BELL CANYON RESERVOIR WATERSHED SANITARY SURVEY 2014 UPDATE FINAL REPORT Prepared for: City of St. Helena Prepared by: FEBRUARY 2014 Bell Canyon Reservoir Watershed Sanitary Survey Third Update FINAL REPORT February 2014 Prepared for: City of St. Helena Prepared by: Leslie Palencia, Palencia Consulting Engineers TABLE OF CONTENTS Page Number Executive Summary Introduction ............................................................................................................... ES-1 Objectives of the Update ........................................................................................... ES-1 Key Findings and Conclusions .................................................................................. ES-1 Source Water Quality ........................................................................ ES-1 Turbidity .................................................................................... ES-2 Coliform ..................................................................................... ES-2 Disinfection By-Product Precursors ........................................... ES-3 Intake Evaluation ............................................................................... ES-3 Turbidity .................................................................................... ES-3 Microbiological Constituent Review ........................................... ES-3 Disinfection By-Products and Precursors .................................. ES-4 Giardia/Virus/Cryptosporidium Reduction Requirements .......... ES-4 Watershed Contaminant Sources ..................................................... ES-5 Spills ......................................................................................... ES-5 Wineries/Vineyards ................................................................... ES-5 Unauthorized Activity ................................................................ ES-5 Storm Water .............................................................................. ES-6 Septic Systems ......................................................................... ES-6 Fires .......................................................................................... ES-6 Recommendations .................................................................................................... ES-7 Section 1 – Introduction Introduction .................................................................................................................. 1-1 Objectives of the Update .............................................................................................. 1-1 Constituents and Potential Contaminating Activities Covered in the Third Update ...... 1-2 Description of How the Third Update was Conducted .................................................. 1-3 Report Organization ..................................................................................................... 1-3 Section 2 – Watershed and Water Supply Systems Watershed Description ................................................................................................. 2-1 General Description and Stream Flow ............................................................... 2-1 Land Use and Population .................................................................................. 2-2 Climate and Precipitation ................................................................................... 2-2 Water Supply System – City of St. Helena ................................................................... 2-2 Service Area and Sources ................................................................................. 2-3 Water Treatment ................................................................................................ 2-3 Section 3 – Bell Canyon Reservoir Water Quality Review Overall Water Quality Review ...................................................................................... 3-1 BELL CANYON RESERVOIR WATERSHED SANITARY SURVEY Page i 2014 UPDATE – FINAL REPORT Selected Constituent Review ....................................................................................... 3-2 Turbidity ............................................................................................................. 3-2 General Characteristics and Background ............................................... 3-2 Evaluation ............................................................................................... 3-3 Summary of Results................................................................................ 3-4 Microbiological Constituents .............................................................................. 3-4 General Characteristics and Background ............................................... 3-4 Evaluation for Total Coliform and E. coli ................................................. 3-6 Summary of Results for Total Coliform and E. coli ................................. 3-8 Disinfection By-Product Precursors (Total Organic Carbon) ............................. 3-9 General Characteristics and Background ............................................... 3-9 Evaluation ............................................................................................... 3-9 Summary of Results................................................................................ 3-9 Algalloo 3 Detectable Title 22 Constituents of Interest 3- Detectable Title 22 Constituents of Interest ..................................................... 3-10 Section 4 – Watershed Contaminant Sources Review Spills ............................................................................................................................. 4-1 Background ....................................................................................................... 4-1 Seasonal Patterns ............................................................................................. 4-1 Related Constituents ......................................................................................... 4-1 Occurrence in Watershed .................................................................................. 4-1 Related Water Quality Issues and Data Review ................................................ 4-2 Regulation and Management ............................................................................ 4-2 Recommended Source Water Protection Activities ........................................... 4-2 Wineries/Vineyards ...................................................................................................... 4-3 Background ....................................................................................................... 4-3 Seasonal Patterns ............................................................................................. 4-3 Related Constituents ......................................................................................... 4-3 Occurrence in Watershed .................................................................................. 4-3 Sewage System Monitoring Permit ......................................................... 4-5 Erosion Control Plan ............................................................................... 4-6 Crops and Pesticide Use ........................................................................ 4-7 Related Water Quality Issues and Data Review ................................................ 4-7 Regulation and Management............................................................................. 4-7 Recommended Source Water Protection Activities ........................................... 4-8 Unauthorized Activity .................................................................................................... 4-9 Background ....................................................................................................... 4-9 Occurrence in Watershed .................................................................................. 4-9 Related Water Quality Issues and Data Review ................................................ 4-9 Regulation and Management........................................................................... 4-11 Recommended Source Water Protection Activities ......................................... 4-11 Storm Water ............................................................................................................... 4-12 Background ..................................................................................................... 4-12 Seasonal Patterns ........................................................................................... 4-12 Occurrence in Watershed ................................................................................ 4-23 BELL CANYON RESERVOIR WATERSHED SANITARY SURVEY Page ii 2014 UPDATE – FINAL REPORT Storm Water Pollution Prevention Plan – County of Napa .................... 4-12 General Industrial Storm Water Permit - SWRCB ................................. 4-13 Related Water Quality Issues and Data Review .............................................. 4-13 Regulation and Management........................................................................... 4-14 Recommended Source Water Protection Activities ......................................... 4-14 Septic Systems .......................................................................................................... 4-15 Background ..................................................................................................... 4-15 Related Constituents