infiltration in clay soils west metro watershed alliance

Infiltration in Clay SoilsWest Metro Watershed Alliance

Protecting our Water Resources - March 23, 2011

• Problem:– Soil composition– The particle, or grain size, of clay soil is 500

times smaller than sand (~1.0mm vs. ~0.002mm)

– The infiltration rate of clay, is 25 times slower than sand (2.5 in/hr vs. 0.1 in/hr).

Infiltration in Clay Soils

Infiltration in Clay Soils

• Problem:– MPCA required selected City’s to address

significant new or expanded water volume discharges in their Storm Water Pollution Prevention Programs…i.e…figure out a way to reduce volume discharge.

– The City of Plymouth included volume requirements in our Surface Water Management Plan (2008)

Infiltration in Clay Soils

• Problem:– Erosion repair and stream restoration capital

improvement projects completed since 2005 to repair the impacts from water volume in Plymouth have cost ~$3,000,000.

– One project example is the Plymouth Creek Stream Restoration Project

Infiltration in Clay Soils

Plymouth Creek Stream Restoration

• Severe erosion existed along the creek.• The erosion was partially the result of increased water

volumes.• This project assists the City in meeting the goals of the

Medicine Lake Total Maximum Daily Load study.• Funding partners include the Bassett Creek Watershed

Management Organization, the Minnesota Board of Water and Soil Resources (through BCWMO), Hennepin County, and the City of Plymouth

Plymouth Creek Stream Restoration

• Problem:– Water volume contributes to erosion and

nutrient loading to lakes, wetlands, streams, and other resources.

Infiltration in Clay Soils

• Solutions:– Conservation Areas– Buffers/Shoreline Restorations– Soil Amendments– Disconnection of Impervious Surfaces– Reduced Street Width– Porous Pavements– Rain Gardens

Infiltration in Clay Soils

• Buffers/Shoreline Restorations:

Infiltration in Clay Soils

• Disconnection of Impervious Surface:

Infiltration in Clay Soils

• Reduced street width:

Infiltration in Clay Soils

33 feet

28 feet

• Porous Pavements:

Infiltration in Clay Soils

• Rain Gardens:

Infiltration in Clay Soils

• Considerations:– Water volume can contribute to water quality

impairments and result in significant capital expenditures to address the problem

– Many practices are available, even in clay soils, to reduce the runoff of water

– Every municipality is unique and some practices may work better than others in your community.

Infiltration in Clay Soils

Questions?Derek Asche

Water Resources Manager763-509-5526

dasche@plymouthmn.gov