Lower North Fork Nancy Creek Streambank Restoration - Design

Purpose:

The design of the Streambank Restoration Project North Fork Nancy Creek from Murphey Candler Dam to Nancy Creek. The project addresses the segment of North Fork Nancy Creek just downstream of Murphey Candler Dam to the confluence with Nancy Creek in the City. The project includes restoration of 800 linear feet of impacted stream channel just upstream of the confluence with Nancy Creek.

SCOPE OF WORK:

This work is being undertaken for the purposes of stream repair and property protection. The entirety of the disturbance will occur on the City-owned Murphy Candler Park at 1551 West Nancy Creek Dr. The left and right banks will be sloped at a 3H:1V slope from approximate elevations 862 to 870. Additionally, several areas will have the existing slopes armored with tree revetments, secured with earth anchors. Existing fallen trees and the trees to be removed will be used for the revetments. Additionally, a J-Hook and rock vanes will be used to create a series of pools that will slow the average velocity and direct base flows towards the middle of the stream rather than towards the banks. Erosion control measures that will be incorporated will include coir log wattles staked along the toe of the slope and hydroseeding along left and right banks of the project area. The bank will be stabilized with live staking plantings.

Task 1 Collect Data Needed to Support Stream Restoration Design:

Additional data is needed to create a successful natural channel design, although data from the Nancy Creek Watershed Improvement Plans (WIP) can be leveraged. Conduct a topographic survey within the project limits. Survey should capture features such as property boundaries, specimen trees and wrested point of vegetation, stream channel cross-sections, and all utilities within the project limits. Deliverable will include two signed and sealed, by a professional land surveyor, paper copies and an electronic copy of the base map of all topographic and site survey data collected.

The drainage area upstream of the project was estimated as part of the WIP, but a more detailed assessment is required to feed the hydrologic/hydraulic analysis and the basic hydrologic calculations performed as part of the WIP will be expanded to determine the discharge during the design storms (i.e., 2, 5, 10, 25, 100). The modeling will also be used to verify the bankfull stage and bankfull discharge. Additional information includes stream velocity, shear stress and/or stream power versus stage or discharge may be needed for the design.

Vendor will deliver a summary of the data collected, and methods used to collect the data to be submitted to Georgia Environmental Protection Division.

Task 2 Community Group Outreach:

Facilitate a meeting with stakeholders to review the draft design with an opportunity for discussion. Where possible, the design will reflect input from the stakeholders.

Task 3 Stream Restoration Design and Permitting:

The design will be performed in two phases; an initial design (approximately 60% complete) and a final design (100%). The initial and final construction documents will follow City of Brookhaven, Dekalb County, and State of Georgia Standards and Specifications, as well as the Manual for Erosion and Sediment Control in Georgia, latest edition. The final design will be a set of plan sheets and specifications, with the final set stamped by a Professional Engineer. The plans and specifications will be bid-ready and used by the contractor to build the restoration project. The design will follow proven natural channel design methods. The plans should include (at a minimum) cover sheet, existing conditions, stream restoration layout, grading plan including profiles for the horizontal and vertical design components, sediment/erosion control plan, details for restoration project, permanent landscape plan specifying native grasses, shrubs, and tress and other drawings required for permitting. The plans are to present the cross sections as well as the location where those cross sections will be place, plotted as the proposed design versus the existing ground surface to clarify the cut and fill areas. The plans will also include the profile showing feature slopes for riffles and pools and the bankfull elevation. The plans will also include information on recommended in-stream structures to provide bank and bed stability. The design will also include plans for maintenance and monitoring the restored stream section. The vegetation maintenance aspect of these plans will rely on Appendix D of the WIP. Preliminary and final bid tabulation table will be required and shown on the plans.

Coordination of pre-submittal meetings with approving authorities will be part of this task. These will include but are not limited to the City of Brookhaven Planning Department, Georgia Department of Natural Resources, and the US Army Corps of Engineers. Construction easements will need to be obtained from the property owner to perform the construction work. This task will include preparing necessary easement documents. The City of Brookhaven staff will obtain signatures from the property owners. Native vegetation will be used with a blend of cover crops, live stakes, and if possible trees and shrubs to accelerate the vegetation. Specific plants species will be identified in the final design plans. The plantings and post-planting care will follow the SOPs in Appendix D of the WIP.

This project will require yearly monitoring and will require identification and location of permanent monitoring stations.

The plans and specifications will be developed to support the permitting process. All permitting is to be obtained for the construction of the project. At a minimum, permits required may include Federal, State, County, and Local permits such as Section 404/401 Clean Water Act Permits, Floodplain development permit, FEMA No-Impact or CLOMR/LOMR Certification, Erosion and Sediment Control, site plan approval, construction drawing approval, and others as necessary. Consultant to provide monthly design and permitting activity reports.

Task 4 Pre and Post-Construction Habitat Assessment:

Habitat assessments are planned for two locations; one within North Fork Nancy Creek, and one downstream of the project in Nancy Creek. The habitat assessments will follow the Georgia Environmental Protection Division’s Standard Operation Procedures (SOP) for Macroinvertebrate Biological Assessments for Wadable Streams in Georgia for high gradient streams. The post-construction assessments will be compared to the pre-construction assessments. The post-construction assessments are planned for approximately six months following completion of construction of the restoration project.