St. Paul, Minnesota – From 1910 until 1962, the 3M Company’s world headquarters was located on a 46-acre parcel of land on the East side of St. Paul, Minnesota. Recently, this area was redeveloped by the Saint Paul Port Authority and renamed Beacon Bluff.
The stormwater runoff from the redevelopment of this area was going to be a major concern for the developers. There was potentially a total of 163 acres of untreated stormwater runoff that could flow through this site, directly into the Mississippi River. This project is one of the largest infiltration projects in the state of Minnesota.
The major component of the water treatment system was three (3) 195-foot rows of ten-foot diameter Aluminized Type 2, 10-gage perforated corrugated steel pipe. This pipe is expected to last 100 years. In order to prohibit fine particles from migrating into the perforated pipe, it was wrapped in a geotextile fabric. This entire system can retain up to one million gallons of runoff, greatly reducing the risk of downstream flooding.
A unique solution occurred during the construction of this retention system. The backfill consisted of compacted engineered fill, up to the top of the pipe. Then, several feet of shredded rubber tires were placed over the top of the engineered backfill. This creates additional void space for the stormwater runoff to infiltrate, allowing more sediment to be captured. The contaminants of the runoff percolate through the various fill types and into the top of the retention pipe. The final lift of fill on top of the shredded rubber tires is two feet of granular sand. The development principles of sustainability were further enhanced through the use of corrugated steel pipe. Corrugated steel pipe is constructed with as much as 95% of recycled material.
This underground retention system traps approximately 90 percent of sediment from stormwater runoff and stores it in a sump, where it can be periodically removed through access ports in the top of the detention system. By removing the sediment from the stormwater runoff, the contaminants – which oftentimes attach themselves to the sediment particles – are removed as well.
Lastly, the effluent runoff from the retention system will be tested and tracked to ensure the systems’ effectiveness. This state-of-the-art stormwater treatment system allows for a cost-effective, ecologically friendly solution to meet updated watershed requirements.
For more information on this and the many other benefits of Corrugated Steel Pipe, contact us by calling (972) 850-1907 or visiting www.ncspa.org.