North Branch Drainage Study

The client had an inactive mine site where they were operating a treatment plant to treat acid mine drainage.  During large storm events, the steep slopes of the site caused rapid increases in the flow conveyed through the onsite drainage network.  These increases in flow resulted in sudden spikes in the flow rates entering the treatment plant.  This project was conducted to provide an evaluation of alternatives for reducing the peak flow rates during storm events that would allow the treatment plant to maintain operation within a preferred flow range during storms.

HMM was tasked with performing a hydraulic and hydrologic study of the site and providing specific alternatives for reducing peak flows at the treatment plant.  These alternatives included additional detention basins and the application of real time controls to better utilize storage available within the existing drainage network.  HMM also provided supplementary services including collecting the necessary flow monitoring and rainfall data to calibrate the hydraulic model.  In addition, HMM provided survey services of the various drainage paths throughout the site that forms the basis of the hydraulic model.

Project Highlights:

• Performed GPS surveying of open drainage channels and various culverts throughout the site
• Collected flow monitoring data using both weirs (open channel) and area-velocity meters (culverts) in an aggressive chemical environment
• Utilized the calibrated hydraulic model to evaluate various alternatives to reduce peak flows entering the treatment plant in addition to reducing the overall operational costs of the plant