Allen Steam Facility (5)

NC®ENR
North Carolina Department of Environment and Natural Resources
Division of Water Quality
Beverly Eaves Perdue Coleen H Sullins
Governor Director
June 24 2010
Ron Lewis
Water Management, Duke Energy
EC13K
PO Box 1006
Charlotte, NG 28201-1006
Dee Freeman
Secretary
Subiect: Review of Duke Energy Carolinas, NPDES Permit NC0004979 (Lake Wylie -Allen Steam Station)
"Balanced and Indigenous Populations (BIP) Assessment Report—Supplemental Mayfly (Hexagenia spp) and
Sediment Sampling, June 10, 2010"
Environmental Sciences Section (ESS) staff has reviewed Duke Energy's resample data for Hexagenia populations
and substrate analyses of Lake Wylie near the Allen Steam Station This resampling of long-term stations for
Hexagenia populations and associated substrates in Lake Wylie was requested by ESS in a letter dated March 11,
2010 and in a subsequent conference call (April 6, 2010) These requests were made in an effort to reduce the
possibility of confounding factors in the interpretation of the Hexagenia data
Based on a review of this additional data, ESS offers the following comments
1) ESS concurs with Duke Energy's interpretation that substrate size is the primary limiting factor in explaining
Hexagenia distributions and densities In general, the additional data supports the theory that the smaller
particle sizes are favoring increased densities of Hexagenia while larger particle sizes reduce (or exclude)
Hexagenia
2) As expected, the earlier seasonal sampling produced record densities of Hexagenia although this was only
documented at Station A This result is consistent with the emergence patterns of these mayflies and supports
the conclusion that fluctuating densities at some stations corresponding with later seasonal sampling dates is
primarily the result of emergence effects and not the result of abiotic effects Therefore, it Is recommended
that subsequent sampling be conducted within the mid-April or mid-May timeframe in an effort to ameliorate
these confounding effects
3) The augmented dataset contained within the June 10, 2010 report suggest that there Is no impairment due to
temperature or dissolved oxygen at the long-term monitoring stations and that these stations generally
support balanced and indigenous populations
If you have any questions, please do not hesitate to contact Eric Reek at eric fleek(c)_ncdenr gov or at 919-743-
8469
cc Rob Krebs, Mooresville Regional Office
Jeff Poupart, Surface Water Protection Section
Sergei Chernikov, Surface Water Protection Section
Kathy Stecker, Planning Section
Alan Clark, Planning Section
Tom Belnick, Surface Water Protection Section
1621 Mail Service Center, Raleigh, North Carolina 27699-1621
Location 4401 Reedy Creek Road, Raleigh, North Carolina 27607
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Sincerely,
Jay Sauber
Chief, Environmental Sciences Section
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NorthCarolina
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