COASTAL MENDOCINO COUNTY STORMWATER RESOURCE PLAN COASTAL MENDOCINO COUNTY STORMWATER RESOURCE PLAN PREPARED FOR MENDOCINO COUNTY WATER AGENCY July 8, 2019 (4th issuance) Original version issued June 30, 2018 Mendocino County Water Agency Contact: Sarah Dukett, Deputy Chief Executive Officer County of Mendocino Executive Office/Water Agency 501 Low Gap Road, Ukiah, California 95482 Prepared by: LACO Associates 776 S. State St., Suite 102A Ukiah, California 95482 (707) 462-0222 LACO Project No. 7746.13 Coastal Mendocino County Stormwater Resource Plan Mendocino County Water Agency TABLE OF CONTENTS 1 . 0 Introduction 1 1 . 1 Purpose and Scope ........................................... 1 1 . 2 S t u d y A r e a D e s c r i p t i o n ..................................... 1 1 . 2 . 1 Pudding Creek - Frontal Pacific Ocean W a t e r s h e d ............................................ 1 1 . 2 . 2 Noyo River Watershed ............................ 2 1 . 2 . 3 Big River Watershed ............................... 2 1 . 3 Physiography .................................................. 2 1 . 4 C l i m a t e .......................................................... 3 1 . 5 L a n d U s e ........................................................ 3 1 . 6 P o p u l a t i o n ...................................................... 4 1 . 7 Previous Work (Literature Review) ...................... 5 1 . 7 . 1 Executive Summary ................................. 5 1 . 7 . 2 Pudding Creek - Frontal Pacific Ocean W a t e r s h e d ............................................ 5 1 . 7 . 3 Noyo River Watershed ............................ 7 1 . 7 . 4 Big River Watershed ............................... 7 1 . 7 . 5 D a t a G r o u p ........................................... 8 1 . 7 . 6 Hydrology Findings ................................ 9 1 . 7 . 7 Hydrogeologic Findings ......................... 11 2 . 0 Watershed Identification ....................................... 13 2 . 1 Watershed and Sub - W a t e r s h e d s ....................... 13 2 . 2 Land Use and Open Space ............................... 14 July 8, 2019 Coastal Mendocino County Stormwater Resource Plan Mendocino County Water Agency 2 . 3 Public Agency Boundaries ............................... 15 2 . 4 Surface and Groundwater Resources ................. 15 2 . 5 Water Quality Priorities ................................. 15 3 . 0 Water Quality Compliance ..................................... 16 3 . 1 Activities Contributing to Polluted Runoff .......... 16 3 . 1 . 1 B i g R i v e r ............................................ 16 3 . 1 . 2 N o y o R i v e r .......................................... 17 3 . 1 . 3 Caspar Creek ...................................... 18 3 . 1 . 4 Pudding Creek ..................................... 18 3 . 2 Strategies to Address Pollutant Runoff and S o u r c e s ........................................................ 19 3 . 2 . 1 State of California .............................. 19 3 . 2 . 2 County of Mendocino ............................ 19 3 . 2 . 3 Regional Efforts ................................... 20 3 . 2 . 4 SWRP Strategies to Reduce Sediment ....... 22 3 . 3 Identify, Monitoring, and Date Requirements to Support SWRP Implementation .......................... 22 3 . 3 . 1 Substrate Composition .......................... 23 3 . 3 . 2 Riffle Embeddedness ............................. 23 3 . 3 . 3 Residual Pool Volume ............................ 23 3 . 3 . 4 Thalweg Profile ................................... 23 3 . 3 . 5 Pool Distribution and Depth ................... 23 3 . 3 . 6 T u r b i d i t y ............................................ 24 3 . 3 . 7 Aquatic Insect Production ...................... 24 July 8, 2019 Coastal Mendocino County Stormwater Resource Plan Mendocino County Water Agency 3 . 3 . 8 Large Woody Debris ............................. 24 3 . 3 . 9 Stream Crossing Failure and Diversion P o t e n t i a l ............................................ 24 3 . 3 . 1 0 Hydrologic Connectivity of Roads ........... 25 3 . 3 . 1 1 Road Inspection and Correction .............. 25 3 . 3 . 1 2 Surfacing, Sidecast Fill, a n d R o a d L o c a t i o n ............................................. 25 3 . 3 . 1 3 Activity in Unstable Areas ..................... 25 4 . 0 Organization, Coordination, and Collaboration ......... 25 4 . 1 SWRP Organization Structure ........................... 25 4 . 1 . 1 Program Intent ..................................... 25 4 . 1 . 2 Purpose of this Strategy ....................... 26 4 . 1 . 3 SWRP Project Boundaries ....................... 26 4 . 2 Coordination between SWRP Organization, TAC, Stakeholders, and S WRCB ............................... 26 4 . 2 . 1 Public Participation and Involvement M e t h o d s .............................................. 27 4 . 3 G o a l s 31 4 . 3 . 1 Goal 1: Develop Public Involvement ........ 31 4 . 3 . 2 Goal 2: Create Opportunities for Citizens to Participate ..................................... 32 4 . 3 . 3 Goal 3: Provide Stormwater Program Information to the Community ................. 32 4 . 3 . 4 Goal 4: Participate in Watershed P l a n n i n g ............................................. 33 July 8, 2019 Coastal Mendocino County Stormwater Resource Plan Mendocino County Water Agency 4 . 4 Action Plan and Responsibilities ....................... 33 5 . 0 Quantitative Methods ........................................... 33 5 . 1 Hydrologic Simulation Model Methodology ......... 34 5.2 Hydraulic Simulation Models ............................ 34 5 . 3 Transport Simulation Models ............................ 35 5 . 4 Empirical Methods .......................................... 36 5 . 5 Selected Quantification Methods ...................... 37 6 . 0 Identification and Prioritization of Projects ............. 38 6 . 1 Project Prioritization ..................................... 38 6 . 1 . 1 Technical Score .................................... 38 6 . 1 . 2 T A C S c o r e ........................................... 41 7 . 0 Project Prioritization and Ranking .......................... 43 8 . 0 Implementation Strategy and Schedule .................... 44 8 . 1 Introduction .................................................. 44 8 . 2 Implementation Strategies ............................... 44 8 . 2 . 1 Stakeholder Involvement ........................ 44 8 . 2 . 2 Performance Measures .......................... 45 8 . 2 . 3 Decision Support Tools .......................... 46 8 . 2 . 4 Monitoring and Data Requirements .......... 47 8 . 2 . 5 Adaptive Management Approach ............. 48 8 . 2 . 6 P l a n Implementation ............................. 50 8 . 2 . 7 Achievement of Multiple Benefits ............ 51 8 . 2 . 8 Project Implementation and Tracking ....... 51 9 . 0 Education, Outreach, and Public Participation .......... 54 July 8, 2019 Coastal Mendocino County Stormwater Resource Plan Mendocino County Water Agency 9 . 1 Outreach Website .......................................... 54 1 0 . 0 R e f e r e n c e s ........................................................ 55 FIGURES Figure 1 SWRP Boundary Map Figure 2 Watershed Map Figure 3 Sub-Watershed Map Figure 4 Water Resources Map Figure 5 Groundwater Resources Map Figure 6 Rural Land Use Map Figure 7 Fort Bragg Land Use Map APPENDI CES Appendix A August 17, 2017 SWRP Meeting Multi-Benefit Results Appendix B Completed Project Submission Form Appendix C Stakeholder Outreach Letter Appendix D Interested Persons Contact List Appendix E Model Applications to Primary and Secondary Benefits Appendix F Projects Appendix G Completed TAC Project Scoring Form Appendix H Big River: Summary of Sediment Substrate Samples Appendix I Noyo River: Summary of In-stream Data, Watershed Sediment Source Analysis, and Sediment Inputs Appendix J Pudding Creek: Summary of Dominant Substrates by Habitat Type and Mean Percentage of Dominant Substrate and Vegetation Appendix K SWAMP Standard Operating Procedures for Field Collection and Processing of Bed Samples L I S T O F PREPARERS Christopher Watt, CEG, CHG, Principal Engineering Geologist, LACO Associates Brian M. Wallace, MS, MBA, EIT, Staff Engineer I, LACO Associates Jordan Blough, Economic Development Specialist, LACO Associates Rebecca Dalske, Associate Planner, LACO Associates July 8, 2019 Coastal Mendocino County Stormwater Resource Plan Mendocino County Water Agency 1 . 0 INTRODUCTION In 2014, the Water Bond (Assembly Bill 1471), or Proposition 1, was passed by California voters. Proposition 1 enacted the Water Quality, Supply, and Infrastructure Improvement Act of 2014, which created a fund to allocate monetary resources to increase water supply reliability, restore and preserve fish and wildlife habitat, and develop resilient and sustainably-managed water systems to withstand future and unforeseen pressures in the coming decades. In 2015, the State Stormwater Resource Plan Guidelines were prepared to build a framework consistent with the requirements of California Water Code sections 10561-10573. The Coastal Mendocino County Stormwater Resource Plan (SWRP) utilizes the State SWRP Guidelines to screen and evaluate projects based on weighted benefit criteria and quantitative analysis. 1.1 Purpose and Scope The Coastal Mendocino County SWRP encompasses three coastal watersheds in Mendocino County, California: Pudding Creek-Frontal Pacific Ocean watershed, Noyo River watershed, and Big River watershed. A map of the study area boundaries is presented in Figure 1. Main rivers and creeks