Design criteria for dry swale (grass swale)

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This page provides a discussion of design elements and design steps for dry swales, which are often called grass swales. The following discussion includes dry swales used as filtration or infiltration practices, with the distinction being the presence of an underdrain for filtration practices.

Green Infrastructure: Dry swales can be an important tool for retention and detention of stormwater runoff. Depending on design and construction, swales may provide additional benefits, including cleaner air, carbon sequestration, improved biological habitat, and aesthetic value.

Terminology

The following terminology is used throughout this design page.

Warning: REQUIRED - Indicates design standards stipulated by the MPCA Construction General Permit (CGP) or other consistently applicable regulations

HIGHLY RECOMMENDED - Indicates design guidance that is extremely beneficial or necessary for proper functioning of the practice, but not specifically required by the MPCA CGP.

RECOMMENDED - Indicates design guidance that is helpful for practice performance but not critical to the design.

Details and CADD images

Use this link to access .pdf diagrams of CADD drawings. To see all filtration CADD images in a combined pdf, click here.

• Links to .dwg files for swales
• Swale layout: File:Swale Layout2 (1).pdf
• Typical dry swale profile section with check dams and draintile: File:MIDS Dry Swale Sections-SHEET 1.pdf
• Typical grass channel cross-section without soil amendment: File:MIDS Dry Swale Sections-SHEET 2.pdf

• Karst
• Shallow soils and shallow depth to bedrock
• Shallow groundwater
• Soils with low infiltration capacity
• Separation distances
• Potential stormwater hotspots
• Wellhead protection
• Contaminated soils and groundwater
• Procedures for investigating sites with potential constraints