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Archive for low permeability

LID Implementation in Low Infiltration Areas

One of the questions that comes up quite often in the research about Low Impact Development is how to implement the design when you have naturally low infiltrating conditions (i.e. low permeable soils or shallow groundwater/bedrock).  In design scenarios like these you are inevitably going to be faced with major drainage issues, ponding, and vector control problems.  Using the State of California as an example, ponding present after 4 days is going to be the limiting factor on your BMP design.

Daniel Apt of RBF consultants presented a nice discussion on this very subject in 2008.  Mr. Apt summarized the measures to help reduce runoff from these sites as follows:

  • Reduce/Minimize Total Impervious Areas
  • Minimize Directly Connected Impervious Areas
  • Limit use of sidewalks
  • Reduce road/driveway length and width
  • Modify/Increase Drainage Flow Paths
  • Maximize overland sheet flow
  • Conserve natural areas
  • Minimize disturbance
  • Preserve infiltratable soils
  • Preserve natural depression areas
  • Preserve vegetation

The presentation goes into the benefits of using measures such as green roofs, rain barrels, cisterns, bioretention strips, and grassed swales as possible ways to working around infiltration issues on a site, while still drastically reducing offsite runoff.

Review the power point presentation in its entirety here.

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