Winter Management
Salt and Snow[edit]
Sodium and chloride ions in de-icing salts applied to asphalt areas travel easily with the runoff water. De-icing salt can also increase the mobility of some heavy metals in soil (e.g. lead, copper or cadmium). This may increase the downstream concentration of the metal(Amrhein et al., 1992; Bauske and Goetz, 1993).
Very few studies have sampled groundwater below infiltration facilities or roadside ditches receiving de-icing salt laden runoff have found concentrations of heavy metals that exceed drinking water standards (e.g., Howard and Beck, 1993; Granato et al., 1995).
To minimize risk of groundwater or soil contamination, the following management approaches are recommended (Pitt et al., 1999; TRCA, 2009b):
- Stormwater infiltration practices should not receive runoff from the following areas:
- Where large amounts of de-icing salts are applied (e.g., busy highways), or
- Pollution hot spots (e.g. vehicle fuelling, servicing or demolition areas, outdoor storage or handling areas for hazardous materials, and some heavy industry sites);
- Prioritize infiltration of runoff from source areas that are comparatively less contaminated such as roofs, low traffic roads and parking areas; and
- Apply pre-treatment practices before infiltration of road or parking area runoff.
Vegetation varies in its reaction to salt-affected soils.
- Salt in soil water generally makes it more difficult for roots to take up water. This phenomenon mimics drought conditions for the plant.
- If passing traffic sprays salty water onto plants it can reduce cold hardiness in buds and new twigs. These then become more susceptible to freezing, mortality or deformation.
- In high enough concentrations sodium and chloride can also be directly toxic to plants. In some species the ions are absorbed by t he plant and build up in the leaves causing them to die
Freezing and Expansion[edit]
Freezing temperatures can cause problems with pipes and cisterns exposed above the frost penetration line[1]. This maybe a significant issue for rainwater harvesting systems, including residential rain barrels.
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