Today I found a 1996 EPA study about the effectiveness of measures to prevent tracking of mud. For preventing the trackout of sediment, gravel pads were found to be the most effective, followed by wood-chip mulch (produced from waste on-site), with sweeping the least effective.
Walking on a street just swept by a Bobcat, you can easily see how ineffective it is--the dirt is just spread about kind of evenly. Nevertheless, we should enforce sweeping when the day is done, because it serves as a backup to the gravel pads. The gutters below check dams should be thoroughly swept with hand brooms, since what's in the gutters goes directly to the lakes when it rains.
The muddy tracks go for miles, although the quantity drops off rapidly with distance. I believe the most effective kind of sweeping would be intensive sweeping, with water, close to the site. Of course, details have to be adapted to each site.
Yesterday, I was downtown on State Street, photographing the Rawson and Tri-North sites. The whole area within several blocks of these sites was more dirty than usual, and it was easy to see dirt was escaping from the sites largely on tires--day in and day out.
These two companies, through their non-compliance--are not just being sloppy neighbors to nearby businesses. They are not just harming the lakes. They are also harming the health of the people who work and shop downtown.
Entrance to the Rawson and Tri-North sites from State St, 7/27.
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Related news item from New York Times: "The quality of air in Chinese cities is increasingly tainted by coal-burning power plants, grit from construction sites and exhaust from millions of new cars squeezing onto crowded roads, according to a government study issued this week."