ARCHIVED REPORTS_XR0009606 - Laserfiche WebLink

Home Browse Search

Quarterly Monitoring and Sensitive Receptor Survey Report Canepa's Car Wash(Park Street) November 5,2001 Page 5 f5.21 DISCUSSION OF BENZENE CONCENTRATIONS The concentration of benzene has decreased with time in monitor well MW-2 as the groundwater elevation has increased (Figure 6, Appendix A) Benzene concentrations in MW-5 have generally increased as the groundwater elevation has increased (Figure 7, Appendix A) It is important to note that both wells are drowned, with 14 5 to 19 5 feet of water above the well screen Therefore, the first ' groundwater, with potentially greater BTEX concentrations, is not being sampled 5 2 2 DISCUSSION OF MTBE CONCENTRATIONS Concentrations of MTBE in monitor well MW-6 have decreased slightly over time, with a recent increase in October 2000,_a decrease in April and July 2001, and an increase in October 2001 (Figure 8, Appendix A) Low concentrations of MTBE have been sporadically present in groundwater samples collected from monitoring wells MW-3 and MW-4 5 2 3 DISCUSSION OF OTHER ANALYTE CONCENTRATIONS Concentrations of toluene, ethyl benzene, total xylenes, and TPH-G have decreased over time in monitor well MW-2, but all have increased in monitor well MW-5 (Table A, Appendix B) In general, concentrations of analytes have decreased as the groundwater elevation has increased, except in MW-5, where contaminant concentrations have increased It is important to note that since all of the monitor wells are drowned, the shallowest water with the potentially highest contaminant concentrations is not being sampled Therefore, the actual concentrations of the plumes have not been measured and are not known According to Figures 4 and 5, the plumes probably extend beyond the site, therefore the current monitoring wells are not useful in evaluation of the northern extent of the contaminant plumes 6 0 SENSITIVE RECEPTOR SURVEY Condor conducted a sensitive receptor survey within a 2,000-foot radius (study area) of the site to identify potential areas of groundwater recharge or discharge (surface water bodies), schools, and potential water well users that could be impacted by migration of groundwater from the site The sensitive receptor survey consisted of inquiries to the California Department of Water Resources (DWR) I Central District in Sacramento, California, contacting public water purveyors, visually inspecting the area within 500 feet of the site, and interviewing residents located in the site vicinity DWR well records were cross-referenced with Assessor's Parcel Maps and city street maps This process helped identify well records pertaining to wells estimated to be within the study area DWR well records may include the well owner's name, a well location map, the address where the well is located, and a log of the well Documents provided by the DWR, associated with Section, Township, and Range, include information pertaining to 18 water wells The DWR records were reviewed based on Assessor's Parcel Maps, area reconnaissance, a topographic quadrangle map, and a city street map Thirteen of the well records pertain I to wells located outside of the study area Five well records pertained to wells that were verified to be within the study area The information provided by the DWR indicated that one of the five wells records located within the study area had been abandoned IkA4 1 � CONDOR