Facts about the King County regional wastewater system
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 |
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| 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 |
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| 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 |
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| 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 |
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| 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 (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 |
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| 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 |
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| Wholesale sewer rate | $45.33 per month (beginning 1/1/2020) $47.37 per month (beginning 1/1/2021) |
|---|---|
| Sewage treatment capacity charge | $66.35 per residential customer equivalent (RCE) per month (beginning 1/1/2020) $68.34 per residential customer equivalent (RCE) per month (beginning 1/1/2021) |
| 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
2019 Highlights -- Sustainability in King County's Wastewater Treatment Division
