WORK PLANS - Laserfiche WebLink

Home Browse Search

Ms.Lori Duncan San Joaquin County Environmental Health Deparment October 15,2010 Page 2 of 3 have been deposited by major to minor west-flowing drainages and their tributaries. In general, these sediments consist of poorly cemented, interbedded sands, silts, and clays deposited as a result of lacustrine and fluvial processes associated with the San Joaquin River system. Shallow groundwater beneath the site is expected to occur at a depth of approximately 50 to 55 feet below ground surface (bgs), with variable flow direction, based upon nearby sites listed on the State's Geotracker database. Regional groundwater flow in the area is highly influenced by large volume agricultural pumping and in the Stockton area is generally northeast, toward a large groundwater pumping depression northeast of Stockton. Previous Subsurface Investigations According to the Geotracker database, a previous occupant of the site (A&A Tool Rentals) utilized several underground fuel storage tanks (USTs), including a 550-gallon waste oil UST, a 550-gallon kerosene UST, a 2,000-gallon gasoline UST, a 3,000-gallon gasoline UST, and a 3,000-gallon diesel UST. According to limited information provided by the San Joaquin County Environmental Health Department(EHD)the USTs were removed in 1992. The site was apparently closed after a brief investigation, but not details were available on Geotracker or from EHD at the time this work plan was prepared. Krazan & Associates, Inc. (Krazan) conducted a subsurface investigation at the site in April 2010 to investigate recognized environmental conditions identified in a Phase I Report dated April 6, 2010, which was prepared by Krazan. The subsurface investigation consisted of drilling and sampling ten soil borings throughout the property, including drilling three soil borings (B1, B2, and B3) near the inactive wash rack/drain/clarifier area in the southern portion of the building. Soil samples collected from borings B2 and B3 contained petroleum hydrocarbons at depths of 10, 15, and 20 feet bgs. No samples were collected beneath 20 feet bgs. Figure 3 presents site plan detail near the inactive clarifier, which shows the approximate locations of borings B1, B2, and B3. Attachment 1 contains a copy of the laboratory results table from the previous investigation. Proposed Scope of Work Lee & Pierce will supervise the drilling and sampling of five soil borings (LPBl through LPB5) in the vicinity of the inactive clarifier. Figure 3 presents the locations of the proposed borings. Fisch Drilling (C57-683865) will advance the borings using a truck mounted Geoprobe 6600 direct push drilling rig. Soil samples will be collected for logging and identification at 5-foot depth intervals. Samples will be collected using a 1.25-inch diameter core sampler lined with clear acetate sleeves. The portion of the sample to be analyzed will be immediately capped and preserved in an iced cooler at a temperature of approximately 4° Centigrade. Any cuttings requiring disposal will be temporarily stored in a 55-gallon drum or lidded 5-gallon pail pending analytical results and characterization for disposal. Up to five soil samples per boring will be submitted for potential analysis of total petroleum hydrocarbons as gasoline (TPHG) using EPA Method 8015 modified or EPA 8260B; and volatile organic compounds (VOCs), including benzene, toluene, ethylbenzene, xylenes (BTEX) and oxygenated gasoline additives using EPA 8260B. Selection of soil samples for laboratory analysis will EN10759_WP1010