Testing for chloride on the Little Falls Branch in the Brookmont neighborhood.
The winter road salt testing seasoned ended April 23 with one final testing for chloride in the local creeks. Results from the season (seen in Figure 1) indicate that the creeks in the Little Falls watershed are experiencing high levels of salt despite the lack of winter storms. Eight sites were sampled over the course of the five months. Seven of the sites had at least one sample above the chronic threshold (230 ppm) and six of the sites had two or more readings above the normal range (0-100 ppm). As the fresh water organisms that live in the creek are impaired by salt levels above 100 ppm, this spells serious problems for our creeks.
Learn more about the results and read the final report HERE.
How does road salt end up in the Creek?
Salt spill along University Avenue in Washington, DC.
When the snow melts, or turns to rain as is often the case in this area, the salt on the streets, driveways, or other surfaces is washed into into the storm drain system which runs directly into the closest creek.
Testing at our Little Falls Branch site downstream from Massachusetts Avenue showed that the effect of the salt can be seen in as little as 24 hours after a storm and can last several weeks.
Salt also makes its way into the creeks when it lands on vegetative areas. When the salt melts on the surface, it is carried through the soil and pollutes the ground water aquifers below the surface. Creeks are fed by the water in these aquifers. It the aquifer is polluted, the stream will be too. It can take months for the salt to make its way into the ground water which accounts for the high baseline levels we saw in both December and April before and after the winter season.
WHAT IS THE IMPACT OF ROAD SALT ON CREEKS?
Stream Life is Threatened: Fish and bugs that live in freshwater streams can't survive in extra salty water. Chloride levels up to 100ppm are considered normal, but over that fish and the macroinvertebrates that are the bottom of the food chain are severely stressed. Many studies show the reduction in the abundance and growth of fresh water organisms and a reduction in the reproductive outputs. We do not have any “before” data, but the Little Falls creek always rates between Poor or Fair for its biological health with regular BIBI scores of less than 2 or lower (out of 5). Our BIBI scores are HERE. It is not unreasonable to suggest that high salt readings contribute to these low scores.
Drinking Water is Threatened: In Montgomery County and in DC, drinking water comes from local creeks and rivers. On their Salt Wise page, WSSC Water reports that they closely monitor the water entering the Patuxent and Potomac Water Filtration Plants and have noticed that over the last 30 years, the average salt levels (sodium and chloride are the two components of salt) have been steadily increasing. Once sodium or chloride enters the drinking water sources, they cannot remove it during the water filtration process. There is a concern that if the level continues to rise, it could impact human health, especially for those on low-sodium diets.
How does our program help reduce Road Salt?
By testing the area creeks and publishing our data on our website and local neighborhood listservs, residents can see how salt on the roads impacts the salinity of the creek. We have used this data to successfully advocate for reduction in residential and commercial application of salt. Appeals to residents to report illegal dumping of salt and excess salt piles led to more than one clean-up. And, we partnered with the Izaak Walton League to paint a snowplow to raise awareness of the over-salting problem.
Thank you
Our salt testing program is made possible by a crack team of citizen scientists who have taken our training and commit to sampling once a month and after storms. We are in awe of their stewardship. Woody Stanley crunches our numbers, helps with the data entry, reminds volunteers to monitor, and prepares the end of year report. The program would not exist without his dedication. We partner with the Izaak Walton League on this project and are part of their Winter Salt Watch Program. Our data is entered into their national data base and contributes to their effort to track to effects of road salt on waterways nation-wide.
