ARCHIVED REPORTS XR0011896 - Laserfiche WebLink

Home Browse Search

, ( WkTc A S S O C I A T E S I N C tom./ stratigraphy to be characterized. The CPT boring was advanced to refusal at approximately 58 feet bgs. Following characterization of the subsurface material, a Hydropunch° type groundwater sampling system was advanced into the subsurface approximately 2 feet north of the initial CPT boring location to collect depth discrete soil and groundwater samples. oBased on the stratigraphic profile indicated in the initial CPT sound boring, the Hydropunch sampler was advanced to 19 feet bgs and the push rods were retracted exposing a stainless steel filter screen to the formation allowing for groundwater infiltration. A groundwater sample was collected by lowering a stainless steel bailer inside the hollow push rods. The groundwater collected inside the bailer was transferred to laboratory supplied containers that were placed in a cooler chilled with ice for subsequent delivery to a State-certified analytical laboratory. After the collection of the first water sample, the soil sampler was attached to the hydropunch rods and advanced to 25 feet bgs to collect a soil sample from a relatively thick interval of clayey silt separating the upper and lower water bearing zones. After the collection of the soil sample, the Hydropunch® sampler was then advanced to 52 feet bgs where the next sand intervals were encountered to collect a water sample from the second water bearing zone. The discrete groundwater and soil samples collected from 19 feet bgs (CPT1-W19), 25 feet bgs (CPT1-S25) and 52 feet bgs (CPT1-W52) were placed in a cooler chilled with ice for transport to the analytical laboratory. 2.2 Sample Analysis Selected soil samples were placed on ice, and transported under chain-of-custody to Argon Laboratories Inc. (ELAP #2359) of Ceres, California for analysis. Soil samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg), and benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA 8015B and 8021B methodologies, respectively, and for oxygenate ` fuel additives utilizing EPA 8260B methodology. The analytical results for soil samples are summarized in Table 1. Laboratory data sheets and chain-of-custody documentation are included ti in Appendix B. The groundwater samples from borings GPI, GP2, GP3, and CPT1 were analyzed by Argon y Laboratories for TPHg, and BTEX by EPA methods 801513/8021B. The groundwater samples were also analyzed for methyl tertiary butyl ether (MTBE) and oxygenate fuel additives by EPA method 8260B. Groundwater analytical results are summarized in Table 2, and laboratory data sheets are presented in Appendix B. 3.0 SUBSURFACE CONDITIONS r 3.1 Geology Tracy, California, is located in San Joaquin County and lies on the west flank of the large northwest trending asymmetrical structural trough called the Central Valley, adjacent to the Sierra-Nevada geomorphic provinces. The Central Valley contains a thick sequence of sediment L that in places reaches a depth of approximately 10 miles bgs. These sediments range in geologic s:\17861\reports\sum2004.doc 4 V