HomeMy WebLinkAboutFile Documents.754 Moore Dr.0034.2018 (46).ARBK1
Drainage Report
FIVE TREES LOT 12
754 MOORE DRIVE
ASPEN, CO
February 15th, 2018
Revised September 12th, 2018
Prepared by Richard Goulding, P.E.
Roaring Fork Engineering
592 Highway 133
Carbondale, CO 81623
09/18/2018
Reviewed by Engineering
10/29/2018 7:41:23 AM
"It should be known that this review shall not
relieve the applicant of their responsibility to
comply with the requirements of the City of
Aspen. The review and approval by the City is
offered only to assist the applicant's
understanding of the applicable Engineering
requirements." The issuance of a permit based
on construction documents and other data shall
not prevent the City of Aspen from requiring the
correction of errors in the construction
documents and other data.
2
Drainage Report
FIVE TREES LOT 12
754 MOORE DRIVE
ASPEN, CO
I HEREBY AFFIRM THAT THIS REPORT FOR THE IMPROVEMENTS AT LOT 12 FIVE TREES, ASPEN,
CO WAS PREPARED BY ME FOR THE OWNERS THEREOF IN ACCORDANCE WITH THE PROVISIONS
OF THE CITY OF ASPEN URBAN RUNOFF MANAGEMENT PLAN AND APPROVED VARIANCES AND
EXCEPTIONS LISTED THERETO. I UNDERSTAND THAT IT IS THE POLICY OF THE CITY OF ASPEN
THAT THE CITY OF ASPEN DOES NOT AND WILL NOT ASSUME LIABILITY FOR DRAINAGE FACILITIES
DESIGNED BY OTHERS.
RICHARD GOULDING, P.E.
RFE Project # 2017-16
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Table of Contents
1.0 General .................................................................................................................................................... 4
1.1 Existing Site ......................................................................................................................................... 4
1.2 Proposed Conditions ........................................................................................................................... 4
1.3 Previous Drainage Studies .................................................................................................................. 5
1.4 Offsite Drainage & Constraints ........................................................................................................... 5
2.0 Drainage Basins and Sub-basins .............................................................................................................. 6
2.1 Drainage Basins ................................................................................................................................... 6
2.2 Peak Discharge Calculations ................................................................................................................ 6
3.0 Low Impact Site Design ........................................................................................................................... 8
3.1 Principles ............................................................................................................................................. 8
4.0 Hydrological Criteria ............................................................................................................................... 9
4.1 Storm Recurrence and Rainfall ........................................................................................................... 9
4.2 Peak Runoff Methodology .................................................................................................................. 9
5.0 Hydraulic Criteria .................................................................................................................................... 9
5.1 Inlets .................................................................................................................................................. 11
5.2 Pipes .................................................................................................................................................. 11
5.3 Vegetated Swale ............................................................................................................................... 16
6.0 Proposed Facilities ................................................................................................................................ 18
6.1 Drywell .............................................................................................................................................. 18
6.2 Infiltration ......................................................................................................................................... 18
7.0 Operation and Maintenance ................................................................................................................. 18
7.1 Drywell .............................................................................................................................................. 18
7.2 Trench Drains and Slot Drains ..................................................................................................... 19
7.3 Shoring Wall Swale ...................................................................................................................... 19
8.0 Appendices ............................................................................................................................................ 21
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1.0 General
1.1 Existing Site
The site under review is an undeveloped lot within the Five Trees Subdivision, and is addressed at 754
Moore Drive. The 0.834 acre parcel is a highly vegetated slope facing north, with native trees and shrubs
covering the site. A viewing deck is currently the only structure on the property. The Moore Drive right of
way is to the south of the site, with the Five Trees Lane right of way enclosing the west and north sides
and a neighboring residential property to the east. A utility easement is offset from the property lines
bordering the right of ways, and a twenty-foot ski easement is located on the neighboring lot to the east
at the property line.
An existing roadside swale is located on the uphill side of both roads, which are used to convey runoff
from the crowned asphalt. The runoff is concentrated near the northwest corner of the site, where a
culvert conveys it under the road and continues through the subdivision’s stormwater infrastructure. The
crowned roadway just to the south of the site sheet-flows onto the property, where it disperses through
the existing foliage until it reaches the roadside swale above Five Trees Lane. It is requested in the HOA
Design Guidelines that the natural drainage courses must be protected and existing drainage patterns
maintained.
Electric, telephone, communications, and water are all located in the easement on the northern side of
the property. Pedestals and the transformer are located on the northeast corner of the property and an
existing water shutoff to the site is west of the pedestals. A gas line is located in the utility easement on
the south side of the parcel, and the sanitary sewer is located under the road in the right of way to the
north and the south.
A geotechnical report was completed on October 26th, 2017. Subsurface conditions encountered in the
exploratory borings consisted of 24 to 29 feet of clayey to silty gravel and sand with sandy clayey lenses,
underlain by very hard sandstone bedrock of the maroon formation. No groundwater was encountered,
but the area is known for zones of groundwater seepage. A percolation test was performed on March
10th, 2017 by HP Kumar, with an infiltration rate of 15 inches per hour.
1.2 Proposed Conditions
The project is classified as a ‘Major Project’ as per Table 1.1 of the URMP. The proposed development will
disturb approximately 21,700 square-feet, which is roughly 60% of the site. This has implications for the
design. The intent of this report is to demonstrate compliance with requirements of the URMP. The Low
Impact Design (LID) Principles in the introduction of the manual were used as a guide throughout the
design process.
The proposed structure will be a 10,000 square-foot, Three-level, single-family residence, including a two-
car garage and exterior pool, pool deck and spa. Due to the location of the structure in proximity of the
natural landscape, shoring walls are to be constructed to tie into the grades on the south and east end of
the site. The largest cut depth for the 4,163 square foot basement will be roughly 24 feet. The main level
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is approximately 3,129 square feet and mostly exposed above grade except for to the south wall. Walls
are required below the driveway for access to the site.
The runoff from impervious surfaces at the residence will be collected in multiple systems through inlets
and roof drains. A system captures the runoff from the driveway, the western portion of the roof, and
offsite basins and conveys to Drywell A. Drywell A is designed to release at the site’s historical 100-year
flow rates off the property, which sheet flows to the roadside swale next to Five Trees Lane. A second
system captures the runoff from the eastern roof, pool deck and patio, east shoring wall, and southeast
shoring wall, and is piped to Drywell B, which releases at historical 100-year flow rates off the property,
and into the roadside swale as well.
1.3 Previous Drainage Studies
There is no record of a drainage master plan for the subdivision.
1.4 Offsite Drainage & Constraints
Moore Drive above the site is crowned, and half of the street has no stormwater management, so the
runoff flows onto the property of discussion. The runoff areas have been split up into two offsite basins
to be captured via grass swales and conveyed to drywells A and B. Sheet C3.0 of the permit set is an
overview of the affected area. Rainfall intensity was calculated using this TOC information. Using
equations and tables from the 100-year, Qmax (maximum flow rate, ft3/sec) was calculated. Offsite Basin
1 and 2 flow paths were under 300 feet, therefore, per the URMP a minimum time of concentration of 5
minutes was used in calculating the peak 5-year and 100-year flows, see below.
Offsite 5 Year Peak Discharge Developed Calculations
1 Hour(P 1)0.64
Return Period 5
Basin ID Total Area Imp. Area Impervious C Value Time of C Intensity Q Max
See(D1)(ft2)(ft2)(%)From Table (Td)I=88.8P 1/(10+Td)1.052 (ft3/sec)
OS1 2815.45 1870.13 66.42%0.450 5 3.29 0.10
OS2 1049.44 464.48 44.26%0.300 5 3.29 0.02
Offsite 100 Year Peak Discharge Developed Calculations
1 Hour(P 1)1.23
Return Period 100
Basin ID Total Area Imp. Area Impervious C Value Time of C Intensity Q Max
See(D1)(ft2)(ft2)(%)From Table (Td)I=88.8P 1/(10+Td)1.052 (ft3/sec)
OS1 2815.45 1870.13 66.42%0.590 5 6.33 0.24
OS2 1049.44 464.48 44.26%0.500 5 6.33 0.08
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2.0 Drainage Basins and Sub-basins
The site was divided into two major drainage basins, which was then subdivided into smaller sub-basins.
A Drainage Exhibit in the appendices illustrates the basin and sub-basin delineations. It lists Impervious
Areas, Runoff Coefficients, Peak Flows, and Required Volume of runoff to be detained.
The sub-basins were created to calculate the concentrated flow from each impervious area, including
patios, decks, roofs, and the driveway. These sub-basin peak flows were then used to size the proposed
stormwater infrastructure.
2.1 Drainage Basins
Basin 1 is 13,176 square feet (sf), 48.14% impervious, and consists of roof drains, inlets, trench drains,
and a reinforced grass swale on the western portion of the property. Runoff from this basin is collected
and conveyed to Drywell A, which has been sized for the Rational Volume Method Capacities required
by the URMP. It consists of 18 sub basins. Sub basins 1.1-1.5, 1.8-1.1, 1.13, 1.14, 1.16, and 1.18 are all
landscaped and hardscaped areas that are concentrated to an inlet, while sub basins 1.6, 1.7, 1.12, 1.15,
and 1.17 are roof areas that are concentrated at downspouts. All sub basins are collected by pipe
networks and runoff is conveyed to the drywell.
Basin 2 is 7,405 square feet (sf), 40% impervious and consists of roof drains, inlets, slot drains, and a
reinforced grass swale on the eastern portion of the property. Runoff from this basin is collected and
conveyed to drywell B. Drywell B has capacity determined using the Rational Volume Method. Basin 2 is
separated into 17 sub basins for calculating pipe and inlet capacities. Basins 2.1, 2.2, 2.4, 2.5, and 2.7-
2.17 are all landscaped and hardscape areas that are collected by inlets into the storm system. Sub
basins 2.3 and 2.6 are both roof areas that are collect and dispersed into the system via downspouts.
2.2 Peak Discharge Calculations
The peak flows are calculated for each basin for the 5 and 100-year storm events. Rainfall intensity was
calculated using a Time of Concentration (Td) of 5 minutes. Actual time of concentration on the site is
significantly less than 5 minutes, but according to the City of Aspen URMP, equations used to calculate
rainfall intensity are only valid for a Time of Concentration of greater than 5 minutes. Therefore, the
smallest valid Time of Concentration value was used. The 1-hour Rainfall depth (P1), given in Table 2.2 if
the URMP as 0.64 inches for the 5-year event and 1.23 inches for the 100-year event. Equation 2.1
(URMP) was referenced when solving for the Rainfall Intensity.
I = 88.8P1/(10+Td )1.052
Runoff Coefficients (C), a function of the Soil Group (in this case B) and the percentage of impervious
area within each basin were developed using Figure 3.2. The Runoff Coefficient (C) was then multiplied
by the Rainfall Intensity (I) and the acreage of the basin (A) to determine the peak discharge for each
Major Basin. Q allowable was calculated the same way except each basin was treated as undeveloped or
100% pervious. The Peak Discharge (Qp) is given by equation 3.1 (URMP).
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Qp= Peak Discharge (cfs)
C= Runoff Coefficient (Unitless)
I= Rainfall intensity (inches per hour)
A= Area (Acres)
Peak flow values were used to calculate the size of the proposed detention and conveyance structures,
such as drywells, inlets and piping. The tables below contain the peak flows for developed and
undeveloped conditions for 5 and 100-year storm events.
5 Year Peak Discharge Developed Calculations
1 Hour(P 1)0.64
Return Period 5
Basin ID Total Area Imp. Area Impervious C Value Time of C Intensity Q Max
See(D1)(ft2)(ft2)(%)From Table (Td)I=88.8P 1/(10+Td)1.052 (ft3/sec)
1 13175.97 6343.34 48.14%0.330 5 3.29 0.33
2 7405.40 2971.03 40.12%0.300 5 3.29 0.17
5 Year Peak Discharge Pre Development Calculations
1 Hour(P 1)0.64
Return Period 5
Basin ID Total Area Imp. Area Impervious C Value Time of C Intensity Q Max
See(D1)(ft2)(ft2)(%)From Table (Td)I=88.8P 1/(10+Td)1.052 (ft3/sec)
1 13175.97 0.00 0.00%0.080 5 3.29 0.08
2 7405.40 0.00 0.00%0.080 5 3.29 0.04
100 Year Peak Discharge Developed Calculations
1 Hour(P 1)1.23
Return Period 100
Basin ID Total Area Imp. Area Impervious C Value Time of C Intensity Q Max
See(D1)(ft2)(ft2)(%)From Table (Td)I=88.8P 1/(10+Td)1.052 (ft3/sec)
1 13175.97 6343.34 48.14%0.510 5 6.33 0.98
2 7405.40 2971.03 40.12%0.500 5 6.33 0.54
100 Year Peak Discharge Pre Development Calculations
1 Hour(P 1)1.23
Return Period 100
Basin ID Total Area Imp. Area Impervious C Value Time of C Intensity Q Max
See(D1)(ft2)(ft2)(%)From Table (Td)I=88.8P 1/(10+Td)1.052 (ft3/sec)
1 13175.97 0.00 0.00%0.350 5 6.33 0.67
2 7405.40 0.00 0.00%0.350 5 6.33 0.38
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3.0 Low Impact Site Design
Low Impact Development (LID) aims to mimic the natural pre-development hydrologic pattern. The goal
is to manage storm water as close to its source as possible. This entire developed site is approximately
44.8 % impervious. The FAA detention areas have enough capacity to meet the Water Quality Capture
Volume (WQCV) in addition to the Flood Control Volumes (FCV) requirements.
3.1 Principles
Principle 1: Consider storm water quality needs early in the design process.
The Grading and Drainage design was coordinated with the architect during the design phase. Due to the
steep slopes and the large retaining walls, coordination in the design process was key.
Principle 2: Use the entire site when planning for storm water quality treatment.
Given steep slopes, utility easements, existing trees and activity envelopes, drywells were determined to
be the best solution for storm water detention. Swales were used for conveyance across and around the
site.
Principle 3: Avoid unnecessary impervious area.
Reinforced grass pavers were used for parking areas and patio areas. Planters are scattered around the
site, and green roofs are implemented in the building design.
Principle 4: Reduce runoff rates and volumes to more closely match natural conditions.
The runoff has been designed to release at the historical 100-year flow rates from Drywells A and B.
Principle 5: Integrate storm water quality management and flood control.
Sumps in inlets and drywells will collect sediment. Reinforced grass swales will filter out water
contaminants. Drywells have capacity for flood control.
Principle 6: Develop storm water quality facilities that enhance the site, the community and the
environment.
The proposed design encourages replenishing groundwater, and does not introduce any additional runoff
into the city infrastructure. This should not impact the Roaring Fork River.
Principle 7: Use treatment train approach.
Sump inlets, drywells, and reinforced grass pavers used for the wall diversion swales will act as
contaminant mitigation before entering the drywells. The historical release rate from the drywells
overtopping will be conveyed through reinforced grass swales.
Principle 8: Design sustainable facilities that can be safely maintained.
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Drainage systems were simply designed so maintenance is minimized. Stormwater infrastructure will be
just below grade providing little labor for maintenance. The Owner will sign a maintenance agreement as
part of their Certificate of Occupancy.
Principle 9: Design and maintain facilities with public safety in mind.
Proper drainage and grading of the driveway and walkways reduces ice buildup and dangerous icy
conditions. All grading was done with safety in mind.
4.0 Hydrological Criteria
4.1 Storm Recurrence and Rainfall
The property is not in the commercial core and is served by city curb and gutter so this property classifies
as a “Sub-urban area not served by public storm sewer”. The total site shall meet detention requirements
for 5 and 100-year historical storm events.
4.2 Peak Runoff Methodology
The peak flows were calculated for each basin using 5 and 100-year storm events in Section 2.2 of this
report. Below is a summary of each FAA basin and its contribution to the required volume of runoff that
needs to be retained to maintain a Qa. This is in addition to satisfying the COA’s Water Quality Capture
Volume requirements. The WQCV and the FAA are added together to find the total volume required to
be detained. The FAA Modified Rational calculations for 5 and 100-year events for each basin are provided
in the appendices.
5.0 Hydraulic Criteria
This property is not connected to the COA’s stormwater infrastructure. All hydraulics are for onsite
infrastructure. Basins 1 and 2 were delineated into sub-basins per the design points of concentrations
created by roof drains and inlets. Pipe networks were then created connecting the sub-basins and
conveying the flows to the overall point of concentration for the basin. The 100-year peak flow for each
sub-basin was calculated.
Rational Volume Method Volumes
WQCV Detention
Required Calculated Volumes Required Total
Basin Total Area Impervious Area Impervious WQCV Tbl. Val.Volume 5-yr 100-yr Volume Volume BMP
(ft2)(ft2)(%)(in)(ft3)(ft3)(ft3)(ft3)(ft3)
1 13175.97 6343.34 48.14%0.093 102.1 144.94 143.70 145.0 247.1 Drywell A
2 7405.40 2971.03 40.12%0.08 49.4 55.42 70.76 71.0 120.4 Drywell B
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100 Year Sub Basin Peak Discharge Developed Calculations
1 Hour(P 1)1.23
Return Period 100
Sub Basin Total Area Imp. Area Impervious C Value Time of C Intensity Sub Basin Flow Rate
(Name)At (ft2)Ai (ft2)Ai/At (%)From Table (Td)I=88.8P1/(10+Td)01.052 Qsub (ft3/sec)
1.1 1042.96 315.39 30.24%0.480 5 6.33 0.07
1.2 894.01 266.08 29.76%0.460 5 6.33 0.06
1.3 933.65 128.95 13.81%0.400 5 6.33 0.05
1.4 3934.58 993.09 25.24%0.460 5 6.33 0.26
1.5 1748.00 734.81 42.04%0.500 5 6.33 0.13
1.6 560.33 560.33 100.00%0.950 5 6.33 0.08
1.7 646.19 646.19 100.00%0.950 5 6.33 0.09
1.8 231.52 231.52 100.00%0.950 5 6.33 0.03
1.9 481.97 0.00 0.00%0.350 5 6.33 0.02
1.10 668.32 625.35 93.57%0.820 5 6.33 0.08
1.11 19.56 19.56 100.00%0.950 5 6.33 0.00
1.12 577.43 577.43 100.00%0.950 5 6.33 0.08
1.13 654.08 611.79 93.53%0.820 5 6.33 0.08
1.14 81.20 0.00 0.00%0.350 5 6.33 0.00
1.15 25.50 25.50 100.00%0.950 5 6.33 0.00
1.16 67.10 67.10 100.00%0.950 5 6.33 0.01
1.17 540.25 540.25 100.00%0.950 5 6.33 0.07
1.18 69.32 0.00 0.00%0.350 5 6.33 0.00
2.1 54.82 54.82 100.00%0.950 5 6.33 0.01
2.2 149.04 149.04 100.00%0.950 5 6.33 0.02
2.3 1613.83 987.77 61.21%0.570 5 6.33 0.13
2.4 148.61 148.61 100.00%0.950 5 6.33 0.02
2.5 79.81 0.00 0.00%0.350 5 6.33 0.00
2.6 2056.16 516.38 25.11%0.460 5 6.33 0.14
2.7 336.21 82.22 24.45%0.450 5 6.33 0.02
2.8 406.87 406.87 100.00%0.950 5 6.33 0.06
2.9 217.09 31.56 14.54%0.400 5 6.33 0.01
2.10 106.11 106.11 100.00%0.950 5 6.33 0.01
2.11 363.94 363.94 100.00%0.950 5 6.33 0.05
2.12 250.68 0.00 0.00%0.350 5 6.33 0.01
2.13 298.03 74.81 25.10%0.460 5 6.33 0.02
2.14 76.48 48.90 63.94%0.570 5 6.33 0.01
2.15 198.23 0.00 0.00%0.350 5 6.33 0.01
2.16 1049.49 0.00 0.00%0.350 5 6.33 0.05
2.17 1145.63 0.00 0.00%0.350 5 6.33 0.06
OS1.1 894.43 506.22 56.60%0.540 5 6.33 0.07
OS1.2 775.09 467.7 60.34%0.570 5 6.33 0.06
OS1.3 524.47 316.15 60.28%0.570 5 6.33 0.04
OS1.4 621.46 580.06 93.34%0.820 5 6.33 0.07
OS2.1 609.03 302.62 49.69%0.510 5 6.33 0.05
OS2.2 440.41 161.86 36.75%0.490 5 6.33 0.03
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5.1 Inlets
The 100-year peak flows were used in the sizing of inlets. Equations 4-17 to 4-20 from the URMP were
used in the analysis. They incorporate a 50% clogging factor and 40% opening in the grates. A water depth
of 0.04’ was assumed and all the inlets were treated as sumps as they will be set a minimum of .04‘(½
Inch) below the flow lines. Below is a summary of each square inlet being tested for capacity against their
tributary basin.
Below is a summary of each round inlet being tested for capacity against their tributary basin.
5.2 Pipes
The pipes were analyzed by calculating the flow from the sub basins entering them. Below is table which
groups what sub basins are conveyed in each pipe. The TOC is below 5 minutes for all sub-basins, so a
reduction was not taken for the intensity. They were tested for hydraulic capacity at 80% of pipe
diameter. Depth of flow was also calculated in the spread sheets below. The pipes are all SDR 35 PVC with
a manning’s coefficient of .01.
Design Q design / Q full charts were downloaded from The Federal Highway Administration. The equations
in Section 4.8.4 was used as the basis for these calculations.
Sub Basin and Rectangular Inlet Calculations
1 Hour(P1)1.23 m=40%Ys=.04 (Depress inlet by 0.04')
Return Period 100 Cg=50%Co=0.65
Inlet ID Basin ID Total Area Imp. Area Impervious C Value Time of Concentration Intensity Q Max Inlet Type Inlet Width Inlet Length Effective Open Area (EQ. 4-20)Inlet Capacity (EQ 4-19)Has Capacity
See(D1)(ft2)(ft2)(%)(From Table) (Td)I=88.8P1/(10+Td)1.052 (ft3/sec)Rectangular Wo (inches)Lo (inches)Ae=(1-Cg)mWoLo Q=CoAe√2gYs (Yes/No)
B3-TRENCH DRAIN 1.6 560.33 560.33 100.00%0.950 5 6.33 0.077 4" x 58.5'4 702 3.900 3.913 Yes
E4-SLOT DRAIN 2.8 406.87 406.87 100.00%0.950 5 6.33 0.056 0.25" x 38'0.25 458 0.398 0.399 Yes
H3-SLOT DRAIN 2.11 363.94 363.94 100.00%0.950 5 6.33 0.050 0.25" x 38'0.25 458 0.398 0.399 Yes
Sub Basin and Circular Inlet Calculations
1 Hour(P1)1.23 m=40%Ys=.04 (Depress inlet by 0.04')
Return Period 100 Cg=50%Co=0.65
Inlet ID Basin ID Total Area Imp. Area Impervious C Value
Concentration Intensity Q Max Inlet Type Diameter
Area(EQ. 4-20)Inlet Capacity (EQ 4-19)Has Capacity
See(D1)(ft2)(ft2)(%)From Table (Td)I=88.8P1/(10+Td)1.052 ft3/sec Wo (inches)Ae=(1-Cg)mA Q=CoAe√2gYs (Yes/No)
A1-INLET 1.1-1.3, 0S1.1-OS1.3 5064.61 2000.49 39.50%0.490 5 6.33 0.360 18" Round 18 0.353 0.412 Yes
A2-INLET 1.4, OS1.4 4556.04 1573.15 34.53%0.480 5 6.33 0.318 18" Round 18 0.353 0.412 Yes
A3-INLET 1.5 1748.00 734.81 42.04%0.500 5 6.33 0.127 12" Round 12 0.157 0.183 Yes
A5-INLET 1.9 481.97 0.00 0.00%0.350 5 6.33 0.024 6" Round 6 0.039 0.046 Yes
A6-INLET 1.10 668.32 625.35 93.57%0.820 5 6.33 0.080 12" Round 12 0.157 0.183 Yes
A7-INLET 1.13 654.08 611.79 93.53%0.820 5 6.33 0.078 12" Round 12 0.157 0.183 Yes
C1-INLET 1.11 39.12 39.12 100.00%0.950 5 6.33 0.005 6" Round 6 0.039 0.046 Yes
D1-CATCH BASIN 1.14 81.20 0.00 0.00%0.350 5 6.33 0.004 8" Round 8 0.070 0.081 Yes
D3-INLET 1.16 67.10 67.10 100.00%0.950 5 6.33 0.009 4" Round 4 0.017 0.020 Yes
D6-CATCH BASIN 1.18 69.32 0.00 0.00%0.350 5 6.33 0.004 8" Round 8 0.070 0.081 Yes
E1-INLET 2.1 54.82 54.82 100.00%0.950 5 6.33 0.008 5" Round 5 0.027 0.032 Yes
E2-INLET 2.2 149.04 149.04 100.00%0.950 5 6.33 0.021 5" Round 5 0.027 0.032 Yes
E5-INLET 2.7 336.21 82.22 24.45%0.450 5 6.33 0.022 6" Round 6 0.039 0.046 Yes
E6-INLET 2.9 217.09 31.56 14.54%0.400 5 6.33 0.013 6" Round 6 0.039 0.046 Yes
E7-INLET 2.13 298.03 74.81 25.10%0.460 5 6.33 0.020 6" Round 6 0.039 0.046 Yes
E8-INLET 2.14 76.48 48.90 63.94%0.570 5 6.33 0.006 6" Round 6 0.039 0.046 Yes
E9-INLET 2.15 198.23 0.00 0.00%0.350 5 6.33 0.010 6" Round 6 0.039 0.046 Yes
F2-INLET 2.4 148.61 148.61 100.00%0.950 5 6.33 0.020 5" Round 5 0.027 0.032 Yes
F3-INLET 2.5 79.81 0.00 0.00%0.350 5 6.33 0.004 6" Round 6 0.039 0.046 Yes
G1-INLET 2.12 250.68 0.00 0.00%0.350 5 6.33 0.013 8" Round 8 0.070 0.081 Yes
G2-INLET 2.12 250.68 0.00 0.00%0.350 5 6.33 0.013 8" Round 8 0.070 0.081 Yes
G4-INLET 2.12 250.68 0.00 0.00%0.350 5 6.33 0.013 8" Round 8 0.070 0.081 Yes
H1-INLET 2.10 106.11 106.11 100.00%0.950 5 6.33 0.015 4" Round 4 0.017 0.020 Yes
I1-INLET 2.16,OS2.1 1658.52 302.62 18.25%0.430 5 6.33 0.104 12" Round 12 0.157 0.183 Yes
I2-INLET 2.17, OS2.2 1586.04 161.86 10.21%0.400 5 6.33 0.092 12" Round 12 0.157 0.183 Yes
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Storm System Pipes
Pipe System Pipe Contibuting Sub-Basins Peak Flows (CFS)
A1 1.1-1.3, OS1.1-1.3 0.36
A2 1.1-1.4, OS1.1-1.4 0.70
A3 1.1-1.5, OS1.1-1.4 0.83
A4 1.1-1.8, OS1.1-1.4 1.03
A5 1.9 0.02
A6 1.1-1.10, OS1.1-1.4 1.13
A7 1.1-1.13, OS1.1-1.4 1.29
A8 1.1-1.18, OS1.1-1.4 1.39
B1 1.6 0.08
B2 1.6, 1.7 0.17
B3 1.8 0.03
B4 1.6-1.8 0.20
C1 1.11 0.00
C2 1.11, 1.12 0.08
D1 1.14 0.00
D2 1.15 0.00
D3 1.14-1.16 0.02
D4 1.14-1.16 0.02
D5 1.17 0.07
D6 1.14-1.18 0.09
E1 2.1 0.01
E2 2.1, 2.2 0.03
E3 2.1, 2.2 0.03
E4 2.8 0.06
E5 2.1-2.8 0.40
E6 2.1-2.9 0.41
E7 2.1-2.13 0.51
E8 2.14 0.01
E9 2.1-2.15 0.53
F1 2.3 0.13
F2 2.3, 2.4 0.15
F3 2.3-2.5 0.16
F4 2.3-2.5 0.16
F5 2.3-2.6 0.30
G1 2.12 0.01
G2 2.12 0.01
G3 2.12 0.01
G4 2.12 0.01
G5 2.12 0.01
H1 2.10 0.01
H2 2.10 0.01
H3 2.10, 2.11 0.06
I1 2.16, OS2.1 0.10
I2 2.16, OS2.1 0.10
I3 2.16, 2.17, OS2.1, OS2.2 0.19
I
F
G
H
A
B
C
D
E
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K=0.462
Pipe Design Flow
Rate
Proposed
Slope
Manning
Coefficient
Required Pipe Diameter
Equation 4-31
Required Pipe
Diameter
Proposed Pipe
Diameter
Qdes (ft3/sec) S (%)n d (ft) = {nQdes/K√S}3/8 Dreq (in) Dpro (in)
A1 0.36 22.00%0.01 0.22 2.59 4.0
A2 0.70 2.00%0.01 0.43 5.20 6.0
A3 0.83 2.00%0.01 0.46 5.53 6.0
A4 1.03 2.00%0.01 0.50 5.99 8.0
A5 0.02 2.00%0.01 0.12 1.48 4.0
A6 1.13 2.00%0.01 0.52 6.22 8.0
A7 1.29 2.00%0.01 0.54 6.53 8.0
A8 1.39 34.00%0.01 0.33 3.94 8.0
B1 0.08 2.00%0.01 0.19 2.27 4.0
B2 0.17 2.00%0.01 0.25 3.03 4.0
B3 0.03 2.00%0.01 0.14 1.63 4.0
B4 0.20 2.00%0.01 0.27 3.24 4.0
C1 0.00 1.50%0.01 0.06 0.68 4.0
C2 0.08 1.50%0.01 0.20 2.46 4.0
D1 0.00 1.50%0.01 0.07 0.80 4.0
D2 0.00 1.50%0.01 0.06 0.75 4.0
D3 0.02 1.50%0.01 0.11 1.36 4.0
D4 0.02 1.50%0.01 0.11 1.36 4.0
D5 0.07 1.50%0.01 0.20 2.37 4.0
D6 0.09 1.50%0.01 0.22 2.59 4.0
E1 0.01 1.50%0.01 0.08 1.00 4.0
E2 0.03 1.50%0.01 0.14 1.64 4.0
E3 0.03 1.50%0.01 0.14 1.64 4.0
E4 0.06 1.50%0.01 0.18 2.13 4.0
E5 0.40 2.00%0.01 0.35 4.22 6.0
E6 0.41 2.00%0.01 0.36 4.27 6.0
E7 0.51 2.00%0.01 0.39 4.62 6.0
E8 0.01 2.00%0.01 0.07 0.89 4.0
E9 0.53 32.00%0.01 0.23 2.78 6.0
F1 0.13 1.50%0.01 0.25 2.94 4.0
F2 0.15 1.50%0.01 0.26 3.11 4.0
F3 0.16 1.50%0.01 0.26 3.14 4.0
F4 0.16 1.50%0.01 0.26 3.14 4.0
F5 0.30 2.00%0.01 0.31 3.76 4.0
G1 0.01 2.00%0.01 0.10 1.22 4.0
G2 0.01 2.00%0.01 0.10 1.22 4.0
G3 0.01 2.00%0.01 0.10 1.22 4.0
G4 0.01 2.00%0.01 0.10 1.22 4.0
G5 0.01 18.00%0.01 0.07 0.81 4.0
H1 0.01 2.00%0.01 0.10 1.22 4.0
H2 0.01 2.00%0.01 0.10 1.22 4.0
H3 0.06 2.00%0.01 0.18 2.13 4.0
I1 0.10 2.00%0.01 0.21 2.49 4.0
I2 0.10 24.00%0.01 0.13 1.56 4.0
I3 0.19 24.00%0.01 0.17 1.99 4.0
Pipe Sizing
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Pipe Design Flow
Rate
Proposed Pipe
Diameter Slope 80% of Proposed
Pipe Diameter
Manning
Coefficient
Full Pipe Cross
Sectional Area Full Pipe Flow Rate Q Design /
Q Full d/D Hydraulic Grade Line
(Depth of Flow)
Depth of Flow Less Than
80% of Pipe Diameter
Qdes (ft3/sec) Dpro(in)S (%)Dpro*.8 (in)n A (ft) = π (Dpro/2)2 Qfull (ft3/s) = A(1.49/n)((Dpro/48)2/3)S1/2 Qdes/Qfull (from Chart)d (in) = (d/D)*Dpro (Yes/No)
A1 0.36 4.0 22.00%3.2 0.01 0.087 1.163 0.31 0.43 1.72 Yes
A2 0.70 6.0 2.00%4.8 0.01 0.196 1.034 0.68 0.68 4.05 Yes
A3 0.83 6.0 2.00%4.8 0.01 0.196 1.034 0.80 0.75 4.50 Yes
A4 1.03 8.0 2.00%6.4 0.01 0.349 2.226 0.46 0.53 4.24 Yes
A5 0.02 4.0 2.00%3.2 0.01 0.087 0.351 0.07 0.20 0.80 Yes
A6 1.13 8.0 2.00%6.4 0.01 0.349 2.226 0.51 0.57 4.56 Yes
A7 1.29 8.0 2.00%6.4 0.01 0.349 2.226 0.58 0.62 4.92 Yes
A8 1.39 8.0 34.00%6.4 0.01 0.349 9.180 0.15 0.30 2.40 Yes
B1 0.08 4.0 2.00%3.2 0.01 0.087 0.351 0.22 0.35 1.40 Yes
B2 0.17 4.0 2.00%3.2 0.01 0.087 0.351 0.47 0.53 2.12 Yes
B3 0.03 4.0 2.00%3.2 0.01 0.087 0.351 0.09 0.24 0.94 Yes
B4 0.20 4.0 2.00%3.2 0.01 0.087 0.351 0.57 0.60 2.40 Yes
C1 0.00 4.0 1.50%3.2 0.01 0.087 0.304 0.01 0.00 0.00 Yes
C2 0.08 4.0 1.50%3.2 0.01 0.087 0.304 0.27 0.38 1.52 Yes
D1 0.00 4.0 1.50%3.2 0.01 0.087 0.304 0.01 0.08 0.32 Yes
D2 0.00 4.0 1.50%3.2 0.01 0.087 0.304 0.01 0.00 0.00 Yes
D3 0.02 4.0 1.50%3.2 0.01 0.087 0.304 0.06 0.18 0.70 Yes
D4 0.02 4.0 1.50%3.2 0.01 0.087 0.304 0.06 0.18 0.70 Yes
D5 0.07 4.0 1.50%3.2 0.01 0.087 0.304 0.25 0.37 1.46 Yes
D6 0.09 4.0 1.50%3.2 0.01 0.087 0.304 0.31 0.43 1.72 Yes
E1 0.01 4.0 1.50%3.2 0.01 0.087 0.304 0.02 0.08 0.32 Yes
E2 0.03 4.0 1.50%3.2 0.01 0.087 0.304 0.09 0.24 0.94 Yes
E3 0.03 4.0 1.50%3.2 0.01 0.087 0.304 0.09 0.24 0.94 Yes
E4 0.06 4.0 1.50%3.2 0.01 0.087 0.304 0.18 0.33 1.30 Yes
E5 0.40 6.0 2.00%4.8 0.01 0.196 1.034 0.39 0.49 2.91 Yes
E6 0.41 6.0 2.00%4.8 0.01 0.196 1.034 0.40 0.50 3.00 Yes
E7 0.51 6.0 2.00%4.8 0.01 0.196 1.034 0.50 0.55 3.30 Yes
E8 0.01 4.0 2.00%3.2 0.01 0.087 0.351 0.02 0.08 0.32 Yes
E9 0.53 6.0 32.00%4.8 0.01 0.196 4.135 0.13 0.28 1.65 Yes
F1 0.13 4.0 1.50%3.2 0.01 0.087 0.304 0.44 0.52 2.06 Yes
F2 0.15 4.0 1.50%3.2 0.01 0.087 0.304 0.51 0.57 2.28 Yes
F3 0.16 4.0 1.50%3.2 0.01 0.087 0.304 0.52 0.57 2.28 Yes
F4 0.16 4.0 1.50%3.2 0.01 0.087 0.304 0.52 0.57 2.28 Yes
F5 0.30 4.0 2.00%3.2 0.01 0.087 0.351 0.84 0.77 3.06 Yes
G1 0.01 4.0 2.00%3.2 0.01 0.087 0.351 0.04 0.16 0.62 Yes
G2 0.01 4.0 2.00%3.2 0.01 0.087 0.351 0.04 0.16 0.62 Yes
G3 0.01 4.0 2.00%3.2 0.01 0.087 0.351 0.04 0.16 0.62 Yes
G4 0.01 4.0 2.00%3.2 0.01 0.087 0.351 0.04 0.16 0.62 Yes
G5 0.01 4.0 18.00%3.2 0.01 0.087 1.052 0.01 0.08 0.32 Yes
H1 0.01 4.0 2.00%3.2 0.01 0.087 0.351 0.04 0.16 0.62 Yes
H2 0.01 4.0 2.00%3.2 0.01 0.087 0.351 0.04 0.16 0.62 Yes
H3 0.06 4.0 2.00%3.2 0.01 0.087 0.351 0.18 0.33 1.30 Yes
I1 0.10 4.0 2.00%3.2 0.01 0.087 0.351 0.28 0.41 1.62 Yes
I2 0.10 4.0 24.00%3.2 0.01 0.087 1.215 0.08 0.22 0.88 Yes
I3 0.19 4.0 24.00%3.2 0.01 0.087 1.215 0.15 0.30 1.20 Yes
Hydraulic Grade Line and Pipe Capacity
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Pipe Design Flow
Rate
Proposed Pipe
Diameter Slope d/D Manning
Coefficient Rh/D Hydraulic Radius Exit Velocity
(ID)Qdes (ft3/sec) Dpro(in)(%)(from Chart)n (from Chart)Rh (ft) = (Rh/D) D pro V (ft/sec) = [1.49/n] Rh2/3 √S
A1 0.364 4.0 22.00%0.43 0.01 0.23 0.23 25.91
A2 0.701 6.0 2.00%0.68 0.01 0.29 0.29 9.27
A3 0.828 6.0 2.00%0.75 0.01 0.30 0.30 9.48
A4 1.026 8.0 2.00%0.53 0.01 0.26 0.26 8.56
A5 0.024 4.0 2.00%0.20 0.01 0.12 0.12 5.14
A6 1.130 8.0 2.00%0.57 0.01 0.27 0.27 8.81
A7 1.291 8.0 2.00%0.62 0.01 0.28 0.28 9.01
A8 1.386 8.0 34.00%0.30 0.01 0.17 0.17 26.76
B1 0.077 4.0 2.00%0.35 0.01 0.19 0.19 7.05
B2 0.166 4.0 2.00%0.53 0.01 0.26 0.26 8.56
B3 0.032 4.0 2.00%0.24 0.01 0.14 0.14 5.58
B4 0.198 4.0 2.00%0.60 0.01 0.28 0.28 8.97
C1 0.003 4.0 1.50%0.00 0.01 0.00 0.00 0.00
C2 0.082 4.0 1.50%0.38 0.01 0.21 0.21 6.37
D1 0.004 4.0 1.50%0.08 0.01 0.05 0.05 2.52
D2 0.004 4.0 1.50%0.00 0.01 0.00 0.00 0.00
D3 0.017 4.0 1.50%0.18 0.01 0.10 0.10 4.04
D4 0.017 4.0 1.50%0.18 0.01 0.10 0.10 4.04
D5 0.075 4.0 1.50%0.37 0.01 0.20 0.20 6.20
D6 0.095 4.0 1.50%0.43 0.01 0.23 0.23 6.76
E1 0.008 4.0 1.50%0.08 0.01 0.05 0.05 2.52
E2 0.028 4.0 1.50%0.24 0.01 0.14 0.14 4.84
E3 0.028 4.0 1.50%0.24 0.01 0.14 0.14 4.84
E4 0.056 4.0 1.50%0.33 0.01 0.18 0.18 5.82
E5 0.402 6.0 2.00%0.49 0.01 0.24 0.24 8.21
E6 0.414 6.0 2.00%0.50 0.01 0.25 0.25 8.36
E7 0.514 6.0 2.00%0.55 0.01 0.26 0.26 8.69
E8 0.006 4.0 2.00%0.08 0.01 0.05 0.05 2.91
E9 0.530 6.0 32.00%0.28 0.01 0.16 0.16 24.49
F1 0.134 4.0 1.50%0.52 0.01 0.25 0.25 7.30
F2 0.154 4.0 1.50%0.57 0.01 0.27 0.27 7.63
F3 0.158 4.0 1.50%0.57 0.01 0.27 0.27 7.63
F4 0.158 4.0 1.50%0.57 0.01 0.27 0.27 7.63
F5 0.295 4.0 2.00%0.77 0.01 0.30 0.30 9.50
G1 0.015 4.0 2.00%0.16 0.01 0.09 0.09 4.32
G2 0.015 4.0 2.00%0.16 0.01 0.09 0.09 4.32
G3 0.015 4.0 2.00%0.16 0.01 0.09 0.09 4.32
G4 0.015 4.0 2.00%0.16 0.01 0.09 0.09 4.32
G5 0.015 4.0 18.00%0.08 0.01 0.05 0.05 8.73
H1 0.015 4.0 2.00%0.16 0.01 0.09 0.09 4.32
H2 0.015 4.0 2.00%0.16 0.01 0.09 0.09 4.32
H3 0.065 4.0 2.00%0.33 0.01 0.18 0.18 6.72
I1 0.098 4.0 2.00%0.41 0.01 0.21 0.21 7.54
I2 0.098 4.0 24.00%0.22 0.01 0.13 0.13 18.85
I3 0.188 4.0 24.00%0.30 0.01 0.17 0.17 22.48
Exit Velocities
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5.3 Vegetated Swale
The proposed swales at the adjacent to the top of the shoring walls have been sized to have the capacity
to convey the large offsite basin around the site to work with the existing infrastructure. The largest flow
through the swale is at the point of concentration of OS1.1-OS1.3 and 1.1-1.3, where the swale is sloped
only at 2%. The next page is an analysis performed by Autodesk Express to insure the swale has capacity.
Given the design of the micropile wall, the design required multiple sections to be analyzed. These
sections have been analyzed as well and are shown on sheet C15.0 of the civil set. 100 year flow lines are
shown on the sections.
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6.0 Proposed Facilities
6.1 Drywell
Proposed drywells A and B collect all runoff from the site and is designed to have capacity for water
quality volume. Drywell A is 5’ in diameter and is 12’deep of storage, with 272 ft3 of storage capacity.
Drywell B is 4’ in diameter and 12’ deep of storage, with 182 ft3 of storage capacity. The discharge leaving
the drywells will be conveyed offsite at the pre-developed rate and will overflow out the grate lid of the
drywell. The overflow will sheet-flow down the hillside to the roadside swale to the north. The hillside
from the drywells will not be a concentrated flow and will be released into a reinforced grass overflow
to prevent erosion.
Drywell A and B are both designed to release at the predeveloped 100-year runoff rate. Specific orifice
calcs have been summarized below to calculate the required diameter to release at these rates. A cap
with the specific orifice size will be installed on the overflow pipe within the drywell.
6.2 Infiltration
The drywells have been verified to drain within 24 hours given the data and the infiltration rate
determined in the geotechnical analysis, as shown in the summary below.
7.0 Operation and Maintenance
7.1 Drywell
Drywells must be inspected and maintained quarterly to remove sediment and debris that has washed
into them. Minimum inspection and maintenance requirements include the following:
Drywell Storage
Drywell Basins Diameter Storage Depth Internal Volume External (18" of Screened Rock) Volume Total Capacity Required Capacity
(Name)(#)D (ft)H (ft)π*H*(D/2)2) (ft3)0.3*π*4*((D/2)+1.5)2 - (D/2)2) (ft3)(ft3)(ft3)
Drywell A 1 5 12 236 37 272 247.1
Drywell B 2 4 12 151 31 182 120.4
Design Maximum Release Rate, Q (cfs)0.67
Coefficient of Discharge, Cd 1.00
Height above Orifice, h (ft)3
Orifice Shape circular
Orifice Area, ft2 0.048
Circular Orifice Diameter, d (in)3.0
Drywell A Orifice Sizing
Input
Output
Design Maximum Release Rate, Q (cfs)0.43
Coefficient of Discharge, Cd 0.60
Height above Orifice, h (ft)2
Orifice Shape circular
Orifice Area, ft2 0.063
Circular Orifice Diameter, d (in)3.4
Drywell B Orifice Sizing
Input
Output
Drywell Infiltration
Name Diameter Perforation Height Perforated Area Total Capacity Infiltration Rate Infiltration Time Volume Infiltrated in 24 Hours
(Name)D (ft)H (ft)A (ft2) = 3.14*D*H V (ft3)I (in/hr)T (hr) = V/(A*I/12)Vtotal (ft3) = V*T
Drywell A 5 4 62.83 272.00 15 3.463211562 941.99
Drywell B 4 4 50.27 182.00 15 2.896619964 527.18
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• Inspect drywells at least four times a year and after every storm exceeding 0.5 inches.
• Dispose of sediment, debris/trash, and any other waste material removed from a drywell at suitable
disposal sites and in compliance with local, State, and Federal waste regulations.
• Routinely evaluate the drain-down time of the drywell to ensure the maximum time of 24 hours is
not being exceeded. If drain-down times are exceeding the maximum, drain the drywell via
pumping and clean out the percolation area (the percolation barrel may be jetted to remove
sediment accumulated in perforations. If slow drainage persists, the system may need to be
replaced.
Table 8.6 Maintenance Recommendations for Grassed Swales (UDFCD 1999)
Required Action Maintenance Objective Frequency of Action
Inspections Check the grass for uniformity of cover,
sediment accumulation in the swale,
and near culverts.
Routine – Annual inspection
is suggested.
Lawn mowing and Lawn
care
Maintain irrigated grass at 2 to
4 inches tall and non-irrigated native
grass at 6 to 8 inches tall. Collect
cuttings and dispose of them offsite or
use a mulching mower.
Routine – As needed.
Debris and Litter removal
Keep the area clean for aesthetic
reasons, which also reduces floatables
being flushed downstream.
Routine – As needed by
inspection, but no less than
two times per year. Check
each spring after snowmelt.
Sediment removal
Remove accumulated sediment near
culverts and in channels to maintain
flow capacity. Replace the grass areas
damaged in the process.
Routine – As needed by
inspection. Check each
spring after snowmelt.
Grass reseeding and
mulching
Maintain a healthy dense grass in
channel and side slope.
Non-routine – As needed by
annual inspection.
7.2 Trench Drains and Slot Drains
Trench drains must be regularly inspected and maintained to prevent clogging and debris from travelling
further into the system. Routinely keep drain grates and surrounding patios clean and free of leaves,
dirt, and other debris. This will prevent clogging and damage to the storm infrastructure. Inspect drain
sumps quarterly and after every storm exceeding 0.5 inches, remove excess sediment and debris buildup
from the catch basin. Inspect system for damage to the concrete and the grate. Inspect all grouted seams
and cracks. If cracks are smaller than ½”, record information and continue inspection regularly. If cracks
are larger than ½”, regrout and repair to prevent further damage. If grate is damaged, repair or replace
as necessary.
7.3 Shoring Wall Swale
Inspect and maintain swale quarterly, along with after every storm exceeding 0.5 inches. After seasonal
snowmelt, check swale for damage from erosion. Any damage to vegetation, grading, or compaction
must be repaired to prevent further erosion. Revegetate damaged areas to original condition. Any
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debris, rocks, or trash must be removed from the structure. The swale must be mowed a minimum of 4
times during the summer, and a fall cleanup of the swale must occur prior to snowfall.
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8.0 Appendices
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