HomeMy WebLinkAboutDrainage Reports - 10/15/1995r
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
Jehn & Associates, Inc.
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
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.
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id . M66re, P.E. #22495
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111 5695 Yukon Street 0 Suite C 0 Arvada, Colorado 80002 (303) 423-6036 9 Fax (303) 467-9438
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CONIFER STREET
HEMLOCK STREET
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VICINITY MAP
I. GENERAL
A LOCATION
This proposed site for an AutoZone Auto Parts Store is situated on a track of land in the
northwest 1/4 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
comer 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 Gr�``�.., �: �n 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 flowing 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 floodvray 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
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.
111. 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 comer 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
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.
i
DRAINAGE CALCULATIONS
Professional Engineers and Surveyors
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MAN-MADE CHANNELS
JARIABLES LIST:
Y - FLOW DEPTH B - CHANNEL BOTTOM WIDTH
Q - FLOWRATE M - CHANNEL SIDE SLOPE
11ARIABLE TO BE SOLVED (Y,Q,B,M,S OR N) ? Y
60 =4(ocLs
(CFS) ? 6.1 = /?3%, or: zioo RESULTS
(FT) ? •1
(FT/FT) ? 3 Y= 0.67 FT
(FT/FT) ? .0094 A= 1.43 SF
(FT-1/6) ? .016 P= 4.36 FT
S - CHANNEL SLOPE
N - CHANNEL ROUGHNESS
V= 4.28 FPS
F= 1.28 SUPER -CRITICAL FLOW
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MAN-MADE CHANNELS
LIABLES LIST:
Y - FLOW DEPTH B - CHANNEL BOTTOM WIDTH
Q - FLOWRATE M - CHANNEL SIDE SLOPE
VARIABLE TO BE SOLVED (Y,Q,B,M,S OR N) ? Y
F.an ' +.2. eA
( CFS )
? 5.7 = l3? of QlQ C
RESULTS
(FT)
? .1
(FT/FT)
? 3
Y=
0.54
FT
(FT/FT)
? .0268
A=
0.92
SF
N (FT-1/6)
? .016
P=
3.49
FT
V=
6.23
FPS
F=
2.09
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----------------------
S - CHANNEL SLOPE
N - CHANNEL ROUGHNESS
SUPER -CRITICAL FLOW
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- Z.Zc�s
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FCOw Pe-Pr4 = 0 , S i '
Qrov v 4.3 c.T5
Fiow Da-.PrN -- 0.48,
JEHN & ASSOCIATES, INC.
PROFESSIONAL ENGINEERS AND SURVEYORS
JOB NO 142-93-197DATE 3/30/95 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+Tt
Ti = 1.8(1.1-.15)(100)^.5/(1.5)^.33 =
Tt= 165'/(60MIN.'3.2 FT/S) =
Tc =
INTENSITY
10 YEAR =
3.6 IN/HR
100 YEAR =
5.8 IN/HR
RATIONAL METHOD Q = CIA
Qio=
0.34 CFS
Qioo=
0.69 CFS
15.0 MINUTES
0.9 MINUTES
15.8 MINUTES
�c KBE c tFA ►.l uEc_ -ro 1���N r� oti/ f�e,.,r i.7
Z
tRIABLES LIST:
Y - FLOW DEPTH
MAN-MADE CHANNELS
B - CHANNEL BOTTOM WIDTH
Q - FLOWRATE M - CHANNEL SIDE SLOPE
LIABLE TO BE SOLVED (Y,Q,B,M,S OR N) ? Y
4
(CFS)
? 6.1
RESULTS
B (FT)
? .1
_________________
(FT/FT)
? 3
Y=
0.60
FT
(FT/FT)
? .0165
A=
1.16
SF
(FT-1/6)
? .016
P=
3.92
FT
V=
5.28
FPS
'
F=
1.67
S - CHANNEL SLOPE
N - CHANNEL ROUGHNESS
SUPER -CRITICAL FLOW
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VARIABLES LIST:
1 Y - FLOW DEPTH
Q - FLOWRATE
MAN-MADE CHANNELS
B - CHANNEL BOTTOM WIDTH
M - CHANNEL SIDE SLOPE
rIABLE TO BE SOLVED (Y,0,B,M,S OR N) ? Y
("i ? 11.8 RESULTS
.1
T/FT) ? 3 Y= 1.10 FT
(FT/FT) ? .0165 A= 3.77 SF
(FT^1/6) ? .04 P=. 7.08 FT
V= 3.13 FPS
F= 0.74
S - CHANNEL SLOPE
N - CHANNEL ROUGHNESS
SUB -CRITICAL FLOW
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' JEHN & ASSOCIATES. INC.
PROFESSIONAL ENGINEERS AND SURVEYORS
JOB NO 142-93-197 DATE 3/31195 BY AJM
PROJECT AUTOZONE FT. COLLINS
1180 N. COLLEGE AVE.
VOLUME CALCULATIONS
CONTOUR
AREA
VOLUME
E VOLUME
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.
„ 5 to SAWCUT EXISTING
CONCRETE BOX
4967.13
4966.20
4965.20
49G4.3
,t A a21 ice
J •�
r
ORIFICES
Lter up to 10 orifices.
Enter <Return> only for flowrate and area to end.
iE L E V A T I O N S.
FLOWRATE AREA COEFF HEADWATER CENTER TAILWATER
r-
(CFS)-------(SF)- (-) (FT)--- (FT)(FT)---
------------------------- ------
------
0.38 0.06 0.610 66.20 64.49 64.49
t214L') (P7,00
Shift> <Prt Sc> print
<Return> repeat ---------<Space Bar> back to menu
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
LOWRATE
AREA COEFF
HEADWATER
CENTER
TAILWATER
(CFS)
(SF) (-)
(FT)
(FT)
(FT)
i.38
0.06 0.610
66.20
64.49
64.49
<Shift> <Prt Sc> print <Return> repeat <Space Bar> back to menu
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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
:.
G �t,sr��u4 izz,4�r�d.0 C-*ANAjr(_ To lZ-( (fineic rG
' User O. i MAiv&ut^tg.5
�•✓ri TJjccK �lECrET.4TIcr.i.
NATURAL CHANNELS
F: _ABLES LIST:
Y - FLOW ELEVATION Q - FLOWRATE S - CHANNEL SLOPE
'ARIABLE TO BE SOLVED (Y,Q OR S) ? Y
(CFS) ? .42
(FT/FT) ? .005
RESULTS
64.45
FT
= 0.85
SF
3.00
FT
= 0.49
FPS
0.16
SUB -CRITICAL FLOW
Enter up to 20 cross-section points.
Enter <Return> only for distance to end.
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
RAFALL PERFORMANCE STANDARD EVALUATION IL
IN
PROJECT: uTo ZON B STANDARD FORM A
, P V DATE: S 4 Sri'
COLLETED BY:
DEVELOPED
E tODIBI7rITY
Asb
Lsb
Ssb
Lb
Sb
PS
SUBBASIN
ZONE
(ac)
(ft)
M
(feet) (
M
M
MDDCRAr'=
.G8
4.2o
/17
2
Movac4Are
. /p(o
sao
/ % .
3
MoDEEarc
.49
21o0
/ o%
3so
/•2S
78.!
83
4 MARCH 1991 8-14 OESIGN CRITERIA
EFFECTIVENESS CALCULATIONS s
PROJECT: Avry ^aa- STANDARD FORM B
COMPLETED BY: G DATE: 4 94
Erosion Control C-Factor P-Factor
Method Value Value Comment
STRaw &LE gA=.,EiZ /. o o 0.80 For. swr# Awe-gC�r'�l5
Qp A-V 5 /i7AvEMe,WT 0.01 1. t� O �i i r it r f
E=-rc�rv�f?EJ <kA5S O.0 9 /. a O F2a�l Flcr��c
11d1r Mut-A 0.04 /.00
MAJOR
PS
SUB
AREA
BASIN
($)
BASIN
(Ac)
CALC=ATIONS
A
78.1
(
•�8
o.s/ Ac. �AvEMiF�-►r
(0,01A.91 y o-ocox.f�)/'6az 4.02
0./9 .aC. MJLc N
C AAC74e =CD.orX.4'?+o.a�x•►9)1.�(o= D.O2.
3
'49
.3 S AC, Af
G•f��ro2. = (0.0/ *.38+ 0.08 �.11¢9 = 0.0g
-FAtTpfL/s d.80
/�
ro rA L
MARCH 1991 8-15 DESIGN CRITERIA
CONSTRUCTION SEQUENCE
-�f s
' PROJECT: A u To T� A_/ z_ STANDARD FORM C
SEQUENCE FOR 19 St�rONLY COMPLETED BY: DATE:
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.
YEAR I
MONTs 51
0 1 fJ ,T,�
E OVERLOT GRADING
t WIND EROSION CONTROL
Soil Roughening
• Perimeter Barrier
' Additional Barriers
'Jecetative Methods
i0il Sealant
Other
.FALL EROSION CONTROL
' 'TRUC:'URAL:
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
STRUCTURES: INSTALLED BY
7EGETATION/MULCHING CONTRACTOR
)ATE SUBMITTED
APPROVED BY CITY OF FORT COLLINS ON
MARCH 1991 8-16 DESIGN CRITERIA
AUTOZONE
1180 North College Avenue
Ft. Collins, CO 80522
Erosion Control Cost Estimate:
Straw Bales 750 LF @ $1.50 LF
Rock 10 T @ $ 8.00/Ton
Plywood Cover I EA @ $50.00 each
$1,125.00
$ 80.00
50.00
$19225.00
Erosion Control Escrow Bond = $1225. X 1.5 $19937.50
APPENDIX
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VELOCITY IN FEET PER SECOND
FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR
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.
5-1-84
URBAN DRAINAGE & FLOOD CONTROL DISTRICT
0.35
0.30
0.25
020
0.15
0.10
0.05
0.00
MARCH 1991
Figure 8-A
ESTABLISHED GRASS AND C-FACTORS
FORT C01dK COLORADO
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GRASS GROUND COVE {�)
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DESIGN CRITERIA
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O rmmGomm mm01C1010f01010f01mmm
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N m m m m m m m m m m m m m m m m m m m m
O 0Md.tn%00 %Orrob rrrrrrrrrhmmmmmm
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O d d d d d d d d d d d d d •? d d d d d d d d d d d d
r1 m m m m m m m m m m CO CO Co m m m Co Co m m m m m m m Co
O mNMdInInInv%0t0%0%0tOrrrrrrrrhhmmm
a M d d d d d d d d d d d d d d d d d d d d d d d d d
m m m m m m m m m m m m m m m m m m m m m m m m m m
O 10 O N M d d In In In In t0 t0 V t0 10 %0 %0 t0 t0 %0 r h r r r r
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m M ddddddddddddd ddd d d d d d d d d d
ao m m m m m m m m m m m m m m m m m m'm m m m m m m
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10 M M M d d d d d d 44 d d d d d d ddd d d d d d d
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m m m m m m m m m m m m m m m m m m m m m m m m m m
to r+w W4 M v M 0 wwfl%rrmmmmmmama00000
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d N N M M M M M M M M M M M M M M M M M M M d d d d d
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d ri N N M M M M M M M M M M M M M M M M M M M M M M M
07 m m m m m m m m m m m m m m m m m m m m m m m m m
m r�rilnrmOOrINNMMMdddddlnlnlntOtOtOrr
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M O ••t.•I rI rI N N N N N N N N N N N N N N N N N N N N N
m m m m m m m m m m m m m m m m m m m m m m m CO CO m
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r m m m m m m m m m m m m m m m m m m m m m m m m m
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tV m a O O O O O O O r1 rl rl rl r1 r1 r♦ r♦ rl rl r♦ rl r1 r1 ri r1 r1
r h m m m m m m m m m m m m m m m m m m m m m m m m
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rl t0 m m a a a a a a a a 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
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O t0 M O d r a 0 r4 N M M d d to In In In 10 w t0 t0 r h 0 t0 10
rl dtOrhhrmmmmmmmmmmmmmmmmmmmm
r r r r r r h r r r r r r r r r h r r h r r r r r r
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a.Z W r4NMdlnwhma0r4NMdin%or%macIn0in0Ina
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MARCH 1991 8-4 DESIGN CRITERIA
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