DEQp00021070

DIVISION OF ENVIRONMENTAL MANAGEMENT
September 22, 1993
MEMORANDUM
To: Dave Goodrich
Rapid Assessment Group
From: Greg Nizich6,50
NPDES Permits Unit
Subject: Permit Renewal Issues
NPDES Permit #NC0003573
DuPont - Fayetteville
Bladen County
Coleen and I met with Mike Gell and Bruce Youtsey, of DuPont, yesterday to discuss their
draft permit. Several questions came up that we were unable to answer:
1- Oil And Grease - Why is monitoring required at 001 for this parameter? It was not in the
previous permit.
2 - OCPSF parameters - Dupont requested reducing the monitoring frequency to annually
for parameters not detected during the previous year (or other acceptable duration). They
have monitored since April 1990, and have not found any parameters in the OCPSF list
above detection. They proposed that they monitor on an annual basis and then if any
parameter is detected, they would begin monitoring on a quarterly basis until samples
collected for four consecutive quarters are less than detection. This appears to be
reasonable, any comments?
3 - PAH limit - What flow was used in determining this limit? The allowable instream is
3 1. 1 ng/l and the permit allows 18.14 ng/l in the effluent. Is this correct? Dupont also
requested that we put in a limit that is detectable and still in compliance, but I don't see how
this can be done. A standard is a standard. We suggested a weekly/daily possibility, but
they said the test results took 6 weeks, so that probably won't work.
4 - Fluoride (002) - Can this be revised to summer/winter? Can we put in a monthly
average/daily max? DuPont is concerned that lower discharge flows (less cooling waters -
flows can vary from 6 to 17 MGD) in the winter will bump up the concentration and would
like a provision to account for the lower total mass.
5. Tox Test - The IWC was not corrected in the WLA to reflect the flow from 001 only.
3.3% seemed low, so I didn't question it when drafting the permit, but that is for 17 MGD,
not 2 MGD. Should the test be a 90% acute and for what species? What is the reason we
use the acute test when IWC is below 1%?
After I receive your input, I will send DuPont a revised draft for their review.