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City of Plymouth. Infiltration in Clay Soils West Metro Watershed Alliance Protecting our Water Resources - March 23, 2011. Infiltration in Clay Soils. Problem: Soil composition The particle, or grain size, of clay soil is 500 times smaller than sand (~1.0mm vs. ~0.002mm)
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City of Plymouth Infiltration in Clay Soils West Metro Watershed Alliance Protecting our Water Resources - March 23, 2011
Infiltration in Clay Soils • 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 • 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
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
Infiltration in Clay Soils • 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: 33 feet 28 feet
Infiltration in Clay Soils • 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.
Questions?Derek AscheWater Resources Manager763-509-5526dasche@plymouthmn.gov