(A) Criteria regarding the location, spacing, sight distance, and other features regarding the design of driveways shall be in accordance with the following publications and regulations:
(1) Indiana Department of Transportation (INDOT) Driveway Permit Manual, latest edition;
(2) The INDOT Design Manual; and
(3) The minimum standards for auxiliary lanes shall be in accordance with Chapter 155. These criteria shall be minimum values. The County Engineer may require the use of higher criteria when significant traffic volumes, a large percentage of truck traffic, or other factors, as determined by the County Engineer, are present.
(B) The applicant shall provide drainage information, including development site plans and drainage calculations showing existing and proposed drainage patterns, including existing contours, to the County Highway Department with proof that there are no adverse effects to drainage patterns in the vicinity caused by the development.
(1) If a drainage permit has been issued by the county for the proposed development, then the information in this division will not be required. Class V drives are also exempt from this requirement.
(2) Any diversion of water flow to the right-of-way shall be fully identified and explained. There shall not be any increase to flows unless the development drains to an adjacent stream of adequate capacity to convey the augmented and future development drainage.
(3) If downstream drainage capacity is inadequate, the applicant shall provide flow detention on the developed property. Absolutely no detention is allowed on a county right-of-way. Detention structures and means of discharge shall be adequately presented and explained on plans and in calculations provided to the County Highway Department. The county strongly discourages the use of orifice plates for the control structures. The preferred method is to install a section of pipe of the appropriate size to restrict the flow.
(4) The 100-year developed property run-off rate shall not exceed the ten-year undeveloped property run-off rate. Thus, the entire Q100 run-off shall be detained on the property and released at the ten-year undeveloped property run-off rate. These criteria shall be followed unless a local agency has a more restrictive ordinance. The rational method for detention design may be used for developments that are two acres or less in total size. Detention analysis for developments larger than two acres shall be performed using a method that generates hydrographs for both the inflow and the outflow.
(5) The minimum size opening for all drainage structures crossing under two-lane county routes shall be 12 inches in diameter for round pipes or 1.1 square feet for deformed pipes. The minimum pipe sizes under driveway approaches shall be 12 inches in diameter for round pipes or 1.1 square feet for deformed pipes. All pipes with diameters from 12 inches to 36 inches shall have pipe end sections appropriate for the type of pipe used. Pipes with diameters greater than 36 inches shall have concrete anchors.
(6) The County Highway Department uses the following design frequencies for any type of drainage structures on a highway:
(a) For arterial routes, a 50-year storm event design;
(b) For collector routes, a 50-year storm event design;
(c) For local routes, a 50-year storm event design;
(d) For driveways, a ten-year storm event design; and
(e) For side ditches, a ten-year storm event design.
(7) The Stormwater Drainage Manual published by the Highway Extension and Research Project for Indiana Cities and Counties (HERPICC), now Indiana Local Technical Assistance Program, or LTAP, provides considerable information about the design of drainage structures.
(8) Adjustments to existing highway storm sewer structures may be necessary, such as relocation of an inlet displaced by the driveway approach. The relocated structure shall be compatible with those servicing the segment of county road. The INDOT English Standard Sheet MD contains the design of drainage structures commonly used along county roads.
(9) Minimum pipe structure materials shall be either corrugated steel or reinforced concrete, Class III. Alternate materials may be used if approved by the County Engineer.
(10) Minimum pipe size is 12 inches in diameter and 24 feet long. End sections are required on culvert pipes.
(11) The table below is a guide. The applicant shall abide by the manufacturer’s specifications for minimum and maximum cover in determining the proper gauge.
Minimum Gauges For Steel Pipes
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Pipe Thickness (Gauge)
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For Pipe Diameters
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0.064 inches (16 gauge) | 12 inches through 21 inches |
0.079 inches (14 gauge) | 24 inches through 36 inches |
0.109 inches (12 gauge) | 42 inches through 60 inches |
0.168 inches (8 gauge) | 66 inches through 96 inches |
(12) Pipes shall not be smaller than structures upstream from their location.
(Ord. 1999-6E, passed 6-28-99)