HomeMy WebLinkAboutFile Documents.134 E Bleeker St.0064-2022-BCHO (9) 134 East Bleeker Street
Drainage Report
CRYSTAL RIYFR(IYII
Reviewed by Engineering
10/19/2023 3:45:59 PM
"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.
March 18, 2022
Prepared By: tCJ&
s4�¢pOOL/C
Jay Engstrom, P.E. ..• cF
Crystal River Civil, LLC ,
Carbondale, CO 81623 '-' 5542
Jay@crystalrivercivil.com
(970) 510-5312 ��� 4, • 7 :••4,4
1911:6:S/ONA0;
(RVSIGIRIVER(IVII
Table of Contents
1.0 General Information 3
1.1 Existing Conditions 3
1.2 Proposed Conditions 4
1.3 Existing Drainage Studies 5
1.4 Drainage Impacts 5
2.0 Drainage Basins and Subbasins 5
2.1 Onsite Drainage Basins 5
2.2 Onsite Drainage Subbasins 5
2.3 Offsite Drainage Basins 5
3.0 Low Impact Site Design 6
3.1 Principles 6
4.0 Hydrologic Criteria 7
4.1 Runoff Calculation Method 7
4.2 Basin Analysis 8
4.3 Sub Basin Analysis 8
4.4 Water Quality and Storage Requirements 9
5.0 Hydraulic Criteria 10
5.1 Inlets 10
5.2 Pipes 10
6.0 Proposed Facilities 11
6.1 D rywe l l 1 11
7.0 Operation and Maintenance 12
7.1 Drywell 12
7.2 Inlets and Trench Drains 12
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1 .0 General Information
1.1 Existing Conditions
The property being discussed in this drainage report is addressed at 134 East Bleeker Street,
Aspen, Colorado 81611. The parcel is located in the City of Aspen,just north of downtown and is
documented as parcel # 27377315002. The site is directly northwest of the intersection of North
Aspen Street and East Bleeker Street, with the south and east property lines touching City of
Aspen Right-of-Way, as well as the alley Right-of-Way to the north. To the west is another single-
family residential lot.
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134 East Bleeker Street Vicinity Map
An existing historic single-family residence is located on the site, which was built in 1888 and
remodeled with an addition in 1992. The structure is 2,975 square feet with a one-car garage that
is accessed from North Aspen Street. Concrete patios are in front and behind the residence, with
landscaping surrounding the structure. Several trees are scattered in front of the house. There
does not appear to be any existing stormwater management for the impervious areas on the site.
The site is relatively flat with a general slope to the northeast. Curb and gutter follow along both
East Bleeker Street and North Aspen Street. The curb and gutter along Bleeker appears to have
been installed somewhat recently and is in good condition, however the curb and gutter along
Aspen is in need of repair.
The existing residence utilizes shallow utilities from the alleyway, including electric,
communications, and gas. A sanitary sewer main owned by Aspen Consolidated Sanitary District
runs through the alley as well, which the residence is tied into. City of Aspen Water is located in
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East Bleeker, in which a service for the site taps into. A fire hydrant is located in the landscaping
Just across the street, in the northeast corner of the intersection of Aspen and Bleeker. A city
owned light pole is in the right of way in front of the residence.
A geotechnical investigation was performed by Kumar and Associates, Inc. on June 14, 2021.
The twenty-six-foot-deep exploratory boring analysis can be found in Figure 2 of their report. It
shows six inches of topsoil, then consistent gravel - sandy, slightly silty, cobbles, transitioning to
gravelly sand with depth, medium dense to dense, slightly moist to moist. A percolation test can
be found on Table 2 of their report, showing a percolation rate of one minute per inch.
1.2 Proposed Conditions
The proposed conditions at 134 East Bleeker includes the remodel of the existing historic
structure. A large basement addition is planned that encompasses a large portion of the building
envelope. The project is considered a "Major Project" per Table 1.1. of the City of Aspen Urban
Runoff Management Plan (URMP). The parcel is zoned for residential use and will not require a
change in land use or zoning.
The residence is proposed to have multiple pervious patios, as well as a walkway that extends
from Bleeker Street Right-Of-Way up to the south facing doors. Several areas are proposed to
have snowmelt and will be impervious. This includes a parking area, the entryway by the parking
area, as well was the entry walkway off Aspen Street. Proposed grading has been minimized as
much as possible to minimize disturbance to existing trees on the parcel as well as prescribed by
the Historic Preservation Committee.
This site has been requested by the City of Aspen to include new Right-of-Way improvements for
this development. The existing curb and gutter will be replaced along North Aspen Street. New
detached sidewalk is proposed along both East Bleeker Street and North Aspen Street, as well
as bidirectional sidewalk ramps at the intersection. The detached sidewalk will tie into a new alley
ramp to the north along Aspen Street. All these improvements are shown in the civil set.
As required for designated "Major Projects", the site requires a stormwater design that meets the
requirements of the URMP. This includes conveyance of major flows and detention for releasing
historic undeveloped flow rates from the site. The Low Impact Design (LID) Principals within the
URMP were used as guidelines in the development of the proposed design. The roof structure
will collect runoff through roof drains and gutters with downspouts. The roof area will tie into the
surrounding storm system. Several inlets located around the residences will collect any runoff
from landscaped areas and patio spaces. The driveway runoff is collected via two separate trench
drains. All runoff is conveyed to an onsite drywell, located south of the garage structure. Due to
the inability to overflow, the drywell has been sized for full detention calculated to meet City of
Aspen URMP requirements. Although the design does not have an adequate location to release
a historic rate, the drywell can overflow into the North Aspen Street Right-of-Way in case of
emergency, which does not directly affect downstream structures.
Utilities on the site will be abandoned as required by each utility provider and replaced with new
services. Electric and telephone will utilize the existing transformers and pedestals in the
alleyway. The Communications Pedestal in the right of way will have to be relocated along the
fence in the northwest corner of the property to allow for vehicular access of the parking area.
Sewer and gas will also tie into the existing sewer main and gas line in the alley. A new water
service for the residence will tie into the water main in the Bleeker Street Right-of-Way.
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1.3 Existing Drainage Studies
Currently there are no known studies performed on or around the site. The project is not within a
mudflow area defined within the URMP.
1.4 Drainage Impacts
The proposed project will not have any impacts to downstream properties, Right-Of-Ways, or
stormwater systems. Given that the proposed project is capturing and treating all stormwater from
impervious areas, the project will decrease the impacts on downstream properties.
2.0 Drainage Basins and Subbasins
2.1 Onsite Drainage Basins
The site has been defined with one basin that contains the proposed development, with the point
of concentration being the proposed drywell. All runoff from the site will be collected within this
drywell.
Basin 1 consists of 4,235 square feet that is 61% impervious. This area includes landscaped
areas surrounding the residence and roof areas collected by downspouts that tie into the
proposed storm system. The patios in this area are sloped towards landscaping and will be
collected by landscape inlets. This basin is collected by Storm System A and B, which run around
the residence in either direction towards the drywell located south of the garage.
All runoff in this basin releases into the onsite drywell, which has capacity for full detention for the
whole site. This basin is shown on the basin analysis sheet within the Civil Set. A summary of the
basin's characteristics and the calculated peak discharge is shown in section 4.1 of this report.
2.2 Onsite Drainage Subbasins
To size all piping and inlets, sub basins were required to be analyzed for the site. Subbasins 1.3-
1.5, 1.8, 1.12-1.15, 1.17-1.18, 1.20-1.21, and 1.23 are all roof areas that are to be collected via
roof drains, gutters and downspouts that tie directly into the storm system. Sub basins 1.1, 1.2,
1.6-1.7, 1.9-1.10, 1.11, 1.16, and 1.22 collect runoff around the structure via inlets, which include
the patios, the driveway area, and the landscaped areas.
These sub basins are shown on the basins analysis sheet within the civil set. A summary showing
all sub basin characteristics and their peak discharges can be seen in section 4.2 of this report.
2.3 Offsite Drainage Basins
From Crystal River Civil's analysis, it has been determined that there are no offsite basins that
impact the site. Bleeker Street and Aspen Street is collected by the curb and gutter and conveyed
to the west and north away from the property. The proposed Right-of-Way work does not impact
the drainage of the roadways and drainage patterns are maintained.
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3.0 Low Impact Site Design
Low Impact Development (LID) aims to mimic the natural pre-development hydrologic patterns.
The goal is to manage storm water as close to its source as is possible. The captured onsite basin
is 61% impervious.
3.1 Principles
Principle 1: Consider storm water quality needs early in the design process.
The previous design team coordinated with the civil design in the schematic design phase to
minimize the impacts to the site while effectively designing a stormwater system that meets
requirements and needs. It was understood that the footprint of the building was going to drive
underground storage and to release at a depth that would not impact the basement.
Principle 2: Use the entire site when planning for storm water quality treatment.
Given the footprint of the proposed residences, minimal space could be utilized for stormwater.
However, the proposed design was utilized in a way to minimize the impacts of the existing
conditions, trees and transitions into existing grade. Patios are proposed to sheetflow into
landscaped areas to allow for a treatment train prior to entering the storm networks.
Principle 3:Avoid unnecessary impervious area.
The proposed hardscaping is kept at a minimum to reduce impervious areas. Sand set pavers
were utilized to promote infiltration into the ground in areas. All areas outside of the foundation
footprint are pervious, excluding the driveway.
Principle 4: Reduce runoff rates and volumes to more closely match natural conditions.
All runoff from impervious surfaces on the property is collected and conveyed to a drywell, which
has been sized for 100-year storm event full detention volume. The proposed onsite detention
ultimately reduces the amount of drainage flows into the Right-of-Way and encourages high rates
of infiltration.
Principle 5: Integrate storm water quality management and flood control.
A drywell is proposed onsite, which is designed to capture and treat stormwater for the entire site.
This drywell has been sized for full detention of a 100-year 1-hour storm event,which will eliminate
any flooding impacts in Aspen that would be generated from this site.
Principle 6: Develop storm water quality facilities that enhance the site, the community, and the
environment.
The proposed stormwater system is designed to be treated onsite and will reduce the runoff into
the public Right-of-Way system. This will minimize ice buildup in the alleyway and impacts of
stormwater on neighboring residences from the existing residence. The design allows for more
than adequate drainage while having minimal visual impacts. Full detention of the stormwater
increases the infiltration amount, which has a positive impact on groundwater.
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Principle 7: Use treatment train approach.
The design proposes patios to release into landscaping to allow treatment prior to entering the
storm system in multiple areas on the site. Sumps are proposed for the inlets in the pipe network
to ensure treatment throughout the system. The filtration system within the dual chamber drywell
allows for an additional treatment level prior to infiltration.
Principle 8: Design sustainable facilities that can be safely maintained.
Inlets, piping, and the drywell will be vacuumed or flushed periodically, as specified in the
maintenance section of this drainage report,to maintain adequate flow as designed. The designed
system includes cleanouts at roof drain connections and downspouts, simplified collection
systems that minimize maintenance, and easy access to the whole system. The dual chamber
drywell minimizes clogging and allows for maintenance of the system for longevity.
Principle 9: Design and maintain facilities with public safety in mind.
The proposed design for driveway and walkways allows for adequate drainage and reduces ice
buildup and dangerous conditions. Walkways and stairways are pitched at recommended slopes
and within building code thresholds to allow for safe circulation within the property. Grading has
been kept to a minimum and retainage has been minimized. Transitions into existing conditions
are smooth and natural. Full Detention of stormwater minimizes the impacts of runoff onto streets
and alleyways, minimizing erosion, road damage, and icy conditions.
4.0 Hydrologic Criteria
4.1 Runoff Calculation Method
Calculations and analyses defined in Chapter 2 and Chapter 3 of the URMP were used to define
the runoff from the basins on the property. The property is classified as a "Sub-urban area not
served by public storm sewer." Pre-developed and developed runoff rates were determined for
both the 5-year 1-hour and the 100-year 1-hour storm events for capacity designs as required by
this classification. The basins defined for the project can be seen on the basins sheet of the civil
set.
The peak discharge shown in this analysis uses the Rational Method, as described in section 3.4
of the URMP. This requires several variables to be determined, including values for intensity, the
runoff coefficient, and basin area. Using the rainfall depths from Table 2-2 and the basin time of
concentration in conjunction with Equation 2-1, the rainfall intensity for the basins can be
calculated. The rainfall intensity equation shown in the URMP is a direct correlation of the Aspen
area Intensity Duration Frequency Curve derived from the NOAA Atlas 14 database. As stated
within the URMP, the time of concentration can be no less than 5 minutes for the calculations to
be effective. Due to the size of the basins on the site, the time of concentration within the basins
is less than five minutes. The runoff coefficient for each basin was established using the percent
impervious of the basin and the soil type in conjunction with the most up-to-date values as
presented in the Mile High Flood District Drainage Design Values for the specified soil type in the
area. For this project, an NRCS Soil Classification of B was utilized.
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4.2 Basin Analysis
The tables below summarize the calculations that were performed on the basins using the
methods described in Section 4.1 of this report.
5-Year 1-Hour Onsite Peak Discharge Calculate
88.8P,
Rainfall depth,P,(i 0.64 Soil Class B Intensity(in/hr) I—0.0+Td)'.052 Discharge(ft3/Sec) Q=CIA,
Note:For basins with a flow length of less than 500 feet,a Time of Concentration is assumed at 5 minutes.These calculations are assuming a NRCS Hydrologic Soil Class B.
Rainfall depth values derived from NOAA Atlas 14 data.Intensity equation has been derived from the Aspen area NOAA Atlas 14 IDF Curve.
Predeveloped Conditions
M. Basin otal Area Impervious Area Percent Impervious C Value Time of Concentration Intensity Peak Discharge
(Name) A,(ft2) A,(ft2) A,/A,(%) T,(min) I(in/hr) Q„(ft2/sec)
1 4235 0 0.00% 0.010 5 3.29 0.00
Developed Conditions
Basin Total Area Impervious Area Percent Impervious C Value 1 Time of Concentration Intensity Peak Discharge
(Name) A,(ft) A(ft) A,/A,(%) T,(min) I(in/hr) Qd(ft3/sec)
1 4235.00 2583.00 60.99% 0.490 5 3.29 0.16
100-Year 1-Hour Onsite Peak Discharge Calculations
88.8P,
Rainfall depth,P,(in) 1.23 Soil Class B Intensity(in/hr) I I—(10+Td)1°12 Discharge(ft3/Sec) Q=CIA,
Note:For basins with a flow length of less than 500 feet,a Time of Concentration is assumed at 5 minutes.These calculations are assuming a NRCS Hydrologic Soil Class B.
Rainfall depth values derived from NOAA Atlas 14 data.Intensity equation has been derived from the Aspen area NOAA Atlas 14 IDF Curve.
Predeveloped Conditions
- Basin Total Area Impervious Area Percent Impervious C Value Time of Concentration Intensity Peak Discharge
(Name) _ A,(ft2) A,(ft2) A,/A,(%) T,(min) I(in/hr) Qo(ft2/sec)
1 -'25 0 0.00% 0.430 5 6.33 0.26
Developed Conditions
Basin Total Area Impervious Area Percent Impervious C Value Time of Concentration Intensity Peak Discharge
(Name) A,(ft) Al(ft) Ai/A,(%) T,(min) I(in/hr) Qd(ft2/sec)
1 4235.00 2583.00 60.99% 0.710 5 6.33 0.44
4.3 Sub Basin Analysis
In addition to determining the peak discharge from basins, the areas are then subdivided into sub
basins to calculate their peak discharges. This allows for verification that all pipes and intakes into
the proposed conveyance structures have capacity. The URMP requires all structures to have
capacity for a 100-year 1-hour storm event. Using the same procedure discussed in 2.1 of this
drainage report, the peak discharge of each sub basin was determined.
Below is a table summarizing the values required for the sub basin analysis.
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Basin Flow Rate Calculations .
Rainfall de th,P in 1.23 Soil Class B Intensityin/hr I= 88.8P, s
P ( ) ( ) (10+Td)"52
Discharge(ft/Sec) Q=CIAt
I.
The values shown in this table are analysing a 100-Year 1-Hour Storm Event.For basins with a flow length of less than 500 feet,a Time of Concentration of 5 minutes is assumed.
Developed Conditions
i_Sub Basin ' Total Area Impervious Area Percent Impervious C Value Time of Concentration Intensity Flow Rate
(Name) A,(ft2) Al(ft2) A;/A,(%) C(From Table) To(min) I(in/hr) Qs(ft3/sec)
1.1 443 0 0.00% 0.43 5 6.33 0.03
1.2 266 0 0.00% 0.43 5 6.33 0.02
1.3 336 336 100.00% 0.89 5 6.33 0.04
1.4 205 205 100.00% 0.89 5 6.33 0.03
1.5 207 207 100.00% 0.89 5 6.33 0.03
1.6 243 0 0.00% 0.43 5 6.33 0.02
1.7 67 67 100.00% 0.89 5 6.33 0.01
1.8 190 190 100.00% 0.89 5 6.33 0.02
1.9 69 0 0.00% 0.43 5 6.33 0.00
1.10 397 0 0.00% 0.43 5 6.33 0.02
1.11 234 0 0.00% 0.43 5 6.33 _ 0.01
1.12 174 174 100.00% 0.89 5 6.33 - 0.02
1.13 113 113 100.00% 0.89 5 6.33 0.01
1.14 197 197 100.00% 0.89 5 6.33 0.03
1.15 206 206 100.00% 0.89 5 6.33 0.03
1.16 236 236 100.00% 0.89 5 6.33 0.03
1.17 78 78 100.00% 0.89 5 6.33 0.01
1.18 79 79 100.00% 0.89 5 6.33 0.01
1.19 15 15 100.00% 0.89 5 6.33 0.00
1.20 142 142 100.00% 0.89 5 6.33 0.02
1.21 168 168 100.00% 0.89 5 6.33 0.02
1.22 26 26 100.00% 0.89 5 6.33 0.00
1.23 144 144 100.00% 0.89 5 6.33 0.02
4.4 Water Quality and Storage Requirements
For a property classified as a "Sub-urban area not served by public storm sewer", runoff from the
site must meet the predeveloped peak discharge of a 100-year 1-hour storm event. Given the
grade of this site being so flat, an overflow is not feasible. The release from the drywell could not
be controlled if overflowing out the manhole lid. Therefore, the design is proposing full detention
of a 100-year 1-hour storm event. To determine how much storage is necessary, the storm event
depth was applied to all impervious areas within the basins to create a volume. The technique
being applied replaces the Modified FAA Method that is prioritized in the URMP. This volume set
the minimum sizing for the drywell, which is shown in the table below.
Full Detention Storage
Basin Point of Concentration Total Area Impervious Area Impervious Full Detention Depth Factor of Safety Full Detention Storage
(Name) (name) (ft2) (ft2) (%) (in) (FOS) (f0)
1 Drywell A 4235.00 2583.00 60.99% 1.23 1.5 397
In addition to this calculation, the URMP requests to verify the system has capacity for the Water
Quality Capture Volume, or WQCV. The WQCV is determined using the basin's percent
impervious in correspondence with Figure 8.13 of the URMP. This WQCV value is then applied
to the basin area, as described in Section 8.4 of the URMP.
The table below summarizes the detention requirements for the site and verifies that the Full
Detention Volumes meet the requirements for WQCV as well.
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Water Quality Capture Volume and FAA Storage Calculation
Water Quality Capture Volume(WQCV),ft3 WQCV=WQCV in Watershed In12hes x Area x FOS
Basin Point Of Concentration Basin Area Impervious Percentage Water Quality Depth Factor Of Safety Water Quality Capture Volume
(Name) (Name) (ft2) (%) (in) (FOS) WQCV(ft3)
1 Drywell A 4235.00 61% 0.12 1.50 62.47
5.0 Hydraulic Criteria
The following analyses were performed using the peak flows of the sub basins described in
Section 4.2 of this report.
5.1 Inlets
The peak flows for the 100-year event in each sub-basin were used to size the proposed inlets.
Equations 4.17 through 4.20 from the URMP were used in these calculations. The equations
incorporate a 50 percent clogging factor and assume a 40 percent opening in the grates. Water
depths used in these calculations are based on the grading around each inlet and safe ponding
levels above the inlets. Each inlet takes the smaller value of the weir intersection capacity and
the orifice opening capacity, whichever is the smallest. The proposed dimensions of each inlet
must be greater than the subbasin peak flow for the 100-year storm. The tables below summarize
the calculations for each inlet as well as for the trench drains.
Round Inlet Capacity Calculation
Effective Inlet Area,A,(ft) A,=(1-Cg)(n(22)')m Inlet Orifice Capacity,Qo(ft'Is) Q,=C,A„/2gY, Weir Flow Capacity,Qw(ft'/s) Qw=C,,,Pell s
Orifice Coefficient,Co 0.65 Clogging Factor,Co 0.5 Area Opening Capacity Ratio,m 0.6
Weir Coefficient,Cw 3 Water Depth Above Inlet,Y,(ft) 0.25 Effective Weir Length,P,(ft) P,=(1-Cg)P
Inlet Associated Subbasin Inlet Diameter Effective Inlet Area Orifice Flow Capacity Weir Flow Capacity Subbasin Flow
L il (Name) D,(in) A,(ft2) Qo(ft3/s) Ow(ft3/s) Q(ft3/s)
Al-Inlet 1.1 8 0.10 0.27 0.79 0.03
PA-Inlet 1.2 8 0.10 0.27 0.79 0.02
Ale-Inlet 1.6 8 0.10 0.27 0.79 0.02
Al2-Inlet 1.10 8 0.10 0.27 0.79 0.02
B1-Inlet 1.11 8 0.10 0.27 0.79 0.01
Cl-Inlet 1 22 6 0.06 0.15 0.59 0.00
Rectangular Inlet Capacity Calculation
�e/12 CwP Yis
Effective Inlet Area,A.(ft') A,=(1-Ce)(n( 2 )')m Inlet Orifice Capacity,Qo(Os) Q�=L,AQ✓Z9Y Qw-
Wier Flow Capacity,CIw(Os)
Orrifice Coefficient,Co 0.65 Clogging Factor,C. 0.5 Area Opening Capacity Ratio,m 0.6
Weir Coefficient,C,, 3 Water Depth Above Inlet,Y,(ft) 0.25 Effective Weir Length,P,(ft) P=(1-C.,)P
Inlet Associated Subbasin Inlet Length Inlet Width Effective Inlet Area Orifice Flow Capacity Wier Flow Capa
(Name) (Name) (in) (in) A,(0') Q,(ft'/s) aw(ft'/s)
A951ot Dra n 1.7 48 0.3 0.08 0.22 1.52 0.01
B9-Trench Drain 1.16 733 4 2.21 5.76 841 0.03
B13-Trench Drain 1.19 265 4 2.21 5.76 8.41 0.00
5.2 Pipes
The pipes were sized using the calculated flows from the sub-basins that release into them
through inlets and downspouts. The Time of Concentration (TOC) is below 5 minutes for all sub-
basins, so a reduction was not taken for the intensity. Depth of flow was also calculated in the
spreadsheets below to verify requirements set within the URMP. The pipes are all SDR-35 PVC
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with a manning's coefficient of.01. Design Q design/Q full values were compared to the wetted area
over the diameter squared for each pipe to generate the correct depth of water over diameter
pipe. All these ratio values are derived from the Manning's Equation for partially full pipes. The
equations in Section 4.8.4 were used as the basis for these calculations. As specified in the
URMP, each pipe was confirmed to be less than 80% full for the 100-year 1-hour storm event.
Design charts giving Qdesigi, / Q full were downloaded from 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.
City of Aspen Pipe Capacity Calculations
/E4'Y Min.Pipe Diameter, _(nQp'i Mannings Equation /1,.9\ /Do\°/a Manning Coefficient,
Pipe Sectional Area(ftZ) Ap=n 2 J Eq.4.31(ft) 0"' kf (ft°/s) Q`=I\-/I Ap I\4B/I n 0.01
Note.Pipe Flow Rate(Q,)is the summation of the flow rates from the the collected sub basins through each pipe,or Q,.
r7� -ins Pipe Flow Rate Slope Min.Pipe Di. 'pe Max Flow Rate Percent of Cap -pth Pipe Depth Percent
Qo(ft3/sec) .S(%) Do fin) Q,(ft3/s) op/Q,(%) (Chart) d (%)
Al 1.1 0.03 1.50% 1.6 4 0.304 9% 0.14 0.56 14%
A2 1.1 0.03 1.50% 1.6 4 0.304 9% 0.14 0.56 14%
A3 1.1 0.03 1.50% 1.6 4 0.304 9% 0.14 0.56 14%
A4 1.1,1.2 0.04 1.50% 1.9 4 _ 0.304 15% 0.20 0.80 _ 20% _
A5 1.3 0.04 1.50% 1.9 4 0.304 14% 0.20 0.80 20%
46 1.1-1.3 0.09 1.50% 2.5 4 0.304 29% 0.33 1.32 33%
A7 1.4 0.03 1.50% 1.6 4 0.304 9% 0.13 0.52 13%
AB 1.4,1.5 0.05 1.50% 2.1 4 0.304 18% 0.23 0.92 23%
A9 1.7 0.01 1.50% 1.1 4 0.304 3% 0.06 0.24 6%
A10 1.1-1.7 0.16 1.50% 3.2 4 0.304 54% 0.53 2.12 53%
All 1.1-1.7 0.16 1.50% 3.2 4 0.304 54% 0.53 2.12 _ 53% _
Al2 1.1-1.10 0.22 1.50% 3.5 4 0.304 72% 0.67 2.68 67%
B1 1.11 0.01 1.50% 1.3 4 0.304 5% 0.09 0.36 9%
B2 1.12 0.02 1.50% 1.5 4 0.304 7% 0.12 0.48 12%
B3 1.11,1.12 0.04 1.50% 1.8 4 0.304 12% 0.17 0.68 17%
B4 1.13 0.01 1.50% 1.3 4 0.304 5% 0.09 0.36 9%
B5 1.11-1.13 0.05 1.50% 2.1 4 0.304 17% 0.22 0.88 22%
B6 1.14 0.03 1.50% 1.6 4 0.304 8% 0.13 0.52 13%
B7 1.11-1.14 0.08 1.50% 2.4 4 0.304 25% 0.30 1.20 30%
B8 1.11-1.15 0.10 1.50% 2.7 4 0.304 34% 0.37 1.48 37%
B9 1.16 0.03 1.50% 1.7 4 0.304 10% 0.15 0.60 15%
B10 1.11-1.16 0.13 1.50% 3.0 4 0.304 44% 0.45 1.80 45% _
B11 1.17 0.01 1.50% 1.1 4 0.304 3% 0.07 0.28 7%
B12 1.11-1.18 0.15 1.50% 3.1 4 0.304 51% 0.50 2.00 _ 50%
B13 1.19 0.00 1.50% 0.6 4 0.304 1% 0.02 0.08 2%
B14 1.11-1.19 0.16 1.50% 3.1 4 0.304 52% 0.51 2.04 51%
B15 1.11-1.20 0.17 1.50% 3.3 4 0.304 58% 0.55 2.20 55%
B16 1.11-1.21 0.20 1.50% 3.4 4 0.304 65% 0.61 2.44 61%
B17 1.11-1.23 0.22 1.50% 3.5 4 0.304 72% 0.67 2.68 67%
C1 1.22 0.00 1.50% 0.7 4 _ 0.304 1% 0.03 0.12 3% _
C2 1.22 0.00 1.50% 0.7 4 0.304 1% 0.03 0.12 3%
C3 1.22-1.23 0.02 1.50% 1.5 4 0.304 7% 0.12 0.48 _ 12% _
Dl 1.9 0.00 1.50% 0.8 4 0.304 1% 0.04 0.16 4%
D2 1.9 0.00 1.50% 0.8 4 0.304 1% 0.04 0.16 4%
r
D3 1.8 0.02 1.50% 1.6 4 0.304 8% 0.13 0.52 13%
D4 1.8 0.02 1.50% 1.6 4 0.304 8% 0.13 0.52 13%
D5 1.8-1.9 0.03 61.90% 0.8 4 1.952 1% 0.04 0.16 4%
6.0 Proposed Facilities
6.1 Drywell 1
The proposed Dual Chamber drywell meets the requirements of the URMP. The sizing of the
drywell was determined using the capacity calculations summarized in Section 4.4 of this drainage
report. Below is a summary showing the drywell dimensions to verify it has capacity. The chamber
divider, flat lid, and manhole lid were not included in these dimensions, which is why the proposed
drywell is 23' deep, not the 19' of storage depth shown in the calculations.
Crystal River Civil LLt 970.510.5312 Page 11 of 12
-'1
RI IAIRI IR I Il
Storage Calculation-Drywells
Internal Capacity,Vi(ft3) V,=hn(i)c External Capacity,V,(ft) Ve=hg(n(d Z1�5)c—n(a)2) Combined Capacity,V(ft3) V=V,+V,
Drywell Name Associated Basin Drywell Diameter Storage Heightravel Height Internal Capacity External Capacity Combined Capacity Calculated Volume Necessary
(Name) (Name) d(ft) h(ft) ha(ft) V,(fl3) Ve((l3) V(ft3) (ft3)
Drywell A 1 5 19 4 373.06 54.19 427.26 397.14
Utilizing the percolation rate of one minute per inch that was provided in the geotechnical analysis,
it was verified that the system will completely release into the surrounding soils within 24 hours.
The calculations for this are shown below.
Drywell Infiltration Calculation
Exterior Infiltrative Area 0t Drywell(!) q —n(On+2Wn+2W,a)ln Infiltration Flow Rate(a,) ,—qe/ I Infiltrative Time(Ti) T,=Q/
Notes:This calulcation confirms all calulcated sotrage volume for a specifed drywell has the ability to drain within 24 hours from the beginning of a storm event.
The exterior Infiltrative area of the drywell accounts for the Interior diameter,concrete thickness(6"for drywells),and the external screened rock width.All equations listed above Include the conversion factors.
ration Flow Rate Kt) Infiltrative Time(Ti)
(Name) ft 9 ft mixtinch ft' ft' fts/hr hours
A 5 4 1.5 1 397.14 113.10 56549 0.70
7.0 Operation and Maintenance
7.1 Drywell
The drywell shall be inspected and maintained at least every three months to remove any
sediment, contaminants, and debris that has settled in the drywell. At minimum, the inspection
and maintenance of the drywell shall include the following steps:
• Drywell shall be continuously inspected. At minimum, every three months and after every
storm event greater than '/2 inches.
• Remove and dispose of any sediment, solids, debris, and any other waste. All material
removed from drywell shall be disposed of at a fitting disposal site and shall meet/comply
with all local, State, and Federal waste regulations/jurisdictions.
• Regularly inspect the drywells functionality in respect to the time it takes for water to drain
in the drywell to mee the maximum required infiltration time of 24 hours is not exceeded.
When drain down times in the drywell are larger than 24 hours, the drywell shall be drained
via pumping and the infiltrative area of the drywell shall be cleaned and all perforation in
the drywell shall be thoroughly washed out. If irregular drainage of the drywell continues
as described above, the system may be required to be replaced.
7.2 Inlets and Trench Drains
Trench drains and other linear drains shall be inspected and maintained on a regular basis to
prevent any clogging and debris from entering the storm system to provide correct functionality.
Grates and the adjacent areas to the trench drain shall be kept clean and clear of any leaves, soil,
and any other solid waste materials to prevent clogging or larger materials from entering in the
storm system. Drain sumps and catch basins shall be inspected, at the very minimum, every three
months and for each storm event that is greater than '/2 inches in depth. All sediment shall be
cleaned out or vacuumed from the drain and catch basin. All sediment shall be disposed of
correctly, meeting local jurisdictional codes and requirements. Any damage to the grate and the
surrounding concrete shall be repaired correctly to maintain functionality of the drain. The grate
shall be replaced if excessive damage is present.
Crystal River Civil LLC 970.510.5312 Page 12 of 12