PROJECT SHOWCASE

Underground Detention System
Gloucester, MA

Installation: Gloucester Crossing - 200,000 sf. grocery-anchored development. Gloucester, MA

Civil Engineer: RJ O’Connell & Associates, Stoneham, MA

Site Contractor: McManus Excavating, Northborough, MA

Structure Description
This project consisted of 4 Underground Detention Area Precast Concrete Galley Chambers. The largest Detention Area (Storage Area #3A) used 1,100 Galleys for a total storage of 90,000 cubic feet. System #3A is rectangular in shape, and is 25 chambers wide by 44 chambers long. Each chamber is 4’ long x 4’ wide x 51” high (50 cf chamber) with an installed storage capacity of 70 cubic feet with 6” stone below. Stone above the chamber is not required to maintain strength and stability. Because of site conditions this project required more stone below the chambers giving an average storage of 82 cubic feet per chamber.

Comments
The above project was initially designed with a 48” diameter HDPE (a competing product), an expensive manifold design, and a larger footprint with more cover than required by Precast Concrete Chambers to maintain H-20 Loading. The contractor chose to use Precast Concrete Galleys in order to reduce the cost as well as complete the project much quicker. The Precast Concrete Galley system had an overall footprint 15% smaller than the original design - saving stone, excavation and backfill as well as time - while still meeting the designed storage capacity the Engineer required.