ARCHIVED REPORTS_XR0012702 - Laserfiche WebLink

Home Browse Search

M41 "glow 275 Grantline Rd. Page 3 of 7 felt below grade. After 4 hours a slight sheen was observed on the surface of the water, although no free product was noticed. Excavation beyond this . depth was halted to avoid any possible impact of the groundwater zone. Six hours after encountering groundwater the water level in the excavation area rose to a depth of about 8.5 feet below grade. On July 12, 1990, approximately 5000 gallons of water was pumped out of the pit by H & H Ship Service Company (220.China Basin Street, San Francisco, California, US EPA ID # CAD004771168) and disposed of at their facility. in San Francisco. The water level returned to a level of 8.5 feet below grade in less than 6 hours. A water sample was taken at this time and stored under blue ice in a thermally-insulated cooler for later analysis for TPL:(as gasoline/ HTEX (EPA Method 8015 and 602) , oil and Grease (Standard Method 503 A & E) and Purgeable Halocarbons - (EPA Method 601) . SOIL SAMPLING On July 11, 12, 13, 1990, 14 soil samples were collected from the Perimeter bf the tank excavation pit, below product lines and the Pump island area. This sampling was accomplished by the composite grab sample method. In this method, a backhoe bucket is used to -; collect a sample of. the soils immediately above .the groundwater interface. A clean 6-inch long, 2--inch diameter brass tube is then Inserted into the soils and a sample is collected. Upon collection, both ends of the tube are sealed with aluminum foil and plastic caps, covered with aluminized tape, labeled, and put on ice in a thermally--insulated cooler for transport to a. State-Certified analytical laboratory for analysis. The tubes are shaken to assure that no headspace was present. The strata encountered were, from surface grade to a depth of 1 foot, a grayish-tan to medium--brown, dry, stiff, clay; from a depth of 1 foot to 2 feet a gray-brown, dry,. stiff, clay was found; a light-to medium--tannish-brown, damp, slightly plastic clay was encountered 2 feet to 6 feet below grade; a moist, grayish-tan to tannish-browli, very fine-grained randy clay, with occasional pebbles, was found at a depth of 6 feet to at least 10.5 feet below grade. Groundwater was first observed at a depth of approximately 8 feet below grade in a saturated thin, pebble,ly, fine-grained sand. .-___-Moderate - to--severe hydrocarbon - -.- -- -- staining `and a slight g_ -- - - _ g reasey odor was observed from a depth of approximately 6.5 feet to 10 below grade. A slight sheen was observed on the surface of the water. The sampling locations are. shown in- the attached Sampling Location Map, Figure 1. Samples SS-1 through SS-6 were collected at a depth Of 8 to 9 feet below grade and immediately above the groundwater interface (saturated zone) on .theperimpter of the excavation area of the tank pit. Sample Ss-9A was collected at a depth of 10 feet to. 10.5 feet in native soils near the eastern edge of the excavation. Samples SS-7, SS-8, 5S-9 and SS-10 where collected at a depth of 2.0 to 2.5 feet below grade in the areas of the product