South Washington Watershed District celebrates 25 years of flood prevention and habitat restoration

Volunteer event scheduled for Oct. 11 in Woodbury

Three years ago, volunteers gathered in a wind-swept field on a rainy spring day to plant 3000 young oak trees for a future oak savanna. The site – located on the border between Woodbury and Cottage Grove – is part of a conservation corridor created by South Washington Watershed District to infiltrate stormwater runoff and protect neighborhoods against flooding. This year, the district will celebrate its 25th Anniversary and the many flood-prevention, habitat restoration, and water-quality improvement projects accomplished over the years. True to form, watershed district staff and board members will gather with community partners and volunteers, once again in the prairie.

Three years ago, Great River Greening organized 200 volunteers to plant 3000 young oak trees in the South Washington conservation corridor between Woodbury and Cottage Grove.

South Washington is the largest watershed management organization in Washington County, covering portions of Oakdale, Lake Elmo, Woodbury, Cottage Grove, Newport, St. Paul Park, Grey Cloud Twp, Afton and Denmark Twp. The conservation corridor runs through the heart of the watershed district and is the result of two-decades of work to protect land-locked portions of Woodbury and Cottage Grove against flooding. The oak-savanna prairie on the Woodbury-Cottage Grove border also functions as a regional infiltration basin that collects stormwater runoff during spring snow melt and very heavy rains. It is capable of holding 1500 acre feet of water (enough to fill 740 Olympic sized swimming pools), most of which soaks into the ground to recharge groundwater aquifers. Eventually, the site will include a city park with an interpretive center and a hub for a regional trail from Lake Elmo Park Reserve to Cottage Grove Ravine Park.

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After large rainstorms, South Washington’s regional infiltration basin fills with water like a small lake. The water soaks into the ground within a few days.

Further south in Cottage Grove, the watershed district recently helped the county to complete a large reconstruction project at Cottage Grove Ravine Park that included new visitor facilities, protection against future flooding and erosion, and woodland habitat restoration. The park is an important part of South Washington Watershed District’s strategy to provide a safe pathway for floodwater from Woodbury and Cottage Grove to reach the Mississippi River during 100-year storm events. Other components of the multi-phase project have included installing large pipes beneath neighborhoods in northern Cottage Grove and stabilizing an intermittent stream that runs south across 3M land from Ravine Park to the Mississippi River.

In addition to its many projects within the conservation corridor, South Washington Watershed District has completed dozens of smaller habitat and water-quality improvement projects over the years. In northern Woodbury, the watershed district has worked with residents living near Colby and Powers Lakes to install raingardens and native shoreline plantings to capture stormwater runoff and keep nutrients from feeding algae in the lakes. In all its communities, the district has partnered with homeowners through its cost-share program to fund raingardens and native habitat plantings.

Colby Lake Raingardens, Woodbury, MN
This collage shows some of the many raingardens planted near Colby Lake in Woodbury with support from the South Washington Watershed District.

Last year, South Washington Watershed District worked with Washington County to build a new bridge over Grey Cloud Slough, which has allowed water to flow freely through the channel for the first time in 50 years. The project will help to reduce algae blooms, create better habitat for fish and wildlife, and provide new recreational opportunities in the area. The watershed district also plans to work with Great River Greening and riverfront landowners to restore two miles of shoreline and 100 acres of aquatic habitat in the channel. Grey Cloud Slough is part of the Mississippi National River and Recreation Area and is also a designated Minnesota State Water Trail.

Currently, South Washington Watershed District is working with Middleton Elementary and Lake Middle Schools in Woodbury to complete a “Campus Greening” project. With help from the watershed district, the schools have converted 15-acres of non-active use turf to prairie, engaged students to plant 200 trees in the spring, and will soon be building two outdoor classrooms. The project will reduce irrigation needs, capture more rainwater on-site, create habitat for birds and pollinators, and provide unique learning opportunities for the students.

Students helped to plant 200 trees as part of the “Campus Greening” project at Lake and Middleton Schools in Woodbury.

On Thursday, October 11, South Washington Watershed District will hold a small anniversary celebration at its oak-savanna prairie. The celebration will include a volunteer planting event from 2:30-4:30pm, followed by an informal open house from 4-6pm.

To sign-up for the Oct. 11 volunteer event, go to:

To learn more about the South Washington Watershed District and its projects, go to: