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DuPont Fluoroproducts
22828 NC Highway 87 W
Fayetteville, NC 28306-7332
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April 23, 2002
Mr. David Goodrich
NCDENR — Division of Water Quality
Water Quality Section — NPDES Unit
1617 Mail Service Center
Raleigh, NC 27699-1617
SUBJECT: Changes in Discharges of Toxic Substances
NPDES Permit No. NC0003573
Dear Mr. Goodrich:
This letter requests that your office clarify a requirement found in Part III of the
subject North Carolina issued NPDES permit.
The DuPont Company —Fayetteville Works facility manufactures many fluorocarbon
compounds. Each of these processes creates a wastewater that is ultimately treated in and
discharged from the on-site wastewater treatment plant (WWTP).
As with all chemical processes, side reactions to the desired product reaction create
dozens or hundreds of byproducts in very low concentrations. The fluorochemistry
involved in this processes is exceptionally complicated, and most of the byproducts are
unknown compounds. There is no standard method to identify these compounds, so a
research methodology utilizing nuclear magnetic resonance (NMR) spectroscopy must be
employed by an on-site DuPont chemist to qualify and quantify an unknown fluorocarbon
compound.
DuPont is considering a research effort to identify and quantify some of the unknown
fluorocarbon byproducts in the various processes at the Fayetteville Works facility.
Samples would be taken from the wastewater discharge nearest to the process so as to
maximize the possibility of a detectable concentration.
In Part III(C) of the subject NPDES permit, there is a requirement for the permittee to
notify the Division of Water Quality "as soon as it knows or has reason to believe... that
an activity has occurred or will occur which would result in the discharge, on a routine or
frequent basis, of any toxic pollutant which is not limited in the permit, if that discharge
will exceed... one hundred micrograms per liter (100 µg/L)".
The question to the Division is whether or not the subject permit requires, pursuant
to Part III(C), reporting of compounds that are detectable only in the discharge of the
manufacturing process, and that would not be detectable exiting the site's WWTP?
E. I. du Pont de Nemours and Company ® Printed on Recycled Paper
FL -4 Rev. 6/99

Mr. David Goodrich
NCDENR — DWQ
April 23, 2002
Page 2 of 2
For example, assume a wastewater sample is taken from the discharge of a
manufacturing process and using NMR spectroscopy, Compound A is detected at a
concentration of 20 mg/L. The NMR detection limit for Compound A is determined to be
1 mg/L, meaning any concentration less than 1 mg/L cannot be detected nor quantified.
Assume that the process wastewater stream is added to the many other wastewater
streams sent to the WWTP and that it represents 1% of the total WWTP influent. This
stream would be diluted 100 times with the other wastewaters, so that the concentration
of Compound A entering the WWTP is now 0.2 mg/L (200 µg/L) and cannot be detected
using the NMR spectroscopy method.
In the above example, Compound A is entering the WWTP at a calculated
concentration of 200 µg/L. There is no literature available to indicate if Compound A is
degraded in an activated sludge biological treatment system. If one assumes that little of
the material is biodegraded, then it follows that there is as much as 200 pg/L of
Compound A exiting the WWTP through the permitted Outfall 001. Per the requirement
of Part III(C), if the discharge exceeds the 100 µg/L "notification level", then the Division
of Water Quality would have to be notified. However, analysis of Outfall 001 shows no
detectable concentration of Compound A because the calculated concentration of
0.2 mg/L is less than the detection limit (1 mg/L) of the only known analytical method for
detecting Compound A.
In the above example, would a permitee be deemed to know or have reason to
believe that a toxic substance is being discharged above the "notification level" and
therefore be required to notify the Division of Water Quality of the discharge of
Compound A pursuant to Part III(C) of its NPDES permit?
If you have any questions regarding this inquiry, or if you need more details, please
feel free to call me at [phone].
Michael E. Johnson
Environmental Manager
cc: Mr. Paul Rawls, NCDENR Division of Water Quality, Fayetteville

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