Drainage

The City of Sammamish works with local property owners to ensure that all private stormwater systems (includes stormwater ponds, catchbasins and pipes) are inspected and adequately maintained every year. This helps these systems to function as they were designed and to prevent flooding, erosion and water quality degradation.

UNDERSTANDING YOUR STORMWATER SYSTEM

A stormwater system is any part of an engineered drainage system that collects rain water. Examples include detention ponds, underground vaults, swales, and catchbasins. In addition, if your home was constructed after January 1, 2017, there is a good chance it includes low impact development stormwater facilities. See the Green Infrastructure & Low Impact Development (LID) page for more information.

MAINTAINING YOUR STORMWATER SYSTEM

In Sammamish, these facilities protect your property from flooding and drain directly into our lakes, rivers, and streams without treatment. This means that any pollutants in the water can cause many problems for our local community and can make contact with the water a health risk.

Maintenance will depend on the type of system in your care and the surrounding conditions in your community. Establishing a maintenance schedule is the best way to ensure your system is functioning properly. In addition, prevent materials that are stored outside from leaking, draining, spilling or being dumped into the stormwater system. Keeping contaminants out of your stormwater system may reduce the disposal costs for materials cleaned from your system.

Sammamish’s maintenance requirements for typical low impact development techniques are available in Appendix A of the 2016 King County Surface Water Design Manual. The City has also prepared this brochure that will be distributed to all homeowners purchasing a newly constructed home in the City of Sammamish. Typical low impact development technique maintenance requirements might include: inspecting the site for trash or debris that may have accumulated and removing said debris, removing weeds/moss present within bioretention facilities, checking for erosion within vegetated flow paths, and vacuuming or pressure washing permeable pavements.

REDUCING STORMWATER RUNOFF FROM YOUR HOME AND IMPERVIOUS SURFACES

Consider replacing impervious surfaces like sidewalks, decks, and driveways around your home with more permeable materials like mulch, turf block, pervious concrete or clean stone.

Review your home for stormwater handling. If your gutters, downspouts, driveways, or decks directly discharge into a water body, retrofit them by redirecting the runoff onto grassy areas or installing berm/swale systems. Make sure that you are not causing a problem for a neighbor or to your own home.

Other things you can do:

  • Plant a tree
  • Improve your soil by adding compost and mulch
  • Install a rain barrel or cistern to collect rainwater for yard and garden watering
  • Shrink your lawn and replace it with native plants

RESOURCES

Rain Garden Handbook for Western Washington Homeowners – Guide for helping residents plan, design and build rain gardens.

Washington Stormwater Center LID Resources – Provides resources on LID practices, operations and maintenance.

King County Surface Water Design Manual – Appendix A Maintenance Requirements – Provides checklists for maintaining stormwater facilities.

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