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<br />Page 20 <br /> <br />TABLE VIII <br />Manhole Spacing <br /> <br />Pipe Size <br />15"to 36" <br />42" or greater <br /> <br />Maximum Spacing <br />500 feet <br />600 feet <br /> <br />Sewer grades shall be such that a minimum l' 6" cover over the cro.'n <br />of the pipe is maintained. If less cover is shown, the Engineer <br />shall submit his pipe structural design to the City Engineer for <br />approval. Uniform slopes shall be maintained between manholes. <br />Final grades shall be set with full consideration to capacity re- <br />quired, sedimentation problems, and other design parameters. The <br />minimum slope shall be capable of producing a velocity of 3 feet per <br />second when the sewer is flowing full carrying the initial storm. <br /> <br />When an existing culvert is to be extended and the grade changed, a <br />concrete collar as shown in design standard No. 28 in the Engi- <br />neering Regulations, Construction Specifications, and Design Stand- <br />ards shall be used. <br /> <br />The minimum width of easement for installation of a storm sewer <br />shall be the pipe diameter plus 10 feet with the pipe normally <br />centered in the easement. <br /> <br />Storm Sewer Criteria shall be as shown in Table IX. <br /> <br />TABLE IX. STORM SEWER DESIGN CRITERIA <br /> <br />Initial Storm <br /> <br />Major Storm <br /> <br />Min. velocity <br />Depth of flow <br />Max. velocity <br />Pressure head <br /> <br />3.0 fps <br />pipe diameter <br />16.0 fps <br />o (open <br />channel flow) <br /> <br />n/a <br />n/a <br />20.0 fps <br />~ pipe diameter <br /> <br />The hydraulic grade line shall be plotted for all storm sewers. The <br />hydraulic grade line (depth plus pressure head) shall be 1. 0 ft. <br />lower than the gutter line. When the hydraulic grade line is not <br />1.0 ft. below the gutter line, then the capacity of the storm sewer <br />shall be taken as the maximum capacity flowing full without pressure <br />head and all excess flow carried in the street. The depth of flow in <br />the street shall meet the criteria specified in Table VII. <br /> <br />C. Detention Facilities: Detention facilities shall be provided as speci- <br />fied in Ordinance 0-81-165 excerpted below: <br /> <br />"Any person, firm, corporation or business proposing to construct <br />buildings, or develop or redevelop land within the City, shall be <br />required to provide storm water runoff control meeting the require- <br />ments of Ordinance 0-81-165 whenever the total area of land under <br />identical ownership, including the land to be developed or upon <br />which buildings are to be constructed, equals or exceeds those shown <br />