ARCHIVED REPORTS XR0012551 - Laserfiche WebLink

Home Browse Search

a WESTERN GE01. 0GIC RESOURCES , INC , 3 I RawU11,115 Navrmber 3964 5 TRENDS The analytic results of groundwater samples collected on 7 September 1989 shows a generally similar distribution of hydrocarbon concentrations across the site to those reported on the initial sampling. Historical analytic data shows a slight decline in hydrocarbon concentrations in groundwater ° samples from monitor wells MW-1 and MW-5 located in the southwest end of the site. The highest concentration of TPPH was detected in the groundwater samples from well MW-1 where concentrations have declined somewhat from 30,000 ppb to 20,000 ppb. TPPH declined significantly in groundwater samples from well MW-5 since the initial 4,OW ppb on 22 March 1989 to 410 ppb in the latest groundwater sample on 7 September 1989. "L TPPH concentrations in groundwater samples from well MW-2,"located to the northeast,of monitor well MW-1 have remained fairly constant over tim;but benzene has steadily increased from 750 ppb in March 1989 to 3,200 ppb for September 89. TPPH at 170 ppb and benzene at 1.7 ppb were delectud in samples from well MW4 for the first time since well MW-4 was installed. The surface of the shallow water-bearing zone has dropped appropmatcly 1.5 ft when compared to the last measurement on 121unc 1989,though the contour of the potentiometric surface is generally the same. The estimated direction of groundwater flow remains to the cast. SUMMARY The highest concentrations of TPPH and BTEX were detected in groundwater samples from monitor wells MW-1 and MW-2 located in the southeast portions of the site with TPPH up to 20,000 ppb and benzene up to 4,100 ppb. Considerably lower concentrations of TPPH of 1.7 ppb and 16 ppb were detected iu monitor wells MW4 and MW-5, respectively. These two wells are located to the northwest of monitor well MW-1.TPPH and BTEX were undetected in groundwater samples previously collected during other sampling rounds from monitor well MW-4, Concentrations of 0.9 ppb EDC and _ 5.3 ppb 1,2-DCB were detected in the groundwater sample collected from monitor well MW4. Halucarbons were not detected in the groundwater samples from the other four monitor wells. The estimated direction of groundwater flow is to the cast at a gradient of about 1%». _ Quarterly monitoring and groundwater sampling will be continued to evaluaic changes in fuel hydrocarbon concentrations in groundwater and to determine variation in the direction of groundwater flow. 101R3NO9 tl,,