HomeMy WebLinkAboutTHE RETREAT AT FORT COLLINS (FORMERLY REDWOOD STREET MULTI-FAMILY) - PDP - PDP180002 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
The Retreat at Fort Collins
Fort Collins, Colorado
June 6, 2018
Prepared for:
Landmark Properties
4455 Epps Bridge Parkway, Suite 20
Athens, GA 30606
Prepared by:
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 1290-002
This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
When a hard copy is absolutely necessary, we recommend double-sided printing.
June 6, 2018
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage Report for
The Retreat @ Fort Collins
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report for
your review. This report accompanies the Preliminary Development Review submittal for the
proposed The Retreat @ Fort Collins. Comments from the Preliminary Development Review Letter
dated July 28, 2017 have been addressed. Written responses thereto can be found in the
comprehensive response to comments letter on file with Current Planning.
This report has been prepared in accordance to the Fort Collins Stormwater Criteria Manual
(FCSCM), and serves to document the stormwater impacts associated with the proposed The
Retreat @ Fort Collins project. We understand that review by the City 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.
Stephanie Thomas, PE
Project Engineer
The Retreat @ Fort Collins
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ....................................................................................................................................... 1
B. Description of Property ................................................................................................................ 2
C. Floodplain .................................................................................................................................... 3
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 4
A. Major Basin Description ............................................................................................................... 4
B. Sub-Basin Description .................................................................................................................. 4
III. DRAINAGE DESIGN CRITERIA ................................................................................... 4
A. Regulations .................................................................................................................................. 4
B. Four Step Process ........................................................................................................................ 5
C. Development Criteria Reference and Constraints ......................................................................... 5
D. Hydrological Criteria .................................................................................................................... 6
E. Hydraulic Criteria ......................................................................................................................... 6
F. Floodplain Regulations Compliance .............................................................................................. 6
G. Modifications of Criteria .............................................................................................................. 6
IV. DRAINAGE FACILITY DESIGN .................................................................................... 7
A. General Concept .......................................................................................................................... 7
B. Detention Ponds and Water Quality/Low Impact Development ................................................. 10
C. Release Rate Compliance ........................................................................................................... 11
D. Low Impact Development (LID) Compliance ............................................................................... 13
V. CONCLUSIONS ...................................................................................................... 14
A. Compliance with Standards ........................................................................................................ 14
B. Drainage Concept ...................................................................................................................... 14
References ....................................................................................................................... 15
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers (For Future Use)
B.2 – Inlets (For Future Use)
B.3 – Detention Facilities (For Future Use)
APPENDIX C – Water Quality Design Computations
APPENDIX D – SWMM Analysis / Model
APPENDIX E – FEMA Firmette
APPENDIX F – Erosion Control Report
The Retreat @ Fort Collins
Preliminary Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing FEMA Floodplains .................................................................................... 4
Table 1 - Drainage Summary Table ...................................................................................... 9
Table 2 – Detention Summary ............................................................................................ 11
Table 3 – Underground Chamber Summary .......................................................................... 11
Table 4 – Allowable Release Rate ....................................................................................... 12
Table 5 – Proposed Release Rate ........................................................................................ 13
MAP POCKET:
C6.00 - Drainage Exhibit
The Retreat @ Fort Collins
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The Retreat @ Fort Collins project is located in the southeast quarter of Section 1,
Township 7 North, Range 69 West of the 6th Principal Meridian, City of Fort Collins,
County of Larimer, State of Colorado.
3. The project site is located east of Redwood Village PUD I and Redwood Street and
south of Evergreen Parkway, Third Filing. The project site encompasses Redwood
Village PUD Phase II.
4. The project is currently bordered to the south by Dry Creek, west by Redwood Village
PUD, Phase II and Redwood Street, north by Evergreen and Park, Third Filing and to
the east by Lake Canal Irrigation Ditch.
The Retreat @ Fort Collins
Preliminary Drainage Report 2
B. Description of Property
1. The Retreat @ Fort Collins is approximately 31.33 net acres. Approximately 1.17
acres of the site consists of the proposed extension of Suniga Road and 2.32 acres of
the site consists of area proposed to remain undeveloped with this project.
Figure 1 – Aerial Photograph
2. The Retreat @ Fort Collins consists of a mix of fee-simple townhomes, multi-family
apartments, duplexes, clubhouse, parking garage, parking lots, private and public
roadways, sidewalks and trails.
3. The existing site consists of undeveloped grasslands.
4. Historically, off-site drainage entering from the Redwood Village neighbor enters the
site along the western boundary. All runoff generated from the project historically
drains to the southeast and is collected in the Lake Canal Irrigation Ditch.
5. In the northwestern corner of the site is an existing detention pond. This detention
pond detains a portion of the Redwood Village and the upstream developments.
6. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey, the vast majority of the site consists of
variations of clay loam, which falls into Hydrologic Soil Groups C. This soil type has a
slow rate of infiltration.
7. The proposed development will include a mix of above ground extended detention
basins and underground detention and water quality chambers. The underground
detention and water quality chambers will provide LID treatment for the site in
accordance with the City of Fort Collins guidance for LID treatment.
The Retreat @ Fort Collins
Preliminary Drainage Report 3
Figure 2– Proposed Site Plan
8. No existing irrigation facilities or major drainageways are located within the property
limits. A regional conveyance, associated with the NECCO project, has been planned
on the property and will be included as a part of this project.
9. The project site is within the Low Density Mixed-Use Neighborhood District (L-M-N)
Zoning District. The proposed use is permitted within the zone district.
C. Floodplain
1. The subject property is located in the FEMA regulatory Dry Creek 100-year floodplain.
A FEMA high-risk floodway and floodplain is located on the very southern tip of the
property. This area is not proposed to be developed at this time.
2. The FEMA Panel 08069C0977G illustrates the proximity of the project site to the
nearest FEMA delineated regulatory floodplain.
The Retreat @ Fort Collins
Preliminary Drainage Report 4
Figure 3 – Existing FEMA Floodplains
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Retreat @ Fort Collins is located within the Dry Creek Basin, which is generally
located in north Fort Collins. This area is also subject to the restrictions as delineated
in the North East College Corridor Outfall (NECCO) Design Report.
B. Sub-Basin Description
1. The property historically drains to the southeast and is collected in the Lake Canal
Irrigation Ditch.
2. Off-site drainage from the Redwood Village neighborhood is routed onto the property
and entering from the western boundary.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
The Retreat @ Fort Collins will be subject to the regulations set forth in the FCSCM, as
well as regulations associated with the Dry Creek Drainage Basin and the NECCO project.
The Retreat @ Fort Collins
Preliminary Drainage Report 5
B. Four Step Process
The overall stormwater management strategy employed with The Retreat @ Fort Collins
project utilizes the “Four Step Process” to minimize adverse impacts of urbanization on
receiving waters. The following is a description of how the proposed development has
incorporated each step.
Step 1 – Employ Runoff Reduction Practices
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 by 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 (MDCIA).
Routing flows, to the extent feasible, through drain rock within the underground
detention section to increase time of concentration, promote infiltration and provide
initial water quality.
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff; however, this
development will still generate stormwater runoff that will require additional BMPs and
water quality. The majority of stormwater runoff from the site will ultimately be
intercepted and treated in proposed underground Stormtech water quality chambers.
Water quality for areas not routed through the Stormtech chambers will be provided within
the detention pond volume.
Step 3 – Stabilize Drainageways
As stated in Section I.B.5, above, there are no major drainageways in or near the subject
site. While this step may not seem applicable to The Retreat @ Fort Collins, the proposed
project indirectly helps achieve stabilized drainageways nonetheless. Furthermore, this
project will pay one-time stormwater development fees, as well as ongoing monthly
stormwater utility fees, both of which help achieve Citywide drainageway stability.
Step 4 – Implement Site Specific and Other Source Control BMPs.
This step typically applies to industrial and commercial developments and is not
applicable for this project.
C. Development Criteria Reference and Constraints
1. The Retreat @ Fort Collins will be subject to the regulations set forth in the FCSCM,
as well as regulations associated with the Dry Creek Drainage Basin and the NECCO
project.
2. This property was included in the NECCO Design Report. As this project is expected
to release into the NECCO drainage system, this project will be subject to the
requirements set forth with the NECCO Design Report.
3. Though this site was not included in the Redwood Village PUD Drainage design. The
Redwood Village neighborhood does discharge to the project site. As such, the
Redwood Village report was referenced for this project.
4. Several constraints have been identified during the course of this analysis that will
impact the proposed drainage system including:
The Retreat @ Fort Collins
Preliminary Drainage Report 6
Tie in elevation into the NECCO Drainage system.
NECCO storm drainage planned to traverse this property. This storm drain will be
designed with this project.
The NECCO design requires a 0.2 cfs/acres release from the developed site. This
minimal release rate does not provide substantial leeway for any undetained flows.
D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with this development. Tabulated data contained in Table RA-7 has been
utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. The EPA Storm Water Management Model (SWMM) software has been utilized for
detention storage calculations.
4. Three separate design storms have been utilized to address distinct drainage
scenarios. The first event analyzed is the “Minor,” or “Initial” Storm, which has a 2-
year recurrence interval. The second event considered is the “Major Storm,” which
has a 100-year recurrence interval. The third storm computed, for comparison
purposes only, is the 10-year event.
5. No other assumptions or calculation methods have been used with this development
that are not referenced by current City of Fort Collins criteria.
E. Hydraulic Criteria
1. As previously noted, the subject property historically drains into the Lake Canal
Irrigation Ditch. This site will be rerouted to drain to the existing NECCO storm
improvements.
2. All drainage facilities proposed with The Retreat @ Fort Collins project are designed in
accordance with criteria outlined in the FCSCM and/or the Urban Drainage and Flood
Control District’s (UDFCD) Urban Storm Drainage Criteria Manual.
3. As stated in Section I.C.1, above, the subject property is located within a FEMA
regulatory floodplain. As such, this project is subject to the development restrictions
as provided by FEMA and the City of Fort Collins.
4. No structures are proposed within the floodplain or floodway.
5. The Retreat @ Fort Collins project does not propose to modify any natural
drainageways.
F. Floodplain Regulations Compliance
1. As previously mentioned, all structures are located outside of any FEMA 100-year or
City floodplain, and thus are not subject to any floodplain regulations.
G. Modifications of Criteria
1. The proposed The Retreat @ Fort Collins development is not requesting any
modification at this time.
The Retreat @ Fort Collins
Preliminary Drainage Report 7
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of The Retreat @ Fort Collins drainage design collect and treat all
developed runoff from the site, direct all stormwater release from the site to the
NECCO stormwater improvements adjacent to the site and minimize the amount of
undetained drainage and/or provide additional detention and treatment of off-site
areas to balance any undetained basins.
2. As previously mentioned, off-site flows from the Redwood Village neighborhood drain
onto the existing property.
3. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within the
sections to which the content best applies.
4. The Retreat @ Fort Collins project is composed of seven major drainage basins,
designated as Basins A, B, C, D, E, UD, and RW. The drainage patterns for each
major basin are further described below.
Basin A
Basin A is located in the northern half of the site. This basin is subdivided into 9 sub-
basins. These basins consist of buildings, parking lots, roadways and landscaping.
Runoff from these basins drains via curb and gutter to curb inlets. These basins are
detained and treated for LID in underground Chambers A2 and A3, and water quality
is provided in Detention Pond 1. This pond releases directly to a proposed outfall pipe
that connects to the NECCO stormwater improvements. 100-year detention of this
basin is provided in Detention Pond 1.
Basin B
Basin B is located in the center and southern area of the site. This basin is subdivided
into 4 sub-basins. These basins consist of buildings, parking lots, roadways and
landscaping. Runoff from these basins drains via curb and gutter to curb inlets and
curb cuts. These basins are detained and treated for LID in underground Chambers
B2 and B3. Water quality is also provided in Detention Pond 2. This pond releases
directly to a proposed outfall pipe that connects to the NECCO stormwater
improvements. 100-year detention of this basin is provided in Detention Pond 2.
Basin C
Basin C is located along the northern boundary of the site adjacent the southern
boundary of the Redwood Village. This basin is subdivided into 4 sub-basins. This
basin consists of buildings, parking lots, roadways and landscaping. Runoff from
these basins drains via curb and gutter to curb inlets and curb cuts. These basins are
detained and treated for LID in underground Chambers C1 and C3. Water quality is
also provided in Detention Pond 3. 100-year detention of this basin is provided by a
combination of Detention Pond 3 and Detention Pond 6. Once Detention Pond 3 is
full it will spill to an inlet in the adjacent parking lot that will convey additional flow to
Detention Pond 6. Detention Pond 6 consists of underground detention chambers.
The Retreat @ Fort Collins
Preliminary Drainage Report 8
Basin D
Basin D is located along the western boundary of the site adjacent the eastern
boundary of the Redwood Village. This basin is subdivided into 2 sub-basins. This
basin consists of buildings, parking lots, roadways and landscaping. Runoff from
these basins drains via curb and gutter to curb cuts and swale. Water quality for this
basin is provided in Detention Pond 4. 100-year detention of this basin is provided by
a combination of Detention Pond 4 and Detention Pond 6. Once Detention Pond 4 is
full it will spill to an inlet in the adjacent parking lot that will convey additional flow to
Detention Pond 6. Detention Pond 6 consists of underground detention chambers.
Basin E
Basin E is located along the southern boundary of the site. This basin consist of
buildings, parking lots, roadways and landscaping. Runoff from this basin drains via
curb and gutter to curb inlets. These basins are detained and treated for water
quality/LID in underground Chambers E1 and Detention Pond 5. Detention Pond 5
consists of underground detention chambers. These ponds release directly to a
proposed outfall pipe that connects to the NECCO stormwater improvements.
Basin UD1
Basin UD1 is located along the western boundary of the site, adjacent Redwood
Street. This basin consists of buildings, parking lots, roadways and landscaping. The
runoff from this basin drains undetained via curb and gutter to existing curb inlets on
Redwood Street. These inlets are connected to the NECCO stormwater improvements.
Basin UD2
Basin UD2 is located along the southern boundary of the site. This basin consists of
Suniga Street. The runoff from this basin drains undetained via curb and gutter to
inlets designed with the NECCO stormwater improvements. Per the NECCO plan, this
basin was not required to be detained by this project. This area is listed as Basin 950
and 951 in the NECCO plan.
Basin UD3
Basin UD3 is located south of Suniga Street. This basin is not planned for
development and will remain as its existing condition. Per the NECCO plan, this basin
was not required to be detained by this project. This area is listed as Basin 413 in
the NECCO plan.
Basin UD4
Basin UD4 is located in the northern corner of the site. This basin consists of a
roadway connection to Conifer Street. Due to grading constraints this area will drain
undetained to existing inlets at the intersection of Conifer Street and Redwood Street.
These inlets discharge to Redwood Detention Pond.
The Retreat @ Fort Collins
Preliminary Drainage Report 9
Basin RW
Basin RW consists of the existing Redwood Village neighborhood. This basin was
further divided into 5 sub-basins. Basin RW1 drains via curb and gutter to the north
and will be collected in proposed inlets. The runoff from Basin RW1 will bypass the
Retreat site. Basin RW2 currently drains via a concrete pan and discharges onto The
Retreat site. This basin’s runoff will be detained in Detention Pond 4. Basin RW3
currently drains via overland flow onto The Retreat site. This basin’s runoff will be
detained in Detention Pond 4 and 6. Basin RW4 currently drains via grass swale onto
The Retreat site. This basin’s runoff will be collected in an inlet and conveyed to the
NECCO system by the planned NECCO extension. The runoff from Basin RW4 will
bypass the Retreat site. Basin RW5 currently drains via overland flow onto The
Retreat site. This basin’s runoff will be detained in Detention Pond 3 and 6.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
Table 1 - Drainage Summary Table
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2
C100
2-yr
Tc
(min)
100-
yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
A1 A1 0.96 0.53 0.66 5.0 5.0 1.45 6.33
A2 A2 3.58 0.69 0.86 12.6 11.7 4.94 22.32
A3 A3 0.20 0.80 1.00 5.0 5.0 0.47 2.04
A4 A4 1.33 0.77 0.96 9.6 8.1 2.30 10.68
A5 A5 2.60 0.68 0.85 12.6 11.9 3.56 16.12
A6 A6 0.94 0.62 0.77 5.0 5.0 1.66 7.22
A7 A7 0.41 0.70 0.88 7.0 5.0 0.74 3.55
A8 A8 0.62 0.71 0.88 7.8 5.6 1.07 5.24
A9 A9 4.04 0.38 0.48 9.5 8.6 3.47 15.76
B1 B1 3.91 0.63 0.79 8.7 7.4 5.79 27.12
B2 B2 0.25 0.82 1.00 5.0 5.0 0.58 2.48
B3 B3 0.22 0.77 0.97 5.0 5.0 0.48 2.09
B4 B4 2.92 0.49 0.61 13.0 11.6 2.89 13.05
C1 C1 0.81 0.78 0.98 11.0 6.2 1.38 7.39
C2 C2 0.35 0.75 0.94 5.0 5.0 0.74 3.25
C3 C3 0.29 0.78 0.98 5.0 5.0 0.64 2.81
C4 C4 1.01 0.45 0.56 7.6 6.8 1.12 5.14
D1 D1 0.69 0.68 0.85 5.3 5.0 1.35 5.89
D2 D2 0.83 0.47 0.58 5.0 5.0 1.11 4.84
E1 E1 0.90 0.56 0.70 9.3 7.5 1.15 5.38
UD1 UD1 0.54 0.57 0.72 7.4 5.8 0.78 3.72
UD2 UD2 1.17 0.80 1.00 5.0 5.0 2.68 11.66
The Retreat @ Fort Collins
Preliminary Drainage Report 10
B. Detention Ponds and Water Quality/Low Impact Development
Due to the complication of designing the underground chambers for both LID treatment
and 100-year detention, the detention ponds and the LID treatments are labeled
differently. The labeling of the detention ponds designed for 100-year detention are
denoted by a number (ie. Pond 1, Pond 2, Pond 3). The labeling for the underground
chambers designed for LID Treatment ONLY are labeled with the basin for which they are
located (ie. Chamber A1, Chamber B2). Some chamber areas are labeled with both a
Detention Pond label and a LID label. These chamber areas, have both LID and
detention components, and these components are calculated separately.
Detention Pond 1 and Chambers A1, A2, and A3
Detention Pond 1 was designed to detain the stormwater runoff during a 100-year event
from the entire Basin A. Water Quality is provided for Basin A9 as extended detention
within Detention Pond 1.
Chambers A1 provides LID and water quality treatment for Basin A1. Chambers A2
provides LID and water quality treatment for Basin A2. Chamber A3 provides LID and
water quality treatment for Basins A3, A4, A5, A6, A7 and A8.
Detention Pond 2 and Chambers B2 and B3
Detention Pond 2 was designed to detain the stormwater runoff during a 100-year event
from Basin B. Water Quality is provided for Basin B4 as extended detention within
Detention Pond 2.
Chambers B2 provides LID and water quality treatment for Basins B1 and B2. Chambers
B3 provides LID and water quality treatment for Basin B3.
Detention Pond 3 and Chambers C1 and C3
Detention Pond 3 was designed to detain a portion of the stormwater runoff during a
100-year event from Basin C and Basin RW5. Water Quality is provided for Basins C2
and C4 as extended detention within Detention Pond 3. During a 100-year event
Detention Pond 3 will spill to the adjacent parking lot and inlet. This inlet will collect the
additional flow and convey it to underground Detention Pond 6.
Chambers C1 provides LID and water quality treatment for Basin C1. Chambers C3
provides LID and water quality treatment for Basin C3.
Detention Pond 4
Detention Pond 4 was designed to detain a portion of the stormwater runoff during a
100-year event from Basin D, Basin RW2 and Basin RW3. Water Quality is provided for
Basin D as extended detention within Detention Pond 4. During a 100-year event
Detention Pond 4 will spill to the adjacent parking lot and inlet. This inlet will collect the
additional flow and convey it to underground Detention Pond 6.
Detention Pond 5 and Chambers E1
Detention Pond 5 was designed to detain the stormwater runoff during a 100-year event
from Basin E within underground chambers.
Chambers E1 provides LID and water quality treatment for Basin E1.
Detention Pond 6
Detention Pond 6 was designed to detain the spill over from Ponds 3 and 4 during a 100-
year event within underground chambers.
The Retreat @ Fort Collins
Preliminary Drainage Report 11
A summary of the detention volumes and water quality volumes for each pond are found
below:
Table 2 – Detention Summary
Open Detention Pond Summary | Proposed Condition
Pond Pond Description
100-yr
Volume
(cf)
100-yr
Volume
(ac-ft)
100-yr WSEL
WQCV
(cf)
WQCV WSEL
Max
Release
(cfs)
1 Open Detention 136,113 3.12 4958.17 1,506 4954.28 2.00
2 Open Detention 62,275 1.43 4957.36 1,670 4954.58 2.50
3 Open Detention 17,541 0.40 4957.67 834 4955.11 0.50
4 Open Detention 17,703 0.41 4959.06 1,013 4956.76 0.50
Table 3 – Underground Chamber Summary
Underground Chamber Summary | Proposed Condition
Chamber Description
100-yr
Volume
(cf)
100-yr
Volume
(ac-ft)
100-yr WSEL
WQCV
(cf)
WQCV WSEL
Max
Release
(cfs)
A1 Underground LID n/a n/a n/a 486
to be provided at
final
n/a
A2 Underground LID n/a n/a n/a 2,387
to be provided at
final
n/a
A3 Underground LID n/a n/a n/a 4,183
to be provided at
final
n/a
B2 Underground LID n/a n/a n/a 2,593
to be provided at
final
n/a
B3 Underground LID n/a n/a n/a 182
to be provided at
final
n/a
The Retreat @ Fort Collins
Preliminary Drainage Report 12
By subtracting the existing undetained flow of 7.32 cfs from the proposed undetained
flow of 6.39 cfs, it is shown that the undetained flow from will be reduced 0.93 cfs from
the existing condition. This 0.93 cfs reduced flow balances the additional 0.63 cfs
release from the ponds. As a whole, the combined Redwood and Retreat sites will have
0.30 cfs less release in the 100-year event than what is allowable.
The table below illustrates these calculations:
Table 4 – Allowable Release Rate
Allowable Stormwater Release from Combined Redwood and
Retreat Site
Basin
Area
(acres)
100-yr Release
Rate (cfs)
Basin A (0.2 cfs/acre) 14.67 2.93
Basin B (0.2 cfs/acre) 7.3 1.46
Basin C (0.2 cfs/acre) 2.46 0.49
Basin D (0.2 cfs/acre) 1.53 0.31
Basin E (0.2 cfs/acre) 0.9 0.18
UD1 (0.2 cfs/acre) 0.54 0.11
UD4 (0.2 cfs/acre) 0.44 0.09
Total On-site Release 27.84 5.57
Off-site Basins
RW1 (100-yr runoff) 3.42 12.71
RW2 (100-yr runoff) 1.08 5.08
RW3 (100-yr runoff) 0.1 0.55
RW4 (100-yr runoff) 1.2 5.65
RW5 (100-yr runoff) 0.31 1.69
Total Off-site Release 6.11 25.68
Total Release from
Combined Redwood and
Retreat Basins
33.95 31.25
The Retreat @ Fort Collins
Preliminary Drainage Report 13
Table 5 – Proposed Release Rate
Proposed Stormwater Release from Combined Redwood and
Retreat Site
Pond/ Basin
100-yr Release
Rate (cfs)
Pond 1 2.00
Pond 2 2.50
Pond 3 0.50
Pond 4 0.50
Pond 5 0.20
Pond 6 0.50
Total Detention Release 6.20
Undetained Basins
RW1 12.71
RW4 5.65
UD1 3.72
UD4 2.67
Total Undetained Release 24.75
Total Release from Combined
Redwood and Retreat Basins
30.95
Based on this, the release from the site is well within the allowable release rate for the
site.
D. Low Impact Development (LID) Compliance
This site provides 74.6% treatment of new impervious area through a Low Impact
Development treatment facility. The LID treatment is provided through underground
detention and water quality chambers. These chambers will be designed as Stormtech
chambers at the time of final design.
The Retreat @ Fort Collins
Preliminary Drainage Report 14
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with The Retreat @ Fort Collins project complies with
the City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with The Retreat @ Fort Collins project complies with
the City of Fort Collins’ Master Drainage Plan for the Old Town Basin.
3. There are no regulatory floodplains associated with The Retreat @ Fort Collins
development.
4. The drainage plan and stormwater management measures proposed with The Retreat
@ Fort Collins development are compliant with all applicable State and Federal
regulations governing stormwater discharge.
B. Drainage Concept
1. The drainage design proposed with this project will effectively limit potential damage
associated with its stormwater runoff. The Retreat @ Fort Collins will detain for
proposed impervious area and release at a rate in conformance with the Dry Creek
major drainage basin of 0.2 cfs/acre.
2. The proposed The Retreat @ Fort Collins development will not impact the Master
Drainage Plan recommendations for the North East College Corridor Outfall (NECCO)
within Dry Creek major drainage basin.
The Retreat @ Fort Collins
Preliminary Drainage Report 15
References
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention Facilities,
November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by Ordinance No.
174, 2011, and referenced in Section 26-500 (c) of the City of Fort Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources Conservation
Service, United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood Control
District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April 2008.
APPENDIX A
HYDROLOGIC COMPUTATIONS
Hydrologic Soil Group—Larimer County Area, Colorado
(The Retreat )
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/18/2018
Page 1 of 4
4494200 4494300 4494400 4494500 4494600 4494700
4494200 4494300 4494400 4494500 4494600 4494700
494200 494300 494400 494500 494600 494700 494800 494900 495000
494200 494300 494400 494500 494600 494700 494800 494900 495000
40° 36' 12'' N
105° 4' 10'' W
40° 36' 12'' N
105° 3' 28'' W
40° 35' 52'' N
105° 4' 10'' W
40° 35' 52'' N
105° 3' 28'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 200 400 800 1200
Feet
0 50 100 200 300
Meters
Map Scale: 1:4,430 if printed on A landscape (11" x 8.5") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
Hydrologic Soil Group
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
22 Caruso clay loam, 0 to 1
percent slope
D 0.6 2.4%
64 Loveland clay loam, 0 to
1 percent slopes
C 6.7 24.5%
73 Nunn clay loam, 0 to 1
percent slopes
C 12.8 47.1%
76 Nunn clay loam, wet, 1
to 3 percent slopes
C 7.1 26.1%
Totals for Area of Interest 27.2 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Hydrologic Soil Group—Larimer County Area, Colorado The Retreat
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/18/2018
Page 3 of 4
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado The Retreat
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/18/2018
Page 4 of 4
The Retreat
CHARACTER OF SURFACE1:
Runoff
Coefficient
Percentage
Impervious Project: The Retreat
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 100% . Date: June 6, 2018
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 90% .
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 40% .
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Single Family Lots 0.55 50%
Lawns and Landscaping
Sandy Soil
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 2-year Cf = 1.00 10-year Cf = 1.00 100-year Cf = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Sub-Basin ID
Sub-
BasinBas
in Area
(ac)
Area of
Asphalt
(ac)
Area of
Gravel
(ac)
Area of
Concrete
(ac)
Area of
Single-Family
Lots
(ac)
Area of
Roofs
(ac)
Soil Type and Average
Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
The Retreat
Overland Flow, Time of Concentration:
The Retreat
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = T
i + Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
The Retreat
Rational Method Equation: Project: The Retreat
Calculations By:
Date:
Rainfall Intensity:
A1 A1 0.96 5 5 5 0.53 0.53 0.66 2.85 4.87 9.95 1.45 2.48 6.33
A2 A2 3.58 13 13 12 0.69 0.69 0.86 2.02 3.45 7.29 4.94 8.44 22.32
A3 A3 0.20 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.47 0.80 2.04
A4 A4 1.33 10 10 8 0.77 0.77 0.96 2.26 3.86 8.38 2.30 3.93 10.68
A5 A5 2.60 13 13 12 0.68 0.68 0.85 2.02 3.45 7.29 3.56 6.09 16.12
A6 A6 0.94 5 5 5 0.62 0.62 0.77 2.85 4.87 9.95 1.66 2.83 7.22
A7 A7 0.41 7 7 5 0.70 0.70 0.88 2.60 4.44 9.95 0.74 1.27 3.55
A8 A8 0.62 8 8 6 0.71 0.71 0.88 2.46 4.21 9.63 1.07 1.83 5.24
A9 A9 4.04 10 10 9 0.38 0.38 0.48 2.26 3.86 8.21 3.47 5.92 15.76
B1 B1 3.91 9 9 7 0.63 0.63 0.79 2.35 4.02 8.80 5.79 9.90 27.12
B2 B2 0.25 5 5 5 0.82 0.82 1.00 2.85 4.87 9.95 0.58 0.99 2.48
B3 B3 0.22 5 5 5 0.77 0.77 0.97 2.85 4.87 9.95 0.48 0.82 2.09
B4 B4 2.92 13 13 12 0.49 0.49 0.61 2.02 3.45 7.29 2.89 4.93 13.05
C1 C1 0.81 11 11 6 0.78 0.78 0.98 2.17 3.71 9.31 1.38 2.35 7.39
C2 C2 0.35 5 5 5 0.75 0.75 0.94 2.85 4.87 9.95 0.74 1.27 3.25
C3 C3 0.29 5 5 5 0.78 0.78 0.98 2.85 4.87 9.95 0.64 1.10 2.81
C4 C4 1.01 8 8 7 0.45 0.45 0.56 2.46 4.21 9.06 1.12 1.91 5.14
D1 D1 0.69 5 5 5 0.68 0.68 0.85 2.85 4.87 9.95 1.35 2.31 5.89
D2 D2 0.83 5 5 5 0.47 0.47 0.58 2.85 4.87 9.95 1.11 1.90 4.84
E1 E1 0.90 9 9 8 0.56 0.56 0.70 2.30 3.93 8.59 1.15 1.97 5.38
UD1 UD1 0.54 7 7 6 0.57 0.57 0.72 2.52 4.31 9.63 0.78 1.33 3.72
UD2 UD2 1.17 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 2.68 4.59 11.66
UD3 UD3 2.32 32 32 29 0.30 0.30 0.37 1.26 2.14 4.60 0.86 1.47 3.96
UD4 UD4 0.44 12 12 10 0.62 0.62 0.78 2.09 3.57 7.72 0.58 0.99 2.67
RW1 RW1 3.42 16 16 15 0.45 0.45 0.56 1.84 3.14 6.62 2.83 4.82 12.71
RW2 RW2 1.08 10 10 8 0.45 0.45 0.56 2.26 3.86 8.38 1.09 1.87 5.08
RW3 RW3 0.10 7 7 6 0.45 0.45 0.56 2.60 4.44 9.63 0.12 0.20 0.55
RW4 RW4 1.20 10 10 8 0.45 0.45 0.56 2.26 3.86 8.38 1.22 2.08 5.65
RW5 RW5 0.31 7 7 6 0.45 0.45 0.56 2.60 4.44 9.63 0.37 0.62 1.69
June 6, 2018
Intensity,
i10
(in/hr)
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
PROPOSED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Detention Facilities
APPENDIX B.1
STORM SEWERS (FOR FUTURE USE)
APPENDIX B.2
INLETS (FOR FUTURE USE)
APPENDIX B.3
DETENTION FACILITIES
The Retreat
1290-002
Fort Collins, Colorado
S. Thomas Date: 6/6/2018
Pond No.: 1
Pond 1
100-yr
0.75 WQCV 1506 ft
3
Area (A)= 14.67 acres Quantity Detention SWMM 136113 ft
3
Max Release Rate = 2.00 cfs Total Volume 136113 ft
3
Total Volume 3.125 ac-ft
*SWMM Model accounts for initial WQCV depth in pond prior to beginning of storm. Therefore, SWMM volume includes WQCV as
additional.
Detention Pond Calculation | SWMM Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
6/6/2018 10:06 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 1.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 6/6/2018
Pond No.: 1
Pond 1
WQCV
1506 ft3 4954.28 ft.
Design Storm 100-yr
Required Volume= 136113 ft3 4958.17 ft.
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
4,952.80 9 0.00 0 0 0 0
4,953.00 220 0.20 23 23 18 18
4,953.20 508 0.20 73 96 71 89
4,953.40 835 0.20 134 230 133 222
4,953.60 1200 0.20 204 433 202 424
4,953.80 1482 0.20 268 702 268 692
4,954.00 1670 0.20 315 1017 315 1007
4,954.20 1825 0.20 349 1366 349 1356
4,954.40 1948 0.20 377 1744 377 1734
4,954.60 2062 0.20 401 2145 401 2135
4,954.80 2345 0.20 441 2585 440 2575
4,955.00 3423 0.20 577 3162 573 3148
4,955.20 5398 0.20 882 4044 875 4023
4,955.40 8918 0.20 1432 5476 1417 5440
4,955.60 13203 0.20 2212 7688 2198 7638
4,955.80 18261 0.20 3146 10834 3133 10771
4,956.00 24662 0.20 4292 15127 4276 15047
4,956.20 32121 0.20 5678 20805 5662 20709
4,956.40 40185 0.20 7231 28036 7216 27925
4,956.60 47095 0.20 8728 36764 8719 36644
4,956.80 53030 0.20 10012 46776 10007 46650
4,957.00 57999 0.20 11103 57879 11099 57749
4,957.20 61898 0.20 11990 69868 11988 69737
4,957.40 64541 0.20 12644 82512 12643 82380
4,957.60 66700 0.20 13124 95636 13123 95503
4,957.80 69288 0.20 13599 109235 13598 109101
4,958.00 72800 0.20 14209 123444 14207 123308
4,958.20 77757 0.20 15056 138500 15053 138361
4,958.40 83826 0.20 16158 154658 16155 154516
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
6/6/201810:06 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 1.xlsm\Stage_Storage
The Retreat
1290-002
Fort Collins, Colorado
S. Thomas Date: 6/6/2018
Pond No.: 2
Pond 2
100-yr
0.73 WQCV 1670 ft
3
Area (A)= 7.30 acres Quantity Detention SWMM 62275 ft
3
Max Release Rate = 2.50 cfs Total Volume 62275 ft
3
Total Volume 1.430 ac-ft
*SWMM Model accounts for initial WQCV depth in pond prior to beginning of storm. Therefore, SWMM volume includes WQCV as
additional.
Detention Pond Calculation | SWMM Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
6/6/2018 10:07 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 2.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 6/6/2018
Pond No.: 2
Pond 2
WQCV
1670 ft3 4954.58 ft.
Design Storm 100-yr
Required Volume= 62275 ft3 4957.36 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
4,954.00 10 0.00 0 0 0 0
4,954.20 1029 0.20 104 104 76 76
4,954.40 4032 0.20 506 610 473 549
4,954.60 8503 0.20 1254 1864 1226 1775
4,954.80 13045 0.20 2155 4018 2139 3914
4,955.00 17294 0.20 3034 7052 3024 6938
4,955.20 19658 0.20 3695 10748 3693 10631
4,955.40 20614 0.20 4027 14775 4027 14657
4,955.60 21173 0.20 4179 18953 4179 18836
4,955.80 21742 0.20 4291 23245 4291 23127
4,956.00 22326 0.20 4407 27652 4407 27534
4,956.20 22936 0.20 4526 32178 4526 32060
4,956.40 23658 0.20 4659 36837 4659 36719
4,956.60 24480 0.20 4814 41651 4814 41533
4,956.80 25449 0.20 4993 46644 4993 46525
4,957.00 26592 0.20 5204 51848 5204 51729
4,957.20 29092 0.20 5568 57416 5567 57295
4,957.40 31732 0.20 6082 63499 6080 63376
4,957.60 36908 0.20 6864 70363 6857 70233
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
6/6/201810:07 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 2.xlsm\Stage_Storage
The Retreat
1290-002
Fort Collins, Colorado
S. Thomas Date: 6/6/2018
Pond No.: 3
Pond 3
100-yr
0.66 WQCV 834 ft
3
Area (A)= 1.36 acres Quantity Detention SWMM 17541 ft
3
Max Release Rate = 0.50 cfs Total Volume 17541 ft
3
Total Volume 0.403 ac-ft
*SWMM Model accounts for initial WQCV depth in pond prior to beginning of storm. Therefore, SWMM volume includes WQCV as
additional.
Detention Pond Calculation | SWMM Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
6/6/2018 10:07 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 3.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 6/6/2018
Pond No.: 3
Pond 3
WQCV
834 ft3 4955.11 ft.
Design Storm 100-yr
Required Volume= 17541 ft3 4957.67 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
4,953.40 13 0.00 0 0 0 0
4,953.60 51 0.20 6 6 6 6
4,953.80 115 0.20 17 23 16 22
4,954.00 205 0.20 32 55 32 54
4,954.20 336 0.20 54 109 54 107
4,954.40 510 0.20 85 194 84 191
4,954.60 710 0.20 122 316 121 313
4,954.80 938 0.20 165 480 164 477
4,955.00 1198 0.20 214 694 213 690
4,955.20 1492 0.20 269 963 268 958
4,955.40 1860 0.20 335 1298 335 1293
4,955.60 2327 0.20 419 1717 418 1711
4,955.80 2766 0.20 509 2226 509 2219
4,956.00 3246 0.20 601 2827 601 2820
4,956.20 3780 0.20 703 3530 702 3522
4,956.40 4376 0.20 816 4345 815 4337
4,956.60 5560 0.20 994 5339 991 5328
4,956.80 7588 0.20 1315 6654 1310 6637
4,957.00 9713 0.20 1730 8384 1726 8363
4,957.20 11850 0.20 2156 10540 2153 10516
4,957.40 14311 0.20 2616 13156 2612 13128
4,957.60 16483 0.20 3079 16236 3077 16205
4,957.80 21239 0.20 3772 20008 3762 19967
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
6/6/201810:07 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 3.xlsm\Stage_Storage
The Retreat
1290-002
Fort Collins, Colorado
S. Thomas Date: 6/6/2018
Pond No.: 4
Pond 4
100-yr
0.71 WQCV 1013 ft
3
Area (A)= 1.53 acres Quantity Detention SWMM 17703 ft
3
Max Release Rate = 0.50 cfs Total Volume 17703 ft
3
Total Volume 0.406 ac-ft
*SWMM Model accounts for initial WQCV depth in pond prior to beginning of storm. Therefore, SWMM volume includes WQCV as
additional.
Detention Pond Calculation | SWMM Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
6/6/2018 10:08 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 4.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 6/6/2018
Pond No.: 4
Pond 4
WQCV
1013 ft3 4956.76 ft.
Design Storm 100-yr
Required Volume= 17703 ft3 4959.06 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
4,955.60 1 0.00 0 0 0 0
4,955.80 45 0.20 5 5 3 3
4,956.00 160 0.20 21 25 19 23
4,956.20 540 0.20 70 95 66 89
4,956.40 1289 0.20 183 278 178 267
4,956.60 2181 0.20 347 625 343 610
4,956.80 3024 0.20 520 1146 518 1128
4,957.00 3999 0.20 702 1848 700 1828
4,957.20 4861 0.20 886 2734 885 2713
4,957.40 5639 0.20 1050 3784 1049 3762
4,957.60 6263 0.20 1190 4974 1190 4951
4,957.80 6900 0.20 1316 6290 1316 6267
4,958.00 7564 0.20 1446 7737 1446 7713
4,958.20 8242 0.20 1581 9317 1580 9293
4,958.40 8933 0.20 1718 11035 1717 11010
4,958.60 9641 0.20 1857 12892 1857 12867
4,958.80 10374 0.20 2001 14894 2001 14868
4,959.00 10969 0.20 2134 17028 2134 17002
4,959.20 11811 0.20 2278 19306 2277 19280
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
6/6/201810:08 AM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 4.xlsm\Stage_Storage
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
POND 1 (WQ FOR A9)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 4.040 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 17.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.1700 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.103 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.035 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 1506 <-- CALCULATED
WQ Depth (ft) = 1.480 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.131 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 2/5 <-- INPUT from Figure 5
number of rows = 4
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
June 6, 2018
POND 2 (WQ FOR B4)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 2.920 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 32.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.3200 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.158 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.038 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 1670 <-- CALCULATED
WQ Depth (ft) = 0.580 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.184 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/2 <-- INPUT from Figure 5
number of rows = 2
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
June 6, 2018
POND 3 (WQ FOR C2 and C4)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 1.360 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 36.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.3600 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.169 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.019 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 834 <-- CALCULATED
WQ Depth (ft) = 1.710 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.074 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/3 <-- INPUT from Figure 5
number of rows = 5
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
June 6, 2018
POND 4 (WQ FOR D1 AND D2)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 1.530 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 41.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.4100 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.182 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.023 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 1013 <-- CALCULATED
WQ Depth (ft) = 1.160 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.096 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/3 <-- INPUT from Figure 5
number of rows = 3
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
June 6, 2018
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 38.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.140 in
A = 0.96 ac
V = 0.0112 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber A1
486 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
A1
WQ
0.53
12.00 min 354 ft3
0.96 acres 0.01 ac-ft
Max Release Rate = 0.19 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 1.425 218 1.00 0.19 58 160
10 1.105 337 1.00 0.19 115 222
15 0.935 428 0.90 0.17 156 273
20 0.805 492 0.80 0.15 184 307
25 0.715 546 0.74 0.14 213 333
30 0.650 595 0.70 0.13 242 353
35 0.585 625 0.67 0.13 271 354
40 0.535 653 0.65 0.12 300 354
45 0.495 680 0.63 0.12 328 352
50 0.460 702 0.62 0.12 357 345
55 0.435 730 0.61 0.12 386 344
60 0.410 751 0.60 0.12 415 336
65 0.385 764 0.59 0.11 444 320
70 0.365 780 0.59 0.11 472 308
75 0.345 790 0.58 0.11 501 289
80 0.330 806 0.58 0.11 530 276
85 0.315 817 0.57 0.11 559 259
90 0.305 838 0.57 0.11 588 250
95 0.290 841 0.56 0.11 616 225
100 0.280 855 0.56 0.11 645 210
105 0.270 865 0.56 0.11 674 192
110 0.260 873 0.55 0.11 703 170
115 0.255 895 0.55 0.11 732 164
120 0.245 898 0.55 0.11 760 137
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1290-002
The Retreat
Project Number :
Project Name :
WQ Chamber A1
A =
Tc =
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 58.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.184 in
A = 3.58 ac
V = 0.0548 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
2387 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber A2
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
A2
WQ
0.69
12.00 min 2018 ft3
3.58 acres 0.05 ac-ft
Max Release Rate = 0.76 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 1056 1.00 0.76 228 828
10 1.105 1638 1.00 0.76 456 1182
15 0.935 2079 0.90 0.68 616 1463
20 0.805 2386 0.80 0.61 730 1657
25 0.715 2649 0.74 0.56 844 1806
30 0.650 2890 0.70 0.53 958 1933
35 0.585 3035 0.67 0.51 1072 1963
40 0.535 3172 0.65 0.49 1186 1986
45 0.495 3301 0.63 0.48 1300 2002
50 0.460 3409 0.62 0.47 1414 1995
55 0.435 3546 0.61 0.46 1528 2018
60 0.410 3646 0.60 0.46 1642 2004
65 0.385 3709 0.59 0.45 1756 1953
70 0.365 3787 0.59 0.45 1870 1917
75 0.345 3835 0.58 0.44 1984 1851
80 0.330 3913 0.58 0.44 2098 1815
85 0.315 3968 0.57 0.43 2212 1757
90 0.305 4068 0.57 0.43 2326 1743
95 0.290 4083 0.56 0.43 2440 1644
100 0.280 4150 0.56 0.43 2554 1596
105 0.270 4202 0.56 0.42 2668 1534
110 0.260 4239 0.55 0.42 2782 1457
115 0.255 4346 0.55 0.42 2896 1451
120 0.245 4357 0.55 0.42 3010 1348
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
C =
Tc =
A =
WQ Chamber A2
Input Variables Results
Design Point
Design Storm Required Detention Volume
Project Location : Fort Collins, Colorado
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Number : 1290-002
Project Name : The Retreat
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 60.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.189 in
A = 6.10 ac
V = 0.0960 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
4183 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber A3
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
A3
WQ
0.70
12.00 min 3617 ft3
6.10 acres 0.08 ac-ft
Max Release Rate = 1.25 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 1825 1.00 1.25 375 1450
10 1.105 2831 1.00 1.25 750 2081
15 0.935 3593 0.90 1.13 1013 2581
20 0.805 4125 0.80 1.00 1200 2925
25 0.715 4580 0.74 0.93 1388 3192
30 0.650 4996 0.70 0.88 1575 3421
35 0.585 5246 0.67 0.84 1763 3483
40 0.535 5483 0.65 0.81 1950 3533
45 0.495 5707 0.63 0.79 2138 3569
50 0.460 5893 0.62 0.78 2325 3568
55 0.435 6130 0.61 0.76 2513 3617
60 0.410 6303 0.60 0.75 2700 3603
65 0.385 6411 0.59 0.74 2888 3524
70 0.365 6546 0.59 0.73 3075 3471
75 0.345 6629 0.58 0.73 3263 3367
80 0.330 6764 0.58 0.72 3450 3314
85 0.315 6860 0.57 0.71 3638 3222
90 0.305 7033 0.57 0.71 3825 3208
95 0.290 7058 0.56 0.70 4013 3046
100 0.280 7174 0.56 0.70 4200 2974
105 0.270 7263 0.56 0.70 4388 2876
110 0.260 7327 0.55 0.69 4575 2752
115 0.255 7513 0.55 0.69 4763 2751
120 0.245 7532 0.55 0.69 4950 2582
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
C =
Tc =
A =
WQ Chamber A3
Input Variables Results
Design Point
Design Storm Required Detention Volume
Project Location : Fort Collins, Colorado
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Number : 1290-002
Project Name : The Retreat
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 53.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.172 in
A = 4.16 ac
V = 0.0595 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
2593 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber B2
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
B2
WQ
0.64
12.00 min 2218 ft3
4.16 acres 0.05 ac-ft
Max Release Rate = 0.80 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 1138 1.00 0.80 239 899
10 1.105 1765 1.00 0.80 479 1286
15 0.935 2240 0.90 0.72 646 1594
20 0.805 2572 0.80 0.64 766 1806
25 0.715 2855 0.74 0.59 886 1970
30 0.650 3115 0.70 0.56 1005 2110
35 0.585 3271 0.67 0.54 1125 2146
40 0.535 3419 0.65 0.52 1245 2174
45 0.495 3558 0.63 0.51 1365 2194
50 0.460 3674 0.62 0.49 1484 2190
55 0.435 3822 0.61 0.49 1604 2218
60 0.410 3930 0.60 0.48 1724 2206
65 0.385 3998 0.59 0.47 1843 2154
70 0.365 4081 0.59 0.47 1963 2118
75 0.345 4133 0.58 0.46 2083 2051
80 0.330 4217 0.58 0.46 2202 2015
85 0.315 4277 0.57 0.46 2322 1955
90 0.305 4385 0.57 0.45 2442 1943
95 0.290 4401 0.56 0.45 2562 1839
100 0.280 4473 0.56 0.45 2681 1792
105 0.270 4529 0.56 0.44 2801 1728
110 0.260 4569 0.55 0.44 2921 1648
115 0.255 4684 0.55 0.44 3040 1644
120 0.245 4696 0.55 0.44 3160 1536
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
C =
Tc =
A =
WQ Chamber B2
Input Variables Results
Design Point
Design Storm Required Detention Volume
Project Location : Fort Collins, Colorado
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Number : 1290-002
Project Name : The Retreat
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 72.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.227 in
A = 0.22 ac
V = 0.0042 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
182 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber B3
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
B3
WQ
0.77
12.00 min 102 ft3
0.22 acres 0.00 ac-ft
Max Release Rate = 0.08 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 72 1.00 0.08 23 50
10 1.105 112 1.00 0.08 46 67
15 0.935 143 0.90 0.07 62 81
20 0.805 164 0.80 0.06 73 91
25 0.715 182 0.74 0.06 84 97
30 0.650 198 0.70 0.05 96 102
35 0.585 208 0.67 0.05 107 101
40 0.535 218 0.65 0.05 119 99
45 0.495 226 0.63 0.05 130 96
50 0.460 234 0.62 0.05 141 92
55 0.435 243 0.61 0.05 153 90
60 0.410 250 0.60 0.05 164 86
65 0.385 254 0.59 0.05 176 79
70 0.365 260 0.59 0.04 187 73
75 0.345 263 0.58 0.04 198 65
80 0.330 268 0.58 0.04 210 59
85 0.315 272 0.57 0.04 221 51
90 0.305 279 0.57 0.04 233 46
95 0.290 280 0.56 0.04 244 36
100 0.280 285 0.56 0.04 255 29
105 0.270 288 0.56 0.04 267 21
110 0.260 291 0.55 0.04 278 13
115 0.255 298 0.55 0.04 290 8
120 0.245 299 0.55 0.04 301 -2
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
C =
Tc =
A =
WQ Chamber B3
Input Variables Results
Design Point
Design Storm Required Detention Volume
Project Location : Fort Collins, Colorado
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Number : 1290-002
Project Name : The Retreat
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 71.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.224 in
A = 0.81 ac
V = 0.0151 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
658 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber C1
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
C1
WQ
0.78
12.00 min 570 ft3
0.81 acres 0.01 ac-ft
Max Release Rate = 0.17 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 1.425 270 1.00 0.17 50 220
10 1.105 419 1.00 0.17 101 318
15 0.935 532 0.90 0.15 136 396
20 0.805 610 0.80 0.13 161 449
25 0.715 678 0.74 0.12 186 491
30 0.650 739 0.70 0.12 212 528
35 0.585 776 0.67 0.11 237 539
40 0.535 811 0.65 0.11 262 549
45 0.495 844 0.63 0.11 287 557
50 0.460 872 0.62 0.10 312 559
55 0.435 907 0.61 0.10 338 569
60 0.410 933 0.60 0.10 363 570
65 0.385 949 0.59 0.10 388 561
70 0.365 969 0.59 0.10 413 555
75 0.345 981 0.58 0.10 438 542
80 0.330 1001 0.58 0.10 464 537
85 0.315 1015 0.57 0.10 489 526
90 0.305 1041 0.57 0.10 514 526
95 0.290 1044 0.56 0.09 539 505
100 0.280 1061 0.56 0.09 564 497
105 0.270 1075 0.56 0.09 590 485
110 0.260 1084 0.55 0.09 615 469
115 0.255 1112 0.55 0.09 640 472
120 0.245 1114 0.55 0.09 665 449
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
C =
Tc =
A =
WQ Chamber C1
Input Variables Results
Design Point
Design Storm Required Detention Volume
Project Location : Fort Collins, Colorado
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Number : 1290-002
Project Name : The Retreat
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 73.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.231 in
A = 0.29 ac
V = 0.0056 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber C3
244 cu. ft.
Drain Time
a =
i =
WQCV =
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
C3
WQ
0.78
12.00 min 166 ft3
0.29 acres 0.00 ac-ft
Max Release Rate = 0.08 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 97 1.00 0.08 24 73
10 1.105 150 1.00 0.08 48 102
15 0.935 190 0.90 0.07 65 126
20 0.805 219 0.80 0.06 77 142
25 0.715 243 0.74 0.06 89 154
30 0.650 265 0.70 0.06 101 164
35 0.585 278 0.67 0.05 113 165
40 0.535 290 0.65 0.05 125 166
45 0.495 302 0.63 0.05 137 166
50 0.460 312 0.62 0.05 149 163
55 0.435 325 0.61 0.05 161 164
60 0.410 334 0.60 0.05 173 161
65 0.385 340 0.59 0.05 185 155
70 0.365 347 0.59 0.05 197 150
75 0.345 351 0.58 0.05 209 142
80 0.330 358 0.58 0.05 221 138
85 0.315 363 0.57 0.05 233 131
90 0.305 373 0.57 0.05 245 128
95 0.290 374 0.56 0.05 257 117
100 0.280 380 0.56 0.04 269 111
105 0.270 385 0.56 0.04 281 104
110 0.260 388 0.55 0.04 293 95
115 0.255 398 0.55 0.04 305 93
120 0.245 399 0.55 0.04 317 82
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
Project Location : Fort Collins, Colorado
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Number : 1290-002
Project Name : The Retreat
C =
Tc =
A =
WQ Chamber C3
Input Variables Results
Design Point
Design Storm Required Detention Volume
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 41.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.146 in
A = 0.90 ac
V = 0.0109 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat June 6, 2018
1290-002 S. Thomas
Landmark
WQ Chamber E1
477 cu. ft.
Drain Time
a =
i =
WQCV =
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
E1
WQ
0.56
12.00 min 442 ft3
0.90 acres 0.01 ac-ft
Max Release Rate = 0.14 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 1.425 215 1.00 0.14 42 173
10 1.105 334 1.00 0.14 84 250
15 0.935 424 0.90 0.13 113 311
20 0.805 487 0.80 0.11 134 352
25 0.715 541 0.74 0.10 155 385
30 0.650 590 0.70 0.10 176 413
35 0.585 619 0.67 0.09 197 422
40 0.535 647 0.65 0.09 218 429
45 0.495 674 0.63 0.09 239 434
50 0.460 696 0.62 0.09 260 435
55 0.435 723 0.61 0.09 281 442
60 0.410 744 0.60 0.08 302 442
65 0.385 757 0.59 0.08 323 433
70 0.365 773 0.59 0.08 344 428
75 0.345 782 0.58 0.08 365 417
80 0.330 798 0.58 0.08 386 412
85 0.315 810 0.57 0.08 407 402
90 0.305 830 0.57 0.08 428 402
95 0.290 833 0.56 0.08 449 384
100 0.280 847 0.56 0.08 470 376
105 0.270 857 0.56 0.08 491 366
110 0.260 865 0.55 0.08 512 352
115 0.255 887 0.55 0.08 533 353
120 0.245 889 0.55 0.08 554 335
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
Project Location : Fort Collins, Colorado
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Project Number : 1290-002
Project Name : The Retreat
C =
Tc =
A =
WQ Chamber E1
Input Variables Results
Design Point
Design Storm Required Detention Volume
Vault ID
Total
Required
WQ Volume
(cf)
Flow,
WQ
(cfs)
Chamber
Type
Chamber Release
Ratea
(cfs)
Chamber
Volumeb
(cf)
Installed
Chamber w/
Aggregatec
(cf)
Mimimum
No. of
Chambersd
Total Release
Ratee
(cfs)
Required
Storage
Volume by
FAA Method
(cf)
Mimimum
No. of
Chambersf
Storage
Provided
within the
Chambersg
(cf)
Total
Installed
System
Volumeh
(cf)
Chamber A1 486 0.72 SC-740 0.024 45.90 74.90 7 0.17 354 8 367 524
Chamber A2 2387 2.47 MC-3500 0.038 109.90 178.90 14 0.53 2018 19 2088 2505
Chamber A3 4183 2.47 MC-3500 0.038 109.90 178.90 24 0.90 3617 33 3627 4294
Chamber B2 2593 2.47 MC-3500 0.038 109.90 178.90 15 0.56 2218 21 2308 2684
Chamber B3 182 0.24 MC-3500 0.038 109.90 178.90 2 0.08 102 1 110 358
Chamber C1 658 0.69 MC-4500 0.028 106.50 162.60 5 0.14 570 6 639 813
Chamber C3 244 0.32 MC-3500 0.038 109.90 178.90 2 0.08 166 2 220 358
Chamber E1 477 0.57 MC-4500 0.028 106.50 162.60 3 0.08 442 5 533 488
a. 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.
Project: The Retreat
Calculations By: S. Thomas
Date: June 6, 2018
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
LID Treatment
A1 41,712 38% 15,745 Chamber A1
A2 155,746 58% 90,928 Chamber A2
A3 8,912 76% 6,730 Chamber A3
A4 58,007 69% 40,287 Chamber A3
A5 113,442 57% 64,957 Chamber A3
A6 40,921 47% 19,379 Chamber A3
A7 17,679 61% 10,787 Chamber A3
A8 26,879 61% 16,400 Chamber A3
B1 170,502 51% 87,078 Chamber B2
B2 10,877 77% 8,351 Chamber B2
B3 9,463 72% 6,807 Chamber B3
C1 35,306 71% 25,220 Chamber C1
C3 12,588 73% Chamber C3
E1 39,037 41% 15,991 Chamber E1
Total Treated 741,071 55% 408,661
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
A9 175,840 17% 29,541
B4 127,071 32% 40,987
C2 15,203 67% 10,242
C4 44,024 26% 11,270
D1 30,238 58% 17,450
D2 36,306 28% 10,132
UD1 23,444 43% 10,075
UD2 51,032 77% 39,522
UD3 101,092 6% 6,042
UD4 19,325 50% 9,704
Total Proposed
Untreated
623,575 30% 184,963
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
Suniga Street UD2 51,032 77% 39,522
Undisturbed Area UD3 101,092 6% 6,042
Not Included in
LID Calcs
T
S
YLOPLA
N
D
RIELITCU
O
N
E
E
E
E
E E
E
E E
E
E E
E
E
E
E
E
E
E
E
E E E E
E
E
E E
E
E
E
E
E
E
E
E
E
E
E
E
E
T
NYLOPLAS
IEL ITCUD
R
NO
PLAST
O
L
NY
CUD
T
LI
E
NORI
OPLAST
L
NY
ELITCUD
APPENDIX D
SWMM ANALYSIS / MODEL
SUB-A
SUB-B
SUB-C
SUB-D
SUB-E
SUB-RW5
SUB-RW2-3
C-1
C-2
C-3
C-4
C-5
C-6
WEIR3
WEIR4
O-1
O-2
O-3
O-4
O-5
O-6
NECCO
J-2
J-3
J-4 J-5
J-6
J-7
POND-1
POND-2
POND-3
POND-4
POND-5
POND-6
FORTCOLLINS
03/15/2016 00:15:00
SWMM 5.1 Page 1
2018-06-04_SWMM Preliminary.inp
[TITLE]
;;Project Title/Notes
[OPTIONS]
;;Option Value
FLOW_UNITS CFS
INFILTRATION HORTON
FLOW_ROUTING KINWAVE
LINK_OFFSETS DEPTH
MIN_SLOPE 0
ALLOW_PONDING NO
SKIP_STEADY_STATE NO
START_DATE 03/15/2016
START_TIME 00:00:00
REPORT_START_DATE 03/15/2016
REPORT_START_TIME 00:00:00
END_DATE 03/17/2016
END_TIME 06:00:00
SWEEP_START 01/01
SWEEP_END 12/31
DRY_DAYS 0
REPORT_STEP 00:15:00
WET_STEP 00:05:00
DRY_STEP 01:00:00
ROUTING_STEP 0:00:30
INERTIAL_DAMPING PARTIAL
NORMAL_FLOW_LIMITED BOTH
FORCE_MAIN_EQUATION H-W
VARIABLE_STEP 0.75
LENGTHENING_STEP 0
MIN_SURFAREA 12.557
MAX_TRIALS 8
HEAD_TOLERANCE 0.005
Page 1
2018-06-04_SWMM Preliminary.inp
SYS_FLOW_TOL 5
LAT_FLOW_TOL 5
MINIMUM_STEP 0.5
THREADS 1
[EVAPORATION]
;;Data Source Parameters
;;-------------- ----------------
CONSTANT 0.0
DRY_ONLY NO
[RAINGAGES]
;;Name Format Interval SCF Source
;;-------------- --------- ------ ------ ----------
FORTCOLLINS INTENSITY 0:05 1.0 TIMESERIES 100-YR
[SUBCATCHMENTS]
;;Name Rain Gage Outlet Area %Imperv Width %Slope CurbLen SnowPack
;;-------------- ---------------- ---------------- -------- -------- -------- -------- -------- ----------------
SUB-A FORTCOLLINS POND-1 14.67 46 380 0.5 0
SUB-B FORTCOLLINS POND-2 7.30 45 270 0.5 0
SUB-C FORTCOLLINS POND-3 2.46 52 150 0.5 0
SUB-D FORTCOLLINS POND-4 1.53 41 110 0.5 0
SUB-E FORTCOLLINS POND-5 0.90 41 190 0.5 0
SUB-RW5 FORTCOLLINS POND-3 0.31 35 110 0.5 0
SUB-RW2-3 FORTCOLLINS POND-4 1.18 35 160 0.5 0
[SUBAREAS]
;;Subcatchment N-Imperv N-Perv S-Imperv S-Perv PctZero RouteTo PctRouted
;;-------------- ---------- ---------- ---------- ---------- ---------- ---------- ----------
SUB-A .016 .025 .1 .3 25 OUTLET
SUB-B .016 .025 .1 .3 25 OUTLET
SUB-C .016 .025 .1 .3 25 OUTLET
SUB-D .016 .025 .1 .3 25 OUTLET
SUB-E .016 .025 .1 .3 25 OUTLET
Page 2
2018-06-04_SWMM Preliminary.inp
SUB-RW5 .016 .025 .1 .3 25 OUTLET
SUB-RW2-3 .016 .025 .1 .3 25 OUTLET
[INFILTRATION]
;;Subcatchment MaxRate MinRate Decay DryTime MaxInfil
;;-------------- ---------- ---------- ---------- ---------- ----------
SUB-A .51 0.5 .0018 7 0
SUB-B .51 0.5 .0018 7 0
SUB-C .51 0.5 .0018 7 0
SUB-D .51 0.5 .0018 7 0
SUB-E .51 0.5 .0018 7 0
SUB-RW5 .51 0.5 .0018 7 0
SUB-RW2-3 .51 0.5 .0018 7 0
[JUNCTIONS]
;;Name Elevation MaxDepth InitDepth SurDepth Aponded
;;-------------- ---------- ---------- ---------- ---------- ----------
NECCO 46 0 0 0 0
J-2 48 4.5 0 0 0
J-3 49 3 0 0 0
J-4 52 3 0 0 0
J-5 53 3 0 0 0
J-6 52 3 0 0 0
J-7 47 4.5 0 0 0
[STORAGE]
;;Name Elev. MaxDepth InitDepth Shape Curve Name/Params N/A Fevap Psi
Ksat IMD
;;-------------- -------- ---------- ----------- ---------- ---------------------------- -------- --------
-------- --------
POND-1 54.6 5.6 1.48 TABULAR POND1 0 0
POND-2 54 3.6 .58 TABULAR POND2 0 0
POND-3 53.7 5 1.71 TABULAR POND3 0 0
POND-4 55.6 4.2 1.16 TABULAR POND4 0 0
POND-5 49 3 0 TABULAR POND5 0 0
Page 3
2018-06-04_SWMM Preliminary.inp
POND-6 53.7 4 0 TABULAR POND6 0 0
[CONDUITS]
;;Name From Node To Node Length Roughness InOffset OutOffset InitFlow MaxFlow
;;-------------- ---------------- ---------------- ---------- ---------- ---------- ---------- ----------
----------
C-1 J-2 J-7 450 .012 0 0 0 0
C-2 J-7 NECCO 50 .012 0 0 0 0
C-3 J-5 J-4 160 .012 0 0 0 0
C-4 J-4 J-3 322 .012 0 0 0 0
C-5 J-3 J-7 84 .012 0 0 0 0
C-6 J-6 J-7 1574 .012 0 0 0 0
[WEIRS]
;;Name From Node To Node Type CrestHt Qcoeff Gated EndCon EndCoeff
Surcharge RoadWidth RoadSurf
;;-------------- ---------------- ---------------- ------------ ---------- ---------- -------- -------- ----------
---------- ---------- ----------
WEIR3 POND-3 POND-6 TRANSVERSE 4 3.33 NO 0 0
YES
WEIR4 POND-4 POND-6 TRANSVERSE 3.2 3.33 NO 0 0
YES
[OUTLETS]
;;Name From Node To Node Offset Type QTable/Qcoeff Qexpon Gated
;;-------------- ---------------- ---------------- ---------- --------------- ---------------- ---------- --------
O-1 POND-1 J-6 0 TABULAR/DEPTH OS-1 NO
O-2 POND-2 J-3 0 TABULAR/DEPTH OS-2 NO
Page 4
2018-06-04_SWMM Preliminary.inp
O-3 POND-3 J-5 0 TABULAR/DEPTH OS-3 NO
O-4 POND-4 J-5 0 TABULAR/DEPTH OS-4 NO
O-5 POND-5 J-2 0 TABULAR/DEPTH OS-5 NO
O-6 POND-6 J-5 0 TABULAR/DEPTH OS-6 NO
[XSECTIONS]
;;Link Shape Geom1 Geom2 Geom3 Geom4 Barrels Culvert
;;-------------- ------------ ---------------- ---------- ---------- ---------- ---------- ----------
C-1 CIRCULAR 4.5 0 0 0 1
C-2 CIRCULAR 4.5 0 0 0 1
C-3 CIRCULAR 3 0 0 0 1
C-4 CIRCULAR 3 0 0 0 1
C-5 CIRCULAR 3 0 0 0 1
C-6 CIRCULAR 2 0 0 0 1
WEIR3 RECT_OPEN 1 10 0 0
WEIR4 RECT_OPEN 1 10 0 0
[CURVES]
;;Name Type X-Value Y-Value
;;-------------- ---------- ---------- ----------
OS-1 Rating 0 0
OS-1 1.48 .1
OS-1 6 2.31
;
OS-2 Rating 0 0
OS-2 .58 .1
OS-2 4 3.05
;
OS-3 Rating 0 0
OS-3 1.71 .05
OS-3 4 .5
;
OS-4 Rating 0 0
OS-4 1.16 .05
OS-4 3.5 .51
Page 5
2018-06-04_SWMM Preliminary.inp
;
OS-5 Rating 0 0
OS-5 3 .29
;
OS-6 Rating 0 0
OS-6 4 .77
;
POND1 Storage 0 9.31
POND1 0.2 219.67
POND1 0.4 507.57
POND1 0.6 834.67
POND1 0.8 1200.35
POND1 1 1482.15
POND1 1.2 1669.73
POND1 1.4 1824.68
POND1 1.6 1948.2
POND1 1.8 2062.12
POND1 2 2345.35
POND1 2.2 3423
POND1 2.4 5398.23
POND1 2.6 8917.52
POND1 2.8 13202.84
POND1 3 18261.24
POND1 3.2 24662.39
POND1 3.4 32121.41
POND1 3.6 40185.08
POND1 3.8 47094.57
POND1 4 53029.55
POND1 4.2 57998.6
POND1 4.4 61897.63
POND1 4.6 64540.55
POND1 4.8 66699.51
POND1 5 69288.23
POND1 5.2 72799.88
POND1 5.4 77757.02
Page 6
2018-06-04_SWMM Preliminary.inp
POND1 5.6 83826.12
;
POND2 Storage 0 9.95
POND2 0.2 1029.25
POND2 0.4 4032.38
POND2 0.6 8502.87
POND2 0.8 13045.34
POND2 1 17294.08
POND2 1.2 19657.51
POND2 1.4 20614.22
POND2 1.6 21172.98
POND2 1.8 21741.68
POND2 2 22325.82
POND2 2.2 22936.15
POND2 2.4 23657.74
POND2 2.6 24479.71
POND2 2.8 25448.59
POND2 3 26592.22
POND2 3.2 29091.68
POND2 3.4 31731.76
POND2 3.6 36907.73
;
POND3 Storage 0 12.69
POND3 0.2 50.64
POND3 0.4 114.68
POND3 0.6 205.41
POND3 0.8 336.39
POND3 1 509.83
POND3 1.2 709.9
POND3 1.4 937.66
POND3 1.6 1197.78
POND3 1.8 1492.03
POND3 2 1859.76
POND3 2.2 2326.79
POND3 2.4 2766.05
Page 7
2018-06-04_SWMM Preliminary.inp
POND3 2.6 3246.08
POND3 2.8 3779.78
POND3 3 4375.52
POND3 3.2 5559.74
POND3 3.4 7588.09
POND3 3.6 9713.27
POND3 3.8 11850.35
POND3 4 14310.55
;
POND4 Storage 0 0.96
POND4 0.2 44.88
POND4 0.4 160.45
POND4 0.6 540.04
POND4 0.8 1289.21
POND4 1 2181.03
POND4 1.2 3023.8
POND4 1.4 3998.81
POND4 1.6 4861.35
POND4 1.8 5639.1
POND4 2 6262.68
POND4 2.2 6900.4
POND4 2.4 7563.73
POND4 2.6 8242.07
POND4 2.8 8933.05
POND4 3 9640.98
POND4 3.2 10373.89
;
POND5 Storage 0 4000
POND5 3 4000
;
POND6 Storage 0 8000
POND6 4 8000
[TIMESERIES]
;;Name Date Time Value
Page 8
2018-06-04_SWMM Preliminary.inp
;;-------------- ---------- ---------- ----------
100-YR 0:05 1
100-YR 0:10 1.14
100-YR 0:15 1.33
100-YR 0:20 2.23
100-YR 0:25 2.84
100-YR 0:30 5.49
100-YR 0:35 9.95
100-YR 0:40 4.12
100-YR 0:45 2.48
100-YR 0:50 1.46
100-YR 0:55 1.22
100-YR 1:00 1.06
100-YR 1:05 1
100-YR 1:10 .95
100-YR 1:15 .91
100-YR 1:20 .87
100-YR 1:25 .84
100-YR 1:30 .81
100-YR 1:35 .78
100-YR 1:40 .75
100-YR 1:45 .73
100-YR 1:50 .71
100-YR 1:55 .69
100-YR 2:00 .67
;
5-YR 0:05 .4
5-YR 0:10 .45
5-YR 0:15 .53
5-YR 0:20 .89
5-YR 0:25 1.13
5-YR 0:30 2.19
5-YR 0:35 3.97
5-YR 0:40 1.64
5-YR 0:45 .99
Page 9
2018-06-04_SWMM Preliminary.inp
5-YR 0:50 .58
5-YR 0:55 .49
5-YR 1:00 .42
5-YR 1:05 .28
5-YR 1:10 .27
5-YR 1:15 .25
5-YR 1:20 .24
5-YR 1:25 .23
5-YR 1:30 .22
5-YR 1:35 .21
5-YR 1:40 .20
5-YR 1:45 .19
5-YR 1:50 .19
5-YR 1:55 .18
5-YR 2:00 .18
;
10-YR 0:05 .49
10-YR 0:10 .56
10-YR 0:15 .65
10-YR 0:20 1.09
10-YR 0:25 1.39
10-YR 0:30 2.69
10-YR 0:35 4.87
10-YR 0:40 2.02
10-YR 0:45 1.21
10-YR 0:50 .71
10-YR 0:55 .6
10-YR 1:00 .52
10-YR 1:05 .39
10-YR 1:10 .37
10-YR 1:15 .35
10-YR 1:20 .34
10-YR 1:25 .32
10-YR 1:30 .31
10-YR 1:35 .3
Page 10
2018-06-04_SWMM Preliminary.inp
10-YR 1:40 .29
10-YR 1:45 .28
10-YR 1:50 .27
10-YR 1:55 .26
10-YR 2:00 .25
;
50-YR 0:05 .79
50-YR 0:10 .9
50-YR 0:15 1.05
50-YR 0:20 1.77
50-YR 0:25 2.25
50-YR 0:30 4.36
50-YR 0:35 7.9
50-YR 0:40 3.27
50-YR 0:45 1.97
50-YR 0:50 1.16
50-YR 0:55 .97
50-YR 1:00 .84
50-YR 1:05 .79
50-YR 1:10 .75
50-YR 1:15 .72
50-YR 1:20 .69
50-YR 1:25 .66
50-YR 1:30 .64
50-YR 1:35 .62
50-YR 1:40 .6
50-YR 1:45 .58
50-YR 1:50 .56
50-YR 1:55 .54
50-YR 2:00 .53
[REPORT]
;;Reporting Options
INPUT NO
CONTROLS NO
Page 11
2018-06-04_SWMM Preliminary.inp
SUBCATCHMENTS ALL
NODES ALL
LINKS ALL
[TAGS]
[MAP]
DIMENSIONS 0.000 0.000 2773.000 1354.000
Units None
[COORDINATES]
;;Node X-Coord Y-Coord
;;-------------- ------------------ ------------------
NECCO 878.333 78.727
J-2 621.814 349.857
J-3 842.615 270.304
J-4 1026.075 525.199
J-5 1212.782 521.952
J-6 2451.540 70.609
J-7 797.156 150.162
POND-1 2454.787 232.963
POND-2 1001.722 283.292
POND-3 1063.416 448.893
POND-4 1417.347 703.788
POND-5 701.368 411.552
POND-6 1209.535 452.140
[VERTICES]
;;Link X-Coord Y-Coord
;;-------------- ------------------ ------------------
WEIR3 1162.452 421.293
WEIR4 1427.088 567.411
[Polygons]
;;Subcatchment X-Coord Y-Coord
Page 12
2018-06-04_SWMM Preliminary.inp
;;-------------- ------------------ ------------------
SUB-A 1482.289 273.551
SUB-A 1527.748 317.387
SUB-A 1548.854 319.010
SUB-A 1581.324 286.540
SUB-A 1618.666 284.916
SUB-A 1688.478 356.352
SUB-A 1792.384 349.857
SUB-A 1794.008 403.434
SUB-A 1759.913 469.999
SUB-A 1750.172 530.070
SUB-A 1750.172 596.635
SUB-A 1690.101 668.071
SUB-A 1677.113 776.847
SUB-A 1652.760 799.577
SUB-A 1660.878 814.189
SUB-A 1665.748 871.013
SUB-A 1693.348 922.966
SUB-A 1703.090 1002.519
SUB-A 1720.948 997.648
SUB-A 1733.937 1015.507
SUB-A 1699.843 1101.555
SUB-A 1711.207 1130.778
SUB-A 1740.431 1127.531
SUB-A 1774.525 1140.520
SUB-A 1798.878 1088.566
SUB-A 1829.725 1069.084
SUB-A 1850.831 1069.084
SUB-A 1868.690 1111.296
SUB-A 2217.751 757.365
SUB-A 2558.693 380.705
SUB-A 2750.270 107.951
SUB-A 1480.665 161.527
SUB-B 1586.195 775.224
SUB-B 1543.983 721.647
Page 13
2018-06-04_SWMM Preliminary.inp
SUB-B 1521.254 739.506
SUB-B 1505.018 723.271
SUB-B 1362.147 593.388
SUB-B 1321.559 528.446
SUB-B 1311.817 442.399
SUB-B 1298.829 442.399
SUB-B 1254.994 396.940
SUB-B 1253.370 372.587
SUB-B 982.239 385.575
SUB-B 899.439 419.669
SUB-B 844.239 460.258
SUB-B 691.626 625.859
SUB-B 668.897 609.623
SUB-B 722.474 552.799
SUB-B 732.215 497.599
SUB-B 728.968 463.505
SUB-B 793.909 385.575
SUB-B 780.921 322.257
SUB-B 740.333 294.657
SUB-B 815.015 193.998
SUB-B 1479.042 158.280
SUB-B 1479.042 268.681
SUB-B 1522.877 323.881
SUB-B 1547.230 325.504
SUB-B 1571.583 291.410
SUB-B 1615.419 286.540
SUB-B 1685.231 354.728
SUB-B 1787.513 343.363
SUB-B 1792.384 408.305
SUB-B 1766.407 455.387
SUB-B 1748.549 521.952
SUB-B 1755.043 598.258
SUB-B 1685.231 671.318
SUB-B 1681.984 768.730
SUB-B 1656.007 801.201
Page 14
2018-06-04_SWMM Preliminary.inp
SUB-B 1644.642 791.459
SUB-B 1608.924 789.836
SUB-C 704.615 642.094
SUB-C 777.674 765.483
SUB-C 866.968 663.200
SUB-C 975.745 552.799
SUB-C 1183.558 533.317
SUB-C 1238.758 590.141
SUB-C 1256.617 565.788
SUB-C 1324.806 531.694
SUB-C 1315.064 442.399
SUB-C 1300.453 444.023
SUB-C 1254.994 396.940
SUB-C 1250.123 377.458
SUB-C 1229.017 377.458
SUB-C 998.475 382.328
SUB-C 927.039 406.681
SUB-C 847.486 458.634
SUB-C 688.379 629.106
SUB-D 1574.830 983.037
SUB-D 1578.077 968.425
SUB-D 1516.383 909.977
SUB-D 1480.665 828.801
SUB-D 1401.112 746.000
SUB-D 1242.005 598.258
SUB-D 1254.994 570.658
SUB-D 1321.559 525.199
SUB-D 1354.029 583.647
SUB-D 1519.630 734.636
SUB-D 1534.242 724.894
SUB-D 1569.960 758.989
SUB-D 1605.677 788.212
SUB-D 1652.760 796.330
SUB-D 1662.501 817.436
SUB-D 1664.125 877.507
Page 15
2018-06-04_SWMM Preliminary.inp
SUB-D 1693.348 922.966
SUB-D 1706.337 1000.895
SUB-D 1685.231 1026.872
SUB-E 547.132 564.164
SUB-E 576.355 564.164
SUB-E 631.556 616.117
SUB-E 668.897 609.623
SUB-E 728.968 543.058
SUB-E 728.968 463.505
SUB-E 793.909 388.822
SUB-E 782.544 325.504
SUB-E 743.580 289.787
SUB-E 548.755 512.211
SUB-RW5 925.416 687.553
SUB-RW5 990.357 614.494
SUB-RW5 1055.299 588.517
SUB-RW5 1116.993 608.000
SUB-RW5 1118.617 541.435
SUB-RW5 978.992 549.552
SUB-RW5 883.204 653.459
SUB-RW2-3 1367.018 713.530
SUB-RW2-3 1453.065 794.706
SUB-RW2-3 1431.959 815.812
SUB-RW2-3 1384.876 797.953
SUB-RW2-3 1341.041 806.071
SUB-RW2-3 1282.594 848.283
SUB-RW2-3 1214.405 927.836
SUB-RW2-3 1128.358 875.883
SUB-RW2-3 1058.546 807.695
SUB-RW2-3 1177.064 692.424
SUB-RW2-3 1253.370 690.800
SUB-RW2-3 1311.817 663.200
[SYMBOLS]
;;Gage X-Coord Y-Coord
Page 16
2018-06-04_SWMM Preliminary.inp
;;-------------- ------------------ ------------------
FORTCOLLINS 592.591 1257.241
[BACKDROP]
FILE "D:\Projects\1290-002\Drainage\Modeling\SWMM\1290-002_SJT DRNG-C6.00.jpg"
DIMENSIONS 0.000 0.000 2773.000 1354.000
Page 17
SWMM OUTPUT.rpt
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.1 (Build 5.1.012)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
RDII ................... NO
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... HORTON
Flow Routing Method ...... KINWAVE
Starting Date ............ 03/15/2016 00:00:00
Ending Date .............. 03/17/2016 06:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:15:00
Wet Time Step ............ 00:05:00
Dry Time Step ............ 01:00:00
Routing Time Step ........ 30.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 8.668 3.669
Page 1
SWMM OUTPUT.rpt
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 1.923 0.814
Surface Runoff ........... 6.717 2.843
Final Storage ............ 0.080 0.034
Continuity Error (%) ..... -0.606
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 6.717 2.189
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 6.821 2.223
Flooding Loss ............ 0.000 0.000
Evaporation Loss ......... 0.000 0.000
Exfiltration Loss ........ 0.000 0.000
Initial Stored Volume .... 0.116 0.038
Final Stored Volume ...... 0.008 0.003
Continuity Error (%) ..... 0.066
********************************
Highest Flow Instability Indexes
********************************
All links are stable.
*************************
Routing Time Step Summary
*************************
Minimum Time Step : 30.00 sec
Average Time Step : 30.00 sec
Maximum Time Step : 30.00 sec
Percent in Steady State : 0.00
Average Iterations per Step : 1.01
Page 2
SWMM OUTPUT.rpt
Percent Not Converging : 0.00
***************************
Subcatchment Runoff Summary
***************************
--------------------------------------------------------------------------------------------------------
Total Total Total Total Total Total Peak Runoff
Precip Runon Evap Infil Runoff Runoff Runoff Coeff
Subcatchment in in in in in 10^6 gal CFS
--------------------------------------------------------------------------------------------------------
SUB-A 3.67 0.00 0.00 0.83 2.83 1.13 77.87 0.771
SUB-B 3.67 0.00 0.00 0.81 2.84 0.56 45.29 0.775
SUB-C 3.67 0.00 0.00 0.68 2.98 0.20 18.82 0.811
SUB-D 3.67 0.00 0.00 0.84 2.83 0.12 11.68 0.771
SUB-E 3.67 0.00 0.00 0.81 2.86 0.07 8.32 0.780
SUB-RW5 3.67 0.00 0.00 0.89 2.79 0.02 2.94 0.761
SUB-RW2-3 3.67 0.00 0.00 0.90 2.77 0.09 10.11 0.755
******************
Node Depth Summary
******************
---------------------------------------------------------------------------------
Average Maximum Maximum Time of Max Reported
Depth Depth HGL Occurrence Max Depth
Node Type Feet Feet Feet days hr:min Feet
---------------------------------------------------------------------------------
NECCO JUNCTION 4.50 4.50 50.50 0 00:01 4.50
J-2 JUNCTION 0.06 0.15 48.15 0 02:09 0.15
J-3 JUNCTION 0.12 0.39 49.39 0 02:12 0.39
J-4 JUNCTION 0.12 0.33 52.33 0 02:17 0.33
J-5 JUNCTION 0.12 0.33 53.33 0 02:17 0.33
J-6 JUNCTION 0.25 0.51 52.51 0 02:24 0.51
J-7 JUNCTION 0.26 0.51 47.51 0 02:30 0.51
POND-1 STORAGE 2.45 5.37 59.97 0 02:24 5.37
Page 3
SWMM OUTPUT.rpt
POND-2 STORAGE 0.67 3.36 57.36 0 02:09 3.36
POND-3 STORAGE 0.98 4.27 57.97 0 00:57 4.27
POND-4 STORAGE 0.91 3.46 59.06 0 00:57 3.45
POND-5 STORAGE 0.49 2.08 51.08 0 02:09 2.07
POND-6 STORAGE 0.61 2.62 56.32 0 02:24 2.61
*******************
Node Inflow Summary
*******************
-------------------------------------------------------------------------------------------------
Maximum Maximum Lateral Total Flow
Lateral Total Time of Max Inflow Inflow Balance
Inflow Inflow Occurrence Volume Volume Error
Node Type CFS CFS days hr:min 10^6 gal 10^6 gal Percent
-------------------------------------------------------------------------------------------------
NECCO JUNCTION 0.00 6.15 0 02:15 0 2.22 0.000
J-2 JUNCTION 0.00 0.20 0 02:09 0 0.0693 0.000
J-3 JUNCTION 0.00 3.96 0 02:12 0 1.02 0.000
J-4 JUNCTION 0.00 1.46 0 02:17 0 0.44 0.000
J-5 JUNCTION 0.00 1.46 0 02:17 0 0.44 0.000
J-6 JUNCTION 0.00 2.00 0 02:24 0 1.14 0.000
J-7 JUNCTION 0.00 6.15 0 02:15 0 2.22 0.000
POND-1 STORAGE 77.87 77.87 0 00:40 1.13 1.14 0.016
POND-2 STORAGE 45.29 45.29 0 00:40 0.564 0.576 0.038
POND-3 STORAGE 21.76 21.76 0 00:40 0.222 0.229 0.180
POND-4 STORAGE 21.79 21.79 0 00:40 0.206 0.214 0.183
POND-5 STORAGE 8.32 8.32 0 00:40 0.07 0.07 0.022
POND-6 STORAGE 0.00 9.15 0 00:57 0 0.173 0.024
*********************
Node Flooding Summary
*********************
No nodes were flooded.
Page 4
SWMM OUTPUT.rpt
**********************
Storage Volume Summary
**********************
--------------------------------------------------------------------------------------------------
Average Avg Evap Exfil Maximum Max Time of Max Maximum
Volume Pcnt Pcnt Pcnt Volume Pcnt Occurrence Outflow
Storage Unit 1000 ft3 Full Loss Loss 1000 ft3 Full days hr:min CFS
--------------------------------------------------------------------------------------------------
POND-1 34.409 22 0 0 136.113 88 0 02:23 2.00
POND-2 8.353 12 0 0 62.275 89 0 02:09 2.50
POND-3 1.829 5 0 0 17.541 52 0 00:57 5.27
POND-4 2.531 9 0 0 17.703 65 0 00:56 4.88
POND-5 1.970 16 0 0 8.315 69 0 02:08 0.20
POND-6 4.904 15 0 0 20.941 65 0 02:24 0.50
********************
Link Flow Summary
********************
-----------------------------------------------------------------------------
Maximum Time of Max Maximum Max/ Max/
|Flow| Occurrence |Veloc| Full Full
Link Type CFS days hr:min ft/sec Flow Depth
-----------------------------------------------------------------------------
C-1 CONDUIT 0.20 0 02:12 1.24 0.00 0.03
C-2 CONDUIT 6.15 0 02:15 7.63 0.02 0.10
C-3 CONDUIT 1.46 0 02:17 3.43 0.03 0.11
C-4 CONDUIT 1.46 0 02:18 4.01 0.02 0.10
C-5 CONDUIT 3.96 0 02:12 7.44 0.04 0.13
C-6 CONDUIT 2.00 0 02:30 3.13 0.14 0.26
WEIR3 WEIR 4.77 0 00:57 0.00
WEIR4 WEIR 4.38 0 00:57 0.00
O-1 DUMMY 2.00 0 02:24
O-2 DUMMY 2.50 0 02:09
O-3 DUMMY 0.50 0 00:44
Page 5
SWMM OUTPUT.rpt
O-4 DUMMY 0.50 0 00:57
O-5 DUMMY 0.20 0 02:09
O-6 DUMMY 0.50 0 02:24
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Analysis begun on: Wed Jun 06 10:44:14 2018
Analysis ended on: Wed Jun 06 10:44:14 2018
Total elapsed time: < 1 sec
Page 6
APPENDIX E
FEMA FIRMETTE
DS,Airbus Source: USDA, Esri, USGS, DigitalGlobe, AeroGRID, GeoEye, IGN, and Earthstar the GIS Geographics, User Community CNES/
National Flood Hazard Layer FIRMette
0 250 500 1,000 1,500 2,000 Feet
Ü
105°4'8.72"W
40°36'20.86"N
105°3'29.76"W
40°35'52.45"N
SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUT
HAZARD SPECIAL AREAS FLOOD
Without Zone A, V, Base A99 Flood Elevation (BFE)
With BFE or Depth
RegulatoryAR Floodway Zone AE, AO, AH, VE,
0.of 2% 1% Annual annual Chance chance Flood flood with Hazard, average Areas
depth areasdrainage of less less than than one one foot square or with mile
Zone X
Future ChanceAnnual Conditions Flood Hazard 1%
Zone X
Area Levee.to with See Reduced Notes. Flood Risk due
Zone X
Area with Flood Risk due to LeveeZone D
NO SCREEN Area of Minimal Flood Hazard Zone X
Area of Undetermined Flood Hazard Zone D
Channel, Culvert, or Storm Sewer
Levee, Dike, or Floodwall
Cross Sections with 1% Annual Chance
17.5 Water Surface Elevation
Coastal Transect
Coastal Transect Baseline
Profile Baseline
Hydrographic Feature
Base Flood Elevation Line (BFE)
Effective LOMRs
Limit of Study
Jurisdiction Boundary
Digital Data Available
No Digital Data Available
Unmapped
This digital map flood complies maps if with it is FEMA's not void standards as described for the below. use of
The accuracy base standards map shown complies with FEMA's base map
The authoritative flood hazard NFHL information web services is derived provided directly by FEMA. from This the map
was reflectnot exported changes on or 3/amendments 12/2018 at subsequent 11:37:03 AM to and this does date and
time. becomeor The superseded NFHL and effective by new data information over time. may change
This elementsmap map image do not is appear: void if base the one map or imagery, more of the flood following zone labels,
legend, FIRM panel scale number, bar, map and creation FIRM effective date, community date. Map identifiers,images for
unmapped regulatoryfor purposes. and unmodernized areas cannot be used
Legend
OTHER FLOOD AREAS HAZARD OF
OTHER AREAS
STRGUECNTUERREASL
FEATURES OTHER
MAP PANELS
8
1:6,241.13
B 20.2
APPENDIX F
EROSION CONTROL REPORT
The Retreat at Fort Collins
Preliminary 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, that any such Erosion and
Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of
the BMPs depicted, and additional or different BMPs from those included may be necessary during
construction, or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living
document, constantly adapting to site conditions and needs. The Contractor shall update the
location of BMPs as they are installed, removed or modified in conjunction with construction
activities. It is imperative to appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices
from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are
not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways
and inlet protection at 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 Utility
Plans at final design 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 will
be required to secure a Stormwater Construction General Permit from the Colorado Department of
Public Health and Environment (CDPHE), Water Quality Control Division – Stormwater Program,
before commencing any earth disturbing activities. Prior to securing said permit, the Site Contractor
shall develop a comprehensive StormWater Management Plan (SWMP) pursuant to CDPHE
requirements and guidelines. The SWMP will further describe and document the ongoing activities,
inspections, and maintenance of construction BMPs
MAP POCKET
C6.00 – OVERALL DRAINAGE EXHIBIT
V.P.
V.P.
D
D
V.P.
F
E
S
F
E
S
F
E
S
MH ELEC
MH
D
MW
MW
MW
F
E
S
D
D
VAULT
CABLE
D
D
IRR
D
D
ELEC
VAULT
ELEC
VAULT
ELEC
D
D
D
VAULT
ELEC
D
CC
C
C
C
D
12" W
12" W
12" W
60" W
60" W
60" W
60" W
42" W
42" W
42" W
X
X
ST ST ST
ST
ST
ST
ST
ST
ST
u
til
VAULT
ELEC
ST ST
D
T
AS
L
N YLOP
CUD
T
ELI I
R
NO
T
O PLAS
L
Y
N
D
CU IT
L
IE NOR
ST
NYL OPLA
D CU
T
ELI I
R
O
N
S T
N YLOPLA
CUD
T
ELI I
R
O
N
(13) SPACES
(16) SPACES
(13) SPACES
(15) SPACES
(12) SPACES
(9) SPACES
UP
TYP.
UP
ELEVATOR
TYP. H.C. SPACE
TYP.
UP
42" HIGH CHAIN LINK
FENCE BARRIER (TYP.)
42" HIGH CHAIN LINK
FENCE ENCLOSURE (TYP.)
STORAGE AREA BELOW RAMP
POND 2
RW1
RW2
RW3
RW4
RW5
UD1
UD2
UD3
UD4
UD1
UD2
UD3
RW5
RW4
RW2
RW1
RW3
FUTURE
NORTHFIELD SUBDIVISION
1ST FILING
REPLAT OF THE
MEADOWS AT REDWOOD
P.U.D PHASE 1
TRACT A
REPLAT OF EVERGREEN
PARK 2ND FILING
LAKE CANAL
LAKE CANAL
OWNER
ROCKY MOUNTAIN
RAPTOR PROGRAM
EVERGREEN PARK
3RD FILING
OWNER
BOARD OF COUNTY
COMMISSIONERS
EXISTING REDWOOD
DETENTION POND
POND 3
POND 4
POND 1
E1
C1
B4 B3 B2
C2
C3
C4
D1
D2
B1
A1
A2
A3
A5
A4
A6
A7
A8
A9
FEMA
HIGH-RISK
FLOODWAY
FEMA
HIGH-RISK
FLOODPLAIN
PROPOSED
OUTLET STRUCTURE
PROPOSED
OUTLET STRUCTURE
NECCO STORMLINE
PROPOSED
INLETS
PROPOSED
INLETS
PROPOSED
CURB CUTS
EXISTING INLET
PROPOSED
INLET
WQ
CHAMBER
B3 WQ
CHAMBER
B2
WQ
CHAMBER
C3
POND 6
WQ
CHAMBER
C1
WQ
CHAMBER
E1
POND 5
WQ
CHAMBER
A2
WQ
CHAMBER
A1 A3
A2
A3
A4
A5
A6
A7
A8
A9
B1
B2
B3
B4
C1
C2
C3
C4
D1
D2
E1
UD4
PLANNED
INLETS
PROPOSED
INLETS
PROPOSED
INLETS
PROPOSED
OUTLET STRUCTURE
PROPOSED
OUTLET
STRUCTURE
PROPOSED
CURB CUTS
PROPOSED
INLET
PROPOSED
INLET
WQ
CHAMBER
A1
( IN FEET )
0
1 INCH = 100 FEET
100 100 200 300
Sheet
THE RETREATE AT FORT COLLINS These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
E NGINEER ING
N O R T H E RN
FORT COLLINS: 301 North Howes Street, Suite 100, 80521
GREELEY: 820 8th Street, 80631
970.221.4158
northernengineering.com
of 24
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner
LEGEND:
5013
PROPOSED CONTOUR 93
EXISTING CONTOUR
PROPERTY BOUNDARY
EXISTING STORM SEWER
1. THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES ARE
APPROXIMATE WHEN SHOWN ON THESE DRAWINGS. IT SHALL BE THE
RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE EXISTENCE OF ALL
UNDERGROUND UTILITIES IN THE AREA OF THE WORK. BEFORE COMMENCING
NEW CONSTRUCTION, THE CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING
ALL UNDERGROUND UTILITIES AND SHALL BE RESPONSIBLE FOR FOR ALL
UNKNOWN UNDERGROUND UTILITIES.
2. REFER TO THE"Preliminary Drainage Report for The Retreat at Fort Collins dated June 6,
2018" FOR ADDITIONAL INFORMATION.
NOTES:
FLOW PATH
DRAINAGE BASIN BUBBLE
A
DESIGN POINT A
BASIN BOUNDARY
PROPOSED STORM SEWER
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
C6.00
DRAINAGE EXHIBIT
23
NORTH
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
A1 A1 0.96 0.53 0.66 5.0 5.0 1.45 6.33
A2 A2 3.58 0.69 0.86 12.6 11.7 4.94 22.32
A3 A3 0.20 0.80 1.00 5.0 5.0 0.47 2.04
A4 A4 1.33 0.77 0.96 9.6 8.1 2.30 10.68
A5 A5 2.60 0.68 0.85 12.6 11.9 3.56 16.12
A6 A6 0.94 0.62 0.77 5.0 5.0 1.66 7.22
A7 A7 0.41 0.70 0.88 7.0 5.0 0.74 3.55
A8 A8 0.62 0.71 0.88 7.8 5.6 1.07 5.24
A9 A9 4.04 0.38 0.48 9.5 8.6 3.47 15.76
B1 B1 3.91 0.63 0.79 8.7 7.4 5.79 27.12
B2 B2 0.25 0.82 1.00 5.0 5.0 0.58 2.48
B3 B3 0.22 0.77 0.97 5.0 5.0 0.48 2.09
B4 B4 2.92 0.49 0.61 13.0 11.6 2.89 13.05
C1 C1 0.81 0.78 0.98 11.0 6.2 1.38 7.39
C2 C2 0.35 0.75 0.94 5.0 5.0 0.74 3.25
C3 C3 0.29 0.78 0.98 5.0 5.0 0.64 2.81
C4 C4 1.01 0.45 0.56 7.6 6.8 1.12 5.14
D1 D1 0.69 0.68 0.85 5.3 5.0 1.35 5.89
D2 D2 0.83 0.47 0.58 5.0 5.0 1.11 4.84
E1 E1 0.90 0.56 0.70 9.3 7.5 1.15 5.38
UD1 UD1 0.54 0.57 0.72 7.4 5.8 0.78 3.72
UD2 UD2 1.17 0.80 1.00 5.0 5.0 2.68 11.66
UD3 UD3 2.32 0.30 0.37 32.0 29.0 0.86 3.96
UD4 UD4 0.44 0.62 0.78 11.8 10.3 0.58 2.67
RW1 RW1 3.42 0.45 0.56 15.9 14.7 2.83 12.71
RW2 RW2 1.08 0.45 0.56 9.6 8.4 1.09 5.08
RW3 RW3 0.10 0.45 0.56 6.8 5.6 0.12 0.55
RW4 RW4 1.20 0.45 0.56 9.6 8.4 1.22 5.65
RW5 RW5 0.31 0.45 0.56 6.8 5.6 0.37 1.69
Open Detention Pond Summary | Proposed Condition
Pond Pond Description
100-yr
Volume
(cf)
100-yr
Volume
(ac-ft)
100-yr WSEL WQCV
(cf) WQCV WSEL
Max
Release
(cfs)
1 Open Detention 136,113 3.12 4958.17 1,506 4954.28 2.00
2 Open Detention 62,275 1.43 4957.36 1,670 4954.58 2.50
3 Open Detention 17,541 0.40 4957.67 834 4955.11 0.50
4 Open Detention 17,703 0.41 4959.06 1,013 4956.76 0.50
Underground Chamber Summary | Proposed Condition
Chamber Description
100-yr
Volume
(cf)
100-yr
Volume
(ac-ft)
100-yr WSEL WQCV
(cf) WQCV WSEL
Max
Release
(cfs)
A1 Underground LID n/a n/a n/a 486 to be provided at final n/a
A2 Underground LID n/a n/a n/a 2,387 to be provided at final n/a
A3 Underground LID n/a n/a n/a 4,183 to be provided at final n/a
B2 Underground LID n/a n/a n/a 2,593 to be provided at final n/a
B3 Underground LID n/a n/a n/a 182 to be provided at final n/a
C1 Underground LID n/a n/a n/a 658 n/a
C3/Pond 6 Underground LID and
Detention
20,941 0.48 to be provided at final 244 to be provided at final 0.50
E1/Pond 5 Underground LID and
Detention
8,315 0.19 to be provided at final 477 to be provided at final 0.20
NORI
FUTURE
NORTHFIELD SUBDIVISION
1ST FILING
REPLAT OF THE
MEADOWS AT
REDWOOD P.U.D
PHASE 1
TRACT A
REPLAT OF
EVERGREEN PARK
2ND FILING
LAKE CANAL
LAKE CANAL
OWNER
ROCKY MOUNTAIN
RAPTOR PROGRAM
EVERGREEN PARK 3RD FILING
OWNER
BOARD OF COUNTY
COMMISSIONERS
S
H
Y
D
WV
S
C
S
WV
V.P.
V.P.
D
H2O
D
V.P.
F
E
S
F
E
S
F
E
S
ELEC
MH
MH
H
Y
D
D
MW
MW
H2O
WV
WV
H2O
W
WV
WV WV
W
H2O
MW
W
h2o
F
E
S
D
D
VAULT
CABLE
D
D
IRR
D
D
ELEC VAULT
ELEC
H2O
VAULT
ELEC
H2O
D
WV WV
WV
WV
H
Y
D
D
D
VAULT
ELEC
D
C
D
H
Y
D
WV
S
H
Y
D
WV
WV
S
S
S
S
WV
WV
WV
S
C
C
C W
C
WV
WV
D
12" W
60" W
60" W
42" W
E
E E
E
CTV
CTV
CTV
E
E
OHU OHU OHU
OHU
OHU OHU
CTV
W
CTV
E
E
CTV
CTV
W
W W
W
W
CTV
CTV
CTV
CTV
W
CTV
X
SS
SS
SS SS
SS
ST
ST
u
til
VAULT
ELEC
D
FEMA
HIGH-RISK
FLOODWAY
FEMA HIGH-RISK
FLOODPLAIN
NECCO STORMLINE
EXISTING INLET
EXISTING REDWOOD
DETENTION POND
POND 4
WQ
CHAMBER
B3
WQ
CHAMBER
B2
WQ
CHAMBER
C3
WQ
CHAMBER
C1
WQ
CHAMBER
E1
WQ
CHAMBER
A2
WQ
CHAMBER
A3
WQ
CHAMBER
A1
LEGEND
DRAINAGE BASIN
DRAINAGE BASIN LABEL
AREA TREATED BY LOW
IMPACT DEVELOPMENT
(LID)
LOW IMPACT
DEVELOPMENT (LID)
TREATMENT
E1
LID TREATMENT EXHIBIT
FORT COLLINS, CO
THE RETREAT AT FORT COLLINS
E NGINEER ING
N O R T H E RN
06.06.2018
D:\PROJECTS\1290-002\DWG\DRNG\1290-002_LID.DWG
( IN FEET )
0
1 INCH = 200 FEET
200 200
PROPOSED LID TREATED AREA
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent Impervious Impervious Area, A
(sf) LID Treatment
A1 41,712 38% 15,745 Chamber A1
A2 155,746 58% 90,928 Chamber A2
A3 8,912 76% 6,730 Chamber A3
A4 58,007 69% 40,287 Chamber A3
A5 113,442 57% 64,957 Chamber A3
A6 40,921 47% 19,379 Chamber A3
A7 17,679 61% 10,787 Chamber A3
A8 26,879 61% 16,400 Chamber A3
B1 170,502 51% 87,078 Chamber B2
B2 10,877 77% 8,351 Chamber B2
B3 9,463 72% 6,807 Chamber B3
C1 35,306 71% 25,220 Chamber C1
C3 12,588 73% Chamber C3
E1 39,037 41% 15,991 Chamber E1
Total Treated 741,071 55% 408,661
PROPOSED LID UNTREATED AREA
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent Impervious Impervious Area, A
(sf)
A9 175,840 17% 29,541
B4 127,071 32% 40,987
C2 15,203 67% 10,242
C4 44,024 26% 11,270
D1 30,238 58% 17,450
D2 36,306 28% 10,132
UD1 23,444 43% 10,075
UD2 51,032 77% 39,522
UD3 101,092 6% 6,042
UD4 19,325 50% 9,704
Total Proposed
Untreated
623,575 30% 184,963
AREA NOT INCLUDED IN LID CALCULATIONS
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent Impervious Impervious Area, A
(sf)
Suniga Street UD2 51,032 77% 39,522
Undisturbed Area UD3 101,092 6% 6,042
Not Included in LID
Calcs
152,124 30% 45,563
LID TREATMENT SUMMARY
Total Site Area (sf) 1,364,646
Total Proposed Impervious Area (sf) 593,624
Total Impervious Area not included in LID
calcs
45,563
Total Net Proposed Impervious Area (sf) 548,061
75% Required Minimum Area to be Treated
by LID measures (sf) 411,046
Total Treated Impervious Area (sf) 408,661
Percent Impervious Treated by LID measures 74.6%
152,124 30% 45,563
1,364,646
593,624
45,563
548,061
411,046
408,661
74.6%
Total Net Proposed Impervious Area (sf)
AREA NOT INCLUDED IN LID CALCULATIONS
Total Impervious Area not included in LID
calcs
Total Treated Impervious Area (sf)
Percent Impervious Treated by LID
75% Required Minimum Area to be
Treated by LID measures (sf)
Total Proposed Impervious Area (sf)
PROPOSED LID COMPUTATIONS
LID TREATMENT SUMMARY
PROPOSED LID UNTREATED AREA
Total Site Area (sf)
PROPOSED LID TREATED AREA
Chamber Configuration Summary
D:\Projects\1290-002\Drainage\WatQual\Chambers_WQ Calcs.xlsx
Page 16 of 17
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e e e
i
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Sub-Basin(s)
S. Thomas
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
Q = C f ( C )( i )( A )
6/6/2018 10:03 AM D:\Projects\1290-002\Drainage\Hydrology\1290-002_Proposed_Rational_Calcs.xlsx\Runoff
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
A1 A1 No 0.53 0.53 0.66 N/A N/A N/A N/A 146 1.72% 1.97 1.2 N/A N/A N/A 5.0 5.0 5.0
A2 A2 No 0.69 0.69 0.86 12 1.83% 2.2 2.2 1.3 N/A N/A N/A 1007 0.65% 1.62 10.4 12.6 12.6 11.7
A3 A3 No 0.80 0.80 1.00 71 3.24% 3.2 3.2 1.1 N/A N/A N/A 34 1.00% 2.00 0.3 5.0 5.0 5.0
A4 A4 No 0.77 0.77 0.96 29 1.83% 2.8 2.8 1.2 N/A N/A N/A 589 0.51% 1.43 6.9 9.6 9.6 8.1
A5 A5 No 0.68 0.68 0.85 15 4.73% 1.8 1.8 1.1 N/A N/A N/A 916 0.50% 1.41 10.8 12.6 12.6 11.9
A6 A6 No 0.62 0.62 0.77 N/A N/A N/A N/A 105 1.71% 1.96 0.9 N/A N/A N/A 5.0 5.0 5.0
A7 A7 No 0.70 0.70 0.88 35 0.69% 5.0 5.0 2.8 N/A N/A N/A 206 0.73% 1.71 2.0 7.0 7.0 5.0
A8 A8 No 0.71 0.71 0.88 69 1.75% 5.1 5.1 2.8 N/A N/A N/A 272 0.68% 1.65 2.7 7.8 7.8 5.6
A9 A9 No 0.38 0.38 0.48 76 4.52% 7.1 7.1 6.2 N/A N/A N/A 270 0.88% 1.87 2.4 9.5 9.5 8.6
B1 B1 No 0.63 0.63 0.79 39 3.26% 3.7 3.7 2.5 N/A N/A N/A 529 0.78% 1.77 5.0 8.7 8.7 7.4
B2 B2 No 0.82 0.82 1.00 65 2.63% 3.1 3.1 1.1 N/A N/A N/A 29 0.49% 1.40 0.3 5.0 5.0 5.0
B3 B3 No 0.77 0.77 0.97 83 3.10% 3.8 3.8 1.6 N/A N/A N/A 36 0.47% 1.37 0.4 5.0 5.0 5.0
B4 B4 No 0.49 0.49 0.61 55 1.93% 6.8 6.8 5.4 N/A N/A N/A 597 0.65% 1.61 6.2 13.0 13.0 11.6
C1 C1 No 0.78 0.78 0.98 120 0.58% 7.8 7.8 3.0 N/A N/A N/A 410 1.15% 2.14 3.2 11.0 11.0 6.2
C2 C2 No 0.75 0.75 0.94 60 3.02% 3.5 3.5 1.6 N/A N/A N/A 94 0.85% 1.85 0.8 5.0 5.0 5.0
C3 C3 No 0.78 0.78 0.98 97 3.03% 4.1 4.1 1.6 N/A N/A N/A 47 0.51% 1.43 0.5 5.0 5.0 5.0
C4 C4 No 0.45 0.45 0.56 58 8.45% 4.6 4.6 3.8 327 1.43% 1.80 3.0 N/A N/A N/A 7.6 7.6 6.8
D1 D1 No 0.68 0.68 0.85 37 3.14% 3.2 3.2 1.9 N/A N/A N/A 217 0.80% 1.79 2.0 5.3 5.3 5.0
D2 D2 No 0.47 0.47 0.58 N/A N/A N/A N/A 368 1.08% 1.56 3.9 N/A N/A N/A 5.0 5.0 5.0
E1 E1 No 0.56 0.56 0.70 61 1.49% 6.9 6.9 5.1 N/A N/A N/A 199 0.49% 1.40 2.4 9.3 9.3 7.5
UD1 UD1 No 0.57 0.57 0.72 87 3.68% 5.9 5.9 4.3 N/A N/A N/A 183 1.04% 2.04 1.5 7.4 7.4 5.8
UD2 UD2 No 0.80 0.80 1.00 N/A N/A N/A N/A N/A N/A N/A 493 0.91% 1.91 4.3 5.0 5.0 5.0
UD3 UD3 No 0.30 0.30 0.37 292 0.52% 32.0 32.0 29.0 N/A N/A N/A N/A N/A N/A 32.0 32.0 29.0
UD4 UD4 No 0.62 0.62 0.78 68 4.13% 4.6 4.6 3.1 N/A N/A N/A 599 0.47% 1.38 7.2 11.8 11.8 10.3
RW1 RW1 No 0.45 0.45 0.56 50 2.00% 6.8 6.8 5.6 N/A N/A N/A 840 0.60% 1.54 9.1 15.9 15.9 14.7
RW2 RW2 No 0.45 0.45 0.56 50 2.00% 6.8 6.8 5.6 100 1.00% 1.50 1.1 197 1.02% 2.02 1.6 9.6 9.6 8.4
RW3 RW3 No 0.45 0.45 0.56 50 2.00% 6.8 6.8 5.6 N/A N/A N/A N/A N/A N/A 6.8 6.8 5.6
RW4 RW4 No 0.45 0.45 0.56 50 2.00% 6.8 6.8 5.6 100 1.00% 1.50 1.1 197 1.02% 2.02 1.6 9.6 9.6 8.4
RW5 RW5 No 0.45 0.45 0.56 50 2.00% 6.8 6.8 5.6 N/A N/A N/A N/A N/A N/A 6.8 6.8 5.6
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
PROPOSED TIME OF CONCENTRATION COMPUTATIONS
S. Thomas
Design
Point
Sub-Basin
Overland Flow Swale Flow Gutter/Pipe Flow Time of Concentration
June 6, 2018
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
6/6/2018 10:02 AM D:\Projects\1290-002\Drainage\Hydrology\1290-002_Proposed_Rational_Calcs.xlsx\Tc
% Imperv.
A1 0.96 0.15 0.00 0.14 0.00 0.10 Clayey | Average 2% to 7% 0.572 0.53 0.53 0.66 38%
A2 3.58 0.87 0.00 0.72 0.00 0.64 Clayey | Average 2% to 7% 1.353 0.69 0.69 0.86 58%
A3 0.20 0.09 0.00 0.04 0.00 0.03 Clayey | Average 2% to 7% 0.043 0.80 0.80 1.00 76%
A4 1.33 0.42 0.00 0.19 0.00 0.38 Clayey | Average 2% to 7% 0.350 0.77 0.77 0.96 69%
A5 2.60 0.54 0.00 0.56 0.00 0.50 Clayey | Average 2% to 7% 1.007 0.68 0.68 0.85 57%
A6 0.94 0.00 0.00 0.07 0.00 0.43 Clayey | Average 2% to 7% 0.445 0.62 0.62 0.77 47%
A7 0.41 0.11 0.00 0.08 0.00 0.07 Clayey | Average 2% to 7% 0.143 0.70 0.70 0.88 61%
A8 0.62 0.15 0.00 0.16 0.00 0.09 Clayey | Average 2% to 7% 0.216 0.71 0.71 0.88 61%
A9 4.04 0.00 0.00 0.49 0.00 0.26 Clayey | Average 2% to 7% 3.283 0.38 0.38 0.48 17%
Basin A 14.67 2.33 0.00 2.44 0.00 2.50 Clayey | Average 2% to 7% 7.413 0.60 0.60 0.75 46%
B1 3.91 0.87 0.00 0.61 0.00 0.64 Clayey | Average 2% to 7% 1.790 0.63 0.63 0.79 51%
B2 0.25 0.10 0.00 0.07 0.00 0.04 Clayey | Average 2% to 7% 0.047 0.82 0.82 1.00 77%
B3 0.22 0.10 0.00 0.04 0.00 0.03 Clayey | Average 2% to 7% 0.055 0.77 0.77 0.97 72%
B4 2.92 0.38 0.00 0.47 0.00 0.16 Clayey | Average 2% to 7% 1.913 0.49 0.49 0.61 32%
Basin B 7.30 1.44 0.00 1.19 0.00 0.86 Clayey | Average 2% to 7% 3.805 0.59 0.59 0.73 45%
C1 0.81 0.24 0.00 0.29 0.00 0.10 Clayey | Average 2% to 7% 0.193 0.78 0.78 0.98 71%
C2 0.35 0.11 0.00 0.08 0.00 0.06 Clayey | Average 2% to 7% 0.100 0.75 0.75 0.94 67%
C3 0.29 0.13 0.00 0.06 0.00 0.03 Clayey | Average 2% to 7% 0.070 0.78 0.78 0.98 73%
C4 1.01 0.00 0.00 0.15 0.00 0.13 Clayey | Average 2% to 7% 0.723 0.45 0.45 0.56 26%
Basin C 2.46 0.48 0.00 0.58 0.00 0.32 Clayey | Average 2% to 7% 1.087 0.64 0.64 0.80 52%
D1 0.69 0.15 0.00 0.18 0.00 0.10 Clayey | Average 2% to 7% 0.266 0.68 0.68 0.85 58%
D2 0.83 0.00 0.00 0.11 0.00 0.15 Clayey | Average 2% to 7% 0.575 0.47 0.47 0.58 28%
Basin D 1.53 0.15 0.00 0.28 0.00 0.25 Clayey | Average 2% to 7% 0.841 0.56 0.56 0.71 41%
E1 0.90 0.11 0.00 0.15 0.00 0.13 Clayey | Average 2% to 7% 0.501 0.56 0.56 0.70 41%
UD1 0.54 0.07 0.00 0.11 0.00 0.08 Clayey | Average 2% to 7% 0.288 0.57 0.57 0.72 43%
UD2 1.17 0.73 0.00 0.20 0.00 0.00 Clayey | Average 2% to 7% 0.244 0.80 0.80 1.00 77%
UD3 2.32 0.00 0.00 0.15 0.00 0.00 Clayey | Average 2% to 7% 2.167 0.30 0.30 0.37 6%
UD4 0.44 0.10 0.00 0.08 0.00 0.06 Clayey | Average 2% to 7% 0.207 0.62 0.62 0.78 50%
TOTAL ON-SITE BASINS 31.33 5.41 5.17 0.00 4.20 Clayey | Average 2% to 7% 16.553 0.58 0.58 0.73 44%
RW1 3.42 0.45 0.45 0.56 35%
RW2 1.08 0.45 0.45 0.56 35%
RW3 0.10 0.45 0.45 0.56 35%
RW4 1.20 0.45 0.45 0.56 35%
RW5 0.31 0.45 0.45 0.56 35%
TOTAL BASIN RW 6.11 0.45 0.45 0.56 35%
ADDITIONAL COMBINED BASINS
FOR CALCULATIONS
Basins required to release at 0.2 cfs
(A, B, C, D, E, UD1, UD4) 27.84 4.68 0.00 4.82 0.00 4.20 Clayey | Average 2% to 7% 14.142 0.59 0.59 0.74 46%
Basins A3-A8 6.10 1.31 0.00 1.09 0.00 1.50 Clayey | Average 2% to 7% 2.204 0.70 0.70 0.87 60%
Basins B1-B2 4.16 0.97 0.00 0.68 0.00 0.68 Clayey | Average 2% to 7% 1.837 0.64 0.64 0.80 53%
Basins C2, C4 1.36 0.11 0.00 0.23 0.00 0.19 Clayey | Average 2% to 7% 0.823 0.53 0.53 0.66 36%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
Composite Runoff Coefficient with Adjustment
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
UTILIZING COEFFICIENTS FROM THE REDWOOD VILLAGE PLANS
6/6/2018 10:02 AM D:\Projects\1290-002\Drainage\Hydrology\1290-002_Proposed_Rational_Calcs.xlsx\Composite C
of the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Survey Area Data: Version 12, Oct 10, 2017
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Mar 20, 2015—Oct
15, 2016
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Hydrologic Soil Group—Larimer County Area, Colorado
(The Retreat )
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
3/18/2018
Page 2 of 4
C1 Underground LID n/a n/a n/a 658
n/a
C3
Underground LID
and Detention
20,941 0.48
to be provided at
final
244
to be provided at
final
0.50
E1
Underground LID
and Detention
8,315 0.19
to be provided at
final
477
to be provided at
final
0.20
C. Release Rate Compliance
The Retreat @ Fort Collins has a total combined area of 27.84 acres that are subject to
the 0.2 cfs/acre release rate as denoted per the NECCO design. As such, the total release
allowed from The Retreat @ Fort Collins site is 5.57 cfs.
Ponds 1, 2, 3, 4, 5 and 6 release directly into the proposed outfall pipe connected to the
NECCO Stormwater improvements. These ponds combined have a total release of 6.20
cfs. This is 0.63 cfs more than the allowable from the site.
The undetained basins UD1 and UD4 have a 100-year runoff rate of 3.72 cfs and 2.67
cfs respectively (total 6.39 cfs). In order to balance this undetained flow, off-site basins
RW2, RW3, and RW5 were detained. These off-site basins have a 100-year runoff rate
of 5.08 cfs, 0.55 cfs, and 1.69 cfs (total 7.32 cfs).
UD3 UD3 2.32 0.30 0.37 32.0 29.0 0.86 3.96
UD4 UD4 0.44 0.62 0.78 11.8 10.3 0.58 2.67
RW1 RW1 3.42 0.45 0.56 15.9 14.7 2.83 12.71
RW2 RW2 1.08 0.45 0.56 9.6 8.4 1.09 5.08
RW3 RW3 0.10 0.45 0.56 6.8 5.6 0.12 0.55
RW4 RW4 1.20 0.45 0.56 9.6 8.4 1.22 5.65
RW5 RW5 0.31 0.45 0.56 6.8 5.6 0.37 1.69