Grassy swale helps CdA church handle stormwater, save money

Fifty-five-thousand square feet of asphalt made it easy to find a parking spot at Coeur d’Alene Assembly Church, but all that blacktop was costing the church a small fortune in stormwater fees.

When the city of Coeur d’Alene reinstated the fees last year, church officials were caught off guard by the $264 monthly bill. The assessment was based on the square footage of impervious surfaces on church property, which collected runoff that flowed into the city’s storm drains.

“It was an expense we hadn’t budgeted for,” said the Rev. Dan Christ, Coeur d’Alene Assembly’s lead pastor.

Fortunately, there was a solution. The church worked with city officials to install a grassy swale at the edge of its parking lot. The swale captures the runoff, allowing the water to filter into the ground. Coeur d’Alene Assembly spent about $5,000 on the project and lost seven parking spaces, but no longer has to pay stormwater fees.

Kim Harrington, city stormwater program manager, highlights the church as an example of how property owners can save money and improve water quality in Lake Coeur d’Alene.

Swales to capture runoff have been required for new development in Coeur d’Alene since 1994, but they can also be added to older developments like Coeur d’Alene Assembly, which was built in the 1950s.The city collects about $1 million per year in stormwater fees. The money helps maintain the storm drain system and pays for federally required water quality monitoring.

Property owners who keep their stormwater on site don’t have to pay the city fee, which ranges from about $4 per month for residential properties to hundreds of dollars per month for properties with large roofs, parking lots or other impervious surfaces. Swales also protect water quality in lakes and streams.

Rain and snowmelt pick up pollutants as they flow over pavement, including pesticides, fertilizers and oil residue. In Coeur d’Alene’s older neighborhoods, that water flows directly into storm drains that empty into Fernan Creek, Lake Coeur d’Alene and the Spokane River.

Urban runoff is a major polluter of waterways, said Dino Marshalonis, a technical adviser for the U.S. Environmental Protection Agency in Seattle. A parking lot, for instance, collects contaminants from automobiles, such as gasoline, heavy metals, antifreeze, oil and grease. None of that is good for water quality.

Swales, which are designed to mimic natural watershed processes, can keep those pollutants out of lakes and streams, Marshalonis said. The soil helps trap and treat pollutants as metals bond to organic material and hydrocarbons break down with exposure to sunlight, plants and microbes.

Allowing stormwater to gradually seep into the ground is also better than flooding streams with runoff, Marshalonis said.

Shane Roberts, a city public works inspector who’s also a deacon at Coeur d’Alene Assembly, oversaw the work at the church.

Rainwater collected from the church’s roof is piped directly into the ground, where it filters into the aquifer.

In addition, a swale was built at the edge of the church parking lot. Before the swale was installed, the water flowed across the sidewalk and into a city storm drain. Now it seeps into the swale. Grasses that will be planted this spring will help trap sediment as well as pollutants, Roberts said.

From a financial and environmental viewpoint, it was a good stewardship project, he said.