A Twin Technical Tour in the Twin Cities

Christine Beckwith, P.E., MBA
Maintenance Research Engineer
Mn/DOT Metro District
Roseville, Minnesota

Editor's Note: Mn/DOT's Regional Transportation Management Center and I-35E Lexington Bridge Anti-Icing System are included in the Technical Tour program during APWA's 2007 North American Snow Conference. On April 25, the final day of the conference, attendees can either tour the Regional Transportation Management Center and see a demo of the pump house and in-pavement equipment, or tour Mn/DOT's Central Services Shop and fabrication facility (see the upcoming March issue for related article). Both of the Technical Tours are included in the registration fee as a part of the Snow Conference educational program. See pages 17-20  for more details on the conference and visit the Snow Conference website at www.apwa.net/snow.

As I write this article, we are experiencing our first real snowstorm of the season in Minneapolis/St. Paul. Freezing rain during the morning and early afternoon of December 21 has turned into big, fluffy white flakes and our snow and ice operations are in full force. A seamless integration of snowplowing and mobile anti/de-icing operations, bridge and roadway automated stationary anti-icing systems, and incident and freeway management through our Metro District Maintenance Dispatch and Traffic Operations groups at the Regional Traffic Management Center (RTMC) are underway. Though many motorists seem unprepared for the first real snow, that certainly isn't the case for Minnesota Department of Transportation (Mn/DOT) snow and ice operations.

This April, after the snow has come and gone, the APWA Minnesota Chapter will be hosting the 2007 APWA Snow Conference. The enthusiasm for hosting the event has been evident, as a record number of abstracts were submitted by the Minnesota Chapter members this year. One of the highlights of the conference will be a joint Technical Tour of the RTMC and a field tour of the I-35E Lexington Bridge automated anti-icing system located just south of St. Paul. Showcasing how Mn/DOT Maintenance Dispatchers monitor the automated anti-icing systems from the RTMC and how those systems actually function in the field gives a complete picture of the management of stationary anti-icing systems in the eight-county Metro District as well as snow and ice operations in general.

The RTMC is located in Roseville, a St. Paul suburb, next to Mn/DOT's Metro District headquarters. It features a second generation, state-of-the-art operations center that integrates Metro District Maintenance Dispatch, the Office of Traffic, Security and Operations' Traffic Operations group and the Department of Public Safety's State Patrol Dispatch into a single communications center. Housing the three operations functions under one roof allows the departments to coordinate transportation management on metro freeways during the normal commuting periods as well as during major incidents and snow and ice events.

Because freeway volumes in the Twin Cities metro area grow roughly four percent per year, one of the RTMC's main goals is to provide motorists with a faster, safer and more predictable trip on metro-area freeways by using cutting-edge technology, progressive programs and real-time information delivery systems.

Among these information systems are the stationary anti-icing systems that are monitored by Maintenance Dispatch, along with several other types of systems and field data throughout the metro area. There are nearly a dozen anti-icing systems statewide; however, only the three systems within the Metro District are monitored at the RTMC including two fully automated systems (one on I-35W in Minneapolis and one on I-35E near St. Paul, both spanning the Mississippi River) and one semi-automated system just north of the Mississippi on I-35W in Minneapolis. An overview of RTMC, and more specifically the software and computer systems that monitor the anti-icing systems, will be provided on the tour. The group will then board buses to visit the I-35E Lexington Bridge anti-icing system just south of St. Paul.

Contractors access the underside of the I-35E Lexington Bridge during system installation in the summer of 2005.

The I-35E anti-icing system treats 1,150 feet of bridge in each of the northbound and southbound directions, with another 1,250 feet of roadway being treated in the northbound direction approaching the bridge. It was installed in the summer of 2005 and was operational in the winter of 2005-2006. This anti-icing system project offers a unique opportunity to study the effects of how treating the approach roadway in one direction may lessen the amount of chlorides used on the bridge for snow and ice control and therefore possibly extend the life of the bridge itself. The anti-icing system instead uses the more environmentally-friendly, although more expensive, Potassium Acetate which is not corrosive to steel rebar, bridge structures or concrete. In the coming years, chloride penetration will be measured on the bridge deck in both directions. If utilizing Potassium Acetate on the bridges through an anti-icing system that applies a measured amount of chemical only when it is needed proves to extend the life of the bridge by reducing chloride usage, it certainly would add another dimension to the cost-benefit of such systems.

Test spray of the Boschung Stationary Anti-Icing System on the I-35E Lexington Bridge

The $1.2 million Boschung anti-icing system on I-35E was installed on a new bridge completed in 2004. It was still considered to be a retrofit installation due to bridge construction staging and scheduling issues that prevented the anti-icing system from being installed during the actual bridge construction. Construction photos, which will illustrate the challenges involved when accessing, constructing and maintaining these complex systems, will be displayed at the pump house. On this system, 73 spray disks (50 on the bridges and 23 on the roadway) utilize a site-specific Road Weather Information System (RWIS) station, along with Boschung's BOSO and ARCTIS active pavement sensors, to automatically apply chemical to the bridge deck and roadway surface to prevent icing conditions. It has been working very well since installation and requires surprisingly little maintenance and intervention.

The Technical Tour at the pump house will allow participants the opportunity to see all of the behind-the-scenes components of an anti-icing system, as well as some of the innovations that Mn/DOT has incorporated into the system as a result of more than seven years of experience with these systems. A test spray will be performed and participants will be able to walk along the bridge to view the driving lanes from an adjacent bicycle/pedestrian path to get an up-close look at the operations.

Another highlight of the field tour will be a discussion of the yearly maintenance performed on the system by Mn/DOT personnel, as well as a successful expansion of the system through the addition of pavement sensors completed by in-house forces in the fall of 2006. As we continue to gain more knowledge of all systems available on the market, we hope eventually to move toward installing more systems with our own staff as other states have done. Though Mn/DOT may have been one of the leaders in installing one of the earliest systems back in 1999 (our I-35W system), many other states have even more extensive anti-icing systems today and we look forward to both sharing our lessons learned as well as learning from the conference participants.

Chris Beckwith can be reached at (651) 582-1431 or Christine.Beckwith@dot.state.mn.us.