Frequently Asked Questions (FAQ)

Question:
Which BMPs are recommended for which pollutants?


ANSWER:
A number of stormwater "pollutants of concern" have been identified as having possible adverse impacts on surface water. The 1994-2000 Integrated Receiving Water Impacts Report found at http://ladpw.org/wmd/NPDES/IntTC.cfm lists some 30 potential stormwater pollutants of concern identified by County of Los Angeles Department of Public Works, including pathogens, trash, nutrients, dissolved metals, and pesticides. The presence, concentration, and loading of these pollutants vary by location, storm intensity, and time of year. All of these factors should be considered when implementing a BMP.

Because BMPs usually cannot treat every pollutant all of the time, some designers utilize what are called BMP treatment trains. These systems consist of various BMPs laid out in series so that one BMP's effluent is the next BMP's influentone BMP would treat one pollutant while the next BMP would treat another. For example, disinfection and infiltration BMPs work best when there are minimum amounts of trash and solids in the stormwater. Therefore, installing some kind of trash and solids separation BMP upstream of a disinfection or infiltration BMP would be a useful design.

Some stormwater quality BMPs are designed for volume of runoff while others are designed for rate of runoff. Volumetric BMPs typically address stormwater storage, groundwater recharge, settling of solids, and vegetative support. Flow-rate BMPs typically involve media filtration and trash separation.


Links:
  LACDPW Trash TMDL Technical Report

  Caltrans BMP Retrofit Pilot Program--Final Report

  '94-2000 Integrated Receiving Water Impacts Report
BMP WMD Watershed groundwater stormwater conservation runoff quality FEMA NPDES TMDL BMP Levees Levee certification Flood insurance NFIP Flood zone determination IRWMP