Questions and Answers

Frequently Asked Questions about LID Practices

Doesn't it cost a lot more than the usual stuff?
How easy is it to install, and who knows how to do it?
Is this suitable for all paved areas?
How will we maintain it?
Where do we get it?
Will this stuff really hold up to our snowy winters? What about snowplowing?
How about our fire trucks/ambulances/police cruisers?
Won't women wearing high heels fall down and break their ankles?
Is this really going to help?

Doesn't it cost a lot more than the usual stuff?

Cost factors obviously depend on the material and the usage. The cost of many pervious alternatives can be more expensive, although manufacturers and installers point out that costs will drop as these materials become more widely used. Care should be taken to look not only at the cost of materials, but at associated costs like installation and maintenance. Installation costs for grassed swales, for instance, are much less than for traditional curbs, when you factor in the cost of storm drains and underground pipes. Similarly, swales may need more frequent - but much less costly - maintenance.

How easy is it to install, and who knows how to do it?

These practices are no more difficult to install than conventional stormwater practices, but there are special considerations that your contractor needs to be aware of. For example, pavers need to have some sort of edging along the perimeter, to limit their lateral shifting. Perhaps the most important factor for proper installation is an understanding by the installer that rainwater infiltration is the goal. Many of these materials are marketed and used for aesthetic reasons, using installation techniques unsuitable for infiltration (for example, pavers placed in cement). A properly designed base is critical for pervious alternatives; a typical base for asphalt paving is not appropriate. Care should be taken not to compact the subsoil during the installation. Bioretention areas and swales also have a specially designed base, and care also needs to be taken with these practices to avoid compaction. The good news is that more and more contractors are getting experience with installing these materials. We suggest that you go to the manufacturer's links and case studies to look for information on contractors, or check the LID database for a list of contractors in your area who have installed LID practices.

Is this suitable for all paved areas?

No. We are not suggesting that you use alternative materials for your favorite interstate highway. However, there are lots of "low traffic" paved areas that are suitable, because of the low intensity and/or frequency of use. And even when asphalt roads are the best choice, think about where the runoff goes and what you can do to help it infiltrate. See our Roads section for information about swales, and where curbs should or should not be used.

How will we maintain it?

To make a very broad generalization, it can be said that pervious alternatives require more frequent, but less complicated and extensive, maintenance. For instance, our feedback suggests that town road crews are much happier maintaining "open" stormwater systems like swales, where trouble can be spotted and dealt with quickly, than in traditional curb-and-gutter systems, where trouble goes undetected for a long time and usually means ripping up the road. Most manufacturers state that porous pavement requires regular vacuuming to retain its permeability, if the pavement is located in an area where sediment is deposited on the surface. Recent research at the University of New Hampshire Stormwater Research site is showing that pervious asphalt may only require about 20% of the salt that normal pavement needs, to melt the same amount of snow. The reason for this is because when the ice or snow melts, it can travel freely to the subgrade, rather than sitting on the surface. The incidence of black ice is also reduced.

Where do we get it?

We can't list all the individual suppliers on this site, but you should be able to find these materials by visiting the links to manufacturers' sites found on our vendors page.

Will this stuff really hold up to our snowy winters? What about snowplowing?

Believe it or not, almost all of the materials and techniques shown on this site are being used in northern climates. Grass parking lots, for instance, are plowed with a simple rubber guard placed on the blade of the plow. Proper subbase and edging prevents frost heave and shifting of pavers in the winter. In general, porous surfaces usually thaw earlier and faster than impervious surfaces. There are some questions about the use of porous pavement in cold climates, since road sand, if not vacuumed regularly, can clog the pore spaces. Bioretention areas also have been found to function through the winter, even with frost in the ground. This has been documented in Haddam, CT at the research bioretention site, and also at the University of New Hampshire Stormwater Research site.

How about our fire trucks/ambulances/police cruisers?

If you are worried about structural strength, don't be - many of these alternatives are as strong as regular pavement. Manufacturers will provide recommended uses for each product. If you're worried about narrower streets and the ability to turn around, be aware that a properly constructed swale is capable of sustaining vehicles for occasional parking and emergency use. Look around your town: chances are that you will see lots of narrow streets built before the 1960's that have not caused undue problems for emergency vehicles.

Won't women wearing high heels fall down and break their ankles?

To be honest, we've never figured out why this doesn't happen more often, no matter what the pavement type! Anyway…while most pervious alternatives provide fairly secure footing, if this of special concern (perhaps for the elderly, more than the well-heeled), you should consider paved walkways where they are needed. Remember, the key is not always the amount of pavement, it's what happens to the water running off of the pavement, so walkways or parking lot fairways that drain to a pervious area are not a big problem.

Is this really going to help?

Yes! First, be assured that there are over 300 scientific studies that link high amounts of impervious surface to water resource degradation. Then, consider that in a typical community, 2/3 of the impervious surfaces are "car related": driveways and roads taking the prize for generating the most pavement in residential areas, and parking lots in commercial and industrial areas. Just as every little bit of added pavement hurts, every little bit of pervious alternative helps. So go ahead - wander around the Reducing Runoff site, gather the information you need, and take the plunge!

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