ARCHIVED REPORTS XR0006801 - Laserfiche WebLink

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GEOLOGICAL AND HYDROGEOLOGICAL OVERVIEW According to information contained within the September, 1991 WaterWork assessment , the Reeve' s site is located on level terrain underlain by flood plain deposits of Pleistocene and Holocene age that are composed of sediments similar to , and probably conformable on, underlying deposits of alluvium and Tulare formation The flood plain deposits are light to dark-brown and grey clay , silty sand, and organic materials with locally high concentrations of salt and alkali . Stream channel deposits of sand and gravel are also included Groundwater within the shallow water bearing zone occurs less than/ten feet below grade at the site as well as over most of the Tracy area . General groundwater gradient is to v/ the north. The flood plain deposits of the shallow water bearing zone have well developed soil profiles and, consequently, exhibit poor permeability . The base of the shallow zone is poorly defined and probably is from five to twenty feet below ground surface RECENT ENVIRONMENTAL COMPLIANCE ACTIVITIES Placement and Saam2ling of Additional Exploratory Sail Borings • On March 17 , 1994 , Del Tech Geotechnical Support Services of Oakdale advanced four ( 4) soil borings (designated EP-1 , EP-2 , EP-3 , and EP-4) at the locations shown on Figure 2 . Each boring was advanced with a hand auger . Discrete sol. samples and a grab water sample were acquired from each borehole. Each soil sample was collected within a 1 . 9 inch diameter by 4.0 inch long clean brass sleeve fitted within a drive sampler lowered into the borehole to a point accessed by the hand auger. Upon being retrieved, the drive sampler was opened and the brass sleeve removed. The ends of each sleeve were then covered with teflon sheeting/aluminum foil , fitted with plastic caps , and sealed with duct tape. Each tube was then marked and placed in an iced, insulated container for transportation to Priority Environmental Labs of Milpitas , a California- state certified hazardous waste analytical laboratory, under chain of custody . Subsequent analyses were performed for Total Petroleum Hydrocarbons as Diesel (TPH-D) , Total Petroleum Hydrocarbons as Gasoline (TPH-G) , benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA Methods 3550/8015 and 5030/8015-8420 , respectively . i Grab water samples from each boring were acquired within a clean, disposable polyethylene bailer lowered into the borehole to a point just below the surface of the water. Page 2