Hanahan Water Treatment Plant Drainage Improvements

Charleston Water System

Charleston Water System engaged Davis & Floyd to stabilize and support a 36” water main crossing of a tributary to the Goose Creek Reservoir, which was washed out during severe weather. Davis & Floyd also worked to develop an alternate roadway alignment for emergency access to the water plant.


Develop hydrologic analysis for the area served by the water main crossing

Design hydraulic model for existing and proposed conditions analysis of the crossing

Create a design for supporting the 36” water main and stabilizing a portion of the remaining embankment

Develop an alternate roadway alignment for emergency access to the water treatment plant

Provide topographic and boundary survey of the project site

Prepare construction documents for both the pipe support and alternate emergency assess roadway alignment

Provide document management and bidding services


Conveyance for the tributary was originally provided by corrugated metal pipe culverts through an embankment. Corrosion degraded the culvert envelope, and during severe weather conditions the culvert and embankment were washed out leaving the 36” water main exposed.

The failed embankment provided not only bedding and support for the 36” water main, but also emergency access to the water treatment plant in the event that the primary ingress/egress route was compromised.

Because the 36” water main is used for the transmission of finished water from the water treatment plant to customers and is a critical piece of infrastructure for Charleston Water System, it could only be shut down for short periods of time.

Proximity of high voltage electrical transmission lines and high-pressure gas main to the project site created a safety hazard.


This project will stabilize critical Charleston Water System infrastructure and restore emergency access to the Hanahan Water Treatment Plant.

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