Increasing Capacity in Raleigh Near Smith Creek

The Smith Creek Interceptor Improvements Project was a major sanitary sewer project completed for the City of Raleigh but located in Wake Forest.

The City of Raleigh owns, operates, and maintains the water and sewer utilities in many neighboring communities, and the project was part of a merger agreement between the Town and City to handle known inflow and infiltration issues in the area, as well as to accommodate for rapid growth in the Town.

The critical interceptor extends from the NC Highway 98 bypass and flows directly to the Smith Creek WWTP. In addition, the Tom’s Creek interceptor was part of the project, flowing from the east and tying to the Smith Creek interceptor just outside of the plant. The 43,000 linear feet of sewer involved had existing diameters ranging from 8-24 inches.
The initial phase of the project was a preliminary study which included a condition assessment of the existing line, geotechnical work, and an environmental study to determine the impacts of construction on the surrounding environment.

Three options were identified to add capacity to the existing system: Parallel and abandon the existing line, parallel the existing line while keeping the existing line in service, or replacing the existing line in place. In the end, a combination of the options was chosen to suit local conditions of the corridor, but generally the existing line was kept in place and in operation while adding a parallel sewer for additional capacity.

After completion of the preliminary phase, The Wooten Company provided hydraulic modeling, design, and permitting services for the project. Unique challenges in the design included the acquisition of over 100 sewer easements, a crossing of a 4 lane controlled access highway (NC Highway 98 Bypass), work around new and existing Town of Wake Forest greenways, and the tight corridor due to North Carolina owned conservation lands.

The newly installed parallel pipe diameters ranged in size from 15” to 36” inch, with approximately 20,000 linear feet of the 43,000 installed being 30 inch diameter.
The project bids for the $10M project came in approximately $1M below the estimated budget and out teams provided as-built survey and record drawings for the project after construction was completed in spring 2016.