ARCHIVED REPORTS_XR0011561 - Laserfiche WebLink

Home Browse Search

PROJECT BACKGROUND 1988: Mobil Oil Corporation abandoned the former bulk storage and distribution plant. All structures were removed from the property including one underground gasoline storage tank and four aboveground diesel fuel storage tanks. August 1988: Following removal of the underground tank, Kaprealian Engineering, Incorporated (KEI), collected and analyzed one ground water sample (W-1) and two soil samples (A and B) for total petroleum hydrocarbons quantified as gasoline (TPH-G); and benzene, toluene, ethylbenzene, and total xylenes (BTEX). TPH-G was detected at 200 and 240 parts per million (ppm) in Soil Samples A and B, while 1,700 parts per billion (ppb) TPH-G was detected in Water Sample W-1 (Kaprealian 1988a). November 21, 1988: KEI supervised drilling of six onsite exploratory borings (EB-1 through EB-6) to depths ranging from 12 to 13 feet below grade (fbg). Analysis of soil samples collected from depths of 5 and 10 feet showed detectable concentrations of total petroleum hydrocarbons quantified as diesel (TPH-D) up to 2,900 ppm and TPH-G up to 360 ppm. Ground water was encountered between 11 and 12 fbg (Kaprealian 1988b). February 1989: Additional soil samples were collected at the site by KEI from 12 test holes at depths of 5 and 10 fbg using a backhoe. Analysis of soil samples detected concentrations of TPH-D up to 3,600 ppm and TPH-G up to 170 ppm. Results of the investigative work revealed the presence of diesel-range hydrocarbons in the subsurface soil extending to a depth of 10 fbg and encompassing an area of approximately 3,700 cubic feet. Analytical data from test holes suggest that gasoline-range hydrocarbon-affected soil was limited to the northern portion of the site (Kaprealian 1989). April 4 and 5, 1990: Alton Geoscience conducted in situ soil profiling for potential excavation activities. Characterization consisted of drilling exploratory borings in a grid pattern and collecting soil samples for analysis (Alton Geoscience 1990). July 9, 1990: Soil excavation was initiated. Balch Petroleum, Inc., of Milpitas, California, was contracted by Mobil Oil to perform the excavation under the supervision of Alton Geoscience personnel. Based on the results of in situ soil characterization, approximately 6,100 cubic yards of soil were excavated (Figure 2). Excavated soil was properly disposed of at either the Class II facility of Liquid Waste Management, Inc., or at the Class III Durham Road Landfill. On July 23, 1990, approximately 7,300 cubic yards of imported clean fill was used to backfill the open excavation (Alton Geoscience 1990). September 26, 1990: Alton Geoscience personnel supervised installation of ground water Monitoring Wells AW-1 through AW-4 (Figure 2). Three soil samples were analyzed for TPH-G, TPH-D, and BTEX; one soil sample from AW-2 at 6 fbg and two samples from AW-4 at 6 and 9.5 fbg. Detectable concentrations of hydrocarbons were not present in the samples (Alton Geoscience 1990). ire.:...