2010-09-01_HYDROLOGY - M1983176 - Laserfiche WebLink

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i August 27, 2010 Adams County Board of Commissioners Final Agency Action: Recommendation for Approval with Conditions Certificate of Designation Application for Speer Inert Landfill - Asphalt Specialties Company Page 2 The Division conducted and completed its comprehensive technical review of Revision 1 and ASCI's May 28, 2010 response document in accordance with procedures outlined in State statute and corresponding Solid Waste Regulations. The comments from the Division's comprehensive technical review of Revision 1 were provided to ASCI in a letter dated July 21, 2010. The Division's July 21St letter required ASCI to modify certain provisions from Revision 1 and its response document and submit an updated Plan. In response to the Division's July 21, 2010 letter, the Division received two documents: (1) a memorandum from ASCI titled "Alluvial Groundwater Levels at Speer Inert Fill Site" dated August 9, 2010, and (2) a revised Operations and Closure Plan dated August 2010 ("Revision 2") received on August 11, 2010..For ease of review, ASCI presented all proposed modificationsTor Revision 2 in bold font. The Division has reviewed Revision 2 for technical merit. It is the determination of the Division that the proposed facility can comply with the technical, environmental, and public health standards in the Act and corresponding Solid Waste Regulations if the facility is constructed, operated, and monitored as detailed in Revision 2, and with the conditions of the Division as stated in this letter. Based on this assessment, the Division recommends, as final agency action, that this facility may be approved by Adams County, with the conditions set forth herein and with any additional local restrictions Adams County may choose to impose. The required conditions are as follows: I . Section 4.1 of Revision 2 stipulates that asphalt materials must be placed at least I foot above the seasonal high alluvial groundwater table elevation. Section 4.1 also includes the following statement: "ASCI has determined that the elevation of one foot above the seasonal-high groundwater elevation is 5008 ft. above MSL. " The groundwater elevation data provided by ASCI shows that the groundwater table elevations prior to dewatering varied significantly across the site. For example, a topographic map of the site from a 1999 aerial survey shows an elevation of 5011.6 feet for surface water in a former pond near the southern end of the site. Given the characteristics of the alluvial soil (i.e., sand and gravel) that existed in 1999, the water elevation in the pond is likely to be a surface expression of the groundwater elevation that existed in that area of the site in 1999 prior to dewatering activities. Consequently, the Division believes that the groundwater table could return to elevations that are higher than 5008 Feet above YASL at somelocattons at the site foil"-Wing ce`ssa -on ofgroundwater dewatering -- activities. Therefore, prior to placement of any asphalt materials, and following cessation of dewatering activities, the Division requires ASCI to assess and document stabilized groundwater elevations at the site. The groundwater level documentation and assessment must be provided to the Division for its review and approval prior to placement of any asphalt materials at the site. 2. Section 8 of Revision 2 includes the following statement: "Approximately 18 inches (1.5 ft.) of topsoil or clean fill dirt will be placed on top of all filled materials as final cover. " Pursuant to the requirements in Section 3.5.3 of the Solid Waste Regulations, the Division requires the final cover to consist of at least 24 inches of clean soil. The upper 6 inches of final cover shall consist of topsoil capable of supporting vegetation. The Division does not require a compaction specification or permeability specification since the site is being proposed as an inert material landfill.