A recent study focused on a water pollutant that we all know very well: salt. In particular, de-icing salts used during the winter. Over the years, the pH level of many streams across Virginia – and the nation – have become more and more basic, endangering aquatic life. WMRA’s Marguerite Gallorini reports.
This is the first study to assess long-term changes in freshwater salinity and pH at the continental scale. And its results show a significant increase in the amount of salt in 232 streams across the country, leading to a basic pH of the water – a phenomenon called alkalinization, which is caused by different factors.
MICHAEL PACE: Road salts, agricultural runoff, municipal land use change, and the presence of more and more paved surfaces and things like that that contribute to runoff. Because, instead of the water infiltrating into the soil, it tends to shoot down on concrete and pathways and get into a ditch or a drain and then out into the stream, so it increases the rate of runoff.
That’s Michael Pace, an aquatic ecologist and a professor in the Department of Environmental Sciences at UVa. He is one of the co-authors of this national study, which was published in the Proceedings of the National Academy of Sciences.
PACE: Freshwater life, the organisms that live in streams and rivers, can't withstand really alkaline conditions. If it's really alkaline, some of the chemicals in the water become toxic and organisms just can't survive under those conditions.
And what consequences would that have for us?
PACE: For human health, there are two issues there: one is that, if your fresh water is more salty, it may be problematic for people that have certain dietary restrictions, people that have diseases where they have to regulate their chemistry very carefully, then you don't want to drink water that's really rich in chemical content. And a second context is that if you pull salty alkaline water into your pipes, that can be hard on the plumbing and create a variety of problems either for the individual homeowner who might have a well, or for the water management agency that might be managing large infrastructure pipes.
Flint, Michigan is a notorious example of a city changing its water source, and then discovering that without treatment, the extra alkalinity degraded the pipes and increased the levels of lead in the water. While this is an extreme case, it shows the kind of cascade of issues water management agencies can face with alkaline water. And not just them: it takes a common effort to address this issue. Here’s Will Isenberg, who works on water quality assessment at the Department of Environmental Quality in Richmond.
WILL ISENBERG: We've been trying to engage a number of different stakeholders that we don't normally work with - we're working with public safety officials, we have the State Police involved, we're working with public water supply purveyors because once this stuff makes it downstream, to where they pull water into then deliver drinking water to the public, they have to deal with the issues that come downstream to them as well. We're really trying to balance all the competing - and in many places, complementary - needs of the stakeholders so that we can try and develop the best strategy for Northern Virginia to reduce these salt loads and of course maintain public safety.
To this end, some practices have changed already. The Virginia Department of Transportation is constantly trying to improve their de-icing strategies: staff training, weather monitoring and now pre-treatment are all part of the equation. They are also testing blue salt – salt died in blue which makes it is easier to spot which zones have been treated and to avoid over-salting. Another thing is a liquid form of deicing salt, called brining.
BRANCO VLACICH: Salt only works when it's in basically liquid form, that's when it's most effective, that's why the brining is so effective.
That’s Branco Vlacich, the State maintenance division administrator at VDOT.
VLACICH: Prior to 2008, we didn't do a lot of brining. But after that, we have found that before every event - plus, brining is only 23% salt so we really get a big bang for the buck. The other thing that we're doing, and this has been significant too: we're installing speed controls on our spreaders. Right now, if you don't have speed controls on your spreaders, it means that you're going to put the same amount of salt on the road whether you're traveling at 5 mph or 50. What this does, basically, if you're at a stop light, it stops: the driver doesn't have to do anything. 5 mph, it puts a little salt, if you're going 50, it's going to put a little more. This makes sure that we're putting the appropriate amount whether we're traveling 5 mph or 35mph, so that we're not over-salting.
VDOT is not the only player though: a lot of deicing salt runoff comes from big shopping centers and airports, for instance, which are more concerned about liability issues from customers slipping on the ice or other related hazards, and so they will tend to over-apply salt. The main issue remains that of communication and awareness to all parties involved, public and private.
ISENBERG: So, beyond just identifying what best practices can allow us to more efficiently, effectively apply salts, there's also a huge education outreach component we're going to need to consider, so we can get the word out on better practices for homeowners to use as well as acknowledgement of what VDOT recommends, and things like that.