Innovations for Managing Stormwater Runoff

Record rainfall during this past spring and summer has served to point out the urgent need for managing stormwater runoff to improve water quality. The two interrelated issues are part of Smart, Green & Growing, an initiative introduced by Gov. Martin O’Malley in 2008 to foster a smarter, greener, more sustainable future for Maryland.

“We’ve got to have clean water,” stated Maryland Department of the Environment Secretary Robert M. Summers at the recent Clean Water Innovations Trade Show. “It really is the foundation of our economic health.

“The Chesapeake Bay is the geographic and economic center of our state. Our public health and economic health depend on clean water — it’s absolutely critical to our future,” he said.

Summers went on to say that most of the state’s urban areas were not designed with stormwater control plans and that restoring the Chesapeake Bay also protects groundwater and drinking water.

Seeking Solutions

Businesses, together with local governments, developers and other stakeholders, are working to find cost-effective and efficient ways to reduce polluted stormwater runoff and improve water quality. That push to enhance regional water quality has led to the development of a range of techniques, products and technologies.

Traditional impermeable pavements can create destructive, often toxic runoff. PaveDrain, a permeable articulating mat of concrete blocks marketed by Ernest Maier Inc., a Bladensburg masonry block manufacturer, creates an aesthetic and durable pavement integrated with a stone reservoir underneath that temporarily stores surface stormwater runoff and allows it to percolate into the subsoil. Gaps between the blocks channel the runoff and the block’s arched shape creates a reservoir for increased storage during heavy runoff events.

The system promotes a more natural, vertical infiltration path, recharges local groundwater, reduces first flush pollutants and filters out suspended sediments, according to the company.

Flexible Mats Provide Life-Cycle Savings

PaveDrain’s durability and savings in life-cycle stormwater management expenses can make it a very cost-effective alternative to traditional pavements. The flexible mats can be pre-assembled in a variety of configurations or customized for specific applications. Installation requires only conventional construction equipment.

Permeable surfaces help manage runoff, and several innovations can significantly increase a paved area’s permeability. Drain-Crete is a pervious concrete mix, supplied by Cheney Enterprises of Waldorf. Rain actually flows through the hard surface into an underlying layer of stone aggregate, then down to the soil. Reducing runoff can reduce the need for retention ponds, swales, storm sewers and other stormwater management devices.

The potential runoff actually replenishes groundwater, reducing impacts on local watersheds and satisfying regulatory requirements.

Drain-Crete also enables trees to receive more air and water at their roots and filters out water-borne pollutants. The material’s light color reflects light and heat, reducing the heat island effect by decreasing ambient temperatures and the need for artificial lighting. As with PaveDrain, Drain-Crete reduces a project’s initial costs by eliminating the need for stormwater management systems and can reduce long-term maintenance costs.

Old Is New

While PaveDrain and Drain-Crete aim to deal with larger scale stormwater runoff situations, the old-fashioned rain barrel has made a comeback for residential applications. RiverSides, a nonprofit Canadian organization dedicated to creating river-friendly communities, has started local production of 750 RiverSafe RainBarrels for the District of Columbia’s RiverSmart Homes program.

RiverSides aims to protect rivers by “reducing runoff pollution from individual properties through education and providing the tools people need to make the connection between personal action and healthy rivers.”

The District’s Department of Environment initially selected the innovative RiverSafe RainBarrel, manufactured at the Ellicott City facilities of C.R. Daniels, as its preferred residential cistern design in 2006. Hooked to a house’s rain gutter downspouts, rain barrels prevent stormwater pollution of local waterways, keep runoff out of municipal sewer systems and can provide a source of non-potable water for domestic use.

The barrels are custom designed from one-piece, UV-stabilized, recycled polyethylene and hold 132 gallons, more than twice the capacity of standard barrels.

“These are top-of-the-line barrels that capture two times the amount of roof runoff of a normal rain barrel,” said Steve Saari, watershed protection specialist for the D.C. Department of the Environment. “They are very well engineered, being more mosquito-proof and easier to maintain than conventional barrels.”

Waterwheel ‘Trash Mill’

Just as RiverSides’ rain barrels update a traditional technology, Clearwater Mills’ “trash mill” uses centuries-old technology to remove trash and debris that washes into stormwater systems then discharges into streams, rivers and eventually the Chesapeake Bay.

The “waterwheel powered trash interceptor” mounts on a small barge or float positioned in a river, outfall or other channel carrying stormwater runoff. Using an undershot waterwheel driven by the current, a conveyor lifts water-borne trash into a dumpster. Electricity from a solar panel or wind generator powers a pump to turn the waterwheel when the river is low.

The entire system is passive and amazingly effective. Positioned at the mouth of Baltimore’s Jones Falls, where the stream enters the Inner Harbor, the initial installation removed 800,000 pounds of trash during its eight-month application, according to Clearwater Mills’ Owner John Kellett,

F. Pierce Linaweaver, former director of Baltimore’s Department of Public Works, commented that: “Instead of skimmer boats or netting, the spinning waterwheel … continuously collects floating trash and debris into a hidden dumpster. It all but eliminates the unsightly view behind the more conventional boom across a stream outlet.”

Currently, the initial Clearwater Mills’ trash mill has been taken out of service by the city to re-engineer portions of the system. Baltimore’s Waterfront Partnership has requested returning the initial installation, and Kellett and the Maryland Port Administration are discussing two other locations for waterwheel powered debris collectors.