Biological Assessment for
Bridge Replacement Project

Old Town, ME

Bridges in Salmon
Critical Habitat
Decibel Noise

Endangered Species Act Consultation for Atlantic Salmon in the Stillwater River

Two bridges carrying Stillwater Avenue over the Stillwater River in Old Town, ME needed replacement. The river crossing is comprised of two bridge structures with lengths of 250 feet and 85 feet, connected by an island.

Since the project is located within the expected range of the federally endangered Atlantic Salmon, consultation with the US Fish & Wildlife Service was required. McFarland Johnson provided a Biological Assessment (BA) in compliance with Section 7 of the Endangered Species Act, as well as an essential fish habitat assessment (EFHA) under the Magnuson Stevens Fishery Conservation and Management Act. The Stillwater River is an approximately 11.5-mile-long side channel of the Penobscot River. The Penobscot River watershed supports the largest runs of Atlantic salmon in the Gulf of Maine Distinct Population Segment. Although there is no upstream passage along the Stillwater River, in-season fall back adult salmon may be present in the action area from April through October.

MJ’s experience with MaineDOT’s BA and EFH procedures allowed us to respond quickly, prepare reports that required few revisions, and stay within budget. The BA and EFHA were prepared in accordance with federal requirements and involved researching the biology and ecology of species of concern, determining the project’s action area, describing existing habitat conditions, and analyzing direct and indirect effects on species and habitat. The effects analysis considered permanent habitat loss, construction phase activities such as noise, turbidity, and water quality, as well as long-term operational effects. It was concluded that, when added to baseline conditions, effects from increased turbidity and underwater noise (up to 190 decibels from pile driving) would likely adversely affect Atlantic salmon adults.

The new bridges were designed to increase the waterway opening, providing increased aquatic habitat. In combination with several avoidance and minimization measures, it was determined that the final project was not likely to adversely affect Atlantic salmon critical habitat.