ARCHIVED REPORTS_XR0004849 - Laserfiche WebLink

Home Browse Search

Quik Stop No 121 Closure Report CCI Project No 12118 Page 5 uses ozone to destroy organic chemicals through the process of chemical oxidation, which breaks the targeted chemical (predominantly MTBE and its daughter products) into carbon dioxide and water In June 2002, CCI installed ten sparge wells into the A-aquifer at the site, eight of the sparge wells were installed to depths of 28 feet and two were installed to depths of 40 feet All the sparge wells were connected to a master control panel, located on the south side of the site The System began operation on July 2, 2002 After 6 to 9 months of operation, the groundwater contaminant concentration had dropped to virtually non-detect levels By January 2005, groundwater samples collected from on-site wells were all free of detectable petroleum hydrocarbons The System operated a total of 9,569 hours until May 13, 2005, at which time the System was shut-down The County requested the System be shut-down to see whether there would be any rebound of petroleum hydrocarbons in the groundwater over four quarters On April 18, 2006, after four additional quarters of groundwater monitoring, the Quik Stop site remained free of detectable petroleum hydrocarbons 2. SITE GEOLOGY The subject site is located at 1196 West Louise Avenue in the City of Manteca, San Joaquin County, California, which lies within the Great Valley geomorphic province of California, between the Sierra Nevada to the east and the Coast Range geomorphic province to the west The region persisted of lowland or shallow marine environments during the late Mesozoic and Cenozoic eras Nearly all of the sediments that filled the Great Valley eroded from the Sierra Nevada In the late Cenozoic era, much of the area was occupied by shallow, brackish and freshwater lakes The San Joaquin section of the valley has had interior drainage since the Pliocene epoch The area was covered by "Lake Corcoran", now extinct, which spread over much of the northern San Joaquin Valley during the middle to late Pleistocene Today, the Sacramento River drains the northern portion of the valley and the San Joaquin River the southern part The near surface soil consists of Quaternary sediments composed of alluvial, flood and delta plains from the two mayor rivers Subsurface Conditions CCI began exploring subsurface soils to depths of 25 feet during the installation of three groundwater monitoring wells (MW-1, MW-2 and MW-3) In general, the upper 6 to 9 feet of soil encountered at the subject site consisted of brown to orange-brown, silty sand Below 9 feet, the subsurface soils became more granular, consisting of an orange-brown, fine-to-medium grain sand This sand horizon extended to depths of 18 to 20 feet on the north side of the site, at well locations MW-1 and MW-2 The one exception was at MW-3, located on the south side of the site, which was found to have light grey to grey-brown, silty clay at depths of 14 to 17 feet . Below 22 feet and extending to a depth of 25 feet at all three monitoring well locations,