2017 TECHNICAL STUDIES AND 20-YEAR RETROSPECTIVE FOR THE CACHE CREEK AREA PLAN Prepared for: Yolo County Administrator’s Office 625 Court Street Woodland, CA 95695 Prepared by: Mark Tompkins, P.E., Ph.D. Paul Frank, P.E., CED Andrew P. Rayburn, Ph.D. In Consultation With: Elisa Sabatini, Manager of Natural Resources, Project Director Heidi Tschudin, TSCHUDIN CONSULTING GROUP, Project Manager Casey Liebler, Natural Resources Program Assistant, Project Assistant March 17, 2017 TABLE OF CONTENTS TABLE OF CONTENTS Table Of Contents ............................................................................................................................ i List of Figures ................................................................................................................................... v Chapter 1 – Fluvial Geomorphology Study .................................................................................. v Chapter 2 – Hydrology and Water Quality Study ........................................................................ vi Chapter 3 – Biological Resources Study .................................................................................... viii List of Tables .................................................................................................................................... x Chapter 1 – Fluvial Geomorphology Study .................................................................................. x Chapter 2 – Hydrology and Water Quality Study ......................................................................... x Chapter 3 – Biological Resources Study ....................................................................................... x Executive Summary ............................................................................................................... 1 ES.1 Overview ..................................................................................................................... ES-1 ES.2 Executive Summary for Lower Cache Creek Fluvial Geomorphology Study .............. ES-1 ES.3 Executive Summary for Lower Cache Creek Hydrology and Water Quality Study ..... ES-3 ES.4 Executive Summary for Lower Cache Creek Biological Resources Study ................... ES-4 Chapter 1.0 – Lower Cache Creek Fluvial Geomorphology Study (1996-2016) ........................... 1 1.1 Introduction ...................................................................................................................... 1-1 1.2 Methods and Assumptions ............................................................................................... 1-1 1.3 Results and Discussion ...................................................................................................... 1-3 1.3.1 Fluvial Geomorphology Findings Summary .................................................................. 1-3 1.3.2 Fluvial Geomorphology Data Availability 1996-2016 ................................................... 1-5 1.3.3 CCRMP Area Results...................................................................................................... 1-6 Hydrology .............................................................................................................................. 1-6 Fluvial Geomorphology......................................................................................................... 1-7 1.3.4 CCRMP Geomorphic Reach Specific Results ............................................................... 1-12 Capay Reach ........................................................................................................................ 1-12 Hungry Hollow Reach ......................................................................................................... 1-16 Madison Reach ................................................................................................................... 1-20 Guesisosi Reach .................................................................................................................. 1-24 Dunnigan Hills Reach .......................................................................................................... 1-28 Hoppin Reach ...................................................................................................................... 1-32 i TABLE OF CONTENTS Rio Jesus Maria Reach ........................................................................................................ 1-36 1.4 Recommendations .......................................................................................................... 1-39 1.4.1 Recommendations on CCAP Documents .................................................................... 1-39 Off-Channel Mining Plan (OCMP) ....................................................................................... 1-39 Cache Creek Resources Management Plan (CCRMP) ......................................................... 1-40 Cache Creek Improvement Program (CCIP) ....................................................................... 1-41 1.4.2 Recommendations on Ordinances .............................................................................. 1-42 Off-Channel Mining Ordinance ........................................................................................... 1-42 Surface Mining Reclamation Ordinance ............................................................................. 1-43 In-Channel Maintenance Mining Ordinance ...................................................................... 1-43 1.4.3 Other Recommendations ............................................................................................ 1-44 Status of Past Recommendations ....................................................................................... 1-45 1.5 References ...................................................................................................................... 1-45 Chapter 2.0 – Lower Cache Creek Hydrology and Water Quality Study (1996-2016) ................. 1 2.1 Introduction ...................................................................................................................... 2-1 2.2 Methods and Assumptions ............................................................................................... 2-1 2.3 Results and Discussion ...................................................................................................... 2-2 2.3.1 Hydrologic Findings Summary ...................................................................................... 2-2 2.3.2 Water Quality Findings Summary ................................................................................. 2-3 2.3.3 Hydrology Results and Discussion ................................................................................ 2-4 Data Availability 1996-2016.................................................................................................. 2-4 Surface Water Hydrology ..................................................................................................... 2-5 Groundwater Hydrology ..................................................................................................... 2-11 2.3.4 Water Quality Results and Discussion ........................................................................ 2-17 CCAP Monitoring Requirements ......................................................................................... 2-17 Regulatory Context ............................................................................................................. 2-18 Water Quality Monitoring Summary and Data Availability ................................................ 2-18 Water Quality Analysis and Trends .................................................................................... 2-20 2.4 Recommendations .......................................................................................................... 2-22 2.4.1 Recommendations on Plan Documents...................................................................... 2-22 Off-Channel Mining Program (OCMP) ................................................................................ 2-22 Cache Creek Resources Management Plan (CCRMP) ......................................................... 2-23 ii TABLE OF CONTENTS Cache Creek Improvement Program (CCIP) ....................................................................... 2-24 2.4.2 Recommendations on Ordinances .............................................................................. 2-25 Off-Channel Mining Ordinance ........................................................................................... 2-25 Reclamation Ordinance ...................................................................................................... 2-25 In-Channel Mining Ordinance ............................................................................................. 2-25 2.4.3 Other Recommendations ............................................................................................ 2-25 Status of Recommendations from the 2006 Status and Trends Report ............................ 2-26 Status of Recommendations from 1998-2015 TAC Annual Reports .................................. 2-26 2.5 References ...................................................................................................................... 2-27 Appendix 2.A – Detailed Surface Water Quality Analysis .......................................................... 2-28 Appendix 2.B – Surface Water Quality Monitoring Program Statistics ....................................