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All data current for 2019, the most recent year for which data are available, unless otherwise noted.

2019

  System West Point South Brightwater Vashon Carnation
Wholesale customers 34 local agencies
(includes 17 cities,
16 sewer districts,
and the Muckleshoot
Indian Tribe)
-- -- -- 1 sewer district City of Carnation
Population Served (estimated) Approximately 1.84 million residents 769,000 815,000 259,000 1,100 (based on census data) 2,000
Area served 424 sq mi 113 sq mi 240 sq mi 69 sq mi 660 ac (by 2050) 821 ac (in city and surrounding
urban growth area)
Key:
-- = not applicable or does not apply
sq mi = square miles
ac = acres
  System West Point South Brightwater Vashon Carnation
Sewage treated (volume expected in average rainfall year)
178 mgd 95 mgd 66 mgd 16.7 mgd 0.15 mgd 0.10 mgd
Sewage treated (2019)
161 mgd* 80.5 mgd 63.8 mgd 16.3 mgd 0.128 mgd 0.105 mgd
Peak day flow (2019)
752 mgd** 391 mgd 216 mgd 20.4 mgd 0.560 mgd 0.185 mgd***
Septage treated (2019)
26.1mg/yr -- 26.1 mg/yr
(2,333 dry tons)
-- -- --
Key:
-- = not applicable or does not apply
*System average includes 0.5 mgd from the CSO Treatment Plants
**System peak flow includes 145 mgd from the CSO treatment plants; System Peak day occurred on 12/20/2019.
***Carnation’s max-day flow of 0.185 mgd was artificially created by storing flow on 4/8/2019 and then releasing it on 4/9/2019. Most high flows were artificially created this way at Carnation.
CSO = combined sewer overflow
mgd = million gallons per day
mg/yr = million gallons per year
  System West Point South Brightwater Vashon Carnation
Treatment plants 5 West Point Treatment Plant, Seattle South Treatment Plant, Renton Brightwater Treatment Plant, Snohomish County north of Woodinville Vashon Treatment Plant, Vashon Island Carnation Treatment Plant, Carnation
Pump stations 48 20 19 4 5 --
Regulator stations 25 23 2 -- -- --
CSO wet weather treatment facilities 4: Alki, Carkeek, Mercer/Elliott West, Henderson/Norfolk -- -- -- -- --
CSO storage facilities 4: Murray, North Beach, Rainier Valley, South Magnolia -- -- -- -- --
Conveyance storage 2: Logboom, North Creek -- -- -- -- --
King County sewer conveyance lines About 383 mi sewer lines (and 14 mi reclaimed water lines) -- -- -- 3.9 mi 1.75 mi
Sewer pipe diameter (smallest to largest) 2.5 in. to 14 ft, 8 in. 8 in. to 14 ft, 8 in. 8 in. to 14 ft, 8 in. 8 in. to 14 ft, 8 in. 2.5 in. to 8 in. 8 in. to 12 in.
Outfalls, length and depth -- 3,600-ft long; 240-ft deep; 1 diffuser at 600 ft-long

Discharge to Puget Sound.
2 parallel pipes, 10,000-ft long each; 625-ft deep; 4 diffusers at 500-ft long each

Discharge to Puget Sound.
2 parallel pipes, 4,600-ft long each; 600-ft deep; 2 diffusers at 250-ft long each

Discharge to Puget Sound.
2,850-ft long; 200-ft deep; no diffuser

Discharge to Puget Sound.
Primary discharge: Chinook Bend Wetland Enhancement Project

Backup: Snoqualmie River at Carnation Farm Road Bridge
Key:
-- = not applicable or does not apply
CSO = combined sewer overflow
ft = feet
in. = inches
mi = miles
  West Point South Brightwater
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). For West Point, the average does not include flow on days with rainfall. For all plants, this number is based on an average that does not show the maximum flows that can be handled at a plant.
133 mgd 115 mgd 30 mgd
(2018-2023)
0.26 mgd (estimated) 0.22 mgd
Maximum monthly average flow: 215 mgd 144 mgd 40.9 mgd
(2018-2023)
0.52 mgd 0.27 mgd
Average dry-weather flow: 110 mgd 96 mgd 25.2 mgd
(2012-2016)
-- 0.21 mgd
Biochemical oxygen demand (BOD) influent loading (annual average) 168,000 lb/day 220,000 lb/day 66,063 lb/day (maximum month 2018-2023)
526 lb/day 707 mg/L
Total suspended solids (TSS) influent loading (annual average) 181,000 lb/day 201,000 lb/day 61,400 lb/day (maximum month 2018-2023)
526 lb/day 707 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 100 mgd (until 2025 or until fifth IPS pump set is installed)
1.14 mgd (2.05 mgd with on-site storage) 1.4 mgd
Key:
-- = not applicable or does not apply
IPS = Influent Pump Station
lb = pounds
mgd = million gallons per day
mg/L = milligrams/liter
  West Point South Brightwater Vashon Carnation
Permit (NPDES) renewal dates: View permit limits (BOD, TSS, fecal coliform, chlorine residual) for each treatment plant.

NPDES permit 1/31/2020

(End date was administratively extended into 2020 while awaiting new permit.)

NPDES permit 7/31/2020

Reclaimed water permit 7/31/2020

(Applications were submitted on time; awaiting renewals.)

NPDES permit 2/28/2023

Reclaimed water permit 4/30/2024

NPDES permit 2/28/2022

NPDES and reclaimed water permit (combined) 12/31/2018

(End date was administratively extended into 2020 while awaiting new permit.)

Key:
BOD = biochemical oxygen demand
NPDES = National Pollutant Discharge Elimination System
TSS = total suspended solids
  System West Point South Brightwater Vashon Carnation
Electricity produced (2019)

17.2 million kWh (produced from plant methane)

17.9 million kWh (total produced from plant methane and purchased natural gas)

17.2 million kWh (produced from plant methane) 0.706 million kWh (produced from purchased natural gas) -- -- --
Methane gas sold (2019)
(Both West Point & Brightwater also use digester gas to power plant equipment, such as boilers and digesters)
2.667 million therms -- 2.667 million therms -- -- --
Loop biosolids produced (2019) 124,958 wet tons (or 30,090 dry tons) 47,439 wet tons at 27.1% solids (or 12,851 dry tons) 63,216 wet tons at 22.6% solids (or 14,278 dry tons)

Note: South Plant receives untreated solids from Vashon and Carnation plants.
14,303 wet tons at 20.7% solids (or 2,961 dry tons) 483,453 gallons at 2% solids (or 40 dry tons). Untreated solids hauled to South Plant for further treatment. 895,683 gallons at 2% solids (or about 75 dry tons). Untreated solids hauled to South Plant for further treatment.
Carbon sequestration (2019)
(From Loop biosolids land application)
38,123 MtCO2e
(the equivalent of taking 9,000 cars off the road)
17,716 MtCO2e 16,337 MtCO2e 4,070  MtCO2e
-- --
Reclaimed/recycled water (filtered) used at treatment plants (2019) 718.9 mg/yr 188 mg/yr

Note: Additional lower quality (non-Class A) water is also used for in-plant processes.
63.9 mg/yr

Note: Additional lower quality (non-Class A) water is also used for in-plant processes.
467 mg/yr
-- --
Reclaimed/recycled water (Class A) distributed offsite (2019) About 82.3 mg/yr -- 3.47 mg/yr
(offsite use for irrigation, street cleaning, & sewer flushing)
40.3 mg/yr
(distributed for irrigation, toilets/urinals, and public art)

-- 38.5 mg/yr
(distributed to Chinook Bend Natural Area Wetland Enhancement Site)
Key:
-- = not applicable or does not apply
kWh = kilowatt-hour
mg/yr = million gallons per year
MtCO2e = metric tons of carbon dioxide equivalents
Wholesale sewer rate $45.33 per month (beginning 1/1/2019)
$45.33 per month (beginning 1/1/2020)
Sewage treatment capacity charge $64.50 per residential customer equivalent (RCE) per month (beginning 1/1/2019)
$66.35 per residential customer equivalent (RCE) per month (beginning 1/1/2020)
Annual spending (2019) Operating: $155.8 million
Capital spending: $212 million
Number of employees (as of Dec. 2019) About 626 full-time equivalents (FTEs); 50 term-limited temporary (TLT) employees and 28 short-term temporaries and interns
WTD expenditures for capital facilities

View projects under construction
$1.8 billion (2019–2024)
Industrial pretreatment program
Industrial/commercial facilities with permits (aka Significant Industrial Users) 104
Industrial/commercial facilities with letters and discharge authorizations 545
Approximate number of compliance samples taken (except BOD and TSS)  1,712
Inspections conducted  244
Key:
BOD = biochemical oxygen demand
TSS = total suspended solids
Combined sewer overflows (CSOs)
CSO control program
Baseline volume (1980–83) 2.3 billion gallons per year
Current volume (Jan.–Dec. 2019) 752 million gallons per year
Number of King County CSOs 39 (view CSO location map)
Total rainfall (measured at SeaTac) Total rainfall (2019): 33.88 inches
Long-term average annual rainfall: 38.29 inches (1945–2016)

Sustainability at WTD

infographic of Sustainability Fast Facts for the King County Wastewater Treatment Division, 2019Info graphic - page 2 of Fast Facts2019 Highlights -- Sustainability in King County's Wastewater Treatment Division