RTD spends about $1 million a year repairing and resetting granite pavers in bus lanes on the 16th Street Mall, so the agency soon expects to experiment with a new material containing epoxy and black sand to better join and seal the pavers.
The Regional Transportation District claims it can no longer bear the full burden of maintaining bus lanes on the 27-year-old mall.
The agency looked into the possibility of replacing granite pavers with textured concrete that might be fashioned to look like the original design, but historic preservationists and others studying mall improvements have come back with a strong message: The paving system must remain granite.
Architects and other design professionals say the mosaic of 400,000 red, white and black granite pavers is the mall’s most distinctive artistic feature and needs to be preserved.
One challenge is to develop new techniques for setting, grouting and sealing pavers that will add durability to the transit lanes and pedestrian walkways of the mall, say representatives of RTD and the Downtown Denver Partnership.
Mall’s required maintenance
The two groups, along with the Downtown Denver Business Improvement District and the city and county of Denver, have led recent studies to chart the mall’s future.
“There is a consensus that we need to respect the original design intent,” said John Desmond, vice president of urban planning and environment for the Partnership. “This probably is the most successful pedestrian mall in the country.”
While RTD is responsible for maintaining granite pavers in the bus lanes, the business improvement district — which is funded with assessments on downtown property owners — cleans the corridor and repairs granite pavers in the pedestrian walkways.
Pavers in the transit lanes, which bear the weight of buses, delivery trucks and other vehicles, typically require more repairs than sidewalks and other pedestrian areas.
“Those in the transit way carry more of a load, require more of a maintenance effort and require more dollars,” said RTD civil engineering manager Stan Szabelak.
Ground-penetrating radar has revealed voids under the bus-lane pavers in some areas, according to the study, and infiltration of water into those damaged joints has increased required maintenance.
The ongoing study of solutions for the mall is looking at a “minimal scenario” that would regrout and reseal the pavers, as well as a more extensive rehabilitation that would include roughening the granite surface to make the pavers less slippery, filling voids in the “setting bed” beneath the granite and regrouting and resealing the joints.
Electrical repairs needed
An even more elaborate alternative calls for removing the pavers and substrate materials on which they sit, flipping the granite, resurfacing it to provide better traction and a cleaner look, reinstalling the pavers with new setting materials and then regrouting and resealing.
The mall study group is expected to have cost estimates for the various options later this year.
The mall also needs extensive repairs to an electrical system buried beneath portions of the corridor, and officials are considering making the electrical upgrades at the same time there is an overhaul of the granite pavers.
All groups involved in the mall’s maintenance hope to better distribute “financial responsibility” for maintaining the bus lanes, Szabelak said.
Jeffrey Leib: 303-954-1645 or jleib@denverpost.com
