ARCHIVED REPORTS_XR0009565 - Laserfiche WebLink

Home Browse Search

Canepa's Car Wash 248 East Park Street,Stockton,Catlforma Fourth Quarter Groundwater Monitormg Report,October 2005 Page 2 of 5 Summary of October 2005 Quarterly Groundwater Monitoring Results Field Activity Number of monitoring wells 7 Number of nioratoring wells sampled 7 Dates monitored 10/07/05 Site Hydrology Average depth to groundwater below Average increase(+)/decrease(—) in monitoring well measuring points 27 01 feet depth to groundwater since last +0 54 foot sampling The lowest(deepest) groundwater Approximate groundwater flow direction North elevation has consistently been measured at monitoring well MW-2 Groundwater Contamination Wells containing free product None Wells with petroleum hydrocarbon odor odor noted Number of wells with benzene Number of wells with benzene concentrations below the benzene MCL 5 concentrations at or above the benzene 2 MCL Range in concentrations Benzene(µg/L) <0 5—10,000 BTEX Toluene(µglL) <0 5— 1,700 MTBE Ethyl Benzene(µg/L) <0 5—1,700 Nature of contamination TPH-G Total Xylenes(µg/L) <1 0—5,600 1,2-DCA MTBE(µg/L) <0 5—2 2 TPH-G(mg/L) <0 05—47 1,2-DCA(lig/L) <0 5—0 6 i FIELD OBSERVATIONS All monitoring wells were purged using a clean, single-use, polypropylene, disposable bailer Approximately three well casing volumes of water were purged from each well No sheen or separate phase petroleum was noted in the initial groundwater field inspection samples from the wells A strong and moderate hydrocarbon odor was noted in monitoring wells MW-2 and MW-5, respectively GROUNDWATER ELEVATIONS AND GRADIENT The static water level in each well was measured to the nearest 0 01 foot with a battery-operated, flat tape, water level indicator 'Be groundwater monitoring field forms and groundwater measurement field form are included in Attachment C The groundwater table has been above the top of all well screens since the August 1996 monitoring event The average groundwater elevation measured during the October 2005 monitoring event was 0 54 foot lower than measured in July 2005 The groundwater elevation contours for the current monitoring event indicate a groundwater gradient variable across the Site, but generally toward the north The groundwater elevation measured on October 7, 2005 in monitor well MW-3 appears to be anomalous and may be a result of a potential calculation/equipment error or malfunction, the data point for MW-3 was consequently not used in groundwater elevation contouring (see Figure 2) • �� CONDOR