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The design of storm sewers, outfalls, culverts and drainage ditches within a subdivision shall conform to the following:
(A) Manholes. Manholes, inlets or junction boxes shall be provided at all changes in grades or alignment, sewer intersections, street intersections and at a maximum of 500 feet on straight lines. Manhole design and detail shall follow acceptable engineering practices. Manholes shall be constructed of reinforced concrete only.
(B) Pipe or storm drain. The pipe or storm, drain shall be constructed of concrete pipe, HDPE Pipe, or as specified by the City Engineer, and shall be sized as shown on the approved plans. Pipe shall be a minimum of 18 inches or larger in diameter. Concrete pipe shall be reinforced ASTM C-76, class 3. HDPE pipe shall be made from virgin polyethylene and comply with the requirements for test methods, dimensions, and markings found in AASHTO Designations M252, M294, and MP7-97. When added strength of pipe is needed for traffic loads or excessive height of backfill, concrete pipe shall be ASTM C-76, class 4 or 5. Pipe shall have a minimum cover of not less than one foot over the top of the pipe.
(C) Pipe bedding and backfill. Details for pipe bedding and backfill shall be approved by the City Engineer.
(D) Ditches. Drainage ditches, where approved by the City Council, may be used for outfalls to natural or manmade major drainage channels. Ditches shall have a minimum grade that will arrive at a velocity of not less than one and one-half feet per second, and not larger than four feet per second. Velocities may exceed four feet per second with the utilization of appropriate erosion control measures. Side slopes shall not be steeper than three horizontal to one vertical. Maximum depth shall be four feet without the use of a guardrail.
(E) Major drainage ways and structures. The design of major drainage ways through a subdivision and major structures, such as box culverts or bridges across major drainage channels, shall be coordinated with the City Engineer and the city's comprehensive plan (latest edition), and if deemed appropriate, the county engineer.
(Ord. 09-0721, passed 7-21-2009; Ord. 19-1022B, passed 10-22-2019) Penalty, see § 155.999