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-PUBLIC HEALTH SERVIChS <br /> SAN JOAQUIN COUNTY r. <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer c.• P <br /> q��Fo,Ra� <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> DALE BOYETT <br /> BOYETT PETROLEUM <br /> P O BOX 1099 <br /> SALIDA CA 95368 <br /> FEB 2 4 2000 <br /> Re: BOYETT PETROLEUM Site Code: 1.433 <br /> 419 S.MAIN ST. <br /> MANTECA CA 95336 <br /> San Joaquin County Public Health Services,Environmental Health Division (PHS/EHD) has reviewed <br /> Quarterly Groundwater Sampling Report dated January 24,2000 and Report of Findings dated October 27, <br /> 1999 prepared by WHF,Inc. Four soil borings were advanced and subsequently converted to <br /> monitoring wells (MW) at the above referenced site on August 27, 1999. Results of the analyses for <br /> Methyl tert-Butyl Ether(MTBE) in the groundwater samples of MW-1 increased from 2,700 parts per <br /> billion (ppb) in September 1999 to 5,400 ppb in December 1999, and sampling results of MW-4 <br /> decreased from 140 ppb in September 1999 to 34 ppb in December 1999.•Analytical results of MTBE in <br /> MW-2 and MW-3 fluctuated much more dramatically. Results of groundwater samples from MW-2 <br /> were 5,700 ppb in September before dropping to non-detect in December,while the results of MW-3 <br /> were non-detect in September before rising to 2,100 ppb in December. Low concentrations of Tertiary <br /> butyl alcohol (TBA) and Tertiary amyl-ether(TAME) were detected in groundwater samples of MW-1 <br /> and MW-2 in September;however, no oxygenates with the exception of MTBE were analyzed for in the <br /> December 1999 monitoring event. Analytical results of the soil sample taken from MW-tat 30 feet <br /> below surface grade(bsg) (the deepest soil sample analyzed)were 65 ppb of MTBE. Depth to water <br /> (DTW) is approximately 17 feet bsg, and dominant groundwater gradient direction is to the north. <br /> PHS/EHD disagrees with the above-mentioned Report of Findings'conclusion that "the source of the <br /> groundwater contamination found underlying this site is not from the subject property, but rather from <br /> an off-site release". The rationale for the report's conclusion is that soil contamination does not exist in <br /> soil columns until the soil-water interface,which is not true. CLS Lab reported analytical results of soil <br /> samples taken at 24 inches bsg from Dispensers#1, #2,and#3 on November 20, 1996 at the time of the <br /> tank removal. The results from Dispenser#1 were 510 ppb of MTBE,from Dispenser#2 were 340 ppb <br /> of MTBE,and from Dispenser#3 were 740 ppb of MTBE. Soil samples were collected from stockpiles <br /> generated during the tank removal activities. Samples were composited at the lab. The results of <br /> composite SP1 and SP2 were 1,100 ppb of MTBE, and of composite SP3 and SP4 were also 1,100 ppb of <br /> MTBE. In addition,the analytical results of the soil sample collected from MW-4 at 10 feet bsg,which <br /> is above the soil-water interface of approximately 16 feet bsg was 22 ppb of MTBE. Given the <br /> propensity for migration and high soluble nature of MTBE, and the (porous) sandy/silty geology at the <br /> site, it is the conclusion of PHS/EHD that this site is the source of the MTBE in the groundwater. <br /> The reports did not discuss the large fluctuations of MTBE detected in the MW groundwater samples <br /> between September 1999 and December 1999. It is unknown if the MTBE contamination in <br /> groundwater is migrating toward MW-1, or if there was mislabeling of samples for MW-2 and MW-3. <br /> A Division of San Joaquin County Health Care Services <br />