PIT_Tag_Antenna

The U.S Army Corps of Engineers, Portland District, began operating a new experimental fish collector at Cougar Reservoir in May 2014 with the goal of attracting and collecting juvenile salmon as part of a research program investigating downstream passage issues at the dam. Past observations by biologists determined juvenile fish had difficulty passing the temperature tower because it was not designed for fish passage.

The PFFC was designed by engineering firm HDR to be positioned near the temperature tower with an adjustable attraction flow of 50 to >100 cubic feet per second. Careful attention to the mooring and anchoring of the structure in a reservoir where the water can fluctuate up to 180 feet annually was required. A PIT tag antenna was designed and installed by West Fork Environmental with the goal of monitoring the collection of fish and provide information on the timing of collection.

Groups of tagged fish will be released to estimate the combination of reservoir survival and trap collection efficiency. The PIT tag study is one of several related research efforts to evaluate surface passage at Cougar Dam.

Design and construction of the thin-bodied ferrite shielded antenna, constructed of high density polyurethane, was technical due to complex geometry of the steel walls of the PIT tag antenna slot located at the tail end of the collector portion of the structure. West Fork designed and installed the antenna, coordinated with HDR engineers, and adapted the design of the antenna as the collection facility plans progressed. The PIT tag antenna was designed to fit into a slot with opposing and uneven angles and that was constructed entirely of mild steel.

The final antenna dimensions measured 2 inches thick by 6 inches wide and included specifications for sloped sides with several notches engineered into the antenna housing so that it could remain fully recessed within the available slot dimensions without disrupting hydraulics of the collector throat. The antenna is powered by a IS1001-ACN controlled through an IS1001-MC. The high noise environment generated from the operation of pumps presented another challenge in designing this particular antenna and was in part addressed with ferrite shielding on three sides of the coil. Data acquired from the PIT tag system on the Cougar Reservoir will be manually downloaded.

The PIT tag antenna, designed to easily remove from its slot, can be used to detect the effectiveness of the structure at collecting juvenile salmonids at other sites. The complex geometry presented in this particular setting, and the capacity to design and install a thin-bodied ferrite shielded antenna to these specifications shows that a good deal of flexibility is possible in fitting these kinds of antennas to various engineered structures.