One of the challenges of building your own fish counting weir is it requires every component to be custom fabricated. This post will focus on fabrication of the substrate rail, which is the anchoring point for which the resistance board weir panels attach. Fabrication requires the tools and skills to cut, drill, and weld steel. The substrate rail has eye-bolts welded along the top in which 3/8 inch stainless steel cable is run to join the substrate rail together and provide the attachment point for the resistance board panels.
The substrate rail is fabricated from ¼ in. structural steel consisting of 10 ft. lengths of 3 in. angle steel and 3 ft. legs. The legs of the substrate rail have holes in which 5 ft. rebar stakes (also custom fabricated) are driven through. In this example 2 stakes will be used on the upstream side and one on the downstream. For this substrate rail we are also applying an expanded steel mesh on the underside to add weight and reduce scouring. During installation duckbill anchors are driven into the river substrate about 20 ft. upstream and attached to the substrate rail with stainless steel cable and ratchets to provide additional holding power.
Photo source: FISHBIO
See our first post in this series: Fish Counting Weir: How to Series