HomeMy WebLinkAbout112 W. MAGNOLIA STREET PARKING LOT - PDP - PDP160040 - REPORTS - DRAINAGE REPORTDRAINAGE REPORT
FOR
Wells Fargo Parking Lot Improvements
112 West Magnolia Street
Fort Collins, CO 80524
Prepared for:
Cox Pavement Consulting, LLC
228 Stratton Park Road
Bellvue, CO, 80512
Prepared by:
www.quality-engineering.com
4045 St. Cloud Drive, Suite 180
Loveland, CO 80538
(970) 416-7891
QE Project No: 7060-001
Date: May 2017
Parking at 112 West Magnolia Street
FINAL DRAINAGE REPORT
ENGINEER’S CERTIFICATION
I hereby certify that this Final Drainage Report for the design of stormwater management facilities
for the Parking at 112 West Magnolia Street Project was prepared by me, or under my direct
supervision, in accordance with the provisions of the City of Fort Collins Storm Drainage Design
Criteria and Construction Standards for the owners thereof.
Cody Geisendorfer, P.E.
Registered Professional Engineer
State of Colorado No. 41326
I. Table of Contents
I. GENERAL LOCATION AND DESCRIPTION....................................... 1
A. Location..................................................................................................................1
B. Description of Property ...........................................................................................1
II. DRAINAGE BASINS AND SUB-BASINS ................................................ 2
A. Major Basin Description .........................................................................................2
B. Sub-Basin Description ............................................................................................2
III. DRAINAGE CRITERIA ............................................................................ 2
A. Regulations .............................................................................................................2
B. Implementation of the “Four Step Process” .............................................................3
C. Development Criteria Reference and Constraints ....................................................4
D. Hydrological Criteria ..............................................................................................4
E. Hydraulic Criteria ...................................................................................................5
F. Modifications of Criteria .........................................................................................5
IV. DRAINAGE FACILITY DESIGN ............................................................ 5
A. General Concept .....................................................................................................5
B. Specific Details .......................................................................................................5
V. CONCLUSIONS ......................................................................................... 6
A. Compliance with Standards .....................................................................................6
B. Drainage Concept ...................................................................................................6
VI. REFERENCES ........................................................................................... 7
VII. APPENDICES
A. Hydrologic Computations
Vicinity Map
Fort Collins Flood Map
USGS Soil Map
Fort Collins Rainfall Intensity Curve
Fort Collins Rainfall Intensity Table
Table RO-11 Rational Method Runoff Coefficients for Composite Analysis
Rational Method Calculated Composite C Tables
Rational Method Calculated Imperviousness
Rational Method Calculated Flows
B. Hydraulic Computations
Modified FAA Method
Permeable Paver Sub-Base Detention Calculation
Orifice Sizing Calculation
C. Map Pocket
Drainage Plan
PG. 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
The proposed site is located in the northeast quarter (NE ¼) of Section 11, Township 7
North, Range 69 West of the 6th P.M. in Larimer County, Colorado. Specifically, the
property is located at the southeast corner of West Magnolia Street and College Avenue.
The property address is 112 West Magnolia Street, Fort Collins, Colorado, 80524. (Please
see the vicinity map located in the Appendix A).
B. Description of Property
The property’s parcel number is 9711424001. The site is located on Lots 1 and 2, Block
113 Fort Collins Subdivision and is currently 0.436 acres of gravel parking lot surrounded
by the clock tower building to the north, Wells Fargo to the south, and office buildings to
the east and west. West Magnolia is located directly south, College Avenue is located
directly east, and an alley is located west of the property. There is an existing access to the
site on all three roadways. The existing accesses on College Avenue and Magnolia Street
are to be abandoned. The access on Magnolia Street will be replaced with a new access.
Both existing West Magnolia Street and College Avenue are paved with curb, gutter,
sidewalk, and utilities installed.
The existing property is a gravel parking lot that drains south to West Magnolia Street and
College Avenue. Existing West Magnolia Street drains west to the existing inlet, where it
is conveyed to the Poudre River. Existing College Avenue drains north towards the
existing storm inlet, where it is conveyed to the Poudre River. There are generally no
offsite flows that drain toward the property. The entire site is located within the 100-year
floodplain. The northern half of the site is located in a moderate risk area, and the southern
half of the site is located within the city flood fringe (see City Flood Risk Map in Appendix
A).
According to the NRCS soils map survey, the native soils consist of the Type “C” soils.
These soils consist chiefly of soils having a layer that impedes the downward movement
of water or soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
There are no irrigation facilities located within the proposed site area. Irrigation for
landscaping is proposed for the new development.
The proposed development will consist of the construction of a 35-space off-street parking
lot that will act as employee parking for the Wells Fargo directly across West Magnolia
Street. The parking lot will be paved concrete with curb and gutter. The existing alley will
PG. 2
be repaved with concrete. Seven on-street parking stalls will be added to West Magnolia
Street.
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
The proposed site is located within the Old Town Drainage Basin, located in north-central
Fort Collins. The basin has a drainage area of approximately 2,120 acres, including
approximately 400 acres of the Colorado State University campus. The entire basin is
urbanized, with some development dating back to the late 1800s. Generally, the basin drains
from west to east. The Old Town Basin receives some runoff water from the Canal
Importation Basin directly west of Old Town. Most of the water from Old Town drains to the
Poudre River, just to the east.
B. Sub-Basin Description
Historically, most of the site drains south to West Magnolia Street.
The developed site is delineated into one sub-basin, with underground detention designed to
provide the required water quality capture volume.
Sub-basin B1, (0.436 acres), consists of an asphalt parking lot, landscaped area, and
permeable pavers. Rainfall travels via overland flow for short distances to gutters and to
permeable pavers in the parking stalls. The parking stalls incorporate the City of Fort Collins
LID water quality feature, which treats the water by filtering it through a layer of #57 Base,
followed by a layer of #2 Rock Sub-Base. The water is then collected in perforated PVC sub-
drains, and routed to the existing City stormwater collection system.
Currently, offsite flows do not enter the site property. This will not change after the site has
been developed.
III. DRAINAGE CRITERIA
A. Regulations
Drainage design criteria specified in the City of Fort Collins Storm Drainage Design Criteria
and Construction Standards Manual (FCSDCM) and the Urban Storm Drainage Criteria
Manual, Volume 3 by the Urban Drainage and Flood Control District (UDFCD) have been
referenced in the preparation of this study.
PG. 3
B. Implementation of the “Four Step Process”
Our stormwater management strategy utilizes the “Four Step Process” to minimize adverse
impacts of urbanization on receiving waters, as follows:
Step 1 – Employ Runoff Reduction Practices.
The first consideration taken in trying to reduce the stormwater impacts of this development
is the site selection itself.
The land use for the site remains unchanged: it has been a gravel parking lot, but to provide
a higher level of service to their employees, Wells Fargo is paving the parking lot. This will
reduce the amount of dirt that is tracked on to the paved streets in the area by vehicles during
precipitation events.
By selecting a site with historically undetained runoff, the burden of development will be
reduced, because underground detention is being provided. Underground detention allows
this high value downtown site to be fully utilized, whereas a pond would consume space in
this busy area. Permeable pavers are used to reduce the area of impervious surfaces.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV)
with Slow Release.
Urban development will cause stormwater runoff to increase from the site.
The primary water quality control will occur in the permeable paver detention, located under
the parking spaces of the lot. Refer to the map pocket for permeable paver details and cross-
sections. The detention will increase water quality and promote infiltration.
Water quality treatment for 50% of the site is provided for in the Udall Natural Area water
treatment facility.
Step 3 – Stabilize Drainageways.
The Poudre River is the governing drainageway for the proposed site. By improving the water
quality and increasing infiltration, the likelihood of bed and bank erosion from this site is
reduced.
Step 4 – Implement Site Specific and Other Source Control BMPs.
Permeable Pavement Systems: Flow from the parking lot will directly flow into the void
area of the pavers, avoiding any extra pollutant-flow contact time.
Landscaping: Personnel from Quality Engineering and CS Design worked with the City of
Fort Collins Forestry Department to preserve a large tree on the west side of the parking lot.
Interception storage, the water caught by plants at the onset of a rainstorm, is significant when
a large tree shades a small lot. Some amount of the intercepted water evaporates, never
PG. 4
reaching the ground. Additionally, water retained by the leaves and branches moves more
slowly through the hydrograph. In the case of this tree, the canopy hangs directly over existing
impervious asphalt area.
With infill development, we need to work around numerous existing infrastructure items, in
three dimensions. The stormwater piping had to be routed around the tree in both the lateral
and vertical directions, and the pavement design slightly altered in the alley in order to retain
the tree.
C. Development Criteria Reference and Constraints
The criteria used as the basis for analysis and design of stormwater management
improvements for this site are found in the references cited.
To the knowledge of the author, there are no other capital drainage improvements planned for
the site that would constrain or otherwise influence the design of the stormwater
improvements for this site.
D. Hydrological Criteria
Stormwater runoff is analyzed for storms with 2-year and 100-year return frequencies.
The Rational Method was chosen for this small site. The Rational Method provides that:
Q = CIA, where:
Q = Design flow in cubic feet per second (cfs)
C = Coefficient of runoff for the area under consideration
I = Rainfall intensity for the design storm duration (in/hr)
A = Area of the drainage sub-basin under consideration (ac)
Peak flows were calculated using the Rational Method for the 2-year and 100-year storm
events. We used the local 1-hour rainfall depth and Fort Collins rainfall intensities, calculated
as a function of the time of concentration. These values were obtained by the City of Fort
Collins Rainfall Intensity-Duration-Frequency (IDF) curve/table; Figure 3-1 and Table 3-1a,
and can be found in Appendix A. Additionally, per the City of Fort Collins, the coefficients
have been multiplied by the appropriate storm factors.
Percent imperviousness values were taken from Table RO-11, Rational Method Runoff
Coefficients for Composite Analysis, FCSCM (See Appendix A). Soils of hydrologic soil
type “C” dominate the site. Onsite runoff was calculated to determine the runoff differential
between existing and developed conditions for use in sizing the WQCV as required by the
FCSDM. The hydrologic basin parameters and runoff rates are included in the Appendices
and include quantification of the allowable volume reduction.
PG. 5
The standards from UDFCD Volume 2, Chapter 10, Section 3.2.3 were used to calculate the
required detention.
The design worksheets included in the Appendices to this Final Drainage Report present
documentation of the hydrologic calculations for the on-site storm drainage systems. We
modified Urban Drainage spreadsheets to incorporate Fort Collins criteria as follows:
• The Modified FAA spreadsheet incorporates the rainfall data from the Fort Collins
Criteria Manual, Volume 1, Table RA-7 and RA-8. The numbers from RA-7 and RA-
8 were manually entered in the first two columns of the UDFCD spreadsheet, which
overrides the automatic table normally provided in the spreadsheet.
• A modified UDFCD Stage Storage Sizing for Detention Basins sheet was used to
calculate the volumes for the underground detention. The volumes corresponding to
drawing C5.0, Drainage Plan are referenced as P1 through P4. The media under the
pavers conforms to Fort Collins Detail D-54, Interlocking Pavers Cross Section, with
the #57 Base thickness 4” and the #2 Rock thickness 16”. The #2 Rock provides the
detention volume. The void space of the #2 Rock is set to 30% in the calculations.
E. Hydraulic Criteria
Within this development, all runoff will be conveyed on the surface, initially as sheet flow
and subsequently as concentrated flow in shallow pans and gutters. The assessment of
required capacity and the sizing of the respective components of the drainage system are based
on the anticipated runoff from the 100-year storm event. The surface runoff will culminate
into the permeable pavers.
F. Modifications of Criteria
There are no modifications or variances requested in connection with the design of the
stormwater management for the parking at 112 West Magnolia site development.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
The storm drainage system is designed to safely convey developed storm flows by sheet flow,
concentrated pan, underdrain, and gutter flow to the permeable pavers and street flowlines.
The design worksheets included in the Appendices to this Final Drainage Report present
details of the hydrologic and hydraulic calculations pertinent to the design of the on-site storm
drainage system. A drainage plan, showing the proposed development of the site and
developed drainage patterns is included in the map pocket following the Appendices.
B. Specific Details
PG. 6
Sub-basin B1, (0.436 acres), consists of a concrete parking lot, landscaped area, and
permeable pavers. Rainfall travels via overland flow to the gutter flowline of the parking area
into the permeable pavers. Overland flow will also infiltrate the permeable pavers in the
parking stalls, where it will be treated. The 100-year flow is released at the 2-year historic
rate, via an 8” pipe with an orifice plate with a 3.25” opening into the storm drain system.
After treatment within the permeable pavers, the WQCV will also be released into storm drain
system, where it will be eventually conveyed to the Poudre River. If the paver system
overflows due to clogging, catch basins at the low point of the pavers will direct runoff into
the underdrain system.
Sub-basin B1 produces a 100-year flow of 2.80 cfs. The UDFCD FAA spreadsheet was
modified to incorporate rainfall data from the Fort Collins Criteria Manual, Volume 1, Table
RA-7 and RA-8. This spreadsheet was used to calculate the outflows and inflows from the
basin, and to generate a Stage Storage Table. A key parameter is the Major Stage Storage
Volume, 2033 ft3.
The underground detention under the pavers is designed per Fort Collins Detail D-54,
Interlocking Pavers Cross Section. The detention volume is the #2 rock, with a height of 16
inches, and a surface area of 5658 ft2 (see sheet C5.0 for a tabulation of areas). 30% of the
volume of the rock is void space. The detention volume is:
(5658 𝑓𝑡
2)(
16
12
𝑓𝑡) (0.3) = 2263 𝑓𝑡3
This compares favorably with our Major Stage Storage Volume of 2033 ft3. Water quality
parameters were also checked in the calculations.
V. CONCLUSIONS
A. Compliance with Standards
The drainage design for the Parking at 112 West Magnolia Street follows the requirements of
the City of Fort Collins Storm Drainage Design Criteria and Construction Standards Manual
as well as the City’s floodplain regulations. The criteria and recommendations of the Urban
Storm Drainage Criteria Manual are also reflected in the design of the drainage systems.
B. Drainage Concept
The drainage design for the Parking at 112 West Magnolia Street will safely convey onsite
flows from the parking lot into the storm drains, by way of the permeable paver detention
system. Underground detention and the preservation of an existing large tree help to minimize
PG. 7
the impact of the development. Excellent water quality treatment will be achieved by the
underground detention system.
VI. REFERENCES
“City of Fort Collins Stormwater Criteria Manual”, City of Fort Collins, Adopted December 2011.
“City of Fort Collins Municipal Code”, Chapter 10 – Flood Protection and Prevention City of Fort
Collins, 1987.
Urban Storm Drainage Criteria Manual, Volumes 1, 2, and 3, Urban Drainage and Flood Control
District, April 2008.
VII. APPENDICES
APPENDIX A: Hydrologic Computations
Vicinity Map
Fort Collins Flood Map
USGS Soil Map
Fort Collins Rainfall Intensity Curve
Fort Collins Rainfall Intensity Table
Table RO-11 Rational Method Runoff Coefficients for Composite Analysis
Rational Method Calculated Runoff Coefficients
Rational Method Calculated Imperviousness
Rational Method Calculated Flows
S COLLEGE AVE
W MAGNOLIA ST
. Printed: 03/25/2016
All floodplain boundaries
are approximate.
This information is based on the Federal Emergency Management
Agency (FEMA) Flood Insurance Rate Map (FIRM) and the City of
Fort Collins Master Drainageway Plans. This letter does not imply
that the referenced property will or will not be free from flooding or
damage. A property not in the Special Flood Hazard Area or in a
City Designated Floodplain may be damaged by a flood greater
than that predicted on the map or from a local drainage problem
not shown on the map. This map does not create liability on the
part of the City, or any officer or employee thereof, for any damage
that results from reliance on this information.
City Flood Risk Map
Moderate Risk
May include:
- Areas of FEMA 500-year floodplain (FEMA Zone X-shaded).
- Areas of FEMA or City 100-year floodplain (sheet flow) with
average depths of less than 1 foot.
- Areas protected by levees from the 100-year flood.
Low Risk
Areas outside of FEMA and City mapped 100-year and 500-year
floodplains. Local drainage problems may still exist.
City Flood Fringe - May Include:
- Areas of FEMA 100-year floodplain (FEMA Zones A, AE, AO, and AH)
- Areas of City 100-year floodplain including ponding areas and sheet
flow areas with average depths of 1-3 feet.
There is a 1% annual chance that these areas will be flooded.
High Risk
City Floodway - Area of 100-year floodplain with greatest depths and
fastest velocities.
0 15 30 60 90 120
Feet
35 C
0.5
0.5
112 W Magnolia Street
8/18/2016
41
Table RO-11
Rational Method Runoff Coefficients for Composite Analysis
Character of Surface Runoff Coefficient
Streets, Parking Lots,
Drives:
Asphalt 0.95
Concrete 0.95
Gravel 0.5
Roofs 0.95
Recycled Asphalt 0.8
Lawns, Sandy Soil:
Flat <2% 0.1
Average 2 to 7% 0.15
Steep >7% 0.2
Lawns, Heavy Soil:
Flat <2% 0.2
Average 2 to 7% 0.25
Steep >7% 0.35
(4) A new Section 2.9 is added, to read as follows:
2.9 Composite Runoff Coefficient
Drainage sub-basins are frequently composed of land that has multiple surfaces or zoning
classifications. In such cases a composite runoff coefficient must be calculated for any
given drainage sub-basin.
The composite runoff coefficient is obtained using the following formula:
( )
t
n
i
i i
A
C A
C
∑
= = 1
*
(RO-8)
Where: C = Composite Runoff Coefficient
Ci = Runoff Coefficient for Specific Area (Ai)
Ai = Area of Surface with Runoff Coefficient of Ci, acres or feet2
n = Number of different surfaces to be considered
At = Total Area over which C is applicable, acres or feet2
(5) A new Section 2.10 is added, to read as follows:
Composite C Values
WELLS FARGO PARKING EXPANSION
Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Roofs (acres) Lawns (acres) Total Area Minor (2-YR) Major (100-YR)
(C = 0.95) (C = 0.95) (C = 0.50) (C = 0.95) (C = 0.15) (acres) Composite "C" Composite "C" (Cf x C)
P1 E1 0.00 0.00 0.44 0.00 0.00 0.44 0.50 0.63
Alley Alley 0.042 0.00 0.00 0.00 0.01 0.047 0.87 1.00
D1 B1 0.21 0.01 0.00 0.00 0.21 0.44 0.53 0.67
Alley Alley 0.00 0.047 0.00 0.00 0.00 0.047 0.95 1.00
Notes:
Composite C values obtained from Table R0-11
Major Storm Runoff factored per Table R0-12
Developed
Design Point Basin(s)
Existing
MAP Wells Fargo Rational Method.xlsx 4/7/2017
Impeviousness
WELLS FARGO PARKING EXPANSION
Asphalt Area (acres) Concrete Area (acres) Gravel (acres) Roofs (acres) Lawns (acres) Total Area Percent
(I = 100) (I = 100) (I = 40) (I = 90) (I = 0) (acres) Imperviousness
P1 E1 0.00 0.00 0.436 0.00 0.00 0.4360 40%
Alley Alley 0.042 0.00 0.00 0.00 0.006 0.0480 88%
D1 B1 0.21 0.01 0.00 0.00 0.21 0.436 51%
Alley Alley 0.00 0.047 0.00 0.00 0.00 0.047 100%
Notes:
Percent Impervious Values per Table R0-3, Urban Drainage Manual
Developed
Design Point Basin (s)
Existing
CAG Wells Fargo Rational Method.xlsx 4/7/2017
Basin Flow Calculations
WELLS FARGO PARKING EXPANSION
Area Minor Major
(acres) Composite "C" Composite "C" Length (ft) Slope (%)
Minor tov
(min)
a
Major tov
(min)
a Length (ft)
Slope
(%)
Channel
Type
Velocity
(fps)
c t
t (min)
Minor TC
(min)
Major TC
(min) 2-yr 10-yr 100-yr 2-yr 10-yr 100-yr
P1 E1 0.4360 0.50 0.63 117 1.77 10.03 7.94 71 0.60 PA 1.55 0.76 10.80 8.71 2.13 3.63 8.21 0.46 0.79 2.24
Alley Alley 0.0470 0.87 1.00 20 1.50 1.69 0.73 88 1.00 PA 2.00 0.73 5.00 5.00 2.85 4.87 9.95 0.12 0.20 0.47
D1 B1 0.4354 0.53 0.67 69 2.00 6.98 5.33 0 1.00 PA 2.00 0.0000 6.98 5.33 2.52 4.31 9.63 0.59 1.00 2.80
Alley Alley 0.0470 0.95 1.00 20 1.50 1.10 0.73 88 1.00 PA 2.00 0.7333 5.00 5.00 2.85 4.87 9.95 0.13 0.22 0.47
Notes:
a
b
HM = Heavy Meadow, TF = Tillage/field, PL = Short pasture and lawns, BG = Nearly bare ground, GW = Grassed Waterway, PA = Paved Areas
c
Velocity alues from Figure 3-3/Table RO-2 Estimate of Average Flow Velocity for use with the Rational Method
Design
Point
Developed
Existing
Initial/Overland Time Final TC Intensity (in/hr) Basin Flows (cfs)
Basin (s)
Travel Time
1 / 3
1 . 87 ( 1 . 1 ) 1 / 2
S
CC D
t f
ov
CAG Wells Fargo Rational Method.xlsx 4/7/2017
APPENDIX B: Hydraulic Computations
Modified FAA Method
Permeable Paver Sub-Base Detention Calculation
Orifice Sizing Calculation
Project:
Basin ID:
Design Information (Input): Design Information (Input):
Catchment Drainage Imperviousness Ia
= 51.00 percent Catchment Drainage Imperviousness I
a = 51.00 percent
Catchment Drainage Area A = 0.436 acres Catchment Drainage Area A = 0.436 acres
Predevelopment NRCS Soil Group Type = C A, B, C, or D Predevelopment NRCS Soil Group Type = C A, B, C, or D
Return Period for Detention Control T = 2 years (2, 5, 10, 25, 50, or 100) Return Period for Detention Control T = 100 years (2, 5, 10, 25, 50, or 100)
Time of Concentration of Watershed Tc = 11 minutes Time of Concentration of Watershed Tc = 11 minutes
Allowable Unit Release Rate q = 1.05 cfs/acre Allowable Unit Release Rate q = 1.05 cfs/acre
Determination of Average Outflow from the Basin (Calculated): Determination of Average Outflow from the Basin (Calculated):
Runoff Coefficient C = 0.53 Runoff Coefficient C = 0.67
Inflow Peak Runoff Qp-in = 0.59 cfs Inflow Peak Runoff Qp-in = 2.80 cfs
Allowable Peak Outflow Rate Qp-out = 0.46 cfs Allowable Peak Outflow Rate Qp-out = 0.46 cfs
Mod. FAA Minor Storage Volume = 60.233 cubic feet Mod. FAA Major Storage Volume = 2,033 cubic feet
5 <- Enter Rainfall Duration Incremental Increase Value Here (e.g. 5 for 5-Minutes)
Rainfall Rainfall Inflow Adjustment Average Outflow Storage Rainfall Rainfall Inflow Adjustment Average Outflow Storage
Duration Intensity Volume Factor Outflow Volume Volume Duration Intensity Volume Factor Outflow Volume Volume
minutes inches / hr cubic feet "m" cfs cubic feet cubic feet minutes inches / hr cubic feet "m" cfs cubic feet cubic feet
(input) (output) (output) (output) (output) (output) (output) (input) (output) (output) (output) (output) (output) (output)
0 0.00 0.000 0.00 0.00 0.000 0.000 0 0.00 0.000 0.00 0.00 0.000 0.000
5 2.85 197.573 1.00 0.46 137.340 60.233 5 9.95 871.978 1.00 0.46 137.340 734.638
10 2.21 306.412 1.00 0.46 274.680 31.732 10 7.72 1,353.100 1.00 0.46 274.680 1,078.420
15 1.87 388.908 0.86 0.39 354.337 34.570 15 6.52 1,714.160 0.87 0.40 357.084 1,357.076
20 1.61 446.447 0.77 0.35 423.007 23.439 20 5.60 1,963.046 0.78 0.35 425.754 1,537.292
25 1.43 495.667 0.72 0.33 491.677 3.989 25 4.98 2,182.136 0.72 0.33 494.424 1,687.712
30 1.30 540.727 0.68 0.31 560.347 -19.620 30 4.52 2,376.688 0.68 0.31 563.094 1,813.594
35 1.17 567.764 0.65 0.30 629.017 -61.254 35 4.08 2,502.884 0.66 0.30 631.764 1,871.120
40 1.07 593.413 0.64 0.29 697.687 -104.274 40 3.74 2,622.069 0.64 0.29 700.434 1,921.635
45 0.99 617.677 0.62 0.28 766.357 -148.680 45 3.46 2,728.985 0.62 0.28 769.104 1,959.881
50 0.92 637.781 0.61 0.28 835.027 -197.246 50 3.23 2,830.643 0.61 0.28 837.774 1,992.869
55 0.87 663.431 0.60 0.27 903.697 -240.267 55 3.03 2,920.908 0.60 0.27 906.444 2,014.464
60 0.82 682.148 0.59 0.27 972.367 -290.219 60 2.86 3,007.668 0.59 0.27 975.114 2,032.554
Determination of MINOR Detention Volume Using Modified FAA Method Determination of MAJOR Detention Volume Using Modified FAA Method
DETENTION VOLUME BY THE MODIFIED FAA METHOD
Wells Fargo Parking Lot Improvements
(For catchments less than 160 acres only. For larger catchments, use hydrograph routing method)
(NOTE: for catchments larger than 90 acres, CUHP hydrograph and routing are recommended)
Project:
Basin ID:
Design Information (Input):
Width of Basin Bottom, W = ft Right Triangle OR…
Length of Basin Bottom, L = ft Isosceles Triangle OR…
Dam Side-slope (H:V), Zd
= ft/ft Rectangle OR…
Circle / Ellipse OR…
Irregular (Use Overide values in cells G32:G52)
MINOR MAJOR
Storage Requirement from Sheet 'Modified FAA': 0.04 acre-ft.
Stage-Storage Relationship: Storage Requirement from Sheet 'Hydrograph': acre-ft.
Storage Requirement from Sheet 'Full-Spectrum': acre-ft.
Labels Water Side Basin Basin Surface Surface Volume Surface Volume Target Volumes
for WQCV, Minor, Surface Slope Width at Length at Area at Area at Below Area at Below for WQCV, Minor,
& Major Storage Elevation (H:V) Stage Stage Stage Stage Stage Stage Stage & Major Storage
Stages ft ft/ft ft ft ft
2
ft
2
User ft
3
acres acre-ft Volumes
(input) (input) Below El. (output) (output) (output) Overide (output) (output) (output) (for goal seek)
92.47 (input) 207 0 0.005 0.000 P1
92.60 0.00 0.00 747 62 0.017 0.001 P1 & P2
92.73 0.00 0.00 1,287 194 0.030 0.004 P1, P2, & P3
92.87 0.00 0.00 1,698 403 0.039 0.009 P1, P2, P3, &P4
93.80 0.00 0.00 1,491 1,886 0.034 0.043 P2, P3, &P4
93.93 0.00 0.00 951 2,045 0.022 0.047 100-YR
94.06 0.00 0.00 411 2,133 0.009 0.049 P4
#N/A #N/A
#N/A #N/A
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Project:
Date:
By:
Qreq = 0.46 cfs
D = 3.20 in (diameter of orifice)
g = 32.2 ft/s2
Ao = 0.056 ft2 (area of orifice)
H = 2.5 ft
Cd = 0.65
Qall = CdAo[(2gH)^1/2]
Qall = 0.46 cfs vs. Qreq = 0.46 cfs
7060-001
1/10/2017
RJP
Directions: Input all known variables. Change the orifice diameter, D, to match
Q all to Q req .
Orifice Calculator
Inputs
Orifice Inputs
Orifice Flow Calculation
www.quality-engineering.com
1501 Academy Court, #201
Fort Collins, CO 80524 (970) 416-7891
APPENDIX C: Map Pocket
Drainage Plan
PLANTING AREA
7
5
8
W
W W
W
W W W W W W W
W W
W W W W W W
W W W
W W
W W W W
W
W W
W W
EXISTING BUILDING
MAGNOLIA STREET
UNDERDRAIN
INV: 93.83'
UNDERDRAIN
INV: 93.79'
C/O
INV: 94.22'
C/O
INV: 93.75'
UNDERDRAIN
INV: 93.57'
UNDERDRAIN
INV: 93.61'
UNDERDRAIN
INV: 93.61'
UNDERDRAIN
INV: 93.33'
UNDERDRAIN
INV: 93.33'
UNDERDRAIN
INV: 93.29'
UNDERDRAIN
INV: 92.89'
UNDERDRAIN
INV: 93.03'
C/O
INV: 93.11'
UNDERDRAIN
INV: 93.34'
UNDERDRAIN
INV: 93.30'
C/O
INV: 93.77'
C/O
INV: 93.51'
UNDERDRAIN
INV: 92.7'
PLANTING AREA
EXISTING STORM INLET
C5.0
10'
SCALE: 1" = 10'
0 20'
WELLS FARGO PARKING LOT IMPROVEMENTS
112 WEST MAGNOLIA STREET
FORT COLLINS CO, 80525
FOR BURIED UTILITY INFORMATION
THREE (3) BUSINESS DAYS
BEFORE YOU DIG
CALL 811
(OR 1-800-922-1987)
UTILITY NOTIFICATION
CENTER OF COLORADO (UNCC)
WWW.UNCC.ORG
R
D1
BASIN ID
MINOR "C" COEFFICIENT
MAJOR "C" COEFFICIENT
DRAINAGE AREA
CITY OF FORT COLLINS, COLORADO
UTILITY PLAN APPROVAL
SYMBOL LEGEND
G G G
(UP)
(UT)
SS
X X
WS WS WS WS
SS
R/W
WS WS
W W
R/W
(OHP)
10.00
W
FS
E E
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STAGE-STORAGE SIZING FOR DETENTION BASINS
Wells Fargo Parking Improvements
Check Basin Shape
Underground Storage
UD-Detention_v2.34 underground.xls, Basin 3/15/2017, 8:23 AM