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Sera By. RWOCB SACRAMENTO; 916 255 3015; Feb-24-99 14:08; Page 316 <br /> 1665 Pacific Avenue �`' -2 - "' 16 February 1999 <br /> California Water Service operates several Municipal Drinking Water Production wells in the vicinity of <br /> this site. The closest well is approximately 800 feet more or less downgradient,and a second well is <br /> about 2000 feet north-northwest of the site. Two other production wells are within about 3,000 feet of <br /> this site,to the south and south-southeast. State Board staff indicate on Page 10,lines 10-13 of their <br /> staff report,that"A review of DWR Well Drillers'Reports far supply wells located in the vicinity of the <br /> site show these wells are constructed with sanitary seals:which extend to depths of 130 to 200 feet below <br /> ground surface.., My review of California Water Service well lags for the four nearby production wells <br /> did not show sanitary seals below 70 to 96 feet bgs. Instead,well completion details show that 16-inch <br /> diameter casing in each well is perforated(screened)from approximately 200 to 400 feet bgs. Each well <br /> is completed inside 30-inch diameter conductor casing to the sanitary seal depth(between 70 and 96 feet <br /> bgs),and a gravel pack extends from ground surface to the total depth of each well. The gravel packed <br /> annular space below 70 to 96 feet may act as a conduit for vertical contaminant migration. In any case, <br /> these wells do not have sanitary seals to 150 to 200 feet bgs as stated by State Board staff. <br /> Additionally,the statement on page 11,lines 6 and 7,"..:disposal of soils from comparable areas of <br /> excavation throughout the stale would greatly impact already limited landfill space,"has no merit <br /> because there is no intent to excavate or dispose of soil at any landfill and it implies that land disposal is <br /> the only method to treat or dispose of petroleuTn contaminated sail. Further,the statement is factually <br /> incorrect. There is no evidence that disposal of soils would greatly impact landfill space. Petroleum <br /> contaminated soils may be used in place of expensive daily cover soils,thus providing a valuable <br /> resource to landfill operators. Competition for these soils has led to rate reductions at the nearby <br /> Altamont Landfill. <br /> SUMMARY: <br /> Petroleum contamination at this site is verified to at least 54 feet bgs in soil and groundwater below the <br /> site,and laterally to approximately 150 feet offsite. Deep contaminant plunge assessment activities were <br /> completed at the site during January and February 1999. The results of these activities have not been <br /> submitted for regulatory review. <br /> Four municipal production wells are located within 3000 feet of the site(the closest at 800 feet away) <br /> and can sustain pumping razes between 450 and 900 gallons per minute. Sanitary seals on these wells do <br /> not extend below 96 feet bgs,providing potential preferential pathways for vertical contaminant <br /> migration. <br /> No estimation of residual contaminant mass in soil and volume in water or time for natural attenuation to <br /> restore the beneficial uses of the impacted groundwater has been presented. The following table presents <br /> statements in the draft order and Regional Board staff responses to these arguments. <br />