Alaska

Alaska Storm Water Guide

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Compare each cited field to the official PDF before relying on it. What this means

Statewide guidance (not binding code). Hydrologic software listed is accepted by some municipalities, not a statewide mandate. Unified sizing criteria and regional WQv depths are recommendations; local ordinances (e.g., Anchorage) may differ. Pipeline excerpt repair removed 1 unlocated citation(s).

Fields not found in document: design_criteria.approved_bmp_categories

Other manuals in Alaska: Alaska, City and Borough of Juneau, Municipality of Anchorage

Document Metadata

Jurisdiction level

State

“This Guide was developed with support of a technical workgroup under the direction of the Alaska Department of Environmental Conservation.”
Preface, page i

State

Alaska

“Anchorage, Alaska 99501”
Title Page

Version / edition

December 2011

“December 2011”
Title Page

Adoption / effective date

2011-12

“December 2011”
Title Page

Last revised date

2011-12

“Alaska Storm Water Guide December 2011”
Title Page

Relationship to state manual

independent

“The concepts presented in this Guide are intended to be guidance for readers rather than stringent rules.”
Preface, page i

Design Criteria

Design storm return periods (years)

1-year, 2-year, 5-year, 100-year

“Provide 24 hours of extended detention of the runoff from the 1-year, 24-hour duration storm event... Provide peak discharge control of the 5-year storm event... Some jurisdictions may require peak discharge control for the 2-year storm event... Evaluate the effects of the 100-year storm”
Table 3-4, Unified sizing criteria, Section 3.3

Water quality volume method

Treat runoff from 90% of average-year storms (goal: 80% average annual post-development TSS reduction). WQv = (Rv) × (A) × (P) / 12, where P is the 90% cumulative frequency rainfall depth (~0.5–1.25 in by climatic region; Table 2-4). Where end-of-season snowmelt volume exceeds the 90% rainfall volume, size BMPs on meltwater instead.

“Treat the runoff from 90% of the storms that occur in an average year. For Alaska, this equates to providing water quality treatment for the runoff resulting from a rainfall depth of 1.25 inches or less. The goal is to reduce average annual post-development TSS loadings by 80%. WQv = (Rv) × (A) × (P) / 12”
Table 3-4; Section 3.3.1

Peak flow calculation method(s)

Rational Method, TR-55 (USDA 1986), WinTR-20 / SCS methods, HEC-HMS, EPA SWMM

“A partial list of hydrologic modeling software accepted by some Alaskan municipalities includes the following: ILLUDAS TR55-1986 WinTR553 WinTR20 SCS HEC-HMS Rational Method”
Section 3.2, page 3-5

Hydrologic/hydraulic software

ILLUDAS, TR55-1986, WinTR55, WinTR20 SCS, HEC-HMS

“A partial list of hydrologic modeling software accepted by some Alaskan municipalities includes the following: ILLUDAS TR55-1986 WinTR553 WinTR20 SCS HEC-HMS”
Section 3.2, page 3-5

Approved BMP categories

Not found in document

“Primary Secondary Secondary Secondary Extended Storage Pond High Low Primary Secondary Secondary Secondary Wet Vaults Medium Lowa Primary Secondary Secondary Minor Detention Dry Pond High Low Secondary Minor Minor Minor Oversized Pipes High Low Minor Minor Minor Minor Oil/Grit”
pp. 180–181