HomeMy WebLinkAboutFile Documents.134 E Bleeker St.0102-2020-BRES (30) Drainage Report
134 E. BLEEKER STREET
ASPEN, CO 81611
Reviewed by Engineering
08/13/2021 10:40:27 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.
May 24, 2021
o �p0 LI.�4,
Prepared by '.r'
Richard Goulding, P.E. "ct 7
Roaring Fork Engineering S/
592 Highway 133 ifr�SS/pj`jp/`��
Carbondale, CO 81623
�e ROARING FORK
l ENGINEERING
RECEIVED
07/23/2021
ASPEN
BUILDING DEPARTMENT
Drainage Report
134 E. BLEEKER STREET
ASPEN, CO 81611
I HEREBY AFFIRM THAT THIS REPORT FOR THE IMPROVEMENTS AT 134 EAST BLEEKER
STREET WAS PREPARED BY ME FOR THE OWNERS THEREOF IN ACCORDANCE WITH THE
PROVISIONS OF CITY OF ASPEN AND APPROVED VARIANCES AND EXCEPTIONS LISTED
THERETO. I UNDERSTAND THAT IT IS THE POLICY OF THE CITY OF ASPEN THAT ASPEN DOES
NOT AND WILL NOT ASSUME LIABILITY FOR DRAINAGE FACILITIES DESIGNED BY OTHERS.
,a //N..
RICHARD GOULDING,P.E. ,*o,, .o 116"$--,
RFE Project#2020-05 26 27
0 RECEIVED
�.sSlpri :.�.,
07/23/2021
ASPEN
BUILDING DEPARTMENT
Table of Contents
1.0 General 4
1.1 Existing Site 4
1.2 Proposed Site 4
1.3 Previous Drainage Studies 5
1.4 Offsite Drainage 5
2.0 Drainage Basins and Sub-basins 5
2.1 Drainage Basins 5
2.2 Peak Discharge Calculations 6
3.0 Low Impact Site Design 7
3.1 Principles 7
4.0 Hydrological Criteria 8
4.1 Storm Recurrence and Rainfall 8
4.2 Storage Volumes Methodology 9
5.0 Hydraulic Criteria 9
6.0 Proposed Facilities 14
6.1 Drywell 14
7.0 Operation and Maintenance 15
7.1 Inlets and Piping 15
7.2 Drywell 15
RECEIVED
07/23/2021
ASPEN
BUILDING DEPARTMENT
1.0 General
1.1 Existing Site
The following report is an evaluation of the proposed redevelopment of the existing residence at
134 East Bleeker Street in Aspen,Colorado,parcel number 273707315002. The property is located
at the Northwest corner of the intersection at North Aspen Street and East Bleeker Street and is
surrounded by other residential lots. The site contains a historic single-family residence with a
non-historic addition consisting of an approximate footprint of 1,220 square feet, along with
another historical structure to the north with an approximate footprint of 510 square feet. The site
has extensive flagstone hardscaping, large existing cottonwoods and maple trees, and an access
driveway located parallel to the alley.
There are neighboring properties with single-family residences located to the west,with street right
of way to the south and east and alley right of way to the north. The existing topography is
generally flat, with a slight grade that flows from the south to the north, following North Aspen
Street. An existing conditions sheet has been included in the submitted building permit drawings.
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Figure 1:Pitkin County GIS vicinity view.Parcel 273707315002 shown in red.
1.2 Proposed Site
This project is classified as a `Major Project' per Table 1.1. of the City of Aspen Urban Runoff
Management Plan(URMP). The proposed development is over 1,000 square feet and disturbs an
area that exceeds 25%of the entire site. The intent of this report is to demonstrate compliance with
the 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. Onsite storm infrastructure has
been sized to convey runoff for a 100-year storm event. RECEIVED
07/ 3/2021
ASPEN
BUILDING DEPARTMENT
The proposed project will be a comprehensive remodel of the entire site. The historic residence
will remain in its existing location, but the basement will be constructed below the structure. An
addition will be made to the residence, including basement space below. The existing historic
garage will remain with minor alterations, and the garage door will be relocated so that it is
accessed via the alley. Landscaping, patios, and walkways are proposed around the site, and the
driveway will be removed and replaced with landscaping.
The proposed drainage infrastructure includes downspouts from roof structures, trench drains
within hardscaped areas, and area drains surrounding the site capture on-site flows before they
reach the adjacent properties and Aspen right-of-way. All onsite drainage is captured from
impervious areas and is routed through an onsite pipe system that connects to a drywell located
between the garage and the main portion of the residence.
Improvements will be made to the right of way, including new curb and gutter along North Aspen
Street, crosswalk ramps for both directions at the intersection, an alley apron, and sidewalk
following East Bleeker Street.All updates are in regards to meeting the City of Aspen Engineering
Design Standards. No improvements to the alley are proposed.
1.3 Previous Drainage Studies
The City of Aspen updated their URMP in 2014 and the property is within the boundaries of the
study. The study indicates that the property is not within a Mudflow area.
1.4 Offsite Drainage
No offsite basins affect the site, so no analysis was required.
2.0 Drainage Basins and Sub-basins
The development on the parcel is proposed as one large onsite basin. This basin will be subdivided
into smaller sub-basins and analyzed to aid with design of the storm water infrastructure for the
permit submittal. Basin delineation is shown on sheet C3 of the HPC submittal. This sheet lists
impervious area,runoff coefficients,peak flows, and the required volume of runoff to be detained.
2.1 Drainage Basins
Basin 1 is a major basin within the parcel and consists of the entire property,including the concrete
driveway,gravel parking space,impervious walkways,pervious walkways,and the roof The basin
has a total area of 4,510 square feet and is 58% impervious. The remaining pervious areas of the
basin include several landscaped areas surrounding the residence. Runoff from the basin is
collected through trench drains, area drains, and downspouts from the roof. The captured runoff is
then conveyed through the piping system to a drywell below a walkway that is sized for full
detention.
RECEIVED
07/p/2021
ASPEN
BUILDING DEPARTMENT
2.2 Peak Discharge Calculations
The peak flows were calculated for the Major Onsite Basin for the 5-year and 100-year storm event
using the Rational Method. The Rational Method is an acceptable method to calculate runoff for
this basin as the area is under 90 acres. Rainfall intensity was calculated using a Time of
Concentration (Td) of 5 minutes. The actual time of concentration for this site is 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 5 minutes or greater, so the smallest valid time of
concentration value was used. The 1-hour Rainfall depths (Pi) used for these calculations were
taken from Table 2.2 of the URMP and are equal to 0.64 inches for the 5-year event and 1.23
inches for the 100-year event.
Equation 2.1 was referenced when solving for the Rainfall Intensity(I).
88.8 P1
I =
(10 -I- Td)1.°52 (Eq. 2.1)
Runoff Coefficients (C), a function of the Soil Group (in this case B for the basins) and the
percentage of impervious area were developed using Figure 3.3. The Runoff Coefficient (C) was
then multiplied by the Rainfall Intensity (I) and the area of the calculated basin (A, in acres) to
determine the peak discharge.
Q = CIA
Qp = Peak Discharge (cfs)
C = Runoff Coefficient
I = Rainfall Intensity (inches per hour)
A = Area (acres)
These peak flow values were used to calculate the size of the proposed detention and conveyance
structures, such as the drywell, inlets and pipes. The tables below contain the peak flows for
developed and undeveloped conditions for 5-year and 100-year storm events for the major basin,
and the 100-year peak flow rate for the sub basins.
5 Year Peak Discharge Developed Calculations
1 Hour(P1) 0.64
Return Period 5
Basin ID Total Area Imp.Area Impervious C Value Time ofC _ Intensity QMax
See(D1) (ft`) (ftZ) (%) From Table (Td) I=88.8Pj(10+Td)''0s2 (ft3/Sec)
1 4510.00 2619.00 58.07% 0.370 5 3.29 C.13
5 Year Peak Discharge Pre Development Calculations
1 Hour(P1) 0.64
Return Period 5
Basin ID _Total Area Imp.Area Impervious _ C Value Time of C Intensity Q Max
See(D1) (ftZ) (ft2) (%) From Table (Td) I.88.8PlI(10+Td)1.°s2 (ft3/sec)
1 4510.00 0.00 0.00% 0.080 5 3.29
KEITIVED
07/?3/2021
ASPEN
BUILDING DEPARTMENT
100 Year Peak Discharge Developed Calculations
1 Hour(P1) 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=88.8P1/(10+Td)1.o52 (ft3/sec)
1'r'r rr ,F..4 55 "•R r?C= 1 51r_
100 Year Peak Discharge Pre Development Calculations
1 Hour(P1) 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) 1=88.8P1/(10+Td)1 es2 (ft3/sec)
cc Occ: C.r_.nS 35 : 5 5 c.'
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 is possible. This entire developed site
is approximately 58% impervious. The treatment train approach is used on all runoff to increase
water quality and infiltration.
3.1 Principles
Principle 1: Consider storm water quality needs early in the design process.
The grading and drainage design was coordinated between the architect, landscape architect, and
civil engineering teams throughout the design process and water quality requirements were
discussed early on. Site visits ensured proper understanding of existing conflicts and opportunities
to improve existing drainage patterns.
Principle 2: Use the entire site when planning for storm water quality treatment.
Storm water quality was considered in the design of every part of the site that is being affected by
the proposed construction.
Principle 3: Avoid unnecessary impervious area.
The total impervious area on the site was kept to a minimum while meeting the architectural design
goals by incorporating pervious landscaped areas throughout the site. Several walkways were
designed with pervious pavers in mind to reduce impervious area.
Principle 4: Reduce runoff rates and volumes to more closely match natural conditions.
RECEIVED
07/?3/2021
ASPEN
BUILDING DEPARTMENT
All runoff from impervious surfaces on the property is collected and routed to BMP structures.
The infrastructure has been sized to capture the 100-year detention volume water quality capture
volume. The drywell is designed to infiltrate storage capacity into the surrounding earth.
Principle 5: Integrate storm water quality management and flood control.
The proposed drywell will capture and treat runoff for water quality, and the drywell will infiltrate
the runoff into the soils, eliminating runoff from the site.
Principle 6: Develop storm water quality facilities that enhance the site, the community and the
environment.
The design is proposing full detention for all stormwater, meaning no runoff will be leaving the
site. The drywell is proposed to be buried under the addition to the home so as to not be visible by
the public.
Principle 7: Use treatment train approach.
The design implements sheetflow across landscaping, pervious pavers, and sumps in the pipe
network to ensure treatment throughout the system.
Principle 8: Design sustainable facilities that can be safely maintained.
Inlets and piping will be vacuumed or flushed periodically to maintain adequate flow. Proper
grading reduces dangerous slopes. Cleanouts are located where necessary to ensure the lifetime of
the drainage infrastructure.
Principle 9: Design and maintain facilities with public safety in mind.
The proposed design for driveway and walkways reduces ice buildup and dangerous conditions.
All grading was done with safety in mind, and no steep slopes occur on site.
4.0 Hydrological Criteria
4.1 Storm Recurrence and Rainfall
The property is not in the commercial core and is served by any city curb and gutter so this property
classifies as a"Sub-urban area served by public storm sewer". However, due to limitations on
the site, the curb and gutter cannot be utilized, so the site cannot disperse into the curb and gutter.
Due to this, the 5-year and 100-year events were analyzed.
The 1-hour Rainfall depth (Pi) is given in Table 2.2 as 0.64 inches for the 5-year event and 1.23
inches for the 100-year event. The Intensity in inches per hour for different storm duration (Td)
was calculated using Equation 2.1 from the City of Aspen URMP.
RECEIVED
0703/2021
ASPEN
BUILDING DEPARTMENT
4.2 Storage Volumes Methodology
The storage requirements for this site were calculated using the total impervious area along with
the historic and developed peak runoff rates that were established in section 2.2. The proposed
storm drainage system is designed for full detention of a 100-year storm event. No detention is
required for pervious areas. Below is a summary of the required storage.
Full Detention Storage
Basin Total Area Impervious Area Impervious Full Detention Depth Factor of Safety Required Storage BMP
(ft2) (ftZ) (%) (in) F.O.S. (ft3)
1 4510.00 2619.00 58.07`2 1.23 1.5 403 E iwelA
5.0 Hydraulic Criteria
This property is not connected to the COA's storm water infrastructure. All hydraulics are sized
for onsite infrastructure. The storm system was designed to route all impervious surfaces to the
drywell located on the site. The 100-year peak flow for each sub-basin was calculated.
100 Year Sub Basin Peak Discharge Developed Calculations
1 Hour(Pi) 1.23
Return Period 100
Basin ID Total Area Imp.Area Impervious C Value Time of C Intensity Sub Basin Flow Rate
See(D1) (ftZ) (ftZ) (%) From Table (Td) I .8PJ(10+Td)l.o (ft3/se()
1.1 336.00 336.00 100.00% 0.950 5 6.33 _ 0.05
1.2 260.00 0.00 0.00% 0.350 5 6.33 0.01
1.3 207.00 207.00 100.00% 0.950 5 6.33 0.03
1.4 205.00 205.00 100.00% 0.950 5 6.33 0.03
1.5 190.00 190.00 100.00% 0.950 5 6.33 0.03
1.6 316.00 I 210.00 66.46% 0.590 5 6.33 0.03
-
1.7 174.00 174.00 100.00% 0.950 5 6.33 0.02
1.8 113.00 113.00 100.00% 0.950 _ 5 _ 6.33 - 0.02
1.9 197.00 197.00 100.00% 0.950 5 6.33 0.03
1.1 18.00 18.00 100.00% 0.950 5 6.33 0.00
1.11 _ 206.00 _ 206.00 100.00% 0.950 5 6.33 0.03
1.12 78.00 78.00 100.00% 0.950 5 6.33 0.01
1.13 79.00 79.00 100.00% 0.950 5 6.33 0.01
1.14 _ 15.00 _ 15.00 100.00% 0.950 5 _ 6.33 0.00
1.15 142.00 142.00 100.00% 0.950 5 6.33 _ 0.02
1.16 168.00 168.00 100.00% 0.950 5 6.33 0.02
1.17 _ 27.00 27.00 100.00% 0.950 5 _ 6.33 0.00
1.18 144.00 144.00 100.00% 0.950 5 6.33 0.02
1.19 167.00 0.00 0.00% 0.350 5 6.33 0.01
5.15.1 Inlets
Basin 1 was divided into sub-basins according to what inlet or downspout they discharged into.
The peak flows for the 100-year event in each sub-basin were used as the flowrate to size the
proposed inlets. Equations 4.17 through 4.20 from the URMP were used in these calculat'
EIVED
07/ 3/2021
ASPEN
BUILDING DEPARTMENT
The equations incorporate a 50% clogging factor and assume a 40% opening in the grates. A
water depth of 0.5 inches was assumed and all the inlets were treated as sumps, as they will be
set a minimum of 0.5 inches below flow lines.
Sub Basin and Rectangular Inlet Calculations
1HouHP,) 1.23 m-01We Y,04(Depress inlet by 0.04')
Return Period 100 Cs=5O% 4=0.65
Inlet ID Basin ID Total Area Imp.Area Impervious CValue lime of Concentration Intensity QMax Inlet Type Inlet Width Inlet length Effective Open Area(EQ.420) Inlet Capacity(EQ4-19) Has Capacity
See(D1) (re) (ft) (%) (From Table) (Td) 1=gB.eP,/IIo.Td''053 (Wsec)Rectangular W.(inches) 4,(inches) A=11[s)ntW4 4=CA 2gY: (Yes/No)
B13-TRENCH DRAIN 1.14 15.00 15.00 100.0016 0.950 5 6.33 0.002 4'x 17.25' 4 207 1.150 1.154 Yes
Sub Basin and Circular Inlet Calculations
1 Hour(P,) 1.23 m-00% Y,=.04(Depress inlet by 0.041
Return Period 100 Cg 50% C,=0.65
Inlet ID Basin ID Total Area Imp.Area Impervious CValue Concentration Intensity Q Max Inlet Type Diameter Area(EQ.4-20) Inlet Capacity(EQ4-19) Has Capacity
See(D1) (ft) (ft2) (%) From Table (Ta) 1=88.8Pt/(104d)t'osz ft3/sec W.(inches) AQ(1-CF)mA Q=C,AeV2gY, (Yes/No)
A2-INLET 1.2 260.00 0.00 0.00% 0.350 5 6.33 0.013 8"Round 8 0.070 0.081 Yes
5.2 5.2 Pipes
Pipes used will be PVC SDR-35 with a Manning's coefficient (n) of 0.01. The pipes were sized
to accommodate peak flows for a 100 year event from all contributing sub-basins. Calculated
pipe sizes were tested for hydraulic capacity at 80% of their full flowrate. Calculations of depth
of flow for each pipe were calculated. Design charts giving Qaes�gll/Q full were downloaded from
Federal Highway Administration(FHWA) and the equations in Section 4.8.4 were used as the
basis for these calculations. Calculated pipe sizes and depth of flow for onsite pipes are shown
below.
RECEIVED
07433/2021
ASPEN
BUILDING DEPARTMENT
Storm System Pipes
Pipe System Pipe Contibuting Sub-Basins Design Flow Rate
QAes
A Al 1.1 0.05
A2 1.1,1.2 0.06
A3 1.3 0.03
A4 1.1-1.3 0.09
A5 1.4 0.03 _
A6 1.1-1.4 0.12 _
A7 1.1-1.4 0.12 _
A8 1.5 0.03
A9 1.6 s _
A10 1.5,1.6 0.05
All 1.1-1.6 0.17
Al2 1.1-1.19 0.37
B B1 1.7 0.02
B2 1.7 0.02
B3 1.8 0.02
B4 1.7,1.8 0.04
B5 1.7-1.9 0.07
B6 1.7-1.9 0.07
B7 1.10 0.00
B8 1.7-1.10 0.07
B9 1.7-1.11 0.10
B10 1.7-1.11 0.10
B11 1.12 0.01
B12 1.7-1.13 0.12
B13 1.14 0.00
B14 1.7-1.14 0.12
B15 1.7-1.15 0.14
B16 1.7-1.15 0.14
B17 1.7-1.16 0.16
C Cl 1.17 0.00
C2 1.17 0.00
C3 1.17,1.18 0.02
C4 1.17,1.18 0.02
C5 1.17-1.19 0.03
RECEIVED
07/{?3/2021
ASPEN
BUILDING DEPARTMENT
Pipe Sizing
K=0.462
Design Flow Proposed Manning Required Pipe Diameter Required Pipe Proposed Pipe
Pipe
Rate Slope Coefficient Equation 4-31 Diameter Diameter
Q .(ft3/sec) 5(%) n d (ft) =(nQ_./KVS; '' D ,(in) D,,,(in)
Al 0.05 2.00% 0.01 0.16 1.88 _ 4.0
A2 0.06 2.00% 0.01 0.17 2.06 4.0
A3 0.03 2.00% _ 0.01 0.13 1.56 4.0
-
A4 0.09 2.00% 0.01 0.20 2.39 4.0
A5 0.03 2.00% 0.01 0.13 1.56 4.0
A6 0.12 2.00% _ Y
0.01 0.22 2.65 4.0
A7 - 0.12 2.00% 0.01 0.22 2.65 4.0
AS 0.03 2.00% 0.01 0.13 1.52 4.0
A9 0.03 2.00% 0.01 0.13 1.53 4.0
A10 0.05 2.00% 0.01 0.16 1.98 4.0
All 0.17 2.00% _ 0.01 0.25 3.05 4.0
Al2 0.37 2.00% 0.01 0.34 4.07 6.0
B1 0.02 1.50% 0.01 0.13 1.55 4.0
B2 0.02 1.50% 0.01 0.13 1.55 4.0
-
B3 0.02 1.50% 0.01 0.11 1.32 4.0
B4 0.04 1.50% 0.01 0.16 1.87 4.0
B5 -
0.07 1.50% 0.01 0.19 2.27 4.0
B6 0.07 1.50% 0.01 0.19 2.27 4.0
B7 0.00 1.50% _ 0.01 0.06 0.66 4.0
-
BS 0.07 1.50% 0.01 0.19 2.30 4.0
B9 0.10 1.50% _ 0.01 0.22 2.62 4.0
B1C 0.10 1.50% 0.01 0.22 2.62 4.0
Bll 0.01 1.50% 0.01 0.10 1.15 4.0
B12 0.12 1.50% _ 0.01 0.24 2.82 4.0
B13 0.00 1.50% 0.01 0.05 0.62 4.0
B14 0.12 1.50% 0.01 0.24 2.84 6.0
B15 0.14 1.50% 0.01 0.25 3.01 6.0
-
B16 0.14 1.50% 0.01 0.25 3.01 6.0
B17 0.16 1.50% _ 0.01 0.27 3.18 6.0
Cl 0.00 2.00% 0.01 0.06 0.73 4.0
C2 0.00 2.00% 0.01 0.06 0.73 4.0
C3 0.02 2.00% _ 0.01 0.12 1.46 4.0
C4 0.02 2.00% 0.01 0.12 1.46 4.0
C5 0.03 2.00% 0.01 0.14 1.63 4.0
RECEIVED
074?3/2021
ASPEN
BUILDING DEPARTMENT
Hydraulic Grade Line and Pipe Capacity
Design Flow Proposed Pipe 80%of Proposed Manning Full Pipe Cross a Design/ Hydraulic Grade Line Depth of Flow Less Than
Pipe Rate Diameter Slope Pipe Diameter Coefficient Sectional Area Full Pipe Flow Rate a Full d/D (Depth of Flow) 80%of Pipe Diameter
a,..(ft'/sec) D„(in) S(%) D....8(in) n A(ft)=n(Da,/2)' Q,,.(ft'/s)=A(1A9/n)((D,J48)'r')S4' Qa=/0e. (from Chart) d(in).(d/D)•D., (Yes/No)
Al 0.05 4.0 2.00% 3.2 0.01 0.087 _ 0.351 0.13 0.28 _ 1.10 Yes
A2 0.06 4.0 2.00% 3.2 0.01 0.087 0.351 0.17 0.31 1.25 Yes
A3 0.03 4.0 2.00% 3.2 0.01 0.087 0.351 0.08 0.22 0.88 Yes
A4 0.09 4.0 2.00% 3.2 0.01 0.087 0.351 0.25 0.38 1.52 Yes
A5 0.03 4.0 2.00%_ 3.2 0.01 0.087 0.351 0.08 0.22 0.88 Yes _
A6 0.12 4.0 2.00%_ 3.2 0.01 0.087 0.351 0.33 0.45 _ 1.80 Yes _
A7 0.12 4.0 2.00% 3.2 0.01 0.087 0.351 0.33 0.45 1.80 Yes
A8 0.03 4.0 2.00% 3.2 0.01 0.087 0.351 0.07 0.20 0.80 Yes _
A9 0.03 4.0 2.00% 3.2 0.01 _ 0.087 _ 0.351 0.08 0.22 _ 0.88 Yes
A10 0.05 4.0 2.00% 3.2 0.01 0.087 0.351 0.15 0.30 1.20 Yes
All 0.17 4.0 2.00% 3.2 0.01 0.087 0.351 0.48 0.55 2.20 Yes _
Al2 0.37 6.0 2.00% 4.8 0.01 0.196 1.034 0.35 0.47 2.82 Yes
B1 0.02 4.0 1.50%_ 3.2 0.01 0.087 0.304 0.08 0.22 0.88 Yes _
B2 0.02 4.0 1.50%_ 3.2 0.01 0.087 0.304 0.08 0.22 0.88 Yes _
B3 0.02 4.0 1.50% 3.2 0.01 0.087 0.304 0.05 0.18 0.70 Yes
B4 0.04 4.0 1.50% 3.2 0.01 0.087 0.304 0.13 0.28 1.10 Yes
B5 0.07 4.0 1.50%V 3.2 0.01 0.087 _ 0.304 0.22 0.35 1.40 Yes
B6 0.07 4.0 1.50% 3.2 0.01 0.087 0.304 0.22 0.35 1.40 Yes
B7 0.00 4.0 1.50% 3.2 0.01 0.087 0.304 0.01 0.00 0.00 Yes _
B8 0.07 4.0 1.50% 3.2 0.01 0.087 _ 0.304 0.23 0.37 _ 1.46 Yes
B9 0.10 4.0 1.50% 3.2 0.01 0.087 0.304 0.32 0.43 _ 1.72 Yes
B10 0.10 4.0 1.50% 3.2 0.01 0.087 0.304 0.32 0.43 1.72 Yes _
811 0.01 4.0 1.50% 3.2 0.01 0.087 0.304 0.04 0.12 0.48 Yes
B12 0.12 4.0 1.50%_ 3.2 0.01 0.087 0.304 0.39 0.49 1.94 Yes _
813 0.00 4.0 1.50% 3.2 0.01 0.087 0.304 0.01 0.00 0.00 Yes _
B14 0.12 6.0 1.50% 4.8 0.01 0.196 0.895 0.14 0.28 1.65 Yes
B15 0.14 6.0 1.50% 4.8 0.01 0.196 0.895 0.16 0.30 1.80 Yes _
B16 0.14 6.0 1.50% 4.8 0.01 0.196 0.895 0.16 0.30 1.80 _ Yes -
B17 0.16 6.0 1.50% 4.8 0.01 0.196 _ 0.895 0.18 0.33 1.95 Yes
Cl 0.00 4.0 2.00% 3.2 0.01 0.087 0.351 0.01 0.00 0.00 Yes -
C2 0.00 4.0 2.00% 3.2 0.01 0.087 _ 0.351 0.01 0.00 0.00 Yes
C3 0.02 4.0 2.00% 3.2 0.01 0.087 0.351 0.07 0.20 0.80 Yes _
C4 0.02 4.0 2.00%_ 3.2 0.01 0.087 0.351 0.07 0.20 0.80 Yes -
C5 0.03 4.0 2.00% 3.2 0.01 0.087 0.351 0.09 0.24 0.94 Yes
RECEIVED
071?3/2021
ASPEN
BUILDING DEPARTMENT
Exit Velocities
Design Flow Proposed Pipe Manning
Pipe Slope d/D Rh/D Hydraulic Radius Exit Velocity
Rate Diameter Coefficient
(ID) Qde,(ft3/sec) Dpra(in) (%) (from Chart) n (from Chart) Rh(ft)=(Rh/D)DPro V(ft/sec)=[1.49/n1 Rh2/3 VS
Al 0.046 4.0 2.00% 0.28 0.01 0.16 0.16 6.12
A2 0.060 4.0 2.00% 0.31 0.01 0.18 0.18 6.61
A3 0.029 4.0 2.00% 0.22 0.01 0.13 0.13 5.44
A4 0.088 4.0 2.00% 0.38 0.01 0.21 0.21 7.35
A5 0.028 4.0 2.00% 0.22 0.01 0.13 0.13 5.44
A6 0.116 ( 4.0 2.00% 0.45 0.01 0.23 0.23 7.98
A7 0.116 4.0 2.00% 0.45 0.01 0.23 0.23 7.98
A8 0.026 4.0 2.00% 0.20 0.01 0.12 0.12 5.14
A9 0.030 4.0 2.00% 0.22 0.01 0.13 0.13 5.44
A10 0.056 4.0 2.00% 0.30 0.01 0.17 0.17 6.49
All 0.172 4.0 2.00% 0.55 0.01 0.26 0.26 8.69
A 12 0.369 6.0 2.00% 0.47 0.01 0.24 0.24 8.14
B1 _ 0.024 4.0 1.50% 0.22 0.01 0.13 0.13 4.71
B2 _ 0.024 4.0 1.50% 0.22 _ 0.01 0.13 0.13 4.71
B3 0.016 4.0 1.50% 0.18 0.01 0.10 0.10 4.04
B4 0.040 4.0 1.50% 0.28 0.01 0.16 0.16 5.30
B5 0.067 4.0 1.50% 0.35 0.01 0.19 0.19 6.11
B6 0.067 4.0 1.50% 0.35 0.01 0.19 0.19 6.11
B7 0.002 4.0 1.50% 0.00 0.01 0.00 0.00 0.00
B8 0.069 4.0 1.50% 0.37 0.01 0.20 0.20 6.20
B9 _ 0.098 4.0 1.50% 0.43 _ 0.01 0.23 0.23 _ 6.76
B10 0.098 4.0 1.50% 0.43 0.01 0.23 0.23 6.76
B11 0.011 4.0 1.50% 0.12 0.01 0.08 0.08 3.26
B12 0.119 4.0 1.50% 0.49 0.01 0.24 0.24 7.11 k
B13 0.002 4.0 1.50% 0.00 0.01 0.00 0.00 0.00
B14 0.121 6.0 1.50% 0.28 0.01 0.16 0.16 5.30
B15 _ 0.141 6.0 1.50% 0.30 0.01 0.17 0.17 5.62
B16 _ 0.141 6.0 1.50% 0.30 _ 0.01 0.17 0.17 _ 5.62
B17 0.164 6.0 1.50% 0.33 0.01 0.18 0.18 5.82
Cl 0.004 4.0 2.00% 0.00 0.01 0.00 0.00 0.00
C2 0.004 4.0 2.00% 0.00 0.01 0.00 0.00 0.00 1
C3 0.024 4.0 2.00% 0.20 0.01 0.12 0.12 5.14
C4 0.024 4.0 2.00% 0.20 0.01 0.12 0.12 5.14
C5 0.032 4.0 2.00% 0.24 0.01 0.14 0.14 5.58
6.0 Proposed Facilities
This property is not connected to the COA's storm water infrastructure, and the onsite drywell is
sized for full detention, as clarified in section 2.2 of this report. Below are the analyses for the
individual detention structure's capacity and infiltration.
Drywell
Below is a table that shows the proposed drywell meeting the capacity required for full detention
of Basin 1.
RECEIVED
07/13/2021
ASPEN
BUILDING DEPARTMENT
Drywell Storage
Drywell Basins Diameter Storage Depth Perforated Depth Internal Volume External(18"of Screened Rods)Volume Total Capacity Required Capacity
(Name) (It) D(ft) H(ft) P(ft) 10H•(D/2)')(ft') 0.3•n1P`((D/2)+1.5)'-(D/2)')(ft') (ft') (ft')
Drywell 1 5 19 4 373 37 410 403
The project is aware that variances will be required for the drywell, as it is within 10' of the
structure. The proposed design will locate the bottom of the drywell even with the bottom of the
footing per Structural Engineer recommendation.
7.0 Operation and Maintenance
7.1 Inlets and Piping
The piping must be maintained periodically to ensure proper operation. Minimum inspection
and maintenance requirements include the following:
• During the first year draw down should be checked for every event exceeding 0.25" of
precipitation to ensure no significant backups are occurring.
• Piping systems and sumps should be checked during and after storms routinely.
• After the first year, the system should be cleaned out at least once a year and more if the
first-year inspection proves more maintenance is required.
• More frequent cleaning reduces the amount of debris entering the system and reduces the
need for more intense maintenance.
• Clean the inside of any perforated pipes with a pipe cleaner accessed through cleanouts.
This should be done yearly, or as necessary if the system is not infiltrating properly or if the
system has become contaminated.
• Ensure heat tape is functioning before colder months to prevent damage to piping.
If the storm system is not maintained properly, replacement of parts or of the entire system may
be necessary.
7.2 Drywell
Drywells must be inspected and maintained quarterly to remove sediment and debris that has
washed into them. A maintenance plan shall be submitted to the City in the Drainage Report
describing the maintenance schedule that will be undertaken by the owners of the new residence
or building. Minimum inspection and maintenance requirements include the following:
• 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.
RECEIVED
07/1?�3/2021
ASPEN
BUILDING DEPARTMENT