Vol. 23, No. 3 May 18, 2015

Deicing Road Salt Clogs Bioretention Facilities!

WSSI investigations showed deicing salt can significantly reduce soil permeability, causing bioretention facilities to clog. We recommend – and provide in our lab – soil testing to confirm your soil blend will achieve its permeability standard, even when subjected to deicing salt.

Deicing salt that is commonly used to treat roads and parking lots during winter months (sodium chloride, NaCl) appears to reduce the permeability of soil media typically used in bioretention facilities. WSSI has observed facilities that drain effectively during spring, summer, and fall and then unexpectedly begin to clog after winter snow and ice storms. Permeability tests conducted in our in-house lab confirmed that some soil types clog after exposure to NaCl deicing salt.

Bioretention Soil Media Testing at WSSI

A partial correction was observed when media was treated with calcium chloride (CaCl2) – another deicing salt product. A recently published article in the Journal for Environmental Science confirmed WSSI’s observations of potentially 90% reduction in permeability for some soils.

WSSI therefore strongly recommends testing soil blends prior to installation in bioretention facilities or other infiltration practices that will be constructed near roads or parking lots where deicing salt is likely to be applied. It is our understanding that the Virginia Department of Transportation (VDOT) is nearing approval of bioretention soil media testing protocols utilizing our recommendations for NaCl exposure testing.

WSSI’s laboratory can test your soil blend to confirm the intended permeability rates are being achieved even with exposure to deicing salt. Prior testing can reduce the incidence of in-field failures resulting from insufficient soil media permeability, saving your projects from costly and time-consuming overhauls.

Contact Kelly Petrey, Mike Rolband, or Frank Graziano for testing services available at WSSI.