Oregon Department of Transportation tests trenchless solution
By Angus W. Stocking
Culverts and other storm water installations in Oregon face a special challenge, according to Oregon Department of Transportation (ODOT) hydraulic engineer Dan Gunther.
“For the last few years, if we planned any work on a culvert in fish-bearing streams, it would trigger the need for a fish passage, and that was typically too expensive for the proposed project budget—sometimes we’d find ourselves being required by the environmental regulations to construct a bridge to fix a culvert,” Gunther said.
Consequently, ODOT frequently has had to hold off culvert repairs if fish passage requirements were triggered. Now, many of these culverts are in critical condition.
Currently, some projects are being approved for relatively low-cost rehabilitation. One of these is the recently completed Trout Creek Overflow Culvert Repair located at milepost 13.1 on Oregon Highway 281. This 526-ft overflow culvert running parallel to the west side of the highway is made of 72-in. corrugated metal pipe (CMP). Time had not been kind to the culvert.
“When we actually got in the pipe and took a look, we found that it was worse than we thought,” Gunther said. Inverts were near failure or completely rusted out, and large voids were visible behind rotten patches for most of the culvert’s length. Oregon’s famous storm events also took a toll; rocks and sand pushed along by occasional high-velocity flows had damaged the CMP.