HomeMy WebLinkAboutTHE QUARRY BY WATERMARK - PDP200019 - - DRAINAGE REPORT (2)
Preliminary Drainage Report
The Quarry by Watermark
Fort Collins, Colorado
November 10, 2020
Prepared for:
Watermark Residential
111 Monument Circle, Suite 1500
Indianapolis, IN 46204
Prepared by:
301 N. Howes Street Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 1791-001
November 10, 2020
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: Preliminary Drainage Report for
The Quarry by Watermark
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage Report for your
review. This report accompanies the combined Preliminary Plan submittal for the
proposed The Quarry by Watermark
This report has been prepared in accordance with the Fort Collins Stormwater Criteria
Manual (FCSCM) and serves to document the stormwater impacts associated with the
proposed The Quarry by Watermark housing project. We understand that review by the
City of Fort Collins is to assure general compliance with standardized criteria contained
in the FCSCM.
If you should have any questions as you review this report, please feel free to contact
us.
Sincerely,
Northern Engineering Services, Inc.
Frederick S. Wegert, PE
Project Engineer
Preliminary Drainage Report November 10, 2020
Watermark Residential Table of Contents
Table of Contents
I. General Location and Description ........................................................................ 1
II. Drainage Basins and Sub-Basins .......................................................................... 4
III. Drainage Design Criteria ..................................................................................... 4
IV. Drainage Facility Design ..................................................................................... 8
V. Conclusions ....................................................................................................... 11
VI. References ......................................................................................................... 13
Tables and Figures
Figure 1 – Vicinity Map .................................................................................... 1
Figure 2 – Aerial Photograph .......................................................................... 2
Figure 3 – FEMA Firmette (Map Numbers 08069CO978G and
08069CO979H) ............................................................................................... 3
Appendices
Appendix A – Hydrologic Computations
Appendix B – Hydraulic Computations
Appendix C – SWMM Models
Appendix D – Water Quality/LID Design Computations
Appendix E – Erosion Control Report
Appendix F – USDA Soils Report
Appendix G – FEMA Firmette
Map Pocket
Drainage Exhibit
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Watermark Residential Page 1 of 15
I. General Location and Description
A. Location
1. Vicinity Map
Figure 1 – Vicinity Map
2. The Quarry by Watermark project site is located in the northwest quarter of
Section 23, Township 7 North, Range 69 West of the 6th Principal Meridian, City
of Fort Collins, County of Larimer, State of Colorado.
3. The project site (refer to Figure 1) is bordered to the north by Hobbit Street; to the
east by Canal Importation Ditch; to the south by Spring Creek; and to the west by
Shields Street.
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4. Spring Creek and Canal Importation Ditch are a major drainageways located
adjacent to the project site. The confluence of Spring Creek and Canal
Importation Ditch is in the southeast corner of the site.
B. Description of Property
1. The Quarry by Watermark is comprised of ±19.38 acres.
2. The site is currently an undeveloped parcel surrounded by multi-family to the
north, west, and south and single-family homes to the east.
Figure 2 – Aerial Photograph
3. The existing groundcover consists of short grasses. The existing on-site runoff
generally drains from the northwest to the southeast across flat grades (e.g.,
<1.00%) into the Canal Importation Ditch. From there, the drainage continues
through Canal Importation Ditch to Spring Creek, and on to the Cache La
Poudre River.
4. According to the United States Department of Agriculture (USDA) Natural
Resources Conservation Service (NRCS) Soil Survey website:
(http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx),
the site consists primarily of Altvan-Satanta loams (Hydrologic Soil Group B)
and Nunn clay loam (Hydrological Soil Group C).
Project Site
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5. Springs Creek and Canal Importation Ditch are the only major drainageways
within or adjacent to the project site.
6. The proposed development will consist of eighteen (18) townhome buildings
containing a total of 329 units with detached garages. Other proposed
improvements include parking lots, sidewalks, pool, clubhouse, and
landscaping.
7. The proposed land use is multi-family. This is a permitted use in the Medium-
Density Mixed-Use Neighborhood District (MMN).
C. Floodplain
1. The eastern and southern edges of the site is in a FEMA regulatory floodplain;
however, the developable project area is outside of the FEMA floodplain. In
particular, the FEMA designated 100-year floodplain Basins E1 and E2 on the
Drainage Exhibit includes the FEMA regulatory floodplains for Spring Creek and
Canal Importation Ditch (Map Numbers 08069CO978G and 08069CO979H and
Figure 3 – FEMA Firmette (Map Numbers 08069CO978G and 08069CO979H)
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effective date of May 2, 2012). No development is proposed within Basins E1
and E2. A copy of the FEMA Firmette is provided in Appendix G.
2. We have analyzed the FEMA Floodplain map and cross sections for Spring Creek
and Canal Importation Ditch and determined that the highest base flood
elevation adjacent to the project site is 5016 (NAVD88). All buildings have been
elevated 1.5’ above this elevation. Furthermore, the buildings all maintain a
minimum of 12” between the finished floor elevation and the top of bank along
the south and east side of the property.
II. Drainage Basins and Sub-Basins
A. Major Basin Description
The north and east halves of The Quarry by Watermark is located within the City of
Fort Collins Canal Importation major drainage basin. The southwest quarter of the
site is located within the City of Fort Collins Spring Creek major drainage basin.
Specifically, the project site is situated at the confluence of the Spring Creek and
Canal Importation major drainage basins.
B. Sub-Basin Description
1. The outfall for the project site is at the confluence of Springs Creek and Canal
Importation Basins.
2. The existing subject site can be defined with twelve (12) sub-basins that
encompasses the entire project site and three (3) offsite basins that drain onto the
project site.
3. The existing site runoff generally drains from northwest-to-southeast and into
the Canal Importation Ditch.
4. The project site receives runoff from Shields Street and Hobbit Street.
III. Drainage Design Criteria
A. Optional Provisions
The project site requests a variance for providing stormwater detention per the City
of Fort Collins “Beat the Peak” alternative within the City’s Stormwater Manual. No
other optional revisions are variances will be required from the City of Fort Collins
Stormwater Manual.
B. Stormwater Management Strategy
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The overall stormwater management strategy employed with The Quarry by
Watermark utilizes the “Four Step Process” to minimize adverse impacts of
urbanization on receiving waters. The following is a description of how the
proposed development has incorporated each step.
Step 1 – Employ Runoff Reduction Practices. The first consideration taken in trying
to reduce the stormwater impacts of this development is the site selection itself. By
choosing an already developed site with public storm sewer currently in place, the
burden is significantly less than developing a vacant parcel absent of any
infrastructure.
The Quarry by Watermark aims to reduce runoff peaks, volumes and pollutant loads
from frequently occurring storm events (i.e., water quality (i.e., 80th percentile) and
2-year storm events) by implementing Low Impact Development (LID) strategies.
Wherever practical, runoff will be routed across landscaped areas or through a rain
garden or water quality pond. These LID practices reduce the overall amount of
impervious area, while at the same time Minimizing Directly Connected Impervious
Areas (MDCIA). The combined LID/MDCIA techniques will be implemented, where
practical, throughout the development, thereby slowing runoff and increasing
opportunities for infiltration.
Step 2 – Implement BMPs that Provide a Water Quality Capture Volume (WQCV)
with Slow Release. The efforts taken in Step 1 will help to minimize excess runoff
from frequently occurring storm events; however, urban development of this
intensity will still have stormwater runoff leaving the site. The primary water quality
treatment will occur in the underground vaults located at the south end of the
project.
Step 3 – Stabilize Drainageways. As stated in Section I.B.5, above, the Spring Creek
and Canal Importation drainage is adjacent to the subject site, however no changes
to the channel are proposed with this project. While this step may not seem
applicable to The Quarry by Watermark, the proposed project indirectly helps
achieve stabilized drainageways, nonetheless. Once again, site selection has a
positive effect on stream stabilization. By developing an infill site with existing
stormwater infrastructure, combined with LID and MDCIA strategies, the likelihood
of bed and bank erosion is reduced. Furthermore, this project will pay one-time
stormwater development fees, as well as ongoing monthly stormwater utility fees,
both of which help achieve Citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs. This step
typically applies to industrial and commercial developments.
C. Development Criteria Reference and Constraints
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1. The subject property is not part of any Overall Development Plan (ODP)
drainage study or similar “development/project” drainage master plan.
2. The site plan is constrained to the north and west by public streets, to the south
by Spring Creek, and to the east by the Canal Importation Ditch.
D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as
depicted in Figure 3.4-1 of the FCSCM, serve as the source for all hydrologic
computations associated with The Quarry by Watermark development.
Tabulated data contained in Table 3.4-1 has been utilized for Rational Method
runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. Since the project is at adjacent to the confluence of Spring Creek and Canal
Importation Basins, the hydrograph for the Canal Importation Basin was
analyzed to determine if the site’s peak reaches the confluence prior to the peak
from the Canal Importation Basin. This is known as the “Beat the Peak”
procedure within the FCSM.
4. Two separate design storms have been utilized to address distinct drainage
scenarios. The first event analyzed is the “Minor,” or “Initial” Storm, which has a
2-year recurrence interval. The second event considered is the “Major Storm,”
which has a 100-year recurrence interval.
E. Hydraulic Criteria
1. The drainage facilities proposed with The Quarry by Watermark project are
designed in accordance with criteria outlined in the FCSCM and/or the Urban
Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria
Manual.
2. As stated in Section I.C.1, above, the subject property is located next to a FEMA
designated floodplain but is not located within the floodplain limits.
F. Floodplain Regulations Compliance
1. As previously mentioned, this project is adjacent to a FEMA regulated
floodplain. The developable area of the project is located outside of the
floodplain, and as such, it will not be subject to any floodplain regulations.
However, the storm outfall will be located within the floodplain, and that work
will be subject to the applicable floodplain regulations.
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2. Despite most of the project not being located within the floodplain,
consideration has been given to the floodplain elevations as they relate to the
proposed buildings and the finished floors have been elevated accordingly.
G. Modifications of Criteria
No formal modifications are requested at this time. However, staff has determined
that detention will not be required with this project as a result of the proximity to the
Canal Importation Ditch.
H. Conformance with Water Quality Treatment Criteria
City Code requires that 100% of runoff from a project site receive some sort of water
quality treatment. This project proposes to provide water quality treatment through
the use of two rain gardens and a water quality pond. The rain gardens are located
along the east edge of the site and will discharge into the Canal Importation Basin.
The water quality pond is located along the south edge of the site and will discharge
into Spring Creek Basin. Due to the physical constraints associated with an infill
project of this nature and the prohibition of providing water quality facilities within
the public right-of-way, there are some small, narrow areas around the perimeter of
the project that cannot be captured. The uncaptured areas tend to be narrow strips of
concrete flatwork that link the building entrances to the public sidewalks as well as
small planter beds between the building and public sidewalks or property lines.
While these small areas will not receive formal water quality treatment, most areas
will still see some treatment as runoff is directed across through the landscaped
areas or across the landscaped parkways before reaching the roadway curb and
gutter.
I. Conformance with Low Impact Development (LID)
The project site will conform with the requirement to treat a minimum of 75% of the
project site using a LID technique.
J. Sizing of LID Facilities
Rain Gardens
1. The rain gardens were sized by first determining the required water quality
capture volume (WQCV) for Basins A1-A2 and B1-B10. A 12-hour drain time
was used in this calculation.
2. Once the WQCV was identified, each rain garden was sized for its respective
WQCV. The rain gardens will be constructed with a biomedia filter and
underdrain. An overflow drain will be provided in each rain garden to pass
storms greater than the WQCV.
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Water Quality Pond
1. The water quality pond was sized by first determining the required water quality
capture volume (WQCV) for Basins D1 and A3. Offsite flows from Basins OS1
and OS2 were designed to pass through the water quality pond. A 40-hour drain
time was used in this calculation.
2. Once the WQCV was identified, the water quality pond was sized to provide the
WQCV. An outlet control structure with overflow will be provided to pass
storms greater than the WQCV.
IV. Drainage Facility Design
A. General Concept
1. The main objective of The Quarry by Watermark drainage design is to maintain
existing drainage patterns, while not adversely impacting adjacent properties.
2. Off-site runoff is expected from Shields Street to pass directly through the project
site. Offsite basins OS1 and OS2 (2.28 acres) drains directly into the west entrance
to the site. Furthermore, an additional 173 acres of single-family homes, on the
west side of Shields Street, has the potential to impact the site during a major
storm event. Two Type-R inlets on the west side of the intersection of Shields
Street and Stuart Street will collect the Minor Storm from the single-family
subdivision, but the Major Storm can potentially overtop the intersection and
into the site. According to City Staff, it’s their policy to inundate arterial roads,
like Shields Street, during a Major Storm Event.
3. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within
the sections to which the content best applies.
4. Drainage for the project site has been analyzed using twenty-one (21) onsite
drainage sub-basins, designated as sub-basins A1- A3, B1-B10, C1-C2, D1-D2, E1-
E2, and F1-F2. Furthermore, there are three (3) offsite drainage sub-basins
designated as sub-basins OS1, OS2, and OS3. The drainage patterns anticipated
for the basins are further described below.
Sub-Basins A1 & A2
Sub-Basins A1 and A2 encompasses approximately 22% the total site area. These
sub-basins are comprised primarily of roof area, concrete flatwork, parking lot
and landscaped areas. The sub-basins will drain into a valley pan and curb and
gutter located in a parking lot, along the north edge of the parking lot, and be
captured by Rain Garden A. Storm sewer will collect and discharge isolated
areas of Basin A1 into Rain Garden A. Flows will then proceed to the confluence
of Spring Creek and Canal Importation Ditch.
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Sub-Basin B1 – B10
Sub-Basins B1 through B10 encompasses approximately 35% the total site area.
These sub-basins are comprised primarily of roof area, concrete flatwork,
parking lot, and landscaped areas. The sub-basins will drain into a valley pan
located within each sub-basin and towards a common storm sewer. The storm
sewer will collect drainage from all the sub-basins and discharge into Rain
Garden B. Flows will then proceed to the Canal Importation Ditch.
Sub-Basin C1
Sub-Basin C1 encompasses approximately 2% the total site area. This sub-basin
is comprised primarily of roof area, concrete flatwork, and landscaped areas. The
sub-basin will drain north into an existing ditch along the north property line
(Ditch C) and into to the Canal Importation Ditch.
Sub-Basin C2
Sub-Basin C2 encompasses approximately 0.8% the total site area. This sub-basin
is comprised primarily of roof area, concrete flatwork, and landscaped areas.
Flows from the sub-basin will flow north into curb and gutter along Hobbit
Street. Hobbit Street will convey runoff, along with drainage from Sub-Basin
OS3, to Ditch C. Flows will then proceed to the Canal Importation Ditch.
Sub-Basin D1 & A3
Sub-Basins D1 and A3 encompasses approximately 13% the total site area. These
sub-basins are comprised primarily of roof area, concrete flatwork, parking lot,
and landscaped areas. The sub-basins will drain into a common storm sewer via
valley pans and curb and gutter. The storm sewer will collect drainage from all
the sub-basins, including Sub-Basins OS1 and OS2, and discharge into Water
Quality Pond D. Flows will then proceed to Spring Creek.
Sub-Basin D2
Sub-Basin D2 encompasses approximately 0.3% the total site area. This sub-basin
is comprised primarily of primarily of landscaped areas. Flows from the sub-
basin will discharge directly into Spring Creek.
Sub-Basin E1
Sub-basin E1 encompasses approximately 17% the total site area. This sub-basin
comprises of the Spring Creek flood plain. No improvements, except for storm
sewer outfalls, are proposed within this sub-basin
Sub-Basin E2
Sub-basin E2 encompasses approximately 7% the total site area. This sub-basin
comprises of the Canal Importation flood plain. No improvements, except for
storm sewer outfalls, are proposed within this sub-basin
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Sub-Basins F1 & F2
Sub-basins F1 and F2 encompasses approximately 1% the total site area. These
sub-basins are comprised primarily of concrete flatwork and landscaped areas.
Flows from the sub-basin will drain into curb and gutter along Shield Street. The
curb and gutter will then convey the flows to the intersection of Shields Street
and Stuart Street (also the west entrance of the site), into Sub-Basin D1, and
ultimately into Water Quality Pond D. Flows will then proceed to Spring Creek.
Sub-Basin OS1 & OS2
Offsite Sub-Basins OS1 and OS2 consists of the west edge of Shields Street that
directly impacts the project site. These sub-basins are comprised primarily of
asphalt, concrete flatwork, and a landscaped parkway. Flows from the sub-basin
will drain into curb and gutter along Shield Street. The curb and gutter will then
convey the flows to the intersection of Shields Street and Stuart Street (also the
west entrance of the site), into Sub-Basin D1, and ultimately into Water Quality
Pond D. Flows will then proceed to Spring Creek.
Sub-Basin OS3
Offsite Sub-Basins OS3 consists of the south edge of Hobbit Street that directly
impacts the project site. These sub-basins are comprised primarily of asphalt and
concrete flatwork. Flows from the sub-basin will drain into curb and gutter
along Hobbit Street. The curb and gutter will then convey the flows to Ditch C
and ultimately into the Canal Importation Ditch.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the
end of this report.
B. Specific Details
1. Since detention is not required with this site, the existing impervious area has not
been considered in determining allowable release from the property.
2. An allowable release rate was not determined for this project due to the
proximity of the site to the confluence of Spring Creek and the Canal Importation
Ditch.
3. The FAA method was not used to size the on-site detention volume for quantity
detention since detention is not required.
4. Since the project is adjacent to the confluence of Spring Creek and the Canal
Importation Basin, the hydrograph for the Canal Importation Basin was analyzed
to determine if the site’s peak reaches the confluence prior to the peak from the
Canal Importation Basin. This is known as the “Beat the Peak” procedure within
the FCSM.
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The north and west halves of the project (approximately 3/4 of the site) will
discharge into the Canal Importation Basin. The SWMM analysis of the City’s
Canal Importation Basin is provided in Appendix C.
The southwest quarter of the site will discharge into Spring Creek. The MOD-
SWMM data for Spring Creek is difficult to analyze using today’s computer
technology, but the proximity of the site to Spring Creek suggests the runoff
from the southwest corner will Beat the Peak for the Spring Creek Basin.
C. Sizing of LID Facilities
Rain Gardens
1. The rain gardens were sized by first determining the required water quality
capture volume (WQCV) for Basins A1-A2 and B1-B10. A 12-hour drain time
was used in this calculation.
2. Once the WQCV was identified, each rain garden was sized for its respective
WQCV. The rain gardens will be constructed with a biomedia filter and
underdrain. An overflow drain will be provided in each rain garden to pass
storms greater than the WQCV.
Water Quality Pond
1. The water quality pond was sized by first determining the required water quality
capture volume (WQCV) for Basins D1 and A3. A 40-hour drain time was used
in this calculation.
2. Once the WQCV was identified, the water quality pond was sized to provide the
WQCV. An outlet control structure with overflow will be provided to pass
storms greater than the WQCV.
V. Conclusions
A. Compliance with Standards
1. The design elements comply with the Beat the Peak Alternative within the City’s
FCSM and meet all LID requirements.
2. The drainage design proposed with The Quarry by Watermark complies with the
City of Fort Collins Master Drainage Plan for the Spring Creek and Canal
Importation Basins.
3. The project is adjacent to the Spring Creek and Canal Importation FEMA
regulatory floodplains. However, the development is constructed outside of the
floodplains, and buildings are located 18-inches above the base flood elevation.
No improvements are proposed within the FEMA regulated floodplains. All
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applicable provisions within Chapter 10 of the City Municipal Code shall be
adhered to.
4. The drainage plan and stormwater management measures proposed with The
Quarry by Watermark project are compliant with all applicable State and Federal
regulations governing stormwater discharge.
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit potential
damage associated with its stormwater runoff. The Quarry by Watermark will
not detain for the pervious area converted to impervious areas to release at the 2-
year existing rate during the 100-year storm.
2. The Quarry by Watermark will not impact the Master Drainage Plan
recommendations for the Canal Importation and Spring Creek major drainage
basin.
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VI. References
Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by
Ordinance No. 159, 2018, and referenced in Section 26-500 of the City of Fort Collins
Municipal Code.
Soils Resource Report for Larimer County Area, Colorado, Natural Resources
Conservation Service, United States Department of Agriculture.
Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood
Control District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April
2008.
Appendix A
Hydrologic Computations
Runoff
Coefficient1
Percent
Impervious1
0.95 100%
0.95 90%
0.50 40%
0.50 40%
0.20 2%
0.20 2%
Basin ID Basin Area
(sq.ft.)
Basin Area
(acres)
Asphalt,
Concrete (acres)Rooftop (acres)Gravel (acres)Pavers (acres)
Undeveloped:
Greenbelts,
Agriculture
(acres)
Lawns, Clayey
Soil, Flat Slope <
2% (acres)
Percent
Impervious
C2*Cf
Cf = 1.00
C5*Cf
Cf = 1.00
C10*Cf
Cf = 1.00
C100*Cf
Cf = 1.25
H-A1 44,062 1.012 0.000 0.000 0.000 0.000 1.012 0.000 2%0.20 0.20 0.20 0.25
H-A2 6,773 0.155 0.000 0.000 0.000 0.000 0.155 0.000 2%0.20 0.20 0.20 0.25
H-B1 110,004 2.525 0.000 0.000 0.000 0.000 2.525 0.000 2%0.20 0.20 0.20 0.25
H-B2 170,633 3.917 0.015 0.000 0.000 0.000 3.902 0.000 2%0.20 0.20 0.20 0.25
H-B3 19,023 0.437 0.020 0.000 0.000 0.000 0.417 0.000 6%0.23 0.23 0.23 0.29
H-C1 32,204 0.739 0.000 0.000 0.000 0.000 0.739 0.000 2%0.20 0.20 0.20 0.25
H-C2 238,190 5.468 0.009 0.000 0.000 0.000 5.459 0.000 2%0.20 0.20 0.20 0.25
H-D1 7,509 0.172 0.000 0.000 0.000 0.000 0.172 0.000 2%0.20 0.20 0.20 0.25
H-E1 147,424 3.384 0.283 0.019 0.000 0.000 3.082 0.000 11%0.27 0.27 0.27 0.33
H-E2 60,287 1.384 0.143 0.002 0.000 0.000 1.239 0.000 12%0.28 0.28 0.28 0.35
H-F1 1,947 0.045 0.028 0.000 0.000 0.000 0.000 0.017 64%0.67 0.67 0.67 0.84
H-F2 7,695 0.177 0.094 0.000 0.000 0.000 0.000 0.082 54%0.60 0.60 0.60 0.75
OS1 21,067 0.484 0.407 0.000 0.000 0.000 0.000 0.077 84%0.83 0.83 0.83 1.00
OS2 78,428 1.800 1.706 0.000 0.000 0.000 0.000 0.094 95%0.91 0.91 0.91 1.00
OS3 20,406 0.468 0.405 0.000 0.000 0.000 0.000 0.063 87%0.25 0.25 0.25 0.31
Total 965,652 22.168 3.111 0.022 0.000 0.000 18.702 0.334 16%0.31 0.31 0.31 0.38
Lawns and Landscaping:
Combined Basins
2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins
Stormwater Manual (FCSM).
Lawns, Clayey Soil, Flat Slope < 2%
USDA SOIL TYPE: C
Undeveloped: Greenbelts, Agriculture Composite Runoff Coefficient2
1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM.
EXISTING RUNOFF COEFFICIENT CALCULATIONS
Asphalt, Concrete
Rooftop
Gravel
Pavers
The Quarry by Watermark
F. Wegert
November 10, 2020
Project:
Calculations By:
Date:
Character of Surface
Streets, Parking Lots, Roofs, Alleys, and Drives:
Page 1 of 3
Project:
Date:
Where:
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)
Ti
2-Yr
(min)
Ti
10-Yr
(min)
Ti
100-Yr
(min)
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)Surface Roughness
(n)
Flow
Area3
(sq.ft.)
WP
3
(ft)
Hydraulic
Radius (ft)
Velocity
(ft/s)
Tt
(min)
Max.
Tc
(min)
Comp.
Tc 2-Yr
(min)
Tc
2-Yr
(min)
Comp.
Tc 10-Yr
(min)
Tc
10-Yr
(min)
Comp.
Tc 100-Yr
(min)
Tc
100-Yr
(min)
h-a1 H-A1 200 15.34 10.61 2.37%17.9 17.9 16.9 159 10.61 7.95 1.67%Swale (4:1)0.025 4.00 8.25 0.48 4.76 0.56 11.99 18.42 11.99 18.42 11.99 17.43 11.99
h-a2 H-A2 45 15.23 14.59 1.42%10.0 10.0 9.5 N/A Swale (4:1)4.00 8.25 N/A N/A 0.00 10.25 10.04 10.04 10.04 10.04 9.48 9.48
h-b1 H-B1 200 14.80 13.63 0.59%28.5 28.5 26.9 278 13.63 11.74 0.68%Swale (8:1)0.025 8.00 16.12 0.50 3.08 1.50 12.66 29.96 12.66 29.96 12.66 28.38 12.66
h-b2 H-B2 148 17.33 16.31 0.69%23.1 23.1 21.8 365 16.31 13.44 0.79%Swale (8:1)0.025 8.00 16.12 0.50 3.31 1.84 12.85 24.94 12.85 24.94 12.85 23.63 12.85
h-b3 H-B3 52 17.33 16.20 2.17%9.0 9.0 8.4 180 16.20 15.20 0.56%Swale (4:1)0.025 4.00 8.25 0.48 2.74 1.09 11.29 10.11 10.11 10.11 10.11 9.50 9.50
h-c1 H-C1 90 17.23 10.63 7.33%8.2 8.2 7.8 175 10.63 10.10 0.30%Swale (4:1)0.025 4.00 8.25 0.48 2.02 1.44 11.47 9.66 9.66 9.66 9.66 9.20 9.20
h-c2 H-C2 60 17.48 16.29 1.98%10.4 10.4 9.8 826 16.29 13.33 0.36%Swale (8:1)0.025 8.00 16.12 0.50 2.24 6.16 14.92 16.52 14.92 16.52 14.92 15.94 14.92
h-d1 H-D1 60 19.31 17.33 3.30%8.8 8.8 8.3 N/A Swale (4:1)4.00 8.25 N/A N/A 0.00 10.33 8.75 8.75 8.75 8.75 8.26 8.26
h-e1 H-E1 65 17.28 11.43 9.00%6.0 6.0 5.6 1272 11.43 3.16 0.65%Floodplain 0.045 46.50 23.32 1.99 4.23 5.01 17.43 11.05 11.05 11.05 11.05 10.57 10.57
h-e2 H-E2 40 14.10 7.58 16.30%3.8 3.8 3.5 735 7.58 4.17 0.46%Floodplain 0.035 18.00 13.00 1.38 3.60 3.40 14.31 7.23 7.23 7.23 7.23 6.91 6.91
h-f1 H-F1 22 18.47 17.99 2.18%2.9 2.9 1.8 175 17.99 17.00 0.57%Gutter 0.012 3.61 19.18 0.19 3.07 0.95 11.09 3.84 5.00 3.84 5.00 2.70 5.00
h-f2 H-F2 40 20.24 19.49 1.88%4.8 4.8 3.4 570 19.49 16.79 0.47%Gutter 0.012 3.61 19.18 0.19 2.81 3.38 13.39 8.18 8.18 8.18 8.18 6.74 6.74
os1 OS1 30 22.53 21.47 3.53%1.8 1.8 0.7 420 21.47 16.95 1.08%Gutter 0.012 3.61 19.18 0.19 4.23 1.65 12.50 3.47 5.00 3.47 5.00 2.33 5.00
os2 OS2 26 36.00 34.55 5.58%1.0 1.0 0.5 1738 34.55 16.79 1.02%Gutter 0.012 3.61 19.18 0.19 4.12 7.02 19.80 8.04 8.04 8.04 8.04 7.56 7.56
os3 OS3 32 20.10 20.05 0.16%16.7 16.7 15.5 615 20.05 12.88 1.17%Gutter 0.012 3.61 19.18 0.19 4.40 2.33 13.59 19.02 13.59 19.02 13.59 17.79 13.59
total Total 60 17.48 16.29 1.98%9.2 9.2 8.3 826 16.29 13.33 0.36%Swale (8:1)0.025 8.00 16.12 0.50 2.24 6.16 14.92 15.31 14.92 15.31 14.92 14.43 14.43
R = Hydraulic Radius (feet)
S = Longitudinal Slope, feet/feet
Maximum Tc:
Combined Basins
Design
Point Basin
Overland Flow Channelized Flow Time of Concentration
Channelized Flow, Velocity:Channelized Flow, Time of Concentration:
V = Velocity (ft/sec)
n = Roughness Coefficient
November 10, 2020
EXISTING TIME OF CONCENTRATION COMPUTATIONS
Overland Flow, Time of Concentration:
Calculations By:
The Quarry by Watermark
F. Wegert
(Equation 3.3-2 per Fort Collins Stormwater Manual)
𝑅𝑖=1.87 1.1 −𝐶∗𝐶𝑓𝐿
𝑅ൗ13
𝑉=1.49
𝑛∗𝑅2/3 ∗𝑅(Equation 5-4 per Fort Collins Stormwater Manual)
𝑅𝑐=𝐿
180 +10 (Equation 3.3-5 per Fort Collins Stormwater Manual)
𝑅𝑡=𝐿
𝑉∗60
(Equation 5-5 per Fort Collins Stormwater Manual)
Notes:
1)Add 5000 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min.
3) Assume a water depth of 6" and a typical curb and gutter per Larimer County Urban Street Standard Detail 701 for curb and gutter channelized flow. Assume a water depth of 1', fixed side slopes, and a triangular swale section for grass
channelized flow. Assume a water depth of 1', 4:1 side slopes, and a 2' wide valley pan for channelized flow in a valley pan .
Page 2 of 3
Tc2 Tc10 Tc100 C2 C10 C100
I2
(in/hr)
I10
(in/hr)
I100
(in/hr)
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
h-a1 H-A1 1.012 11.99 11.99 11.99 0.20 0.20 0.25 2.09 3.57 7.29 0.4 0.7 1.8
h-a2 H-A2 0.155 10.04 10.04 9.48 0.20 0.20 0.25 2.21 3.78 8.03 0.1 0.1 0.3
h-b1 H-B1 2.525 12.66 12.66 12.66 0.20 0.20 0.25 2.02 3.45 7.04 1.0 1.7 4.4
h-b2 H-B2 3.917 12.85 12.85 12.85 0.20 0.20 0.25 2.02 3.45 7.04 1.6 2.7 7.0
h-b3 H-B3 0.437 10.11 10.11 9.50 0.23 0.23 0.29 2.21 3.78 8.03 0.2 0.4 1.0
h-c1 H-C1 0.739 9.66 9.66 9.20 0.20 0.20 0.25 2.26 3.86 8.03 0.3 0.6 1.5
h-c2 H-C2 5.468 14.92 14.92 14.92 0.20 0.20 0.25 1.90 3.24 6.62 2.1 3.6 9.1
h-d1 H-D1 0.172 8.75 8.75 8.26 0.20 0.20 0.25 2.35 4.02 8.38 0.1 0.1 0.4
h-e1 H-E1 3.384 11.05 11.05 10.57 0.27 0.27 0.33 2.13 3.63 7.57 1.9 3.3 8.6
h-e2 H-E2 1.384 7.23 7.23 6.91 0.28 0.28 0.35 2.52 4.31 9.06 1.0 1.7 4.4
h-f1 H-F1 0.045 5.00 5.00 5.00 0.67 0.67 0.84 2.85 4.87 9.95 0.1 0.1 0.4
h-f2 H-F2 0.177 8.18 8.18 6.74 0.60 0.60 0.75 2.40 4.10 9.06 0.3 0.4 1.2
os1 OS1 0.484 5.00 5.00 5.00 0.83 0.83 1.00 2.85 4.87 9.95 1.1 2.0 4.8
os2 OS2 1.800 8.04 8.04 7.56 0.91 0.91 1.00 2.40 4.10 8.59 3.9 6.7 15.5
os3 OS3 0.468 13.59 13.59 13.59 0.25 0.25 0.31 1.95 3.34 6.82 0.2 0.4 1.0
total Total 22.168 14.92 14.92 14.43 0.31 0.31 0.38 1.90 3.24 6.71 12.9 22.0 56.9
Basin Area
(acres)
Runoff C
Combined Basins
Intensity, I from Fig. 3.4.1 Fort Collins Stormwater Manual
Tc (Min)
EXISTING DIRECT RUNOFF COMPUTATIONS
Intensity Flow
The Quarry by Watermark
F. Wegert
November 10, 2020
Project:
Calculations By:
Date:
Rational Equation: Q = CiA (Equation 6-1 per MHFD)
Design
Point
Page 3 of 3
Runoff
Coefficient1
Percent
Impervious1
0.95 100%
0.95 90%
0.50 40%
0.85 90%
0.20 2%
0.20 2%
Basin ID Basin Area
(sq.ft.)
Basin Area
(acres)
Asphalt,
Concrete (acres)Rooftop (acres)Gravel (acres)Residential: High
Density (acres)
Undeveloped:
Greenbelts,
Agriculture
(acres)
Lawns, Clayey
Soil, Flat Slope <
2% (acres)
Percent
Impervious
C2*Cf
Cf = 1.00
C5*Cf
Cf = 1.00
C10*Cf
Cf = 1.00
C100*Cf
Cf = 1.25
A1 90,843 2.085 90%0.85 0.85 0.85 1.00
A2 96,775 2.222 90%0.85 0.85 0.85 1.00
A3 26,902 0.618 90%0.85 0.85 0.85 1.00
B1 29,907 0.687 90%0.85 0.85 0.85 1.00
B2 19,510 0.448 90%0.85 0.85 0.85 1.00
B3 136,713 3.139 90%0.85 0.85 0.85 1.00
B4 12,541 0.288 90%0.85 0.85 0.85 1.00
B5 21,040 0.483 90%0.85 0.85 0.85 1.00
B6 53,225 1.222 90%0.85 0.85 0.85 1.00
B7 3,164 0.073 90%0.85 0.85 0.85 1.00
B8 555 0.013 90%0.85 0.85 0.85 1.00
B9 7,042 0.162 90%0.85 0.85 0.85 1.00
B10 14,332 0.329 90%0.85 0.85 0.85 1.00
C1 19,935 0.458 90%0.85 0.85 0.85 1.00
C2 7,061 0.162 90%0.85 0.85 0.85 1.00
D1 86,072 1.976 90%0.85 0.85 0.85 1.00
D2 2,784 0.064 90%0.85 0.85 0.85 1.00
E1 147,424 3.384 0.283 0.019 0.000 0.000 3.082 0.000 11%0.27 0.27 0.27 0.33
E2 60,287 1.384 0.143 0.002 0.000 0.000 1.239 0.000 12%0.28 0.28 0.28 0.35
F1 1,947 0.045 0.028 0.000 0.000 0.000 0.000 0.017 64%0.67 0.67 0.67 0.84
F2 7,690 0.177 0.094 0.000 0.000 0.000 0.000 0.082 54%0.60 0.60 0.60 0.75
OS1 21,067 0.484 0.407 0.000 0.000 0.000 0.000 0.077 84%0.83 0.83 0.83 1.00
OS2 78,428 1.800 1.706 0.000 0.000 0.000 0.000 0.094 95%0.91 0.91 0.91 1.00
OS3 20,406 0.468 0.405 0.000 0.000 0.000 0.000 0.063 87%0.25 0.25 0.25 0.31
Total 845,750 19.416 90%0.85 0.85 0.85 1.00
DEVELOPED RUNOFF COEFFICIENT CALCULATIONS
Asphalt, Concrete
Rooftop
Gravel
Residential: High Density
The Quarry by Watermark
F. Wegert
November 10, 2020
Project:
Calculations By:
Date:
Character of Surface
Streets, Parking Lots, Roofs, Alleys, and Drives:
Lawns and Landscaping:
Combined Basins
2) Composite Runoff Coefficient adjusted per Table 3.2-3 of the Fort Collins
Stormwater Manual (FCSM).
Lawns, Clayey Soil, Flat Slope < 2%
USDA SOIL TYPE: C
Undeveloped: Greenbelts, Agriculture Composite Runoff Coefficient2
1) Runoff coefficients per Tables 3.2-1 & 3.2 of the FCSM. Percent impervious per Tables 4.1-2 & 4.1-3 of the FCSM.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Assumed Residential: High Desnity with a percent impervious of 90% and runoff coefficient of 0.85.
Page 1 of 4
Project:
Date:
Where:
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)
Ti
2-Yr
(min)
Ti
10-Yr
(min)
Ti
100-Yr
(min)
Length
(ft)
Elev
Up
Elev
Down
Slope
(%)Surface Roughness
(n)
Flow
Area3
(sq.ft.)
WP
3
(ft)
Hydraulic
Radius (ft)
Velocity
(ft/s)
Tt
(min)
Max.
Tc
(min)
Comp.
Tc 2-Yr
(min)
Tc
2-Yr
(min)
Comp.
Tc 10-Yr
(min)
Tc
10-Yr
(min)
Comp.
Tc 100-Yr
(min)
Tc
100-Yr
(min)
a1 A1 70 17.73 17.12 0.87%4.1 4.1 1.6 835 17.12 7.98 1.09%Valley Pan 0.012 6.00 10.25 0.59 0.91 15.31 15.03 19.40 15.03 19.40 15.03 16.95 15.03
a2 A2 55 18.75 17.25 2.73%2.5 2.5 1.0 915 17.25 12.05 0.57%Valley Pan 0.012 6.00 10.25 0.59 0.66 23.28 15.39 25.76 15.39 25.76 15.39 24.27 15.39
a3 A3 45 19.00 18.00 2.22%2.4 2.4 1.0 315 18.00 15.71 0.73%Valley Pan 0.012 6.00 10.25 0.59 0.74 7.09 12.00 9.49 9.49 9.49 9.49 8.05 8.05
b1 B1 50 13.33 12.72 1.22%3.1 3.1 1.2 290 12.72 10.20 0.87%Swale (8:1)0.030 8.00 16.12 0.50 0.29 16.65 11.89 19.75 11.89 19.75 11.89 17.89 11.89
b2 B2 95 14.75 12.70 2.16%3.5 3.5 1.4 20 12.70 12.61 0.45%Valley Pan 0.012 6.00 10.25 0.59 0.58 0.57 10.64 4.10 5.00 4.10 5.00 1.98 5.00
b3 B3 60 18.26 17.21 1.75%3.0 3.0 1.2 725 17.21 11.70 0.76%Valley Pan 0.012 6.00 10.25 0.59 0.76 15.95 14.36 18.96 14.36 18.96 14.36 17.15 14.36
b4 B4 45 16.40 15.58 1.82%2.6 2.6 1.0 150 15.58 13.91 1.11%Valley Pan 0.012 6.00 10.25 0.59 0.92 2.73 11.08 5.29 5.29 5.29 5.29 3.75 5.00
b5 B5 25 16.25 14.99 5.04%1.4 1.4 0.5 205 14.99 14.36 0.31%Swale (4:1)0.030 4.00 8.25 0.48 0.17 20.11 11.28 21.47 11.28 21.47 11.28 20.65 11.28
b6 B6 115 19.00 16.48 2.19%3.9 3.9 1.5 205 16.48 14.32 1.05%Valley Pan 0.012 6.00 10.25 0.59 0.89 3.83 11.78 7.69 7.69 7.69 7.69 5.37 5.37
b7 B7 35 19.00 18.52 1.37%2.5 2.5 1.0 57 18.52 17.21 2.30%Swale (4:1)0.030 4.00 8.25 0.48 0.46 2.04 10.51 4.53 5.00 4.53 5.00 3.04 5.00
b8 B8 30 19.63 17.36 7.57%1.3 1.3 0.5 N/A Swale (4:1)4.00 8.25 N/A N/A 0.00 10.17 1.30 5.00 1.30 5.00 0.52 5.00
b9 B9 40 18.50 17.95 1.38%2.7 2.7 1.1 137 17.95 17.27 0.50%Valley Pan 0.012 6.00 10.25 0.59 0.61 3.73 10.98 6.39 6.39 6.39 6.39 4.79 5.00
b10 B10 40 16.50 15.77 1.83%2.4 2.4 1.0 127 15.77 15.00 0.61%Valley Pan 0.012 6.00 10.25 0.59 0.68 3.13 10.93 5.55 5.55 5.55 5.55 4.10 5.00
c1 C1 50 14.67 11.39 6.56%1.8 1.8 0.7 200 11.39 10.98 0.21%Swale (4:1)0.030 4.00 8.25 0.48 0.14 24.02 11.39 25.78 11.39 25.78 11.39 24.72 11.39
c2 C2 57 16.50 14.52 3.47%2.3 2.3 0.9 187 14.52 13.85 0.36%Gutter 0.012 3.61 19.18 0.19 0.24 12.76 11.36 15.09 11.36 15.09 11.36 13.70 11.36
d1 D1 200 17.31 16.89 0.21%11.1 11.1 4.4 425 16.89 11.29 1.32%Gutter 0.012 3.61 19.18 0.19 0.47 15.13 13.47 26.25 13.47 26.25 13.47 19.58 13.47
d2 D2 65 19.38 17.48 2.92%2.6 2.6 1.1 N/A Swale (4:1)4.00 8.25 N/A N/A 0.00 10.36 2.64 5.00 2.64 5.00 1.05 5.00
e1 E1 65 17.28 11.43 9.00%6.0 6.0 5.6 1272 11.43 3.16 0.65%Floodplain 0.045 46.50 23.32 1.99 0.42 50.12 17.43 56.16 17.43 56.16 17.43 55.68 17.43
e2 E2 40 14.10 7.58 16.30%3.8 3.8 3.5 735 7.58 4.17 0.46%Floodplain 0.035 18.00 13.00 1.38 0.36 34.01 14.31 37.84 14.31 37.84 14.31 37.51 14.31
f1 F1 22 18.47 17.99 2.18%2.9 2.9 1.8 175 17.99 17.00 0.57%Gutter 0.012 3.61 19.18 0.19 0.31 9.51 11.09 12.40 11.09 12.40 11.09 11.26 11.09
f2 F2 40 20.24 19.49 1.88%4.8 4.8 3.4 570 19.49 16.79 0.47%Gutter 0.012 3.61 19.18 0.19 0.28 33.84 13.39 38.63 13.39 38.63 13.39 37.19 13.39
os1 OS1 30 22.53 21.47 3.53%1.8 1.8 0.7 420 21.47 16.95 1.08%Gutter 0.012 3.61 19.18 0.19 0.42 16.54 12.50 18.35 12.50 18.35 12.50 17.21 12.50
os2 OS2 26 36.00 34.55 5.58%1.0 1.0 0.5 1738 34.55 16.79 1.02%Gutter 0.012 3.61 19.18 0.19 0.41 70.24 19.80 71.26 19.80 71.26 19.80 70.78 19.80
os3 OS3 32 20.10 20.05 0.16%16.7 16.7 15.5 615 20.05 12.88 1.17%Gutter 0.012 3.61 19.18 0.19 0.44 23.27 13.59 39.96 13.59 39.96 13.59 38.74 13.59
total Total 65 17.28 11.43 9.00%1.8 1.8 0.7 1272 11.43 3.16 0.65%Floodplain 0.045 46.50 23.32 1.99 0.42 50.12 17.43 51.93 17.43 51.93 17.43 50.85 17.43
R = Hydraulic Radius (feet)
S = Longitudinal Slope, feet/feet
Maximum Tc:
Combined Basins
Design
Point Basin
Overland Flow Channelized Flow Time of Concentration
Channelized Flow, Velocity:Channelized Flow, Time of Concentration:
V = Velocity (ft/sec)
n = Roughness Coefficient
November 10, 2020
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Overland Flow, Time of Concentration:
Calculations By:
The Quarry by Watermark
F. Wegert
(Equation 3.3-2 per Fort Collins Stormwater Manual)
𝑅𝑖=1.87 1.1 −𝐶∗𝐶𝑓𝐿
𝑅ൗ13
𝑉=1.49
𝑛∗𝑅2/3 ∗𝑅(Equation 5-4 per Fort Collins Stormwater Manual)
𝑅𝑐=𝐿
180 +10 (Equation 3.3-5 per Fort Collins Stormwater Manual)
𝑅𝑡=𝐿
𝑉∗60
(Equation 5-5 per Fort Collins Stormwater Manual)
Notes:
1)Add 5000 to all elevations.
2) Per Fort Collins Stormwater Manual, minimum Tc = 5 min.
3) Assume a water depth of 6" and a typical curb and gutter per Larimer County
Urban Street Standard Detail 701 for curb and gutter channelized flow. Assume a
water depth of 1', fixed side slopes, and a triangular swale section for grass
Page 1 of 1
Tc2 Tc10 Tc100 C2 C10 C100
I2
(in/hr)
I10
(in/hr)
I100
(in/hr)
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
a1 A1 2.085 15.03 15.03 15.03 0.85 0.85 1.00 1.87 3.19 6.52 3.3 5.7 13.6
a2 A2 2.222 15.39 15.39 15.39 0.85 0.85 1.00 1.87 3.19 6.52 3.5 6.0 14.5
a3 A3 0.618 9.49 9.49 8.05 0.85 0.85 1.00 2.30 3.93 8.38 1.2 2.1 5.2
b1 B1 0.687 11.89 11.89 11.89 0.85 0.85 1.00 2.09 3.57 7.29 1.2 2.1 5.0
b2 B2 0.448 5.00 5.00 5.00 0.85 0.85 1.00 2.85 4.87 9.95 1.1 1.9 4.5
b3 B3 3.139 14.36 14.36 14.36 0.85 0.85 1.00 1.92 3.29 6.71 5.1 8.8 21.1
b4 B4 0.288 5.29 5.29 5.00 0.85 0.85 1.00 2.85 4.87 9.95 0.7 1.2 2.9
b5 B5 0.483 11.28 11.28 11.28 0.85 0.85 1.00 2.13 3.63 7.42 0.9 1.5 3.6
b6 B6 1.222 7.69 7.69 5.37 0.85 0.85 1.00 2.46 4.21 9.95 2.6 4.4 12.2
b7 B7 0.073 5.00 5.00 5.00 0.85 0.85 1.00 2.85 4.87 9.95 0.2 0.3 0.7
b8 B8 0.013 5.00 5.00 5.00 0.85 0.85 1.00 2.85 4.87 9.95 0.0 0.1 0.1
b9 B9 0.162 6.39 6.39 5.00 0.85 0.85 1.00 2.67 4.56 9.95 0.4 0.6 1.6
b10 B10 0.329 5.55 5.55 5.00 0.85 0.85 1.00 2.76 4.72 9.95 0.8 1.3 3.3
c1 C1 0.458 11.39 11.39 11.39 0.85 0.85 1.00 2.13 3.63 7.42 0.8 1.4 3.4
c2 C2 0.162 11.36 11.36 11.36 0.85 0.85 1.00 2.13 3.63 7.42 0.3 0.5 1.2
d1 D1 1.976 13.47 13.47 13.47 0.85 0.85 1.00 1.98 3.39 6.92 3.3 5.7 13.7
d2 D2 0.064 5.00 5.00 5.00 0.85 0.85 1.00 2.85 4.87 9.95 0.2 0.3 0.6
e1 E1 3.384 17.43 17.43 17.43 0.27 0.27 0.33 1.75 2.99 6.10 1.6 2.7 6.9
e2 E2 1.384 14.31 14.31 14.31 0.28 0.28 0.35 1.92 3.29 6.71 0.7 1.3 3.2
f1 F1 0.045 11.09 11.09 11.09 0.67 0.67 0.84 2.13 3.63 7.42 0.1 0.1 0.3
f2 F2 0.177 13.39 13.39 13.39 0.60 0.60 0.75 1.98 3.39 6.92 0.2 0.4 0.9
os1 OS1 0.484 12.50 12.50 12.50 0.83 0.83 1.00 2.02 3.45 7.04 0.8 1.4 3.4
os2 OS2 1.800 19.80 19.80 19.80 0.91 0.91 1.00 1.63 2.78 5.68 2.7 4.6 10.2
os3 OS3 0.468 13.59 13.59 13.59 0.25 0.25 0.31 1.95 3.34 6.82 0.2 0.4 1.0
total Total 19.416 17.43 17.43 17.43 0.85 0.85 1.00 1.75 2.99 6.10 28.9 49.3 118.4
Combined Basins
DEVELOPED DIRECT RUNOFF COMPUTATIONS
Intensity Flow
The Quarry by Watermark
F. Wegert
November 10, 2020
Project:
Calculations By:
Date:
Rational Equation: Q = CiA (Equation 6-1 per MHFD)
Design
Point Basin Area
(acres)
Runoff C
Intensity, I from Fig. 3.4.1 Fort Collins Stormwater Manual
Tc (Min)
Page 4 of 4
Appendix C
Canal Importation SWMM Model
Project:
Calc. By:
Date:
Description
Max Flow at Conduit 43 570.75 cfs 547.38 cfs
Max Hour at Conduit 43 0:49 6:01
Max Velocity at Conduit 43 2.61 ft/sec 2.61 ft/sec
Description
Avg Depth at Junction J43 3.42 ft 3.42 ft
Max Depth at Junction J43 4.69 ft 4.69 ft
Hour of Max Depth at Junction J43 1:19 1:19
Max Lateral Flow at Junction J43 219.95 cfs 230.62 cfs
Max Total Inflow at Junction J43 546.24 cfs 546.25 cfs
Hour of Max Inflow at Junction J43 1:15 1:15
F. Wegert
November 10, 2020
RESULTS OF CANAL IMPORTATION SWMM MODEL ANALYSIS
Quarry by Watermark
Pre-Developed Pos-Developed
Pre Post 43
Appendix D
Water Quality/LID Design Computations
POND 1
Project: The Quarry
By:B. Ruch
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)=5.461 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT =75.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO =0.7500 <-- CALCULATED
Drain Time (hrs)40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) =0.300 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) =0.136 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) =5938 <-- CALCULATED
WQ Depth (ft) =4.000 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in2) =0.316 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) =5/8 <-- INPUT from Figure 5
number of rows =12
t (in) =0.500 <-- INPUT from Figure 5
number of columns =1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
November 5, 2020
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1.Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =80.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.800
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.26 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area)Area =186,729 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =4,087 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =0.0 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2.Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =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 =2988 sq ft
D) Actual Flat Surface Area AActual =2988 sq ft
E) Area at Design Depth (Top Surface Area)ATop =3929 sq ft
F) Rain Garden Total Volume VT=3,459 cu ft TOTAL VOLUME < DESIGN VOLUME
(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 =N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO =N/A in
Design Procedure Form: Rain Garden (RG)
Benjamin Ruch
Northern Engineering
November 10, 2020
The Quarry - RG A
Fort Collins, CO
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
RG A_UD-BMP_v3.06.xlsm, RG 11/10/2020, 9:26 AM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5.Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6.Inlet / Outlet Control
A) Inlet Control
7.Vegetation
8.Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Benjamin Ruch
Northern Engineering
November 10, 2020
The Quarry - RG A
Fort Collins, CO
Choose One
Choose One
Choose One
Sheet Flow-No Energy Dissipation Required
Concentrated Flow-Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
RG A_UD-BMP_v3.06.xlsm, RG 11/10/2020, 9:26 AM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1.Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia =90.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100)i =0.900
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV =0.32 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area)Area =293,909 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV =7,867 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER =0.0 cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER =cu ft
(Only if a different WQCV Design Volume is desired)
2.Basin Geometry
A) WQCV Depth (12-inch maximum)DWQCV =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 =5290 sq ft
D) Actual Flat Surface Area AActual =2214 sq ft ACTUAL FLAT AREA < MINIMUM FLAT AREA
E) Area at Design Depth (Top Surface Area)ATop =3231 sq ft
F) Rain Garden Total Volume VT=2,723 cu ft TOTAL VOLUME < DESIGN VOLUME
(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 =N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 =N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO =N/A in
Design Procedure Form: Rain Garden (RG)
Benjamin Ruch
Northern Engineering
November 10, 2020
The Quarry - RG B
Fort Collins, CO
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
RG B_UD-BMP_v3.06.xlsm, RG 11/10/2020, 9:27 AM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5.Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6.Inlet / Outlet Control
A) Inlet Control
7.Vegetation
8.Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Benjamin Ruch
Northern Engineering
November 10, 2020
The Quarry - RG B
Fort Collins, CO
Choose One
Choose One
Choose One
Sheet Flow-No Energy Dissipation Required
Concentrated Flow-Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
RG B_UD-BMP_v3.06.xlsm, RG 11/10/2020, 9:27 AM