The St. George Technical High School Project

By John Phelps, Environmental Scientist

The St. George Technical High School located in Middletown, Delaware had a bioretention stormwater management facility was not functioning properly and needed multiple remediation services to bring it back to its as-built design. The 0.30 acre facility had problems from construction. The sediment forebay was installed improperly with the bottom elevation lower than the original design. One of the main drain pipes which connected the facility’s under drains to the outfalls was damaged during installation and an excessive amount of sediment and sand had entered the facility’s main bio basin and had clogged up much of the bio soil which prevented proper infiltration. Due to the existing deficiencies, the facility became overgrown with vegetation which further prevented the system from functioning properly.

SŌLitude Lake Management consulted with Delaware’s Department of Natural Resources and Environmental Control, Division of Watershed Stewardship Sediment and Stormwater Program Manager, Cheryl Gmuer to determine at what depth the existing bio soil was no longer viable. After six month of planning and cooperation from mother nature, the following remediation services were conducted by SŌLitude Lake Management: 1) All unwanted vegetation along with 350 cubic yards of sediment laden bio soil was removed and disposed of properly off site; 2) existing rip rap forebay was excavated down to underlying geotextile fabric; 3) failing under drain was excavated; 4) under drain was repaired; 5) new approved bio soil was brought to facility and raked throughout main bio basin; 6) rip rap forebay was reconstructed.

Overall, the project was a success. The facility is now functioning properly. Stormwater can now enter the facility and is distributed throughout the main bio basin at the designed rate. The clean bio soil allows the stormwater to properly infiltrate to the underlying drain pipes filtering out nutrients and pollutants before the water is discharged to an adjacent stream. Through proper annual maintenance the St. George Technical High School’s Bioretention stormwater management facility can function properly for years to come.