NC0004961_Water Quality Study_19890621

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State of North Carolina
Department of Natural Resources and Community Development
Division of Fnvionmental Management
512 North Sakbury Street ® Raleigh, Norrh Carolina 27611
James G Martin, Governor R Paul Wilms
William W Cobey, Jr, SecretaryDirector
June 21, 1989
Mr. B.K. Sipe
Duke Power Company
P.O. Box 33189
Charlotte, North Carolina 28242
SUBJECT: Water Quality Study
NPDES Permit No. NC0004961
Riverbend Steam Station
Gaston County
Dear Mr. Sipe:
Vic *_cport, "Mountair C:,iand Lake, North Carolina: Water Quality Moni-
curing 19o'81' was received for review oi. May 31, 1989. The report rulfills
condition V of the subject permit by summarizing general spatial water quality
characteristics of the reservoir and documenting trace element concentrations
in sediment and fish tissue.
Members of the Water Quality Section reviewed the report and had the
following comments. Most of the study conclusions appear to be well supported
by the data. However, the discussion of sediment trace elements (page 9) is
inadequate. For example, the data in Table 6 clearly indicate that selenium
was detected in 0% of the samples from the upstream reference station (sta-
tion 16.0), but was found in 80% of the samples from the station near the dam
(station 275.0). No mention of this is made in the body of the report, nor is
the spatial distribution of arsenic values described. The ANOVA summary pre-
sented for the fish tissue results (Table 8) is easy to interpret, and a simi-
lar summary for sediment arsenic and selenium results is needed.
Sediment results show that both arsenic and selenium were more prevalent
at stations near the ash basin and at the dam compared to the reference site
upstream of the ash basin. In addition arsenic concentrations in the water
coliimn were significantly higher near the ash basin (station 277.5) than at
any other ;cation. Fish tissue arsenic and selenium were also significantly
higher at this station. While we agree that the reported concentrations do
not demonstrate environmental concern at present, it is clear that both
arsenic and selenium are being introduced into Mountain Island Lake downstream
of the reference site. Given these observations, my staff has recommended
that Duke Power continue to monitor fish and sediment trace elements, particu-
PO Box 27687, Raleigh, North Carolina 27611-7687 Telephone [phone]
An Equal Opportunity Affirmative Action Employer

` larly arsenic and selenium. An acceptable level of monitoring would be once
per year at the same stations sampled in 1988.
Also, it appears that some of the data are missing from the report. The
approved study plan indicates that specific conductance was to be monitored
along both horizontal and vertical transects at each station. This informa-
tion was requested by DEM to evaluate wastewater/lakewater mixing, but was not
presented in the results. Please submit this information at your earliest
convenience. Also, although mentioned in the text, the vertical transect data
for the other field parameters (i.e. D0, temp. & pH) collect a 1 m intervals
were not reported. Please submit these data along with the conductivity data.
Your participation in assuring the quality of North Carolina's waters is
appreciated.
Sincerely,
��Stteve W. Tedder, Chief
Water Quality Section
cc: Ken Eagleson
Trevor Clements
Rex Gleason
Ralph Roberts
Central Files