Millbrook Exchange Stream Repair

Stormwater

Millbrook Exchange Park Stream Project

Stream Repairs

In 2019, an innovative technique using in-stream stone structures was implemented to reduce stream erosion at Millbrook Exchange Park and prevent pollution from flowing into Perry Creek. After the project was completed, heavy rainfall and streamflow damaged the structures. The City has contracted with Ecosystem Planning & Restoration (EPR) to make necessary repairs to the project. Proposed repairs include raising the elevation of the streambed, armoring the structures with stone, and constructing a floodplain bench that will be planted with native tree and shrub species.

This project was originally supported through a grant from NC Land and Water Fund (formerly Clean Water Management Trust Fund).

Project Details

 
Type:
Stormwater
Budget:
$440,000 (Repair Design + Construction)
Project Lead:
Stormwater Management
Contractors:
Ecosystem Planning & Restoration (EPR)

Contact

 

Megan Walsh
Senior Engineer
919-996-4009

Lead Department:
Engineering Services
Service Unit:
Stormwater

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Design

Design of the repair project is underway. Topographic survey data was collected in August 2022 to help inform the design.

Lead Department:
Engineering Services

Construction

Construction is expected to begin in Summer 2023.

Lead Department:
Engineering Services

Schedule

Date Activity
Winter 2022 Finalize design for repairs
Spring 2023 Receive Permits
Summer 2023 Construction begins

History

This stream flows to Perry Creek and passes through Millbrook Exchange Park.

It receives stormwater runoff from a largely developed 167-acre drainage area. Stormwater runoff coming from the surrounding area caused erosion and the stream’s bed to drop several feet below its natural level. In this condition, the stream lacked many key ecological functions.

In 2019, a low-cost and unique technique was implemented that included fitting eleven (11) boulder structures in the stream to fill with sediment over time and help raise the streambed. This technique was intended to reduce the amount of sediment downstream, transform the energy and flow of the stream, and help prevent erosion to the streambank.

North Carolina State University conducted post-construction monitoring of the stream from Spring 2019 to December 2020. During this time, heavy rainfall and streamflow damaged structures in the stream.

The Technique

Proposed repairs include:

  • Armoring the structures with stone;
  • Raising the streambed using soil and other natural materials; and
  • Constructing a floodplain bench that will reduce erosion by allowing water to spread out along the stream bank.

The floodplain bench will be densely planted with native tree species and riparian vegetation to further stabilize the project, provide wildlife habitat, and replace trees that are removed during construction.