Stormwater Solution Saves Project Costs

By Frank Birney | September 28, 2010

Balancing redevelopment with the environment is tough even when there's a billion dollars of private and public money for urban renewal. The downtown Silver Spring, Maryland, renewal project is found north of Washington, D.C., near the intersections of routes 29 and 97. Started in 1999 to combat urban sprawl, the joint venture by public and private organizations sought to rejuvenate the downtown economy and livability of a historic commercial center at the heart of the second-largest city in Maryland.

The city and developers, led by PFA Silver Spring, LC and owned by Foulger-Pratt Development, Inc. of Rockville, Md., wanted a street-friendly atmosphere reminiscent of the city's historic downtown character during the early to mid-20th century. To do so, they would need to preserve historic facades of buildings and landmarks, make the downtown pedestrian and bicycle-friendly and manage urban-polluted stormwater runoff for 20 acres of impermeable surface.

Although not an incorporated city, Silver Spring is one of the most important business and residential centers in the Washington, D.C., metropolitan area. Once a major shopping center in the 1950s and 1960s, the area is still among the wealthiest in the country, making it a sought-after location to live and work. However, by the 1990s the downtown area became a textbook example of urban blight and the businesses there suffered.

In 1999, Montgomery County led the joint Silver Spring Redevelopment project to bring back the city core as one of its smart growth initiatives. Focusing on renovation, restoration and sustainability, the effort showed how long-term solutions for complex interwoven issues such as economic growth, community revitalization and resource conservation work to the advantage of a city and its people. Part of protecting the area's natural resources included meeting the stormwater requirements for Chesapeake Bay and the Environmental Protection Agency (EPA).

Spanning more than seven years, the redevelopment continually changed throughout its design and construction. The stormwater plan was open-ended and flexible, according to Dave Kuykendall, senior permitting services specialist for Montgomery County.

Restoration of old buildings and limited space made the use of conventional best management practices (BMPs) such as detention ponds and infiltration basins impractical. They were either too costly, wouldn't fit into tight spaces or impacted the existing underground infrastructure. Instead, a series of traffic-bearing, underground stormwater filtration systems seemed better suited for the tight spaces on the site and provided more flexibility for redevelopment. So Loiederman Soltesz Associates incorporated a system using the Stormwater Management StormFilter® from CONTECH as the stormwater control solution and a BMP.

Originally the redevelopment plan divided the 20 downtown acres into eight sections, each needing its own stormwater management system. After installing two StormFilter systems, Loiederman and CONTECH stormwater consultants reviewed the overall runoff plan. They calculated a cost-benefit analysis of the remaining area, and found the slope was ideal for a less costly, end-of-pipe solution. Installed on the eastern edge of the development near a parking building at Town Square and Ellsworth Ave., it would replace the remaining systems.

The end-of-pipe solution saved almost half the cost of the original plan. The ability to change the stormwater plan saved time finding existing underground water, sanitation, electric, and telecommunications lines. It also reduced the possibility of accidental damage to any of these utilities. For subcontractors, it improved site safety and removed the added coordination of working around open holes. The end-of-pipe solution also tapped into an existing 24-inch sanitary system, minimizing the impact on in-ground utilities while meeting stormwater quality needs.

The field-proven performance of the StormFilter and its approval as a stand-alone stormwater treatment system by hundreds of regulatory agencies nationwide made it ideal as the city's end-of-pipe solution. The city installed three culvert vaults holding 358 cartridges near the parking structure. The system filters urban runoff through a naturally occurring puffed volcanic ash media called perlite. Perlite meets stringent regulatory demands and targets a full range of urban runoff pollutants, including total suspended solids (TSS), soluble heavy metals, oil and grease, and total nutrients. A patented siphon-actuated surface cleaning system prevents surface blinding and extends the cartridge life cycle and maintenance intervals. Maintenance crews can easily clean the vaults either manually or using a siphon truck.

The end-of-pipe StormFilter system proved so effective that Loiederman Soltesz Associates won an award from the secretary of the Maryland Department of Natural Resources for its effort for lessening environmental impacts, protecting natural resources and promoting sustainable communities through building and design techniques.

Silver Spring's commitment to redevelopment and an environmentally sound stormwater solution has revitalized its downtown core. Projects are currently open or under construction to expand new retail spaces, restaurants, office space, lodging, and residential development. Some of the completed Silver Spring revitalization accomplishments include preserving historic shop facades and landmarks, creating public spaces such as pocket-parks, increasing pedestrian and bicycle access, redesigning of parking facilities, and installing an effective stormwater management system. To continue funding its stormwater maintenance, Montgomery County recently has levied a $38 fee on each taxpayer once a year. It's among the first in the country to do so.