Environmental Impact Statement - radioactive monticello

Environmental Impacts of Operation
intermediate discharge zone extended across the entire river at spots and extended at least
3.5 mi downstream (Afzal et al. 1975).
Afzal et al. (1975) noted that some fish remained in the discharge canal (during the early years
of operation before the weir was installed) when temperatures were 91 to 95 0 F, but avoided the
canal when temperatures reached 104 0 F. In 1980, an overflow weir that closely approximates
the preconstruction shoreline of the Mississippi River was added to the discharge canal. Under
normal conditions the weir effectively prevents movement of fish from the river into the
discharge canal. Fish species that frequent the area immediately downstream of the weir
included smallmouth bass, black crappie, walleye, northern pike, common carp, shorthead
redhorse, silver redhorse, and white sucker. The fish population inhabiting the discharge canal
in the fall and winter of 1974-1975 was estimated at 147 black bullhead, 354 rock bass
(Ambloplites rupestris), 22 black crappie, and 216 bluegill (Afzal et al. 1975). These
observations were made before the channel catfish (Ictalurus punctatus) first appeared in the
Monticello area.
Spawning areas for shorthead redhorse, silver redhorse, white sucker, and black crappie were
identified from both sides of the Mississippi River and from areas both upstream and
downstream of Monticello (Afzal et al. 1975). Thus, thermal effects would not be expected to
have a significant impact on local fish production. The fish community has been persistent and
stable since the plant became operational, and species composition has been similar between
locations upstream and downstream of the discharge (Xcel Energy 2004).
The Monticello thermal discharge to the Mississippi River does not entrap fish in an area of
elevated temperatures. Thus, acute thermal impacts (e.g., death or immediate disability) are
unlikely. Generally, the maximum plume temperature differential would be within the tolerance
range of most warmwater species (Talmadge and Opreska 1981). Furthermore, the thermal
plume in the Mississippi River encompassed by the 3 0 F isotherm is sufficiently large that fish
would rarely be exposed to abrupt temperature differentials that would be high enough to be
potentially harmful. Also, no currents or physical deterrents are present that would force fish to
remain in areas of potentially harmful water temperatures.
There have been periods of non-compliance with the NPDES permit; however, there have been
no indications of adverse impacts to the aquatic biota within the area of influence from the
Monticello discharge (Afzal.et al. 1975). Based on the results of the CWA 316(a)
Demonstration, the Minnesota Pollution Control Agency concluded that the thermal discharges
from Monticello do not pose a substantial detrimental effect on the fish and benthic
macroinvertebrate communities (MPCA 1979).
The staff has reviewed the available information, including that provided by the applicant, the
staff's site visit, the NPDES permit, the CWA 316(a) demonstration, and other public sources.
During the course of this SEIS preparation, the staff considered mitigation measures for the
continued operation of Monticello during the license renewal period. Based on the staff's
assessment of measures in place at Monticello (e.g., the discharge is located in an area where
NUREG-1437, Supplement 26 4-20 August 2006 1