WQ0000020_Comments_20130815

NCDENR
North Carolina Department of Environment and
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Natural Resources
Division of Water Resources
Water Quality Programs
Pat McCrory Thomas A. Reeder John E. Skvarla, III
Governor Director Secretary
August 14, 2013
RECEIVED/DENRIDWID
John R. Toepfer, P.E. AUG 15 2013
Duke Energy Progress
410 S. Wilmington Street/PEB14 Aquifer Protection Section
Raleigh, NC 27601
RE: Asheville Airport - Area 3 Structural Fill Review Comments Addendum
Dear Mr. Toepfer,
The Asheville Regional Office of the Division of Water Resources (DWR) received
additional comments from the central office pertaining to the latest phase (area 3) of the
Asheville Airport coal ash structural fill project. Please consider this letter an addendum to
the original comments dated August 6, 2013. We offer these additional review comments to
ensure compliance with applicable regulations (15A NCAC 02T.1200) and your permit
(WQ000020) as well as provide further clarification for our review:
1. There is a discrepancy in the details with respect to cover soil thickness of 2' or 4'.
Section "A" on plan sheet 3 - 5.0 has 4' of cover, were as Section "C" on plan sheet 3
-10.0 has 2' of cover and the CQC spec's in section 4.50 Vegetative Cover reference
24"•
2. Plan sheet 3 -11.0, detail 'B" shows HDPE pipe penetration thru the base liner
system and illustrates boot detail for the 60 mil HDPE and how it is to be
constructed. There is no reference to the geosynthetic clay liner (GCL) or how it is to
be penetrated or repaired;
There is a discrepancy in the cap liner thickness. Section "H" on plan sheet 3 -11.0
indicates 30 mil HDPE, but plan sections on plan sheets 3 -10.0 "C" and 3 - 5.0 "A"
indicate 40 mil HDPE;
AQUIFER PROTECTION SECTION
North Carolina Division of Water Resources —Asheville Regional Office
2090 U.S. Highway 70. Swannanoa, N.C. 28778
Phone [phone]
FAX [phone]
Internet: h2o.enr.state.nc.us
An Equal Opportunity/Affirmative Acton Employer

Duke Energy Progress
August 14, 2013
Page 2 of 2
4. Who/Whom is providing the overall certification of the project (i.e. grades met with
respect to SHWT/HDPE base liner and cap installed, tested, repaired per plans and
specs, etc.); Please provide the DWR with a copy of the certification information.
5. The plans do not indicate a minimum cover thickness of coal ash over the HDPE
liner, i.e. 3' or 4' of ash minimum under the tracks, for travel across the cell (s);
6. It would be desirable to have either the geo-composite run completely under the
washed 57 stone column and 8" HDPE leachate pipe or have a rub sheet under the
stone column/pipe for protection of the HDPE (in conjunction with the 12oz
geotextile fabric). This is the most critical area of the liner system and if caution is
not taken during placement of coal ash in this area, damage to the base liner can
occur if sudden stops or turns of tracked equipment take place during the initial lift
of ash across the cell(s);
7. Will the contractor (or liner sub) be required to submit a GCL panel layout drawing
prior to installation for approval by the design engineer?;
8. Will the contractor (or liner sub) be required to submit a HDPE panel
layout/seaming drawing for the base liner system prior to installation for approval
by the design engineer?;
9. Will the contractor (or liner sub) be required to submit an as -built drawing of the
HDPE base liner and HDPE cap liner indicating locations of test samples, seam
repairs and type of membrane repairs made to the panels (i.e. extrusion spot weld,
pinhole repair, intersection of panels extrusion weld, etc.)?.
Please contact me if you have any questions regarding our review comments. I can
be reached at [phone] or brett.laveMPncdenr.gov.
Sincerely,
e'Regional Office
Protection Section
Cc: Jon Risgaard - DWR Central Office APS