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All data current for 2021, the most recent year for which data are available, unless otherwise noted.

2021

  System West Point South Brightwater Vashon Carnation
Wholesale customers 34 local agencies
(includes 18 cities,
15 sewer districts,
and the Muckleshoot
Indian Tribe)
-- -- -- 1 sewer district City of Carnation
Population Served (estimated) Approximately 1.9 million residents 787,000 839,000 268,000 1,100 (based on
2020 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 65 mgd 18 mgd 0.15 mgd 0.10 mgd
Sewage treated (2021)
183 mgd* 95.2 mgd 68.8 mgd 18.7 mgd 0.165 mgd 0.100 mgd
Peak day flow (2021)
580 mgd** 370 mgd 176 mgd 32.6 mgd*** 0.805 mgd**** 0.162 mgd*****
Septage treated (2021)
28.3 mg/yr -- 28.3 mg/yr
(2,360 dry
tons solids)
-- -- --
Key:
-- = not applicable or does not apply
*System average includes 0.5 mgd from the CSO Treatment Plants.
**System peak flow includes 59 mgd from the CSO treatment plants; System Peak day occurred on 1/12/2021.
***Brightwater max day flow occurred on 1/12/2021; South Plant's max day flow occurred on 1/13/2021 but South Plant's flow was still very high on 1/12/2021 at 175.4 mgd.
****Vashon max day flow occurred on 1/12/2021.
*****Carnation’s max day flow which occurred on 10/26/2021, was not due to rainy weather, but due to flow that was stored the day before but released on 10/26/2021.
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, Henderson/Norfolk,
Mercer/Elliott West
-- -- -- -- --
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 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
0.26 mgd 0.37 mgd
Maximum monthly average flow: 215 mgd 144 mgd 40.9 mgd
0.52 mgd 0.48 mgd
Average dry-weather flow: 110 mgd 96 mgd 25.2 mgd
-- 0.37 mgd
Biochemical oxygen demand (BOD) influent loading (annual average) 168,000 lb/day 220,000 lb/day 66,063 lb/day (maximum month)
526 lb/day 321 pounds/day
Total suspended solids (TSS) influent loading (annual average) 181,000 lb/day 201,000 lb/day 61,400 lb/day (maximum month)
526 lb/day 321 pounds/day
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
1.14 mgd (or 2.05 mgd with on-site storage) 1.40 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 2/1/2015-1/31/2020

(Permit renewal application for NPDES was submitted in 2019. Permit administratively extended until new permit.)

NPDES permit 8/1/2015-7/31/2020

Reclaimed water permit 8/1/2015-7/31/2020

(Permit renewal applications for separate NPDES and reclaimed water permits were submitted in 2019. Both permits were administratively extended until new permit.)

NPDES permit 3/1/2018-2/20/2023

Reclaimed Water permit: 5/1/2019-4/30/2024

NPDES permit 3/1/2017-2/28/2022

(Permit renewal application for NPDES was submitted in 2021. Permit administratively extended until new permit.)

NPDES and reclaimed water permit (combined) 11/1/2021-10/31/2026

Key:
BOD = biochemical oxygen demand
NPDES = National Pollutant Discharge Elimination System
TSS = total suspended solids
  System West Point South Brightwater Vashon Carnation
Electricity produced (2021)

13.467 million kWh

12.687 million kWh
0.780 million kWh -- -- --
Methane gas sold (2021)
(Both West Point & Brightwater also use digester gas to power plant equipment, such as boilers and digesters)
2.630 million therms -- 2.630 million therms -- -- --
Loop biosolids produced (2021) 116,182 wet tons (or 28,417 dry tons) 43,090 wet tons (or 11,819 dry tons). Average percent solids: 27.4. 57,655 wet tons (or 13,420 dry tons). Average percent solids: 23.3. 

Note: South Plant receives untreated solids from Vashon and Carnation plants.
15,437 wet tons (or 3,179 dry tons). Average percent solids: 20.6.

244,844 gallons (or 20.4 dry tons). Average percent solids: 2.0.

Untreated solids hauled to South Plant for further treatment.

1,156,594 gallons (or 43.4 dry tons). Average percent solids: 0.9.

Untreated solids hauled to South Plant for further treatment.

Carbon sequestration (2021)
(From Loop biosolids land application)
35,270 MtCO2e (the equivalent of taking almost 8,000 cars off the road)
16,485 MtCO2e 14,407 MtCO2e 4,378  MtCO2e
-- --
Reclaimed/recycled water (filtered) used at treatment plants (2021) 678.8 mg/yr 200 mg/yr

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

Note: Additional lower quality (non-Class A) water is also used for in-plant processes.
404 mg/yr
-- 5 mg/yr (assumed)
Reclaimed/recycled water (Class A) distributed offsite (2021) About 77.8 mg/yr -- 5.2 mg/yr
(offsite use for irrigation, street cleaning, and sewer flushing)
37.3 mg/yr
-- 35.3 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 $47.37 per month (beginning 1/1/2021)
$49.27 per month (beginning 1/1/2022)
Sewage treatment capacity charge $68.34 per residential customer equivalent (RCE) per month (beginning 1/1/2021)
$70.39 per residential customer equivalent (RCE) per month (beginning 1/1/2022)
Biennial budget (2021-2022) Operating budget: $346 million
Capital budget: $620 million (including a disappropriation of $31M of completed projects)
Number of employees (as of Dec. 2021) About 620 full-time equivalents (FTEs); 43 term-limited temporary (TLTs) employees and 9 short-term temporaries (STTs) in December.
WTD expenditures for capital facilities

View projects under construction
$2.3 billion (2021–2026)
Industrial pretreatment program
Industrial/commercial facilities with permits (aka Significant Industrial Users) 103
Industrial/commercial facilities with letters and discharge authorizations 567
Approximate number of compliance samples taken (except BOD and TSS)  1,580
Inspections conducted  220
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. 2021) 1.14 billion gallons per year
Number of King County CSOs 39 (view CSO location map)
Total rainfall (measured at SeaTac) Total rainfall (2021): 43.33 inches
Long-term average annual rainfall: 38.29 inches (1945–2016)

Sustainability at WTD

infographic of Sustainability Highlights for the King County Wastewater Treatment Division, 2021 Info graphic - page 2 of 2021 Highlights2021 Highlights -- Sustainability in King County's Wastewater Treatment Division