Road Salt and Its Impact on Fresh Water

January 12, 2021 By Evan Hunt

As winter quickly approaches so does the threat of salt pollution. Since the 1940s, salt has been the number one choice for fighting road ice in the United States. Over the last five years, PennDOT used an average of 844,000 tons of salt per year to keep Pennsylvania’s roads free of ice during the winter months. As effective as salt is at melting ice, it can cause major environmental problems after it washes off roads and into nearby waterways. Scientists have known for a long time that salt can be a serious pollutant in freshwater ecosystems, affecting multiple species of fish, insects, amphibians, and plants. More recent studies have shown that road salt is the main culprit of salt pollution in the northern United States.

According to a USGS survey, 84% of streams in urbanized areas of the northern United States have seen increases in chloride levels attributed to road salt. While 40% of streams have experienced levels that are considered dangerous to aquatic species. Furthermore, 29% of those streams have seen spikes in chloride levels during the winter that would make the water unsafe for drinking.

Armed with this knowledge, PennDOT and local municipalities have made efforts to limit the amount of salt laid on roadways. PennDOT limits salt treatments to high-traffic areas and dangerous intersections or curves. At the same time, municipalities have started mixing sand in with salt to improve traction and reduce the overall amount of salt used. Unfortunately, these changes might not be enough as private businesses and homeowners still contribute significantly to the amount of salt introduced into the environment. Over-salting of sidewalks and parking lots is far too common since private snow shovelers are understandably more concerned with the safety of pedestrians than the environmental costs associated with using salt.

However, there are ways to achieve a balance that prioritizes safety while also taking into account the risk of salt pollution. The most straightforward solution could be sweeping up salt from sidewalks after the ice has melted but before a snowmelt or rain event can wash the salt away. Not only does this prevent salt from reaching our freshwater ecosystems but the salt can be reused during the next snowstorm to save some money. Adding salt before snowfall rather than after is another technique that could reduce the amount of salt needed to keep sidewalks free from ice. Another option is to reduce the amount of salt used by cutting it with sand or even beet juice like some Canadian cities have successfully experimented with. All of these methods can be implemented by anyone who finds themselves shoveling snow during the winter.

Even those of us who do not have any snow shoveling responsibilities can play a big part in addressing this issue. The Izaak Walton League is a national organization that trains citizen scientists to measure the amount of salt in their local streams, especially after snowstorms. This kind of data can help determine the local impact or source of salt pollution. Maybe more valuable, measurements collected by citizen scientists will increase the national dataset used to help scientists and policymakers make decisions about mitigating the effects of our increased reliance on road salt.

For more information about becoming a volunteer citizen scientist, you can visit iwla.org.

Mapping the Ashbridge Tree Planting

September 23, 2020 By Evan Hunt

The most important part of a tree planting usually comes after the trees are in the ground. Recently planted trees can not be left unattended or else they will be out-competed by invasive plants or eaten by deer. Consistent tree maintenance is crucial to the survival of a young tree until it can get established in its new environment. For a tree planting in a rural setting, like the recent planting at Ashbridge Lake, maintenance includes weeding, mowing, pruning, and replacing tree tubes to keep deer from damaging the trees. Performing all of this maintenance on a tree planting with close to 1,000 trees can get complicated. Fortunately, we can use technology like a geographic information system (GIS) to help us organize tree maintenance and keep track of every tree on a site.

Over this past summer the Watershed Protection Team did exactly that. Using software from ArcGIS, our team mapped every tree that was planted over the last two years at the Ashbridge Lake site in Ashbridge Preserve. That is a total of 691 trees with a few hundred more set to be planted sometime in 2021. We collected the latitude and longitude of every tree and recorded the species, size, health, and date each tree was planted. We also recorded the last time each tree was maintained. All of this data was compiled and each tree was represented with a point to create the maps shown below.

Trees planted at Ashbridge Lake on both banks of Ridley Creek and along the Ridley Creek Loop trail. Each color represents one of the 29 different species planted.

In addition to creating a visualization of all of the trees planted along Ridley Creek these maps create a database of information on all of our trees. Keeping track of when each tree was last maintained will help us create a streamlined maintenance system. Data on health helps us monitor the success of the tree planting and look for any unresolved problems in the planting site like areas with poor soil or frequent flooding. Measuring the size of each tree will allow us to look at growth rates to see which species are best suited for our site. All of this information is very valuable when planning for the next stage of planting at this site or for scoping out other sites that need to be reforested.

The goal of the tree planting at Ashbridge Lake is to restore the riparian buffer along the creek which will provide habitat and food for native wildlife while improving the water quality of the stream. To achieve these goals it is necessary that as many trees as possible reach full maturity. Creating a tree map to help organize a maintenance plan and collect detailed information on each tree is one tool we can use to assure our tree planting reaches its fullest potential as soon as possible.

This tree planting was made possible by generous funding provided by the Pennsylvania Department of Conservation and Natural Resources and TreeVitalize. See below for the full interactive map and list of species.

View larger map

EVAN HUNT joined the team as a Conservation Associate in January. Evan Hunt is a native of southeastern Pennsylvania and graduated from Ursinus College in 2018 with a BA in Environmental Studies. Since then, he has worked on a number of riparian buffer restoration projects and become well-versed in native plant identification.