Denver's Paving Program Delivers Cost-Effective Street Maintenance Approach

"We're not only reconstructing the alleys, but also correcting the height of the road to keep it below the adjacent lots so that it does serve to drain water away from the backyards and into the connecting streets," Roberts says. "We expect the refurbished alleys to last about 15 years, with traffic limited to cars and weekly refuse trucks. So the cost (approximately $6,000 per alley) is a much more economical approach to maintaining the alleys than the annual pothole fix, and homeowners (our customers) are a lot happier with the final results of a new surface versus a patched surface."

The street maintenance division's staff of 190 full-time employees is directly related to the number of personnel required to handle snow removal during the winter. That number also serves the city well in the various street reconstruction projects slated each summer. With a fleet of trucks, used to plow snow in the winter, and the drivers to operate those trucks, the department can easily schedule its hauling needs for removing millings from a project to delivering HMA to that project without worrying about finding independents to do so.

"We're very efficient at what we do and we're always able to keep our people busy," Roberts says. "Even on our contracted hot in-place projects, we still provide the HMA from our plant, so the contractor is never waiting for an independent trucker hauling from an independent plant. We're able to keep our hot in-place contractor moving, and that's good for him, good for us and good for property owners, who know we'll begin and complete work on the street in front of their home that same day.

A methodical approach

A photograph in Roberts' office of the city's paving crew in the 1930s is evidence of the fact that Denver has an extensive history of maintaining its streets, and today's street maintenance division continues to fine tune the process.

"We have an infrastructure management system in place to visually inspect all the roads within our network and to constantly update the condition of our inventoried roads; and now we've added alleys to that inventory," Kennedy says. "Typically, seven years after we construct a new road (or a mill and overlay) we apply a chip seal. Then seven years later we apply another surface treatment. The plan is to achieve a 20-year life cycle out of a road before we have to do another mill and overlay, or a full-depth reconstruction. Most of the city streets are only 3 inches of asphalt over a compacted subgrade, so a mill and overlay on those streets is almost a full-depth reconstruction. But if we can get 20 years out of surface, we're happy with that."

Based on software the department uses to manage its street inventory and monitor the condition of those streets, the department has developed a six-year plan to identify maintenance that needs to be performed on the overall network. The software then narrows the focus to streets that need repair within one to two years.

"We've been collecting data since the early '90s and it's helped us to target our efforts on streets in dire need of repair, as well as preserving good streets to extend their life cycle," Kennedy says. "But like in any other political environment, we make sure we're spreading out the work to include all districts, and over a five-year period our efforts are evenly distributed throughout the city."

Kennedy says efforts by an infrastructure task force helped to identify what needs to be done to maintain a good street system and the city council has been supportive of meeting requests, and very supportive of preventive maintenance programs.

With the city's government supporting the street maintenance division's paving practices since the 1930s; it's unlikely any dramatic changes will be made in how the municipality maintains its street network. Roberts and his staff continue to evaluate how to maintain a quality road system within the constraints of the budget the department receives, and while contracting hot in-place, chip seal and larger paving projects makes sense, the department's in-house paving capabilities has proven to be the most cost-effective way of meeting the quality of roads Denver taxpayers are willing to support.