Phase I Archaeological Survey of the Desert Green Solar LLC – Borrego Springs Solar Farm Offsite Improvements, San Diego County, California. Modification for MUP 09-012, ER No. 09-05-001 County of San Diego Planning and Development Services 5510 Overland Avenue #110 San Diego, California 92123 Preparers: James T. Daniels, Jr., M.A., RPA Jerry Schaefer, Ph.D., RPA Scott Wolf Approved by: Jerry Schaefer, Ph.D., RPA ASM Affiliates, Inc. 2034 Corte del Nogal Carlsbad, California 92011 760-804-5757 Project Proponent: Desert Green Solar Farm LLC 16650 Via Esprillo San Diego, CA 92127 February 2013 PN19410 NADB Information NATIONAL ARCHAEOLOGICAL DATABASE INFORMATION Author: James Daniels, Jerry Schaefer, and Scott Wolf Firm: ASM Affiliates, Inc. Client/Project RBF/Desert Green Solar Farm LLC Proponent: Report Date: February 2013 Phase I Archaeological Survey of the Desert Green Solar LLC – Report Title: Borrego Springs Solar Farm Offsite Improvements, San Diego County, California. Type of Study: Phase I Archaeological Survey Updated Sites: CA-SDI-2366, CA-SDI-19,431, New Sites: CA-SDI-20690, DG-1, DG-2, DG-3 Isolates: P-37-032643; P-37-032645 USGS Quads: Clark Lake 7.5-minute T10S/R6E Sections 27, 34 and 35 Acreage: 14 acres surveyed Borrego Springs, Kumeyaay, Prehistoric Pot Drop, Prehistoric Keywords: Campsite, Historic Trash Deposit; CA-SDI-2366, CA-SDI-19,431,; CA-SDI-20,690; P-37-032643; P-37-032645; Solar Projects Phase I Survey of Desert Green Offsite Improvements i Table of Contents TABLE OF CONTENTS Chapter Page NATIONAL ARCHAEOLOGICAL DATABASE INFORMATION .......................... i LIST OF ACRONYMS ................................................................................................... vii EXECUTIVE SUMMARY ............................................................................................ viii 1.0 INTRODUCTION .................................................................................................. 1 1.1 Project Description .................................................................................................... 4 1.1.1 Project Location and Setting ............................................................................ 4 1.1.2 Proposed Project .............................................................................................. 5 1.1.3 Access and Circulation .................................................................................... 9 1.1.4 Construction Schedule ..................................................................................... 9 1.2 Existing Conditions ................................................................................................. 10 1.2.1 Environmental Setting ................................................................................... 10 1.2.2 Records Search Results .................................................................................. 22 1.3 Applicable Regulations ........................................................................................... 25 2.0 GUIDELINES FOR DETERMINING SIGNIFICANCE ................................ 27 2.1 County of San Diego Resource Protection Ordinance (RPO) ................................. 27 2.2 San Diego County Local Register of Historical Resources .................................... 28 2.3 California Register of Historic Resources and the California Environmental Quality Act ............................................................................................................. 29 3.0 ANALYSIS OF PROJECT EFFECTS............................................................... 31 3.1 Methods ................................................................................................................... 31 3.1.1 Survey Methods ............................................................................................. 31 3.1.2 Native American Participation ...................................................................... 31 3.2 Field Results ............................................................................................................ 32 3.2.1 Palm Canyon Drive Access Road Survey ..................................................... 32 3.2.2 Borrego Valley Road Access and Gen-tie Route .......................................... 36 4.0 INTERPRETATION OF RESOURCE IMPORTANCE AND IMPACT IDENTIFICATION ............................................................................................. 41 4.1 Resource Importance ............................................................................................... 41 4.2 Impact Identification ............................................................................................... 42 5.0 MANAGEMENT CONSIDERATIONS – MITIGATION MEASURES AND DESIGN CONSIDERATIONS................................................................. 45 5.1 Unavoidable Impacts ............................................................................................... 45 5.1.1 Mitigation Measures and Design Considerations .......................................... 45 5.2 Mitigable Impacts .................................................................................................... 45 5.2.1 Mitigation Measures and Design Considerations .......................................... 45 5.3 Effects Found Not to be Significant ........................................................................ 45 Phase I Survey of Desert Green Offsite Improvements iii Table of Contents TABLE OF CONTENTS (Continued) Chapter Page 6.0 REFERENCES ..................................................................................................... 47 7.0 LIST OF PREPARERS AND PERSON AND ORGANIZATIONS CONTACTED .................................................................................................................. 57 8.0 MITIGATION MEASURES AND DESIGN CONSIDERATIONS ............... 59 APPENDICES ................................................................................... Provided Separately Appendix A. Confidential Figures Appendix B. DPR Forms iv Phase I Survey of Desert Green Offsite Improvements Table of Contents LIST OF FIGURES Page Figure 1. Project vicinity map. ............................................................................................... 1 Figure 2. Current investigation study area location map........................................................ 2 Figure 3a. Current investigation survey areas, including proposed development areas and open space easements. ...................................................................................... 3 Figure 3b. Project design plan including offsite improvements assessed during current investigation. Survey areas shown in red. .................................................. 7 Figure 4. Results of previous records search depicting previously recorded sites and isolates within a 1-mile radius of the current study area. .. Confidential Appendix A Figure 5. Results of pedestrian survey depicting the location of the resources encountered during the survey. .......................................... Confidential Appendix A Figure 6. Location of artifacts associated with CA-SDI-2366 encountered during the current investigation........................................................... Confidential Appendix A Figure 7. Location of prehistoric site CA-SDI-20,690 encountered just outside of the current study area. .............................................................. Confidential Appendix A Figure 8. Eastern facing overview of CA-SDI-20,690 on the western slope of a low rise sand dune. ....................................................................................................... 35 Figure 9. Isolate Lower Colorado Buff Ware pot sherd located just south of the Borrego Springs substation. .................................................................................. 35 Figure 10. Overview of the western portion of Borrego Valley Road access and Gen- tie route survey area, view east with SDG&E Borrego Substation to the right. ...................................................................................................................... 36 Figure 11. Location of sites SDI-19,431, DG-1, -2, and -3 in the Borrego Valley Road access and Gen-tie route survey area........................ Confidential Appendix A Figure 12. Overview of site SDI-19,431 looking northwest. Surveyor is standing at the recorded location of the site datum. ................................................................ 37 Figure 13. Site DG-1, historic trash and target shooting scatter, view north. ........................ 38 Figure 14. Quartz biface tip from site DG-2 .......................................................................... 39 Figure 15. Site DG-3 pot drop, view northwest. .................................................................... 39 Figure 16. Location of recorded sites in relation to Borrego Valley Road access and Gentie route. ...................................................................... Confidential Appendix A LIST OF TABLES Page Table 1. Colorado Desert Paleoenvironmental History ...................................................... 12 Table 2. Previous Cultural Resources Reports Addressing the APE and Buffer Area ....... 23 Table 3. Previously Recorded Cultural Resources within a 1-mile Radius of the APE ....................................................................... 24 Table 4 Recommended Mitigation Measures .................................................................... 59 Phase