NC0038377_Comments to Draft Pemit_19871029

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Carolina Power & Light Company
Shearon Harris Energy & Environmental Center
Route 1 Box 327
New Hill North Carolina 27562
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Dr. George Everett, Chief
Water Quality Section
N.C. Division of Environmental Management
P.O. Box 27687
Raleigh, NC 27611-7687
RE: Mayo Electric Generating Plant
NPDES Permit NCO038377
Comments on Draft Permit
Dear Dr. Everett:
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Serial No.: ESS -87-1334
Carolina Power & Light Company (CP&L) has reviewed the subject draft permit
that was received on October 2, 1987• In the public notice published on
September 30, 1987, the Division of Environmental Management (DEM) required
written comments to be submitted by October 30, 1987. Representatives of CP&L
met with Messrs. Arthur Mouberry, Steve Tedder, and others of your staff on
October 23, 1987, and discussed CP&L's comments and concerns. A written
summary of CP&L's comments are enclosed for your consideration. Also enclosed
is a marked -up copy of the draft permit, revised to reflect the changes
requested in our comments.
The time spent by your staff in meeting with us and considering our comments
is greatly appreciated. If you have any questions or require further
Information, please contact Mr. Cam Wheeler at 836-6725 in our General Office.
CCW/dfs (4212CCW)
Enclosures /
cc: Mr. A. Mouberry
Mr. R. W. Van Tilburg
Yours very truly,
G. H. Warriner
Manager
Environmental Services

Enclosure to ESS -87-1334
Carolina Power & Light Company
Comments on Draft NPDES Permit N00038377
For the Mayo Electric Generating Plant
October, 1987
Outfall 001 - Cooling Tower Blowdown
Under the Effluent Characteristics column, the 1112o Priority Pollutants" item
should have a reference to footnote 1 in order to be consistent with the
effluent guidelines. CP&L believes the correct reference for this list of
pollutants is 40 CFR 423, rather than 40 CFR 122 as given.
The first paragraph on the second page should delete references to "more than
one unit" as there is only one unit at this plant. In addition, it is
requested that this paragraph require records of chlorine release times to be
kept at the plant for inspection by DEM, rather than require the regular
submittal of a routine and steady value each month in the monitoring reports.
Outfall 002 - Ash Pond Discharge
Total Iron and Total Copper monitoring and limits were added to this outfall
in the existing permit when DEM originally approved the ash pond equivalency
demonstration submitted by CP&L for treatment of metal cleaning wastes. The
monitoring and limits were to verify that the ash pond had provided treatment
of metal cleaning wastes as required. Since that time, EPA has disapproved
that demonstration and is requiring DEM to permit metal cleaning wastes as a
separate outfall (004). As a result, CP&L will meet the required copper and
iron limits for this outfall prior to discharge to the ash pond, and it should
not be necessary to monitor a second time at the ash pond outfall. Please
delete the iron and copper monitoring and limits from this page.
Outfall 004 - Metal Cleaning Wastes
The release from the metal cleaning wastes treatment basin at the plant is by
gravity flow. Please change the sample type from "Pump log or similar
readings" to "Estimate". The change in level of the basin will be used to
calculate change in volume over time, or flow.
Part III. Condition F - Toxicity Reopener
CP&L believes that the word "shall" in the first sentence should be replaced
with "may". This wording will allow a more flexable response by DEM after all
relevant factors have been considered.
Part III. Condition G - Toxicity Testing Requirement
CP&L is particularly concerned about the proposed toxicity limits applicable
to our effluents. Toxicity testing and the derivation of limits have not been
subject to the usual rulemaking process, including public review and comment
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prior to implementation. In addition, CP&L is cautious of any such new limit
when there has been little or no prior monitoring or other specific study to
determine if, in fact, our effluent can meet this particular limit. Such an
"end of pipe" toxicity limit is significantly different than the instream
effects that have been emphasized in most previous permits and biological
monitoring efforts. Power plant design and most previous environmental
assessments were not intended to address this specific type of NPDES limit.
CP&L takes its responsibility to comply with all permit limits very seriously,
and has strong reservations toward any new limit when the ability to comply is
not clear. While the purpose and necessity of toxicity monitoring is
recognized, CP&L requests that any specific limit for toxicity be deferred
until initial monitoring tests can be completed and any changes in effluent
characteristics that may be necessary to comply with a given limit can be
evaluated and implemented. The permit contains sufficient reopener clauses to
allow DEM to add specific toxicity limits at a later date when all relative
factors can be considered. If DEM decides to keep a toxicity limit in this
permit, the following comments apply.
Toxicity Limit - The draft permit contains the toxicity limit expressed as "no
significant mortality in an effluent concentration of 954". The effluent test
protocol that DEM cites is designed to provide dose -response data for
estimating an LC50. The term "significant mortality" is not defined. CP&L
requests that the toxicity limit be explicitly stated as "an LC50 not lower
than an effluent concentration of ...If
Date of first test - Since CP&L has not recently used the Fathead Minnow as a
toxicity test organism, we may not be prepared to conduct the required tests
in-house before the end of 1987. It is requested that the requirement for
performance of the first test be changed from 30 days to 90 days after
issuance of this permit to allow adequate preparation.
Test Variability - CP&L requests that NCDEM take into account both the
effluent toxicity test method variability and individual test precision when
a) setting the effluent toxicity limit, and b) interpreting the results of an
individual test with respect to the permit toxicity limit.
a) The draft permit contains no reference to the inherent variability of the
acute toxicity test method. The toxicology literature provides some
estimates of coefficients of variation (CV) for acute toxicity tests that
generally range from 254 to 404. CP&L believes it reasonable that the
variability of the test method be incorporated into the permit toxicity
limit so that any routine test of an effluent sample not cause the permit
limit to be failed simply due to random error associated with the
toxicity test method.
b) Given that the permit toxicity limit will be expressed as an LC50 (see
above), CP&L requests that the permit explicitly state that the LC50
confidence interval of any individual test be considered as the unit for
comparison to the permit toxicity limit. Methods for calculating the
LC50 point estimate from a set of toxicity data include estimation of the
confidence interval around the LC50. The toxicity test reporting form
(DEM Form AT -1) suggests methods for calculating the LC50 and an
associated confidence interval and requests that the confidence interval
be reported. The confidence interval represents the range of values
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within which the "true" LC50 lies based on statistical certainty.
Because the true LC50 lies anywhere within the confidence interval it is
the interval itself and not the LC50 point estimate that should be
compared to the permit toxicity limit. Therefore, a permit limit
violation would occur only if the upper limit of the LC50 confidence
interval was less than the permit toxicity limit. Viewing the results in
this fashion would minimize the occurrence of false positives (declaring
the effluent sample toxicity a violation when actual toxicity was less
than the permit allows).
Part III. Condition L
As discussed earlier, since untreated metal cleaning wastes are no longer sent
to the ash pond, the requirements to monitor for iron and copper in ash pond
seepage in Crutchfield Branch are no longer appropriate. Please delete the
iron and copper monitoring requirement in the last sentence.
Part III, Condition H - Priority Pollutant Monitoring
Regarding the monitoring requirement for "priority pollutants", CP&L questions
if such monitoring is necessary. Effluent characteristics for the steam
electric industry have been thoroughly investigated and identified by EPA,
DEM, and the industry itself. As part of the NPDES renewal process, a
thorough analysis for such priority pollutants is conducted every 5 years. In
addition, if any of the referenced pollutants are added by the Company, DEM is
notified in advance and approval obtained if necessary. This process provides
adequate assurances that any listed chemical is properly accounted for or not
present at all. CP&L expects to request that this requirement be deleted
after two or three years of monitoring have demonstrated that there is no
additional information to be gained from the expense and effort required to
comply.
Additional Items
Please add a condition in Part III that will allow the use of upsets as a
defense for noncompliance with technology based effluent limits as per
40 CFR 122.41.
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