Snohomish County Total Maximum Daily Load Monitoring Quality Assurance Project Plan Snohomish River Tributaries, Stillaguamish Basin, North and Swamp Creek TMDL Coverage Areas 2021 – 2024 Prepared by Snohomish County Public Works Surface Water Management Division 3000 Rockefeller Ave Everett, Washington 98201 December 2020 Page is blank for duplex printing Program and Publication Information The monitoring activities described in this Quality Assurance Project Plan (QAPP) are triggered by the Federal Water Pollution Control Act (Clean Water Act) Title 33 United States Code, Section 1251 et seq. and Appendix 2 (Total Maximum Daily Loads) of the 2019-2024 National Pollutant Discharge Elimination Systems Phase 1 Municipal Stormwater Permit issued to Snohomish County by the Washington State Department of Ecology (Ecology). The program is funded by surface water fees collected by Snohomish County Public Works under the authority of the Revised Code of Washington RCW 36.89 and 90.72 and codified in Snohomish County Code Title 25. This plan is available on Snohomish County’s website at: http://snohomishcountywa.gov/Archive.aspx?AMID=73 Data for this project is uploaded to Ecology’s Environmental Information Management (EIM) database at www.ecy.wa.gov/eim/index.htm. Author and Contact Information Steve Britsch Snohomish County Public Works / Surface Water Management 3000 Rockefeller Ave., M/S 607 Everett, WA. 98201 Snohomish County Surface Water Management http://snohomishcountywa.gov/208/Surface-Water Page is blank for duplex printing Page is blank for duplex printing Table of Contents Distribution List ............................................................................................................... 1 Abstract ........................................................................................................................... 2 Introduction and Problem Statement............................................................................. 4 Background ..................................................................................................................... 6 Water Quality Standards and Microbial Water Quality Assessment ............................. 7 TMDL Study Area ............................................................................................................ 9 Snohomish River Tributaries ....................................................................................... 9 Quilceda Creek and Allen Creeks ............................................................................. 9 French Creek Sub-basin ......................................................................................... 13 Pilchuck Sub-basin ................................................................................................. 15 Woods Creek Sub-basin ......................................................................................... 17 Stillaguamish Basin .................................................................................................... 19 North Creek Sub-basin .............................................................................................. 21 Swamp Creek Sub-basin ............................................................................................ 23 Summary of Previous and Existing Data ....................................................................... 25 Snohomish County Surface Water Management ..................................................... 25 Long Term Water Quality Monitoring ................................................................... 25 Bacterial Pollution Identification and Correction (PIC) Grants ............................. 26 Washington State Department of Ecology ................................................................ 27 Long Term Status and Trends ................................................................................ 27 Lower Snohomish River Tributaries TMDL ............................................................ 28 North Creek TMDL ................................................................................................. 30 Swamp Creek TMDL ............................................................................................... 31 Stillaguamish River TMDL ...................................................................................... 33 Snohomish Health District ......................................................................................... 36 King County ............................................................................................................... 37 Stillaguamish Tribe .................................................................................................... 37 Tulalip Tribes ............................................................................................................. 37 Organization, Budget and Project Schedule ................................................................. 38 Project Team ............................................................................................................. 38 Special training and certifications ............................................................................. 38 Project Budget ........................................................................................................... 39 Project Schedule ........................................................................................................ 40 Project Description ....................................................................................................... 41 TMDL Areas ............................................................................................................... 41 Study Objectives ........................................................................................................ 41 Routine Monitoring Design and Hypothesis ............................................................. 41 Establishing Routine Monitoring Stations .................................................................... 42 Sampling Process Design............................................................................................... 46 Surface Water Monitoring ........................................................................................ 46 Logistical Problems .................................................................................................... 46 Field Sampling Procedures ............................................................................................ 47 Calibration ................................................................................................................. 47 Invasive Species Procedures ..................................................................................... 48 Field Sample and Measurement Methods ................................................................... 51 Quality Control .............................................................................................................. 52 Field Measurement Quality Control .......................................................................... 53 Trip Blank Samples .................................................................................................... 58 Lab Quality Control.................................................................................................... 59 Bias ......................................................................................................................... 59 Precision ................................................................................................................ 60 Accuracy ................................................................................................................. 60 Data Verification, Validation and Quality Assessment ................................................. 61 Data Verification........................................................................................................ 63 Data Validation .......................................................................................................... 63 Data Management Procedures ................................................................................. 65 Field Data................................................................................................................... 65 Laboratory Data......................................................................................................... 65 Data Analysis ............................................................................................................. 66 Graphical Representations ........................................................................................ 66 Descriptive Statistics ................................................................................................. 66 Calculation of Geometric Means and Percent Exceedances .................................... 66 Calculation of Probabilities and MWQA Ranks ......................................................... 66 Audits and Reports .................................................................................................... 67 Audits ........................................................................................................................ 67 Reports ...................................................................................................................... 67 References .................................................................................................................... 68 Appendix A. Health