19740917 1974-10ORDINANCE NO. 1974-10
AN ORDINANCE AMENDING THE ZONING ORDINANCE
OF THE CITY OF FAIRFAX, VIRGINIA
BY ADDING THERETO A NEW SECTION 19
DEFINING REQUIRED STOPdVI DRAINAGE FACILITIES
IT IS HEREBY ORDAINED BY THE CITY COUNCIL OF THE CITY
OF FAIRFAX, VIRGINIA, that the Zoning Ordinance of the City of
Fairfax, Virginia be and the same hereby is amended by adding
a new Section 19 as follows:
1.0 PURPOSE
It is the purpose of this Ordinance to define those storm
drainage facilities which must be provided by land owners to
control rainfall runoff from and across their property in a
manner not detrimental to other inhabitants of the City and to
preserve where possible presently existing natural creek channels.
It is the further purpose of this Ordinance to minimize the
adverse effects of storm water runoff on downstream drainage ways
within the City.
2.0 DEFINITIONS
2.0.1 On-Site Drainage Facility - A facility located on a
site which serves the purpose of collecting rainfalll
falling on the site and routing it to Primary
Drainage Facilities, Creeks or Channels.
2.0.2 On-Site Detention Facility - A facility located on
a site which serves the purpose of collecting and
detaining rainfall falling on the site for con-
trolled release to the Primary Facilities as a
result of land alteration.
2.0.3 On-Site Retention Facility - The same as on-site
detention facility except that the lower elevation
of the pond may be at a level lower than the
1974-10
2.0.4
2.0.5
2.0.6
2.0.7
normal hydraulic grade line of the drainage system
into which it drains. Water detained in this lower
elevation must therefore be dissipated by evapora-
tion into the atmosphere or seepage into the soil.
Primary Creeks and Channels Natural creeks and
open channels located on either private or public
property which serve the purpose of collecting rain-
fall runoff from other sites and routing it from
the City to the rivers. A creek or channel shall
be considered a PRIMARY facility if it accommodates
a runoff flow of at least 1.5 times that amount
originating from the site on which it is located.
Primary Drainage Facilities - Culverts, gutters,
enclosed channels, etc., which serve the purpose of
collecting rainfall runoff from other sites and
routing it to Primary Creeks and Channels. Drainage
facilities shall be considered as PRIMARY if they
accommodate a flow of at least 1.5 times that
amount originating from the site on which they are
located.
Municipal Detention Facilities - Municipally-owned
facilities located along Primary Drainage Facilities
Creeks or Channels which serve the purpose of
reducing peak flow by metered release and by
storage of that input flow which exceeds the
metered output.
Design Storm Ail possible combinations of
particular storm intensity - duration events
occurring on the DESIGN STORM CURVE.
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1974-10
2.0.8 Peak Runoff - The largest runoff intensity which
will occur from a particular storm intensity
duration event on the DESIGN STORM CURVE.
2.0.9 Maximum Peak Runoff - The largest Peak Runoff which
can occur from any of the particular storms on the
DESIGN STORM CURVE.
2.0.10 Metering Controlled release of water into the
primary drainage system.
3.0 (RESERVED)
4.0 PERFORMANCE STANDARDS FOR FACILITIES
Facilities shall be designed and maintained in such a
manner as to minimize economic and environmental cost to the
City and its inhabitants. Ponding facilities for the detention
and retention of storm water runoff shall have sufficient capa-
city to safely pass flood flows from a 24-hour storm, caused by
the most severe combination of (critical) meteorologic and
hydrologic conditions considered to be reasonably characteristic
or possible in the area. The time distribution of rainfall durin
the 24-hour period shall be arranged in such a manner as to
maximize storm water runoff. Standard engineering safety factors
will be observed as minimum requirements in the design of all
detention and retention facilities. Nothing in this paragraph
will prevent the City of Fairfax from applying more restrictive
criteria to the design of any and all facilities for the detentior
or retention of storm water runoff. This requirement will be met
if facilities perform as specified under the worst combinations
of the specified design storm as defined in the Fairfax City
Drainage Facility Specifications.
1974-10
a)
b)
c)
d)
e)
f)
4.1
USAGE
On-site drainage
Streets gutters and inlets
Culverts/ storm sewers
Channels
Creek detention
On-site detention
PERFORMANCE REQUIREMENTS
PERFORMANCE REQUIREMENT
Para. 4.1.1
Para. 4.1.2
Para. 4.1.3
Para. 4.1.4
Para. 4.1.5
Para. 4.1.6
4.1.1
4.1.2
4.1.3
DESIGN STORM
Detention storm
10 year storm
100 year storm*
100 year storm
100 year storm
100 year storm
ON-SITE DRAINAGE shall be adequate to prevent flood-
ing or damage to any structure located on the site.
GUTTERS AND INLETS shall be adequate to limit the
spread of water in the street to ten (10) feet.
PRIMARY DRAINAGE FACILITIES
Where culverts, storm sewers or other enclosed
conduits have been approved for use by the Director
of Public Works or his designee as storm drainage
transport they shall, in addition to meeting other
requirements, be adequate in the opinion of the
Director of Public Works or his designee to prevent
flood damage to private or public property. Con-
duits used in conjunction with gutters and inlets
shall be adequate to limit the system hydraulic
grade line to no higher than one (1) foot below
the grade of the gutter.
* In the absence of potentially damaged private or public
property the 25-year design storm shall be used as a minimum.
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4.1.4 CHANNELS.
Where primary channels or other open conduits
have been approved for use by the Director of
Public Works or his designee as storm drainage
transports they shall, in addition to meeting other
requirements, be adequate in the opinion of the
Director of Public Works or his designee to prevent
flooding outside of any flood plain area designated
in the Zoning Ordinance.
4.1.5 CREEK DETENTION SYSTEMS.
These systems shall have adequate capacity and
metering to prevent flooding and flood damage out-
side the flood plain area as designated in the
Zoning Ordinance. Where creek detention is to be
utilized in order to solve an existing flooding
problem within the flood plain, the City Engineer
may specify increased capacity and lower release
rates.
4.1.6 ON-SITE DETENTION SYSTEMS are used to offset the
loss of natural water detention and natural
metering caused by land alteration. The system
shall have adequate capacity and metering to limit
the maximum runoff from the site after land
alteration to a value no greater than that which
existed before the alteration for the specified
design storm.
4.2 DESIGN, CONSTRUCTION, INSPECTION AND MAINTENANCE
REQUIREMENTS shall be as defined in the Fairfax City Storm
Drainage Facility Specifications as they may be hereafter pro-
mulgated by the City Engineer and approved by the City Council
from time to time.
19 7,4-10
5.0 USAGE, IMPROVEMENT, AND PRESERVATION OF CREEKS AND CHANNELS
Natural creeks and drainage channels shall be used where
available to route storm water runoff from the City.
Natural drainage systems will be improved where necessary
to meet the specified performance standards for land conditions
which exist as of September 17, 1974. To the maximum degree
possible, these improvements shall be made in such a manner as to
preserve, enhance or restore the vegetation, including trees,
along the creek line so that the aesthetic, environmental and
ecological values of the vegetation are not lost to the community
Where land alteration after September 17, 1974, will
result in increased runoff, detention or retention ponds must be
provided so that such additional runoff will not appreciably
increase the load on the existing storm drainage system.
6.0 LANDOWNER'S DUTIES AND RESPONSIBILITIES
6.1.1 LAND ALTERATION RESULTING IN SAME OR LESS RUNOFF
THAN FOR SEPTEMBER 17, 1974 USAGE.
The landowner shall provide on-site drainage
facilities where necessary to channel rainfall from
the landowner's property to existing natural
drainage streams or City owned drainage systems.
The design and construction of such facilities
shall be in accordance with the City of Fairfax
Storm Drainage Facility Specifications as they may
be hereafter promulgated by the City Engineer and
approved by the City Council from time to time.
6.1.2 LAND ALTERATION RESULTING IN GREATER RUNOFF THAN
SEPTEMBER 17, 1974 USAGE.
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1974-10
6.1.3
The landowner shall provide on-site detention,
on site drainage, or retention pond facilities in
accordance with the Fairfax City Storm Drainage
Facility Specifications as they may be hereafter
promulgated by the City Engineer and approved by
the City Council from time to time. Retention
ponds will be permitted as an alternative to
detention ponds where necessitated by the
topography of a particular site and with the
approval of the City Engineer. Performance
standards for retention ponds will be the same
as for detention systems. Where on-site detention
or retention cannot be practically accomplished
the landowner shall as an alternative pay for
improvements to those existing drainage systems,
as necessitated by his land alterations. Neither
detention nor retention shall be required where
land alterations do not increase the runoff more
than fifteen (15) percent of the runoff existing
on the site as of September 17, 1974. In addition,
if the area of the site undergoing alteration is
less than one acre and said site or lot exists on
September 17, 1974, neither detention nor retention
shall be required.
NATURAL DRAINAGE CHANNELS ON PRIVATE PROPERTY
Where natural drainage channels pass through a
landowner's property, it shall be the responsi-
bility of the landowner to maintain the natural
channel in a manner which will not be detrimental
to other inhabitants of the City.
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1974-10
No change shall be made in the contours of any
land which affects the course, width or elevation
of any flood plain or natural or other drainage
channel in any manner which will obstruct, inter-
fere with or change the drainage of such land
without providing adequate drainage in connection
therewith, as approved by the City Engineer.
The bounds of the natural stream channel
are to be considered as extending to the water level
identified for the "100 year storm" as defined in
the Zoning Ordinance. Ail natural stream modifi-
cations and maintenance are to be accomplished in
accordance with the Fairfax City Storm Drainage
Facility Specifications as they may be hereafter
promulgated by the City Engineer and approved by
the City Council from time to time.
6.1.4 MAINTENANCE OF ON-SITE DRAINAGE FACILITIES
a) The landowner and his successors in title to the facilities
and the site served thereby shall be responsible for the repair,
replacement and other maintenance of the facility.
b) The landowner and his successors as aforesaid shall perform
periodic maintenance on the facilities and such other repairs,
replacements or maintenance thereon as may be required by the
City Engineer.
c) The City Engineer, his agent or representative, may inspect
the facilities from time to time to determine the necessity of
repair, replacement or other maintenance thereof.
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1974-10
d) If the facilities are determined to be in need of repair, re-
placement or other maintenance, the City Engineer, his agent or
representative, shall serve on the landowner a written notice
describing the condition of the facilities and specifying the
required repairs, replacements or other maintenance to be made to
correct the said deficiencies. Such notice shall require the land
owner to comply with the terms thereof within ten days of
receipt.
e) Any landowner aggrieved by the determination of the City
Engineer his agent or representative, may appeal such deter-
mination to the City Council within ten days of the receipt of
notice thereof. Such appeal shall be placed on the agenda for
the next public Council meeting after notice of the appeal is
given.
f) Upon refusal or neglect by the landowner or his successors
as aforesaid to comply with the repairs, replacements or other
maintenance required by the City Engineer, the City of Fairfax,
Virginia, through its agents or employees, may repair, replace
or otherwise maintain such facilities.
g) In the event the City of Fairfax, Virginia, through its
agents or employees, repairs, replaces or otherwise maintains
any facility after complying with the notice requirements of
this section, the costs or expenses thereof shall be charged to
and paid by the landowner and/or his successors as aforesaid
and may be collected by the City of Fairfax, Virginia, as taxes
and levies are collected.
h) Every charge authorized by this section with which the land-
owner and/or his successors as aforesaid has been assessed and
which remains unpaid shall constitute a lien against the
property.
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7.0
CITY RESPONSIBILITIES
7.0.1 CITY OWNED DRAINAGE SYSTEM
The City shall maintain and control natural
drainage systems and other drainage or detention
or retention systems which have been constructed
by or dedicated to the City. In no event will
the City be financially responsible for maintenance
of private systems.
7.0.2 CITY OWNED DRAINAGE SYSTEM - DEVELOPMENT IMPACTED
The City shall specify, design and construct
off-site improvements to the storm drainage system
when such improvements are made necessary by
changes in land use and when additional runoff
caused by such changed land use cannot be
adequately accommodated by "detention or retention"
systems; such off-site improvements are to be paid
for by those landowners whose land alteration made
the improvements necessary.
8.0 The provisions of this Ordinance are separable and inde-
pendent and in the event that any provision, section, clause or
paragraph hereunder shall be declared illegal, unconstitutional
or null and void by any court of competent jurisdiction, the
remaining provisions, sections, paragraphs and provisions
hereof shall remain in full force and effect.
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1974-10
This ordinance shall become effective immediately upon
its adoption by the City Council.
Adopted: September 17, 1974.
ATTEST:
F cit~ Clerk
CITY COUNCIL OF THE CITY OF
FAIRFAX, VIRGINIA
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