ARCHIVED REPORTS_2019-MAY 15 SITE ASSESSMENT REPORT

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15 May 2019 AGE Project No. 14-3002 Page 7 of 17 The wells were installed by placing the well casing through the hollow stem of the augers to the total depths. The augers were incrementally raised as #3 sand (filter pack) was slowly poured down the annulus between the well casing and the inner wall of the hollow stem auger. The filter pack was placed adjacent to the screened casing from the bottom of the boring to approximately one foot above the top of the screened interval in the wells. A two-foot bentonite seal was installed above the filter packs using bentonite chips. Once the bentonite seals were in place, they were allowed to hydrate a minimum of one half hour prior to grouting. Following hydration of the bentonite seal, the wells were grouted to the surface with Portland type II cement (grout seal), and stovepipe well monuments were installed over the wells. Well construction details are summarized in Table 1. Boring logs summarizing the details of the well completions are presented in Appendix D. 4.5. LOCATION AND ELEVATION SURVEY On 03 April 2019, a California state-licensed survey engineer from Baumbach & Piazza, Inc (B&P) surveyed the locations of the soil borings and monitoring wells and the elevations of MW -1 through MW -4 to the nearest 0.01-foot using coordinate datum NAD 83 (1986) and vertical datum of the North American Vertical Datum (NAVD88) from global positioning satellite (GPS) observations. Additionally, aerial photographs of the subject property were shot on 03 April 2019 using an aerial photography drone. Figures 2 through 5 were developed using the aerial photography and an overlay of the boring and well locations surveyed. Results of the monitoring well survey are recorded in Table 1. The B&P surveying report is presented in Appendix E. An updated site plan (Geomap), and survey data (Geo XY and Geo Z) will be uploaded to the State Water Board GeoTracker database. 4.6. NON-HAZARDOUS WASTE DISPOSAL On 01 May 2019, Instrat Incorporated (Instrat) of Rio Vista, California transported and disposed of approximately 2,500 pounds (5 drums) of investigation derived waste (IDW) generated during site assessment activities. IDW removed from the site was transported, treated and disposed at Instrat’s facilities located in Rio Vista, California. The non- hazardous waste manifest documenting the disposal of the IDW is included in Appendix F. 5.0. FINDINGS Soil stratigraphy, waste identification and delineation, groundwater elevation, flow direction and gradient were calculated and determined from field data. Contaminant impact to soil, waste and groundwater was quantified by laboratory analyses. A total of fifty-eight (58) soil and waste samples and ten (10) groundwater samples were analyzed.