ARCHIVED REPORTS XR0000205 - Laserfiche WebLink

Home Browse Search

Project No 58100-06-62 August 22, 1996 ' Page 2 t ]FIELD ACTIVITIES t Groundwater Level Measurements and Flow Direction A representative of Geocon measured the depths to groundwater in nine groundwater monitoring wells on July 2, 1996 Debris was noted inside the well casing in MW-1 ], consequently, this well was ' dry and omitted from the monitoring event Depth to groundwater measurements were obtained using a battery operated water level meter with measurements obtained from the top of each well casing Groundwater was encountered at depths ranging from 17 96 to 18 30 meters (58 94 to 60 05 feet) below the top of the well casings A review of groundwater elevations from the previous monitoring event in April 1996 indicates that the groundwater table has risen approximately 0 34 meters (1 11 feet) A summary of the top of well casing elevations, groundwater level measurements and groundwater elevations is presented on Table 1 Based on the July 2, 1996 groundwater elevation data, the groundwater flow is directed to the east at an approximate gradient of 0 006 ftlfL 1 Groundwater elevation contours and gradient for the July 1996 monitoring event are depicted on the Site Plan, Figure 2 Well Purging and Sampling Prior to groundwater collection, approximately three well volumes of groundwater were extracted from wells MW-9, MW-12 through MW-14, MW-16, MW-19, MW-20, MW-24, and VW-1 utilizing an electric submersible pump Groundwater extraction was performed to allow fresh formation water to infiltrate the wells During well purging activities the groundwater was monitored for pH, electrical conductivity and temperature Groundwater recovery was monitored to order to ensure 80 percent well recovery prior to well sampling Monitoring well sampling data sheets are presented in ' Appendix A Purged groundwater was discharged to the sanitary sewer system in accordance with a City of Stockton industrial waste water discharge authorization ' Following well recovery, a water sample was collected from each well using polyethylene disposable bailers and decanted into 40-m1 volatile organic analyses vials and one liter amber bottles The samples were sealed, labeled and placed in an ice chest containing ice and were transported to Geocon's Sacramento Office for cold storage at 4 degrees celsius p ending shipment to the analytical laboratory The samples were subsequently transported to Advanced Technology Laboratory (ATL) located to Signal Hill, California, using standard chain-of-custody protocol ANALYTICAL METHODS AND RESULTS ' Laboratory Analysis The groundwater samples were delivered to ATL for the analyses of TPHg and total petroleum hydrocarbons as diesel (TPHd) following EPA Test Method 8015 modified, benzene, toluene, ethylbenzene and total xylenes (BTEX) following EPA Test Method 8020 and methyl-tert butyl ether (MTBE) following EPA Test Method 8020 The laboratory reports and chain of custody documentation are presented in Appendix B