Viewpoint: Watershed’s work on 80th Street start of long-planned project

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For 20 years the South Washington Watershed District (SWWD) has studied, planned and designed a stormwater management/flood control system for the entire watershed. Now in 2012, the watershed district is constructing portions of the overflow that will expand on upstream sections constructed in 2003 and 2004. The next five years, the watershed district is making a significant capital investment to construct the Central Draw Storage Facility Overflow providing overflow and flood capacity for the northern watershed.

Southern portions of the watershed, including Cottage Grove, will also drain to and through the CDSF. Flood control, water quality improvements and stormwater management for new and existing development are primary goals of the CDSF overflow. Secondary goals will integrate with Cottage Grove, Woodbury and Washington County parks/open space and trail systems. The project area stretches from Bailey Lake in Woodbury, south to 70th Street in Cottage Grove through the East Ravine.

The requirement of cities to update their comprehensive plans in 2010 generated the opportunity to include projected 2030 land use and allowed final CDSF overflow design work to begin. As Cottage Grove and Woodbury move into the next phases of development, the need for this project increases. Development of the land around the CDSF will generate the need to provide a controlled overflow for excess stormwater and necessary flood protection. Washington County is preparing for increased traffic volumes by completing a needed safety and mobility project on county roads. This presented an excellent opportunity for the city, county and watershed district to partner on the project.

This background information sets the context for the city of Cottage Grove ED-P5 Water Quality Improvement/80th Street Box Culvert project. The city of Cottage Grove and the watershed district worked cooperatively to develop these stormwater improvements. The emergency overflow for the pond on the north side of 80th Street is 80th Street. The 80th Street project will improve pond operation and provide a designed emergency overflow protecting the integrity of the roadway. Installation of a box culvert under 80th Street accomplishes the emergency overflow. Reconfiguration of the pond upstream of the box culvert increases storage and stormwater rate control benefiting downstream drainage.

Additional ponding adjacent to Kingston Park will improve water quality in this drainage area, ultimately draining to the Mississippi River. These improvements will employ a new technology called Iron Sand Filter. This filter will increase removal efficiency of phosphorus from stormwater runoff.

This multi-purpose project constructs drainage improvements, water quality improvements, emergency overflow, outlet capacity and park/trail enhancements. Park enhancements use the box culvert as a pedestrian crossing creating free flow of pedestrian and bike traffic across 80th Street. This crossing establishes a needed safety improvement for the Cottage Grove park and trail system.

A drainage connection at 70th Street will be a critical element of the CDSF. This allows limited drainage capacity for the CDSF through Cottage Grove prior to the overflow being fully operational. It also gives operational flexibility once the overflow is completed. In cooperation with the city of Cottage Grove this connection will be made during 2013 street reconstruction projects.

The CDSF Overflow project is not a small project. It has been contemplated and anticipated by the Cities since 1980. When the cities established the watershed district in 1993, a major responsibility of the watershed district was to provide for this project. The SWWD has used the most current technology, data, and information to precisely plan and design the overflow project. Updated land use information in 2010 was the last puzzle piece that set final design of the overflow project in motion.

What is being constructed at 80th Street is the beginning of a long awaited project with the cooperation of many local government units.

Matt Moore is administrator of the South Washington Watershed District.

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