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5.9 ADDITIONAL REQUIREMENTS <br />5.9.1 Minimum depth of storm sewer (measured to the top of pipe) shall be twenty-four (24") below the <br />top of curb or finished grade, whichever is lower. Minimum size storm sewer for main land and <br />inlet lead shall be eighteen inch (18"). <br />5.9.2 Storm sewers shall be bedded using cement stabilized sand as shown in the City of La Porte <br />Construction Details. <br />5.9.3 Pipe requirements. <br />A. Reinforced concrete pipe installed at a depth greater that 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 />B. Corrugated steel pipe shall have a minimum thickness as follows: <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 />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 />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 />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 />5.9.4 Storm sewers less that 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 11'/4'. <br />10 APPEARANCES <br />10.1 Manholes <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 six hundred feet (600') <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 />Stormwater Criteria Page 9 of 10 <br />