Environmental Impact Statement - radioactive monticello

Environmental Impacts of Operation
Additional impingement studies were conducted at Monticello between April 16, 1976, and
April 8, 1977, as part of the CWA 316(b) Demonstration (Amish et al. 1978). An estimated
39,767 fish were impinged. The predominant fish impinged were 15,295 shorthead redhorse
(38.5 percent), 7385 silver redhorse (18.6 percent); 3381 logperch (8.5 percent); 2506 common
I carp (6.3 percent); 2254 black crappie (5.7 percent); 2121 white sucker (5.3 percent); and
1799 black bullhead (4.5 percent) (Amish et al. 1978). The maximum number of equivalent
adult fish estimated to have been lost due to this impingement was 10,838, including:
1820 shorthead redhorse; 635 silver redhorse; 3381 logperch; 215 common carp; 230 black
I crappie; 252 white sucker; and 1799 black bullhead (Amish et al. 1978).
Based on the CWA 316(b) Demonstration (Amish et al. 1978), the Minnesota Pollution Control
Agency concluded that impingement at Monticello does not pose a substantial detrimental
effect on the fish population (MPCA 1979). The Mississippi River 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 Monticello site (Xcel Energy 2004).
Under the current State of Minnesota NPDES permit, the location and operation of the intake
will continue to have minimal environmental impact.
During the course of the SEIS preparation, the staff considered mitigation measures for the
continued operation of Monticello. Based on the assessment conducted, the staff expects that.
the measures in place at Monticello (e.g., the intake structure located in an area where fish
congregation does not occur and that is devoid of unique spawning habitat, and a screen wash
system that returns impinged fish to the river) provide mitigation for impacts related to
impingement. Based on the results of past impingement studies and the operating history of
Monticello's intake structure, the staff concludes that the potential impacts of impingement of
fish and shellfish are SMALL, and further mitigation measures would not be warranted.
4.1.4 Heat Shock
For plants with once-through cooling systems, the impacts of heat shock are listed as a
Category 2 issue and require plant-specific evaluation before license renewal. The NRC made
impacts on fish and shellfish resources resulting from heat shock a Category 2 issue because
of continuing concerns about thermal discharge impacts and the possible need to modify
thermal discharges in the future in response to changing environmental conditions (NRC 1996).
Information to be considered includes (1) the type of cooling system (whether once-through or
cooling pond) and (2) evidence of a CWA Section 316(a) variance or equivalent State
documentation. Heat shock can be defined as thermal stress caused by exposure to a sudden
elevation of water temperature that adversely affects the metabolism and behavior of fish and
can lead to death. Heat shock is most likely to occur when an off line unit returns to service. To
perform this evaluation, the staff reviewed the applicant's ER (NMC 2005a) and related
documents (including the CWA 316(a) Demonstration [Afzal et al. 1975]); visited the Monticello
site; and reviewed the applicant's State of Minnesota NPDES Permit No. 0000868, issued on
August 22, 2002, and in force until July 31, 2007 (MPCA 2002).
NUREG-1437, Supplement 26 4-18 August 2006 1