ARCHIVED REPORTS XR0008707 - Laserfiche WebLink

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Mr Ed Ralston April 16, 2001 . Page 3 was updated with appropriate field personal and subcontractor information The field staff and contractors reviewed the SSP before beginning field operations at the site The specific scope of work is discussed below • Monitoring Well Installation. Three on-site deep groundwater monitoring wells (MW-5 through MW-7) were installed at the general locations shown on Figure 3 The wells are 2-inch diameter and were installed to a total depth of approximately 80 feet bgs The wells were constructed with 10-foot screen intervals placed from 70 to 80 feet bgs Off-site well MW-8, proposed for installation in the Harding Way, median was not installed because of subsurface utility corridors located beneath the median • Soil Selection and Analysis. Soil samples were collected every five vertical feet in the borings using a modified California split-spoon sampler Soil samples for laboratory analysis were selected from the saturated zone for vertical delineation of soil impacts based upon field screening results and depth intervals previously assessed A total of 12 soil samples were submitted to a California State-certified laboratory and analyzed for the presence of total petroleum hydrocarbons quantified as gasoline (TPH-g), benzene, toluene, ethylbenzene, and total xylenes (BTEX), and methyl tertiary-butyl ether(MtBE) by EPA Methods 8015 Modified and 8020 Samples with MtBE detection by EPA Method 8020 were confirmed by EPA Method 8260 No additional oxygenate analysis of soil samples was conducted based upon non-detection of Di- isopropyl ether(DIPE), Ethyl tert-butyl ether(ETBE), tert-Amyl methyl ether(TAME) and tert-Butyl alcohol (TBA) in over-excavation soil samples at depths of 11 and 13 feet bgs Sampling and analytical methods are presented in Attachment A • Groundwater Analysis. Gettler Ryan Inc developed and sampled the three deep monitoring wells in conjunction with the First Quarter 2001 groundwater monitoring event Groundwater samples were submitted to a California State-certified laboratory for analysis Groundwater samples were analyzed for the presence of TPH-g, BTEX, and for five oxygenates (MtBE, DIPE, ETBE, TAME and TBA), 1,2-Dicholorethane (1,2-DCA), and Ethylene dibromide (EDB) using EPA Methods 8015 Modified, 8020 and 8260, respectively • Well Surveying.Upon completion of well construction, the wells were surveyed by a licensed surveyor for location and elevation relative to mean sea level FINDINGS Subsurface Conditions Soils encountered during drilling (maximum explored depth of approximately 80 feet bgs) consisted of interbedded sands, silty sands, sandy silts, silty clays and clayey silts (Figure 2) Silts and clays with interbedded lenses of silty sand and sand are present to depths of approximately 45 feet bgs Silt and clay underlie the overexcavation area beneath the former dispensers At NlrancfpITrojectsTrolects1911\011UA101021911011rpt2 doe