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r 1117 Lone Palm Avenue, Suite 201 AFAkT Modesto, California 95351 209-579-2221 ENVIRONMENTAL - GEOTECNNICAL Fax: 209-579-2225 BUILDING SCIENCES • MATERIALS TESTING On August 1, 2013, soil vapor extraction was initiated utilizing VE 1 through VE4. The soil vapor extraction system operated until February 22, 2019, and removed approximately 14,933 pounds of petroleum hydrocarbon vapors. From August 4-31, 2015, approximately 80.75 pounds of ozone were injected into groundwater at the site. In April of 2020, ATC conducted a sensitive receptor survey in the vicinity of the site to identify potential groundwater wells, surface water bodies, and schools located within 2,000 feet of the site. Refer to ATC's Sensitive Receptor Survey Report, dated May 15, 2020, for additional information. SCOPE OF WORK Plannine ATC will schedule field personnel and equipment, notify Underground Services Alert to locate underground utilities as required, and perform other necessary field preparation and job start-up activities. A private utility locating service will also be used to locate underground utilities that may be present in the work areas. A drilling permit application will be completed and submitted to the San Joaquin County Environmental Health Department (SJCEHD) prior to initiation of drilling activities. ATC will submit an encroachment permit to the City of Stockton in order to obtain off-site access for the proposed off-site drilling locations. ATC will require authorization from any off-site property owner prior to conducting drilling activities. Advancement of Soil Borings Groundwater monitoring wells associated with the subject site (Figure 3) are generally screened in multiple zones: shallow, intermediate, and deep. MWI, MW2, MW3, MW8, MW9, MW10, MWI1R are screened from approximately 45 to 68 feet bgs, MW 13 and MW 14 are screened from approximately 45 to 60 feet bgs, and MW 16 and MW 17 are screened from approximately 40 to 59 feet bgs. These wells constitute the shallow groundwater zone monitoring wells. MW4, MW5, MW6, MW12, MW185 and MW 19 are screened from approximately 85 to 90 feet bgs in the intermediate zone. MW7 is screened from approximately 116 to 121 feet bgs and MW 15 is screened from approximately 141 to 151 feet bgs. Well construction details are presented in Table 1. Based on recent subsurface investigation activities conducted at the site, the shallow groundwater plume appears to be adequately defined in all directions with regard to the California State Water Resources Control Board's Low Threat Underground Storage Tank Case Closure Policy. The intermediate groundwater plume appears to be generally defined, except to the east, with regard to the Low Threat Underground Storage Tank Case Closure Policy. The groundwater gradient in the intermediate zone is typically very flat resulting in variability with regard historical groundwater flow direction. In order to further evaluate the lateral extent of the intermediate groundwater plume, two soil borings are proposed to be advanced east of the site in the western right-of-way of Watts Street at the s:\enviromental\28349\reports\2020 Offsite WP CPT.doc 4 ATC