Code of Practice
Your Annual Report
Case Study # 7
Utilizing Technological Advances in the Management of Road Salt Usage in Nova Scotia
Average Annual Snow Fall: ~221CM
of Road Serviced:
Level of Service Standard: Varies
The Nova Scotia Department of Transportation & Public Works (NSTPW) installed its first five Road Weather Information Systems (RWIS) in 1995. The network has since expanded to 19 stations due to a major initiative between December 2000 and January 2004. In this initiative, wherever the Department installs a new RWIS station, the local highway engineer commits to initiating a pre-wetting program in that area. Brine-making equipment is purchased and salt trucks are retrofitted to enable pre-wetting. This growth in RWIS and pre-wetting is allowing the Department to take a proactive approach to snow and ice control and has led to a reduction in salt usage.
Nova Scotia is the third largest salt-using province, behind Quebec and Ontario. The Department applies an average of 280,000 tonnes of salt per year, due to fluctuating temperatures and a high number of freeze/thaw cycles attributable to its proximity to the Atlantic Ocean. The growth of the RWIS network and the implementation of pre-wetting activities are part of an initiative by the department to better manage its salt usage. This is in addition to the construction of new salt storage facilities and increasing efforts in winter weather forecasting.
Description of Winter Maintenance Practices
Brine Making & Pre-Wetting
The Department started pre-wetting out of its Burnside Base in December 2001. A brine-maker was cobbled out of spare parts, including a large fiberglass tank left over from the Swiss Air recovery. Department employees fashioned a grid of copper pipes in the bottom through which compressed air was forced creating a "jacuzzi" effect to mix the salt with the water. This initial effort gave way to tanks specifically designed to make brine. Currently, the Department has brine-makers in 18 bases across the Province. Some typical brine making equipment is shown in Figure 1.
The pre-wetting program takes advantage of the RWIS' capability to give accurate and timely forecasts. In locations where an RWIS site is installed, the local engineer makes a commitment to implement a pre-wetting program. The Department currently has 33 salt trucks with pre-wetting equipment installed in bases across the province. In all cases salt brine at 23% concentration is used as the pre-wetting agent.
A study was conducted at the Department's Brooklyn Base in the winter of 2002-03 to observe changes in salt use as a result of the program. The study showed a 10% reduction in salt used by units that were retrofitted for pre-wetting (Figure 2).
Figure 2 - Salt Use Reduction by Units Retrofitted for Pre-Wetting
Liquid Anti-icing Trial
A liquid anti-icing trial was also set up at the department's Brooklyn Base where a truck was equipped with a liquid tank and spray bar to carry out liquid anti-icing with brine at a 23% concentration. During the 2003-04 season, brine was sprayed on a local paved road in advance of the start of a snowfall. The brine was applied at a rate of 100 litres per lane-kilometre provided the pavement temperature was greater than -6oC. The results were compared to a similar road segment where traditional methods were used.
Figure 3 shows the amount of salt used in areas with anti-icing, compared to estimates of what would have been used without anti-icing between December 19/03 and March 18/04.
Figure 3 - Brooklyn Yard
Comparison of Salt
Used With and Without
Although during this period the total amount of salt used was not significantly reduced, salt use was substantially lower with anti-icing for several storm events. In addition, other benefits were evident. Roads that were anti-iced did not require subsequent additions of salt or sand. The supervisor estimates that four tonnes of salt and 10 tonnes of sand would normally have been required to clear these roads. Operators quickly recognized the benefit of liquid anti-icing and are eager to see the program expanded. In some cases, convincing frontline staff that new technologies are effective can be the biggest challenge.
Anecdotal evidence from the equipment operators and supervisor indicated that anti-icing techniques give them better control of storms and allow them to provide better service to the public.
Winter Weather Forecasting
The Department contracts with the Meteorological Service of Canada (MSC) for the supply of forecasting services, including site-specific atmospheric forecasts and pavement temperature and condition forecasts. Thirty forecast sites receive a site-specific atmospheric forecast, and a pavement temperature/condition forecast is also available for 19 of these sites. The data from which the pavement forecasts are produced is gathered from the nineteen RWIS sites that are located on the Province's 100 series highway system.
Forecasts are produced twice per day, at 4 am and 4 pm. When there is a rapid change in the weather, additional updates are issued by the MSC meteorologists.
The Department use the following three methods to disseminate forecast data to field and managerial staff:
The three main elements of RWIS are:
While the real-time weather information displayed on the RWIS intranet site is important, the greatest benefits are from tailored forecasts aimed specifically at supporting maintenance operations.
Nova Scotia has 19 RWIS stations in place. Five were placed in Kings County in 1995, seven were installed on the Amherst to Halifax corridor in 2001, along with one on Highway 101 at Mt. Uniacke. Five more stations were installed between Truro and North Sydney in the Fall of 2002. An additional station was installed at Yarmouth in the Fall of 2003, along with the complete replacement of the five sites in Kings County.
As part of the National
RWIS network, the Province
plans to install approximately
20 more RWIS sites
over the next two years.
For Further Information:
Case Study Author: McCormick Rankin Corporation / Ecoplans Limited
This Case Study is part of a series on Road Salt Management
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