Clean Water Services

Low Impact Development Approaches Handbook

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

Handbook is a supplement to Clean Water Services Design and Construction Standards; water quality design storm rainfall depth/intensity and peak-flow hydrology methods are deferred to Standards Chapter 4 and are not specified here. Only freeboard references a 25-year water surface elevation for extended dry basins and wetlands.

Fields not found in document: design_criteria.design_storm_return_periods_years, design_criteria.peak_flow_calculation_method, design_criteria.required_hydrologic_hydraulic_software

Other manuals in Oregon: City of Bend, City of Eugene, City of Portland, City of Salem, Oregon

Document Metadata

Jurisdiction level

Special District

“Clean Water Services (the District) is a water resources management utility in urban areas of the Tualatin River Watershed that builds, maintains and enhances the public drainage system in partnership with Washington County and its member Cities.”
Chapter 1: Introduction, Page 4

State

Oregon

“strict water quality regulations set for the Tualatin River basin by the Oregon Department of Environmental Quality (DEQ).”
Chapter 1: Introduction, Page 4

Version / edition

2016

“Low Impact Development Approaches Handbook 2016”
Cover

Adoption / effective date

2016-06

“The handbook was updated in June 2016”
Chapter 1: Introduction, Page 4

Last revised date

2016-06

“The handbook was updated in June 2016”
Chapter 1: Introduction, Page 4

Relationship to state manual

independent

“This handbook is a supplement to the Standards and is to be used in conjunction with them and other applicable regulations.”
Chapter 1: Introduction, Page 4

Design Criteria

Design storm return periods (years)

Not found in document

No evidence cited

Water quality volume method

Size LIDA facilities with District sizing factors based on the water quality design storm and typical soils (WQV rate/volume methods are in Design and Construction Standards Chapter 4). Infiltration planter/rain garden, flow-through planter, LIDA swale, and vegetated filter strip use a sizing factor of 0.06 × contributing impervious area when native infiltration is less than 2 in/hr (smaller factors allowed with demonstrated higher infiltration or deeper amended soil). Porous pavement and green roofs replace impervious area at 1:1 and may be deducted as LIDA credits. Extended dry basins and constructed water quality wetlands must accommodate the water quality design storm with 48-hour drawdown; minimum water quality detention volume equals 1 × WQV.

“The water quality storm runoff rate volume calculations for sizing water quality facilities are presented in Chapter 4 of the Design and Construction Standards. ... LIDA Sizing Form ... based on the water quality design storm and typical soil conditions. ... Infiltration Planters/Rain Garden 0.06 Flow-through Planter 0.06 LIDA Swale 0.06 Vegetated Filter Strip 0.06 ... The minimum water quality detention volume is equal to (1) x the water quality volume (WQV). ... sized for a 48 hour drawdown time.”
Chapter 3 §§3.1–3.2 / LIDA Sizing Form, Pages 17–19; Extended Dry Basin / Constructed Wetland fact sheets, Pages 51 & 55

Peak flow calculation method(s)

Not found in document

No evidence cited

Hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

Porous Pavement, Green Roof, Infiltration Planter/Rain Garden, Flow-Through Planter, LIDA Swale, Vegetated Filter Strip, Vegetated Swale, Extended Dry Basin, Constructed Water Quality Wetland, Proprietary Facility

“Porous Pavement ... Green Roof ... Infiltration Planter/Rain Garden ... Flow-Through Planter ... LIDA Swale ... Vegetated Filter Strip ... Vegetated Swale ... Extended Dry Basin ... Constructed Water Quality Wetland ... proprietary facility may be appropriate.”
Table of Contents / Table 2: LIDA Fact Sheet Table, Pages 3 & 20–21; Chapter 3 §3.2, Page 19