HomeMy WebLinkAboutPLATTE RIVER POWER AUTHORITY CAMPUS - FDP - FDP180004 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1501 Academy Ct. Ste. 203 Fort Collins, Colorado 80524 (970) 530-4044
Final Drainage Report
Platte River Power Authority HQ
Campus
Fort Collins, CO
Prepared for:
Platte River Power Authority
2000 East Horsetooth Road
Fort Collins, CO 80525
February 14, 2018
Drainage Report
Platte River Power Authority HQ Campus
Fort Collins, CO
i U16014-DrainageReport-Final.doc
February 14, 2018
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Platte River Power Authority HQ Campus
Fort Collins, Colorado
Project Number: U16014
Dear Staff:
United Civil Design Group, LLC. is pleased to submit this Final Drainage Report for the Platte
River Power Authority Headquarters Campus site in Fort Collins, Colorado. In general, this
report serves to document the stormwater impacts associated with the proposed
redevelopment of the existing campus.
We understand that review by the City of Fort Collins is to assure general compliance with
standardized criteria contained in the Fort Collins Stormwater Criteria Manual (FCSCM). This
report was prepared in compliance with technical criteria set forth in both the Urban Drainage
and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual and the Fort Collins
Stormwater Criteria Manual.
If you should have any questions or comments as you review this report, please feel free to
contact us at your convenience.
Sincerely,
United Civil Design Group
Kevin Brazelton, PE
Engineering Manager
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TABLE OF CONTENTS
PAGE
I. General Location and Description ........................................................................................... 1
A. Location ............................................................................................................................ 1
B. Description of Property ................................................................................................... 1
C. Description of Development............................................................................................ 2
II. Drainage Basins and Sub-Basins .............................................................................................. 3
A. Major Basin Description .................................................................................................. 3
B. Sub-Basin Description ...................................................................................................... 3
III. Drainage Design Criteria ......................................................................................................... 3
A. Regulations ...................................................................................................................... 3
B. Directly Connected Impervious Area (DCIA) ................................................................... 3
C. Development Criteria Reference and Constraints .......................................................... 4
D. Hydrological Criteria ........................................................................................................ 5
E. Hydraulic Criteria ............................................................................................................. 6
F. Floodplain Regulations .................................................................................................... 6
G. Modifications of Criteria .................................................................................................. 6
IV. Drainage Facility Design .......................................................................................................... 6
A. General Concept .............................................................................................................. 6
B. Specific Details ................................................................................................................. 9
V. Sediment/Erosion Control ..................................................................................................... 16
VI. Conclusions ........................................................................................................................... 16
A. Compliance with Standards ........................................................................................... 16
B. Drainage Concept .......................................................................................................... 16
C. Stormwater Quality ....................................................................................................... 16
VII. References ......................................................................................................................... 17
APPENDICES
APPENDIX A – Hydrology Computations
APPENDIX B – Detention and Water Quality Calculations
APPENDIX C – Hydraulic Computations
C.1 – Storm Pipe Calculations
C.2 – Inlet Sizing Calculations
C.3 – Swale Calculations
APPENDIX D – Referenced Materials
APPENDIX E – Drainage Exhibits
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VICINITY MAP
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I. General Location and Description
A. Location
The Platte River Power Authority Headquarters Campus (referred herein as ”the
site” or “the Campus”) is a parcel of land situated in the Southeast Quarter of
Section 30, Township 7 North, Range 68 West of the 6th
Principal Meridian to
the City of Fort Collins, Larimer County, Colorado. More specifically, the site is
located at the northwest corner of Horsetooth Road and Timberline Road and is
bounded by East Horsetooth Road to the south, Timberline Road to the east,
existing commercial property and Danfield Court to the north, and Union Pacific
Railroad right-of-way to the west.
B. Description of Property
The campus has an existing platted area of 16.7-acres and has acted as the
headquarters for Platte River Power Authority since it was first constructed in
the late 1970s.
The following is a summary of the existing conditions:
Ground Cover - The site currently exists as commercial property and is
currently covered with various buildings, pavements and open areas.
Grades – The majority of the site slopes towards one of three (3) drainage
outfalls. In general, the slopes within each outfall basin range between 0 to
5 percent, with some landscaped berm areas reaching near 20%.
Soil Type - According to the United States Department of Agriculture (USDA)
Natural Resources Conservation Service (NRCS) Soil Survey, the site consists
of Nunn clay loam (Hydrologic Soil Group C).
Utilities – The campus includes an extensive network of existing utilities
including mains and services for water, sanitary sewer, natural gas, electric,
telephone and data lines. These mains and services are located within the
property limits of the campus along with mains located within the rights-of-
ways for Horsetooth Road, Timberline Road and Danfield Court.
Detention Ponds and Storm Sewer – The campus currently has three (3)
drainage outfalls available to accept stormwater flows from the site. These
include the existing wet pond which currently acts as an irrigation and
stormwater retention facility for the campus, an existing 12-inch storm
sewer located at the east side of the campus along Timberline Road, and the
curb and gutter at the Danfield Court cul-de-sac. There are also two (2)
other internal detention areas that drain to the 12-inch storm sewer outfall.
The campus also has limited internal storm drains varying in size from 4-inch
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to 15-inch. Of note, there is an existing storm inlet and drain located on the
north side of Horsetooth Road that collects stormwater from the roadway
and conveys it into the existing wet pond on the south side of the property.
This existing system will be required to be maintained and/or replaced with
the construction of the proposed project.
Drainageways – No known externally owned drainageways currently exist
within the proposed development limits.
Irrigation - City records indicate that there is an existing irrigation pipe
located along the southern property boundary, running from west to east.
Only portions of this irrigation system have been found or identified with
utility locates or site survey but from the information available it is believed
that this system consists of a 20-inch concrete pipe that is located just north
of the existing curb and gutter along Horsetooth Road. The existing onsite
wet Pond A1 also serves as an irrigation system and is supplied by an existing
irrigation well located on the campus.
Floodplains – The campus is not located within either a City or FEMA
floodplain.
C. Description of Development
The planned campus redevelopment is planned to be constructed in phases.
Ultimately, the campus redevelopment will consist of the following
improvements:
• The demolition of most of the existing buildings and much of the existing
pavements throughout the campus.
• The construction of seven (7) proposed commercial buildings including
the main headquarters building and various other support buildings.
• The construction of an internal roadway network with associated parking
areas.
• The construction of utilities in support of the campus including sanitary,
water and storm drainage.
• The construction of detention and water quality facilities located
throughout the site with the main detention area located in the
northeast portion of the site.
• The reconfiguration and relining of the existing wet pond.
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II. Drainage Basins and Sub-Basins
A. Major Basin Description
The site is located within the Foothills drainage basin within the City of Fort
Collins Master Drainage Plan. Stormwater from this basin adjacent to the site is
collected within streets and storm sewer systems and ultimately discharged into
the Fossil Creek Reservoir Inlet Ditch.
B. Sub-Basin Description
Historically, the property has been utilized as the main headquarters for Platte
River Power Authority. The campus has grown over the decades but is currently
largely developed containing a variety of existing buildings, utility infrastructure
systems and open spaces. Stormwater from the campus is collected in one of
three (3) basins that either convey water after detention to public infrastructure
or retain the stormwater onsite. The proposed project will maintain the historic
drainage patterns to the extent feasible, but will eliminate the stormwater
retention aspect of the site and reroute that stormwater to the main detention
facility to be provided on the site.
III. Drainage Design Criteria
A. Regulations
The design criteria for this study are directly from the City of Fort Collins Storm
Drainage Design Criteria and Construction Standards Manual and the Urban
Storm Drainage Criteria Manuals Volumes 2, and 3 (referred to herein as
USDCM).
B. Directly Connected Impervious Area (DCIA)
With the adoption of the USDCM, the City has also adopted the “Four Step
Process” that is recommended in Volume 3 of the USDCM in selecting structural
BMPs for the redeveloping urban areas. The following portions of this summary
describe each step and how it has been utilized for this project:
Step 1 – Employ Runoff Reduction Practices
The objective of this step is to reduce runoff peaks and volumes and to employ
the technique of “minimizing directly connected impervious areas” (MDCIA).
This project accomplishes this by:
• Routing the roof and pavement flows through bioswales, underground
detention treatment/infiltration facilities and vegetated swales to increase
time of concentration, promote infiltration and provide water quality.
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Step 2 – Provide Water Quality Capture Volume (WQCV)
The objective of providing WQCV is to reduce the sediment load and other
pollutants that exit the site. For this project WQCV is provided within
underground treatment facilities and a campus water quality pond.
Step 3 – Stabilize Drainageways
The site is not adjacent or near a major drainageway; however, this project will
pay stormwater development and stormwater utility fees which the City uses, in
part, to maintain the stability of the City drainageway systems.
Step 4 – Consider Need for Site Specific and Source Control BMPs
Site specific and source control BMPs are generally considered for large
industrial and commercial sites. The redevelopment of the existing campus will
include multiple site specific and source controls, including:
• Covered storage areas for vehicles and materials
• A warehouse for materials storage
• A vehicular maintenance building with appropriate internal waste collection
systems
• Dedicated maintenance personnel providing landscape maintenance and
snow and ice management
C. Development Criteria Reference and Constraints
The campus has most recently been included within the Drainage Study entitled,
“Platte River Power Authority Maintenance Facility”, prepared by RBD
Engineering Consultants Inc., and dated March 1984. With the proposed
complete redevelopment of the site and the age of the previous studies, this
report relies very little on previous drainage information and studies prepared
for the site.
Four (4) drainage constraints for the campus have been identified and include
the following:
Existing Storm Outfall
The existing 12-inch storm sewer outfall for the site conveys stormwater north
down Timberline Road. Utilizing invert and hydraulic grade line information
provided within the construction plans entitled, “Collindale Industrial Park Storm
Sewer Extension”, prepared by Meline & Irelan Consulting Engineers and dated
February 1995, the existing system has been analyzed to determine the
maximum allowable release rate from the campus to this existing 12-inch
outfall. Refer to Appendix C for the hydraulic analysis of the existing storm drain
and Appendix D for the information used to create the hydraulic model.
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Utilizing the mentioned information, it was determined that the release rate
from the main detention area will be limited to 3.15 cfs.
Danfield Court Outfall
Storm sewer does not exist at the west end of Danfield Court; therefore, any
drainage outfall at the north property line will be required to tie into the curb
and gutter of the street or construct offsite storm sewer. The current design
does not include offsite storm sewer and the elevation of the existing curb and
gutter in relation to site grades limits the feasibility of providing a significant
amount of detention or water quality. To limit the impact of these constraints,
the design proposes to maintain the existing parking lot with its’ current parking
lot detention system. Per information provided by City personnel, maintaining
the existing parking lot and detention system will be acceptable with the
condition that no new impervious area is added to this existing outfall and only
minor improvements are made to the existing parking area.
Horsetooth Road Drainage
Approximately 1-acre of Horsetooth Road drains to an existing inlet located
immediately west of the south entrance to the existing site. Drainage collected
via the existing inlet is conveyed to the existing wet pond and retained onsite.
The proposed design will alter the design of this existing system but will be
required to collect, treat, and convey the Horsetooth Road runoff through the
proposed redeveloped campus.
Existing Offsite Storm Sewer
The existing property north of the main campus (formerly the “LSI property”)
has existing storm sewer along the west and south perimeters of that property.
Documentation of the design of these storm sewers is not available; therefore, it
has been assumed that the offsite system has only been designed for the
existing property and impervious areas that currently drain to the existing storm
inlets. The proposed design will be required to limit the area draining to the
offsite storm sewer system and ensure that existing flowrates to the system are
not exceeded. In addition, Platte River Power Authority and the offsite
property owner are preparing an agreement to allow Platte River Power
Authority property that has historically flowed to this offsite storm sewer to
continue to do so.
D. Hydrological Criteria
In accordance with the Fort Collins policy, a minor and major storm for the Fort
Collins area is identified as the 2-year and 100-year storms, respectively. A
major storm for the Fort Collins area has a recurrence interval of 100 years and
has a peak intensity of 9.95 in/hr.
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These storms have been used as a basis for planning and system design. The
peak flow rates for design points have been calculated based on the Rational
Method as described in the USDCM with storm duration set equal to the time of
concentration for each sub-basin. This method was used to analyze the
developed runoff from the 2-year (minor) and the 100-year (major) storm
events. The Rational Method is widely accepted for drainage design involving
small drainage areas (less than 160 acres) and short time of concentrations. The
Rational Method is ideal for storm sewer sizing and small detention pond sizing
(for tributary areas no larger than 90 to 160 acres). Runoff coefficients were
assumed based on impervious area and soil type and are given in Appendices.
E. Hydraulic Criteria
The redeveloped campus will convey runoff to the proposed pond(s) via swales,
gutters, concrete pans, and pipes. The FCSCM and USDCM were referenced for
all hydraulic calculations. In addition, the following computer programs were
utilized:
• Hydraflow Storm Sewers Extension for AutoCAD Civil 3D
• Hydraflow Express Extension for AutoCAD Civil3D
• UD-Inlet by UDFCD
F. Floodplain Regulations
The campus is not located within either a City or FEMA floodplain.
G. Modifications of Criteria
The drive lane that extends south onto the property from Danfield Court is being
regraded with this project. As such, water quality treatment is typically
required. Due to the small area and the unchanging imperviousness of the area,
the project has requested a variance to criteria to allow the continued drainage
in its’ current configuration without water quality treatment.
IV. Drainage Facility Design
A. General Concept
The project includes the redevelopment of a vast majority of the existing
campus including the headquarters (HQ) building, support buildings and
supporting roadway, parking and utility infrastructure. In general, the site is
being graded to maintain existing drainage patterns, where feasible, and will
collect stormwater runoff via swales, pans and storm sewer and direct them to
the proposed detention and water quality pond located at the east side of the
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site. The pond will discharge to the existing 12-inch storm sewer located along
the west edge of Timberline Road.
All referenced tables, charts, formulas, etc. are included in the Appendices. The
area, time of concentration, and runoff of each proposed sub-basin is
summarized in Appendix A. The project site was divided into multiple
developed sub-basins as explained further below:
Basin A
Basin A consists of Basins A1-A13 which are designed to be collected via a
series of swales, pans and storm drains that will discharge to the proposed
detention Pond A1 at the east side of the property. Basin A will contain the
majority of the proposed improvements and will ultimately consist of
rooftop, sidewalk, roadway, and landscaped areas. Specifics to each sub-
basin within Basin A include the following:
Basin A1 consists of approximately 3.5 acres and includes the proposed
detention Pond A1 and portions of the proposed paving improvements
around the HQ building. Approximately 8,500 square feet (sf) of future
building is also included within the hydrology and detention Pond A1
calculations. A pond outlet and emergency overflow are provided at the
northeast end of the pond that are directed towards Timberline Road. Refer
to Appendix A for additional information.
Basins A2-A5 consist of approximately 2.3 acres and includes a portion of the
proposed HQ and the employee parking areas for the project north of HQ.
These basins are collected with proposed storm sewer and conveyed to the
proposed detention pond in Basin A1.
Basins A6-A11 consist of approximately 3.0 acres and includes the
maintenance yard facility north of HQ and the employee parking areas.
These basins are collected with proposed storm sewer and conveyed to the
proposed detention pond in Basin A1.
Basin A12 consists of approximately 1.5 acres and includes minimal
proposed improvements with this project. The area is planned for future
expansion of an unknown type. For storm sewer calculations the basin has
been assumed to have a percent imperviousness of 90%. Due to the
unknown nature of the future improvements, Basin A12 will be required to
provide detention, water quality and LID improvements either within Basin
A12 or within Basin A1 with the future improvements. Refer to Appendix A
for additional information.
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Basin A13 consists of approximately 0.25 acres and includes the southern
portion of the HQ building. The basin will be collected with a proposed roof
drain system and conveyed to the detention pond in Basin A1.
Basin B
Basin B includes Basins B1-B2 which consist of approximately 1.9 acres south
of HQ and will include the proposed visitor parking area and landscaping.
The basins are designed to be collected via a bioswale and storm drain that
will discharge to the proposed detention pond in Basin A1. Approximately
10,000 (sf) of future paving is also included within the hydrology and
detention Pond C1 calculations to accommodate for future visitor parking on
the west end of Basin B2. Refer to Appendix A for additional information.
Basin C
Basin C includes Basin C1 which consists of approximately 1.2 acres south HQ
and primarily includes the proposed wet Pond C1 and landscaping.
Detention will be provided for Basin C1 over the permanent water surface of
the proposed wet pond. A pond outlet and emergency overflow are
provided at the east end of the pond that are directed towards Basin A1.
Offsite Basins
The site includes five (5) existing offsite basins that are being maintained
with the proposed redevelopment. Specifics to each offsite basin include
the following:
Basin OS1 consists of approximately 0.7 acres of onsite property that drains
offsite towards the north and east ultimately draining to Timberline Road.
The area of this basin has increased from historic conditions but due to the
removal of pavement area within the basin the percent-imperviousness has
been reduced. Ultimately, the runoff generated from this basin has
increased slightly with the proposed conditions (approximately 0.5 cfs in the
100-year event); however, the additional flow is not anticipated to
negatively impact the street capacity of Timberline Road or downstream
infrastructure.
Basin OS2 consists of approximately 1.2 acres of Horsetooth Road and onsite
property that drain to an existing inlet located just west of the Horsetooth
Road entrance into the property. Drainage from this inlet is currently
conveyed into the existing wet pond located south of HQ. The
redevelopment is raising the permanent water surface of the wet pond by
approximately 3-feet; therefore, Basin OS2 will be collected with a proposed
storm drain system and routed around the proposed wet pond to the
detention pond in Basin A1 where flows from the basin will be treated and
detained prior to being released from the pond.
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Basin OS3 consists of approximately 0.4 acres of onsite property that drains
offsite to the adjacent commercial property east and north of the
redevelopment (formerly the “LSI property”). This basin was originally
owned by, and was designed to drain towards, the offsite property but has
been recently purchased by Platte River Power Authority. In the existing
conditions Basin OS3 includes approximately 2.2 acres or property. The
proposed redevelopment alters the drainage patterns to minimize the size of
Basin OS3; and therefore, the amount of drainage that flows offsite. Much
of the existing basin is now included within the onsite Basins A7-A11. Refer
to the Drainage Plans and Appendix A for additional information. In
addition, note that Platte River Power Authority and the offsite property
owner are preparing an agreement to allow Platte River Power Authority
property that has historically flowed offsite to continue to do so.
Basin OS4 consists of approximately 1.3 acres of onsite property that drains
to Danfield Court. The basin currently exists as a parking lot that includes a
small amount of parking lot detention prior to being released to Danfield
Court. This existing parking lot is remaining largely unmodified with the
proposed redevelopment; therefore, per communications with City
personnel, no drainage improvements are being made to the basin.
Basins OS5 consists of approximately 0.5 acres of landscaped area that
historically drains west offsite and onto Union Pacific Railroad property. The
proposed redevelopment is proposing to maintain the existing drainage
patterns, size and percent imperviousness of this basin.
B. Specific Details
Detention
The proposed redevelopment includes two (2) extended detention ponds for
the proposed improvements. These ponds are located within Basins A1 and
C1 and are shown within this report as Pond A1 and Pond C1.
Pond A1 includes detention and water quality for all of Basins A, B and OS2.
The release rate from the pond is limited by the existing 12-inch storm sewer
outfall for the site which conveys stormwater north down Timberline Road.
As previously mentioned, the release rate from Pond A1 was determined to
be 3.15 cfs by analyzing the existing 12-inch storm sewer system. Refer to
Appendices C and D for additional information. Also, note that neither
detention or water quality are provided for the future conditions of basin
A12. Due to the unknown nature of the future improvements, Basin A12 will
be required to provide detention, water quality and LID improvements
either within Basin A12 or within Basin A1 with the future improvements.
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Refer to Appendix A for additional information. A pond outlet structure and
emergency overflow are at the northeast end of the pond that are directed
towards Timberline Road.
Pond C1 includes only Basin C1 and will provide detention over the
permanent water surface of the proposed wet pond. The pond is designed
to require less than 6-inches of ponding from the permanent water surface
to the 100-year water surface. A pond outlet and emergency overflow are
provided at the east end of the pond that are directed towards Basin A1.
A summary of both detention ponds are as follows:
Pond
Designation
Detention
Volume
Required
(ac-ft)
Detention
Volume
Provided
(ac-ft)
100-year
WSEL
Pond
Release
Rate
(cfs)
WQCV
Required
(ac-ft)
WQCV
Provided
(ac-ft)
Water
Quality
WSEL
Top of
Pond
Elevation
Pond A1 2.58 2.89 4952.25 3.15 0.18 0.24 4949.50 4953.25
Pond C1 0.33 0.35 4955.50 0.50 0.01 0.02 4955.03 4956.50
Stormwater Quality
Several long-term stormwater quality measures have been selected for the
site that will provide treatment of stormwater prior to it being discharged
from the site. For this project the following measures have been included:
Grass Swales - The soft bottom/overbank areas of the swales allow for
infiltration to occur as well as including a flow path across a vegetated
surface slowing the conveyance rate of storm water runoff while also
removing sediment and other pollutants. These have been utilized to
convey and treat stormwater prior to entering the storm sewer systems or
Pond A1.
Grass Open Areas/Buffers – Grass open areas and/or grass buffers allow
for infiltration to occur as well as including a flow path across a vegetated
surface slowing the conveyance rate of storm water runoff while also
removing sediment and other pollutants. These have been utilized to
convey and treat stormwater prior to entering the storm sewer systems or
Ponds A1 and C1.
Bioswales – Bioswales remove sediment and pollution from stormwater
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Underground Detention – Underground detention diverts storm water
runoff during the water quality event and detains the flows underground.
This provides for the removal of sediment and other pollutants from the
runoff while also promoting infiltration. Underground detention has been
utilized to collect, detain and treat storm water runoff prior to it entering
Pond A1.
Wet Pond (Pond C1) – A wet pond provides water quality by acting as a
permanent sedimentation basin which collects and stores the runoff prior
to discharging to the pond outlet structure. This removes sediment from
the flows entirely which settle to the bottom of the pond. The existing
onsite wet pond is being redeveloped as part of this project and will collect
and treat only those areas that drain immediately to the wet pond itself.
Extended Detention Basin – Extended detention basins, in conjunction
with the use of a water quality plate, collect, store and slowly release
minor storm events. This allows runoff to pond, infiltrate into the grass
bottom of the pond, and settle out particulates prior to being discharged
from the site. An extended detention basin has been selected as a highly
effective last treatment option prior to discharging runoff from the site.
Low Impact Development (LID)
In December of 2015, Fort Collins City Council adopted the revised Low
Impact Development (LID) policy and criteria which requires developments
within City limits to meet certain enhanced stormwater treatment
requirements in addition to more standard treatment techniques. The
proposed development will be required to meet the newly adopted LID
criteria which requires the following:
• Treat no less than 75% of any newly added impervious area using one or
a combination of LID techniques.
• Treat no less than 50% of any newly added impervious area using one or
a combination of LID techniques when at least 25% of any newly added
pavement is provided with permeable pavement.
The following measures are being implemented with this proposed
development:
Underground Detention – Basins A3-A11 (with 143,260 sf of proposed
impervious area) will be routed through an underground detention system
located north of HQ. The underground detention system will have an
overall volume of approximately 4,045 cubic feet which exceeds the
minimum design requirements for the area. Refer to Appendix B for
additional information.
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Bioswales – Basins B1-B2 (with 27,050 sf of proposed impervious area) will
be routed through a bioswale (with a surface area of 3,035 sf). Basin B-2
will include future parking area of approximately 10,000 sf. Once the
future parking area is constructed, the bioswale will also require extension
to provide LID treatment of the future parking lot expansion. With future
construction, the bioswale within Basins B1 and B2 will treat approximately
37,050 sf of impervious area.
Wet Pond – Basin C1 (with 5,730 sf of proposed impervious area) will drain
directly into the wet pond within the basin. The basin is approximately
1.23 acres in size and contains largely either water or pervious surface area
(approximately 90% of the basin); therefore, through communications with
the City, the wet pond will be allowed to act as a permanent
sedimentation basin which will remove sediment and pollution from storm
water runoff prior to releasing it downstream. Note that this is an
acceptable LID treatment for this project only due to the small amount of
impervious area draining to the pond.
Future LID Treatment – At the end of construction, Basin A12 will be left as
open space but is planned for future expansion. With the future
development of the basin, it is estimated that a minimum of 19,000 sf of
future impervious area will require to be treated to maintain a total
treatment for the campus of 75%.
In total, the development is proposing to collect and treat 205,024 sf (75%)
of the overall 274,263 sf of impervious area developed (including both
proposed and future developments) with this project. In addition, the site
is also being designed with other various open landscaped areas and
vegetated swales and buffers to provide additional water quality in
addition to the areas being treated with LID techniques.
Standard Operating Procedures (SOPs)
In order for physical stormwater Best Management Practices (BMPs) to be
effective, proper maintenance is essential. Maintenance includes both
routinely scheduled activities, as well as non-routine repairs that may be
required after large storms, or as a result of other unforeseen problems.
Standard Operating Procedures should clearly identify BMP maintenance
responsibility. BMP maintenance is typically the responsibility of the entity
owning the BMP.
Identifying who is responsible for maintenance of BMPs and ensuring that an
adequate budget is allocated for maintenance is critical to the long-term
success of BMPs. Maintenance responsibility may be assigned either publicly
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or privately. For this project, the privately owned BMPs including vegetative
swales and bioswales, underground detention, and the extended detention
ponds are to be maintained by the property owner.
Storm Sewers
Multiple storm sewer systems are being proposed with the redevelopment
of the campus that include storm sewer mains, roof drains and underdrains.
All storm sewer on the property will be private. The system that collects and
conveys the public storm water from Horsetooth Road will be included
within a drainage easement. Due to the complexities of the proposed site
and constraints of the existing site, all storm sewer mains and roof drains are
sized to accommodate the 100-year storm event. Refer to Appendix C for
more information.
Wet Pond
As previously mentioned, the existing wet pond on the site is also being
redeveloped/reconfigured with the project. As part of the reconfiguration,
the following design elements are being provided:
• A 12-foot depth is being provided in the pond to allow for increased
water quality and to allow for the use of a geothermal mechanical
system for HQ. Related to these elements, the elevation difference
between the finished floor of HQ and the permanent water surface of
the pond has been minimized to accommodate a deeper pond while
minimizing the impacts to existing groundwater. The existing pond sits
approximately 6-feet below the existing building. The design has set
the proposed permanent lake water surface 3-feet below the proposed
finished floor.
• The amount of surface drainage conveyed to the pond is being
minimized to limit the amount of storage required above the
permanent water surface due to storm runoff.
• The pond is being provided with an emergency overflow and outlet.
Currently the pond does not have an emergency overflow or any
means of draining the lake other than through irrigation. The
proposed design has located both an emergency overflow and outlet
structure on the east side of the lake.
Phasing
As mentioned previously, the redevelopment of the campus will be
accomplished in phases due to the requirement that the existing
Engineering/Operations (E/O) and Headquarters (HQ) buildings remain fully
operational during the construction of the proposed HQ building. Only when
the proposed HQ is fully operational and in use will the existing E/O and HQ
buildings be demolished. Due to this, it is currently expected that two major
Drainage Report
Platte River Power Authority HQ Campus
Fort Collins, CO
14 U16014-DrainageReport-Final.doc
phases of construction will be required. The initial phase of construction will
construct much of the proposed drainage infrastructure apart from the
southern portion of Pond A1 as this is where the existing HQ building is
located. The final phase of construction will construct the remainder of
Pond A1. Through communication with City personnel, it is currently
anticipated that the Stormwater Department will issue a full CO for the
proposed HQ building with an escrow provision as required.
Drainage Report
Platte River Power Authority HQ Campus
Fort Collins, CO
15 U16014-DrainageReport-Final.doc
Drainage Summaries
The following is a basin summary table for existing and proposed conditions:
Existing Basins
Basin Design
Pt.
Area %I Runoff
Coefficients
Peak
Discharge
acre C2 C100 Q
2 Q100
cfs cfs
EX1 EX1 3.75 48.6% 0.57 0.71 6.10 26.62
EX2 EX2 2.38 32.3% 0.44 0.55 2.07 9.04
EX3 EX3 2.19 80.4% 0.82 1.00 5.10 21.75
EX4 EX4 2.33 18.9% 0.34 0.42 1.68 7.33
EX5 EX5 1.35 12.5% 0.28 0.35 0.81 3.53
OS-1 OS-1 0.31 20.5% 0.35 0.43 0.30 1.32
OS-2A OS-2A 0.33 26.6% 0.39 0.49 0.37 1.61
OS-2B OS-2B 0.93 80.2% 0.81 1.00 2.00 8.62
OS-3 OS-3 2.21 20.1% 0.34 0.43 1.45 6.33
OS-4 OS-4 1.29 73.3% 0.75 0.94 2.75 12.00
OS-5 OS-5 0.54 2.0% 0.20 0.25 0.24 1.05
Totals 22.88 99.21
Proposed Basins
Basin Design
Pt.
Area Area Runoff
Coefficients
Peak
Discharge
acre acre C2 C100 Q
2 Q100
cfs cfs
A-1 A-1 3.49 16.4% 0.32 0.40 2.16 9.43
A-2 A-2 0.91 0.82 0.83 1.00 2.15 9.10
A-3 A-3 0.37 0.90 0.95 1.00 1.01 3.71
A-4 A-4 0.57 0.87 0.86 1.00 1.39 5.64
A-5 A-5 0.40 0.85 0.84 1.00 0.95 3.96
A-6 A-6 0.41 0.41 0.53 0.67 0.62 2.72
A-7 A-7 0.32 0.53 0.63 0.79 0.54 2.37
A-8 A-8 0.21 0.62 0.71 0.89 0.42 1.84
A-9 A-9 0.64 0.90 0.95 1.00 1.74 6.41
A-10 A-10 0.68 0.87 0.92 1.00 1.78 6.74
A-11 A-11 0.97 0.27 0.41 0.51 1.06 4.63
A-12 A-12 1.15 0.06 0.23 0.29 0.68 2.95
A-12
(Future)
A-12
(Future) 1.15 0.90 0.87 1.00 2.86 11.43
A-13 A-13 0.26 0.90 0.95 1.00 0.72 2.63
B-1 B-1 0.42 0.53 0.61 0.76 0.74 3.22
B-2 B-2 1.45 0.43 0.52 0.65 1.90 8.28
C-1 C-1 1.23 0.11 0.28 0.35 0.98 4.27
OS-1 OS-1 0.68 0.02 0.20 0.25 0.33 1.42
OS-2A OS-2A 0.21 0.02 0.20 0.25 0.12 0.51
Drainage Report
Platte River Power Authority HQ Campus
Fort Collins, CO
16 U16014-DrainageReport-Final.doc
V. Sediment/Erosion Control
Erosion control, both temporary and permanent, is a vital part of any development
project. For this project, the site disturbance will be over 1-acre; therefore, a
comprehensive Erosion Control Report has been completed under a separate cover.
The Erosion Control Report will be utilized for site construction activities and will be
prepared in accordance with City and Colorado Department of Public Health and
Environment requirements for use as the Stormwater Management Plan for the
project.
VI. Conclusions
A. Compliance with Standards
Storm drainage designs for the Platte River Power Authority Headquarters
campus have typically followed the guidelines provided by the Fort Collins
Stormwater Criteria Manual and/or the Urban Storm Drainage Criteria Manual.
In addition, the site drainage has been designed to meet City requirements in
terms of detention, water quality and Low Impact Development standards.
B. Drainage Concept
The drainage system has been designed to convey the runoff to the designated
design points and the existing public infrastructure in an effective, safe manner.
No negative impacts are anticipated to the City of Fort Collins Master Drainage
Plan or to downstream properties or infrastructure due to the proposed
improvements.
C. Stormwater Quality
Several long-term stormwater quality measures have been selected for the site
that will provide treatment of stormwater prior it to being discharged from the
site. For this site this includes grass swales, grass open areas/buffers, a
bioswale, underground detention and an extended detention basin.
Drainage Report
Platte River Power Authority HQ Campus
Fort Collins, CO
17 U16014-DrainageReport-Final.doc
VII. References
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, as adopted in 2011.
2. Urban Storm Drainage Criteria Manual, Urban Drainage and Flood Control District,
Wright Water Engineers, Inc., Denver, Colorado, Revised April 2008.
3. Larimer County Urban Area Street Standards, Larimer County, Colorado, Repealed
and Reenacted, Effective April 1, 2007.
4. Geotechnical Engineering Report – PRPA New Headquarters Campus, Terracon
Consultants, Inc., October 30, 2017.
5. Storm Drainage Study for Platte River Power Authority Maintenance Facility, RBD
Engineering Consultants, March 1984.
6. Collindale Industrial Park Storm Sewer Extension Construction Plans, Meline &
Irelan, Inc., Revised May 1995.
7. Collindale Industrial Park Construction Plans, James H. Stewart & Associates, Revised
October 1978.
8. Natural Resources Conservation Service Web Soil Survey at
websoilsurvey.nrcs.usda.gov/app
APPENDIX A
Hydrology Computations
Runoff Coefficients and % Impervious
Platte River Power Authority Campus, Fort Collins, CO
Basin Design Pt. Composite NRCS Soil
Total Total Roof
(1) Asphalt Concrete
(1)
Gravel
(1)
Lawns
(1) Imperviousness Type C
2 C100
%I = 90% %I = 100% %I = 90% %I =40% %I=2% (%I)
acres sf sf sf sf sf sf
EX1 EX1 3.75 163,553 19,370 51,627 8,627 2,670 81,259 48.6% C/D 0.57 0.71
EX2 EX2 2.38 103,485 2,883 22,033 7,506 1,767 69,296 32.3% C/D 0.44 0.55
EX3 EX3 2.19 95,233 17,683 54,408 6,104 1,029 16,009 80.4% C/D 0.82 1.00
EX4 EX4 2.33 101,325 9,012 5,208 4,316 810 81,979 18.9% C/D 0.34 0.42
EX5 EX5 1.35 58,652 16,194 42,458 12.5% C/D 0.28 0.35
OS-1 OS-1 0.31 13,409 928 343 3,331 8,807 20.5% C/D 0.35 0.43
OS-2A OS-2A 0.33 14,302 2,539 1,177 10,586 26.6% C/D 0.39 0.49
OS-2B OS-2B 0.93 40,310 26,568 6,228 7,514 80.2% C/D 0.81 1.00
OS-3 OS-3 2.21 96,274 14,084 4,110 78,080 20.1% C/D 0.34 0.43
OS-4 OS-4 1.29 56,148 38,984 2,061 15,103 73.3% C/D 0.75 0.94
OS-5 OS-5 0.54 23,668 23,668 2.0% C/D 0.20 0.25
17.59 766,361 48,948 216,379 40,472 25,801 434,761 41.2% C/D 0.51 0.64
Notes:
(1) Recommended Runoff Coefficient Values from FCSCM Table RO-11.
(2) Composite Runoff Coefficient is based on FCSCM equation RO-8 and Coefficient Adjustment factors per Table RO-12.
Composite Runoff Coefficients
Areas (2)
Existing Basins
Existing Total
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Runoff Coefficients and % Impervious
Platte River Power Authority Campus, Fort Collins, CO
Existing Basins
Basin Design Pt. Composite NRCS Soil
Total Total Roof
(1) Asphalt Concrete
(1)
Gravel
(1)
Lawns
(1) Imperviousness Type C
2 C100
acres sf %I = 90% %I = 100% %I = 90% %I =40% %I=2% (%I)
sf sf sf sf sf
A-1 A-1 3.49 151,910 11,029 13,397 906 126,578 16.4% C/D 0.32 0.40
A-2 A-2 0.91 39,824 - 26,691 6,604 - 6,529 82.3% C/D 0.83 1.00
A-3 A-3 0.37 16,242 16,242 - - - - 90.0% C/D 0.95 1.00
A-4 A-4 0.57 24,681 3,199 16,739 1,873 - 2,870 86.5% C/D 0.86 1.00
A-5 A-5 0.40 17,344 - 13,831 905 - 2,608 84.7% C/D 0.84 1.00
A-6 A-6 0.41 17,875 117 - 7,834 - 9,924 41.1% C/D 0.53 0.67
A-7 A-7 0.32 14,010 7,965 - 106 - 5,939 52.7% C/D 0.63 0.79
A-8 A-8 0.21 9,097 3,308 2,881 - 2,908 61.9% C/D 0.71 0.89
A-9 A-9 0.64 28,046 5,826 - 22,200 - 20 89.9% C/D 0.95 1.00
A-10 A-10 0.68 29,504 5,872 - 22,521 - 1,111 86.7% C/D 0.92 1.00
A-11 A-11 0.97 42,186 11,235 - 603 - 30,348 26.7% C/D 0.41 0.51
A-12 A-12 1.15 50,020 - - 2,240 - 47,780 5.9% C/D 0.23 0.29
A-12 (Future) A-12 (Future) 1.15 50,020 - 44,900 - - 5,120 90.0% C/D 0.87 1.00
A-13 A-13 0.26 11,517 11,517 - - - - 90.0% C/D 0.95 1.00
A-TOTAL A-TOTAL 10.38 452,256 76,311 57,261 81,164 906 236,615 45.1% C/D 0.56 0.70
B-1 B-1 0.42 18,486 - 5,907 4,218 - 8,361 53.4% C/D 0.61 0.76
B-2 B-2 1.45 62,995 - 23,640 3,277 - 36,078 43.4% C/D 0.52 0.65
B-TOTAL B-TOTAL 1.87 81,481 - 29,547 7,495 - 44,439 45.6% C/D 0.54 0.68
C-1 C-1 1.23 53,361 - - 5,726 - 47,635 11.4% C/D 0.28 0.35
C-TOTAL C-TOTAL 1.23 53,361 - - 5,726 - 47,635 11.4% C/D 0.28 0.35
OS-1 OS-1 0.68 29,533 29,533 2.0% C/D 0.20 0.25
OS-2A OS-2A 0.21 8,940 8,940 2.0% C/D 0.20 0.25
OS-2B OS-2B 0.93 40,310 26,568 6,228 7,514 80.2% C/D 0.81 1.00
OS-3 OS-3 0.42 18,209 11,803 3,921 2,485 84.5% C/D 0.85 1.00
OS-4 OS-4 1.35 58,603 35,778 6,064 16,761 70.9% C/D 0.74 0.92
OS-5 OS-5 0.54 23,668 23,668 2.0% C/D 0.20 0.25
OS-TOTAL OS-TOTAL 4.12 179,263 - 74,149 16,213 - 88,901 50.5% C/D 0.58 0.72
17.59 766,361 76,311 160,957 110,597 906 417,591 44.1% C/D 0.54 0.68
Notes:
(1) Recommended Runoff Coefficient Values from FCSCM Table RO-11.
(2) Composite Runoff Coefficient is based on FCSCM equation RO-8 and Coefficient Adjustment factors per Table RO-12.
(3) Basin A-1 includes approximately 8,500 sf of future building. Basin B-2 includes approximately 10,000 sf of future parking area.
(4) Basin A-12 (Future) is included for storm sewer sizing only and is not included within "A-TOTAL" above. Detention and LID requirements will be required for Basin A-12 with future
development.
Proposed Total
Proposed Basins
Areas Composite Runoff Coefficients
(2)
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
2-Year Time of Concentration
Platte River Power Authority Campus, Fort Collins, CO
Basin Design Pt. Area
C
(1) Length Slope t
i
(2) Length Slope C
v Velocity
(3)
tt
(4) Check t
c? Total Length t
c
(5)
acres ft % min ft % fps min min Urban? ft min min
EX1 EX1 3.75 0.57 35 3.8% 3.8 390 2.3% 20
3.0 2.1 5.9 Yes 425 12 5.9
EX2 EX2 2.38 0.44 275 0.6% 24.2 190 1.0% 7 0.7 4.5 28.7 Yes 465 13 12.6
EX3 EX3 2.19 0.82 20 1.2% 2.2 415 1.0% 20 2.0 3.5 5.7 Yes 435 12 5.7
EX4 EX4 2.33 0.34 50 1.0% 10.1 205 1.1% 7 0.7 4.7 14.7 Yes 255 11 11.4
EX5 EX5 1.35 0.28 105 1.1% 15.2 130 0.1% 7 0.2 9.3 24.5 Yes 235 11 11.3
OS-1 OS-1 0.31 0.35 70 4.4% 7.2 20 4.6% 20 4.3 0.1 7.3 Yes 90 11 7.3
OS-2A OS-2A 0.33 0.39 30 5.9% 4.0 60 1.2% 20 2.2 0.5 4.5 Yes 90 11 5.0
OS-2B OS-2B 0.93 0.81 50 2.0% 3.0 490 0.7% 20 1.6 5.1 8.1 Yes 540 13 8.1
OS-3 OS-3 2.21 0.34 30 10.0% 3.6 610 0.4% 7 0.4 23.0 26.6 Yes 640 14 13.6
OS-4 OS-4 1.29 0.75 60 5.0% 3.0 250 1.1% 20 2.1 2.0 5.0 Yes 310 12 5.0
OS-5 OS-5 0.54 0.20 30 10.0% 4.3 200 0.7% 7 0.6 5.7 10.0 Yes 230 11 10.0
Notes:
(1) C=Cx*Cf
(2)ti = [1.87(1.1-CxCf)L1/2]/S1/3, S= slope in %, L=length of overland flow (400' max)
(3)V=CvS0.5, S=watercourse slope in ft/ft, UDFCD Equation RO-4
(4)tt=L/(V*60 sec/min)
(5)tc check (for urban or developed areas only) = total length/180 + 10
(6)min tc = 5 min
Existing Basins
Initial Overland Flow Time (ti) Travel/Channelized Time of Flow (t
t) ti
+tt t
c Check for Urbanized Basins Final
tc
(6)
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
2-Year Time of Concentration
Platte River Power Authority Campus, Fort Collins, CO
Existing Basins
Basin Design Pt. Area
C
(1) Length Slope t
i
(2) Length Slope C
v Velocity
(3)
tt
(4) Check t
c? Total Length t
c
(5)
acres ft % min ft % fps min min Urban? ft min min
A-1 A-1 3.49 0.32 235 1.5% 19.5 465 0.5% 20
1.4 5.5 25.0 Yes 700 14 13.9
A-2 A-2 0.91 0.83 10 2.0% 1.28 305 0.5% 20 1.4 3.6 4.9 Yes 315 12 5.0
A-3 A-3 0.37 0.95 50 12.5% 0.86 15 30.0% 20 11.0 0.0 0.9 Yes 65 10 5.0
A-4 A-4 0.57 0.86 36 2.0% 2.12 242 2.0% 20 2.8 1.4 3.5 Yes 278 12 5.0
A-5 A-5 0.40 0.84 50 2.0% 2.76 133 1.5% 20 2.4 0.9 3.7 Yes 183 11 5.0
A-6 A-6 0.41 0.53 17 2.0% 3.47 123 2.0% 20 2.8 0.7 4.2 Yes 140 11 5.0
A-7 A-7 0.32 0.63 64 1.5% 6.12 210 1.0% 15 1.5 2.3 8.5 Yes 274 12 8.5
A-8 A-8 0.21 0.71 15 2.0% 2.25 50 2.0% 20 2.8 0.3 2.5 Yes 65 10 5.0
A-9 A-9 0.64 0.95 25 12.5% 0.61 210 0.5% 20 1.4 2.5 3.1 Yes 235 11 5.0
A-10 A-10 0.68 0.92 63 4.0% 1.67 200 1.5% 20 2.4 1.4 3.0 Yes 263 11 5.0
A-11 A-11 0.97 0.41 20 7.0% 3.03 190 0.5% 15 1.1 3.0 6.0 Yes 210 11 6.0
A-12 A-12 1.15 0.23 20 7.0% 3.81 205 0.5% 15 1.1 3.2 7.0 Yes 225 11 7.0
A-12 (Future) A-12 (Future) 1.15 0.87 10 2.0% 1.07 205 2.0% 20 2.8 1.2 2.3 Yes 215 11 5.0
A-13 A-13 0.26 0.95 72 12.5% 1.03 15 30.0% 20 11.0 0.0 1.1 Yes 87 10 5.0
A-TOTAL A-TOTAL 10.38 0.56 51 1.5% 6.35 985 0.4% 20 1.3 13.0 19.3 Yes 1036 16 15.8
B-1 B-1 0.42 0.61 70 2.0% 6.09 40 2.0% 20 2.8 0.2 6.3 Yes 110 11 6.3
B-2 B-2 1.45 0.52 50 25.0% 2.65 290 0.5% 15 1.1 4.6 7.2 Yes 340 12 7.2
B-TOTAL B-TOTAL 1.87 0.54 50 25.0% 2.56 290 0.5% 15 1.1 4.6 7.1 Yes 340 12 7.1
C-1 C-1 1.23 0.28 16 2.0% 4.88 75 10.0% 15 4.7 0.3 5.1 Yes 91 11 5.1
C-TOTAL C-TOTAL 1.23 0.28 16 2.0% 4.88 75 10.0% 15 4.7 0.3 5.1 Yes 91 11 5.1
OS-1 OS-1 0.68 0.20 70 4.4% 8.64 20 4.6% 20 4.3 0.1 8.7 Yes 90 11 8.7
OS-2A OS-2A 0.21 0.20 30 5.9% 5.13 60 1.2% 20 2.2 0.5 5.6 Yes 90 11 5.6
OS-2B OS-2B 0.93 0.81 50 2.0% 3.05 490 0.7% 20 1.6 5.1 8.1 Yes 540 13 8.1
OS-3 OS-3 0.42 0.85 140 1.5% 4.88 165 0.7% 20 1.7 1.6 6.5 Yes 305 12 6.5
OS-4 OS-4 1.35 0.74 60 5.0% 3.10 250 1.1% 20 2.1 2.0 5.1 Yes 310 12 5.1
OS-5 OS-5 0.54 0.20 30 10.0% 4.31 200 0.7% 7 0.6 5.7 10.0 Yes 230 11 10.0
Notes:
(1) C=Cx*Cf
(2)ti = [1.87(1.1-CxCf)L1/2]/S1/3, S= slope in %, L=length of overland flow (400' max)
(3)V=CvS0.5, S=watercourse slope in ft/ft, UDFCD Equation RO-4
(4)tt=L/(V*60 sec/min)
(5)tc check (for urban or developed areas only) = total length/180 + 10
(6)min tc = 5 min
Proposed Basins
Initial Overland Flow Time (ti) Travel/Channelized Time of Flow (t
t) ti
+tt t
c Check for Urbanized Basins Final
tc
(6)
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
100-Year Time of Concentration
Platte River Power Authority Campus, Fort Collins, CO
Basin Design Pt. Area
C
(1) Length Slope t
i
(2) Length Slope C
v Velocity
(3)
tt
(4) Check t
c? Total Length t
c
(5)
acres ft % min ft % fps min min Urban? ft min min
EX1 EX1 3.75 0.71 35 3.8% 2.8 390 2.3% 20
3.0 2.1 4.9 Yes 425 12 5.0
EX2 EX2 2.38 0.55 275 0.6% 20.2 190 1.0% 7 0.7 4.5 24.7 Yes 465 13 12.6
EX3 EX3 2.19 1.00 20 1.2% 0.8 415 1.0% 20 2.0 3.5 4.2 Yes 435 12 5.0
EX4 EX4 2.33 0.42 50 1.0% 8.9 205 1.1% 7 0.7 4.7 13.6 Yes 255 11 11.4
EX5 EX5 1.35 0.35 105 1.1% 13.9 130 0.1% 7 0.2 9.3 23.2 Yes 235 11 11.3
OS-1 OS-1 0.31 0.43 70 4.4% 6.4 20 4.6% 20 4.3 0.1 6.5 Yes 90 11 6.5
OS-2A OS-2A 0.33 0.49 30 5.9% 3.5 60 1.2% 20 2.2 0.5 3.9 Yes 90 11 5.0
OS-2B OS-2B 0.93 1.00 50 2.0% 1.1 490 0.7% 20 1.6 5.1 6.1 Yes 540 13 6.1
OS-3 OS-3 2.21 0.43 30 10.0% 3.2 610 0.4% 7 0.4 23.0 26.2 Yes 640 14 13.6
OS-4 OS-4 1.29 0.94 60 5.0% 1.4 250 1.1% 20 2.1 2.0 3.4 Yes 310 12 5.0
OS-5 OS-5 0.54 0.25 30 10.0% 4.1 200 0.7% 7 0.6 5.7 9.8 Yes 230 11 9.8
Notes:
(1) C=Cx*Cf
(2)ti = [1.87(1.1-CxCf)L1/2]/S1/3, S= slope in %, L=length of overland flow (400' max)
(3)V=CvS0.5, S=watercourse slope in ft/ft, UDFCD Equation RO-4
(4)tt=L/(V*60 sec/min)
(5)tc check (for urban or developed areas only) = total length/180 + 10
(6)min tc = 5 min
Existing Basins
ti+t
t Final
tc
(6)
Initial Overland Flow Time (t tc Check for Urbanized Basins
i) Travel/Channelized Time of Flow (tt
)
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
100-Year Time of Concentration
Platte River Power Authority Campus, Fort Collins, CO
Existing Basins
Basin Design Pt. Area
C
(1) Length Slope t
i
(2) Length Slope C
v Velocity
(3)
tt
(4) Check t
c? Total Length t
c
(5)
acres ft % min ft % fps min min Urban? ft min min
A-1 A-1 3.49 0.40 235 1.5% 17.5 465 0.5% 20
1.4 5.5 23.0 Yes 700 14 13.9
A-2 A-2 0.91 1.00 10 2.0% 0.47 305 0.5% 20 1.4 3.6 4.1 Yes 315 12 5.0
A-3 A-3 0.37 1.00 50 12.5% 0.57 15 30.0% 20
11.0 0.0 0.6 Yes 65 10 5.0
A-4 A-4 0.57 1.00 36 2.0% 0.89 242 2.0% 20 2.8 1.4 2.3 Yes 278 12 5.0
A-5 A-5 0.40 1.00 50 2.0% 1.05 133 1.5% 20
2.4 0.9 2.0 Yes 183 11 5.0
A-6 A-6 0.41 0.67 17 2.0% 2.66 123 2.0% 20 2.8 0.7 3.4 Yes 140 11 5.0
A-7 A-7 0.32 0.79 64 1.5% 4.06 210 1.0% 15
1.5 2.3 6.4 Yes 274 12 6.4
A-8 A-8 0.21 0.89 15 2.0% 1.22 50 2.0% 20 2.8 0.3 1.5 Yes 65 10 5.0
A-9 A-9 0.64 1.00 25 12.5% 0.41 210 0.5% 20
1.4 2.5 2.9 Yes 235 11 5.0
A-10 A-10 0.68 1.00 63 4.0% 0.94 200 1.5% 20 2.4 1.4 2.3 Yes 263 11 5.0
A-11 A-11 0.97 0.51 20 7.0% 2.58 190 0.5% 15
1.1 3.0 5.6 Yes 210 11 5.6
A-12 A-12 1.15 0.29 20 7.0% 3.56 205 0.5% 15 1.1 3.2 6.8 Yes 225 11 6.8
A-12 (Future) A-12 (Future) 1.15 1.00 10 2.0% 0.47 205 2.0% 20
2.8 1.2 1.7 Yes 215 11 5.0
A-13 A-13 0.26 1.00 72 12.5% 0.69 15 30.0% 20 11.0 0.0 0.7 Yes 87 10 5.0
A-TOTAL A-TOTAL 10.38 0.70 51 1.5% 4.72 985 0.4% 20
1.3 13.0 17.7 Yes 1036 16 15.8
B-1 B-1 0.42 0.76 70 2.0% 4.19 40 2.0% 20
2.8 0.2 4.4 Yes 110 11 5.0
B-2 B-2 1.45 0.65 50 25.0% 2.05 290 0.5% 15 1.1 4.6 6.6 Yes 340 12 6.6
B-TOTAL B-TOTAL 1.87 0.68 50 25.0% 1.94 290 0.5% 20
1.4 3.4 5.4 Yes 340 12 5.4
C-1 C-1 1.23 0.35 16 2.0% 4.46 75 10.0% 15
4.7 0.3 4.7 Yes 91 11 5.0
C-TOTAL C-TOTAL 1.23 0.35 16 2.0% 4.46 75 10.0% 15 4.7 0.3 4.7 Yes 91 11 5.0
OS-1 OS-1 0.68 0.25 70 4.4% 8.16 20 4.6% 20 4.3 0.1 8.2 Yes 90 11 8.2
OS-2A OS-2A 0.21 0.25 30 5.9% 4.85 60 1.2% 20
2.2 0.5 5.3 Yes 90 11 5.3
OS-2B OS-2B 0.93 1.00 50 2.0% 1.05 490 0.7% 20 1.6 5.1 6.1 Yes 540 13 6.1
OS-3 OS-3 0.42 1.00 140 1.5% 1.94 165 0.7% 20
1.7 1.6 3.6 Yes 305 12 5.0
OS-4 OS-4 1.35 0.92 60 5.0% 1.54 250 1.1% 20 2.1 2.0 3.5 Yes 310 12 5.0
OS-5 OS-5 0.54 0.25 30 10.0% 4.07 200 0.7% 7
0.6 5.7 9.8 Yes 230 11 9.8
Notes:
(1) C=Cx*Cf
(2)ti = [1.87(1.1-CxCf)L1/2]/S1/3, S= slope in %, L=length of overland flow (400' max)
(3)V=CvS0.5, S=watercourse slope in ft/ft, UDFCD Equation RO-4
Rational Method Peak Runoff
Platte River Power Authority Campus, Fort Collins, CO
Basin Design Pt. Area 2-year 100-year
acre tc t
c C2
C100 I
2 I100
Q2 Q
100
min min in/hr in/hr cfs cfs
EX1 EX1 3.75 6 5 0.57 0.71 2.67 9.95 5.71 26.62
EX2 EX2 2.38 13 13 0.44 0.55 1.98 6.92 2.07 9.04
EX3 EX3 2.19 6 5 0.82 1.00 2.67 9.95 4.78 21.75
EX4 EX4 2.33 11 11 0.34 0.42 2.13 7.42 1.68 7.33
EX5 EX5 1.35 11 11 0.28 0.35 2.13 7.42 0.81 3.53
OS-1 OS-1 0.31 7 6 0.35 0.43 2.52 9.95 0.27 1.32
OS-2A OS-2A 0.33 5 5 0.39 0.49 2.85 9.95 0.37 1.61
OS-2B OS-2B 0.93 8 6 0.81 1.00 2.40 9.31 1.80 8.62
OS-3 OS-3 2.21 14 14 0.34 0.43 1.92 6.71 1.45 6.33
OS-4 OS-4 1.29 5 5 0.75 0.94 2.85 9.95 2.75 12.00
OS-5 OS-5 0.54 10 10 0.20 0.25 2.21 7.72 0.24 1.05
21.94 99.21
Existing Basins
Totals
Runoff Coefficients Rainfall Intensity Peak Discharge
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Rational Method Peak Runoff
Platte River Power Authority Campus, Fort Collins, CO
Existing Basins
Basin Design Pt. Area 2-year 100-year
acre tc t
c C2
C100 I
2 I100
Q2 Q
100
min min in/hr in/hr cfs cfs
A-1 A-1 3.49 14.0 14.0 0.32 0.40 1.92 6.71 2.16 9.43
A-2 A-2 0.91 5.0 5.0 0.83 1.00 2.85 9.95 2.15 9.10
A-3 A-3 0.37 5.0 5.0 0.95 1.00 2.85 9.95 1.01 3.71
A-4 A-4 0.57 5.0 5.0 0.86 1.00 2.85 9.95 1.39 5.64
A-5 A-5 0.40 5.0 5.0 0.84 1.00 2.85 9.95 0.95 3.96
A-6 A-6 0.41 5.0 5.0 0.53 0.67 2.85 9.95 0.62 2.72
A-7 A-7 0.32 8.0 6.0 0.63 0.79 2.40 9.31 0.49 2.37
A-8 A-8 0.21 5.0 5.0 0.71 0.89 2.85 9.95 0.42 1.84
A-9 A-9 0.64 5.0 5.0 0.95 1.00 2.85 9.95 1.74 6.41
A-10 A-10 0.68 5.0 5.0 0.92 1.00 2.85 9.95 1.78 6.74
A-11 A-11 0.97 6.0 6.0 0.41 0.51 2.67 9.31 1.06 4.63
A-12 A-12 1.15 7.0 7.0 0.23 0.29 2.52 8.80 0.68 2.95
A-12 (Future) A-12 (Future) 1.15 5.0 5.0 0.87 1.00 2.85 9.95 2.86 11.43
A-13 A-13 0.26 5.0 5.0 0.95 1.00 2.85 9.95 0.72 2.63
A-TOTAL A-TOTAL 10.38 16.0 16.0 0.56 0.70 1.81 6.30 10.46 45.52
B-1 B-1 0.42 6.0 5.0 0.61 0.76 2.67 9.95 0.69 3.22
B-2 B-2 1.45 7.0 7.0 0.52 0.65 2.52 8.80 1.90 8.28
B-TOTAL B-TOTAL 1.87 7.0 5.0 0.54 0.68 2.52 9.95 2.55 12.59
C-1 C-1 1.23 5.0 5.0 0.28 0.35 2.85 9.95 0.98 4.27
C-TOTAL C-TOTAL 1.23 5.0 5.0 0.28 0.35 2.85 9.95 0.98 4.27
OS-1 OS-1 0.68 9.0 8.0 0.20 0.25 2.30 8.38 0.31 1.42
OS-2A OS-2A 0.21 6.0 5.0 0.20 0.25 2.67 9.95 0.11 0.51
OS-2B OS-2B 0.93 8.0 6.0 0.81 1.00 2.40 9.31 1.80 8.62
OS-3 OS-3 0.42 7.0 5.0 0.85 1.00 2.52 9.95 0.89 4.16
OS-4 OS-4 1.35 5.0 5.0 0.74 0.92 2.85 9.95 2.82 12.31
OS-5 OS-5 0.54 10.0 10.0 0.20 0.25 2.21 7.72 0.24 1.05
Totals 24.92 105.96
Proposed Basins
Runoff Coefficients Rainfall Intensity Peak Discharge
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
APPENDIX B
Detention and Water Quality Calculations
Dention Pond Volume (FAA Method)
Platte River Power Authority Campus, Fort Collins, CO
POND ID: POND A1
100 Year Storm Into Detention Facility
Area = 582,987 square feet
Area = 13.38 acres
C 100 = 0.71
Q 100 = 53.00 cfs
Release Rate Out of Pond
Q OUT = 3.15 cfs
Unit Flow = 0.24 cfs/acre
T C = 15.8 minutes
Notes:
1. Release Rate limited by the existing 12" outfall capacity in Timberline Road.
2. Pond area includes all of Basins A, B and OS-2 but excludes "Basin A-12 (Future)".
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T) Intensity (I) Qin= ∑C100*Area*I Vi=(Qin*T*60) Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 9.95 94.2 28,257 1.00 3.15 945 27,312
10 7.72 73.1 43,849 1.00 3.15 1,890 41,959
15 6.52 61.7 55,549 1.00 3.15 2,835 52,714
20 5.60 53.0 63,615 0.89 2.82 3,379 60,236
25 4.98 47.1 70,715 0.82 2.57 3,851 66,863
30 4.52 42.8 77,019 0.76 2.40 4,324 72,695
35 4.08 38.6 81,109 0.73 2.28 4,796 76,312
40 3.74 35.4 84,971 0.70 2.20 5,269 79,702
45 3.46 32.8 88,436 0.68 2.13 5,741 82,694
50 3.23 30.6 91,730 0.66 2.07 6,214 85,516
55 3.03 28.7 94,655 0.64 2.03 6,686 87,969
60 2.86 27.1 97,467 0.63 1.99 7,159 90,308
70 2.59 24.5 102,976 0.61 1.93 8,104 94,872
80 2.38 22.5 108,145 0.60 1.89 9,049 99,096
90 2.21 20.9 112,973 0.59 1.85 9,994 102,979
100 2.06 19.5 117,006 0.58 1.82 10,939 106,067
110 1.94 18.4 121,209 0.57 1.80 11,884 109,325
120 1.84 17.4 125,412 0.57 1.78 12,829 112,583
Required Detention Volume
V 100 = 112,583 cubic feet
V 100 = 2.58 acre-ft
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Dention Pond Volume (FAA Method)
Platte River Power Authority Campus, Fort Collins, CO
POND ID: POND C1
100 Year Storm Into Detention Facility
Area = 53,361 square feet
Area = 1.23 acres
C 100 = 1.00
Q 100 = 4.27 cfs
Release Rate Out of Pond
Q OUT = 0.50 cfs
Unit Flow = 0.41 cfs/acre
T C = 5.0 minutes
Notes:
1. Release Rate limited to maximize detention volume but keep maximum ponding to less than 6".
2. For Pond C Calculations, C100 has been assumed to be 1.00 assuming that the pond water surface is at the maximum elevation
and all water that falls on the wet pond will pass through the outlet .
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T) Intensity (I) Qin= ∑C100*Area*I Vi=(Qin*T*60) Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 9.95 12.2 3,657 1.00 0.50 150 3,507
10 7.72 9.5 5,674 0.75 0.38 225 5,449
15 6.52 8.0 7,188 0.67 0.33 300 6,888
20 5.60 6.9 8,232 0.63 0.31 375 7,857
25 4.98 6.1 9,151 0.60 0.30 450 8,701
30 4.52 5.5 9,967 0.58 0.29 525 9,442
35 4.08 5.0 10,496 0.57 0.29 600 9,896
40 3.74 4.6 10,996 0.56 0.28 675 10,321
45 3.46 4.2 11,444 0.56 0.28 750 10,694
50 3.23 4.0 11,870 0.55 0.28 825 11,045
55 3.03 3.7 12,249 0.55 0.27 900 11,349
60 2.86 3.5 12,613 0.54 0.27 975 11,638
70 2.59 3.2 13,326 0.54 0.27 1,125 12,201
80 2.38 2.9 13,994 0.53 0.27 1,275 12,719
90 2.21 2.7 14,619 0.53 0.26 1,425 13,194
100 2.06 2.5 15,141 0.53 0.26 1,575 13,566
110 1.94 2.4 15,685 0.52 0.26 1,725 13,960
120 1.84 2.3 16,229 0.52 0.26 1,875 14,354
Required Detention Volume
V 100 = 14,354 cubic feet
V 100 = 0.33 acre-ft
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
STAGE STORAGE TABLE - POND A1 NORTH
ELEV
AREA
(sq. ft.)
DEPTH
(ft)
AVG END
INC. VOL.
(cu. ft.)
AVG END
TOTAL VOL.
(cu. ft.)
CONIC
INC. VOL.
(cu. ft.)
CONIC
TOTAL VOL.
(cu. ft.)
4,948.200 137.56 N/A N/A 0.00 N/A 0.00
4,948.400 1,094.72 0.200 123.23 123.23 108.02 108.02
4,948.600 3,133.91 0.200 422.86 546.09 405.39 513.41
4,948.800 6,000.79 0.200 913.47 1459.56 898.09 1411.50
4,949.000 9,570.39 0.200 1557.12 3016.68 1543.30 2954.79
4,949.200 13,193.81 0.200 2276.42 5293.10 2266.75 5221.54
4,949.400 16,829.99 0.200 3002.38 8295.48 2995.01 8216.55
4,949.600 20,811.40 0.200 3764.14 12059.62 3757.10 11973.65
4,949.800 24,256.08 0.200 4506.75 16566.36 4502.35 16476.00
4,950.000 27,457.60 0.200 5171.37 21737.73 5168.06 21644.07
4,950.200 30,539.89 0.200 5799.75 27537.48 5797.02 27441.08
4,950.400 33,087.44 0.200 6362.73 33900.21 6361.03 33802.12
4,950.600 34,901.34 0.200 6798.88 40699.09 6798.07 40600.19
4,950.800 36,320.29 0.200 7122.16 47821.26 7121.69 47721.88
4,951.000 37,391.61 0.200 7371.19 55192.45 7370.93 55092.81
4,951.200 38,356.39 0.200 7574.80 62767.25 7574.59 62667.41
4,951.400 39,341.32 0.200 7769.77 70537.02 7769.56 70436.97
4,951.600 40,353.45 0.200 7969.48 78506.49 7969.26 78406.23
4,951.800 41,397.19 0.200 8175.06 86681.56 8174.84 86581.07
4,952.000 42,572.75 0.200 8396.99 95078.55 8396.72 94977.79
4,952.200 43,891.77 0.200 8646.45 103725.00 8646.12 103623.91
4,952.400 45,220.87 0.200 8911.26 112636.27 8910.93 112534.84
STAGE STORAGE TABLE - POND A1 SOUTH
ELEV
AREA
(sq. ft.)
DEPTH
(ft)
AVG END
INC. VOL.
(cu. ft.)
AVG END
TOTAL VOL.
(cu. ft.)
CONIC
INC. VOL.
(cu. ft.)
CONIC
TOTAL VOL.
(cu. ft.)
4,949.000 1.34 N/A N/A 0.00 N/A 0.00
4,949.200 237.76 0.200 23.91 23.91 17.13 17.13
Water Quality
Platte River Power Authority Campus, Fort Collins, CO
Required Onsite Water Quality Capture Volume
Basin Area Area Imperviousness Watershed WQCV*
(Extended Detention)
(sf) (acres) (%) (inches) (cf)
A-TOTAL 452,256 10.382 45% 0.19 8,741
B-TOTAL 81,481 1.871 46% 0.19 1,586
C-TOTAL 53,361 1.225 11% 0.08 400
OS-2 TOTAL 49,250 1.131 66% 0.26 1,271
TOTAL REQUIRED 636,348 14.609 44% 0.19 12,109
Less WQ Provided by Underground Detention 4,045
Less WQ Provided in Wet Pond 400
Total WQ Provided in Pond A 7,664
* based on 40 hr storage and additional 20% for extended detention
Designed Water Quality Plate Parameters
Basin WQCV WQCV Area Required Diamter of Space No. of No. of
Provided Depth per WQ Plate Row WQ Hole between rows (in.) Columns Rows
(cf) (ft) (in
2
) (in) (in)
Pond A1 10,409 1.50 0.922 12/16 4 2 5
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Water Quality - Low Impact Development
Platte River Power Authority Campus, Fort Collins, CO
Required Onsite Water Quality Capture Volume For Underground Detention
Basin Area Area Imperviousness Watershed WQCV*
(Extended Detention)
(sf) (acres) (%) (inches) (cf)
Basin A South - Underground Detention LID
A-3 16,242 0.37 90% 0.321 435
A-4 24,681 0.57 87% 0.299 615
A-5 17,344 0.40 85% 0.288 417
A-12 50,020 1.15 6% 0.034 141
0.000 0
108,287 2.49 47% 0.158 1,427
Basin A North - Underground Detention LID
A-6 17,875 0.41 41% 0.146 218
A-7 14,010 0.32 53% 0.171 200
A-8 9,097 0.21 62% 0.194 147
A-9 28,046 0.64 90% 0.321 750
A-10 29,504 0.68 87% 0.300 737
A-11 42,186 0.97 27% 0.113 396
140,718 3.23 59% 0.185 2,172
Total To Underground Detention 3,599
* Based on 12 hr storage forunderground detention
** Basin A-12 Future will be required to provide LID treatment at time of future development.
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Dention Pond Volume (FAA Method)
Platte River Power Authority Campus, Fort Collins, CO
POND ID: Basin A South - Underground Detention LID
WQ Basin Characateristics
Area = 108,287 square feet
Area = 2.49 acres
C 2 = 0.51
Q in = 2.01 cfs
WQ Release Rate Determined from Number of Chambers and Chamber Release Rate
Q OUT = 0.52 cfs
Unit Flow = 0.21 cfs/acre
T C = 15.8 minutes
Notes:
1. Release rate out of pond based on number of chambers multiplied by release rate per chamber.
2. Rainfall intensities approximated as one-half the 2-yr peak runoff rate.
3. C2 utilized for water quality event detention calculation.
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T) Intensity (I) Qin= ∑C100*Area*I Vi=(Qin*T*60) Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 1.425 1.8 542 1.00 0.52 156 386
10 1.105 1.4 841 1.00 0.52 311 529
15 0.935 1.2 1,067 1.00 0.52 467 600
20 0.805 1.0 1,225 0.89 0.46 557 668
25 0.715 0.9 1,360 0.82 0.42 634 725
30 0.650 0.8 1,483 0.76 0.40 712 771
35 0.585 0.7 1,558 0.73 0.38 790 767
40 0.535 0.7 1,628 0.70 0.36 868 760
45 0.495 0.6 1,694 0.68 0.35 946 749
50 0.460 0.6 1,750 0.66 0.34 1,024 726
55 0.435 0.6 1,820 0.64 0.33 1,101 719
60 0.410 0.5 1,871 0.63 0.33 1,179 692
65 0.385 0.5 1,904 0.62 0.32 1,257 647
70 0.365 0.5 1,944 0.61 0.32 1,335 609
75 0.345 0.4 1,968 0.61 0.31 1,413 556
80 0.330 0.4 2,008 0.60 0.31 1,491 518
85 0.315 0.4 2,037 0.59 0.31 1,568 468
90 0.305 0.4 2,088 0.59 0.30 1,646 442
95 0.290 0.4 2,096 0.58 0.30 1,724 372
100 0.280 0.4 2,130 0.58 0.30 1,802 328
105 0.270 0.3 2,157 0.58 0.30 1,880 277
110 0.260 0.3 2,176 0.57 0.30 1,958 218
115 0.255 0.3 2,231 0.57 0.29 2,035 195
120 0.245 0.3 2,236 0.57 0.29 2,113 123
Required Detention Volume
V 100 = 771 cubic feet
V 100 = 0.02 acre-ft
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Dention Pond Volume (FAA Method)
Platte River Power Authority Campus, Fort Collins, CO
POND ID: Basin A North - Underground Detention LID
WQ Basin Characateristics
Area = 140,718 square feet
Area = 3.23 acres
C 2 = 0.68
Q in = 3.06 cfs
WQ Release Rate Determined from Number of Chambers and Chamber Release Rate
Q OUT = 0.71 cfs
Unit Flow = 0.22 cfs/acre
T C = 15.8 minutes
Notes:
1. Release rate out of pond based on number of chambers multiplied by release rate per chamber.
2. Rainfall intensities approximated as one-half the 2-yr peak runoff rate.
3. C2 utilized for water quality event detention calculation.
Detention Volume Calculations
Rainfall Rainfall Inflow Rate Inflow Volume Adjustment
Factor
Average Outflow Volume Required
Duration (T) Intensity (I) Qin= ∑C100*Area*I Vi=(Qin*T*60) Factor Outflow Rate Vo=Qav*T *60 Storage Volume
m= 0.5(1 + Tc/T) Qav = m*Qout Vs=Vi-Vo
min in/hr cfs ft 3 cfs ft 3 ft 3
5 1.425 3.1 942 1.00 0.71 212 730
10 1.105 2.4 1,461 1.00 0.71 425 1,037
15 0.935 2.1 1,854 1.00 0.71 637 1,218
20 0.805 1.8 2,129 0.89 0.63 759 1,370
25 0.715 1.6 2,364 0.82 0.58 865 1,498
30 0.650 1.4 2,578 0.76 0.54 971 1,607
35 0.585 1.3 2,707 0.73 0.51 1,077 1,630
40 0.535 1.2 2,830 0.70 0.49 1,184 1,646
45 0.495 1.1 2,945 0.68 0.48 1,290 1,656
50 0.460 1.0 3,041 0.66 0.47 1,396 1,645
55 0.435 1.0 3,163 0.64 0.46 1,502 1,662
60 0.410 0.9 3,253 0.63 0.45 1,608 1,645
65 0.385 0.8 3,309 0.62 0.44 1,714 1,595
70 0.365 0.8 3,378 0.61 0.43 1,820 1,558
75 0.345 0.8 3,421 0.61 0.43 1,926 1,495
80 0.330 0.7 3,491 0.60 0.42 2,033 1,458
85 0.315 0.7 3,540 0.59 0.42 2,139 1,402
90 0.305 0.7 3,630 0.59 0.42 2,245 1,385
95 0.290 0.6 3,643 0.58 0.41 2,351 1,292
100 0.280 0.6 3,702 0.58 0.41 2,457 1,245
105 0.270 0.6 3,749 0.58 0.41 2,563 1,185
110 0.260 0.6 3,782 0.57 0.40 2,669 1,112
115 0.255 0.6 3,877 0.57 0.40 2,776 1,102
120 0.245 0.5 3,887 0.57 0.40 2,882 1,006
Required Detention Volume
V 100 = 1,662 cubic feet
V 100 = 0.04 acre-ft
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Underground Detention
Platte River Power Authority Campus, Fort Collins, CO
Required Underground Detention/WQ Volume
Chamber Total Required Detention/ Chamber Chamber Unit Chamber *Installed Min. Min. Min. Req'd Design No. of Provided Provided Total
ID Detention/WQ WQ Type Release Rate
c Unit Chamber Unit No. of WQ Isolator Row Control
i Chambers WQ Isolator Installed
Volume
a
Inflow
b
Volume
d Volume inc. Chambers
f Release Volume by Provided Release Row System
Aggregate
e
Rate
g
FAA Method
h
Rate
j
Volume
k
Volume
l
(cf) (cfs) (cfs) (cf) (cf) (sf) (cfs) (cf) (cfs) (cf) (cf)
Basin A South 1427 2.01 SC-740 0.024 45.90 74.90 20.00 0.47 771 WQCV 22 0.52 1,010 1,648
Basin A North 2172 3.06 SC-740 0.024 45.90 74.90 29.00 0.68 1,662 WQCV 30 0.71 1,377 2,247
TOTAL 3599 5.07 SC-740 0.024 45.90 74.90 49.00 1.16 2,433 WQCV 54 1.23 2,479 4,045
*Volume assumes minimum aggregate depth below chamber.
a. Total required WQCV calculated per 12-hr drain time.
b. WQ inflow is approximated as one-half the 2-yr peak runoff rate.
c. Release rate per chamber, limited by flow through geotextile with accumulated sediment.
d. Volume within chamber only, not accounting for void spaces in surrounding aggregate. The Isolator Row(s) are sized per this unit volume.
e. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit. The total system WQCV is sized per this unit volume.
f. Number of chambers required to provide full WQCV within total installed system, including aggregate.
g. Release rate per chamber times number of chambers. This is used at the 'outlet control' for the FAA calculations.
h. Minimum 'chamber-only' volume to ensure dirty water is fully contained within Isolator Row.
i. Determines whether the design is controlled by the Isolator Row volume or WQCV.
j. Release rate per chamber times number of chambers provided. This is the approximate controlled discharge from the WQ event.
k. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.
l. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required 12-hr WQCV.
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Low Impact Development Summary
Platte River Power Authority Campus, Fort Collins, CO
Basin Proposed
Impervious Area
LID Treatment Area Treated % of Site
Treated
(sf) (acres) (sf) (%)
A-1 24,426 None (1) - 0%
A-2 33,295 None - 0%
A-3 16,242 Underground Detention 16,242 6%
A-4 21,811 Underground Detention 21,811 8%
A-5 14,736 Underground Detention 14,736 5%
A-6 7,951 Underground Detention 7,951 3%
A-7 8,071 Underground Detention 8,071 3%
A-8 6,189 Underground Detention 6,189 2%
A-9 28,026 Underground Detention 28,026 10%
A-10 28,393 Underground Detention 28,393 10%
A-11 11,838 Underground Detention 11,838 4%
A-12 (Future) 19,000 Future LID Treatment (2) 19,000 7%
A-13 11,517 None - 0%
B-1 10,125 Bioswale 10,125 4%
B-2 26,917 Bioswale (3) 26,917 10%
C-1 5,726 Wet Pond 5,726 2%
Total Site 274,263 205,024 75%
(1) Basin A-1 includes approximately 8,500 sf of future building area not being treated
(2) Minimum required future LID treatment for basin A-12
(3) Basin B-2 includes 10,000 sf of future treated area by the future extension of the proposed bioswale
Low Impact Development (LID) Treated Areas
Calculations by: KRB
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Orifice Calculations - Pond A1
Platte River Power Authority Campus, Fort Collins, CO
Detention Volume and Depth
Volume Provided, ft 3
= 126,042
Water Quality Volume, ft 3
= 10,409
Total Volume Provided, ft 3
= 136,451
W.S. Elevation, ft = 4952.25
Invert Elevation, ft = 4948.00
100-year Depth D, ft = 4.25
Top of Pond Elevation, ft = 4953.25
FFE of adjacent building = 4958.00
Pond Freeboard = 1.00
Orifice Opening
Orifice Flow Rate, Q (cfs) = CoAo(2gHo)0.5
Co = 0.65
Q = Qout of pond, cfs = 3.15
gravitational acceleration g, ft/sec 2
= 32.2
diam, ft = 0.622
Effective head on orifice Ho = D-1/2diam, ft = 3.94
Area of orifice Ao, ft 2
= 0.30
Area of orifice Ao, in 2
= 43.82
diam, in = 7.47 7 1/2
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Orifice Calculations - Pond C1
Platte River Power Authority Campus, Fort Collins, CO
Detention Volume and Depth
Volume Provided, ft 3
= 14,406
Water Quality Volume, ft 3
= 400
Total Volume Provided, ft 3
= 14,406
W.S. Elevation, ft = 4955.50
Invert Elevation, ft = 4950.58
100-year Depth D, ft = 4.92
Top of Pond Elevation, ft = 4956.50
FFE of adjacent building = 4958.00
Pond Freeboard = 1.00
Orifice Opening
Orifice Flow Rate, Q (cfs) = CoAo(2gHo)0.5
Co = 0.65
Q = Qout of pond, cfs = 0.50
gravitational acceleration g, ft/sec 2
= 32.2
diam, ft = 0.236
Effective head on orifice Ho = D-1/2diam, ft = 4.80
Area of orifice Ao, ft 2
= 0.04
Area of orifice Ao, in 2
= 6.30
diam, in = 2.83 2 13/16
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Orifice Calculations - Underground Detention (Structure DB1)
Platte River Power Authority Campus, Fort Collins, CO
Detention Volume and Depth
Volume Provided, ft 3
= 4,045
Water Quality Volume, ft 3
= 4,045
Total Volume Provided, ft 3
= 4,045
W.S. Elevation, ft = 4952.72
Invert Elevation, ft = 4950.03
100-year Depth D, ft = 2.69
Spill Elevation, ft = 4952.72
FFE of adjacent building = 4958.00
Pond Freeboard = N/A
Orifice Opening
Orifice Flow Rate, Q (cfs) = CoAo(2gHo)0.5
Co = 0.65
Q = Qout of pond, cfs = 1.23
gravitational acceleration g, ft/sec 2
= 32.2
diam, ft = 0.437
Effective head on orifice Ho = D-1/2diam, ft = 2.47
Area of orifice Ao, ft 2
= 0.15
Area of orifice Ao, in 2
= 21.60
diam, in = 5.24 5 1/4
Date: 2/1/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: Outlet 1-1 (Pond A1)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Custom
Wier Perimeter: 15.00
Open Area of Grate (ft2): 4.99
Grate Elevation (ft): 4950.00 Q100 = 3.15 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4950.00 0.00 0.00 0.00
0.05 4950.05 0.25 3.00 0.25
0.10 4950.10 0.71 4.24 0.71
0.15 4950.15 1.31 5.19 1.31
0.20 4950.20 2.01 6.00 2.01
0.25 4950.25 2.81 6.70 2.81
0.27 4950.27 3.15 6.96 3.15 <---- 100-Year Flow
0.35 4950.35 4.66 7.93 4.66
0.40 4950.40 5.69 8.48 5.69
0.45 4950.45 6.79 8.99 6.79
0.50 4950.50 7.95 9.48 7.95
0.55 4950.55 9.18 9.94 9.18
0.60 4950.60 10.46 10.39 10.39
0.65 4950.65 11.79 10.81 10.81
0.70 4950.70 13.18 11.22 11.22
0.75 4950.75 14.61 11.61 11.61
0.80 4950.80 16.10 11.99 11.99
0.85 4950.85 17.63 12.36 12.36
0.90 4950.90 19.21 12.72 12.72
0.95 4950.95 20.83 13.07 13.07
1.00 4951.00 22.50 13.41 13.41
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: Outlet 5-1 (W) (Pond C1)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Type C
Wier Perimeter: 12.29
Open Area of Grate (ft2): 4.09
Grate Elevation (ft): 4955.00 Q100 = 0.50 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4955.00 0.00 0.00 0.00
0.05 4955.05 0.21 2.46 0.21
0.09 4955.09 0.50 3.30 0.50 <---- 100-Year Flow
0.15 4955.15 1.07 4.26 1.07
0.22 4955.22 1.93 5.18 1.93
0.25 4955.25 2.30 5.50 2.30
0.30 4955.30 3.03 6.02 3.03
0.35 4955.35 3.82 6.50 3.82
0.40 4955.40 4.66 6.95 4.66
0.45 4955.45 5.56 7.37 5.56
0.50 4955.50 6.52 7.77 6.52
0.55 4955.55 7.52 8.15 7.52
0.60 4955.60 8.57 8.51 8.51
0.65 4955.65 9.66 8.86 8.86
0.70 4955.70 10.80 9.20 9.20
0.75 4955.75 11.97 9.52 9.52
0.80 4955.80 13.19 9.83 9.83
0.85 4955.85 14.45 10.13 10.13
0.90 4955.90 15.74 10.43 10.43
0.95 4955.95 17.07 10.71 10.71
1.00 4956.00 18.44 10.99 10.99
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Feb 1 2018
Pond A1 - Emergency Overflow Weir
Trapezoidal Weir
Crest = Sharp
Bottom Length (ft) = 40.00
Total Depth (ft) = 1.00
Side Slope (z:1) = 4.00
Calculations
Weir Coeff. Cw = 3.10
Compute by: Known Q
Known Q (cfs) = 62.13
Highlighted
Depth (ft) = 0.62
Q (cfs) = 62.13
Area (sqft) = 26.34
Velocity (ft/s) = 2.36
Top Width (ft) = 44.96
0 5 10 15 20 25 30 35 40 45 50 55 60
Depth (ft) Pond A1 - Emergency Overflow Weir Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
1.50 1.50
2.00 2.00
Weir W.S. Length (ft)
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Feb 1 2018
Pond C1 - Emergency Overflow Weir
Trapezoidal Weir
Crest = Sharp
Bottom Length (ft) = 10.00
Total Depth (ft) = 1.00
Side Slope (z:1) = 4.00
Calculations
Weir Coeff. Cw = 3.10
Compute by: Known Q
Known Q (cfs) = 4.27
Highlighted
Depth (ft) = 0.26
Q (cfs) = 4.270
Area (sqft) = 2.87
Velocity (ft/s) = 1.49
Top Width (ft) = 12.08
0 2 4 6 8 10 12 14 16 18 20 22
Depth (ft) Pond C1 - Emergency Overflow Weir Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
1.50 1.50
2.00 2.00
Weir W.S. Length (ft)
APPENDIX C
Hydraulic Calculations
Culvert Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Jan 18 2018
Storm Line 4
Invert Elev Dn (ft) = 4948.87
Pipe Length (ft) = 50.00
Slope (%) = 0.26
Invert Elev Up (ft) = 4949.00
Rise (in) = 24.0
Shape = Circular
Span (in) = 24.0
No. Barrels = 1
n-Value = 0.012
Culvert Type = Circular Culvert
Culvert Entrance = Smooth tapered inlet throat
Coeff. K,M,c,Y,k = 0.534, 0.555, 0.0196, 0.9, 0.2
Embankment
Top Elevation (ft) = 4952.92
Top Width (ft) = 20.00
Crest Width (ft) = 100.00
Calculations
Qmin (cfs) = 23.76
Qmax (cfs) = 23.76
Tailwater Elev (ft) = (dc+D)/2
Highlighted
Qtotal (cfs) = 23.76
Qpipe (cfs) = 23.76
Qovertop (cfs) = 0.00
Veloc Dn (ft/s) = 7.79
Veloc Up (ft/s) = 7.56
HGL Dn (ft) = 4950.73
HGL Up (ft) = 4951.23
Hw Elev (ft) = 4951.92
Hw/D (ft) = 1.46
Flow Regime = Inlet Control
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 3-3.1 (Basin A-7)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: 15" Nyloplast w/ Domed Grate
Wier Perimeter: 8.45
Open Area of Grate (ft2): 0.85 Q2 = 0.24 cfs
Flowline Elevation (ft): 4954.61 Q100 = 1.17 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4954.61 0.00 0.00 0.00
0.05 4954.66 0.14 0.51 0.14
0.07 4954.68 0.24 0.61 0.24 <---- 2-Year Flow
0.15 4954.76 0.74 0.88 0.74
0.20 4954.81 1.13 1.02 1.02
0.26 4954.87 1.70 1.17 1.17 <---- 100-Year Flow
0.30 4954.91 2.08 1.25 1.25
0.35 4954.96 2.62 1.35 1.35
0.40 4955.01 3.21 1.44 1.44
0.46 4955.07 3.95 1.55 1.55
0.50 4955.11 4.48 1.62 1.62
0.55 4955.16 5.17 1.69 1.69
0.59 4955.20 5.74 1.75 1.75 <---- Spill Elevation
0.65 4955.26 6.64 1.84 1.84
0.70 4955.31 7.42 1.91 1.91
0.75 4955.36 8.23 1.98 1.98
0.80 4955.41 9.07 2.04 2.04
0.85 4955.46 9.93 2.11 2.11
0.90 4955.51 10.82 2.17 2.17
0.95 4955.56 11.74 2.23 2.23
1.00 4955.61 12.68 2.28 2.28
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 3-3.2 (Basin A-7)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: 15" Nyloplast w/ Domed Grate
Wier Perimeter: 8.45
Open Area of Grate (ft2): 0.85 Q2 = 0.25 cfs
Flowline Elevation (ft): 4954.75 Q100 = 1.20 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4954.75 0.00 0.00 0.00
0.05 4954.80 0.14 0.51 0.14
0.07 4954.82 0.25 0.62 0.25 <---- 2-Year Flow
0.15 4954.90 0.74 0.88 0.74
0.20 4954.95 1.13 1.02 1.02
0.28 4955.03 1.83 1.20 1.20 <---- 100-Year Flow
0.30 4955.05 2.08 1.25 1.25
0.35 4955.10 2.62 1.35 1.35 <---- Spill Elevation
0.40 4955.15 3.21 1.44 1.44
0.45 4955.20 3.83 1.53 1.53
0.50 4955.25 4.48 1.62 1.62
0.55 4955.30 5.17 1.69 1.69
0.60 4955.35 5.89 1.77 1.77
0.65 4955.40 6.64 1.84 1.84
0.70 4955.45 7.42 1.91 1.91
0.75 4955.50 8.23 1.98 1.98
0.80 4955.55 9.07 2.04 2.04
0.85 4955.60 9.93 2.11 2.11
0.90 4955.65 10.82 2.17 2.17
0.95 4955.70 11.74 2.23 2.23
1.00 4955.75 12.68 2.28 2.28
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 3-6 (N) (Basin A-9)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Type C
Wier Perimeter: 12.29
Open Area of Grate (ft2): 4.09 Q2 = 1.74 cfs
Flowline Elevation (ft): 4955.14 Q100 = 6.41 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4955.14 0.00 0.00 0.00
0.05 4955.19 0.21 2.46 0.21
0.10 4955.24 0.58 3.48 0.58
0.15 4955.29 1.07 4.26 1.07
0.21 4955.35 1.74 5.00 1.74 <---- 2-Year Flow
0.25 4955.39 2.30 5.50 2.30
0.30 4955.44 3.03 6.02 3.03
0.35 4955.49 3.82 6.50 3.82
0.40 4955.54 4.66 6.95 4.66
0.45 4955.59 5.56 7.37 5.56
0.49 4955.63 6.41 7.73 6.41 <---- 100-Year Flow
0.55 4955.69 7.52 8.15 7.52
0.60 4955.74 8.57 8.51 8.51
0.65 4955.79 9.66 8.86 8.86
0.70 4955.84 10.80 9.20 9.20
0.75 4955.89 11.97 9.52 9.52
0.80 4955.94 13.19 9.83 9.83
0.85 4955.99 14.45 10.13 10.13
0.90 4956.04 15.74 10.43 10.43
0.95 4956.09 17.07 10.71 10.71
1.00 4956.14 18.44 10.99 10.99
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 3-8 (Basin A-10)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Type C
Wier Perimeter: 12.29
Open Area of Grate (ft2): 4.09 Q2 = 1.78 cfs
Flowline Elevation (ft): 4955.64 Q100 = 6.74 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4955.64 0.00 0.00 0.00
0.05 4955.69 0.21 2.46 0.21
0.10 4955.74 0.58 3.48 0.58
0.15 4955.79 1.07 4.26 1.07
0.21 4955.85 1.78 5.04 1.78 <---- 2-Year Flow
0.25 4955.89 2.30 5.50 2.30
0.30 4955.94 3.03 6.02 3.03
0.35 4955.99 3.82 6.50 3.82
0.40 4956.04 4.66 6.95 4.66
0.45 4956.09 5.56 7.37 5.56
0.51 4956.15 6.74 7.86 6.74 <---- 100-Year Flow
0.55 4956.19 7.52 8.15 7.52
0.60 4956.24 8.57 8.51 8.51
0.65 4956.29 9.66 8.86 8.86
0.70 4956.34 10.80 9.20 9.20
0.75 4956.39 11.97 9.52 9.52
0.80 4956.44 13.19 9.83 9.83
0.85 4956.49 14.45 10.13 10.13
0.90 4956.54 15.74 10.43 10.43
0.95 4956.59 17.07 10.71 10.71
1.00 4956.64 18.44 10.99 10.99
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 3-7 (S) (Basin A-11)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Type C
Wier Perimeter: 12.29
Open Area of Grate (ft2): 4.09 Q2 = 1.06 cfs
Flowline Elevation (ft): 4954.38 Q100 = 4.63 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4954.38 0.00 0.00 0.00
0.05 4954.43 0.21 2.46 0.21
0.10 4954.48 0.58 3.48 0.58
0.15 4954.53 1.06 4.24 1.06 <---- 2-Year Flow
0.20 4954.58 1.65 4.92 1.65
0.25 4954.63 2.30 5.50 2.30
0.30 4954.68 3.03 6.02 3.03
0.35 4954.73 3.82 6.50 3.82
0.40 4954.78 4.63 6.93 4.63 <---- 100-Year Flow
0.45 4954.83 5.56 7.37 5.56
0.50 4954.88 6.52 7.77 6.52
0.55 4954.93 7.52 8.15 7.52
0.60 4954.98 8.57 8.51 8.51
0.65 4955.03 9.66 8.86 8.86
0.70 4955.08 10.80 9.20 9.20
0.75 4955.13 11.97 9.52 9.52
0.80 4955.18 13.19 9.83 9.83
0.85 4955.23 14.45 10.13 10.13
0.90 4955.28 15.74 10.43 10.43
0.95 4955.33 17.07 10.71 10.71
1.00 4955.38 18.44 10.99 10.99
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 2-4 (Basin A-12)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Type D
Wier Perimeter: 17.17
Open Area of Grate (ft2): 7.69 Q2 = 2.86 cfs
Flowline Elevation (ft): 4954.11 Q100 = 11.43 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4954.11 0.00 0.00 0.00
0.05 4954.16 0.29 4.62 0.29
0.10 4954.21 0.81 6.53 0.81
0.15 4954.26 1.50 8.00 1.50
0.20 4954.31 2.30 9.24 2.30
0.23 4954.34 2.86 9.93 2.86 <---- 2-Year Flow
0.30 4954.41 4.23 11.32 4.23
0.35 4954.46 5.33 12.22 5.33
0.40 4954.51 6.52 13.07 6.52
0.45 4954.56 7.77 13.86 7.77
0.50 4954.61 9.11 14.61 9.11
0.55 4954.66 10.51 15.32 10.51
0.58 4954.69 11.43 15.76 11.43 <---- 100-Year Flow
0.65 4954.76 13.50 16.66 13.50
0.70 4954.81 15.08 17.29 15.08
0.75 4954.86 16.73 17.90 16.73
0.80 4954.91 18.43 18.48 18.43
0.85 4954.96 20.18 19.05 19.05
0.90 4955.01 21.99 19.60 19.60
0.95 4955.06 23.85 20.14 20.14
1.00 4955.11 25.76 20.66 20.66
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 5-4 (N) (Basin B-1)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Type C
Wier Perimeter: 12.29
Open Area of Grate (ft2): 4.09 Q2 = 0.69 cfs
Flowline Elevation (ft): 4954.89 Q100 = 3.22 cfs
Allowable Capacity: 50% Q100 Carryover= 1.57 cfs
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4954.89 0.00 0.00 0.00
0.05 4954.94 0.21 2.46 0.21
0.11 4955.00 0.69 3.68 0.69 <---- 2-Year Flow
0.15 4955.04 1.07 4.26 1.07
0.20 4955.09 1.65 4.92 1.65 <---- Highpoint location
0.25 4955.14 2.30 5.50 2.30
0.31 4955.20 3.22 6.14 3.22 <---- 100-Year Flow
0.35 4955.24 3.82 6.50 3.82
0.40 4955.29 4.66 6.95 4.66
0.45 4955.34 5.56 7.37 5.56
0.50 4955.39 6.52 7.77 6.52
0.55 4955.44 7.52 8.15 7.52
0.60 4955.49 8.57 8.51 8.51
0.65 4955.54 9.66 8.86 8.86
0.70 4955.59 10.80 9.20 9.20
0.75 4955.64 11.97 9.52 9.52
0.80 4955.69 13.19 9.83 9.83
0.85 4955.74 14.45 10.13 10.13
0.90 4955.79 15.74 10.43 10.43
0.95 4955.84 17.07 10.71 10.71
1.00 4955.89 18.44 10.99 10.99
To Basin B2
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Platte River Power Authority HQ
Fort Collins, CO
Inlet Capacity
______________________________________________________________________________________________________
INLET ID: 5-5 (Basin B-2)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: Type D
Wier Perimeter: 17.17
Open Area of Grate (ft2): 7.69 Q2 = 1.90 cfs
Flowline Elevation (ft): 4954.37 Q100 = 9.85 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Elevation Shallow Orifice Actual
Above Inlet Weir Flow Flow Flow
(ft) (ft) (cfs) (cfs) (cfs)
0.00 4954.37 0.00 0.00 0.00
0.05 4954.42 0.29 4.62 0.29
0.10 4954.47 0.81 6.53 0.81
0.15 4954.52 1.50 8.00 1.50
0.22 4954.59 2.66 9.69 2.66 <---- 2-Year Flow
0.25 4954.62 3.22 10.33 3.22
0.30 4954.67 4.23 11.32 4.23
0.35 4954.72 5.33 12.22 5.33
0.40 4954.77 6.52 13.07 6.52
0.45 4954.82 7.77 13.86 7.77
0.50 4954.87 9.11 14.61 9.11
0.53 4954.90 9.85 15.00 9.85 <---- 100-Year Flow
0.59 4954.96 11.57 15.83 11.57
0.65 4955.02 13.50 16.66 13.50
0.70 4955.07 15.08 17.29 15.08
0.75 4955.12 16.73 17.90 16.73
0.80 4955.17 18.43 18.48 18.43
0.85 4955.22 20.18 19.05 19.05
0.90 4955.27 21.99 19.60 19.60
0.95 4955.32 23.85 20.14 20.14
1.00 4955.37 25.76 20.66 20.66
*Includes 1.57 cfs
carryover from B1
Q = 3 . 0 P H 1 . 5
Q = 0 .67A ( 2 gH ) 0 . 5
Calculations by: NKS
Date: 2/9/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 5.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 20.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 10.0 20.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 7.0 inches
Check boxes are not applicable in SUMP conditions
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Enter Your Project Name Here
2-1 (Basin A2)
UD-Inlet_v4.05-Proposed Inlet.xlsm, 2-1 (Basin A2) 2/1/2018, 2:17 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from above) alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 3.9 7.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 10.00 10.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.16 0.42 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.37 0.66
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 0.78 0.99
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 2.3 12.2 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 2.2 9.1 cfs
CDOT Type R Curb Opening
INLET IN A SUMP OR SAG LOCATION
Version 4.05 Released March 2017
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_v4.05-Proposed Inlet.xlsm, 2-1 (Basin A2) 2/1/2018, 2:17 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 5.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 20.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 10.0 20.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 7.0 inches
Check boxes are not applicable in SUMP conditions
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Enter Your Project Name Here
2-5 (Basin A4)
UD-Inlet_v4.05-Proposed Inlet.xlsm, 2-5 (Basin A4) 2/1/2018, 2:17 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from above) alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 3.9 7.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.16 0.42 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.50 0.90
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 1.8 7.5 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 1.4 5.6 cfs
CDOT Type R Curb Opening
INLET IN A SUMP OR SAG LOCATION
Version 4.05 Released March 2017
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_v4.05-Proposed Inlet.xlsm, 2-5 (Basin A4) 2/1/2018, 2:17 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 5.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 20.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 10.0 20.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 7.0 inches
Check boxes are not applicable in SUMP conditions
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Enter Your Project Name Here
2-6 (Basin A5)
UD-Inlet_v4.05-Proposed Inlet.xlsm, 2-6 (Basin A5) 2/1/2018, 2:17 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from above) alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 3.9 7.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.16 0.42 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.50 0.90
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 1.8 7.5 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 1.0 4.0 cfs
CDOT Type R Curb Opening
INLET IN A SUMP OR SAG LOCATION
Version 4.05 Released March 2017
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_v4.05-Proposed Inlet.xlsm, 2-6 (Basin A5) 2/1/2018, 2:17 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 5.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.021 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 20.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 10.0 20.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 5.0 5.0 inches
Check boxes are not applicable in SUMP conditions
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Enter Your Project Name Here
3-3 (E) (Basin A6)
UD-Inlet_v4.05-Proposed Inlet.xlsm, 3-3 (E) (Basin A6) 2/1/2018, 2:17 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from above) alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 5.0 5.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.25 0.25 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.64 0.64
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 3.48 3.48 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 0.62 2.72 cfs
Warning 5: The width of unit is greater than the gutter width.
CDOT Type R Curb Opening
INLET IN A SUMP OR SAG LOCATION
Version 4.05 Released March 2017
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_v4.05-Proposed Inlet.xlsm, 3-3 (E) (Basin A6) 2/1/2018, 2:17 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 5.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 20.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 10.0 20.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 6.0 inches
Check boxes are not applicable in SUMP conditions
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Enter Your Project Name Here
3-5 (Basin A8)
UD-Inlet_v4.05-Proposed Inlet.xlsm, 3-5 (Basin A8) 2/1/2018, 2:17 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from above) alocal = 3.00 3.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Ponding Depth = 3.9 6.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = N/A N/A feet
Width of a Unit Grate Wo = N/A N/A feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = N/A N/A
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = N/A N/A
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = N/A N/A
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = N/A N/A
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 5.00 5.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.00 6.00 inches
Height of Curb Orifice Throat in Inches Hthroat = 6.00 6.00 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 63.40 63.40 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.60 3.60
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.67 0.67
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = N/A N/A ft
Depth for Curb Opening Weir Equation dCurb = 0.16 0.33 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.50 0.77
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = N/A N/A
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 1.8 5.4 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 0.4 1.8 cfs
CDOT Type R Curb Opening
INLET IN A SUMP OR SAG LOCATION
Version 4.05 Released March 2017
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT Type R Curb Opening
Override Depths
UD-Inlet_v4.05-Proposed Inlet.xlsm, 3-5 (Basin A8) 2/1/2018, 2:17 PM
Project:
Inlet ID:
Gutter Geometry (Enter data in the blue cells)
Maximum Allowable Width for Spread Behind Curb TBACK = 10.0 ft
Side Slope Behind Curb (leave blank for no conveyance credit behind curb) SBACK = 0.020 ft/ft
Manning's Roughness Behind Curb (typically between 0.012 and 0.020) nBACK = 0.013
Height of Curb at Gutter Flow Line HCURB = 6.00 inches
Distance from Curb Face to Street Crown TCROWN = 40.0 ft
Gutter Width W = 2.00 ft
Street Transverse Slope SX = 0.020 ft/ft
Gutter Cross Slope (typically 2 inches over 24 inches or 0.083 ft/ft) SW = 0.083 ft/ft
Street Longitudinal Slope - Enter 0 for sump condition SO = 0.000 ft/ft
Manning's Roughness for Street Section (typically between 0.012 and 0.020) nSTREET = 0.013
Minor Storm Major Storm
Max. Allowable Spread for Minor & Major Storm TMAX = 18.5 40.0 ft
Max. Allowable Depth at Gutter Flowline for Minor & Major Storm dMAX = 6.0 8.3 inches
Check boxes are not applicable in SUMP conditions
MINOR STORM Allowable Capacity is based on Depth Criterion Minor Storm Major Storm
MAJOR STORM Allowable Capacity is based on Depth Criterion Qallow = SUMP SUMP cfs
Version 4.05 Released March 2017
ALLOWABLE CAPACITY FOR ONE-HALF OF STREET (Minor & Major Storm)
(Based on Regulated Criteria for Maximum Allowable Flow Depth and Spread)
Enter Your Project Name Here
5-3 (Basin OS-3)
UD-Inlet_v4.05-Proposed Inlet.xlsm, Existing Horsetooth Inlet 2/1/2018, 2:17 PM
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from above) alocal = 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 2 2
Water Depth at Flowline (outside of local depression) Ponding Depth = 6.0 8.3 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo (G) = 3.00 3.00 feet
Width of a Unit Grate Wo = 1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio = 0.43 0.43
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf (G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw (G) = 3.30 3.30
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co (G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo (C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert = 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat = 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp = 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf (C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.7) Cw (C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co (C) = 0.66 0.66
Low Head Performance Reduction (Calculated) MINOR MAJOR
Depth for Grate Midwidth dGrate = 0.519 0.714 ft
Depth for Curb Opening Weir Equation dCurb = 0.33 0.53 ft
Combination Inlet Performance Reduction Factor for Long Inlets RFCombination = 0.70 0.98
Curb Opening Performance Reduction Factor for Long Inlets RFCurb = 1.00 1.00
Grated Inlet Performance Reduction Factor for Long Inlets RFGrate = 0.70 0.98
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa
= 5.2 12.9 cfs
Inlet Capacity IS GOOD for Minor and Major Storms(>Q PEAK) Q PEAK REQUIRED = 1.9 9.1 cfs
CDOT/Denver 13 Combination
INLET IN A SUMP OR SAG LOCATION
Version 4.05 Released March 2017
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
CDOT/Denver 13 Combination
Override Depths
UD-Inlet_v4.05-Proposed Inlet.xlsm, Existing Horsetooth Inlet 2/1/2018, 2:17 PM
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Feb 8 2018
Basin A7 Swale - Downstream at SE corner of Substation Garage
User-defined
Invert Elev (ft) = 4954.60
Slope (%) = 0.50
N-Value = 0.029
Calculations
Compute by: Known Q
Known Q (cfs) = 1.60
(Sta, El, n)-(Sta, El, n)...
( 0.00, 4955.60)-(4.50, 4954.68, 0.035)-(5.50, 4954.60, 0.013)-(6.50, 4954.68, 0.013)-(12.00, 4955.20, 0.035)
Highlighted
Depth (ft) = 0.37
Q (cfs) = 1.600
Area (sqft) = 1.31
Velocity (ft/s) = 1.22
Wetted Perim (ft) = 6.54
Crit Depth, Yc (ft) = 0.27
Top Width (ft) = 6.49
EGL (ft) = 0.39
-2 0 2 4 6 8 10 12 14
Elev (ft) Section Depth (ft)
4954.00 -0.60
4954.50 -0.10
4955.00 0.40
4955.50 0.90
4956.00 1.40
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Feb 1 2018
Basin A11 Swale - Downstream at SW corner of Fleet Parking A
User-defined
Invert Elev (ft) = 4954.63
Slope (%) = 0.50
N-Value = 0.013
Calculations
Compute by: Known Q
Known Q (cfs) = 5.12
(Sta, El, n)-(Sta, El, n)...
( 0.00, 4955.97)-(4.50, 4955.21, 0.013)-(4.55, 4954.71, 0.013)-(5.55, 4954.63, 0.013)-(6.55, 4954.71, 0.013)-(6.60, 4955.21, 0.013)-(8.60, 4955.64, 0.013)
Highlighted
Depth (ft) = 0.66
Q (cfs) = 5.120
Area (sqft) = 1.31
Velocity (ft/s) = 3.92
Wetted Perim (ft) = 3.87
Crit Depth, Yc (ft) = 0.69
Top Width (ft) = 2.95
EGL (ft) = 0.90
-1 0 1 2 3 4 5 6 7 8 9 10
Elev (ft) Section Depth (ft)
4954.00 -0.63
4954.50 -0.13
4955.00 0.37
4955.50 0.87
4956.00 1.37
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Thursday, Feb 1 2018
Basin B2 Swale - Downstream at Bioswale
User-defined
Invert Elev (ft) = 4954.30
Slope (%) = 0.50
N-Value = 0.024
Calculations
Compute by: Known Q
Known Q (cfs) = 11.01
(Sta, El, n)-(Sta, El, n)...
( 0.00, 4954.82)-(17.00, 4954.43, 0.013)-(18.50, 4954.40, 0.013)-(23.50, 4954.30, 0.035)-(28.50, 4954.40, 0.035)-(33.50, 4955.40, 0.035)
Highlighted
Depth (ft) = 0.43
Q (cfs) = 11.01
Area (sqft) = 6.51
Velocity (ft/s) = 1.69
Wetted Perim (ft) = 26.27
Crit Depth, Yc (ft) = 0.35
Top Width (ft) = 26.23
EGL (ft) = 0.47
-5 0 5 10 15 20 25 30 35 40
Elev (ft) Section Depth (ft)
4953.50 -0.80
4954.00 -0.30
4954.50 0.20
4955.00 0.70
4955.50 1.20
4956.00 1.70
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Feb 7 2018
2' CURB CUT (MAXIMUM CAPACITY)
Rectangular
Bottom Width (ft) = 2.00
Total Depth (ft) = 0.50
Invert Elev (ft) = 100.00
Slope (%) = 2.00
N-Value = 0.025
Calculations
Compute by: Known Depth
Known Depth (ft) = 0.50
Highlighted
Depth (ft) = 0.50
Q (cfs) = 4.040
Area (sqft) = 1.00
Velocity (ft/s) = 4.04
Wetted Perim (ft) = 3.00
Crit Depth, Yc (ft) = 0.50
Top Width (ft) = 2.00
EGL (ft) = 0.75
0 .5 1 1.5 2 2.5 3
Elev (ft) Section Depth (ft)
99.75 -0.25
100.00 0.00
100.25 0.25
100.50 0.50
100.75 0.75
101.00 1.00
Reach (ft)
APPENDIX D
Referenced Materials
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Area, Colorado
Platte River Power Authority
Natural
Resources
Conservation
Service
February 23, 2017
9
Custom Soil Resource Report
Soil Map
4486900 4487100 4487300 4487500 4487700 4487900 4488100 4488300 4488500
4486900 4487100 4487300 4487500 4487700 4487900 4488100 4488300 4488500
495900 496100 496300 496500 496700 496900 497100
495900 496100 496300 496500 496700 496900 497100
40° 32' 50'' N
105° 2' 55'' W
40° 32' 50'' N
105° 1' 59'' W
40° 31' 54'' N
105° 2' 55'' W
40° 31' 54'' N
105° 1' 59'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 400 800 1600 2400
Feet
0 100 200 400 600
Meters
Map Scale: 1:8,480 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
Map Unit Legend
Larimer County Area, Colorado (CO644)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
6 Aquepts, ponded 3.5 1.0%
34 Fort Collins loam, 0 to 1 percent
slopes
8.6 2.4%
35 Fort Collins loam, 0 to 3 percent
slopes
4.2 1.2%
36 Fort Collins loam, 3 to 5 percent
slopes
5.7 1.6%
73 Nunn clay loam, 0 to 1 percent
slopes
180.2 50.8%
74 Nunn clay loam, 1 to 3 percent
slopes
131.4 37.1%
75 Nunn clay loam, 3 to 5 percent
slopes
13.3 3.8%
76 Nunn clay loam, wet, 1 to 3
percent slopes
7.6 2.2%
Totals for Area of Interest 354.6 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
Custom Soil Resource Report
11
73—Nunn clay loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: 2tlng
Elevation: 4,100 to 5,700 feet
Mean annual precipitation: 14 to 15 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period: 135 to 152 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Nunn and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn
Setting
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Pleistocene aged alluvium and/or eolian deposits
Typical profile
Ap - 0 to 6 inches: clay loam
Bt1 - 6 to 10 inches: clay loam
Bt2 - 10 to 26 inches: clay loam
Btk - 26 to 31 inches: clay loam
Bk1 - 31 to 47 inches: loam
Bk2 - 47 to 80 inches: loam
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 7 percent
Salinity, maximum in profile: Nonsaline (0.1 to 1.0 mmhos/cm)
Sodium adsorption ratio, maximum in profile: 0.5
Available water storage in profile: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 4e
Custom Soil Resource Report
18
Hydrologic Soil Group: C
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit: 10 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Wages
Percent of map unit: 5 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
74—Nunn clay loam, 1 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2tlpl
Elevation: 3,900 to 5,840 feet
Mean annual precipitation: 13 to 17 inches
Mean annual air temperature: 50 to 54 degrees F
Frost-free period: 135 to 160 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Nunn and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn
Setting
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Pleistocene aged alluvium and/or eolian deposits
Typical profile
Ap - 0 to 9 inches: clay loam
Bt - 9 to 13 inches: clay loam
Custom Soil Resource Report
19
Btk - 13 to 25 inches: clay loam
Bk1 - 25 to 38 inches: clay loam
Bk2 - 38 to 80 inches: clay loam
Properties and qualities
Slope: 1 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 7 percent
Salinity, maximum in profile: Nonsaline to very slightly saline (0.1 to 2.0
mmhos/cm)
Sodium adsorption ratio, maximum in profile: 0.5
Available water storage in profile: High (about 9.9 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: C
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit: 10 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Satanta
Percent of map unit: 5 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
75—Nunn clay loam, 3 to 5 percent slopes
Map Unit Setting
National map unit symbol: 2tlpm
Custom Soil Resource Report
20
Table—Hydrologic Soil Group (Platte River Power Authority)
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
6 Aquepts, ponded A/D 3.5 1.0%
34 Fort Collins loam, 0 to 1
percent slopes
B 8.6 2.4%
35 Fort Collins loam, 0 to 3
percent slopes
C 4.2 1.2%
36 Fort Collins loam, 3 to 5
percent slopes
B 5.7 1.6%
73 Nunn clay loam, 0 to 1
percent slopes
C 180.2 50.8%
74 Nunn clay loam, 1 to 3
percent slopes
C 131.4 37.1%
75 Nunn clay loam, 3 to 5
percent slopes
C 13.3 3.8%
76 Nunn clay loam, wet, 1 to
3 percent slopes
C 7.6 2.2%
Totals for Area of Interest 354.6 100.0%
Rating Options—Hydrologic Soil Group (Platte River Power
Authority)
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Custom Soil Resource Report
28
References
American Association of State Highway and Transportation Officials (AASHTO).
2004. Standard specifications for transportation materials and methods of sampling
and testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife
Service FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric
soils in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service.
U.S. Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for
making and interpreting soil surveys. 2nd edition. Natural Resources Conservation
Service, U.S. Department of Agriculture Handbook 436. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://
www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/
home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
29
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States,
the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook
296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?
cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf
Custom Soil Resource Report
30
This unofficial copy was downloaded on Nov-02-2016 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact Engineering Office 281 North College Fort Collins, CO 80521 USA
This unofficial copy was downloaded on Nov-02-2016 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact Engineering Office 281 North College Fort Collins, CO 80521 USA
This unofficial copy was downloaded on Nov-02-2016 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact Engineering Office 281 North College Fort Collins, CO 80521 USA
APPENDIX E
Drainage Exhibits
SOUTHEAST CORNER
S30, T.7N., R68W
50' RIGHT-OF-WAY
R.O.W.
WIDTH
VARIES
60' RIGHT-OF-WAY
107.5' RIGHT-OF-WAY
50' RIGHT-OF-WAY
R.O.W.
WIDTH VARIES
2.21
1.29
2.38
3.75
2.33
1.35
2.19
0.31
0.33
0.93
0.54
EX1
EX4
OS1
EX2
EX3
EX5
OS2a
OS3
OS4
OS2b
OS5
EAST HORSETOOTH ROAD
SOUTH TIMBERLINE ROAD
DANFIELD COURT
UNION PACIFIC RAILROAD
OFFSITE PROPERTY OWNED BY:
2001 DANFIELD LLC
EXISTING E/O
BUILDING
EXISTING FITNESS/ EXISTING HQ
POOL CAR GARAGE
EXISTING MICROWAVE
BUILDING
EXISTING WAREHOUSE/
SUBSTATION GARAGE
EXISTING
CARPENTER
SHOP
EXISTING POND
EXISTING DETENTION
EXISTING
DETENTION
EXISTING DETENTION
EXISTING STORM DRAINING
HORSETOOTH ROAD
EXISTING STORM
DRAINING BASIN OS3
PLATTE RIVER POWER AUTHORITY 2/14/18
SOUTHEAST CORNER
S30, T.7N., R68W
50' RIGHT-OF-WAY
R.O.W.
WIDTH
VARIES
60' RIGHT-OF-WAY
107.5' RIGHT-OF-WAY
50' RIGHT-OF-WAY
R.O.W.
WIDTH VARIES
A1
C1
OS1
OS2a
OS3
OS4
OS2b
A2
A3
A13
B1
B2
A5 A4
A6
A7
A9
A10
A11
A8
0.42
1.35
3.49
1.23
0.68
0.21
0.93
0.37 0.26
0.91
0.42
1.45
0.40 0.57
A12
0.41
0.68 0.64 0.32
0.97
0.21
0.54
OS5
DETENTION
POND A1
DETENTION
POND A1
POND OUTLET STRUCTURE
POND OUTLET STRUCTURE
EAST HORSETOOTH ROAD
SOUTH TIMBERLINE ROAD
DANFIELD COURT
UNION PACIFIC RAILROAD
OFFSITE PROPERTY OWNED BY:
2001 DANFIELD LLC
HQ BUILDING
MICROWAVE
BUILDING
MAINTENANCE SHOP
/ TRUCK WASH
POOL CAR
WAREHOUSE
SUBSTATION GARAGE
FLEET PARKING GARAGE A
PROPOSED
POND
FLEET PARKING
GARAGE B
BIOSWALE W/
UNDERDRAIN
POTENTIAL FUTURE
PARKING AREA
POTENTIAL FUTURE BIOSWALE
UNDERGROUND
DETENTION
EXISTING STORM
DRAINING BASIN OS3
DANFIELD COURT
PROPOSED
POND C1
1.15
PLATTE RIVER POWER AUTHORITY 02/14/18
U16014
1" = 60'
1" = N/A
PLATTE RIVER POWER AUTHORITY HQ
NORTH
2/9/2018 5:32:19 AM
P:\U16014 - PRPA CAMPUS\CADD\CP\C6.00_PROPOSED DRAINAGE PLAN.DWG
C6.00_PROPOSED DRAINAGE PLAN
KRB NKS
C6.00
73
DRAINAGE PLAN
0 60' 120'
SCALE: 1" = 60'
30'
PREPARED FOR:
JOB NUMBER
SHEET NUMBER
OF SHEETS
DATE SUBMITTED:
The engineer preparing these plans will not be responsible
for, or liable for, unauthorized changes to or uses of these
plans. All changes to the plans must be in writing and
must be approved by the preparer of these plans.
NO. BY DATE
CAUTION
REVISIONS:
VERTICAL:
HORIZONTAL:
SCALE
PRELIMINARY
PLANS
NOT FOR CONSTRUCTION
1501 Academy Ct.
Ste. 203
Fort Collins, CO 80524
(970) 530-4044
www.unitedcivil.com
Civil Engineering &
Consulting
PROJ. MGR:
DRAWING NAME:
PATH:
DATE: TIME: DESIGNER:
UNITED CIVIL
Design Group LLC
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
APPROVED:
NOTES
1. EXISTING UNDERGROUND AND OVERHEAD PUBLIC AND PRIVATE UTILITIES AS SHOWN ARE INDICATED
ACCORDING TO THE BEST INFORMATION AVAILABLE TO THE ENGINEER.
2. VEGETATIVE SWALES, BIOSWALES, UNDERGROUND DETENTION AND THE WATERQUALITY AND DETENTION POND
SHALL BE MAINTAINED BY THE PROPERTY OWNER AND FOLLOW APPLICABLE STANDARD OPERATING
PROCEDURES AS SHOWN IN DEVELOPMENT AGREEMENT.
3. FUTURE DETENTION AND LID IMPROVEMENTS WILL BE REQUIRED WITHIN BASIN A-12 WITH FUTURE
DEVELOPMENTS.
5124
5124
PROPOSED 1' CONTOUR
EXISTING 1' CONTOUR
STORM SEWER
STORM INLET
LEGEND
EXISTING CURB & GUTTER
PROPOSED CURB & GUTTER
PROPOSED FLOWLINE
LIMITS OF DISTURBANCE
EXISTING PROPERTY LINE
EXISTING R.O.W LINE
EXISTING EASEMENT
BASIN BOUNDARY
SWALE SECTION
D-101
XXXX
BASIN DESIGNATION
BASIN AREA (ACRE)
2 - YR RUNOFF COEFF.
100 - YR RUNOFF COEFF.
DESIGN POINT
FLOW DIRECTION
5125
5125
PROPOSED 5' CONTOUR
EXISTING 5' CONTOUR
A A
DRAINAGE SUMMARY
POND SUMMARY
LOW IMPACT DEVELOPMENT TREATMENT SUMMARY
Basin
Proposed
Impervious
Area
LID Treatment Area Treated % of Site
Treated
(sf) (acres) (sf) (%)
A-1 24,426 None 0 0%
A-2 33,295 None 0 0%
A-3 16,242 Underground Detention 16,242 6%
A-4 21,811 Underground Detention 21,811 8%
A-5 14,736 Underground Detention 14,736 5%
A-6 7,951 Underground Detention 7,951 3%
A-7 8,071 Underground Detention 8,071 3%
A-8 6,189 Underground Detention 6,189 2%
A-9 28,026 Underground Detention 28,026 10%
A-10 28,393 Underground Detention 28,393 10%
A-11 11,838 Underground Detention 11,838 4%
A-12 (Future) 19,000 Future LID Treatment 19,000 7%
A-13 11,517 None 0 0%
B-1 10,125 Bioswale 10,125 4%
B-2 26,917 Bioswale 26,917 10%
C-1 5,726 Wet Pond 5,726 2%
Total Site 274,263 205,024 75%
Pond A1 Pond C1
WQCV REQUIRED 0.18 AC-FT 0.01 AC-FT
WQCV PROVIDED 0.24 AC-FT 0.02 AC-FT
DETENTION VOLUME REQUIRED 2.58 AC-FT 0.33 AC-FT
DETENTION VOLUME PROVIDED 2.89 AC-FT 0.35 AC-FT
WQCV WATER SURFACE ELEVATION 4949.50 4955.03
100-YEAR WATER SURFACE ELEVATION 4,952.25 4,955.50
TOP OF POND ELEVATION 4,953.25 4,956.50
Proposed Basins
Basin Area %I C2
C100 Q
2 Q100
(acre) (cfs) (cfs)
A-1 3.49 16% 0.32 0.40 2.16 9.43
A-2 0.91 82% 0.83 1.00 2.15 9.10
A-3 0.37 90% 0.95 1.00 1.01 3.71
A-4 0.57 87% 0.86 1.00 1.39 5.64
A-5 0.40 85% 0.84 1.00 0.95 3.96
A-6 0.41 41% 0.53 0.67 0.62 2.72
A-7 0.32 53% 0.63 0.79 0.49 2.37
A-8 0.21 62% 0.71 0.89 0.42 1.84
A-9 0.64 90% 0.95 1.00 1.74 6.41
A-10 0.68 87% 0.92 1.00 1.78 6.74
A-11 0.97 27% 0.41 0.51 1.06 4.63
A-12 1.15 6% 0.23 0.29 0.68 2.95
A-13 0.26 90% 0.95 1.00 0.72 2.63
A-TOTAL 10.38 45% 0.56 0.70 10.46 45.52
B-1 0.42 53% 0.61 0.76 0.69 3.22
B-2 1.45 43% 0.52 0.65 1.90 8.28
B-TOTAL 1.87 46% 0.54 0.68 2.55 12.59
C-1 1.23 11% 0.28 0.35 0.98 4.27
C-TOTAL 1.23 11% 0.28 0.35 0.98 4.27
OS-1 0.68 2% 0.20 0.25 0.31 1.42
OS-2A 0.21 2% 0.20 0.25 0.11 0.51
OS-2B 0.93 80% 0.81 1.00 1.80 8.62
OS-3 0.42 84% 0.85 1.00 0.89 4.16
OS-4 1.35 71% 0.74 0.92 2.82 12.31
OS-5 0.54 2% 0.20 0.25 0.24 1.05
U16014
1" = 60'
1" = N/A
PLATTE RIVER POWER AUTHORITY HQ
NORTH
2/2/2018 7:22:16 AM
P:\U16014 - PRPA CAMPUS\CADD\CP\CX.XX_EXISTING DRAINAGE PLAN.DWG
CX.XX_EXISTING DRAINAGE PLAN
KRB NKS
EX-DR
1
EXISTING DRAINAGE PLAN
0 60' 120'
SCALE: 1" = 60'
30'
PREPARED FOR:
JOB NUMBER
SHEET NUMBER
OF SHEETS
DATE SUBMITTED:
The engineer preparing these plans will not be responsible
for, or liable for, unauthorized changes to or uses of these
plans. All changes to the plans must be in writing and
must be approved by the preparer of these plans.
NO. BY DATE
CAUTION
REVISIONS:
VERTICAL:
HORIZONTAL:
SCALE
PRELIMINARY
PLANS
NOT FOR CONSTRUCTION
1501 Academy Ct.
Ste. 203
Fort Collins, CO 80524
(970) 530-4044
www.unitedcivil.com
Civil Engineering &
Consulting
PROJ. MGR:
DRAWING NAME:
PATH:
DATE: TIME: DESIGNER:
UNITED CIVIL
Design Group LLC
NOTES
1. EXISTING UNDERGROUND AND OVERHEAD PUBLIC AND PRIVATE UTILITIES AS SHOWN ARE INDICATED
ACCORDING TO THE BEST INFORMATION AVAILABLE TO THE ENGINEER.
2. VEGETATIVE SWALES, BIOSWALES, UNDERGROUND DETENTION AND THE WATERQUALITY AND DETENTION POND
SHALL BE MAINTAINED BY THE PROPERTY OWNER AND FOLLOW APPLICABLE STANDARD OPERATING
PROCEDURES AS SHOWN IN DEVELOPMENT AGREEMENT.
3. FUTURE DETENTION AND LID IMPROVEMENTS WILL BE REQUIRED WITHIN BASIN A-12 WITH FUTURE
DEVELOPMENTS.
5124
5124
PROPOSED 1' CONTOUR
EXISTING 1' CONTOUR
STORM SEWER
STORM INLET
LEGEND
EXISTING CURB & GUTTER
PROPOSED CURB & GUTTER
PROPOSED FLOWLINE
LIMITS OF DISTURBANCE
EXISTING PROPERTY LINE
EXISTING R.O.W LINE
EXISTING EASEMENT
BASIN BOUNDARY
SWALE SECTION
D-101
XXXX
BASIN DESIGNATION
BASIN AREA (ACRE)
2 - YR RUNOFF COEFF.
100 - YR RUNOFF COEFF.
DESIGN POINT
FLOW DIRECTION
5125
5125
PROPOSED 5' CONTOUR
EXISTING 5' CONTOUR
A A
DRAINAGE SUMMARY
Existing Basins
Basin Area %I C2 C
100 Q2
Q100
(acre) (cfs) (cfs)
EX1 3.75 49% 0.57 0.71 5.71 26.62
EX2 2.38 32% 0.44 0.55 2.07 9.04
EX3 2.19 80% 0.82 1.00 4.78 21.75
EX4 2.33 19% 0.34 0.42 1.68 7.33
EX5 1.35 12% 0.28 0.35 0.81 3.53
OS-1 0.31 20% 0.35 0.43 0.27 1.32
OS-2A 0.33 27% 0.39 0.49 0.37 1.61
OS-2B 0.93 80% 0.81 1.00 1.80 8.62
OS-3 2.21 20% 0.34 0.43 1.45 6.33
OS-4 1.29 73% 0.75 0.94 2.75 12.00
OS-5 0.54 2% 0.20 0.25 0.24 1.05
4,949.400 1,075.80 0.200 131.36 155.27 121.29 138.41
4,949.600 2,508.89 0.200 358.47 513.74 348.51 486.92
4,949.800 4,404.37 0.200 691.33 1205.06 682.50 1169.42
4,950.000 6,253.35 0.200 1065.77 2270.83 1060.38 2229.80
4,950.200 7,637.64 0.200 1389.10 3659.93 1386.79 3616.59
4,950.400 8,940.94 0.200 1657.86 5317.79 1656.15 5272.74
4,950.600 10,218.98 0.200 1915.99 7233.78 1914.57 7187.31
4,950.800 11,462.58 0.200 2168.16 9401.94 2166.97 9354.28
4,951.000 12,663.01 0.200 2412.56 11814.50 2411.56 11765.84
4,951.200 13,750.96 0.200 2641.40 14455.89 2640.65 14406.49
4,951.400 14,634.78 0.200 2838.57 17294.47 2838.12 17244.60
4,951.600 15,276.37 0.200 2991.12 20285.58 2990.89 20235.49
4,951.800 15,698.81 0.200 3097.52 23383.10 3097.42 23332.91
4,952.000 16,080.80 0.200 3177.96 26561.06 3177.89 26510.80
4,952.200 16,467.22 0.200 3254.80 29815.86 3254.73 29765.52
4,952.400 16,858.99 0.200 3332.62 33148.49 3332.54 33098.07
4,952.600 17,256.19 0.200 3411.52 36560.00 3411.44 36509.51
4,952.800 17,658.48 0.200 3491.47 40051.47 3491.39 40000.90
105,852 cf @ 4952.25
30,599 cf @ 4952.25
· 136,451 cf total volume (3.13 ac-ft)
· 2.58 ac-ft required for detention
(2.89 ac-ft provided)
· 0.18 ac-ft required for water quality
(0.24 ac-ft provided)
(4)tt=L/(V*60 sec/min)
(5)tc check (for urban or developed areas only) = total length/180 + 10
(6)min tc = 5 min
Proposed Basins
Initial Overland Flow Time (ti) Travel/Channelized Time of Flow (t
t) ti
+tt t
c Check for Urbanized Basins Final
tc
(6)
Date: 2/7/2018 P:\U16014 - PRPA Campus\Reports\Drainage\Calculations\U16014-Drain Calcs.xlsm
OS-2B OS-2B 0.93 0.80 0.81 1.00 2.00 8.62
OS-3 OS-3 0.42 0.84 0.85 1.00 1.01 4.16
OS-4 OS-4 1.35 0.71 0.74 0.92 2.82 12.31
OS-5 OS-5 0.54 0.02 0.20 0.25 0.24 1.05
Totals 70.49 105.96
runoff via infiltration through an engineered sand media. This slows the
conveyance rate of storm water runoff, reduces runoff and provides a flow
path across a vegetated surface. These have been utilized to convey and
treat stormwater prior to entering the storm sewer system and Pond A1.