ARCHIVED REPORTS XR0012563 - Laserfiche WebLink

Home Browse Search

m Delta / Environmental ii Consultants,Inc. 3300 Data Drive,Shite 100 Rancho Cordova,CA 95670 9181638-2085 FAX:916/638 W85 March 1,1991 Ms.Diane Hinson,R.E.H.S. Department of Environmental Health San Joaquin County Public Health Services P.O.Box 2009 Stockton,California 95201 Subject: Quarterly Ground Water Sampling Results 620 West Charter Way,Stockton,California Shu,11 WIC No.204-75244305 Delta Project No.40-88-586 Dear Ms.Hinson: Delta Environmental Consultants, Inc., has been authorized by Shell Oil Company to conduct an - investigation of soil and ground water conditions at a Shell service station located at 620 West Charter Way, Stockton, California (Figures I and 2). The investigation is intended to characterize the distribution of petroleum ernsti(vents in soil and ground water beneath and adjacent to the site. This letter report summarizes the results of ground water sampling activities performed at the site on January 3l,1991. Quarterly groundwater samples were collected from existing monitoring wells MW-1, MW-5,MW-6,MW-8,and MW-9 identified in Figure 2- All other wells contained free-phase floating product. Water Level Depth, Flow Direction,and IlydraiLlic Gradient Ground water level measurements were made monthly between November and December 1990. Figure 3 depicts the ground water contours for January 31, 1991. Ground water level measurements made from all monitoring wells throughout the duration of this investigation are compiled in Table I. A plot of this historical data(Figure 4)shows a continuous decline in water elevations over the past year,dropping by approximately 2 to 5 feet in the wells. The plot also shows unexpected elevations in monitoring wells MW-1 and MW-5 relative to the historical trend for these wells. We expect future elevations measured in these wells will follow the historical trend. Suhlective AnnlY5I5 nn(I-Ground Water Sampling A subjective analysis for a ground water sample collected from eq,,h well was performed during each sampling event according to methods described in Enclosure A. Table 1 lists the depth of free-phase petroleum product measured in monitoring wells MW-2,MW-3,MW-4,and MkV-7. Figure 5 depicts the inferred extent of product beneath the site. In addition to ille free-phase product in monitoring wells MW-2,NNW-3,MW-4,and MW-7,a slight sheen was observed in monitoring well MW-9 during the period,