University of Maine Hydrological Analysis/BMP Implementation

CES was contracted to assist the University of Maine (UM) in comprehensively evaluating the existing stormwater management system serving drainage areas which encompass the developed area of the campus and covers approximately 625 total acres. The information provided is being used to help assess the stormwater runoff impacts of additional development within the specific drainage areas, and how continued growth impacts older stormwater conveyances both on the Campus and in the Town of Orono.

The model developed provides a functional baseline for assessing future development on the campus of UM. The stormwater modeling method allows critical areas of importance to be identified using a reach routing system of analysis. From the initial results, further detailed analyses can later be performed using the model developed to help with long term infrastructure planning and comprehensive stormwater management planning at UM.

CES performed the following services as part of the hydrological analysis of the developed campus area:

1. Stormwater Structure Survey: CES located and surveyed all known stormwater catch basins and culverts within the above indicated drainage areas to determine to the extent possible the elevation of the catch basins and the inverts, and sizes of the pipes in and out of the catch basins. Photogrametric survey techniques were used to update the topographic information in above mentioned drainage areas, as well as the location of catch basins and pertinent physical site features.

2. Drainage Area Determination: In order to properly analyze the stormwater management system, CES determined the drainage areas that provide the basis for the hydrologic analysis for this project. Within each drainage area, the stormwater infrastructure (e.g. catch basins, culverts, detention ponds, etc.) used to manage stormwater runoff was identified and included in the drainage maps.

3. Evaluation: CES evaluated the capacity of the existing stormwater management system utilizing the HydroCAD® Stormwater Modeling program. CES identified the reaches of the system that are currently under capacity on and off campus for 2, 5, 10, and 25 year storm events. All off-campus structures that could not accept a 2, 5, 10, and 25 year storm event have been identified. CES has been meeting with UM personnel to review the results and to develop strategies to both implement BMPs and determine approximately how much additional impervious area can be developed in each drainage area. CES and UM has been meeting with the MDEP to present the results and involve the MDEP in the selection of BMPs and review the additional impervious area each drainage area can accept.

4. BMP Implementation: Based on discussions with UM and DEP personnel, CES has prepared a table of proposed BMPs, project costs, and implementation schedule to construct off-campus improvement to structures that are currently in danger of flooding or damage. CES will meet with appropriate UM personnel to review and approve the BMP table before presenting to MDEP. CES will remain available to assist UM with exploring other storm water management scenarios, check the impact of future projects, and/or evaluate other means of diverting or handling stormwater on a case-by-case basis.