EcoScience Corporation was asked to model the stream and to determine water profiles for the 25-year flood.  ESC staff visited the site and determined the study parameters.  Available information from prior watershed studies was obtained and evaluated.  Field work was undertaken to determine steam cross sections, profile, and the elevation of the aerial sewer encasement pipe relative to the stream bed.   

Utilizing the collected data, a HEC-RAS model was developed to analyze the impacts of a 25-year storm.  Results from the model indicated that both the existing 20-inch encasement pipe and an exposed 10-inch sewer pipe, resulting from a proposed typical aerial crossing, would impede water flow during the 25-year storm.  To mitigate the impacts, the Town of Cary proposed to convert the encased crossing to a typical aerial crossing providing maximum clearance. 

The proposed mitigation alternative would increase the height of the crossing above the normal water level, would not impede stream flows under most normal conditions, and could be accomplished with very little, if any, stream disturbance.

Results of our study were sufficient to provide regulatory and resource agencies with a level of confidence that the aerial sewer with the proposed mitigation would not significantly impact water quality in the area.  Permits have been issued and the project is moving toward implementation.