HomeMy WebLinkAboutDrainage Reports - 10/15/1995 (2)I•
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•
• FINAL DRAINAGE REPORT
• AUTOZONE AUTO PARTS STORE
1180 NORTH COLLEGE AVENUE
FORT COLLINS, COLORADO
PREPARED FOR:
• AUTOZONE, INC.
3030 POPLAR AVENUE
MEMPHIS, TENNESSEE 38111
•
PREPARED BY:
JEHN & ASSOCIATED, INC.
! 5695 YUKON STREET
ARVADA, COLORADO 80002
(303) 423-6036
•
AUGUST,1994
REVISED: MARCH 31,1995
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Jehn & Associ
Professional Engineers and Surveyors
March 31, 1995
City of Ft. Collins
Stormwater Department
281 N. College Ave.
P.O. Box 580
Fort Collins. CO 80522
Inc.
RE: Revised Drainage Report
Autozone Minor Subdivision
1180 N. College Ave.
Fort Collins, CO 80522
The enclosed revised drainage report have been prepared in compliance with the City
of Fort Collins Storm Water Design Criteria and Construction Standards.
- Z'41
Da id E. oore, P.E. #22495
D
5695 Yukon Street 0 Suite C 0 Arvada, Colorado 80002 (303) 423-6036 • Fax (303) 467-9438
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CONIFER STREET
HEMLOCK STREET SITE
PiNON STREET
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ALPINE STREET <
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CACHE LA.po(jORE RIVER
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VICINITY MAP
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I. GENERAL
A. LOCATION
This proposed site for an AutoZone Auto Parts Store is situated on a track of land in the
northwest 114 of the southwest 1/4 of Section 1, Township 7 North, Range 69 West of the
6th Principal Meridian. More specifically it is located at 1180 North College Avenue in the
City of Fort Collins, County of Larimer, State of Colorado between Hemlock Street and
Conifer Street.
B. DESCRIPTION
The site consists of two tracts. Tract 1 contains 2.112 acres and is the site of the proposed
development. Currently the parcel is occupied by Modular Sales, a mobile sales business.
Ground cover is primarily gravel, except for a 150' x 100' area of asphalt in the southwest
corner of the tract along North College Avenue. The undeveloped southeast comer of the
tract is covered with natural grasses and weeds. A triangular parcel of land of
approximately 0.42 acres has been subdivided off of the east end of Tract 1 along the
existing irrigation ditch and deeded to James E. Quinlin.
Tract 2 contains 0.635 acres and is located south of Tract 1. It is presently undeveloped
and there are no plans at this time to change that. Ground cover consists mainly of natural
grasses and weeds.
The entire site slopes slightly to the east and southeast at approximately 1 %. The property
is zoned "HB" - Highway Business - and is bounded on the north, south and west by
various other businesses. An existing irrigation ditch, which flows east and southeast to
Dry Creek, borders the property on the east.
II. EXISTING HYDROLOGIC CONDITIONS
The site presently drains east and southeast overland to the existing irrigation ditch along
the east property line which eventually makes its way east to Dry Creek. The site falls
within the '' '�a^r'ecrr Major Drainage Basin. Offsite flows from the Kechter
property to the south are minimal due to grading from the existing building located adjacent
to the west property line of Tract 1. The Grenz property adjacent to the west line of Tract 2
contributes minimally to offsite runnoff flowng east toward the existing irrigation ditch,
however, those flows do not impact the proposed development within Tract 1. There are no
offsite flows from the property to the north.
The proposed site is located within the 100-year floodway of Dry Creek. An analysis of
floodplain development has recently been prepared by Dr. Daryl B. Simons, P.E., and Mark
A. Severin, P.E., of Simons and Associates, Inc., of Fort Collins dated September 1993,
revised March, 1995. In the original report, a lowest habitual floor elevation had been set at
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4972.03 with a regulatory base flood protection elevation of 4970.36. The revised report
determined that the 100 year water surface elevation was 4970.25 with the regulatory
floodway elevation of 4970.94. The revised report reflects the changes in the grading plan
with the existing finished floor elevation of 4971.46. The report was based on an HEC-2
model which accounted for the blockage due to the proposed structure as well as the
compensating effect of proposed grading for the site and detention pond. Flow conveyance
below the 100-year water elevation in the detention pond was assumed to be ineffective.
The analysis showed that the proposed structure and grading would decrease the 100-year
floodplain elevation by 0.04 feet and a decrease of 0.03 feet would occur for the 100-year
floodway elevation. The building will be floodproofed to an elevation of 4971.96. See
Flood Proofing sheet in the back of this report.
III. HYDROLOGIC PROCEDURE
The Rational Method has been utilized to determine the magnitude of the stormwater runoff
from the site for both the 10 year and the 100-year storm events for the developed
conditions and for the 2 and 100 year storm events for the historic conditions. Calculations
have been performed to determine the volume necessary to detain the difference between
the two-year historic and the 100-year developed flows. Water from the proposed
detention facility will be released at the two-year historic rate. Rainfall intensities and runoff
coefficients were obtained from the City of Fort Collins Storm Drainage Design Criteria and
Construction Standards Manual. Average flow velocities were obtained from the Urban
Drainage and Flood Control District's Criteria Manual.
Rainfall performance evaluation, effectiveness calculations and construction sequence for
erosion and sediment control have been performed as per the City of Fort Collins
specifications and requirements
IV. DEVELOPED HYDROLOGIC CONDITIONS
The site has will be graded to allow overland flow to the northeast and southeast comers of
the proposed development. Runoff from those two developed sub -basins will be released
• through curb cuts into concrete channels and diverted into the proposed detention pond in
the southeast corner of Tract 1. The two concrete channels have been designed to
accommodate 133% of the developed 100 year storm flows and will meet behind the
southeast comer of the building. The storm flows will be diverted from the concrete
channels to the detention pond through a grass lined channel with a concrete trickle
• channel designed to contain the 10 year developed flow. The grass lined channel has
been designed to contain 133% of the 100 year developed flows. A 1' high berm will be
constructed along the east property line of the Kechter property to prevent any offsite flows
from entering the development.
• The detention pond will release into the existing irrigation ditch along the east property line
at less than the 2 year historic rate of 0.42 cfs. The existing irrigation ditch flows south and
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The detention pond will release into the existing irrigation ditch along the east property line
at less than the 2 year historic rate of 0.42 cfs. The existing irrigation ditch flows south and
then east to Dry Creek and recent field surveys and open channel indicate ample capacity
in the unimproved channel, from the discharge of the pond, with over 1' of freeboard.
Outlet flow control from the detention pond will be regulated by a 3.2" diameter hole cut into
a 12" corrugated aluminum stand pipe that will be welded to the 12" corrugated aluminum
outlet pipe. Bottom of pond elevation will be 64.25 while the top of the outlet structure is
set at 67.13. A notch will be cut into the existing box release the 100 year event at the 100
year historic rate of 3.43 cfs. The pond will provide 12,223 cubic feet of volume for the 100
year event. An 8' long weir will be constructed along the east end of the detention pond for
an emergency overflow. The top of the pond will be set at 67.20 to allow for 1' of freeboard
in the pond.
Hay bale barriers will be placed around all earth moving construction prior to construction
for sediment control. Detention pond excavation and site grading will remove the
necessary quantity of earth along the floodplain to satisfy the floodplain development
report requirements to allow for a zero rise in the floodway water surface elevation during
the 100 year storm event. Hay bales shall remain until grass cover has been well
established after construction.
V. CONCLUSIONS
This proposed drainage plan meets all requirements and specifications from the City of Fort
Collins Storm Drainage Design Criteria and Construction Standards Manual. Furthermore
this plan follows all the recommendations of the Stormwater Utilities Department of the City
of Fort Collins with respect to compliance with the master drainage plan.
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DRAINAGE CALCULATIONS
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Professional Engineers and Surveyors
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JOB NO.
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14 SUBJECT
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DATE S 9 BY CH'K..
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Professional Engineers and Surveyors SHEET —OF —
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Coi.tG2ETE G PrAIQ .NE'L (_4D 176SIC,w! 7T �11e
VARIABLES LIST:
Y - FLOW DEPTH
Q - FLOWRATE
MAN-MADE CHANNELS
B - CHANNEL BOTTOM WIDTH
M - CHANNEL SIDE SLOPE
•
VARIABLE TO BE SOLVED (Y,Q,B,M,S OR N) ? Y
Q,00 = 4-.(Al cLS
Q
(CFS)
? 6.1 = t?3% eF Qteo
RESULTS
B
(FT)
? .1
-----------------
OM
(FT/FT)
3
Y=
0.67
FT
S
(FT/FT)
? .0094
A=
1.43
SF
N
(FT-1/6)
? .016
P=
4.36
FT
V=
4.28
FPS
F=
1.28
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S - CHANNEL SLOPE
N - CHANNEL ROUGH
SUPER -CRITICAL FLOW
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----------------------
Q,d=2.4�-s
�r�ur
�eAr4 = 0,47�
c .�-+�,C
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Professions! Engineers and Surveyors
SHEET —OF—
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JOB NO. DATE 5- 94 BY
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SUBJECT
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VARIABLES LIST:
Y - FLOW DEPTH
Q - FLOWRATE
MAN-MADE CHANNELS
B - CHANNEL BOTTOM WIDTH
M - CHANNEL SIDE SLOPE
VARIABLE TO BE SOLVED (Y,Q,B,M,S OR N) ? Y
Q,.. - 4.3 4A
Q ( CFS ) ? 5.7 = PS? /c oF' Q/o c RESULTS
�B (FT) ? .1
M (FT/FT) ? 3 Y= 0.54 FT
S (FT/FT) ? .0268 A= 0.92 SF
N (FT-1/6) ? .016 P= 3.49 FT
No
V= 6.23 FPS
F= 2.09
<Shift> <Prt Sc> print <Return> repeat
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57 � .54�
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S - CHANNEL SLOPE
N - CHANNEL ROUGH
SUPER -CRITICAL FLOW
<Space Bar> back to menu
------------------------
Q/0 ' Z.Zcr�.-
FLOW 9EDr4 = 0 . S 7 '
PROW PE? r,! 7 0. 48'
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JEHN & ASSOCIATES. INC.
PROFESSIONAL ENGINEERS AND SURVEYORS
JOB NO 142-93-19i DATE 3130195 BY AJM
PROJECT AUTOZONE FT. COLLINS
1180 N. COLLEGE AVE.
DEVELOPED BASIN NO.3
(DETENTION POND)
AREA= 0.63 ACRES
TRAVEL LENGTH: OVERLAND =100', CHANNELED =165'
AVG SLOPE = 1.5%
RUNOFF COEFFECIENTS : 10 YEAR = 0.15 (ENTIRE BASIN
100 YEAR = 0.19 LAWN)
TIME OF CONCENTRATION
Tc=Ti+T,
Ti= 1.8(1.1-.15)(100)".51(1.5)4.33=
T,= 165'1(60MIN.-3.2 FTIS) =
INTENSITY:
10 YEAR = 3.6 IN/HR
100 YEAR = 5.8 IN/HR
RATIONAL METHOD Q = CIA
CIO= 0.34 CFS
Q,00= 0.69 CFS
15.0 MINUTES
0.9 MINUTES
Tc = 15.8 MINUTES
I I 44- C 4A u �,,EL_
L7�scctnl ��oW /33%s er Q .e
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VARIABLES LIST:
Y - FLOW DEPTH
Q - FLOWRATE
MAN-MADE CHANNELS
B - CHANNEL BOTTOM WIDTH
M - CHANNEL SIDE SLOPE
'VARIABLE TO BE SOLVED (Y,Q,B,M,S OR N) ? Y
•
Q (CFS) ? 6.1
B (FT) ? .1
M (FT/FT) ? 3
S (FT/FT) ? .0165
0 (FT-1/6) ? .016
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RESULTS
Y=
0.60
FT
A=
1.16
SF
P=
3.92
FT
V=
5.28
FPS
F=
1.67
S - CHANNEL SLOPE
N - CHANNEL ROUGH.
SUPER -CRITICAL FLOW
<Return> repeat <Space Bar> back to menu
------------------------------------------------
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I VARIABLES LIST:
Y - FLOW DEPTH
Q - FLOWRATE
MAN-MADE CHANNELS
B - CHANNEL BOTTOM WIDTH
M - CHANNEL SIDE SLOPE
VARIABLE TO BE SOLVED (Y,Q,B,M,S OR N) ? Y
? .1
h T/FT) ? 3
S (FT/FT) ? .0165
N (FT^1/6) ? .04
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RESULTS
Y=
1.10
FT
A=
3.77
SF
P=
7.08
FT
V=
3.13
FPS
F=
0.74
S - CHANNEL SLOPE
N - CHANNEL ROUGHNESS
SUB -CRITICAL FLOW
<Return> repeat <Space Bar> back to menu
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J Engineers and Surveyors
SHEET —OF —
JOB NO. — DATE r
By
CUENT AuTv Zat4i5 PROJECT. Fr-
SUi3JECT-De-7-&tJ'77&4 5;1-1-17D
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JEHN & ASSOCIATES, INC.
PROFESSIONAL ENGINEERS AND SURVEYORS
JOB NO 142-93-197 DATE 3131/95 BY AJM
PROJECT AUTOZONE FT. COLLINS
1180 N. COLLEGE AVE.
VOLUME CALCULATIONS
CONTOUR
AREA
VOLUME
EVOLUME
RELEASE RATE
(S.F.)
(C.F.)
(C.F.)
(C.F.S.)
64.25
0
0
0
0
65.00
3904
976
976
0,21
66.00
13708
8309
9285
0.36
HWL 100 YEAR 66.20
15694
2938
12223
3.05
67.00
28220
17322
29545
6.20
VOLUME REQUIRED = 10640 CF
VOLUME PROVIDED = 12223 CF
RELEASE RATE FOR POND USING 3.2" DIAMETER HOLE CUT INTO ORIFICE PLATE.
Q=C'A'(2" g'H)^.5, WHERE C = .61, A = .06 SF, AND H = (66.2-64,49) = 1.71
Q = .38 CFS
CUT NOTCH IN RISER BOX TO PASS FLOW'S GREATER THAN THE 100 YEAR STORM
SEE WIER CALCULATIONS FOR FLOW THROUGH BOX.
S S SAWCUT EXISTING
24 /- CONCRETE BOX
496713 -
A
4966.20 -"
4965.20
I�*
49�4.
3 2 1, a21,=ice
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-7,.U7; fbAi/0
ORIFICES
Enter up to 10
orifices.
Enter <Return>
only for flowrate
and area
to end.
E L
E V A T I
O N S
FLOWRATE
AREA COEFF
HEADWATER
CENTER
TAILWATER
(CFS)
(SF) (-)
(FT)
(FT)
-------------------
(FT)
-----------------------------------------
0.38
0.06 0.610
66.20
64.49
64.49
IV, 6G 7J2 K32.2 x(G7-�4.17) _
<Shift> <Prt Sc> print
----------------------------
<Return> repeat
ORIFICES
'Enter up to 10 orifices.
*Enter <Return> only for flowrate and area to end.
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FLOWRATE
AREA
(CFS)
---------------------
(SF)
0.38
0.06
<Shift> <Prt Sc> print
----------------------
COEFF
0.610
3G 'f25
,4& e.2s
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E L E V A T I O N S
HEADWATER CENTER TAILWATER
(FT) (FT) (FT)
66.20 64.49
<Return> repeat
---------------
ORIFICES
Enter up to 10 orifices.
Enter <Return> only for flowrate and area to end.
64.49
<Space Bar> back to menu
IE L E V A T I O N S
FLOWRATE AREA COEFF HEADWATER CENTER TAILWATER
No
��rsr �Cf IIZZICr/�Tb�i cHAjn/E,_ _m �Y C1rEc K
GrLoSs r GT!Ost1 �E {'may Wc7 FRuri r-f*:Z_D SJ2Vie- o.
UsE 0.1 MANu't--'qS ccE-r u f Fad /L*�Jf $rtJ5Ae-
,4 -10 T!ltcK qC erA77u�.
NATURAL CHANNELS
•
VT_, _ABLES LIST:
Y - FLOW ELEVATION Q - FLOWRATE S - CHANNEL SLOPE
VARIABLE TO BE SOLVED (Y,Q OR S) ? Y
't (CFS) ? .42
S (FT/FT) ? .005
1• RESULTS
Y= 64.45 FT
A= 0.85 SF
P= 3.00 FT
V= 0.49 FPS
�= 0.16 SUB -CRITICAL FLOW
L<Shift> <Prt Sc> print
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��s3o�.TL� ant
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Enter up to 20 cross-section points.
Enter <Return> only for distance to and.
CROSS-SECTION POINTS
DIST ELEV COEFF DIST ELEV COEFF
------------------ -----------------
0 66
.1
2 65
.1
4 64
.1
5 64
.1
7 65
.1
9 66
.1
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EROSION & SEDIMENT CONTROL CALCULATIONS
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RAINFALL PERFORMANCE STANDARD EVALUATION
PROJECT: a-ro aaiE STANDARD FORM A
COMPLETED BY: S P U DATE: S 4 9,;�
DEVELOPED
SUBBASIN
ERODIB_LITY
I ZONE
Asb
(ac)
Lsb
(ft)
SsD
($)
Lb
(feet)
Sb
I M
PS
0)
,�t7Vc.2.4T c
Ga
4Z0
! b
2
3
/✓)ODc�ATc
.9-9
2�OV
� /p
I MARCH 1991 8-14
DESIGN CRR'ERIA
No
EFFECTIVENESS CALCULATIONS
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PROJECT: Afro B-c,.lE STANDARD FORM B
COMPLETED BY: PG DATE: A 4 94
Erosion Control C-Factor P-Factor
Method Value Value Comment
: T-rgAw &LE FAzz:EP— /.00 0.80 Fog So>:F BBB-gGSri./5
'QpP•l75 /F'7AVEMVJr 0.01
E=-rq=L .�.IJEJ 4rZd5S 6.0a
MAJOR PS
SUB
AREA
BNSINI M
BASIN
(Ac)
CALCULATIONS
A
C Sara,-._ �o.oi x .SI + o.oc'x.i-�/ �q= 0.a2
?FAc-7'1rZ
EFF = CI - .02'�•80�:�jpd= ��•�l�
Z
- (o `
f1.q-% AG. PAJcM t-�/T•
0,/`� AG. MJLcN
GGAc:A�=(O.o1X.��f0.0royc.l9���'0= O.oZ
fAcTWe = D, $O
AC, Muc-�a
. /l Ac. �csra�u:NIE7i ClAC�
G- ,gcraf— = 38+ o.as �.11�/¢9 = o.o
j2-0VAc7afZ= 0-8o
/Cal
rorAL
/.83
EFF = 98.2
' MARCH 1991 8-15
DESIGN CRRERIA
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CONSTRUCTION SEQUENCE
_-
t
/�
PROJECT:
/.+ury Fo,-JE
STANDARD FORM C
�D
SEQUENCE
FOR 19 �r' ONLY
COMPLETED BY: /
DATE: f
Indicate
by use of a bar line
or symbols when erosion control measures will be installed.
Major modifications to an approved schedule may require submitting
a new schedule for
approval
by the City Engineer.
OVERLOT GRADING
WIND EROSION CONTROL
Soil Roughening
Perimeter Barrier
Additional Barriers
7ecetative Methods
_I.'I Sealant
Other
FALL EROSION CONTROL
TRUCTURAL:
Sediment Trap/Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving
Other
VEGETATIVE:
Permanent Seed Planting
Mulching/Sealant
Temporary Seed Planting
Sod Installation
Nettings/Mats/Blankets
Other
STRUCTURESs INST+T'21) BY
IEGETATION/MULCHING CONTRACTOR
]ATE SUBMIT= -
sl of tiJI I =1 rtI AI111 1-14
MAINTAINED BY
APPROVED BY CITY OF FORT COLLINS ON
10 MARCH 1991 8.16
DESIGN CRITERIA
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AUTOZONE
1180 North College Avenue
Ft. Collins, CO 80522
Erosion Control Cost Estimate:
Straw Bales 750 L.F @ $1.50 LF
Rock 10 T @ $ 8.00/Ton
Plywood Cover 1 EA. @ $50.00 each
Erosion Control Escrow Bond = $1225. X 1.5
$1,125.00
50.00
$1,225.00
$1,83750
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APPENDIX
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USE WITH THE RATIONAL FORMULA.
*MOST FREQUENTLY OCCURRING"UNDEVELOPED"
LAND SURFACES IN THE DENVER REGION.
REFERENCE: "Urban Hydrology For Small Watersheds" Technical
• Release No. 55, USDA, SCS Jan. 1975.
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