Box culverts are required for drainage areas along Oregon highways, but these culverts can be difficult for fish to traverse when the water running through them is shallow and fast-moving. To alleviate this problem, according to the Oregon Coastal Salmon Restoration Initiative authorized in 1997, we replace existing culverts that do not meet fish passage standards. With the help of materials from Delta Sand & Gravel, Delta Construction Co. is currently working on two projects to replace box culverts along Highway 101 near Coos Bay, Oregon.
Southern Coos Bay Coastal Culvert Project: At the junction of US 101 and OR 42
Our southernmost coastal culvert project will replace an existing box culvert with twin, side-by-side single-span bridges. This project not only replaces failing culverts, it also removes a tide gate that currently obstructs fish passage. The goal of the project is to return the area to prime spawning grounds.
Each bridge is founded on a 20- to 24-inch round steel pile driven 90 feet through the slough into solid sandstone. Considering the corrosive coastal environment, we have constructed each bridge using class HPC 4000 concrete and additives to ensure a dense and impermeable mix fit to protect the structural rebar from salt-water corrosion. In addition to high-performance concrete, we are using stainless steel rebar, hardware, fasteners and tie-wire to ensure long lifespans for each bridge.
Our project deadline is driven by the In-Water Work Window (IWWW). This window is set to limit the work window only to times when water temperatures are the least favorable for fish migration. We are excited to report that the southbound bridge is complete. Next, we will remove the culvert, rehabilitate the stream and complete the northbound bridge. We are currently on track to finish this project prior to our original estimated end date, Oct. 31, 2018.
Northern Coos Bay Coastal Culvert Project: Under US 101 at Wildwood Drive
The northern coastal culvert project will replace two existing steel culverts with a 16-foot by 10-foot by 160-foot concrete box culvert and a 16-foot by 10-foot by 56-foot concrete box culvert. By replacing the current steel culverts, we will remove current fish passage barriers. The new box culverts will be filled with fish rock and native soil to mimic the natural stream environment so that while the concrete will protect fish from predators, the internal environment will encourage fish movement.
The 165-foot culvert runs 50 feet below the road grade of US 101, which requires a “top down” approach to the construction, requiring the installation of a temporary bridge, retaining walls and a shoring system of more than 400,000 pounds of structural steel. Delta’s crew finished setting the last of the 40 precast concrete sections of this longer culvert in late June and has started backfilling 15,000 yards, in addition to starting the shorter cuvlert under Wildwood Drive.
After Labor Day weekend, we will reduce US 101 to one lane with 24-hour flagging (scheduled to last for one month). We will then remove the detour bridge, backfill and complete final paving to meet our Sept. 30 paving window end date. Once both culverts are complete, we will excavate several hundred feet of new stream channel to connect the new culverts with existing streams.
Making Progress While Protecting Local Ecology
Each job at Delta is a team effort. We work closely with ODOT’s in-house biologist and various other regulatory agencies to ensure that we meet necessary regulations and deadlines for our culvert projects. We appreciate ODOT’s focus on moving projects forward, while remaining cognizant of traffic and environmental restrictions.
Delta fully supports the construction of environmentally-friendly structures in the state of Oregon and beyond. It is our hope that with the restoration and replacement of outdated, non-compliant culverts, we may help salmon and other native fish species thrive in the Pacific Northwest for many years to come.