event (Gravity Side)...........................................................................................................87 Figure 22, Future Conditions Pipe and Pump Station Capacity Ratios (Pump Side) ....... 88 Figure 22a, Future Conditions Pipe and Pump Station Capacity Ratios (Gravity Side)... 88 2 Western Lake Superior Sanitary District COMPREHENSIVE WASTEWATER SERVICES PLAN Appendices Enclosed CD A. Collection System Model Update (Brown & Caldwell, August, 2009) B. Collection System Future Conditions Analysis (Brown & Caldwell, August 2009) C. Pump Station Condition Assessment (Brown & Caldwell, September 2009) D. Interceptor Rehabilitation and Replacement Project (Camp, Dresser, McKee, October 2009) 3 Western Lake Superior Sanitary District COMPREHENSIVE WASTEWATER SERVICES PLAN THIS PAGE INTENTIONALLY LEFT BLANK 4 Western Lake Superior Sanitary District COMPREHENSIVE WASTEWATER SERVICES PLAN Western Lake Superior Sanitary District Comprehensive Wastewater Master Plan MAY 2010 Executive Summary This document provides an update to the 2003 Water Quality Management Plan. This is a timely and energetic project entailing a wide variety of water resource, socioeconomic, and engineering issues for a vast area covering approximately 530 square miles. The document has been renamed Comprehensive Wastewater Master Plan to better reflect the broad-scale planning effort. The Plan quickly and efficiently identifies key issues and provides an action plan directly tied to pertinent WLSSD goals and policies. A great deal of data and information has been utilized in formulating a useful and beneficial Comprehensive Plan. Many subject areas are covered quite extensively. Others will require further analysis by the District as important environmental and land use planning issues are discussed and acted upon. The Plan includes the following main sections: I. Introduction and Background II. Plan Goals III. Environmental Characteristics IV. Land Use and Demographics V. Subsurface Sewage Treatment Systems (SSTS) VI. Process and Facility Analysis VII. Asset Management VIII. Plan Recommendations The content of the document centers on the main mission of the WLSSD to provide a Plan that is environmentally sensitive to key water quality and wastewater collection needs. At the same time the Plan also provides a basis for current and future cost effective planning, consistent with local and regional planning guidelines. 5 Western Lake Superior Sanitary District COMPREHENSIVE WASTEWATER