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ADDITIONAL MONITORING The County proposes the following increase in monitoring to ensure the safety of the occupants of the Migrant Labor Housing facility. o Monitor wells GW-1, -2, and -3, and the foundation vents of the structures north of GW-2 on a weekly basis until the concentration of combustible gas at those wells is brought below regulatory limits. Take appropriate action if combustible gas is found at or above 1.25% in the foundation vents. Continue applying aggressive vacuum and adjust the LFG system monthly to maximize LFG collection from landfill adjacent to those wells. o Monitor wells GW-1, -2, and-3 monthly for three months after concentration of combustible gas at wells GW-1, -2, and -3 is first brought below regulatory limits. Some variation in detections may be expected as the soil is purged of combustible gas. A short- term increase above regulatory limits is not considered an indication of renewed migration, but rather that some LFG has been trapped in the soil, and is being vented by natural pressure variations as well as the LFG collection system. Monitor the LFG header on the western side of the primary site monthly for settlement that could cause low spots. This additional monitoring will be provide by: o Monitoring the vacuum along the lengths of all headers monthly. Monitoring the vacuum will be facilitated by measuring the pressure at the six additional pressure monitoring points on the header pipe that were installed in 2005 (Figure 2). Variations in the header vacuum will indicate the accumulation of condensate and an approximate location of the condensate accumulation. The header will be reset to remove such areas of accumulation. REPORTING The results of the additional monitoring will be included in the quarterly migration monitoring report for the Harney Lane Landfill. Additional reports may be made as appropriate. The County will notify the Local Enforcement Agency(LEA) and the Migrant Labor Housing facility immediately if combustible gas above 1.25% is detected in any foundation vent. FURTHER ACTION It is expected that the concentration of all perimeter migration monitoring wells will be brought within regulatory limits by the present LFG system. This expectation is based on: • This system had previously brought all perimeter migration monitoring wells to below regulatory limits • All components of the LFG system are operating properly • The LFG collection system has significant excess capacity Remediation Plan for LFG Migration 3 San Joaquin County Public Works/Solid Waste Harney Lane Sanitary Landfill May 23,2007