SITE INFORMATION AND CORRESPONDENCE

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Greg K. Vaughn • -8- • 11 May 1988 X. Existing Monitoring System Description The existing monitoring system has been adequately described, as required in HSC, Section 25208.8 (k) . Documentation of Effectiveness Well screen and filter pack were not engineered to site specific conditions. The design and development appear to be adequate to ensure the collection of sediment free samples for analysis, however. Future wells constructed to perform aquifer tests (see above) should be designed with more rigorous attention to design principles in order to reduce energy losses associated with ground water flow through the screen and filter pack. The current well locations are insufficient to immediately detect the migration of leachate from the impoundment, due to the large variation in gradient direction. Since much of the source of leachate has been removed, however, additional wells should focus on the extent of waste constituents in ground water as noted above. The vadose zone was characterized by soil sampling rather than emplacement of monitoring devices. If all of the contaminated portions of the vadose zone are removed during closure, there is no need for ongoing vadose zone monitoring. If not, vadose zone monitoring devices may be necessary. Constituents for analysis of ground water are based on the waste - constituents, as required in HSC, Section 25208. 8 (1) (8) , but analysis for phthalates and minerals concentrations should be added to the ongoing monitoring program. A quarterly monitoring schedule may be acceptable for continued ground water monitoring. Requirements of HSC, Sections 25208. 8 (1) (3, 4 , 5, 6 and 9) have been satisfied to the extent possible at this site. Certification by Qualified Person(s) The HAR states (page 3 . 11-1) that waste constituents have migrated from the surface impoundment to the vadose zone and to ground water. This satisfies HSC, Section 25208 .8 (1) (10) . on page 3 . 11. 4 it is stated that the HAR is complete, "except for those tasks inhibited by site conditions, and those omitted with the concurrence of the C'JRWQCB. " The inadequacies outlined above, however, must be addressed to complete the HAR.