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I project is being constructed across the street and the entire area is being de-watered in order to install the sewer trenches. The de-watering has caused a significant drop in the groundwater elevation (up to five feet). Field staff determined through an interview with the pump truck operator that the pumped (extracted) groundwater was not being tested for potential contaminants prior to disposal . 2007 All twenty of the wells located at the project site which consist of the groundwater monitoring well network (MW- 1 through MW-8) and the oxygen delivery well network (IS- 1 through IS- 12) were redeveloped by Gregg Drilling and Testing of Martinez, California, from February 6 through February 9, 2007. The redevelopment included removing the fines that had accumulated at the bottom of each well, mechanically surging the well, and finally pumping the well until monitored aquifer parameters stabilized. The purge water removed from each well was collected into Department of Transportation-approved 55-gallon drums and transported at the end of the event by Clearwater personnel to InStrat Disposal Facility located in Rio Vista, California. Quarterly monitoring activities occurred on March 13 , June 21 , September 12, and December 12, 2007. Monthly operations and maintenance of the iSOC system on January 18, February 6, March 12, April 10, May 8, June 20, July 19, August 7, and September 11 , October 9, November 5, and December 12, 2007 . In their letter dated August 15, 2007, the San Joaquin County Public Heath Services Environmental Health Division concurred with the recommendations made for the completion of a work plan to investigate the impact of the off site dewatering activities that occurred in October 2006 . Clearwater submitted the Groundwater Investigation Work Plan on September 25, 2007 to the San Joaquin County Public Heath Services Environmental Health Division. In their letter dated October 12, 2007, the San Joaquin County Public Heath Services Environmental Health Division concurred with the recommendations for additional investigation presented in the aforementioned work plan . Please note that Figure 2 and all subsequent figures referencing project site details were updated for the third quarter of 2007 report to show more precise locations of the eight groundwater-monitoring wells, the twelve remediation system wells, subsurface utilities, and the off-site dewatering trench for the housing development, Bella Terra (formerly known as Moss Garden) sub-division. Trends in concentrations of TPH-g and benzene were evaluated on a quarterly basis for selected monitoring wells according to their location relevant to the core of the hydrocarbon plum . When natural attenuation or biodegradation occurs within a plume, a reduction in hydrocarbon concentrations or mass is usually observed over time. Natural attenuation usually occurs at a site that has experienced source removal and/or some active remediation. The process or rate at which hydrocarbons degrade often occurs according to a first-order kinetics equation . The first- order degradation rate can be determined by evaluating the change in hydrocarbon concentrations from either individual wells or total plume mass over time . When natural attenuation or biodegradation occurs, the degradation rates exceed the rate at which the petroleum hydrocarbons are being released from the sorbed phase into the dissolved phase. ZB 178 — Site Investigation History 5 Updated March 2010 Barnes Trucking Facility — 1817 South Fresno Avenue, Stockton, California