Ballard’s Stormwater Problems

In the winter when it rains, it pours.  Stormwater runs from our homes and down our streets, down stormwater drains, down hills, and ultimately into Salmon Bay, Shilshole Bay, and Puget Sound.It picks up oil and toxic contaminants from our streets and homes and carries them into the Sound.  Stormwater that flows into Ballard’s combined stormwater/sewer pipes regularly overwhelms the system and spills raw sewage into Salmon Bay.

Combined Sewer Overflows occur regularly during the winter months
Four combined sewer overflow (CSO) outfalls drain into Salmon Bay:
* NPDES Basin 59,(Ballard)
* NPDES Basin 60 (Magnolia)
* NPDES Basin 150/151 (Ballard)
* NPDES Basin 152 (Ballard)  Map with CSO status (updated hourly)

On the Ballard side, the CSOs of concern are 150/151, which is at the foot of 24th Ave. NW, and 152, which is at the foot of 28th Ave. NW.  According to Seattle’s 2011 Annual Report, in 2011 these two outfalls overflowed 73 times, discharging 43,132,180 gallons of untreated sewage into Salmon Bay. As of July 31, 2012, there have been 58 CSO events which have discharged 15,177,537 gallons of untreated sewage into Salmon Bay. CSO 152 accounts for about 94% of the contamination of Salmon Bay.  All four outfalls are managed by Seattle Public Utilities. 2012 CSO Details  Map of CSO Outfalls

Combined sewer control work also is taking place at North Beach, and is planned for 3rd Ave NW and 11th Avenue NW.  These efforts are being addressed by King County.

Untreated Stormwater is Contaminating Area Waters
When it rained in the Shilshole area 200 years ago, the rain fell on thick forest and undeveloped land that was able to absorb and filter it before it reached Puget Sound. Rainfall in Ballard today falls on roofs, sidewalks and streets, which do not absorb it.  The remaining yards, grass and soil quickly become saturated, and the runoff courses down our streets, into sewer or stormwater pipes, or courses down hillsides on its own. It carries oil, pesticides, dog poop and other contaminants with it. Short Video

Other Contamination Problems
Hazardous materials and hazardous products can enter the environment when they are carelessly used, particularly near storm drains, or when they are stored or spilled on permeable ground.  Contamination can occur when materials are improperly disposed of in the municipal sewage system, when they are dumped or when they are carelessly used. Hazardous materials also enter the environment when pharmaceuticals, birth control pills and other materials are metabolized by humans and excreted into the sewage treatment system.  Toxic chemicals also end up in the “gray water” that many residents generate washing dishes, laundry and ourselves. Although the sewage treatment process does a good job of removing sewage and heavy metals, it does not effectively remove many of these other contaminants.

Contributing Factors

* Our Soils are primarily glacial  till and hardpan underlain by till, and typically have low infiltration rates.  A small  portion of the area is Esperance sand, which is more permeable.  In addition site grading and other soil disturbances that have occurred during development have created more variable conditions, which may vary from block to block. Soil map   Presentation   Historical Soil Tests

*Groundwater is a factor to be reckoned with, as evidenced by the seasonal creeks, groundwater springs, and basement flooding that we see on Sunset Hill. Throughout Ballard there is enormous variability in the subsurface soils as well as the groundwater.  This variability leads to groundwater that is “perched” between the subsurface soil layers and top soils, water movement toward “paths of least resistance” within the soil layers, and mounding of groundwater, where the water congregates in “pools” underneath the surface.  Because the variability often is localized, solutions must be tailored to each situation with a broader assumption that water will move elsewhere.

* Increasing population and housing density.  The Ballard CSO area is devoted primarily to single family residences, with some multifamily residences and commercial areas.  Ballard is continuing to grow, with multifamily residences replacing single family residences, particularly in the partially separated areas south of NW 65th Street and to the east of 24th Avenue NW.  This development was encouraged by rezoning decisions that were made in the 1990s. The redevelopment projects are required to disconnect roof drains from the sanitary sewer and to establish stormwater controls. The additional population will add to the baseline sewage flows. However the diversion of some stormwater probably will decrease wet weather flows in the southern portion of the CSO area. The extent to which stormwater will be managed on site is unclear. Land Use Map.

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