Environmental Impact Statement - radioactive monticello

Description of Site and Environment
-Table 2-3.
Threatened or Endangered Aquatic Species Potentially Occurring in the
Vicinity of Monticello and the Associated Transmission Corridors
Status(a)
Scientific Name Common Name Minnesota U.S.
Lampsilis higginsii Higgins' eye pearlymussel E E
Lasmigona compressa creek heelsplitter SPC
Ligumia recta black sandshell SPC
Source: FWS 2005a,c; MNDNR 2005; Kelner and Davis 2002
(a)E = endangered, SPC = species of concern,'- = no listing.
The Higgins' eye pearlymussel was Federally listed as an endangered species on
June 14, 1976 (FWS 1976). It is only found in the Mississippi River, the St. Croix River in
Wisconsin, the Wisconsin River, and the Rock River in Illinois. It was never abundant,
historically comprising approximately 0.5 percent of the mussel population. At the time the
original recovery plan was written in 1982, the Higgins' eye pearlymussel had undergone a
53 percent decrease in its known range (FWS undated). The Higgins' eye pearlymussel most
frequently occurs in medium to large rivers with current velocities of approximately 0.5 to
1.5 ft/s and in depths of 3 to 20 ft, with firm, coarse sand or mud-gravel substrates (FWS 2000,
2001). It is generally found in mussel beds with at 16ast 15 other species present
(Hornbach 2004).
Much of the historic habitat for the Higgins' eye pearlymussel has been altered from a
free-flowing river system to an impounded river system. This has altered flow patterns,
substrates, and fish host habitats and movements (FWS 2001). Other impacts to the species
have included water quality degradation from municipal, industrial, and agricultural run-off;
dredging; waterway traffic; and, particularly, zebra mussels (FWS 2004a; Hornbach 2004).
No critical habitat has been designated for the Higgins' eye pearlymussel. However, ten
Essential Habitat Areas (EHAs) for the Higgins' eye pearlymussel occur within the Upper
Mississippi River watershed. EHAs are locations known to contain reproducing populations of
the Higgins' eye pearlymussel in association with a healthy and diverse unionid community
(e.g., mussel beds) (Hornbach 2004). No EHAs within the Mississippi River occur close to the
Monticello site (RM 900). The most upstream area is at Whiskey Rock, Iowa, (RM 656) which
is over 240 RM downstream of the Monticello site. However, three EHAs occur in the St. Croix
River, which flows into the Mississippi River at RM 811, downstream from Lock and Dam 2
(Hornbach 2004). The furthest upstream Essential Habitat Area on the St. Croix River is the
only EHA that is free of zebra mussels (Hornbach 2004).
Suitable fish hosts for the glochidia of the Higgins' eye pearlymussel include freshwater drum
(Aplodinotus grunniens), largemouth bass (Micropterus salmoides), black crappie, yellow perch,
sauger (Sander canadensis), and walleye; while marginal fish hosts include northern pike,
bluegill (Lepomis macrochirus), and green sunfish (L. cyanellus) (Hornbach 2004).
August 2006 2-23 NUREG-1 437, Supplement 26 1