City of Seattle

Stormwater Manual

CityWashingtonhighNo

Open source PDF ↗Official agency page ↗

Fields not found in document: design_criteria.required_hydrologic_hydraulic_software

Other manuals in Washington: City of Lacey, City of Seattle, Washington

Document Metadata

Jurisdiction level

municipality

“City of Seattle”
Page 2 of 1086

State

Washington

“Washington State Department of Ecology”
Volume 1, Chapter 1, Page 1-1

Version / edition

July 2021

“July 2021”
Page 2 of 1086

Adoption / effective date

2021-07-01

“Effective: 07/01/2021”
Page 2 of 1086

Last revised date

2021-03-23

“Publication: 03/23/2021”
Page 2 of 1086

Relationship to state manual

deemed equivalent to state manual

“Ecology has determined to meet the requirements contained in the Phase I NPDES Municipal Stormwater Permit, with reference to the Stormwater Management Manual for Western Washington (Ecology 2019).”
Volume 1, Chapter 1, Page 1-1

Design Criteria

Design storm return periods (years)

2-year, 5-year, 10-year, 25-year, 50-year, 100-year

“2-year, 5-year, 10-year, 25-year, 50-year, 100-year”
Volume 1 & Volume 3

Water quality volume method

The daily runoff volume at or below which 91 percent of the total runoff volume for the simulation period occurs, as determined using an approved continuous model.

“The daily runoff volume at or below which 91 percent of the total runoff volume for the simulation period occurs, as determined using an approved continuous model.”
Volume 1, Chapter 5, Page 5-14

Peak flow calculation method(s)

Continuous Simulation Method, Single Event Hydrograph Method, Rational Method

“Single Event Hydrograph Method... Continuous Simulation Method... Rational Method”
Volume 3, Chapter 4, Page 4-46 & Page 4-65

Required hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

On-site stormwater management, Flow control, Water quality treatment, Conveyance, Soil amendment, Tree planting and retention, Dispersion, Infiltration, Rainwater harvesting, Alternative surface, Detention, Non-infiltrating

“This volume covers four primary functional categories of stormwater BMPs: On-site stormwater management, Flow control BMPs, Water quality treatment BMPs, Conveyance BMPs”
Volume 3, Chapter 2, Page 2-1