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MONITORING AND REPORTING PROGRAM 11 FOR FOOTHILL SANITARY LANDFILL CLASS III LANDFILL SAN JOAQUIN COUNTY 1. Constituents of Concern The 'COC list' (list of Constituents of Concern required under 23 CCR 2550.3) shall include all constituents listed in Tables I, II, III and IV (above), the Waste Discharge Requirements Order No. 94- and all constituents listed in Attachment D. The Constituents of Concern shall be for water-bearing media (i.e., ground water, surface water, and the vadose zone.) The Discharger shall monitor all COCl every five years, or more frequently as required. 2. Concentration Limits The Concentration Limit for any given Constituent of Concern or Monitoring Parameter in a given monitored medium (i.e., the uppermost aquifer) at a landfill shall be as follows, and shall be used as the basis of comparison with data from the Monitoring Points in that monitored medium: a. The background value established in the Monitoring and Reporting Program for that constituent and medium; b. The constituent's background value, established anew during each Reporting Period using only data from all samples collected during that Reporting Period from the Background Monitoring Points for that monitored medium. Either: i. The mean (or median, as appropriate) and standard deviation (or other measure of central tendency, as appropriate) of the constituent's background data; or ii. The constituent's MDL, in cases where less than 10% of the background samples exceed the constituent's MDL; or c. A concentration limit greater than background, as approved by the Board for use during or after corrective action. Surface water concentration limits will be developed when sufficient data is available. The Discharger proposes to use intrawell comparisons to detect release of wastes from the landfill. Sufficient data to demonstrate that natural ground water variations between upgradient and downgradient wells require the use of intrawell comparisons, has not been submitted. The following table lists proposed concentration limits for each well. Until a satisfactory demonstration is made, the upgradient well MW-1 will serve as the background well for the site. Concentration limits for MW-1 are shown in the following table.