When Mt. Zion Elementary School in Clayton County Georgia, opened its doors in 1976, there were only 31 classrooms for its 800 students and 40 faculty members. With continued growth, today the school houses almost 1150 students and a faculty of more than one hundred.
The school received a facelift during the 2003-2004 school year with renovations to the entire facility, one phase at a time. The renovation resulted in a brand new interior and a much improved traffic flow during arrival and dismissal. It then became clear to officials that it was time to focus on the outside of the school, and attention was turned to the school’s parking facilities. They concluded an expansion was in order to accommodate the ever-growing faculty and traffic for pick-ups and drop-offs.
Stormwater regulations in Jonesboro, GA, require an 80% reduction of solids in runoff from a design storm. For this site, 1.2 inches of rainfall would need to be treated. Oil and grease were pollutants of concern at the site, due to the steady stream of automobiles. Stormwater detention was also required. The design engineer on the project, Carter & Sloope, Inc., had worked with Contech previously, and contacted staff engineers to determine the best solution.
The Vortechs system, a hydrodynamic separator that removes finer sediment, particles, free oil, and debris from stormwater runoff, was selected for treatment. On this site, a model 5000 will treat flows up to 8.5 cfs, as required by regulations. If storm intensity exceeds the design storm, higher flows are directed around treatment by a StormGate system, also available from Contech. These infrequent flows are discharged directly into the detention system. The StormGate also directs treated flow from the Vortechs system into the detention system.
In order to maximize the parking area, design engineers chose an underground detention system rather than an above ground pond. The large area of impervious surface meant a significant volume of runoff would need to be stored, and a corrugated metal pipe (CMP) system ended up being the most economical. The system contained 1,350 linear feet of 60-inch diameter Aluminized Type 2 pipe, and is able to detain almost 25,000 cubic feet of water.
Being able to easily maintain the stormwater management system was important to the clients. The shallow profile of the Vortechs system allows for easy inspection and unobstructed maintenance access. Installing treatment upstream of the detention significantly decreases maintenance requirements for the CMP system, as the majority of solids will be removed prior to discharge. When maintenance is required, design engineers incorporated easy access to the system. CMP manhole access risers with permanent welded ladders were connected to precast catch basins above the detention system.
For George Forum Grading & Hauling, project manager, purchasing from Contech made their job easy because of the ability to purchase all products from one source rather than having to deal with multiple companies. With extensive product knowledge and selection, they could be sure that the most cost-effective solution was chosen. In addition, the speed of execution with precasters and the fabrication plant allowed them to meet project deadlines.
Contech excelled on the project by providing solutions for water quantity as well as for quality. The Stormwater team did an excellent job of coordinating drawing submittals in order to present Mt. Zion Elementary School with a complete stormwater design solution.