Alaska

Alaska Storm Water Guide

StateAlaskahighNo

Other manuals in Alaska: 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

Required 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

Wet Pond, Extended Storage Pond / Dry ED Ponds, Dry Pond, Wet Vaults, Oil/Grit Separator, Dry Swale / Wet Swale, On-Lot Infiltration, Infiltration Basin, Infiltration Trench, Storm Water Wetland / Constructed Wetlands, Surface Sand Filters / Underground Filters / Filtering Practices, Bioretention, Filter Strips, Green Roofs, Rain Tank/Cistern, Permeable Pavers, Erosion and Sediment Control BMPs, Good Housekeeping BMPs, Low Impact Development / Environmental Site Design

“Wet Pond... Extended Storage Pond... Dry Pond... Oil/Grit Separator... Dry Swale... On-Lot Infiltration... Infiltration Basin... Infiltration Trench... Storm Water Wetland... Surface Sand Filters... Bioretention... Filter Strips”
Table 5-1, Storm water treatment suitability matrix