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1 1 According to the California Code of Regulation (CCR), a waste is toxic if it contains lead above 1,000 mg/kg (its Total Threshold Limit Concentration or TTLC) or if it could produce a leachate above its Soluble Threshold Limit Concentration (STLC) of 5.0 milligrams per liter (mg/1). None of the samples exceeded 1,000 mg/kg lead. However, if the reported lead concentration in a soil sample is numerically greater than ten times the STLC, a Toxic Characteristic Leaching Procedure (TCLP) and a Waste Extraction Test(WET or STLC test) are required to see if the sample is able to produce a leachate with a concentration greaterthan the STLC. The reported concentrations in D2 (153 mg/kg) and D3 (177 mg/kg) were above 10 times the STLC (50 mg/kg), so additional testing was conducted. The TCLP is used to determine if a waste is toxic under the federal Resource Conservation and Recovery Act (RCRA). The TCLP procedure uses 20 milliliters (ml) of acetic acid per gram of sample to extract the lead into solution over 18 hours, and the solution is then analyzed. The TCLP results were 0.82 mg/I for D2, and less than 0.1 mg/I for D3. The WET is used to determine if a waste is toxic under the CCR. The WET uses 10 ml of citric acid per gram of sample to extract the lead into solution over 48 hours, and the solution is then analyzed. The WET results were 11.1 mg/I for D2 and 5.2 mg/I for D3. Based on analytical results, samples D2 and D3 were determined to be toxic under CCR, but not under RCRA. They are considered to be California hazardous, non-RCRA wastes. Remedial Excavations On December 13, 2007, with the concurrence of Mr. Nuel Henderson of the SJEHD, TLM dug two 4-foot deep, sloped excavations (Figure 2) to remove the toxic soil. An approximately 2-foot by 4-foot excavation was dug beneath D2, and an approximately 2- foot by 3-foot excavation was dug beneath D3. Soil samples were collected under your supervision at the bottom of each excavation at approximately 4 feet bg using the hand auger, and on the walls in the ordinal directions at approximately 3.5 feet bg by hand. Excavated soils were containerized in two 55-gallon drums to await disposal. The excavations were backfilled with gravel. The ten soil samples were analyzed for total lead using U.S. EPA 6010. Two of the samples contained lead above 50 mg/kg: D2-3.5' S (56 mg/kg) and D2-3.5' W (192 mg/kg). WETs were conducted on the two samples, with results of 0.5 mg/I and 3.6 mg/l, respectively. Soil Disposal On December 28, 2007, the two drums were removed from the site for transport to US Ecology in Beatty, Nevada,for disposed of as California hazardous, non-RCRA hazardous, waste. The uniform hazardous waste manifest is attached. 071001/TLM Stockton Report.doc January 29,2008 3 E N VA P P S