WORK PLANS - Laserfiche WebLink

Home Browse Search

%001 NOW Harding Lawson Associates January 14, 1991 20264,004.02 John Breuner Company Mr. Peter Meier Page 2 After the tank had been emptied and removed, it was visually inspected. The tank was constructed of steel with welded seams and appeared in good condition. No evidence of leakage or holes was observed during the inspection. The tank and appurtenant piping were transported with a hazardous waste manifest by H&H, a licensed hazardous waste transportation company, to their receiving facility in San Francisco, California. The tank was subsequently steam cleaned, cut, and rendered harmless by H&H, and disposed as scrap metal at Levin Metals Corporation, in Richmond, California. Visual observations and organic vapor measurements taken using a photoionization detector(PID) indicated that backfill materials(sand) formerly surrounding the tank did not appear to contain petroleum fuel. PID measurements were generally below 5 parts per million(ppm), and only localized pockets of backfill materials in the vicinity of the dispenser island and a portion of the piping trench contained hydrocarbon odors. PID measurements of these localized pockets ranged from 30 to 100 ppm. Native sediments surrounding the tank backfill materials consisted of very stiff, dark gray, silty clay of high plasticity from the surface(underneath the asphalt-pavement section)to a depth of 4 feet. These sediments graded to a stiff, brown, sandy clay of moderate plasticity to depths of a least 14 feet. Visual inspection and PID readings of these soils did not indicate the presence of petroleum hydrocarbons in native soils adjacent to the tank excavation or piping,with the exception of those odors in localized areas noted above. Soil samples were collected from the native soils 2 feet below the backfill/native soil interface on the floor of the excavation using a backhoe. The soil samples were collected from the backhoe bucket in clean brass tubes, labeled, capped with aluminum foil and plastic caps, and sealed with electrical tape. Samples were stored in a chilled container and transported for analysis to NET Pacific in Santa Rosa, California, a state-certified laboratory. Two soil samples were collected from native soil beneath the bottom of the former tank. Samples were collected from each end of the excavation and were designated TN-14 and TS-14. Four samples were collected in native soils beneath the former product pipe(PP1-3, PP2-2.5, PP3-2.5 and PP4-3), one for each joint located along the 80-foot section of pipe between the dispenser island and tank excavation boundary. One sample, DI-2.5, was collected from beneath the former dispenser island. Sampling locations are shown on Plate 2. The excavation was backfilled, compacted with tank backfill sands and imported sand, and resurfaced with aggregate-base material and asphalt concrete to match existing grade. This work was performed by Trumpp Brothers subsequent to the tank removal. Compaction of the backfill materials in the tank excavation was completed using backhoe-mounted roller equipment on approximately 2-foot-thick lifts from the bottom of the excavation to a depth of about 3 feet; the remaining depth was compacted in 1-foot lifts with portable Whacker vibratory compaction equipment. In the southern end of the excavation, where the tank had extended beneath an aboveground loading dock by about 6 feet, a space of approximately 2 feet beneath the dock could not be backfilled with compacted sand; therefore, a controlled-density cement slurry was injected into this area to provide structural integrity between the