(A) Plans signed by registered professional engineer. The plans for all sewer lines, sewage lift stations, sewage treatment facilities and the like shall be designed, signed and sealed by a registered professional engineer licensed in the state.
(B) Compliance with state’s Health Department requirements. All sewer lines, lift stations, sewage treatment facilities and the like shall be designed in accordance with state’s Health Department requirements.
(C) Size and capacity. Minimum sanitary sewer main size shall be eight-inch diameter. Minimum storm drain size shall be eight-inch diameter. Larger sizes shall be as required by the city’s overall sewer system master plan or as needed to provide adequate sewage carrying capacity for the area (and surrounding developable area) being developed and/or annexed to the city. Minimum service line size shall be four-inch diameter.
(D) Depth. In general, sewers shall be sufficiently deep so as to receive sewage from basements and to prevent freezing. Sewer lines shall have at least three feet of cover (from the top of sewer line pipe to the ground or street surface), unless a special design is approved by the Public Works Superintendent whereby the sewer line is protected from freezing by special means or methods and the sewer is protected from heaving by the installation of crushed gravel backfill material under, around and over the pipe.
(E) Slope.
(1) All sewer mains shall be designed and constructed to provide mean velocities, when flowing full, of not less than two feet per second (fps). All sewer service lines (side sewers) shall be designed and constructed to provide mean velocities, when flowing full of not less than three feet per second. The following are minimum slopes which should be provided, however, slopes greater than these are desirable.
Sewer Size | Minimum Slope in Feet per 100 Feet |
4-inch | 2.00 |
6-inch | 1.00 |
8-inch | 0.40 |
10-inch | 0.33 |
12-inch | 0.31 |
15-inch | 0.15 |
18-inch | 0.12 |
21-inch | 0.10 |
24-inch | 0.08 |
27-inch | 0.067 |
30-inch | 0.058 |
33-inch | 0.046 |
(2) Under special conditions, if detailed justifiable reasons are given, slopes slightly less than those required above (i.e., to provide two or three fps velocity when flowing full) may be permitted. Such decreased slopes will only be considered where the depth of flow will be three-tenths of the diameter or greater for the design average flow. Whenever such decreased slopes are proposed, the design engineer must furnish with his or her report the computations of the depths of flow in such pipes at the minimum and average rates of flow for a typical day.
(3) Sewers shall be laid with uniform slopes between manholes, i.e., a manhole shall be constructed at each point where the sewer line slope or grade changes.
(F) Location of manholes. Manholes shall be located no more than 400 feet apart on lines 15 inches in diameter or smaller. Manholes may be located up to 600 feet apart on lines larger than 15 inches in diameter. Manholes shall be installed at locations where sewer line eight inches in diameter or larger intersect, join together or make a bend. All dead-end sewer lines shall have a manhole installed on the end thereof.
(G) Sewer mainline drop through manholes. The following of the main sewer line as it enters and leaves any manhole shall be dropped as follows:
Mainline Bend of | Drop of |
0 to 10 degrees | (Regular pipe slope) |
11 to 45 degrees | 0.05 |
46 to 90 degrees | 0.10 feet |
(H) Lateral sewer line connections at manholes. Lateral sanitary sewer lines shall not enter a manhole at an elevation appreciably higher than the sewer main line. The flowline(s) of any lateral shall be positioned within the manhole as follows.
(1) The flowline of the main sewer line shall be at least five one-hundredths foot below the flowline of any of the lateral sewer lines entering the manhole. Where the diameter of the main line and the lateral line shall differ by less than five-tenths foot, the top of the lateral line shall be positioned even with the top of the main line on its high (inlet) side.
(2) Where the diameters of the main and lateral differ by five-tenths of a foot or more, the eight-tenths depth points of the two sewer line inverts shall be positioned at the same elevation.
(3) Where a lateral sewer line would enter a manhole at an elevation of three feet or more above the main sewer line, drop manhole construction shall be utilized to locate or position the flowline of the lateral line (in relation to that of the main line) as indicated above.
(4) Where a lateral line would enter a manhole at an elevation of less than three feet above the main sewer line, the grade or slope of the lateral shall be adjusted so that its flowline is located (in relation to that of the main line) as indicated above.
(5) Individual building service lines may not enter manholes, except that no more than two individual building service lines may enter a dead-end manhole (a manhole on the upstream and permanent end of a sewer line); and provided further, that the individual building service lines must enter the manhole at such elevation that the top of the service line is level with the top to the sewer main line and that the poured-in-place concrete floor of the manhole brings the flowlines of the service lines into the flowline of the main line in a smooth continuous manner.
(I) Location of water and sewer lines and storm drains. Sanitary sewer lines and water lines shall, whenever possible, be located 13 feet west or north of the street center line and the sanitary sewer at 13 feet east or south of the street center line. Where storm drains are needed, these shall preferably be located along the street center line. The locations and dimensions referenced in this division (I) may be varied to accommodate unusual circumstances; however, a ten-foot (out-to-out) horizontal separation between water line facilities and sewer facilities (either sanitary or storm) and an 18-inch (out-to-out) vertical separation between these facilities shall always be maintained unless a specific variance to this requirement is obtained from the Public Works Superintendent. The applicable separation requirements of the state’s Health Department shall also be complied with.
(J) Drawings. All drawing shall be on linen or Mylar in pencil or ink and of such quality that they clearly show the dimensions, locations, sizes and the like, of all facilities represented thereon. All sewer line manholes, inlet boxes, building service lines and the like, shall be clearly shown and identified by name and by station or other means of horizontal location. Sewer lines shall be shown in both plan and profile unless the length of the sewer line or sewer extension is so short that the Public Works Superintendent waives this requirement. If a profile of the sewer line is not provided, it shall be located in the vertical plane by elevations on the flowline of the pipe at all manholes, inlet boxes and the like, and at other such locations and intervals as the Public Works Superintendent may require. Drawings shall be drawn on a scale of one inch equals 100 feet unless the amount of detail, topography and the like, necessitates their being drawn on a larger scale (i.e., one inch equals 50 feet or one inch equals 40 feet) to provide the clarity and completeness needed on their drawings.
(K) Design. The design of all sewer lines and all sewer line plans must be approved by the Public Works Superintendent.
(Prior Code, § 8-4-33) (Ord. 92-554, passed 10-21-1992)