Director's Rule

Title

Qualifying Riparian Corridors for Drainage Service Charge Exemption Number

FIN-211.2 Rev. no.

2

Responsibility

Finance Division Supersedes

N/A Pages

2

General Manager/CEO Signature

/s/ Andrew Lee Approval Date

December 13, 2024 Effective Date

January 1, 2025

1. PURPOSE

This Director's Rule ensures that owners of parcels requesting an exemption from drainage rates pursuant to SMC 21.33.030.A.6 are qualified fairly and consistently.

2. DEFINITIONS

Development means all components and activities related to construction or disturbance of a site, including but not limited to land disturbing activities (SMC 25.09.520), and including but not limited to hard surfaces, culverts, bulkheads, armored banks, and rockeries.

Hard Surface means an impervious surface, a permeable pavement, or a vegetated roof. (SMC 22.801.090)

Highly Infiltrative Pervious Surface means a vegetated surface containing significant tree canopy or undeveloped grassland (SMC 21.33.010.K).

Impervious Surface means any surface exposed to rainwater from which most water runs off. Impervious surfaces include, but are not limited to, roof tops, walkways, patios, driveways, formal planters, parking lots or storage areas, concrete or asphalt paving, areas with underdrains designed to remove stormwater from subgrade (e.g. playfields, athletic fields, rail yards), gravel surfaces subjected to vehicular traffic, compact gravel, packed earthen materials, and oiled macadam or other surfaces which similarly impede the natural infiltration of stormwater. (SMC 22.801.100)

Limited Riparian Development Area is (for the purpose of this Director's Rule) the area in the riparian corridor but outside of the watercourse and more than 75 feet from the top of the watercourse bank.

Riparian Corridor means the riparian watercourse and riparian management area as defined in SMC 25.09.020.D.5.a.

Riparian Management Area is the area within 100 feet measured horizontally landward from the top of each bank of the watercourse, or from the ordinary high water mark of the watercourse as surveyed in the field, if the top of the bank cannot be determined. In watercourses with braided channels or alluvial fans, the ordinary high water mark shall be determined so as to include the entire stream feature.

3. RULE

In accordance with SMC 21.33.030.A, that took effect January 1, 2013, that portion of a parcel containing a riparian corridor that contains highly infiltrative pervious surface and meets all the following qualification criteria are exempt from the payment of drainage service charges.

A. Qualification Criteria

In addition to the requirements of SMC 21.33.030.A, that portion of a parcel containing a riparian corridor is considered exempt from the payment of drainage service charges if:

1) The riparian corridor on the parcel is at least 90 percent highly infiltrative pervious surface, and

2) The development occurring within the riparian corridor:

a) Is limited to the limited riparian development area, and

b) The amount of hard surface does not exceed 35 percent of the total area of the limited riparian development area

That portion of the parcel meeting the above criteria based on Geographic Information System (GIS) data will be considered exempt from the payment of drainage service charges. At the owner's request and expense, the Utility may consider other information (e.g. site surveys, site inspection, technical environmental analysis) in identifying qualifying riparian corridors.

B. Development Clarification

For the purposes of this Director's Rule, the following is not considered development:

1) Normal and routine pruning and maintenance of trees and vegetation that meets the requirements of SMC 25.09.320.A.3.a.

2) Restoring or improving vegetation and trees, including removing non-native vegetation or invasive plants and noxious weeds by hand, to promote maintenance or creation of a naturally functioning condition that prevents erosion, protects water quality, or provides diverse habitat that meets the requirements of SMC 25.09.320.A.3.c.

3) Qualifying streets per SPU Director's Rule FIN-211.1.

4. AUTHORITY/REFERENCES

SMC 21.33, Storm Drainage Utility Rates and Charges

SMC 21.33.030.A.6. Effective January 1, 2013, that portion of a parcel containing a riparian corridor that contains highly infiltrative pervious surface and meeting all qualification criteria established by the Utility by Director's Rule under Section 3.32.020 of the Seattle Municipal Code. The Utility may consider Geographic Information System data and any other information determined necessary in identifying qualifying riparian corridors.