City looks to cut back on road de-icing products
Officials looking at different ways to cut through ice and snow this winter
City officials are promising to cut back their use of both traditional salt and calcium chloride this winter to prevent damage to vehicles, bridges and other infrastructure.
They’re hoping new “pre-wetting ” techniques will help a small sprinkle of granular salt stick to the pavement better, said Janet Tecklenborg, the city’s director of infrastructure operations. She said they’ll also be more judicious in deciding when to spray the liquid calcium chloride before a snow storm.
But the goal is still to achieve bare pavement, said Tecklenborg on Thursday while preparing to update city council as the weather turns cold. “That’s the safest option for vehicles, cyclists and pedestrians.”
Edmonton is heading into its third year of a pilot project testing new salting techniques for winter road maintenance. Last year, it treated all arterial roads and many of the bus routes, reducing the use of sand and increasing both kinds of salt.
But many people worried about damage to vehicles, complained about pockmarked concrete parking pads, and were forced to replace parts if they biked regularly on the cleared bike paths.
Calcium chloride is a liquid salt meant to be sprayed onto a street or bike path before a storm to prevent snow and ice from sticking. It and traditional salt were also used to melt the last skiff of snow on streets and paths after plowing.
The city ended up using far more traditional salt than calcium chloride, up to three times as much traditional salt as in previous years.
To reduce the impact, the city will add a corrosion inhibitor to the traditional salt. Tecklenborg said her crews will pre-wet salt chips with calcium chloride before spreading them.
Because calcium chloride has an inhibitor, that should protect metal that either salt touches. It should also reduce the amount of traditional salt needed by 30 per cent, and help the salt stay in place on the road, she said.
PILOT PROVIDING CHANCE TO LEARN AS THEY GO
Tecklenborg said the city has been learning a lot through the pilot. They found calcium chloride is not very effective when humidity is greater that 70 per cent, the dew point is close to the pavement temperature, or either freezing rain or blowing snow is forecasted.
Every city goes through a learning curve, said Patric Nagel, chief operating officer for Tiger Calcium, which won the contract to provide calcium chloride starting last March.
“There is some art to doing this,” he said. “The appropriate quantity and the appropriate timing is very weather-condition based.”
Edmonton used a different kind of inhibited calcium chloride from a short-term contract first. The new product uses an organicbased inhibitor, which includes a component of molasses, said Nagel. That will coat and protect any metal it comes in contact with.
MEASURING SALT IN THE NORTH SASKATCHEWAN
City officials contracted Epcor to monitor changes in water quality at the four largest stormwater outflows on the North Saskatchewan River. It found only 4.5 per cent of the salt coming from city operations was from calcium chloride. The rest was from the 36,789 tonnes of traditional salt (sodium chloride) the city applied to roads last year.
But chloride levels found in the run-off vary widely year to year anyway, even in years with similar amounts of snow, according to an Epcor report released with a city update Thursday. The salt comes from city and private sources.
Engineers could see “no discernible impact” to the water quality in the run-off.
PUBLIC SAFETY AND CORROSION CONSIDERED
City officials said this year’s pilot will come with several new studies. They ’re hiring an external consultant to do field studies on the local impact of calcium chloride on concrete, asphalt, vehicles and bridges.
They’re also hiring a research institute, either the University of Alberta or Olds College, to study the effects on local vegetation.
An internal team will track collisions on streets that have been treated with calcium chloride and compare that to historical data. That should improve on previous attempts to measure safety outcomes, which were hampered by a small data set, said Tecklenborg.
Calcium chloride application will expand in scope to include all bus routes when conditions are right, increasing the total kilometres by 295 kilometres to 3,134 kilometres. Priority bus stops and separated bike lanes are still included.
For the first time, Whitemud Drive, Yellowhead Trail, Calgary Trail, Gateway Boulevard, and Manning Freeway will be plowed by dedicated private contractors.
The issue heads to council’s community services committee Oct. 3.
There is some art to doing this. The appropriate quantity and the appropriate timing is very weather condition based.