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MEMORANDUM TO: Stan Phillippe 3 June 1982 FROM: Liese Schadt SUBJECT: FORWARD, INC. , LANDFILL EVAPORATION PONDS, SAN JOAQUIN COUNTY Jack McCollough of Beta Associates has requested permission to continue use of pond #5 until ponds #1 and #2 have been dried and cleaned. He estimates that this work could be completed by 1 August 1982. , Pond #5 has two structural problems which need consideration prior to an approval . First, the measured plasticity index values of the pond clay liners are below the recommended value (per comments in State Board's pub- lication, "Waste Discharge Requirements for Nonsewerable Waste Disposal to Land") . Second, the liner under the construction joint which separates pond #5 from #1-4 is only one (1 ) foot thick, instead of having the required three (3) feet thickness. However, the apparent discrepancy in the plasticity index values is insignif- icant because these values were used only as a preliminary estimate of the soil permeability. The latter is known to be smaller than the recommended value (per State Board publication mentioned above) by an order of magnitude. In addition, calculations of expected pond-liner saturation rates (see attach- ment) indicate that pond #5 may be used safely until corrective work begins on the liner beneath the construction joint. Therefore, I believe use of pond #5 should be approved, provided that: 1 ) the materials placed in it are limited to drilling mud and brines, and leachate collected from the trench sumps; 2) its contents are analyzed quarterly along with ponds #1-4; and 3) it is cleaned and the entire liner is constructed to a three (3) feet thickness, immediately following completion of the work on ponds #1 and #2. Hopefully, an operations plan will be developed before this time to streamline the process of pond maintenance at this site in the future. 'EIESE SCHADT Staff Geologist LLS:sb Attachment