HomeMy WebLinkAboutSP-24-08 - Supplemental - 0870 Williston Road (39)Version: 11/30/2020
Infiltration (4.3.3)
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2
3
4
5
6
* Questions preceded by an asterix (*) may change based on previously entered values
7
8*
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10
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12
13*
14
15
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18
19*
20*
21*
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23*
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26
Attachment location: Indicate the specific location (i.e. appendix, page, plan sheet) where the requisite support documentation has been provided within the application.
Practice Drainage Area
New Impervious (acres)
Redeveloped Impervious
Design Volume for Infiltration (TV)
Practice Type
Note: If the practice is designed to infiltrate the WQV, then TV = WQV. Designers may use the Practice Drainage Area Runoff Calculator (second tab) for calculation of practice-specific
runoff volumes for other treatment standards. Sizing of the filter bed area/swale bottom need to consider the desired treatment volume (see treatment section). Some design requirements
will change based on the size of storm the practice is designed to treat.
Feasibility (4.3.3.1)
Has the infiltration rate (fc) of the underlying soil been confirmed to be at least 0.2 inches per hour by the soil testing requirements in Section 4.3.3.2?
Is the seasonal high groundwater table (SHGWT) separated at least three (3) feet vertically from the bottom of the practice?
Has a groundwater mounding analysis been performed if the practice is designed to infiltrate >1 year storm and the SHGWT <4 feet?
Have the proper setback requirements for groundwater source protection been observed? (Section 4.3.3.1)
Has the practice been placed so that it will not cause intrusion problems for down-gradient structures? (Section 4.3.3.1)
Is the site free from subsurface contamination or prior approval obtained from the Agency? (If approval is required based on prior contamination, include documentation with the application.)
Conveyance (4.3.3.2)
Have the outfalls and the conveyance to the discharge point been designed/protected to avoid erosive velocities?
Is the practice designed to completely dewater the treatment volume (TV) within 48 hours after the storm event?
If the practice is designed to infiltrate <1 year storm and runoff is delivered by the main conveyance system, has it been designed as an off-line practice?
Pre-Treatment (4.3.3.3)
Has pretreatment been provided for non-rooftop runoff?
What type of pretreatment is being used?
Treatment (4.3.2.4)
Has direct access been provided to the practice for maintenance and rehabilitation?
Has an observation well been installed in every trench, drywell, or subsurface system?
What is the physical storage volume up to the overflow?
What is the treatment volume provided by the STP?
Treatment Volume (TV) for infiltration practices may be calculated using the equations provided as design guidance in Section 4.3.3.5 OR by demonstrating infiltration of the TV using
TR-20 or an approved equavalent.
Landscaping (4.3.2.5)
Does the site plan specify a landscaping plan that ensures dense and vigorous vegetation over the contributing pervious drainage areas and the practice?
Total Area (acres)
WQV to practice
For Permit Coverage
0.56438209825528
0.56438209825528
0
WQV for credit
4.46802494452097E-02
0.139
1
Not for Permit Coverage
0
0
0
WQV not for credit
0
← Tv value to enter on the Standards Compliance Workbook for this practice
Total to Practice
0.56438209825528
0.56438209825528
0
Total WQV
4.46802494452097E-02
3
Project Name:
Discharge Point:
Infiltration Practice #
Modified CN for WQ (1.0") storm
(ac-ft)
TV (ac-ft)
DoubleTree & Catamount Woods
1
1
Response
0
Response
Response
≤ 2 in/hr
> 2 in/hr
0
Response
0.04
0.139
↑ Enter this value on the Standards Compliance Worksheet
Response
99.5701783892676
Attachment location
Plans
Plans
N/A
See Site Plans
1
Attachment location
See Modeling
See Site Plans
Attachment location
Rooftop runoff only
False
Attachment location
See Plans and Details
Inspection ports are included
Enter this on the eNOI
0
Attachment location
Underground chambers
Practice Drainage Area Runoff Calculator
This tool may be used to calculate the required treatment volumes for the area draining to an individual practice where the practices drainage area is only a portion of of the area draining
to a discharge point. Where the practice receives runoff from the entire area to a discharge point, this calculator will give the same information as the Standards Compliance Workbook.
Precipitation Data
Storm
Precipitation (inches)
Drainage Area Information
Pre Development Land Use (acres)
Landuse
Grass
Meadow
Woods
Pavement, roofs, and other impervious
Total
Post Development Land Use (acres)
Landuse
Grass
Meadow
Woods
Pavement, roofs, and other impervious
Total
TV of upstream practices:
Treatment Standard
Channel Protection (Hydrologic Condition Method)
Overbank Flood
Extreme Flood
Information for Calculating TC by the Watershed Lag Method
Pre Development
Post Development, upstream of practice
Post Development, with TV credit from practice
* Preciptation values shall be obtained from
WQ Storm
1
Hydrologic Soil Group
A
0
0
0
0
0
Hydrologic Soil Group
A
0
0
0
0.182003220844812
0.182003220844812
0
Required Treatment Volume
0.077395699984184
0.139567685100858
0.213692564777727
Average Catchment Slope, Y (%)
0
0.01
0
1 yr, 24 hr
1.87
B
0
0
0
0
0
B
0
0
0
0
0
ac-ft
Post Development Runoff Volume
0.077395699984184
0.139567685100858
0.213692564777727
Hydraulic Length, l (ft)
0
70
0
10 yr, 24 hr
3.2
C
0
0
0
0
0
C
0
0
0
0.10055322543618
0.10055322543618
Pre-development Runoff Volume
0
0
0
Time of Concentration, TC (min)
1 yr
0
1.79384115352286
0
Project Name:
Discharge Point:
Infiltration Practice #
NOAA Atlas 14
100 yr, 24 hr
4.78
D
0
0
0
0
0
D
0
0
0
0.281831196051423
0.281831196051423
TV credit of this practice:
Post Composite CN (to practice)
98
98
97.9999999999999
10 yr
0
1.79384115352286
0
DoubleTree & Catamount Woods
1
1
Total (acres)
0
0
0
0
0
Total (acres)
0
0
0
0.564387642332415
0.564387642332415
0
CNAdj (with TV practice credit)
98
98
97.9999999999999
100 yr
0
1.79384115352286
0
ac-ft
Pre Composite CN
0
0
0
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
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
B
61
58
55
96
98
B
6.39344262295082
7.24137931034483
8.18181818181818
0.416666666666666
0.204081632653061
B
0.35
C
74
71
70
96
98
C
3.51351351351351
4.08450704225352
4.28571428571429
0.416666666666666
0.204081632653061
C
0.25
D
80
78
77
96
98
D
2.5
2.82051282051282
2.98701298701299
0.416666666666666
0.204081632653061
D
0