The Town of Merrimack had been experiencing flooding of roadside drainage swales with inundation of the roadway surface during and following major rainfall events which in turn contributed to roadside and roadway deterioration. The existing watershed consists is characterized as a residential development with drainage systems on the side streets that discharge in overland flow to Naticook Road.

Quantum Construction Consultants undertook a hydrologic study of the 65-acre urban watershed and developed hydraulic options Q2, Q10, Q25, and Q50 storm cycles for each of the subcatchment areas and provided an inlet capacity analysis for a number of grate designs with determination of inlet quantity required within the Naticook Roadway for each type of inlet that the Town was considering for installation. Working with the Town’s design team, three potential discharge locations were identified for the proposed drainage system, and options for pipe sizing were then undertaken dependent on location and number of discharge locations. The Town design team utilized this information to develop construction drawings and documents.