HomeMy WebLinkAboutFile Documents.533 E Main St.0004.2017 (15).ACBK
MAJOR DRAINAGE REPORT FOR
ST. MARY CATHOLIC CHURCH
ASPEN, CO
I hereby affirm that this report and the accompanying drawings for the analysis of St. Mary’s, Aspen,
Colorado was prepared 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 and exceptions
listed thereto. I understand that it is the policy of the City of Aspen that the City of Aspen does not and
will not assume liability for drainage facilities designed by others.
May 2017
Prepared by
118 West Sixth St, Suite 200
Glenwood Springs, CO 81601
970.945.1004
970.945.5948 fax
St. Mary Catholic
Church Site
City of Aspen
Received
5/2/17
Building Department
i
Table of Contents
1.0 General ............................................................................................................................................ 1
1.1 Description of Existing Site ........................................................................................................... 1
1.2 Description of Existing Drainage ................................................................................................... 1
1.3 Description of Proposed Project ................................................................................................... 1
2.0 Drainage Basins .............................................................................................................................. 2
2.1 Discussion of Drainage Basins ..................................................................................................... 2
2.2 Drainage Basins ........................................................................................................................... 2
2.3 Peak Discharge Calculations ........................................................................................................ 3
2.4 Analysis of Peak Discharge into Inlet 2 ......................................................................................... 4
3.0 Low Impact Site Design ................................................................................................................... 5
3.1 Principles of LID ........................................................................................................................... 5
4.0 Water Quality Capture Volume......................................................................................................... 6
4.1 Water Quality Capture Volume Storage ........................................................................................ 6
4.1.1 Drywell Percolation Test ........................................................................................................ 7
5.0 Operations and Maintenance ........................................................................................................... 7
5.1 Grass Swale ................................................................................................................................. 7
5.2 Pervious Pavers ........................................................................................................................... 7
5.3 Drywell ......................................................................................................................................... 7
6.0 Summary ......................................................................................................................................... 7
Appendix A ............................................................................................................................................ A
Historic Site Basin Delineation Map .................................................................................................... A
Developed Site Basin Delineation Map............................................................................................... A
Appendix B ............................................................................................................................................ B
Drainage Exhibit ................................................................................................................................. B
Appendix C ............................................................................................................................................ C
Equations ........................................................................................................................................... C
Appendix D ............................................................................................................................................ D
Percolation Test Results .................................................................................................................... D
City of Aspen
Received
5/2/17
Building Department
1
1.0 General
1.1 Description of Existing Site
St. Mary Catholic Church is located in Township 10 South, Range 85 West of the 6th Principal Meridian, in Pitkin
County. The parcel on which the church sits faces the south side of Main St (Highway 82). The church address is
533 E Main St, which is in the Aspen Mountain Drainage Basin. The parcel is bordered by public right of way-
sidewalk, curb and gutter- on all four sides. All building entrances are currently one foot or more above the
flowline of the adjacent gutter. Several large deciduous and coniferous trees are on the parcel. Grass, concrete,
and asphalt shingle roofs cover the large majority of the surface area. The site is gently-sloped with general
drainage patterns from south to north. All utility lines lie outside of the parcel boundary. The receiving system
for onsite runoff is the City of Aspen (COA) storm system.
1.2 Description of Existing Drainage
The selected study area for this project is 0.995 acre. The study area is bounded on the north by Main St, on the
west by Galena St, on the east by Hunter St, and on the south by Hyman St. Topographic mapping obtained from
COA GIS was used to subdivide the study area into 3 basins. The basin delineation maps are presented in
Appendix A. The delineation maps show historic drainage conditions and developed drainage conditions.
Historic conditions for the site were defined to be the existing conditions as the church building dates back to
1882. Under historic conditions, surface runoff from the east and west sides of the parcel drains into five inlets
that surround the parcel. These inlets are all located in the street gutter in the public right of way. Surface runoff
from the middle of the property drains into an existing drywell located in that basin.
For additional information about the existing storm sewer system and its capacity, refer to the Aspen Mountain
Surface Drainage Master Plan that was completed for the City of Aspen in 2001 and updated in 2014. As shown
in the Aspen Mountain Mudflow Zone Map, the property is well outside of any zone for risk of a mudflow.
1.3 Description of Proposed Project
This project is classified as “Major” as the proposed interior work will demolish more than 75% of the existing
interior. The purpose of this report is to demonstrate that the project is in compliance with the requirements of
the Urban Runoff Management Plan (URMP). Throughout the design process, the Low Impact Design Principles
were used as a guide for mitigating stormwater runoff. As the project is located within the Aspen Mountain
Drainage Basin, the Water Quality Capture Volume (WQCV) is required to be detained for the entire remodel
area, including where the impervious area is being increased when the sidewalks are widened.
The proposed project will remove and replace the sidewalks along Main St and Hunter St. The sidewalk along
Hunter St will be widened to the 6 feet as required by the City. The sidewalk along Main St will remain 5 feet in
width west of the church entrance, and the sidewalk will remain 6 feet in width on the east side of the church
entrance. The existing curb cut for the driveway along Main St will be removed and replaced with a new 16 foot
curb cut, meeting Colorado Department of Transportation (CDOT) requirements. 165 square feet of concrete
will be removed within the driveway area and replaced with 165 square feet of pervious pavers. Pervious pavers
will also replace 122 square feet of concrete in front of the church building entrance. A handicap ramp will be
added from Hunter St to access the sidewalk.
The proposed pervious area on the east side of the church will not sufficiently meet the 1:1 ratio with the
impervious roof area that drains onto the grass. Therefore, as requested by the city of Aspen, a grassed swale
with a subsurface detention area will be established on the east side of the church to adequately treat the
WQCV. The grassed swale will be approximately 88 feet long and 2 feet wide. The top 3” of the swale will be
City of Aspen
Received
5/2/17
Building Department
2
sod. Under the sod will be 4” of loamy sand. And lastly, under the sand will be 6” of ¾-inch screened rock (see
Sheet CDT-02 for detail). The screened rock section will be wrapped in a Class 3 geotextile separator fabric to
prevent the materials from migrating. The screened rock section will be drained by a 4”-diameter perforated
drain pipe that will run the length of the screened rock section. This drain pipe will have a 1% minimum slope,
and it will daylight into the existing inlet box of Inlet 2 on Hunter St (see Sheet CRD-01 for details).
2.0 Drainage Basins
2.1 Discussion of Drainage Basins
Drainage basins were determined and delineated using topographic data developed from COA GIS. The basin
delineation maps can be found in Appendix A. The site was divided into 3 basins. The Drainage Exhibit in
Appendix B shows the basins and lists the impervious area, the runoff coefficient, and peak flow of each basin.
The Hydraulic Soil Group (HSG) was classified as HSG B according to Figure 3.1 of the City of Aspen URMP.
Figure 3.1 from the City of Aspen URMP: Soil Map for Aspen
2.2 Drainage Basins
Basin 1 constitutes the southwest portion of the parcel. This basin is 11,121.2 square feet (SF). It consists of
mostly grass, roof, and concrete walkways, and has 38.5% impervious area. Runoff from much of the alley
between Main St and Hopkins Ave drains onto Basin 1. This offsite contribution was accounted for and added to
the total surface runoff for Basin 1. This basin has the same historic and developed conditions as no work is
being done that will change the historic drainage patterns of this basin. Surface runoff from Basin 1 flows across
the sidewalk and green space in the public right of way and into the gutter that runs along Galena St. Ultimately,
runoff from this basin drains into Inlet 1 near the corner of Galena St and Main St.
Basin 2 constitutes the northeast portion of the parcel. This basin is 4,766.3 SF. It consists of grass and roof
surface areas, and has 47.6% impervious area. Under historic conditions, surface runoff from Basin 2 flows over
the sidewalk and green space in the public right of way and into the gutter that runs along Hunter St. Ultimately,
runoff from this basin drains into Inlet 2 near the corner of Hunter St and Main St. Under developed conditions,
surface runoff from the roof of the church and the grass on the side of the church will be conveyed into Inlet 2
by a grassed swale and drain pipe. The WQCV will be detained in a subsurface detention area below the grassed
swale, and the overflow will sheet flow across the sidewalk and into Inlet 2.
Basin 3 is the area between Basins 1 and 2-generally the middle portion of the parcel. This basin is 13,178.3 SF.
It consists mostly of grass, pervious pavers, roof, and concrete, and has 56.4% impervious area. Developed
St. Mary Church
City of Aspen
Received
5/2/17
Building Department
3
drainage conditions for Basin 3 will follow historic drainage patterns; however, a slight decrease in surface
runoff will result from the replacement of 165 SF of concrete driveway with pervious pavers. Area
improvements to Basin 3 include a new 6 foot sidewalk, to replace the existing sidewalk, a new driveway cut,
and pervious pavers. The sidewalk, driveway cut, and pervious pavers all drain into the 5” grass buffer area of
the property. The rest of the ground surface area of Basin 3 and the western portion of the church roof drain
into a drywell that exists inside the basin.
2.3 Peak Discharge Calculations
Peak flows were calculated for the surface runoff of each basin for the 10-Yr and 100-Yr storm events using the
Rational Method since the site is less than 90 acres. The runoff coefficients (C) were determined using the
percentage of impervious area in each basin and Figure 3.3-Runoff Coefficients for NRCS HSG B of the City of
Aspen URMP. Even though the actual Time of Duration (Td) for each basin was considerably less than 5 minutes,
the City of Aspen URMP requires a minimum Td of 5 minutes be used. Rainfall intensity was calculated using a Td
of 5 minutes and 1-hour rainfall depth (P1) of 0.77 inch/hour for the 10-Yr event and 1.23 inch/hour for the 100-
Yr event. See Equation 1 in Appendix C. Lastly, the peak flow (Q) was determined for each basin using Equation 2
for the 10-Yr and 100-Yr storm events. For each basin the runoff coefficient (C), the rainfall intensity (I) for the
storm event, and the area (A) were multiplied together to determine the peak flow (see Appendix C). The tables
below show the peak flows for historic and developed conditions for each basin.
Table 1
1-Hr P1:0.77
Return Period:10
Basin ID Total Area Impervious Area Imperviousness C Value Duration (Td)Intensity Q10
See Basin Exhibit (SF)(SF)(%)From Table 3.3 (min)I=88.8*P1/(10+Td)1.052 (cfs)
1 11121.2 4276.7 38.5 0.36 5 3.96 0.36
2 3882.8 2267.2 58.4 0.45 5 3.96 0.16
3 13178.3 7591.3 57.6 0.44 5 3.96 0.53
On Site 10-Yr Peak Discharge - Historic Conditions
Table 2
1-Hr P1:0.77
Return Period:10
Basin ID Total Area Impervious Area Imperviousness C Value Duration (Td)Intensity Q10
See Basin Exhibit (SF)(SF)(%)From Table 3.3 (min)I=88.8*P1/(10+Td)1.052 (cfs)
1 11121.2 4276.7 38.5 0.36 5 3.96 0.36
2 4766.3 2267.2 47.6 0.39 5 3.96 0.17
Off Site Basin 2 13046.0 11990.8 91.9 0.78 5 3.96 0.92
3 13178.3 7426.3 56.4 0.43 5 3.96 0.52
On Site 10-Yr Peak Discharge - Developed Conditions
Table 3
1-Hr P1:1.23
Return Period:100
Basin ID Total Area Impervious Area Imperviousness C Value Duration (Td)Intensity Q10
See Basin Exhibit (SF)(SF)(%)From Table 3.3 (min)I=88.8*P1/(10+Td)1.052 (cfs)
1 11121.2 4276.7 38.5 0.49 5 6.33 0.79
2 3882.8 2267.2 58.4 0.56 5 6.33 0.32
3 13178.3 7591.3 57.6 0.55 5 6.33 1.05
On Site 100-Yr Peak Discharge - Historic Conditions
City of Aspen
Received
5/2/17
Building Department
4
2.4 Analysis of Peak Discharge into Inlet 2
Under historic conditions, surface runoff from Basin 2 and Off Site Basin 2 drains into the city storm sewer via
Inlet 2. Runoff from Basin 2 flows into the gutter along Hunter St and then into Inlet 2. Runoff from Off Site Basin
2 flows into an inlet near the SE corner of the site, through an 18” reinforced concrete pipe, and into the inlet
box of Inlet 2. Inlet 2 outlets into an existing 10” PVC pipe that then carries the stormwater under Hunter St.
Under developed conditions, surface runoff from Basin 2 will collect in a 4” perforated drain pipe that will run
under a grass swale on the east side of the church. The 4” drain pipe will convey the runoff and daylight into the
inlet box of Inlet 2. No runoff increase will result for the city storm sewer system. In fact, with the grassed swale
and the subsurface detention area, a significant decrease in runoff for smaller storms is expected due to much of
the runoff being infiltrated into the subsoil.
Table 5 below shows the required diameter of the Inlet 2 outlet pipe that is needed to convey the runoff that
drains into Inlet 2 under developed conditions. Table 6 below shows the adequacy of the existing 10” PVC outlet
pipe to convey the 100-Yr storm event at 80% full (refer to Equation 3 in Appendix C).
An analysis of the capacity of Inlet 2 was performed to determine if Inlet 2 had adequate capacity to intercept
the 100-Yr storm event for Basin 2. To be conservative, it was assumed that all runoff from Basin 2 would drain
into the inlet box through the grate and curb-opening. Table 7 below shows that Inlet 2 is adequate to intercept
runoff from Basin 2 (refer to Equations 4-26 and 4-27 from the URMP shown in Appendix C).
Table 4
1-Hr P1:1.23
Return Period:100
Basin ID Total Area Impervious Area Imperviousness C Value Duration (Td)Intensity Q10
See Basin Exhibit (SF)(SF)(%)From Table 3.3 (min)I=88.8*P1/(10+Td)1.052 (cfs)
1 11121.2 4276.7 38.5 0.49 5 6.33 0.79
2 4766.3 2267.2 47.6 0.52 5 6.33 0.36
Off Site Basin 2 13046.0 11990.8 91.9 0.82 5 6.33 1.55
3 13178.3 7426.3 56.4 0.54 5 6.33 1.03
On Site 100-Yr Peak Discharge - Developed Conditions
Table 5
K=0.462
Basin 2 Discharge Off Site Basin 2 Discharge Total Discharge Slope of Outlet Pipe Mannings n Depth Required Diameter
Q100 (cfs)Q100 (cfs)(cfs)SO (ft/ft)Value d=(nQ/(K*SO
0.5)3/8 (Inch)
0.36 1.55 1.91 0.02 0.010 0.62 7.39
Required Pipe Size to Convey Runoff from Basin 2 and Off Site Basin 2
Table 6
Total Discharge Dia. of Ex. Outlet Pipe Slope of Outlet Pipe Required Diameter Design Dia. @ 80% Capacity Adequate Capacity
(cfs)(Inch)SO (ft/ft)(Inch)(Inch)Yes/No
1.91 10 0.02 7.39 8.94 Yes
Existing Storm Sewer Capacity
Table 7 Orifice-Flow Capacity Co=0.65 Effective Opening Area Cg=0.12 Return Period = 100
Inlet 2 Capacity Qo=CoAe(2g(YS-YC))0.5 g=32.2 ft/sec2 Ae=(1-Cg)HL H=.5'
YS=0.43', YC=0.18'L=3'
Inlet Type Inlet Width Inlet Length Effective Opening Area Orifice-Flow Capacity Q100 Adequate Capacity
In-Sump Wo (ft)LO (ft)Eq. 4-27 (ft2)Eq. 4-26 (cfs)(cfs)Yes/No
Curb Opening 2 3 1.32 3.44 1.19 Yes
City of Aspen
Received
5/2/17
Building Department
5
3.0 Low Impact Site Design
Low Impact Development (LID) attempts to reduce runoff and increase infiltration. The St Mary Catholic Church
site was classified as “Institutional/Campus”. Specific design recommendations applied to that classification.
These recommendations and other LID principles were employed to increase the water quality of the runoff and
increase public safety.
3.1 Principles of LID
Principle 1: Consider stormwater quality needs early in the design process.
Opportunities to integrate stormwater quality facilities were limited for this project as the buildings already
existed and sidewalk replacement aimed to largely replace sidewalk in existing locations. However, the site had
favorable historic conditions. All runoff travels through green infrastructure before entering the city storm sewer
system-with the exception of the areas where the concrete sidewalk extends all the way to the back of the curb.
To treat the runoff from the roof on the east side of the church, a subsurface detention area under a grass swale
will be installed to treat the WQCV.
Principle 2: Use the entire site when planning for storm water quality treatment.
The existing conditions of the site will be largely unchanged. The site currently employs good storm water
quality treatment as all impervious areas are bordered by a grass buffer. All runoff passes through this grass
buffer before entering the city storm system.
Principle 3: Avoid unnecessary impervious area.
Sidewalk replacement will largely replace sidewalk to historic widths and lengths. In the areas where the
sidewalk is to be widened, a grass swale or pervious pavers will be installed to increase infiltration of that area
and reduce runoff.
Principle 4: Reduce runoff rates and volumes to more closely match natural conditions.
This principle does not entirely apply, because historic drainage patterns will not be changed. The runoff on the
east side of the church where the grassed swale will be installed will reduce runoff rates as the WQCV will be
detained.
Principle 5: Integrate storm water quality management and flood control.
Runoff from Basin 3 drains into an existing drywell, which increases flood control. Runoff from large storm
events will pass through a grass buffer or grassed swale before entering the city storm system. This increases
both water quality and flood control as much of the runoff will infiltrate through the grass and soil.
Principle 6: Develop storm water quality facilities that enhance the site, the community and the environment.
Much of the contaminants will be removed as the runoff passes over the landscaped areas before it leaves the
site. All runoff from impervious areas will pass through a grass buffer before entering the city storm system.
Additionally, trees and shrubbery cover much of the site.
Principle 7: Use the treatment train approach.
City of Aspen
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5/2/17
Building Department
6
For the majority of the site, runoff will travel through green infrastructure before entering the city storm sewer
system. Two feet of gravel will be placed along the east side of the church to capture runoff before it travels into
the grass swale. Also, all downspouts discharge onto pervious surfaces, increasing filtration and infiltration.
Principle 8: Design sustainable facilities that can be safely maintained.
The drain pipe and inlet on the east side of the church will be well outside of the travel area of the new concrete
sidewalk. The side slopes of the grass swale will drop at one inch per foot to the flowline (~8.3%). New sidewalks
will be cross-sloped at 2% away from the church. All new handicap ramps will be per Americans with Disabilities
Act and City of Aspen Standards.
Principle 9: Design and maintain facilities with public safety in mind.
Proper grading and drainage of new sidewalks will alleviate flooded or icy walking surfaces.
4.0 Water Quality Capture Volume
4.1 Water Quality Capture Volume Storage
As the project site is located in the Aspen Mountain Drainage Basin, only the WQCV is required to be detained.
Minimizing Directly Connected Impervious Areas (MDCIA) helps to control flooding and improve water quality.
To this end, a “green space” between the concrete sidewalks and the back of the curb was left to act as a buffer
for the runoff before it entered the gutter. This green space allows water to sheet flow over its surface,
promoting filtration, infiltration, and settling to remove pollutants. The site qualifies as MDCIA Level 1 as runoff
is treated before entering the city storm sewer system.
Table 8 below shows the calculated WQCV storage required for Basin 2-the area on the east side of the church,
and Basin 3-the area in the center of the lot. Using Figure 8.14 in the City of Aspen URMP, the total
imperviousness of the basin was reduced to a lower effective imperviousness because MDCIA and other LID
practices were used. The WQCV (in watershed-inches) was determined using the effective imperviousness and
Figure 8.13 of the URMP. Finally, Equation 4 was used to determine the WQCV storage based on the watershed-
inches and the area of the basin (see Appendix C).
Table 9 below shows the storage volume of the subsurface detention area. This illustrates that the WQCV
required storage is adequately met by the subsurface detention area.
Table 8
Basin ID Total Area Impervious Area Imperviousness MDCIA Effective Imperviousness WQCV WQCV Storage
See Basin Exhibit (SF)(SF)(%)Level from Figure 8.14 Value from Figure 8.13WQCV-In*Area/12
2 4271.7 2691.1 0.63 1 0.61 0.12 42.7 ft3
3 13178.3 7426.3 0.56 1 0.52 0.10 109.8 ft3
Water Quality Capture Volume Storage required for developed runoff of Basin 2
Table 9
Void Space Volume
Width Length Depth Volume Sand = 30%
(ft)(ft)(Inch)W*L*D/12*0.30 3/4" Screened Rock = 30%
2 87.7 10 43.9 ft3
Storage volume available for developed runoff of Basin 2 in the Subsurface Detention Area
Dimension of the Detention Area
City of Aspen
Received
5/2/17
Building Department
7
Table 10 below shows the storage volume of the existing drywell in Basin 3. The City of Aspen requires 1.5 times
the WQCV Storage to be detained for a drywell. With 197.9 cubic feet of detention volume, the required storage
is adequately met.
4.1.1 Drywell Percolation Test
To verify that the WQCV was being met in the existing drywell a percolation test was performed. The inside
depth of the drywell was found to be 12’-7” and the diameter was 4’. The lower 6’-7’ was perforated. The
drywell percolated at an average rate of 15 inches per hour. Exceeding the City of Aspen minimum percolation
rate of 3 inches per hour. Therefore, it was verified that the existing drywell can handle the runoff from
Drainage Basin 3. The results from the percolation test can be found in Appendix D.
5.0 Operations and Maintenance
5.1 Grass Swale
The grass swale should yield a fairly low amount of necessary maintenance. Regular mowing, trimming and
weed control, as well as trash and debris cleanup around the inlet should allow for the system to work properly.
The landscape and maintenance crew hired by the property owner should already be performing these tasks
around the entire property, so no additional maintenance or cost should be incurred.
5.2 Pervious Pavers
The pervious pavers should be kept clear of debris and litter. The surface of the pavers should be swept
annually. Sand infill may need to be replaced to bring its surface to be 1/4” below the adjacent blocks, this is
non-routine and should only be done when it becomes evident that runoff does not rapidly infiltrate into the
surface. This maintenance should be performed by the landscape and maintenance crew hired by the property
owner.
5.3 Drywell
The existing drywell should be inspected annually and after every storm exceeding 0.5 inches. Any extra
sediment, debris/trash, and other waste material removed from the dry well should be disposed of at suitable
disposal sites and in compliance with local, state, and federal waste regulations. The dry well should be routinely
evaluated for its drain-down time to ensure the maximum time of 24 hours in not being exceeded. If drain-down
times are exceeding the maximum, the well will need to be drained via pumping and clean out of the percolation
area. These inspections should be conducting by the property owner.
Table 10
Drywell Diameter Depth (H1)Conc. Wall Gravel Height (H2)Void Space Total Volume
Basin (Feet)(Feet)(Inches)(Feet)(Feet)(%)Vol=Manhole + Grave Void Space
3 4 12.74 7 1.5 4 30 197.8 ft3
Drywell Capacity Calculations-WQCV
City of Aspen
Received
5/2/17
Building Department
8
6.0 Summary
In this report, it was demonstrated that the proposed project is in compliance with the City of Aspen URMP.
With the effective use of LID principles such as pervious pavers, green spaces between the sidewalks and the
back of curbs, a gravel filtration area, a grass swale, and a subsurface detention area to provide adequate
WQCV, the water quality of surface runoff can be increased. Also, by utilizing these principles, runoff can be
reduced by infiltration and percolation before it can enter the city storm sewer system. In addition to
demonstrating compliance with the URMP, this report also shows that the implementation of these best
management practices will not produce an increase of runoff to the city storm sewer system. Lastly, this report
shows that the existing inlets and culverts are adequate for handling the runoff that leaves the site.
City of Aspen
Received
5/2/17
Building Department
Appendix A
Appendix A
Historic Site Basin Delineation Map
Developed Site Basin Delineation Map
City of Aspen
Received
5/2/17
Building Department
Graphic Scale
In Feet: 1" = 40'
0 20 40 80
Job No.
Drawn by:
Date:
Of
File:
PE:QC:
Revision#Date By
Historic Site
Basin Delineation
2016-195
AWA
11/17/2016
DCS
StMarysBasinDelineationHist
DCS
1
2
St. Mary Catholic Church
Aspen, COFor Submittal 118 West Sixth Street, Suite 200
Glenwood Springs, CO 81601
970.945.1004 www.sgm-inc.com
City of Aspen
Received
5/2/17
Building Department
Graphic Scale
In Feet: 1" = 40'
0 20 40 80
Job No.
Drawn by:
Date:
Of
File:
PE:QC:
Revision#Date By
Developed Site
Basin Delineation
2016-195
AWA
11/17/2016
DCS
StMarysBasinDelineationDev
DCS
2
2
St. Mary Catholic Church
Aspen, COFor Submittal 118 West Sixth Street, Suite 200
Glenwood Springs, CO 81601
970.945.1004 www.sgm-inc.com
City of Aspen
Received
5/2/17
Building Department
Appendix B
Appendix B
Drainage Exhibit
City of Aspen
Received
5/2/17
Building Department
Graphic Scale
In Feet: 1" = 40'
0 20 40 80
Job No.
Drawn by:
Date:
Of
File:
PE:QC:
Revision#Date By
Drainage Exhibit
2016-195
AWA
11/17/2016
DCS
StMarysBasinDrainExhibit
DCS
1
1
St. Mary Catholic Church
Aspen, COFor Submittal 118 West Sixth Street, Suite 200
Glenwood Springs, CO 81601
970.945.1004 www.sgm-inc.com
City of Aspen
Received
5/2/17
Building Department
Appendix C
Appendix C
Equations
City of Aspen
Received
5/2/17
Building Department
Appendix C
Equation 1 – Rainfall Intensity (Eq. 2-1 URMP)
I = (88.8)(𝑃1)
(10+𝑆𝑑)1.052 I = Rainfall Intensity (inch/hour)
P1 = 1-hour rainfall depth (inches)
Td = Time of Duration (minutes)
Equation 2 – Peak Flow (Eq. 3-1 URMP)
Q = (𝐶)(𝐻)(𝐴) C = Runoff Coefficient
(from Figure 3.3 in URMP)
I = Rainfall Intensity (inch/hour)
A = Area (acres)
Equation 3 – Required Depth
d = ((𝑛)(𝑃)
(𝐾)(𝑆𝑂).5)3 8⁄
N = Manning’s value
Q = Peak Flow (cfs)
K = 0.462
SO = Slope of pipe (ft/ft)
Equation 4 – WQCV Storage Volume
Volume (ft3) = (𝑉𝑄𝐶𝑉 �ℎ𝑛 𝑉𝑎𝑟𝑐𝑟𝑟�𝑐𝑐 �ℎ𝑛𝑐�𝑐𝑟)(1 𝑒𝑡
12 𝑖𝑛)(𝐴) WQCV-Inches from Figure 8.13 in URMP
I = Rainfall Intensity (inch/hour)
A = Area (square feet)
Equation 5 – In-Sump Curb-Opening Inlet Capacity (Eq. 4-26 URMP)
Qo = 𝐶𝑛𝐴𝑒√2𝑖(𝑌𝑆−𝑌𝐶) Qo=Inlet Capacity (cfs)
Co = Orifice Coeffecient
(0.65 recommended in URMP)
Ae = Effective Opening Area (sq. feet)
g = gravitational acceleration
(32.2 ft/sec2)
YS = Water Depth (feet)
YC = Center of opening above flow line
(feet)
Equation 6 – Effective Opening Area (Eq. 4-27 URMP)
Ae = (1 −𝐶𝑒)𝐻𝐿 Cg = Clogging Factor (0.12 from URMP)
H = Height of opening area (feet)
L = Width of opening area (feet)
City of Aspen
Received
5/2/17
Building Department
Appendix D
Appendix D
Percolation Test Results
City of Aspen
Received
5/2/17
Building Department
City of Aspen Received 5/2/17Building Department