Bolin Creek Restoration
Baldwin Park, Carrboro, NC
The Department of Biological and Agricultural Engineering (BAE) of the North Carolina State University will work with the Town of Chapel Hill to implement watershed restoration practices and water quality monitoring as a component of an EPA 319 project in the Bolin Creek Watershed. The purpose is to improve ecosystem health and water quality by restoring natural stream functions and treating stormwater runoff in degraded areas in the watershed. The work will be performed by a team of faculty, technicians, and students associated with the Department of Biological and Agricultural Engineering at North Carolina State University.
Task 1: Baldwin Park Stream Restoration
Stream restoration, including changes in channel cross-section, reducing bank slopes, creating a bankfull bench, and improving riffle and pool habitats will be designed and implemented on about 600 feet of stream (2 tributaries). Stream enhancement (vegetating the banks) will be designed and implemented on an additional 400 feet of the Chapel Hill tributary. Invasive plants (privet) will be removed at the restoration/enhancement sites. Three BMPs for handling street runoff will be placed at the upper ends of the streams to prevent degradation of the restored channels.
Task 2: Mill Race Tributary Erosion Control
Stream enhancements will include repairing two gullies by adding pipe to the existing stormwater outfalls and bringing the runoff to the bottom of hill and using a BMP to dissipate energy and allow infiltration. The outfall at the top of the subwatershed is to be retrofitted to reduce scour, permeable pavers (and other methods) have been suggested to replace the gravel sidewalks in that block to reduce the deposition of sand and gravel in the stream, correcting the undermining of the sanitary sewer crossing (possibly by installation of step-pools), and treatment of the sanitary sewer easement to stabilize the streambanks and reduce erosion. This project will also include assistance in planning and implementing kudzu eradication and re-planting with native vegetation at the site.
Task 3: Tanyard Branch Alternatives Analysis
This analysis will evaluate previously recommended projects in upper reaches of the Tanyard Branch watershed. Chapel Hill staff are aware of significant erosion occurring upstream just below a large stormwater outfall. The area draining to this outfall is approximately 98% impervious surface (all downtown Chapel Hill), and includes a historically-known spring that has since been piped. Staff concluded (and have observed) that the energy from this drainage could be sufficient to severely degrade any stream restoration or bank stabilization undertaken downstream. In order to address the high flows and prevent the “blow-out” of possible downstream BMPs and/or stream restorations, staff inquired with EPA about the use of an in-line BMP to control the flow and volume from this combined spring-stormwater system. Because it would be placed along a perennial stream it would need to meet requirements for 401/404 certification.
To meet 401/404 requirements for evaluating alternatives to putting a stormwater management device inline on a perennial stream, would be an analysis of alternatives for the management of runoff flow and volume in this subwatershed, using such methods as cisterns, green roofs, underground storage, etc. that would be appropriate for high-density urban situations, and comparing the costs for implementation of the needed amount of each BMP type to the cost of an in-line BMP at the stormwater outfall. This analysis would also review issues related to general public support, landowner cooperation, compatibility of local ordinances and development plans, and feasibility in general.
Task 4: Watershed Restoration Advising
NCSU faculty will provide technical advising on the following issues:
- BMP implementation, creating maintenance plans, etc.
- Assistance with writing a QAPP level 2
- Guidance on installation and monitoring of bank pins and scour chains, and other sediment/erosion measurement methods
- Advice for Carrboro for their 2 rain gardens
- Guidance/advice with developing Watershed Restoration Plan
- Guidance/advice on selecting and obtaining automated samplers with continuous stage measurement and establishing rating curves, in-situ temperature and DO probes, and setting up this equipment
- Guidance on the control/eradication of kudzu and privet. Guidance on park land management for optimal stormwater infiltration, building a healthy soil profile, reducing erosion, increasing soil cover, etc.
- Guidance on other sampling as needed