Decision Notice - Big Coulee Fish Barrier Enhancement Project

Mar 20, 2025 3:29 PM

Montana Fish, Wildlife & Parks (FWP) is proposing to enhance a previously constructed fish barrier on Big Coulee to protect a nonhybridized population of westslope cutthroat trout Oncorhynchus lewisi (WCT). The fish barrier project site on Big Coulee is located entirely on the Helena-Lewis and Clark National Forest, Judith-Musselshell Ranger District. The proposed enhancements to the Big Coulee fish barrier include constructing a cast-in-place concrete weir on top of a previously blasted bedrock waterfall and pouring a concrete splash pad at the base of the waterfall to eliminate the formation of a plunge pool. Additionally, drilling, blasting, and/or hydraulic hammering of the bedrock directly downstream the barrier would be performed to grade the streambed in a manner that prevents pooling of water during periods of high stream discharge.

PURPOSE AND NEED The intent of the proposed action would be to support the following FWP goals and objectives: • Isolate the upper 2.4 miles of fish habitat in Big Coulee from nonnative fish invasion • Increase the amount of protected WCT habitat in the Upper Missouri-Dearborn River drainage by 40% (from 6 miles to 8.4 miles; FWP 2022) • Create a refugium for an at-risk WCT conservation population of highest conservation need • Use the affected section of Big Coulee as a donor stream for future WCT conservation efforts in north central Montana • Reduce the likelihood of ESA-listing of WCT

Based on the environmental review provided in the Draft EA, and in accordance with all applicable laws, rules, regulations, and policies, FWP determined the proposed action (Alternative 2), will not have significant adverse impacts on the human environment associated with the proposed action and constitutes a reasonable and appropriate strategy to achieve identified objectives. Therefore, preparation of an EIS is unnecessary. FWP hereby adopts the Draft EA as final and approves the Alternative 2, the proposed action. With this DN, FWP hereby adopts the Final EA, without modifications, and approves the proposed action.