ARCHIVED REPORTS_XR0002200 - Laserfiche WebLink

Home Browse Search

1 2.3 Initial Investigation On January 5, 1994, five soil borings were drilled at the site by AST Three of the borings ' were completed as two-inch diameter groundwater monitoring wells Laboratory analysis of soil samples from the borings indicated low concentrations of petroleum hydrocarbons in ' four of the five borings Impacted groundwater was present in samples from two of the three monitoring wells ' Prior to December 1994, groundwater samples have been collected twice from each well at the site Groundwater occurs at a depth of approximately 8 feet and the hydraulic gradient was calculated to be toward the north and northeast 3.0 PROCEDURES 3.1 Drilling and Sampling On December 6, 1994, four soil borings were drilled at the site Boring B-6 was advanced to a depth of 20 feet and completed as groundwater monitoring well MW-4 Borings B-7, B-8 and B-9 were drilled to deptlis of 20 feet, 10 feet and 20 feet and backfilled in the ' entiie depth with Portland cement Auger returns were placed on plastic sheeting and stored on-site Boring locations are shown on Figure 2 The borings were drilled using a truck-mounted HT-55 drill rig The drill rig and two-man crew were supplied by Soils Exploration Services, Inc (SES) of Benicia, California During drilling, auger returns were monitored for the presence of organic vapors using a photo- ionization detector (PID Thermo Environmental 580A, 10 0 eV, calibrated to isobutylene) Soil samples were collected ahead of the drill bit using a split-tube sampler loaded with rthree pre-cleaned 2-inch by 6-inch brass sleeves The samples were collected at five-foot intervals, using a 140-pound hammer to advance the sampler 18 inches The number of blows required to advance the sampler in 6-inch increments was recorded on the boring logs iTo avoid cross-contamination, the sampling equipment was washed in an alconox solution and rinsed twice with water prior to each sampling run Augers were steam-cleaned between borings For each sample, both ends of the lead sleeve were covered with aluminum sheets, capped and sealed with tape The samples were then stored on ice and transpoited under chain-of- custody to Western Environmental Science and Technology (WEST) in Davis, California Selected samples were analyzed for total petroleum hydrocarbons (TPH as gasoline and diesel) and volatile aromatics (BTE&X) in accordance with EPA methods 8015111 and 8020, respectively Oeelo,n�Audis�.� 1.r 4 EsC9a 9a 1D1a0?Rn,a�Lu.o..d Peed QR 111291 E _