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King Street Center
201 S. Jackson St., Suite 505
Seattle, WA 98104-3855
Phone: 206-684-1280
Fax: 206-684-1741
Telecommunication device for the deaf (TTY): 711

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Staff Contacts

Puget Sound shoreline next to the West Point Treatment Plant, Seattle

Facts about the King County regional wastewater conveyance and treatment system

  • All data current for 2008, the most recent year for which data is available, unless otherwise noted.
  • -- means "not applicable" or "does not apply."
  • XX means "information not available at this time."
  • mgd means "million gallons per day," and
    mg/yr means "million gallons per year."

Customers and service area

   System West Point South Vashon Carnation
34 local agencies
(includes 17 cities, 16 sewer districts, and the Muckleshoot Indian Tribe)
-- -- 1 sewer district City of Carnation
Population Served
1.5 million residents -- -- 650 3,817
(by 2017)
420 square miles -- -- 620 acres
(by 2050)
776 acres
(in city and surrounding Urban Growth Area)

Sewage treated

  System West Point South Vashon Carnation
Sewage Treated
(Volume expected in Average Rainfall Year)
About 206 million gallons a day (average) 112 mgd 94 mgd 0.14 mgd 0.10 mgd
Sewage Treated
(2008 – low rainfall year is reflected in lower flows treated)
161.5 mgd 91.5 mgd 70.0 mgd 0.124 mgd --
(data not available yet, plant came online in May 2008)
-- -- 19.78 million gallons -- --

Facilities and Equipment

  System West Point South Vashon Carnation
Treatment plants
4 West Point Treatment Plant,
Seattle
South Treatment Plant,
Renton
Vashon Treatment Plant,
Vashon Island
Carnation Treatment Plant,
Carnation
Treatment plants in construction
1:
Brightwater
-- -- -- --
Pump Stations
42 -- -- 4 --
Regulator Stations
-- 19 -- -- --
CSO treatment facilities
4:
Alki, Carkeek, Mercer/Elliott West, Henderson/Norfolk
-- -- -- --
King County sewer conveyance lines
about 353 miles -- -- 3.2 miles 1.6 miles
Sewer pipe diameter
12 inches to 14 feet -- -- 2 feet 5 inches HDPE 12 inches
Outfalls, length and depth
-- 3,600 ft long;
240 ft deep;
600 ft diffuser
(500 ft plus a 100-ft extension)
10,000 ft long;
625 ft deep;
4 diffusers @ 500 ft L ea.
2,850 ft long;
200 ft deep;
no diffuser
Primary discharge: Chinook Bend Wetland Enhancement Project. Backup: Snoqualmie River at Carnation Farm Road Bridge.

Design criteria

  West Point South Vashon Carnation
Average wet-weather flow (non-storm):
This number is often used to describe the size of the treatment plants. It is based on average wet-season flow (November through April) but does not include extraordinarily large storms in the average. It is based on an average that does not show the maximum flows that can be handled at a plant.
133 mgd 115 mgd -- .22 mgd
Maximum monthly average flow
215 mgd 144 mgd 0.52 mgd .27 mgd
Average dry-weather flow
110 mgd 96 mgd -- .21 mgd
Biological oxygen demand (BOD) influent loading (annual average)
168,000 lbs/day 220,000 lbs/day 526 lbs/day 314 mg/L
Total suspended solids (TSS) influent loading (average annual)
181,000 lbs/day 201,000 lbs/day 526 lbs/day 314 mg/L
Instantaneous maximum capacity:
Maximum flows that can be handled at the plants--often for short periods; some portions of these flows get minimal treatment.
440 mgd 325 mgd 2.05 mgd 1.4 mgd

Permit information

  System West Point South Vashon Carnation
Permit (NPDES) renewal dates:
View permit limits (BOD, TSS, fecal coliform, chlorine residual) for each treatment plant.
-- Pending 10/1/09 9/1/11 River permit 4/15/13
Reuse permit 12/30/13

Resource recovery

  System West Point South Vashon Carnation
Electricity produced annually
-- -- .23 million kilowatt hours -- --
Methane gas sold annually
(Both West Point & South Plant also use digester gas to power plant equipment, such as boilers and digesters)
-- -- 2.1 million therms -- --
Biosolids produced annually
About 116,066 wet tons
(or 28,434 dry tons @ 24.6% solids)
51,701 wet tons (or 13,820 dry tons @ 26.81% solids) 64,364 wet tons (or 14,614 dry tons @ 22.78% dryness) 32.8 dry tons hauled to South Plant for further treatment Preliminary estimate of 19 dry tons/year to South Plant for further treatment.
7.3 dry tons produced in May-Dec 2008.
About 293 million gallons used for landscape irrigation, industrial processes, heating/cooling 195 million gallons 98.4 million gallons -- All effluent reclaimed water to Chinook Bend wetland enhancement site

Financial and budget information

Wholesale sewer rate
$31.90 per month (beginning 1/1/09)
Sewage treatment capacity charge
$47.64 per month (beginning 1/1/09)
($142.92 every three months for new hook ups as of 1/1/09)
Operating: $103.6 million
Capital Improvement Program (CIP): $525.8 million
Number of employees
(as of Jan 2009)
About 563 full-time equivalents (FTEs),
32 term-limited temporary (TLT) employees, and 11 temps/interns.
Cost: $1.802 billion (with inflation)
Will serve: South Snohomish and North King counties
Capacity: 36 mgd, 2010; 54 mgd, 2040
WTD expenditures for capital facilities through 2030
>> view projects under construction
$3.5 billion (2008 dollars)

Other

Total Rainfall
(measured at SeaTac)
Total rainfall 2008, 34.05 inches;
Long-term average annual rainfall 37 to 38 inches
Significant industrial users
134
Industrial/Commercial facilities with discharge authorizations
319
Approximate number of compliance samples taken
2,258
Inspections conducted
435
Combined Sewer Overflows (CSOs)
CSO Control Program
Baseline volume
(1980-83)
2.3 billion gallons per year
Current volume
(June 2006-May 2007)
815 million gallons per year (view CSO reduction graph)
Number of King County CSOs
38; (view CSO location map)