HomeMy WebLinkAboutSP-22-012 Taxiway A - Supplemental - 1200 Airport Drive (10)Vermont Operational Stormwater Permit - Standards Compliance Workbook
The name above will appear on all the discharge point tabs
Site Summary
Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9
New 0.73 0.43 0.30 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Redeveloped 0.11 0.06 0.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Existing 2.06 1.56 0.00 0.50 0.00 0.00 0.00 0.00 0.00 0.00
Previously
Authorized 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Total 2.90 2.05 0.35 0.50 0.00 0.00 0.00 0.00 0.00 0.00
Site Area 6.39 2.77 3.12 0.50 0.00 0.00 0.00 0.00 0.00 0.00
44.46776 44.46776 44.46776 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
-73.15304 -73.15304 -73.15304 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000
Receiving Water Centennial
Brook
Potash
Brook
Potash
Brook 0 0
Recharge
Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9
Required 0.1395 0.0995 0.0150 0.0250 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Provided 0.5440 0.3280 0.2160 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Standard met?Yes Yes Yes No n/a n/a n/a n/a n/a n/a
Notes:
Water Quality
Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9
Required 0.2523 0.1688 0.0439 0.0396 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Provided 0.5440 0.3280 0.2160 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Standard met?Yes Yes Yes No n/a n/a n/a n/a n/a n/a
Notes:
Channel ProtectionImperviousProject Name
Do not fill this tab out, apart from the project name and notes. It will auto-populated based on the values on the discharge point
tabs. Discharge points (SN) will only show on the summary if an area has been entered on that tab. Areas listed below are those
seeking permit coverage.
SN3 is area is being diverted to Permit: 3028-INDS.9 where is will be treated and detained.
Burlington International Airport
Latitude
Longitude
A minimum WQ V of 0.2" (P*R V ) is required for sites with low impervious (<16.67%). This calculation has not been incorporated
into this workbook. Designers should check that the minimum WQ V has been met for their site.
SN3 is area is being diverted to Permit: 3028-INDS.9 where is will be treated and detained.
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9
Standard Applies?Yes Yes Yes Yes Yes 0 0 0 0
Waiver n/a n/a n/a n/a n/a
Method
Hydrologic
Condition
Method
Hydrologic
Condition
Method
Extended
Detention
Hydrologic
Condition
Method
Hydrologic
Condition
Method
n/a n/a n/a n/a
HCV 0.3658 0.2611 -0.0098 0.1145 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
TV Provided 0.5440 0.3280 0.2160 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
Notes:
Overbank Flood Protection
SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9
Standard Applies?Yes Yes Yes Yes Yes 0 0 0 0
Pre-Dev Q (cfs)11.14 0 0 0 0
Routed, Post-Dev Q (cfs)8.03 0 0 0 0
Waiver n/a n/a n/a n/a n/a
Notes:
Extreme Flood Protection
SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9
Standard Applies?Yes Yes Yes Yes Yes
Pre-Dev Q (cfs)22.78 0 0 0 0
Routed, Post-Dev Q (cfs)15.79 0 0 0 0
Waiver n/a n/a n/a n/a n/a
Notes:
General Notes
SN3 is area is being diverted to Permit: 3028-INDS.9 where is will be treated and detained. SN2
is a simple disconnection where an existing infiltration basin reside. A approximate Tv was
calculated based from existing suvey but pavement has been reduced.
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
The high point in between SN1 ands SN2 has been modified and the pre-developed areas are slightly different to post-
developed area creating an area on the workbook. The total area for the pre-developed and post-developed remains
the same of 6.39 acres. SN3 is a small area of disturbance within project limts but the water runoff is diverted
to Permit 3028-INDS.9 in the proposed condition.
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
General Discharge Point Information
Project name
Discharge point serial number (e.g. S/N 001)
Name of receiving water
Latitude (decimal degrees to five decimal places)
Longitude (decimal degrees to five decimal places)
Precipitation Data NOAA Atlas 14
Storm WQ Storm 1 yr, 24 hr 10 yr, 24 hr 100 yr, 24 hr
Precipitation (inches) 1.00 1.90 3.26 4.87
Drainage Area Information
Landuse A B C D Total
Grass 1.240 0.000 0.000 0.000 1.240
Meadow 0.000 0.000 0.000 0.000 0.000
Woods 0.000 0.000 0.000 0.000 0.000
Existing Impervious 1.740 0.000 0.000 0.000 1.740
Impervious previously authorized under 2002 VSMM (not included in calculations)
Total Pre Site Area 2.980
%
Landuse A B C D Total
Grass 0.720 0.000 0.000 0.000 0.720
Meadow 0.000 0.000 0.000 0.000 0.000
Woods 0.000 0.000 0.000 0.000 0.000
New Impervious 0.430 0.000 0.000 0.000 0.430 15.5%
Existing for Permit
Coverage (Treated to New
Standards)
1.560 0.000 0.000 0.000 1.560 56.3%
Existing Impervious Not for Permit Coverage 0.000 0.0%
Redeveloped Impervious 0.060 2.2%
0.000
Total Site Area 2.770
Total Impervious for Permit Coverage 2.050
Net Reduced Impervious 0.000 0.0%
Reduced Existing Impervious (for redevelopment)0.120 66.7%
Average
Catchment
Slope, Y (%)
Hydraulic
Length, l (ft)
Pre Development 0.5 561.00
Post Development 0.5 561.00
Impervious previously authorized under 2002 VSMM
Post Development Land Use (acres)
WARNING: Pre development and post development areas don't match, so evaluation of the Hydrologic
Condition Method is not appropriate within this drainage area. Designer may consider HCM across drainage
Information for Calculating TC by the
Watershed Lag Method
Burlington International Airport
SN1
Pre Development Land Use (acres)
Centennial Brook
44.46776
-73.15304
* Preciptation values shall be obtained from
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Runoff Calculations 1 yr, 24-hr 10 yr, 24-hr 100 yr, 24-hr
0.2429 0.4391 0.6899
0.2862 0.5172 0.8020
Tier 1/Runoff Reduction Practices
Practice TV (ac-ft) TV (ac-ft)
Infiltration Chambers 0.328
Runoff Reduction Calculations
Standard Re WQ CP QP10 QP100
TV Required (ac-ft)0.0995 0.1688 0.2611 0.4717 0.7142
TV Provided (ac-ft)0.3280 0.3280 0.3280 0.3280 0.3280
TV Remaining (ac-ft)0.0000 0.0000 0.0000 0.1437 0.3862
Standard met with HCM?Yes Yes Yes No No
Post-Development CN n/a 97 93 90 87
CNadj n/a n/a n/a 69 71
Pre-Development CN n/a n/a 90 84 80
Groundwater Recharge Standard (Re)1
Standard Applicable?
ReV 0.0995
Standard met with Tier 1
Practices?
Yes
Recharge Notes:
List all Tier 1 practices below with the associated treatment volume (TV ). The T V will be applied to all treatment standards,
except for Green Roofs, which do not receive recharge or water quality credit. Please include the appropriate STP
worksheet(s) with the application.
Predevelopment runoff volume (ac-ft)
Pre-routed, post development runoff volume (ac-ft)
Practice
Yes No
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Water Quality Treatment Standard (WQ)1 1
(ac-ft)Apply Reduction?
WQV - New & Existing 0.1608 0.0%
WQV - Redevelopment 0.0080 66.7%Max 25%
applied
Total WQV 0.1688
WQV met with Tier 1
practices 0.1688 1
WQV to be met with Tier 2
and/or Tier 3 practices 0.0000
WQV Provided
(ac-ft)Tier
Total WQV Provided (ac-ft)0.0000 ac-ft
Is the WQV Standard met?Yes
Water Quality Notes:
Channel Protection Standard (CP)1 1
Standard Applicable?
Standard Met with HCM?Yes
Provide Extended
Detention for:n/a ac-ft
Warm or Cold Water
Fishery?→Provide:
FALSE
Extended Detention STP:
CNAdj n/a 15.8 (Watershed
Lag Method)
Channel Protection Notes:
Modeling Info: When demonstrating CP compliance with extended detention in a hydrologic model, use the CN and TC
below if the practice being modelled is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume
achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'.
OR
The Alternative Extended Detention
Method (§2.2.5.4) is being used.
12 hours of extended
detention
The channel protection standard has been fully met with hydrologic
condition method. Additional treatment of the 1 year storm is not required.
Is all impervious treated by
disconnection?
% Net Reduction
% Removed Existing
Impervious (Redevelopment)
See the Vermont Water Quality Standards for warm and
cold water designations
Post Development TC (min)
Tier 2 & 3 Water Quality Practice
Yes No
Cold
Warm
No
Yes (WQv met)
No Yes
No Yes
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Overbank Flood Protection (QP10)1
Standard Applicable?
Standard Met with HCM?No
STP used:
Pre-development peak discharge rate (cfs)11.14
Pre-routed, post-development peak discharge rate (cfs)13.79
Routed, post-development peak discharge rate (cfs)8.03
Pre-Development CN (Flow-
weighted composite)84 24.4
CNAdj 69 38.7
Overbank Flood Notes:
Extreme Flood Protection (QP100)1
Standard Applicable?
Standard Met with HCM?No
STP used:
Pre-development peak discharge rate (cfs)22.78
Pre-routed, post-development peak discharge rate (cfs)26.71
Routed, post-development peak discharge rate (cfs)15.79
Pre-Development CN (Flow-
weighted composite)80 28.3
CNAdj 71 36.3
Extreme Flood Notes:
(Watershed
Lag Method)
The QP10 standard has not been fully met. Provide additional STPs to ensure
post development peak runoff does not exceed pre development peak runoff
for the 10 yr, 24 hour storm event.
The extreme standard has not been fully met. Provide additional STPs to
ensure post development peak runoff does not exceed pre development peak
runoff for the 100 yr, 24 hour storm event.
Post-developed runoff does not exceed pre-developed flows for the 10-year storm
Modeling Info: When demonstrating Q P10 compliance in a hydrologic model, use the following CN and T C below, if the
practice used to meet QP10 is not itself a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume
achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'.
Post-developed runoff does not exceed pre-developed flows for the 100-year storm
Post Development TC (min)
Post Development TC (min)
Pre Development TC (min)(Watershed
Lag Method)
Pre Development TC (min)
Modeling Info: When demonstrating Q P100 compliance in a hydrologic model, use the following CN and T C below, if the
practice used to meet QP100 is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume achieved
through runoff reduction practices. The T C is calculated by the watershed lag method using CN Adj as CN'.
Yes No
Yes No
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
General Discharge Point Information
Project name
Discharge point serial number (e.g. S/N 001)
Name of receiving water
Latitude (decimal degrees to five decimal places)
Longitude (decimal degrees to five decimal places)
Precipitation Data NOAA Atlas 14
Storm WQ Storm 1 yr, 24 hr 10 yr, 24 hr 100 yr, 24 hr
Precipitation (inches) 1.00 1.90 3.26 4.87
Drainage Area Information
Landuse A B C D Total
Grass 1.210 0.000 0.000 0.000 1.210
Meadow 0.000 0.000 0.000 0.000 0.000
Woods 0.000 0.000 0.000 0.000 0.000
Existing Impervious 2.190 0.000 0.000 0.000 2.190
Impervious previously authorized under 2002 VSMM (not included in calculations)
Total Pre Site Area 3.400
%
Landuse A B C D Total
Grass 1.000 0.000 0.000 0.000 1.000
Meadow 0.000 0.000 0.000 0.000 0.000
Woods 0.000 0.000 0.000 0.000 0.000
New Impervious 0.300 0.000 0.000 0.000 0.300 9.6%
Existing for Permit
Coverage (Treated to New
Standards)
0.000 0.000 0.000 0.000 0.000 0.0%
Existing Impervious Not for Permit Coverage 1.770 56.7%
Redeveloped Impervious 0.050 1.6%
0.000
Total Site Area 3.120
Total Impervious for Permit Coverage 0.350
Net Reduced Impervious 0.070 3.2%
Reduced Existing Impervious (for redevelopment)0.370 88.1%
Average
Catchment
Slope, Y (%)
Hydraulic
Length, l (ft)
Pre Development 0 0.00
Post Development 0 0.00
Information for Calculating TC by the
Watershed Lag Method
WARNING: Pre development and post development areas don't match, so evaluation of the Hydrologic
Condition Method is not appropriate within this drainage area. Designer may consider HCM across drainage
Burlington International Airport
SN2
Potash Brook
44.46776
-73.15304
* Preciptation values shall be obtained from
Pre Development Land Use (acres)
Post Development Land Use (acres)
Impervious previously authorized under 2002 VSMM
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Runoff Calculations 1 yr, 24-hr 10 yr, 24-hr 100 yr, 24-hr
0.3057 0.5526 0.8632
0.2960 0.5349 0.8331
Tier 1/Runoff Reduction Practices
Practice TV (ac-ft) TV (ac-ft)
Simple Disconnection 0.216
Runoff Reduction Calculations
Standard Re WQ CP QP10 QP100
TV Required (ac-ft)0.0150 0.0439 -0.0098 -0.0177 -0.0301
TV Provided (ac-ft)0.2160 0.2160 0.2160 0.2160 0.2160
TV Remaining (ac-ft)0.0000 0.0000 0.0000 0.0000 0.0000
Standard met with HCM?Yes Yes Yes Yes Yes
Post-Development CN n/a 85 92 88 85
CNadj n/a n/a n/a n/a n/a
Pre-Development CN n/a n/a 91 87 83
Groundwater Recharge Standard (Re)1
Standard Applicable?
ReV 0.0150
Standard met with Tier 1
Practices?
Yes
Recharge Notes:
Pavement to existing infiltration system has been reduced. Tv has been estimated
from existing survey information.
Predevelopment runoff volume (ac-ft)
Pre-routed, post development runoff volume (ac-ft)
List all Tier 1 practices below with the associated treatment volume (TV ). The T V will be applied to all treatment standards,
except for Green Roofs, which do not receive recharge or water quality credit. Please include the appropriate STP
worksheet(s) with the application.
Practice
Yes No
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Water Quality Treatment Standard (WQ)1 1
(ac-ft)Apply Reduction?
WQV - New & Existing 0.0355 3.2%
WQV - Redevelopment 0.0084 88.1%Max 25%
applied
Total WQV 0.0439
WQV met with Tier 1
practices 0.0439 1
WQV to be met with Tier 2
and/or Tier 3 practices 0.0000
WQV Provided
(ac-ft)Tier
Total WQV Provided (ac-ft)0.0000 ac-ft
Is the WQV Standard met?Yes
Water Quality Notes:
Channel Protection Standard (CP)1 1
Standard Applicable?
Standard Met with HCM?Yes
Provide Extended
Detention for:n/a ac-ft
Warm or Cold Water
Fishery?→Provide:
FALSE
Extended Detention STP:
CNAdj n/a 0.0 (Watershed
Lag Method)
Channel Protection Notes:
Pavement to existing infiltration system has been reduced. Tv has been estimated
from existing survey information.
The channel protection standard has been fully met with hydrologic
condition method. Additional treatment of the 1 year storm is not required.
12 hours of extended
detention
See the Vermont Water Quality Standards for warm and
cold water designations
OR
The Alternative Extended Detention
Method (§2.2.5.4) is being used.
Modeling Info: When demonstrating CP compliance with extended detention in a hydrologic model, use the CN and TC
below if the practice being modelled is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume
achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'.
Post Development TC (min)
Pavement to existing infiltration system has been reduced. Tv has been estimated
from existing survey information.
% Net Reduction
% Removed Existing
Impervious (Redevelopment)
Is all impervious treated by
disconnection?
Tier 2 & 3 Water Quality Practice
Yes No
Cold
Warm
No
Yes (WQv met)
No Yes
No Yes
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Overbank Flood Protection (QP10)1
Standard Applicable?
Standard Met with HCM?Yes
STP used:
Pre-development peak discharge rate (cfs)
Pre-routed, post-development peak discharge rate (cfs)
Routed, post-development peak discharge rate (cfs)
Pre-Development CN (Flow-
weighted composite)87 0.0
CNAdj n/a 0.0
Overbank Flood Notes:
Extreme Flood Protection (QP100)1
Standard Applicable?
Standard Met with HCM?Yes
STP used:
Pre-development peak discharge rate (cfs)
Pre-routed, post-development peak discharge rate (cfs)
Routed, post-development peak discharge rate (cfs)
Pre-Development CN (Flow-
weighted composite)83 0.0
CNAdj n/a 0.0
Extreme Flood Notes:
Pre Development TC (min)(Watershed
Lag Method)Post Development TC (min)
Pavement to existing infiltration system has been reduced. Tv has been estimated
from existing survey information.
Pavement to existing infiltration system has been reduced. Tv has been estimated
from existing survey information.
The extreme flood standard has been fully met. No additional STPs are
required.
Modeling Info: When demonstrating Q P100 compliance in a hydrologic model, use the following CN and T C below, if the
practice used to meet QP100 is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume achieved
through runoff reduction practices. The T C is calculated by the watershed lag method using CN Adj as CN'.
The QP10 standard has been fully met. No additional STPs are required.
Modeling Info: When demonstrating Q P10 compliance in a hydrologic model, use the following CN and T C below, if the
practice used to meet QP10 is not itself a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume
achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'.
Pre Development TC (min)(Watershed
Lag Method)Post Development TC (min)
Yes No
Yes No
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
General Discharge Point Information
Project name
Discharge point serial number (e.g. S/N 001)
Name of receiving water
Latitude (decimal degrees to five decimal places)
Longitude (decimal degrees to five decimal places)
Precipitation Data NOAA Atlas 14
Storm WQ Storm 1 yr, 24 hr 10 yr, 24 hr 100 yr, 24 hr
Precipitation (inches) 1.00 1.90 3.26 4.87
Drainage Area Information
Landuse A B C D Total
Grass 0.000 0.000 0.000 0.000 0.000
Meadow 0.000 0.000 0.000 0.000 0.000
Woods 0.000 0.000 0.000 0.000 0.000
Existing Impervious 0.180 0.000 0.000 0.000 0.180
Impervious previously authorized under 2002 VSMM (not included in calculations)
Total Pre Site Area 0.180
%
Landuse A B C D Total
Grass 0.000 0.000 0.000 0.000 0.000
Meadow 0.000 0.000 0.000 0.000 0.000
Woods 0.000 0.000 0.000 0.000 0.000
New Impervious 0.000 0.000 0.000 0.000 0.000 0.0%
Existing for Permit
Coverage (Treated to New
Standards)
0.500 0.000 0.000 0.000 0.500 100.0%
Existing Impervious Not for Permit Coverage 0.000 0.0%
Redeveloped Impervious 0.000 0.0%
0.000
Total Site Area 0.500
Total Impervious for Permit Coverage 0.500
Net Reduced Impervious 0.000 0.0%
Reduced Existing Impervious (for redevelopment)0.000 0.0%
Average
Catchment
Slope, Y (%)
Hydraulic
Length, l (ft)
Pre Development 0 0.00
Post Development 0 0.00
Information for Calculating TC by the
Watershed Lag Method
WARNING: Pre development and post development areas don't match, so evaluation of the Hydrologic
Condition Method is not appropriate within this drainage area. Designer may consider HCM across drainage
Burlington International Airport
SN3
Potash Brook
44.46776
-73.15304
* Preciptation values shall be obtained from
Pre Development Land Use (acres)
Post Development Land Use (acres)
Impervious previously authorized under 2002 VSMM
Last Updated 8/28/2018
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Runoff Calculations 1 yr, 24-hr 10 yr, 24-hr 100 yr, 24-hr
0.0251 0.0454 0.0695
0.0698 0.1261 0.1931
Tier 1/Runoff Reduction Practices
Practice TV (ac-ft) TV (ac-ft)
Infiltration Chambers
Runoff Reduction Calculations
Standard Re WQ CP QP10 QP100
TV Required (ac-ft)0.0250 0.0396 0.1145 0.2069 0.3165
TV Provided (ac-ft)0.0000 0.0000 0.0000 0.0000 0.0000
TV Remaining (ac-ft)0.0250 0.0396 0.1145 0.2069 0.3165
Standard met with HCM?No No No No No
Post-Development CN n/a 100 98 98 98
CNadj n/a 100 98 98 98
Pre-Development CN n/a n/a 98 98 98
Groundwater Recharge Standard (Re)1
Standard Applicable?
ReV 0.0250
Standard met with Tier 1
Practices?
No
Recharge Notes:
NOTE: Treatment provided is insufficient to meet the recharge
standard within this drainage area. Add more infiltrating practices
unless recharge is being met site-wide. (check summary tab)
Flows are discharged to Permit: 3028-INDS.9
Predevelopment runoff volume (ac-ft)
Pre-routed, post development runoff volume (ac-ft)
List all Tier 1 practices below with the associated treatment volume (TV ). The T V will be applied to all treatment standards,
except for Green Roofs, which do not receive recharge or water quality credit. Please include the appropriate STP
worksheet(s) with the application.
Practice
Yes No
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Water Quality Treatment Standard (WQ)1 1
(ac-ft)Apply Reduction?
WQV - New & Existing 0.0396 0.0%
WQV - Redevelopment 0.0000 0.0%
Total WQV 0.0396
WQV met with Tier 1
practices 0.0000 1
WQV to be met with Tier 2
and/or Tier 3 practices 0.0396
WQV Provided
(ac-ft)Tier
Total WQV Provided (ac-ft)0.0000 ac-ft
Is the WQV Standard met?No
Water Quality Notes:
Channel Protection Standard (CP)1 1
Standard Applicable?
Standard Met with HCM?No
Provide Extended
Detention for:0.070 ac-ft
Warm or Cold Water
Fishery?→Provide:
FALSE
Extended Detention STP:
CNAdj 98 0.0 (Watershed
Lag Method)
Channel Protection Notes:
Flows are discharged to Permit: 3028-INDS.9
The channel protection standard has not been fully met. Either increase Tv
credit to fully meet HCM or provide extended detention.
12 hours of extended
detention
See the Vermont Water Quality Standards for warm and
cold water designations
OR
The Alternative Extended Detention
Method (§2.2.5.4) is being used.
Modeling Info: When demonstrating CP compliance with extended detention in a hydrologic model, use the CN and TC
below if the practice being modelled is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume
achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'.
Post Development TC (min)
Flows are discharged to Permit: 3028-INDS.9
NOTE: Add more water quality practices unless site balancing is being used. (Check summary tab)
% Net Reduction
% Removed Existing
Impervious (Redevelopment)
Is all impervious treated by
disconnection?
Tier 2 & 3 Water Quality Practice
Yes No
Cold
Warm
No
Yes (WQv met)
No Yes
No Yes
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Vermont Operational Stormwater Permit - Standards Compliance Workbook
Overbank Flood Protection (QP10)1
Standard Applicable?
Standard Met with HCM?No
STP used:
Pre-development peak discharge rate (cfs)
Pre-routed, post-development peak discharge rate (cfs)
Routed, post-development peak discharge rate (cfs)
Pre-Development CN (Flow-
weighted composite)98 0.0
CNAdj 98 0.0
Overbank Flood Notes:
Extreme Flood Protection (QP100)1
Standard Applicable?
Standard Met with HCM?No
STP used:
Pre-development peak discharge rate (cfs)
Pre-routed, post-development peak discharge rate (cfs)
Routed, post-development peak discharge rate (cfs)
Pre-Development CN (Flow-
weighted composite)98 0.0
CNAdj 98 0.0
Extreme Flood Notes:
Pre Development TC (min)(Watershed
Lag Method)Post Development TC (min)
Flows are discharged to Permit: 3028-INDS.9
Flows are discharged to Permit: 3028-INDS.9
The extreme standard has not been fully met. Provide additional STPs to
ensure post development peak runoff does not exceed pre development peak
runoff for the 100 yr, 24 hour storm event.
Modeling Info: When demonstrating Q P100 compliance in a hydrologic model, use the following CN and T C below, if the
practice used to meet QP100 is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume achieved
through runoff reduction practices. The T C is calculated by the watershed lag method using CN Adj as CN'.
The QP10 standard has not been fully met. Provide additional STPs to ensure
post development peak runoff does not exceed pre development peak runoff
for the 10 yr, 24 hour storm event.
Modeling Info: When demonstrating Q P10 compliance in a hydrologic model, use the following CN and T C below, if the
practice used to meet QP10 is not itself a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume
achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'.
Pre Development TC (min)(Watershed
Lag Method)Post Development TC (min)
Yes No
Yes No
Last Updated 8/28/2018
SN3: Page 4 of 4