ARCHIVED REPORTS_FIRST QUARTER 2010 GROUNDWATER MONITORING REPORT

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URS ' Mr.James Barton Page 3 of 8 California Regional Water Quality Control Board, Central Valley Region April 29, 2010 In March 2000,ASE installed groundwater monitoring wells MW-11 through MW-15 and piezometers P-1 though P-5.None of the wells screened below 19 feet bgs contained any compound at concentrations exceeding DHS MCLS. However,various compounds were detected in groundwater samples below DHS MCLS including MTBE,tert-butyl alcohol(TBA),PCE, and 1,2-dichloropropane(DCP).In addition, ethanol was detected in groundwater samples collected from three of these deeper wells. In August 2000,ASE installed one extraction and one air sparge well at the site.A step drawdown pumping test,a constant rate pumping test,an air sparging test, and a dual-phase extraction test were performed at the site. In September 2000, following testing, ASE installed two additional soil borings using CPT, installed five groundwater monitoring wells and two groundwater extraction wells,and converted three piezometers into recovery wells..A groundwater extraction system was installed and began operation on September 29,2000.The system was turned off on February 29,2002,and at that time,the system had recovered 3,177,560 gallons of hydrocarbon-impacted groundwater and approximately 131 gallons of gasoline. Between January 22 and 31,2001, soil borings CPT-17 through CPT-26 were completed north of the site using a CPT direct push drill rig. The investigation was completed to determine the lithology at each ' location.This information was then used to determine the locations of zones of high permeability where groundwater samples were collected and the data used to define the lateral and vertical extent of impacted groundwater. In January 2001,video and cement-bond logs were collected for the wells at 17950, 17926, 17904, 17933, and 17886 Airport Way.The total depths of the wells ranged from 46 to 84 feet bgs. With the ' exception of the irrigation well at 17886 Airport Way,no slots were visible in the well casings,and water appeared to enter most of these wells through an open hole beneath the bottom of the casings. With the exception of the well located behind the easternmost residence at 17933 Airport Way, all of the wells video logged appeared to have at least some form of cement seal. In January 2001,ASE drilled soil borings BH-A through BH-C at the site using a Geoprobe hydraulic sampling rig. These borings were drilled east and west of the line of recovery wells on the northern portion of the site to define the extent of contamination west of RW-1 and east of RW-5.Results from this investigation indicated that there was significant impact beyond the calculated capture zone west of the recovery wells. Between April 2001 and February 2002,ASE installed 11 wellhead treatment systems at properties along Airport Way to remove MTBE and 1,2-dichloroethane (DCA)from their domestic wells.All of the systems incorporate the use of granulated activated carbon(GAC)to remove constituents of concern from well water. One system, at 17950 Airport Way,pre-treats the water with an air stripper prior to flow through the GAC vessels. In late November 2001, ASE installed seven air-sparging(AS)wells and seven vapor extraction(VE) wells at the site. The AS wells were then manifolded together and the VE wells were manifolded ' together. On December 21, 2002, a soil vapor extraction(SVE) and AS system began operation at the site. With the exception of a system shutdown from January to May 2003,the SVE/AS system was in HAWprocess\RESD\Franks One Stop\QTR I0\IQMR 10 Repon,doc