Snow control lets city breathe easy

Handling the day-to-day chores of municipal snow removal and the need for winter and spring street cleaning in small cities can be difficult with limited resources. But doing this while trying to comply with the Environmental Protection Agency’s (EPA) stringent Clean Air Quality standards can be an even more daunting challenge.

That was the case in Sheridan, Wyo., where Tony Pelesky, director of public works, is using two recently developed traction, deicing and anti-icing materials to develop a cost-effective solution to both the city’s 75-inch annual snowfall and a federal mandate to reduce the city’s PM-10 pollution (airborne particulates measuring 10 microns in diameter.)

Pelesky began investigating alternatives to handle the compound issues of maintaining street traction while also addressing the city’s air pollution situation. In january 1994, he began using two new substances that have proven to be effective substitutes for sand-salt and scoria — a soft reddish slate material once used for traction.

WINTER WOES

Each winter, Sheridan’s 15,000 residents create a predictable amount of snow-compacting traffic on the city’s 142 lane-miles of paved streets and 26 lane-miles of gravel roads. Frigid temperatures and nearly 100 days of sunshine combine to cause almost daily thawing and refreezing cycles during snow-removal months.

Adding to its winter woes, Sheridan sits in a pollution-holding natural bowl at the confluence of two small rivers. Although dust and smoke from coal- and wood-fired heating furnaces are the most serious contributors to the city’s air pollution, the residue of sand-salt mixtures and scoria had become significant factors as well. In fact, the biggest drop in the city’s air pollution rating came when scoria was replaced by washed sand in the 1980s.

Recently, the city was threatened with the loss of a portion of its federal street and highway funds due to the high level of air particulates. Tina Jenkins, an air quality engineer with the air quality division of the Wyoming Department of Environmental Quality, said the city exceeded the one-day, 24-hour rating requirement of 150 once in 1991 with an air pollution reading of 198. Another high reading would have meant that the city had failed to meet federal air quality standards and could have jeopardized federal funds.

Jenkins added that after the city stopped using scoria, annual PM-10 readings fell from a high rating of 78 in 1985 to well within the 50 rating allowed by the EPA. In fact most of the city’s PM-10 ratings are now consistently in the 34-35 range.

Sheridan’s PM-10 air pollution has not dropped significantly since january 1993 when the alternative traction and ice-melting materials were first introduced. The city has had unusually dry winter weather during this period, and street maintenance has not required significant amounts of the new materials.

Jenkins believes, however, that as more of the new materials are used, they will not add to the city’s pullution problem.

Typical snowfall accumulations during the city’s 20 or so seasonal snowstorms are between 4 and 8 inches, but occasional snowstorms have dumped more than 20 inches of fresh snow on city streets. A record 24-hour, 28-inch snowfall was recorded on April 26, 1984.

During accumulations of more than 2 inches, the snow is road-graded into windrows in the middle of major streets, immediately opening main traffic arteries for commercial activity, an obvious benefit to the town’s bustling year-round tourism industry. Heavily traveled intersections, curves, steep grades and other trouble spots are immediately de-iced or receive applications of traction material. Residential and secondary streets are cleared to the curbs as snow-plowing and sanding equipment becomes available.

The windrowed snow is removed using a double-blade snowblower with a cab-controlled directional spout. The snow is poured into the city’s nine dump trucks, augmented with bed-mounted blower boards to improve capacity and deposited at several nearby collection points.

NEW SOLUTIONS

Once the snow is removed, Sheridan’s packed snow and ice problems begin in earnest. The short, sunny days and subfreezing temperatures do not allow ice to melt sufficiently to evaporate or run off. As a result, crews wage a continuous battle to maintain adequate traction on the streets.

Liquid magnesium chloride is used as both an anti-icing and a de-icing agent when ambient air temperatures are above 10 degrees Fahrenheit. The liquid is sometimes applied to main streets and intersections just before a predictable light snowstorm and quickly melts the snow as it hits the pavement. Thin layers of ice can also be melted quickly using the liquid.

In order to use the liquid, a truck had to be fitted with a 300-gallon tank for spray distribution. The equipment efficiently doubles as a weed sprayer in the summer.

The liquid does not require cleanup and does not appear to contribute to air pollution. The environmental impact of the liquid runoff on nearby Sheridan waterways is currently being evaluated, but earlier tests have shown it to be harmless when diluted.

Pelesky also began using a crushed shale product that is a ceramic-like rock about half the weight of normal sand-salt compounds. The material is baked in a kiln at 2,000 degrees to make it harder, lighter and more porous before it is saturated in a calcium chloride solution.

The shale is distributed in the same way as sand-salt. Two-ton dump trucks equipped with sand spreaders calibrated to distribute 620 pounds of material per lane mile over 14- to 16-foot widths are used. Spreading can be accomplished much more quickly — at nearly triple the 2 mph speed required of sand-salt distribution — because of the reduction in weight.

The shale stays on top of melting ice longer to provide improved traction and is not kicked out of traffic lanes as readily as sand-salt.

The cost-per-ton for the liquid is about three times that of the shale, which is twice as expensive as sand-salt. About 100 pounds of calcium chloride pellets, which cost $9 per 100-pound bag, are added to each ton of shale to further enhance its ice melting characteristics.

The cost savings for both new materials come in the distribution and cleanup. The liquid requires no post-distribution street sweeping, and the crushed shale, because of its light weight, picks up about three times faster, cutting the cost-per-hour by about a third and saving fuel.

Since it is much lighter and less abrasive than sand-salt, the crushed shale also has reduced excessive wear on the city’s street sweepers. This has been especially noticeable during routine inspection for damage to elevator doors, belts and squeegees.

The shale not only outperforms sand-salt but has several advantages. It eliminates car windshield and headlight breakage and paint chipping, causes less rust damage than sand-salt, is highly visible on snow-covered roads, is much easier to spread and is a third less expensive to clean up.

Through these new methods, Pelesky has found a way to effectively cap spending. Sheridan’s annual public works budget — more than $1 million in 1994 — will not grow due to the change in materials. Additionally, replacing equipment less frequently could provide additional savings. This article was written by John Head, media relations manager for Russell, Karsh & Hagan Public Relations, Englewood, Colo.