[R.O. 1997 §405.070; Ord. No. 1088 §3, 12-9-1991]
A. The area of the lots shall be determined by zoning district regulations,
subject to the availability of public sewer and a public water supply.
Prior to the submission of a preliminary plat, the subdivider shall
obtain a determination from the engineer having jurisdiction as to
whether adequate public sewer and water supply are available.
B. If the proposed subdivision is serviced by a public water supply
and a public sewer system, the minimum lot area requirements shall
be subject to those set forth herein and in the Zoning Regulations.
C. If the proposed subdivision is serviced with a public water supply,
but not with a public sewer system, or is serviced with a public sewer
system, but not a public water supply, the preliminary plat shall
be prepared on the basis of minimum three-acre lots; provided, however,
that additional lot area may be required if the area has or is suspected
of having a high water table or if soil conditions prove to be unsuitable
based on percolation tests.
D. All proposed private water and sewer systems shall be reviewed for
approval by the Barry County Health Department.
[R.O. 1997 §405.080; Ord. No. 1088 §3, 12-9-1991]
A. Length. Intersecting streets (which determine block
length) shall be provided at such intervals as to serve cross traffic
adequately and to meet existing streets in the neighborhood. In residential
districts where no existing plats are recorded, the blocks shall not
exceed one thousand two hundred (1,200) feet in length, except that
a greater length may be permitted where topography or other conditions
justify a departure from this maximum. In blocks longer than eight
hundred (800) feet, pedestrianways and/or easements through the block
may be required near the center of the block. Such pedestrianways
or easements shall have a minimum width of ten (10) feet. Blocks for
business use should normally not exceed six hundred (600) feet in
length.
B. Width. In residential development, the block width
shall normally be sufficient to allow two (2) tiers of lots of appropriate
depth. Blocks intended for business or industrial use shall be of
such width and depth as may be considered most suitable for the prospective
use.
[R.O. 1997 §405.090; Ord. No. 1088 §3, 12-9-1991; Ord. No. 2001-1352 §1, 12-3-2001]
A. Relations To Adjoining Street System. The arrangement
of streets in new subdivisions shall make provisions for the continuation
of the principal existing streets in adjoining additions (or their
proper projection where adjoining property is not subdivided), insofar
as they may be necessary for public requirements. The width of such
streets in new subdivisions shall not be less than the minimum street
widths established herein. Alleys, when required, and street arrangement
must also be such as to cause no hardship to owners of adjoining property
when they plat their land and seek to provide for convenient access
to it. Whenever there exists a dedicated or platted half street or
alley adjacent to the tract to be subdivided, the other half of the
street or alley shall be platted and dedicated as a public way.
B. Street Names. Streets that are obviously in alignment
with others already existing and named shall bear the same alphanumeric
designation adopted by the Board of Aldermen.
C. Arterial And Collector Streets. Major streets through
subdivisions shall conform to the Major Street Plan as adopted by
the Planning and Zoning Commission and the Board of Aldermen.
D. Local Streets. Minor streets shall be so designed
to discourage through or non-local traffic.
E. Culs-De-Sac. An adequate turnaround of not less
than a fifty-foot-radius right-of-way shall be provided at the closed
end of a dead-end street longer than one (1) lot in length. Such local
street segment shall not exceed five hundred (500) feet in length
from the centerline of an intersection of a cross street to the center
of the cul-de-sac; except for suburban, large-lot development, which
shall not exceed one thousand two hundred (1,200) feet.
F. Right-Angle Intersections. Under normal conditions,
streets shall be laid out to intersect, as nearly as possible, at
right angles. Where topography or other conditions justify a variation
from the right-angle intersection, the minimum angle shall be sixty
degrees (60°).
G. Streets Adjacent To A Limited Access Freeway Or Principal
Highway. Where lots front or side, but do not back, on limited-access
freeways, or principal highways, a marginal access street or frontage
road may be required parallel and adjacent to the boundary of such
rights-of-way. The distance from said rights-of-way shall be determined,
with due consideration, to minimum distance required for approach
connections to future grade separation.
H. Half Streets. Dedication of half streets will not
be approved, except where it is essential to the reasonable development
of the subdivision and in conformity with the Major Street Plan and
other requirements of this Chapter.
I. Alleys. Alleys may be required in commercial and
industrial districts. Dead-end alleys shall be avoided wherever possible.
Alleys may be required in certain residential areas.
J. Minimum Requirements. The right-of-way grades, horizontal
curves, and vertical curves for streets and alleys dedicated and accepted
shall not be less than the minimum for each classification, as follows:
1.
Arterial streets:
a.
Minimum right-of-way width: eighty (80) feet.
b.
Maximum gradient: five percent (5%).
c.
Minimum radii of horizontal curves: five hundred (500) feet.
d.
Minimum sight distance on vertical curves: three hundred fifty
(350) feet.
2.
Collector streets:
a.
Minimum right-of-way width: seventy (70) feet.
b.
Maximum gradient: seven percent (7%).
c.
Minimum radii of horizontal curves: three hundred eighty (380)
feet.
d.
Minimum sight distance on vertical curves: three hundred (300)
feet.
3.
Local streets:
a.
Minimum right-of-way width: fifty (50) feet.
b.
Maximum gradient: ten percent (10%).
c.
Minimum radii of horizontal curves: two hundred seventy (270)
feet.
d.
Minimum sight distance on vertical curves: two hundred (200)
feet.
4.
Culs-de-sac:
a.
Minimum right-of-way width: fifty (50) feet.
b.
Maximum gradient: ten percent (10%).
c.
Minimum radii of turnaround: fifty (50) feet.
5.
Frontage roads:
a.
Minimum right-of-way width: sixty (60) feet.
6.
Alleys:
a.
Minimum right-of-way width: twenty (20) feet.
7.
Pedestrianway:
a.
Minimum right-of-way width: ten (10) feet.
8.
The absolute minimum gradient on a street shall be one-half
of one percent (0.5%) and minimum gradient shall be one percent (1%)
wherever practical.
9.
Minimum construction requirements:
[Ord. No. 1893, 9-12-2023]
a.
Driving surface width: twenty-eight (28) feet.
b.
Eighteen (18) inch wide concrete curb and gutter.
c.
Compacted base rock: six (6) inches.
d. A minimum of four (4) inches of machine laid asphalt.
e. The City may require heavier construction for commercial and/or industrial
subdivisions.
K. Additional Requirements. When existing or anticipated
traffic on arterial and collector streets warrants greater widths
of rights-of-way, the additional width shall be dedicated.
L. Street Alignment. On streets with reverse curves,
an appropriate tangent shall be provided between curves to permit
a smooth flow of traffic.
M. Intersections. Local nonaligned intersections shall
be spaced at a minimum of one hundred fifty (150) feet (centerline
to centerline). Collector intersections shall be spaced at a minimum
of five hundred (500) feet (centerline to centerline).
N. Drainage Easements. Drainage easements may be required,
in addition to street rights-of-way, where the street or streets adjoin
or are parallel with streams or drainage areas or where lots back
on where said drainage exist. The width of such drainage easement
shall be determined by the engineer having jurisdiction who shall
notify the Planning and Zoning Commission of his/her recommendation
in writing.
O. Sight Triangle. A sight triangle is a triangular
area at the intersection of two (2) streets in which nothing shall
be erected, placed, planted or allowed to grow high enough above the
elevation of the adjacent roadway to constitute a sight obstruction.
The area included in a sight triangle shall be bounded on two (2)
sides by the center lines of each street, and on the third side by
a line connecting the two (2) lines. The unobstructed sight distance
must be sufficient to allow the operators of vehicles approaching
the intersection simultaneously to see each other in time to prevent
collisions. The sight distance must be related to vehicle speeds and
to the resultant distances traversed during perception, reaction time
and braking. (See the Transportation and Traffic Engineering Handbook,
Second Edition, Institute of Transportation Engineers, 1986, or most
recent edition.)
[R.O. 1997 §405.100; Ord. No. 1088 §3, 12-9-1991]
A. Minimum lot width shall be as specified in the district regulations
of the City of Cassville Zoning Code; however, corner lots shall be
twenty (20) feet wider than that required in those regulations. Lot
width shall be measured at the building setback line.
B. Minimum depth shall be one hundred (100) feet. Lot depth shall be
measured through the center of the lot and shall be perpendicular
to the property line or radial to the property line on curved streets.
C. Minimum lot area shall be subject to the Zoning Regulations of the
district in which the subdivision is located.
D. In subdivisions where septic tanks or other individual sewage disposal devices are to be installed, the size of all lots included in the subdivision shall be subject to regulations as set out in Section
405.070, Water and Sewer.
E. In subdivisions where private water supply is by well or other means, the size of all lots included in the subdivision shall be subject to regulations as set out in Section
405.070, Water and Sewer.
F. All side lot lines shall bear sixty degrees (60°) to ninety degrees
(90°) from the street right-of-way line on a straight street or
from the tangent of a curved street.
G. Corner lots, in residential subdivisions, shall observe the same
setback on both streets.
H. Double-frontage lots shall be avoided unless, in the opinion of the
Planning and Zoning Commission, a variation to this rule will give
better street alignment and lot arrangement.
I. Every lot shall abut on a street other than an alley.
J. Building or setback lines shall be shown on the final plat for all
lots in the subdivision and shall not be less than the setback required
by the Zoning Regulations.
K. The subdivision or re-subdivision of a tract or lot shall not be
permitted where said subdivision or re-subdivision places an existing
permanent structure in violation of the requirements of the Zoning
Regulations.
L. The depth of the lot shall not exceed three (3) times its width.
[R.O. 1997 §405.110; Ord. No. 1088 §3, 12-9-1991]
A. Where alleys are not provided, permanent, continuous easements of
not less than seven and one-half (7 1/2) feet in width shall
be provided on each side of all rear lot lines, and on side lot lines,
where necessary, for utility poles, wires, conduits, storm and sanitary
sewers, gas, water, and heat mains, and other public utilities.
B. An additional twelve-foot temporary construction easement [six (6)
feet on each side of the lot line] shall be provided for initial construction
of water, sewer, and other utility lines.
[R.O. 1997 §405.120; Ord. No. 1088 §3, 12-9-1991]
In subdividing land or re-subdividing an existing plat, due
consideration should be given by the subdivider to the dedication
or reservation of suitable sites for schools, parks, playgrounds,
or other public recreational areas or open spaces. Any areas so dedicated
or reserved shall conform as nearly as possible to the Comprehensive
Plan. All areas to be reserved for, or dedicated to, public use shall
be indicated on the preliminary plat in order that it may be determined
when and in what manner such areas will be dedicated to or acquired
by the appropriate agency. A written statement from the Board of Education
may be required to be submitted by the subdivider indicating whether
or not a school site in the proposed subdivision is desired.
[R.O. 1997 §405.130; Ord. No. 1088 §3, 12-9-1991]
In the interest of public safety and for the preservation of
the traffic-carrying capacity of the street system, the Planning and
Zoning Commission shall have the right to restrict and regulate points
of access to all property from the public street system. Such restrictions
shall be indicated on the final plat.
[R.O. 1997 §405.140; Ord. No. 1088 §3, 12-9-1991]
The design of the subdivision shall provide for efficient traffic
flow, proper mixing of land uses, and a logical link between surrounding
existing development and the proposed layout. The Comprehensive Plan
should be used as a guide in determining if the design of the proposed
subdivision is proper. The Planning and Zoning Commission shall have
the authority to deny a plat or request redesign if, in its opinion,
the layout is not suitable for the site.
[R.O. 1997 §405.143; Ord. No. 2001-1328 §1, 4-2-2001]
A. Current And Enforceable Municipal Ordinances, Regulations
And Statutory Requirements Notwithstanding.
1.
The applicant for a building permit shall submit with the application, plan, drawings and any other such information required by Sections
405.140 to
405.160 of this Article for the management and control of surface water runoff from the tract or tracts for which the permit is requested and to provide that temporary flooding does not occur to other properties during the construction.
2.
Any person or party submitting a final subdivision plat for consideration and approval under the subdivision and zoning ordinance in effect at the time of submittal shall submit plans, drawings, and any other such information required by Sections
405.140 to
405.160 of this Article for the management and control of surface water runoff from the tract or tracts to be subdivided and to provide that temporary flooding does not occur to other properties during construction.
3.
Any person or parties prior to grading, excavating, ditching or otherwise implementing activities that would alter the topography of an area or contiguous areas greater than ten thousand (10,000) square feet or alter, channelize, rechannel or modify a natural or man-made watercourse shall first submit to the City plans, drawings, calculations and other information required by Sections
405.140 to
405.160 of this Article for the management and control of surface water runoff from the area to be altered, or surface water conveyed by any natural or man-made watercourse and to provide that temporary flooding does not occur to other properties during construction.
B. Surface Water Runoff Management And Control.
1.
The applicant or the person or party submitting a final subdivision
plat shall retain the services of a professional engineer, registered
in the State of Missouri, to provide under his/her professional seal
and signature the surface water runoff management and control plans,
drawings, calculations and information required under Appendix A to
these stormwater provisions, which is on file in the City offices.
2.
All facilities constructed or required to be constructed for
approval of a final subdivision plat for the management and control
of surface water runoff shall, during and upon completion of construction,
be inspected by a professional engineer licensed in the State of Missouri.
Upon completion of construction of the surface water runoff management
and control facilities, the City shall receive from the professional
engineer certification that said facilities have been completed and
constructed in accordance with the intent of the plans, drawings and
calculations upon which permits or approval were issued.
3.
Upon written request by the building permittee or person or parties submitting a subdivision plat, the City shall retain the services of a professional engineer licensed in the State of Missouri to perform the inspection and provide certification requirements of Subsection
(B)(2).
4.
In the event certification of completion and compliance with
plans, drawings and calculations are not received by the City, or
should the City determine the improvements facilities as described
in the approved plans are not being constructed to meet minimum standards
set forth in Appendix A of these stormwater provisions, which is on
file in the City offices, the City shall so notify the permittee and
may issue an order revoking the building permit or recommend to the
Governing Body to discontinue provision of municipal utilities until
the deficiencies are corrected.
C. Obstruction Of Watercourses Prohibited.
1.
It shall be unlawful for any person to block, obstruct, destroy,
cover, fill or alter in any way a watercourse or any part thereof
so as to cause damage to the property of the other persons from surface
water.
2.
A watercourse is land which has a conformation so as to give
to surface water flowing from one tract of land to another tract of
land, a fixed and determinate course so as to uniformly discharge
it upon the servient tract at a fixed and definite point. It shall
include, but not be limited to, ravines, swales, sinkholes or depressions
of greater or less depth extending from one tract and so situated
as to gather up the surface water flowing upon the dominant tract
and to conduct along a definite course to a definite point of discharge
upon the servient tract. It shall not be deemed to be important that
the force of water flowing from one tract of land to another has not
been sufficient to wear out a channel or canal having definite or
well marked sides or banks. If the surface water, in fact, uniformly
or habitually flows over a given course having reasonable limits as
to the width of the line of its flow, it shall be considered to have
a definite course.
3.
A violation of Subsection
(C)(1) shall be deemed to be a public nuisance. Whenever the City has determined that a person has blocked, obstructed, destroyed, covered, filled or altered in any way a watercourse so as to cause surface water damage to the property of others, the City Administrator is authorized to proceed in accordance with the Municipal Code of the City of Cassville so as to abate the public nuisance.
4.
In reviewing applications for building permits, the City shall further determine if the work interferes with the use and operation of existing watercourses. If the City has reason to believe that the work may interfere with the use and operation of existing watercourses, then the City shall notify the applicant and request information or revisions to the plans and drawings stipulated in Subsection
(A). When determined by the City to be necessary, the applicant shall comply with the provision set forth in Subsection
(B) of this Section.
D. Wastewater Discharge.
1.
Stormwater and all other unpolluted waters shall be discharged
to storm sewers or waters of the State.
2.
It shall be unlawful to discharge into any storm sewers and/or
waters of the State within the City or in any area where there is
an availability of sanitary sewers any waste water or pollutant, except
where suitable treatment has been provided and approved by the City
and the State of Missouri under the National Pollution Discharge Elimination
Systems (NPDES).
3.
Violations of this Section shall be subject to the enforcement
procedures contained in the Municipal Code of the City of Cassville.
E. Maintenance Of Surface Water Runoff Control Facilities.
1.
When any surface water runoff control facility (hereafter called
"facility") is located on the same lot or tract it is intended to
serve, the facilities shall be maintained at all times by the owner
of the lot or tract. Unless otherwise approved by the City, such facility
shall not be constructed on separate lots and no building permit shall
be issued for any such facility if it is located on a lot or tract
of land other than the lot or tract of land it is intended to serve.
2.
When the facility is designed to serve more than one (1) lot
or tract, the City may permit the construction of such facilities
on a lot other than the lot or tract the facility is intended to serve,
if it is determined that there are sufficient easements and covenants
filed on record with the County Recorder of Deeds imposing the duty
and responsibility to maintain the facilities, together with the liability
for the costs of such maintenance upon the owners of each of the lots
served by the facility, and further covenanting the assessed costs
of any repairs and maintenance work done by the City shall be in lien
enforceable against each of the lots so served. The City shall require
as a precondition to the issuance of a building permit that the owner
of the property file such covenants and easements with the County
Recorder of Deeds allocating such obligations and liabilities for
the cost of the maintenance of the facility, which covenants and easements
shall secure the right of the City to execute remedies and the power
to assess the costs thereof against each lot served by the facility.
3.
In the event the owners of the lots or tracts served by the
facility fail to maintain the facility, then the City, upon ten (10)
days' written notice, may revoke the occupancy permit issued for such
premises, and in addition thereto, or in the alternative, may order
utilities disconnected. Any aggrieved owner shall have the right to
an administrative hearing prior to revocation of the occupancy permit
or disconnect of utilities to determine whether the stormwater detention
facility has been maintained so as to meet the standards set forth,
provided the owner has filed a written demand for hearing with the
City within ten (10) days after notice was given. The hearing shall
be conducted before the City Board of Adjustment within twenty (20)
days of receipt of the owner's demand for hearing. The hearing officer
shall prepare a written decision setting forth his/her findings of
fact and conclusions.
4.
Failure To Maintain Declared A Nuisance — Assessment
Of Costs As A Lien. If the owners of the lots or tracts served
by the facility fail to adequately maintain the facility, the same
is hereby declared to be a nuisance, and the City may require abatement
of the nuisance under the procedures set forth in the City of Cassville
Code. In addition to the procedures set forth above, or in the alternative,
upon determining that a nuisance exists, the City may refuse to issue
or renew licenses for any business on any lot or tract served by the
facility.
F. Development In Areas Of Karst Geological Characteristics
And Sinkholes.
1.
No person shall engage in the altering of topography, grading, excavating or the development of land in a sinkhole area without first securing a permit from the City. To obtain a permit, the owner of the property or person having an interest therein shall submit an application for a permit to the City with a plan set out in Subsection
(C), which shall contain the following additional information:
a.
The plan shall show the location of the sinkhole, the immediate
sinkhole drainage area, a sinkhole cluster area or portions of such
items, along with ground contours, a stormwater analysis of the sinkhole
and significant physical features on the property.
b.
Upon review of the information presented by the applicant, the
site, and such other information as may be available, the City may
issue a permit for work to be performed in the sinkhole area. All
work shall be performed in accordance with the permit. The City may
designate certain areas where grading or construction equipment is
not permitted or is otherwise limited.
2.
In addition to establishing a plan for grading and use of construction
equipment, the City may, based upon the topography, geology, soils
and history of the sinkhole (such as past filling) and the stormwater
analysis and plan of the developer's engineer, establish sinkhole-related
non-buildable areas. No building, parking areas, grading or other
structures shall be permitted within the sinkhole-related non-buildable
area unless otherwise authorized by the City. This non-buildable area
shall follow the limits of the sinkhole in most cases. However, the
non-buildable area may be expanded or contracted by action of the
City where warranted, due to the nature of the specific sinkhole,
the underlying geology, soils, drainage and any related information,
such as depth to bedrock. In sinkhole cluster areas, the City may
require the owner or developer to provide recommendations from a consulting
engineer and a consulting hydrogeologist, based upon substantial and
state-of-the-art field studies and evaluation of the specific sinkhole
system. Such studies shall be submitted to the City's authorized representative
for review.
3.
Development may occur in the immediate sinkhole drainage area
if the developer provides alternative surface drainage away from the
sinkhole, while keeping the water in the same surface drainage basin;
and provided further, that the water shall not go into another stream
of known flooding problems. The immediate sinkhole drainage area (or
portion thereof) which cannot be provided with an alternative drainage
system can be deleted from the development area and can be used to
meet open space requirements. The developer may request the Planning
and Zoning Commission and the City that the density on the remainder
of the developable area be increased, with the total resulting density
no greater than if the entire area were developed to the permitted
density under the Zoning Ordinance.
G. Enforcement And Liability.
1.
In enforcing the provisions of the aforesaid Sections, in addition
to the various remedies provided therein, the City shall have all
other rights, powers and authority granted to it by Missouri law,
including, without limitation, the right to file civil suit against
any person who violates or fails to comply with the aforesaid Sections.
In the event of civil suit, the City any recover reasonable attorney's
fees, court cost and other expenses of litigation.
2.
No person issued a permit under the terms of the aforesaid Section
shall have any recourse whatsoever against the City for any loss,
cost or expense or damage arising out of any of the provisions or
requirements of these Sections, or because of the provisions or requirements
of these Sections, or because of the enforcement thereof by the City.
These Sections shall not cease liability on the part of the City,
its officers, agents or employees as the result of reliance on any
permits issued hereunder or as the result of any administrative decision
lawfully made hereunder.
[R.O. 1997 §405.145; Ord. No. 2001-1328 §1, 4-2-2001]
A. Minimum Requirements For Storm Sewer And Drainage Design.
1.
Drainage Area Plan: a plan of the drainage area at a scale of
one (1) inch equals one hundred (100) feet with two-foot contour internals
using USGS datum for areas less than one hundred (100) acres or a
plan of the drainage area at a scale of one (1) inch equals three
hundred (300) feet with five-foot contour intervals for larger areas.
This plan shall include all proposed streets, drainage and grading
improvements with flow quantities and direction of flow at all critical
points. All areas and sub-areas for drainage calculations shall be
clearly distinguished.
2.
Hydraulic data: Complete hydraulic data showing all calculations
shall be submitted.
3.
Plan and profile: A plan and profile of all proposed improvements
at a scale of one (1) inch equals forty (40) feet horizontal and one
(1) inch equals four (4) feet vertical shall be submitted. This plan
shall include the following:
a.
Locations, size, flow line elevations and grades, type of pipe,
channels, boxes, manholes, and other structures drawn on standard
plan-profile sheets;
b.
Existing and proposed ground line profiles along centerline
of the drainage improvement;
c.
A list of the kind and quantity of material;
d.
Typical sections and reinforcement of all boxes and channels;
e.
Location of property lines, street paving, sanitary sewers and
other utilities, both public and private.
4.
Field study: A field study of the downstream capacity of all
drainage facilities and the effect of additional flow from the area
to be improved shall be submitted. If the effect is to endanger property
or life, the problems must be solved before the plan will be given
approval.
5.
Stormwater flow quantities: Stormwater flow quantities in the
street shall be shown at all street intersections, all inlet openings
and at locations where flow is removed from the streets. This shall
include the hydraulic calculations for all inlet openings and street
capacities. Street flow shall be limited according to Table 1 at the
end of this Section.
6.
Sinkholes or karst areas: Sinkhole or karst areas shall be clearly
defined. If any portion of the stormwater from an area is to be drained
into a sinkhole, all information available shall be obtained and the
capacity of the sinkhole shall be studied, and this study shall be
submitted to determine the effect of the drainage and pollution on
groundwater and streams.
7.
Additional information: Any additional information deemed necessary
by the City for an adequate consideration of the storm drainage effect
on the City of Cassville and surrounding areas must be submitted.
B. Requirements Relating To Improvements.
1.
General Design Requirements.
a.
All bridges shall be designed to accommodate a one-hundred-year
frequency rain. Box culverts, pipe culverts, channels and ditches
shall be designed to accommodate a one-hundred-year frequency rain
at all locations having a drainage area in excess of one (1) square
mile. Locations having a drainage
area of less than or equal to one (1) square mile shall be designed
to accommodate a twenty-five-year frequency rain.
b.
Channel improvements types shall be as follows:
(1) Improvements with a capacity of up to and including
ten (10) C.F.S. shall be open and
(2) Improvements with a capacity above ten (10) cfs
up to and including one hundred (100) cfs shall be closed conduit;
(3) Improvements with a capacity above the one hundred
(100) cfs up to and including two hundred fifty (250) cfs may be open
and:
(a) Concrete paved invert; or
(4) Improvements with a capacity above the two hundred
fifty (250) cfs shall be open and:
(b) Have a one hundred (100) cfs low-flow paved invert.
2.
Specific Requirements For Various Improvements.
a.
Bridges and culverts: Bridges, box culverts or concrete pipe
culverts shall be provided where continuous streets or alleys cross
watercourses. The structure shall be designed in accordance with City
specifications for material and to carry HS-20 loadings in all cases.
b.
Closed storm sewers: Closed storm sewers shall either be reinforced
concrete box or pipe of approved type designed for HS-20 loadings.
Reinforced concrete pipe or reinforced concrete boxes must be used
within two (2) feet of the back of the street curb and under paved
areas. All storm sewers having trench walls within two (2) feet of
the back of the street curb shall be backfilled with granular material.
The use of corrugated steel, zinc-coated pipe and extra-strength clay
pipe will not be permitted within two (2) feet of the curb or under
pavement areas. All pipe material shall meet the requirements of the
latest revision of the City of Cassville standard general conditions
and technical specifications for public works construction. Grades
for closed storm sewers shall be designed so that the velocity shall
not be less than three (3) feet per second nor exceed twelve (12)
feet per second. All other structures such as junction boxes or inlets
shall be in accordance with the standard drawings adopted by the City
of Cassville. Closed storm sewers shall extend to the furthest downstream
point of the development with consideration given to velocities and
to providing discharge energy dissipaters to prevent erosion and scouring
along down- stream properties.
c.
Open paved concrete channels: Grades for open paved channels
shall be designed so that the velocity shall not be less than three
(3) feet per second nor exceed twelve (12) feet per second. Such concrete
channels may be of different shapes according to existing conditions;
however, a channel with a flat bottom and 4:1 to 5:1 side slopes is
the most desirable type and shall be used whenever possible. The thickness
of channel paving shall depend on conditions at site and size of channel;
however, a minimum thickness of six (6) inches is required. A six-inch
freeboard must be provided. An eighteen-inch toe wall is required
at both the outlet and inlet ends of the channel.
d.
Open ditches (earth channels): Ditches shall have a gradient
that limits the velocity within one and one-half (1 1/2) to five
(5) feet per second, depending on existing soil conditions. Such ditches
shall have a minimum side slope ratio of 3:1.
C. Runoff Calculations.
1.
The rate of runoff concentrated at any point shall be determined
by the Rational Formula:
|
Q
|
=
|
CIA, in which:
|
|
Q
|
=
|
Runoff in cubic feet per second
|
|
C
|
=
|
The runoff coefficient for the area
|
|
I
|
=
|
Design rainfall intensity in inches per hour over the area based
on the time of concentration and rainfall
|
|
Intensity curves included as a part of this Section.
|
|
A five-minute time of concentration is the minimum permitted.
|
|
A = Drainage area in acres.
|
2.
Runoff Coefficient. The runoff coefficient
"C" is the variable in the rational formula least susceptible to precise
determination and the one that requires the greatest exercise of engineering
judgment because of the many area characteristics which affect the
coefficient. Among the factors to be considered in influencing the
runoff coefficients are the following: present and future zoning,
terrain, local ponding or depressions, the amount of pavement, roofs,
turf and other areas having different degrees of imperviousness. The
selection of a coefficient should take into consideration the probable
ultimate development of presently undeveloped areas. Suggested values
of runoff coefficients are included in the following table:
|
Suggested Runoff Coefficients "C"
|
---|
|
"C" Value
|
Surface Conditions
|
---|
|
0.10 to 0.15
|
Tall grass, brush
|
|
0.15 to 0.20
|
Parks, golf courses, farms and one-acre single-family residences
|
|
0.35
|
Single-family residences on lots of not less than 15,000 square
feet
|
|
0.45
|
Single-family residences on lots of not less than 10,000 square
feet
|
|
0.47
|
Single-family residences on lots of not less than 7,500 square
feet
|
|
0.51
|
Single-family residences on lots of not less than 6,000 square
feet
|
|
0.90
|
Gravel surfaces
|
|
0.95
|
Asphalt and concrete surfaces
|
|
1.00
|
Buildings and other structures
|
3.
Rainfall Intensity. The average frequency of
rainfall occurrence used for design determines the degree of protection
afforded by a drainage system. Maximum intensity of rainfall of a
given expectancy is greater for a short period of the time than for
longer periods. Therefore, it is assumed that the maximum runoff will
occur as soon as all parts of the drainage area under consideration
are contributing. The length of time from the beginning of rainfall
until runoff from the most remote point in the drainage area reaches
the point under consideration is a channel or gutter flow time. Nomographs
which may be used for determining time of concentration are reproduced
and on file in the City offices. Once the time of concentration is
known, the design intensity rainfall may be determined from the rainfall
intensity curves developed from United States Weather Bureau data.
D. Sizing Of Storm Sewers And Drainage Structures.
1.
The size of closed storm sewers, open channels, culverts and
bridges shall be designed so that their capacity will not be less
than the runoff computed by using the Manning Formula:
|
Q
|
=
|
1.486 (a)(r)2/3(s)(1/2)
|
|
|
|
N
|
|
Q
|
=
|
Capacity = Discharge in cubic feet per second
|
|
a
|
=
|
Cross-sectional area of water in conduit or channel in square
feet
|
|
r
|
=
|
Hydraulic radius of water in conduit or channel equals area/wetted
perimeter
|
|
s
|
=
|
Mean slope of hydraulic gradient in feet per foot
|
|
n
|
=
|
Roughness coefficient based on condition and type of material
of conduit or channel lining
|
|
Values of "n" for various kinds of pipe for use in Manning Formula:
|
---|
|
Concrete pipe
|
0.013
|
|
Corrugated metal pipe
|
0.024
|
|
Concrete lined channel
|
0.015
|
|
Earth channels
|
0.030 to 0.050
|
2.
Design Tabulations. For systems of storm sewers
with inlets in various locations, the time of concentration at any
point will be time of concentration at the most remote inlet upstream,
plus the flow time in the storm sewer to the point under consideration.
Computations for systems lend themselves readily to tabulation showing
the drainage area, time of concentration runoff and capacity of each
inlet and section of sewer under consideration. This data is to accompany
the improvement plans.
|
Table 1 — Street Flow
|
---|
|
Street flow shall be limited by pavement encroachment and depth
of flow as follows:
|
|
Street classification (minor)
|
Maximum encroachment of a two-year storm, no curb overtopping.
Flow may spread to crown of street.
|
|
Collector
|
No curb overtopping. Flow spread must leave the equivalency
of one (1) ten-foot driving lane clear of water.
|
|
Arterials (thoroughfares)
|
No curb overtopping. Flow spread must have the equivalent of
two (2) ten-foot driving lanes clear of water. One lane in each direction.
Where no curbing exists, encroachment shall not extend past property
lines.
|
3.
The storm sewer system shall commence at the point where the
volume of flow equals five (5) cfs.
[R.O. 1997 §405.147; Ord. No. 2001-1328 §1, 4-2-2001]
A. General.
1.
Stormwater runoff and the velocity of discharge are considerably
increased through development and growth of the City.
2.
Prior to the development of the land, surface conditions provide
a higher percentage of permeability and longer time of concentration.
With the construction of buildings, parking lots, etc., permeability
and the time of concentrations are significantly decreased, resulting
in an increase in both the rate and volume of runoff.
3.
These modifications may create harmful effects on properties
downstream. Therefore, to minimize these effects, the following minimum
stormwater detention requirements have been established.
B. Stormwater Detention Plans.
1.
A complete set of stormwater detention plans and calculations
shall be provided for all construction projects that increase stormwater
runoff.
2.
Plans for the construction of public improvements shall be submitted
to and approved by the City.
3.
The required stormwater detention plans for private improvements
shall be submitted, along with the building plans, to the City for
review and approval. An escrow for stormwater detention will not be
accepted.
C. Method Of Evaluation.
1.
Differential runoff evaluation consists of the determination
of the rates of runoff, before and after development, determination
of required volume of detention and verification of adequacy of discharge
and control structures. The one-hundred-year (frequency) runoff coefficients
shall be used. Differential runoff rates shall be evaluated by equation:
|
R = (Cd x I-100) - (Cu x I-100)
|
|
Where:
|
|
|
R
|
=
|
Differential runoff rate
|
|
|
Cd
|
=
|
Runoff coefficient for development conditions
|
|
|
Cu
|
=
|
Runoff coefficient for underdeveloped conditions
|
|
|
I-100
|
=
|
Intensity for one-hundred-year storm
|
2.
"C" values shall be determined from the following table:
|
Suggested Runoff Coefficients
|
---|
|
"C" Value
|
Surface Conditions
|
---|
|
0.10 to 0.15
|
Tall grass, brush
|
|
0.15 to 0.20
|
Parks, golf courses, farms and one-acre single-family residences
|
|
0.35
|
Single-family residences on lots of not less than fifteen thousand
(15,000) square feet
|
|
0.45
|
Single-family residences on lots of not less than ten thousand
(10,000) square feet
|
|
0.47
|
Single-family residences on lots of not less than seven thousand
five hundred (7,500) square feet
|
|
0.51
|
Single-family residences on lots of not less than six thousand
(6,000) square feet
|
|
0.90
|
Gravel surfaces
|
|
0.95
|
Asphalt and concrete surfaces
|
|
1.00
|
Buildings and other structures
|
3.
Use the Chart A (on file in the City offices) to find time of
concentration (tc), then use Chart B (on file in the City offices)
to determine intensity (I). A five-minute time of concentration is
the minimum permitted.
D. Volume Of Detention.
1.
Volume of detention for areas less than twenty (20) acres shall
be evaluated according to the "Simplified Volume Formula." For areas
larger than twenty (20) acres, other methods may be used upon the
approval of the City of Cassville. The Rational Formula method will
generally be accepted for areas greater than twenty (20) acres.
a.
Total volume of detention shall be computed by the equation:
|
V
|
=
|
R x A x tc (min) x 60 (seconds/minute)
|
|
V
|
=
|
Total volume of detention (cubic feet)
|
|
R
|
=
|
Differential runoff rate
|
|
A
|
=
|
Area of project in acres
|
|
tc
|
=
|
Time of concentration as determined for use with differential
runoff rates
|
b.
The design volume of detention shall be determined from the
following table:
|
Calculated Volume
(cubic feet)
|
Design Volume
(cubic feet)
|
---|
|
1 through 500
|
500
|
|
501 through 4,999
|
Round up to nearest 500
|
|
5,000 through 9,999
|
Round up to nearest 1,000
|
|
10,000 through 49,999
|
Round up to nearest 5,000
|
|
50,000 through 99,999
|
Round up to nearest 10,000
|
|
100,000 and above
|
Round up to nearest 25,000
|
2.
Clearing Of Vegetation. Silt and debris connected
with early construction shall be removed periodically from the detention
area and control structure in order to maintain full storage capacity.
E. Temporary Detention. It may be advantageous in some
situations to delay the building of the permanent detention facilities
until after the completion of the other improvements. In these situations,
temporary detention facilities must be provided. The permanent or
temporary detention facilities must be constructed and be functional
before proceeding with any other construction.
F. Off-Site And Regional Detention Concepts.
1.
Off-Site Detention. Stormwater detention facilities
designed and constructed off site or outside the limits of the proposed
development will be considered for approval. This approval is contingent
upon documentation being furnished to verify that drainage easements
have been obtained for the channel area from the proposed development
to the detention facility and including the detention area. The drainage
easements must clearly set out provisions for maintenance.
2.
Regional Detention. Detention facilities designed
and located to provide detention on major drainage channels will be
considered as a regional detention facility and must be one hundred
sixty (160) acres or greater. The facility must provide a detention
volume for a one-hundred-year storm for the entire drainage area and
must be designed with a variable control outlet structure that has
one-year maximum outlet opening. The regional detention facility must
be designed with a low-flow concrete channel through the limits of
the basin. Upon conceptual approval of the location and final approval
of the design and construction, the City of Cassville may accept the
responsibility for the maintenance of the regional facility. Drainage
and access easements will be required giving the City of Cassville
the authority to gain vehicular access to the facility from the public
street.
3.
As additional development occurs upstream of the regional facility,
on-site detention requirements may be waived, provided the regional
detention basin has been designed for full development of the basin,
or if modifications are made to the regional facility by the developer
to provide for the additional volume of detention required for the
new development. Easements must be provided along the drainage channel
from the new development to the regional facility, and the channel
must be constructed to carry the peak rate of runoff from the one-hundred-year
storm for the entire basin upstream from the regional facility.