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5.9.2 Storm sewers shall be bedded using cement stabilized sand (see specification in Section 4.2.3) as <br />shown in the City of La Porte Construction Details. <br /> <br />5.9.3 Pipe requirements. <br /> <br />A. Reinforced concrete pipe installed at a depth greater than thirty feet (30’) shall be designed by the <br />engineer for the specific installation and approved by the City Engineer, Reinforced concrete pipe <br />shall be designed in accordance with the American Concrete Pipe Association, “Concrete Pipe <br />Design Manual”, Maximum cover on the pipe shall be measured from the top of pipe to the <br />ultimate finished grade or natural ground, whichever is greater. <br /> <br />B. Corrugated steel pipe shall have a minimum thickness as follows: <br /> <br /> PIPE SIZE MINIMUM THICKNESS <br /> (Inches) Corrugations (Inches) <br /> 242-2/3” X 1/2” 0.052 <br /> 30- 482-2/3” X 1/21 0.064 <br /> 54- 723’t X 1” or 511 X 1” 0.064 <br /> 78- 102311 X 1” or 5” X 1” 0.079 <br /> <br /> Bedding for corrugated steel pipe shall be cement-stabilized sand. Corrugated steel pipe less than <br /> or equal to fifty-four inches (54”) in diameter and less than thirty feet (30’) deep shall have the <br /> minimum thickness given above. <br /> <br />C. Design storm flow in a street shall not exceed the capacity of the street, for the water surface equal <br /> to the top or curb and shall not exceed the inlet capacity. Design storm flow shall meet Harris <br /> County criteria. <br /> <br />D. All bridges must be a minimum of eighteen inches (18”) above the 100-year water surface <br /> elevation or in accordance with the Federal Emergency Management Agency (FEMA) <br /> regulations, latest revisions, or HCFCD requirements, whichever is greater. <br /> <br />5.9.4 Storm sewers less than forty-two inches (42”) in diameter shall be constructed on a straight <br /> horizontal and vertical alignment between manholes. Storm sewers greater than or equal to forty- <br /> two inches (42”) in diameter may be laid along a curve using manufactured bends of less than or <br /> equal to 11¼’. <br /> <br /> <br />5.10 APPURTENANCES <br /> <br />5.10.1 Manholes <br /> <br /> A. Manholes shall be placed at all changes in alignment, grade and size of the storm sewers; <br /> at the intersection of two or more storm sewers; at all inlet leads; and at the end of all <br /> storm sewers. <br /> B. Maximum spacing between manholes shall be four hundred feet <br /> (400’). <br /> C. Manhole covers shall be cast iron, traffic bearing, type ring and cover with the words <br /> “storm sewer” cast into the cover. <br /> <br /> <br /> <br />5.10.2 Inlets <br /> <br />Stormwater Criteria Page 9 of 10 <br /> <br />