HomeMy WebLinkAboutWEST RANGE FORT COLLINS - PDP - PDP120028 - REPORTS - DRAINAGE REPORTPRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
WEST RANGE FORT COLLINS
Fort Collins, Colorado
December 12, 2012
Prepared for:
Epsilon Theta Corporation
200 South Avenue, Suite 10
Fort Collins, Colorado 80524
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: 875-001
3This 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.
December 12, 2012
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage and Erosion Control Report for
West Range Fort Collins
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control
Report for your review. Comments from the Conceptual Review letter dated 11.16.12 have
been addressed. Written responses thereto can be found in the comprehensive response to
comments letter on file with Current Planning.
This report has been prepared in accordance with the Fort Collins Stormwater Criteria
Manual (FCSCM), and serves to document the stormwater impacts associated with the
proposed West Range Fort Collins student housing 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.
Nicholas W. Haws, PE Herman H. Feissner, PE
Project Manager Project Engineer
West Range Fort Collins
Preliminary Drainage and Erosion Control Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ......................................................... 1
II. DRAINAGE BASINS AND SUB-BASINS ............................................................. 5
III. DRAINAGE DESIGN CRITERIA ......................................................................... 7
IV. DRAINAGE FACILITY DESIGN .......................................................................... 9
V. CONCLUSIONS............................................................................................. 12
References ............................................................................................................. 13
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers (reserved for future use)
B.2 – Street Flow (reserved for future use)
B.3 – Inlets (reserved for future use)
B.4 – Detention Facilities
APPENDIX C – Water Quality Design Computations
APPENDIX D – Operations and Maintenance Guidelines for Rain Gardens
(reserved for future use)
APPENDIX E – Erosion Control Report
LIST OF TABLES AND FIGURES:
MAP POCKET:
C4.00 – Drainage Exhibit
NOTE: TABLE OF CONTENTS WILL BE UPDATED/CORRECTED WITH SUBSEQUENT
REPORT ISSUANCES.
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
Figure 1 – Vicinity Map
2. The West Range Fort Collins project site is located in the Northeast quarter of Section
11, Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort
Collins, County of Larimer, State of Colorado.
3. West Range Fort Collins is bordered to the north by an existing alleyway and existing
multi-family and single family developments; to the south by West Laurel Street and
Colorado State University; to the east by Meldrum Street (100' Right-of-Way); and to
the west by the Kappa Delta Sorority house.
4. There are no major drainageways within or adjacent to the site. The existing Arthurs
Ditch runs parallel to the east property line. As it approaches the north property line,
the enclosed concrete irrigation ditch alignment shifts to the northwest. The existing
irrigation ditch receives excess developed stormwater from two existing inlets near the
project site. The ditch's concrete top slab is at grade, visible and currently used for a
sidewalk along the west side of Meldrum Street.
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 2
B. Description of Property
1. West Range Fort Collins is comprised of ±0.71 acre.
2. The recent existing condition (See Figure 2 - Aerial Photograph) included two (2)
fraternity houses which fronted to West Laurel Street, an associated detached garage
and a duplex which fronted to Meldrum Street. The asphalt parking lot was
constructed in the mid-1990s as a part of the Phase I condition described in the Final
Drainage and Erosion Control Report for the Pi Kappa Alpha Fraternity Expansion
(Shear Engineering or Phase I, Sheet No. 1 - Phase I Grading, Drainage and Erosion
Control Plan is provided for reference in the Map Pocket of the report). The ultimate
condition described in the drainage report was never constructed.
Figure 2 – Aerial Photograph
3. The subject property was fully developed until the late fall of 2011. At that time,
everything was removed from the property except for the asphalt parking lot
(northwest corner), concrete curb and gutter and several mature trees.
The existing groundcover currently consists of weeds and bare soil. The existing on-site
excess runoff drains across flat grades (e.g., <2.00%) into West Laurel Street,
Meldrum Street and the alleyway.
4. A soils report (Soilogic Project # 08-1051) was completed by Soilogic, Inc on
September 29, 2008. The report contains the results of a complete geotechnical
subsurface exploration as well as pertinent geotechnical recommendations. According
to the summary of findings presented in the aforementioned report, the "subsurface
materials encountered in the completed site borings consisted of a thin layer of
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 3
asphaltic concrete and base course or topsoil and vegetation underlain by brown to
reddish brown lean clay with varying amounts of silt and sand. A majority of the site
lean clay tested showed low volume change potential with variation in moisture
content at in-situ moisture and density conditions. Lean clay with low to moderate
swell potential was encountered near surface boring location B-1 completed at the
south end of the development. Groundwater was not encountered in any of the
completed site borings at the time of drilling."
The boring logs show that USCS soil group CL is predominant on-site. These soils are
inorganic clays of low to medium plasticity, gravelly clays, sandy clays, silty clays and
lean clays.
5. There are no major drainageways within or adjacent to the project site.
6. The proposed West Range Fort Collins project site will include a single backwards L-
shaped building with a plan area of approximately 8000 ft2. The completed structure
will be two stories. Other proposed improvements include: a new asphalt parking area,
an enhanced entryway and landscaping. The north-to-south portion of the proposed
building will include an open first level (i.e., breezeway) beneath which approximately
one-half of the total on-site parking will be located..
7. The existing Arthurs Ditch runs parallel to the east property line. As it approaches the
northeast corner of the subject site, the concrete box alignment shifts toward the
northwest (See Figure 3 – Existing Drainage and Irrigation Infrastructure).
Figure 3 – Existing Drainage and Irrigation Infrastructure
8. The proposed land use is residential, multi-family dwellings. This is a permitted use in
the Neighborhood Community - Buffer District (NCB).
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 4
C. Floodplain
1. The subject property is not located in a FEMA regulatory or City of Fort Collins
designated floodplain. In particular, the project site is not located within a FEMA
designated 100-year floodplain per Map Number 08069C0979H (Effective date: May
2, 2012).
Figure 4 – FEMA Firmette (Map Number 08069C0979H)
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 5
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. West Range Fort Collins is located within the City of Fort Collins Old Town major
drainage basin. This basin is located in north-central Fort Collins and has a drainage
area of approximately 2,120 acres, including approximately 400 acres of the Colorado
State University campus. The Old Town major drainage basin generally drains from
west to east. It receives some runoff from the Canal Importation Basin directly west of
Old Town. Most of the runoff from the Old Town major drainage basin drains into the
Poudre River.
Street flooding is a common occurrence in Old Town. Several capital projects such as
the Howes Street, Locust Street and Oak Street Outfall projects have addressed the
problem and improved drainage in the area.
2. As previously mentioned, the Arthurs Ditch runs parallel to the east property line. This
irrigation conveyance was historically influenced by excess developed runoff from the
project site (Shear Engineering: sub-basins 1a and 1c). Excess developed runoff from
the subject site will continue to outfall into this irrigation conveyance as described
below.
B. Sub-Basin Description
1. Shear Engineering, in the Final Drainage and Erosion Control Report for the Pi Kappa
Alpha Fraternity Expansion, described and evaluated an existing condition, Phase I
condition and Ultimate condition. The existing condition was used to establish the
historic release rate. Phase I represented an interim developed condition in which the
existing gravel parking lot was paved and used for on-site detention storage. The pond
was designed to overdetain (i.e., the total site area was used to size the pond instead
of the total area tributary to the pond) and release at the historic 2-year rate (0.50
cfs). The Ultimate condition was never constructed.
2. The subject site can be historically defined by three (3) sub-basins (i.e., Ia. Ib and Ic).
From the center of each of the three (3) previously existing structures, runoff drained
in three directions. First, runoff from the east portion (sub-basin Ib) of the project site
drained into Meldrum Street and travelled north. Second, runoff from the south portion
(sub-basin 1c) of the subject site drained into West Laurel Street. From there, runoff
traveled east, via curb and gutter, and into an existing combination inlet. Excess runoff
from the central and northwest portion of the subject site (sub-basin Ia) currently
drains across the existing asphalt parking lot and into an existing outlet structure. This
structure outfalls to the storm drain system in the alleyway.The West Range Fort
Collins development aims to preserve these existing drainage patterns and will utilize
the historic outfall location.
3. Arthurs Ditch receives developed stormwater runoff from the subject site at two
locations. First, at an existing combination inlet located on the north side of West
Laurel Street (west of Meldrum Street). This inlet is connected to the ditch with a 10”
diameter metal pipe. In addition to local developed runoff from West Laurel Street, the
combination inlet received developed stormwater runoff from the Phase I developed
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 6
condition sub-basin Ic. Developed runoff, which is similar in peak rate, will drain to
this existing inlet from sub-basin C.
The proposed on-site quantity detention pond will outfall at 0.50 cfs (historic 2-year
release rate) into the existing public storm sewer system in the alleyway. This system
ultimately connects to the Arthurs Ditch. A more detailed description of the project’s
drainage patterns follows in Section IV, below.
4. The project site does not receive any notable runoff from off-site properties.
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 7
III. DRAINAGE DESIGN CRITERIA
A. There are no optional provisions outside of the FCSCM proposed with West Range Fort
Collins.
B. The overall stormwater management strategy employed with West Range Fort Collins
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. The first consideration taken in trying to
reduce the stormwater impacts of this development is the site selection itself. By choosing
an already developed site with public storm sewer currently in place, the burden is
significantly less than developing a vacant parcel absent of any infrastructure.
West Range Fort Collins aims to reduce runoff peaks, volumes and pollutant loads from
frequently occurring storm events (i.e., water quality (80th percentile) and 2-year storm
events) by implementing Low Impact Development (LID) strategies. Wherever practical,
runoff will be routed across landscaped areas or through a grass-lined swale and bio-
retention area. This LID practice reduces the overall amount of impervious area, while
Minimizing Directly Connected Impervious Areas (MDCIA) at the same time. The
combined LID/MDCIA techniques will be implemented, where practical, throughout the
development, thereby slowing runoff and increasing opportunities for infiltration.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release. The efforts taken in Step 1 will help to minimize excess runoff from
frequently occurring storm events; however, urban development of this intensity will still
have stormwater runoff leaving the site. The primary water quality will occur in a linear
bio-retention area along the northwest property line (sub-basin A). The bio-retention area
design will be more fully developed at Final Design.
Step 3 – Stabilize Drainageways. As stated in Section I.B.4, above, there are no major
drainageways in or near the subject site. While this step may not seem applicable to West
Range Fort Collins, the proposed project indirectly helps achieve stabilized drainageways
nonetheless. Once again, site selection has a positive effect on stream stabilization. By
repurposing an already developed, under-utilized site with existing stormwater
infrastructure, combined with LID and MDCIA strategies, 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. This step typically
applies to industrial and commercial developments.
C. Development Criteria Reference and Constraints
1. The subject property is not part of any Overall Development Plan drainage study or
similar “development/project” drainage master plan.
2. There are no known drainage studies for any adjacent properties that will have any
effect on West Range project. The Final Drainage and Erosion Control Report for the
Pi Kappa Alpha Fraternity Expansion (Shear Engineering, 1995) was referenced
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 8
during the preparation of this study. The contents of the report served as the basis for
developing our existing drainage conditions, existing pervious/impervious areas/
historic release rate and the existing detention pond volume that was associated with
the historic development.
3. The site plan will be constrained on two sides by public streets and by an alleyway on
the third. An existing and fully developed site constrains the site plan on the fourth. As
previously mentioned, the drainage outfall for Basin A is an existing manhole that ties
into an existing 12” RCP storm sewer in the alleyway. The proposed design matches
the existing historic release rate (i.e., 0.50 cfs).
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 West Range Fort Collins 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 Federal Aviation Administration (FAA) procedure has
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.
E. Hydraulic Criteria
1. The drainage facilities proposed with the West Range Fort Collins project are
designed in accordance with criteria outlined in the FCSCM and/or the Urban
Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria
Manual.
2. As stated in Section I.C.1, above, the subject property is not located in a
FEMA regulatory or a City of Fort Collins designated floodplain.
F. Floodplain Regulations Compliance
1. As previously mentioned, this project is not subject to any floodplain
regulations.
G. Modifications of Criteria
1. No modifications are requested at this time.
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 9
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objective of the West Range Fort Collins drainage design is to maintain
existing drainage patterns, while not adversely impacting adjacent properties.
2. No notable off-site runoff flows directly through 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 project site has been divided into three (3) drainage sub-basins, designated as
sub-basins A, B, and C. The drainage patterns anticipated for each basin are further
described below.
Sub-Basin A
Basin A encompasses a little over of one-half of the total project site area. It is
comprised of roof area, concrete walks and asphalt parking. A large part of the parking
area in this basin will comprise the on-site detention pond (Pond 1). D.P. A is situated
at the proposed outfall. A short section of pipe will connect to an existing manhole in
the alleyway. This basin releases at a 2-year historic rate of 0.50 cfs.
Sub-Basin B
Basin B encompasses the eastern third of the project site. It is comprised of roof area,
a concrete patio and landscaping. The downspouts will direct developed runoff from
the roof into the landscaping. The excess developed runoff will primarily drain into
Meldrum Street as sheet flow (i.e., non-concentrated). The developed flows in this
basin are similar to the existing (i.e., Phase I) condition. During the 2-year and 100-
year storm events, the proposed condition decreases runoff into Meldrum Street by
±0.08cfs and ±0.36cfs, respectively.
Sub-Basin C
Basin C is very similar in composition to Basin B. It is situated along the south portion
of the subject site. The excess developed runoff will primarily drain into West Laurel
Street as sheet flow. In West Laurel Street, the runoff drains into an existing
combination inlet which is connected to the Arthurs Ditch. During the 2-year and
100-year storm events, the proposed condition increases runoff into Meldrum Street
by ±0.08cfs and ±0.35cfs, respectively.
A full-size copy of the Drainage Exhibit (sheet C4.00) can be found in the Map Pocket
at the end of this report.
B. Specific Details
1. The FAA method was used to size the on-site pond for quantity detention. The
Phase I quantity detention volume (computed by Shear Engineering - 1995)
is 2756 ft3. This quantity storage volume calculation was based on the total
site area (i.e., 0.71 acre) and a historic release rate of 0.50 cfs. The pond was
originally designed as though the entire 0.71 acre site was tributary to it. Our
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 10
design approach and FAA method calculation included only sub-basin A. The
required 100-year quantity detention volume is 2957 cf. ft. To this, we added
the available Water Quality Capture Volume of 261 cu. ft. and arrived at a
total pond volume of 3218 cu. The corresponding 100-year Water Surface
Elevation (WSE) is 5001.40. The total ponding depth, at the lowest curb cut
is 1.07 feet. The approximate area for which the depth will exceed one foot is
17 sq. ft. The impact associated a ponding depth 0.07 foot greater than one
foot is negligible.
2. During Final Design, computations will be more fully developed for the proposed bio-
retention area in sub-basin A by utilizing the UDFCD’s UD-BMP Version 3.01 “Rain
Garden (RG)” Design Procedure Form. Preliminary calculations for this area, based on
the characteristics of sub-basin A, indicate a required volume of 461 cu. ft. The
maximum volume available is approximately 261 cu. ft. Site constraints, which
include a shallow storm drain outfall (4999.41) and a low adjacent parking lot
finished grade (5000.33), allow for a total ponding depth at the outlet of 11 inches. A
fully developed bio-retention section generally requires at least eighteen inches for just
the bio-retention soil media.
The proposed water quality area is designed to maximize available volume without
ponding water, during water quality events, in the parking area and releasing this
volume over 12-hours. The aforementioned constraints also eliminate the possibility
for installing an underdrain. The area will infiltrate nuisance flows and allow sediment
to settle during water quality rain events.
The Fort Collins Soil Mix will be used in the base of the water quality area. Tree
plantings within this area as well as those in close proximity are less of an issue
because an underdrain is not being proposed.
3. The detention storage information for Pond 1 is contained in Appendix B.4.
The drainage features associated with West Range Fort Collins project are
private facilities and located on private property.
4. As previously mentioned, the outfall for the West Range Fort Collins project is the
public storm sewer in the neighboring alleyway. This storm sewer flows northwest to
an existing area inlet before heading north towards Myrtle Street. As shown above in
Figure 3, this storm drain outfalls into the Arthurs Ditch due south of Myrtle Street.
There are no additional facilities or upgrades needed off-site in order to accommodate
the developed runoff from West Range Fort Collins.
5. The net effect of West Range on existing runoff rates is zero during the 2-, 10- and
100-year storm events (see below). Note that the Phase I flows used for comparison
were re-calculated using the current City of Fort Collins Intensity-Duration-Frequency
curve.
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 11
Design Point
Runoff Comparison (Proposed Condition vs. Phase I)
Q2 Q10 Q100
A | Ia 0.00 0.00 0.00
B | Ib -0.08 -0.14 -0.36
C | Ic 0.08 0.14 0.35
Net Change: 0.00 0.00 -0.01
Existing and Proposed Runoff Rate Comparison
In particular, there is no change in sub-basin A because the quantity detention release
rate will remain the same. The developed runoff in sub-basin B, which drains into
Meldrum Street, decreased. The runoff draining to Laurel Street will increase during
each of the storm events; however, the magnitude of the increase is negligible relative
to the size of each storm event.
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 12
V. CONCLUSIONS
A. Compliance with Standards
1. The design elements comply without variation.
2. The drainage design proposed with West Range Fort Collins complies with the City of
Fort Collins Master Drainage Plan for the Old Town Basin.
3. There are no regulatory floodplains associated with the West Range Fort Collins
development.
4. The drainage plan and stormwater management measures proposed with the West
Range Fort Collins student housing project 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 potential damage
associated with its stormwater runoff. West Range Fort Collins will detain for the
pervious area converted to impervious areas to release at the 2-year historic rate
during the 100-year storm.
2. The proposed West Range Fort Collins development will not impact the Master
Drainage Plan recommendations for the Old Town Basin.
West Range Fort Collins
Preliminary Drainage and Erosion Control Report 13
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. Final Drainage and Erosion Control Report for Pi Kappa Alpha Fraternity Expansion, October
1995, Shear Engineering Corporation (Project No. 1060-02-95).
3. 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.
4. Geotechnical Exploration Report, Pike Redevelopment, 406 West Laurel Street, Fort Collins,
Colorado, September 29, 2008, Soilogic, Inc. (Soilogic # 08-1051).
5. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
6. 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
West Range Fort Collins
CHARACTER OF SURFACE1:
Runoff
Coefficient
Percentage
Impervious Project: West Range
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: H. Feissner
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
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 0% .
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 0% .
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 2-year Cf = 1.00 10-year Cf = 1.00 100-year Cf = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Basin ID
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Gravel
(ac)
Area of
Roofs
(ac)
Soil Type and Average
Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
Ia 0.34 0.00 0.00 0.16 0.05 Clayey | Flat <2% 0.13 0.45 0.45 0.56 32%
Ib 0.24 0.00 0.02 0.00 0.05 Clayey | Flat <2% 0.17 0.42 0.42 0.52 26%
Ic 0.13 0.00 0.01 0.00 0.03 Clayey | Flat <2% 0.09 0.43 0.43 0.54 28%
Irowb 0.34 0.26 0.02 0.00 0.00 Clayey | Flat <2% 0.06 0.82 0.82 1.00 82%
Irowc 0.13 0.08 0.02 0.00 0.00 Clayey | Flat <2% 0.03 0.78 0.78 0.97 75%
West Range Fort Collins
Overland Flow, Time of Concentration:
Project: West Range
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = T
i + 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,
V
West Range Fort Collins
Rational Method Equation: Project: West Range
Calculations By:
Date:
Rainfall Intensity:
Ia Ia 0.34 5 5 5 0.45 0.45 0.56 3.29 5.64 9.30 0.51 0.87 1.78 To on-site detention pond
Ib Ib 0.24 5 5 5 0.42 0.42 0.52 3.29 5.64 9.30 0.33 0.57 1.17 To Meldrum Street
Ic Ic 0.13 5 5 5 0.43 0.43 0.54 3.29 5.64 9.30 0.18 0.32 0.65 To West Laurel Street
Irowb Irowb 0.34 5 5 5 0.82 0.82 1.00 3.29 5.64 9.30 0.91 1.57 3.16 Meldrum Street
Irowc Irowc 0.13 5 5 5 0.78 0.78 0.97 3.29 5.64 9.30 0.33 0.57 1.17 West Laurel Street
C100 Notes
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
EXISTING CONDITIONS RUNOFF COMPUTATIONS
H. Feissner
October 24, 2012
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
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
10/24/201212:25 PM D:\Projects\875-001\Drainage\Hydrology\875-001_Historic_Rational_Calcs\Runoff_Exist_OLD idf
West Range Fort Collins
CHARACTER OF SURFACE1:
Runoff
Coefficient
Percentage
Impervious Project: West Range
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: H. Feissner
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 100% . Date:
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 90% .
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 40% .
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 22%
Lawns and Landscaping
Sandy Soil
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 0% .
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 0% .
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 2-year Cf = 1.00 10-year Cf = 1.00 100-year Cf = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Basin ID
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Gravel
(ac)
Area of
Roofs
(ac)
Soil Type and Average
Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
Ia 0.340 0.16 0.00 0.00 0.050 Clayey | Flat <2% 0.13 0.66 0.66 0.83 60%
Ib 0.240 0.00 0.02 0.00 0.050 Clayey | Flat <2% 0.17 0.42 0.42 0.52 26%
Ic 0.130 0.00 0.01 0.00 0.030 Clayey | Flat <2% 0.09 0.43 0.43 0.54 28%
Irowb 0.340 0.26 0.02 0.00 0.000 Clayey | Flat <2% 0.06 0.82 0.82 1.00 82%
Irowc 0.130 0.08 0.02 0.00 0.000 Clayey | Flat <2% 0.03 0.78 0.78 0.97 75%
West Range Fort Collins
Overland Flow, Time of Concentration:
Project: West Range
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
West Range Fort Collins
Rational Method Equation: Project: West Range
Calculations By:
Date:
Rainfall Intensity:
Ia Ia 0.34 5 5 5 0.66 0.66 0.83 3.29 5.64 9.30 0.74 1.27 2.62 Modified w/Phase I
Ib Ib 0.24 5 5 5 0.42 0.42 0.52 3.29 5.64 9.30 0.33 0.57 1.17 No change w/Phase I
Ic Ic 0.13 5 5 5 0.43 0.43 0.54 3.29 5.64 9.30 0.18 0.32 0.65 No change w/Phase I
Irowb Irowb 0.34 5 5 5 0.82 0.82 1.00 3.29 5.64 9.30 0.91 1.57 3.16 No change w/Phase I
Irowc Irowc 0.13 5 5 5 0.78 0.78 0.97 3.29 5.64 9.30 0.33 0.57 1.17 No change w/Phase I
* Pond Release Rates for each basin include the 100-year flow rate from the historic impervious area plus the 2-year release rate from the historic pervious area.
Notes
PHASE I 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)
H. Feissner
October 24, 2012
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
Q C f C i A
10/24/201212:25 PM D:\Projects\875-001\Drainage\Hydrology\875-001_Historic_Rational_Calcs\Runoff_Phase I_OLD idf
West Range Fort Collins
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: West Range
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: H. Feissner
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 100% . Date: December 12, 2012
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 90% .
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 40% .
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 22%
Lawns and Landscaping
Sandy Soil
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 0% .
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 0% .
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 2-year Cf
= 1.00 10-year Cf = 1.00 100-year C
f = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Basin ID
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Gravel
(ac)
Area of
Roofs
(ac)
Soil Type and Average
Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
Basin A 0.46 0.12 0.08 0.00 0.20 Clayey | Average 2% to 7% 0.05 0.87 0.87 1.00 83%
West Range Fort Collins
Overland Flow, Time of Concentration:
Project: West Range
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
West Range Fort Collins
Rational Method Equation: Project: West Range
Calculations By:
Date:
Rainfall Intensity:
A Basin A 0.46 5 5 5 0.87 0.87 1.00 2.85 4.87 9.95 1.14 1.94 4.54
B Basin B 0.13 5 5 5 0.56 0.56 0.71 2.85 4.87 9.95 0.20 0.35 0.89
C Basin C 0.12 5 5 5 0.68 0.68 0.85 2.85 4.87 9.95 0.24 0.41 1.05
PROPOSED 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)
H. Feissner
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
December 12, 2012
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
Intensity,
i10
(in/hr)
Q C f C i A
12/12/201211:30 AM D:\Projects\875-001\Drainage\Hydrology\875-001_Proposed_Rational_Calcs\Runoff
West Range Fort Collins
Project: West Range Fort Collins
Project Site Area 30927.6 Calculations By:
Ia 14810.40 Date:
Ib 10454.40
Ic 5662.80
A 19886.42
B 5516.79
C 5394.34
Basin Area, sq. ft. Surface Description % Impervious Area, sq. ft. Notes
Ia 6969.6 Asphalt 100% 6970
Ia 2178.0 Roofs 90% 1960
Impervious Area 8930
% Impervious 60%
Ib 871.2 Concrete (e.g., walks & parking) 90% 784
Ib 2178.0 Concrete (e.g., walks & parking) 90% 1960
Impervious Area 2744
% Impervious 26%
Ic 435.6 Concrete (e.g., walks & parking) 90% 392
Ic 1306.8 Pavers (e.g., wood deck) 22% 287
Impervious Area 680
%Impervious 12%
Total Impervious Area 12354
% Impervious 40%
Basin Area, sq. ft. Surface Description % Impervious Area, sq. ft. Notes
A 5272.39 Asphalt 100% 5272
SUMMARY OF EXISTING AND PROPOSED IMPERVIOUS AREA
Areas, sq. ft.
H. Feissner
December 12, 2012
EXISTING CONDITION
PROPOSED CONDITION
12/12/2012 12:09 PM
A 5272.39 Asphalt 100% 5272
A 3665.45 Concrete 90% 3299
A 8801.00 Roofs 90% 7921
Impervious Area 16492
% Impervious 83%
B 189.76 Asphalt 100% 190
B 723.44 Concrete 90% 651
B 1568.02 Roofs 90% 1411
Impervious Area 2252
% Impervious 42%
C 0 Asphalt 100% 0
C 954.97 Concrete 90% 859
C 2354.16 Roofs 90% 2119
Impervious Area 2978
% Impervious 55%
Impervious Area 21722
% Impervious 70%
Area, sq. ft. Area, acre
Total Impervious Area Increase 9369 0.215
SUMMARY
12/12/2012 12:09 PM
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers (reserved for future use)
B.2 – Street Flow (reserved for future use)
B.3 – Inlets (reserved for future use)
B.4 – Detention Facilities
APPENDIX B.1
STORM SEWERS (reserved for future use)
APPENDIX B.2
STREET FLOW (reserved for future use)
APPENDIX B.3
INLETS (reserved for future use)
APPENDIX B.4
DETENTION FACILITIES
West Range Fort Collins
Detention Pond Calculation | FAA Method
Project Number: West Range Fort Collins
Calculations By: H. Feissner Date: 12/12/2012
Project Number: West Range Fort Collins
Project Location: Fort Collins, Colorado
H. Feissner Date: 12/12/2012
Pond No.: Pond A
Calculations By:
A
Input Variables Results
Design Point A
100-yr
Design Point
Design Storm Required Detention Volume
1.00 WQCV 0 ft2
Area (A)= 0.46 acres 2957 ft3
Developed "C" =
Area (A)= 0.46 acres 2957 ft
Max Release Rate = 0.50 cfs 0.0679 ac-ft
Ft.Collins
Q
Inflow
Outflow
Storage
Time Time 100-yr
Intensity
Q100
(Runoff)
Volume
Outflow
(Release) Volume
Detention
Intensity Volume Volume
(mins) (secs) (in/hr) (cfs) (ft
3
) (ft
3
) (ft
3
)
5 300 9.95 4.6 1373 150 1223
10 600 7.72 3.6 2131 300 1831
15 900 6.52 3.0 2699 450 2249
20 1200 5.60 2.6 3091 600 2491
25 1500 4.98 2.3 3436 750 2686
30 1800 4.52 2.1 3743 900 2843
35 2100 4.08 1.9 3941 1050 2891
40 2400 3.74 1.7 4129 1200 2929
45 2700 3.46 1.6 4297 1350 2947
50 3000 3.23 1.5 4457 1500 2957
55 3300 3.03 1.4 4600 1650 2950
60 3600 2.86 1.3 4736 1800 2936
65 3900 2.72 1.3 4880 1950 2930
12/12/2012 11:37 AM D:\Projects\875-001\Drainage\Detention\875-001__Detention Pond.xlsm\FAA_Current idf
West Range Fort Collins
875-001
Stage - Storage Calculation
Project Number: 875-001
Fort Collins, Colorado
H. Feissner Date: 12/12/2012
Project Number:
Project Location:
Calculations By: H. Feissner Date: 12/12/2012
Pond No.: Pond A
Calculations By:
Design Point A
Required Volume Water Surface Elevation (WSE)
A
WQCV
261 ft3 5000.33 ft.
Design Point
Design Storm
Require Volume= 261 ft3 5000.33 ft.
Design Storm 100-yr
ft3 5001.40 ft.
Require Volume=
Required Volume= 3218 ft3 5001.40 ft.
Contour
Elevation (Y-
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
Area Avg. End Avg. End Conic
values)
ft3 ft ft. ft3 ft ft3 ft ft3 ft ft3 ft
4,999.60 93 0.00 0 0 0 0
4,999.80 254 0.20 35 35 33 33
5,000.00 400 0.20 65 100 65 98
5,000.20 486 0.20 89 189 88 187
5,000.40 560 0.20 105 293 104 291
5,000.60 1063 0.20 162 456 160 451
5,000.80 1996 0.20 306 761 301 752
5,001.00 3355 0.20 535 1297 529 1281
5,001.20 4924 0.20 828 2124 823 2104
5,001.40 6504 0.20 1143 3267 1139 3243
5,001.60 8071 0.20 1457 4725 1455 4698
5,002.00
5,001.50
5,001.00
Contour Elevation
5,000.50
Contour Elevation
5,000.50
Contour Elevation
5,000.00
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
West Range Fort Collins
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 83.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.830
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.28 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 19,886 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 461 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 0.0 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 = 11 in
Design Procedure Form: Rain Garden (RG)
H. Feissner
Northern Engineering
December 12, 2012
West Range Fort Collins
Fort Collins, Colorado
A) WQCV Depth (12-inch maximum) DWQCV = 11 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 0.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 308 sq ft
D) Actual Flat Surface Area AActual = 90 sq ft ACTUAL FLAT AREA < MINIMUM FLAT AREA
E) Area at Design Depth (Top Surface Area) ATop = 520 sq ft
F) Rain Garden Total Volume VT= 280 cu ft TOTAL VOLUME < DESIGN VOLUME
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
Fort Collins Soil Mix
60% Sand (ASTM C-33), 25% Topsoil and 15% Shredded Mulch
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 = N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
875-001_UD-BMP_v3_01, RG 12/12/2012, 12:26 PM
West Range Fort Collins
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?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
December 12, 2012
West Range Fort Collins
Fort Collins, Colorado
Design Procedure Form: Rain Garden (RG)
H. Feissner
Northern Engineering
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
Notes:
875-001_UD-BMP_v3_01, RG 12/12/2012, 12:26 PM
APPENDIX D
OPERATIONS AND MAINTENANCE GUIDELINES FOR RAIN GARDENS(reserved for future use)
APPENDIX E
EROSION CONTROL REPORT
West Range Fort Collins
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 Best Management Practices (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 Sheet C.?? of the Utility Plans. The Final Plans
will contain a full-size Erosion Controlsheet 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 West Range
Fort Collins. 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.
West Range Fort Collins
Preliminary Erosion Control Report
MAP POCKET
C4.00 – DRAINAGE EXHIBIT
X
D
D
VAULT
ELEC
acres
A
0.87 0.46
1.00
acres
B
0.56 0.13
0.71
acres
C
0.68 0.12
0.85
B
C
ROOF
ROOF
ROOF
ROOF
ROOF
ROOF
ROOF
ROOF
ROOF
ROOF
ROOF
W. LAUREL STREET
S. MELDRUM STREET
PROPOSED
MULTIFAMILY
BUILDING
LOT 1
BLOCK 1
A
POND A
No. Revisions:
By: Date:
REVIEWED BY:
N. Haws
DESIGNED BY:
DRAWN BY:
SCALE:
DATE:
12.12.12
PROJECT:
875-001
Sheet
Of 6 Sheets
WEST RANGE FORT COLLINS
T���� �������� ���
����������� �� �������
�������� �� N�������
E���������� S�������, I��.
��� ��� ��� �� �� ���� ���
��� ���� �� ������������
������ ������ ��� ������ ��
� P����������� E������� ��
��� ������ �� N�������
E���������� S�������, I��.
NOT FOR CONSTRUCTION
REVIEW SET
10.24.12
200 S���� C������ A�����, S���� 010
F��� C������, C������� 80524
E N G I N E E R I N G
� � � � � � ��
PHONE: 970.221.4158 FAX: 970.221.4159
���.�������������������.���
C4.00
DRAINAGE EXHIBIT
NORTH
( IN FEET )
1 inch = ft.
20 0 20 Feet
20
40 60
GRAPHIC SCALE:
K��� ����'� �����.
C��� ������ ��� ���.
R
BENCHMARK/BASIS OF BEARING
BENCHMARK #1:
City of Fort Collins Benchmark 6-00
Located on a catch basin at the northwest corner of Mulberry Street
and College Avenue.
Elevation = 4990.68 (NGVD 29 - Unadjusted)
BENCHMARK #2:
City of Fort Collins Benchmark CSU 2
Standard brass Larimer County Geodetic Control Disk set in 2002,
located in the campus of Colorado State University approximately
240.8 feet south from the center line of North Drive, 46.6 feet northeast
from the edge of the CSU Lagoon, 33 feet southwest from the center of
the delivery road to the University Club and 1.1 feet southwest from the
edge of the sidewalk.
Elevation = 5003.12 (NGVD 29 - Unadjusted)
Basis of Bearings
Considering the East line of Lot 8, Block 87, City of Fort Collins and its
southerly extension as bearing South 00�21'57' West (assumed
bearing).
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 ac
PROPOSED 100-YEAR WATER SURFACE ELEVATION
NOTES:
1.REFER TO THE "PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FOR WEST RANGE FORT COLLINS" BY NORTHERN ENGINEERING, DATED
{OCTOBER 24, 2012} FOR ADDITIONAL INFORMATION.{
}
PROPOSED BIO-RETENTION
Contour Elevation
5,000.00
4,999.50
0 500 1000 1500 2000 2500 3000 3500 4000 4500
Cummulative Volume, cu. ft.
12/12/201211:36 AM D:\Projects\875-001\Drainage\Detention\875-001__Detention Pond.xlsm\Stage_Storage_2nd PDP
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
A Basin A No 0.87 0.87 1.00 1 2.00% 0.3 0.3 0.1 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
B Basin B No 0.56 0.56 0.71 1 2.00% 0.8 0.8 0.6 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
C Basin C No 0.68 0.68 0.85 1 2.00% 0.6 0.6 0.4 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
PROPOSED TIME OF CONCENTRATION COMPUTATIONS
H. Feissner
December 12, 2012
Design
Point
Basin
Overland Flow Gutter Flow Swale Flow Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
12/12/201211:29 AM D:\Projects\875-001\Drainage\Hydrology\875-001_Proposed_Rational_Calcs\Tc
Basin B 0.13 0.00 0.02 0.00 0.04 Clayey | Average 2% to 7% 0.07 0.56 0.56 0.71 41%
Basin C 0.12 0.00 0.02 0.00 0.05 Clayey | Average 2% to 7% 0.05 0.68 0.68 0.85 55%
TOTAL (Site ONLY ) 0.71 0.13 0.12 0.00 0.29 Clayey | Average 2% to 7% 0.17 0.78 0.78 0.98 71%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Composite Runoff Coefficient with Adjustment
12/12/201211:29 AM D:\Projects\875-001\Drainage\Hydrology\875-001_Proposed_Rational_Calcs\Composite Runoff Coeff
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Ia Ia No 0.66 0.66 0.83 1 2.00% 0.6 0.6 0.4 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Ib Ib No 0.42 0.42 0.52 1 2.00% 1.0 1.0 0.9 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Ic Ic No 0.43 0.43 0.54 1 2.00% 1.0 1.0 0.8 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Irowb Irowb No 0.82 0.82 1.00 1 2.00% 0.4 0.4 0.1 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Irowc Irowc No 0.78 0.78 0.97 1 2.00% 0.5 0.5 0.2 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
PHASE I TIME OF CONCENTRATION COMPUTATIONS
H. Feissner
October 24, 2012
Design
Point
Basin
Overland Flow Gutter Flow Swale Flow Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
10/24/201212:25 PM D:\Projects\875-001\Drainage\Hydrology\875-001_Historic_Rational_Calcs\Tc_Phase 1
TOTAL (Site ONLY ) 0.710 0.16 0.03 0.00 0.130 Clayey | Flat <2% 0.39 0.54 0.54 0.67 43%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
PHASE I COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
October 24, 2012
Composite Runoff Coefficient with Adjustment
10/24/201212:25 PM D:\Projects\875-001\Drainage\Hydrology\875-001_Historic_Rational_Calcs\Composite Runoff Coeff_Phase I
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Ia Ia No 0.45 0.45 0.56 1 2.00% 1.0 1.0 0.8 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Ib Ib No 0.42 0.42 0.52 1 2.00% 1.0 1.0 0.9 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Ic Ic No 0.43 0.43 0.54 1 2.00% 1.0 1.0 0.8 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Irowb Irowb No 0.82 0.82 1.00 1 2.00% 0.4 0.4 0.1 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
Irowc Irowc No 0.78 0.78 0.97 1 2.00% 0.5 0.5 0.2 1 0.50% 1.41 0.0 1 0.50% 1.06 0.0 5 5 5
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
EXISTING CONDITIONS TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
H. Feissner
October 24, 2012
Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
10/24/201212:25 PM D:\Projects\875-001\Drainage\Hydrology\875-001_Historic_Rational_Calcs\Tc_Exist
TOTAL (Site ONLY ) 0.71 0.00 0.03 0.16 0.13 Clayey | Flat <2% 0.39 0.44 0.44 0.55 29%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
EXISTING CONDITIONS COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
October 24, 2012
Composite Runoff Coefficient with Adjustment
10/24/201212:25 PM D:\Projects\875-001\Drainage\Hydrology\875-001_Historic_Rational_Calcs\Composite Runoff Coeff_Exist