Designing For Northern Climates
Because winter conditions place unique demands on Permeable Pavements, extensive research has been done by the TRCA, the University of New Hampshire and the US EPA among others to evaluate how they perform in cold climates. These are some of the findings. SNOW AND ICE COVER Surface accumulations of snow can occur on Permeable Pavement in the winter. Snow has to melt before it can infiltrate. As with any other paving surface, if the Permeable Pavement is not cleared before traffic drives on the surface, snow packing and ice formation may occur. To prevent ice formation, we recommend traditional snow plowing followed by spreading traction control aggregate as required. Instead of sand, spread the same aggregate used in the Permeable Paver joints.
Paver: Avenue Series
Applying anti-icing or pre-wetting chemicals to Permeable Pavement is not recommended. Anti-icing agents, which melt snow before it can become compacted into ice, will likely infiltrate into the system before a storm and impact local groundwater systems. And their magnesium or calcium chloride ingredients chemically attack the cement bond, causing the pavers to disintegrate. If the use of de-icing salts is required, as in the case of a zero ice policy, it is important to note an observation from the University of New Hampshire Stormwater Center: the use of permeable pavements resulted in a 75% average reduction in annual salt. Initial melt water was able to drain, leaving no standing water to re-freeze on the surface.
SURFACE INFILTRATION RATES Except when packed ice is present on the surface (as noted above), surface infiltration rates of Permeable Pavement are not adversely impacted in cold climates. Although the jointing and reservoir aggregates may become frozen, they still maintain their porosity and permeability. FROST PENETRATION Road construction protocol calls for a non-frost susceptible material for a percentage of the frost penetration depth. Because Permeable Pavement profiles use non-frost susceptible materials (i.e. open graded aggregates) and are normally deeper than non permeable profiles, most Permeable Pavements in cold climates have not shown any slumping or frost heaving after years of monitoring. Where water may be detained for an extended period of time or sub grade soils are prone to differential frost heave (silts), deepening the road profile can be considered. If water freezes in the reservoir, it can expand into the open voids of the base/sub-base without heaving the pavement. Base/sub-base aggregates are also not likely to develop frost lenses (which cause differential frost heave) due to the lack of fines. Permeable Pavement reservoirs tend to thaw more rapidly due to infiltrating melt water.
Winter data showed permeable pavement systems function well even during freezing temperatures.
Source: TRCA
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