1998-07-13_GENERAL DOCUMENTS - M1974052 (3)

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Mr. Glenn Mallory Coal Ash Pilot Project Proposal July 8, 1998 Page 4 9. The length of the proposed pilot study will be based of field and laboratory data. Based on the column leaching tests we anticipate that the duration of the pilot study will depend on the number of pore volumes of water that passes through the coal ash rather than a specific time frame. We propose that approximately 1,000 tons of coal ash be placed in a trench at the location shown on Figure 4. The trench will be dug perpendicular to the inferred groundwater flow direction so that the predetermined number of pore volumes will pass through the coal ash within a reasonable amount of time. It is anticipated that a minimum of three monitoring wells will be constructed in the coal ash trench in order to monitor water quality and hydraulic gradients. Placing the ash in the trench will allow for containment of the ash in the event its removal is required. 10. I believe the state's concern is financial liability associated with corrective action, which will be addressed prior to the coal ash pilot study. The subject of financial assurance needs further discussion with Public Service and Varra Companies. The size of the demonstration project, as now proposed, may mitigate the need for additional financial assurances. 11. In all likelihood any corrective action (if deemed necessary) would consist of relocating the coal ash to an acceptable disposal site. Varra Companies will provide a dry impoundment for the relocation of the ash if necessary. 12. The potential solidification and the residual saturation of the coal ash will be determined as part of the column leaching tests. It is our opinion the evaporative losses from open gravel quarries is substantially greater than the residual saturation of the coal ash. As such water losses will be substantially reduced by the reclamation of gravel quarries; therefore consumptive use should be a non-issue. 13. The potential for exceeding groundwater standards will be addressed from information generated from the column leaching tests. If water quality standards are exceed during the column tests an evaluation of preventative measures and the feasibility of continuing with the pilot project will be made. 14. We anticipate that the deposition of coal ash will modify groundwater flow direction to some degree. The variations in flow direction will be dependent on the geometry of coal ash deposition (i.e. placing ash in parallel channels). Variations in groundwater flow direction can be estimated from permeameter tests mentioned earlier. It is our opinion that the gravel quarries can be reclaimed in a manner which would minimize variations in groundwater travel paths. 15. 1 recommend that a formal proposal will be submitted to all interested parties documenting all testing results and the proposed pilot project. This includes the Weld County Health Department and the Division of Minerals and Geology.