Protect the Environment

Vehicle Waste
Oil stains on your driveway and outdoor spills of antifreeze, brake fluid, and other automotive fluids are easily carried along the stormwater superhighway during a rainstorm. An oily sheen on runoff from your driveway is a sure sign that you need to be more careful. Pans, carpet scraps, and matting can catch drips. Routine maintenance can prevent your car from leaking and help identify potential leaks. If you change your own oil, be careful to avoid spills and collect waste oil for recycling.

Store oily car parts and fluid containers where rain and runoff cannot reach them. Never dump used oil, antifreeze, or gasoline down a storm drain, in a ditch, or on the ground. These wastes will end up in a nearby lake or stream, or they may pollute your drinking water.

Washing your car in the driveway creates runoff without the help of a rainstorm - your hose provides the water. The dirty, soapy runoff drains directly into storm drains, picking up oil and other pollutants as it goes. If possible, try washing your car on your lawn. Better yet, take it to a commercial car wash that sends its dirty water to a wastewater treatment plant.

Household Products
Most people have lawn and garden products like herbicides, insecticides, fungicides, and fertilizers. If stormwater or flood water reaches these products, it can transport them into surface waters.

Pool chemicals, salt for water softeners, and a wide variety of other chemical products are also troublesome pollutants if they wash into stormwater runoff. Keeping such products in waterproof containers and storing them up high and out of the potential path of runoff or floods is important. You can avoid storage problems by buying only as much of a product as you need for a particular task.

Chemical Safety
Safe storage is only the first step in preventing contaminated runoff. Mix chemicals within a washtub so spills will be contained. If you do spill chemicals, act quickly to contain and clean up the spill. This is particularly important on paved surfaces. Using more pesticides or fertilizers than you need invites problems. Timing of applications is also important. Do not apply lawn and garden chemicals if rain is expected within 24 hours.

Bare Soil
Areas of bare soil often exist in vegetable and flower gardens, on newly seeded lawns, and around construction projects. Even on gentle slopes, water from rain and snow can remove large amounts of soil and carry it to wetlands, lakes, streams, and estuaries. Planting grass or other ground covers is the best way to stop erosion. Putting a straw or chip mulch over gardens or newly seeded areas will slow erosion. Straw bales, diversion ditches, and commercially available silt fences placed around construction sites can help slow runoff and trap sediment on-site.

Construction activities (clearing, grading, and/or excavation) can significantly increase and accelerate erosion. To prevent erosion and sediment from entering the storm drain system, exposed areas should be stabilized as quickly as possible. Minimize disturbance and soil exposure by retaining natural vegetation, adopt phased construction techniques, and use temporary cover. Once grading activities are completed, plant temporary / permanent vegetation or other erosion control measures as soon as possible.

Use compacted, vegetated earthen dikes, pipes, or other stable drainage structures to minimize erosion by diverting off-site runoff around or through the construction site.

If erosion generated by runoff from cleared areas of the construction site cannot be prevented, trap and filter sediment to stop eroded soil and debris from being carried off site. Place suitable barriers such as sandbags, hay bales, or silt fences at the following locations:
  • Across large areas of sheet flow, including graded streets, slopes and pad areas
  • Along property or grading boundaries where runoff containing eroded material can leave or enter the site
  • Around or upstream of drainage collection points, such as drainage inlets, catch basins and channel / swale junctions
  • Construct/grade sedimentation basins upstream of critical locations, such as at storm drain catch basins, or where concentrated flow leaves the site
  • Monitor trapping and filtering devices just before, during, and after each rainfall event, and repair / replace where necessary
  • Size sediment trapping and filtering devices to accommodate upstream runoff and sediment.
  • Stabilize dikes with vegetation or physical devices
  • Use compacted earthen dikes to divert runoff or channel water
2009 Flood Woodinville Duvall - Wagon Entrance View

Animal Waste

Droppings from dogs, cats, and other commonly kept animals, such as exotic birds, rabbits, goats, horses, and chickens, can be troublesome in 2 ways. First, pet wastes contain nutrients that can promote the growth of algae if wastes enter streams, lakes, and estuaries. Second, animal droppings contain bacteria that can cause disease. The risk of stormwater contamination increases if pet wastes are allowed to accumulate in animal pen areas or left on sidewalks, streets, driveways, or drainage ways from which they can be carried along the stormwater system to water bodies. Instead of allowing pet wastes to accumulate or sending them to a landfill, consider flushing the wastes down the toilet or burying them.

Yard & Garden Waste

If left on sidewalks, driveways, or roads, grass clippings and other yard wastes will wash away with the next storm. Although leaves and other plant debris accumulate naturally in streams and lakes, homeowners can contribute excess amounts of plant matter, especially in areas with many homes. This can lead to water that is unattractive or green with algae, potential fish kills, and make areas unsuitable for recreation.

Burning yard waste is not an environmentally friendly alternative - and in some areas it's illegal. Hydrocarbons and nutrients released by burning leaves contribute to water pollution as well as to air pollution. Rain washes smoke particles out of the air, and runoff picks up dust and ashes left on pavement or in ditches. Avoiding the problem is easy, sweep clippings back onto the grass, and compost leaves and garden wastes on you property to recycle nutrients.

Eliminate Paved Surfaces or Install Alternatives

Concrete and asphalt roads, driveways, and walkways are impervious; they prevent rainwater from soaking into the ground. When you have the choice, consider alternative materials such as gravel or wood chips for walkways. Avoid paving areas like patios. Where you need a more solid surface, consider using a "porous pavement" made from interlocking cement blocks, hard plastic grids filled with stone or earth, or rubber mats that allow spaces for rainwater to seep into the ground. If you must pour concrete, keep the paved areas as small and narrow as possible.

Roof Drainage

Your house roof, like pavement, concentrates rain water into stormwater runoff. If downspouts from roof gutters empty onto grassy or natural areas, the water will have a chance to soak into the ground. Aim downspouts away from foundations and paved surfaces. For roofs without gutters, plant grass, spread mulch, or use gravel under the drip line to prevent soil erosion and increase infiltration of water into the ground. Consider using cisterns or rain barrels to catch rain for watering your lawn and garden in dry weather.

Landscape Layout

An essential part of stormwater management is keeping water on your property, or at least slowing down its flow as much as possible. Many lawns are sloped to encourage water to runoff onto neighboring property or streets. An alternative approach is to create rain gardens (described in the following section). If your yard is hilly, you can terrace slopes to slow the flow of runoff. If you have a large lot, consider "naturalizing" areas with woodland or wetland plants. If your property adjoins a lake or stream, one of the best ways to slow and filter runoff is to leave a buffer strip of thick vegetation along the waterfront, which is called a riparian buffer.

Rain Gardens

Often runoff can be diverted to localized low spots in your yard. These areas, when planted with water-tolerant vegetation such as Redbuds, St. John's Wort, Cherrybark Oak, and Sweet Pepperbush, are called rain gardens. Rain gardens naturally filter water and provide an effective means for putting surface water back into groundwater.

For great information about natural yard care, visit King County's website.