SITE HISTORY - Laserfiche WebLink

Home Browse Search

(VpkTc 1117 Lone Palm Avenue, Suite Modesto, CA 953511 www.atcassociates.com 209-579-2221 ASS OCIATES I N C . Fax 209-579-2225 Environmental, Geotechnical and Materials Engineers approximately 154 feet bgs . The annulus of the screened portion was backfilled with a #3 sand filter pack from approximately 154 to 136 feet bgs . Approximately three feet of bentonite pellets were placed on top of the upper filter packs of MW13 and MW14 and hydrated to form an annular seal. Approximately eight feet of bentonite pellets were placed on top of the upper filter pack of MW15 . Cement grout was placed on top of the bentonite and the wells were each completed at grade with a watertight, flush-mounted, traffic-rated vault. Well construction details are depicted on the well logs contained in Appendix A. The locations of the monitoring wells are shown on Figure 3 . 2.3 Monitoring Well Development and SurveyinE Groundwater monitoring wells MW13 , MW14, and MW15 were developed on November 9 , 20065 by pumping ten well volumes of groundwater from MW13 and MW14, and six well volumes of groundwater from MW15 . Purged groundwater was temporarily stored on site in 55- gallon drums prior to disposal by Excell Excavating. Development logs for MW13 , MW14, and MW15 are included in Appendix B . On November 9, 2006, monitoring wells MW11R, MW13 , MW14, and MW15 were surveyed relative to NAD 83 and NGVD29 for position and elevation. MW11R is a replacement well for MWl l and was previously surveyed for elevation only. The survey data are presented in Table 1 . The surveyor' s report is included in Appendix C. 2.4 Groundwater Sampling and Analyses The depth to water was measured in MW through MW 10, MWIIR, and MW 12 through MW 15 (Figure 3) on December 7, 2006 . All the monitoring wells were purged on December 7, 2006, with the exception of MW5 , and all the monitoring wells were sampled, with the exception of MW4 and MW5 . On December 8 , 2006, MW5 was purged and sampled and MW4 was also sampled. Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in groundwater purged from the monitoring wells and recorded. Turbidity was visually observed and recorded. Approximately three well casing volumes were purged from each monitoring well prior to sampling. The wells were allowed to recover and samples were collected from each well using disposable polyethylene bailers. The groundwater samples collected from each well were submitted to State-certified Argon Laboratories (Environmental Laboratory Accreditation Program Certification. No. 2359) in Ceres, California for chemical analyses of total petroleum hydrocarbons quantified as gasoline (TPHg) utilizing EPA Method 8015M; and benzene, toluene, ethylbenzene, and xylenes (BTEX), methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl ether (DIPE), tertiary amyl ether (TAME), tertiary butyl ether (TBA), 1 ,2-dichloroethane ( 1 ,2-DCA), and 1 ,2- dibromoethane (EDB) utilizing EPA Method 8260B . Groundwater well purge and sample logs are included in Appendix D . S:\Enviromental\28349keports\sum.doe 4 ATC Associates Inc.