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C A M B R I A Ms. Lori Duncan November 18,2005 monitored to assess DPE effectiveness. Induced vacuum measurements from proximal wells will be measured to evaluate the vacuum radius of influence. If field data suggest the DPE system is sufficiently covering the target area, the routine operation and maintenance program will continue at the site. If field data suggest the DPE system is not sufficiently covering the target area, system adjustments will be implemented accordingly. If additional extraction wells are warranted,they will be incorporated into the system. Sample Collection:During the start-up period and at a minimum frequency of monthly thereafter, Cambria will collect vapor samples from the DPE system influent and effluent streams. The vapor samples will be collected in 1-liter tedlar bags using a Thomas Industries © model 907CDC18F vacuum pump. During normal operation, this sampling schedule will satisfy SJVAPCD permit requirements and allow for verification of field measurements and evaluation of system effectiveness. Influent, mid-point, and effluent water samples will be collected from the carbon vessels during and after start-up. During the normal operation, a sampling schedule that satisfies the discharge permit requirements and allows for effective system evaluation will be implemented. Laboratory Analyses: All vapor and groundwater samples will be submitted to a State-of- California-certified laboratory with a site-specific chain of custody record. The samples will be analyzed for TPHg, BTEX,MTBE, and TBA by EPA Method 8260B. DPE System Evaluation: A detailed review of system performance will be conducted quarterly after start-up. In addition to the standard data previously discussed, mass removal rates, vapor concentration trends, and groundwater concentration trends will be used to evaluate system performance. DPE system data and evaluation will be presented with the quarterly monitoring reports. The system will be operated until clean-up goals are met or asymptotic levels of influent concentrations are observed. At some time, it is anticipated that asymptotic levels of influent concentrations and the cost-effective limit of DPE will be achieved. This may occur before or after clean-up levels are met. If this occurs before the soil and groundwater clean-up levels are met, an alternate approach to reach the clean-up levels, such as monitored natural attenuation, would be implemented as a final remedial approach to obtain regulatory closure. 12