HomeMy WebLinkAboutORD 1985-045 CITY OF GRAPEVINE, TEXAS
ORDINANCE NO. g5-45
AN ORDINANCE OF THE CITY OF GRAPEVINE, TEXAS A-
MENDING APPENDIX E-CONSTRUCTION STANDARDS OF THE
CODE OF ORDINANCES OF THE CITY BY AMENDING ARTICLE
I, ITEM 3 RELATING TO STORM DRAINAGE SYSTEMS; PRO-
VIDING A SEVERABILITY CLAUSE; PROVIDING A PENALTY NOT
TO EXCEED TWO HUNDRED DOLLARS ($200.00) AND A SEPA-
RATE OFFENSE SHALL BE DEEMED COMMITTED EACH DAY
"� �" DURING OR ON WHICH A VIOLATION OCCURS OR CONTINUES;
DECLARING AN EMERGENCY AND PROVIDING AN EFFECTNE
DATE.
�.�
NOW THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF THE
CITY OF GRAPEVINE, TEXAS:
Section 1. That Appendix E-Construction Standards of the Code of
Ordinances of the City of Grapevine, Texas (the "City") is hereby amended in the
following particulars, and that all other Sections, Subsections, Paragraphs,
Sentences, Definitions, Phrases and Words of said Code of Ordinances are not
amended but shall remain intact and are hereby ratified, verified, approved and
affirmed.
A. That Appendix E-Construction Standards of the Code of Ordinances
is amended by amending Article I, Item 3 thereof to read as follows:
See Attached Exhibit "A".
Section 2. If any section, article, paragraph, sentence, clause, phrase or
word in this ordinance, or application thereto any person or circumstance, is held
invalid or unconstitutional by a Court of competent jurisdiction, such holding
shall not affect the validity of the remaining portions of this ordinance; and the
City Council hereby declares it would have passed such remaining portions of the
. ordinance despite such invalidity, which remaining portions shall remain in full
force and effect.
'�° Section 3. Any person violating any of the provisions of this ordinance
shall be deemed guilty of a misdemeanor and upon conviction thereof shall be
subject to a fine in a sum not to exceed One Thousand Dollars ($1,000.00) for
each offense and a separate offense shall be deemed committed upon each day
during or on which a violation occurs.
Section 4. The fact that the present ordinances and regulations of the
City of Grapevine, Texas are inadequate to properly safeguard the health,
safety, morals, peace, and general walfare of the inhabitants of the City of
Grapevine, Texas creates an emergency for the immediate preservation of the
public business, property, health, safety, and general walfare of the public which
requires that this ordinance become effective from and after the date of its
passage and it is accordingly so ordained.
PASSED AND APPROVED this the 3rd day of September, 1985.
G��.%��� �
Mayor, City of Grapevine, Texas
ATTB�T`:
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Lt.1�.�2-„�J L
City ecretary, City of Grapevine, Texas
APPROVED AS TO FORM:
� -
City Attorney, City of Gr ine, Texas
EXHIBIT "A" TO
ORDINANCE NO. 85-45
GRAPEVINE CODE
�;,_,
A.rt. I, Item 3
�;.,,
Item 3. Storm drainage system.
3.1. General:
Stonn drainage facilities shall include all elements of a drainage system
consisting of streets, alleys, stonn drains, channels, culverts, bridges,
swales, and any other facility through which or over which storm water
flows; all of which the city must have a right in, either in the form of a
dedicated right-of-way or floodway and drainage easements.
Street drainage facilities within new developments shall be designed so
that stonn water runoff which results from a design stonn of one hundred
(100) years or greater frequency is contained within the available
right-of-way and/or drainage easements. The capacity of the street and
rightrof-way and/or easements and the stonn drain pipe acting in
ccgnbination must be designed for a capacity to safely contain stonn water
from a design storm of 100-year frequency, without flood damage to nearby
occupied structures.
�,.,
Drainage facilities shall be designed and constructed at such locations and
of such size and diu�nsions to adequately serve the subdivision and the
contributing drainage area above the subdivision. The subdivider shall
«u -• provide all the necessazy ease.n�nts and rightrof-way required for drainage
structures including storm drains and open or lined channels. Easement
widths for storm drain pipe shall not be less than fifteen (15) feet and
easement widths for lined channels shall be at least fifteen (15) feet
wider than the top of the channel and unlined channel easements shall be at
least thirty (30) feet wider than the top of the channel.
The design flows for the drainage system shall be calculated by the
rational method in accordance with standard engineering practice and in
accordance with the requirements set forth herein. Curbs, inlets,
manholes, etc. , shall be in accordance with the standard details.
Materials and construction procedures shall confozm with the requirements
of the standards for construction [Article II of this append�] .
The subdivider shall provide plans and specifications for all drainage
structures. Underground drainage pipes shall be used to accc�nodate flows
up to and including the equivalent capacity of a forty-eight-inch pipe.
For flaws in excess of the capacity of a forty-eight-inch pipe, lined
channels may be used in lieu of pipe. Channel bottan shall be concrete and
walls as approved by the city. For flaws in excess of the capacity of an
eighty-four-inch pipe, unlined channels may be used. Unlined or partially
lined channels will not be accepted by the city for maintenance purposes
'� �F unless a fifteen (15) foot roadway on both sides of the channel is
included and a mixture of Rye, (Buffalo) and Coastal Bermuda or other grass
requiring m;n;mal amounts of water for growing is established in the
easement area. MinimLun side slope shall be 3:1.
(1)
The design, size, type and location of all storm drainage facilities shall
be subject to the approval of the city. The requirements set forth herein
� are considered a mini.m�un requirem�nt. The subdivider and his engineer
shall bear the total responsi.bility of the adequacy of design. The
approval of the facilities by the city in no way relieves the subdivider of
��:,:�
this responsibility.
3.2. Storn. drainage design criteria:
3.2.1. General: For all flood control systems of less than one thousand
(1,000) acres, the rational method of co�nputing runoff will be used.
The method is expressed by the follow:ing equation:
Q = CIA, where
Q = the storm flaw rate at a given point
C = a coefficient of runoff (the ratio of rainfall to peak runoff)
I = the average intensity of rainfall in inches per hour for a
period equal to the time of flow from the farthest point of the
drainage area to a poi.nt under consideration
A = the area in acres that is tributary to the point of design
Runoff Coefficient C
�''.* Adopted runoff
Typ� of area or land use coefficient C
�"`� Parks or open areas 0.30
Residential (lots over one acre) 0.35
Residential (lots one acre or less) 0.50
Townhouses - Duplexes 0.60
Industrial 0.70
Apartn�ents 0.75
Business 0.80
Mercantile district 0.90
Retainage ponds are not acceptable for containment of design flaas.
3.2.2. Time of concentration:
The time of concentration is defined as the longest time, without
unreasonable delay, that will be required for a drop of water to flow
fran the upper limit of a drainage area to the point of concentration.
The tim.e of concentration to any point in a storm drainage system is a
canbination of the inlet time and the ti.me of flow in the drain. The
inlet time is the time for water to flow over the surface of the
ground to the storm drain inlet. The shortest inlet time to be
allowed for impervious areas on steep slopes shall be five (5)
�£�� minutes.
Under average conditions the time of concentration to the upstream and
;�;, of a drainage system shall coincide with the table, Minilrnun Inlet Time
of Concentration.
(2)
�:
� Under unusual circ�n.stances which will produce times of concentration
in excess of those shown in the folla�ing table, the time
concentration shall be detezmined through the use of Fiqure I,
"�"'°� Non�ograph for Time of Concentration. The nomograph, h�wever, sh�uld
be used in a judicious maruzer; otherwise unrealistic ti.�s of
concentration may result. Scane cautions to be exercised in the use of
this nonx�graph are as follaws:
a. The path along which the time of concentration is determined,
should be representative of the drainage areas as a whole. On
some irregularly shaped drainage areas it is possible to find the
time of concentration along a particular path which is
representative of only a small portion of the drainage area.
This time of concentration may greatly exceed the time
concentration which is more representative of the drainage area
as a whole.
b. Overland flow shall be considered channelized at such time as the
distance traveled exceeds two hundred (200) feet.
Minimum Inlet Time of Concentration
Type of area Miniirnun inlet time
Parks and open areas 20 mi.nutes
� , Residential, single-family 15 minutes
Residential, multifamily 10 minutes
(Townhouses, duplexes, apartrnents)
* ` Industrial 10 minutes
Business 10 mi.nutes
Mercantile district 5 minutes
Since urbanization is anticipated on all drainage areas, all
improv�lts shall be designed for the case of full watershed
development.
When the watershed in question is basically undeveloped, the engineer
shall atte�t to anticipate future fully developed conditions and
stonn sewer locations and take the resulting velocities into
consideration when determining the time of concentration.
3.2.3. Design stozm frequencies: The design storm frequencies shall be in
accordance with the tabulation belaw:
Design Stonn Frequencies (Minitrnun)
Area or facility Frequency
Enclosed pipe system 5 years
� � Enclosed pipe system and streets and R.O.W. 100 years
� (3)
� Channels and creek improvements (1) 100 years
Ctiilverts and small bridges 100 years
�:�
Tar�e bridges (2) 100 years
Drainage easements or floodways between 100 years
building lines (3)
S�np conditions 100 years
(1) Channels and creek improvements shall have a one-foot freeboard
within the channel,
(2) Tarc�e bridges have a total span greater than fifty (50) feet.
(3) Minim�un slab elevation - one-foot freeboard where fences could
be constructed to constrict overland flaws the 100-year design stonn
flows shall be carried underground.
The relationship between rainfall intensity-duration-frequency is set
forth in Figure II. These curves have been developed using Technical
Paper No. 40, Rainfall Frequency Atlas of the United States, by the
U.S. Weather Bureau. These curves shall be used in the design of all
storm drain facilities.
3.2.4. Pemu.ssible spread of water:
�, ,,A 3.2.4.1. General: Spread of water refers to the amount of water that
may be allowcd t oollect in streets during a storm of specific
design frequency. In order that excess storm water will not collect
� ,- in streets or thoroughfares during a storm of the design frequency,
the follaving spread of water values shall be used for the various
types of streets.
3.2.4.2. Major thoroughfares (divided) :
3.2.4.2.1. Permissible spread of water: The permissible spread of
water in gutters of major divided thoroughfares shall be
limited so that one traffic lane on each side remains clear.
Gutter flow shall be based on a storm of ten-year design
frequency. The flaas fran a 100-year frequency storm shall
be contained within the street right-of-way.
3.2.4.2.2. Conditions: Inlets shall preferably be located at
street intersections, at low points or grade or where the
gutter flow exceeds the permissible spread of water
criteria and as directed by Director of Public Works.
Inlets shall be located, when possible, on off
side streets or alleys when grades permit. The standard
gutter depression of five (5) inches shall be used so long
as the depression does not fall within a traffic lane. In
no cases shall the gutter depression at inlets exceed the
standard. In super elevated sections, inlets placed against
the center medians shall have no gutter depression and shall
intercept gutter flow at the point of vertical curvatures to
'� � prevent flaw fram crossing the thoroughfare. Unless
expressly approved by the Director of Public Works,
storm waters will not be allowed to cross major
'�` thoroughfares on the surface in valley gutters or othezwi.se.
(4)
3.2.4.3. Major thoroughfares (not divided) :
3.2.4.3.1. Permissible spread of water: The permissible spread of
°�' water in gutters of major undivided thoroughfares shall be
limited so that two (2) traffic lanes will rem�ain clear
during the 10-year design storm. The flaws from a 100-year
�� frequency stonn shall be contained within the rightrof-r.aay.
3.2.4.3.2. Condition: Inlets shall preferably be located at
street intersections, law points of grades, or where the
gutter flow exceeds the perntissible spread of water
criteria and as directed by the Director of Public Work�.
Inlets shall be located, when possible, on off
side streets, or alleys when grades permit. The standard
gutter depression of five (5) inches shall be used so long
as the depression does not fall within a traffic lane. In
no case shall the gutter depression at inlets exceed the
standard. Depressed inlets will be permitted i.n a standard
parking lane. Where inlets are required in traffic lanes,
inlets with no depression or recessed inlets shall be used.
In super elevated sections, intercept gutter flow at the low
point of P.V.C. or P.V.T. to prevent flow frcan crossing
thoroughfare.
3.2.4.4. Collector streets:
3.2.4.4.1. Permissible spread of water: The pezmi.ssible spread of
water in gutters of collector streets shall be limited so
that one standard lane of traffic will remain clear during
the 10-year design storm. The flaws from a 100-year
frequency storm shall be contained within the rightrof-way.
'� �' 3.2.4.4.2. Conditions: Inlets shall preferably be located at
street intersections, low points of grade or where the
�, ,� gutter flow exceeds the perm.issible spread of water
criteria and as directed by the Director of Public 4�orks.
Inlets shall be located, when at all possible, on
off side streets or alleys where grade pezmits. Inlets with
the standard gutter depression of five (5) inches shall be
used. In no case shall the gutter depression at inlets
exceed the standard.
3.2.4.5. Minor streets (residential) :
3.2.4.5.1. Permissible spread of water: The pezmi.ssible spread of
water in gutters for minor streets shall be limited by the
height of the curb for standard street sections for a 5-year
design storm without storm sewer. The flows from a 100-year
frequency storm shall be contained within the rightrof-way.
The permissible spread of water in gutters for minor
streets with split sections shall be limited by the height
of the curb for low gutter flow and the depth of flow at the
face of the curb corresponding to the crown elevation for
high gutter flaa.
3.2.4.5.2. Conditions: Inlets sr.all be located at street
intersections, low points of grade or where the gutter flow
exceeds the permissible spread of water criteria. Inlets
with the standard gutter depression of five (5) inches shall
�"`"`" be used in all cases unless special grading problems are
involved. In no case shall the gutter depression at inlets
exceed the standard.
(5)
� 3.2.4.6. Alleys:
3.2.4,6.1. Permissible spread of water: The permissible spread of
water in alleys shall be limited to confining the flow to
„�.,t�; w�ithin the paved area with inverted crowns and be concrete.
The flcws from a 100-year frequency storm shall be contained
�eithin the paved area.
3.2.5. Flaw in storm drains and their appurtenances, velocities and grade:
3.2.5.1. Miniirnnn grades: Stonn drains should operate with velocities
of flaa sufficient to prevent excessive deposits of solid
m�terials; othezwise objectionable clogging may result. The
controlling velocity is near the bottam of the conduit and
considerably less than the mean velocity of the sewer. Storm
drains shall be designed to have a mini.miun mean velocity flowing
full of two and five-tenths (2.5) feet per second. The follawing
table indicates the minimtun grades for both concrete pipe (n =
0.013) and for corrugated metal pipe (n = 0.024) , flawing at two
and five-tenths (2.5) feet per second.
Miniirnun Grades for Stonn Drains
Pipe size Concrete pipe
(inches) slope ft,/ft.
15 0.0023
'�" ' 18 0.0018
21 0.0015
� , 24 0.0013
2� 0.0011
30 0.0009
33 0.0008
36 0.0007
39 0.0006
42 0.0006
45 0.0005
48 0.0005
54 0.0004
60 0.0004
66 0.0004
72 0.0003
78 0.0003
84 0.0003
96 0.0002
3.2.5.2. Discharge of storm drain pipes discharging into lakes shall
be set at an elevation such that the top of the pipe shall be
belaw the nornial pool level of the lake. Where storm drain pipes
discharge in watercourses the invert of the pipe shall be at the
same grade as the watercourse. Adequate riprap or other erosion
�a�" protection shall be provided, All storm drain pipes in street
and alleys shall be installed at a depth sufficient to permit all
water lines to pass over them when the water line has a minim�n
cover of three (3) feet.
(6)
3.2.5.3. Manholes: Storm drain manholes shall be located at intervals
not to exceed. four hundred (400) feet for twenty-four (24) inches
� in diameter or smaller. In general, manholes should be located
at street intersections, storm pipe junctions or changes of grade
and changes of alignment. Storm drain manholes for pipes greater
w� than twenty-four (24) inches in diameter shall be located at
points where design indicates entrances into the pipe is
desirable. In no case shall the distance between m�-�nholes be
greater than eight hundred (800) feet.
3.2.5.4. Lateral lines: The mininn�n size storm drain line frcan inj.et
box to the collector lines shall be eighteen (18) inches.
3.2.5.5. Hydraulic grade lines: When utilized, shall be established
such that the grade line is maintained a miniirnun of 2.0 feet
belaw the gutter elevation at all inlets.
3.2.6. Drainage ditches or channels: All channels shall have a minimian
bottom width of four {4) feet and a depth based on maxinn,mt flaw. Side
slopes of lined channels shall not be steeper than one foot of rise to
two (2) feet of horizontal distance; unlined channels shall have a 3:1
side slope with provision for a fifteen-foot roadway on both sides of
the channel. All channels shall be designed for a miniimam of one foot
of freeboard at maximtun design flow. Channels discharging into
watercourses shall have the same invert level as the watercourse.
3.2.7. General: In cases when a 100-year storm design utilizes the carrying
capacity of private property between building lines, the minimtun slab
elevations shall be established (with 1 foot freeboard) to prevent
�`"� flood damage.
�,,,,� 3.2.8. Downstream Property Owners Pezmission: There are three (3) major
drainage basins in Grapevine: Denton Creek (Grapevine Lake) , Big Bear
Creek, Little Bear Creek. The dawnstream property cx�mers between the
development and Big Bear Creek or Corps of E.hgineer property or Denton
Creek or the City Limit Boundary respectively must agree, in writing, to
the additional discharge of storm water generated by the development. When
storm drainage discharge crosses the City Limit boundazy, the downstream
City shall be notified and approval may be required. If the land owners
are uncooperative, then a drainage easement can be pursued utilizing the
City's eminent domain powers. An appropriate contract �,iith the City must
be authorized by the City Council and the developer will be responsi.ble for
all city costs. Construction which will increase the runoff shall not
begin until after either all downstream land owners have approved of the
discharge and/or easem�nts obtained.
3.2.9. Downstream structures: Al1 downstream drai.nage structures between
the proposed develo�nent and Denton Creek, Corps of Engineers Property, Big
Bear Creek or the City Limit boundary shall be reviewed for capacity
available. It shall be the developers responsibility to determ.ine the
types, size, grades and capacities of the downstream structures.
3.2.9.1. Downstream structures: Structure improvements: The City
shall require tht the ultimate developed conditions on the water shed be
�"'� analyzed with present structures capacities and future necessary capacities
to be determined. If the capacity is available to acc�date a singular
develoFanent but not full development of the water shed then, each
�
(7)
develo�ent on the water shed shall be reviewed and the percentage share of
'�' the cost of future improvements of any stnzcture shall be collected frcgn
each developer until the capacity of each structure is reached. The City
shall establish an escraw fund for each structure involved. The
�,;;� develo�xnent which increases the flaws beyond the structure's capacity shall
be responsible for improvaments to the stnzcture which will accc�odate the
flaws frcan a fully developed water shed. The City by contract with the
developer shall cause any escrow construction funds established for a
particular structure to be utilized for improvements to that structur.e.
The City Developer Agreement shall provide for reimbursement of
construction funds collected fran future developments after the particular
facility has been improved. Portions of drainage basins which lie outside
the City Limits of Grapevine shall be analyzed and accar�nodated as if fully
developed. The cost of structure iir�rove�nents to acc�date out of City
develoxxnent shall be distributed on a pro-rata basis to all developers
within the drainage basin inside the City of Grapevine ie: if a particular
water shed is 50g within the City of Grapevine and a particular developm�lt
generatesl0o of the ultimate flows which go through a particular stnacture
and the structure improvements to accom�odate fully developed conditions
cost $50,000.00, then the developers contribution would be $5,000.00.
3.3. SL�anittals: Ztao (2) copies of the following shall be sukamitted prior
to review of construction drawings by City Staff:
1. Drainage Area Map showing the entire drainage basin upstream,
downstream and including the improv�ts within the proposed develo�enent
� ' in accordance with ara ra h 3.2.8, and
p g p present downstream structures.
2. Property Ownership Map to show property owners in accordance with
,�.,, paragraph 3.2.8.
3. Property owners written permission and/or easements acquired by the
developer. Any easements which the developer wishes for the City to
acquire by eminent domain proceedings shall have the appropriate legal
instnurent, an appraisal by a certified appraiser, and ttle appropriate
City-Developer agreement executed by the developer.
4. All calculations shall be sukan.itted and shall include canbination
street and stonn sewer capacities, inlet capacities, intercepted flaw
calculations with appropriate street capacities, time of concentration
calculations, capacities of downstream structures, percentage of ultimate
flows and ultimate capacities necessaYy for fully developed conditions.
The effects of the 100-year frequency stonn shall be accemmodated.
Incomplete sul�nittals shall be rejected and a $500.00 fee assessed for each
resul�iittal.
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(8)
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