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cieologtu(heclsxusInc Page 2 George's VETS Work Plan Addendum . May 10, 2002 ' On February 5, 2002, GTI submitted a work plan to operate the vapor extraction system at the site On March 18, 2002, SJC PHS/EHD refected the work plan stating that a feasibility study needed to be conducted On April 11, 2002, Ray Kablanow of GTI talked with ' Rebecca Setliff of SJC PHS/EHD A decision was made to install the system as described in the February 5, 2002, work plan and run it for a three month trial period This addendum includes the details of the system as well as the testing that will be performed to determine ' remedial effectiveness ' 2.0 BIO-VENTING/VAPOR EXTRACTION Operation of a small bio-venting/vapor extraction system in the excavation backfill is proposed at the site for the following reasons ' • Active removal of contaminants that will be sorbed to the backfill material during the seasonal groundwater fluctuation As groundwater fluctuates at the site, as much as 4- feet, petroleum hydrocarbons in the groundwater will sorb onto the backfill materials in the excavation These contaminants can then be removed by vapor extraction ® Removal of vapor phase contaminants from the excavation backfill and sidewalls Petroleum vapors will continue to seep into the excavation backfill from the surrounding soil and groundwater The vapor extraction system will create a low pressure area in the excavation aiding in the volatilization and remove these contaminants helping to reduce the remaining contaminant mass k,,w o Introduction of more oxygen into the subsurface to aid in natural attenuation They[`,`✓ continual sweep of air through the excavation will provide oxygen needed for biological activity and will prevent anoxic conditions, low biological activity, from occurring ' 2.1 Vapor Extraction Wells During the backfill of the excavation, GTI and Del Tech installed two 4-inch diameter ' drainpipes in the excavation pit at the west and east ends, VEW-1 and VEW-2, respectively The drainpipes contain rows of 3/8-1nch diameter holes from approximately 1-foot bgs to a depth of 10-feet bgs Pea gravel was placed around the drainpipes No additional vapor ' extraction wells (VEW) are proposed at this time Figure 2 is a site map showing the locations of the two vapor extraction wells 2.2 Piping & Manifold System It is proposed that the vapor extraction treatment system (VETS), blower and carbon units, ' be placed inside an enclosure along the eastside of the building This will protect the equipment from vehicle damage and is located adjacent to the power supply for the building ' PVC piping will be connected from VEW-2 to the VETS enclosure via an underground trenching and piping system The pipe will be run underground to prevent damage and , L, y reduce the likelihood of someone tripping VEW-1 will be modified to allow it to be used ' as air recharge paint It is not planned to extract from this well due to the cost of trenching through the asphalt ' �