HomeMy WebLinkAboutOrdinance 2023-07 Amending Chapter 9 Article I, Section 9-1 Stormwater Management RegsORDINANCE NO.2023-07
AN ORDINANCE OF THE CITY COMMISSION OF THE
CITY OF WINTER SPRINGS, SEMINOLE COUNTY,
FLORIDA, AMENDING CHAPTER 9, ARTICLE I, SECTION
9-1 OF THE CITY'S CODE OF ORDINANCES; REPEALING
IN ITS ENTIRETY CHAPTER 9, ARTICLE IV, DIVISION 4,
SECTION 9-241, OF THE CITY'S CODE OF ORDINANCES
AND ADOPTING A NEW SECTION 9-241 IN ORDER TO
UPDATE THE CITY'S STORMWATER MANAGEMENT
REGULATIONS; PROVIDING FOR THE REPEAL OF
PRIOR INCONSISTENT ORDINANCES AND
RESOLUTIONS; INCORPORATION INTO THE CODE;
SEVERABILITY; AND AN EFFECTIVE DATE.
WHEREAS, the City of Winter Springs is granted the authority, under § 2(b), Article VIII,
of the State Constitution, to exercise any power for municipal purposes, except when expressly
prohibited by law; and
WHEREAS, several recent severe rainfall events, including Hurricane Ian and Hurricane
Nicole in 2022, have caused or contributed to increased levels of stormwater rtmoff and significant
amounts of flooding throughout the City; and
WHEREAS, as a response to these severe storm events, the City enacted a temporary
moratorium via Ordinance 2022-12 within the jurisdictional limits of the City of Winter Springs
regarding the filing, processing, consideration, and decision of final engineering plan and
subdivision of land applications for development requiring construction of stormwater
management and drainage systems in all zoning districts of the City and requested that the City
staff and City Attorney develop amendments to the applicable comprehensive plan requirements
to enhance the stormwater design requirements of the City; and
WHEREAS, the City's Stormwater Engineer has conducted a thorough review of the
City's stortriwater management policies and has recommended that changes be made to the City's
Land Development Code in order to ensure that future developments within the City are designed
to accommodate the increased amount of stormwater runoff associated with increasingly strong
and frequent severe rainfall events; and
WHEREAS, the City Commission desires to amend Chapter 9, Article I, Section 9-1, and
to repeal the current and create a new Chapter 9, Article IV, Division 4, Section 9-241 of the City
Code in order to update the City's stormwater management policies consistent with the
recommendations of the City's Stormwater Engineer; and
WHEREAS, the City Commission finds that updating the City's stormwater management
policies is vital for the future well-being of the City and its residents and is consistent with Goal 4
of the City's Comprehensive Plan, Infrastructure Element, which is to provide a stormwater system
City of Winter Springs
Ordinance No. 2023-07
Page 1 of 12
of appropriate capacity to protect the life and property of the citizens of the City, as well as decrease
adverse environmental impacts attributable to stormwater runoff; and
WHEREAS, the City Commission of the City of Winter Springs, Florida, hereby finds this
Ordinance to be in the best interests of the public health, safety, and welfare of the citizens of
Winter Springs; and
NOW, THEREFORE, THE CITY COMMISSION OF THE CITY OF WINTER
SPRINGS HEREBY ORDAINS, AS FOLLOWS:
Section. 1. Recitals. The foregoing recitals are true and correct and are fully incorporated
herein by this reference,
Section 2. Code Amendment. The City Code of the City of Winter Springs, Florida, is
hereby amended as follows: (underlined type indicates additions and strike-Aut type indicates
deletions, while asterisks (* * *) indicate a deletion from the Ordinance of text existing in Chapter
9, Article I, Section 9-1. It is intended that the text in Chapter 9, Article 1, Section 9-1 denoted by
the asterisks and set forth in this Ordinance shall remain unchanged from the language existing
prior to the adoption of this Ordinance):
Chapter 9 -- LAND DEVELOPMENT
1.�'�I t� ���i►le'1�►I�7� �l
SEC. 9-1. —Definitions.
The following words, terms and phrases, when used in this chapter, shall have the meanings
ascribed to them in this section, except where the context clearly indicates a different meaning:
Closed Basin means a watershed without a positive outlet into surface waters which under
normal conditions drain by gravity into a Iake, river or other tributary that ultimately discharges
into the Atlantic Ocean.
Critical Duration Matrix of Storm Events means a collection of 48 hypothetical storm
events of specific frequency and duration that will need to be analyzed to demonstrate compliance
with the City's code.
City of Winter Springs
Ordinance No. 2023-07
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Design Storms mean the Critical Duration Matrix of Storm Events in combination with
other storm events of 24-hour duration, including the Mean Annual, 10-year, 25-year and 100-year
storms.
Existing Condition means the land cover that exists before improvements are made within
the project area.
Freeboard means the vertical distance between the design high water elevation and the
lowest elevation of the pond top of bank, levee or berm.
Impervious Area means surfaces which do not allow, or minimally allow, the infiltration of
water. Examples of impervious areas include building roofs, all concrete and asphalt pavements,
compacted soils and traffic -bearing areas such as limerock, lakes, ponds, wetlands, and other areas
as determined by the city engineer. Pervious pavement, porous concrete and turf blocks are not
considered impervious area relative to stormwater management criteria,
Ren Basin means a watershed with a positive outlet into surface waters which under
normal conditions drain by Rravity into a lake, river or other tributary that ultimately discharges
into the Atlantic Ocean. Pumn stations and drainaee wells are not considered positive outlets.
Proposed Condition means the land cover that exists after improvements are made within
the project area.
Storm for Storm Approach means that the discharge rate or discharge volume for proposed
conditions for a particular design storm (frequency and duration) is compared to the discharge rate
or discharge volume for existing conditions for the same design storm fie uency and duration to
ensure no increase.
Table Templates means the formatted tables that must be used to summarize the stormwater
modeling results for the design storms.
City of Winter Springs
Ordinance No.2023-07
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Section 3. Repealer. Chapter 9, Article IV, Division 4, Section 9-241, of the Code of
Ordinances of the City of Winter Springs, Florida, is hereby repealed in its entirety and replaced
as provided in Section 4 of this Ordinance.
Section 4. Adoption of a new Chapter 9, Article IV, Division 4, Section 9-241.
Chapter 9, Article IV, Division 4, Section 9-241, is hereby replaced with the following:
(underlined type indicates additions and q4ilceellt type indicates deletions, while asterisks (* * *)
indicate a deletion from the Ordinance of text existing in Chapter 9. It is intended that the text in
Chapter 9 denoted by the asterisks and set forth in this Ordinance shall remain unchanged from
the language existing prior to the adoption of this Ordinance):
ARTICLE IV. — REQUIRED IMPROVEMENTS
DIVISION 4. — DRAINAGE
Sec. 9-241, -- Stormwater management.
(a) Applicability of regulations and approval by city engineer.
Stormwater regulations, criteria and design requirements of the Florida Department
of Transportation (FDOT), the St. Johns River Water Management District
(SJRWMD), the Department of Environmental Protection (DEP., among others, as
they may exist and be modified from time to time, are to be the regulations, criteria,
and design requirements which the city shall utilize for review of stormwater
management facilities. All city stormwater requirements shall also apply in addition
to any federal and state requirements. If there is a conflict between regulations,
criteria and design requirements, the most stringent shall apply. In the case of any
dispute or question as to the meaning, interpretation or application of any
regulation, criteria or design requirement, the final interpretation shall be made by
the city engineer in favor of the city. Further guidance and technical requirements
related to stormwater management facilities and design may be adopted by
resolution of the Citv Commission.
(2) Stormwater management is required for all new development and significant
redevelopment projects where either cumulatively results in any of the following
A. Anv nroi ect in, on, or over wetlands or other surface waters.
B. A total of more than 4,000 square feet of impervious or semi -impervious
surface area subject to vehicular- traffic,•
C. A total of move than 9,000 square feet of impervious and semi -impervious
surface area,
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Ordinance No. 2023-07
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D. A total project area of more than five acres;
E. A capability of impounding more than 40-acre-feet of water;
F. ALiy dam having a height of more than ten feet as measured from the lowest
elevation of the downstream toe to the dam crest;
G. Any_project that is part of a larger common plan of development or sale;
H. Any dry storage facility storing ten or more vessels that is functionally
associated with a boat launching area; and
I. Any modification or alteration of a project previously permitted under
pt. IV ofch. 373 , F.S.
(3)Notwithstanding the requirements of subsection (2) above, the following activities
shall be exempt from the standards of this Section;
A, Construction, alteration, and maintenance of sinele-familv residences and
duplexes and their associated accessory structures not part of a larger
common plan of development or sale that do not involve any work in
wetlands floodplains, or other surface waters-, and
B. Maintenance, _alteration, renewal, use or improvement to an existing
stormwater management structure not changing or affecting rate or volume
of stormwater runoff or causing a violation of state water quality standards',
and
C. Maintenance, replacement, and repair work on bridges, driveways, and
roadways as provided in Rule 62-330.051(4) F.A.C.; and
D. Installation, maintenance, repair, replacement, and removal of utilities as
provided in Rule_62-330.051(14), F.A.C.; and
E. Construction, alteration, maintenance, removal, or abandonment of
recreational paths for pedestrians, bicycles, and golf carts as provided in
Rule 62-330.051(10). F.A.C.
4) The design concept for drainage systems in oronosed new developments and
significant redevelopments shall be approved by the city engineer except where
otherwise exempt as provided in this Section._ All drainage systems shall have a
positive outlet or overflow unless documented as being unnecessary y
geohydrologic investigation based on the applicable design storms.
b Protection from Flooding.
1 For ro'ects located in an open basin the peak rate of dischar e for -proposed conditions
shall not exceed the peak rate of runoff for existing conditions for each of the storm
events summarized below. Compliance shall be based on a "storm for storm" approach.
• Mean Annual (24-hour duration) in accordance with SJRWMD criteria
• 25-Year, 24-Hour
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Ordinance No. 2023-07
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0 Critical Duration Matrix of Storm Events in accordance with subsection (c) below
Z For ro' ects located in a closed basin the rate and volume ❑f direct runoff for ro osed
conditions must not exceed_ the rate and volume of direct runoff for existing conditions
for each of the storm events summarized below. Compliance shall be based on a "storm
for storm" approach. Proposed designs shall not cause an increase in the existiniz flood
stage, which can be accomplished _by retention with percolation or detention for a
duration that is sufficient to mitigate adverse itnpacts on flood stages.
0 25-Year, 96-Hour in accordance with SJR1WMD criteria
• Critical Duration Matrix of Storm Events in accordance with subsection (c) below
Design Storms and Rainfall.
1 Drainage facilities in open basins shall be analyzed for the following design storms usin
the Type 1I Florida Modified rainfall distribution and the rainfall amounts shown below.
Storm Event Rainfall (inches)
Mean Annual 24-Hour duration....................................................................................4.50
10-Year. 24-Hour.........................................................................................
25-Year. 24-Hour.....................................................................................
0 0-Year. 24-Hour..........................................................................................................11
(2Drainage_ facilities in open basins shall also be analyzed for the following critical duration
matrix of storm events using the MOT rainfall distributions and the rainfall amounts
shown below.
Duration
Average
Recurrence Interval (years)
3-Year
5-Year
10-Year
25-Year
50-Year
100-Year
1-Hour
2.26
2.55
2.89
3.33
3.65
3.95
2-Hour
2.84
3.21
3.64
4.21
4.62
5.01
4-Hour
3.26
3.69
4.23
4.96
5.53
6.08
8-Hour
3.71
4.22
4.89
5.86
6.65
7.49
24-Hour
4.62
5.27
6.23
7.76
9.11
10.60
72-Hour
5.99
6.90
8.22
10.30
12.10
14.10
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Ordinance No. 2023-07
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(3) Drainage facilities in closed basins shall be analyzed for the following design storms
using the St. Johns River Water Management District (SJRWMD) rainfall distribution
and the rainfall amounts shown below.
Storm Event Rainfall inches
Mean Annual 96-Hour duration .6.30
10-Year, 96-Hour. .9.50
25-Year, 96-Hour. .11.50
100-Year, 96-Hour. .15.20
4 Drainage facilities in closed basins shall also be analyzed for the following critical
duration matrix of storm events usiniz the FDOT rainfall distributions and the rainfall
amounts shown below.
Duration
Average
Recurrence Interval (years)
3-Year
5-Year
14-Year
25-Year
50-Year
100-Year
168-Hour
7.57
8.55
9.94
12.10
14.00
16.10
240-Hour
$.58
9.60
11.00
13.20
15.10
17.10
(5) The Type II Florida Modified (24-hour duration) and SJRWMD (96-hour duration)
rainfall_ distributions shall be created from the data provided within Part XIV of the
SJRWMD Permit Information Manual.
(6) Rainfall distributions for the eight (8) different storm event durations associated with the
critical duration matrix shall be created from the data provided within Appendix E of the
FDOT DrainaM Manual.
d Hydrologic Methods.
(1) The Natural Resources Conservation_ Service (MRCS)nit Hydrograph Method shall be
used to compute runoff rates and runoff volumes for all of the design storms.
2) Hydroaraph peak rate factors shall be selected taking into consideration watershed slope
watershed surface storage and existing drainage features. A hydrograph peak rate factor
of 256 is recommended for undeveloped land uses and a peak rate factor of 323 or 484
is recommended for developed land uses. In no case shall the hydrggrmh peak rate factor
for proposed conditions be less than the hvdroaranh peak rate factor for existine
conditions.
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Ordinance No. 2023-07
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3 Time of concentration computations that include a component of sheet flow shall be
limited to a maximum overland flow path of one hundred (100) feet.
(e) Lot Gradin_ and Other Elevation Requirements.
_(I) The drainage system for each subdivision shall include a sufficient facility to remove
stor-rnwater without flooding any lot in the proposed subdivision or in the surrounding
territory.
2 To facilitate proper stormwater surface runoff from residential lots the minimum
residential lot line slope that can be accepted is one and one -quarter percent (1,25%).
This will only be allowed in areas that have goad percolation of rainfall into the soils. In
areas that do not have good percolation of rainfall into the soils, the minimum lot line
slope that can be accepted is one and one-half percent (1.50%). The determination of
good percolation of sails will be made by_the city engineer based on a recent soils report
by a professional engineer registered in the State of Florida with expertise in geotechnical
engineering.
(3) All residential floor elevations shall be elevated to a mitrimum of eighteen (1$)inches
above the applicable 100-year base flood elevation.
(4) All nonresidential finished floor elevation shall be elevated to a minimum of eighteen
1$ inches above the applicable 100- ear base flood elevation unless flood proofed in
accordance with section $-52(2) of the Flood Damage Prevention Code.
(5) One (I) foot of freeboard is required above the peak stage predicted for the 25-year, 24-
hour storm event (8.6-inches of rainfall), which may be reduced to six (6) inches if the
peals stage predicted for the 100-year, 24-hour storm event is contained below the pond
tot) of bank elevation.
(f) Stormwater Manap—ement Systems.
(1) General Design Criteria. Dry bottom ponds, wet bottom ponds, underdrains and
exfiltration systems shall be designed in accordance with criteria presented in the
SJRWMD Permit Information Manual as may be modified and supplemented herein or
as determined by the city engineer.
2 DU bottom ponds. All d bottom retention and detention ands shall have a pond
bottom elevation no less than two 2 feet above the seasonal high ground water
elevation, which is to be determined by a professional engineer registered in the State of
Florida with an expertise in geotechnical engineering. The side slopes of all dry bottom
retention and detention ponds shall not be steeper than „three (3) horizontal to one (1)
vertical. All dry bottom ponds with side slopes that are steel2er than four 4 horizontal
to one 1 vertical shall have a seen vin 1 chainlinlc fence installed with a minimum
City of Winter Springs
Ordinance No, 2023-07
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height of six 6 feet. All fences must meet the setback requirements in section 6-193
buildings and building regulations.
3 Wei bottom ponds. All wet bottom ponds must have side slopes no steeper than four A
horizontal to one ] vertical measured from the top of the berth down to at least three
3 feet below the normal water level measured vertically. This is the side slope
transition point. Side slopes ma then transition from the transition point, to no steeper
than two horizontal to one 1 vertical down to the pond bottom. Wet bottom pond
side slopes steeper than these values are not allowed, If a fence is used it must be of the
same specifications as the fence for dry bottom ponds,
4 All ponds, All ponds shall have a minimum ten 10 foot wide stabilized bean ca able
of supiportiniz a maintenance vehicle. There shall be a minimum ten 1 foot wide
easement for each pond dedicated to the city and the homeowners' association if
Iaiuied . All fenced ponds must have a locked gate with minimum ten 10 foot wide
o enin , The seasonal hi h-water table shall be established by a professional engineer
registered in the State of Florida with ex ertise in geotechnical engineering. There must
be at least two 2 soil borings per pond or other retention areaperformed at a ro riate
locations within the limits of the pond or other retention area as shown in the final
construction plans.
(M Stormwater Modeling for Ponds and Culverts,
1 Taking credit for seepage and percolation during the storm event is not allowed.
2 For dry bottom pwids, the initial stage shall be set at the 36 hour recovery stage for the
water quality volume or the pond bottom if water quality recoveLy is less than 36 hours.
For wet bottom ponds, the initial stage shall be set at the 36 hour recovery elevation for
the water quality volume or at the overflow weir elevation.
3 All ponds shall be designed taking into consideration the tailwater of the receivin
facility. Although tailwater conditions can be established using approved studies re oirts
and other best available information any assumed relationships -must be approved by the
city engineer. If the receiving facility is an existing storm sewer, at a minimull], the
h di-aulic grade line HGL elevation can be assumed to coincide with the existing pipe
crown at the proposed point -of -connection unless a detailed study of the existing system
indicates otherwise.
4 Stormwater modeling results shall be summarized using the cit 's table templates that
are available in various electronic formats.
(h) Stormwater Modeling for Drainage Inlets and Storm Sewers.
1 Pie sizing, HGL computations and roadway spread of water calculations shall be
submitted for the pavement drainage systems. The HGL computations shall be
City of Winter Springs
Ordinance No. 2023-07
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summarized on a FDOT Storm Drain Tabulation Form or a reasonably similar
representation provided as output from a computer program.
(2) Peak rates of runoff shall be computed using the Rational Method. Rainfall intensities
shall be dictated by the computed time of concentrations and based on Intensity -
Frequency -Duration Curves for Zone 7 as contained within Chapter 3 ❑f the FDOT
Drainage Manual. A composite runoff coefficient shall be computed for each draina e
sub -basin based on runoff coefficients of 0.95 for im eivious area and 0.20 for pervious
area.
(3 Pipe sizing shall convey the 10-,year frequency storm event with the computed HGL at
least six (f) inches below the pavement elevation. The minimum pipe size to be used in
designing stone sewers is 15-inches (round barrel) or 12-inches x 18-inches (elliptical
barrel).
4 All storm sewers stems must be designed to produce a minimum velocity of 2.5 feetper
second f s when flowing full. No storm sewers stem or nortion thereof shall be
designed to produce velocities in excess of ten (10) fps, inclusive of all pipe material
types, Erosion_ protection and energy dissipation shall be provided commensurate with
the estimated outlet velocity.
5 The maximumspacing for access structures of any type is summarized below.
Pipe Size
Maximum Spacing
15-inches
200 feet
18-inches
300 feet
24- to 36-inches
400 feet
42-inches and Larger
500 feet
6 All stone sewers stems shall be designed taking into consideration the tailwater of the
receiving facility. In the case where a stormwater pond is the receiving facility, the design
tailwater can be assumed to be the 10-year frequency water level con•esponding to the
time at which peak inflow occurs from the storm sewer into the pond.
(7) HGL computations shall include energy losses associated with entrance and exit from the
system, friction losses throughpipes and structure losses associated with individual
drainage inlets and junction manholes.
(8) Drainage inlets for subdivisions and other residential projects shall be located at all
roadway low points and along continuous grades to prevent the spread of water from
exceeding one-half the traveled lane width. Drainage inlets located at low points (sumps)
shall be designed to intercept one hundred'Percent 100% of the contributing flow
City of Winter Springs
Ordinance No. 2023-07
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without exceeding the allowable spread of water into the traveled lane width. Flanking
inlets shall be provided if needed to meet this criteria or if so directed by the city engineer.
-(9) Drainage inlets and spread of water for collector -and arterial roadways shall be based on
the criteria presented in Chapter 3 of the FDOT Draina e Manual.
(i) Floodplain Management.
(1) The city encourages the preservation of existing swamp areas, ponds (including
intermittent pondswetlands and wet areas, and bayheads for water storage and
conservation _purposes. Existing flood storage quantities shall not be reduced by
development, and flood -plain management shall include provisions for
compensating storage as provided in Section 8-109 of the City Code.
Phased Development.
1 Each phase of a development shall be capable of standing on its own if subsequent areas
planned for development are not developed.
W Use of best management practices and low impact development technologies.
1 For new development or significant redevelopment, those stormwater management
systems that eventually discharge into the cit 's MSS (municipal separate storm
sewer systems) should mitigate any increase in pollutant loads to the maximum
extent practicable. To meet this_requirement,_the city encourages the use of best
management practices such as stormwater reuse and nutrient separating baffle
boxes as well as low impact development technologies, including but not limited
to: replacement of traditional paving materials with porous concrete or pervious
pavement; rass swales, bio-retention basins or rain gardens, green roofs or rain
barrels/cisterns, and other comparable methods.
(2) For _ new development or significant redevelopment abutting natural surface
waterbodies, the developer shall _implement a minimum of one low impact
development_ technology strategy as described in subsection (1).
Section 5. Repeal of Prior Inconsistent Ordinances and Resolutions. All
prior inconsistent ordinances and resolutions adopted by the City Commission, or parts of prior
ordinances and resolutions in conflict herewith, are hereby repealed to the extent of the conflict.
Section 5. Incorporation Into Code. This Ordinance shall be incorporated into the
City Code of the City of Winter Springs and any section or paragraph, number or letter, and any
heading may be changed or modified as necessary to effectuate the foregoing. Grammatical,
City of winter Springs
Ordinance No, 2023-07
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typographical, and like errors may be corrected and additions, alterations, and omissions not
affecting the construction or meaning of this Ordinance and the City Code may be freely made.
Section 7. Severability. If any section, subsection, sentence, clause, phrase, word or
provision of this Ordinance is for any reason held invalid or unconstitutional by any court of
competent jurisdiction, whether for substantive, procedural, or any other reason, such portion shall
be deemed a separate, distinct and independent provision, and such holding shall not affect the
validity of the remaining portions of this Ordinance.
Section 8. Effective Date. This ordinance shall become effective immediately
upon the effective date of Ordinance No. 2023-06 as adopted by the City Commission of the City
of Winter Springs, Florida, and pursuant to the City Charter. If Ordinance No. 2023-06 does not
become effective, then this Ordinance shall become null and void.
ADOPTED by the City Commission of the City of Winter Springs, Florida, in a regular
meeting assembled on the �_ day of Pl _�.v�1Y 52023.
r
KEVIN McCANN
Mayor
ATTEST:
xz�7�z 2,-, -
CHRISTIAN GOWAN
City Clerk
Approved as to legal form and sufficiency for
The City of Winter Springs only:
ANTHONY A. GARGANESE, City Attorney
Legal Ad Published: H" na,
First Reading: : V� I.. A23
Legal Ad Published: —a d-3
Second Reading: 93
Effective Date: .
City of Winter Springs
Ordinance No. 2023-07
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