Flow Chart to Determine Performance Requirements
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Flow Chart to Determine Performance Requirements. Start Here . Is the project Exempt or does not discharge to MS4? . YES NO. Project is < 2,500 ft 2 of new and replaced impervious surface. YES NO. P roject is a detached single-family residence?.

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Flow Chart to Determine Performance Requirements

Start Here

Is the project Exempt or does not discharge to MS4?

YES NO

Project is < 2,500 ft2of new and replaced impervious surface

YES NO

Project is a detached single-family residence?

YES NO

SFR > 2,500 ft2

See Figure A4

EXEMPT

No Stormwater Requirements

All Others

See Figure A2

Figure A1. Initial Screening for All Development Projects


Projects ≥ 2,500 ft2

Project is >5,000 ft2net impervious area but < 15,000 ft2of new and replaced impervious surface

Project is > 2,500 ft2of new and replaced impervious surface but < 5,000 ft2 of net impervious area

Project is >15,000 ft2of new and replaced impervious surface

Performance Requirements #1 (Site Design) and #2 (WQ Treatment)

Performance Requirement #1 (Site Design)

See Figure A3

Figure A2. Requirements for Small to Moderate Development Projects


Projects ≥ 15,000 ft2 New and Replaced Impervious Area

See Special Circumstances

(Performance Requirement #5)

Does the project fall under the

Special Circumstances designation?

Yes

No

Determine WMZ and apply Performance Requirement #3 (Runoff Retention)

Watershed Management Zone

1 2 3 4 5 6 7 8 9 10

Retain 95th Percentile event via infiltration

Retain 95th Percentile event via storage, harvesting, infiltration, and/or evapotranspiration

N/A

Retain 95th Percentile event via infiltration where overlying groundwater basin

Retain 85th Percentile event via infiltration

Retain 85th Percentile event via storage, harvesting, infiltration, and/or evapotranspiration

Retain 95th Percentile event via infiltration where overlying groundwater basin

Retain 85th Percentile event via infiltration

Retain 85th Percentile event via storage, harvesting, infiltration, and/or evapotranspiration

Retain 95th Percentile event via infiltration where overlying groundwater basin

No

No additional Stormwater Requirements

Project in WMZ 1, 2, 3, 6, or 9

Yes

No

Project creates > 22,500 ft2 of new and replaced impervious surface

Yes

  • Apply Performance

  • Requirement #4

  • (Peak Management)

Figure A3. Requirements for Large Development Projects


DetachedSingle-FamilyResidentialProjects

Project is

> 2,500 ft2new and replaced impervious surface,

but

< 15,000 ft2 net impervious area

Project is

> 15,000 ft2 net impervious area, but

< 22,500 ft2 new and replaced impervious surface

Project is

> 22,500 ft2 new and replaced impervious surface

Performance Requirement #s

1, 2, and 3

Performance Requirement #s

1, 2, 3, and 4

Performance Requirement #1

Figure A4. Requirements for Single-Family Residential Projects


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