Monday, June 9, 2008

Ask Deanna: Green Parking Lots

by Deanna Matzen

Here at Earth Ministry, part of my job is to receive and route general information emails that come into The best part of that task is researching answers to all of the interesting questions I get. I've decided that a good use of my blog posts is to share the answers I come up. Not only does that allow Earth Ministry to share information, but it also allows our readers to share their experience and insight.

Today's question comes from Glenn and is about Green Parking Lots. Glenn wrote us saying,

I attended the Green event at SPU last month and found it very stimulating. But, my congregation wants to know how to have a green parking lot. Do you have any information or leads on this topic?

This is such an interesting question because for all the materials and resources we offer, we have no specific information on Green Parking Lots. Yet, most churches have parking lots, and large ones at that. Luckily, I found some good information on the subject and I'll include links at the end of my blog.

But first, a review of why parking lots are a problem.
  1. The accumulation of contaminants from car tires, car engines, and chemical applications such as pesticides and herbicides are washed into nearby streams causing pollution that is damaging to living organisms.
  2. As water hits asphalt, it is unable to penetrate the surface and therefore runs very quickly into nearby streams, or into storm drains and then into streams, causing a rapid rise in water height. Such rapid changes are in contrast to the slow and steady change in stream volume during rain storms in forests or other natural areas. Fish and bugs living in streams are adapted to slow changes. The unnaturally rapid changes can adversely affect the health of these critters.
  3. Without tree cover, most parking lots get really hot and causes several problems including: 1) increased air pollution; and 2) increased temperature of water entering streams, which is detrimental to fish and bugs.
Basically, there are two issues: temperature and run-off.

The simplest way to green your parking lot is to PLANT TREES. Trees provide shade to cool asphalt, reduce rainfall, and their roots can capture runoff and slow its journey to the nearest stream while filtering contaminants.

A more complicated solution is to switch form asphalt to an alternative paver/surface that allows water to penetrate into the soil or that doesn't heat up as much, such as concrete. Another complicated solution is to build bioretention ponds. These two options require a lot more planning, work and money, but would probably have the greatest impact on your local environment.

For more information on green parking lots, see the following resources.
If you have a question about greening that you'd like help with, email Deanna at or post a comment to this blog.

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