A 70-acre recreation area with a large lake, wetlands and trails planned for the West End of Billings will be designed to double as a natural water treatment plant.
It will also help lessen the effects of large runoffs during periods of heavy rain.
Although such projects are common in places like Seattle, project manager Wade Irion said that for Montana, "it's pretty ground-breaking."
The Shiloh Conservation Area, as it will be known, is being developed by the city Public Works Department and will be designed by Dowl HKM, the engineering company where Irion works.
Public Works director Dave Mumford said the department started working on the concept three years ago and then purchased the parcel of open land, just under 70 acres, from Yellowstone County last year. Mumford said the city paid the county $513,000 using fee-generated storm water funds, which are used for maintenance and construction.
The land is just south of the Montana Sapphire subdivision at King Avenue West and Shiloh Road, where several big development projects are under way.
The Shiloh Conservation Area is now open grassland, a rectangle bordered on the north by the Shiloh Drain and on the south by Hogan's Slough. During rainstorms, large portions of the West End drain into those two ditches.
The man-made lakes in the conservation area will "take the head off the storms" by slowing down the flow of water, Mumford said. The water will also be cleansed to some extent during its passage through the area.
Sediments will settle out of the water in holding ponds, and as the water passes through wetlands basins, nutrients like phosphorous and nitrogen will be drawn out by vegetation. The water will undergo additional cleansing as it passes through the lake, possibly helped by man-made floating islands thick with vegetation.
The water from both ditches will come together at the southeastern corner of the conservation area. Eventually the water will flow south into Canyon Creek and then into the Yellowstone River.
Mumford said the conservation area will help the city meet strict new federal water standards for nutrients. Whether water in the valley goes through the city's water treatment plant or not, Mumford said, it ends up in the river and alters the level of nutrients there.
"We're trying to look at the wastewater in Billings as one big puddle," he said. "We look at it as an integrated system."
Plans also call for building a trail around the lake, which could be as large as Lake Josephine at Riverfront Park, Mumford said. The trail would be paved near the parking lot off Shiloh Road, Mumford said, but most of it would be soft trail. The lake will also be stocked with fish.
The whole project should end up costing about $2 million, Mumford said. Some of that cost could be offset by selling gravel on the property. Mumford said the hope is to sell the gravel all at once for use in one of the big construction projects scheduled in the King-Shiloh area. The city also needs to mine the gravel, of course, to create the man-made lake.
Irion, with Dowl HKM, said the project is in the information-gathering stage at this point. Working with a wetlands ecologist from Hamilton, Dowl HKM is gathering data on hydrology and the depth and nature of the water table, as well as doing baseline studies of water quality in the area.
Once all the information is in, he said, Dowl HKM can start working on details of the final design, probably by the end of this summer. Mumford said he'd like to see construction start during the following summer.
"It's kind of hard not to get excited about a nice, vegetated oasis in the middle of an urban area," he said.