• precast
• Shotcrete
• steel

• October 2009
• September 2009

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Corrugated Steel Arch Culvert

Bottomless arch culvert installations are an excellent choice from an environmental and fisheries viewpoint.
OMNR 1988. The typical design for installation of a pre-cast concrete, bottomless arch culvert is shown in this line drawing. It is mounted on footings (poured-in-place) that extend below the scour line. Like a span bridge, they allow for natural stream channel processes that will maintain favorable habitat and fish passage under the structure.

Bottomless arch culvert installations also have the low profile advantage of an ellipse type culvert. Bottomless arch structures may be used at sites with slopes ranging fro 0% to 6%, but bottom materials inside the culvert should include boulders large enough to withstand current flows. On sites with slopes from 3% to 6% this means utilizing D90* size rock (D90 size material refers to the largest 10% of naturally occurring boulders in the stream). In some installations special preparations (like rock placement) are needed to address possible scour erosion of the stream bed that could undermine the culvert footing.

In this photo, the flange footing type, bottomless arch culvert is being lowered onto the prepared streambed. Note the placement of D90 (or larger) boulders in the channel to provide resting places for migrating fish. The term D90 refers to the size of the boulders in the vicinity of the crossing. The size of a D90 boulder is equal to the average of the largest 10% of the boulders in the stream bed.

This corrugated metal, bottomless arch culvert is provided with a metal flange footing and rests on a cement base. It is a highly functional installation, does a great job of maintaining fish habitat and is competitive in price with a round culvert installation. {source}