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WORK PLAN FOR LIMITED SITE INVESTIGATION lierracon Tracy Ridge Tracy, California March 27, 2019 Terracon Project No. NA187052.1 least one of the USTs was removed, and the status of the second reported UST is not known. Based on the absence of UST removal records, the historical USTs represent a significant data gap and a REC in connection with the site. Historical AST Fueling Areas: Three gasoline and/or diesel fueling aboveground storage tanks (ASTs) ranging between approximately 200 gallons and 500 gallons in size were observed at the southwestern portion of the site. During the site reconnaissance, the ASTs were observed on soil and not within secondary containment. Based on the site's history of petroleum hydrocarbon use, absence of secondary containment, and poor housekeeping practices, the historical AST fueling areas represent RECs in connection with the site. Refer to Exhibit 2 for areas of concern. Petroleum Hydrocarbon Staining: Multiple areas were observed to have surface stains at the southwestern corner of the site. Based on site observations, the potential cause of the stains appeared to be from spills and/or leaks associated with vehicle and/or equipment maintenance activities, and leaking containers and/or improper storage or disposal of hazardous material containers. Based on the site's history of petroleum hydrocarbon use, unknown nature of released materials, and poor housekeeping practices, the petroleum hydrocarbon staining represents RECs in connection with the site. Refer to Exhibit 3 for areas of concern. Unlabeled 55-Gallon Drum Storage Area — Approximately ten 55-gallon unlabeled drums stored on soil were observed south of the cattle storm shed. Staining was not observed beneath the former drum area after removal; however, based on the unknown nature of materials stored in the drums and poor housekeeping practices, the former drum storage area represents a REC to the site. Burn Disposal Areas: Two burn disposal areas approximately 35 square feet (SF) feet in size were observed east of the residence garage and north of the milk barn near the southwestern portion of the site. Although there is no evidence that hazardous substances were disposed of at the burn area, the unknown nature of materials burned at this location and their potential for site contamination/releases represents a REC to the site. Off-Site Groundwater Impacts from Adjoining Western Open-Inactive LUST Facility: Herbicide, pesticide, and petroleum hydrocarbon contamination impacting groundwater was identified at the western-adjoining former Haley's Flying Service property at concentrations above regulatory screening levels. For more information see the Terracon Phase I ESA, dated December 21, 2018. Responsive • Resourceful • Reliable 2