What is the difference between pervious and impervious surfaces?
- Examples of pervious surfaces: gravel driveways, wood decking, concrete lattice pavers, brick and porous asphalt
- Allow water to percolate slowly into the ground
- Reduce the amount of polluted runoff flowing into our streams and Torch Lake
- Slow the rate of polluted runoff flowing off your land
- Help to recharge groundwater
- Examples of impervious surfaces: asphalt driveways, stone slabs and steps, concrete garage aprons and sidewalks & patios, buildings (homes, garages, sheds, pole barns)
- Do not allow water to percolate into the ground
- Accelerate rainwater runoff
- Concentrate runoff and create erosion problems or make them worse
How do impervious surfaces impact Torch Lake?
When just 12% of a watershed is covered with impervious surfaces,
- the amount of stormwater run-off flowing off the land and into the lake increases
- the water quality begins to decrease
Stormwater run-off carries pollutants (nutrients, toxins and sediment).
- More stormwater run-off means more pollutants
- More stormwater increases erosion
- More stormwater negatively impacts aquatic creatures and fish
What are the benefits to you and our water?
- Keeps toxins out of Torch Lake so they won't harm fish and aquatic creatures
Keeps sediment out of Torch Lake so it won't harm fish and aquatic creatures
- Keeps nutrients out of Torch Lake, so algae won't grow and change its turquoise color to green
What can you do?
Step 1. Limit impervious surfaces on your property by making your paths, patios and driveways out of pervious or absorbent materials.
Check the ratio of impervious to pervious surfaces on your property.
Estimate the number of square feet of each type of surface,
The best balance should be 10:90, impervious: pervious.
Step 2. Choose these pervious materials.
Gravel and dirt (the old 2 track)
Step 3. Plant more trees
|Setting||% Impervious surfaces||% Stormwater Run-off|
|Low Density Residential|
Area (1 unit/2.5 acres)
Similar to Torch Lake
Consider how much you value the high-water quality of Torch Lake.
Pervious surfaces may cost 4-15% more than impervious surfaces—but Torch Lake is worth it!
If you do have an impervious asphalt driveway already:
- Do NOT coat with coal tar sealant. Instead coat with an asphalt- based sealant.
Coal tar is toxic to you, your family and aquatic life.
It releases PAH (polycyclic aromatic hydrocarbons) dust that gets tracked into your house and carried with stormwater to streams and Torch Lake
- Plant a Rain Garden around the driveway or in a depression running from the driveway to catch and filter stormwater run-off.