6204_UwharrieMSWLF_CommentonUnderdrain_cell14B_DIN27511_20170314

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Chao, Ming-tai
From:Chao, Ming-tai
Sent:Tuesday, March 14, 2017 1:17 PM
To:'[e-mail]'
Cc:Reynolds, Joe; Eric Jackson; Ritter, Christine; Mussler, Ed; Bradford, Teresa
Subject:Comments on the underdrain piping plan at Cell 14 B, Uwharrie MSWLF, 62-04 , DIN
27511
Hi Matt: DIN
27511

The Solid Waste Section (SWS) reviews the underdrain piping plan (DIN 27508) at the Uwharrie Regional
Landfill – Cell 14B and has several concerns on the proposed underdrain piping plan (the Plan) which are stated
below:
1. Please state why the options to construct an underdrain piping which carries seepage to the area on the
south or west sides of the Cell 14B are not viable.

2. The Plan is required to provide approaches to determine if the seeps observed at the Cell 14B area are a
one-time event but dry-up eventually or an intermittent or a permanent flow. To determine if the
underdrain should be placed underneath the landfill in the future, the plan should provide the following
info, but not limited to:
i. The routine (such as daily or weekly) monitoring, measuring, and documenting flow volume at
the exit of the underdrain pipe (inside the future Cell 15) for a specified period prior to
construction of Cell 15. The weather conditions (including the precipitation amount for a period)
should be recorded for the reference.

ii. The personnel conduct the routine task.

iii. The conclusions or findings of the status of seeps (including the data collected from the task
mentioned in the item i) should be a portion of the permit application for construction and
operations of the future Cells 15 or 16. The approaches to manage the seeps in the future must
be discussed in the application, such as plug & abandoned the underdrain piping if the seeps are
terminated naturally, or the construction and extension of the piping to incorporate the future
landfill activities, if the seeps are determined as a permanent flow.

3. Based on the data shown on the cross-section drawing (DIN 27508), the invert depths of the proposed
pipe trench range from approximately 2 to 15 feet below the existing grades. The tasks associated with
excavation of trench, installation of piping, and backfill the trench must be safely executed according to
OSHA Excavation Standards – trenching and shoring which must be provided in the Technical
Specification Section 02722.

4. The existing site-wide WQMP for the landfill must be revised to include the sampling and analyzing of
the seeps at the end of the underdrain piping. The revised plan should be submitted to the SWS for a
review and approval.
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Please submit a hard copy and an electronic copy of the revised plan which are incorporated the responses to the
above-mentioned comments. Should you have any questions of the above-mentioned comments please contact
me. Have a wonderful day.

Ming Chao
Ming-Tai Chao, P.E.
Environmental Engineer
Permitting Branch, Solid Waste Section
NCDEQ, Division of Waste Management
(Mailing Address)
1646 Mail Service Center
Raleigh, NC 27699-1646

(Street Address)
Green Square, 217 West Jones Street
Raleigh, NC 27603
Tel. [phone]
[e-mail]
http://portal.ncdenr.org/web/wm/sw

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