aggressively guards the sources of its water supply to provide safe and
reliable drinking water for our customers. Protecting these water
sources from potential contamination is the first step in ensuring that
Tacoma Water is able to deliver safe drinking water that meets all state
and federal standards. Preventing water quality problems and
contamination from occurring at the source has proven to be the most
cost-effective means of protecting public health and avoiding the
expensive solutions that come with contamination. Protecting our sources
of drinking water helps Tacoma Water maintain competitive rates.
Tacoma Water's Sources
Tacoma Water has long been known for its mountain supply of drinking
water from the pristine Green River watershed.
you know that Tacoma Water has two important sources of drinking water?
The Green River Watershed and groundwater
wells are both used to supply Tacoma's water.
To view a map of Tacoma
Water's service area click
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The Green River Watershed
For more than 80 years, Tacoma Water has
managed the Green River watershed. This forested land serves as a
collecting point for melting snow and seasonal rainfall. It covers
148,884 acres on the west flank of the Cascade Mountains between Chinook
and Snoqualmie passes. Tacoma Water owns only 10 percent of the
watershed but has agreements with other owners to limit activities to
keep the Green River water supply pure and fresh. Currently the Green
River can supply up to 72 million gallons of water each day. This water
flows by gravity into Tacoma, which minimizes expensive pumping costs.
Tacoma Water can supplement its Green
River supply with water from seven wells located along the North Fork of
the Green River. The North Fork well field normally can meet the same 72
million gallons per day production as the Green River in the winter and
spring months. These wells are used only when the water in the river is
too turbid (or cloudy), usually in the fall and winter when rain and
snow melt washes soil sediment into the river.
Tacoma Water is fortunate to have the very
high quality Green River water, the North Fork wells, and an active
watershed control program. Because of these,
Tacoma Water is in a small group of water systems that is not required
to filter the surface water. The
Washington State Department of Health,
Office of Drinking Water has
determined that Tacoma Water does not need to build a water filtration
plant as long as the requirements in
Washington Administrative Code 246-290-690
are met. The requirements to remain unfiltered include watershed
control, quality of the water at the source, redundant disinfection
treatment components, and annual site inspections by the State
Department of Health.
In addition to the sources in the Green
River watershed, Tacoma Water owns 24 wells located in and around the
city. Tacoma Water’s wells pump water from aquifers, which are
underground layers of water saturated sand and gravel. This water comes
from local rainfall, which has percolated deep into the soil.
the picture at right to see well 1-A being dug in 1929
The majority of the groundwater used by
Tacoma Water comes from wells in the South Tacoma wellfield. The South
Tacoma wells pump from very productive underground aquifers that stretch
from the Nalley Valley all the way to Lakewood.
Tacoma Water first began
developing the wells in South Tacoma in the early 1930's
and currently has 14 wells in this wellfield. Tacoma Water’s wells can
pump about 60 million gallons per day.
Not only have these wells been critical
to the past and present of Tacoma Water, but they are critical to the
future drinking water supply for our customers.
During the summer months, Tacoma Water
customers can use in excess of 100 million gallons of water per day.
Because Tacoma Water can use only 72 million gallons per day from the
Green River, the wells help meet peak summer water needs. The need for
groundwater is expected to increase in the coming years as water demands
continue to grow. These wells will be invaluable to help meet Tacoma
Water’s future needs.
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Watershed Protection for the
The watershed is surrounded by mountain
ridges on three sides, and gates and guards strictly limit public access
to minimize contamination that people and their activities can
introduce. Every day, water from the river is sampled at the intake,
which is where Tacoma Water diverts the water into the transmission
pipelines that bring the water into the city. The watershed is also
actively patrolled to inspect for the presence of unsanitary conditions
and to enforce laws and regulations governing the protection of the
water supply. In addition, weekly samples are taken throughout the
watershed from tributary streams that feed the Green River. This helps
Tacoma Water anticipate water quality problems before they have a chance
to reach the intake.
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Groundwater Protection for
Tacoma Water's Wells
Groundwater supplies up to 40 percent of
Tacoma's water in the summer and supplements
the supply from the Green River at other times of the year. Tacoma Water
samples its drinking water wells for bacteria and for traces of over 150
different metals and chemicals. Tacoma Water also samples
dedicated monitoring wells.
Homes for approximately 30,000 people,
as well as hundreds of businesses, are located above the underground
aquifer that supplies the wells in the South Tacoma wellfield. A great
many of these businesses use, handle and store chemicals that can
contaminate groundwater. In addition, most homes have numerous household
chemicals, pesticides, and fertilizers that can contaminate groundwater
if they are disposed of or applied improperly.
If a groundwater well is contaminated,
Tacoma Water must either treat the water or replace the well so that
enough water is available for customers. Both of these options are
expensive. Preventing contamination is much less expensive and more
effective than fixing a problem after it has occurred. Tacoma Water is
working hard to educate both residents and businesses who are located in
areas above our drinking water aquifers about ways to prevent
contamination of our drinking water. For more information about what you
can do to protect your drinking water, click
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Chemical Contamination in
In the early 1980's
Tacoma Water detected chemical contamination in some of the South Tacoma
wells, which required some of the wells to be taken out of service.
Investigation focused on several nearby areas in the Nalley Valley,
where illegal disposal of chemicals are suspected to have occurred since
around the time of World War II. The likely source of the chemicals
found in the Tacoma Water wells was tracked down to an oil-handling
facility operated by Time Oil. The investigation revealed reports and
evidence of illegal disposal of chemicals onto the ground at the site.
To make matters worse, a fire occurred at the site in March 1976, which
likely resulted in additional chemicals being released onto the ground
and washed into the aquifer. Following the investigation, the Time Oil
site was designated as an Environmental Protection Agency Superfund
site, and cleanup of the site is ongoing.
Because of the chemical contamination,
an expensive treatment system was installed on one of the contaminated
wells. This treatment system, which uses air to strip the chemicals out
of the water, continues to operate to the present day. By pumping and
treating the water from this well, Tacoma Water not only removes the
chemicals from the well, but keeps the contamination from spreading to
other nearby wells.
As a result of the drinking water
contamination, the South Tacoma Groundwater Protection District,
was formed in 1988. This district covers an area situated on
environmentally sensitive land that lies over the South Tacoma aquifer.
Commercial and industrial businesses in the area are subject to special
regulations because the soil is highly permeable, increasing the risk of
contaminating the water supply.
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The South Tacoma Groundwater
The South Tacoma Groundwater Protection
District was established in 1988 to help protect some of our most
important wells. Businesses in the area are subject to special
regulations because of the number of wells in the area and because the
gravel and sand found just below the surface in much of South Tacoma
allow water and hazardous chemicals, if present, to move quickly through
the ground down to groundwater. The
South Tacoma Groundwater Protection
District ordinance is currently
being revised to reflect the changes in hazardous waste practices, in
federal, state and local regulations and the increased knowledge of the
For more information, or to comment on
the South Tacoma Groundwater Protection District ordinance, call
502-8207 or 798-4783, or e-mail
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What You Can Do To help
Protect Your Drinking Water
Successful protection of the groundwater
depends on Tacoma Water, businesses and residents. It may seem like the
actions of an individual won’t make a difference, but multiply that by
the 30,000 residents living over the South Tacoma aquifer and you get an
idea of how big a difference residents can make. You can help keep your
drinking water safe by using fewer hazardous chemicals around your home.
Hazardous chemicals, which can include motor oil, pesticides,
fertilizers, and paints, used above ground have the potential to seep
down into the groundwater that supplies the wells. You can adopt home,
yard, and auto care practices that are safer for groundwater.
Here are a few ways you can help keep
your water safe:
- Use non-toxic or less-toxic
- Use and store chemicals safely
- Recycle or properly dispose of
leftover chemicals at the
Household Hazardous Waste Facility
- Create a healthy, beautiful yard —
naturally. To view a brochure on natural yard care click
To learn more, read these Tacoma Water
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Or visit these Web sites:
(Tacoma Water is not responsible for content of these Web sites
and does not endorse products or services)
Alternatives to hazardous
Coalition of South Seattle
Natural Yard Care
WSU Extension’s Gardening in Western
WSU Extension’s Master
Pesticide Education Program
Integrated Pest Management
You can also call
Tacoma Water’s Water Quality division at 502-8702 or
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June 11, 2008