Creating an outlet to the Mississippi River in southern Washington County

In a county hemmed on both sides by the Mississippi and St. Croix Rivers, it may come as a surprise to some people that much of central Washington County is actually landlocked. In fact, most of our local Watershed Districts were originally formed not to deal with water quality issues, but to build infrastructure that carries water away from homes and businesses in landlocked areas during exceptionally wet years.

The Carnelian-Marine Watershed District, which later merged with the Marine Water Management Organization, formed in 1981 to address flooding concerns around Big Marine, Big Carnelian and Little Carnelian Lakes. The district constructed outlets and pipes to create an overflow pathway to the St. Croix River so that homes around these three lakes would no longer get flooded when lake levels rose. The Valley Branch Watershed District, established in 1968, spent its first 19 years completing a massive flood relief project that connects Silver Lake in North St. Paul, the Tri-Lakes, Lake Elmo and many smaller lakes in Lake Elmo and West Lakeland to the St. Croix River via a large pipe that travels alongside Hwy 94. Now, the South Washington Watershed District is midway through with a colossal project that will provide flood relief for southern Woodbury and northern Cottage Grove as those two communities continue to develop.

The Central Draw Storage Facility in June 2014. Often the area is completely dry.

Between Colby Lake in Woodbury and the Cottage Grove Ravine Regional Park, acres of farmland are quickly giving way to new roads, neighborhoods, buildings and businesses. But, there is not always enough room in every new neighborhood to absorb all of the runoff from rain and melting snow without flooding buildings and roads, especially during very wet months, like the spring and early summer of 2014. To address this problem, the South Washington Watershed District built a regional infiltration basin, called the Central Draw Storage Facility, which straddles the border between Woodbury and Cottage Grove. During spring snow melt and very heavy rains, the basin fills up with runoff as well as overflow water pumped from Baily Lake. It is capable of soaking up 1500 acre feet of water, which is enough to fill 740 Olympic sized swimming pools. Once Woodbury and Cottage Grove are fully developed, however, even this basin won’t have enough capacity to handle all of the runoff.

Matt Moore, SWWD District Administrator, shows the Washington County Water Consortium where new pipes are being laid for the overflow project.

Recently, South Washington Watershed District completed the first phase of a long-term project to eventually connect the Central Draw Storage Facility to the Mississippi River in southern Cottage Grove. Capitalizing on the opportunity to install stormwater pipes below ground during the realignment of Keats Ave., Military Road and 70th St. S, the district connected the existing infiltration basin to the Cottage Grove stormwater network and constructed a 6-foot diameter pipe leading to a new stormwater infiltration basin. Eventually, the watershed district plans to connect these new areas to Cottage Grove Ravine Lake, which overflows to East Ravine, a perennial stream that passes through 3M property to the Mississippi River.

Due to the massive scale of South Washington’s flood prevention project, they are completing their work incrementally, as development happens in Woodbury and Cottage Grove. The District is also coordinating with city and county parks and green space plans. The long-term vision is to link together trails, parks and other planned green spaces in southern Washington County and to allow water to flow overland, as it would in a perennial stream, in as many places as possible. The District also plans to work with Washington County Parks, 3M, and local non-profits to improve habitat and reduce erosion within Cottage Grove Ravine Regional Park and the East Ravine.