In the more urban/residential areas of the county where ditching and culvert systems are not feasible, we rely on drywells to advert possible flooding problems. Drywells are underground chambers that collect surface water and disperse it deep into the ground. On the surface, they just appear to be a manhole or grate. Usually the area surrounding the drywell is sloped, so that the water will gravitate toward it. When leaves or pine needles cover this grate, the water will not be able to enter the drywell and pooling will result. These grates need to be kept clear of yard waste in order to function properly.
Occasionally drywells become filled with silt, petroleum-based materials, and other debris that prevents them from adequately discharging the water back into the natural filtering system of the ground. When this happens during wet weather a persistent puddle will form in the area around the manhole cover. Spokane County has specialized equipment called Vactor trucks, these trucks are similar to a large vacuum. They are used to pump the foreign materials out of the drywell. The drywell will normally resume its original function once it has been cleaned. We can all do our part in helping to keep these drywells operating efficiently by sweeping any leaves or pine needles off of the grate and not dumping any petroleum products or other waste liquids into these receptacles. For additional information, please reference the Stormwater Utility site.