The City of Buchanan had been considering improvements to McCoy Creek for over a decade. Local fisherman wanted the City to improve the fish habitat by removing a dam and adding riffles (shallow, rocky areas) and lunkers (wooden structures under stream banks). The Mill Race Restoration group wanted to restore the Pears Mill to operation, which required restoring the mill race to its previous depth and location.
The City worked with a landscape architect to create a plan that would meet the goals of both groups. The project includes:
- Excavating the mill race to its previous grade
- Removing the dam and nearby duck pond
The project also included various improvements to McCoy Creek, including the removal of a dam, erosion protection, and the addition of lunkers. To operate the Pears Mill, the old Mill Race had to be excavated to its previous grade. The dam removal also removed the existing Duck Pond; however, this area still provides storage during a flood. The Mill Race excavation creates a constant flow split for which the hydraulics are critical. During low flows, McCoy Creek must maintain adequate flows for fish habitat while allowing flow to the Pears Mill. During high flows, property must not be placed in more risk to flooding than at present. Prein&Newhof was hired to review the project design and assist with obtaining a permit for construction. A floodplain permit and Inland Lakes and Streams Permit (Parts 31 and 301) were required. To obtain the necessary permit, modeling of McCoy Creek and the Mill Race using HEC–RAS was needed, as well as the Duck Pond. Because of the dam removal, a new channel near the Duck Pond would convey flow and the overall flood elevations will be reduced.
At the diversion for McCoy Creek and the Mill Race, the hydraulic analysis was more complex. This is particular difficult to evaluate since the plan was initially to provide a junction box for controlling low flows. After several iterations, three options were prepared for consideration by the City. Each of these options called for the removal of existing curbing at the diversion for McCoy Creek, and construction of a riffle for improved fish habitat. Prein&Newhof evaluated the design and potential options and made recommendations to increase the potential to obtain the necessary permits. This project required regular communication with City officials and with the MDEQ, as well as communication with the designers and MDNRE. The success of the project, given the complex nature and extended schedule, was due primarily to good communication with all. P&N developed a hydraulic model of the flow diversion and duck pond dam to identify the impacts of the proposed design. Based on the model, P&N made modifications to the design and prepared design drawings of the McCoy Creek / Mill Race diversion. P&N also designed erosion control systems/structures at several locations. The designer used no standard engineering techniques. P&N worked to minimize changes to the design in a cost-effective manner to obtain MDEQ approval. P&N provided a cost-effective effort to obtain the permits. P&N obtained the required floodplain permit and provided construction observation to make sure the project was completed as required.