Stormwater Policies and Regulations

Stormwater is a significant source of pollution in Puget Sound. Municipal stormwater systems are one of the main ways stormwater is discharged to water bodies. To minimize pollution from stormwater, cities must comply with permits.

How is stormwater regulated?

The way cities manage stormwater is regulated through a federal permit system called the National Pollutant Discharge Elimination System (NPDES). The intent of the permit is to reduce or eliminate water quality problems in our streams, rivers and lakes. It accomplishes this by controlling pollution at its source. 

How the NPDES permit works in Washington

The federal permit program regulates the discharge of stormwater and wastewater to waters of the State. In Washington State, the Department of Ecology (Ecology) implements the NPDES program on behalf of the federal government. Ecology issues the Western Washington Phase II Municipal Stormwater Permit.

The Western Washington Phase II Municipal Stormwater Permit was re-issued on August 1, 2024, and will be in effect until July 31, 2029.  This permit authorizes the City of Sammamish to discharge stormwater from its municipal separate storm sewer system (MS4) into waters of the State (i.e. Lake Washington). This requires the city to take certain actions to prevent stormwater pollution.

The full permit can be viewed at the Department of Ecology’s website: NPDES Western Washington Phase II Municipal Stormwater Permit

What does the City need to do to comply?

The permit requires the City to take action in each of the following areas:

• Public education and outreach
• Public involvement and participation
• Illicit discharge detection and elimination
• Controlling stormwater run-off from construction sites
• Operations and maintenance of stormwater facilities after construction

Planned actions are documented each year in a Stormwater Management Program.

The City of Sammamish welcomes comments and feedback on our current Stormwater Management Program. After reviewing the documents and information please provide your feedback via email to stormwater@sammamish.us . Be as detailed as possible, we value your input!

Compliance documentation

These documents and links are provided as part of compliance with the Western Washington Phase II Municipal Stormwater Permit:

• Current NPDES Phase II Annual Report
• 2016 LID Code Integration Report
• Department of Ecology - Construction Stormwater General Permit Notice of Intent (NOI)

Stormwater Facility Maintenance Requirements

According to the NPDES Permit, city-owned and privately-owned stormwater facilities must be maintained within timelines set by the NPDES Permit. Read more in Section S5.C.7.a. and S5.C.7.b. of the Western Washington Phase II Municipal Stormwater Permit.

Unless there are circumstances beyond the Permittee’s control, when an 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.

• Within 2 years for maintenance that requires capital construction of less than $25,000.

Updates to the 2021 Sammamish Addendum, effective October 1, 2024

City Council adopted the below changes to the Addendum to the 2021 KCSWDM.  The changes were presented at the following meetings:

• Planning Commission at the meeting held on May 2, 2024
• Public Hearing at Planning Commission on May 16, 2024
• Public Hearing at City Council on July 2, 2024

Summarized changes to the Addendum include:

1. Reduced restrictions on bioretention underdrains – section C.2.6.1. The adopted change follows Ecology’s standards to allow underdrains for bioretention without the administrative steps of a SWDM adjustment.
2. Dispersion device setbacks for steep slopes – section C.2.4.1 . Minimum Design Requirement for Basic Dispersion of Appendix C in the KCSWDM stipulates that dispersion devices are not permitted within 50 feet of a steep slope hazard area, erosion hazard area, or landslide hazard area. This amendment clarified that the 50-foot setback for dispersion devices only applies to the top of the steep slope.
3. Permanent fixture and signage of rain barrels – section C.2.8.1. This standard stipulates that rain barrels, which were required as a condition of engineering approval must be labeled as permanent stormwater facilities that may not be removed.
4. Allowing shared LID facilities to be permitted to extend across lot lines only if the responsibility for long term maintenance is vested with a single responsible entity (e.g., one property owner, HOA, etc.) – section 1.2.9.2.4. The KWSWDM allows low impact development (LID) facilities to be shared between adjacent properties. Shared LID facility maintenance is difficult to enforce the management and maintenance of the LID facility so this change requires a single responsible party.
5. Clarifying infiltration rate testing procedures – section C.2.6.2. The KCSWDM stipulates infiltration testing procedures for sites and projects. The change clarified required infiltration rate testing procedures for various development scenarios.

History

In 2022, City Council adopted stormwater code updates under Ordinances O2022-541 and O2022-543 amending O2022-541. The ordinances adopted current stormwater regulations including the 2021 King County Surface Water Design Manual (KCSWDM), the Sammamish Addendum (Addendum), and several code amendments to comply with required changes stipulated by the Department of Ecology Phase II Municipal Stormwater Permit.

 

Stormwater Code Enforcement

Note: Changes will be effective January 1, 2024

The Sammamish Unified Development Code 21.03.050 outlines the Surface Water Development charge, runoff regulations and requirements for development activities, the surface water program, and water quality and enforcement. For more background see Ordinance O2023-555.

On January 1, 2024, the revised water quality enforcement code becomes effective. The past practice of only providing outreach and education for a first water quality violation will now allow for civil penalties, depending on the severity and extent of the issue.  The code language will change from “shall initially rely on” public education and outreach to gain compliance to “the director may use public education and warnings as the primary method of gaining compliance.” This will give the Public Works Director the option to move straight to civil penalties and fines.

Financial penalties will be determined using a points-based rating system for water quality violations. The questions below, and associated points for each response, comprise the new rating system and are based on public health risk, environmental damage, intent, and responsiveness by a potential violator. These changes provide a transparent process for assessing water quality violations that is consistent, easy to understand, and fair.  The associated penalty for the range of scores is shown in Table 1.

Table 1. Penalty Points Rating and Corresponding Surface Water Fine Amount*

Rating	1-2	3-4	5-6	7	8	9	10+
Fine	$500	$1,500	$2,500	$4,000	$6,000	$8,000	$10,000

*Please note that repeat violations of SDC 21.03.050 will be strictly enforced, following the desires of the Planning Commission and City Council. SDC 21.03.050(B)(65) will indicate that the fine be multiplied by the number of violations. This means that the fine for a second time violator will be multiplied by two, and the fine for a third time violator will be multiplied by three, and so on.

New financial penalties points-based questions:

1. Did the violation result in a public health risk?

0	There is no evidence to support a claim of public health risk or adverse health effects.
1	Evidence supports a claim of public health risk and there is a plausible connection between this violation and health effect.
2	There is evidence directly linking public health risk or adverse effects with the violation.

 

2. Did the violation result in environmental damage?

0	There is no evidence to support a claim of damage to water or sediment quality, or the environment.
1	Damage to water or sediment quality, or the environment can be reasonably inferred from evidence or knowledge of the effects of the violation.
2	There is evidence directly linking damage to water or sediment quality, or the environment with the violation.

 

3. Did the violation discharge into the municipal separate storm sewer system?

0	There is no evidence to support a claim of impact to municipal storm drain system.
1	Impact to municipal storm drain system can be reasonably inferred from evidence or knowledge of the effects of the violation.
2	There is evidence directly linking municipal storm drain system impacts to the violation.

 

4. Was the responsible party unresponsive in correcting the violation?

0	The violation was corrected as soon as the responsible party learned of it.
1	The violation was corrected, or measures were attempted to be implemented, in a less timely and cooperative fashion.
2	The responsible party made no attempt to correct the violation, or no measures were attempted to be implemented to prevent further violation.

 

5. Was the violation intentional?

0	The responsible party did not know and had no reason to know that the action or inaction constituted a violation.
1	The responsible party appears not to have intended but should have known there was a violation because of permit conditions, inspections, educational resources, or public outreach.
2	If it is clear from the circumstances that the violation was intentional and that permit conditions, inspections, educational resources, or public outreach was provided to the responsible party.

 

6. Was the violation a result of a responsible party(s) failure to properly operate, maintain, or implement a system or required plan?

0	The violation was not the result of improper or inadequate actions or inactions described above.
1	Proper operation or actions described above were completed but a violation still occurred.
2	The violation was a result of improper or inadequate actions or inactions described above.