HomeMy WebLinkAboutSOUTH COLLEGE STORAGE - FDP - FDP170019 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFINAL DRAINAGE REPORT
South College Storage
Fort Collins, Colorado
June 21, 2017
Prepared for:
Brandon Grebe
GYS LLC
Real Estate / Development / Consulting
Prepared by:
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 1269-002
This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
When a hard copy is absolutely necessary, we recommend double-sided printing.
June 21, 2017
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage Report for
South College Storage
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage Report for your review. This report
accompanies the PDP submittal for the proposed South College Storage.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria Manual
(FCSCM). We understand that review by the City is to assure general compliance with standardized
criteria contained in the FCSCM as well as maintaining the overall Master Drainage Plan set forth by
the City.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Nicholas W. Haws, PE Blaine Mathisen
Vice President Project Engineer
South College Storage
Preliminary Drainage Report
TABLE OF CONTENTS
I. General Location and Description ............................................................................... 1
A. Location ............................................................................................................................................. 1
B. Description of Property ..................................................................................................................... 1
C. Floodplain.......................................................................................................................................... 3
II. drainage basins and sub-basins .................................................................................. 3
A. Major Basin Description .................................................................................................................... 3
B. Sub-Basin Description ....................................................................................................................... 3
III. drainage DESIGN CRITERIA ...................................................................................... 4
A. Regulations........................................................................................................................................ 4
B. Four Step Process .............................................................................................................................. 4
C. Development Criteria Reference and Constraints ............................................................................ 5
D. Hydrological Criteria ......................................................................................................................... 6
E. Hydraulic Criteria .............................................................................................................................. 6
F. Floodplain Regulations Compliance .................................................................................................. 6
G. Modifications of Criteria ................................................................................................................... 6
IV. drainage FACILITY DESIGN ....................................................................................... 7
A. General Concept ............................................................................................................................... 7
B. Specific Details .................................................................................................................................. 8
V. CONCLUSIONS ........................................................................................................ 9
A. Compliance with Standards .............................................................................................................. 9
B. Drainage Concept .............................................................................................................................. 9
References ....................................................................................................................... 10
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Detention Facilities
APPENDIX C – Water Quality Design Computations
APPENDIX D – Erosion Control Report
APPENDIX E – Soils Resource Report
South College Storage
Preliminary Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 - Aerial Photograph ................................................................................................. 1
Figure 2 - Proposed Site Plan ............................................................................................... 2
Figure 3 - Fort Collins Floodplains ......................................................................................... 3
MAP POCKET:
Historic Drainage Exhibit
Proposed Drainage Exhibit
South College Storage
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
Figure 1 - Aerial Photograph
2. South College Storage is in a tract of land in southeast quarter of Section 11,
Township 6 North, Range 69 West of the 6th P.M., City of Fort Collins, County of
Larimer, State of Colorado.
3. The project site is located at the northwest corner of Skyway Drive and College
Avenue.
4. Currently the existing site has minimal storm infrastructure to convey runoff.
Historically, the site sheet flows east towards Collage Ave. and is collected in an
existing 30” FES at a low point along the western property line. From there the flow is
conveyed via 30” RCP pipe east. The project site also has an existing drainage ditch
running north to south near the southwest corner of the site. This ditch will be
relocated to the west eventually but that will be associated with the future
development to the south, the property owned by Trilby Holdings Group LLC.
B. Description of Property
1. South College Storage is approximately 13.00 net acres.
2. The runoff generated from the project sheet flows west to east. The runoff generated
in the southwest corner of the site will be collected and conveyed by the existing
drainage ditch that runs north to south. The remaining portion of the site all sheet
flows towards an existing 30” FES that will collect and convey the flows offsite
towards Fossil Creek. The design engineers will maintain these existing flow patterns.
South College Storage
Preliminary Drainage Report 2
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey Skyways Storage consists of several native
soil types. Most the site (70.0 percent) consists of Kim-Thedalund loams, 3 to 15
percent slopes, which falls into Hydrologic Soil Groups B. Kim loam, 3 to 5 percent
slopes, is roughly 18.1% of the site and falls into Hydrologic Soil Group B. Fort
Collins loam consists of 10.7% and falls into Hydrologic Soils Group C. The remaining
1.3% of the site is made up of Midway clay loam, 5 to 25 percent slopes, which falls
into Hydrologic Soils Group D.
4. The proposed development will clear all the existing vegetation along the newly
proposed private drive aisle, building location, and associated parking lots (Tract A).
South College Storage will not be modifying any of the area to the west of the private
drive aisle (Outlot B). The area to the west will be regraded and modified during the
ditch realignment, which will take place when the property to the south begins to
develop. Additionally, South College Storage will try to minimize the limits of
disturbance to the east of the proposed parking lots and building (Tract B). Water
quality will be provided on-site by use of rain gardens and surrounding green space.
South College Storage will be detaining the 100-yr event and releasing at the historic
2-yr event. However, South College Storage will be bypassing regional flows through
the site. This is discussed in more detail within Section IV.
Figure 2 - Proposed Site Plan
5. There is currently an existing drainage ditch that runs south to north and is located
near the southwest corner of the Outlot A. This ditch will be rerouted to run parallel
along the western property line when the property to the south of the South College
Storage begins development.
6. The project site is within a General Commercial (CG) Zoning District. The proposed
use is permitted as a use within this zone district.
South College Storage
Preliminary Drainage Report 3
C. Floodplain
1. The property does not lie within a plottable FEMA floodplain. However, according to
FIRM Panel 08069C1000F for Larimer County, dated December 19th, 2006, this
tract lies in an area of minimal flood hazard, Zone X.
2. Additionally, the project does not lie within a City floodplain either.
Figure 3 - Fort Collins Floodplains
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. South College Storage straddles the boundary between the Mail Creek Basin and the
Fossil Basin. South College Storage has been design in accordance with the Fossil
Creek Master Drainage Plan.
B. Sub-Basin Description
1. South College Storage has historically conveyed all the generated runoff via overland
flow from west to east, to a low point adjacent to College Avenue where it is captured
by an existing flared end section. These flows will bypass the detention and water
quality amenities being proposed for South College Storage and head directly to the
existing flared end section adjacent to College Avenue.
2. Historically, the total amount of flow passing through the project site from the west
(H3 and OS1) is 2.19 cfs for the Historic 2-year, and 11.05 cfs for the Historic 100-
year. These flows are being captured by a Type C Inlet (near the intersection of
Skyway Drive and Mars Drive). From there the runoff is conveyed via 18” RCP pipe
under Mars Drive and enters a swale that will route the runoff to the existing flared
end section adjacent to College Avenue.
South College Storage
Preliminary Drainage Report 4
3. For a more in depth analysis for the areas within the property boundary three basins
were delineated; H1, H2, and H3. These basins were delineated in a way that would
correspond with the proposed basins, in order to accurately determine the max
allowable release rate for South College Storage site specifically.
4. Basin H1 is the area directly to the west of the College Avenue, where the existing
flared end section is located (Outlot B in the proposed plat). Basin H1 is 100%
landscaping and this basin will remain, for the most part, completely untouched when
South College Storage is constructed. There will be some minor grading along the
western portion of the basin as well as two separate swales cut during the
construction but the imperviousness will remain the same.
5. Basin H2 corresponds to the area that will be being developed for South College
Storage as well as half of the Mars Drive expansion. Basin H2 historically has been
100% landscaping with a Historic 2-year flowrate of 1.84 cfs. This flowrate was used
to help determine our max allowable release rate from our site. More information on
the max allowable release rate will be discussed further on in Section IV.
6. Basin H3 is the area to the west of the project site and east of the existing property
boundary (Outlot A in the proposed plat). There is currently a ditch running northwest
to southeast across this basin. However, this ditch will be reconstructed to run north
to south parallel to the western property line when this area is eventually developed.
For analysis purposes, it was assumed that this ditch is constantly full so any flow
generated from this basin will flow east towards the ultimate design point of the
existing flared end section in Basin H1. All flow generated in Basin H3 will bypass
South College Storage.
7. Basin OS1 is the only offsite basin entering our site. The flow is generated by a small
portion of landscaping to the west of Basin H3. Flow from OS1 enter Basin H3 and
then follow the conveyance path that Basin H3 uses.
8. Currently, at the intersection of College Avenue and Skyway Drive there is a 2’ Curb
Chase that is conveying runoff from Skyway to the existing flared end section in Basin
H1. South College Storage is going to replace that 2’ Curb Chase with a 10’ Type R
inlet to help convey any flows that are currently going through that curb chase to their
historic location.
9. There are no known drainage studies for this associated project site.
10. A more detailed description of the project’s proposed drainage patterns follows in
Section IV.A.4., below.
11. A full-size copy (11” x 17”) of the Historic Drainage Exhibit can be found in the Map
Pocket at the end of this report.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no provisions outside of FCSCM being proposed with South College Storage.
South College Storage is releasing at a reduced Historic 2-year rate, providing adequate
WQCV, and also meeting the LID standards set forth by the FCSCM.
B. Four Step Process
The overall stormwater management strategy employed with the South College Storage
project utilizes the “Four Step Process” to minimize adverse impacts of urbanization on
South College Storage
Preliminary Drainage Report 5
receiving waters. The following is a description of how the proposed development has
incorporated each step.
Step 1 – Employ Runoff Reduction Practices
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use by implementing multiple Low-Impact Development (LID) strategies, including:
Reducing the sites footprint as much as possible and limiting the amount of land being
disturbed to the west and east of the site within the property boundary.
Routing flows, to the extent feasible, through a Rain Garden to aid in the removal of
pollutants from the runoff.
Providing on-site detention to increase time of concentration, promote infiltration and
reduce loads on existing storm infrastructure.
100% of Basin M (which will be described in Section IV will receive its water quality
from a Rain Garden.
Please see Section IV for further explanation of drainage patterns and LID treatment.
Additionally, a map indicating how these areas were calculated is included in Appendix C.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff and provide the necessary
BMPs required for water quality. A majority of the stormwater that is generated on the
project site will be routed into a rain garden. For the portion of the site that is unretainable
it will be flowing slowly over a large grass buffer as it makes its way to the existing flared
end section.
Step 3 – Stabilize Drainageways
As stated in Section I.B.5, above, there is a major drainageway within the property
boundary. However, South College Storage is downstream of this drainageway and will not
cause any adverse impacts on the existing drainageway. As previously noted, this
drainageway will be getting rerouted when Outlot A gets developed. This drainageway will
get moved to the west and align parallel with the western property boundary. Additionally,
while this step may not seem applicable to South College Storage, the proposed project
indirectly helps achieve stabilized drainageways nonetheless. Once again, site selection
has a positive effect on stream stabilization. By repurposing an undeveloped, under-
utilized site, combined with LID, the likelihood of bed and bank erosion is greatly reduced.
Furthermore, this project will pay one-time stormwater development fees, as well as
ongoing monthly stormwater utility fees, both of which help achieve citywide drainageway
stability.
Step 4 – Implement Site Specific and Other Source Control BMPs.
South College Storage includes a three story building with an associated drive aisle, all of
which will require the need for site specific source controls including:
A localized trash collection system through use of individual bins stored internally.
C. Development Criteria Reference and Constraints
1. There are no known drainage studies for the existing property.
2. There are no known drainage studies for any adjacent properties that will have any
effect on the South College Storage project.
South College Storage
Preliminary Drainage Report 6
3. The subject property is essentially an "in-fill" development project, as the site is
surrounded by currently developed properties. As such, several constraints have been
identified during the course of this analysis that will impact the proposed drainage
system, including:
Mars Drive will need to tie into the existing elevation of Skyway Drive at the
intersection.
Existing vegetation to the east and west of the project site will be preserved.
The existing grades at the project site are too steep to develop on so these grades
will be modified but historic drainage patterns will be maintained.
D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with this development. Tabulated data contained in Table RA-7 has been
utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. The Rational Formula-based Modified Federal Aviation Administration (FAA)
procedure has been utilized for detention storage calculations.
4. Two separate design storms have been utilized to address distinct drainage scenarios.
The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-year
recurrence interval. The second event considered is the “Major Storm,” which has a
100-year recurrence interval.
5. No other assumptions or calculation methods have been used with this development
that are not referenced by current City of Fort Collins criteria.
E. Hydraulic Criteria
1. As previously noted, the subject property historically drains towards a flared end
section located adjacent to College Avenue via overland flow.
2. All drainage facilities associated with the South College Storage project are in
accordance with the criteria outlined in the FCSCM and/or the Urban Drainage and
Flood Control District’s (UDFCD) Urban Storm Drainage Criteria Manual.
3. As stated in Section I.C.1, above, the subject property is not located within any
regulatory floodplain.
4. The South College Storage project does not propose to modify any natural
drainageways.
F. Floodplain Regulations Compliance
1. As previously mentioned, all structures are located outside of any FEMA 100-year or
City floodplain, and thus are not subject to any floodplain regulations.
G. Modifications of Criteria
1. The proposed South College Storage development is not requesting any modification
to the current criteria.
South College Storage
Preliminary Drainage Report 7
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the South College Storage drainage design is to maintain
historic drainage patterns, and ensure no adverse impacts to downstream properties
or existing downstream infrastructure.
2. As previously mentioned, there is off-site flows entering onto the project site.
3. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within the
sections to which the content best applies.
4. The South College Storage project is composed of four major drainage basins,
designated as Basins E1, M, W1, and OS.1. The drainage patterns for each major
basin are further described below.
Basin E1
Basin E1 is the exact same basin as the previously discussed historic basin, Basin H1.
However, due to such steep grades some additional grading will occur on the western
edges of this basin to eliminate the need for landscaping walls. There will also be two
new swales cut in within Basin E1 to help better convey runoff from the off-site flows
and the released flows to the existing flared end section adjacent to College Avenue.
Basin M
Basin M corresponds to all the detainable area associated with the development of
South College Storage and half of Mars Drive. Basin M is further subdivided into seven
(10) sub-basins, designated as Basins M1, M2, M3.a, M3.b, M3.c, M4,M5, M6, M7
and M8. Sub-basin M1 is composed of the private drive aisle and wraps around the
eastern side of the proposed building. Sub-basin M2 consists of the sidewalk along the
east side of Mars Drive as well as the western section of the private drive aisle
adjacent to the west side of the building. Sub-basins M3.a, M3.b, and M3.c
correspond to portions of the roof that will be conveyed to the drive aisle via down
spouts. Sub-basin M4 is composed of the southern private drive aisle and a small
portion of landscaping area adjacent to the building. Sub-basin M5 corresponds to the
area designated for the Rain Garden as well as the onsite detention pond. Sub-basin
M6 is affiliated with a portion of the east side of Mars Drive between a local high and
low point. Sub-basin M7 is affiliated with a portion of the west side of Mars Drive
between a local high and low point. Sub-basin M8 corresponds to a small portion of
Mars Drive that will be entering the site via a curb chase. All the flow generated within
Basin M will be treated via Rain Garden and detained on site and released at a
reduced Historic 2-year flow towards the existing flared end section. Flows generated
in Basin M will be collected by roof leaders and inlets located within Mars Drive as
well as inlets within the private drive aisles.
Basin W1
Basin W1is the same basin as the historic basin H3. There is currently a drainage
ditch running from northwest to southeast across the southern 1/3 of the basin. Runoff
generated in this basin will bypass the South College Storage project site via a Type C
South College Storage
Preliminary Drainage Report 8
Inlet and 18” RCP and it will be conveyed via swales to the existing flared end section
in Basin E1.
Basin OS.1
Basin OS.1 is within the South College Storage project site but because of steep
slopes and lack of existing storm infrastructure it is uncatchable and therefore will be
sheet flowing offsite undetained and untreated. Basin OS.1 consists of a small portion
of the paved intersection of Mars Drive and Skyway Drive as well as the landscaping
areas on the backside of the private drive aisles. Because this area is leaving the site
undetained the developed 100-year flow rate associated with Basin OS.1 (1.21 cfs)
will be subtracted from the Historic 2-year flow rate from Basin H2 (1.84 cfs) for the
allowable release rate (1.84 – 1.21 = 0.63 cfs).
B. Specific Details
1. The main drainage problem associated with this project site is the deficiency of water
quality present, and lack of existing stormwater infrastructure on the South College
Storage site. The proposed site will mitigate these issues by instituting the following
water quality devices and stormwater structures:
The runoff generated from Basin M will be routed to a designed Rain Garden.
All runoff generated from the proposed building roof will be routed to a designed
Rain Garden as well.
The runoff generated from Basin M will be routed to a detention pond.
The remaining runoff generated from Basin OS.1 is routed across landscape areas.
A 18” RCP will help convey the flows associated with the neighborhood to the
west through the South College Storage site into landscape areas.
2. The allowable release rate was established by calculating the historic 2-year peak
runoff rate of the project area and reducing it by the 100-year peak runoff rate of the
offsite flows associated with the South College Storage project area, resulting in an
overall release of 0.63 cfs (Basin H2 = 1.84 cfs; Basin OS.1 = 1.21 cfs 1.84 –
1.21 = 0.63 cfs)
3. Detention Pond and Water Quality Calculations
Rain Garden M
Rain Garden M was sized for the 12-hour Water Quality Capture Volume (WQCV).
Calculations for Rain Garden M, based on characteristics of Basin M, indicate a
WQCV of 2462 cu. ft. The total WQCV provided is 2897 cu. ft. at a water surface
elevation of 5024.25 feet. All storm events above the water quality storm will overtop
the emergency spillway and be conveyed to the detention pond to the south.
Detention Pond M
The modified FAA method was used to quantify the required detention volume.
Calculations for Detention Pond M, based on characteristics of Basin M and Basin
OS.1 and an adjusted release rate of 0.63 cfs, indicate a detention volume of
38,145 cu. ft. The 100-year water surface elevation in Detention Pond M is at an
elevation of 5024.12 feet. Detention Pond M will not be providing any additional
water quality because Rain Garden M is treating the whole site and conveying the
treated runoff to the Detention Pond. An Emergency Spillway has been set at the
100-year elevation just above the proposed outfall location. In the event that the
South College Storage
Preliminary Drainage Report 9
outlet structure is compromised runoff will be conveyed through the emergency spill
way and flow east towards the existing flared end section adjacent to College Avenue.
The top of the pond along the remaining sides of the pond is set at an elevation of
5025.38. Therefore, more than a foot of freeboard has been provided on all the other
sides of the detention pond.
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with South College Storage project complies with the
City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with the South College Storage project complies with
the City of Fort Collins’ Master Drainage Plan for the Fossil Creek Basin.
3. There are no regulatory floodplains associated with the South College Storage
development.
4. The drainage plan and stormwater management measures proposed with the South
College Storage development are compliant with all applicable State and Federal
regulations governing stormwater discharge.
B. Drainage Concept
1. The drainage design proposed with this project will limit potential damage associated
with its stormwater runoff. South College Storage will detain based on characteristics
of Basin M at a reduced allowable release rate. Water quality will be provided in Rain
Garden M which is considered an LID treatment.
South College Storage
Preliminary Drainage Report 10
References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project:
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By:
Asphalt ……....……………...……….....…...……………….………………………………….0.. 95 100% Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90%
Gravel ……….…………………….….…………………………..……………………………….0.. 50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf = 1.00
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
Composite
% Imperv.
H1 209401 4.81 0.000 0.000 0.000 0.000 0.000 4.81 0.25 0.25 0%
H2 177381 4.07 0.000 0.000 0.000 0.000 0.000 4.07 0.25 0.25 0%
H3 179543 4.12 0.000 0.000 0.000 0.130 0.000 3.99 0.26 0.26 1%
OS1 67342 1.55 0.000 0.000 0.000 0.000 0.000 1.55 0.25 0.25 0%
TOTAL 633667 14.55 0.000 0.000 0.000 0.130 0.000 14.42 0.15 0.15 0%
DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf = 1.00
June 9, 2017
**Soil Classification of site is Clay Loam**
Page 1 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\C-Values
Overland Flow, Time of Concentration:
Project: South College Storage
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
Rational Method Equation: Project: South College Storage
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
h1 H1 4.81 20 20 19 0.25 0.25 0.31 1.61 2.74 5.84 1.93 3.29 8.77
h1 H2 4.07 16 16 15 0.25 0.25 0.31 1.81 3.08 6.62 1.84 3.14 8.42
h1 H3 4.12 27 27 24 0.26 0.26 0.32 1.39 2.37 5.09 1.47 2.51 6.76
h1 OS1 1.55 32 32 30 0.25 0.25 0.31 1.26 2.14 4.56 0.49 0.83 2.20
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
DEVELOPED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
B. Mathisen
June 9, 2017
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Q = C f ( C )( i )( A )
Page 3 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Direct-Runoff
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: South College Storage
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen
Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date: June 9, 2017
Concrete …….......……………….….……….………………..….………………………………… 0.95 90%
Gravel ……….…………………….….…………………………..……………………………….. 0.50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year C
f = 1.00 100-year C
f = 1.25
Design Point Basin IDs
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(sq ft)
Area of
Asphalt
(ac)
Area of
Concrete
(sq ft)
Area of
Concrete
(ac)
Area of
Roofs
(sq ft)
Area of
Roofs
(ac)
Area of
Gravel
(sq ft)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Overland Flow, Time of Concentration:
Project: South College Storage
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf
=1.00)
C*Cf
(10-yr
Cf
=1.00)
C*Cf
(100-yr
Cf
=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
Rational Method Equation: Project: South College Storage
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
h1 H1,H2,H3,OS1 14.55 21 21 16 0.25 0.25 0.32 1.59 2.71 6.30 5.8 9.9 28.9
os H3, OS1 5.67 23 23 17 0.26 0.26 0.32 1.51 2.58 6.10 2.2 3.7 11.1
C100
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
COMBINED DEVELOPED RUNOFF COMPUTATIONS
B. Mathisen
June 9, 2017
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Design
Point
Basin(s)
Area, A
(acres)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Flow,
Q2
(cfs)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C2
C10
Q = C f ( C )( i )( A )
Page 6 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Comb-Direct-Runoff
South College Storage
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1 H1 4.81 0.25 0.31 20.0 18.6 1.93 8.77
h1 H2 4.07 0.25 0.31 16.0 14.8 1.84 8.42
h1 H3 4.12 0.26 0.32 26.5 24.5 1.47 6.76
h1 OS1 1.55 0.25 0.31 31.9 29.6 0.49 2.20
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C10 C100
10-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1 H1,H2,H3,OS1 14.55 0.25 0.32 20.8 16.3 5.82 28.89
os H3, OS1 5.67 0.26 0.32 22.8 17.2 2.19 11.05
Page 7 of 23 D:Historic \Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\SUMMARY-TABLE
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: South College Storage
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen
Asphalt ……....……………...……….....…...……………….………………………………….0.. 95 100% Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90%
Gravel ……….…………………….….…………………………..……………………………….0.. 50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year C
f = 1.00 100-year C
f = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
E1 209401 4.81 0.000 0.000 0.000 0.000 0.000 4.81 0.25 0.25 0.31 0%
M1 21888 0.50 0.428 0.016 0.000 0.000 0.000 0.06 0.87 0.87 1.00 88%
M2 11126 0.26 0.179 0.028 0.000 0.000 0.000 0.05 0.82 0.82 1.00 80%
M3.a 12920 0.30 0.000 0.000 0.297 0.000 0.000 0.00 0.95 0.95 1.00 90%
M3.b 5090 0.12 0.000 0.000 0.117 0.000 0.000 0.00 0.95 0.95 1.00 90%
M3.c 18010 0.41 0.000 0.000 0.413 0.000 0.000 0.00 0.95 0.95 1.00 90%
Overland Flow, Time of Concentration:
Project: South College Storage
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf
=1.00)
C*Cf
(10-yr
Cf
=1.00)
C*Cf
(100-yr
Cf
=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
Rational Method Equation: Project: South College Storage
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
h1 E1 4.81 20 20 19 0.25 0.25 0.31 1.61 2.74 5.84 1.93 3.29 8.77
m1 M1 0.50 5 5 5 0.87 0.87 1.00 2.85 4.87 9.95 1.24 2.13 5.00
m2 M2 0.26 5 5 5 0.82 0.82 1.00 2.85 4.87 9.95 0.60 1.02 2.54
m1 M3.a 0.30 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.80 1.37 2.95
m4 M3.b 0.12 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.32 0.54 1.16
m2 M3.c 0.41 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 1.12 1.91 4.11
m4 M4 0.33 5 5 5 0.81 0.81 1.00 2.85 4.87 9.95 0.77 1.32 3.32
m5 M5 1.09 5 5 5 0.26 0.26 0.33 2.85 4.87 9.95 0.81 1.39 3.55
m6 M6 0.29 5 5 5 0.71 0.71 0.89 2.85 4.87 9.95 0.59 1.01 2.58
m7 M7 0.22 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 0.56 0.95 2.21
m8 M8 0.12 5 5 5 0.78 0.78 0.98 2.85 4.87 9.95 0.26 0.44 1.13
h1 W1 4.12 26 26 24 0.27 0.27 0.34 1.40 2.39 5.15 1.58 2.70 7.27
h1 OS1 0.44 13 13 12 0.31 0.31 0.39 1.98 3.39 7.16 0.27 0.46 1.21
DEVELOPED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
B. Mathisen
June 21, 2017
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
Q = C f ( C )( i )( A )
Page 3 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Direct-Runoff
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: South College Storage
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: B. Mathisen
Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date: June 21, 2017
Concrete …….......……………….….……….………………..….………………………………… 0.95 90%
Gravel ……….…………………….….…………………………..……………………………….. 0.50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.40 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year C
f = 1.00 100-year C
f = 1.25
Design Point Basin IDs
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(sq ft)
Area of
Asphalt
(ac)
Area of
Concrete
(sq ft)
Area of
Concrete
(ac)
Area of
Roofs
(sq ft)
Area of
Roofs
(ac)
Area of
Gravel
(sq ft)
Area of
Gravel
(ac)
Area of
Pavers
(ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Overland Flow, Time of Concentration:
Project: South College Storage
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf
=1.00)
C*Cf
(10-yr
Cf
=1.00)
C*Cf
(100-yr
Cf
=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
Rational Method Equation: Project: South College Storage
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
h1
E1, M1, M2, M3, M4,
M5, M6, M7, W1, OS1
13.00 15 15 10 0.38 0.38 0.48 1.87 3.19 7.72 9.3 15.8 47.8
m1 M1, M3.a, and M8 0.91 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 2.3 3.9 9.1
m2 M2 and M3.c 0.67 5 5 5 0.90 0.90 1.00 2.85 4.87 9.95 1.7 2.9 6.7
m4 M4 and M3.b 0.45 5 5 5 0.85 0.85 1.00 2.85 4.87 9.95 1.1 1.9 4.5
m5
M1, M2, M3, M4, M5,
M6, M7, M8
3.64 5 5 5 0.67 0.67 0.84 2.85 4.87 9.95 7.0 11.9 30.4
Intensity,
i100
(in/hr)
COMBINED DEVELOPED RUNOFF COMPUTATIONS
B. Mathisen
June 21, 2017
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Design
Point
Basin(s)
Area, A
(acres)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Flow,
Q2
(cfs)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C2
C10
C100
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Q = C f ( C )( i )( A )
Page 6 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Comb-Direct-Runoff
South College Storage
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1 E1 4.81 0.25 0.31 20.0 18.6 1.93 8.77
m1 M1 0.50 0.87 1.00 5.0 5.0 1.24 5.00
m2 M2 0.26 0.82 1.00 5.0 5.0 0.60 2.54
m1 M3.a 0.30 0.95 1.00 5.0 5.0 0.80 2.95
m4 M3.b 0.12 0.95 1.00 5.0 5.0 0.32 1.16
m2 M3.c 0.41 0.95 1.00 5.0 5.0 1.12 4.11
m4 M4 0.33 0.81 1.00 5.0 5.0 0.77 3.32
m5 M5 1.09 0.26 0.33 5.0 5.0 0.81 3.55
m6 M6 0.29 0.71 0.89 5.0 5.0 0.59 2.58
m7 M7 0.22 0.88 1.00 5.0 5.0 0.56 2.21
m8 M8 0.12 0.78 0.98 5.0 5.0 0.26 1.13
h1 W1 4.12 0.27 0.34 26.0 23.8 1.58 7.27
h1 OS1 0.44 0.31 0.39 13.5 12.2 0.27 1.21
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1
E1, M1, M2,
M3, M4, M5,
M6, M7, W1,
OS1
13.00 0.38 0.48 15.0 10.5 9.25 47.75
m1
M1, M3.a, and
M8
0.91 0.88 1.00 5.0 5.0 2.31 9.10
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Detention Facilities
APPENDIX B.1
STORM SEWERS
Circular
D or Da,
Pipe
Diameter
(ft)
H or Ha,
Culvert
Height
(ft)
W,
Culvert
Width
(ft)
Yt/D Q/D1.5 Q/D2.5 Yt/H Q/WH0.5
Storm Line A 4.79 1.25 0.50 0.40 3.43 2.74 N/A N/A 5.20 2.74 0.96 3.46 Type M 5.00 3.00 2.0
Storm Line B 11.10 1.50 0.60 0.40 6.04 4.03 N/A N/A 3.90 4.03 2.22 8.58 Type M 7.00 5.00 2.0
Storm Line C 2.35 1.25 0.50 0.40 1.68 1.35 N/A N/A 6.70 1.35 0.47 -2.08 Type M 5.00 3.00 2.0
Storm Line E 0.63 1.00 0.40 0.40 0.63 0.63 N/A N/A 6.70 0.63 0.13 -4.59 Type M 5.00 3.00 2.0
Project: South College Storage
Urban Drainage
pg MD-107
Culvert Parameters
At=Q/V
(ft)
Spec
Length
of
Riprap
(ft)
Box Culvert
CALCULATIONS FOR RIPRAP PROTECTION
Circular
Pipe
(Figure MD-21)
Rectangular
Pipe
(Figure MD-22) Spec
Width
of
Riprap
(ft)
2*d50,
Depth
of
Riprap
(ft)
for L/2
Froude
Parameter
Q/D2.5
Max 6.0
or
Q/WH1.5
Max 8.0
Riprap
Type
(From
Figure
MD-21 or
MD-22)
Page 2 of 3
Location
Pipe
Diameter
(Inches)
Ordinary
Riprap
Type
Riprap
Length
(ft)
Riprap
Width (ft)
Riprap
Depth (ft)
Storm Line A 15 Type M 5.0 3.0 2.0
Storm Line B 18 Type M 7.0 5.0 2.0
Storm Line C 15 Type M 5.0 3.0 2.0
Storm Line E 12 Type M 5.0 3.0 2.0
Page 3 of 3
APPENDIX B.2
INLETS
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 7.5 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.250 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 25.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 25.0 25.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.04 Released November 2016
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
South College Storage
Inlet A2
UD-Inlet_Inlet A2.1.1.xlsm, Inlet A2.1.1 6/15/2017, 11:00 AM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 6.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.33 0.33 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.77 0.77
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 5.4 5.4 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 0.6 2.6 cfs
CDOT Type R Curb Opening
INLET IN A SUMP OR SAG LOCATION
Version 4.04 Released November 2016
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_Inlet A2.1.1.xlsm, Inlet A2.1.1 6/15/2017, 11:00 AM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 7.5 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.250 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 25.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 25.0 25.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.04 Released November 2016
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
South College Storage
Inlet A3
UD-Inlet_Inlet A3.xlsm, Inlet A2.1.2 6/15/2017, 11:02 AM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 6.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.33 0.33 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.77 0.77
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 5.4 5.4 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 0.6 2.2 cfs
CDOT Type R Curb Opening
INLET IN A SUMP OR SAG LOCATION
Version 4.04 Released November 2016
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_Inlet A3.xlsm, Inlet A2.1.2 6/15/2017, 11:02 AM
Grass Type Limiting Manning's n
A 0.06
B 0.04
C 0.033
D 0.03
E 0.024
Analysis of Trapezoidal Grass-Lined Channel Using SCS Method
NRCS Vegetal Retardance (A, B, C, D, or E) A, B, C, D or E C
Manning's n (Leave cell D16 blank to manually enter an n value) n = see details below
Channel Invert Slope SO = 0.0300 ft/ft
Bottom Width B = 10.00 ft
Warning 01 Left Side Slope Z1 = 0.04 ft/ft
Warning 01 Right Side Slope Z2 = 0.25 ft/ft
Check one of the following soil types:
Soil Type: Max. Velocity (VMAX) Max Froude No. (FMAX)
Non-Cohesive 5.0 fps 0.60
Cohesive 7.0 fps 0.80
Paved N/A N/A
Minor Storm Major Storm
Max. Allowable Top Width of Channel for Minor & Major Storm TMAX = 42.00 42.00 feet
Max. Allowable Water Depth in Channel for Minor & Major Storm dMAX = 1.32 1.32 feet
Allowable Channel Capacity Based On Channel Geometry Minor Storm Major Storm
MINOR STORM Allowable Capacity is based on Depth Criterion Qallow = 103.7 103.7 cfs
MAJOR STORM Allowable Capacity is based on Depth Criterion dallow = 1.32 1.32 ft
Water Depth in Channel Based On Design Peak Flow
Design Peak Flow Qo = 2.2 11.0 cfs
Water Depth d = 0.41 0.56 feet
Version 4.04 Released November 2016
AREA INLET IN A SWALE
South College Storage
Inlet B2
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Choose One:
Non-Cohesive
Cohesive
Paved
UD-Inlet_Inlet B2.xlsm, Inlet B2 6/15/2017, 1:43 PM
Version 4.04 Released November 2016
AREA INLET IN A SWALE
South College Storage
Inlet B2
Inlet Design Information (Input)
Type of Inlet Inlet Type =
Angle of Inclined Grate (must be <= 30 degrees) θ = 0.00 degrees
Width of Grate W = 3.00 feet
Length of Grate L = 3.00 feet
Open Area Ratio ARATIO = 0.70
Height of Inclined Grate HB = 0.00 feet
Clogging Factor Cf = 0.50
Grate Discharge Coefficient Cd = 0.84
Orifice Coefficient Co = 0.56
Weir Coefficient Cw = 1.81
MINOR MAJOR
Water Depth at Inlet (for depressed inlets, 1 foot is added for depression) d = 1.41 1.56
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 16.9 17.8 cfs
Bypassed Flow, Qb = 0.0 0.0 cfs
Capture Percentage = Qa/Qo = C% 100 100 %
Warning 01: Sideslope steepness exceeds USDCM Volume I recommendation.
Warning 02: Depth (d) exceeds USDCM Volume I recommendation.
CDOT Type C (Depressed) CDOT Type C (Depressed)
UD-Inlet_Inlet B2.xlsm, Inlet B2 6/15/2017, 1:43 PM
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Jun 15 2017
Existing 2' Curb Chase (Skyway and College)
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 2.00
Total Depth (ft) = 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Depth
Known Depth (ft) = 0.50
Highlighted
Depth (ft) = 0.50
Q (cfs) = 2.355
Area (sqft) = 1.00
Velocity (ft/s) = 2.35
Top Width (ft) = 2.00
0 .5 1 1.5 2 2.5 3
Depth (ft) Existing 2' Curb Chase (Skyway and College) Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 10.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.050 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.018
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 25.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.023 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.028 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 15.0 15.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches
Allow Flow Depth at Street Crown (leave blank for no) check = yes
MINOR STORM Allowable Capacity is based on Spread Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Spread Criterion Qallow = 19.7 19.7 cfs
Minor storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Major storm max. allowable capacity GOOD - greater than the design flow given on sheet 'Inlet Management'
Version 4.04 Released November 2016
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
South College Storage
Inlet C2
UD-Inlet_Inlet C2.xlsm, Inlet C2 6/15/2017, 1:52 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a') aLOCAL = 3.0 3.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening) No = 2 2
Length of a Single Unit Inlet (Grate or Curb Opening) Lo = 5.00 5.00 ft
Width of a Unit Grate (cannot be greater than W, Gutter Width) Wo = N/A N/A ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf-G = N/A N/A
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf-C = 0.10 0.10
Street Hydraulics: OK - Q < Allowable Street Capacity' MINOR MAJOR
Total Inlet Interception Capacity Q = 2.4 2.4 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.0 0.0 cfs
Capture Percentage = Qa/Qo = C% = 100 100 %
CDOT Type R Curb Opening
INLET ON A CONTINUOUS GRADE
Version 4.04 Released November 2016
CDOT Type R Curb Opening
UD-Inlet_Inlet C2.xlsm, Inlet C2 6/15/2017, 1:52 PM
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Monday, Jun 5 2017
Design Point m8
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 2.00
Total Depth (ft) = 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 1.13
Highlighted
Depth (ft) = 0.31
Q (cfs) = 1.130
Area (sqft) = 0.61
Velocity (ft/s) = 1.84
Top Width (ft) = 2.00
0 .5 1 1.5 2 2.5 3
Depth (ft) Design Point m8 Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Monday, Jun 12 2017
20' Curb Cut
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 20.00
Total Depth (ft) = 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 22.06
Highlighted
Depth (ft) = 0.48
Q (cfs) = 22.06
Area (sqft) = 9.57
Velocity (ft/s) = 2.30
Top Width (ft) = 20.00
0 2 4 6 8 10 12 14 16 18 20 22 24
Depth (ft) 20' Curb Cut Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
APPENDIX B.3
DETENTION FACILITIES
Pond No :
m5
100-yr
0.84
5.00 min 38145 ft3
3.64 acres 0.876 ac-ft
Max Release Rate = 0.63 cfs
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 9127 1.00 0.63 189 8938
10 7.720 14163 0.75 0.47 284 13879
15 6.520 17942 0.67 0.42 378 17564
20 5.600 20547 0.63 0.39 473 20075
25 4.980 22840 0.60 0.38 567 22273
30 4.520 24877 0.58 0.37 662 24215
35 4.080 26198 0.57 0.36 756 25442
40 3.740 27445 0.56 0.35 851 26595
45 3.460 28564 0.56 0.35 945 27619
50 3.230 29628 0.55 0.35 1040 28589
55 3.030 30573 0.55 0.34 1134 29439
60 2.860 31481 0.54 0.34 1229 30253
65 2.720 32435 0.54 0.34 1323 31112
70 2.590 33261 0.54 0.34 1418 31843
75 2.480 34123 0.53 0.34 1512 32611
80 2.380 34930 0.53 0.33 1607 33324
85 2.290 35710 0.53 0.33 1701 34009
90 2.210 36489 0.53 0.33 1796 34694
95 2.130 37122 0.53 0.33 1890 35232
100 2.060 37792 0.53 0.33 1985 35807
105 2.000 38526 0.52 0.33 2079 36447
110 1.940 39150 0.52 0.33 2174 36976
115 1.890 39874 0.52 0.33 2268 37606
120 1.840 40507 0.52 0.33 2363 38145
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1269-002
South College Storage
Project Number :
Project Name :
Detention Pond M
A =
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Invert Elevation
Water Quality Volume
100-yr Detention Volume
Total Pond Volume
Min Sc
D = Depth between contours (ft.)
A1
= Surface Area lower contour (ft
2
) t
A2
= Surface Area upper contour (ft
2
) Area/Row
No. of Rows
5019.80 59.27 0.10 1.98 1.98 0.0000
5020.00 678.12 0.20 62.52 64.50 0.0015
5020.20 1179.73 0.20 183.49 247.99 0.0057
5020.40 2877.45 0.20 393.31 641.29 0.0147
5020.60 4043.70 0.20 688.82 1330.11 0.0305
5020.80 5274.32 0.20 929.08 2259.19 0.0519
5021.00 6576.08 0.20 1182.65 3441.84 0.0790 WQCV
5021.20 7734.75 0.20 1429.52 4871.36 0.1118
5021.40 8662.38 0.20 1638.84 6510.20 0.1495
5021.60 9151.41 0.20 1781.16 8291.35 0.1903
5021.80 9557.17 0.20 1870.71 10162.06 0.2333
5022.00 9968.95 0.20 1952.47 12114.53 0.2781
5022.20 10386.77 0.20 2035.43 14149.96 0.3248
5022.40 10810.61 0.20 2119.60 16269.55 0.3735
5022.60 11240.48 0.20 2204.97 18474.52 0.4241
5022.80 11676.37 0.20 2291.55 20766.07 0.4767
5023.00 12118.30 0.20 2379.33 23145.40 0.5313
5023.20 12566.25 0.20 2468.32 25613.72 0.5880
5023.40 13020.23 0.20 2558.51 28172.23 0.6467
5023.60 13480.24 0.20 2649.91 30822.15 0.7076
5023.80 13946.28 0.20 2742.52 33564.67 0.7705
5024.00 14418.35 0.20 2836.33 36401.00 0.8357
5024.20 14896.44 0.20 2931.35 39332.35 0.9029 Total Vol
5024.40 15380.56 0.20 3027.57 42359.92 0.9724
5024.60 15870.70 0.20 3125.00 45484.92 1.0442
5024.80 16366.89 0.20 3223.63 48708.55 1.1182
5025.00 16869.10 0.20 3323.47 52032.02 1.1945
5025.20 17377.33 0.20 3424.52 55456.54 1.2731
Elevation Depth Volume
WQCV 5020.83 1.13 0.0565
100-yr Detention 5024.12 4.42 0.8760
Overall Detention 5024.12 4.42 0.8760
Circular Perforation Sizing
Dia (in.)
1
Pond M
0.05
13
0.0565 ac-ft
5019.70 ft
Pond M Volume
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
Q = 0.63 cfs
C = 0.607
Q = Release Rate (cfs) Eh = 5024.12 ft
C = Discharge Coefficients (unitless) Ei = 5019.17 ft
Aa = Area Allowed of Opening (ft2)
g = Gravity (32.2 ft/s2) 0.058131 ft2
Eh = High Water Surface Elevation (ft) 8.370836 in2
Ei = Elevation of Outlet Invert (ft)
H = Height of Opening (in.)
R = Inner Radius of Outfall Pipe (in.)
Δ = Top of Plate to Center of Pipe (in.)
S = Arc Length of Open Area (in.)
Ac = Area of Opening (in2)
θ = Angle of Plate on Pipe to Center Pipe (radians)
Calculated Area of Opening (Ac)
Design Height of Opening (H)
Proposed Outfall Pipe Diameter
8.16 sq. in.
B. Mathisen
June 8, 2017
Aa =
1-1/2 in
12 in
Branden Grebe
1269-002
South College Storage
Pond M
[ ( ( ) ) ]
2
2
R
Sin S
R
R S
K
−
=
QCA = 2 g ( E h − E i )
S = R θ
( ) ( R )
Cos
R
Cos → = ∆
= ∆ 2 −1
θ 2 θ
Ac = π R 2 − K
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
Project Title Date:
Project Number Calcs By:
Client
Pond Designation
0.8
WQCV = Watershed inches of Runoff (inches) 59.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.186 in
A = 3.64 ac
V = 0.0565 ac-ft 2461.42 cu. ft.
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
South College Storage June 20, 2017
1269-002 B. Mathisen
Brandon Grebe
Rain Garden M
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.186
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq
/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 − 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 − 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia
Ia
= 59.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia
/100) i = 0.590
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.19 watershed inches
(WQCV= 0.8 * (0.91* i
3
- 1.19 * i
2
+ 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 158,371 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV
= cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6
= 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER
= 2,458.5 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER
= cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV
= 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin
= 1639 sq ft
D) Actual Flat Surface Area AActual
= 2506 sq ft
E) Area at Design Depth (Top Surface Area) ATop
= 3288 sq ft
F) Rain Garden Total Volume VT
= 2,897 cu ft
(VT
= ((ATop
+ AActual
) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y
= 0.5 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12
= 2,459 cu ft
iii) Orifice Diameter, 3/8" Minimum DO
= 1.52 in
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
PROVIDE A 30 MIL (MIN) PVC LINER WITH CDOT CLASS B
GEOTEXTILE ABOVE IT. USE THE SAME GEOTEXTILE BELOW
THE LINER IF THE SUBGRADE IS ANGULAR
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
B. Mathisen
Northern Engineering
May 4, 2017
South College Storage
Rain Garden M
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
RainGardens_BMP-Basin M.xlsm, RG 5/4/2017, 4:44 PM
APPENDIX D
EROSION CONTROL REPORT
South College Storage
Final Erosion Control Report
A separate Erosion and Sediment Control Plan (along with associated details) has been included
with the FDP submittal. It should be noted, however, that any such Erosion and Sediment Control
Plan serves only as a general guide to the Contractor. Staging and/or phasing of the BMPs
depicted, and additional or different BMPs from those included may be necessary during
construction, or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living
document, constantly adapting to site conditions and needs. The Contractor shall update the
location of BMPs as they are installed, removed or modified in conjunction with construction
activities. It is imperative to appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices
from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are
not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways
and inlet protection at proposed storm inlets. Vehicle tracking control pads, spill containment and
clean-up procedures, designated concrete washout areas, dumpsters, and job site restrooms shall
also be provided by the Contractor.
Grading and Erosion Control Notes can be found on Sheets C0.01 of the Utility Plans. The Utility
Plans also contain a full-size Erosion Control Plan as well as a separate sheet dedicated to Erosion
Control Details. In addition to this report and the referenced plan sheets, the Contractor shall be
aware of, and adhere to, the applicable requirements outlined in any existing Development
Agreement(s) of record, as well as the Development Agreement, to be recorded prior to issuance of
the Development Construction Permit. Also, the Site Contractor for this project will be required to
secure a Stormwater Construction General Permit from the Colorado Department of Public Health
and Environment (CDPHE), Water Quality Control Division – Stormwater Program, before
commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor shall
develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements
and guidelines. The SWMP will further describe and document the ongoing activities, inspections,
and maintenance of construction BMPs.
APPENDIX E
Soils Resource Report
MAP POCKET
HISTORIC DRAINAGE EXHIBIT
PROPOSED DRAINAGE EXHIBIT
S
S
S
S
VAULT
ELEC
ELEC
T S
B M
CABLE
D
VAULT
ELEC
C
V.P.
V.P.
V.P.
V.P.
F
E
S
S
SS
SS
H
Y
D
X X X
X
X
X
X
S
S
S
S
S
VAULT
ELEC
ELEC
T S
B M
CABLE
D
VAULT
ELEC
C
V.P.
V.P.
V.P.
V.P.
F
E
S
S
SS
SS
H
Y
D
VAULT
ELEC ELEC
T S
B M
CABLE
D
VAULT
ELEC
V.P.
V.P.
V.P.
V.P.
V.P. V.P.
F
E
S
ST
H
Y
D
X
X
X
X
X
X
X
X
X
X X X
X
X X
X
X
X
X
X
X X
X
X X
X X X
X
OHU OHU OHU
OHU OHU OHU
OHU
OHU
OHU OHU OHU
OHU
OHU
X X X
X
X X
X X
X
X
X
X
ELEC
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD LOD LOD
LOD
LOD LOD
LOD
LOD
LOD
LOD
LOD LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD
LOD LOD
LOD
LOD
LOD
LOD
UD
m5
(16.0:1)
(11.8:1)
(15.7:1)
(15.7:1)
(17.2:1)
(15.7:1)
(10.3:1)
(13.1:1)
(10.8:1)
m4
m2
m1
h1
OS
HISTORIC FLOWS
FROM NEIGHBORHOOD
TO THE WEST
EXISTING FLARED
END SECTION
DETENTION POND M
100-YEAR ELEV. = 5024.12 FT.
TOTAL VOLUME = 38,158 CU. FT.
RAIN GARDEN M
SKYWAY DRIVE
(80' R.O.W.)
MARS DRIVE
SOUTH COLLEGE AVENUE
(ROW VARIES)
INLET
INLET
EXISTING
DRAINAGE WAY
m7 m6
M1
W1 E1
OS1
M2
M3.a
M4
M5
M6
M7
INLET
(REPLACED 2' CURB CHASE)
M8 m8
M3.c
M3.b
20' CURB CUT
OUTFALL
No. Revisions: By: Date:
REVIEWED BY:
C. Snowden
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
06.21.2017
PROJECT:
1269-002
Sheet
of 21
SOUTH COLLEGE STORAGE These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
C7.00
DRAINAGE EXHIBIT
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner
1. REFER TO THE "FINAL DRAINAGE REPORT FOR SOUTH COLLEGE STORAGE" BY
NORTHERN ENGINEERING, DATED June 21, 2017 FOR ADDITIONAL INFORMATION.
NOTES:
EXISTING INLET GRATE
EXISTING DECID. TREE
EXISTING CONIF. TREE
EXISTING LIGHT POLE
EXISTING STUMP
EXISTING CURB/GUTTER FLOWLINE
A2
a3
4:1
79.45
HP
SLOPE
PROPOSED OVERLAND FLOW DIRECTION
CONCENTRATED FLOW DIRECTION
EXISTING STORM DRAIN
FUTURE CURB AND GUTTER
PROPOSED STORM DRAIN
DRAINAGE BASIN
PROPOSED CONTOUR
PROPOSED FLOWLINE ELEVATION
EXISTING CONTOUR
DRAINAGE BASIN MINOR/MAJOR COEFF.
DESIGN POINT
DRAINAGE BASIN ID
DRAINAGE BASIN AREA
EXISTING OVERLAND FLOW DIRECTION
RUNOFF SUMMARY TABLE:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
LEGEND:
NORTH
( IN FEET )
0
1 INCH = 40 FEET
40 40 80 120
ST
21
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1 E1 4.81 0.25 0.31 20.0 18.6 1.93 8.77
m1 M1 0.50 0.87 1.00 5.0 5.0 1.24 5.00
m2 M2 0.26 0.82 1.00 5.0 5.0 0.60 2.54
m1 M3.a 0.30 0.95 1.00 5.0 5.0 0.80 2.95
m4 M3.b 0.12 0.95 1.00 5.0 5.0 0.32 1.16
m2 M3.c 0.41 0.95 1.00 5.0 5.0 1.12 4.11
m4 M4 0.33 0.81 1.00 5.0 5.0 0.77 3.32
m5 M5 1.09 0.26 0.33 5.0 5.0 0.81 3.55
m6 M6 0.29 0.71 0.89 5.0 5.0 0.59 2.58
m7 M7 0.22 0.88 1.00 5.0 5.0 0.56 2.21
m8 M8 0.12 0.78 0.98 5.0 5.0 0.26 1.13
h1 W1 4.12 0.27 0.34 26.0 23.8 1.58 7.27
h1 OS1 0.44 0.31 0.39 13.5 12.2 0.27 1.21
PROPOSED UNDERDRAIN UD
PROPOSED CURB AND GUTTER
X X X
X
X
X
X
S
GATEWAY CENTER DR.
POLARIS DR.
AURORA WAY
CONSTELLATION DR.
h1
OS
SKYWAY DR.
COLLEGE AVE.
OS1
H3
H2 H1
EXISTING DRAINAGE EXHIBIT
FORT COLLINS, CO
E NGINEER ING
N O R T H E RN
06.15.2017
D:\PROJECTS\1269-002\DWG\DRNG\1269-002_EX-DRNG.DWG
SOUTH COLLEGE STORAGE
RUNOFF SUMMARY TABLE:
A2
a3
EXISTING CONCENTRATED FLOW DIRECTION
EXISTING CONTOUR
DRAINAGE BASIN MINOR/MAJOR COEFF.
DESIGN POINT
DRAINAGE BASIN ID
DRAINAGE BASIN AREA
EXISTING OVERLAND FLOW DIRECTION
LEGEND:
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
h1 H1 4.81 0.25 0.31 20.0 18.6 1.93 8.77
h1 H2 4.07 0.25 0.31 16.0 14.8 1.84 8.42
h1 H3 4.12 0.26 0.32 26.5 24.5 1.47 6.76
h1 OS1 1.55 0.25 0.31 31.9 29.6 0.49 2.20
Design Procedure Form: Rain Garden (RG)
B. Mathisen
Northern Engineering
May 4, 2017
South College Storage
Rain Garden M
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
RainGardens_BMP-Basin M.xlsm, RG 5/4/2017, 4:44 PM
=
12 hr
Elevation
(ft)
n
1/4
0.059 sq-in
Surface
Area (ft2) Total Outlet
Area
0.65 sq. in.
South College Storage 6/20/2017
1269-002 B. Mathisen
Brandon Grebe
0.8760 ac-ft
0.8760 ac-ft
Required Area
Per Row
Total Vol.
(ac-ft)
Total Vol.
(ft3)
Incremental
Vol. (ft3)
Incremental
Depth (ft)
Calc.
Depths
( )
3
D * A 1 A 2 A 1 * A 2
V
= + +
Tc =
Project Location :
Design Point
C =
Design Storm
Page 1 of 1
1269-002_FAAModified Method.xls
By: Mathisen
Expansion
Factor
1/(2tanθ)
(From
Figure
MD-23 or
MD-24)
Date: June 20, 2017
INPUT CALCULATE OUTPUT
Yt,
Tailwater
Depth
(ft)
Storm
Line/Culvert
Label
Design
Discharge
(cfs)
L=
1/(2tanq)*
[At/Yt)-W]
(ft)
Page 1 of 3
m2 M2 and M3.c 0.67 0.90 1.00 5.0 5.0 1.71 6.66
m4 M4 and M3.b 0.45 0.85 1.00 5.0 5.0 1.09 4.48
m5
M1, M2, M3,
M4, M5, M6,
M7, M8
3.64 0.67 0.84 5.0 5.0 6.96 30.39
Page 7 of 23 D:\Projects\Historic 1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\SUMMARY-TABLE
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
h1
E1, M1, M2, M3, M4,
M5, M6, M7, W1, OS1
Yes 0.88 0.88 1.00 875 3.20% 8.3 8.3 3.8 650 1.50% 2.45 4.4 400 5.50% 4.69 2.3 15 15 10
m1 M1, M3.a, and M8
Yes 0.88 0.88 1.00 150 6.00% 2.8 2.8 1.3 350 5.00% 4.47 1.3 0 N/A N/A 5 5 5
m2 M2 and M3.c
Yes 0.88 0.88 1.00 15 25.00% 0.5 0.5 0.2 150 0.25% 1.00 2.5 0 N/A N/A 5 5 5
m4 M4 and M3.b
Yes 0.88 0.88 1.00 30 2.00% 1.8 1.8 0.8 120 8.00% 5.66 0.4 0 N/A N/A 5 5 5
m5
M1, M2, M3, M4, M5,
M6, M7, M8
Yes 0.88 0.88 1.00 150 6.00% 2.8 2.8 1.3 120 0.50% 1.41 1.4 0 N/A N/A 5 5 5
COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
B. Mathisen
June 21, 2017
Design
Point
Basin IDs
Overland Flow Gutter/Pipe Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
Page 5 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Comb-Tc-10-yr_&_100-yr
Coefficient
Composite
% Imperv.
h1
E1, M1, M2, M3, M4, M5, M6, M7,
W1, OS1
566325 13.00 66377 1.52 3269 0.08 36020 0.83 0 0 0 10.58 0.38 0.38 0.48 18%
m1 M1, M3.a, and M8 39839 0.91 22475 0.52 711 0.02 12920 0.30 0 0 0 0.09 0.88 0.88 1.00 87%
m2 M2 and M3.c 29136 0.67 7799 0.18 1229 0.03 18010 0.41 0 0 0 0.05 0.90 0.90 1.00 86%
m4 M4 and M3.b 19623 0.45 11348 0.26 266 0.01 5090 0.12 0 0 0 0.07 0.85 0.85 1.00 82%
m5 M1, M2, M3, M4, M5, M6, M7, M8 158372 3.64 58735 1.35 3016 0.07 36020 0.83 0 0 0 1.24 0.67 0.67 0.84 59%
COMBINED DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
**Soil Classification of site is Sandy Loam**
10-year Cf
= 1.00
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
Page 4 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Comb-C-Values
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
h1 E1 No 0.25 0.25 0.31 495 5.50% 20.0 20.0 18.6 N/A N/A N/A N/A N/A 20 20 19
m1 M1 No 0.87 0.87 1.00 150 6.00% 2.9 2.9 1.3 350 5.00% 4.47 1.3 N/A N/A N/A 5 5 5
m2 M2 No 0.82 0.82 1.00 15 25.00% 0.7 0.7 0.2 120 0.50% 1.41 1.4 N/A N/A N/A 5 5 5
m1 M3.a No 0.95 0.95 1.00 N/A N/A N/A 35 100.00% 20.00 0.0 N/A N/A N/A 5 5 5
m4 M3.b No 0.95 0.95 1.00 N/A N/A N/A 35 100.00% 20.00 0.0 N/A N/A N/A 5 5 5
m2 M3.c No 0.95 0.95 1.00 N/A N/A N/A 35 100.00% 20.00 0.0 N/A N/A N/A 5 5 5
m4 M4 No 0.81 0.81 1.00 30 2.00% 2.4 2.4 0.8 120 8.00% 5.66 0.4 N/A N/A N/A 5 5 5
m5 M5 No 0.26 0.26 0.33 75 25.00% 4.6 4.6 4.3 N/A N/A N/A N/A N/A 5 5 5
m6 M6 No 0.71 0.71 0.89 25 2.00% 2.9 2.9 1.5 150 0.50% 1.41 1.8 N/A N/A N/A 5 5 5
m7 M7 No 0.88 0.88 1.00 25 2.00% 1.6 1.6 0.7 150 0.50% 1.41 1.8 N/A N/A N/A 5 5 5
m8 M8 No 0.78 0.78 0.98 25 2.00% 2.3 2.3 0.9 140 1.40% 2.37 1.0 N/A N/A N/A 5 5 5
h1 W1 No 0.27 0.27 0.34 355 1.40% 26.0 26.0 23.8 N/A N/A N/A N/A N/A 26 26 24
h1 OS1 No 0.31 0.31 0.39 100 1.60% 12.6 12.6 11.4 120 1.40% 2.37 0.8 N/A N/A N/A 13 13 12
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter/Pipe Flow Swale Flow
Design
Point
Basin
Overland Flow
B. Mathisen
June 21, 2017
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
Page 2 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\Tc-10-yr_&_100-yr
M4 14533 0.33 0.261 0.006 0.000 0.000 0.000 0.07 0.81 0.81 1.00 80%
M5 47459 1.09 0.000 0.019 0.000 0.000 0.000 1.07 0.26 0.26 0.33 2%
M6 12642 0.29 0.192 0.000 0.000 0.000 0.000 0.10 0.71 0.71 0.89 66%
M7 9673 0.22 0.201 0.000 0.000 0.000 0.000 0.02 0.88 0.88 1.00 90%
M8 5031 0.12 0.088 0.000 0.000 0.000 0.000 0.03 0.78 0.78 0.98 76%
W1 179542 4.12 0.143 0.000 0.000 0.000 0.000 3.98 0.27 0.27 0.34 3%
OS1 19010 0.44 0.032 0.006 0.000 0.000 0.000 0.40 0.31 0.31 0.39 9%
TOTAL 566325 13.00 1.524 0.075 0.827 0.000 0.000 10.58 0.30 0.30 0.37 18%
DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf
= 1.00
June 21, 2017
**Soil Classification of site is Clay Loam**
Page 1 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Proposed).xlsx\C-Values
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
h1 H1,H2,H3,OS1 Yes 0.88 0.88 1.00 875 3.20% 8.3 8.3 3.8 1500 1.00% 2.00 12.5 N/A N/A 21 21 16
os H3, OS1 Yes 0.88 0.88 1.00 1230 2.80% 10.3 10.3 4.7 N/A N/A N/A N/A 23 23 17
COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
B. Mathisen
June 9, 2017
Design
Point
Basin IDs
Overland Flow Gutter/Pipe Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
Page 5 of 23 D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Comb-Tc-10-yr_&_100-yr
Coefficient
Composite
% Imperv.
h1 H1,H2,H3,OS1 633667 14.55 0.00 0.00 0.00 0.00 0.00 0.00 5650.00 0.13 0.00 14.42 0.25 0.25 0.32 0%
os H3, OS1 246885 5.67 0.00 0.00 0.00 0.00 0.00 0.00 5650.00 0.13 0.00 5.54 0.26 0.26 0.32 1%
COMBINED DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
**Soil Classification of site is Sandy Loam**
10-year Cf
= 1.00
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
Page 4 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Comb-C-Values
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
h1 H1 No 0.25 0.25 0.31 495 5.50% 20.0 20.0 18.6 N/A N/A N/A N/A N/A 20 20 19
h1 H2 No 0.25 0.25 0.31 335 6.00% 16.0 16.0 14.8 N/A N/A N/A N/A N/A 16 16 15
h1 H3 No 0.26 0.26 0.32 355 1.40% 26.5 26.5 24.5 N/A N/A N/A N/A N/A 27 27 24
h1 OS1 Yes 0.25 0.25 0.31 875 3.20% 31.9 31.9 29.6 N/A N/A N/A N/A N/A 32 32 30
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter/Pipe Flow Swale Flow
Design
Point
Basin
Overland Flow
B. Mathisen
June 9, 2017
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
Page 2 of 23 Historic D:\Projects\1269-002\Drainage\Hydrology\1269-002_Rational-Calcs (Historic).xlsx\Tc-10-yr_&_100-yr