HomeMy WebLinkAboutTHE PARK TOWNHOMES AT FOSSIL RIDGE (FORMERLY ZIEGLER TOWNHOMES) - PDP/FDP - FDP160043 - REPORTS - DRAINAGE REPORTFebruary 15, 2017
FINAL DRAINAGE REPORT
The Park Townhomes at Fossil Ridge
Fort Collins, Colorado
Prepared for:
Russell Baker
Manhattan Land Company, LLC
772 Whalers Way, Suite 200
Fort Collins, Colorado 80525
Prepared by:
301 N. Howes Street Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 1124-002
PThis Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
When a hard copy is absolutely necessary, we recommend double-sided printing.
February 15, 2017
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage Report for
The Park Townhomes at Fossil Ridge
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage Report for your review. This
report accompanies the combined Preliminary & Final Plan submittal for the proposed The
Park Townhomes at Fossil Ridge development (fka – Ziegler Townhomes).
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 Park Townhomes at Fossil Ridge 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.
Andy Reese
Project Manager
The Park Townhomes at Fossil Ridge
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ......................................................... 1
II. DRAINAGE BASINS AND SUB-BASINS ............................................................. 4
III. DRAINAGE DESIGN CRITERIA ......................................................................... 5
IV. DRAINAGE FACILITY DESIGN .......................................................................... 8
V. CONCLUSIONS............................................................................................. 12
References ............................................................................................................. 13
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
APPENDIX C – Water Quality/LID Design Computations
APPENDIX D – Erosion Control Report
APPENDIX E – USDA Soils Report
MAP POCKET:
DR1 – Drainage Exhibit
The Park Townhomes at Fossil Ridge
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I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
Figure 1 – Vicinity Map
2. The Park Townhomes at Fossil Ridge project site is located in the southeast
quarter of Section 5, Township 6 North, Range 68 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 a single family residence
with agricultural uses; to the south by McClelland’s Creek; to the east by Ziegler Road
(ROW varies); and to the west by the Harvest Park Subdivision.
4. McClelland’s Creek is a major drainageway that is located adjacent to the project site.
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B. Description of Property
1. The Park Townhomes at Fossil Ridge are comprised of ±4.03 acres.
2. The site is currently occupied by the foundations of two residential buildings as well as
various concrete sidewalks and gravel parking areas.
Figure 2 – Aerial Photograph
3. The existing groundcover consists of grasses, concrete and gravel. The existing on-site
runoff generally drains from the north-to-south across flat grades (e.g., <2.00%) into
McClelland’s Creek. From there, the drainage continues through the channel to Fossil
Creek Reservoir, 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 Nunn clay loam (Hydrologic Soil Group C).
5. McClelland’s Creek is the only major drainageway within or adjacent to the project
site.
6. The proposed development will consist of six townhome buildings containing a total of
36 single-family attached units. Other proposed improvements include: a new asphalt
drive aisle, new sidewalks and new landscaping.
7. The proposed land use is single-family attached. This is a permitted use in the Low
Density Mixed Use District (LMN).
Project Site
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Floodplain
8. The subject property is not located in a FEMA regulatory floodplain. In particular, the
project site is not located within a FEMA designated 100-year floodplain per Map
Number 08069CO994F (Effective date: December 19, 2006).
The project site is, however, located adjacent to a City of Fort Collins regulated
McClelland’s Creek floodplain.
Figure 4 – FEMA Firmette (Map Number 08069C0979H)
9. We have analyzed the City Floodplain map and cross sections for McClelland’s
Creek and determined that the highest base flood elevation adjacent to the project
site is 4909.19 (NAVD88) at XS #8. All buildings have been elevated 2’ above
this elevation. Furthermore, the buildings all maintain a minimum of 12” between
the finished floor elevation and the emergency spill elevation over Ziegler Road.
Project Site
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II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Park Townhomes at Fossil Ridge are located within the City of Fort Collins
McClelland’s major drainage basin. Specifically, the project site is situated in the
eastern third of this major drainage basin. This basin is located in south-east Fort
Collins and has a drainage area of approximately 3.4 square miles and includes
drainage originating near the College and Harmony intersection and draining through
the Oakridge, Willow Springs, Stetson Creek and Harvest Park developments. The
McClelland’s major drainage basin generally drains from northwest to southeast.
Runoff from the major drainage basin drains to Fossil Creek Reservoir.
B. Sub-Basin Description
1. The outfall for the project site is McClelland’s Creek.
2. The existing subject site can be defined with one (1) sub-basin that encompasses the
entire project site.
The existing site runoff generally drains from northwest-to-southeast and into
McClelland’s Creek.
3. The project site does not receive notable runoff from contiguous off-site properties. In
the developed condition, some drainage from properties to the north will drain through
the project site.
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III. DRAINAGE DESIGN CRITERIA
A. There are no optional provisions outside of the FCSCM proposed with The Park
Townhomes at Fossil Ridge.
B. The overall stormwater management strategy employed with The Park Townhomes at
Fossil Ridge 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 Park Townhomes at Fossil Ridge 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 an infiltration
gallery. 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 Bio-retention planters located in the second level courtyard.
Step 3 – Stabilize Drainageways. As stated in Section I.B.5, above, the McClelland’s
Creek 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 Park
Townhomes at Fossil Ridge, 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
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 on one sides by a public street, on another side by
McClelland’s Creek, and by existing development along the west side. An existing
agricultural use borders the project to the north.
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D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with The Park Townhomes at Fossil Ridge development. Tabulated data
contained in Table RA-7 has been utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. The Rational Formula-based Federal Aviation Administration (FAA) procedure has not
been utilized for detention storage calculations since detention is not required for the
project.
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 Park Townhomes at Fossil Ridge
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 City
of Fort Collins designated floodplain but is not located within the floodplain
limits.
F. Floodplain Regulations Compliance
1. As previously mentioned, this project is adjacent to a City of Fort Collins
regulated floodplain. As a result, no floodplain regulations apply to the
property.
2. Despite 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
1. 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 McClelland’s Creek.
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H. Conformance with Water Quality Treatment Criteria
1. 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 an underground infiltration gallery (aka –
underground chambers) located at the south end of the project, under the
drive aisle. These chambers are considered an LID treatment method. 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)
1. The project site will conform with the requirement to treat a minimum of 75%
of the project site using an LID technique. Please see Appendix C for LID
design information, table, and exhibit(s). As shown in the LID table provided
in the appendix, 86.4% of the proposed site impervious area will receive LID
treatment, which exceeds the minimum required.
J. Sizing of LID Facilities
Infiltration Gallery
1. The Infiltration Gallery was sized by first determining the required water quality
capture volume (WQCV) for Basins A1-A3, B1-B2 and C1-C4. A 12-hour
drain time was used in this calculation.
2. Once the WQCV was identified, the minimum number of vaults needed to
achieve the minimum WQCV was calculated. This volume includes the
adjacent aggregates
3. As a result of all underground vaults being wrapped in a geofabric and the
potential constriction of flows that could result from sedimentation in the
fabric, the total release rate through the fabric was calculated. This rate was
determined by multiplying the vault bottom square footage x 0.35 gpm.
4. A volume calculation utilizing the WQ flow rate into the chamber and the
calculated release rate through the fabric was completed. The number of
chambers have been increased as needed to confirm that the resulting volume
is provided within the empty volume of the underground chambers. This is
intended to ensure that the chambers do not become overwhelmed in the
water quality storm event before “discharging” flows into the surrounding
aggregates.
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IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objective of The Park Townhomes at Fossil Ridge drainage design is to
maintain existing drainage patterns, while not adversely impacting adjacent properties.
2. No notable off-site runoff passes directly through the project site. There is a small
offsite flow from properties to the north that will pass through the project site once
County Fair Lane has been constructed. This drainage will pass through the site
without adversely affecting the townhome buildings.
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 thirteen (13) drainage sub-
basins, designated as sub-basins A1- A3, B1-B3, C1-C3 and D1-D2. The drainage
patterns anticipated for the basins are further described below.
Sub-Basin A1
Sub-basin A1 encompasses approximately 7% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork and landscaped areas. The sub-
basin will drain to a swale located along the west property line and be captured by an
area drain which will then convey runoff from the basin through the storm drain
system and into the infiltration gallery. Flows will then proceed to McClelland’s Creek.
Sub-Basin A2
Sub-basin A2 encompasses approximately 12% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork, and an asphalt drive aisle. Minor
flows for the sub-basin will drain to an on-grade inlet located at the drive aisle
entrance from County Fair. Larger flows will bypass the on-grade inlet and flow to a
combo inlet located on the north side of County Fair Lane. Both Major and Minor
flows will be directed into the storm drain system which will convey runoff from the
basin into the infiltration gallery. Flows will then proceed to McClelland’s Creek.
Sub-Basin A3
Sub-basin A3 encompasses approximately 6% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork and landscaped areas. The sub-
basin will drain to a series of area drains which will then convey runoff from the basin
through the storm drain system and into the infiltration gallery. Flows will then
proceed to McClelland’s Creek.
Sub-Basin B1
Sub-basin B1 encompasses approximately 8% the total site area. This sub-basin is
comprised primarily of asphalt roadway and concrete walks. Flows from the sub-basin
will flow to a combo inlet located on the north side of County Fair Lane and into the
storm drain system which will convey runoff from the basin into the infiltration gallery.
Flows will then proceed to McClelland’s Creek.
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Sub-Basin B2
Sub-basin B2 encompasses approximately 3% the total site area. This sub-basin is
comprised primarily of asphalt roadway and concrete sidewalks. Flows from the sub-
basin will flow to a combo inlet located on the south side of County Fair Lane and into
the storm drain system which will convey runoff from the basin into the infiltration
gallery. Flows will then proceed to McClelland’s Creek.
Sub-Basin B3
Sub-basin B3 encompasses approximately 1% the total site area. This sub-basin is
comprised primarily of asphalt roadway and concrete sidewalks. Flows from the sub-
basin will flow offsite to the west to a pair of combo inlets located on the either side of
County Fair Lane and into the Harvest Park Detention Pond. The flow from this basin
has been calculated at 0.32 cfs in the 100-yr event, which will have a negligible
impact on the overall drainage capacity and operation of the Harvest Park Stormwater
Facilities.
Sub-Basin C1
Sub-basin C1 encompasses approximately 11% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork and landscaped areas. The sub-
basin will drain to a series of area drains which will then convey runoff from the basin
through the storm drain system and into the infiltration gallery. Flows will then
proceed to McClelland’s Creek.
Sub-Basin C2a
Sub-basin C2a encompasses approximately 12% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork, and an asphalt drive aisle. Minor
flows for the sub-basin will drain to an on-grade area inlet located in the drive aisle
drainage pan. Larger flows will bypass the on-grade inlet and flow to another area
inlet in Sub-basin C2b. Both Major and Minor flows will be directed into the storm
drain system which will convey runoff from the basin into the infiltration gallery.
Flows will then proceed to McClelland’s Creek.
Sub-Basin C2b
Sub-basin C2b encompasses approximately 6% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork, and an asphalt drive aisle. Flows
from the sub-basin will drain to an area inlet located in the drive aisle drainage pan.
Bypassed flows from Sub-basin C2a will also drain to this area inlet. All flows will be
directed into the storm drain system which will convey runoff from the basin into the
infiltration gallery. Flows will then proceed to McClelland’s Creek.
Sub-Basin C3
Sub-basin C3 encompasses approximately 9% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork and landscaped areas. The sub-
basin will drain across landscaped areas and the Ziegler Road parkway and into the
Ziegler Road curb and gutter. Flows will then proceed to the existing storm inlet in
Ziegler and into the existing storm drain, which will convey flows from Ziegler Road to
McClelland’s Creek.
Sub-Basin C4
Sub-basin C4 encompasses approximately 3% the total site area. This sub-basin is
comprised primarily of roof area, concrete flatwork and landscaped areas. The sub-
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basin will drain to an area drain which will then convey runoff from the basin to the
existing storm drain from Ziegler Road to McClelland’s Creek.
Sub-Basin D1
Sub-basin D1 encompasses approximately 12% the total site area. This sub-basin is
comprised of native grasses as well as McClelland’s Creek. No improvements are
proposed within this basin, and existing drainage patterns will be maintained. Runoff
from the sub-basin will flow directly into McClelland’s Creek.
Sub-Basin D2
Sub-basin D2 encompasses approximately 10% the total site area. This sub-basin is
comprised primarily of existing asphalt roadway and new concrete sidewalks. Runoff
from the sub-basin will flow to an existing combo inlet located on the west side of
Ziegler Road and into the existing storm drain, which will convey flows from Ziegler
Road to McClelland’s Creek.
Sub-Basin OS1
Sub-basin OS1 is located directly north of the project boundary and includes
approximately 500 LF of Ziegler frontage as well as portions of the adjacent property.
This sub-basin is comprised primarily of asphalt roadway and concrete sidewalks and
also includes several existing buildings. Flows from the sub-basin will flow to the
Ziegler curb and gutter and proceed to a combination inlet located along the north side
of County Fair Lane. Approximately 1.3 cfs will be captured by the inlet before the
storm system reaches capacity. At that time, excess runoff from the site will pond at
the inlet to a depth of 6”, at which point the ponding will crest the centerline of
County Fair Lane. Runoff will again pond on the combo inlet located on the south
side of County Fair Lane. Ponding depth will reach 3” before the offsite stormwater
spills to the south along Ziegler Road, where it will proceed to the existing inlet in
Ziegler Road. Runoff will then be directed into the existing storm drain system which
will convey runoff from the inlet to McClelland’s Creek.
Sub-Basin OS2
Sub-basin OS2 is located directly north of sub-basin OS1 and includes approximately
340 LF of Ziegler frontage as well as portions of the adjacent property. This sub-basin
is comprised primarily of asphalt roadway and concrete sidewalks and also includes
several existing buildings. The sub-basin could be included with Basin OS1, however
the Harvest Park drainage report defined this basin specifically, so we have continued
to show this basin separately from the other offsite basin. Flows from the sub-basin
will flow to the Ziegler curb and gutter and proceed into sub-basin OS1 and C1. Once
the flows have joined with the flows from Basin OS1, the flow path will be the same
as that described for Basin OS1, with an ultimate outfall into McClelland’s Creek.
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
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proximity of the site to McClelland’s Creek.
3. The FAA method was not used to size the on-site detention volume for
quantity detention since detention is not required.
C. Sizing of LID Facilities
Infiltration Gallery
1. The Infiltration Gallery was sized by first determining the required water
quality capture volume (WQCV) for Basins A1-A3, B1-B2 and C1-C4. A 12-
hour drain time was used in this calculation.
2. Once the WQCV was identified, the minimum number of vaults needed to
achieve the minimum WQCV was calculated. This volume includes the
adjacent aggregates
3. As a result of all underground vaults being wrapped in a geofabric and the
potential constriction of flows that could result from sedimentation in the
fabric, the total release rate through the fabric was calculated. This rate was
determined by multiplying the vault bottom square footage x 0.35 gpm.
4. A volume calculation utilizing the WQ flow rate into the chamber and the
calculated release rate through the fabric was completed. The number of
chambers have been increased as needed to confirm that the resulting
volume is provided within the empty volume of the underground chambers.
This is intended to ensure that the chambers do not become overwhelmed in
the water quality storm event before “discharging” flows into the surrounding
aggregates.
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V. CONCLUSIONS
A. Compliance with Standards
1. The design elements comply without variation, and meet all LID requirements.
2. The drainage design proposed with The Park Townhomes at Fossil Ridge complies
with the City of Fort Collins Master Drainage Plan for the Old Town Basin.
3. There are no FEMA regulatory floodplains associated with The Park Townhomes at
Fossil Ridge development. However, the project is adjacent to the McClelland
Floodplain, which is a City Regulated floodplain. All 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 Park
Townhomes at Fossil Ridge 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 Park Townhomes at Fossil Ridge 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 Park Townhomes at Fossil Ridge development will not impact the Master
Drainage Plan recommendations for the McClelland major drainage basin.
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References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
4. 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
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: The Park Townhomes
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: A. Reese
Asphalt ……....……………...……….....…...……………….………………………………….0.95 . 100% Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 90%
Gravel ……….…………………….….…………………………..……………………………….0.50 . 40%
Roofs …….…….………………..……………….…………………………………………….0.95 . 90%
Pavers…………………………...………………..…………………………………………….0.40 . 22%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….0.15 . 0%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 0% 2-year Cf
= 1.00 100-year Cf = 1.25
Basin ID
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Pavers (ac)
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
A1 0.31 0.00 0.04 0.10 0.00 0.00 0.17 0.57 0.57 0.71 41%
A2 0.42 0.09 0.12 0.17 0.00 0.00 0.04 0.88 0.88 1.00 84%
A3 0.24 0.00 0.03 0.09 0.00 0.00 0.12 0.61 0.61 0.76 46%
B1 0.33 0.23 0.05 0.00 0.00 0.00 0.05 0.84 0.84 1.00 83%
B2 0.18 0.08 0.04 0.01 0.00 0.00 0.05 0.75 0.75 0.93 68%
B3 0.03 0.02 0.01 0.00 0.00 0.00 0.01 0.80 0.80 1.00 76%
C1 0.26 0.00 0.04 0.14 0.00 0.00 0.09 0.72 0.72 0.90 60%
C2a 0.44 0.09 0.13 0.22 0.00 0.00 0.00 0.96 0.96 1.00 93%
C2b 0.27 0.06 0.08 0.11 0.00 0.00 0.02 0.90 0.90 1.00 86%
C3 0.35 0.00 0.06 0.14 0.00 0.00 0.15 0.65 0.65 0.82 52%
Overland Flow, Time of Concentration:
Project: The Park Townhomes
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
Rational Method Equation: Project: The Park Townhomes
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
Design
Point
Basin(s)
Area, A
(acres)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
C2 C10 C100
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
Flow,
Q2
(cfs)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
Flow,
WQ
(cfs)
A1 A1 0.31 5 5 5 0.57 0.57 0.71 2.85 4.87 9.95 0.50 0.86 2.20 0.25
A2 A2 0.42 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 1.07 1.82 4.22 0.53
A3 A3 0.24 9 9 9 0.61 0.61 0.76 2.30 3.93 8.21 0.34 0.58 1.52 0.17
B1 B1 0.33 7 7 6 0.84 0.84 1.00 2.60 4.44 9.31 0.72 1.24 3.10 0.36
B2 B2 0.18 6 6 5 0.75 0.75 0.93 2.76 4.72 9.95 0.38 0.64 1.70 0.19
B3 B3 0.03 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.07 0.13 0.32 0.04
C1 C1 0.26 8 8 7 0.72 0.72 0.90 2.46 4.21 8.80 0.46 0.78 2.05 0.23
C2a C2a 0.44 5 5 5 0.96 0.96 1.00 2.85 4.87 9.95 1.19 2.04 4.35 0.60
C2b C2b 0.27 5 5 5 0.90 0.90 1.00 2.85 4.87 9.95 0.70 1.19 2.71 0.35
C3 C3 0.35 7 7 6 0.65 0.65 0.82 2.60 4.44 9.31 0.59 1.01 2.64 0.29
C4 C4 0.11 5 5 5 0.47 0.47 0.59 2.85 4.87 9.95 0.15 0.25 0.64 0.07
D1 D1 0.62 6 6 6 0.25 0.25 0.31 2.67 4.56 9.31 0.41 0.70 1.79 0.21
D2 D2 0.46 5 5 5 0.71 0.71 0.88 2.85 4.87 9.95 0.93 1.59 4.05 0.46
OS1 OS1 2.06 6 6 6 0.39 0.39 0.49 2.67 4.56 9.63 2.16 3.70 9.76 1.08
OS2 OS2 0.41 6 6 5 0.71 0.71 0.89 2.76 4.72 9.95 0.81 1.38 3.63 0.40
DEVELOPED RUNOFF COMPUTATIONS
A. Reese
February 15, 2017
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Overland Flow, Time of Concentration:
Project: The Park Townhomes
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = T
i + Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
B1 A3, B1, OS1, OS2 5.7 5.7 5.3 785 1.26% 2.24 5.8 0 0.0 0.00 N/A 11 11 11
C2b
A1, A2, A3, B1,
B2, C1, C2a, C2b,
C4
5.2 5.2 5.0 544 0.50% 1.41 6.4 0 0.0 0.00 N/A 12 12 11
Rational Method Equation: Project: The Park Townhomes
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
B1 B1, OS1, OS2 2.47 12 12 11 0.56 0.56 0.69 38% 2.09 3.57 7.42 2.89 4.93 12.69 1.44
C2b
A1, A2, A3, B1,
B2, C1, C2a,
C2b, C4
2.57 12 12 11 0.78 0.78 0.91 71% 2.09 3.57 7.42 4.21 7.18 17.36 2.11
C10 C100 Composite
% Imperv.
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Flow,
WQ
(cfs)
COMBINED RUNOFF COMPUTATIONS
A. Reese
February 15, 2017
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Design
Point
Basin(s)
Area, A
(acres)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Intensity,
i100
(in/hr)
Flow,
Q2
(cfs)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C2
Q = C f ( C )( i )( A )
D:\Projects\1124-002\Drainage\Hydrology\1124-002_Rational-Calcs_Proposed.xlsx\Combined Runoff
Design
Point Basin ID
Basin Area
(ac)
Composite
% Imperv.
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Flow,
Q2
(cfs)
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
Flow,
WQ
(cfs)
A1 A1 0.31 41% 0.57 0.57 0.71 0.50 0.86 2.20 0.25
A2 A2 0.42 84% 0.88 0.88 1.00 1.07 1.82 4.22 0.53
A3 A3 0.24 46% 0.61 0.61 0.76 0.34 0.58 1.52 0.17
B1 B1 0.33 83% 0.84 0.84 1.00 0.72 1.24 3.10 0.36
B2 B2 0.18 68% 0.75 0.75 0.93 0.38 0.64 1.70 0.19
B3 B3 0.03 76% 0.80 0.80 1.00 0.07 0.13 0.32 0.04
C1 C1 0.26 60% 0.72 0.72 0.90 0.46 0.78 2.05 0.23
C2a C2a 0.44 93% 0.96 0.96 1.00 1.19 2.04 4.35 0.60
C2b C2b 0.27 86% 0.90 0.90 1.00 0.70 1.19 2.71 0.35
C3 C3 0.35 52% 0.65 0.65 0.82 0.59 1.01 2.64 0.29
C4 C4 0.11 28% 0.47 0.47 0.59 0.15 0.25 0.64 0.07
D1 D1 0.62 0% 0.25 0.25 0.31 0.41 0.70 1.79 0.21
D2 D2 0.46 65% 0.71 0.71 0.88 0.93 1.59 4.05 0.46
OS1 OS1 2.06 20% 0.39 0.39 0.49 0.81 1.38 3.63 0.40
OS2 OS2 0.41 65% 0.71 0.71 0.89 0.00 0.00 0.00 0.00
B1 B1, OS1, OS2 2.47 38% 0.56 0.56 0.69 2.89 4.93 12.69 1.44
C2b A1, A2, A3, B1, B2,
C1, C2a, C2b, C4 2.57 71% 0.78 0.78 0.91 4.21 7.18 17.36 2.11
Rational Method Summary | Proposed Condition
APPENDIX B
Hydraulic Calculations
Storm Drain A
Storm Drain A
Storm Drain A4
Storm Drain A2
Storm Drain A1A
Storm Drain A
Storm Drain A1A
Storm Drain A2
Storm Drain A4
INLET CAPACITY SUMMARY
Project: The Park Townhomes at Fossil Ridge
By: A. Reese
Date:
Inlet A1A-2 C2b Area Inlet South end of vaults Sump 100-Yr 5.87 6.25
Inlet A2-1 C2a Area Inlet North end of vaults Grade 2-yr 1.19 1.19
Inlet A4-1 B2 Single Combo County Fair - South FL Sump 100-yr 1.70 5.80
Inlet A5 B1 Double Combo County Fair - North FL Sump 100-yr 4.32 6.20
Inlet A6 A2 Double Combo North Driveway Grade 2-yr 1.07 2.80
Design
Storm
Design
Flow
(CFS)
Inlet Capacity
(CFS)
February 15, 2017
Inlet
ID
Design
Point Inlet Type Location
Inlet
Condition
D:\Projects\1124-002\Drainage\Inlets\1124-002_Inlet summary.xlsx
Area Inlet Performance Curve:
Project: The Park Townhomes at Fossil Ridge
Calculations By: A. Reese
Design Point: C2b
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: Nyloplast 3299CGR
Length of Grate (ft): 2.90
Width of Grate (ft): 1.90
Open Area of Grate (ft
2
): 3.00
Flowline Elevation (ft): 4910.130
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 4910.13 0.00 0.00 0.00
0.05 4910.18 0.16 1.80 0.16
0.10 4910.23 0.45 2.55 0.45
0.133 4910.263 0.70 2.94 0.70 Q2
0.15 4910.28 0.84 3.12 0.84
0.20 4910.33 1.29 3.61 1.29
0.25 4910.38 1.80 4.03 1.80
0.30 4910.43 2.36 4.42 2.36
0.35 4910.48 2.98 4.77 2.98
0.40 4910.53 3.64 5.10 3.64
0.45 4910.58 4.34 5.41 4.34
0.50 4910.63 5.08 5.70 5.08
0.55 4910.68 5.86 5.98 5.86
0.551 4910.681 5.87 5.99 5.87 Q100
0.60 4910.73 6.68 6.25 6.25
Inlet A1A-2 is designed to intercept the full 2-year flow of 0.70 cfs with 1.6" of flow depth and the full 100-year flow of
5.87 cfs (2.71 cfs + 3.16 cfs from C2a) at a depth of 6.6".
Inlet A1A-2
0.00
1.00
2.00
3.00
4.00
Area Inlet Performance Curve:
Project: The Park Townhomes at Fossil Ridge
Calculations By: A. Reese
Design Point: C2a
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: Nyloplast 3299CGR
Length of Grate (ft): 2.90
Width of Grate (ft): 1.90
Open Area of Grate (ft2): 3.00
Flowline Elevation (ft): 4911.350
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 4911.35 0.00 0.00 0.00
0.05 4911.40 0.16 1.80 0.16
0.10 4911.45 0.45 2.55 0.45
0.15 4911.50 0.84 3.12 0.84
0.190 4911.540 1.19 3.52 1.19 Q2
0.20 4911.55 1.29 3.61 1.29
0.25 4911.60 1.80 4.03 1.80
0.30 4911.65 2.36 4.42 2.36
0.35 4911.70 2.98 4.77 2.98
0.40 4911.75 3.64 5.10 3.64
0.45 4911.80 4.34 5.41 4.34
0.451 4911.801 4.35 5.42 4.35 Q100
0.50 4911.85 5.08 5.70 5.08
Inlet A2-1 is designed to intercept the full 2-year flow of 1.19 cfs with 2.25" of flow depth and bypass the remaining
100-year flow of 3.16 cfs.
Inlet A2-1
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Discharge (cfs)
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal
= 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Flow Depth = 6.0 8.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo
(G) = 3.00 3.00 feet
Width of a Unit Grate Wo
= 1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio
= 0.31 0.31
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf
(G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw
(G) = 3.60 3.60
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co
(G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo
(C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert
= 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat
= 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp
= 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf
(C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.6) Cw
(C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co
(C) = 0.66 0.66
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa = 3.9 5.8 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED
= 0.4 1.7 cfs
INLET IN A SUMP OR SAG LOCATION
The Park Townhomes at Fossil Ridge
Inlet A4-1 (Combo Inlet - Sump)
Denver No. 16 Combination
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
UD Inlet 3.1_Inlet A4-1.xlsm, Inlet In Sump 2/15/2017, 6:29 AM
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal
= 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 2 2
Water Depth at Flowline (outside of local depression) Flow Depth = 6.0 6.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo
(G) = 3.00 3.00 feet
Width of a Unit Grate Wo
= 1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio
= 0.31 0.31
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf
(G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw
(G) = 3.60 3.60
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co
(G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo
(C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert
= 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat
= 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp
= 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf
(C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.6) Cw
(C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co
(C) = 0.66 0.66
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Qa = 6.2 6.2 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q PEAK REQUIRED
= 0.7 4.5 cfs
INLET IN A SUMP OR SAG LOCATION
The Park Townhomes at Fossil Ridge
Inlet A5 (Combo Inlet - Sump)
Denver No. 16 Combination
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
UD Inlet 3.1_Inlet A5.xlsm, Inlet In Sump 2/15/2017, 6:38 AM
Project:
Inlet ID:
Design Information (Input) MINOR MAJOR
Type of Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') aLOCAL
= 2.0 2.0 inches
Total Number of Units in the Inlet (Grate or Curb Opening) No = 2 2
Length of a Single Unit Inlet (Grate or Curb Opening) Lo
= 3.00 3.00 ft
Width of a Unit Grate (cannot be greater than W from Q-Allow) Wo
= 1.73 1.73 ft
Clogging Factor for a Single Unit Grate (typical min. value = 0.5) Cf
-G = 0.50 0.50
Clogging Factor for a Single Unit Curb Opening (typical min. value = 0.1) Cf
-C = 0.10 0.10
Street Hydraulics: WARNING: Q > ALLOWABLE Q FOR MINOR & MAJOR STORM MINOR MAJOR
Total Inlet Interception Capacity Q = 1.0 2.8 cfs
Total Inlet Carry-Over Flow (flow bypassing inlet) Qb = 0.0 1.5 cfs
Capture Percentage = Qa/Q
o = C% = 98 65 %
INLET ON A CONTINUOUS GRADE
The Park Townhomes at Fossil Ridge
Inlet A6 (Combo Inlet - On-Grade)
Denver No. 16 Combination
UD Inlet 3.1_Inlet A6.xlsm, Inlet On Grade 2/15/2017, 6:36 AM
APPENDIX C
WATER QUALITY/LID DESIGN COMPUTATIONS
Project Summary
Total Impervious Area 91,353 sf
Target Treatment Percentage 75%
Minimum Area to be Treated by LID measures 68,514.54 sf
Infiltration Gallery/Underground Vaults
Vault Volume 2,247 cf
Total Vault Treatment Area 78,863 sf
Total Treatment Area 78,863 sf
Percent Total Project Area Treated 86.3%
The Park Townhomes at Fossil Ridge On-Site LID Treatment
Vault ID
Total
Required
WQ Volume
(cf)
InFlow,
WQ
(cfs)
Chamber
Type
Individual
Chamber
Release
Rate
(cfs)
Individual
Chamber
Volume
(cfs)
Individual
Installed
Chamber
Volume
(cfs)
Mimimum
No. of
Chambers
Minimum
Release
Rate
(cfs)
Required
Chamber
Volume by
FAA Method
(cf)
Provided
Number of
Chambers
Provided
Release
Rate
(cfs)
Provided
Chamber
Volume
(cf)
Total
Installed
Chamber
Volume
(cf)
1 2087 2.11 SC-740 0.024 45.90 74.90 28 0.66 1338 30 0.71 1377 2247
Vault Configuration Summary
Note: "Chamber Volume" refers to the open volume within the vaults. "Installed Chamber Volume" refers to the total volume provided, including the surrounding aggregates.
D:\Projects\1124-002\Drainage\LID\1124-002_Vault Summary.xlsx
Chamber Dimensions SC-310 SC-740
Width (in) 34.00 51.00
Length (in) 85.40 85.40
Height (in) 16.00 30.00
Floor Area (sf) 20.16 30.25
Chamber Volume (cf) 14.70 45.90
Chamber/Aggregate Volume (cf) 29.30 74.90
Flow Rate** 0.35 gpm/sf
1 cf = 7.48052 gal
1 gallon = 0.133681 cf
1 GPM = 0.002228 cfs
**Flow rate based on 1/2 of Nov 07 QMAX in Figure 17 of UNH Testing Report
SC-310 SC-740
Flow Rate/chamber (cfs) 0.015724 0.023586
StormTech Chamber Data
Chamber Flow Rate Conversion (gpm/sf to cfs)
Chamber Flow Rate
D:\Projects\1124-002\Drainage\LID\1124-002_Vault Summary.xlsx
Project Title Date:
Project Number Calcs By:
Basin(S)
0.8
WQCV = Watershed inches of Runoff (inches) 71.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.224 in
A = 2.57 ac
V = 0.0479 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
The Park Townhomes at Fossil Ridge February 15, 2017
1124-002 A. Reese
A1, A2, A3, B1, B2, C1, C2a & C2b
2087 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.224
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
ö
ç
The Park Townhomes at Fossil Ridge
Fort Collins, Colorado
A. Reese Date: February 15, 2017
Pond No.: Vault 1
C2
WQ
0.87
Area (A)= 2.57 acres Quantity Detention 1338 ft
3
Max Release Rate = 0.71 cfs
Time Time
Ft.Collins
WQ
Intensity
Q100
Inflow
(Runoff)
Volume
Outflow
(Release) Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs) (ft
3
) (ft
3
) (ft
3
)
5 300 1.43 3.2 956 213 743
10 600 1.11 2.5 1482 426 1056
15 900 0.94 2.1 1882 639 1243
20 1200 0.81 1.8 2160 852 1308
25 1500 0.72 1.6 2398 1065 1333
30 1800 0.65 1.5 2616 1278 1338
35 2100 0.59 1.3 2747 1491 1256
40 2400 0.54 1.2 2871 1704 1167
45 2700 0.50 1.1 2988 1917 1071
50 3000 0.46 1.0 3086 2130 956
55 3300 0.44 1.0 3210 2343 867
60 3600 0.41 0.9 3300 2556 744
65 3900 0.39 0.9 3357 2769 588
70 4200 0.37 0.8 3428 2982 446
75 4500 0.35 0.8 3471 3195 276
80 4800 0.33 0.7 3542 3408 134
85 5100 0.32 0.7 3592 3621 -29
90 5400 0.31 0.7 3683 3834 -151
95 5700 0.29 0.6 3696 4047 -351
100 6000 0.28 0.6 3756 4260 -504
105 6300 0.27 0.6 3803 4473 -670
110 6600 0.26 0.6 3837 4686 -849
115 6900 0.3 0.6 3934 4899 -965
120 7200 0.25 0.5 3944 5112 -1168
Vault Volume Calculation | FAA Method
Project:
Project Location:
Calculations By:
Input Variables Results
Design Point
APPENDIX D
EROSION CONTROL REPORT
The Park Townhomes at Fossil Ridge
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) has
been included with the final construction drawings. It should be noted, however, that any
such Erosion and Sediment Control Plan serves only as a general guide to the Contractor.
Staging and/or phasing of the BMPs depicted, and additional or different BMPs from those
included may be necessary during construction, or as required by the authorities having
jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are
properly maintained and followed. The Erosion and Sediment Control Plan is intended to
be a living document, constantly adapting to site conditions and needs. The Contractor
shall update the location of BMPs as they are installed, removed or modified in conjunction
with construction activities. It is imperative to appropriately reflect the current site
conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be
implemented during construction, as well as permanent erosion control protection. Best
Management Practices from the Volume 3, Chapter 7 – Construction BMPs will be utilized.
Measures may include, but are not limited to, silt fencing and/or wattles along the disturbed
perimeter, gutter protection in the adjacent roadways and inlet protection at existing and
proposed storm inlets. Vehicle tracking control pads, spill containment and clean-up
procedures, designated concrete washout areas, dumpsters, and job site restrooms shall
also be provided by the Contractor.
Grading and Erosion Control Notes can be found on Sheet C001 of the Utility Plans. The
Final Utility Plans will also contain a full-size Erosion Control Plan as well as a separate
sheet dedicated to Erosion Control Details. In addition to this report and the referenced
plan sheets, the Contractor shall be aware of, and adhere to, the applicable requirements
outlined in any existing Development Agreement(s) of record, as well as the Development
Agreement, to be recorded prior to issuance of the Development Construction Permit. Also,
the Site Contractor for this project may be required to secure a Stormwater Construction
General Permit from the Colorado Department of Public Health and Environment (CDPHE),
Water Quality Control Division – Stormwater Program, before commencing any earth
disturbing activities. Prior to securing said permit, the Site Contractor shall develop a
comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE requirements
and guidelines. The SWMP will further describe and document the ongoing activities,
inspections, and maintenance of construction BMPs.
APPENDIX E
USDA SOILS REPORT
United States
Department of
Agriculture
A product of the National
Cooperative Soil Survey,
a joint effort of the United
States Department of
Agriculture and other
Federal agencies, State
agencies including the
Agricultural Experiment
Stations, and local
participants
Custom Soil Resource
Report for
Larimer County
Area, Colorado
Ziegler Townhomes
Natural
Resources
Conservation
Service
October 20, 2016
Preface
Soil surveys contain information that affects land use planning in survey areas. They
highlight soil limitations that affect various land uses and provide information about
the properties of the soils in the survey areas. Soil surveys are designed for many
different users, including farmers, ranchers, foresters, agronomists, urban planners,
community officials, engineers, developers, builders, and home buyers. Also,
conservationists, teachers, students, and specialists in recreation, waste disposal,
and pollution control can use the surveys to help them understand, protect, or enhance
the environment.
Various land use regulations of Federal, State, and local governments may impose
special restrictions on land use or land treatment. Soil surveys identify soil properties
that are used in making various land use or land treatment decisions. The information
is intended to help the land users identify and reduce the effects of soil limitations on
various land uses. The landowner or user is responsible for identifying and complying
with existing laws and regulations.
Although soil survey information can be used for general farm, local, and wider area
planning, onsite investigation is needed to supplement this information in some cases.
Examples include soil quality assessments (http://www.nrcs.usda.gov/wps/portal/
nrcs/main/soils/health/) and certain conservation and engineering applications. For
more detailed information, contact your local USDA Service Center (http://
offices.sc.egov.usda.gov/locator/app?agency=nrcs) or your NRCS State Soil
Scientist (http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/contactus/?
cid=nrcs142p2_053951).
Great differences in soil properties can occur within short distances. Some soils are
seasonally wet or subject to flooding. Some are too unstable to be used as a
foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic
tank absorption fields. A high water table makes a soil poorly suited to basements or
underground installations.
The National Cooperative Soil Survey is a joint effort of the United States Department
of Agriculture and other Federal agencies, State agencies including the Agricultural
Experiment Stations, and local agencies. The Natural Resources Conservation
Service (NRCS) has leadership for the Federal part of the National Cooperative Soil
Survey.
Information about soils is updated periodically. Updated information is available
through the NRCS Web Soil Survey, the site for official soil survey information.
The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs
and activities on the basis of race, color, national origin, age, disability, and where
applicable, sex, marital status, familial status, parental status, religion, sexual
orientation, genetic information, political beliefs, reprisal, or because all or a part of an
individual's income is derived from any public assistance program. (Not all prohibited
bases apply to all programs.) Persons with disabilities who require alternative means
2
for communication of program information (Braille, large print, audiotape, etc.) should
contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a
complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400
Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272
(voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and
employer.
3
Contents
Preface....................................................................................................................2
How Soil Surveys Are Made..................................................................................5
Soil Map..................................................................................................................7
Soil Map................................................................................................................8
Legend..................................................................................................................9
Map Unit Legend................................................................................................10
Map Unit Descriptions........................................................................................10
Larimer County Area, Colorado......................................................................12
34—Fort Collins loam, 0 to 1 percent slopes..............................................12
35—Fort Collins loam, 0 to 3 percent slopes..............................................13
36—Fort Collins loam, 3 to 5 percent slopes..............................................14
41—Garrett loam, 1 to 3 percent slopes.....................................................16
73—Nunn clay loam, 0 to 1 percent slopes.................................................17
74—Nunn clay loam, 1 to 3 percent slopes.................................................18
76—Nunn clay loam, wet, 1 to 3 percent slopes.........................................19
103—Stoneham loam, 5 to 9 percent slopes..............................................21
Soil Information for All Uses...............................................................................23
Soil Properties and Qualities..............................................................................23
Soil Qualities and Features.............................................................................23
Hydrologic Soil Group (Ziegler Townhomes)..............................................23
References............................................................................................................28
4
How Soil Surveys Are Made
Soil surveys are made to provide information about the soils and miscellaneous areas
in a specific area. They include a description of the soils and miscellaneous areas and
their location on the landscape and tables that show soil properties and limitations
affecting various uses. Soil scientists observed the steepness, length, and shape of
the slopes; the general pattern of drainage; the kinds of crops and native plants; and
the kinds of bedrock. They observed and described many soil profiles. A soil profile is
the sequence of natural layers, or horizons, in a soil. The profile extends from the
surface down into the unconsolidated material in which the soil formed or from the
surface down to bedrock. The unconsolidated material is devoid of roots and other
living organisms and has not been changed by other biological activity.
Currently, soils are mapped according to the boundaries of major land resource areas
(MLRAs). MLRAs are geographically associated land resource units that share
common characteristics related to physiography, geology, climate, water resources,
soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically
consist of parts of one or more MLRA.
The soils and miscellaneous areas in a survey area occur in an orderly pattern that is
related to the geology, landforms, relief, climate, and natural vegetation of the area.
Each kind of soil and miscellaneous area is associated with a particular kind of
landform or with a segment of the landform. By observing the soils and miscellaneous
areas in the survey area and relating their position to specific segments of the
landform, a soil scientist develops a concept, or model, of how they were formed. Thus,
during mapping, this model enables the soil scientist to predict with a considerable
degree of accuracy the kind of soil or miscellaneous area at a specific location on the
landscape.
Commonly, individual soils on the landscape merge into one another as their
characteristics gradually change. To construct an accurate soil map, however, soil
scientists must determine the boundaries between the soils. They can observe only
a limited number of soil profiles. Nevertheless, these observations, supplemented by
an understanding of the soil-vegetation-landscape relationship, are sufficient to verify
predictions of the kinds of soil in an area and to determine the boundaries.
Soil scientists recorded the characteristics of the soil profiles that they studied. They
noted soil color, texture, size and shape of soil aggregates, kind and amount of rock
fragments, distribution of plant roots, reaction, and other features that enable them to
identify soils. After describing the soils in the survey area and determining their
properties, the soil scientists assigned the soils to taxonomic classes (units).
Taxonomic classes are concepts. Each taxonomic class has a set of soil
characteristics with precisely defined limits. The classes are used as a basis for
comparison to classify soils systematically. Soil taxonomy, the system of taxonomic
classification used in the United States, is based mainly on the kind and character of
soil properties and the arrangement of horizons within the profile. After the soil
scientists classified and named the soils in the survey area, they compared the
5
individual soils with similar soils in the same taxonomic class in other areas so that
they could confirm data and assemble additional data based on experience and
research.
The objective of soil mapping is not to delineate pure map unit components; the
objective is to separate the landscape into landforms or landform segments that have
similar use and management requirements. Each map unit is defined by a unique
combination of soil components and/or miscellaneous areas in predictable
proportions. Some components may be highly contrasting to the other components of
the map unit. The presence of minor components in a map unit in no way diminishes
the usefulness or accuracy of the data. The delineation of such landforms and
landform segments on the map provides sufficient information for the development of
resource plans. If intensive use of small areas is planned, onsite investigation is
needed to define and locate the soils and miscellaneous areas.
Soil scientists make many field observations in the process of producing a soil map.
The frequency of observation is dependent upon several factors, including scale of
mapping, intensity of mapping, design of map units, complexity of the landscape, and
experience of the soil scientist. Observations are made to test and refine the soil-
landscape model and predictions and to verify the classification of the soils at specific
locations. Once the soil-landscape model is refined, a significantly smaller number of
measurements of individual soil properties are made and recorded. These
measurements may include field measurements, such as those for color, depth to
bedrock, and texture, and laboratory measurements, such as those for content of
sand, silt, clay, salt, and other components. Properties of each soil typically vary from
one point to another across the landscape.
Observations for map unit components are aggregated to develop ranges of
characteristics for the components. The aggregated values are presented. Direct
measurements do not exist for every property presented for every map unit
component. Values for some properties are estimated from combinations of other
properties.
While a soil survey is in progress, samples of some of the soils in the area generally
are collected for laboratory analyses and for engineering tests. Soil scientists interpret
the data from these analyses and tests as well as the field-observed characteristics
and the soil properties to determine the expected behavior of the soils under different
uses. Interpretations for all of the soils are field tested through observation of the soils
in different uses and under different levels of management. Some interpretations are
modified to fit local conditions, and some new interpretations are developed to meet
local needs. Data are assembled from other sources, such as research information,
production records, and field experience of specialists. For example, data on crop
yields under defined levels of management are assembled from farm records and from
field or plot experiments on the same kinds of soil.
Predictions about soil behavior are based not only on soil properties but also on such
variables as climate and biological activity. Soil conditions are predictable over long
periods of time, but they are not predictable from year to year. For example, soil
scientists can predict with a fairly high degree of accuracy that a given soil will have
a high water table within certain depths in most years, but they cannot predict that a
high water table will always be at a specific level in the soil on a specific date.
After soil scientists located and identified the significant natural bodies of soil in the
survey area, they drew the boundaries of these bodies on aerial photographs and
identified each as a specific map unit. Aerial photographs show trees, buildings, fields,
roads, and rivers, all of which help in locating boundaries accurately.
Custom Soil Resource Report
6
Soil Map
The soil map section includes the soil map for the defined area of interest, a list of soil
map units on the map and extent of each map unit, and cartographic symbols
displayed on the map. Also presented are various metadata about data used to
produce the map, and a description of each soil map unit.
7
8
Custom Soil Resource Report
Soil Map
4484100 4484300 4484500 4484700 4484900 4485100
4484100 4484300 4484500 4484700 4484900 4485100
497500 497700 497900 498100 498300 498500 498700 498900 499100 499300
497500 497700 497900 498100 498300 498500 498700 498900 499100 499300
40° 31' 4'' N
105° 1' 46'' W
40° 31' 4'' N
105° 0' 27'' W
40° 30' 25'' N
105° 1' 46'' W
40° 30' 25'' N
105° 0' 27'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 400 800 1600 2400
Feet
0 100 200 400 600
Meters
Map Scale: 1:8,510 if printed on A landscape (11" x 8.5") sheet.
Warning: Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
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: http://websoilsurvey.nrcs.usda.gov
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 of
Map Unit Legend
Larimer County Area, Colorado (CO644)
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
34 Fort Collins loam, 0 to 1 percent
slopes
3.4 0.9%
35 Fort Collins loam, 0 to 3 percent
slopes
24.0 6.6%
36 Fort Collins loam, 3 to 5 percent
slopes
42.9 11.9%
41 Garrett loam, 1 to 3 percent
slopes
1.0 0.3%
73 Nunn clay loam, 0 to 1 percent
slopes
51.4 14.2%
74 Nunn clay loam, 1 to 3 percent
slopes
185.8 51.5%
76 Nunn clay loam, wet, 1 to 3
percent slopes
44.4 12.3%
103 Stoneham loam, 5 to 9 percent
slopes
8.1 2.2%
Totals for Area of Interest 361.0 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the soils
or miscellaneous areas in the survey area. The map unit descriptions, along with the
maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the landscape,
however, the soils are natural phenomena, and they have the characteristic variability
of all natural phenomena. Thus, the range of some observed properties may extend
beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic
class rarely, if ever, can be mapped without including areas of other taxonomic
classes. Consequently, every map unit is made up of the soils or miscellaneous areas
for which it is named and some minor components that belong to taxonomic classes
other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They generally
are in small areas and could not be mapped separately because of the scale used.
Some small areas of strongly contrasting soils or miscellaneous areas are identified
Custom Soil Resource Report
10
by a special symbol on the maps. If included in the database for a given area, the
contrasting minor components are identified in the map unit descriptions along with
some characteristics of each. A few areas of minor components may not have been
observed, and consequently they are not mentioned in the descriptions, especially
where the pattern was so complex that it was impractical to make enough observations
to identify all the soils and miscellaneous areas on the landscape.
The presence of minor components in a map unit in no way diminishes the usefulness
or accuracy of the data. The objective of mapping is not to delineate pure taxonomic
classes but rather to separate the landscape into landforms or landform segments that
have similar use and management requirements. The delineation of such segments
on the map provides sufficient information for the development of resource plans. If
intensive use of small areas is planned, however, onsite investigation is needed to
define and locate the soils and miscellaneous areas.
An identifying symbol precedes the map unit name in the map unit descriptions. Each
description includes general facts about the unit and gives important soil properties
and qualities.
Soils that have profiles that are almost alike make up a soil series. Except for
differences in texture of the surface layer, all the soils of a series have major horizons
that are similar in composition, thickness, and arrangement.
Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity,
degree of erosion, and other characteristics that affect their use. On the basis of such
differences, a soil series is divided into soil phases. Most of the areas shown on the
detailed soil maps are phases of soil series. The name of a soil phase commonly
indicates a feature that affects use or management. For example, Alpha silt loam, 0
to 2 percent slopes, is a phase of the Alpha series.
Some map units are made up of two or more major soils or miscellaneous areas.
These map units are complexes, associations, or undifferentiated groups.
A complex consists of two or more soils or miscellaneous areas in such an intricate
pattern or in such small areas that they cannot be shown separately on the maps. The
pattern and proportion of the soils or miscellaneous areas are somewhat similar in all
areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example.
An association is made up of two or more geographically associated soils or
miscellaneous areas that are shown as one unit on the maps. Because of present or
anticipated uses of the map units in the survey area, it was not considered practical
or necessary to map the soils or miscellaneous areas separately. The pattern and
relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-
Beta association, 0 to 2 percent slopes, is an example.
An undifferentiated group is made up of two or more soils or miscellaneous areas that
could be mapped individually but are mapped as one unit because similar
interpretations can be made for use and management. The pattern and proportion of
the soils or miscellaneous areas in a mapped area are not uniform. An area can be
made up of only one of the major soils or miscellaneous areas, or it can be made up
of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example.
Some surveys include miscellaneous areas. Such areas have little or no soil material
and support little or no vegetation. Rock outcrop is an example.
Custom Soil Resource Report
11
Larimer County Area, Colorado
34—Fort Collins loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: jpw7
Elevation: 4,800 to 5,500 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: 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: Fans, terraces
Landform position (three-dimensional): Base slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 8 inches: loam
H2 - 8 to 18 inches: loam, clay loam
H2 - 8 to 18 inches: loam, silt loam, fine sandy loam
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
H3 - 18 to 60 inches:
Properties and qualities
Slope: 0 to 1 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
(0.60 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 26.0 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3c
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067XY002CO)
Hydric soil rating: No
Custom Soil Resource Report
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Minor Components
Stoneham
Percent of map unit: 6 percent
Hydric soil rating: No
Larim
Percent of map unit: 5 percent
Hydric soil rating: No
Ascalon
Percent of map unit: 4 percent
Hydric soil rating: No
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
Custom Soil Resource Report
13
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
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
36—Fort Collins loam, 3 to 5 percent slopes
Map Unit Setting
National map unit symbol: jpw9
Elevation: 4,800 to 5,500 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: Prime farmland if irrigated
Map Unit Composition
Fort collins and similar soils: 90 percent
Custom Soil Resource Report
14
Minor components: 10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Fort Collins
Setting
Landform: Terraces, fans
Landform position (three-dimensional): Base slope, riser
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 9 inches: loam
H2 - 9 to 20 inches: loam, clay loam
H2 - 9 to 20 inches: loam, silt loam, fine sandy loam
H3 - 20 to 60 inches:
H3 - 20 to 60 inches:
H3 - 20 to 60 inches:
Properties and qualities
Slope: 3 to 5 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
(0.60 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 25.5 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Ecological site: Loamy Plains (R067XY002CO)
Hydric soil rating: No
Minor Components
Ascalon
Percent of map unit: 5 percent
Hydric soil rating: No
Kim
Percent of map unit: 3 percent
Hydric soil rating: No
Stoneham
Percent of map unit: 2 percent
Hydric soil rating: No
Custom Soil Resource Report
15
41—Garrett loam, 1 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpwh
Elevation: 5,200 to 6,000 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: Prime farmland if irrigated
Map Unit Composition
Garrett and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Garrett
Setting
Landform: Terraces, fans
Landform position (three-dimensional): Base slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium derived from sandstone and shale
Typical profile
H1 - 0 to 8 inches: loam
H2 - 8 to 39 inches: sandy clay loam, sandy loam
H2 - 8 to 39 inches: sandy loam
H3 - 39 to 60 inches:
Properties and qualities
Slope: 1 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
(0.60 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: 10 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 12.9 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Ecological site: Overflow (R049XY036CO)
Hydric soil rating: No
Custom Soil Resource Report
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Minor Components
Otero
Percent of map unit: 10 percent
Hydric soil rating: No
Connerton
Percent of map unit: 3 percent
Hydric soil rating: No
Harlan
Percent of map unit: 2 percent
Hydric soil rating: No
73—Nunn clay loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: 2tlng
Elevation: 4,100 to 5,700 feet
Mean annual precipitation: 14 to 15 inches
Mean annual air temperature: 48 to 52 degrees F
Frost-free period: 135 to 152 days
Farmland classification: Prime farmland if irrigated
Map Unit Composition
Nunn and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn
Setting
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Pleistocene aged alluvium derived from igneous, metamorphic and
sedimentary rock and/or eolian deposits
Typical profile
Ap - 0 to 6 inches: clay loam
Bt1 - 6 to 10 inches: clay loam
Bt2 - 10 to 26 inches: clay loam
Btk - 26 to 31 inches: clay loam
Bk1 - 31 to 47 inches: loam
Bk2 - 47 to 80 inches: loam
Properties and qualities
Slope: 0 to 1 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Custom Soil Resource Report
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Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 7 percent
Salinity, maximum in profile: Nonsaline (0.1 to 1.0 mmhos/cm)
Sodium adsorption ratio, maximum in profile: 0.5
Available water storage in profile: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 4e
Hydrologic Soil Group: C
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit: 10 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Clayey Plains (R067BY042CO)
Hydric soil rating: No
Wages
Percent of map unit: 5 percent
Landform: Terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Ecological site: Loamy Plains (R067BY002CO)
Hydric soil rating: No
74—Nunn clay loam, 1 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpxn
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: Prime farmland if irrigated
Map Unit Composition
Nunn and similar soils: 85 percent
Custom Soil Resource Report
18
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn
Setting
Landform: Terraces, fans
Landform position (three-dimensional): Base slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 10 inches: clay loam
H2 - 10 to 60 inches: clay loam, clay
H2 - 10 to 60 inches:
Properties and qualities
Slope: 1 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: High
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.20 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Calcium carbonate, maximum in profile: 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 18.9 inches)
Interpretive groups
Land capability classification (irrigated): 2e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: C
Hydric soil rating: No
Minor Components
Ulm
Percent of map unit: 10 percent
Hydric soil rating: No
Satanta
Percent of map unit: 5 percent
Hydric soil rating: No
76—Nunn clay loam, wet, 1 to 3 percent slopes
Map Unit Setting
National map unit symbol: jpxq
Elevation: 4,800 to 5,600 feet
Custom Soil Resource Report
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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: Prime farmland if irrigated
Map Unit Composition
Nunn, wet, and similar soils: 90 percent
Minor components: 10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Nunn, Wet
Setting
Landform: Alluvial fans, stream terraces
Landform position (three-dimensional): Base slope, tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 10 inches: clay loam
H2 - 10 to 47 inches: clay loam, clay
H2 - 10 to 47 inches: clay loam, loam, gravelly sandy loam
H3 - 47 to 60 inches:
H3 - 47 to 60 inches:
H3 - 47 to 60 inches:
Properties and qualities
Slope: 1 to 3 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Somewhat poorly drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): Moderately low to
moderately high (0.06 to 0.60 in/hr)
Depth to water table: About 24 to 36 inches
Frequency of flooding: Rare
Frequency of ponding: None
Calcium carbonate, maximum in profile: 10 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 19.8 inches)
Interpretive groups
Land capability classification (irrigated): 2w
Land capability classification (nonirrigated): 3s
Hydrologic Soil Group: C
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit: 6 percent
Hydric soil rating: No
Dacono
Percent of map unit: 3 percent
Hydric soil rating: No
Custom Soil Resource Report
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Mollic halaquepts
Percent of map unit: 1 percent
Landform: Swales
Hydric soil rating: Yes
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:
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)
Custom Soil Resource Report
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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
22
Soil Information for All Uses
Soil Properties and Qualities
The Soil Properties and Qualities section includes various soil properties and qualities
displayed as thematic maps with a summary table for the soil map units in the selected
area of interest. A single value or rating for each map unit is generated by aggregating
the interpretive ratings of individual map unit components. This aggregation process
is defined for each property or quality.
Soil Qualities and Features
Soil qualities are behavior and performance attributes that are not directly measured,
but are inferred from observations of dynamic conditions and from soil properties.
Example soil qualities include natural drainage, and frost action. Soil features are
attributes that are not directly part of the soil. Example soil features include slope and
depth to restrictive layer. These features can greatly impact the use and management
of the soil.
Hydrologic Soil Group (Ziegler Townhomes)
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.
23
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.
Custom Soil Resource Report
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25
Custom Soil Resource Report
Map—Hydrologic Soil Group (Ziegler Townhomes)
4484100 4484300 4484500 4484700 4484900 4485100
4484100 4484300 4484500 4484700 4484900 4485100
497500 497700 497900 498100 498300 498500 498700 498900 499100 499300
497500 497700 497900 498100 498300 498500 498700 498900 499100 499300
40° 31' 4'' N
105° 1' 46'' W
40° 31' 4'' N
105° 0' 27'' W
40° 30' 25'' N
105° 1' 46'' W
40° 30' 25'' N
105° 0' 27'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 400 800 1600 2400
Feet
0 100 200 400 600
Meters
Map Scale: 1:8,510 if printed on A landscape (11" x 8.5") sheet.
Warning: 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: http://websoilsurvey.nrcs.usda.gov
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 of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Table—Hydrologic Soil Group (Ziegler Townhomes)
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
34 Fort Collins loam, 0 to 1
percent slopes
B 3.4 0.9%
35 Fort Collins loam, 0 to 3
percent slopes
C 24.0 6.6%
36 Fort Collins loam, 3 to 5
percent slopes
B 42.9 11.9%
41 Garrett loam, 1 to 3
percent slopes
B 1.0 0.3%
73 Nunn clay loam, 0 to 1
percent slopes
C 51.4 14.2%
74 Nunn clay loam, 1 to 3
percent slopes
C 185.8 51.5%
76 Nunn clay loam, wet, 1 to
3 percent slopes
C 44.4 12.3%
103 Stoneham loam, 5 to 9
percent slopes
B 8.1 2.2%
Totals for Area of Interest 361.0 100.0%
Rating Options—Hydrologic Soil Group (Ziegler Townhomes)
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Custom Soil Resource Report
27
References
American Association of State Highway and Transportation Officials (AASHTO). 2004.
Standard specifications for transportation materials and methods of sampling and
testing. 24th edition.
American Society for Testing and Materials (ASTM). 2005. Standard classification of
soils for engineering purposes. ASTM Standard D2487-00.
Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of
wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service
FWS/OBS-79/31.
Federal Register. July 13, 1994. Changes in hydric soils of the United States.
Federal Register. September 18, 2002. Hydric soils of the United States.
Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils
in the United States.
National Research Council. 1995. Wetlands: Characteristics and boundaries.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S.
Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/soils/?cid=nrcs142p2_054262
Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making
and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service,
U.S. Department of Agriculture Handbook 436. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/national/soils/?cid=nrcs142p2_053577
Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of
Agriculture, Natural Resources Conservation Service. http://www.nrcs.usda.gov/wps/
portal/nrcs/detail/national/soils/?cid=nrcs142p2_053580
Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and
Delaware Department of Natural Resources and Environmental Control, Wetlands
Section.
United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of
Engineers wetlands delineation manual. Waterways Experiment Station Technical
Report Y-87-1.
United States Department of Agriculture, Natural Resources Conservation Service.
National forestry manual. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/
home/?cid=nrcs142p2_053374
United States Department of Agriculture, Natural Resources Conservation Service.
National range and pasture handbook. http://www.nrcs.usda.gov/wps/portal/nrcs/
detail/national/landuse/rangepasture/?cid=stelprdb1043084
28
United States Department of Agriculture, Natural Resources Conservation Service.
National soil survey handbook, title 430-VI. http://www.nrcs.usda.gov/wps/portal/
nrcs/detail/soils/scientists/?cid=nrcs142p2_054242
United States Department of Agriculture, Natural Resources Conservation Service.
2006. Land resource regions and major land resource areas of the United States, the
Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296.
http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/soils/?
cid=nrcs142p2_053624
United States Department of Agriculture, Soil Conservation Service. 1961. Land
capability classification. U.S. Department of Agriculture Handbook 210. http://
www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_052290.pdf
Custom Soil Resource Report
29
MAP POCKET
DR1 –DRAINAGE EXHIBIT
Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
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.
Custom Soil Resource Report
26
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
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.
Custom Soil Resource Report
9
Design Storm Required Detention Volume
Developed "C" =
D:\Projects\1124-002\Drainage\LID\1124-002_FAA_Vault 1.xlsm\
è
= æ
12 hr
D:\Projects\1124-002\Drainage\WatQual\1124-002_WQ Volume_Vault 1.xls
Stage (ft)
Stage - Discharge Curves
Weir Flow
Orifice Flow
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
D:\Projects\1124-002\Drainage\Inlets\1124-002_Area Inlets.xls
5.00
6.00
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Discharge (cfs)
Stage (ft)
Stage - Discharge Curves
Weir Flow
Orifice Flow
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
D:\Projects\1124-002\Drainage\Inlets\1124-002_Area Inlets.xls
COMBINED DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
A. Reese
February 15, 2017
Design
Point
Basins
Tc Calculated at
Upstream Design Point
Additional Gutter Flow Additional Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
D:\Projects\1124-002\Drainage\Hydrology\1124-002_Rational-Calcs_Proposed.xlsx\Combined-Tc
Q = C f ( C )( i )( A )
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
A1 A1 No 0.25 0.25 0.31 19 9.31% 3.3 3.3 3.0 0 - - - 220 1.51% 1.84 2.0 5 5 5
A2 A2 No 0.95 0.95 1.00 36 3.03% 1.2 1.2 0.8 162 1.77% 2.66 1.0 0 - - - 5 5 5
A3 A3 No 0.25 0.25 0.31 52 2.51% 8.5 8.5 7.8 145 1.66% 2.58 0.9 - - - 9 9 9
B1 B1 No 0.25 0.25 0.31 24 2.85% 5.4 5.4 5.0 235 1.96% 2.80 1.4 - - - 7 7 6
B2 B2 No 0.25 0.25 0.31 14 1.72% 5.0 5.0 4.6 52 0.52% 1.44 0.6 - - - 6 6 5
B3 B3 No 0.25 0.25 0.31 11 1.76% 4.4 4.4 4.1 21 0.47% 1.36 0.3 - - - 5 5 5
C1 C1 No 0.25 0.25 0.31 15 3.53% 4.0 4.0 3.7 279 0.50% 1.41 3.3 46 1.55% 1.87 0.4 8 8 7
C2a C2a No 0.95 0.95 1.00 31 2.77% 1.1 1.1 0.7 168 1.00% 2.00 1.4 - - - 5 5 5
C2b C2b No 0.95 0.95 1.00 39 3.15% 1.2 1.2 0.8 98 1.00% 2.00 0.8 - - - 5 5 5
C3 C3 No 0.25 0.25 0.31 40 3.07% 6.9 6.9 6.4 - - - - - - 7 7 6
C4 C4 No 0.25 0.25 0.31 17 6.93% 3.5 3.5 3.2 - - - 51 1.63% 1.91 0.4 5 5 5
D1 D1 No 0.25 0.25 0.31 43 4.14% 6.5 6.5 6.0 - - - - - - 6 6 6
D2 D2 No 0.95 0.95 1.00 40 3.39% 1.2 1.2 0.8 237 1.49% 2.44 1.6 - - - 5 5 5
OS1 OS1 No 0.95 0.95 1.00 32 1.56% 1.4 1.4 0.9 326 0.31% 1.11 4.9 - - - 6 6 6
OS2 OS2 No 0.95 0.95 1.00 26 1.97% 1.1 1.1 0.8 505 0.87% 1.86 4.5 - - - 6 6 5
DEVELOPED TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
A. Reese
February 15, 2017
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
C4 0.11 0.00 0.00 0.03 0.00 0.00 0.07 0.47 0.47 0.59 28%
D1 0.62 0.00 0.00 0.00 0.00 0.00 0.62 0.25 0.25 0.31 0%
D2 0.46 0.27 0.03 0.00 0.00 0.00 0.16 0.71 0.71 0.88 65%
Onsite Total 4.03 0.84 0.63 1.02 0.00 0.00 1.54 0.68 0.68 0.85 58%
OS1 2.06 0.27 0.03 0.12 0.00 0.00 1.63 0.39 0.39 0.49 20%
OS2 0.41 0.21 0.06 0.00 0.00 0.00 0.14 0.71 0.71 0.89 65%
DEVELOPED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf = 1.00
February 15, 2017