ARCHIVED REPORTS_XR0005126 - Laserfiche WebLink

Home Browse Search

n � . First Quarter 1996 Status Report 2 Golden Grain Company,Manteca Bean Facility,229 Moffat Boulevard,Manteca,CA March 21, 1996 MONITORING WELL GAUGING Prior to well purging and water sample collection on February 20, 1996, Groundwater Technology personnel gauged all of the site wells to measure the depth to water and the depth to separate-phase hydrocarbons, if present (attachment 2,table 1) The well gauging was completed in accordance with the Leaking Underground Fuel Tank(LUFT)Field Manual published by the State of California Leaking Underground Fuel Tank Task Force,dated October 1989 The depth to water measurements recorded on February 20, 1996,were used to calculate the groundwater elevations for preparation of a potentiometric surface map for the site (figure 2) The depth to water measurements from MW-3 and MW-9 were not used because bent well casings did not allow for accurate measurements In addition, MW-8 was not monitored because it was covered with debris and not accessible The potentiometric surface elevation measured on February 20, 1996, showed an average increase of 3 34 feet since the November 17, 1995, monitoring event The groundwater gradient direction beneath the site is generally to the north at an average gradient of 0 002 foot per foot (ft/ft) The general gradient at the southern portion of the site is slightly greater than that for the northern portion GROUNDWATER SAMPLING Groundwater samples were collected from 12 of the 14 monitoring wells on the site in accordance with the LUFT guidelines Samples were not collected from MW-3 and MW-8 because adequate groundwater was not retrievable in MW-3 and MW-8 was not accessible as a result of activities from the warehouse demolition A copy of the field data sheet from monitoring well gauging and sampling work is included in attachment 3 The samples were submitted under chain-of-custody protocol to American Environmental Network in Concord, California for chemical analyses The samples were analyzed for benzene,toluene, ethylbenzene, and total xylenes (BTEX), and for total petroleum hydrocarbons as gasoline (TPH-g) using Environmental Protection Agency(EPA) Methods 5030/8015/8020 Historic and recent groundwater analytical data are summarized In table 2 The laboratory analytical reports and the chain-of-custody record for the water samples collected on February 20, 1996, are included in attachment 4 Maps showing reported values of dissolved TPH-g and benzene concentrations are included in attachment 1 as figures 3 and 4, respectively . Of the 12 monitoring wells sampled in February 1996,dissolved concentrations of TPH-g and benzene were detected in wells MW-1, MW-2, MW-4, MWA and MW-7 The dissolved TPH-g concentrations 420202134S1 GROUNDWATER �� TECHNOLOGY