LSA ASSOCIATES, INC. FRESNO RIVERSIDE 20 EXECUTIVE PARK, SUITE 200 949.553.0666 TEL BERKELEY PALM SPRINGS ROCKLIN IRVINE, CALIFORNIA 92614 949.553.8076 FAX CARLSBAD PT. RICHMOND SAN LUIS OBISPO MEMORANDUM DATE: January 17, 2017 TO: Matt Collings, Assistant General Manager, Moulton Niguel Water District FROM: Sarah Rieboldt, Ph.D. SUBJECT: Paleontological Analysis of the Moulton Niguel Water District Operations Center and Site Consolidation Project, City of Laguna Hills, County of Orange, California INTRODUCTION The Moulton Niguel Water District (MNWD) proposes the MNWD Operations Center and Site Consolidation Project (project) in the City of Laguna Hills (City), County of Orange, California. The MNWD is currently operating within an infrastructure that combines approximately 40,000 square feet (sf) of buildings with over 100 employees on two separate, noncontiguous sites. In addition, most of the existing buildings on the project site are overcapacity and becoming increasingly inefficient and maintenance intensive. Therefore, this project seeks to consolidate and update the MNWD administrative offices and associated buildings within the project site. This memorandum was prepared to ensure project compliance with all applicable State and City regulations and requirements regarding paleontological resources, including the California Environmental Quality Act (CEQA): Public Resources Code (PRC) Division 13, Chapter 2.6; the State CEQA Guidelines: California Code of Regulations, Title 14, Chapter 3, Appendix G; PRC 5097.5; the General Plan for the City (City of Laguna Hills, 2009); and the Society of Vertebrate Paleontology (SVP, 2010). This memorandum addresses the potential for the project to impact paleontological resources and, if needed, includes mitigation measures and other recommendations to minimize these impacts. The MNWD is the Lead Agency under CEQA. PROJECT DESCRIPTION AND LOCATION In order to accommodate the administrate offices on the project site, MNWD proposes to construct a two-story office building of approximately 45,000 sf to serve as the MNWD Operations Center. The project will also include two new one-story buildings: (1) a 12,500 sf building that will contain various shop uses, lockers, restrooms, and standby facilities; and (2) a 4,800 sf building that will contain fleet uses including service bays, parts, storage, and an emergency generator. Two of the existing buildings on the site totaling approximately 21,735 sf will be refurbished and used primarily for warehouse and storage. The remaining four buildings currently on site will be demolished and removed from the site. The project will also expand and relocate an existing fuel island and relocate various material bins and outdoor storage areas for MNWD supplies. The project will also involve construction of new parking areas and access roads; construction of a retaining wall along the north side of the property; excavation of a retention basin in the northwest corner of the project site; and installation of new wet and dry utilities, fire hydrants, landscaping, fencing, signage, and lighting. 1/17/17 «P:\MNW1501\Paleo\MNWD Operations Center Paleo Memo.docx» LSA ASSOCIATES, INC. The project site is generally located northeast of Moulton Parkway and bordered by Sunnyglen Avenue to the west, Imperial Drive to the south, and residential areas to the north and east. It is depicted on the United States Geological Survey (USGS) San Juan Capistrano, California 7.5-minute topographic quadrangle map in Township 7 South, Range 8 West, Section 10, San Bernardino Baseline and Meridian (USGS, 1981; Figure 1). METHODS LSA Associates, Inc. (LSA) examined geologic maps of the project site and reviewed relevant geological and paleontological literature to determine which geologic units are present within the project site and whether fossils have been recovered within the project site or from those or similar geologic units elsewhere in the region. A search for known fossil localities was also conducted through the Natural History Museum of Los Angeles County (LACM) in order to determine the status and extent of previously recorded paleontological resources within and surrounding the project site. On June 15, 2016, LSA Associate Ivan Strudwick conducted a reconnaissance pedestrian survey of the project site by walking random, nonlinear transects in areas where the ground surface was visible. Built areas (e.g., paved parking lots and areas containing buildings) were not surveyed. RESULTS Literature Review The project is located at the northern end of the Peninsular Ranges Geomorphic Province, a 900-mile (mi) long northwest-southeast-trending structural block that extends from the Transverse Ranges in the north to the tip of Baja California in the south and includes the Los Angeles Basin (California Geological Survey, 2002; Norris and Webb, 1976). This province is characterized by mountains and valleys that trend in a northwest-southeast direction, roughly parallel to the San Andreas Fault. The total width of the province is approximately 225 mi, extending from the Colorado Desert in the east, across the continental shelf, to the Southern Channel Islands (i.e., Santa Barbara, San Nicolas, Santa Catalina, and San Clemente) (Sharp, 1976). It contains extensive pre-Cretaceous (more than 145 million years ago [Ma]) and Cretaceous (145 to 66 Ma) igneous and metamorphic rock covered by limited exposures of post-Cretaceous (less than 66 Ma) sedimentary deposits (Norris and Webb, 1976). Geologic mapping by Morton and Miller (2006) shows that the project site contains Holocene to late Pleistocene in age (less than 126,000 years ago) Young Axial Channel Deposits and the early Pliocene to Miocene siltstone facies of the Capistrano Formation (Figure 2). In addition, the geotechnical report prepared for this project indicates the site is underlain by varying amounts of Artificial Fill placed during earlier development and backfilling of the two retention basins (Petra Geosciences, Inc., 2016). Artificial Fill. Artificial Fill consists of sediments that have been removed from one location and transported to another location by human activity rather than by natural means. The transportation distance can vary from a few feet to many miles, and composition is dependent on the source and purpose. Artificial Fill was encountered throughout the project site from the surface to depths of 2 feet (ft) to 26 ft in borings and test pits conducted for the geotechnical investigation for this project 1/17/17 «P:\MNW1501\Paleo\MNWD Operations Center Paleo Memo.docx» 2 Project Location 55 à Project Vici1n5 ity 22 ¨¦§ à 5 ¨¦§ Ã261 Orange Riverside County County Ã133 ¨¦§405 Ã73 Ã241 Project Location Ã74 Ã1 San Diego ¨¦§5 County LEGEND FIGURE 1 Project Location Moulton Niguel Water District (MNWD) 0 1000 2000 Operations Center and Site Consolidation Project FEET Project Location and Vicinity SOURCE: USGS 7.5' Quad - San Juan Capistrano (1981), CA I:\MNW1501\GIS\ProjectLocation_USGS.mxd (7/13/2016) LEGEND FIGUR E 2 Project Area !Ge!olog ic Unit ! ! ! !! !!! !! ! ! !!! ! ! ! ! Qy a – Young Axial Ch annel Deposits Tn - Nig uel Form ation Moulton Niguel Water District (MNWD) Tcs – Capistrano Form ation, siltstone facies 0 100 200 Operations Center and Site Consolidation Project FEET Tm - Monterey Form ation Geolog y Map SOUR CE: Bing Maps (2014); Morton and Miller (2006) I:\MNW1501\GIS\Geolog y .m xd (7/13/2016) LSA ASSOCIATES, INC. (Petra Geosciences, Inc., 2016). The deepest fill area encountered was in the vicinity of the western retention basin. While Artificial Fill may contain fossils, these fossils have been removed from their original location and are thus out of stratigraphic context. Therefore, they are not considered important for scientific study. As such, Artificial Fill has no paleontological sensitivity. Young Axial Channel Deposits. The Young Axial Channel Deposits are Holocene to late Pleistocene in age (less than 126,000 years ago) and consist of slightly to moderately consolidated silt, sand, and gravel (Morton and Miller, 2006). They formed as streams and washes carried sediment down from higher elevations in the surrounding hills. Although Holocene deposits can contain remains of plants and animals, generally not enough time has passed for the remains to become fossilized. In addition, the remains are conspecific with modern species, and these remains are usually not considered to be scientifically important. However, the older Pleistocene deposits that may be reached below a depth of approximately 10 ft have produced scientifically important fossils elsewhere in the County of Orange and the region (Jefferson, 1991a, 1991b; Miller, 1971; Reynolds and Reynolds, 1991; Springer et al., 2009). These older deposits span the end of the Rancholabrean North American Land Mammal Age (NALMA), which was named for the Rancho La Brea fossil site in central Los Angeles and dates from 240,000 to 11,000 years ago (Alroy, 2000). The presence of Bison defines the beginning of the Rancholabrean NALMA (Bell et al., 2004), but fossils from this time also include other large and small mammals, reptiles, fish, invertebrates, and plants. There is a potential to find these types of fossils in the older sediments of this geologic unit, which may be encountered below a depth of approximately 10 ft. Therefore, these deposits are assigned a low paleontological sensitivity above a depth of 10 ft and a high sensitivity below that mark. Capistrano Formation, Siltstone Facies. The marine Capistrano Formation was