Federal/State Highway Crossings For the replacement of failing or improperly sized culverts/bridges on State and Federal Highways, modification of crossings with in-stream structures are made as necessary (e.g. cross-vanes). Stream crossing remediation on state-owned highways may involve state-let process and additional permitting and coordination. New culverts emulate natural stream conditions, minimize flooding concerns and impacts to road through proper sizing and improves sediment transport and water quality.
A new culvert also reduces maintenance expenses.
Costs can range from $5,000 - $506,000
County/Local Road Crossings Most of the existing culverts identified as fish passage impediments are significantly degraded and need replacement or improvements. Replacement elliptical or round metal pipes, corrugated aluminum box culverts with headwalls and wingwalls, pre-cast concrete boxes with headwalls or wingwalls, rock cross-vane structures to backwater existing or new culvert structures are all used to remediate impediment conditions at the county/local road crossing sites. These projects provide fish passage during a full range of flow events (spring floods, baseflow, etc.), emulate natural stream conditions, minimizing flooding concerns and impacts to the road through proper sizing, improve sediment transport and water quality, and reduce ongoing maintenance expenses.
Costs range from $3,000 to $580,000 per site.
Full Structural Removal When possible, a full structural removal is preferred. Full structural removals provide for natural fish passage conditions, improved sediment transport and water quality, and the removal of ongoing landowner maintenance and liability.
Costs are around $20,000.
Low-Head Dam Modification Low-head dam modifications are made when full structural removals are not possible. Low-head dam modifications provide fish passage during a greater range of flow events (spring floods, baseflow, etc) but still result in ongoing landowner maintenance and regulatory liability.
Costs range from $5,000 to $50,000 per site.
Open Span Bridges An open span bridge is the next preferred alternative if a full structural removal or stone ford crossing is not possible at a culvert crossing site. Open span bridges allow for fish passage while also meeting land owner demands. The bridges are sized to approximate bankful dimensions. The open span bridges provide for near-natural like fish passage conditions during a full range of flow events (spring floods, baseflow, etc), improve sediment transport and water quality, and reduce ongoing maintenance expenses.
Costs range from $8,000 to $15,000 per site.
Stone Ford Crossings If full structural removal or open span bridges are not an option then replacement with a stone ford is the preferred alternative.This involves a removal of the impediment and construction of a stabilized area set at or below the normal stream bed elevation to provide a crossing for people, livestock, equipment, or vehicles. The fords are constructed using larger sized rock as a base and smaller sized stone as a top dressing, sized appropriately to avoid washouts under a variety of flows. Trail approaches are graded at a slope to meet landowner crossing needs, but blended to meet existing bank conditions where possible. Stone ford crossings provide for fish passage conditions during a full range of flow events (spring floods, baseflow, etc), improve sediment transport and water quality, and reduce ongoing maintenance expenses.
Costs range from $6,000 to $9,000 per site.