Stormwater Engineers Collaborate for Cost-Effective Solutions in Charleston, South Carolina
“Charleston Harbor is one of the finest natural harbors on the Atlantic Coast. It is one of the most important economic assets of the State of South Carolina serving both commercial and military navigation”1, as stated in a 1966 Charleston Harbor Water Quality Study. The study goes on to say, “The City of Charleston on the southeast coast of South Carolina, was built on the peninsula between Ashley and Cooper Rivers, and its harbor has been a center of commerce since early colonial days.”1
This aged EPA study is a reminder of the challenges still ahead for South Carolina’s shoreline. Land development and large commercial or industrial sites, in particular, can each have exponential effects on nature’s own management of rainfall and runoff. Introducing new impervious spaces create immediate point sources for pollution which could contribute to nasty algae blooms and environmental deterioration spreading out from the shores, and damaging the local tourism industry.
Charleston Steel & Metal Company’s business is already an “earth-friendly” industry. They recycle massive amounts of material to reduce waste, and preserve energy and natural resources. Their environmentally conscious maxim is now expanding into the development of their newest commercial site located at 107 Brigade Street in Charleston, South Carolina. Brigade Street is within reach of the Cooper River, an area with a rich history of tourism and wildlife, at the mouth of Charleston Harbor. The known groundwater elevations are very shallow, and Thomas & Hutton, the engineer of record, was presented with a design challenge. Are there simple and applicable Best Management Practices that could quickly address a high water table, minimal space, and strict regulations on a swale and protected rivers receiving the site’s runoff?
There are heightened stormwater concerns and regulations around development sites within Charleston Harbor; and this site’s pollutants of concern are TSS, phosphorus, and heavy metals. Beyond the regulations, any stormwater system(s) would have to confront high water tables – adjusting to accommodate high flow rates at a very shallow depth. This was the key hurdle. The collection of challenges is difficult to address, but finding a system that could take more flow at that height was essential.
Beyond that, engineers had to also design within a small footprint, keep costs down, and source systems that have proven treatment and records of requiring minimal maintenance. “Many stormwater products can’t effectively operate at this flow rate in such a shallow restriction, and would cost too much to install and maintain. They’re not economically viable for new developments with site restrictions, space limitations, and local regulations”, states Scott Sertich, Engineering Manager for Bio Clean. Moreover, the stormwater system would need verified/proven data showing high removal rates of Total Suspended Solids (TSS), phosphorus and heavy metals.
The engineer at Thomas & Hutton in Mt. Pleasant, South Carolina and the Bio Clean engineering team worked closely and efficiently to fine-tune each design with simple solutions. First, the Kraken™ Membrane Filter was a clear candidate for its proven ability to sit within relatively small footprints and treat ‘monster’ flow rates as well as large pollution concentrations of TSS (89%), trash, phosphorus, and metals; while still needing far less maintenance service than other filtration devices. The Kraken™ filters are washable and reusable; easy and inexpensive to maintain. The Kraken™ Filter provides higher treatment flow rates in a smaller footprint. Each 7.5 inch diameter filter cartridge has 170 sq. ft. of media surface area. With this much surface, the Kraken™ can operate at a loading rate of only 0.05 gpm/sq. ft. of media surface area.
The second system to address the site’s needs was the SciClone™ Hydrodynamic Separator. The SciClone™ will treat up to 80% TSS, and it is known for its simple and low-cost installation, while the NJCAT verification predicted a, ”Maintenance frequency for all SciClone™ models is 96 months.”
The Bio Clean™ engineering team worked quickly with Thomas & Hutton to solve challenging configuration requests, variations from the standard designs that the systems and Bio Clean’s team could solve without incurring any extra costs.
The Kraken™ and SciClone™ accommodated requests for pipes in configurations different than 180 degrees from each other, ie – an inlet pipe through the sidewall of a Kraken™, or an outlet pipe at 90 degrees in a SciClone™.
Bio Clean engineers were also able to:
- Lower the rim on the SciClone™ to match finished grade.
- Add an anti-flotation collar and thicken the bases of the Kraken™ and SciClone™ in order to overcome buoyancy issues due to high local groundwater.
- Steepen the angle of the inlet pipe into the SciClone™ so that the inlet and outlet pipes would be at the same elevation.
- Shift the Kraken™ Membrane Filters to one side of the vault, accommodating two inlet pipes, and saving the developer an added cost of a junction box.
- Work carefully with the engineer to find finished grade, top of concrete, and pipe elevations. This allowed the Kraken™ to fit into the site, function properly, and provide access for maintenance.
Southeastern coastlines, northern lakes, and western rivers; regardless of the challenges and degree of sensitivity on each water body, resourceful collaboration and versatile stormwater solutions will always have success. For Charleston, limited space, high water tables, and other unique requirements were efficiently overcome with experienced teams of stormwater and engineering experts.
- EPA Website: Charleston Harbor Water Quality Study – https://nepis.epa.gov
- Wikipedia: Charleston Harbor – https://en.wikipedia.org/wiki/Charleston_Harbor
- Charleston Steel & Metal Co. – http://www.charlestonsteelandmetal.com/about-us
The Kraken™ Filter Advantages
The Kraken™ is an efficiently engineered stormwater membrane filter that provides high flow rates and over 170 sq.ft. of surface area.This much filter surface area allows it to operate at a loading rate of only 0.05 gpm per square foot, to ensure maximum performance and minimum maintenance. The Kraken™ Filter’s low loading rate allows it to keep maintenance needs low and prevent clogging issues often found in other filter systems advertising high loading rates.
- Small Footprint Reduces Installation Costs
- No Deep Sump Chamber Reduces Costs
- Reusable Cartridges Are Easily Cleaned
- Fast & Simple Maintenance
- Clean Chamber Easily with a Standard Vacuum Truck