WATER QUANTITY and QUALITY REPORT Foothills Subarea Prepared For: Whatcom County Planning & Development Services
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WATER QUANTITY AND QUALITY REPORT Foothills Subarea Prepared for: Whatcom County Planning & Development Services Project No. 080056-001-01 y July 18, 2008 179 Madrone Lane North Bainbridge Island, WA 98110 Tel: (206) 780-9370 Fax: (206) 780-9438 www.aspectconsulting.com a limited liability company ASPECT CONSULTING Contents Acronyms ...........................................................................................................iv Executive Summary............................................................................................1 Water Quantity .......................................................................................................1 Water Quality..........................................................................................................2 Public Stormwater Facilities ...................................................................................2 1 Introduction ...............................................................................................13 2 Existing Conditions...................................................................................15 2.1 Water Quantity ...........................................................................................15 2.1.1 Surface Water ...................................................................................... 15 2.1.2 Groundwater ........................................................................................ 23 2.2 Water Quality .............................................................................................28 2.2.1 Surface Water Quality Standards ........................................................ 28 2.2.2 Groundwater ........................................................................................ 32 2.3 Public Stormwater Facilities.......................................................................36 3 Impacts.......................................................................................................40 3.1 Water Quantity ...........................................................................................40 3.1.1 Surface Water ...................................................................................... 40 3.1.2 Groundwater ........................................................................................ 47 3.2 Water Quality .............................................................................................50 3.2.1 Surface Water ...................................................................................... 50 3.2.2 Groundwater ........................................................................................ 52 3.3 Public Stormwater Facilities.......................................................................55 4 Potential Mitigation ...................................................................................57 4.1 Alternative 1 ...............................................................................................57 4.1.1 Water Quantity ..................................................................................... 57 4.1.2 Water Quality ....................................................................................... 59 4.1.3 Public Stormwater Facilities................................................................. 60 4.2 Alternative 2 ...............................................................................................60 4.3 Alternative 3 ...............................................................................................60 4.4 Mitigation Elements Common to All Three Alternatives.............................61 PROJECT NO. 080056-001-01 y JULY 18, 2008 i ASPECT CONSULTING Limitations .........................................................................................................65 References.........................................................................................................65 Endnotes............................................................................................................67 List of Tables E.1 Summary of Impacts and Possible Mitigation Measures..........................4 1.1 Population Density Statistics for the Foothills Subarea..........................14 2.1 Summary of Streamflow Records for the Foothills Subarea ..................16 2.2 Monthly Streamflow Statistics (all flows in cfs).......................................17 2.3 WRIA 1 Water Balance applied to the Kendall Creek Watershed..........21 2.4 WWHM Model Land Use Classifications for Existing Conditions ...........23 2.5 WWHM Simulated Annual Water Balance for the Columbia Valley/Kendall UGA ...............................................................................23 2.6 Public Water Systems in the Foothills Subarea .....................................25 2.7 Existing Water Use in the Columbia Valley/Kendall UGA ......................27 2.8 Existing water use in the Rest of the Subarea .......................................28 2.9 Surface Water Use Designations (WAC 173-201A)...............................28 2.10 EPA 303(d) Category 5 Listed Streams in the Foothills Subarea ..........29 2.11 Current and Prior Surface Water Temperature Standard for Foothills Subarea .................................................................................................30 2.12 Groundwater and Drinking Water Standards .........................................33 2.13 Well Head Protection Areas Having Potential Sources of Contamination........................................................................................36 2.14 Inventoried Culverts in the County Right-of-Way in the Columbia Valley/Kendall UGA ...............................................................37 2.15 Inventoried Culverts in the WSDOT Right-of-Way near the Columbia Valley UGA ............................................................................38 2.16 Inventoried Bridges in the WSDOT Right-of-Way near the Columbia Valley ....................................................................................38 3.1 Modeled Land Use for Columbia Valley/Kendall UGA Study Area (all values in acres)......................................................................................42 3.2 Impervious Areas for Columbia Valley/Kendall UGA .............................44 ii PROJECT NO. 080056-001-01 y JULY 18, 2008 ASPECT CONSULTING 3.3 Land Use Classifications for Existing Conditions and Alternatives ........45 3.4 WWHM Simulated Annual Water Balance for the Columbia Valley/Kendall UGA ...............................................................................46 3.5 WWHM Simulated Annual Water Balance assuming 100% infiltration of new runoff..............................................................................................47 3.6 Existing and Future Water Use in the Columbia Valley/Kendall UGA Area ..............................................................................................48 3.7 Existing and Future Water Use in the Rest of the Subarea ...................49 3.8 Nitrate Loading Analysis........................................................................55 4.1 Assessment of Foothills Subarea Plan Goals and Policies related to Surface Water and Groundwater...........................................................63 List of Figures 2.1 Subbasins and Watersheds 2.2 Columbia Valley/Kendall UGA Overview 2.3 Geology and Surficial Aquifers 2.4 Well Logs by Quarter/Quarter Section 2.5 Water Temperature for Maple Creek .....................................................30 2.6 Stormwater Inventory PROJECT NO. 080056-001-01 y JULY 18, 2008 iii ASPECT CONSULTING Acronyms ADD ............................average daily demand BMPs...........................Best Management Practices BOD ............................biochemical oxygen demand CF................................commercial forestry CFR .............................Code of Federal Regulations CSCL...........................Confirmed or Suspected Contaminated Sites List cfs ................................cubic feet per second DOH ............................Washington State Department of Health DU/acre .......................dwelling units per acre Ecology .......................Washington State Department of Ecology EIA ..............................Effective Impervious Area EPA .............................U.S. Environmental Protection Agency EWSD#19 ...................Evergreen Water-Sewer District #19 gpd...............................gallons per day LAMIRD.....................Limited Areas of More Intensive Rural Development LID ..............................low impact development LUSTs .........................leaking underground storage tanks MCL ............................maximum contaminant level mg/L ............................milligrams per liter MIFs ............................Minimum Instream Flows NPDES ........................National Pollution Discharge Elimination System PWS.............................Public Water System RCW............................Revised Code of Washington RF................................rural forestry SEIS.............................Supplemental Environmental Impact Statement TOT.............................time of travel TP ................................total phosphorus TIA ..............................total impervious area TSS..............................total suspended solids USC.............................United States Code USTs............................underground storage tanks USGS...........................U.S. Geological Survey