SITE INFORMATION AND CORRESPONDENCE

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ENV.' A M E R I C A Mr. Duane White California Department of Toxic Substances Control January 11, 2005 Page 3 of 4 The cost estimate for this task includes labor and equipment for field sampling, laboratory analytical services, and preparation of an annual report. Task 2— Biennial MNA Sampling and Evaluation Sampling and evaluation for monitored natural evaluation (MNA) will be conducted once every other year in accordance with the revised groundwater monitoring program summarized on page 2 of this letter. Groundwater samples collected from the wells during the regular monitoring event will be measured and analyzed for bio parameters. The MNA data will be evaluated and presented in the annual monitoring report described under Task 1. The cost estimate for this task includes labor and equipment for the additional field measurements, laboratory analyses for the bio parameters, and preparation of a write-up for the MNA evaluation to be included in the annual monitoring report. Task 3—Annual Cap/Deed Restriction Inspection and Reporting For cost estimating purposes, it is assumed that the cap/deed restriction inspection for the Site includes a visual observation of the asphalt and concrete pavement once per year for cracks, vegetation, water pooling, and other signs of deterioration. The cap conditions will be documented in photographs and presented in an annual report to be submitted to the DTSC. The cost estimate for this task includes labor for field observation and preparation of an annual report. Task 4— Cap Maintenance For cost estimating purposes, the routine cap maintenance activities at the Site are assumed to include: • Sealing minor pavement cracks once per year. • Applying a seal coating to the entire cap area once every five years. • Patching approximately 5% of the cap area once every 15 years. The cost estimate for this task includes labor, equipment, and materials. Task 5— Five-year Review The five-year review includes a feasibility comparison of the implemented remedial actions at the Site (capping and MNA) with alternative technologies available at the time. This review involves an economic evaluation and cost analysis of remedial technologies for the Site. The cost estimate for this task includes labor for the preparation of a report. DTSC Oversight For cost estimating purposes, it is assumed that the DTSC oversight cost is approximately 10% of the O&M costs (Table 1). P:\PG&E\Stockton\correspondence\OM$est Jan2005 final.doc