City of Ann Arbor

Washtenaw County WRC Rules and Guidelines — Procedures & Design Criteria for Stormwater Management Systems (adopted by Ann Arbor Ch.63)

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Open source PDF ↗Official agency page ↗

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

Used 2014 WCWRC Rules PDF (city adopts WCWRC). County may have Oct 2016 update; verify against current washtenaw.org asset if available.

Fields not found in document: design_criteria.required_hydrologic_hydraulic_software

Other manuals in Michigan: City of Detroit, City of Flint, City of Grand Rapids, City of Lansing, Michigan, Michigan, Wayne County

Document Metadata

Jurisdiction level

City

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State

Michigan

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Version / edition

August 6, 2014 (amended / mirror PDF)

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Adoption / effective date

2014-08-06

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Last revised date

2016-10-17

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Relationship to state manual

independent

“independent county WRC rules adopted by city ordinance”
Coverage note

Design Criteria

Design storm return periods (years)

2-year, 100-year

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Water quality volume method

First flush = runoff from the first inch of rain (Rational Method); treat to ≥80% TSS removal or ≤80 mg/L TSS. Bankfull = 2-year/24-hour (NRCS). Infiltrate the greater of (post−pre bankfull volume) OR entire first flush. Flood control storage release ≤0.15 cfs/acre. Also size for 100-year (NRCS).

“First flush volume; the runoff from the first inch of rain ... 80 percent removal of TSS ... Bankfull volume; the 2-year recurrence interval /24 hour storm ... release rate ... will not exceed 0.15 cfs per acre”
§IV Volume Treatment / flood control

Peak flow calculation method(s)

Rational Method (first flush), NRCS Method (bankfull / 100-year), Fixed release rate 0.15 cfs/acre for flood-control storage

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Hydrologic/hydraulic software

Not found in document

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Approved BMP categories

Infiltration BMPs, Detention / retention systems, Bioretention / rain gardens, Swales, Pretreatment / treatment train BMPs, SEMCOG LID practices

No evidence cited