New Corps Requirement to Countersink Stream Crossing Culverts -- Effective Date: September 1, 2004 New regional conditions to Nationwide Permits released by the Norfolk District on July 26, 2004, require countersinking all pipes and culverts in nontidal streams to allow for movement of aquatic organisms. In addition, the Corps is promoting and encouraging the use of bottomless culverts or bridges. Pipes 24 inches or less in diameter must have both the inlet and outlet ends countersunk 3 inches below the natural stream bottom; pipes greater than 24 inches in diameter must be countersunk 6 inches. This requirement applies to all single pipe culverts. In multiple pipe crossings, at least one pipe must be countersunk. At this time, these conditions apply to Nationwide Permits only – but we expect these in most Individual Permits (IPs) and in a future version of the State Program General Permit (SPGP). Extensions of existing culverts that are not currently countersunk are exempt from the new regulations, provided that the inlet and outlet ends of the new culvert remain at the same elevation of the existing pipe/culvert. Other maintenance activities that do not involve a complete pipe/culvert replacement are also exempt, as well as pipes placed above the ordinary high water mark of a stream for the purpose of draining the floodplain. The new regulations also caution that pipes must be sized correctly to account for the loss of hydraulic capacity resulting from the countersinking requirements. Exceptions and Special Considerations For new pipes/culverts in locations where bedrock prevents countersinking, other possibilities must be evaluated to include the use of bottomless structures or even crossing in a different location. If these options are not feasible, a Pre-Construction Notification (PCN) in accordance with General Condition No. 13 of the Nationwide Permit must be submitted. Other information must also be supplied, including documentation of measures evaluated to minimize impacts to the movement of aquatic organisms, as well as documentation of the cost, engineering factors, and site conditions that prevent the countersinking. Within 45 days, the permittee will be notified whether the proposed work qualifies for the nationwide permit. The conditions recommend that the Department of Game and Inland Fisheries (DGIF) be contacted to provide guidance on how to provide for the movement of aquatic organisms when countersinking is not possible. Countersinking pipes on slopes greater than 5 percent must be given special consideration to ensure excessive velocities do not occur that would cause scour or disrupt fish movements. Measures can be taken to facilitate fish movement in cases like this -- contact DGIF for guidance. (Note that if structures are placed within the culvert to facilitate fish passage, the material will be considered as fill and must be included in the total fill for the project. As with constraints due to bedrock, in situations where excessive slopes prevent countersinking, a PCN and supporting documentation must be submitted.) If during the replacement of any pipe/culvert that would require countersinking it is discovered that the stream bed is on bedrock, work must be stopped and the Norfolk District must be contacted. For emergency pipe/culvert replacements, countersinking should be performed at the time of the replacement. If this is not feasible given time constraints, the repair will be considered temporary and the countersunk replacement must be installed at the earliest possible date. Contact Frank Graziano, P.E.; Dan Lucey, P.E.; or Bill Nell, P.E. if you have concerns or questions about your site and these new conditions. 1To minimize stream bed damage from concentrated culvert flows in large storms, one natural stream channel design technique is to provide separate culverts to handle floodplain flows (vs. the stream channel flows) instead of funneling these large event volumes only through a stream channel culvert, as is done traditionally.