ARCHIVED REPORTS XR0007832 - Laserfiche WebLink

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Ms Lori Duncan April 12, 2001 Page 2 of 6 extent of soil contamination and to determine if groundwater beneath the facility has been impacted by past site operations Laboratory analyses of soil and groundwater samples collected during the investigations indicate that petroleum hydrocarbons, VOCs, and lead have impacted soil and groundwater in the immediate vicinity of the former UST The vertical extent of soil contarmnation has been defined at the source (boring SB3) No contaminants were detected deeper than 31 feet below ground surface (bgs) The lateral extent of soil contamination was also largely defined in previous investigations Soil contamination in the vadose zone appears to be limited to a small area in the immediate vicinity of the former UST, and soil contamination in the capillary fringe zone appears to extend no more than 25 feet north, 20 feet west, 10 feet south, and 5 feet east of the former UST Soil analytical results are summarized in Table 2 The estimated extent of soil contamination is shown on Figure 3 Based upon discrete groundwater samples collected from soil borings in previous investigations, groundwater contanunation appears to diminish appreciably within relatively close proximity to the former UST Analytical results suggest that the contaminant plume is localized, and is essentially bounded to the north by borings SB7 and SB8, which are located approximately 35 feet north of the former UST Analytical results of discrete groundwater samples collected from borings SBI through SB8 are summarized in Table 3 • 2.0 PROCEDURES 2.1 Permitting and Protocols Prior to initiating fieldwork, well installation permits were obtained from PHS/EHD All fieldwork was performed in accordance with Ground Zero's Site Safety Plan and Quality Assurance/Quality Control Plan 2.2 Drilling and Soil Sampling On December 13 and 14, 2000, Cascade Drilling (C57-717510) advanced four soil borings at the site (MW 1 through MW4) for the purpose of installing groundwater monitoring wells Well locations are shown on Figure 4 All work conducted at the site was performed under the supervision of field geologist Sean Garvey, and project manager John Lane, a California Registered Geologist Ms Lon Duncan of PHS/EHD conducted grout inspections and observed field activities A CME 75 limited access hollow stem auger rig was used to advance the borings Soil samples were collected from borings MMI, MW2 and MW4 at 5-foot intervals for classification and subjective evaluation for contamination Based upon the close proximity to boring SB3, soil samples were collected from boring MW3 at approximately 10-foot intervals (at 12, 22 and 32 feet bgs) An 18-inch long core sampler lined with new 2-inch diameter brass sleeves was used to collect soil samples The soil samples selected for laboratory analyses, based on field observations G1Data1GROUNDZEIGABBA.RDVvports\WELLRPT doc