Mill Pond Dam Removal Temporary Barrier

Project description

Seattle City Light removed the Mill Pond Dam in fall 2017 as a habitat restoration measure related to the relicensing of the adjacent Boundary Dam project. Mill Pond Dam, located about 3.5 miles east of the town of Metaline Falls in northeastern Washington state, was initially constructed on Sullivan Creek in 1909 and was reconstructed several times since.  A population of non-native brown trout had established in Mill Pond, and Seattle City Light and the state and federal fish and wildlife agencies wanted to prevent the upstream migration of adult non-native trout during dam removal and the subsequent lowering of the pool into upstream native trout habitat. Seattle City Light asked Smith-Root to design and install a mobile, temporary barrier in Sullivan Creek for use before and during construction activities for removal of the Mill Pond Dam.

Smith-Root outfitted a mobile trailer that housed the necessary components of a remote electrical barrier, including two Smith-Root pulse generators; Fish Barrier Telemetry & Communications System; wireless modem, antenna, and signal booster; connection to line power; backup generator and propane tanks; and Automatic Transfer Switch. A temporary service drop was installed by the local power provider to power the system; a backup generator was also provided to power the barrier if the line power was lost.  A simple two-electrode array with stainless steel cables was installed across the main channel of Sullivan Creek a few hundred feet upstream of the headpond created by Mill Pond Dam.

The system was installed in Sullivan Creek from July to November 2017.