About Longfellow Creek
Where Does That Water Go?
By Julie Goodrich
SPU Stormwater Detention System Inspector
After such a remarkably rainy winter, we look forward to the halcyon days of summer. We try not to think about the upcoming winter. However, it's a good time to take a look at the yard, and ask yourself, "Where does all that rain water go?"
Why care about what happens to storm water? The investment of public dollars, the protection of private property and the need to lessen the environmental impact on streams and lakes is why the proper management of storm water is important. The public has an interest in reducing the volume of storm water, since the City must build larger and larger facilities to carry storm water runoff at public expense. A large paved surface collects enough water to cause stream bank erosion, burying aquatic life under tons of silt. The Endangered Species Act listing of the Chinook salmon gives even greater emphasis to the need to reduce the impacts to aquatic life from urban storm water. Clean attractive streams are an asset to our community – huge storm water disposal ditches are not.
In a natural setting, a thick layer of leaves, needles and plants covers the soil, soaking up heavy rainfall and releasing the water slowly into the soil below. But we don't live in natural forests anymore. Cutting woodlands and clearing land, paving roads, driveways and building parking lots, and constructing houses and buildings with large roofs and gutters changes the ground's ability to soak in water. Falling rain has fewer places to soak in gradually. Runoff on hard surfaces occurs faster and in greater volumes. Increased storm water runoff can worsen flooding, erosion, water pollution and can destroy stream habitat. In the parts of West Seattle, the sewer system and storm water systems are separate from each other. The city's storm water system drains directly into a body of water: Longfellow Creek.
To avoid short-term flooding, Seattle Public Utilities (SPU) carries out
inspections of all privately-owned storm water drainage systems on a regular
basis. Because many residential owners do not know about their systems, a map is
included with the initial letter from the inspectors. Since 1979, any property
built with 9,000 square feet or more of developed surface, or the cumulative
addition of 750 square feet after February 1993, must have a detention system in
place, connected to either the city storm water system or the combined sewer
system. This includes most apartment and condominium buildings, and businesses.
The inspection program is in accordance with federal and state laws (including
the Clean Water Act of 1987), and Chapter 22.800 of the Seattle Municipal code.
The parts of the storm water drainage system that are evaluated are catch
basins, maintenance structure-inlets, flow control structures, detention ponds,
and oil/water separators. From the surface, catch basins and maintenance
structure-inlets look like the grates you frequently see in parking lots.
Generally, catch basins filter out sand and gravel, then drain into the detention structure, which stores the water, and the flow control device inside the detention structure "meters" the water that flows into the city's storm system preventing overflows.
The inspectors look for high sediment levels, missing components, and drainage problems. Most of the time, the maintenance that needs to be done is the removal of excessive sediment. When a catch basin or flow control structure gets too full, it stops functioning, and it is time for the property owner to clean it out. Sometimes parts of the drainage system break off or were never installed.
Property owners and managers can get more information and request an inspection by calling Seattle Public Utilities storm water detention system inspectors at (206) 615-1257 or (206) 616-0551. After the inspection, the inspectors send a follow-up letter detailing what needs to be corrected, how it can be done, and a list of contractors who specialize in this kind of repair work.
Summer is the perfect time to think about water. Let's keep Longfellow Creek clean!