By Whitney Forman-Cook
The district manager of a Vermont conservation district spoke before the state’s House Committee on Natural Resources recently on an important issue in the northern U.S.
Road salt, Corrina Parnapy told lawmakers this winter, is making its way into American riparian, aquatic, and terrestrial ecosystems.
Following a thaw or rain event, Parnapy testified, salt applied to control ice on roads and bridges is flushed into waterways and lakes. “Studies say between 10 to 55 percent of road salt makes its way into groundwater,” she said, and “up to 63 percent road salt is transported by air into the surrounding environment.”
Made up of 40 percent sodium and 60 percent chloride, road salt can shift algae dominance in lakes from chlorophyte (green algae) to cyanobacteria (blue-green algae that can lead to toxic algal blooms). At 210 mg/l of chloride, sensitive zooplankton species are impacted, which can increase phytoplankton populations and lead to toxic algal blooms, too. At 250 mg/l, native brook trout populations are impacted.
“Many streams within Vermont have already been identified as impacted by chloride through water quality monitoring efforts and exceed EPA standards and levels,” Parnapy testified.
Roadside soils and vegetation are also affected, in some cases, at even lower levels of chloride concentration. Soil bacteria near roadways is affected at 90 mg/l and seed germination is impaired at 100 mg/l. “Sodium chloride strips the soil of calcium, magnesium, and other important components needed for healthy soils, allowing invasive species to take hold,” she added. “It can also cause drought conditions by limiting available water in soils and trees, and can burn the needles and leaves of tree species within 15 to 650 feet of roads.”
To address the soil and water health impacts from road salt, Parnapy suggests implementing a monitoring system and best management practices to reasonably reduce salt application rates.
“Municipalities can reduce road salt applications without reducing the safety benefits of spreading road salt if BMPs are followed,” she said. “We all would like to see a reduction in costs to our towns and the state, plus increased protection of our natural resources.”
Winooski Natural Resources Conservation District recommends using the following BMPs:
- Apply road salt before or just as a snow or ice storm begins. This prevents or weakens the bond between the ice and pavement. By being proactive and not reactive, salt applications can provide safer surfaces sooner, save money, and protect the environment. Studies have shown it costs up to six times more to melt ice and snow from the top down than the bottom up.
- Incorporate reduced salt application zones on roads near stream crossings, known vernal pools, wetlands, and lakes.
- Apply product at the recommended vehicle speed; spreaders are most effective at 25 mph.
- Pre-wet or apply a salt-brine. This is a cost-effective, anti-icing technique that sticks to the road surface.
- Utilize a Road Weather Information System (RWIS) linked to road temperature sensors and onboard monitoring software. By tracking application rates and current real-time weather, applicators can make adjustments and reduce waste.
- Ensure all applicators (both public employees and private contractors) are trained in proper techniques, calibration, and environmental risk assessment. States that have implemented successful road salt reduction strategies have made private applicator certification mandatory through legislation.
- Assess chemical alternatives. Some salt alternatives contain higher levels of phosphorus and can potentially lower the dissolved oxygen in waterways, causing anoxic conditions.
For more information on road salt reduction strategies and this district’s Road Salt Reduction Initiative, visit: www.winooskinrcd.org.