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Mr. Wayne Deitz • • June 25,2008 Workplan—Groundwater Sampling Page 2 of 5 2.0 REGULATORY REQUIREMENTS Currently SHI is conducting this groundwater sampling as a private, voluntary action and this work is not being directed by any local, state or federal regulatory agency. However, at this time ROKEN is submitting this workplan to San Joaquin County Environmental Health Department (SJCEHD) to obtain a soil boring permit in compliance with San Joaquin Development Title, chapter 9-1115.3 and the standards of SJCEHD. 3.0 BACKGROUND SHI has provided certain documentation presenting information about the site. A brief summary of findings is provided below: Krazan conducted a Phase I ESA1 and reported that the southern portion of the subject site appeared to have been occupied by a gasoline service station from at least 1938 until approximately 1970. No documentation was identified regarding the removal/ abandonment of the underground storage tanks (USTs). Krazan reported a moderate potential that past on- site operations which "potentially utilized USTs, subsurface hydraulic hoists and oil/water separators"to have environmentally impacted the subject site. Additionally, historical aerial photographs dated 1957 through 2002, depicted what appeared to be several small commercial structures located along the western and southern boundary of the subject site but the specific uses of these properties were not made apparent during the assessment. Krazan also reported that the Quick-N-Save facility at 2057 El Dorado Street, located approximately 288 feet north-northwest of the subject site is listed on the LUST database as the location of an November 23, 1999 unauthorized release of gasoline which impacted soil and groundwater. The groundwater flow direction was assumed to be to the east. Krazan conducted a Geotechnical Investigation which included installing six (6) soil borings on the site. They reported that upper native soils and fill material were identified as clayey gravel, sandy gravel, sandy silty clay, sandy clayey silt, and silty sand. The clayey soil has a high shrink-swell potential. Previous structures were located on the site and the site is surrounded by existing developments. Buried structures associated with these developments such as underground utilities extend on to the site. Groundwater was encountered at approximately 31 feet below surface grade (bsg). The groundwater flow direction was not determined. SCA conducted exploratory trenching and soil sampling at the site to investigate the suspected on-site USTs. Nine trenches were installed in the front of the property and eight (8)trenches were installed in the rear of the property. SCA reported that four(4) USTs are Phase I Environmental Site Assessment,Vacant Land,2154 South El Dorado Street,Stockton,California,Project No. 114-06148,Krazan&Associates,Inc.,December 11,2006. 2 Geotechnical Engineering Investigation,Proposed Dorado Court,2154 South El Dorado Street,Stockton, California,Project No.032-06015,Krazan&Associates,Inc.,January 22,2007. 3 Exploratory Trenching and Soil Sampling,Dorado Court, Stockton,California,SCA Project No.F8311,SCA Environmental Inc.,April 19,2007. 2