ARCHIVED REPORTS XR0001809 - Laserfiche WebLink

Home Browse Search

URS Ms Margaret Lagorio, Supervising REHS Page 2 ' San Joaquin County Environmental Health Department October 11, 2004 1. SUBSURFACE CONDITIONS The total depth explored at the site during previous investigations is approximately 75 feet bgs Recent drilling activities confirmed previously collected information about the subsurface geology at the site Soil encountered during these activities consisted of sand, silty sand, sandy silt, and silt A URS geologist logged the soils encountered according to the Unified Soil Classification System Groundwater was encountered in poorly graded sand at approximately 58 feet bgs in boring B-25, at approximately 62 5 feet bgs in boring B-26, and at approximately 61 feet bgs in boring B-27 Groundwater flow at the 1 site is to the southeast at a gradient of approximately 0 013 feet per foot Boring logs are presented as Attachment B ASSESSMENT ACTIVITIES AND FINDINGS On March 22 and 23, 2004, three off-site vertical soil borings were advanced to depths of 65 feet bgs, and depth-discrete soil and grab groundwater samples were collected for the purpose of assessing the lateral extent of 1,2-DCA in the groundwater beneath the site Boring locations for each drilling event are shown on Figure 2 Watermark Drilling of Zamora, California, drilled the soil borings using a hollow-stem auger (HSA) drill rig with 6 5/8 -inch-outside-diameter (OD) augers After the borings were completed, the boreholes were abandoned by filling with neat cement grout to ground surface and the surface was repaired to match pre-drilling conditions Presented below is a discussion of laboratory analytical methods, soil sampling and analytical results, groundwater grab sampling and analytical results, equipment decontamination, and disposal procedures for soil cuttings and wastewater ' Laboratory Analytical Methods All soli and groundwater samples selected for laboratory analysis were analyzed for gasoline-range organics (GRO)by EPA Method 8015B/8021B (preparation EPA Method 5030 for soil), benzene, ethylbenzene, toluene, xylene, (BTEX), methyl tert-butyl ether (MtBE), tert-butyl alcohol (TBA), di- isopropyl ether(DTPE), ethyl tert-butyl ether(ETBE), tert-amyl methyl ether(TAME), 1,2-DCA, ethylene dibromide (EDB), and ethanol by EPA Method 8260B (preparation EPA Method 5030 for soil) Soil Sampling and Analytical Results Soil samples were collected from all three borings at 10-foot intervals with a modified California split- spoon sampler The samples were sealed in 6-inch long, 2-inch-diameter, brass liners with the ends sealed with Teflon®tape and plastic end caps, labeled, and placed in a cooler on ice for delivery to Sequoia Analytical Laboratories (Sequoia) in Petaluma, California, under chain of custody Hydrocarbon staining and a very faint odor were observed in the soil sample collected at the 30-foot interval from boring B-26, a photoionization detector(PTD) reading of 6 1 parts per million (ppm) for volatile organic compounds (VOC) was reported No hydrocarbon odor or staining was observed in any K 1WprocessV5 BP ARCOW076012004 Assessment1760 site assessment report with workplan V2 04 doe