By Norwalk (CT) Mayor Richard A. Moccia
March 10, 2008

The Norwalk “Filter Demonstration Project” supercedes an earlier local initiative spawned in the early 1990s as a result of state and local concern about the quality of stormwater entering the Norwalk River and Harbor and ultimately into Long Island Sound. Norwalk has a reputation as an environmentally progressive community. The city area is 36.3 square miles (13 of which are water surface) with 255 miles of roads, 9,000 (plus) catch basins, 200 miles of storm drainage pipes and 215 known outfalls into Norwalk Harbor. The underground infrastructure is aging and has been undergoing repair and replacement over the last several decades. The initiative was spurred by concern over the recreational use of riverfront beaches, preservation of an active shellfishing industry in the Norwalk Harbor area that adds to the local economy and represents a proud local heritage, and an overall concern with the health of Long Island Sound.

The goal of the initiative was to reduce contaminants in the urban runoff. The initial plan relied primarily on a technology approach involving traditional hydrodynamic units (large concrete box structures placed underground to capture sediment and debris). The units would be sited in strategic areas, in combination with increased street sweeping, to capture and remove sediment and debris.

Back in the 1990s, this strategy was certainly an improvement over uncontrolled runoff. This initial project plan stalled due to fatal flaws that became apparent. The vortechnic units were never installed because it was very difficult to find sites that wouldn’t interfere with underground utilities in place. Also, the economics of the strategy were troublesome. The units cost about $100,000 each and the cost effectiveness of contaminant removal was marginal. Participants in the project also expressed concern that the filtration strategy should be expanded to address a broader array of water quality contaminates such as heavy metals, oils and grease.

Rather than abandon the effort entirely, it formed the basis for an intelligent design strategy to recast the project to accomplish more. A number of individuals and organizations came together to develop the Filter Demonstration Project, kicked-off in November 2004. Norwalk planned this new approach with: the US EPA, the Connecticut Department of Environmental Protection, the Maritime Aquarium at Norwalk, the Norwalk River Watershed Initiative, the Fairfield County Community Foundation, and others. Senator Joe Lieberman (CT) won a $400,000 grant for the project. AbTech Industries provided the technology solution- the Ultra Urban Smart Sponge. The Smart Sponge is essentially a semi'soft filter designed to absorb and remove bacteria, hydrocarbons, oils and greases, as well as sediment and debris. The filters can be easily sited in the urban environment (in catch basins). They are relatively inexpensive, ranging from $600 to $850 per installation site, and have a useful life of three to five years.

The Filter Demonstration Project has shown the approach to be effective and is now a Best Practice gaining popularity in the region. Testing was conducted in two watershed areas in Norwalk: 275 filter structures containing the Smart Sponge were sited in one area (the test area); the contiguous control area included 60 catch basins. Each area had its own single discharge sub-basin (outfall) into Norwalk Harbor so measurements could be taken. The test protocol included a baseline of testing for contaminants before installation, and testing after the filters and inserts were sited. Routine weights and contaminant testing was performed up until June 30, 2007 at the discharge outfalls. Additional testing was conducted in conjunction with rain events.

The results of the demonstration were impressive and suggest that the strategy could have a major positive impact. Bacteria removal (E. coli) averaged 75 percent, and ranged up to 95 percent in some places. Oil and grease removal reached 70 percent (1,200 gallons). Heavy metals that are normally found in urban runoff in minute concentrations, including copper, titanium and zinc were removed by the Smart Sponge. An additional and significant accomplishment was 19 tons (13 cubic yards) of sediment and debris were removed by the filters.

The Demonstration Project was a small test with positive effects achieving multiple public and environmental benefits. Norwalk realized cost-avoidance by preventing 13 cubic yards of sediment and debris from entering the Harbor. The substantial removal of E. coli bacteria helps protect our shellfishing economic activity and has a salutary effect on the two oyster hatcheries in the city.

The environmental benefits are impressive as well. The Norwalk River and Harbor are swimmable areas. The beachfront is dotted with both public and private recreational areas where primary human water contact is a valued amenity in our community. It adds to property values and increases the quality of life for our residents. Many of these same benefits extend to Long Island Sound because the Norwalk River feeds directly into the Sound. Preventing bacteria, heavy metals, grease and oil from entering the Sound helps protect a valuable yet vulnerable ecosystem that millions of people, as well as wildlife and other species, depend on and enjoy.

This Demonstration Project shows on a small scale what can be done on a larger scale to prevent urban runoff from impairing streams, lakes and estuaries around the nation. It can be cost-effective, and it requires local initiative with cooperation from state and regional authorities. But the bottom line is that Norwalk took action to make it happen.

For more information on Norwalk's Filter Demonstration Project, contact Hal Alvord, Director, Norwalk Department of Public Works, (203) 854-7791, or E-mail halvord@norwalkct.org or Michael Yeosock, Senior Engineer, yeosock@norwalkct.org.