Stormwater management program components

The program can be assessed for the region as a whole.

Regional efforts are required to develop a consistent messade, determine the best methods of communicating that message, and when appropriate, create strategies to effect behaviour change. The program does not need to represent all sectors in the region, but permittees should consider their target audiences when choosing to participate in regional efforts.

Statewide | Aug. 1, 2019

In this situation, permittees have two options.

The first — and usually preferable — option is to identify and then evaluate a different behavior change effort that was implemented more widely.

For the second option, permittees can evaluate the behavior change effort that did not succeed.

While understanding and adoption of the desired behavior by the target audience is expected to be low, it is quite likely that you can identify ways to improve program implementation in the future. This, too, is an important aspect of the report to us.  

Self-assessment is a valuable step

If a permittee's community had little participation, it is worthwhile to gain a better understanding as to why.

Conduct a self-assessment:

• Were the wrong outreach methods used?
• Did the message not resonate with the target audience?
• Was it the wrong message or behavior to target?

The overall goal of this permit requirement is to train every community to educate the public and change behavior effectively. This helps us work with every local government to protect water quality across Washington.

Western Washington | Nov. 2019

The answer depends on the proposed changes to the project description.

The local jurisdiction should follow their procedures to determine whether the project has changed enough from the original subdivision/plat application to require a new stormwater plan.

The jurisdiction will determine whether the changes make your proposal: 

• A new project
• A distinct addition
• A revision to the project
• A minor change that could be considered part of the original project

Some considerations to determine whether a new project has been submitted include:

• Changes that intensify the use of the site
• Increasing the hard surfaces
• Increasing the area of land to be disturbed

If the change is determined to be a new project

The original stormwater plan would not apply to a new project, and the stormwater regulations in effect at the time of the new (building) application would apply.

If the change is determined to be an addition or revision

If the jurisdiction accepts the proposed changes as a distinct addition or revision to the original permit project description, then the original stormwater plan may still apply to the portion of the development considered originally.

The proposed additions or revisions to the original project description must be reviewed under the stormwater regulations in effect at the time of the revised application. In other words, the original stormwater plan did not envision the revised project description (with additions) now being considered, and therefore did not address stormwater for the complete proposed project.

If the change is determined to be a minor change

You may still need to evaluate the project against stormwater regulations, but the project should be able to use the stormwater plan developed for the original proposal. 

Please contact us if you have questions.

Western Washington | Dec. 2019

The answer depends on if a development project has multiple phases. 

Typical single-phase development projects

Typically when a plat is approved, the approval includes the stormwater requirements for the entire plat, including the individual lots. The stormwater infrastructure that is common to the plat (e.g., conveyance system associated with the road, and treatment and/or flow control facilities) is typically built concurrently with the roads and utilities.

If the plat's stormwater site plan included restrictions or requirements for the individual lots, those requirements should be recorded for each lot and must enforced by the local government when the individual lot is developed.

Examples of restrictions include:

• Maximum impervious surface
• Low Impact Development best management practices
• Declaration of covenant
• Grant of easement

This means that individual lots do not need to apply the updated stormwater control requirements because the entire plat had already started construction before the applicable deadline. 

Multi-phase development needs control timing for each phase

Multi-phased development — such as a multi-phased subdivision which may have had a stormwater approval for all the phases — should be evaluated differently.

Each distinct phase should have its own start of construction date. Therefore, if the start of construction for a phase exceeds the construction deadline set by the permit, the local government needs to apply the updated stormwater requirements.

Western Washington | Nov. 2019

Snohomish County, et al. v. Pollution Control Hearings Bd., et al.

On Dec. 29, 2016, the Washington State Supreme Court issued a decision in Snohomish County, et al. v. Pollution Control Hearings Board, et al. The ruling holds that municipal stormwater regulations adopted under the federal and state National Pollution Discharge Elimination System (NPDES) program are not "land use control ordinances" subject to state vesting statutes. 

This means that the provisions of the 2013-2018 Phase I and Phase II Western Washington Municipal Stormwater Permits that pertain to the timing of applicability of the updated stormwater controls for new and redevelopment are in effect.

1. Phase I S5C5a.iii

“The local program adopted to meet the requirements of S5.C.5.a.i through ii shall apply to all applications submitted after June 30, 2015 and shall apply to applications submitted no later than June 30, 2015, which have not started construction by June 30, 2020.”

Refer to the permit for full citation including footnotes.

2. Phase II WWA S5C4a

“The local program adopted to meet the requirements of S5.C.4.a(i) through (iii) below, shall apply to all applications submitted on or after January 1, 2017 and shall apply to applications submitted prior to January 1, 2017, which have not started construction by January 1, 2022.”

Refer to the permit for full citation including footnotes and language applicable to permittees in Lewis and Cowlitz counties, and City of Aberdeen.

Vesting statutes do not preclude compliance with the cited conditions above.

Western Washington | Aug. 2019

Snohomish County, et al. v. Pollution Control Hearings Board, et al. ruling

The State Supreme Court ruling made clear that the provisions of the 2013-2018 Phase I and Phase II Western Washington Municipal Stormwater Permits that pertain to the timing of applicability of the updated stormwater controls for new and redevelopment are in effect.

What does this mean for my project?

If stormwater is being addressed at the subdivision/plat level or a multi-phase project, the stormwater codes in effect at the time the plat/subdivision application is submitted apply to all subsequent building permits.

The subdivision/plat application is the relevant application for determining the applicable stormwater requirements. Any building applications submitted later on can rely on the stormwater design that was included with the subdivision/plat application. This is because stormwater has already been done for the geographic area of the subdivision/plat.

Under the municipal stormwater permits the only place that the recent supreme court decision comes into play is if the developer does not start construction on the subdivision/plat until after June 30, 2020, for Phase I permits* or Jan. 1, 2022, for Phase II permits*.

_{*Note these dates vary for different permittees, see your Phase I or Phase II permit for details.}

Important terminology

For the purposes of the municipal stormwater permits, both the terms application and start construction are defined in the permits.

Application means, at a minimum:

• A complete project description
• A site plan
• If applicable, a complete State Environmental Policy Act (SEPA) checklist

Start of construction means, at a minimum:

• The site work associated with and directly related to the permitted project has begun.
• For example: grading the project site to final grade or utility installation.

Western Washington | Aug. 2019

In some situations, when only Minimum Requirements #1-5 apply, you might not be required to have an engineer develop site plans. Be aware that there are situations (such as building near steep slopes) that may require an engineer even if only MRs #1-5 apply.

In general — if all of the following are true — an engineer may not be needed:

• The project only requires Minimum Requirements #1-5
• The developer chooses the list approach for Minimum Requirement 5
• No engineering calculations are necessary to complete the Construction Stormwater Pollution Prevention Plan for the site

If the project requires Minimum Requirements #6-9 — or any of the above are not true — an engineer should be involved.

Most engineering work requires a licensed professional

State law requires that engineering is done by — or under the direction of — a professional engineer licensed to practice in Washington State.

The following should be prepared by or under the direction of a licensed engineer:

• Plans involving construction of treatment facilities
• Plans involving flow control facilities (detention ponds or infiltration basins)
• Structural source control best management practices (BMPs)
• Drainage conveyance systems
• Construction Stormwater Pollution Prevention Plans that involve engineering calculations

Western Washington | Aug. 2019

In this scenario, the subdivision application did not address stormwater management during the initial phase of the project. If stormwater requirements are left to the building permit stage of the process, each building permit should be reviewed to meet the stormwater requirements in effect at the time of the building permit application.

If this is the case, you would use the codes in place at the time the building permits are issued, not those in place when the initial phase of the project began. 

Western Washington | Aug. 2019

Refer to the Minimum Requirements in effect at the time the facility is designed. Permit requirements that incorporate this phrase should be interpreted in that way.

For example, a facility designed in 2013 would refer to the 2012 Stormwater Management Manual; a facility designed in 2015 would refer to the 2014 version of the manual.

Statewide | Dec. 2019

They could choose to do either option.

If they choose to simply reference our manual’s II-3, they would need to be aware of a couple of potential issues:

• Some content in Ecology’s II-3 reference other sections of the 2019 manual. If Clark County’s manual references II-3, they are also referencing all the other sections within Ecology’s manual that II-3 references. If they copy in the BMPs, they will need to review the text for these references, and edit them to refer to the appropriate places within their own manual.
• If they reference II-3, they will lose the control to make any County-specific edits to the BMPs.

PH I | Dec. 2019

A Phase I permittee should use best professional judgement when determining if a change is significant or not. Did you raise or lower a threshold in some way (like Ecologys change from requiring a 1 hr time step to a 15 min time step for continuous simulation modeling)?  Did you lower the percentage of organic content required in your amended soils?  Err on the side of caution — if you are going back and forth on whether a change is significant, it probably is and should be reviewed.

PH I | Dec. 2019

YES, except in cases where the permittee submits additional significant changes. If additional significant changes are submitted to Ecology in the format outlined in Appendix 10, they will be reviewed for equivalency as well.

PH I | Dec. 2019

Permittees must update their current approved equivalent manuals to address the 9 significant changes identified by Ecology in Appendix 10.

PH I | Dec. 2019

Yes. All municipal stormwater permittees must report illicit discharges, spills, and water quality concerns associated with their MS4 permits. 

The percent of the MS4 that must be screened can be determined by whatever works best for the permittee.

The percentage may be based on:

• Linear feet of the MS4.
• Geographic area served by the MS4 (aerial extent based on delineation of MS4 basins).
• Percent of outfalls.*

*Note that using the percent of outfalls method implies that each outfall is representative of the same MS4 service area, which is not actually true, but it may be the best fit given the state of MS4 maps.

Statewide | Nov. 2019

In order to answer this, it's important to separate the field screening methods from the performance measure for how much to screen. Field screening methodology is flexible and up to the permittee to determine. Each permittee chooses which field screening method to use.

A method might be based on, for example:

• Outfall screening
• Junction points or nodes of the MS4
• A more detailed inventory of some sections using a camera

We expect permittees to vary in their approach for different sections of their MS4, as appropriate.

Reporting your preferred method of IDDE field screening

The permit requires that you describe the method in the annual report, but does not prescribe what that method must be. 

All | Nov. 2019

Phase II Municipal Stormwater permittees may be required to have inspection and maintenance standards for private best management practices (BMPs) and facilities that discharge to their system.

These requirements apply to private facilities that were built to meet permit requirements enacted by the Feb. 16, 2010 ordinance, or earlier if a jurisdiction was an early adopter of the regulations. Only private facilities built to satisfy those permit requirements are subject to inspection and maintenance standards by the municipality.

Private facilities built prior to those requirements have no specific inspection requirements.

This is addressed in Minimum Requirement 6/Core Element #5 for runoff treatment or Minimum Requirement 7/Core Element #6 for flow control.

• Western Washington Phase II permit sections S5.C.7
• Eastern Washington Phase II permit sections S5.B.6

Statewide, PH II | Dec. 2019

A detailed catch basin inspection guidance report is available. 

Statewide | Dec. 2019

Yes. Western Washington permittees can allow owners of a private stormwater facility to use a qualified third party to certify that required inspection and proper maintenance has occurred.

However, the permittee must retain the legal authority to inspect and enforce for cases where a private landowner does not elect to use a qualified third party.

Permittees may establish this type of program through the same legal authority required in their permit.

The self-certification program must use qualified personnel as defined in the permits. As the permittee, you are required to track inspections, maintain records, and ensure the inspections are occurring on schedule to achieve the target percentage for number of inspections. 

Permittees retain ultimate responsibility

Regardless of who inspects the stormwater facilities, the permittee is ultimately responsible for the discharges from its MS4. Discharges that violate any water quality standard are prohibited and may require additional attention under S4.F.

Western Washington | Dec. 2019

Yes. Drainage systems serving municipal owned properties — like fire stations, parks, and schools — need to be included in the inspection and maintenance activities outlined in the Operations & Maintenance (O&M) program.

Operations and Maintenance requirements apply to all "municipally owned or operated" facilities, including those on individual municipally-owned properties. This also includes maintenance responsibilities for a county to maintain a county-owned facility located within a city boundary.

Statewide | Dec. 2019

Individual maintenance projects with capital costs greater than $25,000 are not explicitly addressed in the Washington Phase II permit condition S5.C.4.c.vi.

Although "typical maintenance" and "capital construction" are addressed in Western Washington Phase II permit S5.C.7 and Phase I permit S5.C.10, permittees have the flexibility to define the terms as needed.

We suggest using the Stormwater Municipal Manual for Western Washington Vol. 5, Chapter 4 for guidance.

Western Washington | Dec. 2019

There are three places to refer to for maintenance standards guidance:

• The 2019 Stormwater Management Manual for Western Washington, or the 2019 Stormwater Management Manual for Eastern Washington (for non-proprietary devices).
• The manufacturer's O&M manual.
• The Use Level Designation documents through TAPE.

Statewide | Dec. 2019

If a project includes multiple surfaces that are all the same surface type in the “List” (e.g. a project with a sidewalk, a roadway, a driveway, and a patio are all a surface type of “Other Hard Surfaces”), each of the individual surfaces (e.g. the sidewalk, the roadway, the driveway, and the patio) must be evaluated separately using the List Approach, and the first feasible BMP must be applied for each separate surface.

The following text from the 2019 SWMMWW states that the List Approach is intended to be applied to each surface:

“For each surface, evaluate the feasibility of the BMPs in the order listed, and use the first BMP that is considered feasible. The designer must document the site conditions and infeasibility criteria used to deem BMPs infeasible. Once a BMP is deemed feasible and used for a surface, no other BMP from the list is necessary for that surface.”

See Additional Resources within the interactive online version of the 2019 Stormwater Management Manual for Western Washington for details and examples.

Western Washington | Sept. 2021

Short answer:

In most situations, the designer must choose one compliance method and cannot ‘mix and match' methods.  

Longer answer:

1. In most situations, MR5 requires the designer to choose one compliance method or the other, either the “List Approach” or the “LID Performance Standard.” This intent is captured by the text describing the compliance options for a project. For example, a project that triggers only MRs 1-5 has the following compliance options (underline added for emphasis):

Projects that are not Flow Control exempt that trigger only Minimum Requirements #1 through #5 (per I-3.3 Applicability of the Minimum Requirements) shall either:

• Use the LID BMPs from List #1 for all surfaces within each type of surface in List #1;

or

• Use any Flow Control BMP(s) desired to achieve the LID Performance Standard, and apply BMP T5.13: Post-Construction Soil Quality and Depth.

2. MR5 does include an exception, which allows a designer to choose different compliance methods for different parcels, if the site spans multiple parcels.

“Note that the site may contain multiple parcels. The designer may choose different compliance methods for different parcels, depending on the proposed design and the options for each parcel as detailed below.”

This exception was made, in part, because in some cases the compliance options are limited based on parcel size and location (e.g. parcels 5 acres or larger outside the UGA do not have the option of the List Approach).

3. If a designer has a strong reason for wanting to “mix and match” compliance methods, the local jurisdiction has the option to consider an “Adjustment” to the Minimum Requirement for that project (See I-3.6.1 Adjustments to the MRs).

Western Washington | Sept. 2021

No. Minimum Requirements #5 and #7 are independent.

Regardless of decisions made and methods used to comply with Minimum Requirement #5, projects must also comply with Minimum Requirement #7, if applicable. 

No. You are still required to conduct TMDL-related monitoring.

Appendix 2 requirements stand separate from other requirements in the permit. Permittees that have done everything required of them in the body of the permit still have to do the additional actions described in Appendix 2.

Western Washington Both | Nov. 2019

See our frequently asked questions document for answers to the most commonly asked S4.F questions.