Facts about the King County regional wastewater system
All data current for 2018, 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"
Learn more about operational, financial, regulatory and safety performance of the utility.
2018
| System | West Point | South | Vashon | Carnation | Brightwater | |
|---|---|---|---|---|---|---|
| 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 1.8 million residents | 754,900 | 799,900 | 1,100 (based on census data) | 2,000 | 252,600 |
| Area served |
424 square miles | 113 square miles | 241 square miles | 660 acres (by 2050) | 821 acres (in city and surrounding urban growth area) | 67 square miles |
| System | West Point | South | Vashon | Carnation | Brightwater | |
|---|---|---|---|---|---|---|
| Sewage treated (volume expected in average rainfall year) (million gallons/day) | 179 mgd | 95 mgd | 66 mgd | 0.15 mgd | 0.09 mgd | 16.7 mgd |
| Sewage treated (2018) (million gallons/day) *West Point's average includes discharges from the CSO Treatment Plants |
176.6 mgd |
91.6 mgd* | 68.5 mgd | 0.154 mgd | 0.10 mgd | 16.2 mgd |
| Septage treated (2018) (million gallons/year) | 26.3 mg/yr | -- | 26.3 mg/yr (2,196 dry tons) | -- | -- | -- |
| System | West Point | South | Vashon | Carnation | Brightwater | |
|---|---|---|---|---|---|---|
| Treatment plants | 5 | West Point Treatment Plant, Seattle | South Treatment Plant, Renton | Vashon Treatment Plant, Vashon Island | Carnation Treatment Plant, Carnation | Brightwater Treatment Plant, Snohomish County north of Woodinville |
| Pump stations | 47 | 20 | 19 | 4 | -- | 4 |
| Regulator stations | 25 | 23 | 2 | -- | -- | -- |
| CSO wet weather treatment facilities | 4: Alki, Carkeek, Mercer/Elliot 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 395 miles | -- | -- | 3.2 miles | 1.6 miles | -- |
| Sewer pipe diameter (smallest to largest) | 2.5 inches to 14 feet, 8 inches | 8 inches to 14 feet, 8 inches | 8 inches to 14 feet, 8 inches | 2.5 inches to 8 inches | 8 inches to 12 inches | 8 inches to 14 feet, 8 inches |
| Outfalls, length and depth | -- | 3,600 feet long; 240 feet deep; 1 diffuser at 600 feet long Discharge to Puget Sound. |
2 parallel pipes, 10,000 feet long each; 625 feet deep; 4 diffusers at 500 feet long each Discharge to Puget Sound. |
2,850 feet long; 200 feet deep; no diffuser Discharge to Puget Sound. |
Primary discharge: Chinook Bend Wetland Enhancement Project Backup: Snoqualmie River at Carnation Farm Road Bridge |
2 parallel pipes, 4,600 feet long each; 600 feet deep; 2 diffusers at 250 feet long each Discharge to Puget Sound. |
| West Point | South | Vashon | Carnation | Brightwater | |
|---|---|---|---|---|---|
| Average wet-weather flow (non-storm) (million gallons/day): 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 | 0.26 mgd (estimated) | 0.22 mgd | 30 mgd (2018-2023) |
| Maximum monthly average flow (million gallons/day): | 215 mgd | 144 mgd | 0.52 mgd | 0.27 mgd | 40.9 mgd (2018-2023) |
| Average dry-weather flow (million gallons/day): | 110 mgd | 96 mgd | -- | 0.21 mgd | 25.2 mgd (2012-2016) |
| Biochemical oxygen demand (BOD) influent loading (annual average) | 168,000 pounds/day | 220,000 pounds/day | 526 pounds/day | 314 milligram/liter | 66,063 pounds/day (maximum month 2018-2023) |
| Total suspended solids (TSS) influent loading (annual average) | 181,000 pounds/day | 201,000 pounds/day | 526 pounds/day | 314 milligram/liter | 61,400 pounds/day (maximum month 2018-2023) |
| Instantaneous maximum capacity (million gallons/day): 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 | 1.14 mgd (2.05 mgd with on-site storage) | 1.4 mgd | 100 mgd (until 2025 or until fifth IPS pump set is installed) |
| West Point | South | Vashon | Carnation | Brightwater | |
|---|---|---|---|---|---|
| Permit (NPDES) renewal dates: View permit limits (BOD, TSS, fecal coliform, chlorine residual) for each treatment plant. | NPDES permit 1/31/2020 | NPDES permit 7/31/2020 Reclaimed water permit 7/31/2020 |
NPDES permit 2/28/2022 |
NPDES and reclaimed water permit (combined) 12/31/2018 (End date was administratively extended while awaiting new permit) |
NPDES permit 2/28/2023 Reclaimed water permit 4/30/2024 |
| System | West Point | South | Vashon | Carnation | Brightwater | |
|---|---|---|---|---|---|---|
| Electricity produced (2018) |
13.139 million kilowatt hours (produced solely from plant methane) 14.677 million kilowatt hours (total produced from plant methane and purchased natural gas) |
10.926 million kilowatt hours (produced solely from plant methane) | 3.751 million kilowatt hours (produced from plant methane and purchased natural gas) | -- | -- | -- |
| Methane gas sold (2018) (Both West Point & Brightwater also use digester gas to power plant equipment, such as boilers and digesters) | 2.465 million therms | -- | 2.465 million therms | -- | -- | -- |
| Loop biosolids produced (2018) | 129,568 wet tons (or 31,344 dry tons) |
49,258 wet tons at 27% solids (or 14,086 dry tons) |
64,332 wet tons at 22% solids (or 14,116 dry tons) Note: South Plant receives untreated solids from Vashon and Carnation plants. |
485,851 gallons at 2% solids (or 41 dry tons). Untreated solids hauled to South Plant for further treatment. | 1,050,119 gallons at 2% solids (or about 88 dry tons). Untreated solids hauled to South Plant for further treatment. | 15,460 wet tons at 20% solids (or 3,103 dry tons) |
| Carbon sequestration (2018) (From Loop biosolids land application. MtCO2e = metric tons of carbon dioxide equivalents) | 40,611 MtCO2e (the equivalent of taking 9,000 cars off the road) | 19,557 MtCO2e | 16,705 MtCO2e | -- | -- | 4,349 MtCO2e |
| Reclaimed/recycled water (filtered) used at treatment plants (2018) | 669 million gallons per year | 168 million gallons per year Note: Additional lower quality (non-Class A) water is also used for in-plant processes. |
35.6 million gallons per year Note: Additional lower quality (non-Class A) water is also used for in-plant processes. |
-- | -- | 465 million gallons per year |
| Reclaimed/recycled water (Class A) distributed offsite (2018) | About 76.9 million gallons per year | -- | 4.9 million gallons per year (offsite use for irrigation, street cleaning, & sewer flushing) | -- | 31.3 million gallons per year (distributed to Chinook Bend Natural Area Wetland Enhancement Site) | 40.7 million gallons per year (distributed for irrigation, toilets/urinals, and public art) |
| Wholesale sewer rate | $45.33 per month (beginning 1/1/2018) $45.33 per month (beginning 1/1/2019) |
|---|---|
| Sewage treatment capacity charge | $62.60 per residential customer equivalent (RCE) per month (beginning 1/1/2018) $64.50 per residential customer equivalent (RCE) per month (beginning 1/1/2019) |
| Annual budget (2018) | Operating: $172.8 million Capital-related: $226.1 million |
| Number of employees (as of Jan. 2019) | About 597 full-time equivalents (FTEs); 55 term-limited temporary (TLT) employees and 15 short-term temporaries and interns |
| WTD expenditures for capital facilities through 2030 View projects under construction |
$4.1 billion (2018–2030) |
| Industrial pretreatment program |
|
| Industrial/Commercial facilities with permits (aka Significant Industrial Users) | 109 |
| Industrial/commercial facilities with letters and discharge authorizations | 551 |
| Approximate number of compliance samples taken (except BOD and TSS ) | 1,777 |
| Inspections conducted | 297 |
| Combined sewer overflows (CSOs) CSO control program |
|
| Baseline volume (1980–83) | 2.3 billion gallons per year |
| Current volume (Jan.–Dec. 2018) | 839 million gallons per year |
| Number of King County CSOs | 39 (view CSO location map) |
| Total rainfall (measured at SeaTac) | Total rainfall (2018): 35.73 inches Long-term average annual rainfall: 38.67 inches (1949–2017) |