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�N <br /> PUBLIC HEALTH SERVICES c C� <br /> SAN JOAQUIN COUNTY <br /> JOGI KHANNA M.D.,M.P.H. <br /> Health Officer <br /> P.O. Box 2009 • (1601 East Hazelton Avenue) Stockton, California 95201 cqi F...ot <br /> (209)468-3400 <br /> BILL KELLER <br /> GENSTAR WESTERN STONE PRODUCTS <br /> P O BOX 3171 <br /> MODESTO CA 95353 OCT 0 2 19921' <br /> RE: Genstar SITE CODE: 1393 <br /> Western Stone Products <br /> 8181 West Eleventh Street <br /> Tracy CA 95376 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) <br /> has reviewed the "1992 Third Quarter Groundwater Monitoring Report" prepared by <br /> RESNA and dated August 28, 1992, which also included a work plan and a health and <br /> safety plan. The report indicated that petroleum hydrocarbon constituents were detected <br /> in groundwater samples of MW3 and MW4. The results of the July 1992 soil sampling <br /> documented soil contamination. The work plan proposed re-excavation of contaminated <br /> soil to the depth of 14 feet. PHS/EHD has the following comments for your <br /> consideration. <br /> The work plan proposed the collection and analysis of eight soil samples to confirm that <br /> re-excavation had removed all accessible contaminated soil. These soil samples were to <br /> be taken from the sidewall of the excavation at depths of 5 and 8 feet below grade. <br /> PHS/EHD recognizes the value of obtaining sidewall samples at 5 and 8 feet depths since <br /> the highest soil contamination detected, 740 ppm TPH-diesel, was collected at 5 feet and <br /> since the depth to water has been at approximately 8 feet. PHS/EHD further <br /> recommends that sidewall soil sampling occur every 20 linear feet to characterize the <br /> excavation based on size. Additionally, the excavation is proposed to be evacuated of <br /> seeped groundwater by two pumping events. PHS/EHD requests that a minimum of two <br /> bottom samples of the excavation be collected, immediately following pumping. <br /> PHS/EHD suggests that depth to water measurements of monitoring wells, be taken <br /> during pumping events. This information is requested in order to provide information <br /> regarding the influence pumping may have on groundwater contamination. <br /> The work plan proposed that one 4 container composite sample be collected from the <br /> stockpiled soil, removed during the re-excavation. The volume of soil which is estimated <br /> to be removed was 78 cubic yards. PHS/EHD recommends that one soil sample be <br /> collected every 25 cubic yards to be 2:1 composited in the lab. This sampling frequency <br /> provides information which can be used to assess disposal options. <br /> A Division of San Joaquin Counry Hcaifh rare Semcm f(> <br />