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9611 SE 36th Street
Mercer Island, WA 98040
Phone: 206.275.7605
Email: epermittech@mercer. . .

Open to the public:
8:30 AM - 4:00 PM
on Mon, Tue, Thu, & Fri

10:00 AM - 4:00 PM on Wed

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Low Impact Development

Rain garden- one LID technique!

Mercer Island is among many cities in the United States that is beginning to establish zoning (land use) and construction (building) code regulations that facilitate  "sustainable" building and development practices.

What does "sustainable building and development" really mean?

The phrase "sustainable building and development" is best described as balancing the need for development (i.e building construction) and growth (i.e population increase) against the need to protect the natural environment. The ultimate goal is to meet the needs of the present generation without compromising the ability for future generations to meet their needs.

What is Low Impact Development (LID)?

One approach to sustainable development is called Low Impact Development (LID). Without development, rainfall naturally evaporates, absorbs into the ground, or is taken up by the roots of plants and trees. Now, with an influx of buildings, infrastructure, and lawns, rainfall is becoming stormwater runoff. It often times carrying pollutants to streams, rivers, and lakes. LID is a set of techniques that mimic natural watershed hydrology by slowing, evaporating/transpiring, and filtering water before it reaches a stream or Lake Washington. 

LID contrasts with traditional drainage techniques that collect and transport water to streams quickly; these traditional techniques can damage stream channels and degrade water quality. LID uses various land planning and design practices to conserve and protect natural resources and reduce infrastructure costs.

What are some LID techniques?

  • Minimize/eliminate impervious surfaces
  • Retain site vegetation
  • Amend soils with compost to improve water retention
  • Construct bio-retention swales or cells (natural areas that have specifically-chosen plans and engineered soils that slow, filter, and absorb water)
  • Use of permeable pavement or pavers for roadways, driveways, and walkways
  • Installation of green roofs and/or rooftop gardens
  • Installation of cisterns or rain barrels to hold and reuse rain water

When combined, such techniques can greatly reduce the amount of stormwater runoff from developed sites- which can improve water quality and reduce flooding downstream!

Do you want to learn more about LID?

Click on the links below to view informational brochures:

How can residents and businesses implement LID?

LID is not just for developers- there are many ways residents and businesses can implement LID! Some common and effective ways are to use Natural Yard Care techniques in your landscaping, replace your lawn with native plants, and use rain barrels to capture runoff from your roof. Click here for specific WA State rules on rain barrels.

Do I live in an area with good stormwater infiltration potential? Click here for a map that shows infiltration potential on Mercer Island.

Where can I learn more about LID?

Check out these sites to learn more about LID and how it can help the environment!


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