Small sinkhole forms on River Road west of Guerneville, Repairs are under way by Russian River Sanitation District

A small hole near the top of an underground manhole created a small sinkhole adjacent to River Road Tuesday afternoon near the Russian River County Sanitation District (District) main lift station. The approximately 24” x 36” sinkhole located on the edge of the roadway prompted Caltrans and the California Highway Patrol to temporarily limit traffic to one lane in the 17000 block of River Road (Highway 116), near the intersection with Riverside Drive.

The hole in the manhole is believed to be the result of corrosion in the 40-year-old structure. The hole created by the corrosion on the side of the manhole is located 3-4 feet below the surface of the ground. Soil falling through the hole from outside the manhole weakened the area around manhole and created the sinkhole. The incident did not result in any discharge or spill. Wastewater continued to flow into the lift station, which pumps wastewater to the District’s treatment plant. Traffic restrictions will be in place until a temporary steel plate is installed Tuesday evening, and will remain in place until repairs are made.

There was no interruption of service to sanitation customers as a result of the sinkhole. District officials will consult with Caltrans officials Wednesday to develop a repair plan and emergency repairs are expected to start immediately, and are expected to take 2-3 days.