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Apr., e <br /> Chevron <br /> 1 <br /> Chevron U.S.A. Inc. <br /> E 2410 Camino ;Raman, San Ramon, California • Phone 15101 842-9500 <br /> ,Mail Address:P.O.Box 5004,San Ramon,CA 94583-0804 y ' <br /> NOV 15 <br /> Marketing Department <br /> ENVIkONMr VITAL HEALTH <br /> I* €�r�Ir��C�ivicsr <br /> November 12, 1991 <br /> Ms. Linda Turkatte , . {;- :;. X. <br /> San Joaquin County Environmental Health Division <br /> P.O. Box 2009 <br /> Stockton, CA 95201 F l <br /> -'Re: Chevron Station*9-6465 <br /> 5608 North Pershing Avenue, Stockton, CA <br /> 4 <br /> 7 > <br /> Dear Ms. Turkatte: <br /> * :I have received the letter(attached)dated October 21, 1991 from Laurie Cotulla of the San Joaquin <br /> Cou- Tnvironmental Health Division (SJCEHD) regarding the site referenced above, and I <br /> would like to make the following observations and continents. <br /> In regard to the assumption put forth by the SJCEHD that soil-in the area of wells MW-1, MW72, <br /> :and MW-3'is contaminated based on odors noted during the drilling of these wells in October <br /> 1986, I would like to refer to the actual field observations on the boring logs for these wells. From <br /> the three borings there was only a single note of a strong gas odor, from MW-1 at a depth of four <br /> feet below the surface. I would also like to point out that no odor was noticed throughout the next <br /> ten feet of silty clays in this borehole. In order to compare the qualitative observations from MW- <br /> 1, MW-2, and MW-3 to actual laboratory analyses, one may want to consider that soil samples <br /> were collected for analysis during the March 1990 drilling of MW-2A, which is located <br /> immediately adjacent to MW-2. While the boring log from MW-2 reveals that slight odors were <br /> noticed when drilling, none of the soil samples.from MW-2A contained total volatile petroleum <br /> - hydrocarbons above'the detection limit. In fact,of the 23 soil-samples analyzed from the 11 wells <br /> installed after 1986, none contained total volatile petroleum'hydrocarbons above the detection limit. <br /> It is also worth noting that the soil at,4.feel below-grade in MWV 2 -strong-odorswhich-contained In1986, was in the immediate vicinity- of-the` underground piping.running:,from the former <br /> underground tanks to'the former dispenser islands. Soils from around and beneath this piping <br /> were removed during the replacement of the former underground tanks and piping with double <br /> walled fiberglass tanks and piping in September 1988. <br /> Based upon the information presented.above, I believe that.any soil contamination which may be <br /> present at the site would be very localized, thus posing only a slight threat to groundwater quality. <br /> r In addition, the clay layers present in the subsurface, one from 0 to 10 feet below grade and one <br /> from 30 to 40 feet below grade, would act to retard the migration of hydrocarbons into the <br /> groundwater which is 35 feet below the surface. This seems to be supported by the lack of elevated <br /> levels of dissolved hydrocarbons in the groundwater samples collected from the monitoring wells <br /> at the site. z <br /> r� in light of the above information, I respectfully ask that the SJCEHD reconsider its request for a <br /> F corrective action plan from Chevron since the threat to groundwater is minimal. Instead Chevron <br /> proposes to have its consultant, Alton Geoscience(Alton), collect groundwater samples for <br /> R <br />