millbrook park stream

Stormwater

Millbrook Exchange Park Stream Project

Stream Repairs

We used an innovative technique to reduce erosion in a stream at Millbrook Exchange Park and prevent pollution from flowing into Perry Creek. After project completion, heavy rainfall and streamflow damaged structures in the stream. Now, we've contracted with Ecosystem Planning & Restoration (EPR) to make necessary repairs to the project. This will require significant earthwork, armoring of structures, and the creation of a new floodplain bench planted with native tree species.

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

Project Details

 
Type:
Lakes, Streams, and Dams
Budget:
$440,000
Project Lead:
Stormwater Management
Contractors:
Ecosystem Planning & Restoration (EPR)

Contact

 

Heather Dutra
Senior Engineer
919-996-4012

Lead Department:
Engineering Services
Service Unit:
Stormwater

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Design

The repair project is in the early stages of design. Surveyors will be onsite in August 22 to gather data.

Phase Contacts

 

Heather Dutra
Senior Engineer
919-996-4012

Lead Department:
Engineering Services

Construction

Expected to begin Summer 2023.

Phase Contacts

 

Heather Dutra
Senior Engineer
919-996-4012

Lead Department:
Engineering Services

Schedule

Date Activity
Fall 2022 Design finalized for repairs
Winter 2022 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 167-acre largely developed drainage area. Erosion from stormwater runoff coming from the surrounding area caused the stream’s bed to drop several feet below its natural level. The stream was between 5-12 feet with high banks.

In this condition - The stream lacks many key functions that preserve it and protect wildlife in the area.

The Technique

We used a low-cost and unique design that included fitting 11 boulder structures in the stream to fill with sediment (i.e. silt, sand, and gravel) over time and raise the streambed. This stream technique reduces the amount of sediment downstream, transforms the energy and flow of the stream, and prevents any further 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. 

Proposed repairs include armoring the structures with stone, raising the streambed using soil and other natural materials, and constructing a wide floodplain bench to allow water to spread out and further decrease pressure on the structures. 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.