Little Bear Solar Project Draft
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Appendix J Hydrology and Water Quality Appendix J1, Hydrology and Water Quality Technical Report for the Little Bear Solar Project Appendix J2, Water Supply Assessment for Little Bear Solar Project Appendix J3, Identification of Sources of Water for the Little Bear Solar Project Pursuant to Requirements of Fresno County Solar Facility Guidelines Appendix J4, Water Supply Little Bear Solar Project J-1 ESA / 160635.01 Draft Environmental Impact Report August 2018 Appendix J. Hydrology and Water Quality Appendix J1 Hydrology and Water Quality Technical Report for the Little Bear Solar Project Little Bear Solar Project ESA / 160635.01 Draft Environmental Impact Report August 2018 HYDROLOGY AND WATER QUALITY TECHNICAL REPORT for the Little Bear Solar Project Mendota, California Prepared for: Little Bear Solar 1 LLC, Little Bear Solar 3 LLC, Little Bear Solar 4 LLC, Little Bear Solar 5 LLC, and Little Bear Solar 6 LLC 135 Main Street, 6th Floor San Francisco, California 94105 Prepared by: 605 Third Street Encinitas, California 92024 Contact: Jonathan Martin 760.479.4104 SEPTEMBER 2017 INTENTIONALLY LEFT BLANK Printed on 30% post-consumer recycled material. Hydrology and Water Quality Technical Report Little Bear Solar Project TABLE OF CONTENTS Section Page No. 1 INTRODUCTION..............................................................................................................1 1.1 Scope and Purpose .................................................................................................. 1 1.2 Project Location ...................................................................................................... 1 1.3 Project Description and Activity ............................................................................. 2 2 HYDROLOGIC SETTING...............................................................................................7 2.1 Project Hydrologic Characteristics ......................................................................... 7 2.2 Floodplain ............................................................................................................... 8 2.3 Groundwater ........................................................................................................... 8 2.4 Beneficial Uses for Surface Water and Groundwater ............................................. 9 3 EXISTING DRAINAGE (PRE-DEVELOPMENT CONDITION) ............................15 3.1 Existing Topography ............................................................................................. 15 3.2 Existing Hydrologic Soil Group ........................................................................... 15 3.3 Existing Land Use ................................................................................................. 16 3.4 Existing Run-on and Runoff ................................................................................. 16 4 PROPOSED DRAINAGE (POST-DEVELOPMENT CONDITION) ........................23 4.1 Proposed Topography ........................................................................................... 23 4.2 Proposed Hydrologic Soil Group .......................................................................... 23 4.3 Proposed Land Use ............................................................................................... 23 4.4 Proposed Run-on and Runoff................................................................................ 23 5 CHARACTERIZATION OF PROJECT RUNOFF .....................................................27 5.1 Potential Pollutants ............................................................................................... 27 5.2 Receiving Waters Impairments, TMDLs, and Beneficial Uses ............................ 27 6 STORMWATER MANAGEMENT MEASURES .......................................................29 6.1 Best Management Practices .................................................................................. 29 6.2 Proposed Detention Basins – Preliminary Sizing Calculations ............................ 30 6.3 BMP Maintenance ................................................................................................ 32 7 PROJECT IMPACTS .....................................................................................................33 7.1 CEQA Significance Criteria ................................................................................. 33 7.2 Identified Impacts ................................................................................................. 35 8 CONCLUSIONS ..............................................................................................................37 9 REFERENCES .................................................................................................................39 9974 i September 2017 Hydrology and Water Quality Technical Report Little Bear Solar Project TABLE OF CONTENTS (CONTINUED) Page No. ATTACHMENT A Fresno County Basin Design Standards FIGURES 1-1 Regional Map .......................................................................................................................3 1-2 Little Bear Solar – Project Facilities and Parcels.................................................................5 2-1 Little Bear Hydrologic Setting ...........................................................................................11 3-1 Little Bear Solar – Existing Conditions .............................................................................17 4-1 Little Bear Solar – Proposed Conditions ...........................................................................25 TABLES 2-1 Project Hydrologic Characteristics ......................................................................................7 2-2 Project Contribution to Hydrologic Subarea ........................................................................7 2-3 Westside Subbasin Summary ...............................................................................................9 2-4 Beneficial Uses for Surface Waters and Groundwaters .....................................................10 3-1 Rainfall Intensities (in/hr) per NOAA Atlas 14 .................................................................20 3-2 Designation of Runoff Coefficients ...................................................................................21 3-3 Project Watershed – Existing Conditions – Weighted Runoff Coefficient .......................22 3-4 Peak Discharge – Existing Conditions ...............................................................................22 4-1 Project Watershed – Proposed Conditions – Weighted Runoff Coefficient ......................24 4-2 Peak Discharge – Proposed Conditions .............................................................................24 5-1 CWA Section 303(d) Water Bodies – 2010 303(d) List of Water Quality Segments ...............28 6-1 Recommended Best Management Practices ......................................................................30 6-2 Detention Basin Sizing Calculations .................................................................................31 7-1 Comparison of Existing and Proposed Conditions – Runoff .............................................35 9974 ii September 2017 Hydrology and Water Quality Technical Report Little Bear Solar Project 1 INTRODUCTION 1.1 Scope and Purpose This preliminary Hydrology and Water Quality Technical Report (Study) was prepared for the Little Bear Solar Project (Project) in support of the Environmental Impact Report (EIR) and in accordance with the 1966 Fresno County Improvement Standards (FCIS; County of Fresno 1966). The purpose of this Study is to identify hydrology and water quality impacts of the Project and to describe best management practices (BMPs) required for mitigating potential short and long term hydrology and water quality impacts. This Study uses the Rational Method, as defined by the FCIS, to quantify the peak-discharge for pre- and post-development conditions for the 5-year, 10-year and 100-year storm events. In addition, the Project is evaluated in the context of water quality standards contained in the Tulare Lake Water Pollution Control Plans (Basin Plan) (Central Valley RWQCB 2016). This Study is based on Project plans and specifications that are preliminary in nature and not approved for construction purposes. As such, contractors shall refer to the final approved construction documents, which will be developed as the Project plans are finalized. Because preliminary construction plans were used for the hydrological calculations, this Study provides a general estimate of the hydrological conditions which are likely to exist at the Project location following construction completion. The results of hydrologic modeling herein are based on 8.46 acres of impervious surfaces proposed on site (or a change in site imperviousness from 0.01% to 0.94%). 1.2 Project Location The Project site is located in the San Joaquin Valley, approximately 2.5 miles southwest of the City of Mendota. From Interstate 5 (I-5), the Project is approximately 13 miles east, and is situated immediately west of State Route 33 (SR-33). This area is in the western portion of the San Joaquin Valley, in unincorporated Fresno County, Sections 13 and 14, Township 14 South, Range 14 East, Mount Diablo Base and Meridian (MDBM). Specifically, the Project site is bounded by West California Avenue to the north, West Jensen Avenue to the south, San Bernardino Avenue to the west, and SR-33 to the east. The Project area currently consists of eight