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{ Mr. Wayne Dietz July 14, 2008 2154 S . El Dorado Street Investors, a California Limited Partnership Page 2 of 8 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 present on the site. Buried debris was also reported in the area. The reported tank sizes were described as 1000-gallon USTs on the south side and 5,000-gallon USTs on the north side. They noted liquid pooling on the west side of UST No. 1 . SCA collected soil samples and analyzed the samples for a variety of compounds. SCA found total petroleum hydrocarbons (TPH) as gasoline and lead near the UST No. 1 , and TPH as diesel and motor oil, low levels of DDT and DDE, and arsenic in fill on the east side of the site. SCA also identified large amounts of debris in the eastern portion of the site. INVESTIGATION METHODS AND PROCEDURES In order to assess the potential on-site groundwater impacts from the neighboring Leaking UST (LUST) property located to the north of the site and from other on-site environmental concerns (such as the identified on-site USTs), ROKEN procured the services of RSI Drilling, a licensed drilling contractor to advance ten ( 10) borings at various locations within the site as depicted in FIGURE 1 . Collection of groundwater samples were planned for each boring location. ROKEN anticipated that groundwater would be encountered at a depth ranging from approximately 25 to 45 feet bsg. z Geotechnical Engineering.Investigation, Proposed Dorado Court, 2154 South EI Dorado Street, Stockton, California, Project No. 032-06015, Krazan & Associates, Inc., January 22, 2007. ' Exploratory Trenching and Soil Sampling, Dorado Court, Stockton, California, SCA Project No. F8311, SCA Environmental Inc., April 19, 2007.