HomeMy WebLinkAboutWATERFIELD THIRD FILING - PDP - PDP130037 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTNovember 1, 2013
PRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT FOR
WATERFIELD THIRD FILING
Fort Collins, Colorado
Prepared for:
Risheill Homes, LLC
Curly Risheill
PO Box 400
Castle Rock, CO 80104
Prepared by:
200 South College Avenue, Suite 10
Fort Collins, Colorado 80524
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 889-001
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.
November 1, 2013
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage and Erosion Control Report for
WATERFIELD THIRD FILING
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report
for your review. This report accompanies the Project Development Plan submittal for the
proposed Waterfield Third Filing development.
This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM),
and serves to document the stormwater impacts associated with the proposed project. We
understand that review by the City is to assure general compliance with standardized criteria
contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
NORTHERN ENGINEERING SERVICES, INC.
Aaron Cvar, PE
Project Engineer
Waterfield Third Filing
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ............................................................................................................................................. 1
B. Description of Property ..................................................................................................................... 2
C. Floodplain.......................................................................................................................................... 4
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 4
A. Major Basin Description .................................................................................................................... 4
III. DRAINAGE DESIGN CRITERIA ................................................................................... 5
A. Regulations........................................................................................................................................ 5
B. Four Step Process .............................................................................................................................. 5
C. Development Criteria Reference and Constraints ............................................................................ 6
D. Hydrological Criteria ......................................................................................................................... 6
E. Hydraulic Criteria .............................................................................................................................. 6
G. Modifications of Criteria ................................................................................................................... 7
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 - Water Quality Design Computations
APPENDIX C – Stormwater Management Model (SWMM)
APPENDIX D – Erosion Control Report
LIST OF TABLES AND FIGURES:
Waterfield Third Filing
Preliminary Drainage Report
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing Floodplains ............................................................................................. 4
MAP POCKET:
Proposed Drainage Exhibit
Waterfield Third Filing
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The project site is located in the west half of Section 5, Township 7 North, Range 68
West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of
Colorado .
3. The project site is located on the north side of Vine Drive and is just northwest of the
intersection of Vine Drive and Timberline Road.
4. The project site lies within the Dry Creek Basin. Detention requirements are to detain
the difference between the 100-year developed inflow rate and the historic 2-year
release rate. The historic release rate for this basin is 0.20 cfs per acre.
5. The existing Waterfield P.U.D. First Filing residential development exists to the
southeast of the proposed Third Filing site. The Lake Canal crosses the southwest
corner of the property, and is within the property limits. The Larimer and Weld Canal
runs along the northern border of the property.
6. Any offsite flows that would enter the site on the north are intercepted by the Larimer
and Weld Canal.
Waterfield Third Filing
Preliminary Drainage Report 2
B. Description of Property
1. The development area is roughly 117 net acres.
Figure 1 – Aerial Photograph
2. The subject property is currently leased for farming purposes. The ground cover
generally consists of row crops. Existing ground slopes are mild to moderate (i.e., 1 -
6±%) through the interior of the property. General topography slopes from north to
south. The existing wetland area within the interior of the site collects a significant
amount of storm drainage and excess irrigation flows.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey website:
http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx,
the site consists of Paoli fine sandy loam and Table Mountain Loam, which fall into
Hydrologic Soil Group B.
Waterfield Third Filing
Preliminary Drainage Report 3
4. The proposed project site plan is composed of residential and commercial
development. Associated roadways, water and sewer lines will be constructed with
the development. The existing wetland within the interior of the site be utilized for
stacked detention (detention over the permanent pool elevation of the wetland). The
existing detention pond constructed with Waterfield P.U.D. First Filing, located along
the south boundary of the site, will be expanded and utilized for detention and water
quality treatment.
Figure 2– Proposed Site Plan
5. The Lake Canal crosses the southwest corner of the property, and is within the
property limits. The Larimer and Weld Canal runs along the northern border of the
property.
6. The proposed land use is residential and commercial.
Waterfield Third Filing
Preliminary Drainage Report 4
C. Floodplain
1. The project site is not encroached by any City or FEMA floodplain.
Figure 3 –Area Floodplain Mapping
2. No offsite improvements are proposed with the project.
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
3. The project site lies within the Dry Creek Basin. Detention requirements are to detain
the difference between the 100-year developed inflow rate and the historic 2-year
release rate. The historic release rate for this basin is 0.20 cfs per acre. The site
outfall is the existing outfall structure for the existing detention pond constructed with
Waterfield P.U.D., First Filing. The outfall for this pond is a siphon storm line
which conveys flows under the Lake Canal. This pond is to be modified with
the currently proposed development to incorporate detention and water quality
measures for the existing development, as well as the proposed Waterfield
Third Filing development. It is understood that the siphon outfall for this pond
is the responsibility of the development to maintain.
Waterfield Third Filing
Preliminary Drainage Report 5
B. Sub-Basin Description
4. The subject property historically drains overland from north to south. Runoff from a
portion of the site has historically collected in the existing wetland located within the
interior of the site. The remainder of the site historically sheet flows to the existing
detention pond at the southern boundary of the site. This pond outfalls via a siphon
under the Lake Canal into the Vine Drive roadside ditch. The proposed site will
generally maintain these historic drainage patterns. A more detailed description of the
project drainage patterns follows in Section IV.A.4., below.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the proposed
project.
B. Four Step Process
The overall stormwater management strategy employed with the proposed project utilizes
the “Four Step Process” to minimize adverse impacts of urbanization on 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:
Conserving existing amenities in the site including the existing vegetated areas.
Providing vegetated open areas throughout the site to reduce the overall impervious
area and to minimize directly connected impervious areas (MDCIA).
Routing flows, to the extent feasible, through vegetated swales to increase time of
concentration, promote infiltration and provide initial water quality.
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; however, urban
development of this intensity will still generate stormwater runoff that will require
additional BMPs and water quality. The majority of stormwater runoff from the site will
ultimately be intercepted and treated using extended detention methods prior to exiting the
site.
Step 3 – Stabilize Drainageways
There are no major drainageways within the subject property. While this step may not
seem applicable to proposed development, the project indirectly helps achieve stabilized
drainageways nonetheless. By providing water quality where none previously existed,
sediment with erosion potential is removed from the downstream drainageway systems.
Furthermore, this project will pay one-time stormwater development fees, as well as
ongoing monthly stormwater utility fees, both of which help achieve City-wide drainageway
stability.
Waterfield Third Filing
Preliminary Drainage Report 6
Step 4 – Implement Site Specific and Other Source Control BMPs.
The proposed project will improve upon site specific source controls compared to historic
conditions:
Trash, waste products, etc. that were previously left exposed with the historic trailer
park will no longer be allowed to exposure to runoff and transport to receiving
drainageways. The proposed development will eliminate these sources of potential
pollution.
C. Development Criteria Reference and Constraints
The subject property is surrounded by currently developed properties. Thus, several
constraints have been identified during the course of this analysis that will impact the
proposed drainage system including:
Existing elevations along the property lines will generally be maintained.
As previously mentioned, overall drainage patterns of the existing site will be
maintained.
Elevations of existing downstream facilities that the subject property will release to
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 the proposed 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. Three separate design storms have been utilized to address distinct drainage
scenarios. A fourth design storm has also been computed for comparison purposes.
The first design storm considered is the 80th percentile rain event, which has been
employed to design the project’s water quality features. The second event analyzed is
the “Minor,” or “Initial” Storm, which has a 2-year recurrence interval. The third
event considered is the “Major Storm,” which has a 100-year recurrence interval.
The fourth storm computed, for comparison purposes only, is the 10-year event.
4. 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 maintains historic drainage patterns.
2. All drainage facilities proposed with the project are designed in accordance with
criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District
(UDFCD) Urban Storm Drainage Criteria Manual.
3. As stated above, the subject property is not located in a City or FEMA regulatory
floodplain.
4. The proposed project does not propose to modify any natural drainageways.
Waterfield Third Filing
Preliminary Drainage Report 7
F. Modifications of Criteria
1. The proposed development is not requesting any modifications to criteria at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the project drainage design are to maintain existing drainage
patterns, and to ensure no adverse impacts to any adjacent properties.
2. The existing wetland within the interior of the site be utilized for stacked detention
(detention over the permanent pool elevation of the wetland). The existing detention
pond constructed with Waterfield P.U.D. First Filing, located along the south
boundary of the site, will be expanded and utilized for detention and water quality
treatment.
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 drainage patterns anticipated for proposed drainage basins are described below.
Basins 1-4, 6-8
Basins 1 through 4 and Basins 6 through 8 consists of open space, residential and
commercial development. These basins will drain generally via street curb and gutter
to the existing wetland, noted as Pond 1, which will be utilized for stacked detention.
A PLD section with an underdrain is proposed within the center median of Gargeney
Drive. This street will have an inverted crown, sloping to the center median, and will
collect drainage from Basins 2 through 7. This PLD will serve as an onsite LID
feature, and will treat runoff prior to entry to Pond 1.
Basin 5
Basin 5 consists of open space and a portion of Vine Drive. This basin will drain via
street curb and gutter and via sheet flow to the proposed Pond 2.
Basins 9-12, 14
Basins 9 through 12, and Basin 14 consist of residential development. These basins
will drain generally via street curb and gutter to the existing detention pond
constructed with Waterfield P.U.D., First Filing which is noted as Pond 3 with the
current project. The outfall for this pond is a siphon storm line which conveys
flows under the Lake Canal. This pond is to be modified with the currently
proposed development to incorporate detention for the existing Waterfield
P.U.D. First Filing development, as well as the proposed Third Filing
development
Basin 13
Basin 13 consists of backs of residential lots and will drain via sheetflow undetained
to offsite property to the southwest, and immediately into the Lake Canal, located at
the southwest corner of the site.
Waterfield Third Filing
Preliminary Drainage Report 8
Basin 15
Basin 15 consists of Right of Way for Merganser Street. This basin will drain
undetained south into Vine Drive.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Specific Details
1. Standard water quality treatment in the form of Extended Detention is being
provided for the proposed development in Pond 3. Further documentation of
treatment volumes and removal rates of stormwater BMPs will be documented
with the Final Drainage Report prepared during the City FCP process.
2. Pond 1 will provide water quality treatment in the wet component of this
pond. As previously discussed, Pond 1 is an existing wetland with a
permanent water surface. The wetland vegetation and permanent pool will
greatly enhance water quality for runoff discharging from the site. Water
quality forebays will be provided for pre-treatment at all concentrated points of
entry to the existing wetland.
3. LID features will be incorporated in the design of the PLD running along
Garganey Drive at Final design.
4. Final design details, construction documentation, and Standard Operating
Procedures (SOP) Manual shall be provided to the City of Fort Collins for
review prior to Final Development Plan approval. A final copy of the approved
SOP manual shall be provided to City and must be maintained on-site by the
entity responsible for the facility maintenance. Annual reports must also be
prepared and submitted to the City discussing the results of the maintenance
program (i.e. inspection dates, inspection frequency, volume loss due to
sedimentation, corrective actions taken, etc.).
5. Table 1, below, summarizes preliminary detention and water quality volumes for
Ponds 1 through 3.
Table 1 – Pond Summary Table
Detention Water Quality Total Required Detention
Volume Capture Volume Volume Release Rate
(AC-FT) (AC-FT) (FT) (CFS)
14.35 0.00 14.35 1.25
1.04 0.00 1.04 2.26
10.71 0.55 11.26 7.64
6. Proper maintenance of the drainage facilities designed with the proposed
development is a critical component of their ongoing performance and effectiveness.
The water quality pond will be designed at Final to be easily accessed by
maintenance staff via gentle slopes provided to the bottom of the pond.
7. The drainage features associated with the proposed project are all private facilities,
located on private property.
Waterfield Third Filing
Preliminary Drainage Report 9
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the proposed project complies with the City of Fort
Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with this project complies with requirements for the
Dry Creek Basin.
3. The drainage plan and stormwater management measures proposed with the
proposed 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 effectively limit any potential
damage associated with its stormwater runoff by providing detention and water
quality mitigation features.
2. The drainage concept for the proposed development is consistent with requirements
for the Dry Creek Basin.
Waterfield Third Filing
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: 889-001
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: ATC
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
= 1.00 100-year Cf = 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
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
1 1780641 40.88 Note: For preliminary calculations, Composite Runoff Coefficients are 0.20 0.20 0.25 20%
2 233407 5.36 based on Table RO-10. 0.55 0.55 0.69 45%
3 519624 11.93 Composite % Imperviousness has been estimated based 0.55 0.55 0.69 45%
4 301114 6.91 on UDFCD USDCM, Vol. I, Figures RO-3 and RO-4. 0.55 0.55 0.69 45%
5 260471 5.98 0.20 0.20 0.25 20%
6 114325 2.62 0.55 0.55 0.69 45%
7 243526 5.59 0.95 0.95 1.00 80%
8 366211 8.41 0.95 0.95 1.00 80%
9 51924 1.19 0.55 0.55 0.69 45%
10 195492 4.49 0.55 0.55 0.69 45%
Overland Flow, Time of Concentration:
Project: 889-001
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
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,
V
(ft/s)
Tt
(min)
2-yr
Tc
Rational Method Equation: Project: 889-001
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
1 1 40.88 30 30 28 0.20 0.20 0.25 1.31 2.23 4.69 10.7 18.2 47.9
2 2 5.36 13 13 11 0.55 0.55 0.69 1.98 3.39 7.57 5.8 10.0 27.9
3 3 11.93 20 20 17 0.55 0.55 0.69 1.63 2.78 6.10 10.7 18.2 50.0
4 4 6.91 15 15 12 0.55 0.55 0.69 1.90 3.24 7.16 7.2 12.3 34.0
5 5 5.98 25 25 23 0.20 0.20 0.25 1.45 2.47 5.20 1.7 2.9 7.8
6 6 2.62 11 11 9 0.55 0.55 0.69 2.13 3.63 8.03 3.1 5.2 14.5
7 7 5.59 11 11 10 0.95 0.95 1.00 2.17 3.71 7.88 11.5 19.7 44.0
8 8 8.41 11 11 11 0.95 0.95 1.00 2.13 3.63 7.57 17.0 29.0 63.6
9 9 1.19 9 9 8 0.55 0.55 0.69 2.30 3.93 8.59 1.5 2.6 7.0
10 10 4.49 12 12 10 0.55 0.55 0.69 2.05 3.50 7.88 5.1 8.6 24.3
11 11 9.34 15 15 12 0.55 0.55 0.69 1.90 3.24 7.16 9.7 16.6 46.0
12 12 6 17 17 15 055 055 069 175 299 652 65 11 1 30 2
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)
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)
ATC
10/31/13
Q C f C i A
12 12 6.74 17 17 15 0.55 0.55 0.69 1.75 2.99 6.52 6.5 11.1 30.2
13 13 1.52 12 12 9 0.55 0.55 0.69 2.09 3.57 8.03 1.7 3.0 8.4
14 14 5.15 22 22 21 0.20 0.20 0.25 1.53 2.61 5.46 1.6 2.7 7.0
33
(11) Section 4.0 is amended to read as follows:
4.0 Intensity-Duration-Frequency Curves for Rational Method:
The one-hour rainfall Intensity-Duration-Frequency tables for use the Rational Method
of runoff analysis are provided in Table RA-7 and in Table RA-8.
Table RA-7 -- City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
for Use with the Rational Method
(5 minutes to 30 minutes)
2-Year 10-Year 100-Year
Duration
(min)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
5 2.85 4.87 9.95
6 2.67 4.56 9.31
7 2.52 4.31 8.8
8 2.4 4.1 8.38
9 2.3 3.93 8.03
10 2.21 3.78 7.72
11 2.13 3.63 7.42
12 2.05 3.5 7.16
13 1.98 3.39 6.92
14 1.92 3.29 6.71
15 1.87 3.19 6.52
16 1.81 3.08 6.3
17 1.75 2.99 6.1
18 1.7 2.9 5.92
19 1.65 2.82 5.75
20 1.61 2.74 5.6
21 1.56 2.67 5.46
22 1.53 2.61 5.32
23 1.49 2.55 5.2
24 1.46 2.49 5.09
25 1.43 2.44 4.98
26 1.4 2.39 4.87
27 1.37 2.34 4.78
28 1.34 2.29 4.69
29 1.32 2.25 4.6
30 1.3 2.21 4.52
34
Table RA-8 -- City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
for Use with the Rational Method
(31 minutes to 60 minutes)
2-Year 10-Year 100-Year
Duration
(min)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
31 1.27 2.16 4.42
32 1.24 2.12 4.33
33 1.22 2.08 4.24
34 1.19 2.04 4.16
35 1.17 2.0 4.08
36 1.15 1.96 4.01
37 1.16 1.93 3.93
38 1.11 1.89 3.87
39 1.09 1.86 3.8
40 1.07 1.83 3.74
41 1.05 1.8 3.68
42 1.04 1.77 3.62
43 1.02 1.74 3.56
44 1.01 1.72 3.51
45 0.99 1.69 3.46
46 0.98 1.67 3.41
47 0.96 1.64 3.36
48 0.95 1.62 3.31
49 0.94 1.6 3.27
50 0.92 1.58 3.23
51 0.91 1.56 3.18
52 0.9 1.54 3.14
53 0.89 1.52 3.1
54 0.88 1.5 3.07
55 0.87 1.48 3.03
56 0.86 1.47 2.99
57 0.85 1.45 2.96
58 0.84 1.43 2.92
59 0.83 1.42 2.89
60 0.82 1.4 2.86
36
RAINFALL INTENSITY-DURATION-FREQUENCY CURVE
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
0.00 10.00 20.00 30.00 40.00 50.00 60.00
STORM DURATION (minutes)
RAINFALL INTENSITY (inches/hour)
2-Year Storm 10-Year Storm 100-Year Storm
Figure RA-16 City of Fort Collins Rainfall Intensity-Duration-Frequency Curves
(13) Section 5.0 is deleted in its entirety.
(14) Section 6.0 is deleted in its entirety.
(15) Section 7.0 is deleted in its entirety.
(16) Section 7.1 is deleted in its entirety.
(17) Section 7.2 is deleted in its entirety.
(18) Section 7.3 is deleted in its entirety.
(19) Section 8.0 is deleted in its entirety.
(20) Table RA-1 is deleted in its entirety.
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:
42
2.10 Runoff Coefficient Adjustment for Infrequent Storms
The runoff coefficients provided in tables RO-10 and RO-11 are appropriate for use with
the 2-year storm event. For storms with higher intensities, an adjustment of the runoff
coefficient is required due to the lessening amount of infiltration, depression retention,
evapo-transpiration and other losses that have a proportionally smaller effect on storm
runoff. This adjustment is applied to the composite runoff coefficient.
These frequency adjustment factors are found in Table RO-12.
Table RO-12
Rational Method Runoff Coefficients for Composite Analysis
Storm Return Period
(years)
Frequency Factor
Cf
2 to 10
11 to 25
26 to 50
51 to 100
1.00
1.10
1.20
1.25
Note: The product of C times Cf cannot exceed the value of 1, in the cases where it does a value of
1 must be used
(6) Section 3.1 is deleted in its entirety.
(7) Section 3.2 is deleted in its entirety.
(8) Section 3.3 is deleted in its entirety.
(9) A new Section 4.3 is added, to read as follows:
4.3 Computer Modeling Practices
(a) For circumstances requiring computer modeling, the design storm hydrographs must
be determined using the Stormwater Management Model (SWMM). Basin and
conveyance element parameters must be computed based on the physical characteristics
of the site.
(b) Refer to the SWMM Users’ Manual for appropriate modeling methodology, practices
and development. The Users’ Manual can be found on the Environmental Protection
Agency (EPA) website (http://www.epa.gov/ednnrmrl/models/swmm/index.htm).
(c) It is the responsibility of the design engineer to verify that all of the models used in
the design meet all current City criteria and regulations.
4.3.1 Surface Storage, Resistance Factors, and Infiltration
Table RO-13 provides values for surface storage for pervious and impervious surfaces
and the infiltration rates to be used with SWMM. Table RO-13 also lists the appropriate
infiltration decay rate, zero detention depth and resistance factors, or Manning’s “n”
values, for pervious and impervious surfaces to be used for SWMM modeling in the city
of Fort Collins.
40
Table RO-10
Rational Method Minor Storm Runoff Coefficients for Zoning Classifications
Description of Area or Zoning Coefficient
R-F 0.3
U-E 0.3
L-M-In 0.55
R-L, N-C-L 0.6
M-M-N, N-C-M 0.65
N-C-B 0.7
Business:
C-C-N, C-C-R, C-N, N-C, C-S 0.95
R-D-R, C-C, C-L 0.95
D, C 0.95
H-C 0.95
C-S 0.95
Industrial:
E 0.85
I 0.95
Undeveloped:
R-C, T 0.2
P-O-L 0.25
For guidance regarding zoning districts and classifications of such districts please refer to
Article Four of the City Land Use Code, as amended.
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
Table RO-3—Recommended Percentage Imperviousness Values
Land Use or
Surface Characteristics
Percentage
Imperviousness
Business:
Commercial areas 95
Neighborhood areas 85
Residential:
Single-family *
Multi-unit (detached) 60
Multi-unit (attached) 75
Half-acre lot or larger *
Apartments 80
Industrial:
Light areas 80
Heavy areas 90
Parks, cemeteries 5
Playgrounds 10
Schools 50
Railroad yard areas 15
Undeveloped Areas:
Historic flow analysis 2
Greenbelts, agricultural 2
Off-site flow analysis
(when land use not defined)
45
Streets:
Paved 100
Gravel (packed) 40
Drive and walks 90
Roofs 90
Lawns, sandy soil 0
Lawns, clayey soil 0
* See Figures RO-3 through RO-5 for percentage imperviousness.
C A = K A + ( 1 . 31 i 3 − 1 . 44 i 2 + 1 . 135 i − 0 . 12 ) for CA ≥ 0, otherwise CA = 0 (RO-6)
C CD = K CD + ( 0 . 858 i 3 − 0 . 786 i 2 + 0 . 774 i + 0 . 04 ) (RO-7)
C B = (CA + C CD ) 2
2007-01 RO-9
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
Table RO-5— Runoff Coefficients, C
Percentage
Imperviousness Type C and D NRCS Hydrologic Soil Groups
2-yr 5-yr 10-yr 25-yr 50-yr 100-yr
0% 0.04 0.15 0.25 0.37 0.44 0.50
5% 0.08 0.18 0.28 0.39 0.46 0.52
10% 0.11 0.21 0.30 0.41 0.47 0.53
15% 0.14 0.24 0.32 0.43 0.49 0.54
20% 0.17 0.26 0.34 0.44 0.50 0.55
25% 0.20 0.28 0.36 0.46 0.51 0.56
30% 0.22 0.30 0.38 0.47 0.52 0.57
35% 0.25 0.33 0.40 0.48 0.53 0.57
40% 0.28 0.35 0.42 0.50 0.54 0.58
45% 0.31 0.37 0.44 0.51 0.55 0.59
50% 0.34 0.40 0.46 0.53 0.57 0.60
55% 0.37 0.43 0.48 0.55 0.58 0.62
60% 0.41 0.46 0.51 0.57 0.60 0.63
65% 0.45 0.49 0.54 0.59 0.62 0.65
70% 0.49 0.53 0.57 0.62 0.65 0.68
75% 0.54 0.58 0.62 0.66 0.68 0.71
80% 0.60 0.63 0.66 0.70 0.72 0.74
85% 0.66 0.68 0.71 0.75 0.77 0.79
90% 0.73 0.75 0.77 0.80 0.82 0.83
95% 0.80 0.82 0.84 0.87 0.88 0.89
100% 0.89 0.90 0.92 0.94 0.95 0.96
TYPE B NRCS HYDROLOGIC SOILS GROUP
0% 0.02 0.08 0.15 0.25 0.30 0.35
5% 0.04 0.10 0.19 0.28 0.33 0.38
10% 0.06 0.14 0.22 0.31 0.36 0.40
15% 0.08 0.17 0.25 0.33 0.38 0.42
20% 0.12 0.20 0.27 0.35 0.40 0.44
25% 0.15 0.22 0.30 0.37 0.41 0.46
30% 0.18 0.25 0.32 0.39 0.43 0.47
35% 0.20 0.27 0.34 0.41 0.44 0.48
40% 0.23 0.30 0.36 0.42 0.46 0.50
45% 0.26 0.32 0.38 0.44 0.48 0.51
50% 0.29 0.35 0.40 0.46 0.49 0.52
55% 0.33 0.38 0.43 0.48 0.51 0.54
60% 0.37 0.41 0.46 0.51 0.54 0.56
65% 0.41 0.45 0.49 0.54 0.57 0.59
70% 0.45 0.49 0.53 0.58 0.60 0.62
75% 0.51 0.54 0.58 0.62 0.64 0.66
80% 0.57 0.59 0.63 0.66 0.68 0.70
85% 0.63 0.66 0.69 0.72 0.73 0.75
90% 0.71 0.73 0.75 0.78 0.80 0.81
95% 0.79 0.81 0.83 0.85 0.87 0.88
100% 0.89 0.90 0.92 0.94 0.95 0.96
2007-01 RO-11
Urban Drainage and Flood Control District
RUNOFF DRAINAGE CRITERIA MANUAL (V. 1)
TABLE RO-5 (Continued)—Runoff Coefficients, C
Percentage
Imperviousness Type A NRCS Hydrologic Soils Group
2-yr 5-yr 10-yr 25-yr 50-yr 100-yr
0% 0.00 0.00 0.05 0.12 0.16 0.20
5% 0.00 0.02 0.10 0.16 0.20 0.24
10% 0.00 0.06 0.14 0.20 0.24 0.28
15% 0.02 0.10 0.17 0.23 0.27 0.30
20% 0.06 0.13 0.20 0.26 0.30 0.33
25% 0.09 0.16 0.23 0.29 0.32 0.35
30% 0.13 0.19 0.25 0.31 0.34 0.37
35% 0.16 0.22 0.28 0.33 0.36 0.39
40% 0.19 0.25 0.30 0.35 0.38 0.41
45% 0.22 0.27 0.33 0.37 0.40 0.43
50% 0.25 0.30 0.35 0.40 0.42 0.45
55% 0.29 0.33 0.38 0.42 0.45 0.47
60% 0.33 0.37 0.41 0.45 0.47 0.50
65% 0.37 0.41 0.45 0.49 0.51 0.53
70% 0.42 0.45 0.49 0.53 0.54 0.56
75% 0.47 0.50 0.54 0.57 0.59 0.61
80% 0.54 0.56 0.60 0.63 0.64 0.66
85% 0.61 0.63 0.66 0.69 0.70 0.72
90% 0.69 0.71 0.73 0.76 0.77 0.79
95% 0.78 0.80 0.82 0.84 0.85 0.86
100% 0.89 0.90 0.92 0.94 0.95 0.96
RO-12 2007-01
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
Figure RO-3— Watershed Imperviousness, Single-Family Residential Ranch Style Houses
2007-01 RO-15
Urban Drainage and Flood Control District
RUNOFF DRAINAGE CRITERIA MANUAL (V. 1)
Figure RO-4—Watershed Imperviousness, Single-Family Residential Split-Level Houses
RO-16 2007-01
Urban Drainage and Flood Control District
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
Figure RO-5—Watershed Imperviousness, Single-Family Residential Two-Story Houses
Figure RO-6—Runoff Coefficient, C, vs. Watershed Percentage Imperviousness NRCS Hydrologic
Soil Group A
2007-01 RO-17
Urban Drainage and Flood Control District
RUNOFF DRAINAGE CRITERIA MANUAL (V. 1)
Figure RO-7—Runoff Coefficient, C, vs. Watershed Percentage Imperviousness NRCS Hydrologic
Soil Group B
Figure RO-8—Runoff Coefficient, C, vs. Watershed Percentage Imperviousness NRCS Hydrologic
Soil Groups C and D
RO-18 2007-01
Urban Drainage and Flood Control District
APPENDIX B
WATER WAWAWATER QUALITY DESIGN COMPUTATIONS
WATER QUALITY POND DESIGN CALCULATIONS
Pond 3
Project: 889-001
By: ATC
Date: 10/31/13
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA = 28.440 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 45.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.4500 <-- CALCULATED
WQCV (watershed inches) = 0.193 <-- CALCULATED from Figure EDB-2
WQCV (ac-ft) = 0.549 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
WQ Depth (ft) = ** <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = ** <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = ** <-- INPUT from Figure 5
n = ** <-- INPUT from Figure 5
t (in) = ** <-- INPUT from Figure 5
number of rows = ** <-- CALCULATED from WQ Depth and row spacing
**To be completed at final design
APPENDIX C
STORMWATER MANAGEMENT MODEL (SWMM)
1
3
2
4
out1
out3
out2
outfall
pond1
pond3
pond2
FtCollins-100yr
11/21/2012 00:15:00
SWMM 5 Page 1
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.0 (Build 5.0.022)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... HORTON
Flow Routing Method ...... KINWAVE
Starting Date ............ NOV-21-2012 00:00:00
Ending Date .............. NOV-21-2012 06:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:15:00
Wet Time Step ............ 00:05:00
Dry Time Step ............ 01:00:00
Routing Time Step ........ 30.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 35.888 3.669
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 8.447 0.864
Surface Runoff ........... 27.212 2.782
Final Surface Storage .... 0.430 0.044
Continuity Error (%) ..... -0.560
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 27.212 8.867
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 3.245 1.057
Internal Outflow ......... 0.000 0.000
Storage Losses ........... 0.000 0.000
Initial Stored Volume .... 0.000 0.000
Final Stored Volume ...... 23.968 7.810
Continuity Error (%) ..... -0.003
********************************
SWMM 5 Page 1
Highest Flow Instability Indexes
********************************
All links are stable.
*************************
Routing Time Step Summary
*************************
Minimum Time Step : 30.00 sec
Average Time Step : 30.00 sec
Maximum Time Step : 30.00 sec
Percent in Steady State : 0.00
Average Iterations per Step : 1.00
***************************
Subcatchment Runoff Summary
***************************
--------------------------------------------------------------------------------------------------------
Total Total Total Total Total Total Peak Runoff
Precip Runon Evap Infil Runoff Runoff Runoff Coeff
Subcatchment in in in in in 10^6 gal CFS
--------------------------------------------------------------------------------------------------------
1 3.67 0.00 0.00 0.82 2.83 4.74 424.15 0.770
3 3.67 0.00 0.00 0.87 2.77 2.14 173.17 0.756
2 3.67 0.00 0.00 1.31 2.35 0.38 23.82 0.640
4 3.67 0.00 0.00 0.86 2.79 1.60 132.25 0.759
******************
Node Depth Summary
******************
---------------------------------------------------------------------
Average Maximum Maximum Time of Max
Depth Depth HGL Occurrence
Node Type Feet Feet Feet days hr:min
---------------------------------------------------------------------
outfall OUTFALL 0.00 0.00 96.00 0 00:00
pond1 STORAGE 2.19 2.50 107.50 0 02:25
pond3 STORAGE 2.62 3.06 103.06 0 02:19
pond2 STORAGE 2.50 3.01 106.01 0 02:18
*******************
Node Inflow Summary
*******************
-------------------------------------------------------------------------------------
Maximum Maximum Lateral Total
Lateral Total Time of Max Inflow Inflow
Inflow Inflow Occurrence Volume Volume
Node Type CFS CFS days hr:min 10^6 gal 10^6 gal
-------------------------------------------------------------------------------------
outfall OUTFALL 0.00 7.64 0 02:19 0.000 1.057
pond1 STORAGE 424.15 424.15 0 00:40 4.739 4.739
pond3 STORAGE 305.41 306.42 0 00:40 3.746 4.049
pond2 STORAGE 23.82 24.49 0 00:40 0.381 0.558
SWMM 5 Page 2
**********************
Node Surcharge Summary
**********************
Surcharging occurs when water rises above the top of the highest conduit.
---------------------------------------------------------------------
Max. Height Min. Depth
Hours Above Crown Below Rim
Node Type Surcharged Feet Feet
---------------------------------------------------------------------
pond1 STORAGE 6.01 2.500 7.500
pond3 STORAGE 6.01 3.055 6.945
pond2 STORAGE 6.01 3.007 6.993
*********************
Node Flooding Summary
*********************
No nodes were flooded.
**********************
Storage Volume Summary
**********************
--------------------------------------------------------------------------------------------
Average Avg E&I Maximum Max Time of Max Maximum
Volume Pcnt Pcnt Volume Pcnt Occurrence Outflow
Storage Unit 1000 ft3 Full Loss 1000 ft3 Full days hr:min CFS
--------------------------------------------------------------------------------------------
pond1 523.840 5 0 625.018 6 0 02:24 1.25
pond3 373.796 7 0 466.672 9 0 02:18 7.64
pond2 34.256 7 0 45.199 9 0 02:17 2.25
***********************
Outfall Loading Summary
***********************
-----------------------------------------------------------
Flow Avg. Max. Total
Freq. Flow Flow Volume
Outfall Node Pcnt. CFS CFS 10^6 gal
-----------------------------------------------------------
outfall 97.23 6.73 7.64 1.057
-----------------------------------------------------------
System 97.23 6.73 7.64 1.057
********************
Link Flow Summary
********************
-----------------------------------------------------------------------------
Maximum Time of Max Maximum Max/ Max/
|Flow| Occurrence |Veloc| Full Full
Link Type CFS days hr:min ft/sec Flow Depth
-----------------------------------------------------------------------------
out1 DUMMY 1.25 0 02:25
out3 DUMMY 7.64 0 02:19
SWMM 5 Page 3
out2 DUMMY 2.25 0 02:18
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Analysis begun on: Tue Aug 13 15:34:29 2013
Analysis ended on: Tue Aug 13 15:34:29 2013
Total elapsed time: < 1 sec
SWMM 5 Page 4
35
(12) A new Section 4.1 is added, to read as follows:
4.1 Intensity-Duration-Frequency Curves for SWMM:
The hyetograph input option must be selected when creating SWMM input files.
Hyetographs for the 2-, 5-, 10-, 25-, 50-, and 100-year City of Fort Collins rainfall events
are provided in Table RA-9.
Table RA-9 – City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
for Use with SWMM
2-Year 5-Year 10-Year 25-Year 50-Year 100-Year
Duration
(min)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
5 0.29 0.40 0.49 0.63 0.79 1.00
10 0.33 0.45 0.56 0.72 0.90 1.14
15 0.38 0.53 0.65 0.84 1.05 1.33
20 0.64 0.89 1.09 1.41 1.77 2.23
25 0.81 1.13 1.39 1.80 2.25 2.84
30 1.57 2.19 2.69 3.48 4.36 5.49
35 2.85 3.97 4.87 6.30 7.90 9.95
40 1.18 1.64 2.02 2.61 3.27 4.12
45 0.71 0.99 1.21 1.57 1.97 2.48
50 0.42 0.58 0.71 0.92 1.16 1.46
55 0.35 0.49 0.60 0.77 0.97 1.22
60 0.30 0.42 0.52 0.67 0.84 1.06
65 0.20 0.28 0.39 0.62 0.79 1.00
70 0.19 0.27 0.37 0.59 0.75 0.95
75 0.18 0.25 0.35 0.56 0.72 0.91
80 0.17 0.24 0.34 0.54 0.69 0.87
85 0.17 0.23 0.32 0.52 0.66 0.84
90 0.16 0.22 0.31 0.50 0.64 0.81
95 0.15 0.21 0.30 0.48 0.62 0.78
100 0.15 0.20 0.29 0.47 0.60 0.75
105 0.14 0.19 0.28 0.45 0.58 0.73
110 0.14 0.19 0.27 0.44 0.56 0.71
115 0.13 0.18 0.26 0.42 0.54 0.69
120 0.13 0.18 0.25 0.41 0.53 0.67
43
Table RO-13
SWMM Input Parameters
Depth of Storage on Impervious Areas 0.1 inches
Depth of Storage on Pervious Areas 0.3 inches
Maximum Infiltration Rate 0.51 inches/hour
Minimum Infiltration Rate 0.50 inches/hour
Decay Rate 0.0018 inches/sec
Zero Detention Depth 1%
Manning’s n Value for Pervious Surfaces 0.025
Manning’s n Value for Impervious Surfaces 0.016
4.3.2 Pervious-Impervious Area
Table RO-14 should be used to determine preliminary percentages of impervious land
cover for a given land-use or zoning. The final design must be based on the actual
physical design conditions of the site.
Table RO-14
Percent Imperviousness Relationship to Land Use*
LAND USE OR ZONING
PERCENT IMPERVIOUS
(%)
Business:
T
CCN, CCR, CN
E, RDR, CC, LC
C, NC, I, D, HC, CS
20
70
80
90
Residential:
RF,UE
RL, NCL
LMN,NCM
MMN, NCB
30
45
50
70
Open Space:
Open Space and Parks (POL)
Open Space along foothills ridge
(POL,RF)
RC
10
20
20
*For updated zoning designations and definitions, please refer to Article Four of the City Land
Use Code, as amended
APPENDIX D
EROSION CONTROL REPORT
Waterfield Third Filing
Preliminary Erosion Control Report
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included
with the final construction drawings. 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 existing and 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 the Utility Plans. The Final Plans will contain a
full-size Erosion Control sheet 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 the Development Agreement for the development. 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, prior to any earth disturbance 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.
MAP POCKET
DRAINAGE EXHIBITS
�
�
�
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
�
�
R R
UD UD UD
UD UD UD UD UD UD
VINE DRIVE
MERGANSER
VINE DRIVE
MERGANSER
VINE DRIVE
BLACK SCOTER
DRIVE
OUZEL DRIVE
GOSLYN DRIVE
CAPE
TEAL DRIVE
MUSCOVY DRIVE
ROSYBILL DRIVE
SHEARWATER DRIVE
ALEUTIAN DRIVE
MANDARIN DRIVE
GARGANEY DRIVE
MANDARIN DRIVE
TRACT C
OUTLOT A
OUTLET B
TRACT H
TRACT I
TRACT A
TRACT B
TRACT D
TRACT E
TRACT J
TRACT K
TRACT K
TRACT K
1
40.88
2
5.36
3
11.93
4
6.91
7
5.59
8
8.41
11
9.34
10
4.49
12
6.74
14
5.15
1
2 3 4
6 7
8
5
9
10
11
12
14
15
5
5.98
9
1.19
13
1.52
6
2.62
13
POND 2
POND 1 (EXISTING WETLAND)
FOREBAY
FOREBAY
POND 3
15
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DATE:
06/28/13
PROJECT:
889-001
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KEYMAP
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MERGANSER
VINE DRIVE
MERGANSER
TIMBERLILNE
WETLAND
AREA
ALEUTION DRIVE
OUZEL DRIVE
MUSCOVY DRIVE
SHEARWATER DRIVE
CAPE TEAL DR.
MANDARIN DRIVE
GARGANEY DRIVE
ROSYBILL DRIVE
ROSYBILL DRIVE
GOSLYN DRIVE
BLACK SCOOTER DRIVE
VINE DRIVE
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TIMBERLILNE
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( IN FEET )
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300 450
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DRAINAGE PLAN
OVERALL C. SNOWDON
D. FRY
1" = 150'
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU DIG, GRADE, OR EXCAVATE FOR THE MARKING OF UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
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GENERAL NOTES:
1.THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES
ARE APPROXIMATE PER THE BEST AVAILABLE INFORMATION PROVIDED WHEN
SHOWN ON THESE DRAWINGS. IT SHALL BE THE RESPONSIBILITY OF THE
CONTRACTOR TO VERIFY THE EXISTENCE OF ALL UNDERGROUND UTILITIES IN
THE AREA OF THE WORK. BEFORE COMMENCING NEW CONSTRUCTION, THE
CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING ALL UNDERGROUND
UTILITIES AND SHALL BE RESPONSIBLE FOR ALL UNKNOWN UNDERGROUND
UTILITIES.
2.ALL WATER CONSTRUCTION SHALL BE PER THE CITY OF FORT COLLINS
STANDARD CONSTRUCTION SPECIFICATIONS, LATEST EDITION.
3.ALL SEWER CONSTRUCTION SHALL BE PER ST. VRAIN SANITATION DISTRICT
STANDARD CONSTRUCTION SPECIFICATIONS, LATEST EDITION.
4.ALL WATER FITTINGS AND VALVES ARE ONLY GRAPHICALLY REPRESENTED
AND ARE NOT TO SCALE.
5.UTILITY SERVICES ARE SHOWN IN A SCHEMATIC FASHION ONLY. EXACT
LOCATIONS SHALL BE PER THE REQUIREMENTS OF THE RESPECTIVE UTILITY
PROVIDERS, AND ARE SUBJECT TO CHANGE IN THE FIELD.
6.MAINTAIN 10' HORIZONTAL AND 18" VERTICAL MINIMUM SEPARATION
BETWEEN ALL SANITARY SEWER MAINS, WATER MAINS & SERVICES.
7.EXISTING SANITARY SEWER LOCATION IS APPROXIMATE AND WAS SUPPLIED
BY MOUNTAIN SHADOWS FILING I AND NOT VERIFIED WITHIN THE FIELD
SURVEY. CONTRACTOR TO VERIFY LOCATION PRIOR TO CONSTRUCTION AND
ORDERING OF MATERIAL.
8.LOTS 1-3, BLOCK 1 & LOTS 1-3, BLOCK 3 TO BE SERVICED FROM EXISTING
SANITARY SEWER MAIN. CONTRACTOR TO VERIFY IF SERVICES ARE
CURRENTLY INSTALLED. IF NO SERVICES EXIST, CONTRACTOR SHALL
CONTACT THE ENGINEER.
9.EXISTING SANITARY SEWER MANHOLE LOCATION IS ESTIMATED IN THE
SHORES ANNEXATION TO THE TOWN OF FIRESTONE, AND NOT VERIFIED WITHIN
THE FIELD SURVEY. CONTRACTOR TO VERIFY LOCATION PRIOR TO
CONSTRUCTION AND ORDERING OF MATERIAL.
OD1
LEGEND:
4953
PROPOSED CONTOUR 93
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
BASIN
DESIGNATION
BASIN
AREA (AC)
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
1 1
B2
1.45 ��
15 15 0.77 8 8 7 0.95 0.95 1.00 2.46 4.21 8.80 1.8 3.1 6.8
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
11No0.20 0.20 0.25 370 2.50% 23.9 23.9 22.5 614 0.75% 1.73 5.9 0 0.00% N/A N/A 30 30 28
22No0.55 0.55 0.69 120 2.00% 8.9 8.9 6.7 439 0.75% 1.73 4.2 0 0.00% N/A N/A 13 13 11
33No0.55 0.55 0.69 185 2.00% 11.1 11.1 8.3 905 0.75% 1.73 8.7 0 0.00% N/A N/A 20 20 17
44No0.55 0.55 0.69 122 2.00% 9.0 9.0 6.8 584 0.75% 1.73 5.6 0 0.00% N/A N/A 15 15 12
55No0.20 0.20 0.25 340 2.00% 24.6 24.6 23.3 0 0.00% N/A N/A 0 0.00% N/A N/A 25 25 23
66No0.55 0.55 0.69 98 2.00% 8.1 8.1 6.1 320 0.75% 1.73 3.1 0 0.00% N/A N/A 11 11 9
77No0.95 0.95 1.00 180 2.00% 3.0 3.0 2.0 832 0.75% 1.73 8.0 0 0.00% N/A N/A 11 11 10
87No0.95 0.95 1.00 120 2.00% 2.4 2.4 1.6 935 0.75% 1.73 9.0 0 0.00% N/A N/A 11 11 11
97No0.55 0.55 0.69 75 2.00% 7.1 7.1 5.3 243 0.75% 1.73 2.3 0 0.00% N/A N/A 9 9 8
10 7 No 055 055 069 145 2 00% 98 98 74 247 0 75% 173 24 0 0 00% N/A N/A 12 12 10
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
ATC
10/31/13
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
10 7 No 0.55 0.55 0.69 145 2.00% 9.8 9.8 7.4 247 0.75% 1.73 2.4 0 0.00% N/A N/A 12 12 10
11 7 No 0.55 0.55 0.69 150 2.00% 10.0 10.0 7.5 474 0.75% 1.73 4.6 0 0.00% N/A N/A 15 15 12
12 7 No 0.55 0.55 0.69 105 2.00% 8.4 8.4 6.3 941 0.75% 1.73 9.1 0 0.00% N/A N/A 17 17 15
13 7 No 0.55 0.55 0.69 170 2.00% 10.6 10.6 8.0 134 0.75% 1.73 1.3 0 0.00% N/A N/A 12 12 9
14 7 No 0.20 0.20 0.25 165 2.00% 17.2 17.2 16.2 437 0.50% 1.41 5.2 0 0.00% N/A N/A 22 22 21
15 7 No 0.95 0.95 1.00 50 2.00% 1.6 1.6 1.0 622 0.75% 1.73 6.0 0 0.00% N/A N/A 8 8 7
11 406929 9.34 0.55 0.55 0.69 45%
12 293752 6.74 0.55 0.55 0.69 45%
13 66265 1.52 0.55 0.55 0.69 45%
14 224433 5.15 0.20 0.20 0.25 20%
15 33680 0.77 0.95 0.95 1.00 95%
Existing 1st Filing 923482 21.20 0.55 0.55 0.69 45%
1-4,6-8 3558848 81.70 0.44 0.44 0.55 32%
9-14 1238795 28.44 0.55 0.55 0.69 45%
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
10/31/13