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PRELIMINARY DRAINAGE REPORT
THE CROWNE AT SUNIGA
FORT COLLINS, COLORADO
JUNE 14, 2023
NORTHERNENGINEERING.COM
970.221.4158
FORT COLLINS
GREELEY
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FORT COLLINS | GREELEY COVER LETTER
June 14, 2023
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80526
RE: PRELIMINARY DRAINAGE REPORT FOR
THE CROWNE AT SUNIGA (1893-001)
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage Report for your review. This report
accompanies the Preliminary Development Review submittal for the Crowne at Suniga.
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 Crowne at Suniga multi-family
project. We understand 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.
SCHYLER KING, EIT BLAINE MATHISEN, PE
Project Engineer Project Engineer
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FORT COLLINS | GREELEY TABLE OF CONTENTS
TABLE OF CONTENTS
GENERAL LOCATION AND DESCRIPTION .......................................................... 1
DRAIN BASINS AND SUB-BASINS ..................................................................... 3
DRAINAGE DESIGN CRITERIA .......................................................................... 4
DRAINAGE FACILITY DESIGN ........................................................................... 7
CONCLUSIONS .............................................................................................. 9
REFERENCES ................................................................................................ 9
TABLES AND FIGURES
FIGURE 1 - VICINITY MAP .................................................................................................. 1
FIGURE 2 - AERIAL PHOTO ................................................................................................ 2
FIGURE 3 - FIRMETTE MAP 08069C0981G ........................................................................ 3
TABLE 1 - MAXIMUM RELEASE RATE CALCULATED BY AREA. ......................................... 8
TABLE 2 - SUMMARY OF NEW IMPERVIOUS AREAS BEING TREATED BY LID ................... 8
APPENDICES
APPENDIX A – HYDROLOGIC COMPUTATIONS
APPENDIX B – HYDRAULIC CALCULATIONS – FOR FUTURE USE
APPENDIX C –WATER QUALITY/LID COMPUTATIONS
APPENDIX D – EROSION CONTROL REPORT
APPENDIX E – EXCERPTS FROM PREVIOUS REPORTS AND USDA SOILS REPORT
MAP POCKET
DR1 – EXISTING DRAINAGE EXHIBIT
DR2 – DRAINAGE EXHIBIT
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GENERAL LOCATION AND DESCRIPTION
A. LOCATION
Vicinity Map
The Crowne at Suniga project site is located in the southwest quarter of Section 6, Township 7
North, Range 68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State
of Colorado.
The project site (refer to Figure 1) is bordered to the west by a multi-family complex and to the
north, east, and south by vacant lots.
There are no major drainageways located adjacent to the project site.
The NECCO Backbone runs parellel to East Suniga Road along the southern boundary of the
project site.
B. DESCRIPTION OF PROPERTY
The Crowne at Suniga project is comprised of ±11.07 acres.
The site is currently vacant with native grasses.
The existing on-site runoff generally drains from the northwest-to-southeast across flat grades
(e.g., <2.00%) into either North Lemay Avenue or an area inlet located in the southeast corner of
the site, along the southern property boundary. Runoff leaving the east side of the site is
routed to a 15' Type R inlet on the west side on North Lemay Avenue, just north of East Sungia
Road. From there, runoff is then routed via a 24” RCP storm drain to the NECCO Backbone,
Storm line A1, which outfalls into the Vine Detention Pond. Runoff leaving the southern side of
Figure 1 - Vicinity map
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the site is routed to an area inlet via a swale that runs west-to-east along the north side of East
Suniga Road. Runoff is then routed to the NECCO Backbone, Storm Line A1, via an 18” RCP
storm drain. Both the the Vine Detention Pond and Storm Line A1 of the NECCO Backbone are
defined in the North East College Corridor Outfall (NECCO) Design Report, dated August 2009.
The Crowne at Suniga will maintain historical drainage patterns by routing runoff into the Vine
Detention Pond via Storm Line A1 of the NECCO Backbone.
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), 79.6% of the site consists of
Loveland Clay loam (Hydrologic Soil Group C), 19.2% of the site consists of Nunn clay loam
(Hydrologic Soil Group C), and 1.2% of the site consists of Fort Collins loam (Hydrologic Soil
Group C).
According to “Geotechnical Subsurface Exploration Report Proposed Apartment Complex
Developmenet – Graham Property Northeast Corner of 9th Street and Suniga Road” dated June
1, 2022 by Earth Engineering Consultants, LLC shows that groundwater at this location is
roughly 7’ deep.
There is no major drainageway within or adjacent to the project site.
The proposed development will consist of six multi-family buildings containing a total of 260
units. Other proposed improvements include a clubhouse, new concrete drive aisles, new
sidewalks, and new landscaping.
The proposed land use is multi-family dwellings. This use is permitted in the Medium Density
Mixed-use Nebighborhood (M-M-N).
Figure 2 - Aerial Photo
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C. FLOODPLAIN
A small portion of the subject property is located within the 500-year FEMA regulatory
floodplain. However, the project site is not located within a FEMA-designate 100-year
floodplain per Map Number 08069CO981G (Effective date: June 17, 2006). A small portion of
the site is located within LOMR 19-08-0751P eff. 06/15/2020. Additionally, the project site is
not located in a City of Fort Collins regulated floodplain.
DRAIN BASINS AND SUB-BASINS
A. MAJOR BASIN DESCRIPTION
The Crowne at Suniga Project is located within the City of Fort Collins Dry Creek major
drainage basin. Specifically, the project site is situated in the south-central portion of this
major drainage basin. This basin is located in north central Fort Collins and has a drainage
area of approximately 62 square miles. The land use in the upper and middle portions of the
basin is primarily rangeland and irrigated hay meadows and pastures. The majority of the
lower basin is developed and includes commercial, industrial and residential uses. The
natural channel has disappeared in some areas of the lower basin because of urbanization.
Figure 3 - FIRMette Map 08069C0981G
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B. SUB-BASIN DESCRIPTION
The project will outfall into Storm Line A1 of the NECCO Backbone which outfalls into the Vine
Detention Pond.
The subject site lies within basin 417 as described in the “North East College Corridor Outfall
(NECCO) Design Report”. Basin 417 is approximetley 17.0 Acers and was modeled as a
devloped basin that drains into the manhole riser A3 of the NECCO Backbone with a release
rate of 0.2 cfs per acer. Please refer to appendix E for exerpts from the NECCO Design Report.
The existing subject site can be defined with one (1) major sub-basins that encompasses the
entire project site.
The existing site runoff generally drains from the northwest-to-southeast and into either North
Lemay Avenue or an area inlet located in the southeast corner of the site, along the southern
property boundary. Runoff leaving the east side of the site is routed to a 15' Type R inlet on the
west side on North Lemay Avenue, just north of East Sungia Road. From there, runoff is then
routed via a 24” RCP storm drain to the NECCO Backbone, Storm line A1, which outfalls into the
Vine Detention Pond. Runoff leaving the southern side of the site is routed to an area inlet via a
swale that runs west-to-east along the north side of East Suniga Road. Runoff is then routed to
the NECCO Backbone, Storm Line A1, via an 18” RCP storm drain.
The project site does not receive runoff from contiguous off-site properties.
DRAINAGE DESIGN CRITERIA
A. ORIGINAL PROVISIONS AND PREVIOUS STUDIES
After coordination with City staff on 2/13/2023, the stormwater design for the Crowne at
Suniga will use the 2-year release rate as prescribed by the NECCO Design Report, but with
the understanding that basins OS1-OS4 are fringe basins and are mostly pervious and
therefore will be allowed to free release into adjacent curb & gutter which will convey runoff
into the Storm Line A1 of the NECCO Backbone. The rest of the site will be captured, treated,
and detained per the FCSWCM with a release rate of 0.2 cfs per acre which will apply only to
the interior basins and not the mostly pervious fringe basins previously discussed.
The max release rate for Crowne at Suniga is 1.88 cfs. This was calculated using the 0.2
cfs/acre from the NECCO report and multiplying it by the area that is able to be captured
(9.41 acres). Refer to Major Basin SC in the Proposed Rational Calculations spreadsheet
found in Appendix A for additional clarification.
Please refer to Appendix E for excerpts from previous drainage studies. Complete copies can
be provided at request.
B. STORMWATER MANAGEMENT STRATEGY
The overall stormwater management strategy employed with the Crowne at Suniga 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.
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Step 1 – Employ Runoff Reduction Practices.
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use of implementing multiple Low Impact Development (LID) strategies, including:
· Providing vegetated open areas throughout the site to reduce the overall
impervious area and to minimize directly connected impervious areas.
· Routing runoff through the drain rock within the Stormtech system to increase
concentration-time and promote 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. Water quality treatment will occur in the Stomtech Isolator chambers on the
south side of the site.
Step 3 – Stabilize Drainageways.
As stated in Section I. B. 6. above, there is no major drainageway adjacent to the subject site.
While this step may not seem applicable to the Crowne at Suniga, the proposed project
indirectly helps achieve stabilized drainageways, nonetheless. Once again, site selection has
a positive effect on stream stabilization. Developing an infill site with existing stormwater
infrastructure, combined with LID and DCIA strategies, reduces the likelihood of bed and
bank erosion. Furthermore, this project will pay one-time stormwater development fees and
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. However, trash will
be stored internal to buildings, this will reduce the potential impacts of garbage making its
way downstream.
C. DEVELOPMENT CRITERIA REFERENCE AND CONSTRAINTS
The project site falls within the NECCO report boundary. Therefore, Crowne at Suniga must
follow the criteria set forth by the NECCO report dated August, 2009. Crowne at Suniga is
responsible for detention, water quality, and LID.
The site plan is constrained on all three sides by public streets. It is bound by 9th Street to the
west, East Suniga Road to the south, and North lemay Avenue to the East and North.
D. HYDROLOGICAL CRITERIA
The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in Figure
3.4-1 of the FCSCM, serves as the source for all hydrologic computations associated with the
Crowne at Suniga development. Tabulated data contained in Table 3.4-1 has been utilized for
Rational Method runoff calculations.
The Rational Method has been employed to compute stormwater runoff utilizing coefficients
contained in Tables RO-11 and RO-12 of the FCSCM.
The Rational Formula-based Modified Federal Aviation Administration (FAA) procedure has
been utilized for detention storage calculations.
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Three separate design storms have been utilized to address distinct drainage scenarios. The
first event analyzed is the "Minor" or "Initial" Storm, with a 2-year recurrence interval. The
second event considered is the "Major Storm," which has a 100-year recurrence interval. The
final event analyzed was the 10-year recurrence interval for comparative analysis only.
E. HYDRAULIC CRITERIA
The drainage facilities proposed with the Crowne at Suniga project are designed in accordance
with criteria outlined in the NECCO Backbone Design Report, FCSCM and/or the Mile High Flood
District's (UDFCD) Urban Storm Drainage Criteria Manual.
As stated in Section I. C. 1. above, the subject property is not located within a FEMA 100-year or
a City of Fort Collins designated floodplain.
F. FLOODPLAIN REGULATIONS COMPLIANCE
As stated in Section I. C. 1. above, the subject property is not located within a FEMA 100-year
or a City of Fort Collins designated floodplain.
G. MODIFICATIONS OF CRITERIA
No formal modifications are requested at this time.
H. CONFORMANCE WITH LOW IMPACT DEVELOPMENT (LID)
The project site will conform with the requirement to treat a minimum of 75% of newly or
modified impervious area 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, 85%
of the proposed site will receive LID Treatment, which exceeds the minimum required.
I. SIZING OF LID FACILITIES
The Stormtech isolator chambers were sized by determining the required water quality capture
volume (WQCV) for Major Basin SC. A 12-hour drain time was used in this calculation. Once the
WQCV was identified, the minimum number of vaults needed to achieve this volume was
calculated. The required WQCV for Major Basin SC is 13,162 cf . A minimum of 54, MC-7200
chambers will be required to meet the storage needs and will supply 14,434 cf of WQCV. Each
isolator row will have an inspection port and a Nyloplast basin at the end for easy maintenance
and cleanout.
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 has been increased as needed
to confirm the resulting volume is provided within the empty volume of the uderground
chambers. This is intended to ensure the chambers do not become overwhelmed in the water
quality storm event before "discharging" flows into the surrounding aggregates.
For additional clarification, please refer to Appendix C.
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DRAINAGE FACILITY DESIGN
A. GENERAL CONCEPT
The main objective of the Crowne at Suniga drainage design is to maintain existing drainage
patterns and to not adversely impact downstream infrastructure.
No notable off-site runoff passes directly through the project site.
A list of tables and figures used within this report can be found in the Table of Contents at the
front of this document. The tables and figures are located within the sections to which the
content best applies.
Drainage for the project site has been analyzed using two (2) Major Drainage Basins, designated
as Basins SC, & OSC. Both basins have associated sub-basins. The drainage patterns
anticipated for the basins are further described below.
Major Basin SC
Major Basin SC (Stormtech Combined) has 27 sub-basins A-L & R1-R15. Sub-basins A-L
consist of asphalt & concrete paving, and landscaping. Sub-basins R1-R15 consist of
building roofs only. Major Basin SC has a total area of 9.41 acres and an impervious value of
82%. All runoff generated within Major Basin SC is routed via a combination of overland
flow, storm line conveyance, and curb and gutter routing to the Stormtech system. All ‘R’
sub-basins will have roof drain connections to adjacent storm drains and will be detailed at
final. Major Basin SC will receive LID treatment and detention within the Stormtech system
through two isolator rows that consist of 86 MC-7200 chambers. All flows within the Major
Basin SC will first be routed through the isolator rows for water quality treatment. After
treatment, flows will be detained by the remaining Stormtech system. After being treated
and detained by the Stormtech system runoff from Major Basin SC will be routed to the
NECCO Backbone via an HDPE pipe that is connected to a proposed manhole, which will
replace the existing area inlet located in the south-east portion of the site. A detailed
description of each sub basin will be provided at final.
Major Basin OSC
Major Basin OSC (off-Site Combined) has four (4) sub-basins (OS1-OS4) and is associated
with the outer permitter of the Crowne at Suniga project site. Major Basin OSC has a total
area of 1.66 acres and an impervious value of 6%. Major Basin OSC consists of primarily
landscaping and some concrete and asphalt paving. All runoff generated within Major Basin
OSC is routed via a combination of overland flow, and curb and gutter routing to existing
and proposed inlets located on Lindenmeier Road, East Suniga Road, & North Lemay
Avenue. These existing inlets outfall into the NECCO Backbone. Runoff generated in Major
Basin OSC is negligible and will not have an adverse impact on downstream infrastructure.
A detailed description of each sub basin will be provided at final.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of this report.
In addition, excerpts from earlier drainage reports referenced in this Section can be found in
Appendix E.
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B. SPECIFIC DETAILS
As mentioned in Section III.A. the historical 2-year release rate, as perscribed by the NECCO
Design Report, will be used as the allowable release rate for the project site. City staff agreed
that the Major Basin OSC is mostly pervious and therefore will be allowed to free release into
adjacent curb & gutter. However, Major Basin OSC’s area of 1.66 acres will be subtracted from
the the project sites total area of 11.07 acres and the remaining area of 9.41 acres (Major Basin
SC) will be multiplied by the perscirbed 0.2 cfs/acre to obtain the release rate from the
Stormtech system. See Table 1. below.
Max Release Rate Calculation by Area
Project Site Area (acres) 11.07
Major Basin OSC Area (acres) 1.66
Major Basin SC Area (acres) 9.41
Max Release Rate (cfs) (9.28 ac x 0.2 cfs/ac) 1.88
Table 1 - Maximum release rate calculated by area.
LID treatment will be provided for Major Basin SC within the Stormtech System.
LID Summary Table
Area (ac)
%
Impervious
Area of
Impervious
(ac)
%
Impervious
Area
Total Area Treated (Basin SC) 9.41 82% 7.72 99%
Total Area Not Being Treated by LID (Basin OSC) 1.66 6% 0.10 1%
Table 2 - Summary of new impervious areas being treated by LID
The area that is not getting treated by LID is unable to be captured and routed to the Stormtech
system for a few reasons.
A. Existing sanitary lines in this area are very shallow and it makes it impossible to
have storm lines that are capable of bucking grade all the way back to the Stormtech
system.
B. The site is bordered by existing easements and Crowne at Suniga is unable to
modify the grading in these areas that allow for drainage to flow back into the site.
It should be noted that the areas that are not getting LID treatment are mostly landscaping and
thus will have negligible impact on downstream water quality.
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CONCLUSIONS
A. COMPLIANCE WITH STANDARDS
The design elements comply without the need for variances and meet all LID requirements.
The drainage design proposed for the Crowne at Suniga complies with the City of Fort Collins
Stormwater Criteria Manual as well as the NECCO report.
There are no FEMA 100-year regulatory floodplains associated with the Crowne at Suniga
development.
The drainage plan and stormwater management measures proposed with the Crowne at
Suniga project are compliant with all applicable State and Federal regulations governing
stormwater discharge.
B. DRAINAGE CONCEPT
The drainage design proposed with this project will ensure that all downstream infrastructure
is not adversely impacted with this development. The Crowne at Suniga project will provide on-
site detention and LID treatment for runoff.
The Crowne at Suniga development will not impact the Master Drainage Plan
recommendations for the Dry Creek Major Drainage Basin.
REFERENCES
1. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, adopted by Ordinance No.
159, 2018, and referenced in Section 26-500 of the City of Fort Collins Municipal Code.
2. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation Service,
United States Department of Agriculture.
3. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control District,
Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
4. Geotechnical Subsurface Exploration Report Proposed Apartment Complex Development – Graham
Property Northeast Corner of 9th Street and Suniga Road, Earth Engineering Consultants, Windsor,
Colorado, June 2022
5. North East College Corridor Outfall (NECCO) Design Report, Ayres Associates, Fort Collins, Colorado,
August 2009
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FORT COLLINS | GREELEY APPENDIX
APPENDIX A
HYDROLOGIC COMPUTATIONS
CHARACTER OF SURFACE1:
Percentage
Impervious
2-yr Runoff
Coefficient
10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.00
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
EX 11.08 11.08 2%0.25 0.25 0.31
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
EXISTING BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
EX 0.25 0.31 488 0.81% 37.7 35.1 160 1.27% 0.013 0.08 2.45 1.1 13.6 38.8 36.2 13.6 13.6
EXISTING DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10
Rational Method Equation:
Rainfall Intensity:
EX 11.08 13.6 13.6 0.25 0.31 1.95 3.34 6.82 5.40 9.25 23.40
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
EXISTING RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
Tc100
(min)
()()()AiCCQf=
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100
Q2
(cfs)
Q100
(cfs)
EX 11.08 13.6 13.6 0.25 0.31 5.40 23.40
Rational Flow Summary | Existing Basin Flow Rates
2/8/20234:23 PM P:\1893-001\Drainage\Hydrology\1893-001_Existing Rational Calcs (FCSCM).xlsx\Summary Tables
Project Site Area (acres)11.07
Major Basin OSC Area (acres)1.66
Major Basin SC Area (acres)9.41
Max Release Rate (cfs) (9.28 ac x 0.2 cfs/ac)1.88
Max Release Rate Calculation by Area
CHARACTER OF SURFACE1: Percentage
Impervious
2-yr Runoff
Coefficient 10-yr Runoff
Coefficient
100-yr Runoff
Coefficient
Developed
Asphalt .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Concrete .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………100%0.95 0.95 1.00
Rooftop .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………90%0.95 0.95 1.00
Gravel .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Pavers .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………40%0.50 0.50 0.63
Landscape or Pervious Surface
Playgrounds .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………25%0.35 0.35 0.44
Lawns Clayey Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.25 0.25 0.31
Lawns Sandy Soil .…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..……………………………………………….…………………………..………………………………………………2%0.15 0.15 0.19
Notes:
Basin ID Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Rooftop
(ac)
Area of Lawns
(ac)
Composite
% Imperv.
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
A 0.54 0.41 0.06 0.00 0.07 86% 0.85 0.85 1.00
B 0.50 0.39 0.05 0.00 0.06 89% 0.87 0.87 1.00
C 0.62 0.39 0.04 0.00 0.19 70% 0.73 0.73 0.91
D 0.41 0.32 0.04 0.00 0.05 88% 0.87 0.87 1.00
E 0.84 0.63 0.08 0.00 0.13 84% 0.84 0.84 1.00
F 0.34 0.00 0.34 0.00 0.00 100% 0.95 0.95 1.00
G 0.45 0.23 0.07 0.00 0.15 66% 0.71 0.71 0.89
H 0.65 0.44 0.11 0.00 0.11 83% 0.83 0.83 1.00
I 1.45 1.02 0.13 0.00 0.30 80% 0.81 0.81 1.00
J 0.24 0.17 0.04 0.00 0.02 91% 0.88 0.88 1.00
K 0.22 0.08 0.04 0.00 0.09 58% 0.65 0.65 0.81
L 0.15 0.00 0.02 0.00 0.14 12% 0.32 0.32 0.40
R1 0.16 0.00 0.00 0.16 0.00 90% 0.95 0.95 1.00
R2 0.12 0.00 0.00 0.12 0.00 90% 0.95 0.95 1.00
R3 0.24 0.00 0.00 0.24 0.00 90% 0.95 0.95 1.00
R4 0.17 0.00 0.00 0.17 0.00 90% 0.95 0.95 1.00
R5 0.14 0.00 0.00 0.14 0.00 90% 0.95 0.95 1.00
R6 0.22 0.00 0.00 0.22 0.00 90% 0.95 0.95 1.00
R7 0.15 0.00 0.00 0.15 0.00 90% 0.95 0.95 1.00
R8 0.15 0.00 0.00 0.15 0.00 90% 0.95 0.95 1.00
R9 0.20 0.00 0.00 0.20 0.00 90% 0.95 0.95 1.00
R10 0.26 0.00 0.00 0.26 0.00 90% 0.95 0.95 1.00
R11 0.14 0.00 0.00 0.14 0.00 90% 0.95 0.95 1.00
R12 0.34 0.00 0.00 0.34 0.00 90% 0.95 0.95 1.00
R13 0.24 0.00 0.00 0.24 0.00 90% 0.95 0.95 1.00
R14 0.31 0.00 0.00 0.18 0.13 53% 0.66 0.66 0.83
R15 0.18 0.00 0.00 0.18 0.00 90% 0.95 0.95 1.00
OS1 0.48 0.00 0.02 0.00 0.46 6% 0.28 0.28 0.35
OS2 0.56 0.02 0.02 0.00 0.52 9% 0.30 0.30 0.38
OS3 0.34 0.00 0.00 0.00 0.34 2% 0.25 0.25 0.31
OS4 0.27 0.00 0.01 0.00 0.26 6% 0.28 0.28 0.35
MAJOR BASIN SC (STORMTECH, COMBINED)9.41 4.08 1.00 2.88 1.45
82% 0.84 0.84 1.00
MAJOR BASIN OSC (OFF-SITE, COMBINED)1.66 0.02 0.05 0.00 1.59
6% 0.28 0.28 0.35
DEVELOPED BASIN % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
2) Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Chapter 3. Table 3.2-1 and 3.2-2
1) Percentage impervious taken from the Fort Collins Stormwater Criteria Manual, Chapter 5, Table 4.1-2 and Table 4.1-3
Combined Basins
Overland Flow, Time of Concentration:
Channelized Flow, Time of Concentration:
Total Time of Concentration :
T c is the lesser of the values of Tc calculated using T c = T i + T t
C2 C100
Length,
L
(ft)
Slope,
S
(%)
Ti2 Ti100
Length,
L
(ft)
Slope,
S
(%)
Roughness
Coefficient
Assumed
Hydraulic
Radius
Velocity,
V
(ft/s)
Tt
(min)Tc (Eq. 3.3-5) Tc2 = Ti +Tt Tc100 = Ti +Tt Tc2 Tc100
a1 A 0.85 1.00 50 2.10%2.6 1.0 244 1.15%0.013 0.08 2.33 1.7 11.6 4.3 2.8 5.0 5.0
b1 B 0.87 1.00 50 1.36%2.7 1.2 244 1.15%0.013 0.08 2.33 1.7 11.6 4.5 2.9 5.0 5.0
c1 C 0.73 0.91 60 1.27%5.0 1.9 90 2.79%0.013 0.08 3.63 0.4 10.8 5.4 2.3 5.4 5.0
d1 D 0.87 1.00 90 2.10%3.2 1.4 75 0.61%0.013 0.08 1.70 0.7 10.9 3.9 2.1 5.0 5.0
e1 E 0.84 1.00 90 2.12%3.6 1.0 200 0.59%0.013 0.08 1.67 2.0 11.6 5.6 3.0 5.6 5.0
f1 F 0.95 1.00 120 1.15%2.9 2.0 0 N/A N/A N/A N/A N/A 10.7 2.9 2.0 5.0 5.0
g1 G 0.71 0.89 30 3.20%2.7 2.2 132 0.84%0.013 0.08 1.99 1.1 10.9 3.8 3.3 5.0 5.0
h1 H 0.83 1.00 30 2.10%2.2 0.8 225 0.80%0.013 0.08 1.94 1.9 11.4 4.1 2.7 5.0 5.0
i1 I 0.81 1.00 75 1.92%3.8 1.0 300 0.84%0.013 0.08 1.99 2.5 12.1 6.3 3.5 6.3 5.0
j1 J 0.88 1.00 30 2.10%1.8 0.8 165 1.12%0.013 0.08 2.30 1.2 11.1 3.0 2.0 5.0 5.0
k1 K 0.65 0.81 40 4.73%3.2 3.0 125 3.34%0.013 0.08 3.97 0.5 10.9 3.7 3.5 5.0 5.0
l1 L 0.32 0.40 75 8.49%6.2 5.6 0 N/A N/A N/A N/A N/A 10.4 6.2 5.6 6.2 5.6
R1 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R2 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R3 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R4 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R5 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R6 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R7 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R8 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R9 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R10 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R11 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R12 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R13 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
R14 0.66 0.83 46 2.19%4.3 2.7 0 N/A N/A N/A N/A N/A 10.3 4.3 2.7 5.0 5.0
R15 0.95 1.00 46 2.19%1.5 1.0 0 N/A N/A N/A N/A N/A 10.3 1.5 1.0 5.0 5.0
os1 OS1 0.28 0.35 71 10.95%5.8 5.3 557 1.01%0.013 0.08 2.19 4.2 13.5 10.1 9.6 10.1 9.6
os2 OS2 0.30 0.38 42 2.29%7.3 6.6 592 0.60%0.013 0.08 1.68 5.9 13.5 13.2 12.5 13.2 12.5
os3 OS3 0.25 0.31 70 6.91%7.0 6.5 379 0.58%0.013 0.08 1.66 3.8 12.5 10.8 10.3 10.8 10.3
os4 OS4 0.28 0.35 42 2.29% 7.5 6.9 592 0.60% 0.013 0.08 1.68 5.9 13.5 13.4 12.7 13.4 12.7
MAJOR BASIN SC
(STORMTECH, COMBINED)0.84 1.00 50 2.10% 2.7 1.0 244 1.15% 0.013 0.083 0.23 17.4 10.3 1.5 1.0 5.0 5.0
MAJOR BASIN OSC (OFF-
SITE, COMBINED)0.28 0.35 71 10.95% 5.8 5.3 59 9.49% 0.013 0.083 0.67 1.5 12.5 10.1 9.6 10.1 9.6
Combined Basins
DEVELOPED DIRECT TIME OF CONCENTRATION
Channelized Flow
Design
Point Basin
Overland Flow Time of Concentration
Frequency Adjustment Factor:
(Equation 3.3-2 FCSCM)
(Equation 5-5 FCSCM)
(Equation 5-4 FCSCM)
(Equation 3.3-5 FCSCM)
Table 3.2-3 FCSCM
Therefore Tc2=Tc10
Rational Method Equation:
Rainfall Intensity:
a1 A 0.54 5.0 5.0 0.85 1.00 2.85 4.87 9.95 1.30 2.23 5.35
b1 B 0.50 5.0 5.0 0.73 0.91 2.85 4.87 9.95 1.03 1.77 4.51
c1 C 0.62 5.0 5.0 0.73 0.91 2.85 4.87 9.95 1.29 2.21 5.63
d1 D 0.41 5.0 5.0 0.84 1.00 2.85 4.87 9.95 0.98 1.68 4.08
e1 E 0.84 5.0 5.0 0.84 1.00 2.85 4.87 9.95 2.01 3.44 8.37
f1 F 0.34 5.0 5.0 0.71 0.89 2.85 4.87 9.95 0.69 1.17 3.00
g1 G 0.45 5.0 5.0 0.71 0.89 2.85 4.87 9.95 0.90 1.55 3.95
h1 H 0.65 5.0 5.0 0.81 1.00 2.85 4.87 9.95 1.51 2.58 6.52
i1 I 1.45 5.0 5.0 0.81 1.00 2.85 4.87 9.95 3.34 5.72 14.42
j1 J 0.24 5.0 5.0 0.65 0.81 2.85 4.87 9.95 0.44 0.75 1.91
k1 K 0.22 5.0 5.0 0.65 0.81 2.85 4.87 9.95 0.40 0.69 1.75
l1 L 0.15 5.6 5.6 0.95 1.00 2.76 4.72 9.63 0.40 0.68 1.47
R1 0.16 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.45 0.76 1.64
R2 0.12 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.32 0.54 1.17
R3 0.24 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.64 1.09 2.35
R4 0.17 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.45 0.78 1.67
R5 0.14 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.37 0.64 1.37
R6 0.22 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.61 1.04 2.24
R7 0.15 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.41 0.69 1.49
R8 0.15 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.41 0.70 1.50
R9 0.20 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.53 0.91 1.95
R10 0.26 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.70 1.19 2.56
R11 0.14 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.38 0.65 1.40
R12 0.34 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.92 1.56 3.36
R13 0.24 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.64 1.10 2.36
R14 0.31 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.85 1.45 3.12
R15 0.18 5.0 5.0 0.95 1.00 2.85 4.87 9.95 0.49 0.83 1.79
os1 OS1 0.48 9.6 9.6 0.30 0.38 2.26 3.86 7.88 0.33 0.56 1.43
os2 OS2 0.56 12.5 12.5 0.30 0.38 2.05 3.50 7.16 0.34 0.58 1.50
os3 OS3 0.34 10.3 10.3 0.28 0.35 2.21 3.78 7.72 0.21 0.36 0.93
os4 OS4 0.27 12.7 12.7 0.28 0.35 2.02 3.45 7.04 0.15 0.26 0.67
MAJOR BASIN SC
(STORMTECH,
COMBINED)
9.41 5.0 5.0 0.84 1.00 2.85 2.85 9.95 22.54 26.83 93.67
MAJOR BASIN OSC (OFF-
SITE, COMBINED)1.66 9.6 9.6 0.28 0.35 2.26 2.26 7.88 1.05 1.31 4.57
DEVELOPED RUNOFF COMPUTATIONS
Design
Point Basin(s)Area, A
(acres)
Tc2
(min)
Flow,
Q2
(cfs)
Flow,
Q100
(cfs)
C2 C100
IDF Table for Rational Method - Table 3.4-1 FCSCM
Intensity,
i10
(in/hr)
Flow,
Q10
(cfs)
Combined Basins
Tc100
(min)
Intensity,
i2
(in/hr)
Intensity,
i100
(in/hr)
()()()AiCCQf=
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100
Q2
(cfs)
Q100
(cfs)
A 0.54 5.0 5.0 0.85 1.00 1.30 5.35
B 0.50 5.0 5.0 0.87 1.00 1.03 4.51
C 0.62 5.0 5.0 0.73 0.91 1.29 5.63
D 0.41 5.0 5.0 0.87 1.00 0.98 4.08
E 0.84 5.0 5.0 0.84 1.00 2.01 8.37
F 0.34 5.0 5.0 0.95 1.00 0.69 3.00
G 0.45 5.0 5.0 0.71 0.89 0.90 3.95
H 0.65 5.0 5.0 0.83 1.00 1.51 6.52
I 1.45 5.0 5.0 0.81 1.00 3.34 14.42
J 0.24 5.0 5.0 0.88 1.00 0.44 1.91
K 0.22 5.0 5.0 0.65 0.81 0.40 1.75
L 0.15 5.6 5.6 0.32 0.40 0.40 1.47
R1 0.16 5.0 5.0 0.95 1.00 0.45 1.64
R2 0.12 5.0 5.0 0.95 1.00 0.32 1.17
R3 0.24 5.0 5.0 0.95 1.00 0.64 2.35
R4 0.17 5.0 5.0 0.95 1.00 0.45 1.67
R5 0.14 5.0 5.0 0.95 1.00 0.37 1.37
R6 0.22 5.0 5.0 0.95 1.00 0.61 2.24
R7 0.15 5.0 5.0 0.95 1.00 0.41 1.49
R8 0.15 5.0 5.0 0.95 1.00 0.41 1.50
R9 0.20 5.0 5.0 0.95 1.00 0.53 1.95
R10 0.26 5.0 5.0 0.95 1.00 0.70 2.56
R11 0.14 5.0 5.0 0.95 1.00 0.38 1.40
R12 0.34 5.0 5.0 0.95 1.00 0.92 3.36
R13 0.24 5.0 5.0 0.95 1.00 0.64 2.36
R14 0.31 5.0 5.0 0.66 0.83 0.85 3.12
R15 0.18 5.0 5.0 0.95 1.00 0.49 1.79
OS1 0.48 9.6 9.6 0.28 0.35 0.33 1.43
OS2 0.56 12.5 12.5 0.30 0.38 0.34 1.50
OS3 0.34 10.3 10.3 0.25 0.31 0.21 0.93
OS4 0.27 12.7 12.7 0.28 0.35 0.15 0.67
MAJOR BASIN SC (STORMTECH, COMBINED)9.41 5.0 5.0 0.84 1.00 22.54 93.67
MAJOR BASIN OSC (OFF-SITE, COMBINED) 1.66 9.6 9.6 0.28 0.35 1.05 4.57
Rational Flow Summary | Developed Basin Flow Rates
Combined Basins
6/12/202310:47 PM P:\1893-001\Drainage\Hydrology\1893-001_Proposed Rational Calcs (FCSCM).xlsx\Summary Tables
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE CROWNE AT SUNIGA
FORT COLLINS | GREELEY APPENDIX
APPENDIX B
B.1 - DETENTION SYSTEM CALCULATIONS
B.2 - HYDRAULIC CALCULATIONS – FOR FUTURE USE
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE CROWNE AT SUNIGA
FORT COLLINS | GREELEY APPENDIX
APPENDIX B.1
DETENTION SYSTEM CALCULATIONS
B2
100-yr
1.00
5.00 min Storage 133119 ft3
11.07 acres
Max Release Rate =1.88 cfs 3.06 ac-ft
Time (min)
Ft Collins
100-yr
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 9.950 33044 1.00 1.88 564 32480
10 7.720 51276 1.00 1.88 1128 50148
15 6.520 64959 1.00 1.88 1692 63267
20 5.600 74390 1.00 1.88 2256 72134
25 4.980 82693 1.00 1.88 2820 79873
30 4.520 90066 1.00 1.88 3384 86682
35 4.080 94848 1.00 1.88 3948 90900
40 3.740 99364 1.00 1.88 4512 94852
45 3.460 103416 1.00 1.88 5076 98340
50 3.230 107268 1.00 1.88 5640 101628
55 3.030 110689 1.00 1.88 6204 104485
60 2.860 113977 1.00 1.88 6768 107209
65 2.720 117431 1.00 1.88 7332 110099
70 2.590 120419 1.00 1.88 7896 112523
75 2.480 123541 1.00 1.88 8460 115081
80 2.380 126464 1.00 1.88 9024 117440
85 2.290 129287 1.00 1.88 9588 119699
90 2.210 132109 1.00 1.88 10152 121957
95 2.130 134401 1.00 1.88 10716 123685
100 2.060 136825 1.00 1.88 11280 125545
105 2.000 139482 1.00 1.88 11844 127638
110 1.940 141740 1.00 1.88 12408 129332
115 1.890 144364 1.00 1.88 12972 131392
120 1.840 146655 1.00 1.88 13536 133119
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
Storage System :
DETENTION VOLUME CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1893-001
The Crowne at Suniga
Project Number :
Project Name :
Stormtech System - Detention
Page 1 of 1
1893-001_Pond_FAA_Fort Collins_Detention Volume.xls
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE CROWNE AT SUNIGA
FORT COLLINS | GREELEY APPENDIX
APPENDIX B.2
HYDRAULIC CALCULATIONS – FOR FUTURE USE
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FORT COLLINS | GREELEY APPENDIX
APPENDIX C
WATER QUALITY/LID COMPUTATIONS
Project Title Date:
Project Number Calcs By:
City
Basins
0.8
WQCV = Watershed inches of Runoff (inches)82%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100)0.273 in
A =11.07 ac
V = 0.3022 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
13162 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Crowne at Suniga June 12, 2023
1893-001 S. King
Fort Collins
Stormtech LID Pond
0.273
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
00.10.20.30.40.50.60.70.80.91WQCV (watershed inches)Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
()iii78.019.10.91aWQCV 23 +-=
()iii78.019.10.91aWQCV 23 +-=
12 hr
1.20
WQCV
12 ∗
Pond No :
Stormtech Pond
WQ
0.85
5.00 min 9485 ft3
11.07 acres 0.22 ac-ft
Max Release Rate =2.26 cfs
Time (min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage Volume
(ft3)
5 1.425 4023 1.00 2.26 677 3345
10 1.105 6238 1.00 2.26 1355 4884
15 0.935 7918 0.67 1.51 1355 6563
20 0.805 9090 0.63 1.41 1694 7396
25 0.715 10092 0.60 1.35 2032 8059
30 0.650 11009 0.58 1.32 2371 8638
35 0.585 11560 0.57 1.29 2710 8850
40 0.535 12082 0.56 1.27 3049 9033
45 0.495 12576 0.56 1.25 3387 9189
50 0.460 12985 0.55 1.24 3726 9259
55 0.435 13507 0.55 1.23 4065 9443
60 0.410 13888 0.54 1.22 4403 9485
65 0.385 14128 0.54 1.22 4742 9386
70 0.365 14425 0.54 1.21 5081 9344
75 0.345 14608 0.53 1.20 5420 9189
80 0.330 14905 0.53 1.20 5758 9146
85 0.315 15116 0.53 1.20 6097 9019
90 0.305 15497 0.53 1.19 6436 9062
95 0.290 15554 0.53 1.19 6775 8779
100 0.280 15808 0.53 1.19 7113 8695
105 0.270 16006 0.52 1.18 7452 8554
110 0.260 16147 0.52 1.18 7791 8356
115 0.255 16556 0.52 1.18 8129 8427
120 0.245 16598 0.52 1.18 8468 8130
*Note: Using the method described in FCSCM Chapter 6 Section 2.3
A =
Tc =
Project Location :
Design Point
C =
Design Storm
WATER QUALITY CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1893-001
The Crowne at Suniga
Project Number :
Project Name :
Stormtech LID Pond
Page 2 of 5
1893-001 LID Chamber Summary.xlsx
Vault IDTotal RequiredWQ Volume(cf)Flow,WQ(cfs)ChamberTypeChamber Release Ratea(cfs)ChamberVolumeb(cf)Installed Camber w/ Aggregatec(cf)Mimimum No. of ChambersdTotal Release Ratee(cfs)Required Storage Volume by FAA Method(cf)Mimimum No. of ChambersfStorage Provided within the Chambersg(cf)Minimum Total Installed System Volumeh(cf)Stormtech LID Pond 13162 11.37 MC-7200 0.045 175.90 267.30 50 2.26 9485549499 14434a. Release rate per chamber, limited by flow through geotextile with accumulated sediment.b. Volume within chamber only, not accounting for void spaces in surrounding aggregate.c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.d. Number of chambers required to provide full WQCV within total installed system, including aggregate.e. Release rate per chamber times number of chambers.f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage).g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV.Chamber Configuration SummaryP:\1893-001\Drainage\LID\1893-001 LID Chamber Summary.xlsx
Design Point (Basin ID)1
Total Area
(ac) Treatment Method Area Treated (ac)
Percent
Impervious
(%)
Area of
Impervious
(ac)2
Required LID
(cu. ft.)
Percent of
Impervious
Area
Major Basin SC 9.41 Stormtech Chambers 9.41 82%7.72 14,434 99%
Major Basin OSC 1.66 N/A N/A 6%0.10 N/A 1%
1. Refer to Rational Calculations for additional clarification.
2. Calculated by multiplying the percent impervious by area treated
LID Summary Table
DDDDDDDDDEEEEEEGGGGG
GXXXXUDUDUDUDUDUDMONITORING WELL
TRAFFIC RATED
TFTF TFTFTFTFE
EEEEEEEEEEEETF
EETFE E
EBUILDING 1000
DFC NORTH FIELD LLC
981 LINDENMEIER ROAD EAST SUNIGA ROADNORT
H LE
MAY AVE
N
UE
GRAHAM JOHN C / GINGER L
1100 E VINE DRIVE
BUILDING 2000
BUILDING 3000
BUILDING 4000
BUILDING 5000
BUILDING 6000
DOG
PARK
500-YEAR
FLOODPLAIN
STORM DRAIN
(TYP.)
AREA INLET
(TYP.)
EXISTING NECCO
BACKBONE STORM DRAIN
WATER QUALITY
BASIN w/ WEIR
EXISTING NECCO
STORM DRAIN A3
EXISTING
TYPE R INLET
EXISTING
TYPE R INLET
EXISTING
AREA INLET
STORMTECH MC-7200 SYSTEM
- 538 CHAMBERS REQUIRED.
- MINIMUM OF 54 CHAMBERS
TO BE ISOLATORS.
- 86 ISOLATORS PROVIDED.
- 538 CHAMBERS PROVIDED.
500-YR
FLOOD PLANE
LINDENMEIER ROAD
WATER QUALITY
BASIN w/ WEIR
LID EXHIBIT
FORT COLLINS, CO
CROWNE AT SUNIGA
E N G I N E E R N GI
EHTRON R N
02.22.23
P:\1893-001\DWG\DRNG\1893-001_LID.DWG
( IN FEET )
0
1 INCH = 100 FEET
100 100 200 300
NOTES:
1.REFER TO THE CROWNE AT SUNIGA - UTILITY PLANS FOR
ADDITIONAL CLARIFICATION ON BASIN BREAKDOWNS,
GRADING, AND UTILITY SIZING.
LID SUMMARY AND LEGEND:
LID Summary Table
Design Point
(Basin ID)
Total
Area
(ac)
Area
Treated
(ac)
Percent
Impervious
(%)
Area of
Impervious
(ac)2
Required
LID (cu.
ft.)
Percent of
Impervious
Area
Major Basin SC 9.41 9.41 82%7.72 14,434 99%
Major Basin OSC 1.66 N/A 6%0.10 N/A 1%
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE CROWNE AT SUNIGA
FORT COLLINS | GREELEY APPENDIX
APPENDIX D
EROSION CONTROL REPORT
NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE CROWNE AT SUNIGA
FORT COLLINS | GREELEY EROSION CONTROL REPORT
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included with the
final construction drawings. It should be noted; however, 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 CS2 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 Storm Water 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.
NNORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE CROWNE AT SUNIGA
FORT COLLINS | GREELEY APPENDIX
APPENDIX E
EXCERPTS FROM PREVIOUS REPORTS
AND USDA SOILS REPORT
DRAFT FINAL
NORTH EAST COLLEGE CORRIDOR OUTFALL
(NECCO)
DESIGN REPORT
Prepared for
City of Fort Collins Utilities
700 Wood Street
Fort Collins, Colorado 80521
3.7 Ayres Associates
• Basin 412 is currently an undeveloped basin consisting of the Raptor Center. It was
modeled as a developed basin that drains into proposed Manhole A1. The storm sewer
that would be required to connect this basin with the proposed manhole was not
designed with the NECCO project.
• Basin 413 is currently an undeveloped basin. It was modeled as a developed basin that
drains into the proposed Regional Detention Pond. The storm sewer that would drain
this basin to the proposed detention facility was not designed with the NECCO project.
The future pipe will cross the re-aligned Vine Drive. This pipe crossing must take into
account the GWET and NEWT waterline clearances. These clearances are very critical.
• Basin 414 consists of the Alta Vista development. If redeveloped, the basin was
modeled as discharging into proposed Manhole Riser A4 (or downstream of transition
A1). The storm sewer that would be required to connect this basin with the proposed
manhole was not designed with the NECCO project.
• Basin 417 is currently an undeveloped basin. It was modeled as a developed basin that
drains into proposed Manhole Riser A3.
• Basin 417 is currently an undeveloped basin. It will drain into the future east Vine
Diversion Channel.
• Basin 418 is currently an undeveloped basin. It was modeled as a developed basin that
drains downstream of the proposed Manhole Riser A2.
• Basin 419 is currently an undeveloped basin. It will drain into the future east Vine
Diversion Channel.
• Basin 420 is currently an undeveloped basin. It will drain into the future east Vine
Diversion Channel.
• Basin 421 is currently an undeveloped basin. It will drain into the future east Vine
Diversion Channel.
• Basin 422 is currently an undeveloped basin. It will drain into the future east Vine
Diversion Channel.
• Basin 424 drains overland to proposed Inlet B6A. If redeveloped, the basin will continue
to drain to the inlet. This basin drains through basins 324 and 326 and will need to
accounted for in the drainage of these basins.
• Basin 426 is currently an undeveloped basin. It was modeled as a developed basin that
drains to proposed Manhole B5. Basin 226 drains through this basin and will need to be
accounted for in the redevelopment of basin 426.
• Basin 427 drains overland to proposed Inlet B6A.
• Basin 510 currently drains into the Lake Canal. This basin was not further analyzed with
the NECCO project.
4.1 Ayres Associates
4. FINAL STORM SEWER DESIGN AND HYDRAULIC ANALYSIS
ModSWMM was used to develop the basin hydrographs only, while EPA SWMM 5.0.013
was used for the hydraulic routing of the basins in the developed condition with proposed
facilities model. EPA SWMM was used to model the inflows and outflows of the existing
Evergreen West and Redwood Ponds as well as model the proposed storm sewer lines A, B,
C, and E.
The input requirements for the EPA SWMM 5.0.013 model include the following:
• Pipe lengths, diameters, inverts and material
• Reservoir stage vs. area information for each pond
• Inflow hydrographs – These were developed from the ModSWMM analysis described
previously
• Geometry of outlet structures, i.e., weirs, orifices etc.
UD Inlet version 2.14a was used to size inlets for each system. The City of Fort Collins
Storm Drainage Criteria was followed to determine the street carrying capacity and
encroachment for the 100-year storm event. The same criterion was followed to size the
inlets along re-aligned Vine Drive for the 10-year storm event. Snout oil-water debris
separators are incorporated into the design of the inlets along realigned Vine Drive (refer to
Appendix D for the inlet calculations).
Following is a list summarizing the detention and water quality assumption made for
each basin during the final design process:
• Undeveloped properties east of Redwood require future on-site detention and water
quality. These basins were modeled assuming a proposed detention facility 100-year
release rate of 0.2 cfs/acre.
- Basins: 113, 114*, 115, 116, 117, 313, 320, 412, 417, 418, 419*, 420*, 421*, 422*
*These basins do not discharge into the proposed NECCO Storm Sewer.
• The undeveloped area south of Conifer Street, west of Redwood and north of the
proposed re-aligned Vine Drive would discharge into the regional pond without on-site
detention or water quality.
- Basins: 126, 127, 327*, 408, 526, 726
*Proposed Regional Detention Pond
• Dry Creek, behind Autozone and south to the Proposed East Vine Drive, will be filled in.
Currently basins 407, 316 and 315 drain into Dry Creek.
Currently Basin 407 drains into an existing detention pond. This pond will be connected
into the proposed storm sewer. This pond can be removed as long as basin 407
ultimately discharges into the proposed NECCO storm sewer system.
Currently Basin 316 drains into an existing detention pond. This pond will be removed
with the construction of the re-aligned Vine Drive. The flow that currently travels to the
southern pond will be conveyed overland to Vine Drive where it will be collected in the
proposed storm sewer.
LEGENDDRAINAGE BASINBASIN NUMBERBASIN AREA (ACRES)EXHIBIT 4.2FUTURE DETENTION AND WATER QUALITY REQUIREMENTSRESTRICT AMOUNT OF RUNOFFTO EXISTING CONDITIONS IFRE-DEVELOPED. WATER QUALITYPROVIDED IN REDWOOD PONDREQUIRE FUTURE ON-SITEDETENTION & WATERQUALITY. RELEASE RATE @ 0.20 cfs/acreREQUIRE FUTURE ON-SITEDETENTION.WATER QUALITY PROVIDEDIN REGIONAL POND.FUTURE RE-ALIGNED VINEDRIVE. WATER QUALITYPROVIDED WITH SNOUTS.DISCHARGE INTOREGIONAL POND WITHOUTFUTURE DETENTION ORWATER QUALITY.RESTRICT AMOUNT OF RUNOFFTO EXISTING CONDITIONS IFRE-DEVELOPED. FUTURE WATERQUALITY REQUIRED.RESTRICT AMOUNT OF RUNOFFTO EXISTING CONDITIONS IFRE-DEVELOPED. WATER QUALITYPROVIDED IN REGINAL POND.BASIN 103: NO DETENTION ORWATER QUALITY REQURED IFDISCHARGING INTOEVERGREEN WEST PONDCOLLEGE AVENUERED CEDAR CIRCLELEMAY AVENUE
DRY CREEK BRISTLECONE DRIVECONIFER STREETNOKOMIS COURTBLUE SPRUCE DRIVE
CONIFER STREETLUPINE DRIVEREDWOODPONDREGIONALPONDREDWOOD STREETCOLLEGE AVENUEJEROME STREETBONDELL STREET OSIANDER STREETEAST VINE DRIVE70.0 ac68.2 ac13.2 ac18.5 ac8.7 ac29.3 ac11.4 ac9.8 ac11.4 ac4.8 ac16.4 ac3.3 ac1.3 ac31.6 ac52.7 ac21.3 ac7.4 ac18.1 ac17.0 ac2.5 ac2.7 ac2.0 ac4.6 ac2.5 ac13.1 ac3.9 ac13.7 ac1.8 ac0.2 ac7.2 ac6.0 ac3.8 ac0.6 ac2.4 ac5.2 ac1.6 ac2.6 ac35.7 ac2.6 ac1.8 ac1.8 ac1.6 ac1.2 ac0.7 ac4.2 ac2.6 ac13.6 ac13.0 ac8.6 ac7.1 ac5.1 ac4.5 ac4.2 ac10.9 ac8.2 ac19.2 ac16.0 ac32.4 ac17.5 ac9.8 ac16.6 ac29.3 ac6.0 ac10.3 ac5.9 ac1.5 ac1.3 ac21.2 ac1.2 ac1.5 ac1.1 ac1.1 ac8.2 ac1.0 ac8.6 ac5.2 ac14.8 ac2.0 ac1.6 ac3.3 ac1.4 ac5.3 ac1.2 ac1.0 ac2.7 ac2.2 ac3.9 ac3.3 ac3.4 ac4.4 ac7.9 ac0.2 ac4.2 ac1.1 ac1.7 ac2.4 ac2.0 ac1.0 ac36.2 ac5.5 ac49.1 ac
4.4 Ayres Associates
Figure 4.1. Proposed storm infrastructure.
GEOTECHNICAL SUBSURFACE EXPLORATION REPORT
PROPOSED APARTMENT COMPLEX DEVELOPMENT - GRAHAM PROPERTY
NORTHEAST CORNER OF 9TH STREET AND SUNIGA ROAD
FORT COLLINS, COLORADO
EEC PROJECT NO. 1222009
Prepared for:
Crowne Partners, Inc.
505 North 20th Street - Suite 1150
Birmingham, AL 35203
Attn: Mr. Cary Levow (clevow@crownepartners.com)
Prepared by:
Earth Engineering Consultants, LLC
4396 Greenfield Drive
Windsor, Colorado 80550
4396 GREENFIELD DRIVE
W INDSOR, COLORADO 80550
(970) 545-3908 FAX (970) 663-0282
June 1, 2022
Crowne Partners, Inc.
505 North 20th Street - Suite 1150
Birmingham, AL 35203
Attn: Mr. Cary Levow (clevow@crownepartners.com)
Re: Geotechnical Subsurface Exploration Report
Proposed Apartment Complex Development – Graham Property
Approximate 11-Acres Parcel – Northeast Corner of 9th Street and Suniga Road
Fort Collins, Colorado
EEC Project No. 1222009
Mr. Levow:
Enclosed, herewith, are the results of the geotechnical subsurface exploration completed by Earth
Engineering Consultants, LLC (EEC) for the proposed multi-family apartment complex planned
for construction in Fort Collins, Colorado. For this exploration, EEC personnel advanced twenty-
one (21) soil borings to depths of approximately 4 to 13 feet below present site grades at pre-
selected locations within the various proposed building footprints and associated on-site
pavement improvements. This exploration was completed in general accordance with our
proposal dated January 17, 2022.
In summary, the subsurface conditions encountered beneath the surficial vegetation/fescue grass
generally consisted of cohesive to slightly cohesive lean clay with sand to silty/clayey sand soils
extending to granular gravel/sand with silt/clay soils at depths of approximately ½ to 8 feet. The
cohesive soils were generally dry to moist and soft/very loose to stiff/dense and exhibited nil to
low with an occasional high swell potential (at boring B-15) and slight tendency to hydro-
compact at current moisture and density conditions. Gravel/sand with silt/clay soils were
encountered below the cohesive to slightly cohesive soils and extended to the depths explored at
approximately 4 to 13 feet below the site grades. Zones of larger cobbles were also encountered
in the gravel/sand soils. The gravel/sand soils were generally dry to moist and medium dense to
very dense. Groundwater was observed in the two deepest borings; B-14 and B-20 which
advanced to depths of approximately 13 and 10 feet below the site grades at depths of
approximately 7 to 9 feet, respectively. Groundwater was not observed in the rest of the borings
advanced to maximum depths of approximately 7 feet below the ground surface at the time of
drilling.
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
The Crowne at Suniga
Natural
Resources
Conservation
Service
January 24, 2023
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
(https://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
2
alternative means 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..................................................................................................................8
Soil Map................................................................................................................9
Legend................................................................................................................10
Map Unit Legend................................................................................................11
Map Unit Descriptions.........................................................................................11
Larimer County Area, Colorado......................................................................13
35—Fort Collins loam, 0 to 3 percent slopes..............................................13
64—Loveland clay loam, 0 to 1 percent slopes...........................................14
76—Nunn clay loam, wet, 1 to 3 percent slopes.........................................15
References............................................................................................................17
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
5
scientists classified and named the soils in the survey area, they compared the
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
Custom Soil Resource Report
6
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
7
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.
8
9
Custom Soil Resource Report
Soil Map
449424044942904494340449439044944404494490449454044945904494640449424044942904494340449439044944404494490449454044945904494640495090 495140 495190 495240 495290 495340 495390
495090 495140 495190 495240 495290 495340 495390
40° 36' 9'' N 105° 3' 29'' W40° 36' 9'' N105° 3' 15'' W40° 35' 55'' N
105° 3' 29'' W40° 35' 55'' N
105° 3' 15'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 50 100 200 300
Feet
0 30 60 120 180
Meters
Map Scale: 1:2,050 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil 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:
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
Survey Area Data: Version 17, Sep 7, 2022
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jul 2, 2021—Aug 25,
2021
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
10
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
35 Fort Collins loam, 0 to 3 percent
slopes
0.1 1.2%
64 Loveland clay loam, 0 to 1
percent slopes
8.7 79.6%
76 Nunn clay loam, wet, 1 to 3
percent slopes
2.1 19.2%
Totals for Area of Interest 10.9 100.0%
Map Unit Descriptions
The map units delineated on the detailed soil maps in a soil survey represent the
soils or miscellaneous areas in the survey area. The map unit descriptions, along
with the maps, can be used to determine the composition and properties of a unit.
A map unit delineation on a soil map represents an area dominated by one or more
major kinds of soil or miscellaneous areas. A map unit is identified and named
according to the taxonomic classification of the dominant soils. Within a taxonomic
class there are precisely defined limits for the properties of the soils. On the
landscape, however, the soils are natural phenomena, and they have the
characteristic variability of all natural phenomena. Thus, the range of some
observed properties may extend beyond the limits defined for a taxonomic class.
Areas of soils of a single taxonomic class rarely, if ever, can be mapped without
including areas of other taxonomic classes. Consequently, every map unit is made
up of the soils or miscellaneous areas for which it is named and some minor
components that belong to taxonomic classes other than those of the major soils.
Most minor soils have properties similar to those of the dominant soil or soils in the
map unit, and thus they do not affect use and management. These are called
noncontrasting, or similar, components. They may or may not be mentioned in a
particular map unit description. Other minor components, however, have properties
and behavioral characteristics divergent enough to affect use or to require different
management. These are called contrasting, or dissimilar, components. They
generally are in small areas and could not be mapped separately because of the
scale used. Some small areas of strongly contrasting soils or miscellaneous areas
are identified by a special symbol on the maps. If included in the database for a
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
Custom Soil Resource Report
11
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
12
Larimer County Area, Colorado
35—Fort Collins loam, 0 to 3 percent slopes
Map Unit Setting
National map unit symbol: 2tlnc
Elevation: 4,020 to 6,730 feet
Mean annual precipitation: 14 to 16 inches
Mean annual air temperature: 46 to 48 degrees F
Frost-free period: 135 to 160 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:Stream terraces, interfluves
Landform position (three-dimensional):Interfluve, tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Pleistocene or older alluvium 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
Drainage class:Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat):Moderately high to high
(0.20 to 2.00 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Calcium carbonate, maximum content:12 percent
Maximum salinity:Nonsaline to very slightly saline (0.1 to 2.0 mmhos/cm)
Available water supply, 0 to 60 inches: High (about 9.1 inches)
Interpretive groups
Land capability classification (irrigated): 3e
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: C
Ecological site: R067BY002CO - Loamy Plains
Hydric soil rating: No
Custom Soil Resource Report
13
Minor Components
Nunn
Percent of map unit:10 percent
Landform:Stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R067BY002CO - Loamy Plains
Hydric soil rating: No
Vona
Percent of map unit:5 percent
Landform:Interfluves
Landform position (three-dimensional):Interfluve, side slope
Down-slope shape:Linear
Across-slope shape:Linear
Ecological site:R067BY024CO - Sandy Plains
Hydric soil rating: No
64—Loveland clay loam, 0 to 1 percent slopes
Map Unit Setting
National map unit symbol: jpx9
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
Loveland and similar soils:90 percent
Minor components:10 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Loveland
Setting
Landform:Flood plains, stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Alluvium
Typical profile
H1 - 0 to 15 inches: clay loam
H2 - 15 to 32 inches: loam
H3 - 32 to 60 inches: very gravelly sand
Custom Soil Resource Report
14
Properties and qualities
Slope:0 to 1 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Poorly drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat):Moderately high (0.20
to 0.60 in/hr)
Depth to water table:About 18 to 36 inches
Frequency of flooding:OccasionalNone
Frequency of ponding:None
Calcium carbonate, maximum content:15 percent
Maximum salinity:Very slightly saline to slightly saline (2.0 to 4.0 mmhos/cm)
Available water supply, 0 to 60 inches: Moderate (about 7.5 inches)
Interpretive groups
Land capability classification (irrigated): 3w
Land capability classification (nonirrigated): 3w
Hydrologic Soil Group: C
Ecological site: R067BY036CO - Overflow
Hydric soil rating: No
Minor Components
Aquolls
Percent of map unit:5 percent
Landform:Swales
Hydric soil rating: Yes
Poudre
Percent of map unit:5 percent
Ecological site:R067BY036CO - Overflow
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
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.
Custom Soil Resource Report
15
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
H3 - 47 to 60 inches: gravelly loam
Properties and qualities
Slope:1 to 3 percent
Depth to restrictive feature:More than 80 inches
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:NoneRare
Frequency of ponding:None
Calcium carbonate, maximum content:10 percent
Maximum salinity:Nonsaline to very slightly saline (0.0 to 2.0 mmhos/cm)
Available water supply, 0 to 60 inches: High (about 9.9 inches)
Interpretive groups
Land capability classification (irrigated): 2w
Land capability classification (nonirrigated): 3s
Hydrologic Soil Group: C
Ecological site: R067BY038CO - Wet Meadow
Hydric soil rating: No
Minor Components
Heldt
Percent of map unit:6 percent
Ecological site:R067BY042CO - Clayey Plains
Hydric soil rating: No
Dacono
Percent of map unit:3 percent
Ecological site:R067BY042CO - Clayey Plains
Hydric soil rating: No
Mollic halaquepts
Percent of map unit:1 percent
Landform:Swales
Hydric soil rating: Yes
Custom Soil Resource Report
16
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
17
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
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NORTHERNENGINEERING.COM | 970.221.4158 PRELIMINARY DRAINAGE REPORT: THE CROWNE AT SUNIGA
FORT COLLINS | GREELEY APPENDIX
MAP POCKET
DR1 – EXISTING DRAINAGE EXHIBIT
DR2 – PROPOSED DRAINAGE EXHIBIT
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NO
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GRAHAM JOHN C / GINGER L
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9TH STREETEX
EXISTING NECCO
STORM LINE A4
EX-INLET
RIM = 4951.07
BOTTOM OF BOX = 4937.43
EX-STRM MH
RIM = 4952.17
INV IN = 4942.96 (S)
INV OUT = 4942.91 (N)
EX-STRM MH
RIM = 4953.11
BOTTOM OF BOX = 4942.18
EX-INLET
GRATE = 4947.87
INV IN = 4942.06 (N)
INV OUT = 4941.86 (S)
EXISTING MANHOLE RISER A3
RIM = 4950.62
BOTTOM OF BOX = 4941.50
EX-INLET
GRATE = 4947.90
INV OUT = 4941.38 (S)
EX-INLET
RIM = 4946.67
INV IN = 4941.87 (S)
INV OUT = 4941.24 (N)
EX-INLET
RIM = 4946.75
INV OUT = 4941.81 (E)
125'
ROW
15' SLOPE & UTILITY
EASEMENT (REC. #20180037021)
15' SLOPE & UTILITY
EASEMENT (REC. #20180037021)
EX-INLET
30' UTILITY & DRAINAGE
EASEMENT (REC. #20200000602)
GREELEY WATER LINE EASEMENT
(WIDTH VARIES)
(REC. #20080062293)
50' DRAINAGE & UTILITY EASEMENT
(REC #20190075879 & #20180037022)
EXISTING NECCO
BACKBONE STORM LINE A1
500-YEAR
FLOODPLAIN
EX-STRM MH
RIM = 4951.44
INV IN = 4943.74 (N)
INV OUT = 4943.54 (S)
SheetCROWNE AT SUNIGAThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealed bya Professional Engineer inthe employ of NorthernEngineering Services, Inc.NOT FOR CONSTRUCTIONREVIEW SETof 9
DR1 DRAINAGE EXHIBITEXISTING8
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
0
1 INCH = 50 FEET
50 50 100 150
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION 11
NOTES:
1.REFER TO THE PRELIMINARY DRAINAGE REPORT, DATED MARCH 15, 2023 FOR
ADDITIONAL INFORMATION.
A
LEGEND:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
EXCLUSIVE PERMANENT
ELCO WATER LINE EASEMENT
(REC. #20080070035)
(WIDTH VARIES)
RUNOFF SUMMARY:
Rational Flow Summary | Developed Basin Flow Rates
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100 Q2
(cfs)
Q100
(cfs)
EX 11.08 13.6 13.6 0.25 0.31 5.40 23.40
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os2
os3
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BUILDING 1000
BUILDING 2000
BUILDING 3000
BUILDING 4000
BUILDING 5000
BUILDING 6000
DOG
PARK
125'
ROW
15' SLOPE & UTILITY
EASEMENT (REC. #20180037021)
15' SLOPE & UTILITY
EASEMENT (REC. #20180037021)
30' UTILITY & DRAINAGE
EASEMENT (REC. #20200000602)
GREELEY WATER LINE EASEMENT
(WIDTH VARIES)
(REC. #20080062293)
50' DRAINAGE & UTILITY EASEMENT
(REC #20190075879 & #20180037022)
30' UTILITY
EASEMENT
AREA INLET
(TYP.)
STORM DRAIN
(TYP.)
STORM DRAIN
(TYP.)
EXISTING NECCO
STORM DRAIN A3
EX-INLET
RIM = 4951.07
BOTTOM OF BOX = 4937.43
EX-STRM MH
RIM = 4952.17
INV IN = 4942.96 (S)
INV OUT = 4942.91 (N)
EX-STRM MH
RIM = 4953.11
BOTTOM OF BOX = 4942.18
EX-INLET
GRATE = 4947.87
INV IN = 4942.06 (N)
INV OUT = 4941.86 (S)
EXISTING
MANHOLE RISER A3
RIM = 4950.62
BOTTOM OF BOX = 4941.50
STRM MH
CONNECT TO
EXISTING 18" RCP
INV IN = 4941.48 (W)
INV OUT = 4941.28 (S)
EX-INLET
RIM = 4946.67
INV IN = 4941.87 (S)
INV OUT = 4941.24 (N)
EX-INLET
RIM = 4946.75
INV OUT = 4941.81 (E)
EX-INLET
EXISTING NECCO
BACKBONE STORM LINE A1
12'x4' RCBC @ 0.21%
WATER QUALITY
BASIN w/ WEIR
500-YEAR
FLOOPLAIN
BOTTOM OF BOX = 4941.04 (S)
EX-STRM MH
RIM = 4951.44
INV IN = 4943.74 (N)
INV OUT = 4943.54 (S)
A
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STORMTECH MC-7200 SYSTEM
CHAMBERS REQ. = 538
ISOLATOR ROW CHAMBERS REQ. = 54
ISOLATOR ROW CHAMBERS PROVIDED = 86
TOTAL CHAMBERS PROVIDED = 539
MIN. BOTTOM ELEVATION = 4945
EXISTING 24" RCP STORM DRAIN
AREA INLET WITH
VEGETATED BUFFER
TREATMENT TRAIN
(BY OTHERS)
DR1 DRAINAGE EXHIBITDEVELOPED12
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
before you dig.Call
R
NORTH
( IN FEET )
0
1 INCH = 50 FEET
50 50 100 150
SheetCROWNE AT SUNIGAThese drawings areinstruments of serviceprovided by NorthernEngineering Services, Inc.and are not to be used forany type of constructionunless signed and sealed bya Professional Engineer inthe employ of NorthernEngineering Services, Inc.NOT FOR CONSTRUCTIONREVIEW SETof 12
EXCLUSIVE PERMANENT
ELCO WATER LINE EASEMENT
(REC. #20080070035)
(WIDTH VARIES)
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
A
DESIGN POINT
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
11
NOTES:
1.REFER TO THE PRELIMINARY DRAINAGE REPORT, DATED JUNE 14, 2023 FOR
ADDITIONAL INFORMATION.
A
LEGEND:
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
RUNOFF SUMMARY:
LID SUMMARY:
Rational Flow Summary | Developed Basin Flow Rates
BASIN
TOTAL
AREA
(acres)
Tc2
(min)
Tc100
(min)
C2 C100 Q2
(cfs)
Q100
(cfs)
A 0.54 5.0 5.0 0.85 1.00 1.30 5.35
B 0.50 5.0 5.0 0.87 1.00 1.03 4.51
C 0.62 5.0 5.0 0.73 0.91 1.29 5.63
D 0.84 5.0 5.0 0.84 1.00 0.98 4.08
E 0.34 5.0 5.0 0.95 1.00 2.01 8.37
F 0.45 5.0 5.0 0.71 0.89 0.69 3.00
G 0.65 5.0 5.0 0.83 1.00 0.90 3.95
H 0.15 5.0 5.0 0.32 0.40 1.51 6.52
I 0.16 5.0 5.0 0.95 1.00 3.34 14.42
J 0.12 5.0 5.0 0.95 1.00 0.44 1.91
K 0.24 5.0 5.0 0.95 1.00 0.40 1.75
L 0.17 5.6 5.6 0.95 1.00 0.40 1.47
R1 0.16 5.0 5.0 0.95 1.00 0.45 1.64
R2 0.12 5.0 5.0 0.95 1.00 0.32 1.17
R3 0.24 5.0 5.0 0.95 1.00 0.64 2.35
R4 0.17 5.0 5.0 0.95 1.00 0.45 1.67
R5 0.14 5.0 5.0 0.95 1.00 0.37 1.37
R6 0.22 5.0 5.0 0.95 1.00 0.61 2.24
R7 0.15 5.0 5.0 0.95 1.00 0.41 1.49
R8 0.15 5.0 5.0 0.95 1.00 0.41 1.50
R9 0.20 5.0 5.0 0.95 1.00 0.53 1.95
R10 0.26 5.0 5.0 0.95 1.00 0.70 2.56
R11 0.14 5.0 5.0 0.95 1.00 0.38 1.40
R12 0.34 5.0 5.0 0.95 1.00 0.92 3.36
R13 0.24 5.0 5.0 0.95 1.00 0.64 2.36
R14 0.31 5.0 5.0 0.66 0.83 0.85 3.12
R15 0.18 5.0 5.0 0.95 1.00 0.49 1.79
OS1 0.48 9.6 9.6 0.28 0.35 0.33 1.43
OS2 0.56 12.5 12.5 0.30 0.38 0.34 1.50
OS3 0.34 10.3 10.3 0.25 0.31 0.21 0.93
OS4 0.27 12.7 12.7 0.28 0.35 0.15 0.67
Combined Basins
MAJOR BASIN SC
(STORMTECH,
COMBINED)
9.41 5.0 5.0 0.84 1.00 22.54 93.67
MAJOR BASIN OSC
(OFF-SITE,
COMBINED)
1.66 9.6 9.6 0.28 0.35 1.05 4.57
LID Summary Table
Design Point
(Basin ID)
Total Area
(ac)
Area
Treated
(ac)
Percent
Impervious
(%)
Area of
Impervious
(ac)2
Required
LID (cu.
ft.)
Percent of
Impervious
Area
Major Basin SC 9.41 9.41 82%7.72 14,434 99%
Major Basin OSC 1.66 N/A 6%0.10 N/A 1%