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FINAL DRAINAGE AND EROSION
CONTROL REPORT
'
SEVEN GENERATIONS OFFICE PARK
(Lot 2 and a part of Lot 4, New Hampshire Subdivision)
1
Prepared for:
'
Sustainable Strategies LLC
3500 JFK Parkway
'
Fort Collins, CO 80525
'
Prepared by:
Interwest Consulting Group
1218 West Ash, Suite C
Windsor, Colorado 80550
'
(970)674-3300
Revised October 12, 2006
'
Revised September 5, 2006
Revised August 15, 2006
Revised April 12, 2006
'
February 14, 2006
Job Number 1050-035-00
1
1
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October 12, 2006
Basil Hamdan
City of Fort Collins Stormwater
'
700 Wood Street
Fort Collins, CO 80522-0580
1
INTERWEST M C O N S U t T I N G G R O U P
RE: Final Drainage and Erosion Control Report for Seven Generations Office Park
Dear Basil,
I am pleased to submit for your review and approval, this revised Final Drainage and Erosion
Control Report for Seven Generations Office Park. I certify that this report for the drainage
design was prepared in accordance with the criteria in the City of Fort Collins Storm Drainage
Manual.
This report reflects very minor changes from the reports submitted in August and September.
The only substantial change in this document is the change in project name from Eastbrook
Office Park to Seven Generations Office Park. Some of the appendices are still noted as
Eastbrook Office Park and are taken from the original report when North Star Design was the
project's engineer.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
1 Sincerely,
1
Michael Oberlander, P.E., L.S.I.
ii
1216 W. ASH, STE. C • WINDSOR, COLORADO 80550
ru.990.62<.3300 • 1�x.920.624.3303
TABLE OF CONTENTS
TABLEOF CONTENTS............................................................................................................... iii
1. GENERAL LOCATION AND DESCRIPTION
1.1 Location...................................................................................................................1
1.2 Description of Property ............................................................................................1
2.
DRAINAGE BASINS AND SUB -BASINS
2.1 Major Basin Description..........................................................................................1
2.2 Sub -Basin Description.............................................................................................1
3.
DRAINAGE DESIGN CRITERIA
3.1 Regulations..............................................................................................................2
3.2 Development Criteria Reference and Constraints....................................................2
3.3 Hydrologic Criteria..................................................................................................3
3.4 Hydraulic Criteria....................................................................................................3
4.
DRAINAGE FACILITY DESIGN
4.1 General Concept.......................................................................................................4
4.2 Specific Flow Routing.............................................................................................4
4.3 Drainage Summary.......................... ............................................................
I ............ 5
5.
EROSION CONTROL
5.1 General Concept .................................... :.................................................................
5
5.2 Specific Details........................................................................................................6
6.
CONCLUSIONS
6.1 Compliance with Standards....................................................................................6
6.2 Drainage Concept.....................................................................................................6
7.
REFERENCES....................................................................................................................7
APPENDICES
A Vicinity Map
B Hydrologic Computations
C Hydraulic Calculations
D Water Quality Pond Sizing
E Erosion Control Calculations
F Excerpts from Foothills Basin Master Plan
G Figures and Tables
iii
' 1. GENERAL LOCATION AND DESCRIPTION
' 1.1 Location
' Seven Generations Office Park is located in southeast Fort Collins. The project includes
Lot 2 and the south portion of Lot 4, New Hampshire Subdivision. It is. located in the
southeast quarter of Section 30, Township 7 North, Range 68 West of the Sixth Principal
' Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in
Appendix A.
' The project is located west of Eastbrook Drive and east of the Union Pacific Railroad. A
' large drainage easement is located on the north side of the property (Tract A of
Timberline Village PUD) and an office building is south of the site.
' 1.2 Description of Property
' The entire project consists of approximately 3.6 acres of land, all of which will undergo
grading and other construction activity. Three office buildings are proposed for the site
' with associated parking and drives. The land currently slopes to the north at
approximately 2%. There is an existing swale west of the property (in the UP Right of
Way). There is a larger drainage channel and easement north of the property, and there is
a very shallow drainage swale on the east side of the property. The swale on the east
drains the lot located south of the site (Lot 1). This swale presently drains north within
the property and then over the existing walk and curb into Eastbrook Drive. There are no
mapped floodplains on the property, although the floodplain is adjacent to the west and
' north property lines.
2. DRAINAGE BASINS AND SUB -BASINS
2.1 Major Basin Description
The proposed development lies within the Foothills Master Drainage Basin.
' 2.2 Sub -basin Description
' This site drains north to the existing drainage easement north of the site. This drainage
path will be maintained with the development of this site.
' 1
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' In the Foothills Basin Master Plan, this site is in SWMM Basin 50. This basin was
modeled with an imperviousness of 65%.
3. DRAINAGE DESIGN CRITERIA
'
3.1 Regulations
This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage
'
Design Criteria Manual' specifications. Where applicable, the criteria established in the
"Urban Storm Drainage Criteria Manual" (UDFCD), developed by the Denver Regional
'
Council of Governments, has been used.
3.2 Development Criteria Reference and Constraints
The runoff from this site has been routed to conform to the requirements of the City
'
Stormwater Department. Water quality facilities are required for the new construction
proposed on the site.
'
As stated above, the Foothills Basin Master Plan drainage basin studied this area (Basin
50) as being 65% impervious. The. Master Drainage Plan recommends that all developing
sites provide water quantity detention to the 2-year historic rate. It also states that if a site
drains prior to the overall peak in the Foothills Channel, detention may not be required. It
is proposed that no detention be required for this development with the following
justification:
'
1. This site peaks at approximately 10 minutes and the peak flow in the channel is
over 3 hours. Runoff from this site does not contribute to the peak flow (detained
or undetained.) Additionally, this site is at the lower end of the basin and only
needs to be conveyed through a few structures to reach its ultimate outfall.
2. The overall Basin 50 is currently 40% impervious (based on aerial photography
and conservative impervious calculations). The Master Plan is intended to show
'
existing conditions, but is actually calculating the imperviousness considerably
higher than actual conditions. It has been determined that with the development
of Seven Generations Office Park and the unlikely development of Tract A (to the
north), the imperviousness for the overall basin would only reach 61%. It should
'
2
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be noted that the developer plans to place some sort of restriction on Tract A that
' will permanently make it open space. If Tract A remains undeveloped, the overall
basin imperviousness is only 52%.
3. The development site itself is only 61 % impervious.
' Supporting calculations, exhibits, and excerpts from the Master Plan are included in
' Appendix F. The basis for requesting no detention basically comes down to the premise
that if the model were rerun with the proposed development undetained, there would be
I no change to the peak flow in the channel, or the floodplain delineation. This variance
from stormwater quantity detention has been discussed in depth with the Stormwater
Department, and they have offered their support of this variance. Stormwater Quality
' Facilities will be provided.
3.3 Hydrologic Criteria
' Runoff computations were prepared for the 10-year minor and 100-year major storm
frequency utilizing the rational method.
'
All hydrologic calculations associated with the basins are included in Appendix B of this
report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub -
basins. Standard Form 9 (SF-9) provides a summary of the design flows for all Sub -
basins and Design Points associated with this site.
tWater
quality volume was calculated using the method recommended in the "Urban
Storm Drainage Criteria Manual".
3.4 Hydraulic Criteria
'
All hydraulic have been in
calculations within this report prepared accordance with the
City of Fort Collins Drainage Criteria and are included in Appendix C of this report. The
'
storm sewer system for this project is only designed to convey the 10-year storm. Larger
Storms will surcharge the system, and overflows have been provided which are at least 1'
'
lower than the adjacent building floors.
.1 3
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4. DRAINAGE FACILITY DESIGN
' 4.1 General Concept
' The majority of the proposed development will be routed via sheet and gutter flow to the
proposed water quality pond in the northwest comer of the site. The pond releases to the
' north. There is a small portion of the east side of the site that will sheet flow to
Eastbrook Drive.
4.2 Specific Flow Routing
' A summary of the drainage patterns within each basin is provided in the following
paragraphs.
Basin 1 includes the central portion of the site. The site has been designed with three
' buildings and a perimeter drive and parking area. With this building configuration and
grading design, it is difficult to get water to drain overland to the perimeter drive areas.
This basin includes the areas (mostly roof) that are assumed to drain to the landscaping
between the buildings. A small storm sewer system has been designed to accept flows
from roof drains and the areas between the buildings. This system has been designed for
about 6 cfs, which is more than the 10-year runoff, but less than the 100-year flow, but all
of the areas, if inundated, will overtop to adjacent sidewalks and drives without flooding
the buildings. The storm sewer system is not intended to take the entire major storm, but
will easily take minor storm flows. Because this system is mainly for small stones, the 6
' ADS inlets provided have not been sized individually. There is a calculation in the
appendix showing that each inlet can accept about 1.25 cfs and the largest 10-year flow to
' any inlet is about 0.7 cfs. Again, if the inlets are overwhelmed, flows will overtop to the
drives and will not get to the building floor elevations.
' Basin 2 includes the majority of the site. It includes all of the parking and drive areas,
much of the building area, and the water quality pond. This basin drains west and north
' in the gutters to two curb cuts and into the water quality pond. The water quality pond
has been designed to overtop a concrete spillway in large storms and does not have a pipe
Ioutlet. The pond is slightly oversized and meets City criteria
1 4
L
' Basin 3 includes the far west and east portions of the site as well as the adjacent half right
of way of Eastbrook Drive. This basin has been extended to the centerline of the street in
' order to demonstrate that the site as modeled in the Master Plan is less than the 65%
impervious percentage.
' Basin OS includes the office building and parking lot south of this site. There are no
' plans on file for this Lot, so aerial photos were used to estimate the flow from this site.
This Basin drains to the northeast and across the southeast corner of the Seven
' Generations Office Park. It appears that the entire site drains to this point, but it is
possible that larger storms top into the street prior to reaching the corner. A 2' sidewalk
culvert is proposed on the south side of the proposed driveway at the point where this off
' site flow crosses the project. Because of the proximity to the driveway cut, it is not
possible to route all of these flows under the walk. The existing walk is attached and the
drive cut is basically a crosspan and there is no opportunity to create any head to push
water through the sidewalk culvert. The sidewalk culvert will take very small flows, but
larger flows will reach Eastbrook through the new drive cut.
' 4.3 Drainage Summary
Drainage facilities located outside of the right of way (including the water quality pond,
' proposed storm drain system and the pond outlet) will be maintained by the owners of the
property.
5. EROSION CONTROL
' 5.1 General Concept
' This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort
Collins Zone Maps. The potential exists for silt movement from the site and into the
existing drainage areas on the west and north sides of the site. Potential also exists for
tracking of mud onto existing streets which could then wash into existing storm systems.
' The required performance standard for the site is 75.6%. During construction and after
final paving and building construction, this figure has been exceeded with the use of silt
fence, straw bales and by using the water quality pond and a sediment trap during
' construction.
1
5
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1 The erosion control escrow amount is $8,385.
' 5.2 Specific Details
To limit the amount of silt leaving the site several erosion control measures shall be
implemented during construction. Wattles will be used where appropriate, and the north,
' east and west boundaries shall have silt fence installed. A vehicle tracking pads shall be
installed at the proposed north drive connection to Eastbrook Drive to control the mud
' being tracked onto the existing pavement. During overlot grading, disturbed areas are to
be kept in a roughened condition and watered to reduce wind erosion. The water quality
pond will be used as a sediment trap during construction.
6. CONCLUSIONS
' 6.1 Compliance with Standards
' All computations that have been completed within this report are in compliance with the
' City of Fort Collins Erosion Control Reference Manual for Construction Sites and the
Storm Drainage Design Criteria Manual. Requirements placed on the site related to the
new rainfall criteria have been followed.
1
The site is 61% impervious (which meets the Master Plan model) and the overall Master
' Plan Basin will not reach 65% imperviousness with this development. This site is not
proposing water quantity detention and a variance is requested. Supporting information
' for this variance is in Appendix F.
' 6.2 Drainage Concept
The proposed drainage concepts presented in this report and on the construction plans
' adequately provide for stormwater quality treatment of proposed impervious areas.
Conveyance elements have been designed to pass required flows and to minimize future
' maintenance.
If, at the time of construction, groundwater is encountered, a Colorado Department of
Health Construction Dewatering Permit will be required.
1 6
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1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March,
1986.
2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated June 2001, and Volume 3 dated September
1999.
7
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APPENDIX A
' VICINITY MAP
1
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' A
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PROJECT
LOCATION
Ee
FORT COLUNS N.S.
VICINITY MAP
SCALE: 1' - i.000'
APPENDIX B
HYDROLOGIC COMPUTATIONS
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HYDRAULIC CALCULATIONS
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'
ADS Area Inlet Capacity
ADS 18" Diam Standard Grate
'
LOCATION:
EASTBROOK
PROJECT NO:
265-01
'
COMPUTATIONS BY:
SUBMITTED BY:
WO
North Star Design
DATE:
08/10/2006
Inlet Data: Diameter
1.50 ft
Open Area
98.7 Sq. Inch
Solve for h using Orifice Equation
' Q = Ck sgrt(2gh)
where Q. = flow through orifice (cfs)
' C, = orifice discharge coefficient
g = gravitational acceleration = 32.2 ft/s
Ae = effective area of the orifice (ftZ)
h = head on the orifice (ft) /
' Qo = 0.70 cfs (MAX 10 YR FLOW TO ANY INLET) C'
A. = 0.34 ft(Assume 50% clogged)
C. = 0.65
' Solve for h: 0.15 ft
' Solve for It using Weir Equation
' Q = CLH3n
where C = weir coefficient
H = overflow height
L = length of the weir
Q = 0.70 cfs
' C = 3.00
L = 4.71 ft
' Solve for H: 0.13 ft
ORIFICE CONTROLS Q= 0.7 cfs
' Required Head d= 0.15 ft
Available Head Prior to Overtopping 0.50 ft OK
1
T 1,
LOCATION:
PROJECT NO:
COMPUTATIONS BY:
SUBMITTED BY:
DATE:
Inlet Data: Diameter
Open Area
ADS Area Inlet Capacity
ADS 18" Diam Standard Grate
EASTBROOK
265-01
MPO
North Star Design
08/10/2006
Solve for h using Orifice Equation
1.50 ft
98.7 Sq. Inch
Q = C,Aosgrt(2gh)
where Q, = flow through orifice (cfs)
Co = orifice discharge coefficient,
g = gravitational acceleration = 32.2 ft/s
Ao = effective area of the orifice (f Z)
h = head on the orifice (ft)
%= 1.25 cfs (MAX FLOW WITH 0.5- HEAD)
A. = 0.34 ftt (Assume 50% clogged)
Co = 0.65
Solve for h: 0.49 ft
Solve for It using Weir Equation
Q = CLH"
where C = weir coefficient
H = overflow height
L = length of the weir
Q = 1.25 cfs
C = 3.00
L = 4.71 ft
Solve for H: 0.20 ft
ORIFICE CONTROLS Q= 13 cfs
Required Head d= 0.49 It
Available Head Prior to Overtopping 0.50 ft
OK
1
1
1
1
1
1
1
1
1
APPENDIX D
WATER QUALITY POND SIZING
IC
Sheet 1 of 3
Designer. MPO
Company: NORTH STAR DESIGN
Date: August 15, 2006
Project: EASTBROOK OFFICE PARK
Location:
1. Basin Storage Volume
A) Tributary Area's Imperviousness Ratio (i = 1./ 100)
1. - 67.00 %
1=py Qiel, l
B) Contributing Watershed Area (Area)
Q
Area = 3.17 acres
C) Water Quality Capture Volume (WOCV)
',...
WOCV = r�a4�0)2fiSE;;ri+'t. watershed inches
(WOCV=1.0'(0.91 •1'-1.19'1'+0.78'1))
D) Design Volume: Vol = (WOCV! 12) • Area • 1.2
Vol=9'C7088'�fl acre-feet =_
2. Outlet Works
A) Outlet Type (Check One)
X Orifice Plate
Perforated Riser Pipe
Other:
B) Depth at Outlet Abov_.....
e Lowest Perforation (H)
H = 2.40 feet
C) Required Maximum Outlet Area per Row, (A.)
D) Perforation Dimensions (enter one only):sE
i) Circular Perforation Diameter OR
A. = Oa.45'9 square inches
D = 0.387 inches, OR l, /
"0
316 / �
OS6
ii) 2" Height Rectangular Perforation Width
W = inches
E) Number of Columns (nc, See Table 6a-1 For Maximum)
nc= number
F) Actual Design Outlet Area per Row (A.)
A. =OUM2.'fs't i square inches
G) Number of Rows(nr)
nr= number
H) Total Outlet Area (A.)
A.,=rnr0i8S{'f square inches
3. Trash Rack
A) Needed Open Area: A, = 0.5(Figure 7 Value) • A,k
M —$;: 31 "'-square inches
B) Type of Outlet Opening (Check One)
,nfi"§b152' Diameter Rou nd
-"`=s 2' High Rectanaular _
Other.
C) For 2', or Smaller, Round Ooenina (Ref.: Figure 5a):
i) -Width of Trash Rack and Concrete Opening (W.J
from Table ea-1
WW,K=.,''a F3 i("r'.� inches
ii) Height of Trash Rack Screen (HTO
H, = 2(tl^' S9C �`rl':' inches
USDCM VOL 3 BMP Design Forms v2.03 (20030121).)ds, EDB
214 PM
1
1
1
1
1
1
PROPOSED POND VOLUME
LOCATION: EASTBROOK OFFICE PARK
PROJECT NO: 265-01
COMPUTATIONS BY: MPO
SUBMITTED BY: North Star Design
DATE: 08/22/2006
Water quality required = 3616 ac-ft
100-Year Detention Required = 0 ac-ft
Total Detention Required = 3616 ae-ft
Water Quality WSEL
Spillway
Top of Berm
Stage
(ft)
Surface
Area
(ft')
Incremental_
Storage
(ac-ft)
Detention
Storage
(ac-ft)
Tota
Storage
(ac-
4940.2
0
0
4940.5
290
29
29
4941.0
800
262
291
4941.5
1500
566
857
4942.0
2500
989
184
4942.5
3600
1517
6
4942.6
3800
370
E3E733
4942.8
4200
800
4533
4943.0
4943.5
' Emergency Overflow Spillway Sizing
LOCATION: EASTBROOK OFFICE PARK
PROJECT NO: 265-01
' COMPUTATIONS BY: MPO
SUBMITTED BY: NORTH STAR DESIGN
DATE: 08/22/2006
' Equation for flow over a broad crested weir
' Q = CLH32 9 H spill
where C = weir coefficient = 2.6 �_ L _�
H = overflow height 17 10(
L = length of the weir
1 The pond has a spill elevation 0.0 ft above the maximum water surface elevation in the pond
Spillways will be designed with 0.7 ft max flow depth, thus H = 0.7 ft
Q (100) =
24.6
cfs
'
Spill elev =
4942.80
ft
Min top of berm elev.=
4943.50
'
Weir length required:
L=
16
ft
Use L =
26
ft
'
v =
1.22
ftfs
1
1
SPILLWAY.As
100 yr WSEL = 4942.60 ft
ACTUAL DEPTH =
0.51 ft
gE1
KS
AW
ggg9ggg1
t,1
e
1
1
1
1
1
I1» 04017 ►'i
EROSION CONTROL CALCULATIONS
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North Star Design
700 Automation Dr. Unit i
Windsor, CO 80550
1
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i
1
1
1
1
1
EFFECTNENESSCALCULATIONS
PROJECT: EASTBROOK STANDARD FORM B
COMPLETED BY: MPO DATE: 09-Feb-06
EROSION CONTROL
C-FACTOR
P-FACTOR
METHOD
VALUE
VALUE
COMMENT
BARE SOIL
1.00
1.00
SMOOTH CONDITION
ROUGHENED GROUND
1.00
0.90
SEDIMENT BASIN
1.00
0.50 -tc—
ROADSJWALKS
0.01
1.00
GRAVEL FILTERS
1.00
0.80
PLACED AT DILETS
SILT FENCE
1.00
0.504—
STRAW MULCH
0,06 it
1.00
ESTABLISHED GRASS
0.08
1.00
STRAW BARRIERS
1.00
0.80
EFF = (I-C•P)• 100
MAJOR
SUB
BASIN AREA
EROSION CONTROL METHODS
BASIN
BASIN
(Ac)
XwerS
ALA— '5 rc&xz
pw To 5ED
I o o
TOTAL AREA = 3, Z ,A C.
TOTAL EFF= (�p $
%
REQUIRED PS = % S `p
Erosion.xls
1 of 1
1
1
1
1
1
1
1-
1
1
1
i
1
1
1
1
1
North Star Design
700 Automation Dr. Unit 1
Windsor, CO 80550
EFFECTIVENESS CALCULATIONS — 1 0sr
PROJECT: EASTBROOK STANDARD FORM B I
COMPLETED BY: MPO DATE: 09-Feb-0¢
EROSION CONTROL
C-FACTOR
P-FACTOR
METHOD
VALUE
VALUE
COMMENT
BARE SOIL
1.00
1.00
SMOOTH CONDITION
ROUGHENED GROUND
1.00
0.90
SEDDAENT BASIN
1.00
0.50ir
ROADSIWALKS
0.01 f
1.00
GRAVEL FILTERS
1.00
0.80
PLACED AT INLETS
SILT FENCE
1.00
0.50
STRAW MULCH
0.06
1.00
ESTABLISHED GRASS
0.08E
1.00
STRAW BARRIERS
1.00
0.80
'
EFF - (lL'P)• I00
MAJOR
SUB
BASIN AREA
EROSION CONTROL METHODS
BASF]
BASIN
(AC)
+2
2.4 Ac. 064b)
�: 2.� o,o1+co.a o.ca
IJAt.lf- 113L=6 S
O. S At✓. 6ea56
3' Z
C, — O.O e>
�p= O. 5-
Au.To wQ Rio
TOTAL AREA a 3 2 AC,.
TOTAL EFF = �o
REQUIRED PS
O
f
Eroslon.xis
1
1 of
ION
I
1
U
I
I
1
1
1
1
1
CONSTRUCTION SEQUENCE
PROJECT: EASTBROOK OFFICE PARK DATE: 9/5/06
Indicate by use of a bar line when construction will occur and when BMP"s will be installed/removed
in relation to the CONSTRUCTION phase.
CONSTRUCTION PHASE (MONTH)
1
2
3
4
5
6
7
8
9
10
11
12
GRADING INCLUDES OVERLOT
OVERLOT
DETENTION WO PONDS
SWALES, DRAINAGE WAYS, STREAMS
DITCHES
PIPELINE INSTALLATION INCLUDES OFFSITE
WATER
SANITARY SEWER
STORM SEWER
CONCRETE INSTALLATION INCLUDES OFFSITE
:.. AREA INLETS
CURB INLETS
POND OUTLET STRUCTURES '
CURB AND GUTTER
BOX CULVERTS AND BRIDGES
STREET INSTALLATION INCLUDES OFFSITE
GRADING BASE
PAVEMENT
MISCELLANEOUS INCLUDES OFFSITE
DROP STRUCTURES
OTHER LIST
BEST MANAGEMENT PRACTICES
STRUCTURAL
SILT FENCE BARRIERS
CONTOUR FURROWS RIPPING DISKING
SEDIMENT TRAP FILTER
VEHICLE TRACKING PADS
FLOW BARRIERS BALES, WATTLES, ETC
INLET FILTER
SAND BAGS
BARE SOIL PREPARATION
TERRACING
STREAM FLOW DIVERSION
RIPRAP
OTHER LIST
VEGETATIVE
TEMPORARY SEED PLANTING
MULCHING SEALANT
PERMANENT SEED PLANTING
SOD INSTALLATION
NETTING BLANKETS ATS
OTHER LIST
Cost Est
EROSION CONTROL COST ESTIMATE
Project: EASTBROOK
Prepared by: MPO
ITEM
IQUANTITY
JUNIT
COST/UNIT
TOTAL COST
Silt Fence
1130
LF
$3
$3,390
Straw Bale Barrier
5
EA
$150
$750
Inlet Protection
6
EA
$150
$900
Construction Entrance
1
EA
$550
$550
Subtotal
Contingency (50%)
Total
$5,590
$2,795
$8,385
CITY RESEEDING COST
Reseed/Mulch
3.9
ACRE
$775
$3,023
Subtotal
Contingency (50%)
Total
$3,023
$1,511
$4,534
EROSION CONTROL ESCROW AMOUNT $8,385
Page 1
APPENDIX F
EXCERPTS FROM FOOTHILLS BASIN MASTER PLAN
F
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1
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JO
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eqx
yr
s s.r , All
b t i •y <S (� t,r i' F' ! Nit. +� ? P{. "}' 6
00
60
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jer, <-•�ti""a 1V'r rn `"7, f ty E y, '�"' d -C �t t °c. y ¢ s'M
Al t
trig' S t fY �. > �'•} ��`Fy ,.,,ty t s< "� r •' r,}A
el
owl
,f "+ •' y�� `S�`'�V• i r /r.a ^+w r vL'+ " s s r � .V r ....
"'+a+ < �j/y}. .P rr ST`a"`�• 1 t Y' �,+ r Qom.
- x E' + may'•/�yT�' �. <:. '� C•. y 86
~ yM• ..Y t6/ f RVi .3 KMA l i.
�Iqr'' �I. S .�,. .� {i' } +. r{ �✓ �. fro.
a of r
.t ,Ysi y Y L +h
t T ( 1
yy '
t z, t a, � x�5 e•�• 0
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T.✓ f? _� ix.+y 1 � y xt,,�
> at � R r�jr. �•.;�,* ��t. wJ J t.�.� G fi'v , '�' r v .. t y„/„�,`aA`, �x y , � ._
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PTO
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i
L
ENVIRONMENTAL PROTECTION AGENCY - STORM HATER MANAGEMENT MODEL - VERSION PC.1
DEVELOPED BY METCALF ♦ EDDY, INC.
UNIVERSITY OF FLORIDA
WATER RESOURCES ENGIINEESAS, INC, (SEPTEMBER 1970)
UPDATED BY UNIVERSITY OF FLORIDA (JUNE 1973)
HYDROLOGIC ENGINEERING CENTER, CORPS OF ENGINEERS
MISSOURI RIVER DMSION, CORPS OF ENGINEERS 'ISEPTE BER 1976)
TAPE OR DISA ASSIGNMENTS
BOYLE ENGINEERING CORPORATION (MARCH 1985' , JULY 1985)
JIN(1) JIN(2) JIN(3) J3N(6) JIN(5) JIN(6) JIN(7) JIN(8) JIN(9) JIN(1D)
2 1 0 0 0 0 0 0 0 0
JOUT(1) JOOT(2) JOOT(3) JOUT(6) JOUT(5) JOUT(6) JOUT(7) JOUT(8) JOUT(9) JOUT(10)
1" 2 _ 0 0 0 0 0 0 0 0
NSCRAT(1) NSCRAT(21 NSCRAT(3) NSCRAT(4) ---- NSCRAT(5)
3 6 0 0 0
WATERSHED 1/PROGRAM CALLED
'.ENTRY MADE TO RUNOFF MODEL '.
FOOTHILLS BASIN - FULLY DEVELOPED CONDITION WITH REVISED RAINFALL 100-YEAR EVENT
CITY MODIFIED ACE 99 PONDS 57 6 157 RATING CURVES FOR HOfESTATE SUBMITTAL 11-2000 FILENAME FOOT100.DAT
NIANHER OF TIME STEPS- 680
INTEGRATION TIME 1NTERV7LL (MINUTES) '1.00
1 1.0 PERCENT OF IMPERVIOUS AREA HAS ZERO DETENTION DEPTH"
FOR 24 RAINFALL STEPS, THE TIME INTERVAL IS 5.00 MINUTES
FOR RAINGAGE NUMBER 1 RAINFALL. HISTORY IN INCHES PER HOUR
1.00 1.14 - 1.33 2.23 2.84 5.49 9.95 4.12 2.68 1.66
' 1,22 1,06 1,00 .15 .91 .07 .86 .81 .78 .75
.73 .71 .69 .67
FOOTHILLS BASIN - FULLY DEVELOPED CONDITION WITH REVISED RAINFALL IGO-YEAR EVENT
' CITY MODIFIED.ACE 99 PONDS 57 1. 157 RATING CURVES FOR HOMESTATE SUBMITTAL 11-2000 FILENAMEFOOT100:DAT,'.
L
I
I
SUBAREA
COTTER
WIDTH
AREA
PERCENT
-SLOPE
NUMBER
OR MANHOLE (FT)
(AC)
INPERV.
(PT/FT)
-2
0
.0
.0
.0
.0300
70
400
3100.0
20.0
18.0
.0110
71
601
6300.0
67.8
19.0
.0120
2
102
6000.0
29.0
38.0
.0100
3
610
1600.0
16.5
60.0
.0130
75
413
2584.0
8.9
40.0
.0110
6
152
2500.0
37.6
17.0
.0090
78
104
1710.0
5.5
53.0
.0070
105
7
1500.0
7.5
60.0
.0210
5
201
1700.0
7.8
90.0
.0100
6
8
4000.0
32.1
70.0
.0070
7
9
1300.0
10.0
40.0
.0100
8
11
3000.0
28.3
40.0
.0050
10
14
6600.0
73.0
40.0
.0110
11
16
5600.0
53.0
0.0
.0100
12
18
7000.0
66.9_
28.0
.0030
13
12
1600.0
7.3
10.0
.0120
IN
26
1000.0
5.3
60.0
.0130
15
29
2600.0
12.3
10.0
.0/00
16
98
1600.0
11.8
90.0
.0100
17
24
3050.0
6.6
80.0
.0150
18
25
2000.0
20.1
80.0
.00SO
19
27
2000.0
16.3
90.0
.0080
22
129
3200.0
26.0
90.0
.0090
26
33
3900.0
60.5
60.0
.0100
25
36
6700.0
87.5
90.0
.0150
26
35
3000.0
35.5
50.0
.0100
27
36
1100.0
11.6
50.0
.0100
28
37
725.0
5.0
50.0
.0600
29
63
5800.0
66.5
50.0
.0090
30
61
3200.0
69.1
21.0
.0100
31
38
5200.0
56.5
60.0
.0100
32
62
1600.0
26.9
27.0 ,
.0080
33
48
365.0
2.7
90.0
.0070
36
45
1700.0
16.5
90.0
.0200
RESISTANCE FACTOR SURFACE STORAGE(IN)
SHERRY.
PERV.
IMPERV.
PERV.
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.019
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250;.
'.100
.300-•
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
. ,016..
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.200
.300
.015
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
.016
.250
.100
.300
INFILTRATION RATE(IN/HR)
GAGE
MAZIMNN
MINIMUM
DECAY RATE
NO
.51
.50
.00180
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.SO
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00100
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00100
1
.31
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00160
1
.51
.50
.00180
1
.51
.SO
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
:.50
- .00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.50
.00180
1
.51
.30
.00180
1
.51
.50
.00100
1
.51
.50
.001BD
1
'
35 46 3250.0
20.9
80.0
36 45 2390.0
21.5
90.0
.0150
.0300
.016
.016
.250
.250
.100
.100
.300
.300
.51
.51
.50
.50
.00100
.00180
1
1
37 50 70500.0
255.7
74.0
.0300
.016
.250
.100
.300
.51
.50
.00180
1
38 51 5200.0
41.7
40.0
.0100
.016
.250
.100
.300
.51
.50
1
1
39 53 2200.0
40 55 13400.0
'32.6
218.6
10.0
45.0
.0200
.0070
.016
.016
.250
.250
.200
.200
.300
.51
.50
.00180
'-i00180
1
142 172 4300.0
44.5
50.0
.0100
.016
.250
.100
.300
.300
.51
.51
.50
.50
.00180
.00180
1
1
43 172 585.0
24.2
7.0
.0100
.016
.250
.200
.300
.51
.50
.00180
1
44 58 5000.0
42.3
40.0
.0050
.016
.250
.100
.300
.51
.50
.00180
1
144 159. 1400.0
18.7
30.0
.0190
.016
.250
.100
.300
.51
.50
.00180
1
'
45 62 11000.0
117.6
60.0
.0080
.016
.250
.100
.300
.51
.50
.00180
1
46 60 3900.0
26.6
40.0
.0070
.016
.250
.100
.300
.51
.50
.00180
1
47 63 7200.0
88.0
40.0
.0080
.016
.250
.100
.300
.51
.50
.00180
1
48 65 7200.0
96.5
40.0
.0060
.016
.250
.100
.300
.51
.50
.00180
1
'
49 67 5000.0
.�= 50 57 2400.0
42.4
19.5
4400 .0
m�. o_�
.0100
.0220
.016
.016
.250
.250
.100
.100
.300
.300
.51
.51
.50
.50
.00180
.00180
1
1
ISO 157 2700.0
20.4
0
.0080
.016
.250
.100
.300
.51
.50
.00180
1
51 70 7400.0
-68.0
40.0
.0070
.016
.250
.100
.300
.51
.50
.00180
1
52 79 2200.0
14.7
70.0
.0050
.016
.250
.100
.300
.51
.50
.00180
1
53 75 2200.0
14.7
70.0
.0050
.016
.250
.100
.300
.51
.50
.00180
1
54 81 5500.0
50.9
60.0
.0030
.016
.250
.100
.300
.51
.50
.00180
1
'
55 208 6000.0
55.2
40.0
.0060
.016
.250
.100
.300
.51
.50
.00180
1
56 209 3500.0
31.7
40.0
.0030
.016
.25D
.100
.300
.51
.50
.00180
1
57 85 13000.0
208.1
40.0'
.0200
.016
.250
.100
.300
.51
.50
.00180
1
58 288 6000.0
41.3
50.0
.0100
.016
.25G
.300
.300
.51
.50
.00180
1
S81 184 3400.0
22.2
90.0
.0080
.016
.250
.100
.300
.51
.50
.00180
1
'
582 212 5000.0
34.2
85.0
.0200
.016
..250
.100
.300
.51
.50
.00180
1
59 211 1500.0
20.7
40.0
.0060
.016
.250
.100
.300
.51
.50
.00180
1
60 78 1500.0
24.6
47.0
.0050
.016
.250
.100
.300
.51
.50
.00180
1
61 210 1050.0
12.2 -
64.0
.0090
.016
.250
.100
.300
.51
.50
.00180
1
62 77 1800.0
3.3
99.0
.0070
.016
.250
.100
.300
.51
.50
1
621 306 865.0
5.9
66.0
.0090
.016
.250
.100
.300
.51
.50
.00180
.00180
1
622 303 1400.0
10.5
18.0
.0100
.016
.250
.100
.300
.51
.50
.00180
1
623 313 2200.0
3.4
33.0
.0100
.016
.250
.100
.300
.51
.50
.00180
1
624 213 6200.0
70.7
43.0
.0130
.016
.250
.100
.300
.51
.50
.00180
1
63 193 9964.0
91.5
40.0
.0050
.016
.250
.100
.300
.51
.50
.00180
1
64 361 7200.0
66.0
40.0
.0130
.016
.250
.100
.300
.51
.50
.00180
1
'
650 88 - 2100.0
19.6
40.0
.0100
.016
.250 ,
.100
.300
.51
.50
.00180
1
651 251 700.0
6.6
9.0
.0230
.016
.250 --
.100
.300
.51
.50
.00180
1
65 88 1200.0
5.7
10.0
.0300
.016
.250
.100
.300
.51
.50
.00180
1
66 94 4700.0
27.3
20.0
.0200
.016
.250
.300
.300
.51
.50
.00180
1
67 86 10000.0
68 94 I900.0
95.4
17.9
55.0
55.0
.0210
.0150
.111
.016
.250
.250
.100
.100
.300
.300
.51
.51
.50
.50
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.OD180
1
1
681 288 850.0
7.5
55.0
.0150
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.250
.100
.300
.51
.50
.00180
1
69 95 . 7100.0
65.2
55.0
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.250
.100
.300
.51
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.00180
1
TOTAL NUMBER OF SUBCATCHNENTS, 79
TOTAL TRIBUTARY AREA (ACRES),
3195.20
1
FOOTHILLS BASIN - FULLY DEVELOPED CONDITION WITH REVISED
RAINFALL 300-YEAR
EVENT
CITY MODIFIED ACE'99. PONDS
57 8 157
RATING CURVES FOR'HOMESTATE SUBMITTAL- 11=2000'FILENAME
FOOT100.DAT
•" CONTINUITY CHECK FOR SUBCATCNMEMT ROUTING
IN UDSWM2-PC MODEL
•••
WATERSHED AREA (ACRES)
3195.200
:- TOTAL RAINFALL (INCHES)
,3.669
,•
-
TOTAL INFILTRATION (INCHES)
.591
TOTAL WATERSHED OUTFLOW (INCHES)
2.880
TOTAL SURFACE STORAGE AT END OF STRCM (INCHES)
.198
ERROR IN CONTINUITY, PERCENTAGE OF RAINFALL
.000
1 FOOTHILLS BASIN - FULLY DEVELOPED CONDITION WITH REVISED RAINFALL 100-YEAR EVENT
CITY MODIFIED ACE 99 PONDS 57 6 157 RATING CURVES FOR HOMESTATE SUBMITTAL 11-2000 FILENAME FOOT100.DAT
'
GUTTER
CUTTER
NDP
UP
WIDTH
OR DIM
LENGTH
INVERT
SIDE SLOPES
OVERSANR/SURCHARGE
SLOPE
HORIE
TO VERT
MANNING
DEPTH
JE
NUMBER
CONNECTION
(PT)
(FT)
(PT/PT)
L
R
N
(FT)
'
400
156
0
4
CHANNEL
OVERFLOW
.0
40.0
800.
800.
.0070
.0070
50.0
10.0
50.0
10.0
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.40
2.00
0
156
102
0
5
PIPE
1.5
780.
.0100
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1.50
0
OVERFLOW
36.0
780.
.0100
50.0
50.0
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10.00
163
102
0
4
CHANNEL
.0
1800,
.0110
.0
50.0
.035
.70
0
OVERFLOW
35.0
1800.
.0110
.0
10.0
.035
2.00
401
163
0
4
CHANNEL
.0
1200.
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50.0
50.0
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0
'
OVERFLOW
40.0
1200.
.0040
10.0
10.0
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2.00
410
102
2
2
PIPE
.1
1000.
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.0
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0
RESERVOIR STORAGE IN
ACRE-FEET VS SPILLWAY OUTFLOW
.10
.0
.0
2.9 2.8
202
154
9
2
PIPE
.1
1.
.0010
.0
.0
.013
0
'
RESERVOIR STORAGE IN
ACRE-PRET VS. SPILLWAY OUTFLOW -
.10
.0
.0
1.5 1.6
3.7
1.8
6.6
2.1
10.3
2.3
14.4 2.5
17.5
2.6
19.8 2.7
22.9
21.2
154
153
0
5
PIPE
1.3
418.
.0040
.0
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.013
2.25
0
413
153
2
2
OVERFLOW
PIPE
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d38.
1000.
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50.0
.0
50.0
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5.00
0
RESERVOIR STORAGE IN
ACRE-FEET VS SPILLWAY OUTFLOW
.10
.0
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1.9 1.5
SECTIONTHREE
1..
I
1
[1
3.1 ON -SITE DETENTION REQUIREMENTS
Development Criteria
According to the City of Fort Collins Storm Drainage Criteria Manual, new developments must
provide on -site detention that release at the adopted basin unit release rate or the 2-year historic
peak discharge from the development during a 100-year storm event.. This holds true unless
_otherwise specified in the master plan or it can be shown that the development peadischargek
conveyed prior to the main drainage peak discharge. The 2-year historic peak discharge is
determined on a basin -by -basin basis since subbasins may be completely undeveloped or
partially developed. The Plan addresses the City's development criteria as described in Section
2.
There are several areas within the Foothills Basin where new development and/or re-
development opportunities exist. The City must enforce their development criteria as a
component of the Plan. The mitigation of flooding hazards were evaluated based on existing
conditions, therefore, it is imperative that new development does not cause an increase in
stormwater runoff peak discharge that may in turn increase the potential for flooding.
Development regulations for new construction must minimize the impacts to existing
development and the stream corridor. The regulations should require on -site detention to offset
the impacts of increased discharge peaks and volumes and decreased travel times, and limit new
development within the floodplain. It is recommended that developers provide on -site detention
for future development based on the release rates shown in Table 3.1 below or if not specified
below, utilize a 2-year existing condition release rate.
Table 3.1
On -site Detention within MODSWMM for Selected Plan
�" fR-�1�..k
sy�g y e t
"PC
X.-I 1 • j{�[,
� �M' '� `�
e '�' v l i
A;E Y �M1�
Yr`
5i �4 .�1.�4Slivu'.v��'iu6a�
4v'S. �L'.iea2�
5 ��` :f:5 �•�ui.4-wae
4P�i..•�•�et�a�5�
.,rut
For future development sites greater than 20-acres, MODSWMM shall be used to model the
hydrology of the development because larger developments can have a significant impact on
peak discharges in the larger system.
3.2 WATER QUALITY TREATMENT
No regional detention is proposed for the Foothills Basin. It is assumed that the City's water
quality criteria will be followed as part of the upgrade of the existing detention ponds in the
Foothills Basin. The water quality capture volume (wqcv) for future development will be
considered during development review.
Ulm 3-1
No Text
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APPENDIX G
FIGURES AND TABLES
G
No Text
DRAINAGE SUMMARY TABLE
OE9O1
PONE
I AREA
oesa
I AIRA I CIO
C 100
h f0
Th 100
O 10
1 O 100
1
1
1.m a]B
aw
33
ao
17
ae
E
0
213I a]1
I O.W
I 0.7
I 60
I SA
I I"
Qn 1 0.4
033
1 a]
13
I 11
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1
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1
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1RRAn1.� REL \
6wRL-OAII•
------------
ItIIj 11)Il1
1� UI� � 1
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I1 1111
F1�
� ♦Wo ara�
TRACT A
TIMBERLINE
VILLAGE
r Raowolao
ram\
I' 10 li 1 1 I
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martial ma. r" 0mata10" WN- BE T Rim s1F► O oErnDT
MAi POMS SHALL BE WANED OF SFDBOff AM SROW(T A FOBm
MADE mam TO SITE GWWMTIM AM IANvSQAPMa
2 ANY LCT NCA MT O OMMLY 8WT M SNNL BE 9 AM LR1am.
VEZTATEO MTHE APAD(SD WOS'X! P(A1L �9m' R ILL
0[
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4 SOIN SILT FEAR[ AM mBIRUC110N FTTILE ARE REUM M YW %ARM OF
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ASE73
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CONSTRUCTION SEQUENCE
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LEGEND
Z
p
f RAW ORECTIM EASELQlT ABBREMADMS
O
(r)
1
DOSING PIPES ME - UTI(TTY EASOIENTD.
( 1
1
I
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® PROPOSED 5(IX(Y PIPE A M EABELIENT T
W
I
♦♦
EAE - OAONFHCY ACCESS EASELENT
0
i I
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