Thomas & Hutton was retained to provide design, permitting, bid, and construction-related services for the first phase of improvements in the combined Forest Acres/5th Avenue drainage basin in the historic Maryville and Forest Acres neighborhoods in the West Ashley area of Charleston, South Carolina. The improvements were based on findings from a study previously completed in the same year by Thomas & Hutton. The project included the survey, design, and permitting to increase the basin’s outfall capacity and to eliminate the need for the existing stormwater pump station located near the intersection of Playground Road and the West Ashley Bikeway.
The drainage improvement project extended from Playground Road, southeast across Magnolia Road, St. Andrews Boulevard, and 5th Avenue. The improvements included the replacement of an existing stormwater pump station and forcemain with over 2,500 linear feet of box culvert improvements, 2,000 linear feet of channel improvements, and improvements to various secondary systems in the 450-acre watershed. In addition to providing survey, design, permitting, and construction administration services for the approximately $10 million construction contract, Thomas & Hutton provided public outreach and communication services, coordinated independent laboratory QA/QC testing and vibration monitoring, and Stormwater Pollution Prevention Plan (SWPPP) inspections. These services were all a part of Thomas & Hutton’s comprehensive involvement in this project.
Based on the analysis of various factors, including drainage and flood control effectiveness, life cycle costs, environmental impacts, and others, Thomas & Hutton’s original recommended that the City implement a gravity drainage option as the Phase 1 improvements for the basins. The gravity drainage option resulted in significant capital and life cycle cost savings for the City over the previously proposed pump station option.
These drainage improvements address the flooding issues that made roads impassable and, in some cases, caused significant damage to some homes. This system offers the same level of protection to the properties in the drainage basin as a modern pumped system would but has the added benefit of not relying on electric power – therefore, if power is lost during a rain event, the system will continue to drain under the force of gravity. The improvements also include handrails, where necessary, for safety precautions, a debris screen at the 5th Avenue culvert crossing to keep trash from entering the Ashley River, and an articulated block mat outfall at the 5th Avenue culvert crossing to prevent potential erosion and minimize impact to adjacent wetlands. The final product will also include a more aesthetically pleasing site with a paved bike path and new landscaping.
Forest Acres Drainage Improvements Study and Phase I Design received an APWA South Carolina Project of the Year Award in the Environmental – Large Projects category.