BRATTLEBORO — The same weather combination of frigid nights and sunny days that signals sugar maples to release their sap also leads to a less-pleasant part of Vermont's spring: mud season.
As the warm days cause the frost deep in dirt roads to thaw, the extra water turns the roads into the soupy bane of a car's exhaust system.
Throughout mud season, Director of Public Works Steve Barrett sends a member of the DPW to drive all 30 miles of Brattleboro's dirt roads. The staff member then rates the road “good,” “fair,” “poor,” or “closed.”
The ratings are sent to Central Dispatch so emergency services know if they need to alter their travel plans. The information is also added to the daily Gravel Road Conditions Report and posted on the town's website, brattleboro.org.
“We've had multiple mud seasons this year,” he said. “It's been a mixed bag of weather.”
As of April 1, the report noted 21 roads in fair condition. Fair means drivers should expect “heavy rutting, washboards, and substantial mud.” Cars with low clearance could be damaged. Emergency vehicles will get through, but their travel could be delayed.
The full DPW report lists 29 roads. Seven are listed in good condition, but even on a road rated as “good,” drivers can encounter ruts and mud.
Gibson Road, with no houses along its path, is closed outright.
Barrett said the roads are slowly drying out. Still, he expects mud season to last at least two more weeks.
Ultimately, the department's mission is to keep roads passible enough so residents can get the supplies they need - heating oil, for example - and so emergency vehicles can get through to help residents stay safe, Barrett said.
Sometimes the department will work with delivery companies, such as a fuel-oil company, to alter their schedules.
When such companies make their deliveries later at night or early in the morning when temperatures are lower, that shift helps preserve the road, Barrett said.
'Drainage, drainage, drainage'
While mud season can prove a yearly challenge for all drivers, Barrett said some of the historic trouble spots, such as Sunset Lake Road, are in better shape due to extensive repairs.
Keeping a dirt road in tip-top shape is all about “drainage, drainage, drainage,” said Barrett. Getting water off and away from a road is the first and best thing for maintenance, he explained.
Many of the town's dirt roads started as pathways, Barrett said. As a result, many are built without the materials that support good drainage.
“There's actually a science” to gravel that includes the percentage of rock contained in the mix, he said.
A well-constructed dirt road includes layers of gravel in varying sizes, said Barrett.
The lower layer is a heavy gravel called “bank run gravel,” a mix that ranges in size from sand and dirt to heavier rock. The road's top layer is ideally 6 inches of a finer gravel, Barrett said.
Another component to keeping a road dry are drainage ditches and culverts that channel the water away from the road, he added.
After Tropical Storm Irene in 2011 washed out some dirt roads, the DPW took the opportunity to add better-draining gravel and to upgrade the size of culverts, said Barrett.
The department also tracks chronic problem mud zones and plan for repairs in its capital budget.
Even with good drainage, however, the department must return $30,000 to $40,000 a year of gravel to roads annually for spot repairs and to replenish what's been blown away or eroded.
“We lose a lot of gravel to wind and rain,” he said.
Once mud season ends, Barrett said crews will grade the roads. In May, the department will coat the dirt roads with magnesium chloride, a compound that reduces dust and erosion and keeps the soil compacted.
First, do no harm
Barrett described maintaining dirt roads in mud season as “a delicate balance.”
Driving heavy equipment over a dirt road to reach a trouble spot can sometimes lead to new trouble spots, he said.
Much as they advise the delivery companies, the department will take advantage of cooler temperatures and do the work early in the morning.
And then, the crew will “get off the road,” Barrett said.