5.4. SR 05-17-2010 - Laserfiche WebLink

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. -- - ~ - Page 2 of 3 March 18, 2005 The mvdificati.ans included as part of the MSE Cell 17 ConstYZictlOn Plans and Specifications are as follows: 1. Cell ll7 Basegrades: As approved in a letter dated January 16, 2003, Cell 17 will be constructed at the same elevations as the base grades in Ce1116. This volume addition was included in the ERL's current permit, SW-74, dated October 8, 2003. 2. Southern Berm Construction: The southern berm of Cell 17 has been modified such that it will now be constructed with an inbound slope ranging from 2:1 to 4.5:1 (horizontal: vertical). The initial construction, as shown on the plan sheets (Sheets 3 and 4) would be for a berm that is approximately 4.5 feet high. The initial berm will be constructed very similar to the phase separation berms typically placed between each cell. As the filling of Cell 17 progresses, this berm will be extended up in 7.5 foot vertical increments. The berm will continue to be extended until the Southern Development Area is permitted or closure grades are reached. The phased construction of this berm is detailed on the attached Figure 1. 3. West Berm Construction: The west berm is currently permitted with an outside slope to be constructed at approximately 1.5:1 (horizontal: vertical) in an effort to preserve trees located i.n the set-back area. During a recent field survey it was noted that there were few trees located in close proximity to the proposed outside toe of the slope, and none of the trees in close proximity of the berm were of significant size. Therefore, the ERL proposes to construct the outside slope of the Cell 17 west berm at a 2:1 slope. The 2:1 slope will be easier to construct and easier to maintain than the currently permitted 1.5:1 slope. This modified berm is shown on Sheet 3 and associated details. 4. Alternative Liner D esign: As recently discussed on the phone, the ERL would also like the option to substitute a layer of Geosynthetic Clay Liner (GCL) for the upper 12-inches of . compacted clay. The techzucal specifications for the GCL and installation of the GCL are included in the enclosed Cell 17 Construction Plans and Specifications. The ERL is requesting to keep the base of the clay liner at the same elevation as would.be used in the currently approved 2-foot clay layer design, and therefore an additional 1-foot of air space would be gained, see Figure 2, Option A, If approval for the Option A base liner modification is obtainable by the start of construction, the reserve capacity already permitted is sufficient to accommodate this modification. The Option A modification will increase the permitted capacity by approximately 6,700 cubic yards. However, as previously stated, the ERL is anticipating the initiation of Ce1117 construction in April and cannot postpone or delay this construction time-fraime..A.s a result, the ERL has. also submitted an additional liner detail (Figure 2, Option B) that will maintain the currently permitted base of waste elevations, and therefore substituting GCL for the 1-foot of clay; will raise the base of the clay liner by 1 foot. Ultimately, the decision as to whether or not GCL will be used'in place of 1-foot of clay will be dependent on the costs associated with clay layer placement and GCL material and placement at the ERL. S. Sand Drainage Layer: Lastly, as a point of clarification, the ERL's pernut requires a 12- inch sand drainage layer meeting the necessary permeability requixements. The enclosed