Why did WSDOT replace the Sand Hollow Culvert?
In the fall of 2005, about a mile south of the I-90 Vantage bridge, a deep, 15-foot diameter sinkhole from the fog line to beyond the guardrail undermined the outside truck-climbing lane. WSDOT Geologists and engineers determined the sinkhole was caused by failure of a deep culvert below the roadway. They investigated several alternatives and formulated a repair plan. Necessary emergency funding and permits were acquired for the culvert replacement. This section of SR 26 was constructed in 1954. The four-foot diameter culvert that failed is located at the bottom of a 35-foot embankment. Replacing that culvert required reconstructing approximately 250-feet of roadway. The new replacement pipe is a high-flow six-foot diameter culvert that meets the U.S. Bureau of Reclamation’s current flow requirements. A five-foot diameter overflow culvert was also replaced. During construction, water flowing from above SR 26 under the highway down to Sand Hollow was re-routed, utilizing a temporary str
