ARCHIVED REPORTS_XR0007144 - Laserfiche WebLink

Home Browse Search

1 � Groundwater Elevation Data Depth to groundwater was obtained from the existing groundwater monitor wells at the site using a water level indicator graduated to 0 01 foot The depth to groundwater measurement was converted to a groundwater elevation for each well and used to construct a groundwater elevation contour map (Figure 2), and calculate the local groundwater flow direction and hydraulic gradient Groundwater at the site was measured at depths between 7100 to 84 80 feet below ground surface (bgs) The groundwater potentiometric surface elevation averaged approximately 25 68 feet bgs during this monitoring event The groundwater elevation decreased approximately 127 feet since the last sampling event in May 2002 The groundwater flow direction during this reporting period is toward the southwest with a hydraulic gradient of approximately 0 02 ft/ft A summary of data regarding groundwater levels measured through July 25, 2002 is presented in Table 1 Copies of field observations documenting work performed at the site are presented in Attachment I Groundwater Analytical Results The distribution of groundwater sample analytical results obtained from monitor wells at the site on July 25, 2002, is presented on Figure 3 and summarized in Table 2 The highest concentration of petroleum hydrocarbons is in the vicinity of monitor well MW-1 TPHg and benzene concentrations were below method detection limits for all wells sampled during this monitoring event MTBE concentrations ranged from 2 2 micrograms per litter(ug/1-) in MW-10 to below method detection limits in monitor wells MW-2,MW-3,MW-6 and MW-8 Attachment II contains photocopies of the laboratory analytical report and the chain-of-custody form It should be noted, monitor well MW-5 was not sampled this quarter due to the well was dry Approximately 0 01 feet of LPH was detected in MW-1 during this monitoring event and therefore the well was not sampled LPH continues to be monitored and removed(if necessary)from MW-1 by hand bailing methods and the use of a passive,down-hole petroleum skimmer on a weekly basis A total of approximately 62 gallons of LPH has been removed from MW-1 since its detection in February 2000 Purge Water Purge water generated during groundwater purging is currently contained on-site in Department of Transportation rated 55-gallon drums pending removal to a disposal/recycling facility SITE REMEDIATION Construction of a soil and groundwater remediation system was completed at the site in December 1999 The remediation system consists of seven soil vapor extraction (SVE) wells (W-1, W-3 through W-8), two groundwater monitor wells modified for SVE (MW-1 and MW-3) and four air sparge wells (AS-1 through AS-4) with catalytic oxidation treatment A Site Plan depicting the locations of the remediation wells, subsurface piping, and remediation equipment compound is included as Figure 4 Initial start-up air discharge compliance testing was completed on December 13, 1999 The San Joaquin County Valley Air Pollution Control District(SJVAPCD)has approved . an air permit for the site C%nme OW,ockefo'dQ202 2 5ECOR 770T Q737 W 0063