by the Riverside Park Conservancy Sustainability Team
New York States uses about 500,000 tons of rock salt on our roads annually. You’re most likely wondering how do we consume that much? Well, Department of Transportation has a policy that requires an application rate of rock salt to be 225 pounds per lane-mile for light snow conditions and 270 pounds for heavy snow conditions. So how does that intense concentration of salt affect our local environment? 55% of road-salt melt runs off with snow melt into streams and rivers while 45% infiltrates into soil and contaminates groundwater in parts of the state where groundwater is the main source of drinking water. Approximately, 6,000 miles of the state’s paved roads are near water sources. When salt melts it is absorbed by the soils adjacent to these water sources, causing the structure of the soil to disintegrate and erode into streams and rivers. The salt is then carried along with the eroded soil altering water quality to levels beyond safe consumption.
Most believe that the salt will evaporate from the water eventually, but it doesn’t and continues to persist damaging aquatic ecosystems in the process. Ecosystems on land also face their own challenges with excessive salt loading.
Navigating Storm Readiness in an Urban Park
As we slip into the latter of these seemingly warm New York City winter days, with the slight promise of snow on the way, let’s talk about snowstorm readiness in New York City and how it relates to Riverside Park. Even before snow and ice blanket the city, the city’s already preparing for the icy and snowy conditions that make travel within the city seem impossible. The same goes for us at Riverside Park, as we prepare for the influx of parkgoers who love using our rolling hills and slopes for sledding, open spaces for snowball fights, and taking strolls through the levels of the park from drive to river.
To ensure safe conditions for travel by car or sidewalk, the night prior to the storm things like anti-icers and deicers are applied to road ways and sidewalks. Anti-icers are applied liquids that prevent ice from bonding to roadways while deicers are solids applied to break the already existing bonds between ice and pavement (e.g., when plowing is required to clear roadways). In this blog post, we will be exclusively talking about the most used deicer in New York State which is rock salt. Rock salt keeps roads and sidewalks navigable by melting ice and snow into a brine that has a freezing point lower than water.
New York States uses about 500,000 tons of rock salt on our roads annually. You’re most likely wondering how do we consume that much? Well, Department of Transportation has a policy that requires an application rate of rock salt to be 225 pounds per lane-mile for light snow conditions and 270 pounds for heavy snow conditions. So how does that intense concentration of salt affect our local environment? 55% of road-salt melt runs off with snow melt into streams and rivers while 45% infiltrates into soil and contaminates groundwater in parts of the state where groundwater is the main source of drinking water. Approximately, 6,000 miles of the state’s paved roads are near water sources. When salt melts it is absorbed by the soils adjacent to these water sources, causing the structure of the soil to disintegrate and erode into streams and rivers. The salt is then carried along with the eroded soil altering water quality to levels beyond safe consumption.
Most believe that the salt will evaporate from the water eventually, but it doesn’t and continues to persist damaging aquatic ecosystems in the process. Ecosystems on land also face their own challenges with excessive salt loading.
Protecting Our Planted Spaces
Riverside Park from 59th Street to 181st Street hosts a myriad of beautiful and visually stimulating gardens along its meandering hills and slopes, but that only be true if the soils of our park are healthy and well preserved. In the colder months, many of our plants are barren and in hibernation waiting for the warmer seasons to grace the park again. Yet, the colder months also bring the promise of snow and the excessive use of rock salt in New York City.
Unfortunately, to maintain the walkability of our paths and entrances rock salt is employed to keep them from icing over. Which is a plus for parkgoers enjoying the winterized landscape of our park. But, the salt-laden water from the snow melt can be, as aforementioned, absorbed by surrounding soil affecting soil particles, soil microbes, and plant roots. The excess salt:
- creates conditions for water stress where water availability is limited to plant roots because salt ions hold on tightly to water molecules.
- transforms soil quality through displacing potassium and phosphorus as sodium ions bind to soil particles.
- soil becomes denser and more compacted affecting drainage and aeration.
- produces sodium and chloride ions in excess causes plants to preferentially absorb them instead of nutrients like potassium and phosphorus.
- concentrates chloride in plant tissue by being absorbed into roots and leaves. Repeated exposure to salt over long periods time result in leaf burn and twig die-back.
Some plants are salt tolerant, but the level of tolerance varies across herbaceous and woody species. Plants that can handle high concentrations of salinity do well in saline soils as well as soils under normal conditions. In some cases, grasses can adapt readily to high concentrations of salt. [ not all of our plants are tolerant to salinity but the ones that are waxy and have scaled foliage along with protected buds are better adapted to handle plant stress]. The plants in Riverside Park that are more sensitive to high salt concentrations result in poor growth, stunted leaves, die-back of branches and twigs, leaf scorch, and premature leaf drop. Weakening of these plants leaves them vulnerable to biotic disease and pests. Yet, there are available alternatives to help support the viability of our planted landscapes and the urban wildlife that depends on them year-round.
Weighing Park Friendly Alternatives
To better support our planted landscapes and park ecosystems there are more sustainable low impact alternatives to anti-snow and ice measures. One such alternative is alfalfa meal. Alfalfa meal has the ability to melt snow and ice while providing traction. Best part is, alfalfa meal acts as natural fertilizer. This means when winter eventually transitions to spring and the ice and snow melt, the fertilizer will be absorbed into the soil and support the gardens in the warmer months.
Another alternative is sand. Sand is mostly used as a traction aid for pathways and roadways. The crystals in sand help decrease the risk of tires skidding on icy roads and prevents the formation of new ice. This alternative does come with its drawbacks though. Sand has to be laid out at a rate 3 to 7 times higher than rock salt and come spring the snow-sand melt may clog already stressed park stormwater infrastructure. Nevertheless, it works the best in low impact areas such as pathways and sidewalks in parks due to the fact that no vehicle traffic (other than the Conservancy staff and Parks staff) is present. Maybe we will have to brace for a winter storm this season or maybe not, but trust we at the Conservancy are taking every measure possible to make Riverside Park accessible and safe to our neighbors. Even our non-human neighbors who visit and their home in the park year-round.