Location: Near NC16. Residential (Webbs chapel Cove) street (SR1698) over a creek where segmental block walls were used as headwalls for a pipe culvert.
Item(s) of Interest: Contractors and Developers especially have shown a lot of interest in these types of proprietary, low-cost walls. Though these type of walls certainly have their place, there is some concern over their long-term durability in some applications.
Observations and Points of Discussion:
96" corrugated metal pipe culvert used under roadway.
Roadway shoulder width did not appear to be adequate.
Modular block headwalls were used to artificially shorten the length of the pipe culvert to avoid the need for a wetland's permit.
Some of the regulatory agencies are recommending this type of setup.
Many structures built by private developers, such as the culvert at this site, are installed without Department inspection oversight.
Most culvert inverts should be buried at least a foot. In this case invert should be buried two feet for scour reasons.
Several group members raised questions on the hydraulic efficiency of the pipe culvert installed at this site.
Is this type of wall suitable for any encroachment?
The Geotechnical Engineering Unit generally has no problems with the modular wall concept. However developers need to utilize approved systems, which are built according to Department policy and specifications. The Geotechnical Unit is developing a policy and specifications.
The Project Service Unit will be coordinating the policy on use of and approval of these types of wall systems.
Bridge Maintenance is not in favor of using modular walls as headwalls for culverts.
The Department's Subdivision Roads Manual needs to be updated.
NC DOT
NC DOH
NC GOV
