COMPLIANCE INFO_1973-2003 - Laserfiche WebLink

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This assumption was obtained from computer modeling regarding the site. As is well established, output from a computer model is dependent on input parameters. If the input parameters do not accurately reflect conditions at the site, then conclusions generated by the model will not be accurate. Board staff feel that the following parameters were not representative of conditions at the site: 1) There is approximately 264, 000 cubic yards of untreated ASW currently in place at the site. The computer model is based on treated ASW. Treated ASW has a PH of 11.0 to 11.5, much higher then untreated ASW. The high PH of treated ASW in conjunction with the proposed cementing agent will significantly reduce the mobility of the metal contaminants in the treated ASW. Metals contained in untreated ASW are more mobile than those in treated ASW. For this reason, the Modeling using treated ASW is not representative of the actual conditions at the site. A complete characterization of the untreated ASW must be done. Part of the characterization must be to sample the untreated ASW and run the Waste Extraction Test (WET test) on the waste to determine the actual mobility of the metals in the waste and to determine if other hazardous constituents exist at the site. 2) The computer model used a 12 foot clay separation layer between the existing ASW and ground water with a permeability of 1x10-5 cm/sec. Cross sections of the site included in the 12/90 Report of Disposal Site Information (RDSI) and a statement in the Solid Waste Assessment Test (SWAT) indicate that ASW has been and currently is in contact with ground water (Attachment 4) . Therefore, the clay separation layer must to removed from the Model. Other information submitted by Cove does not support the conclusion of no impact on ground water for instance, levels detected in monitoring well MW-5 located between the landfill and Walker Slough exceeded the MCL for Barium (1 mg/1) and levels detected in -9 located along the north property boundary, exceeded the MCL for Cadmium (0.01 mg/1) . A surface water sample (SW-2) collected from Walker Slough exceeded the MCL for Barium and Lead (0. 05 mg/1) (SWAT) . The location of the monitoring wells and surface water samples are shown in Attachment 5. this data does not corroborate the conclusion that no impact to ground water or surface water has occurred. The ground water model concluded that the site will not significantly impact ground water for an additional 10 years. Due to the incorrect input parameters and the inconsistent analytical data, Board staff can not agree with Coves conclusion, of no significant impact on ground water. 2