HomeMy WebLinkAboutTHE RETREAT AT FORT COLLINS (FORMERLY REDWOOD STREET MULTI-FAMILY) - PDP - PDP180002 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTPRELIMINARY DRAINAGE REPORT
The Retreat at Fort Collins
Fort Collins, Colorado
July 25, 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.
July 25, 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.
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 ........................................................................................................... 12
D. Low Impact Development (LID) Compliance ............................................................................... 14
V. CONCLUSIONS ...................................................................................................... 15
A. Compliance with Standards ........................................................................................................ 15
B. Drainage Concept ...................................................................................................................... 15
References ....................................................................................................................... 16
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 .................................................................................... 10
Table 2 – Detention Summary ............................................................................................ 12
Table 3 – Underground Chamber Summary .......................................................................... 12
Table 4 – Allowable Release Rate ....................................................................................... 13
Table 5 – Proposed Release Rate ........................................................................................ 14
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 31.49 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. These Firmette for this FEMA panel is
provided in the Appendix.
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 eight major drainage basins,
designated as Basins A, B, C, D, E, F, 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 8 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 A7, and water quality is
provided in Detention Pond 1. This pond releases directly to a proposed outfall pipe
that connects outfalls into the proposed Detention Pond 2. 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 11 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 B2, B6 and
B9. 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.
This pond receives the detained release from Detention Pond 1. 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 consists of one sub-basin. 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 water quality in Detention Pond 3. 100-year detention of this
basin is provided by Detention Pond 3.
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 3. Once Detention Pond 4 is
full it will spill to the adjacent parking lot that will convey additional flow to Detention
Pond 3.
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 F
Basin F 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 to the
existing inlets at the intersection of Conifer Street and Redwood Street. These inlets
discharge to Redwood Detention Pond. Based on the proposed plans to the Redwood
Pond that were delineated in the NECCO report. This basin can easily be detained in
the Redwood Pond without much consequence. Further discussion is provided in the
Detention Pond section of this report
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.
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 3. 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.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
The Retreat @ Fort Collins
Preliminary Drainage Report 10
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 0.66 0.62 0.78 5.0 5.0 1.17 5.11
A2 A2 1.61 0.69 0.86 13.8 11.4 2.16 10.25
A3 A3 1.33 0.76 0.95 9.0 7.6 2.37 10.83
A4 A4 1.42 0.67 0.84 7.2 5.2 2.39 11.81
A5 A5 0.71 0.76 0.95 6.7 5.0 1.38 6.63
A6 A6 2.11 0.70 0.87 10.5 9.3 3.19 14.74
A7 A7 0.20 0.84 1.00 5.0 5.0 0.49 2.04
A8 A8 3.54 0.38 0.47 10.4 9.5 2.96 13.20
B1 B1 1.59 0.70 0.88 11.8 10.4 2.33 10.76
B2 B2 1.26 0.45 0.56 9.1 7.6 1.31 6.11
B3 B3 1.23 0.85 1.00 8.3 5.0 2.51 12.25
B4 B4 2.07 0.68 0.85 6.7 5.4 3.66 17.55
B5 B5 0.52 0.74 0.93 5.9 5.0 1.07 4.84
B6 B6 0.67 0.49 0.62 6.4 5.2 0.89 4.14
B7 B7 1.30 0.77 0.96 6.8 5.0 2.60 12.48
B8 B8 0.27 0.77 0.97 5.3 5.0 0.60 2.62
B9 B9 0.14 0.80 1.00 5.0 5.0 0.31 1.36
B10 B10 0.81 0.77 0.96 5.1 5.0 1.77 7.70
B11 B11 1.43 0.34 0.42 9.9 9.0 1.09 4.83
C1 C1 1.16 0.54 0.68 7.6 6.3 1.56 7.36
D1 D1 0.83 0.64 0.80 7.0 5.2 1.34 6.61
D2 D2 0.83 0.51 0.63 5.0 5.0 1.20 5.24
E1 E1 0.79 0.62 0.77 8.3 6.6 1.17 5.53
F1 F1 0.72 0.38 0.47 14.2 13.3 0.52 2.36
UD1 UD1 0.79 0.52 0.65 8.0 6.6 0.99 4.66
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
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
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
The Retreat @ Fort Collins
Preliminary Drainage Report 11
Detention Pond 1 and Chambers A7
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 A8 as extended detention
within Detention Pond 1. Detention Pond 1 releases to Detention Pond 2.
Chambers A7 provides LID and water quality treatment for Basin A1-A7.
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 B11 as extended detention within
Detention Pond 2. Detention Pond 2 also takes the release from Detention Pond 1.
Chambers B2 provides LID and water quality treatment for Basins B1 and B2. Chambers
B6 provides LID and water quality treatment for Basins B3-B6. Chambers B9 provides
LID and water quality treatment for Basins B7 and B9-B10.
Detention Pond 3
Detention Pond 3 was designed to detain the stormwater runoff during a 100-year event
from Basin C and Basin RW5. Water Quality is provided for Basin C1 as extended
detention within Detention Pond 3. During a 100-year event Detention Pond 3 will spill
to the adjacent parking lot, and be detained within the parking lot.
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. This additional flow will be
detained in Detention Pond 3.
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 and Basin B8.
Redwood Detention Pond
As Basin F drains to the existing Redwood Pond, the Redwood Pond can be considered to
detain runoff from Basin F. Basin F is a 0.72 acre basin with a 25% imperviousness.
The total existing tributary area that drains to the Redwood Pond from the existing
neighborhoods is 49.8 acres of 70% imperviousness. Therefore, this small additional
basin area is minimal in comparison to the full tributary.
The Redwood Pond is planned to be updated by the City with the NECCO project. The
reconstruction of the pond will have a total 100-year volume of 9.86 ac-ft (2.12 ac-ft of
that volume is water quality) and an updated outfall pipe (built by The Retreat). The
100-year depth shown in the NECCO report was shown at 4.65 feet deep.
The Redwood Pond was included in the SWMM model in order to see the effect this
additional area from Basin F will have on the proposed Redwood Pond. The addition of
Basin F was shown to raise the 100-year water level by about 0.04 ft and the total
volume by 0.13 ac-ft. This change is negligible.
A summary of the detention volumes and water quality volumes for each pond are found
below:
The Retreat @ Fort Collins
Preliminary Drainage Report 12
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 116,789 2.68 4956.93 1,319 4956.93 0.70
2 Open Detention 112,201 2.58 4949.65 377 4956.52 1.60
3 Open Detention 9,363 0.21 4955.03 746 4857.14 3.80
4 Open Detention 17,091 0.39 4959.04 1,131 4956.80 2.25
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)
A7 Underground LID n/a n/a n/a 5,507
to be provided at
final
n/a
B2 Underground LID n/a n/a n/a 1,619
to be provided at
final
n/a
B6 Underground LID n/a n/a n/a 3,124
to be provided at
final
n/a
B9 Underground LID n/a n/a n/a 1,827
to be provided at
final
n/a
E1/Pond
5
Underground LID and
Detention
7,683 0.18
to be provided at
The Retreat @ Fort Collins
Preliminary Drainage Report 13
Table 4 – Allowable Release Rate
Allowable Stormwater Release from Combined Redwood and Retreat Site
Basin
Area
(acres)
100-yr Release
Rate (cfs)
Basin A 11.57 2.31
Basin B 11.3 2.26
Basin C 1.16 0.23
Basin D 1.66 0.33
Basin E 0.79 0.16
Basin F 0.72 0.14
UD1 0.79 0.16
Total On-site Release 27.99 5.60
Off-site Basins
RW1 3.42 12.71
RW2 1.08 5.08
RW3 0.1 0.55
RW4 1.2 5.65
RW5 0.31 1.69
Redwood Pond 49.8 12.00
Total Off-site Release 55.91 37.68
Total Release from Combined
Redwood and Retreat Basins
83.9 43.28
The Retreat @ Fort Collins
Preliminary Drainage Report 14
Table 5 – Proposed Release Rate
Proposed Stormwater Release from Combined Redwood and Retreat
Site
Pond/ Basin
100-yr Release
Rate (cfs)
Pond 2 1.60
Pond 3 3.80
Pond 4 2.25
Pond 5 0.20
Redwood Pond 12.00
Total Detention Release 19.85
Undetained Basins
RW1 12.71
RW4 5.65
UD1 4.66
Total Undetained Release 23.02
Total Release from Combined
Redwood and Retreat Basins
42.87
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 73.5% 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 15
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 16
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 SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: The Retreat
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: July 24, 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
The Retreat
Overland Flow, Time of Concentration:
The Retreat
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ 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
The Retreat
Rational Method Equation: Project: The Retreat
Calculations By:
Date:
Rainfall Intensity:
A1 A1 0.66 5 5 5 0.62 0.62 0.78 2.85 4.87 9.95 1.17 2.00 5.11
A2 A2 1.61 14 14 11 0.69 0.69 0.86 1.95 3.34 7.42 2.16 3.69 10.25
A3 A3 1.33 9 9 8 0.76 0.76 0.95 2.35 4.02 8.59 2.37 4.05 10.83
A4 A4 1.42 7 7 5 0.67 0.67 0.84 2.52 4.31 9.95 2.39 4.09 11.81
A5 A5 0.71 7 7 5 0.76 0.76 0.95 2.60 4.44 9.95 1.38 2.37 6.63
A6 A6 2.11 11 11 9 0.70 0.70 0.87 2.17 3.71 8.03 3.19 5.44 14.74
A7 A7 0.20 5 5 5 0.84 0.84 1.00 2.85 4.87 9.95 0.49 0.83 2.04
A8 A8 3.54 10 10 10 0.38 0.38 0.47 2.21 3.78 7.88 2.96 5.07 13.20
Basin A Basin A 11.57 21 21 19 0.60 0.60 0.75 1.59 2.71 5.84 11.08 18.90 50.97
B1 B1 1.59 12 12 10 0.70 0.70 0.88 2.09 3.57 7.72 2.33 3.97 10.76
B2 B2 1.26 9 9 8 0.45 0.45 0.56 2.30 3.93 8.59 1.31 2.24 6.11
B3 B3 1.23 8 8 5 0.85 0.85 1.00 2.40 4.10 9.95 2.51 4.28 12.25
B4 B4 2.07 7 7 5 0.68 0.68 0.85 2.60 4.44 9.95 3.66 6.26 17.55
B5 B5 0.52 6 6 5 0.74 0.74 0.93 2.76 4.72 9.95 1.07 1.84 4.84
B6 B6 0.67 6 6 5 0.49 0.49 0.62 2.67 4.56 9.95 0.89 1.52 4.14
B7 B7 1.30 7 7 5 0.77 0.77 0.96 2.60 4.44 9.95 2.60 4.45 12.48
B8 B8 0.27 5 5 5 0.77 0.77 0.97 2.85 4.87 9.95 0.60 1.03 2.62
B9 B9 0.14 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.31 0.53 1.36
B10 B10 0.81 5 5 5 0.77 0.77 0.96 2.85 4.87 9.95 1.77 3.02 7.70
B11 B11 1.43 10 10 9 0.34 0.34 0.42 2.26 3.86 8.03 1.09 1.86 4.83
Basin B Basin B 11.30 14 14 10 0.64 0.64 0.81 1.92 3.29 7.72 13.99 23.97 70.31
C1 C1 1.16 8 8 6 0.54 0.54 0.68 2.46 4.21 9.31 1.56 2.66 7.36
Basin C Basin C 1.16 8 8 6 0.54 0.54 0.68 2.46 4.21 9.31 1.56 2.66 7.36
D1 D1 0.83 7 7 5 0.64 0.64 0.80 2.52 4.31 9.95 1.34 2.29 6.61
D2 D2 0.83 5 5 5 0.51 0.51 0.63 2.85 4.87 9.95 1.20 2.05 5.24
Basin D Basin D 1.66 11 11 9 0.57 0.57 0.72 2.17 3.71 8.03 2.07 3.53 9.56
E1 E1 0.79 8 8 7 0.62 0.62 0.77 2.40 4.10 9.06 1.17 2.00 5.53
F1 F1 0.72 14 14 13 0.38 0.38 0.47 1.92 3.29 6.92 0.52 0.90 2.36
UD1 UD1 0.79 8 8 7 0.52 0.52 0.65 2.40 4.10 9.06 0.99 1.69 4.66
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
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
A3, A2
Basins A1-A3 (100-
year Overtopping) 3.59
14 14 11 0.70 0.70 0.88 1.95 3.34 7.42 4.92 8.43 23.41
A5
Basins A1-A5 (100-
year Overtopping) 5.72
18 18 15 0.70 0.70 0.88 1.73 2.95 6.52 6.91 11.80 32.66
A7
Basins A1-A7
(Channel Calc) 8.03
18 18 15 0.70 0.70 0.88 1.73 2.95 6.52 9.74 16.63 46.02
B5
Basins B3-B5 (100-
year Overtopping) 3.82
11 11 6 0.74 0.74 0.93 2.17 3.71 9.31 6.17 10.54 33.10
B6
Basins B1-B6 (Storm
Sewer Calc) 7.35
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: 7/24/2018
Pond No.: 1
Pond 1
100-yr
0.75 WQCV 1319 ft
3
Area (A)= 11.57 acres Quantity Detention SWMM 116789 ft
3
Max Release Rate = 0.70 cfs Total Volume 116789 ft
3
Total Volume 2.681 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" =
7/24/2018 1:09 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 1.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 7/24/2018
Pond No.: 1
Pond 1
WQCV
1319 ft3 4953.81 ft.
Design Storm 100-yr
Required Volume= 116789 ft3 4956.93 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft2 ft. ft3 ft3 ft3 ft3
4,953.20 171 0.00 0 0 0 0
4,953.40 923 0.20 109 109 99 99
4,953.60 2525 0.20 345 454 332 431
4,953.80 5861 0.20 839 1293 816 1247
4,954.00 10369 0.20 1623 2916 1602 2848
4,954.20 15731 0.20 2610 5526 2591 5440
4,954.40 21779 0.20 3751 9277 3735 9174
4,954.60 28255 0.20 5003 14280 4989 14164
4,954.80 34853 0.20 6311 20591 6299 20463
4,955.00 39212 0.20 7406 27997 7402 27865
4,955.20 41748 0.20 8096 36093 8095 35960
4,955.40 43189 0.20 8494 44587 8493 44453
4,955.60 44201 0.20 8739 53326 8739 53192
4,955.80 45225 0.20 8943 62269 8942 62134
4,956.00 46270 0.20 9149 71418 9149 71284
4,956.20 47348 0.20 9362 80780 9362 80645
4,956.40 48465 0.20 9581 90361 9581 90226
4,956.60 49588 0.20 9805 100167 9805 100031
4,956.80 50717 0.20 10030 110197 10030 110062
4,957.00 51852 0.20 10257 120454 10257 120318
4,957.20 52995 0.20 10485 130939 10485 130803
4,957.40 54145 0.20 10714 141653 10714 141517
4,957.60 55303 0.20 10945 152598 10945 152461
4,957.80 56466 0.20 11177 163774 11177 163638
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
7/24/20181:09 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 1.xlsm\Stage_Storage
The Retreat
1290-002
Fort Collins, Colorado
S. Thomas Date: 7/24/2018
Pond No.: 2
Pond 2
100-yr
0.81 WQCV 377 ft
3
Area (A)= 11.30 acres Quantity Detention SWMM 112201 ft
3
Max Release Rate = 1.60 cfs Total Volume 112201 ft
3
Total Volume 2.576 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" =
7/24/2018 1:11 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 2.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 7/24/2018
Pond No.: 2
Pond 2
WQCV
377 ft3 4949.65 ft.
Design Storm 100-yr
Required Volume= 112201 ft3 4956.52 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft2 ft. ft3 ft3 ft3 ft3
4,949.40 425 0.00 0 0 0 0
4,949.60 2054 0.20 248 248 228 228
4,949.80 4477 0.20 653 901 638 865
4,950.00 7632 0.20 1211 2112 1197 2062
4,950.20 10024 0.20 1766 3878 1760 3822
4,950.40 10786 0.20 2081 5959 2081 5903
4,950.60 11144 0.20 2193 8152 2193 8096
4,950.80 11505 0.20 2265 10417 2265 10361
4,951.00 11870 0.20 2337 12754 2337 12698
4,951.20 12238 0.20 2411 15165 2411 15109
4,951.40 12612 0.20 2485 17650 2485 17594
4,951.60 12992 0.20 2560 20210 2560 20154
4,951.80 13378 0.20 2637 22847 2637 22791
4,952.00 13770 0.20 2715 25562 2715 25506
4,952.20 14196 0.20 2797 28359 2796 28302
4,952.40 14629 0.20 2882 31241 2882 31184
4,952.60 15069 0.20 2970 34211 2970 34154
4,952.80 15517 0.20 3059 37270 3059 37213
4,953.00 15973 0.20 3149 40419 3149 40362
4,953.20 16437 0.20 3241 43660 3241 43603
4,953.40 16908 0.20 3334 46994 3334 46937
4,953.60 17388 0.20 3430 50424 3429 50366
4,953.80 17874 0.20 3526 53950 3526 53892
4,954.00 18366 0.20 3624 57574 3624 57516
4,954.20 18865 0.20 3723 61297 3723 61239
4,954.40 19372 0.20 3824 65121 3824 65063
4,954.60 19886 0.20 3926 69046 3926 68989
4,954.80 20410 0.20 4030 73076 4030 73018
4,955.00 20945 0.20 4136 77212 4135 77154
4,955.20 21491 0.20 4244 81455 4243 81397
4,955.40 22047 0.20 4354 85809 4354 85751
4,955.60 22616 0.20 4466 90275 4466 90217
4,955.80 23196 0.20 4581 94856 4581 94798
4,956.00 23790 0.20 4699 99555 4698 99496
The Retreat
1290-002
Fort Collins, Colorado
S. Thomas Date: 7/24/2018
Pond No.: 3
Pond 3
100-yr
0.68 WQCV 746 ft
3
Area (A)= 1.16 acres Quantity Detention SWMM 9363 ft
3
Max Release Rate = 3.80 cfs Total Volume 9363 ft
3
Total Volume 0.215 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" =
7/24/2018 1:11 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 3.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 7/24/2018
Pond No.: 3
Pond 3
WQCV
746 ft3 4955.03 ft.
Design Storm 100-yr
Required Volume= 9363 ft3 4957.14 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft2 ft. ft3 ft3 ft3 ft3
4,953.20 0 0.00 0 0 0 0
4,953.40 13 0.20 1 1 1 1
4,953.60 52 0.20 7 8 6 7
4,953.80 119 0.20 17 25 17 24
4,954.00 213 0.20 33 58 33 56
4,954.20 347 0.20 56 114 55 112
4,954.40 524 0.20 87 201 86 198
4,954.60 726 0.20 125 326 124 323
4,954.80 952 0.20 168 494 167 490
4,955.00 1208 0.20 216 710 216 706
4,955.20 1497 0.20 271 981 270 976
4,955.40 1846 0.20 334 1315 334 1309
4,955.60 2217 0.20 406 1721 406 1715
4,955.80 2609 0.20 483 2204 482 2197
4,956.00 3020 0.20 563 2767 562 2759
4,956.20 3488 0.20 651 3417 650 3410
4,956.40 4276 0.20 776 4194 775 4185
4,956.60 5422 0.20 970 5163 968 5152
4,956.80 7025 0.20 1245 6408 1241 6393
4,957.00 8862 0.20 1589 7997 1585 7979
4,957.20 10464 0.20 1933 9930 1930 9909
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
7/24/20181:11 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 3.xlsm\Stage_Storage
The Retreat
1290-002
Fort Collins, Colorado
S. Thomas Date: 7/24/2018
Pond No.: 4
Pond 4
100-yr
0.68 WQCV 1131 ft
3
Area (A)= 1.66 acres Quantity Detention SWMM 17091 ft
3
Max Release Rate = 2.25 cfs Total Volume 17091 ft
3
Total Volume 0.392 ac-ft
ft
2
*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" =
7/24/2018 1:12 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 4.xlsm\SWMM_FC
The Retreat
1290-001
Fort Collins, CO
S. Thomas Date: 7/24/2018
Pond No.: 4
Pond 4
WQCV 1131
2.25 1131 ft3 17091 4956.80 ft.
Design Storm 100-yr
Required Volume= 17091 ft3 4959.04 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft2 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
4,956.00 161 0.20 21 25 19 23
4,956.20 541 0.20 70 95 66 89
4,956.40 1289 0.20 183 278 178 267
4,956.60 2176 0.20 347 625 343 610
4,956.80 3007 0.20 518 1143 516 1126
4,957.00 3966 0.20 697 1841 695 1821
4,957.20 4807 0.20 877 2718 876 2697
4,957.40 5557 0.20 1036 3754 1036 3732
4,957.60 6151 0.20 1171 4925 1170 4903
4,957.80 6760 0.20 1291 6216 1291 6193
4,958.00 7389 0.20 1415 7631 1414 7608
4,958.20 8037 0.20 1543 9174 1542 9150
4,958.40 8705 0.20 1674 10848 1674 10824
4,958.60 9394 0.20 1810 12658 1809 12633
4,958.80 10106 0.20 1950 14608 1950 14583
4,959.00 10843 0.20 2095 16703 2094 16677
4,959.20 10844 0.20 2169 18871 2169 18846
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
7/24/20181:12 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 4.xlsm\Stage_Storage
4.14 Ayres Associates
outlet structure is proposed prior to discharging into the proposed storm sewer system. A 4-
foot concrete trickle pan is incorporated into the pond bottom to direct low flows due to
minimal slope across the pond. The overall footprint encompasses approximately 3.5 acres
at an approximate depth of 6 ft. The required 100-year detention volume is 7.70 ac-ft with
an additional 2.16 ac-ft of storage below the detention storage for water quality. Table 4.6
shows the major characteristics of Redwood Pond.
Table 4.6. Redwood Pond.
Description
Elevation
(ft)
Pond Volume
(ac-ft)
Pond Depth
(ft)
Pond Invert 4953.10 --- ---
Outlet Structure
Elevation
4955.12 2.16 2.02
100-year WSEL 4957.75 9.86 4.65
Spillway into
Pond
4958.39 11.94 5.29
Top of Pond 4959 14.00 5.90
WSEL = Water Surface Elevation
The outlet structure for the redwood pond is a combination of two Type C inlets in series.
The inlets will be separated by a steel plate with an orifice opening sized to provide a 40-
hour drain time for the water quality portion of the pond. One of the frequent maintenance
issues associated with water quality structures is the clogging of the orifice plates. For this
reason we are proposing to install an 18F snout oil-water debris separator inside the first
Type C inlet over the water quality plate. The snout should prevent the orifice plate from
clogging. The second Type C inlet will be set at the water quality elevation and the outlet
pipe from the inlet controls the release rate from the pond.
Currently an undersized storm sewer system conveys flow from inlets along Redwood Street
into Redwood Pond. The series of existing inlets surcharge during the minor events creating
localized flooding at the intersection of Redwood Street and Conifer Street. The existing
inlets and storm sewer do not have the capacity for the 100-year runoff from the surrounding
basins. An adequate storm system would require large diameter storm pipe and deep inlets
to prevent surcharging. Due to existing water and sanitary conflicts in the area, and a
controlled invert into Redwood Pond, the only storm sewer system that could fit within the
existing constraints would be multiple shallow 12-inch diameter storm sewer culverts. These
storm sewer culverts would still not alleviate the minor and major storm flooding problem.
To mitigate the flooding, the design incorporates a 90-foot overflow weir graded into the
pond embankment. The 100-year storm event (approximately 85 cfs) will overtop the curb at
an elevation of approximately 4958.39 and be conveyed to the pond through the weir. Minor
event flows will continue to be captured by the existing inlets located north of the pond. This
design can be looked at in more detail during the final design process.
EPA SWMM Hydraulic Modeling
The proposed weir into Redwood Pond was modeled using a weir in EPA SWMM. The
transverse weir option was chosen with a discharge coefficient of 3.0. During a 100-year
event the 90 foot weir will convey approximately 80 cfs at a max depth of 0.45 ft.
APPENDIX C
WATER QUALITY DESIGN COMPUTATIONS
Project: The Retreat
Calculations By: S. Thomas
Date: July 24, 2018
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
LID Treatment
A1 28,709 62% 17,883 WQ Chamber A7
A2 69,932 69% 48,143 WQ Chamber A7
A3 57,726 76% 43,924 WQ Chamber A7
A4 61,860 67% 41,369 WQ Chamber A7
A5 30,720 76% 23,234 WQ Chamber A7
A6 91,912 70% 63,956 WQ Chamber A7
A7 8,912 84% 7,458 WQ Chamber A7
B1 69,286 70% 48,558 WQ Chamber B2
B2 54,867 45% 24,793 WQ Chamber B2
B3 53,646 85% 45,476 WQ Chamber B6
B4 90,005 68% 61,471 WQ Chamber B6
B5 22,787 74% 16,965 WQ Chamber B6
B6 29,364 49% 14,512 WQ Chamber B6
B7 56,825 77% 43,708 WQ Chamber B9
B8 11,887 77% 9,184 WQ Chamber E1
B9 5,943 80% 4,758 WQ Chamber B9
B10 35,151 77% 26,979 WQ Chamber B9
E1 34,607 62% 21,297 WQ Chamber E1
Total Treated 814,139 69% 563,667
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
A8 154,227 38% 58,414
B11 62,396 34% 20,969
C1 50,565 54% 27,544
D1 36,109 64% 23,143
D2 36,306 51% 18,366
UD1 34,414 52% 17,953
UD2 51,032 80% 41,030
UD3 101,092 30% 29,972
F1 31,311 38% 11,887
Total Proposed
Untreated
557,452 45% 249,277
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
Suniga Street UD2 51,032 77% 39,522
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
SD SD
SD SD
SD
SD
SD
SD
SD
SD SD
E
E
E
SD SD SD SD
SD
SD
SD
SD
SD
E
E
E
E
E
E
T
PLAS
O
NYL
LITCUD
E
NORI
PLAST
O
L
NY
CUD
T
LI
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 = 8.03 ac
V = 0.1264 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
5507 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat July 21, 2018
1290-002 S. Thomas
Landmark
WQ Chamber A7
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 :
A7
WQ
0.70
18.00 min 3772 ft3
8.03 acres 0.09 ac-ft
Max Release Rate = 1.98 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 2403 1.00 1.98 594 1809
10 1.105 3727 1.00 1.98 1188 2539
15 0.935 4730 1.00 1.98 1782 2948
20 0.805 5430 0.95 1.88 2257 3173
25 0.715 6029 0.86 1.70 2554 3474
30 0.650 6577 0.80 1.58 2851 3725
35 0.585 6905 0.76 1.50 3148 3757
40 0.535 7217 0.73 1.44 3445 3772
45 0.495 7512 0.70 1.39 3742 3770
50 0.460 7757 0.68 1.35 4039 3718
55 0.435 8069 0.66 1.31 4336 3733
60 0.410 8297 0.65 1.29 4633 3663
65 0.385 8440 0.64 1.26 4930 3510
70 0.365 8617 0.63 1.24 5227 3390
75 0.345 8727 0.62 1.23 5524 3202
80 0.330 8904 0.61 1.21 5821 3082
85 0.315 9030 0.61 1.20 6118 2912
90 0.305 9258 0.60 1.19 6415 2843
95 0.290 9292 0.59 1.18 6712 2579
100 0.280 9443 0.59 1.17 7009 2434
105 0.270 9561 0.59 1.16 7306 2255
110 0.260 9646 0.58 1.15 7603 2042
115 0.255 9890 0.58 1.14 7900 1990
120 0.245 9915 0.58 1.14 8197 1718
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
DETENTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
1290-002
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 46.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.156 in
A = 2.85 ac
V = 0.0372 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 July 21, 2018
1290-002 S. Thomas
Landmark
WQ Chamber B2
1619 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 :
B2
WQ
0.59
12.00 min 1661 ft3
2.85 acres 0.04 ac-ft
Max Release Rate = 0.38 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 1.425 719 1.00 0.38 114 605
10 1.105 1115 1.00 0.38 228 887
15 0.935 1415 0.90 0.34 308 1107
20 0.805 1624 0.80 0.30 365 1260
25 0.715 1803 0.74 0.28 422 1382
30 0.650 1967 0.70 0.27 479 1489
35 0.585 2066 0.67 0.26 536 1530
40 0.535 2159 0.65 0.25 593 1566
45 0.495 2247 0.63 0.24 650 1598
50 0.460 2320 0.62 0.24 707 1614
55 0.435 2414 0.61 0.23 764 1650
60 0.410 2482 0.60 0.23 821 1661
65 0.385 2525 0.59 0.23 878 1647
70 0.365 2578 0.59 0.22 935 1643
75 0.345 2611 0.58 0.22 992 1619
80 0.330 2663 0.58 0.22 1049 1615
85 0.315 2701 0.57 0.22 1106 1596
90 0.305 2769 0.57 0.22 1163 1607
95 0.290 2780 0.56 0.21 1220 1560
100 0.280 2825 0.56 0.21 1277 1548
105 0.270 2860 0.56 0.21 1334 1526
110 0.260 2885 0.55 0.21 1391 1495
115 0.255 2959 0.55 0.21 1448 1511
120 0.245 2966 0.55 0.21 1505 1461
*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 B2
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) 61.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.192 in
A = 4.49 ac
V = 0.0717 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 July 21, 2018
1290-002 S. Thomas
Landmark
WQ Chamber B6
3124 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 :
B6
WQ
0.71
8.00 min 2343 ft3
4.49 acres 0.05 ac-ft
Max Release Rate = 1.22 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 1363 1.00 1.22 366 997
10 1.105 2114 1.00 1.22 732 1382
15 0.935 2683 0.77 0.94 842 1841
20 0.805 3080 0.70 0.85 1025 2055
25 0.715 3419 0.66 0.81 1208 2211
30 0.650 3730 0.63 0.77 1391 2339
35 0.585 3916 0.61 0.75 1574 2343
40 0.535 4093 0.60 0.73 1757 2336
45 0.495 4261 0.59 0.72 1940 2321
50 0.460 4399 0.58 0.71 2123 2277
55 0.435 4576 0.57 0.70 2306 2270
60 0.410 4705 0.57 0.69 2489 2217
65 0.385 4787 0.56 0.69 2672 2115
70 0.365 4887 0.56 0.68 2855 2032
75 0.345 4949 0.55 0.68 3038 1911
80 0.330 5050 0.55 0.67 3221 1829
85 0.315 5121 0.55 0.67 3404 1718
90 0.305 5250 0.54 0.66 3587 1664
95 0.290 5270 0.54 0.66 3770 1500
100 0.280 5356 0.54 0.66 3953 1403
105 0.270 5423 0.54 0.66 4136 1287
110 0.260 5470 0.54 0.65 4319 1152
115 0.255 5609 0.53 0.65 4502 1107
120 0.245 5623 0.53 0.65 4685 939
*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 B6
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) 71.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.224 in
A = 2.25 ac
V = 0.0419 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 July 21, 2018
1290-002 S. Thomas
Landmark
WQ Chamber B9
1827 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 :
B9
WQ
0.77
7.00 min 1653 ft3
2.25 acres 0.04 ac-ft
Max Release Rate = 0.45 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 1.425 741 1.00 0.45 135 606
10 1.105 1149 1.00 0.45 270 879
15 0.935 1458 0.73 0.33 297 1161
20 0.805 1674 0.68 0.30 365 1309
25 0.715 1858 0.64 0.29 432 1426
30 0.650 2027 0.62 0.28 500 1528
35 0.585 2128 0.60 0.27 567 1561
40 0.535 2225 0.59 0.26 635 1590
45 0.495 2315 0.58 0.26 702 1613
50 0.460 2391 0.57 0.26 770 1621
55 0.435 2487 0.56 0.25 837 1650
60 0.410 2557 0.56 0.25 905 1653
65 0.385 2601 0.55 0.25 972 1629
70 0.365 2656 0.55 0.25 1040 1616
75 0.345 2690 0.55 0.25 1107 1583
80 0.330 2744 0.54 0.24 1175 1570
85 0.315 2783 0.54 0.24 1242 1541
90 0.305 2853 0.54 0.24 1310 1544
95 0.290 2864 0.54 0.24 1377 1487
100 0.280 2911 0.54 0.24 1445 1466
105 0.270 2947 0.53 0.24 1512 1435
110 0.260 2973 0.53 0.24 1580 1393
115 0.255 3048 0.53 0.24 1647 1401
120 0.245 3056 0.53 0.24 1715 1342
*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 B9
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) 54.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.174 in
A = 1.07 ac
V = 0.0155 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
676 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
The Retreat July 21, 2018
1290-002 S. Thomas
Landmark
WQ Chamber E1
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
0.66
8.00 min 643 ft3
1.07 acres 0.01 ac-ft
Max Release Rate = 0.20 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 1.425 302 1.00 0.20 59 243
10 1.105 468 1.00 0.20 118 351
15 0.935 594 0.77 0.15 135 459
20 0.805 682 0.70 0.14 165 518
25 0.715 757 0.66 0.13 194 563
30 0.650 826 0.63 0.12 223 603
35 0.585 868 0.61 0.12 253 615
40 0.535 907 0.60 0.12 282 625
45 0.495 944 0.59 0.12 312 632
50 0.460 975 0.58 0.11 341 634
55 0.435 1014 0.57 0.11 370 643
60 0.410 1042 0.57 0.11 400 643
65 0.385 1060 0.56 0.11 429 631
70 0.365 1083 0.56 0.11 459 624
75 0.345 1096 0.55 0.11 488 608
80 0.330 1119 0.55 0.11 517 601
85 0.315 1135 0.55 0.11 547 588
90 0.305 1163 0.54 0.11 576 587
95 0.290 1167 0.54 0.11 606 562
100 0.280 1186 0.54 0.11 635 551
105 0.270 1201 0.54 0.11 664 537
110 0.260 1212 0.54 0.11 694 518
115 0.255 1243 0.53 0.10 723 519
120 0.245 1246 0.53 0.10 753 493
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
C =
Tc =
A =
WQ Chamber E1
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
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 A7 5507 6.50 SC-740 0.024 45.90 74.90 74 1.75 3772 83 3810 5543
Chamber B2 1619 1.82 MC-4500 0.028 106.50 162.60 10 0.28 1661 16 1704 1626
Chamber B6 3124 4.06 SC-740 0.024 45.90 74.90 42 0.99 2343 52 2387 3146
Chamber B9 1827 2.34 MC-4500 0.028 106.50 162.60 12 0.34 1653 16 1704 1951
Chamber E1 676 0.89 MC-4500 0.028 106.50 162.60 5 0.14 643 7 746 813
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.
Chamber Configuration Summary
D:\Projects\1290-002\Drainage\WatQual\Chambers_WQ Calcs.xlsx
POND 1 (WQ FOR A8)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 3.540 <-- 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) = 0.030 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 1319 <-- CALCULATED
WQ Depth (ft) = 0.610 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.144 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 3/7 <-- 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
July 24, 2018
POND 2 (WQ FOR B11)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 1.430 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 11.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.1100 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.073 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.009 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 377 <-- CALCULATED
WQ Depth (ft) = 0.300 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.045 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/4 <-- INPUT from Figure 5
number of rows = 1
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
July 24, 2018
POND 3 (WQ FOR C1)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 1.160 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 39.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.3900 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.177 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.017 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 746 <-- CALCULATED
WQ Depth (ft) = 1.830 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.066 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 2/7 <-- 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
July 24, 2018
POND 4 (WQ FOR D1 AND D2)
Project: The Retreat
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 1.660 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 43.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.4300 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.188 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.026 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Adjusted WQCV (cu-ft) = 1131 <-- CALCULATED
WQ Depth (ft) = 1.200 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.106 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 3/8 <-- 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
July 24, 2018
APPENDIX D
SWMM ANALYSIS / MODEL
SUB-RW5
SUB-RW2-3
SUB-A
SUB-B
SUB-C
SUB-D
SUB-E
SUB-F
SUB-OFFSITE2REDWOOD
C-1
C-2
C-3
C-4
C-5
C-6
C-7
C-8
OVERFLOWTOPOND3
O-1
O-2
O-3
O-4
O-5
OS-REDWOOD
NECCO
J-2
J-3
J-4 J-5
J-6
J-7
J-9
J-10
OFFLINE
POND-1
POND-2
POND-3
POND-4
POND-5
POND-REDWOOD
FORTCOLLINS
03/15/2016 00:15:00
SWMM 5.1 Page 1
2018-07-19_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 03/20/2016
END_TIME 00:00:00
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
SYS_FLOW_TOL 5
LAT_FLOW_TOL 5
MINIMUM_STEP 0.5
Page 1
2018-07-19_SWMM Preliminary.inp
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-RW5 FORTCOLLINS POND-3 0.31 35 110 0.5 0
SUB-RW2-3 FORTCOLLINS POND-4 1.18 35 160 0.5 0
SUB-A FORTCOLLINS POND-1 11.57 47 500 0.5 0
SUB-B FORTCOLLINS POND-2 11.30 53 300 0.5 0
SUB-C FORTCOLLINS POND-3 1.16 39 150 0.5 0
SUB-D FORTCOLLINS POND-4 1.66 43 131 0.5 0
SUB-E FORTCOLLINS POND-5 .79 55 170 0.5 0
SUB-F FORTCOLLINS POND-REDWOOD .72 25 100 0.5 0
SUB-OFFSITE2REDWOOD FORTCOLLINS POND-REDWOOD 49.8 70 700 .6 0
[SUBAREAS]
Page 2
2018-07-19_SWMM Preliminary.inp
;;Subcatchment N-Imperv N-Perv S-Imperv S-Perv PctZero RouteTo PctRouted
;;-------------- ---------- ---------- ---------- ---------- ---------- ---------- ----------
SUB-RW5 .016 .025 .1 .3 25 OUTLET
SUB-RW2-3 .016 .025 .1 .3 25 OUTLET
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
SUB-F .016 .025 .1 .3 25 OUTLET
SUB-OFFSITE2REDWOOD .016 .025 .1 .3 25 OUTLET
[INFILTRATION]
;;Subcatchment MaxRate MinRate Decay DryTime MaxInfil
;;-------------- ---------- ---------- ---------- ---------- ----------
SUB-RW5 .51 0.5 .0018 7 0
SUB-RW2-3 .51 0.5 .0018 7 0
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-F .51 0.5 .0018 7 0
SUB-OFFSITE2REDWOOD 3 0.5 .0018 7 0
[JUNCTIONS]
;;Name Elevation MaxDepth InitDepth SurDepth Aponded
;;-------------- ---------- ---------- ---------- ---------- ----------
NECCO 46 4.5 0 0 0
J-2 48 4.5 0 0 0
J-3 49 3 0 0 0
J-4 51 3 0 0 0
J-5 52 3 0 0 0
J-6 52 3 0 0 0
J-7 47 4.5 0 0 0
J-9 50 3 0 0 0
J-10 52.5 3 0 0 0
OFFLINE 0 0 0 0 0
Page 3
2018-07-19_SWMM Preliminary.inp
[STORAGE]
;;Name Elev. MaxDepth InitDepth Shape Curve Name/Params N/A Fevap
Psi Ksat IMD
;;-------------- -------- ---------- ----------- ---------- ---------------------------- -------- --------
-------- --------
POND-1 53.1 4.6 .61 TABULAR POND1 0 0
POND-2 49.4 7.4 .25 TABULAR POND2 0 0
POND-3 53.2 4 1.83 TABULAR POND3 0 0
POND-4 55.6 4.2 1.2 TABULAR POND4 0 0
POND-5 49 3 0 TABULAR POND5 0 0
POND-REDWOOD 53.1 5 2.12 TABULAR PONDREDWOOD 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-9 1574 .012 0 0 0 0
C-7 J-9 POND-2 50 .012 0 0 0 0
C-8 J-10 J-5 644 .013 0 0 0 0
[WEIRS]
;;Name From Node To Node Type CrestHt Qcoeff Gated EndCon
EndCoeff Surcharge RoadWidth RoadSurf
Page 4
2018-07-19_SWMM Preliminary.inp
;;-------------- ---------------- ---------------- ------------ ---------- ---------- -------- --------
---------- ---------- ---------- ----------
OVERFLOWTOPOND3 POND-4 POND-3 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
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
OS-REDWOOD POND-REDWOOD J-10 0 TABULAR/DEPTH OS-REDWOOD 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 3 0 0 0 1
C-7 CIRCULAR 3 0 0 0 1
C-8 CIRCULAR 3 0 0 0 1
OVERFLOWTOPOND3 RECT_OPEN 1 10 4 4
[CURVES]
;;Name Type X-Value Y-Value
Page 5
2018-07-19_SWMM Preliminary.inp
;;-------------- ---------- ---------- ----------
OS-1 Rating 0 0
OS-1 .61 .01
OS-1 5 .98
;
OS-2 Rating 0 0
OS-2 .25 .003
OS-2 7.4 1.67
;
OS-3 Rating 0 0
OS-3 1.83 .005
OS-3 4 3.9
;
OS-4 Rating 0 0
OS-4 1.2 .008
OS-4 4.2 3.02
;
OS-5 Rating 0 0
OS-5 3 .31
;
OS-REDWOOD Rating 0 0
OS-REDWOOD 2.02 .7
OS-REDWOOD 5 13.03
;
POND1 Storage 0 170.8
POND1 0.2 923.29
POND1 0.4 2525.22
POND1 0.6 5860.63
POND1 0.8 10368.92
POND1 1 15730.52
POND1 1.2 21779
POND1 1.4 28255.43
POND1 1.6 34853.05
POND1 1.8 39211.5
POND1 2 41748.03
POND1 2.2 43189.26
POND1 2.4 44201.36
POND1 2.6 45224.89
Page 6
2018-07-19_SWMM Preliminary.inp
POND1 2.8 46269.76
POND1 3 47348.37
POND1 3.2 48464.91
POND1 3.4 49587.62
POND1 3.6 50716.56
POND1 3.8 51852.29
POND1 4 52995.08
POND1 4.2 54145.24
POND1 4.4 55302.64
POND1 4.6 56466.46
;
POND2 Storage 0 424.86
POND2 0.2 2054.07
POND2 0.4 4477.42
POND2 0.6 7632.47
POND2 0.8 10024.38
POND2 1 10786.09
POND2 1.2 11143.65
POND2 1.4 11504.81
POND2 1.6 11869.68
POND2 1.8 12238.46
POND2 2 12612.16
POND2 2.2 12992.03
POND2 2.4 13377.96
POND2 2.6 13769.77
POND2 2.8 14195.92
POND2 3 14629.04
POND2 3.2 15069.37
POND2 3.4 15517.31
POND2 3.6 15973.07
POND2 3.8 16436.65
POND2 4 16908.08
POND2 4.2 17387.54
POND2 4.4 17873.63
POND2 4.6 18366.23
POND2 4.8 18865.42
POND2 5 19371.64
POND2 5.2 19886.19
Page 7
2018-07-19_SWMM Preliminary.inp
POND2 5.4 20410.49
POND2 5.6 20945.15
POND2 5.8 21490.68
POND2 6 22047.3
POND2 6.2 22615.5
POND2 6.4 23195.58
POND2 6.6 23790.35
POND2 6.8 24337.76
POND2 7 24972.48
POND2 7.2 25629.07
POND2 7.4 26305.51
;
POND3 Storage 0 0.03
POND3 0.2 12.86
POND3 0.4 52.44
POND3 0.6 118.91
POND3 0.8 212.69
POND3 1 347.07
POND3 1.2 523.87
POND3 1.4 725.7
POND3 1.6 952.44
POND3 1.8 1208.46
POND3 2 1496.75
POND3 2.2 1845.56
POND3 2.4 2216.68
POND3 2.6 2609.22
POND3 2.8 3019.8
POND3 3 3487.71
POND3 3.2 4275.86
POND3 3.4 5422.49
POND3 3.6 7025.37
POND3 3.8 8861.79
POND3 4 10463.68
;
POND4 Storage 0 0.96
POND4 0.2 44.83
POND4 0.4 160.84
POND4 0.6 540.61
Page 8
2018-07-19_SWMM Preliminary.inp
POND4 0.8 1289.37
POND4 1 2176.44
POND4 1.2 3007.29
POND4 1.4 3965.73
POND4 1.6 4807.37
POND4 1.8 5557.16
POND4 2 6151
POND4 2.2 6759.62
POND4 2.4 7388.66
POND4 2.6 8036.84
POND4 2.8 8705.27
POND4 3 9394
POND4 3.2 10106.07
POND4 3.4 10842.6
;
POND5 Storage 0 4000
POND5 3 4000
;
PONDREDWOOD Storage 0 45700
PONDREDWOOD 2.02 45700
PONDREDWOOD 2.1 140000
PONDREDWOOD 5 140000
[TIMESERIES]
;;Name Date Time Value
;;-------------- ---------- ---------- ----------
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
Page 9
2018-07-19_SWMM Preliminary.inp
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
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
;
Page 10
2018-07-19_SWMM Preliminary.inp
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
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
Page 11
2018-07-19_SWMM Preliminary.inp
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
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-3 860.474 241.081
J-4 1013.087 499.223
J-5 1214.405 499.223
J-6 2454.787 52.750
J-7 813.392 129.056
J-9 1079.652 119.315
J-10 1527.748 961.931
Page 12
2018-07-19_SWMM Preliminary.inp
OFFLINE 1959.608 1294.756
POND-1 2461.281 198.869
POND-2 1016.334 245.951
POND-3 1086.146 429.411
POND-4 1375.135 625.859
POND-5 655.909 478.117
POND-REDWOOD 1552.101 1150.261
[VERTICES]
;;Link X-Coord Y-Coord
;;-------------- ------------------ ------------------
OVERFLOWTOPOND3 1552.101 421.293
[Polygons]
;;Subcatchment X-Coord Y-Coord
;;-------------- ------------------ ------------------
SUB-RW5 928.663 669.926
SUB-RW5 993.604 596.867
SUB-RW5 1058.546 570.890
SUB-RW5 1120.240 590.373
SUB-RW5 1121.864 523.808
SUB-RW5 982.239 531.925
SUB-RW5 886.451 635.832
SUB-RW2-3 1362.689 700.948
SUB-RW2-3 1448.736 782.124
SUB-RW2-3 1427.630 803.230
SUB-RW2-3 1380.547 785.371
SUB-RW2-3 1336.712 793.489
SUB-RW2-3 1278.265 835.701
SUB-RW2-3 1210.076 915.254
SUB-RW2-3 1124.029 863.301
SUB-RW2-3 1054.217 795.113
SUB-RW2-3 1172.735 679.842
SUB-RW2-3 1249.041 678.218
SUB-RW2-3 1307.488 650.618
SUB-A 2688.576 57.621
SUB-A 2602.529 208.610
SUB-A 2493.752 359.599
Page 13
2018-07-19_SWMM Preliminary.inp
SUB-A 2367.116 525.199
SUB-A 1943.373 994.401
SUB-A 1927.138 991.154
SUB-A 1876.808 1031.743
SUB-A 1832.972 1083.696
SUB-A 1808.619 1052.849
SUB-A 1759.913 1121.037
SUB-A 1735.560 1117.790
SUB-A 1743.678 966.801
SUB-A 1724.196 890.495
SUB-A 1675.489 776.847
SUB-A 1675.489 749.247
SUB-A 1719.325 703.788
SUB-A 1821.608 541.435
SUB-A 1868.690 330.375
SUB-A 1863.820 99.833
SUB-B 1719.325 1056.096
SUB-B 1720.948 997.648
SUB-B 1681.984 996.025
SUB-B 1670.619 926.213
SUB-B 1681.984 919.719
SUB-B 1686.854 895.366
SUB-B 1664.125 828.801
SUB-B 1636.525 781.718
SUB-B 1599.183 780.095
SUB-B 1558.595 755.742
SUB-B 1519.630 710.282
SUB-B 1506.642 723.271
SUB-B 1480.665 705.412
SUB-B 1344.288 560.917
SUB-B 1284.217 453.764
SUB-B 1282.594 413.175
SUB-B 1263.111 374.210
SUB-B 1188.429 370.963
SUB-B 1084.522 406.681
SUB-B 1066.663 427.787
SUB-B 1019.581 431.034
SUB-B 1008.216 385.575
Page 14
2018-07-19_SWMM Preliminary.inp
SUB-B 954.639 408.305
SUB-B 1000.098 484.611
SUB-B 948.145 512.211
SUB-B 909.180 491.105
SUB-B 828.004 582.023
SUB-B 829.627 598.258
SUB-B 876.710 646.965
SUB-B 808.521 731.388
SUB-B 746.827 679.435
SUB-B 741.956 627.482
SUB-B 699.744 583.647
SUB-B 748.450 528.446
SUB-B 737.085 510.588
SUB-B 740.333 450.517
SUB-B 782.544 445.646
SUB-B 805.274 431.034
SUB-B 806.898 357.975
SUB-B 790.662 288.163
SUB-B 756.568 254.069
SUB-B 836.121 156.657
SUB-B 1863.820 103.080
SUB-B 1870.314 330.375
SUB-B 1816.737 538.188
SUB-B 1719.325 705.412
SUB-B 1675.489 742.753
SUB-B 1673.866 783.342
SUB-B 1707.960 848.283
SUB-B 1745.302 965.178
SUB-B 1732.313 1114.543
SUB-B 1707.960 1108.049
SUB-C 829.627 603.129
SUB-C 826.380 583.647
SUB-C 905.933 492.729
SUB-C 946.522 515.458
SUB-C 996.851 482.987
SUB-C 956.263 409.928
SUB-C 1006.593 382.328
SUB-C 1017.957 431.034
Page 15
2018-07-19_SWMM Preliminary.inp
SUB-C 1065.040 426.164
SUB-C 1081.275 403.434
SUB-C 1188.429 370.963
SUB-C 1264.735 377.458
SUB-C 1280.970 413.175
SUB-C 1280.970 457.011
SUB-C 1311.817 507.340
SUB-C 1261.488 536.564
SUB-C 1235.511 573.905
SUB-C 1172.193 520.329
SUB-C 982.239 531.694
SUB-C 876.710 643.718
SUB-D 1462.806 804.448
SUB-D 1495.277 896.989
SUB-D 1556.971 961.931
SUB-D 1556.971 984.660
SUB-D 1662.501 1020.378
SUB-D 1677.113 1041.484
SUB-D 1714.454 1072.331
SUB-D 1724.196 1000.895
SUB-D 1683.607 996.025
SUB-D 1670.619 926.213
SUB-D 1678.737 921.342
SUB-D 1688.478 900.236
SUB-D 1668.995 836.918
SUB-D 1639.772 780.095
SUB-D 1597.560 776.847
SUB-D 1556.971 752.494
SUB-D 1519.630 711.906
SUB-D 1508.265 724.894
SUB-D 1487.159 715.153
SUB-D 1347.535 565.788
SUB-D 1310.194 508.964
SUB-D 1259.864 538.188
SUB-D 1237.135 577.153
SUB-E 594.214 536.564
SUB-E 652.662 595.011
SUB-E 699.744 586.894
Page 16
2018-07-19_SWMM Preliminary.inp
SUB-E 750.074 528.446
SUB-E 740.333 512.211
SUB-E 743.580 450.517
SUB-E 780.921 450.517
SUB-E 806.898 427.787
SUB-E 806.898 353.105
SUB-E 793.909 293.034
SUB-E 769.556 270.304
SUB-E 569.861 533.317
SUB-F 1670.619 1250.920
SUB-F 1670.619 1358.073
SUB-F 1738.807 1351.579
SUB-F 1743.678 1226.567
SUB-F 1948.244 991.154
SUB-F 1927.138 991.154
SUB-F 1875.184 1033.366
SUB-F 1831.349 1085.319
SUB-F 1808.619 1052.849
SUB-F 1758.290 1122.661
SUB-F 1707.960 1108.049
SUB-F 1714.454 1072.331
SUB-F 1665.748 1036.613
SUB-OFFSITE2REDWOOD 1436.830 1319.109
[SYMBOLS]
;;Gage X-Coord Y-Coord
;;-------------- ------------------ ------------------
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
THE RETREAT - 100-YR 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 .............. 03/20/2016 00:00:00
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
Page 1
THE RETREAT - 100-YR SWMM OUTPUT.rpt
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 23.999 3.669
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 6.118 0.935
Surface Runoff ........... 17.691 2.705
Final Storage ............ 0.305 0.047
Continuity Error (%) ..... -0.475
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 17.691 5.765
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 19.897 6.484
Flooding Loss ............ 0.000 0.000
Evaporation Loss ......... 0.000 0.000
Exfiltration Loss ........ 0.000 0.000
Initial Stored Volume .... 2.437 0.794
Final Stored Volume ...... 0.223 0.073
Continuity Error (%) ..... 0.037
********************************
Highest Flow Instability Indexes
********************************
All links are stable.
*************************
Routing Time Step Summary
Page 2
THE RETREAT - 100-YR SWMM OUTPUT.rpt
*************************
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
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-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
SUB-A 3.67 0.00 0.00 0.77 2.89 0.91 77.20 0.786
SUB-B 3.67 0.00 0.00 0.71 2.94 0.90 62.91 0.802
SUB-C 3.67 0.00 0.00 0.85 2.82 0.09 10.01 0.770
SUB-D 3.67 0.00 0.00 0.81 2.86 0.13 13.12 0.780
SUB-E 3.67 0.00 0.00 0.61 3.05 0.07 7.48 0.830
SUB-F 3.67 0.00 0.00 1.05 2.64 0.05 5.92 0.718
SUB-OFFSITE2REDWOOD 3.67 0.00 0.00 1.04 2.59 3.51 165.55 0.707
******************
Node Depth Summary
******************
---------------------------------------------------------------------------------
Average Maximum Maximum Time of Max Reported
Page 3
THE RETREAT - 100-YR SWMM OUTPUT.rpt
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 0.03 0.15 48.15 0 02:09 0.15
J-3 JUNCTION 0.25 1.07 50.07 0 01:46 1.07
J-4 JUNCTION 0.24 1.07 52.07 0 01:45 1.07
J-5 JUNCTION 0.41 1.76 53.76 0 02:34 1.76
J-6 JUNCTION 0.20 0.34 52.34 0 02:32 0.34
J-7 JUNCTION 0.22 0.79 47.79 0 01:51 0.79
J-9 JUNCTION 0.20 0.34 50.34 0 02:45 0.34
J-10 JUNCTION 0.41 1.76 54.26 0 02:31 1.76
OFFLINE JUNCTION 0.00 0.00 0.00 0 00:00 0.00
POND-1 STORAGE 1.84 3.73 56.83 0 02:32 3.73
POND-2 STORAGE 2.64 7.12 56.52 0 02:39 7.11
POND-3 STORAGE 0.72 3.94 57.14 0 01:05 3.92
POND-4 STORAGE 0.54 3.43 59.03 0 00:55 3.41
POND-5 STORAGE 0.20 1.92 50.92 0 02:09 1.91
POND-REDWOOD STORAGE 1.29 4.75 57.85 0 02:31 4.75
*******************
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 17.28 0 01:51 0 6.48 0.000
J-2 JUNCTION 0.00 0.20 0 02:09 0 0.0653 -0.000
J-3 JUNCTION 0.00 17.09 0 01:51 0 6.42 0.000
J-4 JUNCTION 0.00 15.57 0 01:45 0 4.61 0.000
Page 4
THE RETREAT - 100-YR SWMM OUTPUT.rpt
J-5 JUNCTION 0.00 15.58 0 01:45 0 4.61 0.000
J-6 JUNCTION 0.00 0.70 0 02:32 0 0.907 0.000
J-7 JUNCTION 0.00 17.28 0 01:51 0 6.48 0.000
J-9 JUNCTION 0.00 0.70 0 02:45 0 0.907 0.000
J-10 JUNCTION 0.00 12.00 0 02:31 0 4.27 0.000
OFFLINE JUNCTION 0.00 0.00 0 00:00 0 0 0.000 gal
POND-1 STORAGE 77.20 77.20 0 00:40 0.906 0.917 0.006
POND-2 STORAGE 62.91 62.93 0 00:40 0.903 1.81 0.009
POND-3 STORAGE 12.95 12.95 0 00:40 0.112 0.154 0.063
POND-4 STORAGE 23.23 23.23 0 00:40 0.218 0.226 0.219
POND-5 STORAGE 7.48 7.48 0 00:40 0.0654 0.0654 0.023
POND-REDWOOD STORAGE 171.47 171.47 0 00:40 3.56 4.33 0.022
*********************
Node Flooding Summary
*********************
No nodes were flooded.
**********************
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 36.176 22 0 0 116.789 71 0 02:32 0.70
POND-2 30.411 25 0 0 112.201 94 0 02:39 1.60
POND-3 0.258 3 0 0 9.363 94 0 01:04 3.80
POND-4 0.634 2 0 0 17.091 64 0 00:54 6.04
POND-5 0.783 7 0 0 7.683 64 0 02:09 0.20
Page 5
THE RETREAT - 100-YR SWMM OUTPUT.rpt
POND-REDWOOD 79.660 16 0 0 470.988 93 0 02:30 12.00
********************
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 02:13 1.24 0.00 0.03
C-2 CONDUIT 17.28 0 01:51 10.31 0.06 0.16
C-3 CONDUIT 15.57 0 01:45 6.88 0.27 0.36
C-4 CONDUIT 15.57 0 01:46 6.86 0.27 0.36
C-5 CONDUIT 17.09 0 01:51 11.42 0.15 0.26
C-6 CONDUIT 0.70 0 02:45 1.58 0.03 0.11
C-7 CONDUIT 0.70 0 02:46 3.45 0.01 0.07
C-8 CONDUIT 12.00 0 02:34 2.79 0.65 0.59
OVERFLOWTOPOND3 WEIR 3.79 0 00:55 0.00
O-1 DUMMY 0.70 0 02:32
O-2 DUMMY 1.60 0 02:39
O-3 DUMMY 3.80 0 01:05
O-4 DUMMY 2.25 0 00:55
O-5 DUMMY 0.20 0 02:09
OS-REDWOOD DUMMY 12.00 0 02:31
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Page 6
THE RETREAT - 100-YR SWMM OUTPUT.rpt
Analysis begun on: Tue Jul 24 14:00:16 2018
Analysis ended on: Tue Jul 24 14:00:17 2018
Total elapsed time: 00:00:01
Page 7
THE RETREAT - 100-YR SWMM OUTPUT-SUBBASIN F NOT ROUTED TO REDWOOD POND.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 .............. 03/20/2016 00:00:00
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
Page 1
THE RETREAT - 100-YR SWMM OUTPUT-SUBBASIN F NOT ROUTED TO REDWOOD POND.rpt
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 23.999 3.669
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 6.118 0.935
Surface Runoff ........... 17.691 2.705
Final Storage ............ 0.305 0.047
Continuity Error (%) ..... -0.475
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 17.691 5.765
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 19.898 6.484
Flooding Loss ............ 0.000 0.000
Evaporation Loss ......... 0.000 0.000
Exfiltration Loss ........ 0.000 0.000
Initial Stored Volume .... 2.437 0.794
Final Stored Volume ...... 0.222 0.072
Continuity Error (%) ..... 0.034
********************************
Highest Flow Instability Indexes
********************************
All links are stable.
*************************
Routing Time Step Summary
Page 2
THE RETREAT - 100-YR SWMM OUTPUT-SUBBASIN F NOT ROUTED TO REDWOOD POND.rpt
*************************
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
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-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
SUB-A 3.67 0.00 0.00 0.77 2.89 0.91 77.20 0.786
SUB-B 3.67 0.00 0.00 0.71 2.94 0.90 62.91 0.802
SUB-C 3.67 0.00 0.00 0.85 2.82 0.09 10.01 0.770
SUB-D 3.67 0.00 0.00 0.81 2.86 0.13 13.12 0.780
SUB-E 3.67 0.00 0.00 0.61 3.05 0.07 7.48 0.830
SUB-F 3.67 0.00 0.00 1.05 2.64 0.05 5.92 0.718
SUB-OFFSITE2REDWOOD 3.67 0.00 0.00 1.04 2.59 3.51 165.55 0.707
******************
Node Depth Summary
******************
---------------------------------------------------------------------------------
Average Maximum Maximum Time of Max Reported
Page 3
THE RETREAT - 100-YR SWMM OUTPUT-SUBBASIN F NOT ROUTED TO REDWOOD POND.rpt
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 0.03 0.15 48.15 0 02:09 0.15
J-3 JUNCTION 0.25 1.07 50.07 0 01:46 1.07
J-4 JUNCTION 0.24 1.07 52.07 0 01:45 1.07
J-5 JUNCTION 0.41 1.74 53.74 0 02:34 1.74
J-6 JUNCTION 0.20 0.34 52.34 0 02:32 0.34
J-7 JUNCTION 0.22 0.79 47.79 0 01:50 0.79
J-9 JUNCTION 0.20 0.34 50.34 0 02:45 0.34
J-10 JUNCTION 0.41 1.74 54.24 0 02:31 1.74
OFFLINE JUNCTION 0.00 0.00 0.00 0 00:00 0.00
POND-1 STORAGE 1.84 3.73 56.83 0 02:32 3.73
POND-2 STORAGE 2.64 7.12 56.52 0 02:39 7.11
POND-3 STORAGE 0.72 3.94 57.14 0 01:05 3.92
POND-4 STORAGE 0.54 3.43 59.03 0 00:55 3.41
POND-5 STORAGE 0.20 1.92 50.92 0 02:09 1.91
POND-REDWOOD STORAGE 1.28 4.71 57.81 0 02:31 4.71
*******************
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 17.11 0 01:50 0 6.43 0.000
J-2 JUNCTION 0.00 0.20 0 02:09 0 0.0653 -0.000
J-3 JUNCTION 0.00 16.92 0 01:50 0 6.37 0.000
J-4 JUNCTION 0.00 15.40 0 01:45 0 4.56 0.000
Page 4
THE RETREAT - 100-YR SWMM OUTPUT-SUBBASIN F NOT ROUTED TO REDWOOD POND.rpt
J-5 JUNCTION 0.00 15.40 0 01:45 0 4.56 0.000
J-6 JUNCTION 0.00 0.70 0 02:32 0 0.907 0.000
J-7 JUNCTION 0.00 17.11 0 01:50 0 6.43 0.000
J-9 JUNCTION 0.00 0.70 0 02:45 0 0.907 0.000
J-10 JUNCTION 0.00 11.83 0 02:31 0 4.22 0.000
OFFLINE JUNCTION 5.92 5.92 0 00:40 0.0515 0.0515 0.000
POND-1 STORAGE 77.20 77.20 0 00:40 0.906 0.917 0.006
POND-2 STORAGE 62.91 62.93 0 00:40 0.903 1.81 0.009
POND-3 STORAGE 12.95 12.95 0 00:40 0.112 0.154 0.063
POND-4 STORAGE 23.23 23.23 0 00:40 0.218 0.226 0.219
POND-5 STORAGE 7.48 7.48 0 00:40 0.0654 0.0654 0.023
POND-REDWOOD STORAGE 165.55 165.55 0 00:40 3.51 4.28 0.022
*********************
Node Flooding Summary
*********************
No nodes were flooded.
**********************
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 36.176 22 0 0 116.789 71 0 02:32 0.70
POND-2 30.411 25 0 0 112.201 94 0 02:39 1.60
POND-3 0.258 3 0 0 9.363 94 0 01:04 3.80
POND-4 0.634 2 0 0 17.091 64 0 00:54 6.04
POND-5 0.783 7 0 0 7.683 64 0 02:09 0.20
Page 5
THE RETREAT - 100-YR SWMM OUTPUT-SUBBASIN F NOT ROUTED TO REDWOOD POND.rpt
POND-REDWOOD 79.064 16 0 0 465.189 92 0 02:31 11.83
********************
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 02:13 1.24 0.00 0.03
C-2 CONDUIT 17.11 0 01:50 10.28 0.06 0.16
C-3 CONDUIT 15.40 0 01:45 6.86 0.27 0.35
C-4 CONDUIT 15.40 0 01:46 6.84 0.27 0.36
C-5 CONDUIT 16.92 0 01:50 11.38 0.15 0.26
C-6 CONDUIT 0.70 0 02:45 1.58 0.03 0.11
C-7 CONDUIT 0.70 0 02:46 3.45 0.01 0.07
C-8 CONDUIT 11.83 0 02:34 2.78 0.64 0.58
OVERFLOWTOPOND3 WEIR 3.79 0 00:55 0.00
O-1 DUMMY 0.70 0 02:32
O-2 DUMMY 1.60 0 02:39
O-3 DUMMY 3.80 0 01:05
O-4 DUMMY 2.25 0 00:55
O-5 DUMMY 0.20 0 02:09
OS-REDWOOD DUMMY 11.83 0 02:31
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Page 6
THE RETREAT - 100-YR SWMM OUTPUT-SUBBASIN F NOT ROUTED TO REDWOOD POND.rpt
Analysis begun on: Tue Jul 24 14:03:23 2018
Analysis ended on: Tue Jul 24 14:03:23 2018
Total elapsed time: < 1 sec
Page 7
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
SD
SD
SD SD
SD SD SD
SD
SD
SD
SD SD
SD
SD
SD
SD
SD
SD
SD
SD SD
SD SD SD
SD
SD
SD
SD
SD SD SD SD SD SD SD SD SD SD SD SD SD
SD
SD
SD
SD
SD
SD
SD
SD
AST
NY LOPL
UD
C
ELIT
I
NOR
ST
NYL OPLA
D CU
T
ELI I
R
O
N
S T
N YLOPLA
CUD
T
ELI I
R
O
N
ST
A
NYLOPL
TCUD
LI RIE
O
N
LAST
P
O
NYL
D CU
ELIT
NORI
AST
L
NYLOP
CUD
T
I IEL
R
NO
AS T
L
N YLOP
CUD
T
ELI I
R
NO
PLAST
O
NYL
D
U
LITC
E
I NOR
T
S
Y LOPLA
N
D
ITCU
EL NORI
T
OPL AS
N YL
D
ITCU
L
ORIE N
L AST
NYLOP
UD
C
IT EL
ORI N
LOP LAST
Y
N
D
TCU I
L
RIE NO
T
S
YLOPL A
N
D
ITCU
L ORIE N
T
S
YLOPLA
N
D
ITCU
EL NORI
T
S
YLO PLA
N
D
TCU I
RIEL NO
T
S
LOPL A
Y
N
D
ITCU L
ORIE N
T
LOPLA S
Y
N
D
ITCU
L
E NORI
LOPL AST
Y
N
D
ITCU
L
ORIE N
T
S
YLOP LA
N
D
TCU
I
RIEL NO
AST
L
P
NY LO
D U
C
ELIT I
NOR
UP
UP
ELEVATOR
UP
C
C
C
C C
C
C C C
C
C
C
C C C
C
C
C
(52)BIKE SPACES
C
C
C C C
C
C
C
C
POND 2
EXISTING REDWOOD
DETENTION POND
POND 3
POND 4
POND 1
WQ
CHAMBER
B6
WQ
CHAMBER
B9
WQ
CHAMBER
E1
POND 5
WQ
CHAMBER
A7
WQ
CHAMBER
B2
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
FEMA
HIGH-RISK
FLOODWAY
FEMA
HIGH-RISK
FLOODPLAIN
PROPOSED
OUTLET STRUCTURE
PROPOSED
OUTLET STRUCTURE
NECCO STORMLINE
PROPOSED
INLETS
PROPOSED
INLETS
(2-YR)
PROPOSED
INLETS
EXISTING INLET
PROPOSED
INLET
PLANNED
INLETS
PROPOSED
INLETS
(2-YR)
PROPOSED
INLETS
(2-YR)
PROPOSED
OUTLET STRUCTURE
PROPOSED
OUTLET
STRUCTURE
PROPOSED
CURB CUTS
PROPOSED
INLET
PROPOSED
INLET
(2-YR)
UD1
UD2
UD3
RW5
RW4
RW2
RW1
RW3
D1
D2
E1
F1
A1
A3
A2
A4
A5
A6
PROPOSED
INLETS
A7
A8
B1
B2
B3
B4
PROPOSED
INLETS
(2-YR)
B5
B6
B7
B8
B9
B10
B11
C1
RW1
RW2
RW3
RW4
RW5
UD1
UD2
UD3
F1
E1
C1
B5
B7
B9
D1
D2
B3
B1
A6
A7
A1
A3
A4
A5
A8
A2
B2
B6
B8
B10
B11
PROPOSED B4
INLET
(2-YR)
AJ - 4960.6 NAVD 88
AL - 4962.04 NAVD 88
AI - 4960.31 NAVD 88
AK - 4961.08 NAVD 88
( IN FEET )
0
1 INCH = 100 FEET
100 100 200 300
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 July 25,
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
25
NORTH
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 116,789 2.68 4956.93 1,319 4956.93 0.70
2 Open Detention 112,201 2.58 4949.65 377 4956.52 1.60
3 Open Detention 9,363 0.21 4955.03 746 4857.14 3.80
4 Open Detention 17,091 0.39 4959.04 1,131 4956.80 2.25
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)
A7 Underground LID n/a n/a n/a 5,507 to be provided at final n/a
B2 Underground LID n/a n/a n/a 1,619 to be provided at final n/a
B6 Underground LID n/a n/a n/a 3,124 to be provided at final n/a
B9 Underground LID n/a n/a n/a 1,827 to be provided at final n/a
E1/Pond 5 Underground LID and
Detention
7,683 0.18 to be provided at final 676 to be provided at final 0.20
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 26
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 0.66 0.62 0.78 5.0 5.0 1.17 5.11
A2 A2 1.61 0.69 0.86 13.8 11.4 2.16 10.25
A3 A3 1.33 0.76 0.95 9.0 7.6 2.37 10.83
A4 A4 1.42 0.67 0.84 7.2 5.2 2.39 11.81
A5 A5 0.71 0.76 0.95 6.7 5.0 1.38 6.63
A6 A6 2.11 0.70 0.87 10.5 9.3 3.19 14.74
A7 A7 0.20 0.84 1.00 5.0 5.0 0.49 2.04
A8 A8 3.54 0.38 0.47 10.4 9.5 2.96 13.20
B1 B1 1.59 0.70 0.88 11.8 10.4 2.33 10.76
B2 B2 1.26 0.45 0.56 9.1 7.6 1.31 6.11
B3 B3 1.23 0.85 1.00 8.3 5.0 2.51 12.25
B4 B4 2.07 0.68 0.85 6.7 5.4 3.66 17.55
B5 B5 0.52 0.74 0.93 5.9 5.0 1.07 4.84
B6 B6 0.67 0.49 0.62 6.4 5.2 0.89 4.14
B7 B7 1.30 0.77 0.96 6.8 5.0 2.60 12.48
B8 B8 0.27 0.77 0.97 5.3 5.0 0.60 2.62
B9 B9 0.14 0.80 1.00 5.0 5.0 0.31 1.36
B10 B10 0.81 0.77 0.96 5.1 5.0 1.77 7.70
B11 B11 1.43 0.34 0.42 9.9 9.0 1.09 4.83
C1 C1 1.16 0.54 0.68 7.6 6.3 1.56 7.36
D1 D1 0.83 0.64 0.80 7.0 5.2 1.34 6.61
D2 D2 0.83 0.51 0.63 5.0 5.0 1.20 5.24
E1 E1 0.79 0.62 0.77 8.3 6.6 1.17 5.53
F1 F1 0.72 0.38 0.47 14.2 13.3 0.52 2.36
UD1 UD1 0.79 0.52 0.65 8.0 6.6 0.99 4.66
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
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
FLOODPLAIN NOTES:
1. REFER TO THE PLAT FOR LOT AREAS, TRACT SIZES, EASEMENTS, LOT DIMENSIONS,
UTILITY EASEMENTS, OTHER EASEMENTS, AND OTHER SURVEY INFORMATION
2. THIS PROJECT IS LOCATED WITHIN A FEMA 100-YEAR FLOODWAY AND FLOOD
FRINGE AND MUST COMPLY WITH CHAPTER 10 OF THE CITY CODE.
3. ALL ELEVATIONS DEPICTED IN PLAN VIEW AND BENCHMARKS LISTED HEREON ARE
PER NAVD 88 DATUM.
4. ANY ITEMS LOCATED IN THE FLOODWAY THAT CAN FLOAT (E.G., PICNIC TABLES,
BIKE RACKS, ETC.) MUST BE ANCHORED.
5. THE LOWEST FLOOR AND THE FINISHED FLOOR FOR ANY BUILDING IN THE
FLOODPLAIN SHALL BE FLOODPROOFED UP TO THE REGULATORY FLOOD
PROTECTION ELEVATION.
6. A FLOODPLAIN USE PERMIT SHALL BE REQUIRED FOR EACH SITE CONSTRUCTION
ELEMENT IN THE FLOODPLAIN.
7. A FLOODPLAIN USE PERMIT AND NO RISE CERTIFICATION IS REQUIRED PRIOR TO
PERFORMING ANY WORK WITHIN THE FLOODWAY (I.E., CURB CUT REMOVAL,
LANDSCAPING).
8. NO STORAGE OF MATERIALS OR EQUIPMENT SHALL BE ALLOWED IN THE
FLOODWAY, WHETHER TEMPORARY (DURING CONSTRUCTION) OR PERMANENT.
LANDSCAPING SHALL ALSO MEET THE REQUIREMENTS FOR NO RISE IN THE
FLOODWAY.
9. REFER TO THE PRELIMINARY DRAINAGE REPORT FOR THE RETREAT AT FORT
COLLINS DATED JULY 25, 2018 FOR ADDITIONAL INFORMATION.
Page 10 of 11
Chambers_WQ Calcs.xlsx
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Page 8 of 11
Chambers_WQ Calcs.xlsx
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Page 6 of 11
Chambers_WQ Calcs.xlsx
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Page 4 of 11
Chambers_WQ Calcs.xlsx
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The Retreat
Project Number :
Project Name :
WQ Chamber A7
Page 2 of 11
Chambers_WQ Calcs.xlsx
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E
NORI
OPLAST
L
NY
ELITCUD
NORI
T
S
NYLOPLA
LIT CUD
E
NORI
AST L
P
LO
Y
N
OR IELITCUD
N
ST
A
NYLOPL
IELITCUD
R
O
N
T
S
YLOPLA
N
D
RIELITCU
O
N
T
S
NYLOPLA
D
ELITCU
I
NOR
T
NYLOPLAS
CUD
T
LI
E
NORI
ST
A
NYLOPL
ITCUD
L
RIE
O
N
LOPLAST Y
N
ORIE LITCUD
N
YLOPLAST
N
D
U
ORIELITC
N
T
OPLAS
L
NY
ELITCUD
NORI
T
S
A
NYLOPL
D
U
ITC
L
NORIE
LOPLAST
Y
N
NORIELIT CUD
YLOPLAST
N
CUD
T
ORIELI
N
AST
L
LOP
Y
N
O RIELITCUD
N
NYLOPLAST
UD
C
ELIT
I
NOR
PLAST O
L
NY
LITCUD
E
I
NOR
YLOPLAST
N
ORIEL ITCUD
N
UP
UP
ELEVATOR
UP
C
C C C
C
C C C C
C
C
C
C C C
C
C
C
(
52)BIKE SPACES
C C
C
C C C C
C
C
EXISTING REDWOOD
DETENTION POND
FEMA
HIGH-RISK
FLOODWAY
FEMA HIGH-RISK
FLOODPLAIN
NECCO STORMLINE
EXISTING INLET
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
RW1
RW2
RW3
RW4
RW5
UD1
UD2
UD3
F1
E1
C1
B5
B7
B9
D1
D2
B3
B1
A6
A7
A1
A3
A4
A5
A8
A2
B2
B6
B8
B10
B11
B4
WQ CHAMBER
B6
WQ CHAMBER
B9
WQ CHAMBER
E1
POND 5
WQ CHAMBER
A7
WQ CHAMBER
B2
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
LEGEND
DRAINAGE BASIN
DRAINAGE BASIN LABEL
AREA TREATED BY LOW
IMPACT DEVELOPMENT
(LID)
LOW IMPACT
DEVELOPMENT (LID)
TREATMENT
B2
LID TREATMENT EXHIBIT
FORT COLLINS, CO
THE RETREAT AT FORT COLLINS
E NGINEER ING
N O R T H E RN
07.25.2018
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 28,709 62% 17,883 WQ Chamber A7
A2 69,932 69% 48,143 WQ Chamber A7
A3 57,726 76% 43,924 WQ Chamber A7
A4 61,860 67% 41,369 WQ Chamber A7
A5 30,720 76% 23,234 WQ Chamber A7
A6 91,912 70% 63,956 WQ Chamber A7
A7 8,912 84% 7,458 WQ Chamber A7
B1 69,286 70% 48,558 WQ Chamber B2
B2 54,867 45% 24,793 WQ Chamber B2
B3 53,646 85% 45,476 WQ Chamber B6
B4 90,005 68% 61,471 WQ Chamber B6
B5 22,787 74% 16,965 WQ Chamber B6
B6 29,364 49% 14,512 WQ Chamber B6
B7 56,825 77% 43,708 WQ Chamber B9
B8 11,887 77% 9,184 WQ Chamber E1
B9 5,943 80% 4,758 WQ Chamber B9
B10 35,151 77% 26,979 WQ Chamber B9
E1 34,607 62% 21,297 WQ Chamber E1
Total Treated 814,139 69% 563,667
PROPOSED LID UNTREATED AREA
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent Impervious Impervious Area, A
(sf)
A8 154,227 38% 58,414
B11 62,396 34% 20,969
C1 50,565 54% 27,544
D1 36,109 64% 23,143
D2 36,306 51% 18,366
UD1 34,414 52% 17,953
UD2 51,032 80% 41,030
UD3 101,092 30% 29,972
F1 31,311 38% 11,887
Total Proposed
Untreated
557,452 45% 249,277
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) 1,371,591
Total Proposed Impervious Area (sf) 812,944
Total Impervious Area not included in LID
calcs
45,563
Total Net Proposed Impervious Area (sf) 767,381
75% Required Minimum Area to be Treated
by LID measures (sf) 575,536
Total Treated Impervious Area (sf) 563,667
Percent Impervious Treated by LID measures 73.5%
Undisturbed Area UD3 101,092 6% 6,042
Not Included in LID
Calcs
152,124 30% 45,563
1,371,591
812,944
45,563
767,381
575,536
563,667
73.5%
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
4,956.20 24338 0.20 4813 104368 4813 104309
4,956.40 24972 0.20 4931 109299 4931 109240
4,956.60 25629 0.20 5060 114359 5060 114300
4,956.80 26306 0.20 5193 119553 5193 119493
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
7/24/20181:11 PM D:\Projects\1290-002\Drainage\Detention\1290-002_Detention Pond 2.xlsm\Stage_Storage
15 15 11 0.66 0.66 0.83 1.90 3.24 7.57 9.21 15.75 46.00
B7
Basins B7-B10
(Storm Sewer Calc) 2.52
8 8 5 0.77 0.77 0.96 2.46 4.21 9.95 4.78 8.17 24.16
PROPOSED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
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
July 24, 2018
Intensity,
i10
(in/hr)
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
Q = C f ( C )( i )( A )
7/24/2018 12:21 PM D:\Projects\1290-002\Drainage\Hydrology\1290-002_Proposed_Rational_Calcs.xlsx\Runoff
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
A1 A1 No 0.62 0.62 0.78 50 3.18% 4.3 4.3 2.9 N/A N/A N/A N/A N/A N/A 5.0 5.0 5.0
A2 A2 No 0.69 0.69 0.86 127 3.31% 5.8 5.8 3.4 N/A N/A N/A 672 0.49% 1.40 8.0 13.8 13.8 11.4
A3 A3 No 0.76 0.76 0.95 29 2.72% 2.4 2.4 1.1 N/A N/A N/A 589 0.56% 1.50 6.5 9.0 9.0 7.6
A4 A4 No 0.67 0.67 0.84 34 0.74% 5.2 5.2 3.2 N/A N/A N/A 206 0.73% 1.71 2.0 7.2 7.2 5.2
A5 A5 No 0.76 0.76 0.95 55 1.76% 3.9 3.9 1.8 N/A N/A N/A 272 0.67% 1.64 2.8 6.7 6.7 5.0
A6 A6 No 0.70 0.70 0.87 39 5.00% 2.8 2.8 1.6 N/A N/A N/A 653 0.49% 1.40 7.8 10.5 10.5 9.3
A7 A7 No 0.84 0.84 1.00 71 3.24% 2.8 2.8 1.1 N/A N/A N/A 34 1.00% 2.00 0.3 5.0 5.0 5.0
A8 A8 No 0.38 0.38 0.47 65 4.20% 6.7 6.7 5.9 N/A N/A N/A 419 0.91% 1.90 3.7 10.4 10.4 9.5
Basin A Basin A No 0.60 0.60 0.75 127 3.31% 7.0 7.0 4.9 N/A N/A N/A 1344 0.66% 1.63 13.8 20.8 20.8 18.7
B1 B1 No 0.70 0.70 0.88 44 3.18% 3.4 3.4 1.9 N/A N/A N/A 826 0.66% 1.62 8.5 11.8 11.8 10.4
B2 B2 No 0.45 0.45 0.56 61 1.28% 8.7 8.7 7.2 62 2.61% 2.42 0.4 N/A N/A N/A 9.1 9.1 7.6
B3 B3 No 0.85 0.85 1.00 203 1.08% 6.6 6.6 2.6 N/A N/A N/A 192 0.85% 1.84 1.7 8.3 8.3 5.0
B4 B4 No 0.68 0.68 0.85 38 3.34% 3.2 3.2 1.9 N/A N/A N/A 427 1.03% 2.03 3.5 6.7 6.7 5.4
B5 B5 No 0.74 0.74 0.93 53 3.62% 3.2 3.2 1.5 N/A N/A N/A 308 0.89% 1.88 2.7 5.9 5.9 5.0
B6 B6 No 0.49 0.49 0.62 65 3.42% 6.1 6.1 4.8 N/A N/A N/A 28 0.50% 1.41 0.3 6.4 6.4 5.2
B7 B7 No 0.77 0.77 0.96 72 2.65% 3.8 3.8 1.6 N/A N/A N/A 320 0.80% 1.79 3.0 6.8 6.8 5.0
B8 B8 No 0.77 0.77 0.97 90 1.49% 5.1 5.1 2.1 N/A N/A N/A 51 2.63% 3.24 0.3 5.3 5.3 5.0
B9 B9 No 0.80 0.80 1.00 54 5.33% 2.4 2.4 0.8 N/A N/A N/A 12 1.00% 2.00 0.1 5.0 5.0 5.0
B10 B10 No 0.77 0.77 0.96 50 6.32% 2.4 2.4 1.0 N/A N/A N/A 331 1.01% 2.01 2.7 5.1 5.1 5.0
B11 B11 No 0.34 0.34 0.42 53 2.36% 7.8 7.8 7.0 58 12.36% 5.27 0.2 161 0.50% 1.42 1.9 9.9 9.9 9.0
Basin B Basin B No 0.64 0.64 0.81 203 1.08% 11.8 11.8 7.6 N/A N/A N/A 449 2.19% 2.96 2.5 14.4 14.4 10.2
C1 C1 No 0.54 0.54 0.68 61 3.28% 5.5 5.5 4.1 313 2.57% 2.40 2.2 N/A N/A N/A 7.6 7.6 6.3
Basin C Basin C No 0.54 0.54 0.68 61 3.28% 5.5 5.5 4.1 313 2.57% 2.40 2.2 N/A N/A N/A 7.6 7.6 6.3
D1 D1 No 0.64 0.64 0.80 37 1.08% 5.1 5.1 3.3 216 1.56% 1.87 1.9 N/A N/A N/A 7.0 7.0 5.2
D2 D2 No 0.51 0.51 0.63 N/A N/A N/A N/A N/A N/A N/A 368 1.08% 2.08 2.9 5.0 5.0 5.0
Basin D Basin D No 0.57 0.57 0.72 37 1.08% 5.8 5.8 4.3 216 1.56% 1.87 1.9 368 1.08% 2.08 2.9 10.7 10.7 9.1
E1 E1 No 0.62 0.62 0.77 61 2.26% 5.4 5.4 3.7 N/A N/A N/A 199 0.33% 1.14 2.9 8.3 8.3 6.6
F1 F1 No 0.38 0.38 0.47 68 4.13% 6.9 6.9 6.0 N/A N/A N/A 599 0.47% 1.38 7.2 14.2 14.2 13.3
UD1 UD1 No 0.52 0.52 0.65 87 3.68% 6.5 6.5 5.1 N/A N/A N/A 183 1.04% 2.04 1.5 8.0 8.0 6.6
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
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
A3, A2
Basins A1-A3 (100-
year Overtopping) No 0.70 0.70 0.88 127 3.31% 5.6 5.6 3.1 N/A N/A N/A 672 0.49% 1.40 8.0 13.6 13.6 11.2
A5
Basins A1-A5 (100-
year Overtopping) No 0.70 0.70 0.88 127 3.31% 5.6 5.6 3.2 N/A N/A N/A 944 0.42% 1.29 12.2 17.8 17.8 15.4
A7
Basins A1-A7 (Channel
Calc) No 0.70 0.70 0.88 127 3.31% 5.6 5.6 3.1 N/A N/A N/A 978 0.44% 1.32 12.3 17.9 17.9 15.5
B5
Basins B3-B5 (100-
year Overtopping) No 0.74 0.74 0.93 203 1.08% 9.2 9.2 4.4 N/A N/A N/A 192 0.85% 1.84 1.7 11.0 11.0 6.1
B6
Basins B1-B6 (Storm
Sewer Calc) No 0.66 0.66 0.83 203 1.08% 11.4 11.4 7.1 N/A N/A N/A 288 0.48% 1.38 3.5 14.8 14.8 10.5
B7
Basins B7-B10 (Storm
Sewer Calc) No 0.77 0.77 0.96 90 1.49% 5.1 5.1 2.1 N/A N/A N/A 380 1.41% 2.37 2.7 7.8 7.8 5.0
* 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
July 24, 2018
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
7/24/2018 12:20 PM D:\Projects\1290-002\Drainage\Hydrology\1290-002_Proposed_Rational_Calcs.xlsx\Tc
Coefficient
Composite
% Imperv.
A1 0.66 0.00 0.00 0.13 0.00 0.23 Clayey | Average 2% to 7% 0.308 0.62 0.62 0.78 48%
A2 1.61 0.41 0.00 0.23 0.00 0.37 Clayey | Average 2% to 7% 0.600 0.69 0.69 0.86 59%
A3 1.33 0.41 0.00 0.43 0.00 0.13 Clayey | Average 2% to 7% 0.358 0.76 0.76 0.95 69%
A4 1.42 0.14 0.00 0.39 0.00 0.32 Clayey | Average 2% to 7% 0.571 0.67 0.67 0.84 55%
A5 0.71 0.19 0.00 0.15 0.00 0.17 Clayey | Average 2% to 7% 0.195 0.76 0.76 0.95 68%
A6 2.11 0.41 0.00 0.52 0.00 0.41 Clayey | Average 2% to 7% 0.766 0.70 0.70 0.87 59%
A7 0.20 0.10 0.00 0.04 0.00 0.04 Clayey | Average 2% to 7% 0.033 0.84 0.84 1.00 80%
A8 3.54 0.00 0.00 0.34 0.00 0.31 Clayey | Average 2% to 7% 2.889 0.38 0.38 0.47 17%
Basin A 11.570 1.66 0.00 2.22 0.00 1.97 Clayey | Average 2% to 7% 5.720 0.60 0.60 0.75 47%
B1 1.59 0.49 0.00 0.38 0.00 0.15 Clayey | Average 2% to 7% 0.566 0.70 0.70 0.88 61%
B2 1.26 0.09 0.00 0.11 0.00 0.16 Clayey | Average 2% to 7% 0.896 0.45 0.45 0.56 27%
B3 1.23 0.16 0.00 0.70 0.00 0.20 Clayey | Average 2% to 7% 0.180 0.85 0.85 1.00 78%
B4 2.07 0.48 0.00 0.30 0.00 0.50 Clayey | Average 2% to 7% 0.788 0.68 0.68 0.85 58%
B5 0.52 0.17 0.00 0.10 0.00 0.09 Clayey | Average 2% to 7% 0.154 0.74 0.74 0.93 67%
B6 0.67 0.08 0.00 0.07 0.00 0.09 Clayey | Average 2% to 7% 0.439 0.49 0.49 0.62 33%
B7 1.30 0.52 0.00 0.27 0.00 0.18 Clayey | Average 2% to 7% 0.337 0.77 0.77 0.96 71%
B8 0.27 0.09 0.00 0.07 0.00 0.05 Clayey | Average 2% to 7% 0.069 0.77 0.77 0.97 70%
B9 0.14 0.08 0.00 0.02 0.00 0.00 Clayey | Average 2% to 7% 0.029 0.80 0.80 1.00 77%
B10 0.81 0.26 0.00 0.15 0.00 0.19 Clayey | Average 2% to 7% 0.210 0.77 0.77 0.96 70%
B11 1.43 0.00 0.00 0.08 0.00 0.10 Clayey | Average 2% to 7% 1.256 0.34 0.34 0.42 11%
Basin B 11.298 2.42 0.00 2.25 0.00 1.71 Clayey | Average 2% to 7% 4.925 0.64 0.64 0.81 53%
C1 1.16 0.10 0.00 0.20 0.00 0.18 Clayey | Average 2% to 7% 0.672 0.54 0.54 0.68 39%
Basin C 1.161 0.10 0.00 0.20 0.00 0.18 Clayey | Average 2% to 7% 0.672 0.54 0.54 0.68 39%
D1 0.83 0.17 0.00 0.16 0.00 0.14 Clayey | Average 2% to 7% 0.366 0.64 0.64 0.80 52%
D2 0.83 0.00 0.00 0.12 0.00 0.19 Clayey | Average 2% to 7% 0.529 0.51 0.51 0.63 33%
Basin D 1.662 0.17 0.00 0.28 0.00 0.32 Clayey | Average 2% to 7% 0.895 0.57 0.57 0.72 43%
E1 0.794 0.13 0.00 0.09 0.00 0.20 Clayey | Average 2% to 7% 0.380 0.62 0.62 0.77 49%
F1 0.719 0.10 0.00 0.08 0.00 0.01 Clayey | Average 2% to 7% 0.371 0.38 0.38 0.47 25%
UD1 0.790 0.07 0.00 0.11 0.00 0.14 Clayey | Average 2% to 7% 0.453 0.52 0.52 0.65 37%
UD2 1.172 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 2.321 0.00 0.00 0.15 0.00 0.00 Clayey | Average 2% to 7% 2.167 0.30 0.30 0.37 6%
TOTAL ON-SITE BASINS 31.49 5.48 5.65 0.00 4.53 Clayey | Average 2% to 7% 15.827 0.60 0.60 0.75 47%
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, F, UD1) 28.00 4.75 0.00 5.30 0.00 4.53 Clayey | Average 2% to 7% 13.416 0.61 0.61 0.77 49%
Basins A1-A7 (WQ Chamber A7) 8.03 1.66 0.00 1.88 0.00 1.66 Clayey | Average 2% to 7% 2.831 0.70 0.70 0.88 60%
Basins B1-B2 (WQ Chamber B2) 2.85 0.58 0.00 0.49 0.00 0.31 Clayey | Average 2% to 7% 1.463 0.59 0.59 0.74 46%
Basins B3-B6 (WQ Chamber B6) 4.49 0.89 0.00 1.16 0.00 0.88 Clayey | Average 2% to 7% 1.561 0.71 0.71 0.88 61%
Basins B7, B9-B10 (WQ Chamber B9) 2.25 0.86 0.00 0.44 0.00 0.37 Clayey | Average 2% to 7% 0.576 0.77 0.77 0.96 71%
Basins B8, E1 (WQ Chamber E1) 1.07 0.21 0.00 0.16 0.00 0.25 Clayey | Average 2% to 7% 0.449 0.66 0.66 0.82 54%
Basins A1-A3 (100-year Overtopping) 3.59 0.82 0.00 0.79 0.00 0.72 Clayey | Average 2% to 7% 1.266 0.70 0.70 0.88 61%
Basins A1-A5 (100-year Overtopping) 5.72 1.15 0.00 1.32 0.00 1.20 Clayey | Average 2% to 7% 2.032 0.70 0.70 0.88 60%
Basins A1-A7 (Channel Calc) 8.03 1.66 0.00 1.88 0.00 1.66 Clayey | Average 2% to 7% 2.831 0.70 0.70 0.88 60%
Basins B3-B5 (100-year Overtopping) 3.82 0.82 0.00 1.09 0.00 0.79 Clayey | Average 2% to 7% 1.122 0.74 0.74 0.93 66%
Basins B1-B6 (Storm Sewer Calc) 7.35 1.48 0.00 1.66 0.00 1.19 Clayey | Average 2% to 7% 3.023 0.66 0.66 0.83 55%
Basins B7-B10 (Storm Sewer Calc) 2.52 0.95 0.00 0.51 0.00 0.42 Clayey | Average 2% to 7% 0.646 0.77 0.77 0.96 71%
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
7/24/2018 2:16 PM 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
final
676
to be provided at
final
0.20
C. Release Rate Compliance
The Retreat @ Fort Collins has a total combined area of 27.99 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 5.60 cfs. By adding the release from the
Redwood Pond (12 cfs), the total release allowable from all Ponds is 17.60 cfs.
Ponds 2, 3, 4, 5 and the Redwood Pond release directly into the proposed outfall pipe
connected to the NECCO Stormwater improvements. These ponds combined have a total
release of 19.85 cfs. This is 2.25 cfs more than the allowable from the site.
The undetained basin UD1 100-year runoff rate of 4.66 cfs combined with the additional
2.25 cfs release from the ponds shows an increase of release of 6.91 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).
By subtracting the existing undetained flow of 7.32 cfs from the proposed additional
developed flow of 6.91 cfs, it is shown that the development will decrease the stormwater
release from the site by 0.41 cfs.
The table on the next page illustrates these calculations:
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 A7, 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.