The City of Seattle has enacted a Stormwater Ordinance in order to establish minimum stormwater management requirements and controls to protect and safeguard the general health, safety, and welfare of the public residing in watersheds within this jurisdiction. The City of Seattle is the permitting authority for all land disturbing activities and requires the land owner to maintain all on-site stormwater control facilities and all open space areas (e.g. parks or “green” areas) required by the approved stormwater control plan. The City of Seattle will only provide construction permits to projects that establish a plan to manage stormwater runoff occurring during the construction process. The City of Seattle, under the NPDES program, also has the authority to inspect properties for noncompliance and can issue a notice of violation (NOV) for any deficiency or infraction onsite. Property owners are responsible for the maintenance of any stormwater facilities or practices located on the property. The City of Seattle has the authority to inspect stormwater facilities and practices in order to ascertain that they are properly maintained and functioning.
A. Compliance. City agencies shall comply with all the requirements of this subtitle except as specified below:
B. Inspection
C. Certification of compliance. City agencies shall meet the same standards as non-City projects, except as provided in subsection 22.800.070.A, and shall certify that each individual project meets those standards.
(Ord. 126336 , § 1, 2021; Ord. 124919 , § 89, 2015; Ord. 124872 , § 5, 2015; Ord. 123105, § 2, 2009.)
22.800.075 - Compliance by public agencies
Whether or not they are required to obtain permits or submit documents, public agencies are subject to the substantive requirements of this subtitle, unless adjustments or exceptions are granted as set forth in Section 22.800.040 (Exemptions, Adjustments, and Exceptions) or the requirements have been waived under subsection 22.807.020.A.3.
(Ord. 123105, § 2, 2009.)
City of Seattle Drainage
The City’s current drainage infrastructure includes three different types (Figure I.1.1): the separate storm sewer system (in purple), the partially separated system (in green), and the combined sewer system (in yellow) each serving approximately one third of the geographical area of Seattle. A graphical representation of the combined, separated and partially separated systems can be seen in Figure I.1-2.
In the separate system, storm drainage is directed to a separate storm drain system, while wastewater goes to a sanitary sewer and on to the wastewater treatment plant before discharge. While parts of the City’s separated drainage system are formal and piped, some parts of the separate stormwater runoff are managed primarily through an informal system of ditches and culverts, most of which drain to creeks or larger receiving waters. The area north of NE 85th Street, which the City annexed in 1954, is an example of an area still served primarily by ditch and culvert drainage systems..
In partially separated sewer areas of the City, all drainage once flowed in the combined system. During the 1960’s, storm drain separation projects were built that diverted street runoff in pipes to the separate storm drainage system and receiving waters. Rooftop and other private property drainage continue to be directed to wastewater treatment plants.
The combined sewer system is a formal piped system that continues to carry both sanitary wastewater and stormwater runoff from some parts of the City to one of the area’s wastewater treatment plants. Combined sewers and areas of the City that drain to combined sewers, are outside the NPDES municipal stormwater permit structure. The City’s SWMP is implemented for discharges from, and property draining to, the City’s separate storm sewer system and partially separated system (MS4 for short). Because of the scope of the MS4 permit, the City’s SWMP is not implemented for discharges to or from the combined sewer system or for areas that drain to the combined sewer system.
II.9.1 Requirements
The Permit (Section S5.C.9) requires the City to develop and implement an operations and maintenance (O&M) program to reduce stormwater impacts associated with the City’s municipal separate stormwater system and regulate municipal operations and maintenance activities in areas served by the City’s MS4. The minimum performance measures include the following areas with more detailed requirements included in the Permit text:
II.9.3 Responsible City Departments
SPU is responsible for operation and maintenance of stormwater facilities owned, operated or maintained by the City and located in the right of way and for conducting inspections of private stormwater facilities to determine that those stormwater facilities meet operation and maintenance standards. Other City Departments, SDOT, FAS, Parks, and SCL are responsible for operation and maintenance of stormwater facilities and implementation of operation and maintenance policies and procedures specific to the properties they manage.
II.9.4.1 Maintenance Standards
The City has a program based on maintenance standards in place to reduce stormwater impacts associated with runoff from impervious surfaces and operation and maintenance of stormwater facilities that discharge to the City’s MS4. This program follows the current Stormwater Code (2009) and the current Director’s Rule DR 17-2009, SPU 2009-005, Vol. III - Stormwater Flow Control and Water Quality Treatment Technical Requirements Manual, Appendix D of Vol. III outlines inspection, maintenance, and record keeping requirements for stormwater management facilities, both public and private, in the City. In some cases, the City owns or operates facilities with site-specific maintenance requirements that require facility-specific maintenance standards. For these situations the City has developed facility specific standard operating procedures that incorporate the inspection and maintenance requirements of Appendix D as well as detailed information such as the location and access restrictions of facilities, necessary equipment, safety procedures and maintenance procedures.
Information on 2021 Stormwater Code and Manual Updates