SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Former Vernalis Pump Station - 3 - 19 March 2004 Bellini and Arcos Properties San Joaquin and Stanislaus Counties impacted soil in this area of the site has been adequately delineated. TPH compounds were not detected in soil boring SB-1 advanced (32 feet deep) approximately 250 feet north of MW-4. Groundwater Four groundwater monitoring wells (MW-1 through 4) are located in the southeast corner of the site. Depth to groundwater is approximately 31 to 37 feet with an east-northeast gradient. According to the reports, the wells were installed and sampled in 1998 and 2002. In 1998 and 2002, MW-1 contained floating product of 0.5 and 0.25 feet, respectively. In 1998, the remaining wells, reported TPH-d at 230 pg/L, ND, and 150 lig/L; in 2002, MW-2 contained TPH-d at 97 pg/L and the other wells were ND. A grab groundwater sampled obtained from a 2002 soil boring near - MW-1, reported TPH-d at 540 pg/L. Additionally, both years' sampling results were ND for TPH-g, and ND or slightly above the laboratory reporting limits for PAH and BTEX compounds. MTBE was not detected in any of the 1998 samples, therefore, subsequent analysis did not include MTBE. RECENT INVESTIGATION RESULTS In August and October 2003, Geomatrix advanced borings to collect soil and groundwater samples for analysis from the two sites (Bellini and Arcos). According to the 5 January 2004 Soil and Groundwater Investigation Report, the purpose of the Bellini site investigation was to: a) assess the lateral and vertical extent of TPH in soil and groundwater both on and offsite; and, b) confirm the vertical extent of affected soil and groundwater at depths greater than 45 feet in the area of boring SB-14. The purpose of the Arcos investigation was to characterize soil and groundwater conditions onsite in accordance with the Consistent Technical Approach (CTA) guidance document used to address ChevronTexaco's OVP and pump station sites. Bellini Propertv The investigation generally focused on drilling and sampling at locations offset from previous borings, including groundwater sampling at four locations in close proximity and downgradient of existing data points. Three borings were advanced offsite, downgradient of the site monitoring wells, and east across Highway 33. Twenty-two soil samples and five groundwater samples were submitted for analysis. Soil Soil borings (SB-15 to SB-21) ranging from 15 to 80 feet deep were advanced at four different onsite locations. Two borings were located laterally from previous boring SB-14, to evaluate the vertical extent of impacted groundwater greater than 45 feet deep. The two remaining borings were to evaluate and/or delineate the lateral and vertical extent of soil and groundwater impacts, northwest and southeast of the monitoring wells. Three borings were placed offsite on the opposite side of Highway 33, approximately 200 feet downgradient of MW-2. -�