City of Rockford

Stormwater Technical Guidance Manual

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May 2015 edition; quantity-focused release-rate standard with BMP hierarchy.

Other manuals in Illinois: City of Chicago, City of Peoria, City of Springfield, Cook County, Illinois, Illinois EPA / Association of Illinois Soil and Water Conservation Districts

Document Metadata

Jurisdiction level

City

No evidence cited

State

Illinois

No evidence cited

Version / edition

May 18, 2015

“May 18, 2015”
Cover

Adoption / effective date

2015-05-18

No evidence cited

Last revised date

2015-05-18

No evidence cited

Relationship to state manual

independent

“independent city technical manual (supplements Stormwater Ordinance)”
Introduction

Design Criteria

Design storm return periods (years)

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

“minor system criteria (typically 10-year) ... major system criteria (the 100-year) ... Bulletin 70”
T2-02 / Table 1

Water quality volume method

Peak release rate from a development site shall not exceed 0.2 cfs/acre for the 100-year (0.01 AEP) storm. Minor system typically 10-year; major system 100-year. Design rainfall from Illinois State Water Survey Bulletin 70 Northwest sectional statistics. BMPs required for water quality; Illinois Urban Manual referenced for practice design.

“The peak release rate from a development site shall not exceed 0.2 cfs/acre of development for the 0.01 probability in any year”
T2-03(b)

Peak flow calculation method(s)

HEC-HMS / HEC-1 (SCS runoff), SWMM, TR-20, TR-55 tabular method, Bulletin 70 critical-duration storms

“HEC-HMS, HEC-1 with SCS runoff method, SWMM, TR-20, and TR-55 tabular”
T2-02(e)

Hydrologic/hydraulic software

HEC-HMS, HEC-1, SWMM, TR-20, TR-55

No evidence cited

Approved BMP categories

Site runoff storage / detention, Overland flow paths, Best Management Practices hierarchy (avoidance → LID → structural), Illinois Urban Manual practices

No evidence cited