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gh This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document In Its entirety.
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I City of Ft. Collin ppro ad Plans
Approved By r 9
"Data` 1-18 -19
Prepared for:
CA Ventures
130 East Randolph St., Suite:2100
Chicago, IL 60601
Prepared by:
(NORTHERN
ENGINEERING
361 North Howes Street, Suite 100
Fen Collins, Colorado 80521
Phone: 970.221.4158 Fax: 970.221.4159
Project Number: 1287-005
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.NorthernEnolnaorino.com.!! 970.221A158
NORTHERN
ENGINEERING
July 12, 2019
e City of Fort Collins
Stormw.ater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE. Final Drainage Report for
WILLOW STREET RESIDENCES
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage and Erosion Control Report for your
' review. This report ,accompanies the Final Plan submittal for the proposed Willow Street
Residences development.
This report has been prepared in accordance to Fort Collins Stormwater Criteria Manual (FCSCM),
and serves to document the stormwater impacts associated with the proposed 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.
1 Aaron Cvar, PhD, PE
Senior Project Engineer
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Blaine Mathisen, El
Project Engineer
FORT COLLINS: 301 North Howes Street, Suite 100, 80521 1970.221.4158
GREELEY: 820 81h Street, 80631 1970.395.9880 1 WEB: www.northernengineering.com
I W NORTHERN
ORT ENGINEERING
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TABLE OF CONTENTS
I. GENERAL LOCATION AND. DESCRIPTION...................................................................1
A: Locatlon..::::::.::.....:::::::.:...:::::.:::...:.::.::::..:::::.:....::::::s...:::::..:..:::.::::.::.....o.... _.... . - .
B. Description of Property...::. ...::............:........ ...... ......... .......2
C. Floodplain..........................................................................................................................................3
_
II. DRAINAGE BASINS AND SUB-BASINS.......................................................................4
A. Major Basin Description .... .........:.............. .:........ ...:.:: 4
R. Sub -Basin Description........- "i...........
--:....... _ .:................. ..... .;..- :.....5
III. DRAINAGE DESIGN CRITERIA................................................................................... 5
C. Regulations:....... .........:- ......... ......... .........-......... ....................5
D. Four Step Process ....... .. ....... .. ...... ...... S
E. Development Criteria Reference and Constraints ...:...- 6
F. Hydrological Criteria ........ ............ :.:... ......._....... ...I - ........;,...6
G. HydraulicCriteria ..............................................................................................................................6
H. Modifications of Criteria .................................................. _................................ _................. _.......... 7
IV. DRAINAGE FACILITY DESIGN.................................................................................... 7
I. General Concept ;. .. ........ . ........... ................... . ........9
J. Specific Details..................................................................................................................................7
V. CONCLUSIONS........................................................................................................8
K. Compliance with Standards i ... ........ .::.. ...:.......:.......... ..............:.....8
LDrainageConcept.......................:......... ::;:: - .... - - ...... ;. _ ...................
APPENDICES:
APPENDIX
A —
Hydrologic Computations
APPENDIX
B —
Hydraulic Computations
B.1 —
Storm Sewers
B.2 =
Inlets
B.3 —
Detention Facilities
APPENDIX
C —
Water Quality Design Computations
APPENDIX
D —
Erosion Control Report
Flea/ Dialiiege Report
NORTHERN
ENGINEERING
NB
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LIST OF TABLES AND FIGURES:
1 Figure 1— Aerial Photograph ... _ . 2
Figure 2— Proposed Site Plan ..... ......... ......... ......... ......... ......... ................. 3
Figure 3 —Area Floodplain Mapping....................................................................................... 4
MAP POCKET:
Figure 1 - Existing Drainage Exhibit
Figure 2 — C-500 - Drainage Exhibit
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Fnal Drainage Report
■� NORTN HER
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1. GENERAL LOCATION AND DESCRIPTION
' A. Location
1. Vicinity Map
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2;
The project site is located in the northwest quarter of Section 12, Township 7 North,
Range 69 West of the 6'" Principal Meridian, City of Fort Collins, County of Larimer,
State of Colorado.
3.
The project site Is located just east of the intersection of College Ave. and Willow
Street.
4.
The project site lies within the Poudre River Basin. Detention will be provided with
an allowable release rate based on historic pervious and impervious areas. Historic
developed area will be granfather. and will be allowed to release at a historic 100-
year rate. Historic undeveloped area will be allowed to release at a historic 2=year
rate. Please see Appendix A for computation of allowable release rate.
5.
Water quality treatment for the project site will be provided in the form of LID
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treatment within a proposed underground chamber system, as described in further
detail below.
6.
As this is an infili site, much of the area surrounding the site is fully developed.
Final Drainage Report 1
NORTHERN
I: ni:I NEI: RING
Willow Street Residences
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B. Description of Property
1. The development area is roughly 2.0 net acres.
Figure 1 — Aerial Photograph
2. The subject property is currently composed of existing buildings, gravel surfaced drive
and parking areas, and landscaped areas. Existing ground slopes are mild to
moderate (i.e., 1 - 3.t%) through the interior of the property. General topography
slopes from southwest to northeast.
3. According to the United States Department of Agriculture (USDA) Natural Resources
Conservation Service (NRCS) Soil Survey website:
hftp://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx,
the site consists of Paoli Fine Sandy Loam, which falls into Hydrologic Soil Group A.
4. The proposed project site plan is composed of the development of two apartment
buildings and amenities. Associated site work, water, and sewer lines will be
constructed with the development. Onsite water quality treatment is proposed within
an underground chamber system, as discussed in Section IV, below.
Final Drainage Report
2
.V INORTHERN
ENGINEERING
Figure 2— Proposed Site Plan
5. There are no known irrigation laterals crossing the site.
6. The proposed land use is residential/apartments.
C. Floodplain
1. The project site is not encroached by any City designated or FEMA 100-year
Floodplain.
Final Drainage Report 3
,V NORTHERN
ENGINEERING
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FEMA High Risk- Floodway
I� FEMA High Risk- 10C Year
ED FEMA Moderate Risk - 100 J 500
Figure 3 —Area Floodplain Mapping
DRAINAGE BASINS AND SUB -BASINS
A. Major Basin Description
1. The project site lies within the Poudre River Basin. Detention will be provided with
an allowable release rate based on historic pervious and impervious areas. Historic
developed area will be grandfathered and will be allowed to release at a historic 100-
year rate. Historic undeveloped area will be allowed to release at a historic 2-year
rate. Generally, historic developed areas consist of gravel surfaced drive and parking
areas, which have been accounted for in the computation of the composite historic
release rate from the site. An allowable release rate of 13.15 cfs has been calculated
for the overall site. However, Basins OS1 and OS2 will release undetained into
Willow Street, thus, allowable release rate has been reduced by 0.86 cfs, which is
the peak 100-year discharge from these basins. Please see Appendix A for
computation of allowable release rate.
2. The entire site area has allowance for water quality treatment in the existing Baysaver
located just southeast of the site. As identified in the "Downtown River District
(DTRD) Final Design Report", by Ayres Associates, dated February 2012, the current
project area was considered part of master sub -basins 210 and 213, which was
accounted for in the original sizing of the existing Baysaver. Please see the DTRD
Plan, "Exhibit B-Future Development Map for DTRD Area" provided in Appendix D.
3. The Downtown River District (DTRD) Final Design Report accounts for all of Willow
Street Right of Way area in its fully developed condition draining into the recently
completed storm main in Willow Street. Because of this, the project site does not
provide Water Quality or detention for the adjacent half street (Willow Street).
1 rinal Drainage Report 4
1 NORTHERN
ENGINEERING Willow Street Residence
4. Please see Appendix B for detention volume calculations. All detention is provided in
underground storage chamber systems as discussed below.
5. A 24-inch diameter offsite pipe from the southwest is being routed through the site..
1 We have estimated maximum capacity of this offsite storm line at28.0 cis, and have
conservatively added this full flow rate to our developed onsite design flow rate.
Please see Appendix B.1 for calculation of maximum pipe flow calculations for the
offsite storm line;
B. Sub -Basin Description
1. The subject property historically drains overland from southwest to north-east. Runoff
from the majority of the site has historically been collected in the adjacent Willow
Street Right of Way. There is an existing storm main and a series of inlets within
Willow Street, which collected historic runoff from the existing site. The proposed
outfalI for the project site is this existing storm main. Please see Appendix D for
information on the Willow Street storm main.
2. A more detailed description of the project drainage pattems is provided below.
Ill. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the proposed
project.
B. Four Step Process
The overall stormwater management strategy'e_mployed with the proposed 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 usebyimplementing multiple Low Impact Development (LID) strategies including:
was Conserving existing amenities in the site.
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, urban
development of this intensity will still generate stormwater runoff that will require
additional BMPs and water quality. Water quality treatment is fully provided in existing
Baysaver located just southeast of the site, as identified in the "Downtown River District
(DTRD) Final Design Report", by Ayres Associates, dated February 2012. Onsite LID
treatment will occur in the underground chamber systems as described below.
Step 3 — Stabilize Drainageways
There are no major drainageways within the subject -property. While this step may not
seem applicable to proposed development, the project indirectly helps achieve stabilized
drainageways nonetheless. By providing water quality treatment, where none previously
Final Drainage Report 5
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■� NORTHERN
ENGINEERING Willow Street Reside
existed, sediment with erosion potential is removed from downstream drainageway
systems. Furthermore, this projectwill pay one-time stormwater development fees, as
Well as ongoing monthly stormwater utility fees, both of which help achieve City-wide
drainageway stability.
Step 4 — Implement Site Specific and Other Source Control BMPs.
The proposed project will improve upon site specific source controls compared to historic
conditions:
The proposed development will provide LID treatment; thus, eliminating sources of
potential pollution previously left exposed to weathering and runoff processes.
C. Development Criteria Reference and Constraints
The subject property is surrounded by currently developed properties. Thus, several
constraints have been identified during the course of this analysis that will impact the
proposed drainage system including:
rim Existing elevations along the property lines wiitgenerally be maintained.
Ka As previously mentioned, overall drainage patterns of the existing site will be
maintained.
Elevations of existing downstream facilities that the subject property will release to
will be maintained.
D. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity -Duration -Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with the proposed 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 R0-12 of the FCSCM.
3. Three separate design storms have been utilized to address distinct drainage
scenarios. A fourth design storm has also been computed for comparison purposes.
The first design storm considered is the S& percentile rain event, which has been
employed to design the pmjecrs water quality features. The second event analyzed is
the "Minor," or "Initial" Storm, which has a 2-year recurrence interval. The third
event considered is the "Major Storm," which has a 100-year recurrence interval.
The fourth storm computed, for comparison purposes only, is the 10-year event.
4. No other assumptions or calculation methods have been used. with thisdevelopment
that are not referenced by current City of Fort Collins>criteria.
E. Hydraulic Criteria
L As previously noted, the subject property maintains historic drainage patterns.
2. All drainage facilities proposed with the project are designed in accordance with
criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District
(UDFCD) Urban Stonn Drainage Criteria Manual.
3. As stated above, the subject property is not located in a City designated floodplain.
The proposed project does not. propose to modify any natural drainageways.
Final Drainage Repot 6
1 .tS NORTHERN
ENNI KEEN INN
Willow Street Residence
F. Modification of Criteria
1. The proposed development is not requesting any modifications to criteria at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the project drainage design are to maintain existing drainage
patterns, and to ensure no adverse impacts to any adjacent properties..
2. Water Quality treatment is provided in the existing Baysaver located just southeast of
the site. LID treatment will be provided in the proposed underground chamber
system, as discussed further below.
3. Drainage patterns anticipated for drainage basins shown in the Drainage Exhibit are
described below. Drainage basins have been defined for preliminary design purposes
and are subject to change at Final design; however; general drainage patterns and
concepts are not expected to be significantly altered.
Basins Wl — W3
Basins W1 through W3 generally consist of paved parking areas, rooftop areas, and
' landscaped areas. These basins Will generally drain via sheet flow and proposed
concrete pans to collection points and inlets, which will convey flows into the
proposed west underground chamber system.
Basins El -. E3
Basins E-1 through E3 generally consist of paved parking areas, rooftop areas, and
landscaped areas.. These basins -will generally drain via sheet flow and proposed
concrete pans to collection points and inlets, which will convey flows into the
proposed east underground chamber system.
Basins OSl. OS2
Basins OS1 and OS2 generally consist of paved drive areas, and landscaped areas.
Basin OSl will sheet flow to proposed curb and gutter which will drain to the adjacent
Willow Street Right of Way. Basin OS2 will sheet flow directly into the adjacent
Willow Street Right of Way.. Concrete pavers are proposed in Basin OSl to provide LID
treatment of the majority of this basin. Allowable overall site release rate has been
reduced to compensate.for undetained runoff from Basins OS1 and OS2.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
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this report.
B. Specific Details
1. An open bottom chamber system is proposed as the primary LID treatment
method for the site. The system will provide standard 12-hour holding time
per UDFCD criteria (please see computations provided in Appendix C), The
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chamber system will provide treatment of a minimum of 75% of the proposed
site.
2. The entire site area has allowance for water quality treatment in the existing Baysaver
located just southeast of the site. As identified in the "Downtown River District
(DTRD) Final Design Report", by Ayres Associates, dated February 2012, the current
Final Drainage Repal 7
.� NORTHERN
ENB IN EER ING Willow Street Resident
project area was considered part. of master sub -basins 210 and 213, which was
accounted for in the original sizing of the existing Baysaver. Please see the DTRD
Plan, "Exhibit B-Future Development Map for DTRD Area" provided in Appendix F.
3. A detention volume of 0.033 acre-feet is provided in the "East Pond", noted on the
Drainage Exhibit, which is an underground chamber system. This system has been
designed with a peak 100=year release rate of'3.85 cfs. Please see calculations
provided in Appendix B.
4. A detention volume of 0.040 acre-feet is provided in the "West Pond", noted on the
Drainage Exhibit, which is an underground chamber system. This system has been
designed with a peak 100-year release rate of'8.45 cfs. Please see calculations
provided in Appendix B.
5. Final design details, and construction documentation shall be provided to the
City of Fort Collins for review prior to Final Development Plan approval.
6. Stormwater facility Standard Operating Procedures (SOP) will be provided by
the City of Fort Collins in the Development Agreement.
V. CONCLUSIONS
®
C. Compliance with Standards
4, The drainage design proposed with the proposed project complies with the City of Fort
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Collins' Storrnwater Criteria Manual.
5. The drainage design proposed with this project complies with requirements for the
Poudre River Basin,
6. The drainage plan and stormwater management measures proposed with the
proposed development are compliant with all applicable State and Federal regulations
governing stormwater discharge.
D. Drainage Concept
7. The drainage design proposed with this project will effectively limit any potential
damage associated with its stormwater runoff by providing detention and water
quality mitigation feature;.
8. The drainage concept for the proposed development is consistent with requirements
for the Poudre River Basin.
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_ Flrie/ D,ainage�Reporl � 9
NORTHERN
ENO NEER I NO Willow Street Residence.,
References
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1. 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.
2. Latmer County Urban Area Street Standards. Adopted January 2, 2001, Repealed and
Reenacted, Effective October 1, 2002, Repealed and Reenacted, Effective April 1, 2607.
3. Soils Resource Report for Latimer County Area. Colorado. Natural Resources Conservation
Service, United States Department of Agriculture.
4- Downtown River District (DTRD) Final Design Reoort, Ayres Associates, February 2012.
' 5. .Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drain -age and Flood Control
District, Wright -McLaughlin Engineers, Denver, Colorado.
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Final &&Inge Report 9
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VYillow Street Residences Drainage Summary
Pond ID
LID Vol a. ft
Detention Vol. a. ft
Total Vol. a, ft.
Provided Vol. a. ft
Pmposed Release ds
East
699
1419
21H
2119
3.85
West
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1746
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JWWNTION POND CALCULATION; MODIFIED FAA METHOD w/ Ft Collins
Project Number 1287-005
Project Name Willow Street Residences
Project Location Fort Collins, Colorado
Pond No East Pond
Input Variables Results
Design Point East Pond
Design Storm 100-yr
C = 0.87
Tc = 5.00 min
A = 0.73 acres
Max Release Rate = 3.85 cfs
Required Detention Volume
ft3
ac-ft
Time (min)
Ft Collins
100-yr
Intensity
n/hr
Inflow
Volume
(fta)
Outtlow
Adjustment
Factor
Qav
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Outflow a
Volume
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Storage
Volume
(ft3)
5
9.950
1896
1.00
3.85
1154
742
10
7.720
2942
0.75
2.88
1731
1211
15
6.520
3727
0.67
2.56
2308
1419
20
5.600
4268
0.63
2.40
2885
1383
25
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4744
0.60
2.31
3462
1283
30
4.520
5167
0.58
2.24
4039
1129
35
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5442
0.57
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4616
826
40
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5701
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5192
508
45
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5933
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5769
164
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6154
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6346
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55
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6539
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8414
0.52
2.00
14424
-6010
'Note: Using
the method described in Urban
Storm Drainage Criteria Manual Volume 2.
1287-005 FAA East Pond.xls
Page 1 of 1
' 10122/2018
ADS Design Tool Site
jtVf I I-ITe;bIT-
Mule
User Inputs
Chamber Model
SC-740
Outlet Control Structure
Yes (Outlet)
'
Project Name
Willow Street Residences
Engineer
B. Mathisen
Project Location
Fort Collins, CO - East Pond
Project Date
10/22/2018
Measurement Type
Imperial
Required Storage Volume
,118 wbioft.
Stone Porosity
40%
Stone Foundation Depth
6 in.
Stone Above Chambers
6 in.
Average Cover Over Chambers
18 in.
Design Constraint
Length
Design Constraint Dimension
175 ft
FAA DETENTION +
WQCV =
REQUIRED STORAGE VOLUME
(1,419 CF + 699 CF
= 2,118 CF)
Results
System Volume and Bed Size
Installed Storage Volume 2119 cubic ft.
Storage Volume Per Chamber 74.90 cubic IL.
Number Of Chambers Required
/ 21 each
Number Of End Caps Required
2 each
Rows/Chambers
1 row(s) of 21
chamber(s)
Maximum Length
160.54 ft.
Maximum Width
6.85 ft.
Approx. Bed Size Required
1100 squareft.
System Components
Amount Of Stone Required
107 cubic yards
Volume Of Excavation (Not Including
143 cubic yards
Fill)
Non -woven Filter Fabric Required
368 square yards
Length Of Isolator Row
151.06 ft.
Non -Woven Isolator Row Fabric
133 square yards
Woven isolator Row Fabric
166 square yards
TPAVEMENT LAVER (DESIGNED
BY SITE DESIGN ENGINEER)
6"
(150 mm) MIN
I I
Ih��l
vtiit�
16' (2.! mJ
(450mm)MINRI MAX
1
DEPTH OF STONE TO BE DETERMINED
I. BY DESIGN ENGINEER 6"(150 mm)MIN
`— 51" (1285 mm) 12" (300 mm) TYP
Ill. TO BOTTOM OF FLFMBU P WENT rM U1 AWD
Iu5f T10NSwKRE fW71NO FROM �=S WYOLpM.
IN[AFgSE CONER 102.- l mm)
iD ADS Stormtech 2016
' https://designtool.stonntech.com/index.htmi
1/1
DRESS:
ITE:
■_ r�
ENGINEERING
sm.u+i+sa
Project Title
Willow Street Residences
Date:
October 30, 2018
Project Number
1287-005
Calcs By:
B. Mathisen
Client
Richmark
Pond Designation
East Pond
Q = Release Rate (cfs)
C = Discharge Coefficients (unitless)
A, = Area Allowed of Opening (it)
g = Gravity (32.2 ft/s')
Es = High Water Surface Elevation (ft)
Ei = Elevation of Outlet Invert (ft)
E, = Elevation of Outlet Centroid (ft)
Circular Orifice
Soo -Year Ortlfce
Orifice Size (in.)
8 - 1/2 in.
Area (Inz)
58.33 sq-in
1
Q
3.64 cfs
Rectanzular Orifice
SOO-Year Orifice
Orifice Height (in.)
7 in.
Orifice Width (in.)
8 - 1/2 in.
Area (In')
58.33 sq-in
Q
3.68 ds
Q=
3.85 cis
C =
0.65
E„ =
4969.23 ft
E, =
4965.91 ft
Er =
4966.27 ft
Circular
Er=4966.20ft
Rectangular
0,40507496
ft
A.
58.330794
ins
1
■� NORTHERN
ENGINEERING
I
I
I
I
I
I
LATION; MODIFIED FAA METHOD wl Ft Collins 1DF
Project Number : 1287-005
Project Name : Willow Street Residences
Project Location : Fort Collins, Colorado
Pond No West Pond
Input Variables Results
Design Point n1
Design Storm 100-yr
C = 0.96
Tc = 5.00 min
A = 1.21 acres
Max Release Rate = 8.45 cfs
Required Detention Volume
ft3
ac-ft
Time (min)
Ft Collins
100-yr
Intensity
nfhr
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
0av
(cfs)
Volume
Outflow 3
(ft)
Storage
Volume
(ft3)
5
9.950
3467
1.00
8.45
2535
932
10
7.720
5381
0.75
6.34
3803
1578
15
6.520
6816
0.67
5.63
5070
1746
20
5.600
7806
0.63
5.28
6338
1468
25
4.980
8677
0.60
5.07
7605
1072
30
4.520
9451
0.58
4.93
8873
578
35
4.080
9953
0.57
4.83
10140
-187
40
1 3.740
10427
0.56
4.75
11408
-981
45
3.460
10852
0.56
4.69
12675
-1823
50
3.230
11256
0.55
4.65
13943
-2687
55
3.030
11615
0.55
4.61
15210
-3595
60
2.860
11960
0.54
4.58
16478
-4518
65
2.720
12322
0.54
4.55
17745
-5423
70
2.590
12636
0.54
4.53
19013
-6377
75
2.480
12963
0.53
1 4.51
20280
-7317
80
1 2.380
13270
0.53
4.49
21548
-8277
85
2.290
13566
0.53
4.47
22815
-9249
90
2.210
13863
0.53
4.46
24083
-10220
95
2.130
14103
0.53
4.45
25350
-11247
100
2.060
14357
0.53
4.44
26618
-12260
105
2.000
14636
0.52
4.43
27885
1 -13249
110
1.940
14873
1 0.52
4.42
29153
-14279
115
1.890
15148
0.52
4.41
30420
-15272
120
1.840
15389
0.52
4.40
31688
-16299
Not Using
the method described in Urban Storm Drainage Criteria
Manual Volume 2.
1287-005_FAA West Pond.xls
' Page 1 of 1
415/2C18 ADS Design Tool Site
e- _ T `_ I
.71V 11 I l l ICC:I 1
ULIV
'
User Inputs
Chamber Model
SC-740
Outlet Control Structure
Yes (Outlet)
Project Name
Willow Street Residences
Engineer
B. Mathisen
Project Location
Fort Collins, CO - West Pond
Project Date
04/04/2018
Measurement Type
Imperial
Required Storage Volume
Stone Porosity
2,973 cubic R
40%
Stone Foundation Depth
6 in.
'
Stone Above Chambers
Average Cover Over Chambers
6 in.
18 in.
Design Constraint
Width
'
Design Constraint Dimension
20 ft.
' FAA DETENTION + WQCV =
REQUIRED STORAGE VOLUME
(1,746 CF + 1,227 CF = 2,973 CF)
1
Results
-System Volume and Bed Size
Installed Storage Volume
2994 cubic ft.
Storage Volume Per Chamber
74.90 cubic ft.
Number IN Chambers Required
34 each
Number IN End Caps Required
6 each
Rows/Chambers
1 row(s) of 12
chamber(s)
Leftover Rows/Chambers
2 row(s) of 11
chamber(s)
Maximum Length
92.61 ft.
Maximum Width
16.35 ft.
Approx. Bed Size Required
1469 square ft.
System Components
Amount Of Stone Required
133 cubic yards
Volume Of Excavation (Not Including
190 cubic yards
Fill)
Non -woven Filter Fabric Required
408 square yards
Length Of Isolator Row
87.01 ft.
Non -Woven Isolator Row Fabric
76 square yards
Woven Isolator Row Fabric
95 square yards
' PAVEMENT LAYER (DESIGNED
BY SITE DESIGN ENGINEER
/III/ �/II�VlII� /IIv pll� //II�� 411�`qllTgll�/Pti
B"(1
a"
(150 mm) MIN
I
MIN
30"
(760 mm)
8�
6" (2.4 m)
(450 mm)MIN 111 MAX
DEPTH OF STONE TO BE DETERMINED
BY DESIGN ENGINEER 6'(150 mm) MIN
51" (1295 mm) 1 Y (300 mm) TYP
III. TO BMW OFRMBUPA4E WFORONPANEO
IWTi TIONSWHEREROTIINORWWHMESIMr OL R,
INCRE COVER TO 24-M.)
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Ihttp://sto"techcaic.murewebsites.nett
Project Title
Project Number
Client
NORTHERN '°
101 ". "w.. fwwr. f.N. rW 910S2tAt9i aIlE831TE:
ENGINEERING
70.221A1f9 _
Willow Street Residences Date: October 30, 2018
1287-005 Cabs By: B. Mathisen
Richmark
Q = Release Rate (cfs)
C = Discharge Coefficients (unitless)
k = Area Allowed of Opening (ft)
g = Gravity (32.2 ftls)
E„ = High Water Surface Elevation (ft)
Ei = Elevation of Outlet Invert (ft)
E, = Elevation of Outlet Centroid (ft)
Circular Orifice
13 in.
Area (in) 134.68 sq-in
Q 7.64 cfs
Rectangular Orifice
Orilvel g f' ffiT. 9 in.
Orifice Width (in.) 15 In.
Area (in2) 134.68 sq-in
Q 7.90 cfs
Eh 4970.33 ft
E114967.71
4967.33 ft
Et4967.88ft Circular
Ec.ft Rectangular
0.9352-16002 ft`
134.679744 in 2
II
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NORTHERN
ENGINEERING
Project Title
Willow Street Residences
Project Number
1287-005
Client
Richmark
Basin
East Pond
Date: April 5, 2018
Calcs By: B. Mathisen
WQCV=a0.91i'-1.19i'+0.78i Drain TIM 12hr
a = 0.8
WQCV = Watershed inches of Runoff (inches) i = 80.24%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwa/100) WQCV 10.264 in
Water Quality Capture Volume
0.5
0.45 WQCV=a(0.91i'-1.19i'+0.78i)
0.4 0.35
c 35
.����■■■■■■■
0 c o 0 0 0 0-W-0 0�IV o
AJW
f+ N W A Ln in V N W
Total Imperviousness Ratio (1= W100)
Figure EDB-2 - Water Quality Capture Volume (WQCV), Both Percentile Runoff Event
V _ WQCV
12 J
= I 0.0161 ac-ft 699 cu. ft.
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
I
11
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LJ
1
[l�
I
■� NORTHERN
ENGINEERING
TENTION POND CALCULATION; MODIFIED FAA METHOD wl Ft Collins I
Project Name Willow Street Residences
Project Number : 1287-005
Client Richmark
Pond No East Pond
Input Variables Results
Design Point east pond
Design Storm WQ
C = 0.87
= . A0min
A = .73 73 acres
Max Release Rate = 0.26 cfs
Required Detention Volume
ac-ft
�
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft )
Outflow
Adjustmen
t Factor
QaV
(cfs)
Outflow 3 olume
(ft)
Storage
Volume
(ft')
5
1.425
272
1.00
0.26
78
194
10
1.105
421
1.00
0.26
156
265
15
0.935
534
0.67
0.17
156
379
20
0.805
614
0.63
0.16
195
419
25
0.715
681
0.60
0.16
233
448
30
0.650
743
0.58
0.15
272
471
35
0.585
780
0.57
0.15
311
469
40
0.535
815
0.56
0.15
350
465
45
0.495
849
0.56
0.14
389
460
50
0.460
876
0.55
0.14
428
448
55
0.435
912
0.55
0.14
467
445
60
0.410
937
0.54
0.14
506
431
65
0.385
954
0.54
0.14
545
409
70
0.365
974
0.54
1 0.14
584
390
75
0.345
986
0.53
0.14
623
363
80 1
0.330
1006
0.53
0.14
662
344
85
0.315
1020
0.53
0.14
700
320
90
0.305
1046
0.53
0.14
739
307
95
0.290
1050
0.53
0.14
778
271
100
0.280
1067
0.53
0.14
817
250
105
0.270
1080
0.52
0.14
856
224
110
0.260
1090
0.52
0.14
895
195
115
0.255
1117
0.52
0.14
934
183
120
0.245
1120
0.52 1
0.14
973
147
`Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
1287-005 Chamber Summary.xlsx
Page 2 of 7
NORTHERN
ENGINEERING
Project Title Willow Street Residences Date: April 5, 2028
Project Number 1287-005 Calcs By: B. Mathisen
Client Richmark
Basin West Pond
WQCV=a0.91i3-1.1V+078i Drain Time 12hr
a = 0.8
WQCV = Watershed inches of Runoff (inches) i = 83.08%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iµo/100) WQCV = 0.279 in
Water Quality Capture Volume
0.5
0.45 WQCV =a(0.91i'-1.19i'+0.78i)
v 0.4
L
c 0.35
m 0.3
L
W Q' 6M
N 0 uw,
3
0. Hr
3 D bw
0. ... ... _.._ ..._ _.-..,-
O O O O
F+ N W P Vt O1 J 40 in
Total Imperviousness Ratio (i = I�/100)
Figure EDB-2 - Water Quality Capture Volume (WQCV), 8Dth Percentile Runoff Event
V _ ( WQ12 ) * A 1.21 ac CV
0.0282 ac-ft 1227 cu. ft.
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
�I
1
I
NORTHERN
ENGINEERING
Project Name Willow Street Residences
Project Number : 1287-005
Client Richmark
Pond No West Pond
Input Variables Results
Design Point west pond
Design Storm WQ
C = 0.96
Tc = 5.00 min
A = 1.21 acres
Max Release Rate = 0.47 cfs
Required Detention Volume
$8B fta
0.02 ac-ft
Time
(min)
Ft Collins
WQ
Intensity
(in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustmen
t Factor
QeV
(cfs)
Outflow Volume
3
(ft)
Storage
Volume
(ft3)
5
1.425
497
1.00
0.47
142
356
10
1.105
771
1.00
0.47
283
488
15
0.935
979
0.67
0.31
283
696
20
0.805
1124
0.63
0.29
354
770
25
0.715
1248
0.60
0.28
425
823
30
0.650
1361
0.58
0.28
495
866
35
0.585
1429
0.57
0.27
566
863
40
1 0.535
1494
0.56
0.27
637
857
45
0.495
1555
0.56
0.26
708
847
50
0.460
1606
0.55
0.26
778
827
55
0.435
1670
0.55
0.26
849
821
60
0.410
1717
0.54
0.26
920
798
65
0.385
1747
0.54
0.25
991
756
70
0.365
1784
0.54
0.25
1061
722
75
0.345
1806
0.53
0.25
1132
674
80
0.330
1843
0.53
0.25
1203
640
85
0.315
1869
0.53
0.25
1274
596
90
0.305
1916
0.53
0.25
1344
572
95
0.290
1923
0.53
0.25
1415
508
100
0.280
1955
0.53
0.25
1486
469
105
0.270
1979
0.52
0.25
1557
422
110
0.260
1997
0.52
0.25
1627
369
115
0.255
2047
0.52
0.25
1 1698
349
120
0.245
2052
0.52
0.25
1769
284
`Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
1287-005 Chamber Summary.xlsx
Page 4 of 7
I
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StormTech Chamber Data
Chamber Dimensions
SC-160
SC-310
SC-740
Width (in).
25.0.
34.0
S1.0
Length (in)_.
84.4
85.4
_ _ 8S.4 _
Hei ht (in)
12.0
16:0
30.0
Floor Area (sf)
14.7
20.2
30.2
Chamber Volume (cn
6.9
14.7
459
Chamber/Aggregate Volume (cf)
16.0
293
749
Chamber Flow Rate Conversion
(gpm/sf to cis)
Flow Rate•
0.35
gpm/sf
1 cf =
_ 7A8052ligal
igallon=l
0.133681
cf
1GPM=
1 0.002228
cfs
'Flow rate based on lA of Nov 07 Qa¢ In figure 17 of UNH Testing Report
Chamber Flow Retie
SC-160 I
SC310 I
SC-740
Flow Rate/chamber(cfe)
1 0.0114261
0.0157241
0:023586
NORTHERN
ENGINEERING
1 D:\Projects\1287-005\Drainage\WatQual\1287-005 Chamber Summary.xlsx
1
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NORTHERN
ENGINEERING Willow Street Residences
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) has been
included with the final construction drawings. It should be noted, however, that any such Erosion
and Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing
of the BMPs depicted, and additional or different BMPs from those included may be necessary
during construction, or 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 conswetion
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 ezisttng and proposed storm inlets. Vehicle tracking control pads, spill
containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site
restrooms shall also be provided by the Contractor.
Grading and Erosion Control Notes can be found on the Utility Plans. The Final Plans will contain a
full-size Erosion Control sheet 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 the Development Agreement for the development. Also,
1 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, prior to any earth disturbance activities. Prior to securing
said permit, the Site Contractorshall develop a comprehensive StormWater Management Plan
(SWMP) pursuant to CDPHE requirementsand guidelines. The SWMP will further describe and
document the ongoing activities, inspections, and maintenance of construction BMPs.
1
Final -Erosion CmbN Report
I
1
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ill i 7
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9� #1 I p ITT ( i
3!:a
s
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a 6
15f
DOWNTOWN RIVER DISTRICT
CITY OF FORT COLLINS
i
STORM O PLAN 8 PFi�p:E
STA 10+00 TO END
A9SOCIATE3 i�w: �r
Tit
n .U®M
11
1
11
1
1
1
1
i
1
1
I
1
1
1
1
1
1
1
1
[J
1
1
1
1
1
1
1
�J
1
1
1
1
Nor1LamEnolneaHna.mm 11 970.211.4158
GRAPHIC SCALE
1\ /I -----------------------
0 NORTH
I IN FEED
LEGEND:
EXISTING MuOR COXTCUR
—---30%"--
03—
PROPOSED STORE R
"WING VOW SEINER
PROPOSED STORM I
EXISTING CURB & GU n OR
DRAMIGESIDGKID
—
u
DruiNAGESASINNIN_ .__.comma
A
SAGN DeEwEwnou
II EERIER, MI
W(VYFO WEFMXp RtlX
.iy
RKipE0P1ECIFLpV
y
NOTES:
1. REGFAT®TOry YVt WIXVIE REPORT FOR MGM SFREETREWBFNCES
MIT6p FH91EFAIX00X WSI.IBFgi O➢gTCWi
_
RUNOFF SUMMARY:
WTVAL
IN
ID
MG
aF
Q
ctw
Wa
0100
faa
WI
03%
0.76
WR$
OM
3.74
W3
A)
M
130
nM
IIIED
El
0399
OD
1.%
I 0.6)
i.W
Ei
0.110
1 OAS
1 O37
1 0.12
ON
IS
03N
0.%
I I.W
I 1G
3A1
%1
Sam
OJ9
I %m
I RIX
Ob9
%i
VAR
I 0%
I UA1
I M%
"I
coLVRAv
cuH.suHrXOORW VxcerERff
o
a•
GwwN.retlelow.
.CAL 2 .FOR FORD POOR
I NP I�I�E �ap.wauna,
City
of Fart Collins. Colorado
._UTILITY PLAN APPROVAL
w Ro Eq
qy ERaR..r
CHECKED V.
WI R N..l.wo" VERY
D.0
CHECKED BY:
tt�
vi,
seam ev:
v..ls a RQ ^ BED
CHECKED BY:
�_ �
v�i.
FNFwrV
ZU'
Aptl
W�
F
= W
Z
Oc
N
Z W
If
A
�pp
�N
sE
Sheet
C-500
140f 22