(A) General. These design criteria are not intended to cover extraordinary situations. Deviations will be allowed and may be required in those instances where considered justified by the City Council.
(B) Design factors. Sanitary sewer systems should be designed for the ultimate tributary population. Due consideration should be given to current zoning regulations and approved planning reports where applicable. Sewer capacities should be adequate to handle the anticipated maximum hourly quantity of sewerage and industrial waste together with an adequate allowance for inflow/infiltration and other extraneous flow.
(C) Maximum size. The diameter of sewers proposed shall not exceed the diameter of the existing or proposed outlet, whichever is applicable, unless otherwise approved by the appropriate agencies.
(D) Minimum size. No public sewer shall be less than eight inches in diameter; except that, the use of six-inch diameter sewers may be permitted in situations where it cannot be extended, and no more than 400 feet will be installed in any one place.
(E) Velocity of flow. All sewers shall be designed and constructed with hydraulic slopes sufficient to give mean velocities, when flowing full, of not less than two feet per second (based on Kutter’s or Manning’s Formula, using an “n” value of 0.013). Use of other practical “n” values will be approved for the longer pipe sections if deemed justifiable on the basis of research or field data presented. The following are the minimum slopes which should be provided:
Minimum Slopes for Sewer Sizes | |
Sewer Size (Inches) | Minimum Slope in Feet, per 100 Feet |
Minimum Slopes for Sewer Sizes | |
Sewer Size (Inches) | Minimum Slope in Feet, per 100 Feet |
6” | 0.50 |
8” | 0.40 |
10” | 0.29 |
12” | 0.22 |
15” | 0.15 |
16” | 0.14 |
18” | 0.12 |
21” | 0.10 |
24” | 0.08 |
(F) Alignment. All sewers shall be laid with straight alignment between manholes, unless otherwise directed or approved by the appropriate agencies.
(G) Manhole location. Manholes shall be installed at the end of each line; at all changes in grade, size or alignment; at all intersections; and at distances not greater than 400 feet for sewers 15 inches and smaller, and 500 feet for sewers 18 inches in diameter and larger. The installation of cleanouts is prohibited.
(H) Manholes. The difference in elevation between an incoming sewer and the manhole invert shall not exceed 24 inches, except where required to match crowns. The use of drop manholes will require approval by the appropriate agencies. The minimum inside diameter of the manholes shall conform to those specified by the state’s Department of Environmental Quality. When a smaller sewer joins a larger one, the crown of the smaller sewer shall not be lower than that of the larger one. The minimum drop through manholes shall be 0.2 feet.
(I) Lift stations and payment for wastewater systems components.
(1) Lift stations are discouraged.
(2) However, when no other engineering solution is available, lift stations shall be constructed at the developer’s expense.
(J) Ownership of sanitary sewer system components. After completion and acceptance of the developer’s sewers constructed pursuant hereto, the sewers shall thereupon be and become a part of the city’s sewerage system.
(K) Sewerage locations. Sanitary sewers shall be located within street, alley rights-of-way or utility easements, unless topography dictates otherwise. When located in easements on private property, access shall be available to all manholes. A manhole shall be provided at each street or alley right-of-way, where possible. Cover on the sewer lines shall be in accordance with the state’s Department of Environmental Quality Standards.
(L) Water supply interconnection. There shall be no physical connection between a public or private potable water supply system and a sewer which will permit the passage of any sewage or polluted water into the potable supply. Sewers shall be kept away from water supply wells and other water supply sources and structures.
(M) Relation of sewers to water mains. A minimum horizontal distance of ten feet shall be maintained between parallel water and sewer lines. At points where sewers cross water mains, the sewer shall be constructed of water line pipe or encased in concrete for a distance of ten feet in each direction from the crossing measured perpendicular to the water line. This will not be required when the water main is at least two feet above the sewer.
(2002 Code, § 153.088) (Ord. 230, passed 9-8-1986; Ord. 651, passed 10-26-2009) Penalty, see § 153.999