Recharged Solution for Drainage Impacts

Shemin Nurseries, Inc. is a wholesale supplier of landscape and nursery supplies. The company also stocks a wide assortment of trees, shrubs, perennials, annuals and irrigation and drainage products. With twenty-eight locations across fourteen states, Shemin has been a top-performing wholesale landscape supply company for over fifty-five years.
UP CLOSE: SHEMIN NURSERIES
In 2008, the company pursued the subdivision of its entire Greenwich, Connecticut, based location, splitting the property into five lots with a private right-of-way roadway. Under this new arrangement, four lots would be marketed and sold as separate residential properties and the fifth would be the nursery. A significant portion of the property is wetlands; however, a majority of the upland areas will be part of the new residential lots. At the beginning of 2014, Shemin Nurseries implemented the design and began construction on the common improvements of the approved subdivision.
With the addition of the roadway and other impervious surfaces, Stamford, Connecticut, based Redniss & Mead, Inc. engineers needed to include a new stormwater management system to mitigate the increased stormwater runoff. In addition, the roadway leading into the development had to be mitigated for peak flows and stormwater volume. The project required that the team provide detention on the site using a subsurface stormwater management system.
RECHARGER 330XLHD CHAMBER
Given the requirements of the site, the team chose CULTEC, Inc.’s Recharger® 330XLHD, an efficient chamber that has a relatively low volume in the early stages of a storm. The chambers were supplied by the client, Shemin Landscape Supply, and installed by White Contractors of Old Greenwich, Connecticut.
A stormwater system, which includes 204 chambers, was placed beneath Shemin’s current employee parking lot of approximately fifty parking spaces. This location was chosen because during the approval process, the Town of Greenwich ruled that the wetlands were not to be used as a volume control function for the drainage.
“In the Town of Greenwich, we are particularly mindful of drainage impacts associated with development and while the Wetlands and Watercourses Agency always promotes natural alternatives to maintaining existing flow rates, we have been pleased with the results stemming from the growing use of recharge chambers,” says Michael Chambers, director of Greenwich’s  Wetlands and Watercourses Agency. “In an industry that is ever-evolving, recharge chambers appear to be a storage system that has remained the preferred means of controlling rates of runoff, and in this case, CULTEC’s chambers met our strict stormwater drainage requirements.”
“Of the 44-acre site, 19 percent is made up of wetlands, which encouraged us to consider a low-impact solution for the stormwater management system,” says Lou DiMarzo, P.E., Redniss & Mead. “The unique feature about this project is just how close those wetlands are to the development. We really took precautions to preserve the site from an environmental perspective.”
MAXIMUM CAPACITY, MINIMUM FOOTPRINT
CULTEC’s Recharger 330XLHD has a capacity of over 400 gallons (1514.16 liters), making it one of the largest CULTEC chambers available. The unit itself measures 52 inches wide by 30.5 inches high (1321 by 775 millimeters) and has an installed length of 7.5 feet (2.29 meters) long with a bare chamber capacity of 7.5 cubic feet per linear foot. The CULTEC system provides a total of 17,429 cubic feet (493.53 cubic meters) of storage, maximizing storage capacity within a small footprint to best satisfy the requirements of the site.
In addition, a Vortechs® Model 2000 and a VortSentry® HS unit produced by another manufacturer are placed upstream from the pipes leading to the CULTEC system. These oil-grit separators pre-treat stormwater runoff before it flows into the chambers using a cyclonic separation method to control pollution. Another two hydrodynamic separators will be placed in the roadway to provide pre-treatment for the pipes that will be in-letting into a rain garden and a surface water quality detention basin.
The CULTEC chambers are encased with an impervious liner supplied by LidTech to stop the system from infiltrating due to the presence of seasonal high ground-water. The liner is located beneath the CULTEC chambers and spans the entire width of the bed. In addition, CULTEC’s No. 410™ Filter Fabric encases the entire bed and prevents soil intrusion into the chamber bed.
RIGHT ON TIME
“One important consideration for this installation was the project timeline,” says Tom White, president and manager of field operations for White Contractors. “We needed to have the work done before the spring gardening season began, so the employees could use their parking lot and have access to the yard to start stocking supplies and plant material. Most of the work was completed in the company’s offseason, but that presented its own set of challenges because we had such a harsh winter. In the end, we were able to provide the client with a high-quality installation by the deadline.”
CULTEC manufactures several chamber sizes ranging from 8.5 to 48 inches (216 to 1219 millimeters) to accommodate almost any site parameter. The chambers’ perforated sidewalls and fully open bottoms promote maximum infiltration capability and allow for the transfer of high volumes of water at a low velocity.
In addition, CULTEC developed its own in-line side portal manifold system, which eliminates the need for a conventional pipe header system, and water quality unit for maintaining CULTEC chamber systems. CULTEC products are currently modeled in HydroCAD®, Bentley Systems, Inc.’s PondPack® V8i, Autodesk’s Storm & Sanitary Analysis in Civil 3D, and Streamline Technologies’ ICPR®. ■
About the Author
CULTEC’s technical staff offers free design assistance including preliminary calculations and job-specific CAD details. For additional information about Shemin Landscape Supply, visit www.shemin.net or follow them on Facebook. For more information about CULTEC’s stormwater chambers, call 203.775.4416 or visit www.cultec.com.