[R.O. 2012 §525.090; Ord. No. A-5926 part 1 §A, 6-9-1994; Ord. No. A-7097, 10-26-2001]
A. 
Drainage Area Plan. A plan of the drainage area at a scale of one (1) inch = one hundred (100) feet with two (2) foot contour intervals 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 = three hundred (300) feet with five (5) 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.
B. 
Hydraulic Data. Complete hydraulic data showing all calculations shall be submitted. A copy of all nomographs and charts used in the calculations shall be submitted if other than those included herein are utilized.
C. 
Plan And Profile. A plan and profile of all proposed improvements at a scale of 1 inch = 40 feet horizontal and 1 inch = 4 feet vertical shall be submitted. This plan shall include the following:
1. 
Locations, sizes, flow line elevations and grades, type of pipe, channels, boxes, manholes, and other structures drawn on standard plan-profile sheets;
2. 
Existing and proposed ground line profiles along centerline of the drainage improvement;
3. 
A list of the kind and quantity of material;
4. 
Typical sections and reinforcement of all boxes and channels;
5. 
Location of property lines, street paving, sanitary sewers, and other utilities, both public and private.
D. 
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 problem must be solved before the plan will be given approval.
E. 
Storm Water Flow Quantities. Storm water 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 Article.
F. 
Sinkholes Or Karst Areas. Sinkholes or karst areas shall be clearly defined. If any portion of the storm water 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 ground water and streams.
G. 
Additional Information. Any additional information deemed necessary by the Superintendent of Utilities for an adequate consideration of the storm drainage effect on the City of Monett and surrounding areas must be submitted.
H. 
Discharge flow from the storm water detention outlet structure shall be directed into existing channels, existing natural draws, watercourses, drainage easements or to public rights-of-way. Discharge flow shall connect to existing downstream storm sewers if directed by the City of Monett.
Discharge to Developed Property that Contains Existing Structures or Improvements:
The developer shall obtain drainage easements across already-developed property and construct facilities to drain to existing channels, existing natural draws, watercourses, drainage easements, or to the public right-of-way.
Discharge to Undeveloped Property that Does Not Contain Existing Structures or Improvements:
The developer shall discharge water to a point, existing channel, existing natural draw or water-course that will contain a drainage easement in the future when the property develops.
[R.O. 2012 §525.100; Ord. No. A-5926 part 1 §B, 6-9-1994]
A. 
General Design Requirements.
1. 
All bridges shall be designed to accommodate a one hundred (100) year frequency rain. Box culverts, pipe culverts, channels, and ditches shall be designed to accommodate a one hundred (100) year frequency rain at all locations having a drainage area in excess of 1.00 square mile. Locations having a drainage area of less than or equal to 1.0 square mile shall be designed to accommodate a twenty-five (25) year frequency rain.
2. 
Channel improvement types shall be as follows:
a. 
Improvements with a capacity of up to and including 10 C.F.S. shall be open and (1) sodded; or (2) concrete paved invert; (3) concrete lines; or (4) closed conduit;
b. 
Improvements with a capacity above 10 C.F.S. up to and including 100 C.F.S. shall be closed conduit;
c. 
Improvements with a capacity above the 100 C.F.S. up to and including 250 C.F.S. may be open and (1) concrete paved invert; or (2) concrete lined; or (3) closed conduit;
d. 
Improvements with a capacity above 250 C.F.S. shall be open and (1) concrete lined; or (2) have a 100 C.F.S. low flow paved invert.
B. 
Specific Requirements For Various Improvements.
1. 
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 materials and to carry HS-20 loadings in all cases.
2. 
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 materials shall meet the requirements of the latest revision of the City of Monett 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 Monett.
Closed storm sewers shall extend to the furthest downstream point of development with consideration given to velocities and to providing discharge energy dissipators to prevent erosion and scouring along downstream properties.
3. 
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 (6) inch freeboard must be provided. An eighteen (18) inch toe wall is required at both the outlet and inlet ends of the channel.
4. 
Open ditches (earth channels). Ditches shall have a gradient that limits the velocity within 1.5 to 5.0 feet per second depending on existing soil conditions. Such ditches shall have a minimum side slope ratio of 3:1. The designer's attention is directed to the fact that the Subdivision Regulations prohibit encroachment of buildings and improvements on natural or designated drainage channels or the channel's flood plains. Such flood plains are areas of land adjacent to an open paved channel or an open sodded ditch that may receive a flood condition from a one hundred (100) year frequency rain. The limits of such flood plains shall be indicated on drainage improvement plan.
[R.O. 2012 §525.110; Ord. No. A-5926 part 1 §C, 6-9-1994]
A. 
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 time of concentration and rainfall intensity curves included as a part of this Article.
A 5-minute time of concentration is the minimum permitted.
A = Drainage area, in acres.
1. 
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
.10-.15
Tall grass, brush
.15-.20
Parks, golf courses,farms, and one (1) acre single-family residences
.35
Single-family residences on lots of not less than 15,000 square feet
.45
Single-family residences on lots of not less than 10,000 square feet
.47
Single-family residences on lots of not less than 7,500 square feet
.51
Single-family residences on lots of not less than 6,000 square feet
.90
Gravel surfaces
.95
Asphalt and concrete surfaces
1.00
Buildings and other structures
2. 
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 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 called the time of concentration. This may include overland flow time and channel or gutter flow time. Nomographs which may be used for determining time of concentration are reproduced at the end of this Chapter. Once the time of concentration is known, the design intensity rainfall may be determined from the rainfall intensity curves developed from U.S. Weather Bureau data.
[R.O. 2012 §525.120; R.O. 2012 Tbl. 1 to Section 525.120; Ord. No. A-5926 part 1 §D, 6-9-1994; Ord. No. A-5926 Tbl. 1, 6-9-1994]
A. 
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/n ar2/3 s1/2
Q = Capacity = Discharge in cubic feet/sec.
a = Cross sectional area of water in conduit or channel in square feet
r = Hydraulic radius of water in conduit or channel = 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
B. 
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
C. 
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 TO SECTION 525.120. STREET FLOW
Street flow shall be limited by pavement encroachment and depth of flow as follows:
Street Classification
*Maximum Encroachment of a two (2) year storm
Local
No curb overtopping. Flow may spread to crown of street
Collector
No curb overtopping. Flow spread must leave the equivalent of one (1) ten (10) foot driving lane clear of water.
Arterials
No curb overtopping. Flow spread must leave the equivalent of two (2) ten (10) foot driving lanes clear of water.
*Where no curbing exists, encroachment shall not extend past property lines.
The storm sewer system shall commence at the point where the volume of flow equals 5 cfs.