Tuesday, December 17, 2013

Don’t Rock the Salt!

This season, Clean Ocean Action is offering tips on how to green your holiday. Here is the eighth of twelve in COA's '12 Days of Green Giving' series.

By: Sean Dixon, Coastal Policy Attorney

Picture this (or look outside) – it’s cold, dark, and snowing.  Maybe it is also sleeting, or both.  Now, imagine you have to head out to work, or welcome some friends over for dinner.  The road are icy and your sidewalk treacherous.  What’s your solution? Spread some salt! Call the salt trucks! Melt that ice and say hello to easy driving and safe steps.  Right?


The way rock salt for melting ice works is that the salts themselves reduce the melting point of water – so instead of 32 degrees, water around the salt crystals will melt at a lower temperature (like 25 degrees).  If it’s -20 degrees, well, then you probably don’t want to go out anyways, and your normal rock salt won’t work.  During the summer, in most parts of the urban landscape, over-use of fertilizers can be what leads to significant local water quality problems.  Fertilizers can also be bad for your soil and for your pets.  Rock salt is the winter version of fertilizer, and can cause a host of problems:

First, rock salt is bad for your pets.  

The crystals can get ingested (they stick to paws, fur to be eaten later indoors, or eaten while in the ice and snow) and can lead to burned skin (apparently, the crystals can reach over 150 degrees!).  It’s also bad for other wild animals – in natural ecosystems, salt is a rare commodity and deposits of salt, called “salt licks,” are the coffee shops of the animal world.  Road salt in many places can attract animals to roadways, endangering both the wildlife and drivers.

Second, it can be really bad for drinking water and water quality.  

According to a Stormwater journal article, the New York City watershed (from which all NYC’ers get their tap water), there are “approximately 6,000 mi. of paved roadways in the watersheds, where road-salt application ranges from 37 to 298 tons/lane-mi./yr.”  That’s upwards of 300 tons per mile per lane deposited through the watershed!  The USEPA warns that salt in drinking water can impair water quality to the point where it’s dangerous for aquatic life, corrodes drinking water infrastructure, and endangers human health. 

In 2010, in New Jersey, a Times of Trenton article that “Road salt already has caused problems in some drinking-water supplies in Bergen and Morris counties.  Mahwah stopped using one of its 12 municipal wells years ago because of a high sodium content officials believe came from road salt dumped on Route 17.” According to the article, the state DEP thinks that “up to 60 percent of road salt infiltrates ground water.”

Third, it’s bad for soils.  

In some cases, soils have been tested at double the levels considered too high for normal bacteria functions.  Without healthy bacteria, soils become dirt, dust, and then run off into waters – losses for agriculture, parks, habitat, and downstream water quality.  Salt in soils is also bad for plants – inhibiting long-term growth, causes chlorine toxicity in leaves, and creates micro-drought conditions.

Fourth, it’s really bad for our infrastructure.  

Most people from wintry areas know that salt is bad for your car (corroding the undercarriage), but it’s also really bad for concrete and pavement.  Basically, the way it works is that your melted ice becomes really, really salty water – and that salty water (at the microscopic scale) enters micro-holes in concrete (concrete is full of these mini-holes, called pores).  Once inside the concrete, that salty water re-freezes (usually at night when temperatures drop).  Frozen salt water expands and creates salt particles – both of which are bad for your sidewalk, causing pits and cracks.

According to an August 2010 USEPA factsheet, over 15 million tons of rock salt are spread on our pavement, sidewalks, and parking lots each year.  What’s to be done?

Fortunately, there are a few solutions, though as one blog puts it, “you probably won’t like to hear” the best solution…shovel more!

Ideally, the best solutions are simple: shovel snow off your driveway so that it doesn't melt and freeze into dangerous ice, don’t use rock salt (or any salt), and put boots on your pets if you’re walking on other people’s sidewalks where there is rock salt.  This keeps your pets, your soils, your drinking water, you, and your concrete happy and healthy! 

To avoid slipping, you can use cat litter, sand, or sawdust to coat your icy pavement, or build your walkways out of gravel or rocks – avoiding the problem altogether.

Finally, one amazingly cool (or warm?) solution is also an energy efficiency one: use excess heat from power plants or geothermal heat to melt snow and ice! 

Heated sidewalks and driveways are all the rage in many colder cities and towns. In Holland, Ohio, in 1988, the city’s leaders (with a substantial private donation) converted all of their downtown’s public walkways to heated-sidewalks by piping hot water from the nearby power plant through pipes under the pavement.  The call this the “snowmelt” system, and claim it can melt 1 inch of snow per hour at 15-20 degrees F.  This is hot water that would have to be cooled anyways, so the town gets an added benefit!  Over 120 miles of tubes keep the sidewalks walkable all winter long.  Homes and small businesses can do this too – and can tie it into geothermal systems to use the ground’s natural warmth to keep the surfaces ice-free!

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