1990-058AN ORDINANCE OF THE CITY OF DENTON, TEXAS, AMENDING ARTICLE 4.15 OF
CHAPTER IV OF ARTICLE III OF APPENDIX A OF THE CODE OF ORDINANCES
TO PROVIDE FOR AMENDED DRAINAGE REQUIREMENTS AND DESIGN STANDARDS;
AMENDING SECTION 10 1/2-17 (FLOOD DAMAGE PREVENTION) OF THE CODE OF
ORDINANCES RELATING TO FLOOR ELEVATIONS; PROVIDING FOR A
SEVERABILITY CLAUSE; PROVIDING A PENALTY IN THE AMOUNT OF $500.00
FOR VIOLATIONS THEREOF OCCURRING WITHIN THE CITY OF DENTON; AND
PROVIDING FOR AN EFFECTIVE DATE.
WHEREAS, the City of Denton has found that revisions of the
Denton Development Code are needed to provide for more under-
standable, effective, and efficient land development requirements
and regulations; and
WHEREAS, the City of Denton has undertaken a program to revise
and implement the new and amended land development regulations and
requirements; and
WHEREAS, the revised regulations applicable to drainage
requirements and design standards have been completed; and
WHEREAS, a public hearing on the amended drainage requirements
and design standards has been held in compliance with the
provisions of the Local Government Code; NOW, THEREFORE,
THE COUNCIL OF THE CITY OF DENTON HEREBY ORDAINS:
SECTION I. That article 4.15 of Chapter IV of Article III of
Appendix A of the Code of Ordinances is amended to read as follows:
DIVISION V.
DRAINAGE REQUIREMENTS AND DESIGN STANDARDS
Article 4.15. All developments shall provide the drainage
facilities and improvements to serve the development in accordance
with the following requirements and design standards.
A. PURPOSE.
The following standards and requirements are adopted for the
following purposes:
1. To protect human life, health and property;
2. To minimize the expenditure of public monies for costly
flood control projects;
3. To minimize the need for rescue and relief efforts
associated with flooding and generally undertaken at the
expense of the general public;
4. To minimize prolonged business interruptions;
5. To minimize damage to public facilities and utilities
located in floodplains;
6. To provide for the sound use and development of all
areas in such a manner as to minimize future flood
blight areas;
7. To retain natural floodplains in a condition that
minimizes interference with flood water conveyance,
flood water storage, aquatic and terrestrial ecosystems,
and ground and surface water;
8. To minimize erosion and sedimentation problems and
enhance water quality; and
9. To minimize future operational and maintenance expenses.
B. DEFINITIONS.
In addition to the words herein defined, the words defined in
the Drainage Manual shall apply to any word used herein which is
not otherwise defined.
Access Ramp. A route used to provide entry for vehicles and
machinery into a channel.
Access Road. A route parallel to and at the top of the bank
of a channel used to allow maintenance of channels from the
top of bank.
Base Flood. The flood having a one percent chance of being
equaled or exceeded in any given year. Also known as the 100-
2
year flood.
Channel. An open conduit in which water flows with a free
surface.
Conduit. Any open or closed device for conveying flowing
water.
Drainage Area or Basin. The land area upon which all rainfall
that falls on that area is directed towards or flows to a
given point or stream.
Drainaqe Facilities or System. One or more conduits,
channels, ditches, swales, pipes, detention devices, or any
other device, work, or improvement, natural or man-made, which
is used, designed, or intended to be used to carry, direct,
detain, or otherwise control storm water.
Drainage Manual. The Denton Drainage Design Manual as adopted
by this Division.
Detention. The storage of storm runoff for a controlled
release during or immediately following the design storm.
Regional detention refers to storage of storm runoff from an
entire drainage area or basin.
Flood Hazard Boundary Map (FHBM). An official map of a
community, issued by the Federal Insurance Administration,
where the areas within the boundaries of special flood hazards
have been designated.
Flood Insurance Rate Map (FIRM). An official map of a
community, on which the Federal Insurance Administration has
delineated both the areas of special flood hazards and the
risk premium zones applicable to the community.
Flood Insurance Study. The official report provided by the
Federal Insurance Administration containing flood profiles,
the water surface elevation of the base flood, and the flood
hazard boundary map.
Floodplain. The area designated as subject to flooding from
the base flood (100-year flood) on the Flood Insurance Rate
Map. The floodplain includes the floodway.
Floodway. A river, channel or other watercourse and the
adjacent land areas that must be reserved in order to
discharge the base flood without cumulatively increasing the
water surface elevation more than a designated height.
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Normally, the floodway will include the stream channel and
that portion of the adjacent land areas required to pass the
base flood (100-year flood) discharge without cumulatively
increasing the water surface elevation at any point more than
one (1) foot above that of the pre-floodway condition,
including those designated on the Flood Insurance Rate Map.
Floodway Frinqe. The area located within the floodplain and
outside the floodway.
Freeboard. The vertical distance between the design water
surface level and the top of an open conduit left to allow for
wave action, floating debris, or any other condition or
emergency without overtopping the structure.
Grade. (1) The inclination or slope of a conduit, channel, or
natural ground surface, usually expressed in terms of the
percentage of number of units of vertical rise (or fall) per
unit of horizontal distance; (2) the elevation of the invert
of the bottom of a conduit, canal, culvert, sewer, etc; or (3)
the finished surface of a canal bed, road bed, top of an
embankment, or bottom of excavation.
Hydrograph. A graph showing stage, flow, velocity or other
property of water versus time at a given point on a stream or
conduit.
Inlet. An opening into a storm drain system for the entrance
of surface storm runoff.
Time of Concentration. The estimated time in minutes required
for storm water runoff to flow from the most hydraulically
remote section of the drainage area to a specific design
point.
Inverted Crown Section. A street cross section usually
reserved for alleys in which the center of the street is lower
than the edges so that drainage is carried down the center of
the street.
Lane. A driving surface of a street with a width as specified
in the street design standards for that class of street.
Local Drainage System. Any drainage facility or system which
serves an area have a contributing drainage basin of less than
one (1) square mile in area.
Off-site. Located outside the boundary of a development.
On-site. Located within the boundary of a development.
Pilot Channel. A concrete channel section used to convey
normal low flows, fix the location of the flow line of a
channel, minimize erosion, and provide access for
maintenance.
Pipe. A closed conduit through which water flows.
Spread Limits. The width of pavement covered by water based
on a flood of a certain frequency (10-year, 100-year flood).
Street Crown. The highest point of a street cross section,
normally located at the center line of the street.
Tailwater. The water surface elevation directly downstream of
a drainage facility.
C. GENERAL DRAINAGE REQUIREMENTS.
1. Drainaqe Improvements Required. All developments shall
provide for any new drainage facilities, the improvement
of any existing drainage facilities, channel improve-
ments or grading, driveway adjustments, culvert improve-
ments, or any other improvement, drainage facility, or
work which is necessary to provide for the storm water
drainage needs of the development, in accordance with
the requirements and design standards of this division,
including, but not limited to any drainage facilities,
improvements, or other work which is necessary:
a. To provide for the conveyance of all storm water
from the development when fully developed, to an
adequate discharge point.
b. To fulfill any purpose for which these requirements
are imposed.
c. To adequately protect the development from flooding,
including the effects of the 100-year flood.
d. To properly control any increase in the upstream or
downstream stage, concentration, or watersurface
elevation caused by the development.
e. To provide for the conveyance of existing storm
drainage flowing through the development.
2. Off-Site Drainaqe. Off-site drainage facilities and
improvements shall be provided by the development
whenever additional storm water runoff from the develop-
ment would adversely affect any off-site property or
would overload an existing drainage facility, whether
natural or man-made. Where storm water runoff from
three or more acres has been collected or concentrated
to one point, it shall not be discharged onto adjacent
properties, except into existing creeks, channels, or
storm drains, unless drainage or flowage easements are
obtained for those properties. If the developer cannot
obtain the necessary easements to make required off-site
drainage improvements, upon the request of the developer
after compliance with the provisions of this Code, the
City may bring condemnation proceedings to obtain the
offsite drainage easements.
3. Permeable Area Storm Water Control. Any development may
provide for storm water runoff by reserving a sufficient
amount of land within the development for landscaping,
green space, or other permeable areas, excluding
detention facilities, if sufficient to alleviate the
need for particular drainage facilities or improvements.
The city Engineer may require the submission of any
drainage computations necessary to determine that the
permeable areas reserved are adequate in size, design,
or location so as not to require particular drainage
facilities or improvements. If a plat is approved on
that basis, the permeable areas proposed to be reserved
shall be shown on the plat or otherwise referenced by
the plat, in the manner specified by the City Engineer.
No building, structures, or other impermeable improve-
ments shall be constructed or installed in the permeable
areas so designated on the final plat.
4. Detention Facilities. Publicly dedicated detention
facilities may be used to reduce peak discharges where
conditions prevent conveying storm water to an adequate
discharge point or studies show that off-site structural
facilities will not mitigate hydraulic effects more
efficiently. On-site detention facilities shall be a
minimum size of one acre. All detention facilities
shall comply with the design criteria of this Division.
A development may provide for drainage by participating
in the design and construction of a regional detention
facility. Detailed engineering studies of the entire
basin shall be required to insure that the timing of
peak flows has not been altered to create higher peak
flow elsewhere in the basin. Detention facilities may
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be constructed in phases, if phased so as to provide for
the timely needs of the development.
5. Floodplains. Where these regulations would require a
development to make any drainage improvements in or
adjacent to a floodplain in order to provide for the
ultimate base flood, the development may, in lieu of
making the required improvements, restrict development
in the area that would be subject to flooding by the
ultimate base flood because of the failure to provide
for the drainage improvements. In such cases the area
to be left undeveloped shall be dedicated to the public
as a drainage easement on the final plat.
6. Floodway Frinqe Areas. Where any development would fill
a floodway fringe area where the floodway has not been
designated on the Flood Hazard Boundary Map, the
necessary engineering studies to show the limits of the
floodway shall be submitted. If the floodway fringe
area is not proposed to be filled, the area within the
floodplain which will be necessary to provide for the
drainage needs of the development shall be dedicated to
the public as a drainage easement on the final plat.
7. Floodways and Improvements.
a. Generally, floodways serving drainage areas larger
than one square mile in area and which are still
functioning primarily in a natural and adequate
state shall not be altered or improved to provide
for the drainage needs of a development, unless
there is no other reasonable means of method to
provide for such drainage.
b. As part of the required improvements, all debris,
small brush, vines, and other obstructions shall be
cleared once from that portion of any channel
located within or on the perimeter of the develop-
ment as directed by the City Engineer, prior to the
connection of any utilities for any building within
a development. A development may also be required
to provide clearing of off-site floodways to the
extent necessary to adequately receive or convey
storm water runoff from the development, based on
the roughness coefficient approved during the design
process for the final plat.
c. Developments discharging storm water runoff into a
floodway shall provide supplemental vegetation, on
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and off-site, when necessary to preserve or restore
any disruption to the natural state. The vegeta-
tion planted shall be coastal bermuda grass or
similar vegetation proposed by the developer and
approved by the City Engineer. The vegetation
requirement shall apply to any portion of any
floodway, on-site or off-site, which would be
affected by runoff from the development.
d. Any approvals necessary for completion or occupancy
of the development may be withheld, including
utility connections and Certificates of Occupancy,
unless and until the clearance and vegetation
requirements for floodways are satisfied.
8. Site Erosion Control. To minimize erosion resulting
from the removal of vegetation and to reduce the
introduction of erosion materials into the storm
drainage systems, all developments and any person
undertaking any development activity shall make use of
erosion and sediment control devices in accordance with
the recommendations of the Drainage Manual, as directed
by the City Engineer. The erosion and sediment control
devices shall be installed and thereafter maintained
until sufficient vegetation cover has been provided or
been replaced to control erosion and sediment, as
directed by the city Engineer.
9. Payment in Lieu of Improvements. Any development
required to provide drainage facilities or improvements
in accordance with this Code may elect to pay to the
City the total construction cost of the required
facilities or improvements, excluding engineering and
design cost, when:
a. The city's approved Capital Improvement Plan
proposes to provide, within two years of the date
the required improvements are to be undertaken, for
the same or similar drainage improvements that would
make the drainage improvements required by the
development unnecessary, and
b. Failure to provide the drainage improvements at the
time of development would not adversely affect the
development or any off-site properties, as
determined by the City Engineer.
The payment herein allowed shall be made prior to
beginning any construction of the development. If the
money paid to the City is not used for the required
improvements within five years of payment, the funds
shall be returned to the person making the payment.
D. GENERAL DESIGN STANDARDS.
1. Drainage Manual Adopted. The city of Denton Drainaqe
Design criteria (1990), a copy of which is on file with
the city Engineer, is adopted by reference as a part of
the regulations and standards of this Code. In addition
to meeting the requirements expressly set out in this
Code, all drainage systems shall comply with the design
standards and requirements contained in the latest
edition of the Drainage Criteria adopted by ordinance.
Where there is any conflict between a provision set
forth in this Code and a provision of the Drainage
Criteria, the provision of this Code shall apply.
2. Drainaqe Computation Data. Design standards for drain-
age facilities and improvements shall be based on
hydraulic and hydrologic computation data submitted and
approved by the city Engineer prior to submission of the
final plat to the Commission. The city Engineer may
specify the form and manner in which the necessary data
is to be submitted.
3. Separation of Storm Water and Sanitary Sewer Systems.
Storm water and sanitary sewer systems are intended to
be used and maintained as separate systems. Drainage
facilities shall be designed so as not to connect,
direct, or allow storm water, whether by pool backwash
or otherwise, into the sanitary sewer system.
4. Street Access Crossing Channels. No development shall
be designed to access a public street across a channel
without providing adequate clearance for the channel
under design storm conditions as required by the
Drainage Manual. Bridges crossing channels serving
drainage areas greater than one (1) square mile in area
shall have one foot of freeboard between the design
water surface and the lowest beam of the bridge.
Bridges crossing channels serving drainage areas less
than one (1) square mile in area shall have one foot of
freeboard between the design water surface and the
lowest top of road elevation of the bridge.
5. Channel Requirements. Channel regulations and
improvement requirements shall be based on the amount
and concentration of the storm water runoff from the
development. All developments shall provide for the
permanent improvement and modification of existing
drainage channels as necessary to serve the development,
subject to and in accordance with the following:
a. Channels which serve as floodways serving drainage
basins larger than one square mile shall be
maintained in a natural state as provided for in
these regulations. Undeveloped branches of natural
channels and creeks of local drainage systems may be
allowed to remain in a natural state if maintenance
and hydraulic considerations do not require
improvements.
b. Channels of local drainage systems serving a
development shall be fully lined with concrete to a
level at least one foot above the water surface
resulting from the 25-year frequency storm.
c. If a development provides for the reservation of
permeable areas as provided for in this Division so
that a fully lined channel is not necessary to
adequately convey storm water runoff, the channel
shall be provided with a concrete pilot channel
meeting the specifications of the Drainage Manual.
d. The minimum grade allowed on an outfall channel or
ditch shall be 0.3 foot per 100 feet for concrete
lined channels and 0.5 foot per 100 feet for grass
lined channels.
e. Improved channels shall have one (1) foot of
freeboard above the 100-year flood.
f. The design for all open channels shall be based on
geotechnical investigations, unless determined to be
unnecessary by the City Engineer.
6. Channel Access Roads and Ramps. Any development which
makes use of any channel within or on the perimeter of
the development to provide for storm water runoff may
be required to provide adequate access roads and ramps
for the channel for maintenance purposes as follows:
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a. For all channels serving drainage basins larger than
one square mile, access ramps shall be provided
where the channel intersects any public roadway.
b. For all improved, unlined channels serving basins
less than one square mile, access to channels shall
be provided by one of the following methods, as
approved by the City Engineer:
(1) By constructing a flexible base road or
equivalent.
(2) By providing a combination of the bottom
access and an access road on one side of the
channel, if the depth of the channel will
allow maintenance from the access road.
(3) For channels exceeding a depth of four feet
(4') and 4: 1 side slopes, an access road
shall be provided on both sides of the
channel where none of the other methods
would be sufficient to provide for main-
tenance of the channel.
c. To insure adequate access, all lined and pilot
channels shall have a minimum bottom width of ten
(10) feet and shall be provided with access ramps
located as directed by the city Engineer. Access
ramps shall not be less than twelve (12) feet wide,
with a minimum cross grade of 6:1. All access roads
shall be located within a dedicated easement of the
size required by this Division.
7. Major Drainaqe Systems. Major drainage systems are
intended to provide for conveyance of major flooding and
usually consist of channels, detention reservoirs,
street rights-of-way and overflow swales. Major drain-
age systems shall be designed to convey the 100-year
flood and may be planned as an integral, useable part of
a development.
8. Minor Drainaqe Systems. Minor drainage systems are
intended to provide for conveyance of nuisance type
flooding and usually consist of streets, storm drain
inlets and pipes. Minor drainage systems shall be
designed to convey the 10-year frequency flood. Addi-
tional capacity requirements may be required where there
are flow width restrictions or other special conditions.
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9. Maximum and Minimum Times of Concentration. Drainage
systems for all developments shall be designed so as to
comply with the minimum and maximum time of concentra-
tion for the proposed land use, as specified in the
Drainage Manual. In cases where it is evident, as
determined by the city Engineer, that the actual time of
concentration is less than the minimum specified in the
Drainage Manual, a shorter time of concentration may be
required.
10. Tailwater Considerations. Proposed storm drains may
discharge into existing watercourses shown on the
current Flood Insurance Rate Map. The tailwater eleva-
tion used in hydraulic calculations of the proposed
storm drain system shall consider the water surface
elevation of the watercourse for the same design fre-
quency as the storm drain system. All storm drainage
systems shall be designed in reference to the water-
course flood elevation at the time the storm drainage
discharges into the watercourse, except when the
watercourse into which the storm drain discharges is
located outside Zone X of the Flood Insurance Rate Map,
the tailwater elevation of the proposed storm drain
system shall be the water surface elevation of the
watercourse when its peak discharge occurs.
11. Lot Drainaqe. Generally, each lot shall be designed or
graded to direct storm water into an abutting street,
alley, channel, or inlet. If drainage is provided in
the rear of any lot by an alley or closed storm drainage
system consisting of inlets and pipes, the alley or
drainage system shall be designed for the 100-year
flood. Where it is not practical to provide abutting
drainage facilities for each lot, drainage facilities
shall generally be required whenever the storm water
runoff from more than two lots used for one or two-
family dwellings is directed across a third residential
lot, or whenever the facilities are necessary to avoid
an adverse effect on any other lot. It shall be unlawful
for any person to fill, modify, or otherwise obstruct
any public drainage easement designed or used as an
overflow channel or structure.
E. DESIGN CRITERIA.
1. Desiqn Flood Frequencies. The following listed
facilities shall be designed to handle the flood
frequencies indicated:
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Facility Flood Frequency
(years)
Street Capacity and Enclosed
Pipe System (if needed) 10
Driveway Culverts and Roadside Ditches 25
Street Right-of-Way 100
Improved Channels 100
Culverts 100
Bridges 100
Floodways 100
2. Street Drainaqe Requirements.
a. The permissible water spreads for streets are based
on the 10-year flood. All streets shall be capable
of conveying a 100-year flood without water
exceeding the right-of-way limits. The spread
limits listed below shall apply to the following
streets and facilities:
Permissible Water Spread - 10-Year Flood
Arterial Street
(divided/undivided) 1 lane open in each
direction.
Collector Street 1 lane open
Local/Residential Street Top of Curb
b. The allowable drainage flow across street
intersections for the 10-year flood shall be as
follows:
Street Classification Cross Flow
Arterial (divided and undivided) None
Collector None
Local/Residential:
Inlets at intersection 10% of inlet
capacity.
No inlets at intersection Gutter flow of
4" or less.
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c. Inverted crown sections are permitted only in
alleys.
d. Street crowns shall be reduced for approximately one
hundred (100') feet on each side of valleys, and
only one valley crossing for each street shall be
used at an intersection.
e. For streets with culverts or bridges, an emergency
overflow shall be provided to contain the 100-year
flood without encroaching into an area in which a
building could be constructed. Water shall not
encroach on the building side of the building
setback line.
3. Pipe System Requirements.
a. Storm drain systems capable of conveying the 10-year
frequency flood are required when water spread and
intersection cross flow limits are exceeded. Closed
pipe systems shall be required for discharges up to
and including the equivalent flow of a 48-inch pipe,
unless the grade of the natural ground is less than
0.5%, then an enclosed pipe system shall be required
for discharges up to and including 100 c.f.s.
b. The minimum velocity with the pipe flowing full
shall be three (3) feet per second.
c. The minimum storm drain pipe diameter shall be
eighteen (18) inches.
d. Pipe diameters shall not normally decrease
downstream.
e. Pipe soffits at changes in pipe sizes should be set
at the same elevation.
f. Vertical curves in the conduit will not be
permitted, and horizontal curves will be permitted
only with the approval of the City Engineer.
g. Manholes shall be placed at the connection of two
(2) or more laterals, at pipe junctions having pipe
sizes greater than twenty-four (24") inches, at
alignment changes and at the beginning of the storm
drain system. Maximum manhole spacing shall be as
follows:
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Pipe Size Maximum Spacinq
(inches) (feet)
18 - 36 600
42 - 60 1,000
Larger than 60 No limit
4. Driveway Culverts. All driveway culvert construction
shall be inspected by the city during construction and
shall meet the following requirements:
a. Culverts shall be of sufficient size to carry the
expected water flow within the channel; be made of
approved classes of reinforced concrete pipe (RCP)
or corrugated metal pipe (CMP); and shall be jointed
together properly by materials approved by the City
Engineer.
b. The safety standards for ends to driveway culverts
adopted by the Texas Department of Highways and
Public Transportation (TDH&PT), as amended, on file
in the office of the City Engineer, are hereby
adopted by reference to the following extent:
(1) Culverts of twenty-one (21) inches in size or
larger shall have 6:1 safety end sections. The
ground around the end section shall have a grade
of 6:1.
(2) Culverts less than twenty-one (21") inches in
size shall have Type B end sections (Texas
Highway Department Drawing CH-11). Type B
headwalls and guardrails may be used for pipes
larger than twenty-one (21") inches, when
approved by the City Engineer.
(3) Culverts of thirty (30") inches or less do not
require safety pipe runners. Culverts above
thirty (30") inches shall meet THD & PT
standards.
5. Detention Ponds. All detention ponds shall be in
compliance with any applicable design requirements of
any State or Federal law or regulations, as amended,
including the regulations of the Texas Water Commission,
or its successor agency. The following requirements and
design standards shall apply to detention ponds to the
extent they do not conflict with any applicable Federal
or State laws or regulations, as amended:
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a. The 100-year flood shall be used to determine the
volume of detention storage required. Detention
facilities shall be designed so that any additional
runoff generated by the proposed development will
not increase the amount of original discharge for
storm frequencies from the 5-year to the 100-year
flood.
b. The Modified Rational Method shall be used to
construct runoff hydrographs for detention storage
design when the contributing drainage area is 200
acres or less. The procedures outlined in Soil
Conservation Service Technical Release No. 20 (TR-
20), or in the Corps of Engineers Flood Hydrograph
Package (HEC-1), shall be used to determine runoff
hydrographs for detention storage design when the
contributing drainage area exceeds 200 acres. The
City Engineer may approve the use of other methods
for runoff hydrographs when appropriate.
c. An emergency spillway or overflow area shall be
provided at the maximum 100-year pool level and
shall be capable of conveying discharges as required
by the regulations of the Texas Water Commission, or
its successor agency. The spillway shall be
constructed of concrete, unless alternative
materials are approved by the City Engineer.
d. Any outflow structure which conveys water through
the embankment in a conduit shall be reinforced
concrete designed to support the external loads.
The conduit shall withstand the internal hydraulic
pressure without leakage under full external load or
settlement and must convey water at the design
velocity without damage to the interior surface of
the conduit.
e. The outflow structure of a detention basin
discharging water into any natural stream or unlined
channel shall discharge at a non-erosive rate,
unless approved erosion protection is provided in
accordance with the Drainage Manual.
f. Detention basins resulting from excavation shall
provide positive drainage in accordance with the
Drainage Manual. The side grade for any excavated
detention basin, which is not in rock, shall not
exceed 4:1.
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g. Earthen embankments used for water impoundments must
be constructed according to specifications for fill
material and be designed based upon geotechnical
investigations of the site. The minimum crown width
of the embankment shall be twelve (12) feet.
h. Detention basins shall be designed with adequate
ingress and egress to allow for regular maintenance,
including periodic desilting and debris removal.
Detention basins designed for permanent water
storage must include dewatering facilities to allow
for maintenance. Detention basins designed to serve
drainage areas of 320 acres or more must include a
desilting basin in the upstream pool area.
i. Security fencing of a minimum height of six (6')
feet shall encompass the detention storage area if
the velocity, depth, or slopes create a potentially
dangerous condition. The fence shall be designed so
as to allow access for maintenance and so as not to
restrict stormwater flow into or out of the
detention basin.
F. EASEMENTS.
In addition to any other provisions of this Code relating to
easements for public improvements, the following requirements for
easements for public drainage improvements, channels, and
facilities required for any development by this Division shall
apply:
1. All public drainage systems and facilities which are not
to be included within an existing or proposed public
street right-of-way shall be located within easements to
be dedicated to the City and shall have adequate access
to a public street. Prior to acceptance of any public
drainage facilities, all easements within which the
facilities are located shall be cleared of all
buildings, structures, fences, or other obstacles that
would interfere with access to the easements.
2. Easements for closed drainage systems shall meet the
following minimum standards, unless special
circumstances warrant additional or reduced easements,
as determined by the City Engineer:
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Pipe Size Minimum Easement Width
36" and under 15 feet
42" through 54" 20 feet
60" through 66" 25 feet
72" and above 30 feet
3. Where an access road is required adjacent to a channel,
an easement of a minimum width of fifteen feet (15')
shall be provided.
4. Utilities shall not be located within any existing
drainage easement, unless it is also designated for
utility use. No utilities shall be located in any lined
channel in such a way as to interfere with maintenance
of or access to the channel.
5. A drainage easement shall be provided for the area
within a required outfall channel or ditch to the point
where the flowline "day lights" on natural grade.
6. To provide for maintenance, a drainage easement shall be
provided at least twenty-five feet (25') beyond any
outfall headwall.
G. FLOOD DAMAGE PREVENTION.
All developments regulated by this Code shall be subject to
and comply with any applicable provision of the flood damage
prevention ordinance, presently codified in Chapter 10-1/2 of the
Code of Ordinances, as amended, and the following requirements:
1. Minimum Finished Floor Elevation. Minimum finished
floor elevations for proposed development areas shall be
eighteen (18") inches above the 100-year flood elevation
based on encroached stream conditions as contained in
the appropriate flood insurance study. If a one hundred
year water surface elevation for encroached stream
conditions has not been determined by a flood insurance
study, the finished floor elevations in the development
area shall be eighteen (18") inches above the lO0-year
flood elevation based on ultimate watershed development
conditions.
2. Floodway and Floodplain Modification and Permitting. No
land shall be modified in any floodplain or floodway
until the drainage modification plans have been reviewed
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and a permit issued by the City Engineer in accordance
with Chapter 10-1/2 of the Code of Ordinances, as
amended.
SECTION II. That paragraphs (a) and (b) of section 10 1/2-17
of the Code of Ordinances are amended to read as follows:
(a) Residential construction. New construction or
substantial improvement of any residential
structure shall have the lowest floor,
including basement, elevated eighteen inches
(18") above the 100-year water surface
elevation based on encroached stream conditions
in the appropriate flood insurance study or if
unavailable 100 year flood elevations based on
ultimate development watershed conditions. A
registered professional engineer, architect, or
land surveyor shall submit a certification to
the City Engineer, in accordance with section
10 1/2-14 (a), that the standard of this
subsection is met.
(b) Nonresidential construction. New construction
or substantial improvement of a commercial,
industrial or other nonresidential structure
shall have the lowest floor, including any
basement, elevated eighteen inches (18") above
the 100-year water surface elevation based on
encroached stream conditions as shown in the
appropriate flood insurance study. If the
flood insurance study does not include the
property the required 100-year water surface
elevations shall be based on ultimate
development watershed conditions. Attendant
utility and sanitary facilities shall be
floodproofed so that below the base flood level
the structure is water tight with walls
substantially impermeable to the passage of
water and structural components have the
capability of resisting hydrostatic and
hydrodynamic loads and the effects of buoyancy.
A registered professional engineer, architect,
or land surveyor shall submit a certification
to the City Engineer, in accordance with
section 10 1/2-14 (a), that the requirements of
this subsection are met.
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SECTION III. That if any provision of this ordinance or
application thereof to any person or circumstance is held invalid
by any court, such holding shall not affect the validity of the
remaining portions of this ordinance, and the City Council of the
city of Denton, Texas, hereby declares that it would have enacted
such remaining portions despite any such invalidity.
SECTION IV. That any person violating any provision of this
ordinance as it applies to property located within the City of
Denton, shall, upon conviction, be fined a sum not exceeding
$500.00. Each day that a provision of this ordinance is violated
shall constitute a separate and distinct offense.
SECTION V. That this ordinance shall become effective
fourteen (14) days from the date of its passage, and the City
Secretary is hereby directed to cause the caption of this ordinance
to be published twice in the Denton Record-Chronicle, the official
newspaper of the City of Denton, Texas, within ten (10) days of the
date of its passage.
PASSED AND APPROVED this the ~/~ day of ~ , 1990.
ATTEST:
J WR LTE S, CiTY SECRETARY
APPROVED AS TO LEGAL FORM:
DEBRA A. DRAYOVITCH, CITY ATTORNEY
work,drain5
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