Slow in the Land of Speed

Landscaping at the Village of Slinger (Wis.) Wastewater Treatment Plant provides eye appeal and adds a level of protection for surrounding wetlands

In a town whose speedway has given birth to some of auto racing’s rising stars for the past 60 years, you might not expect a treatment plant upgrade to aim to slow things down. But that’s exactly what happened when the Village of Slinger, Wis., renovated its 26-year-old facility.

Buildings were retrofitted to slow their energy consumption. Natural plantings slow maintenance requirements. A vegetated berm and spillway slow surface runoff to nearby wetlands. Natural detention basins detain overflow and provide filtration. And modern lighting slows the deterioration of night sky views in the village’s rural surroundings.

Protecting a lake

Situated on roughly 6 acres, the Slinger Wastewater Treatment Plant was the state’s first orbal oxidation ditch system, designed by the Ruekert/Mielke engineering firm in 1980. When the plant reached functional capacity, the village embarked on a major upgrade with the same firm in July 2006.

The upgrade doubled capacity to 1.5 mgd. Heading the project were Greg Moser, superintendent of utilities, and James Haggerty, P.E., village engineer and director of public works. The $7.9 million renovation was completed in January 2009.

The plant is surrounded by wetlands at the headwaters of the Rubicon River and discharges to a tributary. Permit parameters are strict because the plant also protects popular Pike Lake and Pike Lake State Park, a few miles downstream.

Capturing runoff

At the facility entrance, two infiltration basins planted with a prairie mix of natural grasses and wildflowers detain water up to 24 hours before it percolates into the ground. The system functions as a rain garden, handling roof flow from plant buildings and runoff from the parking lot and lawns.

If runoff exceeds the soil infiltration rate, it can spill over into the wetland, so a vegetated berm and spillway were designed to slow that flow. As the detention pond fills, overflow moves through a landscaped weir engineered into the berm. Once it passes through this square-shaped notch, it is filtered through a channel planted with turf lawn, which plant staff members mow regularly.

Another visible feature of the plant is a solar panel array mounted on the south-facing, asphalt-shingled roof of the new Return Activated Sludge building. In a triangular configuration 38 feet wide at the base, the 4.5-kW array stands 10 feet high. It produces 6,000 kWh.

The system serves as an educational tool as well as an energy saver. “We own our own municipal electric utility,” Haggerty says. “We have a test project going with these solar panels to show school groups that we can produce our own energy, right here on site, and put it back into the grid.”

This process is monitored via Web-based software called Solar Plant Vision (Fat Spaniel Technologies). Visitors can watch the readout on Internet-connected computers. The software tracks the flow of electricity back into the utility system.

Controlling light pollution

Some of the electricity feeds new exterior light fixtures designed to minimize light pollution: Residents moving to rural areas value a dark night sky. The fixtures have directional hoods that focus light downward.

The public was invited to an Open House event in September 2009. About 50 residents attended, Haggerty recalls. “We gave tours and got very positive response. They appreciated our foresight in planning the highest quality into our renovation. They seemed satisfied that we’re looking out for the best interests of the community.”



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