DEQp00021054

DuPont Fluoroproducts
22828 NC Highway 87 W
Fayetteville, NC 28306-7332
DuPont Fluoroproducts 07
Mr. David Goodrich
NCDENR — Division of Water Quality
Water Quality Section — NPDES Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
if t� , j October 20, 2000
j
_ OCT 2 5 2000
- Y
SUBJECT: Relocation of Final Effluent Discharge
NPDES Permit No. NC0003573
Dear Mr. Goodrich:
First of all, thank you for giving me the opportunity to meet with you, Tom Belnick,
and Mike Myers last month to discuss the issue of the DuPont — Fayetteville Work's
effluent channel and the sedimentation problem that occurred from this channel during
the summer of 1999.
The purpose of this letter is to request from the Division of Water Quality a
regulatory determination as to any change in the NPDES permit limits should this site
relocate its final discharge from the current position downstream of Lock and Dam #3 to
a new position upstream of the Lock and Dam.
As you recall, the total permitted wastewater discharge from this site, which averages
about 15 MGD, enters an effluent channel that conveys the water approximately one mile
to the Cape Fear River at a point downstream of Lock and Dam #3. Over the thirty-year
history of this site, the continuously flowing effluent has eroded the channel to the point
where most of its walls are nearly vertical and the streambed is now fifteen to twenty feet
below grade. During the drought of the summer of 1999, we experienced sloughing of
the channel's banks that resulted in substantial amounts of sediment exiting the effluent
channel into the Cape Fear River. I will point out that we have not seen this problem
since that time, which I contribute to the normal rainfall we experienced this summer.
On August 20, 1999, DuPont met with Mr. Paul Rawls and Mr. Ricky Revels of the
DWQ staff in the Fayetteville Regional Office to inform them of the effluent channel
sedimentation problem. Since that time, we have been working on determining the most
effective and cost efficient means to minimize the possibility of a future recurrence of the
sedimentation problem.
After a rponsiderable amount of field investigation and preliminary design work,
DuPont has identified two possible solutions that would minimize the future sediment
discharge from the existing effluent channel. Each of these projects would cost
E. I. du Pont de Nemours and Company ® Printed on Recycled Paper
FA Rev. 6/99

Mr. David Goodrich
NCDENR — DWQ
October 20, 2000
Page 2 of 3
approximately two million dollars ($2,000,000) and their details will be discussed later in
this letter. However, the most attractive and permanent solution apparently could result
in a lowering of the existing permitted limits in the DuPont NPDES permit, which would
make that solution unattractive. Therefore, before we can proceed, we need a definitive
answer as to whether or not the permit limits would be affected.
DESIGN OPTION 1
The first potential solution is to make physical modifications to the effluent channel
as it approaches and enters the Cape Fear River, and to install a dam structure to allow
sediment settling. This design requires straightening out the channel to reduce the
amount of stream bank erosion that occurs from the dynamic scouring of the water at
turns, and widening the channel at the river itself to slow down the water's velocity and
reduce the streambed erosion. At some point between the Lock and Dam road and the
river, a dam would be installed to create a quiescent pool for water -borne sediment to
settle before reaching the dam. An obvious downside to this plan is that there would be
substantial ongoing maintenance cost associated with the dam as well as periodic required
dredging to remove accumulated sediment from upstream of the qam. Another downside
is that with the frequent flooding of the Cape Fear River, this dam structure would be
occasionally submerged and could sustain major damage that would result in expensive
repair costs. This design has been estimated to cost approximately $1.8 million.
DESIGN OPTION 2
The second potential solution is to pipe the entire DuPont final effluent directly to
the Cape Fear River, which would allow the existing effluent channel to return to its
original, natural state as a stormwater ditch that would be dry except for rainfall runoff. It
is believed that without the continuous flow of the DuPont effluent, the channel would in
time naturally vegetate and thereby virtually eliminate all future sediment discharge to the
river. To make this option cost effective, the pipe would be laid in a line that is the
shortest distance to the river, which would place the discharge of the effluent upstream of
Lock and Dam #3. Obvious benefits of this plan are that there would be no routine
maintenance costs to DuPont, the pipeline would be less vulnerable to damage from
flooding, and overall we believe that the sediment to the river will be less than would be
seen under Option 1. This design has been estimated to cost approximately $2.2 million,
and while it would cost more for DuPont to construct this project than the one described
in Option 1, the maintenance -free aspect of this project and the complete remediation of
the sediment problem makes it an attractive option to consider.
PERMIT LIMITATION POTENTIAL CHANGE
As discussed in our meeting, there is apparently a rule or policy that could result in
lower permitted limits for this site's NPDES permit if the DuPont effluent were

Mr. David Goodrich
NCDENR — DWQ
October 20, 2000
Page 3 of 3
discharged upstream of Lock and Dam #3 because of the water body behaving as a
reservoir instead of as a flowing stream.
You indicated that a modeling exercise would have to be performed for this area of
the Cape Fear River to determine whether or not the DuPont effluent would have any
negative impact on the water system upstream of the Lock and Dam. If the modeling
demonstrates that the effluent would result in some water impairment, then more
restrictive permit limitations would be placed on our NPDES permit. DuPont feels that
this information is imperative before we can make a decision on which of the two above
multi-million dollar projects we would select.
Therefore, I am asking that the Division of Water Quality take the needed steps to
perform the necessary modeling to determine what, if any, changes would occur to the
DuPont — Fayetteville Works NPDES permit should the final effluent be discharged
upstream of Lock and Dam #3.
Enclosed for your use is a map indicating the approximate location of the proposed
pipeline. If you should need any additional information, please let me know and I will be
happy to provide it to you.
If you have any questions regarding this letter or if you need more details, please feel
free to call me at [phone]. o Ansty-, t
rr,
cit d
k01A ILI 7
�IA el
CW
tolf'�
Enclosure
i�
cc: Mr. Paul Rawls, NCDENR Division of Water Quality, Fayetteville
Mr. Ricky Revels, NCDENR Division of Water Quality, Fayetteville