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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

    Title 21 - Utilities

    Subtitle II - Sewers; Chapter 21.33 -  Storm Drainage Utility Rates and Charges

    21.33.040 - Stormwater facility credit program

    A. The Utility may apply a stormwater facility credit to be effective beginning January 1 of the 2009 billing year, in accordance with this Section 21.33.040, to reduce the annual drainage service charge for a particular parcel within the City if the stormwater originating from the parcel being billed is managed by one or more approved stormwater management facilities that are installed on the parcel being billed; or that are installed on a parcel different than the parcel being billed, subject to the following conditions:

    1. The applicant must be able to demonstrate that the approved stormwater management facility located on a different parcel is designed to manage the stormwater originating on the parcel being billed; and
    2. If the owner of the parcel being billed does not own the parcel on which the approved stormwater management facility is installed, the applicant must be able to provide adequate documentation confirming that the Utility will have the right to inspect the facility for the applicable purposes under subsection 21.33.040.C; and
    3. The approved stormwater management facility managing the stormwater from the parcel being billed must not be owned by the Utility, except where the applicant for the credit is the Utility.

    B. Property owners must complete a stormwater facility credit application and submit it to the Utility by November 1st of any calendar year for credit against the subsequent year's drainage service charge. The stormwater facility credit will not be applied until the Utility has approved the application in writing.

    C. Prior to approving a stormwater facility credit, and annually after a facility credit is approved, the Utility shall have the right to inspect the approved stormwater management facility(ies) and parcel being billed to confirm application information and continued eligibility for the credit. Inspection may include confirmation of parcel characteristics, such as impervious surface area, and determination that the facility meets the technical design requirements and is being inspected and maintained in accordance with Stormwater Code Chapters 22.800 through 22.808 and associated Director's Rules.

    D. The Utility will calculate a stormwater facility credit for each eligible parcel that has applied for such credit based on the following:

    1. The type and size of the approved stormwater management facility(ies). The Utility will assign a uniform rate credit to each type of approved stormwater management facility based on a weighting of the stormwater performance goals the facility satisfies and that are applicable to the appropriate drainage discharge point for the parcel being billed;
    2. The percentage of impervious surface on the parcel that is managed by the approved stormwater management facility(ies); and
    3. The percentage of the parcel's drainage service charge which is based on runoff from impervious surfaces, as determined using flow calculation data for the applicable drainage service charge rate category.

    E. To assign the uniform rate credit by facility type under Section 21.33.040.D.1 and calculate the stormwater facility credit only, the Utility will use the stormwater performance goals under the Stormwater, Grading and Drainage Code adopted by Ordinance No. 119965 , effective July 5, 2000, for any approved stormwater management facility installed prior to July 5, 2000. The Utility will use the stormwater performance goals under the Stormwater Code in effect at the time the approved stormwater management facility is installed for any such facility installed after July 5, 2000.

    F. The allowable maximum credit to the drainage service charge per parcel, including the stormwater facility credit and the reduction for rainwater harvesting systems under Section 21.33.030.D.4, may not exceed 50 percent of the drainage service charge for the parcel. The stormwater facility credit and reduction for rainwater harvesting systems may not reduce the drainage service charge per parcel below the minimum drainage service charge under Section 21.33.030.E.

    G. The Utility may terminate the stormwater facility credit for any parcel, upon written notice, for the following reasons:

    1. The property owner does not maintain the approved stormwater management facility in a clean and properly functioning manner and does not take corrective action within the time specified by a Utility inspector;
    2. the parcel changes ownership;
    3. the parcel is re-developed or the parcel boundaries change.

    (Ord. 124801 , § 3, 2015; Ord. 123106, § 4, 2009; Ord. 122682 , § 3, 2008.)

    Title 22 - Building and Construction Codes

    Subtitle VIII - Stormwater Code

    22.800.030 - Scope and Applicability

    A. All grading and drainage and erosion control, whether or not a permit is required;

    B. All land disturbing activities, whether or not a permit is required;

    C. All discharges directly or indirectly to a public drainage system or a public combined sewer;

    D. All discharges directly or indirectly into receiving waters within or contiguous to Seattle city limits;

    E. All new and existing land uses; and

    F. All real property.

    (Ord. 124872 , § 2, 2015; Ord. 123105, § 2, 2009.)

    22.800.040 - Exemptions, Adjustments, and Exceptions

    1. The following land uses are exempt from the provisions of this subtitle:

    a. Commercial agriculture, including only those activities conducted on lands defined in RCW 84.34.020(2), and production of crops or livestock for wholesale trade; and

    b. Forest practices regulated under Title 222 Washington Administrative Code, except for Class IV general forest practices, as defined in WAC 222-16-050, that are conversions from timber land to other uses.

    2.The following land disturbing activities are not required to comply with the specific minimum requirements listed below.

    a. Maintenance, repair, or installation of underground or overhead utility facilities, such as, but not limited to, pipes, conduits and vaults, and that includes replacing the ground surface with in-kind material or materials with similar runoff characteristics are not required to comply with Section 22.805.070 (Minimum Requirements for On-site Stormwater Management), Section 22.805.080 (Minimum Requirements for Flow Control), or Section 22.805.090 (Minimum Requirements for Treatment), except as modified as follows:

    1) Installation of a new or replacement of an existing public drainage system, public combined sewer, or public sanitary sewer in the public right-of-way shall comply with Section 22.805.060 (Minimum Requirements for Roadway Projects) when these activities are implemented as publicly bid capital improvement projects funded by Seattle Public Utilities; and

    2) Installation of underground or overhead utility facilities that are integral with and contiguous to a road-related project shall comply with Section 22.805.060 (Minimum Requirements for Roadway Projects).

    b. Pavement maintenance practices limited to the following activities are not required to comply with Section 22.805.060 (Minimum Requirements for Roadway Projects), Section 22.805.070 (Minimum Requirements for On-site Stormwater Management, Section 22.805.080 (Minimum Requirements for Flow Control), or Section 22.805.090 (Minimum Requirements for Treatment):

    1) Pothole and square cut patching;

    2) Overlaying existing asphalt or concrete or brick pavement with asphalt or concrete without expanding the area of coverage;

    3) Shoulder grading;

    4) Reshaping or regrading drainage ditches;

    5) Crack sealing; and

    6) Vegetation maintenance.

    3. Sites that produce no runoff as determined by a licensed civil engineer using a continuous runoff model approved by the Director are not required to comply with Section 22.805.080 (Minimum Requirements for Flow Control).

    4. When a portion of the site being developed discharges only to the public combined sewer, that portion is not required to comply with the provision of subsection 22.805.020.I (Install Source Control BMPs) unless the Director determines that these activities pose a hazard to public health, safety or welfare; endanger any property; adversely affect the safety and operation of city right-of-way, utilities, or other property owned or maintained by the City; or adversely affect the functions and values of an environmentally critical area or buffer.

    5. Residential activities are not required to comply with the provision of subsection 22.805.020.I (Install Source Control BMPs) unless the Director determines that these activities pose a hazard to public health, safety or welfare; endanger any property; adversely affect the safety and operation of city right-of-way, utilities, or other property owned or maintained by the City; or adversely affect the functions and values of an environmentally critical area or buffer.

    6. With respect to all state highway right-of-way under Washington State Department of Transportation (WSDOT) control within the jurisdiction of the City of Seattle, WSDOT shall use the current, approved Highway Runoff Manual (HRM) for its existing and new facilities and rights-of-way, as addressed in WAC 173-270-030(1) and (2). Exceptions to this exemption, where more stringent stormwater management requirements apply, are addressed in WAC 173-270-030(3)(b) and (c).

    a. When a state highway is located in the jurisdiction of a local government that is required by Ecology to use more stringent standards to protect the quality of receiving waters, WSDOT shall comply with the same standards to promote uniform stormwater management.

    b. WSDOT shall comply with standards identified in watershed action plans for WSDOT rights-of-way, to the extent required by state law.

    c. Other instances where more stringent local stormwater standards apply are projects subject to tribal government standards or to the stormwater management-related permit conditions imposed under Chapter 25.09 to protect environmentally critical areas and their buffers (under the Growth Management Act), an NPDES permit, or shoreline master programs (under the Shoreline Management Act). In addition, WSDOT shall comply with local jurisdiction stormwater standards when WSDOT elects, and is granted permission, to discharge stormwater runoff into a municipality's drainage system or combined sewer system.

    B. Adjustments

    1. The Director may approve a request for adjustments to the requirements of this subtitle when the Director finds that:

    a. The adjustment provides substantially equivalent environmental protection; and

    b. The objectives of safety, function, environmental protection, and facility maintenance are met, based on sound engineering practices.

    2. During construction, the Director may require, or the applicant may request, that the construction of drainage control facilities and associated project designs be adjusted if physical conditions are discovered on the site that are inconsistent with the assumptions upon which the approval was based, including but not limited to unexpected soil and/or water conditions, weather generated problems, or changes in the design of the improved areas.

    3. A request by the applicant for adjustments shall be submitted to the Director for approval prior to implementation. The request shall be in writing and shall provide facts substantiating the requirements of subsection 22.800.040.B.1 and, if made during construction, the factors in subsection B.2. Any such modifications made during the construction of drainage control facilities shall be recorded on the final approved drainage control plan, a revised copy of which shall be filed by the Director.

    C. Exceptions

    1. The Director may approve a request for an exception to the requirements of this subtitle when the applicant demonstrates that the exception will not increase risks in the vicinity and/or downstream of the property to public health, safety and welfare, or to water quality, or to public and private property, and:

    a. The requirement would cause a severe and unexpected financial hardship that outweighs the requirement's benefits, and the criteria for an adjustment cannot be met; or

    b. The requirement would cause harm or a significant threat of harm to public health, safety and welfare, the environment, or public and private property, and the criteria for an adjustment cannot be met; or

    c. The requirement is not technically feasible, and the criteria for an adjustment cannot be met; or

    d. An emergency situation exists that necessitates approval of the exception.

    2. An exception shall only be granted to the extent necessary to provide relief from the economic hardship, to alleviate the harm or threat of harm, to the degree that compliance with the requirement becomes technically feasible, or to perform the emergency work that the Director determines exists.

    3. An applicant is not entitled to an exception, whether or not the criteria allowing approval of an exception are met.

    4. The Director may require an applicant to provide additional information at the applicant's expense, including, but not limited to, an engineer's report or analysis.

    5. When an exception is granted, the Director may impose new or additional requirements to offset or mitigate harm that may be caused by granting the exception, or that would have been prevented if the exception had not been granted.

    6. Public notice of an application for an exception and of the Director's decision on the application shall be provided in the manner prescribed for Type II land use decisions, as set forth in Chapter 23.76.

    7. The Director's decision shall be in writing with written findings of fact. Decisions approving an exception based on severe and unexpected economic hardship shall address all the factors in subsection 22.800.040.C.8.

    8. An application for an exception on the grounds of severe and unexpected financial hardship must describe, at a minimum, all of the following:

    a. The current, pre-project use of the site; and

    b. How application of the requirement(s) for which an exception is being requested restricts the proposed use of the site compared to the restrictions that existed prior to the adoption of this current subtitle; and

    c. The possible remaining uses of the site if the exception were not granted; and

    d. The uses of the site that would have been allowed prior to the adoption of this subtitle; and

    e. A comparison of the estimated amount and percentage of value loss as a result of the requirements versus the estimated amount and percentage of value loss as a result of requirements that existed prior to adoption of the requirements of this subtitle; and

    f. The feasibility of the owner or developer to alter the project to apply the requirements of this subtitle.

    9. In addition to rights under Chapter 3.02, any person aggrieved by a Director's decision on an application for an exception may appeal to the Hearing Examiner's Office by filing an appeal, with the applicable filing fee, as set forth in Section 23.76.022. However, appeals of a Notice of Violation, Director's order, or invoice issued pursuant to this subtitle shall follow the required procedure established in Chapter 22.808.

    10. The Hearing Examiner shall affirm the Director's determination on the exception unless the examiner finds the determination is clearly erroneous based on substantial evidence. The applicant for the exception shall have the burden of proof on all issues related to justifying the exception.

    11. The Director shall keep a record, including the Director's written findings of fact, on all approved requests for exceptions.

    (Ord. 124872 , § 3, 2015; Ord. 124758 , § 1, 2015; Ord. 123105, § 2, 2009.)

    Excerpt from City of Seattle Stormwater Manual (2017)


    City of Seattle Seattle Public Utilities Department of Planning and Development

    March 2014


    2.1. Required Citywide Best Management Practices

    Per SMC, Section 22.803.030, all real property must implement and maintain the following source control BMPs to prevent or minimize pollutants from leaving a site or property.

    Owners, operators, and occupants of property, and anyone causing or contributing to a violation of the Stormwater Code are each considered a “responsible party” relative to a Code violation (SMC, Section 22.801.190).

    2.1.2. BMP 2: Perform Routine Maintenance for Drainage System

    Sediment and pollutants can accumulate over time in various components of drainage collection, conveyance, and treatment systems, such as catch basins, ditches, storm drains, and oil/water separators. When a storm event occurs, the pollutants can become mobilized and carried into receiving waters. Performing routine maintenance is required and helps prevent sediment and pollutants from discharging downstream.

    Required elements of this BMP include:

    • Inspect all conveyance, detention and treatment systems at least annually and clean or repair structures whenever the condition thresholds described in Appendix G are triggered. Systems in industrial areas or areas that receive excessive sediment, foliage or debris may require more frequent inspection and maintenance. If leaves or woody debris accumulate on catch basins and inlets, clean as needed to prevent flooding.
    • Specifically, clean catch basins when they are greater than 60 percent full of sediment, within 18 inches of the bottom of the lowest pipe, or there are obvious signs of pollution visible. At 60 percent capacity, there is not enough settling space to remove sediment from stormwater and they cease to function as designed.
    • All catch basins are required to have outlet traps (downturned elbow) similar to City of Seattle Standard Plan No. 267. Replace or repair outlet traps when missing or damaged.
    • Properly dispose of all solids, polluted materials, and stagnant water that is collected through drainage system cleaning. Do not decant water back to the system. Do not jet material downstream into the drainage system. In all systems, known or suspected contaminated material may need to be tested for additional disposal requirements.
    • Consider posting “Dump No Waste” or other warning signs adjacent to storm drains where possible.
    • If pollutants are found in the drainage system, select additional required BMPs from Chapter 3 according to the activities conducted at the site.

    2.1.7. BMP 7: Site Maintenance

    Good site maintenance reduces the potential for stormwater to come into contact with pollutants and can reduce maintenance intervals for the drainage system.

    Required elements of this BMP include:

    • Maintain all site source controls to keep them working as designed.
    • Evaluate site drainage and where feasible, consider locating pollution generating activities away from stormwater pathways.
    • Sweep paved areas used for material handling and storage as needed to prevent pollutant transport offsite or to the drainage system.
    • Promptly contain and clean up solid and liquid leaks and spills (refer to BMP 5 for specific information on spill prevention and cleanup).
    • Inspect production, material handling, material/waste storage, and vehicle parking areas on a frequent basis for housekeeping needs and pollution risks.

    Excerpt from City of Seattle 2014 NPDES Phase I Municipal Stormwater Permit Stormwater Management Program

    May 2014

    The City of Seattle Stormwater Management Plan was developed for compliance with the Ecology issued 2013 NPDES Phase I Municipal Stormwater Permit and is designed to:

    • Protect water quality
    • Reduce the discharge of pollutants to the “maximum extent practicable”
    • Satisfy appropriate requirements of the Clean Water Act
    • Meet state requirements to use all known, available, and reasonable methods to prevent and control pollution to waters of the state

    The document below contains updated information on the City of Seattle's 2014 stormwater management activities for compliance with the Permit.


    The NPDES program is a key element of the Federal Clean Water Act aimed at controlling and reducing waterborne pollutants discharged from point sources such as wastewater and stormwater. The Washington State Department of Ecology (Ecology) has jurisdiction for implementing the federal NPDES program in the State of Washington. In implementing this program, Ecology issues NPDES permits to cover individual facilities or groups of multiple entities with common activities under a general NPDES permit. These permits must meet federal minimum requirements. For regulated municipal stormwater discharges, the NPDES program requires permits for large, medium and small MS4s as defined in federal regulations. The Phase I regulations of the MS4 program went into effect in 1990 and apply to MS4s in municipalities with populations of more than 100,000 (medium and large MS4s).

    The first Phase I MS4 permit was issued by Ecology in July 1995 to the cities of Seattle and Tacoma and counties of Clark, King, Pierce and Snohomish. The MS4s owned or operated by the Washington State Department of Transportation (WSDOT) located in these cities and counties were also regulated under the 1995 permits. To meet the requirements of the 1995 Permit, the City prepared and managed stormwater under a SWMP that was approved by Ecology in 1997. The City provided updates on stormwater management activities to Ecology in annual reports that were submitted from 1996 to 2005. The new format for SWMPs and Annual Reports pursuant to the 2007 and 2013 Permits replaces the City’s 1997 SWMP.

    On January 17, 2007, Ecology re-issued the Phase I MS4 permit. The Permit became effective on February 16, 2007, was modified on June 17, 2009 and September 1, 2010 and bore an expiration date five years later, February 15, 2012. (The Phase II MS4 permit was issued concurrently and applied to approximately 90 small cities and counties in Western Washington and approximately 30 cities and counties in Eastern Washington).

    On August 1, 2012, Ecology re-issued, with limited changes, the Phase I MS4 permit, effective September 1, 2012 and having an expiration date of July 31, 2013 (Ecology, 2012a). Ecology also reissued the updated 2013-2018 Phase I MS4 permit on August 1, 2012, to become effective on August 1, 2013 (Ecology 2012b). The 2013 permit was appealed to the Washington State Pollution Control Hearing Board. Appeal hearings were held in October 2013, and the Findings of Fact, Conclusions of Law, and Order was issued on March 21, 2014. The Pollution Control Hearing Board’s ruling on vesting was appealed to the courts. Detailed information about the PCHB ruling, a Phase II MS4 permit settlement, and the appeal process can be found on Ecology’s webpage. It is anticipated that Ecology will modify the Phase I and Phase II permits in response.

    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.

    Figure I.1-1 Map of City Drainage Systems

    II.9 Operation and Maintenance-S5C.9

    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.9.2 O&M Program

    The City’s municipal stormwater permit-related O&M program is comprised of the activities outlined below.

    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 Current and Planned Activities

    The following sections outline completed or planned activities needed to meet the key Permit requirements.

    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.

    II.9.4.2 Maintenance Standards for Private Stormwater Facilities Regulated by the City

    The SC group at SPU is responsible for inspecting private facilities regulated by the City, based on maintenance standards established by the City in the Stormwater Code and DR 17-2009, SPU 2009-005, Vol. III - Stormwater Flow Control and Water Quality Treatment Technical Requirements Manual. During a facility inspection, all aspects of the system are inspected (e.g., flow control devices, catch basins). When any part of that system (including catch basins) is found to be out of compliance with Stormwater Code requirements for maintenance, a corrective action letter is sent to the facility owner, and the owner must certify that the work has been completed to correct the noncompliance.

    SPU and other City departments have revised the public and private facility maintenance programs to reflect the new requirements of the Permit and revised Stormwater Code.

    There are approximately 1,800 privately-owned water quality and flow control facilities regulated by the City (hereafter in this subsection, “facilities”) that drain to the City’s MS4s, and up to 250 are added each year due to new development or redevelopment requirements. Maintenance standards for private stormwater facilities regulated by the City Stormwater Code are defined and described in Appendix D of the 2009 DR 17-2009, SPU 2009-005, Vol. III - Stormwater Flow Control and Water Quality Treatment Technical Requirements Manual. The Directors’ Rule provides a summary of the inspection and maintenance requirements. The inspection and maintenance requirements include information about what features to inspect at each facility, when and how often these private systems should be inspected, and how to identify specific defects that warrant corrective action. Corrective actions are described that should be taken to maintain system performance.

    The permit requires that the City implements an ongoing inspection schedule to annually inspect all stormwater treatment and flow control facilities (other than catch basins) regulated by the City in areas that drain to the City’s MS4s. To comply with this requirement, SPU conducted a study during 2010 of private stormwater facility compliance to evaluate whether there would be sufficient justification to reduce the frequency of inspections of private storm water facilities from the level specified in the permit (annually starting in 2012). The study was completed, and the results support a change in the inspection frequency of private stormwater facilities.

    Starting on January 1, 2012, SPU changed the inspection frequency for all private stormwater facilities that discharge to the City of Seattle’s MS4 to once every two years. However, if SPU receives a complaint about a private stormwater facility via its Water Quality Hotline or SPU determines during a Source Control Inspection that a site’s stormwater facility is out of compliance, SPU will use progressive enforcement to bring the private stormwater facility into compliance with the City ordinances and rules.

    II.9.4.3 Maintenance of Catch Basins Owned or Operated by the Permittee

    SPU has continued its catch basin maintenance and inspection program that focuses on maintaining catch basins for public health, safety and property and by nature includes water quality benefits. Staff implemented a catch basin inspection and maintenance program to meet Permit requirements. FAS, SCL and Parks each continue to implement programs for catch basin inspection and maintenance for catch basins on City owned properties that the department manages or operates.

    II.9.4.4 Inspection and Maintenance of Private Stormwater Facilities

    The SC group at SPU is responsible for inspections of privately owned stormwater flow control and treatment facilities that drain to the City’s MS4. The inspection determines that the system functions as designed and is properly maintained. Inspectors conduct a site inspection and inform the owner of the stormwater facility of the required maintenance. SC uses the progressive enforcement process as detailed in DR 18-2009, SPU 2009-006, Vol. 4: Stormwater Code Enforcement Manual. SC has developed an alternative inspection schedule as provided in S5. C.9.b.ii.3., which results in each system being inspected every 2 years effective September 1, 2013. Facility owners may self-certify that the work needed for compliance has been completed by providing a signed copy of the corrective action letter with a copy of the work detail performed. SC performs random re-inspections of self-certified properties to for quality control of this process.

    DPD is responsible for conducting inspections of private stormwater facilities in new development and during the period of heaviest construction to identify maintenance needs and enforcing compliance as needed. DPD is incorporating this requirement into the inspection process described in Section II.

    Seattle Stormwater Resources

    Information on 2021 Stormwater Code and Manual Updates

    City of Seattle Stormwater Code

    City of Seattle Stormwater Manual (2017)