Old Village Watershed Study
Mount Pleasant, SC
The Town of Mount Pleasant retained Thomas & Hutton to complete Phase 1 of a comprehensive study of the Old Village Watershed. The study was commissioned to study the hydrology and hydraulics of the area, assess and make a formal report on the conditions of the Town’s existing drainage system, and recommend infrastructure improvements.
The study area is approximately 975 acres and is bounded by the Charleston Harbor on the south, the marshes of the Intracoastal Waterway (ICWW) on the east, Ben Sawyer Boulevard to the north, and Coleman Boulevard and Shem Creek to the west. The Old Village study area has been identified as part of the Town’s stormwater infrastructure in need of critical repair due to system/structural failures, issues related to tidal influences and sea level rise, and a lack of full engineering design at the time it was constructed. Before repairs and improvements to the stormwater infrastructure can be designed and constructed, an assessment of the existing drainage systems and problems needed to be performed.
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The study included the following tasks:
- Data collection, including the Town’s existing GIS stormwater inventory database, as-built drawings, construction permits, drainage service requests, and FEMA claims information
- Field inspections/survey to confirm/refine basin delineations and the existing stormwater inventory
- Utilizing information from the data collection exercise, field inspections, and research of available topographic, soils, land-use and tidal data, a ranking system resulted in the selection of two of the identified watersheds with the most critical needs for more detailed analysis
- A full stormwater system assessment to determine the existing conditions and level of service (LOS) in the two selected watersheds
- A future conditions assessment to determine the potential future level of service of the stormwater infrastructure based on the estimate of redevelopment in the study area and incorporating researched changes in rainfall data and estimated projections on sea level rise
- Development of existing and future conditions hydrologic/hydraulic models
- Recommendations on drainage improvement scenarios for multiple design storm events
- An opinion of probable costs for stormwater system improvements to achieve the level of service desired by the Town
- Alternative improvement projects identified for several other basins in the overall Old Village watershed
- Recommendations on inspection and maintenance schedules, as well as the education of property owners, to minimize the potential of the blocking or filling of stormwater system components with sediment and debris and ultimately reducing the number of complaints and service requests
Based on the results of the Old Village Watershed Study, Thomas & Hutton proposed drainage infrastructure improvement projects (with resulting costs) and was recently selected to perform the surveying, engineering, permitting, and construction oversight for these projects.
