Frequently Asked Questions (FAQ)

Question:
What is the impact on ground water from infiltration or porous pavement BMPs?


ANSWER:
Impacts on ground water quality due to the infiltration of stormwater and urban runoff can vary, depending on many factors like the types and concentrations of pollutants in the runoff, the underlying soil type, the depth to ground water, and the proximity of the BMP to production wells.

There is general acknowledgment that some pollutants can be removed by the natural filtration and neutralization of the stormwater as it percolates through the soil. At the same time, however, there is also a general understanding that certain other pollutants do not get filtered by the soil and could possibly contaminate ground water supplies. Accordingly, the L.A. Regional Water Quality Control Board recommends avoiding hazardous materials "hot spots," avoiding areas subject to hazardous spills, avoiding soils that are too sandy or too clay, insuring at least 10 feet depth to the seasonal high ground water level, and locating at least 100 feet from a water production well. Contact the Regional Board (213-620-2094) for more details.

A study sponsored in part by the County of Los Angeles Department of Public Works and the Los Angeles/San Gabriel Rivers Watershed Council, called the Ground Water Augmentation Study, evaluated the impacts on ground water due to infiltration-type BMPs. More information on this study can be found by clicking on the link below.


Links:
  A 2nd Look at Porous Pavement/Underground Recharge

  Contamination Risk from Stormwater Infiltration

  EPA Underground Injection Control Program
BMP WMD Watershed groundwater stormwater conservation runoff quality FEMA NPDES TMDL BMP Levees Levee certification Flood insurance NFIP Flood zone determination IRWMP