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E CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD * CENTRAL VALLEY REGION 3443 Routier Road, Suite A Phone: (916) 255-3000 Sacramento, California 95827-3098 CALNET: 8-494-3000 TO: Greg Vaughn �'4 Senior Engineer Waste Discharge to Land Unit DATE: 24 July 1995 FROM: Gail Wiggett Associate Engineering Geologist Waste Discharge to Land Unit SIGNATURE: (/V SUBJECT: REVIEW OF CLOSURE AND POST -CLOSURE MAINTENANCE PLAN FOR COVE CONTRACTORS LANDFELL, SAN JOAQUIN COUNTY (CASE NO. 2797) I have reviewed the Closure and Post -Closure Maintenance Plan (CPCMP or Plan) submitted by Kleinfelder on behalf of Cove Contractors. This site is an auto shredder waste landfill occupying property that was in part a former clay mine. The site's southern border is bounded by a drainage slough, Duck Slough, and the northern boundary abuts on property owned by Martin Metals. The landfill has received both inert (demolition) waste and auto shredder waste, but has not taken any wastes in 13 years. There is also thought to be a small, but unknown, amount of Class III putrescible waste. The Plan proposes using a geosynthetic (flexible membrane) as the barrier layer instead of clay in the final cover, and leaving the landfill with a final configuration that includes a deep area at the north end of the site. This deep area represents a former mine pit that has been only partially infilled with wastes. The Plan proposes impounding stormwater in this deep area for diversion to surface drainage channels when sufficient water accumulates. Both of these proposals represent engineered alternatives to procedures prescribed by California Code of Regulations, Title 23, Chapter 15 (Chapter 15), which regulates discharges of wastes to land. The Plan refers to issues of stability on steep slopes in the landfill, particularly in the northern area where the impoundment is proposed. It does not provide a n engineering analysis of the slopes. Additionally, the Plan proposes a water quality monitoring program based on Detection Monitoring rather than an Evaluation Monitoring Program. The monitoring is proposed to be continued for five years during the post -closure monitoring and maintenance period, after which time the need for continued monitoring will be assessed. Appendix B of the Plan includes a proposed water quality Sampling and Analysis Plan (SAP). Much of the Plan is acceptable in concept, but additional design details and engineering analyses are needed to justify the proposals and address technical and regulatory concerns. Detailed comments on the CPCMP are given below. The water quality SAP will be reviewed separately.