CASTLE ROCK — A damaged two-lane bridge near Castle Rock will be temporarily replaced by a one-lane bridge in the fall — roughly six months after the damage occurred.
The north end of Pleasant Hill Road has been closed since a culvert collapsed and caused a section to sink in February. Culverts are bridges that allow water to flow under structures like roads or rail lines.
The county section of Pleasant Hill Road, outside of Castle Rock, was closed Wednesday because a culvert under the road appears to be collapsing, dropping the road surface two feet.
Cowlitz County Department of Public Works Communications Manager Mark Koelsch said a short-term bridge will be installed by September, but there is no timeline for the road to return to two lanes. He said crews will install the one-lane bridge as a temporary solution used during “emergencies.”
Koelsch said crews are obtaining permits to remove the partially collapsed culvert located southwest of the Huntington Avenue underpass at Interstate 5’s exit 48. Installation of the temporary bridge could start in August.
Crews will then need to design and request funds for a new, two-lane bridge to replace the culvert and return the road to normal operating conditions. Koelsch did not have a timeline for this construction.
In February, the damaged culvert caused the road to dip roughly 2 feet. The culvert is 10 feet in diameter and directs water from Salmon Creek under Pleasant Hill Road, Koelsch said.
Previous studies showed the metal culvert was too small for the amount of water that drains in the area, he added, particularly water that runs off a hill east of the highway.
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Salmon Creek runs parallel to Pleasant Hill Road, crosses under the street and eventually flows into the Cowlitz River.
Road closure signs are 1.5 miles prior to the closed section. Koelsch said alternative routes include “I-5, Bond Road east of the freeway or West Side Highway.”