Stormwater Atlas

King County

Surface Water Design Manual

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King County SWDM 2021/2024; text extract truncated but core requirements and WQ/flow-control structure clear. Pipeline excerpt repair removed 2 unlocated citation(s).

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Jurisdiction level
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State
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Version / edition
2021 Amended November 14, 2024

July 23, 2021 Amended November 14, 2024

Title

Adoption / effective date
2021-07-23

July 23, 2021

Title

Last revised date
2024-11-14

Amended November 14, 2024

Title

Relationship to state manual
independent

King County Code (KCC) Chapter 9.04

Chapter 1

Design Criteria

Design storm return periods (years)
2-year, 10-year, 25-year, 100-year

Flow Control / design standards

Chapter 3

Water quality volume method
Core Requirement #8: Water Quality. Water quality menus (Basic Water Quality Menu and others) in Chapter 6. Continuous simulation / WWHM-based sizing typical for flow control and WQ facilities.

Core Reqmt #8: Water Quality

Section 1.2.8

Peak flow calculation method(s)
Core Requirement #3: Flow Control, Flow Control Design standards (Chapter 3), Flow control design using continuous hydrologic modeling (WWHM), Core Requirement #9: Flow Control BMPs (dispersal/infiltration LID BMPs)

Core Reqmt #3: Flow Control

Section 1.2.3

Hydrologic/hydraulic software
Western Washington Hydrology Model (WWHM) / continuous simulation tools as specified

Flow Control Design Using the

Section 3.3.2

Approved BMP categories
Flow control facilities, Water quality treatment facilities (Basic WQ menu and others), Flow control BMPs / LID, Infiltration facilities

Basic Water Quality Menu

Section 6.1.1