ARCHIVED REPORTS XR0003751 - Laserfiche WebLink

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• en vrroso On May 1, 1995 Wells MW-I and RW-I were properly destroyed prior to excavation of the UST complex The four USTs were removed on May 2, 1995 An estimated 1,044 cubic yards of soil containing petroleum hydrocarbons were removed from the UST complex vicinity prior to backfilling the excavation Two new 15,000 gallon USTs were installed May 11, 1995 in anew location at the site In late May 1995, Well RWAA was drilled and installed in the former UST vicinity Quarterly ground water monitonng has been performed at the site since the first quarter of 1995 Ground water flow direction has been predominantly northeasterly, but has shown variations The hydraulic gradient in the vicinity of the site has ranged from 0 001 to 0 015 2 0 FIELD PROCEDURES 21 Exploratory Soil Barings Two exploratory soil borings (MW-6 and MW-8) were drilled and sampled on January 2, 1997, and two additional borings (MW-7 and RW-B 1) were drilled and sampled on January 28, 1997 The borings were drilled using hollow stem auger drilling equipment Borings MW-6, MW-7, and MW-8 were converted to ground water monitoring wells • (Wells MW-6, MW-7, and MW-8, respectively) The locations and designations of each well are shown on Plate 2 An Enviros geologist supervised the drilling and described encountered soils using the Unified Soil Classification System and Munsell Color chart Encountered lithology is described on the exploratory boring logs presented in Appendix A Soil samples were collected for lithologic description and chemical analysis from the borings at five-foot intervals using a Cal-modified split spoon sampler Soil sample tubes selected for laboratory analysis were covered with Teflon tape, capped, labeled, entered onto a Chain-of-Custody record, and stored in a cooler with ice The samples were transported to Sequoia Analytical (Sequoia), a state-certified environmental laboratory located in Redwood City, California, for analysis The soil samples were analyzed for Total Purgeable Petroleum Hydrocarbons (TPPH) according to EPA Method 8015 (Modified), and benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl-tertiary-butyl-ether(MTBE) according to EPA Method 8020 2.2 Monitoring Well Installations Barings MW-6, MW-7, and MW-8 were completed as ground water monitoring wells constructed of 2-inch diameter threaded Schedule 40 PVC well casing Well screen was placed in the first encountered water bearing zone from 5 to 20 feet below grade (fbg) in each well Well construction included the placement of filter pack sand across the screened interval and one foot above the top of the screen interval A one foot thick bentonite seal was placed above the sandpack followed by a cement-grout seal to grade The well was secured with a locking well plug and a vault box Well completion details are presented in Table 1 and on the exploratory boring logs contained in Appendix A 371 2