This data depicts the areas of sewer service for local sewer providers in King County and the KC-WTD service area. This data was created for planning and project purposes for the King County Wastewater Treatment Division. The data is based upon the best available information including service area boundaries, conveyance pipe locations and Sewer Comprehensive Plans issued by the local providers. This data can/will differentiate from the corporate boundaries for each of the local providers. This data is in no way the final authority, but simply the best available information. If specific questions regarding service areas and local providers arise, the local provider would be the entity to contact.

This data layer describes the boundaries of combined water & sewer utility districts. This data does not describe water service or sewer service areas of the districts.

Vector polygon map data of sewer districts from King County, Washington containing 10 features.

A sewer district, also known as a sanitary district or wastewater district, is a local government agency responsible for managing and maintaining sewer systems within a specific geographical area. These districts are tasked with collecting and treating wastewater and sewage from homes, businesses, and industries to prevent pollution of waterways and protect public health.

Sewer districts typically oversee the construction, operation, and maintenance of sewer pipes, pump stations, treatment plants, and other infrastructure necessary for wastewater management. They may also implement regulations and programs to promote water conservation and pollution prevention within their jurisdiction.

This sewer district data is available for viewing and sharing as a map in a Koordinates map viewer. This data is also available for export to DWG for CAD, PDF, KML, CSV, and GIS data formats, including Shapefile, MapInfo, and Geodatabase.

King County Wastewater System with Local Sewer Service Providers. 11x17 inch PDF map.

This data layer describes the boundaries of sewer districts in King County. These are district boundaries which do not always coincide with service area boundaries.

SPU LateralSewerline

King County Wastewater Coal Creek Sewer Upgrade Project Location Map

The WTD Sewer Service Area - Wastewater Flow Basins map provides a detailed spatial overview of the sewer infrastructure managed by the King County Wastewater Treatment Division (WTD). It is designed to help visualize the extent and features of the sewer service area, particularly focusing on wastewater flow basins.Key Features and Layers:Minor FacilitiesDisplays smaller infrastructure elements that support the sewer network, such as access structures and monitoring points.Major FacilitiesHighlights significant infrastructure like wet weather treatment stations, pump stations, or regulator stations that play a critical role in the network.Treatment FacilitiesIdentifies wastewater treatment plants that process sewage from the service area.Sewer LinesShows the layout of the sewer pipeline network, distinguishing mainlines and other types of conduits for transporting wastewater.Wastewater Flow BasinsDelineates the areas that contribute wastewater to specific sections of the sewer system, providing insights into flow patterns and basin-level management.County BoundaryOutlines the overall boundary of King County for context in relation to the service area.This map is a vital tool for planning, management, and public information, providing insights into how the WTD infrastructure interacts with urban development and municipal boundaries.

The purpose of this project is to find, count and map onsite septic system (OSS) served parcels in King County. Additionally, sewer connected parcels were also identified to exclude them from expected OSS parcels. The starting base layer was a parcel layer for all of King County (Plibrary.PROPERTY.parcel_area) from about September of 2015. The parcel base layer was updated in 2020. Project staff used various means to identify and catalogue sewer connected, OSS served, vacant and other identified parcels for all of King County.

Area of combined sewer overflow where it flows toward lower duwamish waterway area. This area was defined using WTD CSO basins.

Components of Open Conveyance (Ditch and Natural Drainage) Ditch: A long narrow constructed channel. Natural Drainage: Non-engineered, non-constructed flow paths following existing land contours. When a stream isn’t mapped and the natural drainage system (stream) may be confused with a ditch that is part of King County’s MS4, the stream is mapped as Natural Drainage to prevent future confusion.

Other Control (Polygon) Component TypesBioretention Cell: Shallow depressions with a designed planting soil mix and a variety of plant material, including trees, shrubs, grasses, and/or other herbaceous plants. Bioretention cells may or may not have an under-drain and are not designed as a conveyance system.Bioretention Planter: Designed soil mix and a variety of plant material including trees, shrubs, grasses, and/or other herbaceous plants within a vertical walled container usually constructed from formed concrete, but could include other materials. Planter boxes are completely impervious and include a bottom (must include an under-drain).Permeable Pavement (Vegetated): Vegetated pavement that allows water to infiltrate to the ground.Permeable Pavement (Non-Vegetated): Non-vegetated pavement that allows water to infiltrate to the ground.

This layer is used to map point based features that are part of facilities that are not part of the stormwater framework, but are included in the county inventory becasue they still require maintenance actions. An example would be a facility sign.

The area identified in this data represents all properties that may be subject to a capacity charge.

This layer contains facility features such as fence lines, check dams and other linear features that require tracking but are not specifically part of the MS4 framework.

Wastewater Sewer flow basins, the delineated areas are derived from mdlbsn boundaries and show where the overall flow goes.

Undefined features are components that have not been created in the stormwater framework. This could include new stormwater designs or potentially archaic features that were not included in the development of the stormwater framework.

Components of Access FeaturesAccess Riser: A vertical maintenance access to a Vault, Tank or other similar structure. The access opening is wide enough for entry to support maintenance and inspection. Cleanout: A Pipe with a cap that allows for cleaning or inspection of the Conveyance System. Non-Standard Access: An access structure that does not meet the structural requirement of any contemporary design standards. Manhole: Manholes connect one Pipe to another Pipe, with an opening to the surface. Structurally, manholes are cylindrical, deeper than wide, has an access opening, and without a Sump. Pipe outlet(s) are at the base of structure, often in “channel and shelf.”

Component Types for Control Other (Point)Dry Well: Gravel filled holes or structures used for temporary storage and infiltration of stormwater runoff.Injection Well: A structure that is deeper than it is wide that is designed to infiltrate stormwater runoff.Full Dispersion: Features a native vegetated flowpath segment of at least 100ft (25ft for sheet flow from a non-native pervious surface) along the flowpath that runoff would follow upon discharge. The flowpath segment must be either onsite or in an offsite tract or easement area reserved for dispersion and should be designated as a “native growth retention area” on the flow control BMP site plan attached to the required declaration of covenant and grant of easement. Full dispersion involves use of splash blocks, rock pads, gravel filled trenches or sheet flow.

This layer maps features such as mowing areas and other features that are mapped as polygons and are part of stormwater facilities.