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Table 1 shows the monitoring parameters and COCs for groundwater and surface water analyses for the Corral Hollow Sanitary Landfill corrective action monitoring program along with the frequency of analysis. 6.3 Monitoring Program Length To evaluate the effectiveness of the corrective action monitoring plan, monitoring may need to be continued for the duration of the postclosure maintenance period which will be at least 30 years. The monitoring data from MW-5 will be evaluated for trends using the Kendall-Mann trend method. The statistical evaluation procedures for trend analysis are described in Section 7.2. Because the groundwater flow velocity is very slow (approximately 3 feet per year) in the shallow perched zone, a determination of corrective action effectiveness may take at least 10 years. If a downward trend in VOC concentrations has not been established within 10 years, the corrective action monitoring plan will be re-evaluated, and a phase II CAP may be proposed for the Corral Hollow Sanitary Landfill. The final stage of corrective action monitoring will begin when the monitoring parameters are detected at or below their respective concentration limits. At this time, all COCs will be analyzed. To cease corrective action monitoring activities, the concentration of each COC for each monitoring point included in the corrective action monitoring plan must remain at or below its concentration limit during a proof period of at least one year (CCR, Title 23, Section 2550.10 [g][1]). The concentration limits proposed for the COCs are described in Section 7.2. The proof period consists of at least eight sampling events per year. With some exceptions, each COC will be analyzed and each monitoring point sampled during eight sampling events evenly distributed throughout the proof period of one year. If synthetic constituents that are not already monitoring parameters (i.e., semivolatile organic compounds, pesticides, PCBs, and herbicides) are not detected in groundwater during the first sampling event of the proof period, they will not be analyzed during the remaining seven sampling events. 6.4 Reporting Water quality monitoring reports will be submitted to the RWQCB on a quarterly basis by the 15th of the month following each quarter. The quarterly reports will include the quarterly analytical results, tabular summaries of historical data, groundwater flow direction and velocity calculations, a groundwater contour map, and statistical evaluation of the monitoring data. SAC\N.\PJ0\0939M390031.9$G-94\Bb:1 Rev.O 4/21/95 1 5 0939-003.19 6-3