Engineers working on the Port Mann/Highway 1 project have identified solutions to prevent snow and ice buildup on the Port Mann Bridge cables.

A custom-designed cable sweeper has been developed that will be fitted around the bridge cables and used to remove snow and ice before it can accumulate. In addition, engineers have identified highly water repellent, or hydrophobic, coatings and de-icing sprays that could be applied to the bridge cables to further prevent the accumulation of snow and ice.

The sweeper fits around the outside of the bridge cable and is lowered and raised along its length using a specially-designed winch, while scrapers and brushes on the sweeper remove snow and ice buildup. Fabrication of the sweepers is now underway and installation and additional testing will begin this week. The sweepers will be installed on the 152 bridge cables that cross the roadway.

To complement the cable sweepers, four types of hydrophobic coatings are now being tested to confirm which may perform best on the Port Mann Bridge cables. Tests will be conducted on the bridge, as well as in a specialized laboratory where specific and severe weather conditions, including temperature, humidity, wind and precipitation, can be recreated.

In addition, engineers have identified a de-icing solution that can be applied to the bridge cables as a further preventative measure. Similar to de-icing applications on aircraft, the solution would be sprayed onto the bridge cables. The environmentally friendly product, which is also used to de-ice ships, forms a barrier that prevents the formation of ice.

The government of B.C., Transportation Investment Corporation and Kiewit/Flatiron are confident that this combination of solutions will prevent the accumulation of snow and ice on the bridge cables.

Quotes:

Minister of Transportation and Infrastructure Mary Polak -

"We were confident that the engineering team at Kiewit/Flatiron would develop a solution to ensure snow and ice wouldn't build up on the bridge cables, and I thank them for their efforts."

"The new Port Mann Bridge is making a real difference to the lives of Lower Mainland commuters. I encourage those who haven't yet made the crossing a part of their commute to try it and see how much valuable time they could save."

Transportation Investment Corporation CEO Mike Proudfoot -

"These solutions are the product of tremendous effort on the part of the engineering and design team. Over the past four weeks they have canvassed international experts and considered and refined numerous technologies. That hard work has resulted in a combination of solutions that will allow us to keep the bridge operating safely and efficiently."

President of Kiewit Infrastructure Group Inc. Scott Cassels -

"Safety is Kiewit/Flatiron's primary concern. We're working closely with our partners, TI Corp and the Ministry of Transportation, to identify the most effective ways to reduce the impact that adverse weather conditions may have on the Port Mann Bridge and the traveling public. Over the last month, we've installed additional weather stations to help identify threatening weather conditions well in advance."

"We must finish real-world testing, but we believe that the cable sweepers, coatings and de-icing sprays will be effective enhancements to the bridge. We appreciate the public's patience as we move as quickly and safely as possible to finish testing and begin installing these enhancements to ensure the safety of the traveling public."

A backgrounder follows.

Media Contacts:

Kate Trotter
Government Communications and Public Engagement
Ministry of Transportation and Infrastructure
250 356-8241

Max Logan
Communications Director
Transportation Investment Corporation
778 783-1218

BACKGROUNDER

Cable sweepers:

• The cable sweepers are custom-designed devices that fit around the outside of the bridge cables and move along their lengths to remove snow and ice before it can accumulate.

• The sweepers are lowered and raised along the cables using a specially designed winch system. Scrapers and brushes on the sweeper remove snow and ice buildup.

• Sweepers will be installed on 152 of the bridge's 288 cables that cross the roadway.

• The sweepers are approximately 60 cm (two feet) long and are comprised of five principal components:

• Four scrapers, shaped like snow ploughs, are set at the front of the sweeper. As the sweeper descends down the cable, the scrapers dislodge any snow or ice in its path. The scrapers are set one centimetre off the cable to avoid scratching or damaging the cable sheath. The scrapers will dislodge any snow thicker than one centimetre.

• Four thick-bristled brushes that wrap around the cable are mounted behind the snow scrapers. The brushes remove any remaining snow not removed by the scrapers. The brushes surround the cable and rest directly against the surface of the cable sheath.

• The sweeper moves on eight caster wheels, four on the top and four on the bottom. The wheels ensure the sweeper glides smoothly down the cable and does not scrape or damage the cable sheath.

• A counter weight keeps the sweeper stable and properly aligned, moving smoothly down the cable.

• A steel frame houses the components described above and attaches to the winch and cable system used to move the sweeper.

• The sweepers are moved along the length of the cable using a winch at speeds of approximately 61 metres (200 feet) per minute.

• The winch moves the sweepers up and down the cable. Any snow remaining on the cables after the downward pass will be dislodged by the brushes as the sweeper returns.

• The 152 cables fitted with sweepers range in length from 70 metres (230 feet) to 250 metres (820 feet).

• The emphasis will be placed on preventing snow and ice accumulation and deployment of the sweepers will begin as soon as snow begins to fall. An ongoing visual inspection of the bridge cables will be performed to prioritize redeployment of the sweepers.

Hydrophobic coatings:

• Water, ice and snow-repellent solutions that can be applied to the existing cable sheaths are being tested to evaluate effectiveness and compatibility with the Port Mann Bridge. These solutions, sometimes referred to as hydrophobic, are silicon-based and reduce the adhesion of water and ice to surfaces.

• The properties of the coating are an important consideration in the testing as they could affect the aerodynamic response of the cable sheaths.

• The cable sheaths are ringed with a 1.6-millimetre raised lip, or fillet, that winds along the cables in a spiral, or helical pattern. This lip acts to shed rainwater from the cable sheaths, preventing streams of water from forming along the length of the cables. Long streams of water could disrupt the cables' aerodynamics.

• Engineers will be conducting tests at a specialized lab that will recreate a range of severe winter conditions, providing a realistic assessment of the effectiveness of the various solutions, as well as verifying that the coatings would not impact the wind loading and aerodynamic properties of the cables.

• Pending the outcome of the testing, the coating will be applied during the summer of 2013 during warm and dry conditions.

De-icing solution:

• A de-icing spray could be applied to the bridge cables as a preventative measure in addition to the solutions listed above. The de-icing solution would be applied to the bridge cables before a forecast snow storm. Similar preventative solutions are used to prevent ice buildup on aircraft and ocean-going ships.

• Port Mann / Highway 1 engineers have identified a de-icing solution that is non-corrosive, environmentally friendly and can act as a preventative ice barrier.

Media Contacts:

Kate Trotter
Government Communications and Public Engagement
Ministry of Transportation and Infrastructure
250 356-8241

Max Logan
Communications Director
Transportation Investment Corporation
778 783-1218