Agenda - 04-05-2011 - 8a - Laserfiche WebLink

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JANE C(4 ]MPANY 1 LT'.RarZy SdL~~Z~~SSM ~~ 1 ~~ ro: Gayle Wilson ~4range County} I"r~m: poug DeCesare HDR} Project: Prange County MSW Landfill ~~~ Ed Shuffler HDR} Date: October 28, 201 D Job N°~ 352D7-142839-018 Revised February 3, 2D11 RE: MSUV Landfill Expansion Capacity Under Wark Crder No. 2 HDR has prepared different options regarding the proposed final grades of the landfill. It is intended to prepare a permit modification that revises the current permitted side slopes of 4:1 to 3:1. The steeper side slopes provide better drainage, enhances positive drainage after settlement, and provides additional capacity. If the revised permitted capacity of the landfill increases by 1 D°/° or mare, North Carolina General Statutes considers the permit modification to be a substantial amendment. A substantial amendment requires public involvement during the review and approval process with NCDENR. The public involvement process would generally follow 15NCAC 13B .16D3~c} of the Solid Vvaste Management Rules. Upon approval of a substantial amendment, NCDENR would prepare a draft permit and a fact sheet for the applicant and anyone who may request a copy. When the draft permit is ready, NCDENR would give public notice that a draft permit has been prepared at which time a 45-day public comment period is opened andlar a public hearing is scheduled. The public notice may be in the form of publication in a daily or weekly Inca! newspaper of general circulation or by pasting the notice in the post office and public places of the municipalities nearest the site. All comments received would be considered by NGDENR in making the final decision. At the time of final permit decision, NCDENR would provide a response to all comments received. Currently the bottom third of the landf fl has been constructed at slopes steeper than 4:1 to account for future settlement. HDR has projected the remaining final grades at a 3:1 beginning at existing side slopes that closely represent 3:1 slopes. By projecting 3:1 slopes and remaining below the 1 D°/° threshold, the landfill would have a remaining capacity of about 452, D00 CY as of 3119110 date of latest survey}. At 51,120 tanslyear and a waste density of 1,320 Iblcy, the remaining site life would be 7D months and reach capacity in January 2D16. Additional capacity could be realized beyond the 452,ODD CY if the 1 D°/° threshold were exceeded. In the event the County elects to maximize the landfill, HDR projected the final grades at a 3:1 slope from the existing slopes to a higher elevation that results in a remaining capacity of about 530,ODD GY. In this case the remaining site life would be 82 months and reach capacity in January 2017, Maximizing the landfill capacity based on these grades is achievable and can be easily constructed. If the County was interested in reworking all the slopes and begin the 3:1 slopes at the toe of the landfill fat the base liner anchor trench}, the maximum capacity of the landfill would be greater than 53D,DDD CY. In addition to projecting the 3:1 slopes from the existing slopes, HDR projected grades from the toe of the landfill which creates an additional wedge of airspace between the existing slopes and the projected slopes. V1rth the additional wedge, the maximum remaining capacity of the landfill is about 617,DDD CY. This yields a remaining site life of about 96 months which reaches capacity in March 2018. Per our meeting October 27, 201 D, it was concluded to proceed with the permit modification such that the 1 D% threshold will not be exceeded. Unless otherwise directed by the County, HDR proceeded with the preparation of a permit modification to steepen the side slopes and remain under the 10% capacity increase threshold. HQR Et~gineerirtg, Inc, 3733 tiatinnai Drive Phone (919 785-1118 Page 1 of 1 C:~pwwnrkingltpa~d0235~511~a11-a2-04 DTD-Wilson Capacity Mem°.DOC Suite 2~7 Fax (919} 785-1187 ' Raleigh, fVC X7612 vrww.hdrinc,cnm