HomeMy WebLinkAboutFile Documents.219 N Monarch St.0179.2017 (11).ARBK
DRAINAGE REPORT
FOR
219 NORTH MONARCH
CITY OF ASPEN, COLORADO
PARCEL ID: 273707316004
PREPARED FOR:
Alius Design Corps
1311 East Sopris Creek Road
Basalt, CO 81621
PREPARED BY:
High Country Engineering, Inc.
1517 Blake Avenue, Suite 101
Glenwood Springs, CO 81601
(970) 945-8676
July 24, 2017
Revised: November 16, 2017
HCE JOB NUMBER: 2171613.01
11/27/17
Reviewed by Engineering
02/13/2018 8:54:10 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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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
Aspen Charts and Figures
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Engineers Certification
“I hereby affirm that this report and the accompanying plans for the construction of driveway
and roof improvements 219 North Monarch Street was prepared by me (or under my direct
supervision) for the owners thereof in accordance with the provisions of the City of Aspen
Urban Runoff Management Plan and approved variances are exceptions listed thereto. I
understand that it is the policy of the City of Aspen that the City of Aspen does not and will not
assume liability for drainage facilities designed by others.”
License No. __39307__________
Dan R. Dennison, P.E.
Licensed Professional Engineer, State of Colorado
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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.
B. Previous Drainage Studies
Per the November 2001 study completed by WRC Engineering, Inc. titled, “Storm Drainage
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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
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
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 or from downspouts before
discharging into the northeast bioretention area. This bioretention area also directly receives
sheet flow from the surrounding pervious areas and roof downspouts. Should the bioretention
facility reach over capacity, the storm drainage will spill over a weir and into a drainage swale
leading to the northwest bioretention area. Design point 2 is associated with the overflow
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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. Should the bioretention area exceed capacity, runoff will enter a grated
outlet before travelling through a 6-inch pipe and discharging into 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 0.40 2.46 0.09 0.52 3.93 0.19
PR-2 0.039 0.43 3.35 0.06 0.54 5.35 0.11
PR-3 0.073 0.37 3.96 0.11 0.52 6.33 0.24
PROS-1 0.054 0.35 2.28 0.04 0.49 3.65 0.10
ONSITE
TOTAL 0.26 ONSITE
TOTAL 0.54
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 4,147 2,023 48.8 42.0
PR-2 1,691 892 52.7 44.6
PR-3 3,185 1,466 46.0 40.4
TOTAL 9,023 4,381 48.6 41.9
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BASIN BIORETENTION AREA WQCV (Watershed inches) WQCV (CF)
PR-1 NORTHWEST 0.082 28.3
PR-2 NORTHEAST 0.088 12.4
PR-3 SOUTHEAST 0.080 21.2
TOTAL 0.082 61.9
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 proposed conditions and hydraulic calculations
sections.
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 proposed trench drains and drain basin shall be inspected and cleared of rubbish and
debris quarterly, as well as after large storm events. The grates for the drain basin and trench
drains must also be inspected to make sure they have not clogged. Review of the overflow
drain basin, piping and pop-up emitter should occur at least every 6 months or after large
storm events, to insure proper function. If standing water is observed within the inlet basin and
pipes, then the grate shall be removed and the inlet basin and pipes shall be jetted clear.
Trench drains, inlets and piping with depths equal to or less 36” than shall be heat taped.
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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APPENDICES
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HYDROLOGIC
COMPUTATIONS 11/27/17
EXISTING CONDITIONS
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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)
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219 MONARCH, ASPEN CODRAINAGE REPORTBY: BDBCHECKED BY: DRD DATE: 7-19-17REACHI P1-10yr P1-100yr TdEX-1 2.35 0.77 14.7EX-1 3.75 1.23 14.7I P1-10yr P1-100yr TdTcEX-2 2.19 0.77 16.3TCEX-2 3.50 1.23 16.3Tc10 YEAR INTENSITYI P1-10yr P1-100yr Td100 YEAR INTENSITYEXOS-1 3.12 0.77 8.8To = [0.395 (1.1 - C5) SQRT(L)] / (S0.333) EQUATION 3-4EXOS-1 4.98 1.23 8.8C= 5 YR runoff coefficient from City of Aspen Urban Runoff Management PlanTc=To+TtINTENSITY I=29p/((10+T)^0.789) EQUATION 2-1Rainfall Intenstity Chart EXOS-110.75.010.22.193.505.0EX-20.021614.7EX-1105.3 36.4EX-20.08119.916.3OVERLAND FLOWTRAVEL TIMEFLOW SLOPE, S (ft./ft.) 0.0000010.0Rainfall Intenstity Chart EX-1Rainfall Intenstity Chart EX-2EXOS-10.088.800.00000.019MINIMUM 5 MINUTES14.7RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.08FLOW 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)116.3EX-12.355.08.8TRAVEL TIME = L/(60V) (min.)URBAN CHECK = 10+L/180BASIN0.010.6AREA IDENTIFIER4.98EXOS-10.000013.120.03.7511/27/17
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 7-19-17 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)CHANNEL FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(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 2.19DESIGN POINTDIRECT 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
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CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 7-19-17 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)CHANNEL FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(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.DESIGN POINTDIRECT 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
11/27/17
PROPOSED CONDITIONS
11/27/17
219 MONARCH, ASPEN CODRAINAGE REPORTBY: BDBCHECKED BY: DRDDATE: 7-19-17PR-1 4,147.0 0.095 2023.0 48.8 42.0 0.082 28.3 0.28 0.35 0.40 0.52PR-2 1,691.0 0.039 892.0 52.7 44.6 0.088 12.4 0.32 0.37 0.43 0.54PR-3 3,185.0 0.073 1466.0 46.0 40.4 0.080 21.2 0.27 0.34 0.37 0.52PROS-1 2,350.0 0.054 882.0 37.5 0.22 0.28 0.35 0.49 Onsite Only 9,023.0 0.207 4381.0 48.6 41.90 0.082 62.0 0.67 0.69 0.73 0.78Type B Soils BASIN AREA (S.F.) AREA (ACRE)IMPERVIOUS AREA (SF)PERCENT IMPERVIOUS2 YR RUNOFF COEFFICIENT10 YR RUNOFF COEFFICIENT100 YR RUNOFF COEFFICIENTWQCV (Watershed inches) WQCV (CF)5 YR RUNOFF COEFFICIENTEFFECTIVE IMPERVIOUS (%)11/27/17
219 MONARCH, ASPEN CODRAINAGE REPORTBY: BDBCHECKED BY: DRDDATE: 7-19-17REACHBasin I P1-2yr P1-10yr P1-100yr TdPR-1 1.50 0.47 13.6PR-1 2.46 0.77 13.6PR-1 3.93 1.23 13.6Basin I P1-2yr P1-10yr P1-100yr TdTcPR-2 2.05 0.47 7.6TCPR-2 3.35 0.77 7.6TcPR-2 5.35 1.23 7.62 YEAR INTENSITYBasin I P1-2yr P1-10yr P1-100yr Td10 YEAR INTENSITY100 YEAR INTENSITYPR-3 2.42 0.47 5.0PR-3 3.96 0.77 5.0To = [0.395 (1.1 - C5) SQRT(L)] / (S0.333) EQUATION 3-4PR-3 6.33 1.23 5.0C= 5 YR runoff coefficient from City of Aspen Urban Runoff Management PlanINTENSITY I=29p/((10+T)^0.789) EQUATION 2-1Basin I P1-2yr P1-10yr P1-100yr TdP 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 15.3OS-1 2.28 0.77 15.3OS-1 3.65 1.23 15.3Rainfall Intenstity Chart OS-1OS-11.392.283.650.01181015.310.6OS-10.28116.20.011815.30Rainfall Intenstity Chart PR-3Rainfall Intenstity Chart PR-1Rainfall Intenstity Chart PR-20.330.04.210.515.05.0PR-30.3495.60.334.20.03.96PR-32.05 2.426.335.35PR-23.350.010.35.00.02541OVERLAND FLOWFLOW VELOCITY, V (FIGURE *RO-1 UDFCD) (fps.)FLOW LENGTH, L (ft.)TRAVEL TIMESURFACE DESCRIPTIONFLOW LENGTH, L (TOTAL <300 FT.) (ft.)LAND SLOPE, S (ft./ft.)BASINMINIMUM 5 MINUTES3.93PR-12.461.50PR-1127.7RATIONAL COEFFICIENT. C (FIGURE 3.2 OF URMP) 0.35AREA IDENTIFIERFLOW SLOPE, S (ft./ft.)(MIN)TRAVEL TIME = L/(60V) (min.)URBAN CHECK = 10+L/1800.0PR-20.01510.70.3759.8To (MIN)0.02545.010.01513.60.07.613.60.07.611/27/17
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 7-19-17 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)
0.020 2.42 0.05 Design Piont 33 PR-3 0.073 0.27 5.00
2.05
Design Point 1
Design Piont 2PR-2
1
0.32
PR-1 13.560.095
0.039
PROJECT: 219 MONARCH
JOB NO. 2171613.01
DIRECT RUNOFF
2
0.04
STRUCTURE NO.DESIGN POINTREMARKS
0.03
DESIGN STORM: PROPOSED 2 YEAR
0.28
7.58 0.012
0.03 1.50
TRAVEL TIMEPIPESTREETTOTAL RUNOFF
4 OS-1 0.054 0.22 15.31 Design Piont 40.012 1.39 0.02
11/27/17
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 7-19-17 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)
0.11 Design Piont 3
Design Piont 2
3 PR-3 0.073 0.37 5.00 0.027 3.96
0.017 3.35 0.062 PR-2 0.039 0.43 7.58
0.09 Design Point 1
TRAVEL TIME
REMARKS
1 PR-1 0.095 0.40 13.56 0.04 2.46
JOB NO. 2171613.01
PROJECT: 219 MONARCH
DESIGN STORM: PROPOSED 10 YEAR
STRUCTURE NO.DESIGN POINTDIRECT RUNOFF TOTAL RUNOFF STREET PIPE
4 OS-1 0.054 0.35 15.31 Design Piont 40.019 2.28 0.04
11/27/17
CALCULATED BY: BDB STANDARD FORM SF-3
DATE: 7-19-17 STORM DRAINAGE SYSTEM DESIGN
CHECKED BY: DRD (RATIONAL METHOD PROCEDURE)
Contributing Area
AREA (AC)RUNOFF COEFF.Tc (MIN)C * A (AC)I (IN/HR)Q (CFS)Tc (MIN)SUM (C*A) (AC)I (IN/HR)Q (CFS)SLOPE (%)STREET FLOW (CFS)DESIGN FLOW (CFS)SLOPE (%)PIPE SIZE (INCHES)LENGTH (FT)VELOCITY (FPS)Tt (MIN)(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)
0.24 Design Piont 3
Design Piont 2
3 PR-3 0.073 0.52 5.00 0.038 6.33
0.021 5.35 0.112 PR-2 0.039 0.54 7.58
0.19 Design Point 1
TRAVEL TIME
REMARKS
1 PR-1 0.095 0.52 13.56 0.05 3.93
JOB NO. 2171613.01
PROJECT: 219 MONARCH
DESIGN STORM: PROPOSED 100 YEAR
STRUCTURE NO.DESIGN POINTDIRECT RUNOFF TOTAL RUNOFF STREET PIPE
4 OS-1 0.054 0.49 15.31 Design Piont 40.026 3.65 0.10
11/27/17
POND WQCV DEPTH AND AREA CALCULATIONS
Basin PR-1:
Total Area: 4152 ݂ݐଶ
Impervious Area: 2023 ݂ݐଶ
Coniferous Dripline Area: 639 ݂ݐଶ
Deciduous Dripline Area: 605 ݂ݐଶ
Effective Area: 2023 ݂ݐଶ െ ሺ639 ݂ݐଶ ൈ0.3ሻ െ ሺ605 ݂ݐଶ ൈ0.15ሻ ൌ 1740.6 ݂ݐ
ଶ
Effective Imperviousness: ଵସ.௧మ
ସଵହଶ௧మ ൈ 100 ൌ 42%
WQCV (watershed-inches): 0.082
WQCV ሺ݂ݐଷሻ: 0.082ሺݓܽݐ݁ݎݏ݄݁݀ െ ݄݅݊ܿ݁ݏሻ ൈ ቀ ଵ௧
ଵଶቁ ൈ 4152 ݂ݐ
ଶ ൌ28.37 ݂ݐଷ
Northwest Pond:
WQCV Depth Capacity ൌ1݂ݐ
Flat Area Required ൌ ଶ଼.ଷ௧య
ଵ௧ ൌ 28.37݂ݐ
ଶ
Flat Area Provided ൌ ૠ.ૠ ࢌ࢚
Basin PR-2:
Total Area: 1691 ݂ݐଶ
Impervious Area: 892 ݂ݐଶ
Coniferous Dripline Area: 418 ݂ݐଶ
Deciduous Dripline Area: 78 ݂ݐଶ
Effective Area: 892 ݂ݐଶ െ ሺ418 ݂ݐଶ ൈ0.3ሻ െ ሺ78 ݂ݐଶ ൈ0.15ሻ ൌ 755 ݂ݐ
ଶ
Effective Imperviousness: ହହ௧మ
ଵଽଵ௧మ ൈ 100 ൌ 44.6%
WQCV (watershed-inches): 0.088
WQCV ሺ݂ݐଷሻ: 0.088ሺݓܽݐ݁ݎݏ݄݁݀ െ ݄݅݊ܿ݁ݏሻ ൈ ቀ ଵ௧
ଵଶቁ ൈ 1691 ݂ݐ
ଶ ൌ12.4 ݂ݐଷ
Northeast Pond:
WQCV Depth Capacity ൌ1݂ݐ
Flat Area Required ൌ ଵଶ.ସ௧య
ଵ௧ ൌ12.4݂ݐଶ
Flat Area Provided ൌ . ࢌ࢚
11/27/17
Basin PR-3:
Total Area: 3185 ݂ݐଶ
Impervious Area: 1466 ݂ݐଶ
Coniferous Dripline Area: 538 ݂ݐଶ
Deciduous Dripline Area: 117 ݂ݐଶ
Effective Area: 1466 ݂ݐଶ െ ሺ538 ݂ݐଶ ൈ0.3ሻ െ ሺ117 ݂ݐଶ ൈ0.15ሻ ൌ 1287 ݂ݐ
ଶ
Effective Imperviousness: ଵଶ଼௧మ
ଷଵ଼ହ௧మ ൈ 100 ൌ 40.4%
WQCV (watershed-inches): 0.080
WQCV ሺ݂ݐଷሻ: 0.080ሺݓܽݐ݁ݎݏ݄݁݀ െ ݄݅݊ܿ݁ݏሻ ൈ ቀ ଵ௧
ଵଶቁ ൈ 3185 ݂ݐ
ଶ ൌ21.23 ݂ݐଷ
Northwest Pond:
Depth Capacity ൌ 0.50݂ݐ
Flat Area Required ൌ ଶଵ.ଶଷ௧య
.ହ௧ ൌ 42.46 ݂ݐ
ଶ
Flat Area Provided ൌ ૠૠ. ࢌ࢚
11/27/17
HYDRAULIC
COMPUTATIONS
11/27/17
TRENCH DRAIN CALCULATIONS
11/27/17
NORTH 8IN TRENCH DRAIN AT 10YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Rectangular
Solving for ..................... Depth of Flow
Flowrate ........................ 0.2100 cfs
Slope ........................... 0.0100 ft/ft
Manning's n ..................... 0.0130
Height .......................... 6.0000 in
Bottom width .................... 8.0000 in
Computed Results:
Depth ........................... 1.5903 in
Velocity ........................ 2.3770 fps
Full Flowrate ................... 1.3031 cfs
Flow area ....................... 0.0883 ft2
Flow perimeter .................. 11.1805 in
Hydraulic radius ................ 1.1379 in
Top width ....................... 8.0000 in
Area ............................ 0.3333 ft2
Perimeter ....................... 20.0000 in
Percent full .................... 26.5045 %
Critical Information
Critical depth .................. 1.7467 in
Critical slope .................. 0.0076 ft/ft
Critical velocity ............... 2.1641 fps
Critical area ................... 0.0970 ft2
Critical perimeter .............. 11.4934 in
Critical hydraulic radius ....... 1.2158 in
Critical top width .............. 8.0000 in
Specific energy ................. 0.2203 ft
Minimum energy .................. 0.2183 ft
Froude number ................... 1.1511
Flow condition .................. Supercritical
Page 1
11/27/17
NORTH 8IN TRENCH DRAIN AT 100YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Rectangular
Solving for ..................... Depth of Flow
Flowrate ........................ 0.4500 cfs
Slope ........................... 0.0100 ft/ft
Manning's n ..................... 0.0130
Height .......................... 6.0000 in
Bottom width .................... 8.0000 in
Computed Results:
Depth ........................... 2.7012 in
Velocity ........................ 2.9987 fps
Full Flowrate ................... 1.3031 cfs
Flow area ....................... 0.1501 ft2
Flow perimeter .................. 13.4024 in
Hydraulic radius ................ 1.6124 in
Top width ....................... 8.0000 in
Area ............................ 0.3333 ft2
Perimeter ....................... 20.0000 in
Percent full .................... 45.0198 %
Critical Information
Critical depth .................. 2.9032 in
Critical slope .................. 0.0082 ft/ft
Critical velocity ............... 2.7900 fps
Critical area ................... 0.1613 ft2
Critical perimeter .............. 13.8065 in
Critical hydraulic radius ....... 1.6822 in
Critical top width .............. 8.0000 in
Specific energy ................. 0.3648 ft
Minimum energy .................. 0.3629 ft
Froude number ................... 1.1143
Flow condition .................. Supercritical
Page 1
11/27/17
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
11/27/17
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
11/27/17
SWALE CALCULATIONS
11/27/17
SWALE 'A' AT 10YR EVENT
Channel Calculator
Given Input Data:
Shape ........................... Trapezoidal
Solving for ..................... Depth of Flow
Flowrate ........................ 0.1000 cfs
Slope ........................... 0.0200 ft/ft
Manning's n ..................... 0.0300
Height .......................... 2.2800 in
Bottom width .................... 0.0000 in
Left slope ...................... 0.0950 ft/ft (V/H)
Right slope ..................... 0.0950 ft/ft (V/H)
Computed Results:
Depth ........................... 1.2010 in
Velocity ........................ 0.9484 fps
Full Flowrate ................... 0.5526 cfs
Flow area ....................... 0.1054 ft2
Flow perimeter .................. 25.3981 in
Hydraulic radius ................ 0.5978 in
Top width ....................... 25.2842 in
Area ............................ 0.3800 ft2
Perimeter ....................... 48.2161 in
Percent full .................... 52.6755 %
Critical Information
Critical depth .................. 1.0690 in
Critical slope .................. 0.0372 ft/ft
Critical velocity ............... 1.1971 fps
Critical area ................... 0.0835 ft2
Critical perimeter .............. 22.6065 in
Critical hydraulic radius ....... 0.5321 in
Critical top width .............. 22.5052 in
Specific energy ................. 0.1141 ft
Minimum energy .................. 0.1336 ft
Froude number ................... 0.7474
Flow condition .................. Subcritical
Page 1
11/27/17
SWALE 'A' AT 100YR 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 ..................... 0.0300
Height .......................... 2.2800 in
Bottom width .................... 0.0000 in
Left slope ...................... 0.0950 ft/ft (V/H)
Right slope ..................... 0.0950 ft/ft (V/H)
Computed Results:
Depth ........................... 1.5863 in
Velocity ........................ 1.1417 fps
Full Flowrate ................... 0.5526 cfs
Flow area ....................... 0.1839 ft2
Flow perimeter .................. 33.5454 in
Hydraulic radius ................ 0.7896 in
Top width ....................... 33.3950 in
Area ............................ 0.3800 ft2
Perimeter ....................... 48.2161 in
Percent full .................... 69.5730 %
Critical Information
Critical depth .................. 1.4383 in
Critical slope .................. 0.0337 ft/ft
Critical velocity ............... 1.3886 fps
Critical area ................... 0.1512 ft2
Critical perimeter .............. 30.4173 in
Critical hydraulic radius ....... 0.7159 in
Critical top width .............. 30.2810 in
Specific energy ................. 0.1524 ft
Minimum energy .................. 0.1798 ft
Froude number ................... 0.7829
Flow condition .................. Subcritical
Page 1
11/27/17
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
11/27/17
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
11/27/17
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)
11/27/17
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)
11/27/17
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
11/27/17
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
11/27/17
WEIR CALCULATIONS
11/27/17
EAST BIORETENTION POND RECTANGULAR WEIR
Weir Calculator
Given Input Data:
Weir Type ....................... Rectangular
Equation ........................ Contracted
Solving for ..................... Depth of Flow
Flowrate ........................ 0.4500 cfs
Coefficient ..................... 0.6500
Height .......................... 2.0000 in
Computed Results:
Depth of Flow ................... 1.4845 in
Full Flow ....................... 0.7017 cfs
Velocity ........................ 1.2125 fps
Width ........................... 36.0000 in
Area ............................ 0.5000 ft2
Perimeter ....................... 40.0000 in
Wet Perimeter ................... 38.9690 in
Wet Area ........................ 0.3711 ft2
Percent Full .................... 74.2250 %
Page 1
11/27/17
WEST BIORETENTION POND RECTANGULAR WEIR
Weir Calculator
Given Input Data:
Weir Type ....................... Rectangular
Equation ........................ Contracted
Solving for ..................... Depth of Flow
Flowrate ........................ 0.6400 cfs
Coefficient ..................... 0.6500
Height .......................... 4.0000 in
Computed Results:
Depth of Flow ................... 1.1788 in
Full Flow ....................... 3.9692 cfs
Velocity ........................ 1.0859 fps
Width ........................... 72.0000 in
Area ............................ 2.0000 ft2
Perimeter ....................... 80.0000 in
Wet Perimeter ................... 74.3575 in
Wet Area ........................ 0.5894 ft2
Percent Full .................... 29.4689 %
Page 1
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PIPE CALCULATIONS
11/27/17
6IN OVERFLOW PIPE FROM BIORETENTION POND A
Manning Pipe Calculator
Given Input Data:
Shape ........................... Circular
Solving for ..................... Depth of Flow
Diameter ........................ 6.0000 in
Flowrate ........................ 0.3400 cfs
Slope ........................... 0.0100 ft/ft
Manning's n ..................... 0.0100
Computed Results:
Depth ........................... 2.8795 in
Area ............................ 0.1963 ft2
Wetted Area ..................... 0.0932 ft2
Wetted Perimeter ................ 9.1838 in
Perimeter ....................... 18.8496 in
Velocity ........................ 3.6498 fps
Hydraulic Radius ................ 1.4607 in
Percent Full .................... 47.9920 %
Full flow Flowrate .............. 0.7294 cfs
Full flow velocity .............. 3.7150 fps
Critical Information
Critical depth .................. 3.5472 in
Critical slope .................. 0.0049 ft/ft
Critical velocity ............... 2.8105 fps
Critical area ................... 0.1210 ft2
Critical perimeter .............. 10.5192 in
Critical hydraulic radius ....... 1.6561 in
Critical top width .............. 6.0000 in
Specific energy ................. 0.4470 ft
Minimum energy .................. 0.4434 ft
Froude number ................... 1.4901
Flow condition .................. Supercritical
Page 1
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ASPEN CHARTS AND
FIGURES
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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 60Intensity (inch/hr)Duration in Minutes
Rainfall IDF for Aspen, Colorado
2‐yr 5‐yr 10‐yr 25‐yr 50‐yr 100‐yr
11/27/17
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).
11/27/17
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 11/27/17
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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