Wohler Culvert Repair

The project is to repair a culvert occurring on Sonoma County Regional Parks' property near Wohler Road. Last winter this culvert backed up substantially causing flooding on Wohler Road and causing water to flow over the road and reroute around a portion of the drainage with riparian vegetation restoration. The purpose of the project is to repair and stabilize the existing culvert so that water can flow to the restoration area, downstream sedimentation is avoided, and Wohler Road does not flood. In summer of 2025, under guidance of the Northern California Regional Water Quality Control Board, Regional Parks retained Miksis Services to unblock the culvert and stabilize deteriorating culvert ends. Once the work to remove about 20 feet of roots grown into the culvert and resulting trapped sediment had been performed, Miksis determined that the culvert needed to be lined to preserve long-term function. Regional Parks approved the additional scope and work was scheduled to be conducted during the remaining small window of dry weather. This became impossible because, when Miksis came to begin work on the culvert lining, they discovered that the culvert changes size from 18” to 24” partway through. The intended culvert lining, Dynaliner, can only expand 1 culvert size (for instance, to 21” would be possible, but not all the way to 24”). To maintain functional stability over the long term, the culvert needs to be lined with one continuous liner. Miksis Services will remove the upstream 17’ of the 18” CMP upstream of the 22-degree bend, digging to the culvert invert in the existing road, and replace it with 24” CMP. A confined space crew will clean the damaged 40’ of 24” CMP with a dry-vacuum industrial loader truck. Once the preparatory work is completed, a 24” Dynaliner seamless thermoformed PVC pipe liner will be installed to achieve a continuous diameter pipe. Both ends of the culvert will be stabilized. The project will benefit residents of Sonoma County by protecting water quality and winter users of Wohler Road by preventing or limiting flooding.