Valley Creek Road Infiltration System

A stormwater treatment system catches runoff before reaching Tamarack Swamp.

Prior to project construction, storm water from a 128-acre residential area drained untreated into Tamarack Swamp, a pristine natural area in Woodbury. This rare ecosystem showed signs of damage from nutrient-rich runoff draining into it.

The purpose of this project was to remove an estimated 60 percent of the total phosphorous load from stormwater draining through it prior to discharging into Tamarack Swamp. The removal of this phosphorous load is expected to have a positive long-term effect on the swamp. Its secondary purpose is to be a demonstration project for community officials, engineers, developers and the general public.

The Valley Creek Road Infiltration System features three different best management practices: a series of infiltration basins with check dams, a flow splitter with an infiltration basin, and an extended detention pond and filtration system. In addition, the project included stabilization of an eroded gully along the flow path to Tamarack Swamp.

The site was originally sown with a mixture of native and non-native grasses. Native trees and shrubs were planted by the District and City of Woodbury in 2005. Since 2008, additional native grasses and wildflowers have been seeded on the site. Control of exotic plants species, most notably thistle and reed canary grass, is being coordinated by District staff. Prescribed burns are used periodically to control weeds and to stimulate the native plant communities.

The shrub plantings have thrived here, providing sustenance for birds. Watch for cedar waxwings on red cedar in fall and highbush cranberry in the spring. Prairie grasses such as big and little bluestem, side oats grama and switchgrass are well established in many upland areas, and wetland species such as prairie cordgrass, lake sedge and blueflag iris surround the wet basins. We continue to work with the City of Woodbury and other partners to control invasive plants, and expand the prairie flowers and grasses.