[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
(a) 
Sodded, or
(b) 
Closed conduit;
(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
(b) 
Concrete lined; or
(c) 
Closed conduit;
(4) 
Improvements with a capacity above the two hundred fifty (250) cfs shall be open and:
(a) 
Concrete-lined; or
(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.