Aspen to continue use of deicer on downtown streets

Water quality tests not clear from last winter’s testing of IceSlicer but appear unremarkable in damaging aquatic life

Pedestrians navigate ice buildup on the crosswalk beside Rubey Park Transit Center in downtown Aspen on Thursday, Dec. 23, 2021. IceSlicer, a granular blend of chlorides, was used last winter on the roads in town and will be used again this winter. (Kelsey Brunner/The Aspen Times)

With fewer instances of buses sliding, improved road conditions and unremarkable changes in chloride levels in the Roaring Fork River, the city of Aspen will continue using a deicing agent on roads in the downtown core and on Main Street this winter.

The city used a product called IceSlicer last winter as a test to see how its effect would be in reducing dangerous road conditions for vehicles and pedestrians.

IceSlicer is a granular blend of chlorides, which has the ability to lower the freezing point of water and accelerate the melting of snow and ice, said April Long, the city’s clean river program manager.

Its granular nature also provides some traction, like sand, which can improve road conditions for vehicles, she noted.

IceSlicer was applied on Highway 82 from the roundabout through town on Main Street and onto Cooper Avenue to the bridge over the Roaring Fork River. It also was applied on Spring Street up to Durant Avenue, down to South Aspen Street and back to Main Street, which are the main bus routes to and from the Rubey Park transit station.

Jerry Nye, the city’s superintendent of streets, said his department received fewer calls last winter from the Roaring Fork Transportation Authority requesting to put sand on the road so drivers could navigate buses in problem areas.

“With the IceSlicer, RFTA can negotiate the corners better,” he said. “In our trouble spots we had less issues.”

Some of those spots are on Durant Avenue and Spring and South Aspen streets, as well as at intersections on Main Street and at the S-Curves.

Those areas have significant winter traffic accident counts and RFTA requests, according to Nye.

Dan Blankenship, CEO of RFTA, said the main problem area for buses is in front of Rubey Park heading west on Durant Avenue when the road canters past Wagner Park toward Monarch and South Aspen streets.

That’s where buses are more susceptible to slide toward parked vehicles and onto the curbs, which then creates worker’s compensation situations when drivers get out to deal with the accident and potentially slip on an icy road, Blankenship noted.

Anecdotally, he said having the city apply IceSlicer has helped with driver safety.

“I’m feeling we had a better year after the city started applying deicer,” he said. “The streets department does a great job to make sure the streets of Aspen are passable during these big snowstorms.”

The streets department applied 58 tons of IceSlicer from November 2020 to March, which saw 53 days with snow accumulation.

Long said using the deicer also was to reduce the amount of sand applied through the winter because 3/8″ rock presents its own environmental impacts, especially as it is ground down to a finer particle that is more easily carried in snowmelt into the city’s stormwater system and discharged into the Roaring Fork River and its tributaries.

Nye said a significant amount of sand doesn’t make it from the roads to the river because it’s picked up through the snow removal process and winter street sweeping.

Prior to last winter, the city applied on average 392 tons of sand per season, ranging from 155 tons in 2016-2017 and 586 tons in 2010 – 2011, the latter of which was a high snow year.

The city applied only 131 tons of sand when IceSlicer was tested last winter.

While sand can negatively affect water quality, so can chlorides, according to Long, who noted that when conductivity and salinity values extend too far from their normal range, it can be detrimental to the aquatic life.

But chloride levels are difficult to measure because samples must be hand-collected and sent to a lab for analysis, she said.

So rather than using intensive staff time and labor, Long’s team used conductivity probes for data collection every 15 minutes at three locations along the river.

Those locations are near the Stillwater Bridge east of town, as well as a catch basin in Rio Grande Park and the outfall just downstream of that.

Conductivity is directly impacted by changes in chloride levels and salinity, but it is also related to water temperature and flow.

By measuring conductivity and comparing it with temperature and flow, staff anticipated the ability to indicate if chloride levels were affecting the river, Long said.

At the two in-river locations, conductivity generally increased as water temperature increased, which was expected, but it stayed within a small range.

At the Mill Street bioswale, conductivity was much higher and fluctuated quite a bit, decreasing significantly in March when the streets department stopped applying IceSlicer.

“Because the bioswale showed extremely high levels of conductivity, but the river just downstream of this outfall did not follow those fluctuations and did not record those same high conductivity levels, staff believes that the flow and temperature of the river assimilated the conductivity levels in this location,” Long wrote in a memo to Aspen City Council.

She added that some data was difficult to understand and assign cause, so staff will continue the study for another season.

They will return to council in the summer with a proposed winter road ice management plan, which will specify when, where and how much de-icing agents should be applied.