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D. Manholes <br />1. Pipe Grades and Channel Slope <br />Manholes shall be designed to minimize head loss through the structure. The crown <br />of the pipes exiting the manhole shall not be higher than the lowest crown of the pipes <br />entering the manhole, or, 80 percent of the flow depth of the pipe exiting the manhole <br />shall not be higher than the lowest flow depth of the pipes entering the manhole. <br />The slope of the channel through a manhole shall be the same as the pipe upstream <br />from the manhole; any change of pipe grade shall occur at the manhole outlet. <br />2. Locations <br />Manholes shall be installed at each of the following locations: <br />• End of each main line <br />• Changes in grade, size or alignment (vertical and horizontal) <br />• Distances not greater than 400 feet for pipes 24 inches and smaller <br />Manhole spacing for pipes 30 inches and larger shall be as directed by the City to meet <br />operational considerations at each location. In no case shall the manhole spacing <br />exceed 800 feet for pipes 30 inches and larger. <br />Blind connections are allowed for catch basins, area drains and curb inlets where <br />structures serve roadway drainage and are located at right angles to the storm mains <br />in the roadway. <br />Manholes shall be positioned outside normal wheel travel paths (centered in the lane <br />or between lanes) and outside the center of an intersection where the turning path <br />of vehicles may place a wheel path over them. <br />3. Shallow/Flat Top Manhole <br />A shallow or flat top manhole shall be used when there is less than 5 feet of cover <br />over a pipe. <br />4. Size and Diameter <br />See City Standard Specification for Construction and Standard Drawings for manhole <br />style, size and material properties. <br />Public Improvement Design Standards Manual, 2016 Page 2-12 <br />