10002_ROSCANS_1998

@McGill
A S S O C I A T E S
May 11, 1998
Mr. Jason Robinson
Yancey County
Room 11
County Courthouse
Burnsville, North Carolina 28714
RE: Yancey -Mitchell Landfill
Erosion Problems
C&D Landfill
Dear Mr. Robinson:
Per your telephone call on Friday, May 8"i, 1 visited the C&D landfill site this morning to
investigate the erosion problems cited by Mr. Al Hetzell with the NCDEHNR, Solid Waste
Division. Mr. Hetzell has requested that the problems be corrected as soon as possible to avoid
any further damage to the C&D landfill slopes.
The major erosion problem has occurred in what was the natural drainage between the
closed sanitary landfill and the new C&D landfill. The original grading plan called for a slope to be
constructed across this drainage and construction and demolition waste to be placed behind the
slope. As you are aware, due to the existing landfill boundaries extending significantly further out
than originally shown on the CDM drawings, the C&D landfill boundary had to be moved further
away from the old landfill. This is reflected in the latest revised drawings dated May 26, 1997.
The area indicated on these plans as waste fill (beneficial fill or earth waste) on the southern slope
is the area where most of the erosion has occurred.
It appears that a pipe used to conduct surface drainage tom above the C&D landfill
through the fill area plugged up, forcing the water to run around and next to the pipe and washing
out the slope. The eroded area does not impact the C&D landfill slope integrity and the material
lost was essentially waste material (earth, not C&D) in excess of what was needed for
construction of the slopes for the landfill. The landfill slopes have suffered some erosion problems
also but not to the extent of this drainage area.
Mr. Hetzell suggested, and I agree, that the best course of action at this point is not to try
to reinstall the drainage pipe and rebuild the slope in this area. Instead the slopes on either side of
the natural drainage between the sanitary and C&D landfills should be repaired and a rip rap ditch
constructed between the two landfills. A ditch in the low point will allow the water to flow
directly down the drainage without any problems with maintaining pipes. This should eliminate
E n g i n e e r i n g • P l a n n i n g • F i n a n c e
McGill Associates, P.A. • P.O. Box 2259, Asheville, NC 18802 • 55 Broad Street, Asheville, NC 28801
704-252-0575 • FAX [phone]

Ms. Minnie Powell
February 7, 1997
Page 2
any further damage to the existing slopes from the surface water coming from above the C&D
landfill.
The proposed rip rap ditch should be constructed on filter fabric and be wide enough and
deep enough to ensure that it carries the water and does not allow water to erode the toe of the
repaired slopes. The rip rap ditch detail on the original CDM C&D landfill plans should be
sufficient for this proposed ditch, except I suggest at least 4' of width and 3' of depth to carry the
water. A wide section of rip rap at the outlet of the ditch for dissipating the water flow would also
be advisable.
At the same time as the ditch construction, the slopes on both the sanitary landfill and the
C&D landfill should be repaired by regrading to a minimum of 2:1 slopes, although 2 ''/z:l or 3:1
would be preferable. The remaining earth material near the bottom of the eroded slopes should be
brought back up onto the repaired slopes and the entire slope of both landfills should be regraded
and prepared for seeding as soon as possible. The new slope can be tied to natural ground above
the proposed rip rap ditch and will not impact the C&D material already placed or compromise
the future use of the C&D landfill cells yet to be built.
It is extremely important that the slope repairs are completed quickly, as continued rain on
the damaged areas can create even worse problems. It is also very important that the slopes be
seeded immediately upon completion of the slope repairs. I recommend that a hydroseeder be
used on the slopes to improve the chances of stabilizing the slopes with a stand of grass. Without
the grass on the slopes, the current minor erosion problems on the C&D landfill slopes will
become worse and could expose C&D material already placed.
I am enclosed a small print from the plans of the affected areas for your reference. If you
have any questions, please call me at any time. I would be glad to come back on -site to assist if
you feel it is required.
Sincerely,
McGILL ASSOCIATE"
VANN WATERS
Enclosure
cc: Mr. Mike Robinson
Al Hetzell
orsillo\95297.01 \jr I 1 my&doc