HomeMy WebLinkAboutFile Documents.219 N Monarch St.0279.2018 (19).ARBK
DRAINAGE REPORT
FOR
219 NORTH MONARCH
CITY OF ASPEN, COLORADO
PARCEL ID: 273707316004
PREPARED FOR:
EIGELBERGER ARCHITECTURE & DESIGN
220 West Main Street
Suite 201
Aspen, CO 81611
PREPARED BY:
High Country Engineering, Inc.
1517 Blake Avenue, Suite 101
Glenwood Springs, CO 81601
(970) 945-8676
July 24, 2017
Revised: October 31, 2018
HCE JOB NUMBER: 2171613.02
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TABLE OF CONTENTS
SECTION PAGE
I. GENERAL LOCATION AND HISTORIC DESCRIPTION 4
II. DRAINAGE STUDIES 4
III. DRAINAGE DESIGN CRITERIA 5
IV. DRAINAGE FACILITY DESIGN 8
V. CONCLUSION 12
VI. REFERENCES 13
EXHIBITS:
1. Vicinity Map (8.5”x11”)
2. SCS Soils Map (8.5”x11”)
3. FEMA Map (11”x17”)
4. Flow Path to City System (8.5”x11”)
5. Historic Drainage Conditions (24”x36”)
6. Proposed Drainage Conditions (24”x36”)
7. Tree Canopy Credit (11”x17”)
8. Detail Sheet (24”x36”)
9. Soil Reports (H-P/Kumar)
Appendices
Hydrologic Computations
Historic Conditions
Proposed Conditions
Hydraulic Computations
Trench Drain Calculations
Swale Calculations
Weir Calculations
Pipe Calculations
Inlet and Slot Drain Calculations
Aspen Charts and Figures
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11/15/2018
Reviewed by Engineering
12/14/2018 9:55:22 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.
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I. GENERAL LOCATION AND DESCRIPTION
A. Location
The site is located at 219 North Monarch Street within the City of Aspen, County of Pitkin,
State of Colorado, along the southeast corner of the North Monarch Street and East Hallam
Street intersection. A Vicinity Map has been included as Exhibit #1.
B. Description of Existing Property
The proposed site is approximately 9,023 square feet (0.21 acres). The existing lot consists of
a home, deck, driveway, garage, landscaping and numerous trees. The site is bordered by a
private property to the west, a gravel alley to the south, East Hallam Street to the north and
North Monarch Street to the east. The site drains from the southeast to the northwest and
offsite in the curb and gutter of East Hallam Street. One offsite basin drains onto the site.
Existing grades range from approximately 1-percent to 5-percent.
C. Soils Description
H-P/Kumar, Inc. on April 21, 2017, project number 17-7-317, completed a site-specific
geotechnical soil study. The geotechnical study describes the site as having 1 to 11/2 feet of
topsoil overlying dense, silty sandy gravel with cobbles and boulders. There was no free
water encountered in the boring at the time of excavation, and the subsoils were slightly moist.
The report classifies the soil as Type B having a moderate infiltration rate. Results from the
completed 4-inch diameter borehole indicate a suitable infiltration rate of 1 minute per inch
for bioretention. The site is also well above the river elevation, and groundwater was not
encountered to the borehole depth of 12 feet. The City of Aspen soils map locates this site in
the Type “B” soils area. According to the USDA Web Soil Survey, the property is within
section 107 and the report states that it consists of soil Type “B”; see USDA Web Soil Survey
exhibit #2
II. DRAINAGE STUDIES
A. Major Drainage Way Planning and Influential Parameters
The site is located within FEMA’s major drainage study of the area on its Flood Insurance
Rate Map (FIRM) No. 08097C0203C which has an effective date of June 4, 1987. The area of
interest within the site is located in Zone X. This zone is described as areas determined to be
outside the 100-year and 500-year floodplains. Refer to Exhibit #3 for the FEMA map.
Mud flow was not analyzed for the site since the site is located outside of the Mud Flow Zone
as indicated in the Storm Drainage Master Plan for the City of Aspen, Colorado by WRC
Engineering, Inc. in November of 2001.
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B. Previous Drainage Studies
Per the November 2001 study completed by WRC Engineering, Inc. titled, “Storm Drainage
Master Plan for the City of Aspen, Colorado,” the site is located within System 3. According
to the City of Aspen Master Drainage Plan figure ES-3, an existing 48-inch corrugated metal
pipe travels from a catch basin at the intersection of East Hallam and North Garmisch Street to
an adjoining 36-inch HDPE pipe at the intersection of North Garmisch Street and West
Francis Street. This 36-inch HDPE pipe conveys runoff to the outfall point. Per figures ES-6
and ES-7, the site is located outside of any 100-year storm water flooding and 100-year mud
flow zones.
C. Receiving System and Effects of Adjacent Drainage Issues
There are no major drainage issues with the adjacent properties that affect the site or that the
site affects. The existing site directly discharges a majority of the runoff to the north property
line. The existing flow leaves the property to the north, then travels west down the curb and
gutter system of East Hallam Street. The runoff will begin to flow west in the previously
mentioned curb and gutter until the flow enters the catch basin at the intersection of East
Hallam Street and North Garmisch Street. Once captured in the City of Aspen catch basin, the
runoff will be conveyed with a 36” HDPE pipe to the outfall point at the Jennie Adair
Wetlands.
III. DRAINAGE DESIGN CRITERIA
A. Criteria
This drainage study was prepared in conformance with the City of Aspen, Colorado Urban
Runoff Management Plan (URMP), dated April of 2010 and the revised sections dated
thereafter. More than 1,000 square feet of area will be disturbed with the proposed
construction; therefore, the site is viewed as a Major Project per the URMP. More than 1,000
square feet are being disturbed and more than 25-percent of the overall site is being disturbed,
so water quality for the entire site will be necessary per the URMP. The existing site was
analyzed in its historic condition (i.e. no improvements). The offsite basins consisting of an
alley and landscaping was analyzed as existing (open space and impervious area) per the
URMP. The onsite water treatment systems were sized to pass the offsite flow.
Water Quality Capture Volume (WQCV) will be determined for the site that will undergo site
grading as per the URMP standards. The WQCV is defined as the treatment for up to the 80th
percentile runoff event, corresponding to between a 6-month to 1-year event. The WQCV was
determined using the equations and Figure 8.13 from Chapter 8 of the URMP. The WQCV
equation is: Volume (ft3) =WQCV (watershed-inches) x 1/12(ft./in) x area(acres) x 43,560
ft2/acre. The runoff for the onsite basins will be routed through a series of swales receiving
storm water from sheet flow and downspouts to three bioretention areas/planters, where the
runoff will be treated for WQCV.
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B. Hydrologic Criteria
The hydrologic methods for this study are outlined in the URMP from the City of Aspen,
Colorado (April, 2010) and the Microsoft Excel spreadsheet for the Rational Method.
The rainfall amounts for each basin were obtained using Figure 2.1 “IDF Curves for Aspen,
Colorado” in the URMP publication from the City of Aspen, Colorado. Using these curves,
the rainfall intensity corresponding to the 2-yr, 1-hr storm 10-yr, 1-hr storm, and 100-yr, 1-hr
storm event were determined based on the time of concentration for each basin.
Figure 3.3 from the URMP was used to determine the runoff coefficients for the 2-year, 10-
year and 100-year storm events since the soils were determined to be type ‘B’ soils.
For areas within the Aspen Mountain Drainage Basin capable of discharging runoff into the
City’s system without impacting neighboring properties, detention is not required beyond
WQCV. The site meets the previously mentioned requirements, thus the volume for detention
was calculated for WQCV only, as outlined in the URMP. Exhibit 4 shows the flow path to
the City’s system.
The bioretention areas were sized to handle the WQCV, but do not detain the 10-year and 100-
year runoff per the URMP. Type ‘B’ soils were determined for the site per the NRCS Soil
Map for Aspen and confirmed by a site specific geotechnical study.
All charts and figures mentioned from the URMP are located in the last section of the
appendices under the “Aspen Charts/Figures” section.
C. Hydraulic Criteria
The swales, trench drains, weirs and overflow pipe within the system have been calculated
utilizing the Hydrology calculator with AutoCAD’s system. All drainage features and
structures have the ability to carry entire basin design flows anticipated in a major rain event.
See basin descriptions below for explanation.
D. Site Constraints
There are no utilities, streets or structures that cause major site constraints for the drainage
system design. The site is in close proximity with adjacent properties and located on the
corner of two local streets.
E. Easements and Irrigation Facilities
There are no major drainage ways, drainage easements or tracts located on the site. There are
also no irrigation facilities onsite that affect the overall proposed development.
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F. Low Impact Site Design
Three bioretention areas will be implemented to allow for the capture of the required WQCV
per the URMP code. Should the bioretention areas exceed the WQCV capacity, runoff will
reach the City of Aspen drainage system and outfall in the Jennie Adair Wetlands where water
is absorbed and naturally treated before reaching the Roaring Fork River.
G. 9 Principles
The 9 Principles for storm water quality management were followed during the design process
to create the best storm water design and water quality management. The following is a
summary of compliance with the Storm Drainage Principles outlined in the City of Aspen
Urban Runoff Management Plan:
1. Consider storm water quality needs early in the design process
Storm water quality needs were considered early in the design process, as
recommended.
2. Use the entire site when planning for storm water quality treatment.
With the use of three bioretention ponds and vegetated swales, the entire site is
utilized for water quality treatment.
3. Avoid unnecessary impervious area
Efforts were made to avoid unnecessary impervious areas in drainage design.
Existing impervious areas will be redeveloped, but the site will have an overall
increase in impervious area.
4. Reduce runoff rates and volumes to more closely match natural conditions
Runoff rates and volumes have been reduced, as recommended, by implementing a
series on bioretenion areas connected by vegetated swales. All impervious areas
will drain to at least one bioretention area. The lot is two blocks from the city storm
sewer system that is sized for the developed lots in this portion of the city.
5. Integrate storm water quality management and flood control
Three proposed bioretention areas capture runoff onsite and are connected by
vegetated swales in the case of overflow. Downstream swales have been sized to
accommodate overflow from upstream basins. The south bioretention area contains
an overflow outlet that will discharge to the northeast bioretention area. The two
north bioretention areas incorporate weirs to discharge overflow in a controlled
manner. The proposed site has been designed for water quality only, which does not
provide flood control detention, but has an overflow path to suitably convey runoff
into the City of Aspen’s drainage system.
6. Develop storm water quality facilities that enhance the site and environment.
The proposed water quality facilities enhance the site and the environment with
bioretention areas that will become part of the landscape.
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7. Use a treatment train approach
The treatment train approach has been implemented by incorporating bioretention
areas connected by vegetated swales.
8. Design sustainable facilities that can be safely maintained
The proposed storm water quality facilities have been designed to be easily
accessible and safely maintained, as recommended.
9. Design and maintain facilities with public safety in mind
The proposed storm water quality facilities have been designed with public safety
in mind, as requested. For example, the south bioretention area has been designed
with more gradual slopes because of the close proximity to foot traffic.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
The proposed construction calls for the redevelopment existing site. A proposed two-story
residence with a basement will be constructed after the removal of the existing residence,
detached garage and two driveways. The impervious areas for the entire site will be treated for
WQCV by bioretention areas. Runoff will be routed through sheet flow and drainage swales
receiving runoff from downspouts and hardscape. Swales with slopes less than two-percent
will contain an impermeable liner with an underdrain, thus having no impact on existing or
proposed facilities. Offsite stormwater enters the site from the landscape area between the site
property line and North Monarch Street, as well as the alley south of the site. Runoff, greater
than WQCV, will leave the site in historical fashion to the City of Aspen’s drainage system.
B. Historic Drainage Basins Descriptions
The proposed site’s historic drainage pattern is from the southeast to the northwest and offsite
to the curb and gutter system of East Hallam Street before being captured by the City of
Aspen’s catch basin and conveyed to the Jennie Adair wetlands. The existing site has been
analyzed in its historic conditions.
The historic site has been broken into two on-site basins and one off-site. Refer to sheet
EXDR (exhibit #4) for a map of existing basin layouts. Two low points delineate basins EX-1
and EX-2 to encompass the entire lot. Basin EXOS-1 encompasses an area to the east and
south of the lot.
Historic Flow Path One:
Runoff from basin EX-1 sheet flows northwest from the southeast corner of the site to the west
before entering the neighboring property approximately midway between the north and south
property lines. Design point one has been associated with the southwestern half of the lot.
Basin EX-1 receives additional runoff from off-site basin EXOS-1. Table 1 below is a
summary of the existing basin information.
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Historic Flow Path Two:
Runoff from basin EX-2, similarly to basin EX-1, sheet flows from the southeastern corner of
the site to the northwest. This basin discharges at the northwest corner offsite into the right of
way and into the curb and gutter system on East Hallam Street. Once in the curb and gutter
systems, the storm water continues to the previously mentioned outfall point. Design point two
has been associated with the northeast half of the lot. Basin EX-1 receives additional runoff
from off-site basin EXOS-1. Table 1 below is a summary of the existing basin information.
There are no negative impacts from the runoff to the adjacent properties because the runoff
has low discharge rates that sheet flow across permeable land and drains directly into City of
Aspen curb and gutter system. No runoff drains directly to any downstream structures. Refer
to Exhibit #4 in the appendices for the existing basin delineation and information. Table 1,
below, is a summary of the existing basin information.
Table 1. Historic Basin Characteristics
C. Proposed Basin Description
The proposed site has been separated into three proposed onsite drainage basins, and one
offsite basin.
Proposed basin PR-1 encompasses the western portion of the site and consists of almost half
of the proposed residence including hardscape. The runoff from basin PR-1 is captured by a
vegetated swale with underdrain and discharges into a proposed bioretention area.
Downspouts from the proposed roof and a trench drain along the proposed driveway discharge
into the previously mentioned swale. Runoff will also sheet flow into the swale. Design point
one is located in the northwest corner of the basin and is associated with all onsite and offsite
basins, as the bioretention of the other two basins are interconnected to overflow into the
bioretention area in basin PR-1. Should the PR-1 bioretention over exceed the required
WQCV amount, runoff overtop the bioretention’s spillway weir into a wide, shallow swale
before continuing flow north into the East Hallam Street curb and gutter system, as it did
historically.
Proposed basin PR-2 encompasses the area at the northeast corner of the site. A drainage
swale east of the proposed residence receives runoff as sheet flow discharging into the
northeast bioretention area. This bioretention area also directly receives sheet flow from the
surrounding pervious areas and as well as pipe flow from the slot drain capturing runoff from
roof downspouts and patios in the southeast corner of house. Should the bioretention facility
reach over capacity, the storm drainage will spill over a weir and into a drainage swale leading
BASIN AREA,
ACRES
C,
10YR I, 10YR Q10-YEAR,
CFS C, 100YR I, 100 YR Q100-YEAR,
CFS
EX-1 0.10 0.15 2.35 0.03 0.35 3.75 0.13
EX-2 0.10 0.15 2.19 0.04 0.35 3.50 0.14
EXOS-1 0.065 0.15 3.12 0.03 0.35 4.98 0.11
ONSITE
TOTAL 0.10 ONSITE
TOTAL 0.38
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to the northwest bioretention area. Design point 2 is associated with the overflow swale
conveying runoff from basins PR-2, PR-3 and PROS-1.
Proposed basin PR-3 is located at the southeastern portion of the site. Storm drainage sheets
flows across impervious hardscape and pervious landscape before entering the southern
bioretention area. The bioretention area also receives channel flow from a swale that captures
runoff from the landscape east of the terrace. Should the bioretention area exceed capacity,
runoff will enter a grated outlet before travelling through a 4-inch pipe and discharging into
perforated pipe within the growing media mix of the northeast bioretention area. Design point
3 located at the northern end of the basin and associated with basins PR-3 and PROS-1.
See Exhibit #5 for the proposed basin delineation. Table 2, below, is a summary of the
proposed (developed) basins.
Table 2. Proposed (Developed) Basin Characteristics
BASIN AREA,
ACRES
C,
10YR I, 10YR Q10-YEAR,
CFS C, 100YR I, 100 YR Q100-YEAR,
CFS
PR-1 0.095 0.38 3.96 0.14 0.51 6.33 0.31
PR-2 0.067 0.45 3.96 0.12 0.56 6.33 0.24
PR-3 0.045 0.32 3.73 0.05 0.47 5.96 0.13
PROS-1 0.054 0.35 2.28 0.04 0.49 3.65 0.10
ONSITE
TOTAL 0.31 ONSITE
TOTAL 0.68
D. Downstream Impacts
The proposed onsite grading and detention facilities will have positive downstream impacts
during frequent storm events by capturing and treating the onsite WQCV. This will result in
less flow from the site during frequent storm events. There are no downstream facilities from
the site to be negatively impacted by the site’s redevelopment.
The onsite runoff will leave the site after cleansed in the water quality facilities thus
preventing the spread of pollutants downstream.
Table 3. Proposed WQCV Table
BASIN AREA (S.F.)
IMPERVIOUS
AREA (SF)
PERCENT
IMPERVIOUS (%)
EFFECTIVE
IMPERVIOUS (%)
PR-1 4,149 2,014 48.5 44.9
PR-2 2,904 1,861 64.1 60.6
PR-3 1,970 599 30.4 29.5
TOTAL 9,023 4,474 49.6 47.0
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BASIN BIORETENTION AREA WQCV (Watershed inches) WQCV (CF)
PR-1 NORTHWEST 0.088 30.4
PR-2 NORTHEAST 0.119 28.8
PR-3 SOUTHEAST 0.060 9.8
TOTAL 0.09 69.1
If the bioretention facilities surpass the WQCV, the system will allow runoff to overflow
the pond weirs before entering the City of Aspen curb and gutter system, as it did
historically. Calculations for the proposed drainage facilities are included in the
appendices of this report under the Facility Calculations section.
F. Operation and Maintenance
The proposed drainage facilities are to be constructed in conformance with the City of Aspen
Urban Runoff Management Plan, dated April 2010 and revised thereafter.
The bio-retention basins will need to be inspected and maintained quarterly to make sure that
the reservoirs have not become clogged and that the reservoirs are functioning properly.
Debris and liter removal shall occur routinely.
The perforated pipe beneath the surface of the northeast bioretention pond will need to be
inspected and maintained quarterly for clogging and standing water. Clean outs can be used to
inspect pipes by cameras to determine the location of clogging or collapsed pipe. If clogging
or standing water is observed, thoroughly run a sewer snake through the pipe to unclog.
Should clogging or standing water remain, the growing media mix layer shall be removed and
the perforated pipe shall be exposed and cleaned. After cleaning the perforated pipe, discard
old growing media mix, wrap perforated pipe with new filter fabric sock, and add new
growing media mix. It is not recommended to jet clear the perforated pipe to prevent the filter
fabric from tearing. Solid pipes may be jetted clear if clogged.
The owners of the property will be responsible for the maintenance and upkeep of the drainage
facilities. The property owner shall dispose of sediment and any other waste material removed
from a reservoir at suitable disposal sites and in compliance with local, state, and federal waste
regulations.
This project includes “Low Impact Site Design” to mimic the natural pre-development
hydraulic pattern. Storm water runoff is to be in contact with soils and plants prior to reaching
the City of Aspen curb and gutter system. The plants and soil are to act as filters to remove
pollutants. The proposed plants and soils are present along the lengths of proposed graded
swales and within the proposed bio-retention basins.
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V. CONCLUSION
A. Compliance with Standards
This drainage report has been prepared in accordance with City of Aspen Regulations. The
proposed bio retention ponds will capture and treat the proposed WQCV for all impervious
areas added to the site.
B. Drainage Concept
The proposed drainage design will be effective in controlling any adverse downstream impacts
on landowners or structures. Water quality issues will be minimal as the runoff will be
intercepted and routed to the proposed bio retention ponds.
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VI. REFERENCES
United States Department of Agriculture, Soil Conservation Service: Soil Survey of Aspen-
Gypsum Area, Colorado, Parts of Eagle, Garfield, and GARFIELD Counties, May 1992.
City of Aspen, Colorado: Design and Construction Standards, June 2005.
City of Aspen, Colorado: Urban Runoff Management Plan. April 2010.
WRC Engineering, Inc. Storm Drainage Master Plan for the City of Aspen, Colorado.
November 2001.
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EXHIBITS
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ENGINEERING ADVICE MAY BE REQUIRED.
ENGINEERING ADVICE MAY BE REQUIRED.
SPECIFICATION CLAUSE
KS100 KLASSIKDRAIN W/S.S. BRICKSLOT
100 HEEL RESISTANT - LOAD CLASS A
GENERAL
THE SURFACE DRAINAGE SYSTEM SHALL BE POLYMER
CONCRETE KS100 CHANNEL SYSTEM WITH STAINLESS
STEEL EDGE RAILS AND BRICKSLOT AS MANUFACTURED
BY ACO POLYMER PRODUCTS, INC.
MATERIALS
CHANNELS SHALL BE MANUFACTURED FROM POLYESTER
RESIN POLYMER CONCRETE WITH AN INTEGRALLY CAST-IN
STAINLESS STEEL EDGE RAIL. MINIMUM PROPERTIES OF
POLYMER CONCRETE WILL BE AS FOLLOWS:
COMPRESSIVE STRENGTH: 14,000 PSI
FLEXURAL STRENGTH: 4,000 PSI
TENSILE STRENGTH: 1,500 PSI
WATER ABSORPTION: 0.07%
FROST PROOF YES
DILUTE ACID AND ALKALI RESISTANT YES
B117 SALT SPRAY TEST COMPLIANT YES
THE SYSTEM SHALL BE 4" (100mm) NOMINAL INTERNAL
WIDTH WITH A 5.1" (130mm) OVERALL WIDTH. ALL
CHANNELS SHALL BE INTERLOCKING WITH A MALE/FEMALE
JOINT.
THE COMPLETE DRAINAGE SYSTEM SHALL BE BY ACO
POLYMER PRODUCTS, INC. ANY DEVIATION OR PARTIAL
SYSTEM DESIGN AND/OR IMPROPER INSTALLATION WILL
VOID ANY AND ALL WARRANTIES PROVIDED BY ACO
POLYMER PRODUCTS, INC.
CHANNEL SHALL WITHSTAND LOADING TO PROPER LOAD
CLASS AS OUTLINED BY EN 1433. BRICKSLOT SHALL BE
APPROPRIATE TO MEET THE SYSTEM LOAD CLASS
SPECIFIED AND INTENDED APPLICATION. CHANNEL AND
BRICKSLOT SHALL BE CERTIFIED TO MEET THE SPECIFIED
EN 1433 LOAD CLASS. THE SYSTEM SHALL BE INSTALLED IN
ACCORDANCE WITH THE MANUFACTURER'S
INSTRUCTIONS AND RECOMMENDATIONS.
THE BRICKSLOT GRATING SYSTEM SHALL HAVE AN
OVERALL INTERNAL WIDTH OF 0.88" (22.35mm) WITH TWO
0.31" (8mm) SLOT OPENINGS AND WITH A 0.25" (6.35mm)
TAPERED BAR BETWEEN THE TWO OPENINGS TO PREVENT
DEBRIS FROM BEING TRAPPED. THE BRICKSLOT GRATING
SYSTEM ADDS 3.27" (83mm) TO THE OVERALL HEIGHT OF
THE KS100 SYSTEM
11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
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11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
11/15/2018
APPENDICES
11/15/2018
HYDROLOGIC
COMPUTATIONS
11/15/2018
EXISTING CONDITIONS
11/15/2018
219 MONARCH, ASPEN CO
DRAINAGE REPORT
BY: BDB
CHECKED BY: DRD
DATE: 7-19-17
EX-1 4,194.0 0.10 0.0 0.0 0.08 0.15 0.35
EX-2 4,829.0 0.11 0.0 0.0 0.08 0.15 0.35
EXOS-1 2,812.0 0.065 0.0 0.0 0.08 0.15 0.35
TOTAL ON-SITE 9,023.0 0.21 0.0 0.0 0.08 0.15 0.35
Type B Soils
5 YR RUNOFF
COEFFICIENT
10 YR RUNOFF
COEFFICIENT
100 YR RUNOFF
COEFFICIENTPERCENT IMPERVIOUSBASIN AREA (S.F.) AREA (ACRE) IMPERVIOUS AREA (SF)
11/15/2018
219 MONARCH, ASPEN CO
DRAINAGE REPORT
BY: BDB
CHECKED BY: DRD
DATE: 7-19-17
REACH
I P1-10yr P1-100yr Td
EX-1 2.35 0.77 14.7
EX-1 3.75 1.23 14.7
I P1-10yr P1-100yr Td
Tc EX-2 2.19 0.77 16.3
TC EX-2 3.50 1.23 16.3
Tc
10 YEAR INTENSITY I P1-10yr P1-100yr Td
100 YEAR INTENSITY
EXOS-1 3.12 0.77 8.8
To = [0.395 (1.1 - C5) SQRT(L)] / (S0.333) EQUATION 3-4 EXOS-1 4.98 1.23 8.8
C= 5 YR runoff coefficient from City of Aspen Urban Runoff Management Plan
Tc=To+Tt
INTENSITY I=29p/((10+T)^0.789) EQUATION 2-1
Rainfall Intenstity Chart EXOS-1
10.7
5.0
10.2
2.19
3.50
5.0
EX-2
0.0216
14.7
EX-1
105.3 36.4
EX-2
0.08
119.9
16.3OV
E
R
L
A
N
D
FL
O
W
TR
A
V
E
L
T
I
M
E
FLOW SLOPE, S (ft./ft.) 0.0000
0
1
0.0
Rainfall Intenstity Chart EX-1
Rainfall Intenstity Chart EX-2
EXOS-1
0.08
8.8
0
0.0000
0.019
MINIMUM 5 MINUTES
14.7
RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.08
FLOW LENGTH, L (ft.)
FLOW VELOCITY, V (FIGURE *RO-1 UDFCD) (fps.)
FLOW LENGTH, L (TOTAL <300 FT.) (ft.)
0.0200LAND SLOPE, S (ft./ft.)
SURFACE DESCRIPTION
0
(MIN)
To (MIN)
1
16.3
EX-1
2.35
5.0
8.8
TRAVEL TIME = L/(60V) (min.)
URBAN CHECK = 10+L/180
BASIN
0.0
10.6
AREA IDENTIFIER
4.98
EXOS-1
0.0000
1
3.12
0.0
3.75
11/15/2018
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 7-19-17 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AR
E
A
(
A
C
)
RU
N
O
F
F
C
O
E
F
F
.
Tc
(
M
I
N
)
C
*
A
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
Tc
(
M
I
N
)
SU
M
(
C
*
A
)
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
SL
O
P
E
(
%
)
CH
A
N
N
E
L
F
L
O
W
(C
F
S
)
DE
S
I
G
N
F
L
O
W
(C
F
S
)
SL
O
P
E
(
%
)
PI
P
E
S
I
Z
E
(
I
N
C
H
E
S
)
LE
N
G
T
H
(
F
T
)
VE
L
O
C
I
T
Y
(
F
P
S
)
Tt
(
M
I
N
)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)
DESIGN POINT 1
DESIGN POINT 2
DESIGN POINT 3
0.111EX-2 0.152 0.02 2.19
DE
S
I
G
N
P
O
I
N
T
DIRECT RUNOFF
0.15 14.71 EX-1 0.032.35
PROJECT: 219 MONARCH
JOB NO. 2171613.01
PIPE
DESIGN STORM: EXISTING 10 YEAR
TRAVEL TIME
REMARKS
CHANNEL
STRUCTURE NO.
0.01
8.8 0.01 3.12 0.03
16.3 0.04
3 EXOS-1 0.065 0.15
TOTAL RUNOFF
0.096
11/15/2018
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 7-19-17 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AR
E
A
(
A
C
)
RU
N
O
F
F
C
O
E
F
F
.
Tc
(
M
I
N
)
C
*
A
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
Tc
(
M
I
N
)
SU
M
(
C
*
A
)
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
SL
O
P
E
(
%
)
CH
A
N
N
E
L
F
L
O
W
(C
F
S
)
DE
S
I
G
N
F
L
O
W
(C
F
S
)
SL
O
P
E
(
%
)
PI
P
E
S
I
Z
E
(
I
N
C
H
E
S
)
LE
N
G
T
H
(
F
T
)
VE
L
O
C
I
T
Y
(
F
P
S
)
Tt
(
M
I
N
)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)
DESIGN POINT 1
DESIGN POINT 2
DESIGN POINT 3
EX-2 0.111 0.35 0.14216.3 0.04 3.50
JOB NO. 2171613.01
PROJECT: 219 MONARCH
DESIGN STORM: EXISTING 100 YEAR
STRUCTURE NO.
DE
S
I
G
N
P
O
I
N
T
DIRECT RUNOFF TOTAL RUNOFF CHANNEL PIPE TRAVEL TIME
REMARKS
1 EX-1 0.096 0.35 14.7 0.03 3.75 0.13
3 EXOS-1 0.065 0.35 8.8 0.02 4.98 0.11
11/15/2018
PROPOSED CONDITIONS
11/15/2018
219 MONARCH, ASPEN CO
DRAINAGE REPORT
BY: BDB
CHECKED BY: DRD
DATE: 10-31-18
PR-1 4,149.3 0.095 2014.1 48.5 44.9 0.088 30.4 0.26 0.32 0.38 0.51
PR-2 2,904.3 0.067 1861.0 64.1 60.6 0.119 28.8 0.36 0.41 0.45 0.56
PR-3 1,969.5 0.045 598.5 30.4 29.5 0.060 9.8 0.18 0.25 0.32 0.47
PROS-1 2,350.0 0.054 882.0 37.5 0.22 0.28 0.35 0.49
Onsite Only 9,023.1 0.207 4473.6 49.6 46.8 0.09 69.1 0.67 0.69 0.73 0.78
100 YR RUNOFF
COEFFICIENT
WQCV (Watershed
inches) WQCV (CF)
5 YR RUNOFF
COEFFICIENT
EFFECTIVE
IMPERVIOUS (%)
Type B Soils
BASIN AREA (S.F.) AREA (ACRE)
IMPERVIOUS AREA
(SF)
PERCENT
IMPERVIOUS
2 YR RUNOFF
COEFFICIENT
10 YR RUNOFF
COEFFICIENT
11/15/2018
219 MONARCH, ASPEN CO
DRAINAGE REPORT
BY: BDB
CHECKED BY: DRD
DATE: 10-31-18
REACH
Basin I P1-2yr P1-10yr P1-100yr Td
PR-1 2.42 0.47 5.0
PR-1 3.96 0.77 5.0
PR-1 6.33 1.23 5.0
Basin I P1-2yr P1-10yr P1-100yr Td
Tc PR-2 2.42 0.47 5.0
TC PR-2 3.96 0.77 5.0
Tc PR-2 6.33 1.23 5.0
2 YEAR INTENSITY Basin I P1-2yr P1-10yr P1-100yr Td
10 YEAR INTENSITY
100 YEAR INTENSITY PR-3 2.28 0.47 5.9
PR-3 3.73 0.77 5.9
To = [0.395 (1.1 - C5) SQRT(L)] / (S0.333) EQUATION 3-4 PR-3 5.96 1.23 5.9
C= 5 YR runoff coefficient from City of Aspen Urban Runoff Management Plan
INTENSITY I=29p/((10+T)^0.789) EQUATION 2-1 Basin I P1-2yr P1-10yr P1-100yr Td
P TAKEN FROM TABLES 2.2 AND 2.3 WITHIN THE URMP
*INTENSITIES TAKEN FROM FIGURE 2.1 "IDF CURVES FOR ASPEN, COLORADO" FROM URMP OS-1 1.39 0.47 15.3
OS-1 2.28 0.77 15.3
OS-1 3.65 1.23 15.3
0.02
5.0
1.9
0.02
2.6
0.4
3.63.7
1.1
3.2
(MIN)
TRAVEL TIME = L/(60V) (min.)
URBAN CHECK = 10+L/180
126.3
PR-2
0.016
10.7
0.41
10.0
To (MIN)
PR-1
5.4
RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.32
AREA IDENTIFIER
FLOW SLOPE, S (ft./ft.)
BASIN
MINIMUM 5 MINUTES
6.33
PR-1
3.96
2.42
OV
E
R
L
A
N
D
FL
O
W
FLOW VELOCITY, V (FIGURE *RO-1 UDFCD) (fps.)
FLOW LENGTH, L (ft.)
TR
A
V
E
L
T
I
M
E
SURFACE DESCRIPTION
FLOW LENGTH, L (TOTAL <300 FT.) (ft.)
LAND SLOPE, S (ft./ft.)
72.3
10.5
5.0
0.02
2.82
3.73
PR-3
2.42 2.28
5.966.33
PR-2
3.96
5.0
PR-3
0.25
33.8
0.04
5.7
20.8
Rainfall Intenstity Chart PR-3
Rainfall Intenstity Chart PR-1
Rainfall Intenstity Chart PR-20.02
0.2
5.9
10.3
2.12
5.0
OS-1
0.28
116.2
0.0118
15.3
0
Rainfall Intenstity Chart OS-1
OS-1
1.39
2.28
3.65
0.0118
1
0
15.3
10.6
11/15/2018
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 10-31-18 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AR
E
A
(
A
C
)
RU
N
O
F
F
C
O
E
F
F
.
Tc
(
M
I
N
)
C
*
A
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
Tc
(
M
I
N
)
SU
M
(
C
*
A
)
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
SL
O
P
E
(
%
)
ST
R
E
E
T
F
L
O
W
(
C
F
S
)
DE
S
I
G
N
F
L
O
W
(
C
F
S
)
SL
O
P
E
(
%
)
PI
P
E
S
I
Z
E
(
I
N
C
H
E
S
)
LE
N
G
T
H
(
F
T
)
VE
L
O
C
I
T
Y
(
F
P
S
)
Tt
(
M
I
N
)
(1) (2)(3)(4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)
0.008 2.28 0.02 Design Piont 33PR-3 0.045 0.18 5.86
2.42
Design Point 1
Design Piont 2PR-2
1
0.36
PR-1 5.000.095
0.067
PROJECT: 219 MONARCH
JOB NO. 2171613.01
DIRECT RUNOFF
2
0.06
STRUCTURE NO.
DE
S
I
G
N
P
O
I
N
T
REMARKS
0.06
DESIGN STORM: PROPOSED 2 YEAR
0.26
5.00 0.024
0.02 2.42
TRAVEL TIMEPIPESTREETTOTAL RUNOFF
4 OS-1 0.054 0.22 15.31 Design Piont 40.012 1.39 0.02
11/15/2018
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 10-31-18 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AR
E
A
(
A
C
)
RU
N
O
F
F
C
O
E
F
F
.
Tc
(
M
I
N
)
C
*
A
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
Tc
(
M
I
N
)
SU
M
(
C
*
A
)
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
SL
O
P
E
(
%
)
ST
R
E
E
T
F
L
O
W
(
C
F
S
)
DE
S
I
G
N
F
L
O
W
(
C
F
S
)
SL
O
P
E
(
%
)
PI
P
E
S
I
Z
E
(
I
N
C
H
E
S
)
LE
N
G
T
H
(
F
T
)
VE
L
O
C
I
T
Y
(
F
P
S
)
Tt
(
M
I
N
)
(1) (2)(3)(4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)
0.05 Design Piont 3
Design Piont 2
3 PR-3 0.045 0.32 5.86 0.014 3.73
0.030 3.96 0.122PR-2 0.067 0.45 5.00
0.14 Design Point 1
TRAVEL TIME
REMARKS
1 PR-1 0.095 0.38 5.00 0.04 3.96
JOB NO. 2171613.01
PROJECT: 219 MONARCH
DESIGN STORM: PROPOSED 10 YEAR
STRUCTURE NO.
DE
S
I
G
N
P
O
I
N
T
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
4 OS-1 0.054 0.35 15.31 Design Piont 40.019 2.28 0.04
11/15/2018
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 10-31-18 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AR
E
A
(
A
C
)
RU
N
O
F
F
C
O
E
F
F
.
Tc
(
M
I
N
)
C
*
A
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
Tc
(
M
I
N
)
SU
M
(
C
*
A
)
(
A
C
)
I
(
I
N
/
H
R
)
Q
(
C
F
S
)
SL
O
P
E
(
%
)
ST
R
E
E
T
F
L
O
W
(
C
F
S
)
DE
S
I
G
N
F
L
O
W
(
C
F
S
)
SL
O
P
E
(
%
)
PI
P
E
S
I
Z
E
(
I
N
C
H
E
S
)
LE
N
G
T
H
(
F
T
)
VE
L
O
C
I
T
Y
(
F
P
S
)
Tt
(
M
I
N
)
(1) (2)(3)(4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21)(22)
0.13 Design Piont 3
Design Piont 2
3 PR-3 0.045 0.47 5.86 0.021 5.96
0.037 6.33 0.242PR-2 0.067 0.56 5.00
0.31 Design Point 1
TRAVEL TIME
REMARKS
1 PR-1 0.095 0.51 5.00 0.05 6.33
JOB NO. 2171613.01
PROJECT: 219 MONARCH
DESIGN STORM: PROPOSED 100 YEAR
STRUCTURE NO.
DE
S
I
G
N
P
O
I
N
T
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
4 OS-1 0.054 0.49 15.31 Design Piont 40.026 3.65 0.10
11/15/2018
POND WQCV DEPTH AND AREA CALCULATIONS
Basin PR-1:
Total Area: 4149 ݂ݐ ଶ
Impervious Area: 2014 ݂ݐ ଶ
Coniferous Dripline Area: 200 ݂ݐ ଶ
Deciduous Dripline Area: 605 ݂ݐ ଶ
Effective Area: 2014 ݂ݐ ଶ െ ሺ200 ݂ݐ ଶ ൈ0.3ሻ െ ሺ605 ݂ݐ ଶ ൈ0.15ሻ ൌ 1863.2݂ݐ
ଶ
Effective Imperviousness: ଵ଼ଷ.ଶ௧ మ
ସଵସଽ௧ మ ൈ 100 ൌ 45%
WQCV (watershed-inches): 0.088
WQCV ሺ݂ݐ ଷ ሻ: 0.088ሺݓܽݐ݁ݎݏ݄݁݀ െ ݄݅݊ܿ݁ݏ
ሻ ൈ ቀ ଵ௧
ଵଶቁ ൈ 4149 ݂ݐ
ଶ ൌ30.42 ݂ݐଷ
Northwest Pond:
WQCV Depth Capacity ൌ1݂ݐ
Flat Area Required ൌ ଷ.ସଶ௧ య
ଵ௧ ൌ 30.42 ݂ݐ
ଶ
Flat Area Provided ൌ ૠ.ૠ ࢌ࢚
Basin PR-2:
Total Area: 2904 ݂ݐ ଶ
Impervious Area: 1861 ݂ݐ ଶ
Coniferous Dripline Area: 293.3 ݂ݐ ଶ
Deciduous Dripline Area: 80 ݂ݐ ଶ
Effective Area: 1861 ݂ݐ ଶ െ ሺ293.3 ݂ݐ ଶ ൈ0.3ሻ െ ሺ80 ݂ݐ ଶ ൈ0.15ሻ ൌ 1761 ݂ݐ
ଶ
Effective Imperviousness: ଵଵ௧ మ
ଶଽସ௧ మ ൈ 100 ൌ 60.6%
WQCV (watershed-inches): 0.119
WQCV ሺ݂ݐ ଷ ሻ: 0.119ሺݓܽݐ݁ݎݏ݄݁݀ െ ݄݅݊ܿ݁ݏ
ሻ ൈ ቀ ଵ௧
ଵଶቁ ൈ 2904 ݂ݐ
ଶ ൌ28.8 ݂ݐଷ
Northeast Pond:
WQCV Depth Capacity ൌ1݂ݐ
Flat Area Required ൌ ଶ଼.଼௧ య
ଵ௧ ൌ28.8 ݂ݐଶ
Flat Area Provided ൌ. ࢌ࢚
11/15/2018
Basin PR-3:
Total Area: 1969.5 ݂ݐ ଶ
Impervious Area: 598.5 ݂ݐ ଶ
Coniferous Dripline Area:0 ݂ݐ ଶ
Deciduous Dripline Area: 117 ݂ݐ ଶ
Effective Area: 598.5 ݂ݐ ଶ െ ሺ0 ݂ݐ ଶ ൈ0.3ሻ െ ሺ117 ݂ݐ ଶ ൈ0.15ሻ ൌ 581 ݂ݐ
ଶ
Effective Imperviousness: ହ଼ଵ௧ మ
ଵଽଽ.ହ௧ మ ൈ 100 ൌ 29.5%
WQCV (watershed-inches): 0.060
WQCV ሺ݂ݐ ଷ ሻ: 0.06ሺݓܽݐ݁ݎݏ݄݁݀ െ ݄݅݊ܿ݁ݏ
ሻ ൈ ቀ ଵ௧
ଵଶቁ ൈ 1969.5 ݂ݐ
ଶ ൌ9.8 ݂ݐଷ
Southeast Pond:
Depth Capacity ൌ 0.42݂ݐ
Flat Area Required ൌ ଽ.଼௧ య
.ସଶ௧ ൌ 23.33 ݂ݐ
ଶ
Flat Area Provided ൌ ૠ. ࢌ࢚
11/15/2018
HYDRAULIC
COMPUTATIONS
11/15/2018
TRENCH DRAIN CALCULATIONS
11/15/2018
SOUTH 10IN TRENCH DRAIN AT 10YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Rectangular
Solving for ..................... Depth of Flow
Flowrate ........................ 0.1300 cfs
Slope ........................... 0.0075 ft/ft
Manning's n ..................... 0.0130
Height .......................... 6.0000 in
Bottom width .................... 10.0000 in
Computed Results:
Depth ........................... 1.0753 in
Velocity ........................ 1.7409 fps
Full Flowrate ................... 1.5361 cfs
Flow area ....................... 0.0747 ft2
Flow perimeter .................. 12.1506 in
Hydraulic radius ................ 0.8850 in
Top width ....................... 10.0000 in
Area ............................ 0.4167 ft2
Perimeter ....................... 22.0000 in
Percent full .................... 17.9217 %
Critical Information
Critical depth .................. 1.0934 in
Critical slope .................. 0.0071 ft/ft
Critical velocity ............... 1.7122 fps
Critical area ................... 0.0759 ft2
Critical perimeter .............. 12.1867 in
Critical hydraulic radius ....... 0.8972 in
Critical top width .............. 10.0000 in
Specific energy ................. 0.1367 ft
Minimum energy .................. 0.1367 ft
Froude number ................... 1.0253
Flow condition .................. Supercritical
Page 1
11/15/2018
SOUTH 10IN TRENCH DRAIN AT 100YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Rectangular
Solving for ..................... Depth of Flow
Flowrate ........................ 0.2900 cfs
Slope ........................... 0.0075 ft/ft
Manning's n ..................... 0.0130
Height .......................... 6.0000 in
Bottom width .................... 10.0000 in
Computed Results:
Depth ........................... 1.8229 in
Velocity ........................ 2.2908 fps
Full Flowrate ................... 1.5361 cfs
Flow area ....................... 0.1266 ft2
Flow perimeter .................. 13.6458 in
Hydraulic radius ................ 1.3359 in
Top width ....................... 10.0000 in
Area ............................ 0.4167 ft2
Perimeter ....................... 22.0000 in
Percent full .................... 30.3818 %
Critical Information
Critical depth .................. 1.8667 in
Critical slope .................. 0.0070 ft/ft
Critical velocity ............... 2.2371 fps
Critical area ................... 0.1296 ft2
Critical perimeter .............. 13.7333 in
Critical hydraulic radius ....... 1.3592 in
Critical top width .............. 10.0000 in
Specific energy ................. 0.2335 ft
Minimum energy .................. 0.2333 ft
Froude number ................... 1.0362
Flow condition .................. Supercritical
Page 1
11/15/2018
SWALE CALCULATIONS
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Nov 1 2018
Swale A @ 10yr flowrate for 16.3% of PR2 and 23.3% of OS1
Triangular
Side Slopes (z:1) = 10.53, 10.53
Total Depth (ft) = 0.19
Invert Elev (ft) = 7896.06
Slope (%) = 2.00
N-Value = 0.030
Calculations
Compute by: Known Q
Known Q (cfs) = 0.03
Highlighted
Depth (ft) = 0.07
Q (cfs) = 0.030
Area (sqft) = 0.05
Velocity (ft/s) = 0.58
Wetted Perim (ft) = 1.48
Crit Depth, Yc (ft) = 0.06
Top Width (ft) = 1.47
EGL (ft) = 0.08
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
Elev (ft)Depth (ft)Section
7895.75 -0.31
7896.00 -0.06
7896.25 0.19
7896.50 0.44
7896.75 0.69
7897.00 0.94
Reach (ft)
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Nov 1 2018
Swale A @ 100yr flowrate for 16.3% of PR2 and 23.3% of OS1
Triangular
Side Slopes (z:1) = 10.53, 10.53
Total Depth (ft) = 0.19
Invert Elev (ft) = 7896.06
Slope (%) = 2.00
N-Value = 0.030
Calculations
Compute by: Known Q
Known Q (cfs) = 0.06
Highlighted
Depth (ft) = 0.09
Q (cfs) = 0.062
Area (sqft) = 0.09
Velocity (ft/s) = 0.73
Wetted Perim (ft) = 1.90
Crit Depth, Yc (ft) = 0.08
Top Width (ft) = 1.90
EGL (ft) = 0.10
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
Elev (ft)Depth (ft)Section
7895.75 -0.31
7896.00 -0.06
7896.25 0.19
7896.50 0.44
7896.75 0.69
7897.00 0.94
Reach (ft)
11/15/2018
EAST OVERFLOW SWALE 'B(1)' AT 10YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 0.2100 cfs
Slope ........................... 0.0200 ft/ft
Manning's n ..................... 0.0200
Height .......................... 3.0000 in
Bottom width .................... 0.0000 in
Left slope ...................... 0.2500 ft/ft (V/H)
Right slope ..................... 0.2500 ft/ft (V/H)
Computed Results:
Depth ........................... 1.9712 in
Velocity ........................ 1.9457 fps
Full Flowrate ................... 0.6436 cfs
Flow area ....................... 0.1079 ft2
Flow perimeter .................. 16.2547 in
Hydraulic radius ................ 0.9562 in
Top width ....................... 15.7694 in
Area ............................ 0.2500 ft2
Perimeter ....................... 24.7386 in
Percent full .................... 65.7059 %
Critical Information
Critical depth .................. 2.1181 in
Critical slope .................. 0.0136 ft/ft
Critical velocity ............... 1.6851 fps
Critical area ................... 0.1246 ft2
Critical perimeter .............. 17.4664 in
Critical hydraulic radius ....... 1.0274 in
Critical top width .............. 16.9449 in
Specific energy ................. 0.2231 ft
Minimum energy .................. 0.2648 ft
Froude number ................... 1.1969
Flow condition .................. Supercritical
Page 1
11/15/2018
EAST OVERFLOW SWALE 'B(1)' AT 100YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 0.4500 cfs
Slope ........................... 0.0200 ft/ft
Manning's n ..................... 0.0200
Height .......................... 3.0000 in
Bottom width .................... 0.0000 in
Left slope ...................... 0.2500 ft/ft (V/H)
Right slope ..................... 0.2500 ft/ft (V/H)
Computed Results:
Depth ........................... 2.6233 in
Velocity ........................ 2.3541 fps
Full Flowrate ................... 0.6436 cfs
Flow area ....................... 0.1912 ft2
Flow perimeter .................. 21.6323 in
Hydraulic radius ................ 1.2725 in
Top width ....................... 20.9864 in
Area ............................ 0.2500 ft2
Perimeter ....................... 24.7386 in
Percent full .................... 87.4434 %
Critical Information
Critical depth .................. 2.8731 in
Critical slope .................. 0.0123 ft/ft
Critical velocity ............... 1.9625 fps
Critical area ................... 0.2293 ft2
Critical perimeter .............. 23.6920 in
Critical hydraulic radius ....... 1.3936 in
Critical top width .............. 22.9846 in
Specific energy ................. 0.3047 ft
Minimum energy .................. 0.3591 ft
Froude number ................... 1.2553
Flow condition .................. Supercritical
Page 1
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
Swale B(1) Under Bridge @ 10yr Flowrate
Triangular
Side Slopes (z:1) = 6.34, 6.34
Total Depth (ft) = 0.24
Invert Elev (ft) = 7895.37
Slope (%) = 1.00
N-Value = 0.027
Calculations
Compute by: Known Q
Known Q (cfs) = 0.22
Highlighted
Depth (ft) = 0.18
Q (cfs) = 0.220
Area (sqft) = 0.21
Velocity (ft/s) = 1.07
Wetted Perim (ft) = 2.31
Crit Depth, Yc (ft) = 0.15
Top Width (ft) = 2.28
EGL (ft) = 0.20
0 .5 1 1.5 2 2.5 3 3.5 4 4.5
Elev (ft)Depth (ft)Section
7895.00 -0.37
7895.25 -0.12
7895.50 0.13
7895.75 0.38
7896.00 0.63
Reach (ft)
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
Swale B(1) Under Bridge @ 100yr Flowrate
Triangular
Side Slopes (z:1) = 6.34, 6.34
Total Depth (ft) = 0.24
Invert Elev (ft) = 7895.37
Slope (%) = 1.00
N-Value = 0.027
Calculations
Compute by: Known Depth
Known Depth (ft) = 0.24
Highlighted
Depth (ft) = 0.24
Q (cfs) = 0.470
Area (sqft) = 0.36
Velocity (ft/s) = 1.32
Wetted Perim (ft) = 3.05
Crit Depth, Yc (ft) = 0.21
Top Width (ft) = 3.01
EGL (ft) = 0.26
0 .5 1 1.5 2 2.5 3 3.5 4 4.5
Elev (ft)Depth (ft)Section
7895.00 -0.37
7895.25 -0.12
7895.50 0.13
7895.75 0.38
7896.00 0.63
Reach (ft)
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Nov 16 2017
SWALE B(2) 10 YEAR EVENT
Trapezoidal
Bottom Width (ft) = 2.00
Side Slopes (z:1) = 4.05, 6.67
Total Depth (ft) = 0.22
Invert Elev (ft) = 1.00
Slope (%) = 1.00
N-Value = 0.020
Calculations
Compute by: Known Q
Known Q (cfs) = 0.21
Highlighted
Depth (ft) = 0.08
Q (cfs) = 0.210
Area (sqft) = 0.19
Velocity (ft/s) = 1.08
Wetted Perim (ft) = 2.87
Crit Depth, Yc (ft) = 0.07
Top Width (ft) = 2.86
EGL (ft) = 0.10
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
Elev (ft)Depth (ft)Section
0.75 -0.25
1.00 0.00
1.25 0.25
1.50 0.50
1.75 0.75
2.00 1.00
Reach (ft)
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Nov 16 2017
SWALE B(2) 100 YEAR EVENT
Trapezoidal
Bottom Width (ft) = 2.00
Side Slopes (z:1) = 4.05, 6.67
Total Depth (ft) = 0.22
Invert Elev (ft) = 1.00
Slope (%) = 1.00
N-Value = 0.020
Calculations
Compute by: Known Q
Known Q (cfs) = 0.45
Highlighted
Depth (ft) = 0.12
Q (cfs) = 0.450
Area (sqft) = 0.32
Velocity (ft/s) = 1.42
Wetted Perim (ft) = 3.31
Crit Depth, Yc (ft) = 0.11
Top Width (ft) = 3.29
EGL (ft) = 0.15
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
Elev (ft)Depth (ft)Section
0.75 -0.25
1.00 0.00
1.25 0.25
1.50 0.50
1.75 0.75
2.00 1.00
Reach (ft)
11/15/2018
SWALE 'C' AT 100YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 0.2900 cfs
Slope ........................... 0.0160 ft/ft
Manning's n ..................... 0.0300
Height .......................... 6.0000 in
Bottom width .................... 24.0000 in
Left slope ...................... 0.2500 ft/ft (V/H)
Right slope ..................... 0.2500 ft/ft (V/H)
Computed Results:
Depth ........................... 1.1985 in
Velocity ........................ 1.2101 fps
Full Flowrate ................... 5.9433 cfs
Flow area ....................... 0.2397 ft2
Flow perimeter .................. 33.8832 in
Hydraulic radius ................ 1.0185 in
Top width ....................... 33.5882 in
Area ............................ 2.0000 ft2
Perimeter ....................... 73.4773 in
Percent full .................... 19.9753 %
Critical Information
Critical depth .................. 0.9834 in
Critical slope .................. 0.0319 ft/ft
Critical velocity ............... 1.5202 fps
Critical area ................... 0.1908 ft2
Critical perimeter .............. 32.1091 in
Critical hydraulic radius ....... 0.8555 in
Critical top width .............. 31.8670 in
Specific energy ................. 0.1226 ft
Minimum energy .................. 0.1229 ft
Froude number ................... 0.7291
Flow condition .................. Subcritical
Page 1
11/15/2018
SWALE 'C' AT 10YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 0.1300 cfs
Slope ........................... 0.0160 ft/ft
Manning's n ..................... 0.0300
Height .......................... 6.0000 in
Bottom width .................... 24.0000 in
Left slope ...................... 0.2500 ft/ft (V/H)
Right slope ..................... 0.2500 ft/ft (V/H)
Computed Results:
Depth ........................... 0.7540 in
Velocity ........................ 0.9190 fps
Full Flowrate ................... 5.9433 cfs
Flow area ....................... 0.1415 ft2
Flow perimeter .................. 30.2176 in
Hydraulic radius ................ 0.6741 in
Top width ....................... 30.0319 in
Area ............................ 2.0000 ft2
Perimeter ....................... 73.4773 in
Percent full .................... 12.5665 %
Critical Information
Critical depth .................. 0.5896 in
Critical slope .................. 0.0371 ft/ft
Critical velocity ............... 1.2046 fps
Critical area ................... 0.1079 ft2
Critical perimeter .............. 28.8619 in
Critical hydraulic radius ....... 0.5385 in
Critical top width .............. 28.7168 in
Specific energy ................. 0.0760 ft
Minimum energy .................. 0.0737 ft
Froude number ................... 0.6815
Flow condition .................. Subcritical
Page 1
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
Swale C by Tree @ 10yr Flowrate
Triangular
Side Slopes (z:1) = 7.65, 1.47
Total Depth (ft) = 0.23
Invert Elev (ft) = 7895.53
Slope (%) = 1.60
N-Value = 0.027
Calculations
Compute by: Known Q
Known Q (cfs) = 0.14
Highlighted
Depth (ft) = 0.16
Q (cfs) = 0.140
Area (sqft) = 0.12
Velocity (ft/s) = 1.20
Wetted Perim (ft) = 1.52
Crit Depth, Yc (ft) = 0.15
Top Width (ft) = 1.46
EGL (ft) = 0.18
0 .5 1 1.5 2 2.5 3 3.5
Elev (ft)Depth (ft)Section
7895.00 -0.53
7895.25 -0.28
7895.50 -0.03
7895.75 0.22
7896.00 0.47
Reach (ft)
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
Swale C by Tree @ 100yr Flowrate
Triangular
Side Slopes (z:1) = 7.65, 1.47
Total Depth (ft) = 0.23
Invert Elev (ft) = 7895.53
Slope (%) = 1.60
N-Value = 0.027
Calculations
Compute by: Known Q
Known Q (cfs) = 0.31
Highlighted
Depth (ft) = 0.22
Q (cfs) = 0.310
Area (sqft) = 0.22
Velocity (ft/s) = 1.40
Wetted Perim (ft) = 2.09
Crit Depth, Yc (ft) = 0.20
Top Width (ft) = 2.01
EGL (ft) = 0.25
0 .5 1 1.5 2 2.5 3 3.5
Elev (ft)Depth (ft)Section
7895.00 -0.53
7895.25 -0.28
7895.50 -0.03
7895.75 0.22
7896.00 0.47
Reach (ft)
11/15/2018
WEIR CALCULATIONS
11/15/2018
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
East Weir (Pond 'B')
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 3.00
Total Depth (ft) = 0.17
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 0.47
Highlighted
Depth (ft) = 0.13
Q (cfs) = 0.470
Area (sqft) = 0.39
Velocity (ft/s) = 1.20
Top Width (ft) = 3.00
0 .5 1 1.5 2 2.5 3 3.5 4
Depth (ft)Depth (ft)East Weir (Pond 'B')
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)Weir W.S.11/15/2018
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
West Weir (Pond 'C')
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 6.00
Total Depth (ft) = 0.25
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 0.78
Highlighted
Depth (ft) = 0.11
Q (cfs) = 0.780
Area (sqft) = 0.69
Velocity (ft/s) = 1.13
Top Width (ft) = 6.00
0 1 2 3 4 5 6 7 8
Depth (ft)Depth (ft)West Weir (Pond 'C')
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)Weir W.S.11/15/2018
PIPE CALCULATIONS
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
4in Pipe @ 10yr Flowrate for PROS+PR3+33% of PR2
Circular
Diameter (ft) = 0.33
Invert Elev (ft) = 7894.66
Slope (%) = 2.00
N-Value = 0.009
Calculations
Compute by: Known Q
Known Q (cfs) = 0.14
Highlighted
Depth (ft) = 0.14
Q (cfs) = 0.140
Area (sqft) = 0.03
Velocity (ft/s) = 4.04
Wetted Perim (ft) = 0.47
Crit Depth, Yc (ft) = 0.22
Top Width (ft) = 0.33
EGL (ft) = 0.39
0 1
Elev (ft)
7894.00
7894.25
7894.50
7894.75
7895.00
11/15/2018
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
4in Pipe @ 100yr Flowrate for PROS+PR3+33% of PR2
Circular
Diameter (ft) = 0.33
Invert Elev (ft) = 7894.66
Slope (%) = 2.00
N-Value = 0.009
Calculations
Compute by: Known Q
Known Q (cfs) = 0.31
Highlighted
Depth (ft) = 0.23
Q (cfs) = 0.310
Area (sqft) = 0.06
Velocity (ft/s) = 4.86
Wetted Perim (ft) = 0.65
Crit Depth, Yc (ft) = 0.31
Top Width (ft) = 0.30
EGL (ft) = 0.60
0 1
Elev (ft)
7894.00
7894.25
7894.50
7894.75
7895.00
11/15/2018
INLET & SLOT DRAIN CALCULATIONS
11/15/2018
Inlet Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
Slot Drain @ 10yr Flowrate for 33% of PR-2
Drop Grate Inlet
Location = Sag
Curb Length (ft) = -0-
Throat Height (in) = -0-
Grate Area (sqft) = 1.29
Grate Width (ft) = 0.05
Grate Length (ft) = 25.75
Gutter
Slope, Sw (ft/ft) = 0.020
Slope, Sx (ft/ft) = 0.020
Local Depr (in) = -0-
Gutter Width (ft) = 0.67
Gutter Slope (%) = -0-
Gutter n-value = -0-
Calculations
Compute by: Known Q
Q (cfs) = 0.04
Highlighted
Q Total (cfs) = 0.04
Q Capt (cfs) = 0.04
Q Bypass (cfs) = -0-
Depth at Inlet (in) = 0.05
Efficiency (%) = 100
Gutter Spread (ft) = 1.07
Gutter Vel (ft/s) = 0.17
Bypass Spread (ft) = -0-
Bypass Depth (in) = -0-
11/15/2018
Inlet Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Oct 31 2018
Slot Drain @ 100yr Flowrate for 33% of PR-2
Drop Grate Inlet
Location = Sag
Curb Length (ft) = -0-
Throat Height (in) = -0-
Grate Area (sqft) = 1.29
Grate Width (ft) = 0.05
Grate Length (ft) = 25.75
Gutter
Slope, Sw (ft/ft) = 0.020
Slope, Sx (ft/ft) = 0.020
Local Depr (in) = -0-
Gutter Width (ft) = 0.67
Gutter Slope (%) = -0-
Gutter n-value = -0-
Calculations
Compute by: Known Q
Q (cfs) = 0.08
Highlighted
Q Total (cfs) = 0.08
Q Capt (cfs) = 0.08
Q Bypass (cfs) = -0-
Depth at Inlet (in) = 0.08
Efficiency (%) = 100
Gutter Spread (ft) = 1.31
Gutter Vel (ft/s) = 0.17
Bypass Spread (ft) = -0-
Bypass Depth (in) = -0-
11/15/2018
ASPEN CHARTS AND
FIGURES
11/15/2018
City of Aspen Urban Runoff Management Plan
Chapter 2 - Rainfall 2-4 Rev 9/2014
Note: Accuracy is more reliable at 5 minute increments.
Figure 2.1 IDF Curves for Aspen, Colorado
0
1
2
3
4
5
6
7
0 5 10 15 20 25 30 35 40 45 50 55 60
In
t
e
n
s
i
t
y
(i
n
c
h
/
h
r
)
Duration in Minutes
Rainfall IDF for Aspen, Colorado
2‐yr 5‐yr 10‐yr 25‐yr 50‐yr 100‐yr
11/15/2018
City of Aspen Urban Runoff Management Plan
Chapter 2 - Rainfall 2-2 Rev 9/2014
into thunderstorms. Autumn in Aspen is usually dry and warm and during September daytime temperatures
can reach 70°F, but night temperatures can drop to freezing. Aspen is renowned for its warm winter sun.
Winter daytime temperatures typically range from 20 to 40°F in the City and from 10 to 30°F on the
mountain. Once the sun goes down, the temperature drops dramatically. Table 2.1 presents monthly
statistics for temperature, precipitation, snowfall, and snow depth in the Aspen area.
Table 2.1 Monthly Statistics for Temperature and Precipitation in Aspen
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Average Max. Temperature (F) 35 39 45 52 63 72 78 76 69 58 43 35 55.5
Average Min. Temperature (F) 9.1 12 20 26 35 41 47 46 39 30 19 9.7 27.7
Average Total Precipitation (in.) 1.7 2.1 2.7 2.5 2.1 1.4 1.8 1.6 2.1 2 2.6 1.9 24.37
Average Total Snowfall (in.) 25 27 28 20 7.8 1 0 0 1 11 28 25 173.8
Average Snow Depth (in.) 21 28 27 12 1 0 0 0 0 1 6 14
(Source: Station 050372 at Aspen 1 SW, Colorado)
2.3 Rainfall Depth, Duration, Frequency, and Intensity
The rainfall intensity-duration-frequency (IDF) curve is a statistical formula to describe the relationship
among the local rainfall characteristics and return periods. The IDF curve is used in the Rational Method
for peak runoff predictions of basins smaller than 90 acres. Based on the NOAA Atlas Volume 3, the
IDF curve for the City of Aspen can be derived according to the locality and elevation. The City of Aspen is
located at approximately 39°11′32″N and 106°49′28″W, at an elevation of approximately 8,100 feet.
Based on depth and duration data (Appendix B, Table 1), rainfall intensities can be calculated for various
frequencies. Rainfall intensity data, which form the basis of the Intensity-Duration-Frequency (IDF) curves
in Figure 2.1 are provided in Table 2.2.
Table 2.2 Rainfall Intensity-Duration-Frequency in Aspen, Colorado
Return Rainfall Intensity in inch/hr for Various Periods of Duration
Period 5-min 10-min 15-min 30-min 1-hr (P1) 2-hr 3-hr 6-hr 24-hr
2‐yr 2.06 1.51 1.23 0.77 0.47 0.28 0.21 0.13 0.06
5-yr 2.98 2.17 1.77 1.09 0.64 0.36 0.26 0.16 0.07
10-yr 3.72 2.72 2.22 1.35 0.77 0.43 0.30 0.18 0.08
25‐yr 4.75 3.47 2.82 1.71 0.95 0.53 0.36 0.21 0.09
50‐yr 5.53 4.05 3.30 1.98 1.09 0.60 0.41 0.24 0.11
100-yr 6.32 4.63 3.76 2.24 1.23 0.67 0.45 0.26 0.12
Using the data in Table 2.2 (derived from NOAA Atlas 14 Volume 8), the following equation was derived
that can be used to determine intensities not shown in the IDF table or curve:
052.1
1
)10(
8.88
dT
PI (Equation 2-1)
Where, I = rainfall intensity (inch/hr),
P1 = 1-hr rainfall depth (inches), and
Td = duration or time of concentration (minutes).
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City of Aspen Urban Runoff Management Plan
Chapter 3 - Runoff 3-6 Rev 10/2014
Figure 3.2 – Runoff Coefficients for NRCS Hydrologic Soil Group A
Figure 3.3 – Runoff Coefficients for NRCS Hydrologic Soil Group B
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City of Aspen Urban Runoff Management Plan
Chapter 8 – Water Quality 8-33 Rev 8/2009
Figure 8.13 Aspen Water Quality Capture Volume
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City of Aspen Urban Runoff Management Plan
Chapter 3 - Runoff 3-2 Rev 2/2010
Figure 3.1 Natural Resource Conservation Service (NRCS) Soil Map for Aspen
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