Yakama Nation Fisheries (YNF) removed a six-foot diameter culvert and the concrete fill material associated with it. The culvert was located on Toppenish Creek (watershed area is greater than 200 sq. mi.) near the confluence of Toppenish and Simcoe Creeks, approximately ½ mile west of Brownstown Rd. The culvert is on property recently acquired by the Yakama Nation.
A reach assessment of the area adjacent to the culverts was conducted to identify any risks such as potential head-cuts or areas primed for avulsion.
After the culvert and concrete was removed, YNF staff revegetated the site with riparian species appropriate for the site. The stream adjacent to the culvert site will be stabilized using grade control structures made of large rocks.
- Remove undersized culvert
- Remove fish passage barrier created by excessive culvert outlet velocity
- Remove delay to fish immigration caused by culvert velocity barrier
- Remove potential for physical damage to fish leaping and impacting on concrete support structure
- Remove recurring problem of stream washing out banks on both sides of culvert creating downstream sedimentation problems
Rock for this project was staged onsite prior to beginning the work. The rock was delivered by side-dump semi truck and sorted and placed in piles. A tracked excavator was used to remove the concrete debris and the culvert. The excavator was also used to place the rocks that formed the grade control.
The target species for this project is Mid-Columbia steelhead. The removed culvert was grossly undersized for a watershed area of more than 200 square miles upstream and had been observed to block passage to adult steelhead due to the outlet velocity of the culvert during the migration period. In some years, we believe this culvert delayed adult steelhead migration for as much as ¼ of the spawning season, so that steelhead were missing opportunities for migration through the Toppenish Creek system and maintaining optimal distribution and spawning/rearing density. Adult steelhead had been observed jumping onto the concrete fill material surrounding the culvert and we felt that some fish were injured or predated in addition to being impeded. The culvert crossing had been breached a number of times by high flows, scattering crossing fill downstream.
By removing the culvert and re vegetating the stream banks, we have restored the ability of the steelhead to move through the system unimpeded and restored the streams ability to handle high-flow events.