Requirements for Gaining Approval of Stormwater Quality Treatment Technologies in King County, Washington

King County Stormwater Services staff receive frequent inquiries from businesses, consultants, and manufacturers about new stormwater treatment technologies.

The Most Common Questions Asked Are:

• Is a specific technology approved (such as a catch basin insert)?
• Does the County endorse any specific devices or technologies?
• Can a business get credit for installing such a device?
• What is the process for getting a technology approved?
• Can I use a catch basin insert?

The information below is intended to answer these questions.

King County Requires:

1. Treatment of stormwater for new development (King County Surface Water Design Manual); as well as
2. Pollutant source control (Stormwater Pollution Prevention Manual) for existing development

King County Stormwater Treatment Performance Requirements

Stormwater from new development is required to be treated using standard treatment facilities (i.e. wet ponds, stormwater wetlands, sand filter, biofiltration swales).

There are specific pollutant removal goals that these facilities are expected to meet - 80% TSS removal, or 50% Total Zinc for resource streams, or 50% Total Phosphorous for sensitive lakes.

In order to use an alternate treatment device in lieu of a standard facility, the user, engineer, or manufacturer would have to provide data that shows that the alternate treatment meets these performance requirements.

Avenues for Requesting Approval in King County

If someone wants to use a new product in King County for a specific project, the applicant can request an "experimental design adjustment" per the Surface Water Design Manual.

The technology would need to meet the following criteria:

1. The new design is likely to meet the identified target pollutant removal performance based on limited data and theoretical considerations, AND
2. The facility can be physically constructed as designed, AND
3. The ongoing maintenance requirements are identified during the design, and the ongoing maintenance requirements and costs are not excessive (although this responsibility may be borne by the applicant or property owner with demonstration that it is reliably performed), AND
4. The applicant or property owner contributes a share of the cost of monitoring to determine the facility performance.

After enough data is collected to assure that the technology will meet the applicable pollutant removal goal and that performing the required maintenance is attainable and reasonable, then the technology may be added as an acceptable treatment method.

Washington State Department of Ecology (Ecology) Sampling Protocol for 'Emerging Technologies':

Ecology has established an Emerging Technology Committee, and they have developed protocols for gaining approval of emerging technologies for use in Washington State. They have also reviewed and approved some treatment technologies. Several categories of approvals can be granted.

Links to this Ecology information are below:

http://www.ecy.wa.gov/programs/wq/stormwater/newtech/02-10-037%20TAPE.pdf

King County encourages manufacturers of emerging technologies to seek approval through the Ecology review and approval process. Approval by Ecology does not guarantee approval by King County, however. When King County staff review applications to use such devices for a specific project, they are looking at the ongoing operations and maintenance requirements associated with the facility, in addition to the treatment efficacy.

Use of Catch Basin Inserts in King County

Oil Control Requirements for High Use Sites (for New Development):

New development in King County may also have an oil control requirement for sites that meet the high-use threshold. Technologies such as catch basin inserts may be an option to meet this requirement, but conditions are imposed:

• The flow to these catch basins is restricted (in volume and drainage area)
• The oil absorbent must pass a test that shows that it will not release the oil
• Additional maintenance requirements are imposed, and
• The facility must be privately maintained

More specific requirements are covered in the King County Surface Water Design Manual

Using Catch Basin Inserts to meet a Businesses' Source Control Requirements (for Existing Development):

Businesses in King County are required to provide pollutant source control per the Stormwater Pollution Prevention Manual to prevent pollutants from getting into the stormwater.

Inserts can be a component of the source control strategy, but they are not the only treatment option. BMP activity sheets for businesses are found in the Stormwater Pollution Prevention Manual.

Even if a business uses an insert, that does not change their source control requirements (i.e. spill cleanup, covering of pollutants, etc).

King County Endorsement of Products, or Participation in Pilot Projects

King County does not typically endorse or have joint pilot projects with specific treatment technologies. If the treatment technology meets the King County goals identified above, we will allow the use of the technology to meet the stormwater treatment requirement.

For questions about the Stormwater Web Site, please contact Mary Lear.