Projects

Pennington Bridge Restoration

A 1% for the River Conservation Fund Project

Impairment: Bank loss; infrastructure damage (county road, bridge)

Proposal: Phase 1– Remove approximately 3,500 cubic yards of sand and gravel from point bar upstream of bridge. Plant native riparian vegetation along riprap.

Benefits: Reduce risk to infrastructure; reduced sedimentation; increased stream shading; improved aquatic habitat.

Calendar: April, 2021- Construction

Estimated Cost: $22,000

Big Hole Conservation Fund Goal: $1,500

DONATE TO SUPPORT THE PENNINGTON BRIDGE RESTORATION PROJECT

Project Description

Due to two county bridges constraining the floodplain and side channels, this section of the lower Big Hole River has accelerated flows which have forced large-scale erosion and bank loss upstream of one bridge. In 2016, Madison County placed 175 cubic yards of riprap along 205 ft of the bank to protect the Pennington Bridge infrastructure and private ground. The riprap has held but is slowly being flanked by the river. This flanking, combined with the continual bank loss and erosion, poses a substantial risk to the Pennington Bridge abutments and infrastructure downstream. BHWC and partners are approaching this issue in two phases.

Phase 1

Phase 1 will create a more effective solution to continual rip-rapping of the bank. The project will remove approximately 3,500 cubic yards of sand and gravel off the point bar feature, opposite the erosive stream bank. Removing the point bar will activate an adjacent overflow/high flow channel, decreasing shear stress and erosive forces on streambanks. Additionally, the BHWC will plant native riparian vegetation (mechanically transplanted willow clumps and hand-planted stakes/whips) on top of and throughout the existing 2016 riprap bank.

Phase 2

With grant funds from the Bureau of Reclamations WaterSMART program, BHWC has hired Great West Engineering and Applied Geomorphology to design a long-term solution involving activation of side channels. BHWC will be actively engaging landowners in the lower section of the Big Hole and work with Madison County to co-develop a solution for this problem that provides for water reliability, safety to infrastructure and private property, and improve ecological function.