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→Surface Infiltration Rate Testing
==Surface Infiltration Rate Testing==
==Surface Infiltration Rate Testing==
For LID BMPs like [[bioretention]] and [[bioswales]], [[enhanced swales]], [[vegetated filter strips]] and [[permeable pavements]], the rate at which stormwater infiltrates through the BMP surface greatly affects its drainage performance. If the surface infiltration rate (i) is too low, inflowing stormwater will quickly begin to pond on the surface and, once the overflow outlet elevation is reached, will by-pass treatment by the BMP. In extreme cases the BMP may pond water on the surface for longer than 24
hours, creating nuisance conditions (e.g., poor vegetation cover, ice formation, ideal mosquito breeding ground habitat).
Causes of excessively low surface infiltration rates include use of soil during construction that does not meet design specifications, accumulation of fine sediment on the
soil surface or in permeable pavement joints or pore spaces, and over-compaction of the soil, that can occur during construction or routine operation. Therefore it is important to test the surface infiltration rate of LID BMPs as part of Assumption and Verification inspections. As part of Assumption inspections it helps determine if the BMP is ready to
be assumed by the property owner. As part of Verification inspections it provides an indication of whether or not the surface drainage performance of the BMP is still within an acceptable range, if it is being adequately maintained, and to diagnose the cause of any problems with drainage or [[vegetation]] detected through visual inspection or other types of testing. Tests may also be done as part of '''Forensic Inspection and Testing (FIT)''' work to diagnose the cause of problems with drainage or vegetation, with the number and locations of test determined by the nature of the problem being investigated.
==Natural or Simulated Storm Event Testing==
==Natural or Simulated Storm Event Testing==