Understanding Your Drainage Fee

About the Fee

Where is my drainage fee?

Your drainage fee does not appear on your Seattle Public Utilities (SPU) bill. SPU uses King County as its billing agent for this fee, so it appears on your property tax statement as “Surface Water Management” or “Drainage.” These statements are typically mailed by the County in mid-February each year, and can also be viewed online by entering your property tax account or parcel number in the King County Property Tax Information System. If your mortgage company pays your property tax bill, they will include payment for drainage services which is factored into your escrow fees. Drainage fees are assessed on an annual basis.

Where can I find my property tax account and/or parcel number?

The property tax account number is in the upper left corner of your King County Real Estate Tax Statement. You can also call the King County Assessor's office at (206) 296-7300 and they will give it to you. The first ten digits of your account number are usually the same as your parcel number. You can also look up your property online by address or parcel number using the King County Parcel Viewer.

Who must pay a drainage fee in Seattle?

SPU imposes a drainage fee on all properties in Seattle, except for exempted parcels as noted in the Exemptions section. Seattle's drainage system is a City-wide utility: all properties contribute to the problem of stormwater runoff and benefit from a robust drainage system through flood control and water quality improvement.

Who is responsible for paying the fee?

The property owner of record according to the King County Assessor is responsible for paying the drainage fee. For example, the owner of a shopping center parcel who is leasing space to six separate businesses will be charged only one drainage fee. The six businesses, who are not the property owners, will not be charged. Any decision to share this cost with the six businesses is entirely between the property owner and six businesses, with no involvement from SPU or the County.

I own a condo unit. Is the drainage fee charged to me or to the condo association? How is my portion of the fee calculated?

Condominium complex drainage fees are divided equally among the complex’s units and sent separately to each unit owner listed in the King County Assessor's Real Property File. For example, if there are 10 condo units in the complex, each will be charged one-tenth of the total complex drainage fee.

I own more than one piece of property in Seattle. Will all drainage fees be consolidated or will they appear separately?

The drainage fee will appear on each of your King County property tax statements. Thus, if you own three properties in the City, you will receive three statements with three separate drainage fees. Note that municipalities outside of Seattle but within King County may also assess stormwater/drainage fees. In these cases you may see a drainage fee on your property tax statement that was assessed in a different manner than described here, with a different rate structure. Please consult the appropriate municipality for more information.

I own a rental property. Will I still be billed if it is vacant and all utilities are shut off?

Yes. The property still sends stormwater runoff into and benefits from the City drainage system, even when unoccupied.

SPU maintains, repairs, and replaces pipes and pumps.

Fee Calculation

How is my drainage fee calculated?

The method for calculating your fee depends on the type of property you own.

Single family and duplex properties smaller than 10,000 square feet are considered “small residential properties” and assigned to flat drainage rate tiers based on their square footage. All such properties in a given tier (e.g., 2,000-3,499 square feet) pay the same flat rate. See the Drainage Rates schedule for the current small residential rates.
All other properties, including residential properties 10,000 square feet and larger, are assigned to a rate category based on the percentage of hard (i.e., impervious) surface contained within the parcel. The property is charged by dividing its square footage by 1,000, then multiplying it by the appropriate rate category. See the Drainage Rates schedule for the current “all other properties” rates.
In special cases a portion of the parcel square footage may be exempted from the fee calculation – for more information see the Exemptions section. A limited number of discounts are also available as described in the Special Programs section.

How did Seattle Public Utilities (SPU) determine what the rate categories are?

SPU's drainage rate structure combines parcels with similar surface characteristics into rate tiers which will, in turn, produce similar amounts of stormwater runoff. SPU estimates the fraction of rainfall that becomes "runoff" from a parcel using standard runoff coefficients derived from hydrological modeling. These coefficients vary depending on how pervious (permeable) a surface is. More stormwater will flow off hard/impervious surfaces and into the City’s drainage system, while pervious/permeable surfaces will absorb more water.

The amount of stormwater that will flow off a property depends on its size and surface characteristics. The SPU rate categories incorporate both factors. The fee structure for some rate categories relies on category averages for surface type while the structure for other categories is based on parcel-specific surface characteristics and size. However, the assumptions regarding how much stormwater will flow off a given surface are consistent across all rate categories, regardless of structure.

Single family and duplex properties below 10,000 square feet (“small residential” properties) are charged one of six flat rates based on their size. For instance, a 4,200 square foot small residential parcel would fall within the third rate tier: 3,500 to 4,999 square feet. These flat rate properties, which account for approximately 93% of all Seattle residential parcels, are mostly homogeneous in terms of surface cover, which makes property size the key determinant for stormwater flow contribution. SPU used sample data collected from city-wide aerial photographs to estimate the typical surface types for each parcel size range. This surface type information was combined with the stormwater runoff data previously mentioned to develop the small residential flat rate tiers.

The drainage fees for all other properties – including commercial properties of all sizes and residential properties 10,000 square feet and larger – are calculated by dividing the parcel’s square footage by 1,000, then multiplying by one of seven rates. The rate used depends on the percentage of hard (impervious) surface on the parcel. This rate structure is employed because there is too much variation between these properties in terms of parcel size and surface characteristics to be fairly captured in a flat rate structure. Each of the seven rate tiers represents a percentage range of hard surface (e.g., 66-85 percent). In addition, low impact discounts are available for commercial and large residential parcels which contain significant tree canopy and/or unmanaged grass coverage, and which are composed of no more than 20% hard surface area.

What is hard surface?

Hard (also called “impervious”) surface is any surface that resists the penetration of rainwater, such as blacktop, rooftops, parking lots, patios, hardpan, and hard-packed athletic fields. This type of surface absorbs much less rainwater than pervious surfaces covered with grass, trees, or other vegetation. Rainwater tends to flow off these surfaces and into the City’s drainage system.

How did you determine the percentage of hard surface area on my property?

SPU uses surface type mapping data derived from aerial photos to determine the percentage of hard surface area on each property.

What parcels qualify for low impact discounts?

Non-residential and large residential (10,000 square feet or larger) properties may be eligible for a “low impact” discount if they meet the following criteria:

Contain 20 percent or less hard surface coverage, and
Contain 50 percent or more tree canopy and/or unmanaged grass coverage

These discounts range from 30 to 55 percent, and apply to the first two (0-10 or 11-20 percent) hard surface rate categories as follows:

Rate Tier	% Hard Surface	Tree Canopy + Undeveloped Grass %	Bill Discount
1	0-10%	65%+	55%
1	0-10%	50-64%	35%
2	11-20%	65%+	45%
2	11-20%	50-64%	30%

Low impact discounts are automatically assigned to commercial and large residential parcels which meet the above criteria as determined by periodically updated aerial imagery. See the Fee Adjustments section if you would like to appeal the denial of a discount.

Why are low impact discounts available to some and not other properties – even those with the same hard surface percentage?

Parcels containing substantial tree canopy and/or unmanaged grass coverage will generate much less stormwater runoff than those with the same percentage of hard surface whose pervious areas lack such coverage (e.g., contain only sparse vegetation, or a managed lawn).

Why do only small residential properties pay a flat rate?

Drainage rates are structured so that each property is assigned a cost proportionate to its impact on the drainage system. Properties assigned to small residential rate classes are relatively homogenous in terms of size (limited square feet ranges for each rate category) and the type/size of structures on their properties. Therefore, using actual hard surface information for a sampling of these properties allows us to develop a good estimate of stormwater runoff from properties in a narrow lot size band. In addition, since they account for 74% of all Seattle properties, collecting and maintaining property data for a sample of them – rather than the entire population – holds down administrative costs.

There is a much greater variance in lot size and property composition on residential properties 10,000 square feet and greater. Likewise, non-residential properties vary considerably in terms of lot size and the type/amount of surface covering these parcels. Therefore, the fairest way to bill these properties is to use their actual lot size and percentage of hard surface.

Is my drainage rate the same thing as my drainage fee?

This depends on the size and type of your property. For small residential parcels – single family and duplex properties smaller than 10,000 square feet – the drainage rate is a flat rate, so it is equal to the total drainage fee, unless some of the square footage is exempted (see Exemptions). For all other properties, the parcel lot size should be divided by 1,000 then multiplied by the appropriate hard surface drainage rate to calculate the total drainage bill. Here too an exemption (see Exemptions) or a low impact discount (see Low impact discounts) could reduce the final drainage fee owed.

Is my drainage rate the same thing as my drainage bill?

That depends on the size and type of your property. For small residential and duplex properties smaller than 10,000 square feet, the drainage rate, which is a flat fee, is equal to the total drainage bill. For all other properties, the drainage rate for the assigned category must be multiplied by the lot area (in 1,000's of square feet) to calculate the total drainage bill.

Protecting local waterways from pollution is the highest priority.

Exemptions

Which properties are partially or completely exempt from paying drainage fees?

The following properties, or qualifying portions of properties, are exempt from payment of drainage charges:

submerged land,
houseboats,
piers,
City streets, State of Washington highways, and other streets that provide drainage services in the same manner as City streets,
islands that contain highly infiltrative pervious surface and less than ten percent impervious surface area,
riparian corridors that contain highly infiltrative pervious surface and meet certain qualification criteria
wetlands that meet certain qualification criteria

How did you determine which land is submerged?

Submerged land was identified using Geographic Information System data developed to describe the interface between land water, and other surface characteristics.

My property is partially submerged. Am I still required to pay a drainage fee?

Yes. However, your fee will be calculated on the unsubmerged portion of the property.

How are streets other than City streets qualified?

Streets are qualified through an application process. To qualify, properties and streets must meet the guidelines outlined in the 2017 SPU Directors Rule FIN-211.1 (PDF). For more information about qualifying streets or to request an application, please contact SPUDrainageBilling@seattle.gov (preferred method; please include your property address or parcel number) or (206) 684-0292.

How are exempt islands and riparian corridors qualified?

SPU qualifies properties based on its analysis of both impervious and pervious surface billing data collected from aerial photos and other sources. Detailed qualification criteria for exemption of riparian corridors can be found in SPU Director's Rule FIN-211.2 (PDF). Property owners may request a review of their property's characteristics through the fee adjustment process (see Fee adjustments) if they believe their property meets the qualification criteria for these exemptions.

How are exempt wetlands qualified?

Property owners must submit an application and required supporting documentation to be considered for a wetlands exemption. To request an application packet, please contact Trina Mannery at (206) 639-9637 or Trina.Mannery@seattle.gov. Detailed qualification criteria and administrative procedures can be found in in SPU Director's Rule FIN-211.3 (PDF).

We engineer solutions to protect local waterways from stormwater runoff.

Special Programs

Does SPU offer any credits or discounts?

Drainage fee discounts are available for properties that help reduce the impact of stormwater on the City's system. SPU currently offers discounts for both natural areas whose characteristics enhance retention of stormwater runoff, as well as to engineered systems that provide stormwater flow control and/or provide water quality treatment for run-off from impervious area.

Low Impact Discounts
Large residential and commercial properties with significant tree canopy and/or unmanaged grass coverage may be eligible for a “low impact” discount on their drainage fee. These discounts range from 30 to 55 percent and are only available to properties which fall within the first two (0-10 or 11-20 percent) hard surface rate categories. See “What parcels may qualify for low impact drainage discounts?” for more information.
Stormwater Facility Credit Program (SFCP)
This program offers credits of up to 50 percent for privately-owned systems that slow down stormwater flow and/or provide water quality treatment for run-off from impervious areas, thus lessening the impact to the City's stormwater system, creeks, lakes or Puget Sound. Stormwater systems are structures such as vaults, rain gardens, permeable pavements and filtration systems. View qualification criteria, application procedures, and more about the Stormwater Facility Credit.
Rainwater Harvest Credit
SPU offers a 10 percent discount for any new or remodeled commercial buildings that utilizes a rainwater harvesting system meeting credit requirements. Those systems that involve indoor uses of rainwater must be permitted by Seattle-King County Department of Health in order to qualify for the rate reduction. Systems must meet the applicable stormwater and drainage code requirements for the building and site.

Will properties with on-site detentions systems be billed?

Yes, but they may qualify for a discount. View the Stormwater Facility Credit page for more information.

Is there a discount for low-income, elderly, or handicapped people?

Yes. If you qualify for a discount on your sewer bill, you will automatically receive an additional discount for drainage. However, please note this adjustment will be included on your combined SPU utility bill rather than your King County property tax statement.

Fee Payments

Can I pay my drainage fee at the Community Service Centers?

No. The drainage fee is included on your property tax statement and must be paid with your property taxes.

Can I pay my drainage fee in two halves, just as with my property taxes?

Yes. The drainage fee can be paid in two halves just like your property taxes.

My property was sold after I paid my drainage fee. How do I get a refund for part of the year?

Since the drainage fee is included on your property tax bill, if a property is sold in the middle of the year any portion of the unused drainage fee is included in the escrow settlement process.

What happens if I don't pay my drainage fee?

Delinquency charges will be applied for delinquent drainage fees. If the drainage fee is not paid, a lien may be attached to your property.

Is the drainage fee deductible on my federal income tax?

No. This charge is a utility fee like water, sewer, or garbage charges.

Fee Adjustments

I feel my drainage fee is incorrect, how can I get it adjusted?

In order to be considered for an adjustment, the following criteria must be met:

Payment on the account must be current. Requests for adjustments on delinquent accounts will not be considered for review.
Requests for adjustments must be received within 90 days from the billing date, requests received after that point will still be considered but will be applied to subsequent years only
Requests for adjustments must be made in writing. Please email your request to SPUDrainageBilling@seattle.gov with your property address and/or parcel number.
The burden of proof is on the applicant to show that an adjustment should be made

How do I request an adjustment?

Customers may request an adjustment by emailing their parcel number or parcel address to the SPU Drainage Billing Team: SPUDrainageBilling@seattle.gov.

What happens after the Utility reviews my property?

If the Utility grants an adjustment that reduces the charge for the current year, the customer will receive a revised bill and/or a refund of the overpaid amount
If the Utility determines that an adjustment should be made which increases the charge due for the current year, the applicant will receive a revised bill that will be due within 45 days of the date of issue
All customers will be notified of the Utility's decision
All decisions of the Utility are final

What number can I call if I still have questions?

Contact SPU Customer Service at (206) 684-3000.