4.3.1 Applications & Limitations

The following applications and limitations generally apply to dispersion BMPs:
  • Dispersion can be effective at managing stormwater runoff from a variety of impervious surfaces such as walkways, driveways, and roofs within either private property or the public right-of-way.
  • Sheet flow must be maintained through vegetated areas located downslope of contributing impervious areas.
  • Dispersion for driveways will generally only be effective for single-family residences on large lots and in rural short plats. Lots in urban areas will generally be too small to provide effective dispersion of driveway runoff.
  • Sheet flow may need to be re-established for runoff from steep roadways or driveways through the use of level spreaders.
  • Runoff discharge toward landslide hazard areas should be evaluated by a geotechnical engineer or a qualified geologist. The discharge point should not be placed on or above slopes greater than 20 percent or above erosion hazard areas without the evaluation by a geotechnical engineer or qualified geologist and approval by the local jurisdiction.
  • For sites with septic systems, the discharge point must be downslope of the drain field primary and reserve areas, unless the local jurisdiction deems that the site topography clearly prohibits flows from intersecting the drain field.

More detailed discussion of applications and limitations for each type of dispersion BMP is provided in Section 4.3.3: Sizing.