In older neighborhoods in Seattle we have what are called Combined Sewers. Combined Sewers are used for both waste water (sewage from inside the house) and storm water (all the water flowing off the roof, driveway, sidewalk, road, etc).
Combined Sewers cannot handle the entire amount of water during heavy rain events and are designed to overflow so that raw sewage doesn’t back up into your home. When they overflow a combination of raw sewage and storm water is discharged into nearby bodies of water like Lake Washington, Lake Union, Elliot Bay, the Duwamish River, and Puget Sound. Besides the raw sewage, oil from the road, pesticides and fertilizer from your garden and other toxins are sent untreated into our environment.
The Federal and State government have legislated that only one CSO (combined sewer overflow) shall occur each year. According to Seattle Public Utilities:
• We average 318 Overflows per year during the wet season, October through May.
• In Ballard alone on average 43 million gallons overflow into Puget Sound.
• The amount of overflow from Ballard is equivalent to 65 Olympic sized swimming pools.
• Ballard accounts for 25% of the total CSO from all areas of Seattle.
We can all be part of the solution even if we don’t live in an area with Combined Sewers. In fact in newer neighborhoods with separate storm water and waste water systems, the storm water and all the accompanying pollution is dumped without any treatment whatsoever into nearby bodies of water.
The solution is two-fold:
• Find ways to slow down the immediate flow of storm water into the sewer systems during peak rains.
• Reduce pollutants like fertilizer, pesticides, oil and pet waste.
How do we slow down storm water inflows?
• Plant a tree.
• Reduce paved areas.
• Try porous or semi-permeable paving options.
• Improve your soil with compost and mulch.
• Install rain gardens and cisterns
If you think about our native forests rain gets slowed down and absorbed by trees. They catch some of the rain in their needles and leaves, some of it evaporates off their leaves, and some is taken up by the roots of the trees. The rest that does fall to the ground is spread out and absorbed by wonderful spongy soils that filter out pollutants and then gradually allow the water to flow to nearby bodies of water.
In urban environments we have far fewer trees and our soils are often hard-packed and not very absorbent. We also have many more paved surfaces so there is less opportunity for the earth to do its water control work naturally.
In our gardens we can slow the flow by planting more trees, improving our soils so that they are more spongy, and reducing concrete and blacktop by substituting semi-permeable paving options like sand-set flagstone or pavers that allow water to be absorbed by the earth. We can also install rain gardens and cisterns.
What is a Rain Garden and how does it work?
A rain garden is an area in the garden that has been excavated and then back-filled with a specially blended highly absorbent soil that acts like a sponge. Rain gardens do not have to be big holes in your garden. They can be slight depressions and beautifully planted. The idea is to capture water from the roof and driveway and temporarily hold it until it can be absorbed by the earth rather than sending it down the storm drains. A properly designed rain garden can be quite small but capture an amazing amount of water. They typically also include an area that can pool water up to 6” deep for emergencies during a real down pour and an overflow that will allow extra water to flow back into the storm drain in case the storm water is too great for the system. They are beautifully planted with appropriate plants that can also help absorb the water and that like wet feet during the winter.
What is a Cistern and how does it work?
Think about a rain barrel on steroids. A cistern is a large containment vessel that catches storm water from the roof and then slowly sends it to a rain garden or back to the combined sewer system after the rains have subsided and the sewer system can handle the additional water. Unlike a rain barrel they are kept empty between rainstorms from October to May so that they can be ready to catch the rain from the roof during the next storm.
The sewer overflow problem is so large and Ballard is such a huge part of it that the Seattle Public Utility is now offering a rebate program for over 4000 Ballard residents to install rain gardens and cisterns. In most cases the rebate pays 100% of the cost of installation.
To qualify for the rebate the rain garden and/or cisterns must be installed by a licensed landscape contractor (not the homeowner) and the property must be in the rebate area. The installation is inspected before the project begins and after it is completed by the city for no charge. Rebate checks are sent to the homeowner within 6 to 8 weeks after submitting the request and again, in most instances the rebate pays 100% of the cost of installation so you can get a beautiful landscape, free of charge, from a professional landscape company.
If you live in Ballard (or know someone who does) check these websites for more information and to see if you are in the rebate area, and then call Falling Water Designs so we can give you an estimate to install either a rain garden, cisterns, or both. www.seattle.gov/util/rainwise and https://rainwise.seattle.gov
If you don’t live in the rebate area you can still make a difference by doing (or having Falling Water Designs do) any of the water retention improvements mentioned above in your own garden. Next spring additional neighborhoods that are on Combined Sewer systems are being added to the rebate program.