Put Sidewalk & Drive on a Low-Salt Diet
For safety reasons, we need to keep driveways and sidewalks clear of ice and snow. However, choosing the right product and using it correctly is important to help protect our water resources. The following information has been adapted from "Snow, Road Salt, and the Chesapeake Bay" by Tom Schueler, Center for Watershed Protection.
1. Shovel Early, Shovel Often
There's no substitute for muscle and elbow grease for snow and ice removal. Remove as much snow as you can during the storm if possible. Use a hoe or other tools to chip or scrape ice off the surface before any deicers are applied. Deicers work best when there is only a thin layer of snow or ice that must be melted. Divert the melting snow away from your sidewalk and driveway to an area where ice won't be a problem.
2. Buy Early
Make sure to buy your deicing product well before the big storm hits, otherwise you will be looking at empty shelves, and have few, if any, environmental choices to make at the store.
3. Check the Label
The following products list shows how the main ingredients of common deicing products compare. Check the package closely to see what you're buying. Often a product may contain several of the ingredients listed, but the first one listed is usually the main ingredient.
Product: Calcium Chloride
- Works Down To: -25 degrees Fahrenheit
- Cost: Three times more than rock salt
- Environmental Concerns: Use three times less than rock salt, No Cyanide, Chloride impact
Product: Magnesium Chloride
- Works Down To: 5 degrees Fahrenheit
- Cost: N/A
- Environmental Concerns: Less toxic and safer for environment than calcium chloride
Product: NaCl - Sodium Chloride or "Rock Salt"
- Works Down To: 15 degrees Fahrenheit
- Cost: About $5 for a 50-pound bag
- Environmental Concerns: Contains cyanide, Chloride impacts
- Works Down To: 20 to 25 degrees Fahrenheit
- Cost: Five times more than rock salt
- Environmental Concerns: Needless nutrients, less Corrosion
Product: Calcium Magnesium Acetate (CMA)
- Works Down To: 22 to 25 degrees Fahrenheit
- Cost: 20 times more than rock salt
- Environmental Concerns: Less toxic
- Works Down To: No melting effect
- Cost: About $3 for a 50-pound bag
- Environmental Concerns: Accumulates in streets and streams, needs to be swept up
4. Apply Salt Early, but Sparingly
No matter which chloride product you choose, a little goes a long way. Additional salt won't speed up the melting process, so follow directions for application carefully and remember to first remove as much snow and ice as you can. The recommended application rate for sodium chloride is about a handful per square yard. Calcium chloride works at much colder temperatures and you need a lot less (about a handful per three square yards, about the area of a single bed). Choose calcium chloride over sodium chloride when you can.
5. Avoid Kitty Litter & Ashes
Although these products may seem environmentally friendlier, they don't work to melt snow and ice-they merely provide some traction and make a mess on your floors. Stick with sand for traction, which is cheaper and easier to clean up.
6. Avoid Products that Contain Urea
Urea has been recommended as a safer alternative, reasoning that it does not contain chlorides and, as a form of nitrogen, will help fertilize your yard when it washes off. However, urea-based deicing products are a poor choice as it is fairly expensive and performs poorly when temperatures drop below 20 degrees F. The application rate for urea during a single deicing is ten times greater than that needed to fertilize the same area of your yard, and ultimately, very little of the urea will actually get onto your lawn, but will end up washing into the street and storm drain and eventually to the nearest lake or stream. Given that nitrogen is a problem for surface water resources, it doesn't make sense to use nitrogen-based products for de-icing.
7. Consider Nearby Vegetation
Look at the plants growing within five or ten feet of your driveway, sidewalk, and road. Salt-sensitive plants are listed under the following "Species at Risk from Salting" heading. If you have salt-sensitive tree, shrub or grass close to these paved surfaces, you should avoid any deicing product that contains chlorides (magnesium chloride, rock salt, or calcium chloride), or use very small amounts. You may want to use CMA as a safer alternative, or use sand for traction.
Species at Risk from Salting
- Conifers: Balsam fir, White pine, Hemlock, Norway Spruce
- Deciduous Trees: Tulip polar, Green ash, Hickory, Red maple, Sugar Maple
- Grasses: Kentucky bluegrass, Red fescue
- Shrubs: Dogwood, redbud, hawthorn, rose, spirea