R equirements Figure A1 Initial Screening for All Development Projects SFR gt 2500 ft 2 See Figure A4 Is the project Exempt or does not discharge to MS4 Project is lt 2500 ID: 918313
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Slide1
Start Here
EXEMPT
No Stormwater Requirements
Figure A1. Initial Screening for All Development Projects
SFR
> 2,500 ft2 See Figure A4
Is the project Exempt or does not discharge to MS4?
Project is < 2,500 ft2 of new and replaced impervious surface
Project is a detached single-family residence?
All Others
See Figure
A2
YES NO
YES NO
YES NO
Flow Chart to Determine Performance Requirements
Slide2Figure
A2.
Requirements for Small to Moderate Development Projects
Projects ≥ 2,500 ft
2
Project is > 2,500 ft2 of new and replaced impervious surface but < 5,000 ft2 of
net impervious area
Project is > 5,000 ft2 net impervious area but < 15,000 ft2 of new and replaced impervious
surfaceProject is >
15,000 ft2
of new and replaced impervious surface
Performance Requirement #1 (Site Design)Performance Requirements #
1 (Site Design) and #2 (WQ Treatment)
See Figure A3
Slide3P
roject creates
> 22,500 ft2 of new and replaced impervious surface
Figure A3. Requirements for Large Development Projects
Yes
No additional Stormwater RequirementsDoes the project fall under theSpecial Circumstances designation?
See Special Circumstances(Performance Requirement #5) No
NoWatershed Management Zone1 2 3 4 5 6
7 8 9 10Apply
Performance Requirement #4 (Peak Management
)Projects ≥ 15,000 ft
2 New and Replaced Impervious Area
Yes
Retain 95
th Percentile event via infiltrationRetain 95th Percentile event via storage, harvesting
, infiltration, and/or evapotranspirationN/A
Retain 95th Percentile event via infiltration where overlying
groundwater basinRetain 85th Percentile
event via infiltrationRetain 85th Percentile
event via storage, harvesting,
infiltration,
and/or evapotranspiration
Retain
95
th
Percentile event via infiltration where
overlying groundwater basin
Retain
85
th
Percentile
event via
infiltration
Retain 85
th
Percentile
event via storage, harvesting,
infiltration,
and/or evapotranspiration
Retain
95
th
Percentile event via infiltration where overlying
groundwater basin
Determine WMZ and apply Performance Requirement #3 (Runoff Retention)
Project in WMZ 1, 2, 3, 6, or
9
No
Yes
Slide4Performance Requirement #1
Project is
>
2,500 ft2 new and replaced impervious
surface,
but< 15,000 ft2 net impervious areaProject is
> 15,000 ft2 net impervious area, but
< 22,500 ft2 new and replaced impervious surfacePerformance Requirement #s
1, 2, and 3Project is>
22,500 ft2 new
and replaced impervious surface
Performance Requirement #s
1, 2, 3, and 4
Figure
A4.
Requirements for Single-Family Residential
Projects
Detached
Single-Family
Residential
Projects