ARCHIVED REPORTS XR0010108 - Laserfiche WebLink

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595 East 11th Street, Tracy, CA November 8 1993 OBJECTIVES The objective of the quarterly groundwater sampling event was to initiate a new quarterly sampling program to determine the extent of petroleum hydrocarbon impacts to groundwater and to morutor the groundwater flow direction and gradient PROCEDURES Monitor wells MW-1, MW-2, and MW-3 were sampled on October 6, 1993 The locations of the wells are shown in Figure 2 Sampling activities consisted of a depth to water measurement, and then purging and sampling groundwater from each well Depth to water measurements were used to calculate the elevation of the groundwater level at each well to determine the groundwater gradient and flow direction Details of the sampling procedures are described below 1 Measure the static depth to groundwater at each well using a Sohnst electronic water level indicator 2 Using a pre-cleaned Teflon bailer, purge each well a nurumum of 5 well casing volumes, or until pH, conductivity, and temperature levels have stabilized 3 Following purging, re-measure static depth to groundwater at each well to deternune if groundwater has recovered to within 80%of the initial level 4 Using a pre-cleaned Teflon bailer, collect groundwater samples from each well and transfer samples into preserved 40-m1 VOA sample vials 5 Seal and label each sample and place into iced storage 6 Following chain of custody documentation,transport samples to a State Certified analytical laboratory All samples were submitted to Anametn• Laboratories of San Jose, California for certified analyses for TPHg and BTEX using modified EPA Methods 8015/8020 All sampling equipment was pre-cleaned before use, using an Alconox soap solution and a distilled water rinse All liquid wastes derived during purging procedures were placed in D O T rated 55-gallon drums contained on-site FINDINGS The results of the groundwater sampling are presented in Table 1, and the complete laboratory analysis report and chain of custody are included as attachment A Attachment A also includes soil sample results These results are from separate characterization work which was conducted at the same time, and presented in another report TPHg was found at wells MW-2, and MW-3 with concentrations of 5,500 and 2 900 parts per billion (ppb), respectively In addition, BTEX constituents ranging from 42 to 1,000 ppb were also detected Ho%Nc%er, TPHg and BTEX were not present at MW-1 No petroleum hydrocarbon sheen or floating product was noted in any of the monitor -."ells, but a moderate hydrocarbon odor v.as detected at MW-2 and MW-3 The results of depth to groundwater measurements and surface elevation data are presented in Table 2, and the current groundwater flow direction and surface elevations are illustrated in Figure 3 2