HomeMy WebLinkAboutRIDGEWOOD HILLS FIFTH FILING - PDP190018 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTPREPARED FOR:
Goodwin Knight
PREPARED BY:
Galloway & Company, Inc.
5265 Ronald Regan Blvd., Suite 210
Johnstown, Colorado 80534
ORIGINAL PREPARATION:
November 13, 2019
REVISED:
February 12, 2020
RIDGEWOOD HILLS – FIFTH FILING
FORT COLLINS, COLORADO
PRELIMINARY DRAINAGE REPORT
PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing)
February 12, 2020
Galloway & Company, Inc. Page 2 of 16
I. CERTIFICATIONS ..................................................................................................................................... 3
CERTIFICATION OF ENGINEER .................................................................................................... 3
CERTIFICATION OF OWNER ......................................................................................................... 3
II. GENERAL LOCATION AND DESCRIPTION ........................................................................................... 4
SITE LOCATION .............................................................................................................................. 4
DESCRIPTION OF PROPERTY ...................................................................................................... 4
III. DRAINAGE BASINS AND SUB-BASINS ................................................................................................. 5
MAJOR BASIN DESCRIPTION ....................................................................................................... 5
SUB-BASIN DESCRIPTION ............................................................................................................ 5
IV. DRAINAGE DESIGN CRITERIA ............................................................................................................. 7
REGULATIONS ............................................................................................................................... 7
DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS ................................................. 7
HYDROLOGICAL CRITERIA ........................................................................................................... 8
HYDRAULIC CRITERIA................................................................................................................... 9
V. DRAINAGE FACILITY DESIGN ............................................................................................................. 10
GENERAL CONCEPT ................................................................................................................... 10
VI. EROSION AND SEDIMENT CONTROL MEASURES .......................................................................... 13
VII. FLOODPLAIN ....................................................................................................................................... 14
VIII. CONCLUSIONS .................................................................................................................................. 15
COMPLIANCE WITH STANDARDS .............................................................................................. 15
VARIANCES .................................................................................................................................. 15
IX. REFERENCES ...................................................................................................................................... 16
Appendices:
A. Appendix A – Reference Material
B. Appendix B – Hydrologic Calculations
C. Appendix C – Hydraulic Calculations
D. Appendix D – Existing Drainage Study Excerpts
E. Appendix E – Proposed Condition Drainage Map
TABLE OF CONTENTS
PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing)
February 12, 2020
Galloway & Company, Inc. Page 3 of 16
I. CERTIFICATIONS
CERTIFICATION OF ENGINEER
“I hereby certify that this report for the preliminary drainage design of the Ridgewood Hills Fifth Filing was
prepared by me (or under my direct supervision) in accordance with the provisions of the Fort Collins
Stormwater Criteria Manual (December 2018) for the owners thereof.”
To be signed and sealed at time of Final Drainage Report
______________________________________
Donald Bender Cecil, P.E.
Registered Professional Engineer
State of Colorado No. 0052303
For and on behalf of Galloway & Company, Inc.
CERTIFICATION OF OWNER
“Goodwin Knight hereby certifies that the drainage facilities for Ridgewood Hills Fifth Filing shall be
constructed according to the design presented in this report. We understand that the City of Fort Collins
does not and will not assume liability for drainage facilities designed and/or certified by our engineer. We
also understand that the City of Fort Collins relies on the representation of others to establish that
drainage facilities are designed and constructed in compliance with City of Fort Collins guidelines,
standards or specifications. Review by the City of Fort Collins can therefore in no way limit or diminish
any liability, which we or any other party may have with respect to the design or construction of such
facilities.”
____________________________________
Goodwin Knight
Attest:
___________________________________
Name of Responsible Party
__________________________________
Notary Public
__________________________________
Authorized Signature
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II. GENERAL LOCATION AND DESCRIPTION
SITE LOCATION
The Ridgewood Hills Fifth Filing (hereafter referred to as “the site” or “project site”) is a 34.81-acre project
site located in the City of Fort Collins, Larimer County, Colorado. The project site is bound to the north by
Triangle Drive, to the east by South College Avenue (US HWY 287), and to the south by undeveloped
land. The west property boundary is adjacent to parkland and open space to the north and portions of
Ridgewood Hills Filings Nos. 3 and 4 to the south. Ridgewood Hills Filing No. 4 is currently under
construction. The project site is located on four separate parcels. Parcel 1 is described as Tract A of the
Shenandoah P.U.D. Filing No. 1. Parcel 2 is described as a portion of the East ½ of the Southeast ¼ of
Section 14, Township 6 North, Range 69 West of the 6th Prime Meridian, in Larimer County Colorado.
Parcel 3 is described as a portion of the East ½ of the Southeast ¼ of Section 14, Township 6 North,
Range 68 West of the 6th Prime Meridian, in Larimer County Colorado. Parcel 4 is described as a portion
of the Tract C of the Shenandoah P.U.D.
DESCRIPTION OF PROPERTY
The 34.81-acre project site is currently undeveloped and consists of open fallow land. Vegetation on the
project site consists of mostly invasive weeds and grasses. The project site currently drains from west to
east at slopes ranging from 2% to 50%. The steeper slopes up to 50% occur adjacent to the east
property boundary at South College Avenue.
There are several existing delineated natural areas and buffer zones present on the site, as defined by
Section 3.4.1 of the City of Fort Collins Land Use Code. There are four wetland areas delineated on the
project site – two at the northeast corner of the site, near the intersection of Triangle Drive and South
College Avenue, and two at the southwest corner of the site. A section of the North Loudon Ditch bisects
the project site, which is also classified as a natural area. Proposed development that disturbs these
areas and their buffer zones will require mitigation as required by the Land Use Code.
An inlet swale bisects the north quarter of the site and conveys offsite drainage from the neighborhood to
the north of Triangle Drive and additional Louden Ditch overflow to an existing 48” RCP under College
Avenue that outlets to Robert Benson Lake to the east. Undetained offsite drainage areas, immediately
to the west of the project site, were delineated as part of the Ridgewood Hills Filings No. 3. These offsite
basins are currently being constructed as part of the Ridgewood Hills Filing No. 4. While the majority of
the Filing No. 3 basins will be captured and detained with the construction of the Filing No. 4, a small
portion of runoff generated from the Filing No. 4 development will flow undetained onto the project site.
These offsite areas drain onto the project site and will be routed through as part of the project
development. A copy of the drainage maps from the Ridgewood Hills Filing Nos. 3 and 4 are included in
Appendix E.
Proposed improvements with the Fifth Filing project include the construction of multi-family, single-family
attached, and single-family detached residential units with associated roads, drives and utilities
infrastructure. Detention of the project site will be divided amongst three separate constructed ponds that
will control release rates to allowable measures. Stormwater quality features will be constructed to satisfy
the City of Fort Collins Low Impact Development (LID), and Natural Areas mitigation requirements.
According to the Natural Resources Conservation Service (NRCS) Web Soil Survey, the project site
consists of a mix of soil types and Hydrologic Soil Groups (HSGs)including:
PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing)
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- Fort Collins Loam, HSG ‘C’, 41.9% of total project area
- Heldt Clay Loam, HSGs ‘C’, 12.2%
- Longmont Clay, HSGs ‘D’, 18.2%
- Renohill Clay Loam, HSGs ‘D’, 1.0%
- Santana Loam, HSGs ‘B’, 9.7%
- Wiley Silt Loam, HSGs ‘B’, 17.0%
The predominant on-site HSG is ‘C’. Group C soils are described as having a slow infiltration rate when
thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of
water or soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission. Refer to Appendix A, for the Web Soil Survey and soils information.
A geotechnical report was prepared by CTL Thompson, Incorporated in August 2019 for the project site.
The report included site-specific borings for the project site. Twelve exploratory borings were performed
across the project site and discovered that subsurface conditions generally consisted of sandy clay over
weathered and competent bedrock. Bedrock consisted primarily of sandy claystone. Groundwater was
observed at depths of approximately 0.5’ to 23.5’ below the ground surface. Areas that experience
shallow groundwater under the existing condition are located primarily at the south end of the site, at the
location of the existing wetlands. The shallow groundwater present on the site contributes to the existing
wetlands and should help reestablish wetlands within areas proposed as mitigation for those to be
disturbed.
III. DRAINAGE BASINS AND SUB-BASINS
MAJOR BASIN DESCRIPTION
The project site is enveloped entirely within the Fossil Creek drainage basin, as delineated by the City of
Fort Collins Drainage Basin Master Plan. The Drainage Basin Master Plan was approved by City Council
in June of 2004 and describes the flooding history of the specified basins and offers guidance for new
development within the basins. Onsite detention is required for the runoff volume difference between the
100-year developed flow rate and the 2-year historic release rate. In the Fossil Creek basin the two year
historic release rate is 0.2 cfs/acre.
The project site is shown on FEMA Map Number 08069C1200F. The floodplain map indicates the project
exists within Zone X - Area of Minimal Flood Hazard and is, therefore, not impacted by an existing
floodplain/floodway. Refer to Appendix A for a Firmette of the Flood Plain Hazard Map.
SUB-BASIN DESCRIPTION
The sub-basin development included herein is intended as a step toward informing future detailed
preliminary and final storm drain infrastructure design. The developed drainage basins shown on sheet
C5.0 will be further subdivided as the grading design evolves.
A Basins: These basins are compositionally similar and comprised of the north and east portion of the
project site, east of Strasburg Drive, Strasburg Drive, and portions of Castle View Drive, west of Strasburg
Drive. The composition of the development consists of the building roof areas from the multifamily
buildings and clubhouse building, asphalt, curb and gutter, sidewalks, landscaping, and outdoor amenity
areas. These basins are intended to be captured via the on-site drainage system and routed to Detention
PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing)
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Galloway & Company, Inc. Page 6 of 16
Pond A at the northeast corner of the site, near the intersections of College Avenue and Triangle Drive.
The outlet flows from Detention Pond A will be routed to the inlet swale and eventually into the existing
48” RCP storm drain that passes under College Avenue and discharges into Robert Benson Lake.
B Basins: These basins are compositionally similar and are comprised of a portion of the proposed
Castle View Drive right-of-way; a portion of the Field View Drive right-of-way, north of Avondale Road; a
portion of the east right-of-way of the Avondale Road extension, north of Field View Drive; and a portion
of the detached single-family buildings to the south of Castle View Drive. The composition of
development consists of paved roadways and sidewalks, paved parking areas, roof areas from detached
single-family homes, landscaped areas and other hardscape. These basins are intended to be captured
via the curb and gutter, overland flow and on-site storm sewer system and routed to Detention Pond B to
the southwest of the intersection of Strasburg Drive and Castle View Drive. The outlet flows from
Detention Pond B will be routed to an inlet swale and eventually into the existing 48” RCP storm drain that
passes under College Avenue and discharges into Robert Benson Lake.
C Basins: These basins are compositionally similar and are comprised of the Avondale Road right-of-way
extension, south of Field View Drive; the detached single-family buildings to the north and south of Field
View Drive, east of Avondale Road; the proposed Maroon Vista Way, Pyramid Vista Way and Long Vista
Way; and the attached single-family buildings along Longmont St and Field View Drive. The composition
of development consists of paved roadways and sidewalks, paved parking areas, roof areas from
attached and detached single-family homes, landscaped areas and other hardscape. These basins are
intended to be captured via the on-site drainage system and routed to Detention Pond C at the southwest
corner of the site. The outlet flows from Detention Pond C will be routed to the existing 24” RCP that runs
parallel to the south property boundary and discharges into Stanton Creek on the east side of College
Avenue.
D Basins: These basins are not to be captured and conveyed offsite via the proposed on-site stormwater
conveyance system. Basins D1 and D3 are comprised of a portion of roof areas of the west facing garage
buildings along the east property line, landscaped areas, and sidewalk that runs parallel to College
Avenue. Due to the location of these basin directly adjacent to the College Avenue right-of-way, runoff
generated in these basins cannot be captured via the on-site drainage system and will runoff directly into
College Avenue. Basin D2 consists of the Robert Benson Lake inlet swale and all runoff is conveyed to
the existing 48” RCP storm drain that passes under College Avenue and discharges into Robert Benson
Lake. Basin D4 consists of landscaped areas, sidewalk and other hardscapes. Due to the location of this
basin directly adjacent to the Triangle Drive right-of-way, runoff generated in these basins cannot be
captured via the on-site drainage system and will runoff directly into Triangle Drive. Basin D5 is located
at the southwest corner of the site and consists of the existing wetland area. This area is to remain
undeveloped as undisturbed wetland area.
Ridgewood Hills Filings Nos. 3 and 4 Offsite Basins: These basins exist along the west property
boundary. These basins were originally delineated with the Ridgewood Hills Filing No. 3 development
and consist of portions of single family residential lots, paved roadway associated with the Avondale
Road extension to the east, and undeveloped fallow land. Under current conditions, runoff from these
basins sheet flow directly onto the project site. Upon completion of the Ridgewood Hills Filing No. 4,
which is currently under construction, the Avondale Road extension and the majority of the developed
areas will be captured and routed to existing detention ponds constructed with the Ridgewood Hills Filing
No. 3. A small portion of Filing No. 4 along the west property boundary slopes sharply to the Fifth Filing
project site and will not be captured and directed to the existing detention ponds. These areas will remain
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undeveloped and will primarily consist of lawn and landscaped areas. The basins will be diverted at the
property boundary via a system of swales and curb and gutter and directed into the Ridgewood Hills
Filing No. 5 underground storm sewer system.
Shenandoah P.U.D. First Filing Offsite Basins: The basins consist of a developed neighborhood
subdivision to the north of Triangle Drive. These basins were delineated with the Shenandoah P.U.D.
First Filing development and consist of portions of single family residential lots, paved roadways,
sidewalk, landscape, and other hardscape. These basin are captured via a system of underground storm
sewer that discharges on the project site into the Robert Benson Inlet Swale. The swale will be removed
with this project. The underground storm drain from the Shenandoah First Filing will be re-routed through
the project site where it will discharge into the inlet swale and eventually into the 48” RCP culvert under
College Avenue that discharges into Robert Benson Lake.
Louden Irrigation Ditch: A portion of the Louden Irrigation Ditch bisects the existing project site. The
ditch enters the site at the north property boundary, where it passes under Triangle Drive and continues
open channel flow on the project site. The ditch continues to meander across the property, generally from
north to south. It continues open channel flow to the southwest corner of the property where it crosses
the south property line. The Ridgewood Hills Fifth Filing project requires the relocation of the ditch. The
ditch will be intercepted at the north property line and conveyed via a system of underground storm sewer
to the south where it will discharge, still on the project site, to its current alignment.
IV. DRAINAGE DESIGN CRITERIA
REGULATIONS
This preliminary drainage design presented herein is prepared in accordance with the Fort Collins
Stormwater Criteria Manual (December 2018).
DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
The project site is enveloped entirely within the Fossil Creek drainage basin, as delineated by the City of
Fort Collins Drainage Basin Master Plan. The Drainage Basin Master Plan was approved by City Council
in June of 2004 and describes the flooding history of the specified basins and offers guidance for new
development within the basins. Several site specific constrains helped develop the Low Impact Design
Water Quality BMPs and detention pond design presented here.
• The outfall for the proposed Detention Pond A and Detention Pond B is the inlet swale at the
northeast corner of the site that drains to a 48” RCP culvert under South College Avenue.
• The outfall for the proposed Detention Pond C is a 24” RCP storm sewer that runs parallel to the
south property boundary. This storm sewer passes under South College Avenue where it
discharges into Stanton Creek on the west side of South College Avenue. The 24” RCP was
designed and constructed with the Ridgewood Hills P.U.D. Filing No. 3.
• The project site currently drains from west to east at slopes ranging from 2% to 50%. The
steeper slopes up to 50% occur adjacent to the east property boundary at South College Avenue,
however slopes as great as 30% exist at several locations throughout the project site.
• The property has direct frontage along South College Avenue to the east and Triangle Drive to
the north.
• The existing soils are unsuitable for infiltrating stormwater runoff and generally consist of clayey
sand/sandy lean clay and/or lean clay with sand subsoils
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Due to the project site being encumbered by these constraints, we developed a strategy for implementing
“The Four-Step Process” for stormwater quality management to the Maximum Extent Practicable (MEP).
Each step is listed below along with a brief narrative describing the implementation strategy.
Step 1 – Employ Runoff Reduction Practices
All developed runoff from Drainage Basin A, B, and C will be routed through the on-site detention ponds.
The detention ponds will restrict the flowrate of stormwater leaving the site and reduce the impact on
downstream drainage areas. Further, the design will allow for greater than 75% of the project’s added
impervious area will be routed through an approved LID water quality treatment Best Management
Practice (BMP), including underwater stormwater quality chambers and sand filtration basins.
Step 2 – Implement BMPs that provide a Water Quality Capture Volume
Approximately 75% or more of the project’s added impervious area will be routed through the underwater
stormwater quality chambers or bioretention basins to meet the LID requirements set forth. Generated
runoff from the majority of Basin B, which will not be routed through the LID BMPs, will be treated for
water quality in extended detention basin within Detention Pond B before it is piped directly into the inlet
swale that flows into the 48” RCP culvert under South College Avenue.
Step 3 – Stabilize Drainageways
The existing Louden Ditch is to be removed and replaced with an underground storm drain. The Robert
Benson Lake Inlet Swale will be preserved to the greatest extent possible. Contributing areas to the inlet
swale will be piped across the project site. Earthen swales and embankments exceeding slopes of 4:1
(horizontal: vertical) will be planted to stabilize the shallow embankments and prevent erosion.
Step 4 – Implement site specific and other source control BMPs
An erosion control plan and Stormwater Management Plan will be implemented to prevent erosion and
control sediment on the project site and downstream drainageways during and after construction.
HYDROLOGICAL CRITERIA
For urban catchments that are not complex and generally 160 acres or less in size, it is acceptable to
estimate the design storm runoff with the rational method. The rational method is often used when only
the peak flow rate or total volume of runoff is needed (e.g., inlet sizing, storm sewer sizing or simple
detention basin sizing).
The Rational Method is based on the Rational Formula:
Q = CiA
where:
Q = the maximum rate of runoff, cfs
C = a runoff coefficient that is the ratio between the runoff volume from an area and the average rate of
rainfall depth over a given duration for that area
i = average intensity of rainfall in inches per hour for a duration equal to the time of concentration
A = area, acres
The runoff coefficient, C, for each basin is a weighted average of the runoff coefficient associated with
each zoning classifcation type (e.g., commercial = 0.85). Refer to Appendix A and Tables 3.2-1 and 3.2-3
which list runoff coefficient associated with each zoning classification type and the Frequency Adjustment
Factors (Cf) that were used to adjust the runoff coefficients for lower probability storm events.
The one-hour rainfall Intensity-Duration-Frequency tables for use with the Rational Method of runoff
analysis are provided in Table 3.4.1 (refer to Appendix B).
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The 2-year and 100-year storm events serve as the basis for the drainage system design. The 2-year
storm is considered the minor storm event. It has a fifty percent probability of exceedance during any
given year. The 100-year storm is considered the major storm event. It has a one percent probability of
exceedance in any given year.
The 2-year drainage system, at a minimum, must be designed to transport runoff from the 2-year
recurrence interval storm event with minimal disruption to the environment. The 100-year drainage
system, as a minimum, must be designed to convey runoff from the 100-year recurrence interval flood to
minimize life hazards and health, damage to structures, and interruption to traffic and services.
HYDRAULIC CRITERIA
The storm drain system is limited to culverts and swales on the project site that will convey runoff
underneath drives and parking areas to the water quality and detention BMPs. The storm drain system
hydraulic analysis will completed in a future submittal using Bentley StormCAD V8i. This software routes
flows based on the longest upstream Time of Concentration (tc) at each junction. Given the controlling tc,
StormCAD V8i calculates the flow at the junction with the corresponding intensity (e.g., i2 and i100) and
aggregate CA.
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V. DRAINAGE FACILITY DESIGN
GENERAL CONCEPT
The preliminary design presents the design of a system for collecting and conveying developed runoff
from the proposed development at the Ridgewood Hills Fifth Filing project site into the on-site water
quality and detention BMPs.
Developed runoff will generally consist generally of flows generated from roof areas, paved roads/drives
and parking areas, landscaped areas, and hardscape. The developed runoff for each basin begins as
overland flow at numerous locations throughout the project site. The runoff then flows via a stormwater
conveyance system consisting of swales, curb and gutter, and underground storm sewer into the
assigned water quality BMPs above ground detention ponds.
Significant work is required beyond that which is included herein to design the on-site stormwater
conveyance and water quality and detention system. This work includes:
• fine grading design;
• further sub-basin delineation;
• area inlet design;
• swale design;
• storm drain system design (i.e., hydraulic grade line analysis).
SPECIFIC DETAILS
A Basins
These basins comprise approximately 8.76 acres. The developed runoff from these basins is captured
via a system of overland flow, swales, curb and gutter, and an underground storm sewer system. Runoff
from the A Basins is diverted through the below ground water quality treatment basins. Runoff treated in
the below ground water quality treatment basins are then conveyed via underground storm sewer to
Detention Pond A.
The total contributing area from A Basins to the underground water quality treatment system is 8.76
acres. The underground water quality treatment system will be comprised on the Stormtech Subsurface
Stormwater Management System (Stormtech) manufactured by Advanced Drainage Systems, Inc., which
is an allowed method by the City of Fort Collins for the Low Impact Development (LID) stormwater
management technique requirements. Stormtech utilizes underground stormwater collection chambers to
achieve the necessary volume required to be treated for Water Quality. The captured volume then
infiltrates through a filtering fabric at the floor of the chamber, removing contaminants. An underdrain
system then captures the filtered runoff and conveys the runoff to the on-site detention pond. The
required water quality capture volume routed through the chambers was determined using the City of Fort
Collins Modified FAA Method for the 2-year Return Period. Calculations for the sizing of the Underground
Water Quality System are included in Appendix C.
All on-site detention ponds were sized using City of Fort Collins Modified FAA Method for the 2-year
Return Period. The proposed release rate for the detention ponds were determined using the allowable
0.2 cfs per acre of project area for projects within the Fossil Creek Drainage Basin. The allowable
release rate for Pond A was calculated to be 2.0 cubic feet per second (cfs). The pond has a volume of
148,077 cubic feet and provides the required detention control for the 100-year return period.
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Calculations for the sizing of the Detention Pond A are included in Appendix C. The detention pond will
discharge via an outlet structure that is connected to underground storm sewer that conveys discharge
from the pond directly into the Robert Benson Lake Inlet Swale and eventually to the 48” RCP culvert
under South College Avenue.
B Basins
These basins comprise approximately 2.99 acres. The developed runoff from these basins is captured
via a system of overland flow, swales, curb and gutter, and an underground storm sewer system. Runoff
from the B Basins is conveyed via the underground storm sewer into Detention Pond B.
The allowable release rate for Pond B was calculated to be 0.8 cubic feet per second (cfs). The pond has
a volume of 61,404 cubic feet and provides the required detention control for the 100-year return period.
In addition to detention for the 100-year return period, the basin will be designed as an extended
detention basin (EDB) to capture the required water quality volume for the B Basins. Calculations for the
sizing of the Detention Pond B are included in Appendix C. The detention pond will discharge via an
outlet structure that is connected to underground storm sewer that conveys discharge from the pond
directly into the Robert Benson Lake Inlet Swale and eventually to the 48” RCP culvert under South
College Avenue.
C Basins
These basins comprise approximately 13.10 acres. The developed runoff from these basins is captured
via a system of overland flow, swales, curb and gutter, and an underground storm sewer system. Runoff
from the C Basins is diverted trough an above ground bioretention/rain garden system. Runoff treated in
the bioretention/rain garden system will infiltrate into a below ground underdrain system that conveys
treated runoff to Detention Pond C.
Developed runoff from the C basins and will drain into a Bioretention Pond. The UDFCD defines a
Bioretention Pond as “A BMP that utilizes bioretention is an engineered, depressed landscape area
designed to capture and filter or infiltrate the water quality capture volume (WQCV). BMPs that utilize
bioretention are frequently referred to as rain gardens or porous landscape detention areas (PLDs).”
During storm events exceeding the water quality event, the bioretention pond is designed to fill to the design
volume and spill excess runoff into the detention pond. The incoming runoff will spill through a weir designed
to pass the 100-year incoming flows at a flow depth of 18”. The downstream face of the spillway will be
protected with a turf reinforcement mat. The spillway and downstream protection are designed for peak
100-year developed runoff entering the bioretention pond and passing through the wier. The downstream
spillway slope is exposed because the water surface elevation in the detention pond has not reached the
weir elevation.
The allowable release rate for Detention Pond C was calculated to be 3.2 cubic feet per second (cfs).
The pond has a volume of 181,562 cubic feet and provides the required detention control for the 100-year
return period. Calculations for the sizing of the Detention Pond C are included in Appendix C. The
detention pond will discharge via an outlet structure that is connected to underground storm sewer that
conveys discharge from the pond directly into the 24” RCP storm sewer that runs parallel to the south
property boundary and was constructed with the Ridgewood Hills Filing No. 3 project.
Avondale Road Improvements
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An extension of Avondale Road is proposed with the Ridgewood Hills Fifth Filing. The road will be
dedicated as public right-of-way and will connect the northwest corner of the proposed development to
the southeast corner of the site. The roadway will connect to an extension of Avondale Road to the
project’s west property line that is currently under construction with the Ridgewood Hills Filing No. 4. A
series of curb inlets in Avondale to be constructed within Filing No. 4 will intercept runoff before it shall
continue southeast down the portion of Avondale Drive proposed with this project. Runoff generated
within the right-of-way associated with the Fifth Filing will be conveyed via the proposed curb and gutter
to curb inlets on the Fifth Filing project site. Runoff captured in the curb inlets will convey runoff via the
underground storm sewer system into the proposed on-site detention ponds.
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VI. EROSION AND SEDIMENT CONTROL MEASURES
A General Permit for Stormwater Discharge Associated with Construction Activities issued by the
Colorado Department of Public Health and Environment (CDPHE), Water Quality Control Division
(WQCD), will be acquired for the project site. Prior to any earth disturbing activity a Stormwater
Management Plan (SWMP) will be prepared to identity the Control Measures which, when implemented,
will meet the requirements of said General Permit.
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VII. FLOODPLAIN
According to FEMA FIRM Map Numbers 08069C1200F - effective date: 12/19/2006, the project site
resides in Zone X – Area of Minimal Flood Hazard. Refer to Appendix A, pages A-X and A-X for the
FIRM Map and Firmette.
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VIII. CONCLUSIONS
COMPLIANCE WITH STANDARDS
The design presented in this preliminary drainage report for Ridgewood Hills Fifth Filing has been
prepared in accordance with the design standards and guidelines presented in the Fort Collins
Stormwater Criteria Manual.
VARIANCES
No variance(s) requested at this time.
PRELIMINARY DRAINAGE REPORT – Ridgewood Hills (Fifth Filing)
February 12, 2020
Galloway & Company, Inc. Page 16 of 16
IX. REFERENCES
1. Fort Collins Stormwater Criteria Manual (December (2018)
2. Urban Drainage and Flood Control District, Drainage Criteria Manual Volumes 1 and 2, prepared
by Wright-McLaughlin Engineers, originally published March 1969 and updated August 2018, and
the Volume 3, prepared by Wright-McLaughlin Engineers, originally published September 1992
and updated April 2018.
`
APPENDIX A
REFERENCE MATERIAL
`
VICINITY MAP
SCALE: NTS
VICINITY MAP
S. COLLEGE AVE
W. TRILBY RD
SITE
CARPENTER RD
TRIANGLE
DRIVE
AVONDALE
ROAD
STRASBURG
DRIVE
`
NRCS SOILS MAP
Hydrologic Soil Group—Larimer County Area, Colorado
(Ridgewood Hills - Fifth Filing)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/6/2019
Page 1 of 4
4481000 4481100 4481200 4481300 4481400 4481500 4481600 4481700 4481800
4481000 4481100 4481200 4481300 4481400 4481500 4481600 4481700 4481800
493000 493100 493200 493300 493400 493500
493000 493100 493200 493300 493400 493500
40° 29' 14'' N
105° 5' 1'' W
40° 29' 14'' N
105° 4' 33'' W
40° 28' 46'' N
105° 5' 1'' W
40° 28' 46'' N
105° 4' 33'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,250 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
37 Fort Collins loam, 5 to 9
percent slopes
C 15.8 41.9%
49 Heldt clay loam, 3 to 6
percent slopes
C 4.6 12.2%
63 Longmont clay, 0 to 3
percent slopes
D 6.9 18.2%
90 Renohill clay loam, 3 to
9 percent slopes
D 0.4 1.0%
96 Satanta loam, 3 to 5
percent slopes
B 3.7 9.7%
108 Thedalund loam, 3 to 9
percent slopes
C 0.0 0.0%
119 Wiley silt loam, 3 to 5
percent slopes
B 6.4 17.0%
Totals for Area of Interest 37.7 100.0%
Hydrologic Soil Group—Larimer County Area, Colorado Ridgewood Hills - Fifth Filing
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/6/2019
Page 3 of 4
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado Ridgewood Hills - Fifth Filing
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/6/2019
Page 4 of 4
`
FEMA FIRMETTE
01820/69C1200F19/2006
Not Printed
AREA OF MINIMAL Zone FLOOD X HAZARD
T6N R69W S14 T6N R69W S13
T6N R69W S23 T6N R69W S24
CITY OF 080102 FORT COLLINS
LARIMER 080101 COUNTY
USGS The National Map: Orthoimagery. Data refreshed April, 2019.
National Flood Hazard Layer FIRMette
0 250 500 1,000 1,500 2,000 Feet
Ü
105°5'1.75"W
40°29'12.38"N
105°4'24.30"W
40°28'45.01"N
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
HAZARD SPECIAL FLOOD AREAS
Without Zone A, V, Base A99 Flood Elevation (BFE)
With BFE or Depth Zone AE, AO, AH, VE, AR
Regulatory Floodway
0.of 2% 1% Annual annual Chance chance Flood flood with Hazard, average Areas
depth areasdrainage of less less than than one one foot square or with mile
Zone X
Future ChanceAnnual Conditions Flood Hazard 1%
Zone X
Area Levee.to with See Reduced Notes. Flood Risk due
Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood Hazard Zone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This digital map flood complies maps if with it is FEMA's not void standards as described for the below. use of
The accuracy basemap standards shown complies with FEMA's basemap
The authoritative flood hazard NFHL information web services is derived provided directly by FEMA. from This the map
was reflectnot exported changes on or 11/amendments 6/2019 at 11:subsequent 19:16 AM to and this does date and
time. becomeor The superseded NFHL and effective by new data information over time. may change
This elementsmap map image do not is appear: void if basemap the one or imagery, more of flood the following zone labels,
legend, FIRM panel scale number, bar, map and creation FIRM effective date, community date. Map identifiers,images for
unmapped regulatoryfor purposes. and unmodernized areas cannot be used
Legend
OTHER FLOOD AREAS HAZARD OF
OTHER AREAS
STRGUECNTUERREASL
FEATURES OTHER
MAP PANELS
8
`
APPENDIX B
HYDROLOGY CALCULATIONS
`
PROPOSED RUNOFF
CALCULATIONS
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 8
Table 3.4-1. IDF Table for Rational Method
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
Duration
(min)
Intensity
2-year
(in/hr)
Intensity
10-year
(in/hr)
Intensity
100-year
(in/hr)
5 2.85 4.87 9.95
39 1.09 1.86 3.8
6 2.67 4.56 9.31
40 1.07 1.83 3.74
7 2.52 4.31 8.80
41 1.05 1.80 3.68
8 2.40 4.10 8.38
42 1.04 1.77 3.62
9 2.30 3.93 8.03
43 1.02 1.74 3.56
10 2.21 3.78 7.72
44 1.01 1.72 3.51
11 2.13 3.63 7.42
45 0.99 1.69 3.46
12 2.05 3.50 7.16
46 0.98 1.67 3.41
13 1.98 3.39 6.92
47 0.96 1.64 3.36
14 1.92 3.29 6.71
48 0.95 1.62 3.31
15 1.87 3.19 6.52
49 0.94 1.6 3.27
16 1.81 3.08 6.30
50 0.92 1.58 3.23
17 1.75 2.99 6.10
51 0.91 1.56 3.18
18 1.70 2.90 5.92
52 0.9 1.54 3.14
19 1.65 2.82 5.75
53 0.89 1.52 3.10
20 1.61 2.74 5.60
54 0.88 1.50 3.07
21 1.56 2.67 5.46
FORT COLLINS STORMWATER CRITERIA MANUAL Hydrology Standards (Ch. 5)
3.0 Rational Method
3.4 Intensity-Duration-Frequency Curves for Rational Method
Page 9
Figure 3.4-1. Rainfall IDF Curve – Fort Collins
Subdivision: Triangle Development Project Name: Triangle Development
Location: CO, Fort Collins Project No.:
Calculated By: HHF
Checked By: HHF
INPUT User Input Date: 2/11/20
OUTPUT Calculated Value Single-Family Alley-Loaded SF Duplex/AttachedMulti-Family
95% 5% 60% 70% 75% 80%
A1 0.73 95 0.00 0 20 0.73 20 60 0.00 0 0.85
A2 4.14 95 0.00 0 20 4.14 20 60 0.00 0 0.85
A3 1.85 95 0.00 0 20 1.85 20 60 0.00 0 0.85
A4 0.66 95 0.00 0 21 0.66 21 61 0.00 0 0.85
A5 1.06 95 0.00 0 22 1.06 22 62 0.00 0 0.65
A6 0.32 95 0.00 0 23 0.32 23 63 0.00 0 0.65
pondA 1.37 95 0.00 0 20 1.37 20 60 0.00 0 0.20
8.76
B1 0.25 95 0.00 0 20 0.25 20 60 0.00 0 0.65
B2 1.78 95 0.00 0 20 1.78 20 60 0.00 0 0.65
B3 0.96 95 0.00 0 20 0.96 20 60 0.00 0 0.65
pondB 0.80 95 0.00 0 20 0.80 20 60 0.00 0 0.20
2.99
C1 2.46 95 0.00 0 20 2.46 20 60 0.00 0 0.65
C2 0.23 95 0.00 0 20 0.23 20 60 0.00 0 0.20
C3 0.38 95 0.00 0 20 0.38 20 60 0.00 0 0.65
C4 0.46 95 0.00 0 20 0.46 20 60 0.00 0 0.85
C5 0.24 95 0.00 0 20 0.24 20 60 0.00 0 0.85
C6 1.11 95 0.00 0 20 1.11 20 60 0.00 0 0.85
C7 0.96 95 0.00 0 20 0.96 20 60 0.00 0 0.65
C8 1.07 95 0.00 0 20 1.07 20 60 0.00 0 0.85
C9 1.03 95 0.00 0 20 1.03 20 60 0.00 0 0.85
C10 0.34 95 0.00 0 20 0.34 20 60 0.00 0 0.85
C11 0.17 95 0.00 0 20 0.17 20 60 0.00 0 0.85
C12 0.49 95 0.00 0 20 0.49 20 60 0.00 0 0.65
C13 1.12 95 0.00 0 20 1.12 20 60 0.00 0 0.85
C14 1.61 95 0.00 0 20 1.61 20 60 0.00 0 0.85
C15 0.60 95 0.00 0 20 0.60 20 60 0.00 0 0.85
C16 0.84 95 0.00 0 20 0.84 20 60 0.00 0 0.65
pondC 2.81 95 0.00 0 20 2.81 20 60 0.00 0 0.20
13.10
D1 0.29 95 0.00 0 20 0.29 20 60 0.00 0 0.20
D2 0.75 96 0.00 0 21 0.75 21 61 0.00 0 0.20
D3 0.72 97 0.00 0 22 0.72 22 62 0.00 0 0.20
D4 0.23 98 0.00 0 23 0.23 23 63 0.00 0 0.20
D5 3.71 95 0.00 0 20 3.71 20 60 0.00 0 0.20
5.71
Σ Basins 35.54
ΣDetention Pond Tributary Area 29.83
Area Weighted
Runoff
Coefficient
Area (ac)
GNK10.20
Area
Weighted
C2
COMPOSITE RUNOFF COEFFICIENTS
Basin ID Total Area (ac)
Runoff
Coefficient
Area (ac)
Lots (e.g., Single-Family, Alley Loaded)
Subdivision: Triangle Development Project Name: Triangle Development
Location: CO, Fort Collins Project No.:
Calculated By: HHF
Checked By: HHF
Date: 2/11/20
1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 20 21 22 23 24
BASIN D.A. Hydrologic C2 C5 C100 L S Ti | 2-Year Ti | 100-Year L Calculated S Cv VEL. Tt COMP. Tc | 2-Year COMP. Tc | 100-Year TOTAL Urbanized Tc Tc | 2-Year Tc | 100-Year
ID (AC) Soils Group Cf=1.00 Cf=1.00 Cf=1.25 (FT) (%) (MIN) (MIN) (FT) Slope, % (%) (FPS) (MIN) (MIN) (MIN) LENGTH(FT) (MIN) (MIN) (MIN)
A1 0.73 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0 0.4 0.1 2 10.0 5.0 5.0
A2 4.14 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
A3 1.85 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
A4 0.66 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
A5 1.06 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
A6 0.32 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
pondA 1.37 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
0.00
B1 0.25 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
B2 1.78 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
B3 0.96 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
pondB 0.80 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
0.00
C1 2.46 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
C2 0.23 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
C3 0.38 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
C4 0.46 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C5 0.24 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C6 1.11 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C7 0.96 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
C8 1.07 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C9 1.03 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C10 0.34 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C11 0.17 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C12 0.49 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
C13 1.12 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C14 1.61 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C15 0.60 C 0.85 0.85 1.06 1 2.00 0.4 0.1 1 25.00 0.00 20 10.0 0.0 0.4 0.1 2 10.0 5.0 5.0
C16 0.84 C 0.65 0.65 0.81 1 2.00 0.7 0.4 1 25.00 0.00 20 10.0 0.0 0.7 0.4 2 10.0 5.0 5.0
pondC 2.81 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
0.00
D1 0.29 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
D2 0.75 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
D3 0.72 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
D4 0.23 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
D5 3.71 C 0.20 0.20 0.25 1 2.00 1.3 1.3 1 25.00 0.00 20 10.0 0.0 1.3 1.3 2 10.0 5.0 5.0
NOTES:
Ti = (1.87*(1.1 - CCf)*(L)^0.5)/((S)^0.33), S in % Cv
Tt=L/60V 2.5
Velocity V=Cv*S^0.5, S in ft/ft 5
Tc Check = 10+L/180 7
For urbanized basins a minimum Tc of 5.0 minutes is required. 10
For non-urbanized basins a minimum Tc of 10.0 minutes is required 15
20
DATA
Type of Land Surface
Heavy Meadow
Tillage/Field
Short Pasture and Lawns
(Tt) (URBANIZED BASINS)
Paved Areas and Shallow Paved Swales
Nearly Bare Ground
Project Name: Triangle Development
Subdivision: Triangle Development Project No.: GNK10.20
Location: CO, Fort Collins Calculated By: HHF
Design Storm: Checked By: HHF
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff. | C 2
Tc | 2-Year (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
Tt (min)
REMARKS
A1 A1 0.73 0.85 5.0 0.62 2.85 1.8
A2 A2 4.14 0.85 5.0 3.52 2.85 10.0
A3 A3 1.85 0.85 5.0 1.57 2.85 4.5
A4 A4 0.66 0.85 5.0 0.56 2.85 1.6
A5 A5 1.06 0.65 5.0 0.69 2.85 2.0
A6 A6 0.32 0.65 5.0 0.21 2.85 0.6
A pondA 1.37 0.20 5.0 0.27 2.85 0.8
B1 B1 0.25 0.65 5.0 0.16 2.85 0.5
B2 B2 1.78 0.65 5.0 1.16 2.85 3.3
B3 B3 0.96 0.65 5.0 0.62 2.85 1.8
B pondB 0.80 0.20 5.0 0.16 2.85 0.5
C1 C1 2.46 0.65 5.0 1.60 2.85 4.6
C2 C2 0.23 0.20 5.0 0.05 2.85 0.1
C3 C3 0.38 0.65 5.0 0.25 2.85 0.7
C4 C4 0.46 0.85 5.0 0.39 2.85 1.1
C5 C5 0.24 0.85 5.0 0.20 2.85 0.6
C6 C6 1.11 0.85 5.0 0.95 2.85 2.7
C7 C7 0.96 0.65 5.0 0.62 2.85 1.8
C8 C8 1.07 0.85 5.0 0.91 2.85 2.6
C9 C9 1.03 0.85 5.0 0.87 2.85 2.5
C10 C10 0.34 0.85 5.0 0.29 2.85 0.8
C11 C11 0.17 0.85 5.0 0.14 2.85 0.4
C12 C12 0.49 0.65 5.0 0.32 2.85 0.9
C13 C13 1.12 0.85 5.0 0.96 2.85 2.7
C14 C14 1.61 0.85 5.0 1.36 2.85 3.9
C15 C15 0.60 0.85 5.0 0.51 2.85 1.4
C16 C16 0.84 0.65 5.0 0.54 2.85 1.5
C pondC 2.81 0.20 5.0 0.56 2.85 1.6
D1 D1 0.29 0.20 5.0 0.06 2.85 0.2
D2 D2 0.75 0.20 5.0 0.15 2.85 0.4
D3 D3 0.72 0.20 5.0 0.14 2.85 0.4
D4 D4 0.23 0.20 5.0 0.05 2.85 0.1
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
Project Name: Triangle Development
Subdivision: Triangle Development Project No.: GNK10.20
Location: CO, Fort Collins Calculated By: HHF
Design Storm: Checked By: HHF
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff. | C 100
Tc | 100-Year (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
Slope (%)
Street Flow (cfs)
Design Flow (cfs)
Slope (%)
Pipe Size (inches)
Length (ft)
Velocity (fps)
Tt (min)
REMARKS
A1 A1 0.73 1.06 5.0 0.77 9.95 7.7
A2 A2 4.14 1.06 5.0 4.40 9.95 43.7
A3 A3 1.85 1.06 5.0 1.97 9.95 19.6
A4 A4 0.66 1.06 5.0 0.70 9.95 7.0
A5 A5 1.06 0.81 5.0 0.86 9.95 8.6
A6 A6 0.32 0.81 5.0 0.26 9.95 2.6
A pondA 1.37 0.25 5.0 0.34 9.95 3.4
8.76
B1 B1 0.25 0.81 5.0 0.20 9.95 2.0
B2 B2 1.78 0.81 5.0 1.45 9.95 14.4
B3 B3 0.96 0.81 5.0 0.78 9.95 7.7
B pondB 0.80 0.25 5.0 0.20 9.95 2.0
2.99
C1 C1 2.46 0.81 5.0 2.00 9.95 19.9
C2 C2 0.23 0.25 5.0 0.06 9.95 0.6
C3 C3 0.38 0.81 5.0 0.31 9.95 3.1
C4 C4 0.46 1.06 5.0 0.49 9.95 4.9
C5 C5 0.24 1.06 5.0 0.26 9.95 2.5
C6 C6 1.11 1.06 5.0 1.18 9.95 11.8
C7 C7 0.96 0.81 5.0 0.78 9.95 7.7
C8 C8 1.07 1.06 5.0 1.14 9.95 11.3
C9 C9 1.03 1.06 5.0 1.09 9.95 10.9
C10 C10 0.34 1.06 5.0 0.37 9.95 3.6
C11 C11 0.17 1.06 5.0 0.18 9.95 1.8
C12 C12 0.49 0.81 5.0 0.40 9.95 3.9
C13 C13 1.12 1.06 5.0 1.19 9.95 11.9
C14 C14 1.61 1.06 5.0 1.71 9.95 17.0
C15 C15 0.60 1.06 5.0 0.64 9.95 6.3
C16 C16 0.84 0.81 5.0 0.68 9.95 6.8
`
APPENDIX C
HYDRAULIC CALCULATIONS
Project Number: GNK10.20 Date: 2/11/2020
Project Location: Fort Collins, Colorado
Calculations By: HHF
Pond Description: pondA
User Input Cell: Blue Text
100-year 108879
0.92 2.50
10.13
2.0
0.2
minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet
5 300 9.95 27819 608 27211 0.62
10 600 7.72 43168 1216 41953 0.96
15 900 6.52 54687 1823 52864 1.21
20 1200 5.60 62628 2431 60197 1.38
25 1500 4.98 69617 3039 66578 1.53
30 1800 4.52 75824 3647 72177 1.66
35 2100 4.08 79850 4255 75596 1.74
40 2400 3.74 83653 4862 78790 1.81
45 2700 3.46 87064 5470 81594 1.87
50 3000 3.23 90307 6078 84229 1.93
55 3300 3.03 93187 6686 86501 1.99
60 3600 2.86 95955 7294 88661 2.04
65 3900 2.71 98499 7901 90597 2.08
70 4200 2.59 101379 8509 92869 2.13
75 4500 2.48 104007 9117 94890 2.18
80 4800 2.38 106467 9725 96742 2.22
85 5100 2.29 108844 10333 98511 2.26
90 5400 2.21 111220 10940 100280 2.30
95 5700 2.13 113149 11548 101601 2.33
100 6000 2.06 115190 12156 103034 2.37
105 6300 2.00 117427 12764 104663 2.40
110 6600 1.94 119328 13372 105957 2.43
115 6900 1.88 120894 13979 106914 2.45
120 7200 1.84 123466 14587 108879 2.50
Catchment 'C': Required Storage, ac-ft:
Modified FAA Method- Storage Volume Calculations
Inputs | Tributary Area Output | Detention Volume
Return Period for Detention Control: Required Storage, cubic feet:
Average
Outflow
Storage
Volume
Storage
Volume
Catchment Drainage Area, ac:
Release Rate, cfs:
Storm Duration Time
Rainfall
Intensity
Inflow Volume
Project Number: GNK10.20
Project Location: Fort Collins, Colorado Date: 2/11/2020
Calculations By: H. Feissner
Pond Description: pondA
User Input Cell: Blue Text
Design Point: N/A
Design Storm: WQCV
Required Volume: 0 ft3 N/A ft
Design Storm: N/A
Required Volume: 0 ft3 N/A ft
Design Storm: 100-year
Required Volume: 108879 ft3 5033.5 ft
Contour
Elevation
Contour
Area
Depth
Incremental
Volume
Cummulative
Volume
Incremental
Volume
Cummulative
Volume
Cummulative
Volume
ft ft2 ft ft3 ft3 ft3 ft3 ac-ft
5025.90 0 0 0 0 0 0 0.0
5026.00 5726 0.10 286 286 191 191 0.0
5027.00 7836 1.00 6781 7067 6753 6944 0.2
5028.00 10043 1.00 8940 16007 8917 15861 0.4
5029.00 12352 1.00 11198 27204 11178 27039 0.6
5030.00 14774 1.00 13563 40767 13545 40584 0.9
5031.00 17313 1.00 16044 56811 16027 56610 1.3
5032.00 19978 1.00 18646 75456 18630 75240 1.7
5033.00 22775 1.00 21377 96833 21361 96601 2.2
5034.00 25714 1.00 24245 121077 24230 120831 2.8
5035.00 28808 1.00 27261 148338 27246 148077 3.4
Detention Pond Stage-Storage Calculations
Average End Area Method:
Required Volume Water Surface Elevation
Conic Volume Method:
100-year
5019
5021
5023
5025
5027
5029
5031
5033
5035
5037
0 20000 40000 60000 80000 100000 120000 140000 160000
Contour Elevation, ft
Cummulative Volume, ft3
Stage - Storage | pondA
Project Number: GNK10.20 Date: 2/11/2020
Project Location: Fort Collins, Colorado
Calculations By: HHF
Pond Description: pondA - LID Calculations
User Input Cell: Blue Text
2-year 14902
0.74 0.34
10.13
2.0
0.2
minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet
5 300 2.85 6409 608 5801 0.13
10 600 2.21 9940 1216 8724 0.20
15 900 1.87 12616 1823 10793 0.25
20 1200 1.61 14483 2431 12051 0.28
25 1500 1.43 16079 3039 13040 0.30
30 1800 1.30 17541 3647 13894 0.32
35 2100 1.17 18418 4255 14164 0.33
40 2400 1.07 19250 4862 14388 0.33
45 2700 0.99 20037 5470 14567 0.33
50 3000 0.92 20690 6078 14612 0.34
55 3300 0.87 21522 6686 14836 0.34
60 3600 0.82 22129 7294 14835 0.34
65 3900 0.78 22803 7901 14902 0.34
70 4200 0.73 22983 8509 14474 0.33
75 4500 0.70 23613 9117 14496 0.33
80 4800 0.66 23748 9725 14023 0.32
85 5100 0.64 24468 10333 14135 0.32
90 5400 0.61 24692 10940 13752 0.32
95 5700 0.58 24782 11548 13234 0.30
100 6000 0.56 25187 12156 13031 0.30
105 6300 0.54 25502 12764 12738 0.29
110 6600 0.52 25727 13372 12355 0.28
115 6900 0.51 26379 13979 12400 0.28
120 7200 0.49 26447 14587 11859 0.27
Average
Outflow
Storage
Volume
Storage
Volume
Catchment Drainage Area, ac:
Release Rate, cfs:
Storm Duration Time
Rainfall
Intensity
Inflow Volume
Catchment 'C': Required Storage, ac-ft:
Modified FAA Method- Storage Colume Calculations
Inputs | Tributary Area Output | Detention Volume
Return Period for Detention Control: Required Storage, cubic feet:
1 2 3 4 5 6 7 8 9 10 11 12 13
UDSCM
WQCV
(CF)
WQ
FLOW
(CFS)
CHAMBER
TYPE
(A)
RELEASE
RATE/
CHAMBER
(CFS)
VOLUME/
CHAMBER
(CF)
VOLUME/
CHAMBER +
AGGREGATE
(CF)
NUMBER OF
CHAMBERS
REQUIRED
PER WQCV
COMBINED
RELEASE
RATE WQCV
METHOD
(CFS)
FAA
REQUIRED
STORAGE
VOLUME (CF)
NUMBER OF
CHAMBERS
PER FAA
METHOD
TOTAL
VOLUME
(CF)
COMBINED
RELEASE
RATE FAA
METHOD
(CFS)
TOTAL NUMBER
OF CHAMBERS
PROVIDED
8494.2 10.25 SC-740 0.024 45.9 74.9 114 2.69 14902 199 9134.1 4.69 199
85.4
51.0
4355.4
30.25
0.35
10.59
0.024 (A - COLUMN 4)
FLOW RATE (GPM/SF)
FLOW RATE PER CHAMBER (GPM)
FLOW RATE PER CHAMBER (CFS))
Project Number: GNK10.20 Date: 2/11/2020
Project Location: Fort Collins, Colorado
Calculations By: HHF
Pond Description: pondB
User Input Cell: Blue Text
100-year 29187
0.69 0.67
3.79
0.8
0.2
minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet
5 300 9.95 7806 227.4 7579 0.17
10 600 7.72 12113 454.8 11658 0.27
15 900 6.52 15345 682.2 14663 0.34
20 1200 5.60 17573 909.6 16664 0.38
25 1500 4.98 19535 1137 18398 0.42
30 1800 4.52 21276 1364.4 19912 0.46
35 2100 4.08 22406 1591.8 20814 0.48
40 2400 3.74 23473 1819.2 21654 0.50
45 2700 3.46 24430 2046.6 22384 0.51
50 3000 3.23 25340 2274 23066 0.53
55 3300 3.03 26148 2501.4 23647 0.54
60 3600 2.86 26925 2728.8 24196 0.56
65 3900 2.71 27639 2956.2 24683 0.57
70 4200 2.59 28447 3183.6 25263 0.58
75 4500 2.48 29185 3411 25774 0.59
80 4800 2.38 29875 3638.4 26237 0.60
85 5100 2.29 30542 3865.8 26676 0.61
90 5400 2.21 31209 4093.2 27115 0.62
95 5700 2.13 31750 4320.6 27429 0.63
100 6000 2.06 32323 4548 27775 0.64
105 6300 2.00 32950 4775.4 28175 0.65
110 6600 1.94 33484 5002.8 28481 0.65
115 6900 1.88 33923 5230.2 28693 0.66
120 7200 1.84 34645 5457.6 29187 0.67
Catchment 'C': Required Storage, ac-ft:
Modified FAA Method- Storage Colume Calculations
Inputs | Tributary Area Output | Detention Volume
Return Period for Detention Control: Required Storage, cubic feet:
Average
Outflow
Storage
Volume
Storage
Volume
Catchment Drainage Area, ac:
Release Rate, cfs:
Storm Duration Time
Rainfall
Intensity
Inflow Volume
Sheet 1 of 3
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia
Ia
= 70.0 %
B) Tributary Area's Imperviousness Ratio (i = Ia
/ 100 ) i = 0.700
C) Contributing Watershed Area Area = 6.050 ac
D) For Watersheds Outside of the Denver Region, Depth of Average d6
= in
Runoff Producing Storm
E) Design Concept
(Select EURV when also designing for flood control) 1
F) Design Volume (WQCV) Based on 40-hour Drain Time VDESIGN
= 0.139 ac-ft
(VDESIGN
= (1.0 * (0.91 * i
3
- 1.19 * i
2
+ 0.78 * i) / 12 * Area )
G) For Watersheds Outside of the Denver Region, VDESIGN OTHER
= ac-ft
Water Quality Capture Volume (WQCV) Design Volume
(VWQCV OTHER
= (d6
*(VDESIGN
/0.43))
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VDESIGN USER
= ac-ft
(Only if a different WQCV Design Volume is desired)
I) NRCS Hydrologic Soil Groups of Tributary Watershed
i) Percentage of Watershed consisting of Type A Soils HSG A
= %
ii) Percentage of Watershed consisting of Type B Soils HSG B
= %
iii) Percentage of Watershed consisting of Type C/D Soils HSG C/D
= %
J) Excess Urban Runoff Volume (EURV) Design Volume
For HSG A: EURVA
= 1.68 * i
1.28
EURVDESIGN
= ac-f t
For HSG B: EURVB
= 1.36 * i
1.08
For HSG C/D: EURVC/D
= 1.20 * i
1.08
K) User Input of Excess Urban Runoff Volume (EURV) Design Volume EURVDESIGN USER
= ac-f t
(Only if a different EURV Design Volume is desired)
2. Basin Shape: Length to Width Ratio L : W = : 1
(A basin length to width ratio of at least 2:1 will improve TSS reduction.)
Project Number: GNK10.20
Project Location: Fort Collins, Colorado Date: 2/11/2020
Calculations By: H. Feissner
Pond Description: pondA
User Input Cell: Blue Text
Design Point: N/A
Design Storm: WQCV
Required Volume: 6055 ft3 5048.26 ft
Design Storm: N/A
Required Volume: 0 ft3 N/A ft
Design Storm: 100-year
Required Volume: 35242 ft3 5051.1 ft
Contour
Elevation
Contour
Area
Depth
Incremental
Volume
Cummulative
Volume
Incremental
Volume
Cummulative
Volume
Cummulative
Volume
ft ft2 ft ft3 ft3 ft3 ft3 ac-ft
5046.00 0 0 0 0 0 0 0.0
5047.00 1941 1.00 971 971 647 647 0.0
5048.00 5534 1.00 3738 4708 3584 4231 0.1
5049.00 8518 1.00 7026 11734 6973 11204 0.3
5050.00 11130 1.00 9824 21558 9795 20999 0.5
5051.00 13532 1.00 12331 33889 12311 33310 0.8
5052.00 15864 1.00 14698 48587 14683 47993 1.1
5052.80 17681 0.80 13418 62005 13411 61404 1.4
Detention Pond Stage-Storage Calculations
Required Volume Water Surface Elevation
Average End Area Method: Conic Volume Method:
100-year
5019
5024
5029
5034
5039
5044
5049
5054
5059
0 10000 20000 30000 40000 50000 60000 70000
Contour Elevation, ft
Cummulative Volume, ft3
Stage - Storage | pondA
Project Number: GNK10.20 Date: 2/11/2020
Project Location: Fort Collins, Colorado
Calculations By: HHF
Pond Description: pondC
User Input Cell: Blue Text
100-year 149926
0.82 3.44
15.91
3.2
0.2
minutes seconds in/hr cubic feet cubic feet cubic feet acre-feet
5 300 9.95 38943 955 37988 0.87
10 600 7.72 60430 1909 58521 1.34
15 900 6.52 76555 2864 73691 1.69
20 1200 5.60 87670 3818 83852 1.92
25 1500 4.98 97455 4773 92682 2.13
30 1800 4.52 106144 5728 100416 2.31
35 2100 4.08 111780 6682 105098 2.41
40 2400 3.74 117103 7637 109466 2.51
45 2700 3.46 121878 8591 113286 2.60
50 3000 3.23 126418 9546 116872 2.68
55 3300 3.03 130449 10501 119948 2.75
60 3600 2.86 134324 11455 122868 2.82
65 3900 2.71 137885 12410 125475 2.88
70 4200 2.59 141917 13364 128552 2.95
75 4500 2.48 145596 14319 131277 3.01
80 4800 2.38 149040 15274 133766 3.07
85 5100 2.29 152367 16228 136138 3.13
90 5400 2.21 155693 17183 138511 3.18
95 5700 2.13 158394 18137 140257 3.22
100 6000 2.06 161251 19092 142159 3.26
105 6300 2.00 164382 20047 144336 3.31
110 6600 1.94 167044 21001 146042 3.35
115 6900 1.88 169235 21956 147280 3.38
120 7200 1.84 172836 22910.4 149926 3.44
Catchment 'C': Required Storage, ac-ft:
Modified FAA Method- Storage Colume Calculations
Inputs | Tributary Area Output | Detention Volume
Return Period for Detention Control: Required Storage, cubic feet:
Average
Outflow
Storage
Volume
Storage
Volume
Catchment Drainage Area, ac:
Release Rate, cfs:
Storm Duration Time
Rainfall
Intensity
Inflow Volume
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 75.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.750
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 581,933 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 11,620 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 8729 sq ft
D) Actual Flat Surface Area AActual = sq ft
E) Area at Design Depth (Top Surface Area) ATop = sq ft
F) Rain Garden Total Volume VT= cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = cu ft
iii) Orifice Diameter, 3/8" Minimum DO = in
Design Procedure Form: Rain Garden (RG)
Donald Cecil
Galloway & Company, Inc.
February 11, 2020
Ridgewood Hills Filing No. 5 | C BASINS
Fort Collins, CO
UD-BMP (Version 3.07, March 2018)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
GNK10.20_UD-BMP_v3.07, RG 2/11/2020, 1:53 PM
Project Number: GNK10.20
Project Location: Fort Collins, Colorado Date: 2/11/2020
Calculations By: H. Feissner
Pond Description: pondC
User Input Cell: Blue Text
Design Point: N/A
Design Storm: WQCV
Required Volume: 0 ft3 N/A ft
Design Storm: N/A
Required Volume: 0 ft3 N/A ft
Design Storm: 100-year
Required Volume: 149926 ft3 5048.4 ft
Contour
Elevation
Contour
Area
Depth
Incremental
Volume
Cummulative
Volume
Incremental
Volume
Cummulative
Volume
Cummulative
Volume
ft ft2 ft ft3 ft3 ft3 ft3 ac-ft
5039.50 0 0 0 0 0 0 0.0
5040.00 964 0.50 241 241 161 161 0.0
5041.00 4494 1.00 2729 2970 2513 2674 0.1
5042.00 8425 1.00 6460 9430 6357 9031 0.2
5043.00 12052 1.00 10239 19668 10185 19216 0.4
5044.00 15526 1.00 13789 33457 13752 32968 0.8
5045.00 19438 1.00 17482 50939 17445 50414 1.2
5046.00 24108 1.00 21773 72712 21731 72145 1.7
5047.00 30192 1.00 27150 99862 27093 99238 2.3
5048.00 38327 1.00 34260 134122 34179 133416 3.1
5049.10 49446 1.10 48275 182397 48146 181562 4.2
Detention Pond Stage-Storage Calculations
Required Volume Water Surface Elevation
Average End Area Method: Conic Volume Method:
100-year
5038
5040
5042
5044
5046
5048
5050
5052
0 20000 40000 60000 80000 100000 120000 140000 160000 180000 200000
Contour Elevation, ft
Cummulative Volume, ft3
Stage - Storage | pondC
Project Number: GNK10.20
Project Location: Fort Collins, Colorado Date: 2/11/2020
Calculations By: H. Feissner
Pond Description: pondC - Bioretention/Rain Garden
User Input Cell: Blue Text
Design Point: N/A
Design Storm: WQCV
Required Volume: 11620 ft
3
5054.16 ft
Design Storm: N/A
Required Volume: 0 ft
3
N/A ft
Design Storm: 100-year
Required Volume: 0 ft
3
N/A ft
Contour
Elevation
Contour
Area
Depth
Incremental
Volume
Cummulative
Volume
Incremental
Volume
Cummulative
Volume
Cummulative
Volume
ft ft
2
ft ft
3
ft
3
ft
3
ft
3
ac-ft
5053.00 8835 0 0 0 0 0 0.0
5054.00 10802 1.00 9819 9819 9802 9802 0.2
5054.50 12578 0.50 5845 15664 5839 15641 0.4
Detention Pond Stage-Storage Calculations
Required Volume Water Surface Elevation
Average End Area Method: Conic Volume Method:
5038
5040
5042
5044
5046
5048
5050
5052
5054
5056
`
APPENDIX D
DRAINAGE MAPS + VARIANCE
APPLICATION
EXISTING DRAINAGE
STUDY EXCERPTS
8-UNIT
8-UNIT
6-UNIT
6-UNIT
TOT
LOT
SPORTS
COURT
(110' X 50')
CLUB
HOUSE
POOL
AVONDALE ROAD
TRIANGLE DRIVE
2' CURB CUT
RIP RAP TYPE VL
AS SHOWN D50=6"
1
N1
0.353 0.36
N2
0.36
2
N3
0.41
3
N4
0.33
4
5
6
7b
8
9
N5
0.55
0.276
0.301
0.211
1.872
12
STORM A PIPE - (45)
STORM A PIPE - (44)
FLOW TO EX. POND 1
EXISTING DETENTION
POND
7a
11b
52.11 LF 12"
HDPE @ 5.95%
YARD INLET LATERALS
HDPE N-12 (TYP)
YARD INLET LATERALS
HDPE N-12 (TYP)
STORM A
PIPE - (63)
CDOT TYPE D
AREA INLET
STMH A1
EXISTING INLET CORE
8-UNIT
6-UNIT
24-UNIT
16-UNIT
16-UNIT
24-UNIT
24-UNIT
PEYTON DRIVE
AVONDALE ROAD
TRIANGLE DRIVE
RIP RAP TYPE VL
AS SHOWN D50=6"
31
10
13
S2
0.125 0.25
S4
0.121 0.31
S5
0.125 0.29
S6
0.154 0.61
S7
0.155 0.25
S8
0.575 0.55
S9
0.112 0.63
S10
0.119 0.56
S11
0.201 0.46
S12
0.436 0.50
S13
0.041 0.45
S14
1.866 0.49
S15
1.153 0.66
S18
0.990 0.28
S17
0.810 0.18
S16
0.204 0.68 S19
0.352 0.25
14
15
16b
17
19
20
21
22
23
24 25
26
27
This unofficial copy was downloaded on Aug-27-2019 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 Aug-27-2019 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 Aug-27-2019 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 Aug-27-2019 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 D
DRAINAGE MAPS + VARIANCE
DRAINAGE APPLICATION MAPS
E
acres
C1
0.65
0.81
2.46
acres
C2
0.20
0.25
0.23
acres
A1
0.85
1.00
0.73
acres
A3
0.85
1.00
1.85
acres
pondB
0.20
0.25
0.80
acres
C3
0.65
0.81
0.38
B1
acres
A4
0.85
1.00
0.66
acres
A5
0.65
0.81
1.06
acres
pondA
0.20
0.25
1.37
acres
A2
0.85
1.00
4.13
acres
D1
0.20
0.25
0.29
acres
D2
0.20
0.25
STM
acres
C8
0.85
1.00
1.07
acres
C12
0.65
0.81
0.49
acres
C13
0.85
1.00
1.12
acres
C10
0.85
1.00
0.34
acres
C14
0.85
1.00
1.61
acres
C9
0.85
1.00
1.03
acres
C7
0.65
0.81
0.96
acres
C5
0.85
1.00
0.24
acres
C6
0.85
1.00
1.11
acres
pondC
0.20
0.25
2.81
acres
C4
0.85
1.00
0.46
acres
B1
0.65
0.81
0.25
acres
D5
0.20
0.25
3.71
acres
C15
0.85
1.00
0.60
acres
C16
0.65
0.81
0.84
acres
C11
0.85
1.00
0.17
C8
C12
C13
C10
C14
C9
C7
C5
C6
C
D5
C15
C16
C11
1
10
6
3
3
3
2
3
3
2
2
5
6
6
OFF-SITE RUNOFF FROM BASIN S13 OF
RIDGEWOOD HILLS FOURTH FILING
S13=0.35 ac
3
-
-
-
-
-
-
-
-
-
-
-
-
-
-
STAMP
Date:
Drawn By:
Project No:
Checked By:
H:\Goodwin Knight\CO, Fort Collins - GNK000010 - Triangle Dr. and College Ave\CADD\3-CD\UTIL\GNK10_C5.0_Drainage.dwg - Donald Cecil - 2/11/2020
# Date Issue / Description Init.
RIDGEWOOD HILLS - FIFTH FILING
PRELIMINARY UTILITY PLAN
FORT COLLINS, CO
THESE PLANS ARE AN INSTRUMENT OF SERVICE
AND ARE THE PROPERTY OF GALLOWAY, AND MAY
NOT BE DUPLICATED, DISCLOSED, OR REPRODUCED
WITHOUT THE WRITTEN CONSENT OF GALLOWAY.
COPYRIGHTS AND INFRINGEMENTS WILL BE
ENFORCED AND PROSECUTED.
COPYRIGHT
GallowayUS.com
5265 Ronald Reagan Blvd., Suite 210
Johnstown, CO 80534
970.800.3300
PRELIMINARY
NOT FOR BIDDING
NOT FOR CONSTRUCTION
11.13.2019
GNK000010
JEP
DBC
LEGEND:
PROPOSED STORM SEWER
EXISTING STORM SEWER
PROPOSED STORM INLET
PROPOSED LOTLINE
EASEMENT LINE
EXISTING MINOR CONTOUR
EXISTING MAJOR CONTOUR
PROPOSED MINOR CONTOUR
PROPOSED MAJOR CONTOUR
PROPERTY BOUNDARY
EXISTING MANHOLE
DRAINAGE SYMBOLS:
DESIGN POINT
MAJOR BASIN BOUNDARY (i.e., C-STORE)
SUB-BASIN BOUNDARY (i.e., RATIONAL METHOD)
OVERLAND FLOW DIRECTION
(I.E., LANDSCAPING)
DIRECT FLOW DIRECTION
(I.E., PAVEMENT, CURB AND
GUTTER)
BASIN ID
MINOR (2YEAR) RUNOFF
COEFFICIENT
MAJOR (100YEAR) RUNOFF
COEFFICIENT
BASIN AREA
(ACRES)
acres
A1
0.23
0.45
1.00
A1
SCALE: 1"=60'
0 10 30 60
MATCHLINE-SEE SHEET C5.0
DRAINAGE PLAN
C5.1
KEYMAP
US HWY 287
STRASBURG DR
TRIANGLE DR
AVONDALE
RD
DRAINAGE NOTES
PROPOSED OUTLET STRUCTURE
PROPOSED STORM DRAIN PIPE
PROPOSED STORM DRAIN INLET (CDOT TYPE R CURB INLET, No. 16 COMBINATION
INLET, AREA INLET, ETC.)
PROPOSED GRASS-LINED SWALE W/CONCRETE PAN
PROPOSED RE-ALIGNMENT OF EXISTING IRRIGATION DITCH
EXISTING IRRIGATION DITCH TO BE PROTECTED IN-PLACE
PROPOSED INTERIM OUTFALL
PROPOSED HEADWALL w/ORIFICE PLATE
PROPOSED SIDEWALK CHASE
PROPOSED BIORETENTION BASIN
PROPOSED ADS STORMTECH SYSTEM
EXISTING 48" OUTFALL TO ROBERT BENSON LAKE
1
2
3
4
5
6
7
8
9
10
11
12
C5.1
C5.0
0.75
acres
D3
0.20
0.25
0.72
acres
D4
0.20
0.25
0.23
acres
A6
0.65
0.81
0.32
C2
C1
A5
A4
A1
A2
A6
A3
A
B
C4
C3
B1
D1
D2
D3
D4
1
2
1
11
5
5
5
5
3
3
3
3
3
3
2
2
2
2
2
OFF-SITE RUNOFF FROM BASIN N7 OF
RIDGEWOOD HILLS FOURTH FILING
N7=0.90 ac
12
3
3
3
3
3
3
3
3
2
3
acres
B2
0.65
0.81
1.78
acres
B3
0.65
0.81
0.96
-
-
-
-
-
-
-
-
-
-
-
-
-
-
STAMP
Date:
Drawn By:
Project No:
Checked By:
H:\Goodwin Knight\CO, Fort Collins - GNK000010 - Triangle Dr. and College Ave\CADD\3-CD\UTIL\GNK10_C5.0_Drainage.dwg - Donald Cecil - 2/11/2020
# Date Issue / Description Init.
RIDGEWOOD HILLS - FIFTH FILING
PRELIMINARY UTILITY PLAN
FORT COLLINS, CO
THESE PLANS ARE AN INSTRUMENT OF SERVICE
AND ARE THE PROPERTY OF GALLOWAY, AND MAY
NOT BE DUPLICATED, DISCLOSED, OR REPRODUCED
WITHOUT THE WRITTEN CONSENT OF GALLOWAY.
COPYRIGHTS AND INFRINGEMENTS WILL BE
ENFORCED AND PROSECUTED.
COPYRIGHT
GallowayUS.com
5265 Ronald Reagan Blvd., Suite 210
Johnstown, CO 80534
970.800.3300
PRELIMINARY
NOT FOR BIDDING
NOT FOR CONSTRUCTION
11.13.2019
GNK000010
JEP
DBC
LEGEND:
PROPOSED STORM SEWER
EXISTING STORM SEWER
PROPOSED STORM INLET
PROPOSED LOTLINE
EASEMENT LINE
EXISTING MINOR CONTOUR
EXISTING MAJOR CONTOUR
PROPOSED MINOR CONTOUR
PROPOSED MAJOR CONTOUR
PROPERTY BOUNDARY
EXISTING MANHOLE
DRAINAGE SYMBOLS:
DESIGN POINT
MAJOR BASIN BOUNDARY (i.e., C-STORE)
SUB-BASIN BOUNDARY (i.e., RATIONAL METHOD)
OVERLAND FLOW DIRECTION
(I.E., LANDSCAPING)
DIRECT FLOW DIRECTION
(I.E., PAVEMENT, CURB AND
GUTTER)
BASIN ID
MINOR (2YEAR) RUNOFF
COEFFICIENT
MAJOR (100YEAR) RUNOFF
COEFFICIENT
BASIN AREA
(ACRES)
acres
A1
0.23
0.45
1.00
A1
SCALE: 1"=60'
0 10 30 60
DRAINAGE PLAN
MATCHLINE-SEE SHEET C5.1 C5.0
KEYMAP
US HWY 287
STRASBURG DR
TRIANGLE DR
AVONDALE
RD
C5.1
C5.0
DRAINAGE NOTES
PROPOSED OUTLET STRUCTURE
PROPOSED STORM DRAIN PIPE
PROPOSED STORM DRAIN INLET (CDOT TYPE R CURB INLET, No. 16 COMBINATION
INLET, AREA INLET, ETC.)
PROPOSED GRASS-LINED SWALE W/CONCRETE PAN
PROPOSED RE-ALIGNMENT OF EXISTING IRRIGATION DITCH
EXISTING IRRIGATION DITCH TO BE PROTECTED IN-PLACE
PROPOSED INTERIM OUTFALL
PROPOSED HEADWALL w/ORIFICE PLATE
PROPOSED SIDEWALK CHASE
PROPOSED BIORETENTION BASIN
PROPOSED ADS STORMTECH SYSTEM
EXISTING 48" OUTFALL TO ROBERT BENSON LAKE
1
2
3
4
5
6
7
8
9
10
11
12
28
29
32
33
30
STORM B PIPE - (24)
STORM B PIPE - (23)
STORM B PIPE - (22)
34
16a
EX. STM MANHOLE AND APPROX. 44 LF OF EX. 30"
D/S STORM DRAIN TO BE REMOVED AND
REPLACED AT GRADE SHOWN.
36.5 LF 24" RCP @ 2.00%
64.10 LF 12"
HDPE @ 6.99%
YARD INLET LATERALS
HDPE N-12 (TYP)
5' TYPE R INLET
RIM EL. = 5087.6
INV IN = 5077.68
INV OUT = 5075.93
STMH B1
20' TYPE R INLET
5' TYPE R INLET
6' DENVER #16 STMH B2
COMBO INLET
STMH C1
TYPE D M-604-11
AREA INLET
RIM EL. = 5070.0
STMH B3
STORM C PIPE - (34)
CORE DRILL
12" HDPE
STORM B PIPE - (21)
STORM C PIPE - (59)
24" ADS
AREA DRAIN
RIM: 5091.50
INV: 5089.50
24" ADS
AREA DRAIN
RIM: 5090.44
INV: 5087.87
24" ADS
AREA DRAIN
RIM: 5094.25
INV: 5088.18
66.15 LF 12" HDPE @ 4.07%
24" ADS
AREA DRAIN
RIM: 5091.00
INV: 5085.05
24" ADS
AREA DRAIN
RIM: 5091.20
INV: 5085.09
24" ADS
AREA DRAIN
RIM: 5090.74
INV: 5087.57
24" ADS
AREA DRAIN
RIM: 5083.40
INV: 5078.42
24" ADS
AREA DRAIN
RIM: 5083.40
INV: 5078.83
24" ADS
AREA DRAIN
RIM: 5083.40
INV: 5079.05
53.65 LF 12" HDPE @ 1.0%
54.47 LF 12" HDPE @ 1.0%
7.00 LF 6" PVC
@ 1.00%
7.00 LF 6" PVC
@ 1.00%
2' SIDEWALK
CHASE AND
CURB CUT
7.00 LF 6" PVC
@ 1.00%
7.00 LF 6" PVC
@ 1.00%
35.54 LF 12"
HDPE @ 5.97%
STORM C PIPE - (60)
CORE DRILL
12" HDPE
61.24 LF 12"
HDPE @ 5.97%
72.51 LF 12"
HDPE @ 5.97%
50.00 LF 12"
HDPE @ 4.07%
6.65 LF 12"
RCP @ 7.50%
16.4 LF 12" HDPE @ 2.01%
24" ADS
AREA DRAIN
RIM: 5083.32
INV: 5075.00
12.38 LF 6"
PVC @ 1.00%
20.00 LF 8"
HDPE @ 4.20%
EXIST. FIRE HYDRANT
IS TO BE RELOCATED
CORE DRILL
12" HDPE
35.45 LF 12"
HDPE @ 6.99%
TEE
12" HDPE
TEE
12" RCP
92.88
INV.
92.03
INV.
90.60
INV.
90.47
INV.
12" TEE
INV=5084.21
28.27 LF 12" HDPE @ 1.0%
25.65 LF 12" HDPE @ 1.0%
20.07 LF 12" HDPE @ 1.0%
24" BASIN
COVERED LID
INV.=78.22
12" TEE
12" TEE INV.=78.57
INV.=78.76
2' SIDEWALK
CHASE
95.45
INV.
95.38
INV.
94.60
INV.
94.54
INV.
89.45
INV.
89.38
INV.
88.65
INV.
88.57
2' SIDEWALK INV.
CHASE
45.12 LF HDPE @ 1.75%
2' CURB CUT
(TYP X3)
SEE SEPARATE
L.I.D. PLAN SET
FOR SUBDRAIN
DETAILS
S1
0.560 0.43
8.0 LF 8"
HDPE @ 2.05%
93.86
INV.
93.69
INV.
4'
VALLEY
PAN
24" ADS
AREA DRAIN
RIM: 5083.22
INV: 5081.22
87.11 LF 12"
HDPE @ 1.75%
12" TEE
INV: 5080.43
12" FES
INV: 5078.90
EXISTING MANHOLE
STORM C PIPE - (59)
NORTH
0 15' 30' 60' 90'
SCALE: 1"= 30'-0"
MATCHLINE
(SEE SHEET 6 OF 9)
1-800-922-1987
NOTES
1. SEE SHEET 5 FOR DRAINAGE DATA SUMMARY TABLE
2. SEE SHEETS 19 - 21 FOR STORM DRAIN
PLAN & PROFILES.
MATCHLINE
(SAME SHEET)
MATCHLINE
(SAME SHEET)
LEGEND:
DRAINAGE BASIN I.D.
DESIGN POINT
OVERLAND
FLOW DIRECTION
#
#
0.000 0.00 MINOR STORM RUNOFF COEFFICIENT
DRAINAGE BASIN AREA (AC)
CITY OF FORT COLLINS, COLORADO
UTILITY PLAN APPROVAL
THIS DRAWING, AS AN INSTRUMENT OF SERVICE, IS AND SHALL REMAIN THE PROPERTY OF TFG DESIGN, LLC. AND SHALL NOT BE REPRODUCED, PUBLISHED OR USED IN ANY WAY WITHOUT THE PERMISSION OF THE
LANDSCAPE ARCHITECT.
1269 N Cleveland Ave, Loveland CO 80537
(970) 669.3737
design@tfgdesign.com www.tfgdesign.com
ATTN:
SHEET OF
SHEET NUMBER:
SHEET TITLE:
REVISIONS:
PROJECT INFORMATION:
OWNER:
DRAWN BY:
FILE LOCATION: T:\Projects\1000 General\1053 TFG\1053-001 RidgewoodHills4th\DWGS\C2.0_Drainage Plans.dwg
PLOT DATE: 11/19/2013 7:34 AM
PROJECT NUMBER:
DATE:
PHASE:
M. TIMM DEVELOPMENT
BILL TIMM
233 CARILLO STREET
SANTA BARBARA, CA 93101
(805) 963-0358
RIDGEWOOD HILLS
FOURTH FILING
AVONDALE RD & TRIANGLE
FORT COLLINS, COLORADO
111-122FC
AUG 07, 2014
FP
36
DRAINAGE PLAN
SOUTH
6
6
SOUTH WALL OF INLET BOX
TO ACCEPT PIPING FROM
PROPOSED DEVELOPMENT
STMH A2 W/ NEENAH
R-2553 GRATE
RIM EL. = 5080.33
INV. EL. (W) = 5075.30
INV. EL. (E) = 5075.10
24" ADS
AREA DRAIN
RIM: 5098.25
INV: 5096.25
24" ADS
AREA DRAIN
RIM: 5093.00
INV: 5091.00
24" ADS AREA DRAIN
RIM: 5085.25
INV: 5083.25
24" ADS
AREA DRAIN
RIM: 5080.25
INV: 5078.25
24" ADS AREA DRAIN
RIM: 5098.25
INV: 5095.30
12" TEE
INV: 5089.90
12" TEE
INV: 5082.76
24" ADS AREA DRAIN
RIM: 5079.91
INV: 5077.45
24" ADS
AREA DRAIN
RIM: 5098.25
INV: 5095.79
24" ADS AREA DRAIN
RIM: 5098.25
INV: 8093.60
24" ADS
AREA DRAIN
RIM: 5094.20
INV: 5090.81
24" ADS
AREA DRAIN
RIM: 5092.34
24" ADS
AREA DRAIN
RIM: 5092.76
INV: 5086.60
24" ADS
AREA DRAIN
RIM: 5088.15
INV: 5083.50
24" ADS
AREA DRAIN
RIM: 5084.85
INV: 5081.13
24" ADS
AREA DRAIN
RIM: 5084.50
INV: 5080.18
24" ADS
AREA DRAIN
RIM: 5094.25
INV: 5090.22
24" ADS
AREA DRAIN
RIM: 5094.25
INV: 5092.25
25.00 LF 12"
HDPE @ 4.07%
45.82 LF 12"
HDPE @ 1.00%
47.06 LF 12"
HDPE @ 1.00%
46.83 LF 12"
HDPE @ 3.64%
76.60 LF 12"
HDPE @ 3.64%
76.12 LF 12"
HDPE @ 1.16%
39.91 LF 12"
HDPE @ 4.96%
36.83 LF 12"
HDPE @ 6.05%
64.60 LF 12"
HDPE @ 3.67%
23.78 LF 12"
HDPE @ 0.51%
71.42 LF 12"
HDPE @ 0.51%
79.12 LF 12"
HDPE @ 1.20%
21.96 LF 12"
HDPE @ 2.55%
68.75 LF 12"
HDPE @ 0.33%
12" TEE
INV: 5078.02
34.29 LF 12"
HDPE @ 6.27%
EXIST. 24" RCP
EXIST. 36" RCP
12" ELBOW
INV: 5083.13
12" ELBOW
INV: 5090.79
37.30 LF 12"
HDPE @ 5.78%
63.98 LF 12"
HDPE @ 2.00%
12" HDPE
INV: 5074.48
12" ELBOW
INV: 5091.23
25.00 LF 12"
HDPE @ 4.07%
SEE SEPARATE
L.I.D. PLAN SET
FOR SUBDRAIN
DETAILS
S3
0.235 0.29
N6
0.830 0.71
N7
0.900 0.25
OS-1
0.401 0.61
18.42 LF 12"
HDPE @ 1.16%
NORTH
0 15' 30' 60' 90'
SCALE: 1"= 30'-0"
MATCHLINE
(SEE SHEET 7 OF 9)
DRAINAGE DATA SUMMARY TABLE
1-800-922-1987
LEGEND:
DRAINAGE BASIN I.D.
DESIGN POINT
OVERLAND FLOW DIRECTION
#
#
0.000 0.00 MINOR STORM RUNOFF COEFFICIENT
DRAINAGE BASIN AREA (AC)
CITY OF FORT COLLINS, COLORADO
UTILITY PLAN APPROVAL
THIS DRAWING, AS AN INSTRUMENT OF SERVICE, IS AND SHALL REMAIN THE PROPERTY OF TFG DESIGN, LLC. AND SHALL NOT BE REPRODUCED, PUBLISHED OR USED IN ANY WAY WITHOUT THE PERMISSION OF THE
LANDSCAPE ARCHITECT.
1269 N Cleveland Ave, Loveland CO 80537
(970) 669.3737
design@tfgdesign.com www.tfgdesign.com
ATTN:
SHEET OF
SHEET NUMBER:
SHEET TITLE:
REVISIONS:
PROJECT INFORMATION:
OWNER:
DRAWN BY:
FILE LOCATION: T:\Projects\1000 General\1053 TFG\1053-001 RidgewoodHills4th\DWGS\C2.0_Drainage Plans.dwg
PLOT DATE: 11/19/2013 7:34 AM
PROJECT NUMBER:
DATE:
PHASE:
M. TIMM DEVELOPMENT
BILL TIMM
233 CARILLO STREET
SANTA BARBARA, CA 93101
(805) 963-0358
RIDGEWOOD HILLS
FOURTH FILING
AVONDALE RD & TRIANGLE
FORT COLLINS, COLORADO
111-122FC
AUG 07, 2014
FP
36
NOTES
1. SEE SHEETS 19 - 21 FOR STORM DRAIN
PLAN & PROFILES.
DRAINAGE PLAN
NORTH
5
5
0 2000 4000 6000 8000 10000 12000 14000 16000 18000
Contour Elevation, ft
Cummulative Volume, ft3
Stage - Storage | pondC
3. Basin Side Slopes
A) Basin Maximum Side Slopes Z = ft / ft
(Horizontal distance per unit vertical, 4:1 or flatter preferred)
4. Inlet
A) Describe means of providing energy dissipation at concentrated
inflow locations:
0.139
5. Forebay
A) Minimum Forebay Volume VFMIN
= 0.003 ac-ft
(VFMIN
= 2% of the WQCV)
B) Actual Forebay Volume VF
= ac-ft
C) Forebay Depth
(DF
= 18 inch maximum) D
F = in
D) Forebay Discharge
i) Undetained 100-year Peak Discharge Q100
= cfs
ii) Forebay Discharge Design Flow QF
= cfs
(QF
= 0.02 * Q100
)
E) Forebay Discharge Design
F) Discharge Pipe Size (minimum 8-inches) Calculated DP
= in
G) Rectangular Notch Width Calculated WN
= in
Design Procedure Form: Extended Detention Basin (EDB)
Ridgewood Hills Filing No. 5 | B Basins
Galloway & Company, Inc.
February 11, 2020
Fort Collins, CO
Herman Feissner
UD-BMP (Version 3.07, March 2018)
Flow too small for berm w/ pipe
Choose One
Excess Urban Runoff Volume (EURV)
Choose One
Wall with Rect. Notch
Berm With Pipe
Water Quality Capture Volume (WQCV)
Wall with V-Notch Weir
GNK10.20_UD-BMP_v3.07, EDB 2/11/2020, 1:54 PM
SC-740 CHAMBER SPECIFICATIONS
STORMTECH CHAMBER VOLUME AND RELEASE RATE CALCULATIONS
CHAMBER LENGTH (IN)
CHAMBER WIDTH (IN)
CHAMBER FOOTPRINT (SQ IN)
CHAMBER FOOTPRINT (SF)
C pondC 2.81 0.25 5.0 0.70 9.95 7.0
13.10
D1 D1 0.29 0.25 5.0 0.07 9.95 0.7
D2 D2 0.75 0.25 5.0 0.19 9.95 1.9
D3 D3 0.72 0.25 5.0 0.18 9.95 1.8
D4 D4 0.23 0.25 5.0 0.06 9.95 0.6
D5 D5 3.71 0.25 5.0 0.93 9.95 9.2
5.71
100-Year
DIRECT RUNOFF TOTAL RUNOFF STREET
2/11/20
PIPE
Page 1 of 1 2/11/2020
D5 D5 3.71 0.20 5.0 0.74 2.85 2.1
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
2-Year
2/11/20
Page 1 of 1 2/11/2020
Grassed Waterway
STANDARD FORM SF-2
TIME OF CONCENTRATION
SUB-BASIN Tc CHECK
GNK10.20
FINAL
INITIAL/OVERLAND
(Ti)
TRAVEL TIME
Page 1 of 1 2/11/2020
Runoff
Coefficient
Area (ac)
Area
Weighted
Asphalt + Concrete Walks Lawns, Heavy Soil: Flat <2%
Page 1 of 1 2/11/2020
55 0.87 1.48 3.03
22 1.53 2.61 5.32
56 0.86 1.47 2.99
23 1.49 2.55 5.20
57 0.85 1.45 2.96
24 1.46 2.49 5.09
58 0.84 1.43 2.92
25 1.43 2.44 4.98
59 0.83 1.42 2.89
26 1.4 2.39 4.87
60 0.82 1.4 2.86
27 1.37 2.34 4.78
65 0.78 1.32 2.71
28 1.34 2.29 4.69
70 0.73 1.25 2.59
29 1.32 2.25 4.60
75 0.70 1.19 2.48
30 1.30 2.21 4.52
80 0.66 1.14 2.38
31 1.27 2.16 4.42
85 0.64 1.09 2.29
32 1.24 2.12 4.33
90 0.61 1.05 2.21
33 1.22 2.08 4.24
95 0.58 1.01 2.13
34 1.19 2.04 4.16
100 0.56 0.97 2.06
35 1.17 2.00 4.08
105 0.54 0.94 2.00
36 1.15 1.96 4.01
110 0.52 0.91 1.94
37 1.16 1.93 3.93
115 0.51 0.88 1.88
38 1.11 1.89 3.87
120 0.49 0.86 1.84
1:6,000
B 20.2
The point pin selected displayed by the on the user map and is does an approximate not represent
an authoritative property location.
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 14, Sep 13, 2019
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Aug 11, 2018—Aug
12, 2018
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Hydrologic Soil Group—Larimer County Area, Colorado
(Ridgewood Hills - Fifth Filing)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
11/6/2019
Page 2 of 4