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U.S. Army Corps of Engineers
St. Paul District
Public Affairs Office
332 Minnesota St., Suite E1500
St. Paul, MN 55101

Phone: (651) 290-5807
Fax: (651) 290-5752 


Mississippi River shoreline foam not harmful

Published June 5, 2012
ST. PAUL, Minn. – The U.S. Army Corps of Engineers, St. Paul District, received numerous citizen inquiries about shoreline foam along the Mississippi River near Reads Landing Island, north of Winona, Minn.

This foam, which sometimes can appear as thin white lines and at other times thick grey and brown floating islands of foam, is most likely naturally occurring organic compounds that possess soap-like properties. These organic compounds, commonly called surfactants, are often produced by plants and algae inhabiting the river. (All surfactants, natural or manmade, can cause foam by reducing the tension between water molecules at the surface of the water.)

This reduction of tension allows bubbles created by rushing, turbulent water or waves to persist and collect into foam instead of breaking under the stress of the water’s natural surface tension. Surfactants can reduce the water tension by their unique water-loving and water-repelling properties that allow them to reside at the interface of water and air which significantly interferes with the cohesive forces between neighboring water molecules.

The naturally occurring surfactants are most likely the cause of the foam seen downstream of the Reads Landing dredging activities. The dredging operations are creating large amounts of turbulent water mixed with organic sediment materials as the dredge cutter is moving sands and silts hydraulically from the temporary placement site to the upland site. This is a perfect situation for natural surfactants to be released from the sediment and vigorously mixed with water and air causing brownish colored foam downstream of the dredge.

The U.S. Army Corps of Engineers, St. Paul District, serves the American public in the areas of environmental enhancement, navigation, flood risk reduction, water and wetlands regulation, recreation sites and disaster response. It contributes around $181 million to the five-state district economy. The 700 employees work at more than 40 sites in five upper-Midwest states. For more information, see


Release no. 12-058