City of Lacey

City of Lacey 2010 Stormwater Design Manual

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

Document Metadata

Jurisdiction level

municipality

“minimum "Core Requirements" for development, redevelopment and road projects of all sizes within the City of Lacey”
Introduction, Page xv

State

Washington

“Washington State Department of Ecology Stormwater Management Manual for Western Washington (SMMWW)”
Introduction, Page xv

Version / edition

2010 (Chapters 1–5 excerpt)

“The City of Lacey 2010 Stormwater Design Manual (SDM) is a completely revised and updated replacement for the 1994 Drainage Design and Erosion Control Manual for Lacey.”
Introduction, Page xv

Adoption / effective date

2010

“This manual has been adopted by local ordinance and has force of law.”
Introduction, Page xvi

Last revised date

Not found in document

No evidence cited

Relationship to state manual

deemed equivalent to state manual

“The 2010 SDM is based on the 2005 edition of the Washington State Department of Ecology Stormwater Management Manual for Western Washington (SMMWW). In creating the 2010 SDM, the City of Lacey Department of Public Works has edited and reorganized Ecology's 2005 SMMWW for ease of use and local application.”
Introduction, Page xv

Design Criteria

Design storm return periods (years)

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

“Table 5.4 Lacey Design Storm Volumes... 24-hour Rainfall Return Frequency (years) Precipitation (inches)... 2 2.80... 5 3.75... 10 4.35... 25 5.10... 50 5.65... 100 6.15”
Chapter 5, Table 5.4, Page 5-7

Water quality volume method

Water Quality Design Storm Volume is the 91st percentile, 24-hour runoff volume calculated using WWHM with Thurston County enhancements (most current version). Water Quality Design Flow Rate is the flow rate at or below which 91% of the runoff volume (WWHM/Thurston) will be treated when preceding detention or when detention is not required; downstream of detention, use the full 2-year release rate from the detention facility. Treatment facility design criteria are assigned to achieve the applicable performance goal at that rate (e.g., 80% TSS removal).

“Water Quality Design Storm Volume: the 91st percentile, 24-hour runoff volume calculated using WWHM with Thurston County enhancements, most current version.”
Chapter 1, Core Requirement #6, Page 1-18

Peak flow calculation method(s)

Western Washington Hydrology Model (WWHM) continuous simulation (default; Thurston County enhancements), Calibrated continuous simulation based on EPA HSPF (prior City approval; large/complicated sites), Santa Barbara Urban Hydrograph (SBUH), NRCS TR-55, Rational Method (when no hydrologic analysis is otherwise required)

“For the purpose of designing runoff treatment and flow control BMPs, the most current version of the Western Washington Hydrology Model (WWHM) with Thurston County enhancements is the standard requirement.... Alternatively, for very large or complicated sites, a calibrated continuous simulation hydrologic model based on the EPA's HSPF... may be used subject to prior approval of the City of Lacey.”
Chapter 5, Section 5.1, Pages 5-1 to 5-2

Required hydrologic/hydraulic software

Western Washington Hydrology Model (WWHM) with Thurston County enhancements / WWHM3, EPA HSPF (calibrated continuous model; prior approval)

“Runoff and volume calculations shall be provided by the Western Washington Hydrology Model (WWHM) with Thurston County enhancements, most current version. The Thurston County version of the Western Washington Hydrology Model (WWHM3), has been modified to track and compute recharge”
Chapter 1, Core Requirement #7, Page 1-21

Approved BMP categories

Construction ESC BMPs (preserving vegetation, buffer zones, seeding/mulching, silt fence, sediment trap/pond, inlet protection, chemical treatment/filtration), Runoff conveyance and treatment BMPs (interceptor dike/swale, grass-lined channels, check dams, outlet protection), LID site design BMPs (native vegetation, reduce effective impervious, full dispersion), Roof downspout controls (infiltration, dispersion, perforated stub-outs), Bioretention / permeable paving / vegetated (green) roofs, Detention ponds, tanks, vaults, and parking lot detention, Infiltration basins and trenches, Pre-treatment BMPs (pre-settling basin/wetvault, hydrodynamic devices), Biofiltration swales and filter strips, Wetponds, wetvaults, stormwater treatment wetlands, Media filtration (sand filters, commercial media filters), Oil control (catch basin inserts, oil/water separators), Source control BMPs

“Chapter 6 - Flow Control Design... LID Site Design BMPs... Detention Facilities... Infiltration Facilities... Chapter 7 - Water Quality Treatment... Pre-Treatment BMPs... Biofiltration Facilities... Wetpool Facilities... Media Filtration Treatment BMPs... Oil Control Facilities”
Table of Contents, Pages v–vii