ARCHIVED REPORTS XR0003751 - Laserfiche WebLink

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en vir®s® • The elevations of the newly installed wells have been surveyed by a licensed surveyor relative to the existing site wells The top of casing and top of vault box elevations for each of the new wells were surveyed to the nearest 0 01 foot Decontamination Procedures Drilling and sampling equipment were decontaminated prior to beginning work and between activities performed at each boring Drilling equipment was inspected prior to drilling each boring 2.3 Ground Water Sampling and Well Development On February 6, 1997, Blaine Tech Services (Blaine) of San Jose, California developed Wells MW-6, MW-7, and MW-8 by surging and purging the wells and pumping 10 casing volumes from each well Water level measurements and ground water samples were collected from Wells MW-2 through MW-8 by Blaine on February 6, I997 The results of this ground water sampling event were reported in Enviros' March 4, 1997 "Quarterly Monitoring Report- First Quarter 1997" Analytical data from the first quarter 1997 ground water sampling event are summarized in Table 3 of this report • 3 0 FINDINGS 3.2+ Geology and Hydrogeology Lithology encountered during the drilling of the exploratory soil borings consisted of clay, silt, clayey sand, silty sand, sand, and gravel to a depth of approximately 46 5 fbg First encountered ground water occurred in the borings at depths of 8 5 to 9 fbg Ground water in the wells later stabilized at approximately 5 6 to 7 8 fbg Water level data collected during the ground water sampling event on February 6, 1997 was used to construct the ground water contour map shown in Plate 3 The direction of ground water flow was determined to be generally southwesterly on site and northwesterly north of the site The hydraulic gradient was determined to be 0 006 3.2 Soil Chemical Analytical Data Soil samples from 5 and 10 fbg from boring MW-6 and from 6 5 and 11 5 fbg from Boring MW-7 contained non-detectable (ND) levels of TPPH and benzene Soil samples collected from Boring MW--8 at the depths of 5, 10, and 15 fbg contained ND levels of TPPH and benzene The soil sample collected at 20 fbg from Boring MW-8 contained 960 parts per million (ppm) TPPH and 5 2 ppm benzene Soil samples collected from RW-B1 at the depths of 11, 31 5, 36 5, 41 5, and 46 5 fbg contained TPPH at concentrations ranging from ND to 82 ppm and benzene concentrations . ranging from 0 014 to 1 6 ppm 371 3