HomeMy WebLinkAboutSP-24-08 - Supplemental - 0870 Williston Road (36)Standard Compliance Workbook Instructions
This workbook is designed to guide you through how to calculate and demonstrate compliance the standards in the 2017 Vermont State Stormwater Manual (VSMM). Before filling this workbook,
you should always refer to the Stormwater Program homepage to ensure that you are using the most recent application materials.
Vermont Stormwater Application Materials webpage
Filling out the Workbook
Blue boxes
Yellow boxes
Grey boxes
This workbook is protected so that the user can only edit blue and yellow boxes.
Workbook Tabs
This workbook is comprised of a "Summary" tab and several discharge point tabs labelled SN1, SN2, etc. Fill out one tab for each discharge point in your project. This workbook will be
supported by sizing calculations and treatment volume (TV) information completed via specific STP worksheets that must also be completed for each practice. The Summary tab provides
an overview of how the standards are met across discharge points.
This workbook is designed to work with up to nine (9) discharge points or points of interest (POI) which come preloaded. Changing Discharge Point Names: If discharge points need to be
renamed, the user must change both the label in line 5 of the summary tab AND the tab label in order for the summary tab to be able to pull data from the right sheet.
Designers working on a projects with more discharge points should contact their district reviewer. If your project contains fewer discharge points, unneeded tabs may be deleted, but
cannot be added back. It is preferrable to right-click on the tab label and selecting "hide".
If you have questions regarding the completion of the workbook, contact the stormwater program:
Stormwater Technical Reviewers
Types of Impervious
When entering impervious on the discharge point tabs, the user is presented with several options depending on the type of permit coverage that is required.
Pre Development
w Existing Impervious: Any impervious, other than impervious previously authorized under another permit that exists within the drainage area prior to the development for which permit
coverage is being sought.
w Impervious Previously Authorized under 2002 VSMM: Any impervious previously authorized under the 2002 VSMM that is not being modified by the current permit application. The workbook
will not calculate required treatment volumes for this impervious. It is included here only to maintain a record of the total impervious covered by the permit. This will automatically
transfer through to the post development totals.
Post Development
w New Impervious: Impervious created as a part of the proposed development.
w Existing Impervious for Permit Coverage: Impervious that existed prior to the proposed development that is not undergoing alteration, but for which permit coverage is being sought.
Treatment volumes will be calculated as for new development.
w Existing Impervious NOT for Permit Coverage: Impervious that existed prior to the proposed development that is not undergoign alteration and for which permit coverage is not being
sought. Treatment volumes will not include this area.
w Redeveloped Impervious: Existing impervious that will be redeveloped under the proposed development and meets the jurisdictional threshold for redevelopment. Treatment volumes for
this impervious will be calculated in accordance with the Section 2.4 in the Manual. Redevelopment within a discharge point that does meet jurisdictional threshold for redevelopment
may be included as "Existing Not for Permit Coverage" unless voluntary permit coverage is being sought.
Printing/PDF Instructions
In order to select specific tabs of this worksheet to print or save as a pdf, hold down control while clicking on the desired tabs. The summary tab and any discharge points used in the
project must be included with the permit application.
Notes
CNAdj in Tc is currently restricted to 50-95, consistent with NEH, Part 630. If the CNAdj falls outside this range, the outer bound of the range is used.
All curve numbers (CN) calculated in this workbook are flow-weighted. Pre and post-development CN are back calculated from the flow volume of the storm of interest.
must be filled out by the designer
may be filled out by the designer, but are optional
contain values calculated from the information entered in the blue boxes
0
0
0
0
0
0
Project Name
Site Summary
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.
Impervious
Recharge
Water Quality
A minimum WQV of 0.2" (P*RV) is required for sites with low impervious (<16.67%). This calculation has not been incorporated into this workbook. Designers should check that the minimum
WQV has been met for their site.
Channel Protection
Overbank Flood Protection
Extreme Flood Protection
General Notes
New
Redeveloped
Existing
Previously Authorized
Total
Site Area
Latitude
Longitude
Required
Provided
Standard met?
Notes:
Required
Provided
Standard met?
Notes:
Standard Applies?
Waiver
Method
HCV
TV Provided
Notes:
Notes:
Notes:
DoubleTree & Catamount Woods
The name above will appear on all the discharge point tabs
Total
1.82
9.35
0
0
11.17
15.98
Receiving Water
Total
3.46541666666667E-02
0.139
Yes
Total
0.58674375
0.6865
Yes
Total
9.81443190065827E-02
0.139
Standard Applies?
Pre-Dev Q (cfs)
Routed, Post-Dev Q (cfs)
Waiver
Standard Applies?
Pre-Dev Q (cfs)
Routed, Post-Dev Q (cfs)
Waiver
SN1
1.82
9.35
0
0
11.17
15.98
44.47322
-73.1838
Tributary of Centennial Brook
SN1
3.46541666666667E-02
0.139
Yes
SN1
0.58674375
0.6865
Yes
SN1
Yes
n/a
Hydrologic Condition Method
9.81443190065827E-02
0.139
SN1
Yes
15.78
9.85
n/a
SN1
No
0
0
< 10 ac impervious
SN2
0
0
0
0
0
0
0
0
SN2
0
0
n/a
SN2
0
0
n/a
SN2
0
n/a
0
0
SN2
0
SN2
SN3
0
0
0
0
0
0
0
0
SN3
0
0
n/a
SN3
0
0
n/a
SN3
0
n/a
0
0
SN3
0
SN3
SN4
0
0
0
0
0
0
0
0
SN4
0
0
n/a
SN4
0
0
n/a
SN4
0
n/a
0
0
SN4
0
SN4
SN5
0
0
0
0
0
0
0
0
SN5
0
0
n/a
SN5
0
0
n/a
SN5
0
n/a
0
0
SN5
0
SN5
SN6
0
0
0
0
0
0
0
0
SN6
0
0
n/a
SN6
0
0
n/a
SN6
0
n/a
0
0
SN6
0
SN6
SN7
0
0
0
0
0
0
0
0
SN7
0
0
n/a
SN7
0
0
n/a
SN7
0
n/a
0
0
SN7
0
SN7
SN8
0
0
0
0
0
0
0
0
SN8
0
0
n/a
SN8
0
0
n/a
SN8
0
n/a
0
0
SN8
0
SN8
SN9
0
0
0
0
0
0
0
0
SN9
0
0
n/a
SN9
0
0
n/a
SN9
0
n/a
0
0
SN9
0
SN9
General Discharge Point Information
Precipitation Data
Storm
Precipitation (inches)
Drainage Area Information
Pre Development Land Use (acres)
Landuse
Grass
Meadow
Woods
Existing Impervious
Post Development Land Use (acres)
Landuse
Grass
Meadow
Woods
New Impervious
Existing for Permit Coverage (Treated to New Standards)
Information for Calculating TC by the Watershed Lag Method
Runoff Calculations
Predevelopment runoff volume (ac-ft)
Pre-routed, post development runoff volume (ac-ft)
Tier 1/Runoff Reduction Practices
List all Tier 1 practices below with the associated treatment volume (TV). The TV 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
Infiltration Chambers
Runoff Reduction Calculations
Standard
TV Required (ac-ft)
TV Provided (ac-ft)
TV Remaining (ac-ft)
Standard met with HCM?
Post-Development CN
CNadj
Pre-Development CN
Groundwater Recharge Standard (Re)
Standard Applicable?
ReV
Standard met with Tier 1 Practices?
Recharge Notes:
Water Quality Treatment Standard (WQ)
WQV - New & Existing
WQV - Redevelopment
Total WQV
WQV met with Tier 1 practices
WQV to be met with Tier 2 and/or Tier 3 practices
NOTE: Please include a copy of the appropriate STP worksheet(s) with the application.
Water Quality Notes:
Channel Protection Standard (CP)
Standard Applicable?
Standard Met with HCM?
Provide Extended Detention for:
Warm or Cold Water Fishery?
See the Vermont Water Quality Standards for warm and cold water designations
Extended Detention STP:
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 CNAdj
takes into account the reduction in runoff volume achieved through Tier 1 practices. The TC is calculated by the watershed lag method using CNAdj as CN'.
CNAdj
Channel Protection Notes:
Overbank Flood Protection (QP10)
Standard Applicable?
Standard Met with HCM?
STP used:
Modeling Info: When demonstrating QP10 compliance in a hydrologic model, use the following CN and TC below, if the practice used to meet QP10 is not itself a Tier 1 practice. The CNAdj
takes into account the reduction in runoff volume achieved through Tier 1 practices. The TC is calculated by the watershed lag method using CNAdj as CN'.
Pre-Development CN (Flow-weighted composite)
CNAdj
Overbank Flood Notes:
Extreme Flood Protection (QP100)
Standard Applicable?
Standard Met with HCM?
STP used:
Modeling Info: When demonstrating QP100 compliance in a hydrologic model, use the following CN and TC below, if the practice used to meet QP100 is not a Tier 1 practice. The CNAdj takes
into account the reduction in runoff volume achieved through runoff reduction practices. The TC is calculated by the watershed lag method using CNAdj as CN'.
Pre-Development CN (Flow-weighted composite)
CNAdj
Extreme Flood Notes:
* Preciptation values shall be obtained from
WQ Storm
1
A
1.49
0
0.689
3.765
A
1.984
0
0
0.449
0
Impervious previously authorized under 2002 VSMM
TV (ac-ft)
0.139
Re
3.46541666666667E-02
0.139
0
Yes
n/a
n/a
n/a
3.46541666666667E-02
Yes
(ac-ft)
0.2028375
0.38390625
0.58674375
0.139
0.44774375
Tier 2 & 3 Water Quality Practice
Gravel Wetland
Gravel Wetland
Yes
n/a
Gravel Wetland
n/a
No
Gravel Wetland
90.0711243423881
90.2528657981124
No
88.0653105907724
88.7327276153761
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)
1 yr, 24 hr
1.87
B
0.103
0
0.281
0.89
B
0.183
0
0
0.257
0
Practice
WQ
0.58674375
0.139
0.44774375
No
92.8072287289779
90.4243085676119
n/a
% Net Reduction
% Removed Existing Impervious (Redevelopment)
The channel protection standard has been fully met with hydrologic condition method. Additional treatment of the 1 year storm is not required.
ac-ft
→
Post Development TC (min)
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.
Pre-development peak discharge rate (cfs)
Pre-routed, post-development peak discharge rate (cfs)
Routed, post-development peak discharge rate (cfs)
Pre Development TC (min)
Post Development TC (min)
Waiver (if No is selected):
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.
Pre-development peak discharge rate (cfs)
Pre-routed, post-development peak discharge rate (cfs)
Routed, post-development peak discharge rate (cfs)
Pre Development TC (min)
Post Development TC (min)
DoubleTree & Catamount Woods
1
Tributary of Centennial Brook
44.47322
-73.1838
10 yr, 24 hr
3.2
C
0.603
0
0.226
3.632
C
0.736
0
0
0.226
0
Pre Development
Post Development
1 yr, 24-hr
1.52881979838357
1.62696411739015
CP
9.81443190065827E-02
0.139
0
Yes
93.3371298055909
n/a
92.3704920177458
Is all impervious treated by disconnection?
Total WQV Provided (ac-ft)
Is the WQV Standard met?
Provide:
15.78
54.1
9.85
NOAA Atlas 14
100 yr, 24 hr
4.78
D
1.228
0
0.918
2.15
Impervious previously authorized under 2002 VSMM (not included in calculations)
Total Pre Site Area
D
1.905
0
0
0.885
0
Existing Impervious Not for Permit Coverage
Redeveloped Impervious
Total Site Area
Total Impervious for Permit Coverage
Net Reduced Impervious
Reduced Existing Impervious (for redevelopment)
Average Catchment Slope, Y (%)
0.0765
0.0765
10 yr, 24-hr
2.89532112945369
3.05579797928954
TV (ac-ft)
QP10
0.16047684983585
0.139
2.14768498358502E-02
No
91.406072453482
90.2528657981124
90.0711243423881
1
0
0.104148701734215
WQV Provided (ac-ft)
0.5116
0.0359
0.5475
Yes
2
24 hours of extended detention
OR
The Alternative Extended Detention Method (§2.2.5.4) is being used.
41.2763261174672
74.8935174574042
51.2615168244268
<10 acres impervious
81.0910945427002
54.4930517259543
Total
3.424
0
2.114
10.437
0
15.975
Total
4.808
0
0
1.817
0
0
9.35
0
15.975
11.167
0
1.087
Hydraulic Length, l (ft)
915
575
100 yr, 24-hr
4.61536128749334
4.84422192894454
QP100
0.228860641451192
0.139
8.98606414511918E-02
No
89.7523765882553
88.7327276153761
88.0653105907724
1
1
Apply Reduction?
Tier
Tier 2
Tier 2
ac-ft
1
(Watershed Lag Method)
1
(Watershed Lag Method)
2
(Watershed Lag Method)
%
0.113740219092332
0
0
0.58528951486698
0
0.104148701734215
1
False
Curve Numbers
Landuse
Grass
Meadow
Woods
Gravel/ Unpaved Roads
Pavement, Roofs, and other impervious
S=1000/CN - 10
Landuse
Grass
Meadow
Woods
Gravel/ Unpaved Roads
Pavement, Roofs, and other impervious (not gravel)
Recharge Factors
Hydrologic Soil Group
Recharge Factor
Simple Disconnection Required Treatment Length
HSG
A/B
C/D
Disconnection to filter strips and vegetated buffers - Required Treatment Lengths
HSG
A/B
C/D
Hydrologic Soil Group
A
39
30
30
96
98
Hydrologic Soil Group
A
15.6410256410256
23.3333333333333
23.3333333333333
0.416666666666666
0.204081632653061
A
0.6
Disconnection Slope
<8%
35
65
Disconnection Slope
<4%
35
65
B
61
58
55
96
98
B
6.39344262295082
7.24137931034483
8.18181818181818
0.416666666666666
0.204081632653061
B
0.35
8-15%
50
85
4-6%
50
85
C
74
71
70
96
98
C
3.51351351351351
4.08450704225352
4.28571428571429
0.416666666666666
0.204081632653061
C
0.25
6-8%
65
105
D
80
78
77
96
98
D
2.5
2.82051282051282
2.98701298701299
0.416666666666666
0.204081632653061
D
0
Waivers
Recharge Waivers
All Redevelopment
HSG D Soils
Hotspot land use
STPs
Tier 1/Runoff Reduction Practices
Reforestation
Simple Disconnection
Disconnection to FS/VB
Bioretention (infiltrating)
Dry Swales (infiltrating)
Infiltration Basin
Infiltration Chambers
Infiltration Trench
Drywell(s)
Filters (infiltrating)
Permeable Pavement
Rainwater Harvesting
Green Roofs
Reduced Impervious
Re-development
Net Reduction
CPv
All Redevelopment
Direct discharge to drainage area ≥10 sq.mi
<2 cfs pre-routed, post development 1 yr discharge
Net Reduction
Tier 2 & 3 WQ Practices
STP
Bioretention (not designed to infiltrate)
Filter (not designed to infiltrate)
Dry Swale (not designed to infiltrate)
Wet Pond
Shallow Surface Wetland
Gravel Wetland
Alternative Treatment Practice
Minimum WQ depth
Yes
No
QP10
All Redevelopment
Direct discharge to drainage area ≥10 sq.mi
<2 cfs pre-routed, post development 10 yr discharge
Downstream analysis
Net Reduction
Tier
Tier 2
Tier 3
Tier 3
Tier 3
Tier 3
Tier 2
Justification Required
QP100
All Redevelopment
<10 acres impervious
Direct discharge to drainage area ≥10 sq.mi
Net Reduction
Downstream analysis
Extended Detention Practices
Wet Pond
Shallow Surface Wetland
Gravel Wetland
Dry Pond
Subsurface Detention
Waiver Name
All Redevelopment
<10 acres impervious
Direct discharge to drainage area ≥10 sq.mi
Net Reduction
Downstream analysis
<2 cfs pre-routed, post development 10 yr discharge
<2 cfs pre-routed, post development 1 yr discharge
Short Name
n/a
Re-dev
< 10 ac impervious
≥10 sq mi
Net Reduction
Down-stream Analysis
<2 cfs
<2cfs