Driving along Lamar Ave. through Old Cottage Grove is like touring through the land that time forgot. On summer evenings, families gather at Lamar Fields for adult league softball games and you can still get darn cheap beer at the Boondock’s Bar. Most of the homes were built around the turn of the century – last century that is, and when the houses peter out, the woods and farm fields take over. Just two miles west and south, the scene is completely different. Modern houses line suburban cul de sacs and construction crews are hard at work making way for even more new development.
When the City of Cottage Grove built a state-of-the-art new City Hall three years ago, they chose a location at the top of Cottage Grove Ravine Park with an eye toward the future, knowing that the growing community of 35,000 would soon be spreading east and bridging the gap between old and new. Because Ravine Park contains unique habitat and a well-loved fishing lake, the city sought to minimize the environmental footprint of their new building and set a good example for how development could happen in the area. You’ll find only a small amount of lawn around the City Hall (most of the land on the property is native plantings that don’t require watering) and the city took the bold step of installing a rainwater collection and reuse system to provide water for irrigation as a way to both reduce groundwater use and minimize stormwater runoff to Ravine Lake.
Collecting and saving rainwater for later use is a practice that used to be common, back when Old Cottage Grove was just plain Cottage Grove. There was a time when every farm had a cistern to collect rainwater and people wouldn’t dream of pouring perfectly clean drinking water on the ground just to grow grass; after all, only the very rich had lawns then anyway. Ironically, water reuse projects are now considered cutting edge in Minnesota, with high visibility projects happening recently at the new Twins and Saints Stadiums, as well as at several local golf courses. A new dormitory at the University of Minnesota has even figured out a way to use stormwater runoff from the roof to flush toilets in the building.
Though the water reuse system at the Cottage Grove City Hall is simple in concept, it employs some fairly robust technology to ensure that the water is clean and free of harmful bacteria and pathogens. When it rains, water from the roof is directed into a 20,000 gallon tank underground. The water then passes through a filtration system that removes particles down to 5 microns in size (the size of a human red blood cell) and then an ultraviolet treatment unit that disinfects the water before it is used for irrigation.
The benefits of the rainwater reuse system are two-fold. First, it reduces the amount of potable water the city needs to use to irrigate lawns and gardens during the summer by up to 570,000 gallons. Second, it reduces the amount of water that runs off of the nearly one-acre rooftop, helping to protect the park and Ravine Lake from erosion and pollution due to increased rain runoff. The tank holds enough water to capture a one-inch rainfall.
As Cottage Grove continues to develop, City Engineer Jennifer Levitt hopes that more businesses will follow the city’s example and begin looking for ways to conserve groundwater resources and protect nearby lakes and the Mississippi River. “We would really like to see more businesses converting lawns to native landscaping or installing water reuse systems that make use of existing stormwater ponds to irrigate the grounds,” she said during a recent tour of the City Hall. Happily, help is available for water-friendly projects. Local watershed districts provide grants to help cover the costs of landscaping projects that reduce stormwater runoff and many are interested in helping to get more water reuse projects built in the area. South Washington Watershed District provided $50,000 in assistance for the Cottage Grove City Hall project and recently helped to fund water reuse projects at Prestwick and Eagle Valley Golf Courses in Woodbury as well. In Stillwater, the Washington Conservation District and Middle St. Croix Watershed Management Organization recently worked with DiaSorin (behind Valley Ridge Mall) to build a stormwater reuse system, and in Hugo, Rice Creek Watershed District spearheaded a large-scale project at Oneka Ridge Golf Course in 2014.
For more information about and examples of water reuse projects in Minnesota, check out the Metropolitan Council Stormwater Reuse Guide.