HomeMy WebLinkAboutTRAIL HEAD TRACTS F & G TOWNHOMES - PDP - PDP170035 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTDRAINAGE AND EROSION CONTROL REPORT
FOR
TRAIL HEAD COTTAGE NEIGHBORHOOD
Prepared For:
Trail Head LLC
5013 Bluestem Court
Fort Collins, CO 80525
October 24, 2017
Project No. 39145.51
Prepared By:
JR Engineering, LLC
2900 South College Avenue, Suite 3D
Fort Collins, CO 80525
Page i
TABLE OF CONTENTS
Table of Contents ............................................................................................................................................... i
Vicinity Map .............................................................................................. Error! Bookmark not defined.
General Description and Location .................................................................................................................. 1
Location And Existing Site Characteristics ................................................................................................. 1
Site Soils ........................................................................................................................................................... 1
Floodplain ........................................................................................................................................................ 1
Drainage Basins and Sub-Basins ....................................................................................................................... 2
Major Basin ...................................................................................................................................................... 2
Historic Sub-Basins ........................................................................................................................................ 2
Developed Sub-Basins.................................................................................................................................... 3
Drainage Design Criteria .................................................................................................................................. 8
Regulations ...................................................................................................................................................... 8
Low-Impact Development ............................................................................................................................ 8
Hydrologic Criteria ........................................................................................................................................ 8
Hydraulic Criteria........................................................................................................................................... 8
Drainage Facility Design .................................................................................................................................... 9
General Concept ............................................................................................................................................ 9
Water Quality/ Detention Facilities ............................................................................................................ 9
Stormwater Pollution Prevention ..................................................................................................................10
Temporary Erosion Control ......................................................................................................................10
Permanent Erosion Control .......................................................................................................................10
Summary & Conclusions .................................................................................................................................11
References .........................................................................................................................................................12
APPENDIX
Appendix A – Site & Soil Descriptions and Characteristics
Appendix B – Hydrologic Calculations
Appendix C – Hydraulic Calculations
Appendix D – Previous Report
Appendix E – Existing & Proposed Drainage Plans
Appendix F – LID Exhibit
Page ii
Engineer’s Certification Block
I hereby certify that this Project Development Plan Drainage Report for Trail Head Cottage
Neighborhood was prepared by me (or under my direct supervision) for JR Engineering, LLC and
the owners thereof and meets or exceeds the criteria of the City of Fort Collins Stormwater
Design Standards.
________________________________________
Timothy J. Halopoff, PE
Registered Professional Engineer
State of Colorado No. 37953
Page 1
GENERAL DESCRIPTION AND LOCATION
LOCATION AND EXISTING SITE CHARACTERISTICS
Trail Head Cottage Neighborhood is located in the Southwest quarter of Section 4, Township 7
North, Range 68 West of the 6th Principal Meridian in the City of Fort Collins, Larimer County,
Colorado within Tracts F & G of the Trail Head Subdivision. The site is bounded on the south by
East Vine Drive and is surrounded on every other side by developed portions of the Trail Head
Subdivision. A vicinity map is provided in Appendix A. More specifically, the Trail Head Cottage
Neighborhood site is composed of approximately 5.19 and 5.54 acres of land within the existing
Tracts F and G respectively. Both tracts of land are currently undeveloped, zoned LMN, and will
support the proposed attached single family townhomes.
Tract G generally slopes from the northeast to southwest with slopes ranging from 0.60% to 2.50%.
The property is generally covered with sparse native grasses. Tract F generally slopes from the
northwest to southeast with slopes ranging from 0.60% to 4.60%. The property is generally covered
with sparse native grasses which have taken over the undeveloped site. When the Trail Head
Subdivision was developed two large detention ponds with water quality measures were installed to
handle the majority of the developments storm water runoff. Tract G utilizes an existing drainage
system to convey storm water to the detention pond (Pond A) located on the southwest portion of
the Trail Head Subdivision. Tract F utilizes an existing drainage system to convey storm water to
the detention pond (Pond B) located on the southeast portion of the Trail Head Subdivision. Both
of the existing storm sewer systems were designed to convey runoff from Tracts F & G in the
ultimate developed condition.
SITE SOILS
The Trail Head Cottage Neighborhood soils primarily consist of loamy soil, predominately Fort
Collins loam. Fort Collins clay loam belongs to hydrologic soils Group C. Group C soils have 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. Runoff is moderately high, and the hazards of wind erosion
are moderately low. Supporting figures can be found in the Appendix, page A-1.
FLOODPLAIN
The site is shown on FEMA FIRM panel 08069C0982F, dated December 19, 2006. The site lies
within an area determined to be outside the 500yr floodplain. The “City of Fort Collins Floodplain
Review Checklist for 50% Submittals” checklist is not applicable for this Drainage and Erosion
Control Report. An annotated FIRM exhibit is included in Appendix A.
Page 2
DRAINAGE BASINS AND SUB-BASINS
MAJOR BASIN
Trail Head Cottage Neighborhood lies within the Boxelder Creek/Cooper Slough Basin. The
master study for this area is the “Drainage and Erosion Control report for the Trail Head
Property” by JR Engineering, dated October 13, 2004, henceforth referred to as the master
drainage plan in this report. Excerpts from the previous report can be found in Appendix D.
EXISTING SUB-BASINS
Trail Head Cottage Neighborhood is an infill development piece of property. The ultimate design
of Tracts F & G was accounted for in the master drainage report. The following basin descriptions
reflect both the existing condition and ultimate condition laid out in the master drainage plan.
Existing Onsite Sub-Basins:
The site has eleven existing onsite drainage basins which were all analyzed in the master drainage
plan.
Sub-basin 221.1 totals about 4.6 acres located in the mid-east portion of the property,
was designed to contain multi-family development. Runoff sheet flows south to a double
type c area inlet at design point 21.1 and is piped to Pond B.
Sub-basin 221.2 totals about 1.5 acres located in the mid-east portion of the property,
was designed to contain multi-family development. The runoff from these basins is
conveyed via overland flow and gutter flow north along Camp Fire Drive where a quadruple
type 16 combination sump inlet will collect and convey runoff to Pond B.
Sub-basins 221.4 totals about 0.25 acres and is located in the southeastern portion of the
property. Runoff from this basin is collected in the gutters of Camp Fire Drive and
conveyed south to the quadruple type 16 combination on-grade inlet (design point 21.4).
These flows will then be conveyed via storm pipe to Pond B.
Sub-basins 221.5 totals about 1.2 acres and is located south of the property in the
ultimate condition. Runoff from this basin is collected in the gutters of East Vine Drive and
conveyed east to a type 16 combination on-grade inlet (design points 21.5). These flows
will then be conveyed via storm pipe to Pond B.
Sub-basin 345 totals about 2.3 acres located in the Northwest portion of the property.
Flows are conveyed via overland flow to Wagon Trail Road, and gutter flow to a quadruple
type 16 combination on-grade inlet located on Wagon Trail Road at design point 45. Sub-
basin 345 is planned for multi-family and a future park. These flows will be conveyed via
storm pipe to Pond A for detention and water quality.
Page 3
Sub-basin 352.1 and 352.2 total about 6.6 acres and is located in the west-central
portion of the property. Flows are conveyed via overland flow to two type C area inlets.
These two sub-basins are planned for multi-family development. These flows will be
conveyed storm pipe to Pond A for detention and water quality.
Sub-basins 221.3 and 352.3 total about 0.8 acres and are located in the central portion
of the property. Flows are conveyed via overland flow to Greenfields Drive where it then
travels south via curb and gutter to two quadruple type 16 combination on-grade inlets
located on Greenfields Drive at design points 21.3 and 52.3. These flows will be conveyed
via storm pipe to Pond A for detention and water quality.
Sub-basin 352.4 totals about 0.5 acres and is located in the west portion of the property.
Flows are conveyed via overland flow to Wagon Trail Road where it then travels south and
north via curb and gutter to two triple type 16 combination on-grade inlets located on
Green Lake Drive at design points 52.4A and 52.4B. These flows will be conveyed via
storm pipe to Pond A for detention and water quality.
Sub-basin 359, totaling about 2.5 acres, is located in the southwestern portion of the site.
The runoff from sub-basin 359 is conveyed via overland flow to East Vine Drive where it
then flows west to design point 59 and is collected by a quadruple type 16 on-grade
combination inlet. These flows will then be conveyed via storm pipe to Pond A for
detention and water quality.
DEVELOPED SUB-BASINS
The proposed developed condition sub-basins have been designed to mimic the historic basins’
runoff patterns. The following describes the proposed conditions on-site drainage basins. Refer to
the “Proposed Drainage Plan” in the appendix for review.
Proposed Onsite Sub-Basins:
This site has 22 proposed onsite drainage sub-basins and 5 existing basins.
Sub-basin A consists of 0.23 acres on the northern portion of the subject property west
of Greenfields Drive. Runoff from this basin is minimal due to an impervious percentage of
18%. This basin will flow onto the property to the north where it will continue to sheet
flow west ultimately to the quadruple type 16 combination on-grade inlet on Wagon Trail
Road.
Sub-basin B consists of 0.25 acres on the west portion of the subject property west of
Greenfields Drive. This basin consists of roofs and tree lawn running along the east side of
Wagon Trail Road. Flows are conveyed via overland flow to Wagon Trail Road where it
then travels south and north via curb and gutter to two triple type 16 combination on-grade
Page 4
inlets located on Green Lake Drive at design point 3. These flows will be conveyed via
storm pipe to Pond A for detention and water quality.
Sub-basin C consists of 0.79 acres on the north portion of the subject property west of
Greenfields Drive. Runoff from the proposed homes and driveways travels west along the
private drive before entering a chase drain which conveys runoff on to Green Lake Drive
where runoff is combined with sub-basin E runoff. These flows will be conveyed via storm
pipe to Pond A for detention and water quality.
Sub-basin D consists of 0.29 acres on the east portion of the subject property west of
Greenfields Drive. This basin consists of roofs and tree lawn running along the west side of
Greenfields Drive. Flows are conveyed via overland flow to Greenfields Drive where it then
travels south via curb and gutter to a type 16 combination on-grade inlet located on
Greenfields Drive at design point 7. These flows will be conveyed via storm pipe to Pond A
for detention and water quality.
Sub-basin E consists of 1.29 acres running along Green Lake Drive west of Greenfields
Drive. Runoff from the proposed homes and surface of Green Lake flows west along curb
and gutter on either side of the street before being intercepted by two type 16 on grade
inlets located at design point 2. These flows will be conveyed via storm pipe to design point
5 and continue to Pond A for detention and water quality.
Sub-basin F consists of 1.01 acres in the central portion of the subject property west of
Greenfields Drive. Runoff from the proposed homes and open area travels southwest along
an LID bio-swale to design point 4. These flows will be conveyed via storm pipe to design
point 10.1 and ultimately to Pond A for detention and additional water quality.
Sub-basin G consists of 1.09 acres on the southern portion of the subject property west
of Greenfields Drive. Runoff from the proposed homes and driveways travels south and
west along the private drive before entering a inlet at design point 5 which conveys runoff
to the LID isolator row. Following LID treatment these flows will be conveyed via storm
pipe to design point 10.1 and Pond A for detention and additional water quality.
Sub-basin H consists of 0.26 acres in the southwest portion of the subject property west
of Greenfields Drive. Runoff from the proposed basin sheet flows north towards design
point 10 before being collected at the proposed inlet at design point 5. The inlet at design
point 5 conveys runoff to the LID isolator row. Following LID treatment these flows will be
conveyed via storm pipe to design point 10.1 and ultimately to Pond A for detention and
additional water quality.
Page 5
Sub-basin I is comprised of 0.12 acres along the southern portion of the subject property
west of Greenfields Drive. Runoff from the proposed basin sheet flows north towards
design point 9 before being collected at the proposed inlet at design point 5. The inlet at
design point 5 conveys runoff to the LID isolator row. Following LID treatment these flows
will be conveyed via storm pipe to design point 10.1 and ultimately to Pond A for detention
and additional water quality.
Sub-basin J is comprised of 0.20 acres along the southeast portion of the subject property
west of Greenfields Drive. Runoff from the proposed basin sheet flows north towards
design point 8 before being collected at the proposed inlet at design point 5. The inlet at
design point 5 conveys runoff to the LID isolator row. Following LID treatment these flows
will be conveyed via storm pipe to design point 10.1 and ultimately to Pond A for detention
and additional water quality.
Sub-basin K consists of 0.05 acres on the northwest portion of the subject property east
of Greenfields Drive. Runoff from this basin is minimal due to an impervious percentage of
39%. Runoff from this sub-basin will drain on to Greenfields Drive and to the north.
Sub-basin L is comprised of 1.30 acres on the north portion of the subject property east
of Greenfields Drive. Runoff from the proposed homes and driveways travels east and then
south along the private drive before entering a chase drain at design point 18 which conveys
runoff on to Green Lake Drive where runoff is combined with sub-basin Q runoff. These
flows will be collected at the proposed inlets at design point 19 and piped to Pond B for
detention and water quality.
Sub-basin M consists of 0.26 acres on the northeast portion of the subject property east
of Greenfields Drive. Runoff from this basin is minimal due to an impervious percentage of
40%. The runoff from these basins is conveyed via overland flow and gutter flow north
along Camp Fire Drive to design point 20 where a quadruple type 16 combination sump
inlet will collect and convey runoff to Pond B.
Sub-basin N consists of 0.33 acres on the west portion of the subject property east of
Greenfields Drive. This basin consists of roofs and tree lawn running along the east side of
Greenfields Drive. Flows are conveyed via overland flow to Greenfields Drive where it then
travels south via curb and gutter to a type 16 combination on-grade inlet located on
Greenfields Drive at design point 6. These flows will be conveyed via storm pipe to Pond A
for detention and water quality.
Sub-basin O consists of 0.62 acres in the central portion of the subject property east of
Greenfields Drive. Runoff from the proposed homes and open area travels southeast along
Page 6
an swale at design point 11 where flows will be collected at an area inlet and piped south
ultimately towards Pond B for detention and water quality.
Sub-basin P consists of 0.22 acres on the east portion of the subject property east of
Greenfields Drive. This basin consists of roofs and tree lawn running along the west side of
Campfire Drive. These flows will be conveyed via Campfire Drive curb and gutter to design
point 20 and continue to Pond B for detention and water quality.
Sub-basin Q consists of 0.91 acres running along Green Lake Drive east of Greenfields
Drive. Runoff from the proposed homes and surface of Green Lake flows east along curb
and gutter on either side of the street before being combined with runoff from sub-basin L
at design point 19. These flows will be collected at the proposed inlets at design point 19
and piped to Pond B for detention and water quality.
Sub-basin R is comprised of 0.26 acres on the southwest portion of the subject property
east of Greenfields Drive. Runoff from the proposed homes and driveways travels south
along the private drive before entering a curb opening at design point 13 which conveys
runoff to a swale located within sub-basin U and to an area inlet at design point 14. These
flows will ultimately be conveyed to Pond B for detention and additional water quality.
Sub-basin S consists of 0.48 acres in the central portion of the subject property east of
Greenfields Drive. Runoff from the proposed homes and open area travels southeast along
a swale and be conveyed to an area inlet at design point 12. These flows will be conveyed
via storm pipe to Pond B for detention and additional water quality.
Sub-basin T is comprised of 0.23 acres on the southeast portion of the subject property
east of Greenfields Drive. Runoff from the proposed homes and driveways travels south
along the private drive before entering a curb opening at design point 15 which conveys
runoff to the area inlet located at design point 16 within sub-basin V. These flows will
ultimately be conveyed to Pond B for detention and additional water quality.
Sub-basin U consists of 0.30 acres in the southwest portion of the subject property west
of Greenfields Drive. Runoff from the surrounding sub-basins is combined with runoff from
the landscaped areas within sub-basin U to be collected are the area inlet at design point 14.
These flows will be conveyed east via storm pipe to design point 17.1 and ultimately to
Pond B for detention and additional water quality.
Sub-basin V consists of 0.23 acres in the southeast portion of the subject property west of
Greenfields Drive. Runoff from the surrounding sub-basins is combined with runoff from
the landscaped areas within sub-basin V to be treated in the area inlet at design point 16.
Page 7
These flows will be conveyed east via storm pipe to design point 17.1 and ultimately to
Pond B for detention and additional water quality.
Sub-basin EX1 consists of 0.44 acres and is described in the existing basin section under
sub-basin 352.3.
Sub-basin EX2 consists of 0.38 acres and is described in the existing basin section under
sub-basin 221.3.
Sub-basin EX3 consists of 0.19 acres and is described in the existing basin section under
sub-basin 221.4.
Sub-basin EX4 consists of 1.10 acres and is described in the existing basin section under
sub-basin 221.5.
Sub-basin EX5 consists of 0.43 acres and is described in the existing basin section under
sub-basin 352.4.
Page 8
DRAINAGE DESIGN CRITERIA
REGULATIONS
This report was prepared to meet or exceed the City of Fort Collins stormwater criteria. The City
of Fort Collins Storm Drainage Design Criteria and Construction Manual (with all current 2016
Revisions)(FCSDDCCM) and the Urban Drainage Flood Control District’s (UDFCD) Drainage
Criteria Manual (USDCM) Volumes 1, 2 and 3 were referenced as guidelines for this design.
LOW-IMPACT DEVELOPMENT
Volume reduction is an important part of the Four Step Process and is fundamental to effective
stormwater management. Per City criteria, a minimum of 50 percent of new impervious surface
area must be treated by a Low-Impact Development (LID) best management practice (BMP). The
proposed LID BMPs will have the effect of slowing runoff through the site lot and increasing
infiltration and rainfall interception by encouraging infiltration and careful selection of vegetative
cover. The improvements will decrease the runoff coefficient from the site and are expected to
have no adverse impact on the timing, quantity, or quality of stormwater runoff. Site-specific LID
BMPs are discussed in the following sections of this report and an illustrative LID/Surface map is
provided in Appendix E.
HYDROLOGIC CRITERIA
All hydrologic data was obtained from the City of Fort Collins Stormwater Criteria Manual (FCSCM)
or the Urban Storm Drainage Criteria Manual (USDCM). Onsite drainage improvements were designed
using the 2-year storm event (minor) and the 100-year storm event (major). Runoff was calculated using
the Rational Method, and rainfall intensities for the 2-year and 100-year storm return frequencies were
obtained from Table RA-7 and RA-8 of the FCSCM. Runoff coefficients were determined based on data
presented in Tables RO-11 from the FCSCM. Basin percent impervious values were calculated based on
proposed future land use and from data on Table RO-3 from the USDCM. Time of concentrations were
developed using equations from the FCSCM. All runoff calculations, and applicable charts and graphs are
included in the Appendix B of this report.
HYDRAULIC CRITERIA
The rational method and the USDCM’s SF-2 and SF-3 forms were used to determine the runoff from
the minor and major storms on this site. In order to size the infrastructure onsite, the runoff quantities
and street grades flowmaster was used to size the storm sewer. Inlets were sized using the Urban
Drainage UD-Inlet v4.05 spreadsheet. All storm sewers were sized to fully convey the 100-year storm
event, while maintaining the 100-year HGL below the ground surface. All runoff calculations, and
applicable charts and graphs are included in Appendix C of this report.
Page 9
DRAINAGE FACILITY DESIGN
GENERAL CONCEPT
The proposed improvements to Tracts F & G of the Trail Head Subdivision will result in developed
condition runoff being conveyed around the proposed buildings and to the south via swales. Low-
impact development best management practices are proposed to improve the quality of runoff and
aid in reducing peak flows. Specifically, water quality isolator rows will be used to treat roof and
driveway drainage, and grass lined bio-swales (soft-swales) are proposed to improve water quality.
About 55% of the proposed impervious area runoff from the site is captured in LID basins and
swales located around site and in open areas adjacent to the homes. Runoff is conveyed via sheet
flow, curb & gutter and bio-swales in a southerly direction to the proposed isolator row at the
southwest corner of the site.
The existing drainage outfall from the site is located in two separate locations on the property.
There is an outfall located near the southwest portion of Tract G. There is another outfall located
near the southeast portion of Tract F. The proposed drainage system is not intended to detain
runoff but designed to implement LID infiltration areas while conveying runoff as designed in the
master drainage report.
In accordance with the criteria this site has implemented the four step process to minimize adverse
impacts of urbanization. The four step process includes reducing runoff volumes, treating the water
quality capture volume (WQCV), stabilizing drainageways, and implementing long-term source
controls. In order to reduce runoff volume the new impervious area for the site was minimized
including minimizing the driveway and impervious surface areas. The WQCV is treated through the
exising detention ponds A & B as well as proposed on-site LID facilities. Some site specific source
control BMPs that will be implemented include, but are not limited to, silt fence placed around
downstream areas of disturbance, construction vehicle tracking pad at the entrances, designated
concrete truck washout basin, designated vehicle fueling areas, covered storage areas, spill
containment and control, a full infiltration sand filter, etc.
WATER QUALITY/ DETENTION FACILITIES
Water and detention will be provided for the site through the existing detention ponds A & B
located to the west and east. The existing detention ponds were previously designed to handle
developed flows from the Trail Head Cottage Neighborhood site.
Page 10
STORMWATER POLLUTION PREVENTION
TEMPORARY EROSION CONTROL
A temporary erosion control plan is to be implemented for the site during construction.
Temporary erosion control measures include, but are not limited to, slope and swale protection,
silt fence placed around downstream areas of disturbance, construction vehicle tracking pad at
entrances, a designated concrete truck washout basin, designated vehicle fueling areas, inlet
protection, and others. All temporary erosion control measures are to be removed after they are
deemed unnecessary.
PERMANENT EROSION CONTROL
Permanent erosion control measures include, but are not limited to, the constructed
detention/water quality ponds, riprap pads placed for culvert outlet protection, seeding and mulch
placed to enable and established vegetative growth, etc. Long-term maintenance of these erosion
control measures shall be the responsibility of the owner of the property. JR will provide a detailed
Storm Water Management and Erosion Control Plan at the time of the FDP submittal that will meet
all requirements of the City of Fort Collins.
Page 11
SUMMARY & CONCLUSIONS
The existing conditions drainage has eleven onsite sub-basins with separate outfall points. The
proposed drainage condition was designed to mimic the historic basins’ runoff patterns. The existing
conditions drainage patterns are maintained in the design of the project. The proposed
improvements will have positive impacts on the timing, flow rate, and quality of runoff leaving the
site; and will reduce potential impacts for flooding downstream of this site.
The hydrologic calculations were performed using the required methods as outlined in the City of
Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual. The
proposed drainage improvements meet or exceed the City’s requirements. This PDP Drainage
Report and the complimenting drainage plans and LID plans propose appropriate grading,
permanent landscaping, LID BMPs, and onsite facilities (e.g. storm sewer, inlets, detention facilities)
that are shown in their preliminary configuration and will be designed for construction in the Final
Drainage Report along with supporting calculations.
The proposed concept for the development of the Trail Head Cottage Neighborhood site involves
routing developed condition flows to the existing offsite detention ponds. LID site enhancements
will treat the site runoff at the source before allowing the runoff to be conveyed to the existing
detention ponds. The site’s storm water facilities are designed to meet the City of Fort Collins
“Storm Drainage Criteria Manual and Construction Standards” for both LID treatment and
conveyance.
Page 12
REFERENCES
1. Urban Storm Drainage Criteria Manual (Volumes 1, 2, and 3), Urban Drainage and Flood
Control District, June 2001.
2. Storm Drainage Criteria Manual and Construction Standards, City of Fort Collins Storm Water
Utility, City of Fort Collins, Colorado, Updated January, 1997.
3. “Hydrologic Group Rating for Larimer County Area, Colorado”, USDA-Natural Resources
Conservation Service, National Cooperative Soil Survey. Web Soil Survey URL:
http://websoilsurvey.nrcs.usda.gov. [July 21, 2010]
4. “Drainage and Erosion Control report for the Trail Head Property”, JR Engineering, October 13,
2004.
APPENDIX A
SITE & SOIL DESCRIPTIONS AND CHARACTERISTICS
TRAIL HEAD COTTAGE NEIGHBORHOOD DRAINAGE AND EROSION CONTROL REPORT
Project No. 39145.51 FIGURE 1- VICINITY MAP
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/22/2017
Page 1 of 4
4493900 4493920 4493940 4493960 4493980 4494000 4494020 4494040 4494060 4494080 4494100
4493900 4493920 4493940 4493960 4493980 4494000 4494020 4494040 4494060 4494080 4494100
498850 498870 498890 498910 498930 498950 498970 498990
498850 498870 498890 498910 498930 498950 498970 498990
40° 35' 52'' N
105° 0' 49'' W
40° 35' 52'' N
105° 0' 42'' W
40° 35' 44'' N
105° 0' 49'' W
40° 35' 44'' N
105° 0' 42'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 50 100 200 300
Feet
0 15 30 60 90
Meters
Map Scale: 1:1,070 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
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
35 Fort Collins loam, 0 to 3
percent slopes
C 4.9 95.0%
73 Nunn clay loam, 0 to 1
percent slopes
C 0.1 1.7%
95 Satanta loam, 1 to 3
percent slopes
B 0.1 2.3%
103 Stoneham loam, 5 to 9
percent slopes
B 0.1 1.1%
Totals for Area of Interest 5.1 100.0%
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/22/2017
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
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/22/2017
Page 4 of 4
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/22/2017
Page 1 of 4
4493900 4493920 4493940 4493960 4493980 4494000 4494020 4494040 4494060
4493900 4493920 4493940 4493960 4493980 4494000 4494020 4494040 4494060
498610 498630 498650 498670 498690 498710 498730 498750 498770 498790 498810 498830 498850
498610 498630 498650 498670 498690 498710 498730 498750 498770 498790 498810 498830 498850
40° 35' 50'' N
105° 0' 59'' W
40° 35' 50'' N
105° 0' 48'' W
40° 35' 45'' N
105° 0' 59'' W
40° 35' 45'' N
105° 0' 48'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 50 100 200 300
Feet
0 15 30 60 90
Meters
Map Scale: 1:1,190 if printed on A landscape (11" x 8.5") 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
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
35 Fort Collins loam, 0 to 3
percent slopes
C 5.1 99.2%
73 Nunn clay loam, 0 to 1
percent slopes
C 0.0 0.8%
Totals for Area of Interest 5.2 100.0%
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.
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/22/2017
Page 3 of 4
Larimer County Area, Colorado
35—Fort Collins loam, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2tlnc
Elevation: 4,020 to 6,730 feet
Mean annual precipitation: 14 to 16 inches
Mean annual air temperature: 46 to 48 degrees F
Frost-free period: 143 to 154 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Fort collins and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Fort Collins
Setting
Landform: Interfluves
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Pleistocene or older alluvium derived from igneous, metamorphic
and sedimentary rock and/or eolian deposits
Typical profile
Ap - 0 to 4 inches: loam
Bt1 - 4 to 9 inches: clay loam
Bt2 - 9 to 16 inches: clay loam
Bk1 - 16 to 29 inches: loam
Bk2 - 29 to 80 inches: loam
Properties and qualities
Slope: 0 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.20 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 12 percent
Salinity, maximum in profile: Nonsaline (0.1 to 1.0 mmhos/cm)
Sodium adsorption ratio, maximum in profile: 0.5
Available water storage in profile: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 4c
Hydrologic Soil Group: C
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
Custom Soil Resource Report
13
Minor Components
Nunn
Percent of map unit: 10 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
Vona
Percent of map unit: 5 percent
Landform: Interfluves
Landform position (two-dimensional): Backslope, footslope
Landform position (three-dimensional): Side slope, base slope
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Sandy Plains (R067BY024CO)
Hydric soil rating: No
103—Stoneham loam, 5 to 9 percent slopes
Map Unit Setting
National map unit symbol: jptw
Elevation: 4,800 to 5,600 feet
Mean annual precipitation: 13 to 15 inches
Mean annual air temperature: 48 to 50 degrees F
Frost-free period: 135 to 150 days
Farmland classification: Farmland of local importance
Map Unit Composition
Stoneham and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Stoneham
Setting
Landform: Benches, terraces
Landform position (three-dimensional): Side slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Mixed alluvium and/or eolian deposits
Typical profile
H1 - 0 to 3 inches: loam
H2 - 3 to 9 inches: clay loam, sandy clay loam, loam
H2 - 3 to 9 inches: loam, clay loam, sandy clay loam
H2 - 3 to 9 inches:
Custom Soil Resource Report
14
H3 - 9 to 60 inches:
H3 - 9 to 60 inches:
H3 - 9 to 60 inches:
Properties and qualities
Slope: 5 to 9 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to
high (0.60 to 2.00 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 15 percent
Salinity, maximum in profile: Nonsaline to very slightly saline (0.0 to 2.0
mmhos/cm)
Available water storage in profile: Very high (about 27.7 inches)
Interpretive groups
Land capability classification (irrigated): 6e
Land capability classification (nonirrigated): 6e
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067XY002CO)
Hydric soil rating: No
Minor Components
Kim
Percent of map unit: 8 percent
Hydric soil rating: No
Larimer
Percent of map unit: 5 percent
Hydric soil rating: No
Fort collins
Percent of map unit: 2 percent
Hydric soil rating: No
Custom Soil Resource Report
15
APPENDIX B
HYDROLOGIC CALCULATIONS
Subdivision: Trail Head 2nd Subdivision Project Name: Trail Head Cottage Neighborhood
Location: Fort Collins Project No.:
Calculated By: JMF
Checked By: 0
Date: 10/24/17
A 0.23 0.95 0.00 0.01 0.95 0.04 0.18 0.20 0.19 0.16 0.35 0.43
B 0.25 0.95 0.03 0.11 0.95 0.12 0.46 0.20 0.10 0.08 0.65 0.81
C 0.79 0.95 0.34 0.41 0.95 0.31 0.38 0.20 0.14 0.03 0.82 1.02
D 0.29 0.95 0.04 0.12 0.95 0.12 0.41 0.20 0.13 0.09 0.62 0.77
E 1.29 0.95 0.66 0.49 0.95 0.29 0.21 0.20 0.34 0.05 0.75 0.94
F 1.01 0.95 0.11 0.10 0.95 0.32 0.30 0.20 0.58 0.11 0.52 0.65
G 1.09 0.95 0.42 0.37 0.95 0.49 0.42 0.20 0.18 0.03 0.83 1.03
H 0.26 0.95 0.00 0.01 0.95 0.02 0.08 0.20 0.24 0.18 0.27 0.34
I 0.12 0.95 0.00 0.03 0.95 0.00 0.00 0.20 0.12 0.19 0.22 0.28
J 0.20 0.95 0.00 0.00 0.95 0.02 0.10 0.20 0.18 0.18 0.28 0.35
K 0.05 0.95 0.00 0.08 0.95 0.02 0.33 0.20 0.03 0.12 0.52 0.65
L 1.30 0.95 0.43 0.31 0.95 0.44 0.33 0.20 0.42 0.07 0.71 0.88
M 0.26 0.95 0.02 0.08 0.95 0.09 0.33 0.20 0.15 0.11 0.53 0.66
N 0.33 0.95 0.04 0.12 0.95 0.15 0.42 0.20 0.14 0.09 0.63 0.78
O 0.62 0.95 0.09 0.14 0.95 0.19 0.29 0.20 0.34 0.11 0.53 0.67
P 0.22 0.95 0.02 0.11 0.95 0.12 0.53 0.20 0.07 0.07 0.70 0.88
Q 0.91 0.95 0.49 0.51 0.95 0.15 0.16 0.20 0.27 0.06 0.73 0.91
R 0.26 0.95 0.09 0.32 0.95 0.15 0.55 0.20 0.02 0.02 0.89 1.11
S 0.48 0.95 0.07 0.14 0.95 0.16 0.31 0.20 0.26 0.11 0.55 0.69
T 0.23 0.95 0.07 0.31 0.95 0.14 0.60 0.20 0.01 0.01 0.92 1.15
U 0.30 0.95 0.00 0.00 0.95 0.04 0.13 0.20 0.26 0.17 0.30 0.38
V 0.23 0.95 0.00 0.01 0.95 0.05 0.19 0.20 0.18 0.16 0.36 0.45
EX1 0.44 0.95 0.36 0.76 0.95 0.00 0.00 0.20 0.09 0.04 0.80 1.00
EX2 0.43 0.95 0.35 0.77 0.95 0.00 0.00 0.20 0.08 0.04 0.80 1.01
EX3 0.19 0.95 0.15 0.75 0.95 0.00 0.00 0.20 0.04 0.04 0.80 0.99
EX4 1.10 0.95 0.94 0.81 0.95 0.00 0.00 0.20 0.16 0.03 0.84 1.05
EX5 0.43 0.95 0.27 0.60 0.95 0.00 0.00 0.20 0.16 0.07 0.68 0.84
Total to Bio-Swale #1 1.01 0.52 0.65
Total to Isolator Row 3.75 0.71 0.89
TOTAL TO PONDS 10.73 0.65 0.81
Runoff
Coefficient
Basins Total
Weighted Runoff
Area (ac) Coefficient C100
39145.51
COMPOSITE RUNOFF COEFFICIENT CALCULATIONS
Weighted Runoff
Coefficient
Basins Total
Weighted Runoff
Basin ID Total Area (ac) Coefficient C2
Runoff
Coefficient
Area (ac)
Lawns & Landscaping
Runoff
Coefficient
Area (ac)
Weighted Runoff
Coefficient
Asphalt/ Concrete Roofs
Weighted Runoff
Coefficient
X:\3910000.all\3914551\Excel\Drainage\3914551 Drainage_Calcs_v2.05.xlsm Page 1 of 1 10/26/2017
APPENDIX C
HYDRAULIC CALCULATIONS
Subdivision: Trail Head 2nd Subdivision Project Name: Trail Head Cottage Neighborhood
Location: Fort Collins Project No.:
Calculated By: JMF
Checked By: 0
Date: 10/24/17
FINAL
BASIN D.A. Hydrologic % Imp. C2
C100 L S
o t i
L t S
o K VEL. t t
COMP. t c TOTAL Urbanized t
c t c
ID (ac) Soils Group (%) (ft) (%) (min) (ft) (%) (ft/s) (min) (min) LENGTH (ft) (min) (min)
A 0.23 C 18% 0.35 0.43 60 5.0% 6.2 550 1.0% 7.0 0.7 13.1 19.3 610.0 21.0 19.3
B 0.25 C 55% 0.65 0.81 52 5.0% 3.4 123 1.0% 20.0 2.0 1.0 4.5 175.0 10.5 5.0
C 0.79 C 79% 0.82 1.02 80 5.0% 2.7 550 0.8% 20.0 1.8 5.1 7.8 630.0 9.5 7.8
D 0.29 C 51% 0.62 0.77 53 5.0% 3.7 365 1.0% 20.0 2.0 3.0 6.8 418.0 12.8 6.8
E 1.29 C 71% 0.75 0.94 66 5.0% 3.0 560 1.1% 20.0 2.1 4.4 7.5 626.0 10.4 7.5
F 1.01 C 39% 0.52 0.65 100 5.0% 6.2 130 2.0% 7.0 1.0 2.2 8.4 230.0 12.8 8.4
G 1.09 C 79% 0.83 1.03 70 5.0% 2.4 550 1.2% 20.0 2.2 4.2 6.6 620.0 8.8 6.6
H 0.26 C 9% 0.27 0.34 100 10.0% 7.0 50 0.6% 7.0 0.5 1.5 8.5 150.0 17.5 8.5
I 0.12 C 3% 0.22 0.28 20 10.0% 3.3 210 0.6% 7.0 0.5 6.5 9.8 230.0 21.1 9.8
J 0.20 C 9% 0.28 0.35 75 10.0% 6.0 110 0.6% 7.0 0.5 3.4 9.4 185.0 18.2 9.4
K 0.05 C 39% 0.52 0.65 50 5.0% 4.4 20 0.8% 20.0 1.7 0.2 4.6 70.0 12.3 5.0
L 1.30 C 64% 0.71 0.88 100 5.0% 4.2 434 0.6% 20.0 1.5 4.9 9.1 534.0 12.0 9.1
M 0.26 C 40% 0.53 0.66 100 1.4% 9.2 20 0.6% 20.0 1.5 0.2 9.4 120.0 12.2 9.4
N 0.33 C 52% 0.63 0.78 50 5.0% 3.6 385 1.0% 20.0 2.0 3.2 6.8 435.0 12.7 6.8
O 0.62 C 41% 0.53 0.67 68 5.0% 5.0 103 0.6% 7.0 0.5 3.3 8.3 171.0 12.8 8.3
P 0.22 C 61% 0.70 0.88 60 2.0% 4.4 290 4.0% 20.0 4.0 1.2 5.7 350.0 9.7 5.7
Q 0.91 C 69% 0.73 0.91 55 5.0% 2.9 420 1.3% 20.0 2.3 3.1 6.0 475.0 9.8 6.0
R 0.26 C 86% 0.89 1.11 35 5.0% 1.3 125 2.0% 20.0 2.8 0.7 2.1 160.0 5.5 5.0
S 0.48 C 43% 0.55 0.69 75 5.0% 5.1 140 3.0% 7.0 1.2 1.9 7.0 215.0 12.1 7.0
T 0.23 C 89% 0.92 1.15 45 5.0% 1.3 100 2.0% 20.0 2.8 0.6 1.9 145.0 5.0 5.0
U 0.30 C 12% 0.30 0.38 80 20.0% 4.8 140 1.5% 7.0 0.9 2.7 7.5 220.0 17.4 7.5
V 0.23 C 20% 0.36 0.45 60 20.0% 3.8 60 1.0% 7.0 0.7 1.4 5.3 120.0 15.6 5.3
EX1 0.44 C 80% 0.80 1.00 15 5.0% 1.2 440 1.0% 20.0 2.0 3.7 4.9 455.0 8.3 5.0
EX2 0.43 C 81% 0.80 1.01 15 5.0% 1.2 440 1.0% 20.0 2.0 3.7 4.9 455.0 8.2 5.0
EX3 0.19 C 79% 0.80 0.99 15 5.0% 1.3 300 2.0% 20.0 2.8 1.8 3.0 315.0 7.2 5.0
EX4 1.10 C 85% 0.84 1.05 15 5.0% 1.1 740 1.5% 20.0 2.4 5.0 6.1 755.0 8.3 6.1
EX5 0.43 C 63% 0.68 0.84 15 5.0% 1.7 200 1.0% 20.0 2.0 1.7 3.4 215.0 9.7 5.0
NOTES:
t c =t
i +t t
(Equation 6-2)
t i = (0.395*(1.1 - C
5)*(L)^0.5)/((So
)^0.33) (Equation 6-3)
t i = overland (initial) flow time (minutes) K
S = Average Slope along the overland flow path, ft/ft 2.5
t t =L/(60K*(S
o)^0.5 (Equation 6-4) 5
t t = channelized flow time (minutes) 7
S = waterway slope, ft/ft 10
V t = travel time velocity (ft/sec) = K*S
o^0.5 15
20
First Design Point Time of Concentration:
t c =(18-15*i )+L
t/(60*(24*i +12)*(So
Project Name: Trail Head Cottage Neighborhood
Subdivision: Trail Head 2nd Subdivision Project No.:
Location: Fort Collins Calculated By: JMF
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
QCO, Street Flow (cfs)
Slope (%)
C*A (Ac)
QCAP, Pipe Flow (cfs)
Slope (%)
Pipe Size (inches)
C*A (Ac)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
2-Year
A 0.23 0.43 19.3 0.10 5.71 0.6 Runoff flows to north than west along north PL
B 0.25 0.81 5.0 0.21 9.95 2.1 Runoff conveyed via Wagon Trail C&G to DP3
Chase Drain
1 C 0.79 1.02 7.8 0.80 8.47 6.8 Runoff conveyed along the private drive to DP1
Quadruple Type 16 Inlet
D 0.29 0.77 6.8 0.22 8.92 2.0 Runoff conveyed south via Greenfields C&G to DP9
Type 16 Inlets
2 E 1.29 0.94 7.5 1.21 8.61 10.4 7.8 2.01 8.47 17.0 Runoff conveyed west via Green Lake C&G to DP2
Under Drain w/ overflow Area Inlet
4 F 1.01 0.65 8.4 0.65 8.26 5.4 Runoff conveyed via bio-swale to DP4
Inlet
5 G 1.09 1.03 6.6 1.13 9.00 10.2 9.8 1.32 7.79 10.3 Runoff conveyed along the private drive to DP5
5 9.8 3.33 7.79 25.9 piped to LID and DP10.1
10 H 0.26 0.34 8.5 0.09 8.19 0.7 Runoff conveyed along the private drive to DP5
10.1 9.8 5.34 7.79 41.6 Pipe conveyance following DP10.1
9 I 0.12 0.28 9.8 0.03 7.79 0.2 9.8 0.10 7.79 0.8 Runoff conveyed along the private drive to DP5
8 J 0.20 0.35 9.4 0.07 7.91 0.6 Runoff conveyed along the private drive to DP5
K 0.05 0.65 5.0 0.03 9.95 0.3 Runoff conveyed via Greenfields C&G to North
Chase Drain
18 L 1.30 0.88 9.1 1.14 8.01 9.1 Runoff conveyed along the private drive to DP18
M 0.26 0.66 9.4 0.17 7.90 1.3 Runoff conveyed via Campfire C&G to North DP20
N 0.33 0.78 6.8 0.26 8.92 2.3 Runoff conveyed south via Greenfields C&G to DP6
Area inlet
11 O 0.62 0.67 8.3 0.41 8.29 3.4 Runoff conveyed via swale to DP11 piped to DP19.1
P 0.22 0.88 5.7 0.19 9.53 1.8 Runoff conveyed south via Campfire C&G to DP20
Type 16 Inlets
19 Q 0.91 0.91 6.0 0.83 9.32 7.7 9.1 1.97 8.01 15.8 Runoff conveyed east via Green Lake C&G to DP19
MH
19.1 9.1 2.38 8.01 19.1 piped to DP12
Project Name: Trail Head Cottage Neighborhood
Subdivision: Trail Head 2nd Subdivision Project No.:
Location: Fort Collins Calculated By: JMF
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
QCO, Street Flow (cfs)
Slope (%)
C*A (Ac)
QCAP, Pipe Flow (cfs)
Slope (%)
Pipe Size (inches)
C*A (Ac)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
39145.51
100-Year
10/24/17
13 R 0.26 1.11 5.0 0.29 9.95 2.9 Runoff conveyed south along the private drive to DP13
bio-swale w/ overflow weir
12 S 0.48 0.69 7.0 0.33 8.80 2.9 9.1 3.11 8.01 24.9 Runoff conveyed to DP12, piped to Dp16
15 T 0.23 1.15 5.0 0.26 9.95 2.6 Runoff conveyed south along the private drive to DP15
Area inlet
14 U 0.30 0.38 7.5 0.11 8.59 0.9 7.5 0.40 8.59 3.4 Runoff flows to inlet at DP14 piped to DP12
Area inlet
16 V 0.23 0.45 5.3 0.11 9.78 1.1 5.3 0.37 9.78 3.6
16 9.1 3.48 8.01 27.9 Runoff flows to inlet at DP16, piped to DP17.1
Inlet
7 EX1 0.44 1.00 5.0 0.45 9.95 4.5 6.8 0.67 8.92 6.0
7 6.8 1.36 8.92 12.1 Piped to DP7.1
MH
7.1 8.4 2.01 8.26 16.6 Piped to DP10.1
Inlet
6 EX2 0.43 1.01 5.0 0.43 9.95 4.3 6.8 0.69 8.92 6.2 Piped to DP7
20 EX3 0.19 0.99 5.0 0.19 9.95 1.9 9.4 0.55 7.90 4.3
20.1 9.4 5.18 7.90 40.9 Pipe conveyance following DP20.1
17 EX4 1.10 1.05 6.1 1.15 9.26 10.6
17.1 9.1 4.63 8.01 37.1 Pipe conveyance following DP17.1
3 EX5 0.43 0.84 5.0 0.36 9.95 3.6 5.0 0.57 9.95 5.7
Notes:
Carryover (Street) and Captured (Pipe) C*A values are determined by QCO/i or Q
Project Name: Trail Head Cottage Neighborhood
Subdivision: Trail Head 2nd Subdivision Project No.:
Location: Fort Collins Calculated By: JMF
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
QCO, Street Flow (cfs)
Slope (%)
C*A (Ac)
QCAP, Pipe Flow (cfs)
Slope (%)
Pipe Size (inches)
C*A (Ac)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
2-Year
A 0.23 0.35 19.3 0.08 1.64 0.1 Runoff flows to north than west along north PL
B 0.25 0.65 5.0 0.17 2.85 0.5 Runoff conveyed via Wagon Trail C&G to DP3
Chase Drain
1 C 0.79 0.82 7.8 0.64 2.43 1.6 Runoff conveyed along the private drive to DP1
Quadruple Type 16 Inlet
D 0.29 0.62 6.8 0.18 2.55 0.5 Runoff conveyed south via Greenfields C&G to DP9
Type 16 Inlets
2 E 1.29 0.75 7.5 0.97 2.47 2.4 7.8 1.61 2.43 3.9 Runoff conveyed west via Green Lake C&G to DP2
Under Drain w/ overflow Area Inlet
4 F 1.01 0.52 8.4 0.52 2.36 1.2 Runoff conveyed via bio-swale to DP4
Inlet
5 G 1.09 0.83 6.6 0.90 1.64 1.5 9.8 1.06 2.23 2.4 Runoff conveyed along the private drive to DP5
5 9.8 2.67 2.23 6.0 piped to LID and DP10.1
10 H 0.26 0.27 8.5 0.07 2.35 0.2 Runoff conveyed along the private drive to DP5
10.1 9.8 4.29 2.23 9.6 Pipe conveyance following DP10.1
9 I 0.12 0.22 9.8 0.03 2.23 0.1 9.8 0.09 2.23 0.2 Runoff conveyed along the private drive to DP5
8 J 0.20 0.28 9.4 0.06 2.26 0.1 Runoff conveyed along the private drive to DP5
K 0.05 0.52 5.0 0.03 2.55 0.1 Runoff conveyed via Greenfields C&G to North
Chase Drain
18 L 1.30 0.71 9.1 0.91 1.64 1.5 Runoff conveyed along the private drive to DP18
M 0.26 0.53 9.4 0.14 2.26 0.3 Runoff conveyed via Campfire C&G to North DP20
N 0.33 0.63 6.8 0.21 2.56 0.5 Runoff conveyed south via Greenfields C&G to DP6
Area inlet
11 O 0.62 0.53 8.3 0.33 2.37 0.8 Runoff conveyed via swale to DP11 piped to DP19.1
P 0.22 0.70 5.7 0.15 2.73 0.4 Runoff conveyed south via Campfire C&G to DP20
Type 16 Inlets
19 Q 0.91 0.73 6.0 0.66 2.67 1.8 9.1 1.57 2.29 3.6 Runoff conveyed east via Green Lake C&G to DP19
MH
19.1 9.1 1.90 2.29 4.4 piped to DP12
Project Name: Trail Head Cottage Neighborhood
Subdivision: Trail Head 2nd Subdivision Project No.:
Location: Fort Collins Calculated By: JMF
Design Storm: Checked By: 0
Date:
TRAVEL TIME
STREET
Design Point
Basin ID
Area (Ac)
Runoff Coeff.
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
tc (min)
C*A (Ac)
I (in/hr)
Q (cfs)
QCO, Street Flow (cfs)
Slope (%)
C*A (Ac)
QCAP, Pipe Flow (cfs)
Slope (%)
Pipe Size (inches)
C*A (Ac)
Length (ft)
Velocity (fps)
tt (min)
REMARKS
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
2-Year
39145.51
10/24/17
13 R 0.26 0.89 5.0 0.23 2.85 0.7 Runoff conveyed south along the private drive to DP13
bio-swale w/ overflow weir
12 S 0.48 0.55 7.0 0.27 2.52 0.7 9.1 2.49 2.29 5.7 Runoff conveyed to DP12, piped to Dp16
15 T 0.23 0.92 5.0 0.21 2.85 0.6 Runoff conveyed south along the private drive to DP15
Area inlet
14 U 0.30 0.30 7.5 0.09 2.46 0.2 7.5 0.32 2.46 0.8 Runoff flows to inlet at DP14 piped to DP12
Area inlet
16 V 0.23 0.36 5.3 0.08 2.80 0.2 5.3 0.29 2.80 0.8
16 9.1 2.78 2.29 6.4 Runoff flows to inlet at DP16, piped to DP17.1
Inlet
7 EX1 0.44 0.80 5.0 0.36 2.85 1.0 6.8 0.54 2.55 1.4
7 6.8 1.10 2.55 2.8 Piped to DP7.1
MH
7.1 8.4 1.62 2.36 3.8 Piped to DP10.1
Inlet
6 EX2 0.43 0.80 5.0 0.35 2.85 1.0 6.8 0.56 2.56 1.4 Piped to DP7
20 EX3 0.19 0.80 5.0 0.15 2.85 0.4 9.4 1.86 2.26 4.2
20.1 9.4 5.56 2.26 12.6 Pipe conveyance following DP20.1
17 EX4 1.10 0.84 6.1 0.92 2.55 2.4
17.1 9.1 3.70 2.29 8.5 Pipe conveyance following DP17.1
3 EX5 0.43 0.68 5.0 0.29 2.85 0.8 5.0 0.46 2.85 1.3
Notes:
Carryover (Street) and Captured (Pipe) C*A values are determined by QCO/i or Q
Tributary Area Percent tc
Q2 Q
100
Sub-basin (acres) Impervious C2
C100 (min) (cfs) (cfs)
A 0.23 18% 0.35 0.43 19.3 0.1 0.6
B 0.25 55% 0.65 0.81 5.0 0.5 2.1
C 0.79 79% 0.82 1.02 7.8 1.6 6.8
D 0.29 51% 0.62 0.77 6.8 0.5 2.0
E 1.29 71% 0.75 0.94 7.5 2.4 10.4
F 1.01 39% 0.52 0.65 8.4 1.2 5.4
G 1.09 79% 0.83 1.03 6.6 1.5 10.2
H 0.26 9% 0.27 0.34 8.5 0.2 0.7
I 0.12 3% 0.22 0.28 9.8 0.1 0.2
J 0.20 9% 0.28 0.35 9.4 0.1 0.6
K 0.05 39% 0.52 0.65 5.0 0.1 0.3
L 1.30 64% 0.71 0.88 9.1 1.5 9.1
M 0.26 40% 0.53 0.66 9.4 0.3 1.3
N 0.33 52% 0.63 0.78 6.8 0.5 2.3
O 0.62 41% 0.53 0.67 8.3 0.8 3.4
P 0.22 61% 0.70 0.88 5.7 0.4 1.8
Q 0.91 69% 0.73 0.91 6.0 1.8 7.7
R 0.26 86% 0.89 1.11 5.0 0.7 2.9
S 0.48 43% 0.55 0.69 7.0 0.7 2.9
T 0.23 89% 0.92 1.15 5.0 0.6 2.6
U 0.30 12% 0.30 0.38 7.5 0.2 0.9
V 0.23 20% 0.36 0.45 5.3 0.2 1.1
EX1 0.44 80% 0.80 1.00 5.0 1.0 4.5
EX2 0.43 81% 0.80 1.01 5.0 1.0 4.3
EX3 0.19 79% 0.80 0.99 5.0 0.4 1.9
EX4 1.10 85% 0.84 1.05 6.1 2.4 10.6
EX5 0.43 63% 0.68 0.84 5.0 0.8 3.6
BASIN SUMMARY TABLE
X:\3910000.all\3914551\Excel\Drainage\3914551 Drainage_Calcs_v2.05.xlsm Page 2 of 6 10/26/2017
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge for 2-Year Return Period Q2 = 1.20 cfs
2. Hydraulic Residence Time
A) : Length of Grass Swale LS = 215.0 ft
B) Calculated Residence Time (based on design velocity below) THR= 5.6 minutes
3. Longitudinal Slope (vertical distance per unit horizontal)
A) Available Slope (based on site constraints) Savail = 0.020 ft / ft
B) Design Slope SD = 0.020 ft / ft
4. Swale Geometry
A) Channel Side Slopes (Z = 4 min., horiz. distance per unit vertical) Z = 6.00 ft / ft
B) Bottom Width of Swale (enter 0 for triangular section) WB = 0.00 ft
5. Vegetation
A) Type of Planting (seed vs. sod, affects vegetal retardance factor)
6. Design Velocity (0.717 ft / s maximum for desirable 5-minute residence time) V2 = 0.64 ft / s
7. Design Flow Depth (1 foot maximum) D2 = 0.56 ft
A) Flow Area A2 = 1.9 sq ft
B) Top Width of Swale WT = 6.7 ft
C) Froude Number (0.50 maximum) F = 0.21
D) Hydraulic Radius RH = 0.28
E) Velocity-Hydraulic Radius Product for Vegetal Retardance VR = 0.18
F) Manning's n (based on SCS vegetal retardance curve D for sodded grass) n = 0.143
G) Cumulative Height of Grade Control Structures Required HD = 0.00 ft
8. Underdrain
(Is an underdrain necessary?)
9. Soil Preparation
(Describe soil amendment)
10. Irrigation
Notes:
Design Procedure Form: Grass Swale (GS)
RAB
JR Engineering
October 26, 2017
Trail Head
Bio-swale #1
UD-BMP (Version 3.06, November 2016)
Choose One
Temporary Permanent
Choose One
Grass From Seed Grass From Sod
Choose One
YES NO
UD-BMP_v3.06 (bio-swale 1).xlsm, GS 10/26/2017, 12:24 PM
Subdivision: 0 Project Name: Trail Head
Location: Fort Collins Project No.: 39145.51
Calculated By: RAB
Checked By: RAB
Date: 10/26/17
Basin
Area
(ac) % Imp.
C 0.79 79.0%
E 1.29 71.0%
G 1.09 79.0%
H 0.26 9.0%
I 0.12 3.0%
J 0.20 9.0%
Total 3.75 70.0%
WQCV Drain Time (hr): 12
Coefficient, a (Table 3-2): 0.8
WQCV (in): 0.22
WQCV (ac-ft): 0.01
WQCV (cf): 559.1
StormTech Chamber Sizing for Water Quality
LID Isolator Row #1
Subdivision: Trail Head Project Name: Trail Head Cottage
Location: Fort Collins Project No.: 39145.51
Calculated By: RAB
Checked By: RAB
Date: 10/18/17
Area (acres) 3.75 Area of Catchment tributary to storage facility (Acres)
2yr Runoff Coefficient 'C' 0.71 the runoff coefficient
Release Rate (cfs) 0.08 the allowable maximum release rate from the detention facility
Time of Concentration (min) 10
ft3 acre-ft.
4385.1 0.101
Time
(min) C * A
WQ
Intensity
(in/hr)
Inflow
Rate (cfs)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t factor
(m)
Average
Outflow
Rate (cfs)
Outflow
Volume
(ft3)
Detention
Volume
(ft3)
Detention
Volume
(acre-ft)
5 2.66 1.43 3.79 1138.22 1.00 0.08 24.00 1114.22 0.0256
10 2.66 1.11 2.94 1765.24 0.99 0.08 47.52 1717.72 0.0394
15 2.66 0.94 2.49 2240.49 0.83 0.07 59.52 2180.97 0.0501
20 2.66 0.81 2.14 2571.98 0.75 0.06 71.52 2500.46 0.0574
25 2.66 0.72 1.90 2855.53 0.70 0.06 83.52 2772.01 0.0636
30 2.66 0.65 1.73 3115.13 0.66 0.05 95.52 3019.61 0.0693
35 2.66 0.59 1.56 3270.88 0.64 0.05 107.52 3163.36 0.0726
40 2.66 0.54 1.42 3418.65 0.62 0.05 119.52 3299.13 0.0757
45 2.66 0.50 1.32 3558.43 0.61 0.05 131.52 3426.91 0.0787
50 2.66 0.46 1.22 3674.25 0.60 0.05 143.52 3530.73 0.0811
55 2.66 0.44 1.16 3822.02 0.59 0.05 155.52 3666.50 0.0842
60 2.66 0.41 1.09 3929.85 0.58 0.05 167.52 3762.33 0.0864
65 2.66 0.39 1.03 3997.74 0.58 0.05 179.52 3818.22 0.0877
70 2.66 0.37 0.97 4081.61 0.57 0.05 191.52 3890.09 0.0893
75 2.66 0.35 0.92 4133.53 0.57 0.05 203.52 3930.01 0.0902
80 2.66 0.33 0.88 4217.40 0.56 0.04 215.52 4001.88 0.0919
85 2.66 0.32 0.84 4277.31 0.56 0.04 227.52 4049.79 0.0930
90 2.66 0.31 0.81 4385.14 0.55 0.04 239.52 4145.62 0.0952
95 2.66 0.29 0.77 4401.11 0.55 0.04 251.52 4149.59 0.0953
100 2.66 0.28 0.75 4473.00 0.55 0.04 263.52 4209.48 0.0966
105 2.66 0.27 0.72 4528.91 0.55 0.04 275.52 4253.39 0.0976
110 2.66 0.26 0.69 4568.85 0.54 0.04 287.52 4281.33 0.0983
115 2.66 0.26 0.68 4684.67 0.54 0.04 299.52 4385.15 0.1007
Subdivision: 0 Project Name: Trail Head
Location: Fort Collins Project No.: 39145.51
Calculated By: RAB
Checked By: RAB
Date: 10/26/17
Pond ID
Required
WQ CV
(cf)*
Required
Storage
Volume by
FAA methoud
StormTech
Chamber
Type
Chamber
Volume
(cf)
Chamber
Volume with
Aggregate
(cf)
Chamber
Release
Rate (cfs)
Number of
Chambers
Required for
WQ CV**
Release
Rate
(cfs)
Number of
Chambers
Required for
Storage by FAA
Minimum
Number of
Chambers
Required
Storage
Provided
within
Chambers
Total System
Volume (cf)
Isolator Row #1 559.1 4384.7 MC-4500 106.5 162.6 0.026 3 0.08 41 41 4367 6667
* based on 12hr drain time
** based on required WQCVstorage volume and storage provided within chambers and surrounding aggergate
*** based on required storage volume per FAA methoud and storage provided within chambers only
StormTech Chamber Sizing for Water Quality
APPENDIX D
PREVIOUS DRAINAGE REPORT
DRAINAGE AND
EROSION CONTROL REPORT
Trail Head Property
Prepared for:
Trail Head Partners, LLC
Mr. Ken Crumb, Manager
P.O. Box 337600
Greeley, Colorado 80633
(970) 304-1392
Prepared by:
JR Engineering
2620 E. Prospect Road, Suite 190
Fort Collins, Colorado 80525
(970) 491-9888
October 13, 2004
Drainage and Erosion Control Report Page 6
Trail Head Property October 13, 2004
Sub-basin 221.1, totaling about 4.6 acres and located in the mid-east portion of the property,
is planned to contain multi-family development. Runoff sheet flows south to a double type c
area inlet at design point 21.1 and is piped to Pond B.
Sub-basins 221.2 and 226, totaling about 2.1 acres and located in the mid-east portion of the
property, are planned to contain multi-family development. The runoff from these basins is
conveyed via overland flow and gutter flow north along Camp Fire Drive to design points
21.2 and 26 where two quadruple type 16 combination sump inlets will collect and convey
flows to Pond B. This sump will also collect carry over flows from design points 13, 19, 20
and 23 inlets.
Runoff from Sub-basins 222- 223, located in the southeastern portion of the site and totaling
about 1.4 acres, is conveyed via overland flow to Camp Fire Drive and gutter flow south to
design point 23 where a quadruple type 16 combination on-grade inlet will collect and convey
flows to Pond B. These basins are planned for single-family development.
Sub-basin 224 totals about 0.4 acres and is located at the Bear River Court cul-de-sac.
Runoff from this basin is collected in the gutters of Bear River Court and is conveyed to a
single type 16 sump inlet and then by storm pipe to Pond B.
Sub-basins 221.4 and 225 totals about 0.7 acres and is located in the southeastern portion
of the property. Runoff from this basin is collected in the gutters of Camp Fire Drive and
conveyed south to quadruple type 16 combination on-grade inlets (design points 21.4 and 25).
These flows will then be conveyed via storm pipe to Pond B, which encompasses sub-basin
227 and contains about 3.5 acres. Please refer to Section 4.4 for a description of Pond B.
Runoff from Sub-basins 328-330, located in the mid-west portion of the property and
totaling about 3.6 acres, is conveyed via overland flows to Wagon Trail Road and gutter flow
west and south to a triple type 16 combination on-grade inlet at design point 30. These flows
will then be conveyed via storm pipe to Pond A for detention and water quality. These sub-
basins are planned to contain single-family development.
Flows fromSub-basins 358 and 331 are conveyed to design point 31 via overland and gutter
flow south along Wagon Trail Road to a quadruple type 16 combination on-grade inlet.
Drainage and Erosion Control Report Page 8
Trail Head Property October 13, 2004
Sub-basins 342, 343, 344.2 and 345 total about 6.5 acres and are located in the center of the
property. Flows are conveyed via overland flow to Yule Trail Drive, Roaring Creek Drive
and Wagon Trail Road, and gutter flow to a quadruple type 16 combination on-grade inlet
located on Wagon Trail Road at design point 45. This inlet will collect carry-over flows from
inlets located at design points 41, 44.1A and 44.1B. Sub-basins 342 and 343 are planned for
single-family development. Sub-basins 344.2 and 345 are planned for multi-family and
commercial development. These flows will be conveyed via storm pipe to Pond A for
detention and water quality.
Runoff from Sub-basins 346 and 347 are conveyed via overland flow to Glacier Creek Drive
and gutter flow west to a quadruple type 16 sump inlet at design point 47 on Three Forks
Drive. Sub-basins 346 and 347 total about 1.5 acres, are located in the southwestern portion
of the site and are planned for single-family development. The inlet located at design point 47
will also collect carry over flows from inlets 45 and 51.1.
Runoff from Sub-basins 348 and 349 are also conveyed via overland flow to an alley and
gutter flow to a quadruple type 16 combination sump inlet (design point 47) on Lower Loop
Drive. These flows will then be conveyed via storm pipe to Pond A for detention and water
quality. Sub-basins 345 and 346 total about 1.2 acres, are located in the southwestern portion
of the site and are planned for single-family development.
Sub-basins 350, 351.1 and 351.2 total about 2.6 acres and are located in the southwestern
portion of the property. Flows are conveyed via overland flow to Green Lake Drive and
gutter flow to triple type 16 combination inlets located on Three Forks Drive at design point
51.1 and 51.2. These sub-basins are planned for single-family development. These flows will
be conveyed via storm pipe to Pond A for detention and water quality.
Sub-basin 352.1 and 352.2 total about 6.6 acres and is located in the south-central portion
of the property. Flows are conveyed via overland flow to two type C area inlets. These two
sub-basins are planned for multi-family development. These flows will be conveyed storm
pipe to Pond A for detention and water quality.
Drainage and Erosion Control Report Page 13
Trail Head Property October 13, 2004
Where hL = headloss
K = headloss coefficient
V = average velocity (ft/s)
g = gravitational constant (32.2 ft/s2)
The storm pipe design was performed for the complete construction of the Trail Head
development and all calculations are provided in Appendix E of this report.
4.4 Pond Description
There are two (2) ponds that are being proposed for Trail Head Property. All pond design
was completed utilizing ModSwmm. Pond A is located in the southwestern portion of the
development at the intersection of Three Forks Drive and Vine Drive. This pond is designed
for water quality and detention. Pond A requires about 0.85 ac-ft of water quality capture
volume and 9.80 ac-ft of detention for a total required volume of about 10.65 ac-ft. The
outlet structure of Pond A is a water quality structure per UDFCD criteria. It is designed to
release the 100-year event at or below 9.5 cfs for the 100-year event creating a 100-year
water surface elevation of approximately 4969.90 feet. An 11-3/8” orifice plate on the 24-
inch outlet pipe regulates the release rate. The flows will be released to an existing swale
located on the Whitham Property directly to the south of the Trail Head Property.
Pond B is located in the southeastern portion of the development and is also designed for
water quality and detention. Pond B requires about 0.64 ac-ft of water quality capture
volume and 7.70 ac-ft of detention for a total required volume of about 8.34 ac-ft. The flow
released from this area is being reduced in the 2-year historic storm creating a 100-year water
surface elevation of approximately 4964.90 feet and a discharge of 5.9 cfs during the major
storm event. The outlet structure of Pond A is a water quality structure per UDFCD criteria.
A 9-1/2” orifice plate on the 18-inch outlet pipe regulates the release rate. The flows will be
released to an existing swale located on the Waterglenn Property directly to the east of the
Trail Head Property.
Please refer to Appendix F for all pond calculations and the Drainage Acceptance Letter
signed by the owner of the Whitham property.
APPENDIX E
EXISTING & PROPOSED DRAINAGE PLANS
Know what's
Tributary Area Percent tc Q2 Q100
Sub-basin (acres) Impervious C2 C100 (min) (cfs) (cfs)
221.1 4.57 45% 0.55 0.69 11.4 5.0 23.1
221.2 1.52 49% 0.58 0.72 12.8 2.5 11.1
221.3 0.38 87% 0.86 1.00 5.0 0.9 3.8
221.4 0.25 61% 0.68 0.84 5.0 0.5 2.1
221.5 1.24 85% 0.83 1.00 6.5 2.5 11.2
345 2.26 10% 0.32 0.40 13.4 1.4 6.1
352.1 2.52 26% 0.43 0.53 11.7 2.2 9.8
352.2 4.07 43% 0.54 0.67 13.8 4.2 18.4
352.3 0.45 77% 0.79 0.79 5.0 1.0 4.5
352.4 0.54 61% 0.68 0.68 5.0 1.0 4.6
359 2.51 44% 0.56 0.70 15.5 2.6 11.2
BASIN SUMMARY TABLE
Know what's
Tributary Area Percent tc Q
2 Q100
Sub-basin (acres) Impervious C2 C
100 (min) (cfs) (cfs)
A 0.23 18% 0.35 0.43 19.3 0.1 0.6
B 0.25 55% 0.65 0.81 5.0 0.5 2.1
C 0.79 79% 0.82 1.02 7.8 1.6 6.8
D 0.29 51% 0.62 0.77 6.8 0.5 2.0
E 1.29 71% 0.75 0.94 7.5 2.4 10.4
F 1.01 39% 0.52 0.65 8.4 1.2 5.4
G 1.09 79% 0.83 1.03 6.6 1.5 10.2
H 0.26 9% 0.27 0.34 8.5 0.2 0.7
I 0.12 3% 0.22 0.28 9.8 0.1 0.2
J 0.20 9% 0.28 0.35 9.4 0.1 0.6
EX1 0.44 80% 0.80 1.00 5.0 1.0 4.5
EX2 0.43 81% 0.80 1.01 5.0 1.0 4.3
EX5 0.43 63% 0.68 0.84 5.0 0.8 3.6
BASIN SUMMARY TABLE
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
WAGON TRAIL RD.
GREEN LAKE DR.
GREENFIELDS DR.
EAST VINE DR.
x:\3910000.all\3914551\Drawings\sheet dwgs\Drainage\3914551DR01.dwg, Proposed Drainage, 10/30/2017 1:48:45 PM, FC
Know what's
Tributary Area Percent tc Q
2 Q100
Sub-basin (acres) Impervious C2 C
100 (min) (cfs) (cfs)
K 0.05 39% 0.52 0.65 5.0 0.1 0.3
L 1.30 64% 0.71 0.88 9.1 1.5 9.1
M 0.26 40% 0.53 0.66 9.4 0.3 1.3
N 0.33 52% 0.63 0.78 6.8 0.5 2.3
O 0.62 41% 0.53 0.67 8.3 0.8 3.4
P 0.22 61% 0.70 0.88 5.7 0.4 1.8
Q 0.91 69% 0.73 0.91 6.0 1.8 7.7
R 0.26 86% 0.89 1.11 5.0 0.7 2.9
S 0.48 43% 0.55 0.69 7.0 0.7 2.9
T 0.23 89% 0.92 1.15 5.0 0.6 2.6
U 0.30 12% 0.30 0.38 7.5 0.2 0.9
V 0.23 20% 0.36 0.45 5.3 0.2 1.1
EX3 0.19 79% 0.80 0.99 5.0 0.4 1.9
EX4 1.10 85% 0.84 1.05 6.1 2.4 10.6
BASIN SUMMARY TABLE
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
GREENFIELDS DR.
GREEN LAKE DR.
EAST VINE DR.
CAMPFIRE DR.
x:\3910000.all\3914551\Drawings\sheet dwgs\Drainage\3914551DR01.dwg, Proposed Drainage (2), 10/30/2017 1:48:48 PM, FC
APPENDIX F
LID EXHIBITS
Know what's
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
New Impervious Area 277,962 sq. ft.
Required Minimum Impervious Area to be Treated (=50% of new impervious area) 138,981 sq. ft.
Impervious Area Directly Treated by LID Treatment Method #1- Bio-Swale #1 18,682 sq. ft.
Impervious Area Directly Treated by LID Treatment Method #2- Isolator Row #1 134,742 sq. ft.
Total Impervious Area Treated 153,424 sq. ft.
Actual % of Impervious Area Treated 55.2 %
50% On-Site Treatment by LID Requirement
WAGON TRAIL RD.
GREEN LAKE DR.
GREENFIELDS DR.
EAST VINE DR.
X:\3910000.all\3914551\Drawings\Sheet Dwgs\3914554 IMPERVIOUS AREA.dwg, LID SURFACE DRAINAGE PLAN (1), 10/26/2017 12:22:42 PM, FC
Know what's
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
CityDate Engineer
WaterDate & Wastewater Utility
StormwaterDate Utility
ParksDate & Recreation
TrafficDate Engineer Date
EnvironmentalDate Planner
Date
Larimer County, Colorado
UTILITY PLAN APPROVAL
LarimerDate County Engineer
New Impervious Area 277,962 sq. ft.
Required Minimum Impervious Area to be Treated (=50% of new impervious area) 138,981 sq. ft.
Impervious Area Directly Treated by LID Treatment Method #1- Bio-Swale #1 18,682 sq. ft.
Impervious Area Directly Treated by LID Treatment Method #2- Isolator Row #1 134,742 sq. ft.
Total Impervious Area Treated 153,424 sq. ft.
Actual % of Impervious Area Treated 55.2%
50% On-Site Treatment by LID Requirement
GREENFIELDS DR.
GREEN LAKE DR.
EAST VINE DR.
CAMPFIRE DR.
X:\3910000.all\3914551\Drawings\Sheet Dwgs\3914554 IMPERVIOUS AREA.dwg, LID SURFACE DRAINAGE PLAN (2), 10/26/2017 12:23:25 PM, FC
120 2.66 0.25 0.65 4696.65 0.54 0.04 311.52 4385.13 0.1007
Required detention
Detention Pond Sizing FAA Methoud
CAP/I using the catchment's intensity value.
X:\3910000.all\3914551\Excel\Drainage\3914551 Drainage_Calcs_v2.05.xlsm Page 2 of 2 10/26/2017
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
2-Year
39145.51
10/24/17
X:\3910000.all\3914551\Excel\Drainage\3914551 Drainage_Calcs_v2.05.xlsm Page 1 of 2 10/26/2017
CAP/I using the catchment's intensity value.
X:\3910000.all\3914551\Excel\Drainage\3914551 Drainage_Calcs_v2.05.xlsm Page 2 of 2 10/26/2017
DIRECT RUNOFF TOTAL RUNOFF STREET PIPE
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
39145.51
100-Year
10/24/17
X:\3910000.all\3914551\Excel\Drainage\3914551 Drainage_Calcs_v2.05.xlsm Page 1 of 2 10/26/2017
)^0.5) (Equation 6-5)
i = imperviousness (expressed as a decimal)
t c is lesser of Equation 6-2 and Equation 6-5.
For Urbanized basins a minimum t c of 5.0 minutes is required.
For non-urbanized basins a minimum t c of 10.0 minutes is required.
Table 6-2. NRCS Conveyance Factors, K
Nearly bare ground
Grassed waterway
Paved areas and shallow paved swales
Type of Land Surface
Heavy Meadow
Tillage/field
Short pasture and lawns
STANDARD FORM SF-2
TIME OF CONCENTRATION
SUB-BASIN tc CHECK
39145.51
DATA (URBANIZED BASINS)
INITIAL/OVERLAND
(Ti)
TRAVEL TIME
(Tt)
X:\3910000.all\3914551\Excel\Drainage\3914551 Drainage_Calcs_v2.05.xlsm Page 1 of 1 10/26/2017
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 11, Sep 23, 2016
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 20, 2015—Oct
15, 2016
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
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/22/2017
Page 2 of 4
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 11, Sep 23, 2016
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 20, 2015—Oct
15, 2016
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
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
8/22/2017
Page 2 of 4