Laserfiche WebLink
; <br /> Closure Report 11 <br /> Golden Grain Manteca Bean Facility,299 Moffat Boulevard,Manteca,California July 16, 19% <br /> i <br /> changed from the tray air stripper to liquid-phase GAC This system modification reduced electrical <br /> and maintenance costs associated with the air stripper, as well as off gas treatment requirements, <br /> while continuing to remove the hydrocarbons from the extracted groundwater In addition, the sod <br /> vapor extraction system was placed in a pulsed mode of operation in July 1995 The pulsed mode of <br /> ' operation consisted of operating the soil vapor extraction system for one week and turning it off for <br /> three weeks This operating change was made to more efficiently remove hydrocarbons from the <br /> vadose zone by allowing them to reach an equilibrium state pnor to turning on the system The <br /> pulsed mode of operation continued until November 1995, when operation of the vapor extraction <br /> system was discontinued The system was turned off because no measureable amounts of <br /> hydrocarbons were being extracted from the vadose zone <br /> ; <br /> Presently,the groundwater extraction and treatment system continues to operate at 5 gpm with <br /> treatment through two GAC vessels arranged in series The system continues to operate, <br /> maintaining hydraulic control, however concentrations of hydrocarbons in the extracted groundwater <br /> ' have diminished to asymptotic levels <br /> 33 Remediation System Effectiveness <br /> ' This section presents a brief chronology of treatment system operation and effectiveness, and <br /> quantifies the amount of petroleum hydrocarbons removed from the subsurface overtime In <br /> ' addition, the trend of hydrocarbon removal to asymptotic levels is presented <br /> ; <br /> A brief chronology of treatment system operation and effectiveness is presented below <br /> ■ free-phase product removal continued until elimination -April 1990 <br /> ■ system installation and start-up- September 1992 <br /> ■ initial groundwater TPH-g concentrations in the monitoring well adjacent to former tank pit <br /> ' area -greater than 50,000 ug/L (figure 12) <br /> ■ present groundwater TPH-g concentrations in the monitoring well adjacent to former tank <br /> pit area- maximum 6,800,ug/L, a decrease of 86% (see figure 17) <br /> a initial system groundwater influent TPH-g concentrations of 1,700,ug/L <br /> ' 42020213 CR <br /> FLUOR DANIEL GTI <br />