ARCHIVED REPORTS_XR0004259 - Laserfiche WebLink

Home Browse Search

1 lie Quarterly Groundwater Monitoring Report Frontier Transportation ' 0998-011 October 16, 1998 ' Site Layout Map), Sol] samples were collected every five feet. Laboratory analysis of soil samples identified no detectable concentrations of TPH-g, BTEX, or MTBE. Groundwater samples were subsequently collected. Results are tabulated in Table 1. ' 3.0) SITE GEOLOGY/HYDR OGEOLOGY ' The site is located on the boundary of the Sacramento Valley and the San Joaquin Valley within the west-central portion of the Great Valley Geomorphic province of California. The Great Valley has been filled with a sequence of older to younger alluvium of Pliocene to Holocene ' age which overlay sedimentary rocks of Cretaceous to Tertiary age. These sedimentary units, in turn, overlay a crystalline basement of Paleozoic and Mesozoic metamorphic and igneous rocks. The shallow subsurface geology in the site vicinity is a heterogeneous mix of gravel, sand, silt, and clay(Reference; Site Characterization Report, Twining Laboratories, October 16, 1996). BEI, Inc. encountered clay and a heterogeneous mix of clay from 0' to 25' bg in January of 1998. First subsurface water was encountered at depths from I P to 12' b duringtank removal and monitoring well installation at this site in 1995 and 1996. BE[, Inc. encountered first 10 subsurface water between l 0' and 16' bg. Previous investigations identified flow direction for this subsurface water as northwesterly with a shallow gradient of 0.002 feet per foot (Reference; Site h r eri a i n Repogrt, Twining Laboratories, October 16, 1996) and to the south with a ' shallow gradient of 0.003 feet per foot (Reference; Report of Findings, BEI, Inc., March 27, 1998). Data collected in September of 1998 identified the flow of groundwater in a generally western direction beneath the site (See Figure 3, Groundwater Gradient Map), 4.0) QUARTERLY GROUNDWATER SAMPLE RESULTS On September 2, 1998, BEI, Inc. collected groundwater samples from MW-1 through MW-7 for laboratory analysis. Groundwater parameters (pH, temperature, and conductivity) were measured before, during, and after well purging (See Appendix A for Groundwater Parameters). Groundwater samples were analyzed for TPH-d, TPH-g, and BTEX with MTBE using EPA methods 8015 modified for gasoline, 8015 modified for diesel, and 8020, respectively. Groundwater samples were also analyzed for oxygenates using EPA method 8260. Laboratory ' analysis results for all monitoring episodes are presented in Table 1 and Table 2 (Table 2 included as Appendix B). Recent analytical reports are included as Appendix C. 1 • 2