Seabrook Island Stormwater Drainage Study
Charleston County, SC
Water Resource

Thomas & Hutton assisted Seabrook Island Property Owners Association (SIPOA) to assess and analyze the stormwater management system within the private Seabrook Island community. The services provided include stormwater system inventory and condition assessment, GIS consulting, geodatabase development and population, hydraulic/hydrologic modeling, recommendations, and conceptual design of system improvements.


As part of the study, Thomas & Hutton collected and reviewed the SIPOA’s existing stormwater inventory GIS data, topographic data, a previous stormwater management study, stormwater outfall maps, stormwater pump station drawings, and specifications. A comprehensive review of the acquired data and previous studies were performed to identify key components for incorporation into the study and data gaps that should be addressed as part of this study.

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    Thomas & Hutton made full use of previously collected data and only recommended collecting additional data to supplement the SIPOA’s existing data if it was not previously addressed. To fill in some data gaps, Thomas & Hutton provided a survey-grade stormwater infrastructure inventory for nearly 500 additional stormwater structures to enhance the completeness and accuracy of the SIPOA’s existing inventory data. Structures are generally defined as a catch basin, inlet, junction box, outfall, or culvert. The stormwater inventory collected the following data:


    • Location
    • Type of structure
    • Number and direction of inlet and outlet pipes
    • Diameter and material of inlet and outlet pipes
    • Measurements for inverts
    • Condition assessment of the structure and connecting pipes
    • Observations regarding sediment build-up, trash accumulation, or erosion
    • issues
    • Survey-grade elevation for the top of each structure
    • Photographs


    Additionally, Thomas & Hutton conducted an assessment and inspection of the three existing stormwater pump stations to determine the condition, original design capacity, and recommendations for rehabilitation or upgrading. The previous information available, in combination with the Thomas & Hutton stormwater system inventory, was compiled by our GIS team and a geodatabase was developed. This geodatabase and other relevant information were utilized to perform hydrologic/hydraulic modeling to make recommendations for stormwater system improvements/rehabilitation

    Thomas & Hutton designed and permitted four of the recommended improvement projects (including a larger, more modern stormwater pump station), and is currently working with SIPOA to bid and construct the projects.