[Greenbuilding] Green Streets?

[YankeePerm at aol.com]

Brick surfaces might allow more water to percolate on the surface, instead of 
being diverted to run-off.   This is very beneficial, especially in your 
region.   You might achieve the same effect or better through development of 
roadside swales that hold water until it percolates instead of diverting it to 
runoff.   This, done on a wide scale, will increase groundwater levels, decrease 
groundwater salinity (in the upper levels), stabilize stream flow fluctuations, 
and improve the health of nearby trees and other deep rooted vegetation.  The 
down side of permeable surfacing would depend upon the severity of your 
winters and the sort of soil underlying the road.   If water accumulates under the 
road and freezes, the frost heave will be pretty awful.   This depends   on 
the shaping of the subsoil layer (crowning to drainage would help), the depth of 
freezing, and the duration of freeze cycles.   If water freezes under a road, 
even one with good drainage under the pavement, then it forms an impervious 
layer and more water can build up a freeze.   You can imagine the results.   I 
believe that your region experiences relatively wet winters, on average.   
Therefore, impervious pavement that sheds water to swales where it is held for 
percolation may be preferable.   Keep the swales well back from the road to 
minimize lateral seepage under the road surface.   Keep surfaces well crowned to 
shed water, as they do in colder climates (which also reduces the risk of 
hydroplaning which is common in your summer downpours).   

I'd be interested to hear what the experts say, particularly experience with 
the brick surfacing in Oregon, which may give you a better idea of winter 
performance.

Dan Hemenway



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