Mountain Top Inn Chittenden, VT Stormwater Management … · 2016-04-22 · Chittenden, VT...

Mountain Top Inn

Chittenden, VT

Stormwater Management System

Worksheets and Basis of Design

General Permit 3-9015

March 6, 2015

Revised April 22, 2016

Index

Pre & Post-Development Drainage Areas

Peak Flows

Water Quality Volume Worksheet - Subarea 1

Recharge Volume Worksheet - Subarea 1





Water Quality Volume Worksheet - Subarea 4A

Recharge Volume Worksheet - Subarea 4A

Water Quality Volume Worksheet - Subarea 4B

Recharge Volume Worksheet - Subarea 4B

5 Treatment Criteria Design - Subarea 1




Dry Swale Worksheet - Dry Swale 1




Dry Pond Worksheet - Dry Swale 1




Appendix A: HydroCAD Calculations

of 48

The Annex Long Trail Engineering, P.C.

Mountain Top Inn Job No. 0807.2

Chittenden, VT Copyright 2016

Pre & Post-Development Drainage Areas March 6, 2015

Revised: April 22, 2016

Pre-Development Areas

S/N 001

Areas

Subarea Soil Class sq. ft. sq. mi. ac.

1A Project Area C 31,886 0.0011 0.73

(Parking Imp Existing 17,123 0.0006 0.39

Lot) 49,009 0.0018 1.13

Start End Slope

Watercourse Lengths & Slopes Length (ft) Elev (ft) Elev (ft) (ft/ft)

Sheet 60 1786 1782 0.067

Areas


1 Project Area C 57,767 0.0021 1.33

(East Imp Existing 8,354 0.0003 0.19

Meadow) 66,121 0.0024 1.52

Start End Slope


Sheet 100 1768 1756 0.120

Ditch 680 1756 1690 0.097

Channel Details (Roadside)

Bott. Width (ft) 1 Side (ft) 1.1

Top Width (ft) 2 P (ft) 3.2

Depth (ft) 1 A (sf) 1.5


2 B 63,019 0.0023 1.45

C 13,597 0.0005 0.31

Imp Existing 2,441 0.0001 0.06

79,057 0.0028 1.81

Start End Slope


Sheet 100 1618 1614 0.040

Shallow 200 1614 1602 0.060

Note: Expanded western parking lot (constructed 2011) considered to be a pervious surface for pre-

development calculations.

Pre and Post Areas of 48






Areas


3 Project Area B 24,362 0.0009 0.56

Imp Existing 961 0.0000 0.02

25,323 0.0009 0.58

Start End Slope


Sheet 50 1596 1590 0.120

Areas


4A Project Area B 11,538 0.0004 0.26

C 81,547 0.0029 1.87

93,085 0.0033 2.14

Start End Slope


Sheet 120 1608 1600 0.067

Areas


4B Project Area B 33,705 0.0012 0.77

C 17,575 0.0006 0.40

51,280 0.0018 1.18

Start End Slope


Sheet 70 1602 1594 0.114

Sheet 15 1594 1584 0.667







Post-Development Areas

S/N 001

Areas


1A Project Area C 16,034 0.0006 0.37

Imp Existing (1) 14,234 0.0005 0.33

Imp Existing (2) 2,889 0.0001 0.07

Imp Existing (3) 15,852 0.0006 0.36

Imp Proposed (4) 0 0.0000 0.00

49,009 0.0018 1.13

(1) Existing area to be treated, counting towards site balancing

(2) Existing area to be treated, NOT counting towards site balancing

(3) Expanded western parking lot area, constructed 2011

(4) Proposed impervious, Annex project

Start End Slope


Sheet 84 1790 1782 0.095

Ditch 250 1782 1778 0.016

18" Culvert 55 1778 1776 0.036

Areas


1 Project Area C 52,239 0.0019 1.20

Imp Existing (1) 6,727 0.0002 0.15

Imp Existing (2) 1,627 0.0001 0.04

Imp Existing (3) 0 0.0000 0.00

Imp Proposed (4) 5,528 0.0002 0.13

66,121 0.0024 1.52


(2) Existing area to be treated, NOT counting towards site balancing

(3) Expanded western parking lot area

(4) Proposed impervious, Annex project







Start End Slope


Sheet 100 1762 1752 0.100

Channel 670 1752 1690 0.093

Dry Swale 130 1690 1685.5 0.035




Depth (ft) 2 A (sf) 12

Channel Details (Dry Swale)




2 Project Area B 62,029 0.0022 1.42

C 12,692 0.0005 0.29

Imp Existing (1) 2,441 0.0001 0.06

Imp Proposed 1,895 0.0001 0.04

79,057 0.0028 1.81


Start End Slope


Sheet 80 1625 1621 0.020

Channel 360 1621 1602 0.053

Dry Swale 210 1602 1597.5 0.021















3 Project Area B 15,858 0.0006 0.36

Imp Existing (1) 961 0.0000 0.02

Imp Proposed 8,504 0.0003 0.20

25,323 0.0009 0.58


Start End Slope


Sheet 25 1596 1588 0.32

Channel 410 1588 1580 0.020

Channel Details




4A Project Area B 8,632 0.0003 0.20

C 47,979 0.0017 1.10

Imp Proposed 36,474 0.0013 0.84

93,085 0.0033 2.14

Start End Slope


Sheet 130 1601 1598 0.020

Channel 1 158 1598 1596 0.013

Channel 2 150 1596 1590 0.040

Channel 3 51 1590 1588 0.039

18" Culvert 290 1588 1578 0.034









Channel Details










4B Project Area B 27,205 0.0010 0.62

C 17,575 0.0006 0.40

Imp Proposed 6,500 0.0002 0.15

1.18

Start End Slope


Sheet 45 1601 1600 0.022

40 1600 1580 0.500





Peak Flows March 6, 2015


Subarea 1A

Pre-Development Post-Development

Storm Peak Flow t(c) Peak Flow t(c)

Event (cfs) (hrs) (cfs) (hrs)

1 1.7 0.01 2.9 0.01

10 4.1 0.01 5.6 0.01

100 8.2 0.01 9.8 0.01

Subarea 1




1 1.2 0.11 1.6 0.09

10 3.6 0.11 4.2 0.09

100 8.1 0.11 9.0 0.09

Subareas 1A & 1

Pre-Development Post-Development Post-Detention

Storm Peak Flow t(c) Peak Flow t(c) Peak Flow t(c)

Event (cfs) (hrs) (cfs) (hrs) (cfs) (hrs)

1 2.9 --- 4.5 --- 0.09 ---

10 7.7 --- 9.8 --- 4.3 ---

100 16.3 --- 18.8 --- 15.8 ---

Subarea 2




1 0.14 0.34 0.18 0.33 0.01 ---

10 1.3 0.34 1.4 0.33 0.6 ---

100 4.1 0.34 4.3 0.33 3.2 ---

Subarea 3




1 0.04 0.11 1.10 0.02 0.05 ---

10 0.6 0.11 2.4 0.02 0.5 ---

100 1.9 0.11 4.5 0.02 3.6 ---

Subarea 4A




1 1.19 0.02 7.26 0.03

10 4.5 0.02 14.6 0.03

100 11.3 0.02 26.3 0.03

Peak Flows of 48




Peak Flows March 6, 2015


Subarea 4B




1 0.28 0.16 0.66 0.12

10 1.5 0.16 2.3 0.12

100 4.2 0.16 5.5 0.12

Subareas 4A & 4B

Pre-Development Total Post-Development Post-Detention



1 1.5 --- 7.9 --- 0.16 ---

10 6.0 --- 16.9 --- 4.1 ---

100 15.5 --- 31.9 --- 24.2 ---

Peak Flows of 48




Water Quality Volume March 6, 2015


Page 1 of 2

Version: 9/06 For the area draining to*:

Located in drainage area for S/N: 001

WQ Volume and Modified Curve Number Calculation for Water Quality Treatment in Flow-Based Practice

Water Quality Volume Calculations

Line value/calculation units

1 Area draining to practice A= 2.64 acres

2 Impervious area 1.08 acres

3 Percent Impervious Area = [(line 2/line 1) * 100] = I = 40.70 % (whole #)

4 Precipitation P = 0.9 inches

5 Runoff coefficient calculation = (0.05 + (0.009*I)) Rv = 0.416

6 WQ Volume (in watershed inches) Calculation =( P * Rv) = 0.375 Qa (watershed inches, a.k.a. inches of runoff)

7 Minimum WQ Volume10.2 watershed inches

8 Enter the greater of line 6 or line 7 WQv = 0.375 watershed inches

9 WQ Volume Calculation = (line 8 *A)/12 = WQv = 0.083 ac. ft.

10 WQ Volume Calculation = (line 9 * 43560) = WQv = 3595 cu. ft.

Subarea 1 (Includes Subarea 1A)

Use this worksheet to calculate your WQv if you need to determine the Peak Q for the WQ storm (i.e. designing a grass channel, flow-splitter or other flow

based practice) and you are not using any of the site design credits in section 3 of the 2002 VSWMM. See page 2 for "Calculating Peak WQ Discharge

Rate (0.9" storm) using the Modified Curve Number." Please note that in the case of grass channels you must include any off-site area draining to the

practice as this will affect the peak discharge rate which will ultimately affect the hydraulics, and thus residence time, in your channel.

WQv Subarea 1 of 48

Notes:

Page 2 of 2



Steps:

1. Transfer information from WQv calculation worksheets.

Enter the Qa ( line 8 from WQv sheet )

Qa = 0.375 inches

Enter the area (site +off-site draining to practice) used in calculating the percent impervious (I)

A = 2.6 acres

2. Use the following equation to calculate a corresponding curve number

where P = 0.9 inches

CN = 1000/(10 +(5*P)+(10*Qa) - (10*(Qa^2 + (1.25*Qa*P))^0.5))

CN = 93.0

Above, you should have calculated the WQv in watershed inches draining to the facility/practice for which you need to calculate the WQ-

peak discharge. As provided in the guidance listed on the grass channel worksheet, please remember that the WQv calculation should include

runoff from on-site as well as off-site area draining to the grass channel since this will have an impact on the channel hydraulics and thus the

velocity and residence time.

1: Sites with low impervious cover ( ~19%) but that do not employ a significant use of the stormwater design credits in Section 3 of the VSWMM are

required to treat the minimum water quality volume of 0.2 watershed inches. Sites that have a significant portion of their impervious cover addressed via

the stormwater credits (section 3 of the VSWMM) will be able to reduce this WQv and will only be required to treat the volume calculated on the "WQ

Volume (with credit reduction)" worksheet which will be less than the 0.2 watershed inches.

Subarea 1 (Includes Subarea 1A)

Calculating Peak WQ Peak Discharge Rate (0.9" storm) using the Modified Curve Number

Because NRCS methods underestimate the peak discharge for rainfall events of less than 2", simply plugging in 0.9" of rainfall into your

hydrologic model with the standard curve numbers will not produce the correct peak discharge during the WQv storm, nor will it produce a

volume of runoff equivalent to that which you have calculated using the WQv formula (WQv = P*Rv*A/12). In order to calculate the peak

discharge for the 0.9" storm, a modified curve number must be calculated. This modified curve number is based on the runoff (in inches)

calculated using the short cut method formula (WQv = P*Rv) that is also the basis of the familiar WQv calculations provided in the 2002

VSWMM (and on the WQv calculation worksheets). Essentially, the curve number that is calculated using the methods below is the curve

number that will generate the volume of runoff calculated using the WQv formula.

WQv Subarea 1 of 48




Recharge March 6, 2015




Site Information value/calculation units

Site Area (impervious + disturbed pervious) A= 2.64 acres

Impervious area 1.08 acres

Percent Impervious Area = [(line 2/line 1)] = I = 0.41 % (decimal percent)

Composite Recharge Factor Calculation

Enter site acreage of each HSG draining to POI or S/N value/calculation

HSG A acres

HSG B acres

HSG C 2.64 acres

HSG D acres

Total Site Area 2.643

Composite Recharge Factor 0.100

0.009 acre feet

390 cubic feet

0.108 acres

4,686 square feet

Subarea 1

Groundwater Recharge Treatment Standard - Calculation & Waiver Worksheet

The average annual groundwater recharge rate for the prevailing hydrologic soil group(s) (HSG) must be maintained in order to preserve existing water table elevations.

Recharge is determined as a function of annual predevelopment recharge for a given HSG, the average annual rainfall and the amount of impervious surface at the site. The

Groundwater Recharge Treatment Standard can be met by using one or both of the following methods: volume method and/or percent area method. See Table 2.2 in the

VSMM - Volume I for a list of acceptable STPs or credits that satisfy this requirement. Use NRCS's Web Soil Survey to obtain specific soil data at your site, available at:

http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm

ReV (Percent Volume Method)

The percent volume method is commonly used to meet recharge. Designers must demonstrate that a proposed STP

allows at least the Rev to enter the ground. The Rev is contained within the WQv. So, if a practice is infiltrating the

entire WQv, then Rev is automatically met. Please use the applicable STP worksheets to verify the Groundwater

Recharge Treatment Standard has been met. Note that not all STPs can be used to meet this standard.

ReA (Percent Area Method)

The percent area method is used when meeting recharge via nonstructural design credits(disconnection of

rooftop/non-rooftop surfaces, stream buffer, grass channel credit, or ESRD). In this case, the designer must

demonstrate that stormwater runoff from a portion of the new impervious area, equivalent to the area calculated

under the percent area method, drains into a nonstructural design credit practice.

Additional notes:

*Recharge is one of the unified sizing criteria that can be achieved site wide, rather than at each point of interest (POI) or discharge point (S/N), assuming the receiving water

is the same for each discharge point.

Re Subarea 1 of 48

http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm?TARGET_APP=Web_Soil_Survey_application_e5jsjr3bms3z4t45guzh0ybz






Page 1 of 2
















Subarea 2





WQv Subarea 2 of 48

Notes:

Page 2 of 2



Steps:



Qa = 0.200 inches


A = 1.8 acres



CN = 1000/(10 +(5*P)+(10*Qa) - (10*(Qa^2 + (1.25*Qa*P))^0.5))

CN = 88.1









Subarea 2









WQv Subarea 2 of 48














HSG A acres

HSG B 1.45 acres

HSG C 0.31 acres

HSG D acres



0.002 acre feet

78 cubic feet

0.022 acres

939 square feetReA (Percent Area Method)





Additional notes:



Subarea 2












Re Subarea 2 of 48







Page 1 of 2
















Subarea 3





WQv Subarea 3 of 48

Notes:

Page 2 of 2



Steps:



Qa = 0.348 inches


A = 0.6 acres



CN = 1000/(10 +(5*P)+(10*Qa) - (10*(Qa^2 + (1.25*Qa*P))^0.5))

CN = 92.4









Subarea 3









WQv Subarea 3 of 48














HSG A acres

HSG B 0.58 acres

HSG C acres

HSG D acres



0.005 acre feet

197 cubic feet

0.054 acres

2366 square feet

Subarea 3

















Additional notes:



Re Subarea 3 of 48







Page 1 of 2
















Subarea 4A





WQv Subarea 4A of 48

Notes:

Page 2 of 2



Steps:



Qa = 0.362 inches


A = 2.1 acres



CN = 1000/(10 +(5*P)+(10*Qa) - (10*(Qa^2 + (1.25*Qa*P))^0.5))

CN = 92.7









Subarea 4A









WQv Subarea 4A of 48














HSG A acres

HSG B 0.26 acres

HSG C 1.87 acres

HSG D acres



0.008 acre feet

360 cubic feet

0.099 acres

4326 square feet

Subarea 4A

















Additional notes:



Re Subarea 4A of 48







Version: 9/06 (calcs embedded) For the area draining to*:


WQ Volume calculation (with credit reduction) for Volume Based Practice

Line Base values value/calculation units

1 Site Area (impervious + disturbed pervious) 1.18 acres note 1



Impervious Area Reductions

Rooftop disconnection

Completed credit sheet yes / no

4 Enter roof-top area disconnected 0.11 acres

Non-rooftop disconnection

Completed credit sheet yes/no

5 Enter non-rooftop area disconnected 0.04 acres

6 Total impervious area disconnected (line 4 + line 5) 0.15 acres

7 New impervious area total (line 2 - line 6) 0.00 acres

8 Percent Impervious = [(line 7 line 1) * 100] I = 0.00 %

Subarea 4B

Use this worksheet to calculate the water quality volume draining to your volume based (i.e. not a grass channel) STP if you are not using any of the site

design credits in section 3 of the 2002 VSWMM. Do not use this worksheet to calculate your WQv if you need to determine the Peak Q for the WQ storm

(i.e. designing a grass channel, flow-splitter or other flow based practice). See the worksheet "Water Quality Volume and Modified Curve Number Calculation

(with credit reduction) for Water Quality Treatment in Flow-Based Practice."

WQv Subarea 4B of 48

Site Area Reductions

Stream Buffer Credit


9 Enter area draining to a stream buffer acres note 2

Grass Channel Credit


10 Enter site area draining to grass channels acres

Natural Area Conservation Credit


11 Natural Area to be conserved (in the drainage to this S/N) acres

12 Total Site Area Reductions (line 9 + line 10 + line 11) 0.0 acres

13 New site area total ( line 1 - line 12) A = 1.2 acres

Runoff coefficient calculation = (0.05 + (0.009*I)) Rv = 0.050

14 Water Quality Volume Calculation = (P*Rv) WQv = 0.045 Qa (watershed inches or inches of runoff)

15 Water Quality Volume Calculation [(line 14* line 13)/12] WQv = 0.0000 ac. ft SEE BOLD NOTE BELOW

16 Water Quality Volume Calculation = line 15 *43560 WQv = 0 cu. ft.

Note 1: In most situations, site area = disturbed area (i.e. impervious + disturbed pervious for the project). If using the Natural Area Conservation Credit, the Site Area =

(disturbed area + area to be conserved).

Note 2: If using rooftop/ non-rooftop disconnection, credit can only be taken for the pervious area draining to the stream buffer

Addt'l notes: If all impervious has been disconnected and the percent impervious is thus zero (0 %) then WQv and Recharge are assumed to have been met and WQv = 0.

If significant use of site design credits has been employed, the designer may treat the reduced WQv and is not required to treat the minimum water quality volume of 0.2

watershed inches.

WQv Subarea 4B of 48














HSG A acres

HSG B 0.77 acres

HSG C 0.40 acres

HSG D acres



0.002 acre feet

108 cubic feet

0.030 acres

1291 square feet

Subarea 4B

















Additional notes:



Re Subarea 4B of 48





5 Treatment Criteria Design - Subarea 1 March 6, 2015


Five Sizing Criteria

Water Quality, WQ(v) See Below & WQv Worksheet

Recharge Volume, Re(v) See Below & Re Worksheet

Channel Protection, Cp(v) See Below

Overbank Flood, Qp(10) See Below

Extreme Flood, Qp(100) Waived Less than 10 acres of impervious surface

Water Quality Treatment

Subarea 1

WQ(v) treatment provided by Dry Swale 1

Wq(v) 3,595 cf

Compute minimum surface area of swale

A(f), surface area required = WQv*d(f)/[k*(h(f) +d(f))*t(f)]

d(f), filter bed depth 1 ft

k (permeability coefficient 3.5 (sand)

h(f), average height above filter bed 0.19 ft (from HydroCAD)

t(f), design drain time 1.67 days (40 hours)

WQ(v) 3,595 cf

A(f) 517 sf

Dry Swale width 4 ft

Minimum Dry Swale length 129

Swale Length provided 130

Dry Swale provides sufficient surface area.

Cp(v)

Calculated maximum velocity 3.3 fps

Maximum non-erosive velocity 5.0 fps (per Table D-5, VSMM)

Note: channel will be lined with tall fescue or Kentucky bluegrass

Qp(10)

Calculated flow depth 0.4 ft

Required freeboard 0.5 ft

Total depth required 0.9 ft

Channel depth provided 2.0 ft

Area 1 Five Treatment Criteria of 48






Recharge Treatment

Subarea 1

Re(v) treatment provided by Dry Swale 1

Cp(v), Qp10 Treatment

Cp(v), Qp(10) treatment provided by Dry Pond 1

Basin Bottom Elevation 1683.5 ft

Cp(v) Elevation 1685.3 ft

Qp(10) Elevation 1685.8 ft


Top of Embankment 1686.0 ft

Cp(v) Controlled Release

From HydroCAD Modeling

Cp(v) Provided 5,379 cf


Cp(v), Predevelopment 2.9 cfs

Cp(v), Postdevelopment 4.5 cfs

Qp(v), Post Attenuation 0.09 cfs

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

1683.0 1684.0 1685.0 1686.0

Po

nd

Sto

rag

e (

cf)

Elevation (ft)

Dry Pond 1 Storage - Stage Curve







Qp(10) Controlled Release


Qp(10) Provided 7,375 cf


Qp(10), Predevelopment 7.7 cfs

Qp(10), Postdevelopment 9.8 cfs

Qp(10), Post Attenuation 4.3 cfs














Subarea 2


Wq(v) 1,318 cf


A(f), surface area required = WQv*d(f)/[k*(h(f) +d(f))*t(f)





WQ(v) 1,318 cf

A(f) 211 sf





Cp(v)




Qp(10)











Recharge Treatment

Subarea 1



Cp(v), Qp(10) treatment provided by Dry Pond 1








Cp(v) Provided 774 cf





0

2,000

4,000

6,000

8,000

10,000

12,000

1596.0 1597.0 1598.0

Po

nd

Sto

rag

e (

cf)

Elevation (ft)















Subarea 3


Wq(v) 734 cf







WQ(v) 734 cf

A(f) 114 sf





Cp(v)




Qp(10)











Recharge Treatment

Subareas 3



Cp(v), Qp(10) treatment provided by ponding in lower portion of Dry Swale 3






Note: Refer to HydroCad modeling. Infiltration pond has no outfall for Cp(v), Qp(10) & Qp(100) rainfall events



Cp(v) Provided 952 cf




Qp(v), Post Attenuation 0.05 cfs (Note: the minimum orifice size of 1" is used; can not reduce

orifice size to reduce flows any further)

0

500

1,000

1,500

2,000

2,500

3,000

3,500

1578.0 1579.0 1580.0 1581.0 1582.0

Po

nd

Sto

rag

e (

cf)

Elevation (ft)

Infiltration Pond Storage - Stage Curve













Qp(10), Post Attenuation 0.46 cfs (100% infiltration)














Subarea 4A


Wq(v) 2,811 cf







WQ(v) 2,811 cf

A(f) 382 sf





Cp(v)

Calculated maximum velocity 4.9 fps (Upper Dry Swale)



Qp(10)

Calculated flow depth 0.94 ft (Upper Dry Swale)




Subarea 4B

WQ(v) treatment provided by Rooftop & Non-Rooftop Disconnections

Area 4 Five Treatment Criteria) of 48






Recharge Treatment

Subarea 4A


Subarea 4A

Re(v) treatment provided by Rooftop & Non-Rooftop Disconnection


Cp(v), Qp(10) treatment provided by Dry Pond






Note: Refer to HydroCad modeling. Infiltration pond has no outfall for Cp(v), Qp(10) & Qp(100) rainfall events



Cp(v) Provided 9,668 cf





0

5,000

10,000

15,000

20,000

25,000

1578.0 1579.0 1580.0

Po

nd

Sto

rag

e (

cf)

Elevation (ft)






Dry Swale 1 March 6, 2015


Project Name:

Discharge Point:

Line

Indicate the treatment standards met for the site area draining to this practice:

1 WQv x

2 Rev x

3 Cpv

4 Qp10 Dry swales are not typically appropriate to provide Cpv, Qp10 or Qp100 except under ideal conditions.

5 Qp100

6

Response Attachment location

7 yes


8 yes See Basis of Design





12 yes

Channel Width (Feet)

13 4







19


20 yes Underdrain increased to 6" diam.

Page 2

2112 hours for cold water

24 hours for warm water


22 yes / no

Version: 4/10 The Annex at Mountain Top Inn

S/N 001

Dry Swale (O-1)

Dry Swale #1

Treatment Standards

This practice automatically meets Rev if you have met the WQv treatment standards

{

Water Quality Volume (WQv) WQv (Cubic Feet)

Provide the WQv for the site area draining to this swale (from WQv worksheets) 3595

Feasibility (2.7.5.A)

Is the maximum longitudinal slope of the swale 4% or less?

Conveyance (2.7.5.B)

Is the peak velocity for the 1-year storm non-erosive?

Are the design side slopes less than or equal to the 2:1 maximum?

Does the practice safely convey the 10-year storm with a minimum of 6 inches of freeboard?

Has the swale been designed with an underdrain system?

Pretreatment (2.7.5.C)

Has pre-treatment been provided for non-rooftop runoff?

Treatment (2.7.5.D)

What is the bottom width of the channel? (no greater than 8 feet, but no less than 2 feet)

Is the swale designed to accommodate a portion of the WQv through surface ponding?

Is the swale bottom designed to drain the WQv in less than 40 hours?

Does the swale design release the WQv over a minimum of 30 minutes?

Is the average head (height of water above the bottom of the swale) below 12 inches?

Does the soil media meet the open vegetated swale specifications?

What infiltration rate (if any) is used for exfiltration (in/hour)?

Cold Climate Design Considerations (2.7.5.G)

Have the potential impacts of Vermont's severe winter climate been addressed in your design?

Dry Swale: Cpv, Qp10 and Qp100 NOT APPLICABLE

Channel Protection Treatment Standard (Cpv) Response

Check which detention time standard must be used, based on the fisheries designation of the

receiving water:

Did you use the Storage Volume Estimation Method? If yes, skip to Line 26.*

Dry Swale 1 of 48






23

24

25


26 yes / no


27 yes / no

*Please review the guidance sheet "Channel Protection Storage Volume Estimation" and attach the specified information. This method is not

appropriate if more than a one subwatershed drains to the practice. Using the center of mass detention time calculated by a hydrologic model

that accounts for pond routing is the preferred method.

What storage volume (cubic feet) necessary to meet the Channel Protection Standard?

What is the calculated average release rate (cfs)?

What is the controlled peak release rate (cfs) during the 1-year storm as indicated by the model?

Overbank Flood Protection Treatment Standard (Qp10)

Have you demonstrated that Qp10 post is less than or equal to Qp10 pre at the discharge point?*

*Please include runoff and routing calculations of the 10-year storm event.

Extreme Flood Protection Treatment Standard (Qp100)



A dry swale is a volume-based treatment channel. Check dams, weirs or coir logs are encouraged to promote ponding. Convey larger storms through

overflow weirs or outlet control structures. See VSMM-Vol. II, Appendix D7 for guidance about maintaining non-erosive conditions.

Attachment location: Please indicate the specific location (i.e. appendix, page, plan sheet) where the requisite support documentation has been provided within the application.

Dry Swale 1 of 48






Project Name:

Discharge Point:

Line


1 WQv x

2 Rev x

3 Cpv


5 Qp100

6


7 yes







12 yes


13 4







19



Page 2




22 yes / noDid you use the Storage Volume Estimation Method? If yes, skip to Line 26.*



receiving water:












Treatment (2.7.5.D)










Treatment Standards


{



S/N 001

Dry Swale (O-1)

Dry Swale #2

Dry Swale 2 of 48






23

24

25


26 yes / no


27 yes / no
















Dry Swale 2 of 48






Project Name:

Discharge Point:

Line


1 WQv x

2 Rev x

3 Cpv


5 Qp100

6


7 yes







12 yes


13 4







19



Page 2







receiving water:












Treatment (2.7.5.D)










Treatment Standards


{



S/N 001

Dry Swale (O-1)

Dry Swale #3

Dry Swale 3 of 48






23

24

25


26 yes / no


27 yes / no
















Dry Swale 3 of 48






Project Name:

Discharge Point:

Line


1 WQv x

2 Rev x

3 Cpv


5 Qp100

6


7 yes







12 yes


13 4







19



Page 2







receiving water:












Treatment (2.7.5.D)










Treatment Standards


{



S/N 001

Dry Swale (O-1)

Dry Swale #4

Dry Swale 4 of 48






23

24

25


26 yes / no


27 yes / no
















Dry Swale 4 of 48




Dry Pond 1 March 6, 2015


Project Name:

Discharge Point:

Line

1 Cpv x

2 Qp10 x

3 Qp100 Not Applicable - Qp100 Waived

Response

4 Yes

5 Yes

6 Yes

8 Yes

9 Yes

10 Yes

11 Yes

12 Yes

13

Response

14 no

15

16

17

18

Response

19 Yes

Response

Yes


S/N 001

Dry Detention Pond (LA-1)

Dry Detention Pond #1


Attachment location

Have you performed a site evaluation to establish the Hazard Classification of the pond? n/a - site visit

Have you determined depth to bedrock and soil properties using geotechnical investigations? n/a - site visit

Have the outfalls been designed/protected to avoid erosive velocities? See Plans

Is the principal spillway accessible from land and equipped with a removable trash rack? See Plans

Have all low flow orifices been designed or sized to ensure no clogging occurs? See Plans

Have the potential impacts of frozen culverts and deicers on vegetation been addressed in the design? See Plans

Does the application include oultet elevation and size information for the basin?. See Plans

Has the peak storage volume and elevation information for the 1, 10 and 100-year storms been included? See Plans


Check which detention time must be used, based on the fisheries designation of the receiving water: x12 hours for cold water


Attachment location


*Please review the guidance sheet "Channel Protection Storage Volume Estimation" and attach the specified information. This method is not appropriate if more than a one

subwatershed drains to the practice. Using the center of mass detention time calculated by a hydrologic model that accounts for pond routing is the preferred method.

What storage volume (cubic feet) necessary to meet the Channel Protection Standard? 5,379

What orifice size (inches) is necessary to meet the required detention time? 1.60

What is the calculated average release rate (cfs)? (Divide the Vs by detention time) 0.09

What is the controlled peak release rate (cfs) during the 1-year storm as indicated by the model? 0.09

Overbank Flood Protection Treatment Standard (Qp10) Attachment location

Have you demonstrated that Qp10 post is less than or equal to Qp10 pre at the discharge point?* See Peak Flow Summary


Please see VSMM-Vol. II, Appendix D7 for guidance about maintaining non-erosive conditions. Ensure that appropriate overflow outlets are designed to safely release all off-site water

that may also be entering the pond. Visit VSMM-Vol.II, Appendix B for dam safety design specifications.

Attachment location: Indicate the specific location (i.e. appendices, pages, plan sheets) where the requisite support documentation has been provided within the application.


Extreme Flood Protection Treatment Standard (Qp100) Attachment location


Dry Pond 1 of 48






Project Name:

Discharge Point:

Line

1 Cpv x

2 Qp10 x


Response

4 Yes

5 Yes

6 Yes

8 Yes

9 Yes

10 Yes

11 Yes

12 Yes

13

Response

14 no

15

16

17

18

Response

19 Yes

Response

Yes*Please include runoff and routing calculations of the 100-year storm event.












What storage volume (cubic feet) necessary to meet the Channel Protection Standard? 774




Attachment location












Attachment location



S/N 001



Dry Pond 2 of 48






Project Name:

Discharge Point:

Line

1 Cpv x

2 Qp10 x


Response

4 Yes

5 Yes

6 Yes

8 Yes

9 Yes

10 Yes

11 Yes

12 Yes

13

Response

14 no

15

16

17

18

Response

19 Yes

Response

n/a*Please include runoff and routing calculations of the 100-year storm event.






Have you demonstrated that Qp100 post is less than or equal to Qp100 pre at the discharge point?* Not Required






What storage volume (cubic feet) necessary to meet the Channel Protection Standard? 952




Attachment location












Attachment location



S/N 001



Dry Pond 3 of 48






Project Name:

Discharge Point:

Line

1 Cpv x

2 Qp10 x


Response

4 Yes

5 Yes

6 Yes

8 Yes

9 Yes

10 Yes

11 Yes

12 Yes

13

Response

14 no

15

16

17

18

Response

19 Yes

Response

n/a*Please include runoff and routing calculations of the 100-year storm event.






Have you demonstrated that Qp100 post is less than or equal to Qp100 pre at the discharge point?* Not Required






What storage volume (cubic feet) necessary to meet the Channel Protection Standard? 9,668




Attachment location












Attachment location



S/N 001



Dry Pond 4 of 48

Mountain Top Inn Chittenden, VT Stormwater Management … · 2016-04-22 · Chittenden, VT...

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Transcript of Mountain Top Inn Chittenden, VT Stormwater Management … · 2016-04-22 · Chittenden, VT...