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Road realignment, a sediment pond and an unsuspected spring play part in county project

August 1st, 2007 / By: / Drainage Materials, Feature, Transportation

Introduction

This project showcases the use of a geosynthetic drainage system as an outfall for a sediment pond, and the accompanying road realignment, both built in Steele County, Minn., in 2006.

In this example, the land usage was primarily agricultural, the watershed approximately 90 acres, and the disturbed area about 5 acres. Because of the realignment of Dane Road and the location of the sediment pond, no additional right-of-way was required (Photo 1). Photo 1 | Photo courtesy of the Steele County Highway Department.

Photo 2 | Construction: As is common with many projects, utilities can be a problem. Photo courtesy of the Steele County Highway Department. Photo 3 | Field design and options: The elevation of the pond was based on the flow line of the culvert at the township road. The outfall was installed at 0.1ft grade. Photo courtesy of the Steele County Highway Department. Photo 4 | Installation of the geocomposite drain. Photo courtesy of the Steele County Highway Department. Photo 5 | Next, the drainage sheets were covered and the dike was compacted in preparation for riprap placement. Photo courtesy of the Steele County Highway Department. Photo 6 | Next, the drainage sheets were covered and the dike was compacted in preparation for riprap placement. Photo courtesy of the Steele County Highway Department. Photo 7 | Construction: One of the issues was not having a V-weir. Photo courtesy of the Steele County Highway Department. Photo 8 | Construction: Another issue was that the riprap was not yet completely installed, and the forecast was for rain the next day. Photo courtesy of the Steele County Highway Department. Photo 9 | First rain event: Of course, the rain did come. Stormwater overtopped the dike. The stormwater permit (NPDES) required basin design for a 2-year, 24-hour storm. Photo courtesy of the Steele County Highway Department. Photo 10  |  Water quality: This photo was taken 24 hours after the first rain event. Photo courtesy of the Steele County Highway Department. Photo 11 | Downstream water quality: In comparing the water quality, there was a definite difference. Photo courtesy of the Steele County Highway Department. Photo 12 | The sediment: How thick? This photo was taken 48 hours after the first rain event. Photo courtesy of the Steele County Highway Department. Photo 13 | Wow! A quarter-height’s worth of sediment for the pond’s first rain event! Photo courtesy of the Steele County Highway Department. Photo 14 | Rolling out the ECB: Finally, stabilization of the basin with MnDOT category-3 straw blanket. Photo courtesy of the Steele County Highway Department. Photo 15 | Rolling out the ECB: Finally, stabilization of the basin with MnDOT category-3 straw blanket. Photo courtesy of the Steele County Highway Department. Photo 16 | Installation of the bio-roll ECB downstream from the basin. Photo courtesy of the Steele County Highway Department. January 2007: The system works even under the ice. Photo courtesy of the Steele County Highway Department. Photo 18 | Water quality: The color of coffee. Photo courtesy of the Steele County Highway Department. Photo 19 | After December rain event: What an improvement in the downstream water quality! Photo courtesy of the Steele County Highway Department. Photo 20 | January 2007: The system works even under the ice. Photo courtesy of the Steele County Highway Department. “Photo “Photo “Photo “Photo “Photo “Photo “Photo “Photo

Why a pond?

Why was a sediment pond constructed in conjunction with the Dane Road realignment?

Assistant Steele County Engineer Larry Berkland explained: “It is a requirement of the Clean Water Act, General Permit Authorization to Discharge Storm Water Associated with Construction Activity under the National Pollutant Discharge Elimination System program (NPDES), which is administered by Minnesota PCA.

“Any time a project disturbs 1 acre or more, this permit is required. The stipulations of the permit are to minimize erosion, collect sediment before leaving the project, and to maintain water quality. In this particular project, the pond was constructed to collect sediment and maintain water quality.”

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Larry Berkland is the assistant county engineer for Steele County in Owatonna, Minn.

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