ARCHIVED REPORTS_XR0008146 - Laserfiche WebLink

Home Browse Search

i Appendix A - Historical Background PACIFIC MINI-MART 4511 Pacific Avenue, Stockton, California ' was calculated at 205 ft'/day(equivalent to 1,536 gallons per day/ft) and a storativity value was calculated at 0 054 • Based on a transmissivity value of 205 ftz/day and the extraction well screen thickness equal ' to 25 ft (screen Interval at EW-1), a hydraulic conductivity value was calculated at 6144 ft/day, or 0 022 cm/s, a hydraulic conductivity of 0 022 cm/s is consistent with a screened Interval located within a well sorted sand to clean sand I0 Laboratory analysis of extracted water during the pumping test detected elevated concentrations of TPH-g, BTEX and MTBE On 05 and 06 June 2001 four ground water monitoring wells were Installed off-site as part of the Investigation Borings MW13 through MW16 were completed as ground water monitoring wells MW-13 through MW-16 MTBE was detected in the soil samples collected from thirty feet bsg from borings MW 15 and MW 16, these concentrations maybe more reflective of impacted groundwater in the pore spaces of the soil than of adsorbed MTBE The highest concentration of dissolved hydrocarbons quantified as TPH-g,TPH-d and overall BTEX • compounds occurs in the areas east and northeast of the dispenser Islands, on-site The highest concentration of MTBE detected in the ground water occurs in monitoring well MW-11, which is situated in the median of Pacific Avenue Lower or non-detectable concentrations in the down- gradient and cross gradient wells define the dissolved MTBE plume toward the north and west This suggests that the dissolved MTBE plume is detaching from the TPHBTEX hydrocarbon plume ' In September and October 2001, a low-flow, ground water extraction and treatment system was Installed at the site The system utilizes the newly installed ground water extraction well on site and a small volume treatment system As of 16 December 2002, approximately 1,315,454 gallons of ' hydrocarbon-Impacted ground water have been extracted and treated for disposal On 04 and 05 February 2003 two additional ground water monitoring wells were installed oft-site ' as part of the Investigation Boring MW 17 was completed as groundwater monitoring well MW-17 using two-Inch diameter PVC casing with 0 020-Inch slotted screen installed from approximately 25 feet to 45 feet bsg and boring MW18 was completed as ground water monitoring well MW-18 o,"ev tx,r�_Infh diameter 1P-x7(— oagirnv with n 4 O-inr-h clnttarl ,rrFPn installed f om approximately �b a 60 feet to 65 feet bsg and with blank casing extended to the surface ' At that time,the dissolved MTBE plume has been defined down-gradient of the site(east)by wells MW-12, MW-16, MW-17 and 18 Advanced GeoEnvironmental Inc I