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    City of Seattle

    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.

    Excerpt from City of Seattle Municipal Code

    22.800.070 - Minimum requirements for City agency projects

    A. Compliance. City agencies shall comply with all the requirements of this subtitle except as specified below:

    1. City agencies are not required to obtain permits and approvals under this subtitle, other than inspections as set out in subsection 22.800.070.B and review and approval when applying roadway project infeasibility as provided in subsection 22.805.060.E, for work performed within a public right-of-way or for work performed for the operation and maintenance of park lands under the control or jurisdiction of the Department of Parks and Recreation. Where the work occurs in a public right-of-way, it shall also comply with Title 15, Street and Sidewalk Use, including the applicable requirements to obtain permits or approvals.
    2. A City agency project, as defined in Section 22.801.170, that is not required to obtain permit(s) and approval(s) pursuant to subsection 22.800.070.A.1 and meets all of the conditions set forth below, is not required to comply with the amendments to Sections 22.800.020 through 22.808.110 that take effect on July 1, 2021, except the amendments to this subsection 22.800.070.A.2.
      1. The project begins land disturbing activities within five years of the effective date of this subtitle; and
      2. The project complies with the Stormwater Code that was made effective January 1, 2016, by Ordinance 124872 which requires compliance with Directors' Rules SDCI 17-2017/SPU DWW 200 effective January 1, 2016; and
      3. The project meets one or more of the following criteria:
        1. Project funding was appropriated as identified in Ordinance 126237 titled, "An ordinance adopting a budget, including a capital improvement program and position modifications, for The City of Seattle for 2021"; or
        2. Project received or will receive voter approval of financing before January 1, 2021; or
        3. Project received or will receive funds based on grant application(s) submitted before January 1, 2021.

    B. Inspection

    1. When the City conducts projects for which review and approval are required under Chapter 22.807 (Drainage control review and application requirements) the work shall be inspected by the City agency conducting the project or supervising the contract for the project. The inspector for the City agency shall be responsible for ascertaining that the drainage control is done in a manner consistent with the requirements of this subtitle.
    2. A City agency need not provide an inspector from its own agency provided either:
      1. The work is inspected by an appropriate inspector from another City agency; or
      2. The work is inspected by an appropriate inspector hired for that purpose by a City agency; or
      3. The work is inspected by the licensed civil or geotechnical engineer who prepared the plans and specifications for the work; or
      4. A permit or approval is obtained from the Director of SDCI, and the work is inspected by the Director.

    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:

    • Implement maintenance standards for facilities that are as protective, or more protective, of facility function than those specified in Chapter 4 of Volume V of the 2012 Stormwater Management Manual for Western Washington (Ecology, 2012). Unless there are uncontrollable circumstances, when and inspection identifies an exceedance of the maintenance standard, maintenance shall be performed within 1 year for typical maintenance of facilities, (except catch basins), within 6 months for catch basins, and within 2 years for maintenance that requires capital construction of less than $25,000.
    • Evaluate and, if necessary, update existing ordinances or other enforceable documents requiring maintenance of existing permanent stormwater facilities regulated by the City. Establish an initial and ongoing inspection program for stormwater facilities and catch basins regulated by the City.
    • Implement an ongoing inspection schedule for all known, permanent stormwater treatment and flow control facilities (other than catch basins) regulated by the City to enforce compliance with adopted maintenance standards as needed based on the inspection.
    • Manage maintenance activities to inspect all new permanent stormwater treatment and flow control facilities, including catch basins, in new residential development every 6 months until 90% of the lots are constructed to identify maintenance needs and enforce compliance.
    • Require cleaning of catch basins regulated by the City if found to be out of compliance during source control or IDDE program activities or if part of treatment or flow control system inspected under this O&M program.
    • Implement an inspection process for all permanent stormwater facilities owned or operated by the City. Conduct spot checks of potentially damaged stormwater facilities after storm events. Conduct repairs or maintenance actions in compliance with maintenance standards.
    • Implement a program to annually inspect all catch basins and inlets owned or operated by the City.
    • Maintain records of inspections and repair activities conducted by the City.
    • Establish and implement processes and procedures to reduce stormwater impacts associated with runoff from municipal operation and maintenance activities including but not limited to streets, parking lots, roads or highways owned or maintained by the City, and to reduce pollutants in discharges from all lands owned or maintained by the City.
    • Implement an ongoing training program for employees who have primary construction, operations or maintenance job functions that could impact stormwater quality. Track and maintain training records.
    • Develop and implement SWPPPs for all heavy equipment maintenance or storage yards, and material storage facilities owned or operated by the City in areas covered by the Permit that are not covered by another Ecology-issued stormwater discharge permit.
    • Maintain records of inspection and maintenance or repair activities.

    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.


    Seattle Stormwater Resources

    Information on 2021 Stormwater Code and Manual Updates

    City of Seattle Stormwater Code

    City of Seattle Stormwater Manual