A. Generally. The subdivider shall provide a sanitary sewer system in accordance with the following criteria:
1. The system shall be of a size not less than that which is specified by the sanitary sewer master plan on file with the public works director.
2. The system shall have adequate capacity to serve the subdivision and the full service area tributary thereto in accordance with the city design standards. The tributary area shall be determined by the public works director.
3. When required, the subdivider shall provide a pumping plant to convey the effluent to an existing system.
The director will determine the point of connection to the existing sewer system. The subdivider’s engineer shall prepare a design analysis of the proposed sanitary sewer system in accordance with the sanitary sewer master plan on file with the public works director. When staged construction is proposed, the analysis shall thoroughly cover the design of the entire system.
B. Design Flow. Recommended design criteria for the determination of the sanitary sewer design flow for residential and commercial development are given in Table 5.
The director will determine on all individual basis if industrial waste will be accepted into the city system or if other provision for its on-site disposal will be made.
C. Conduit Design.
1. Type. Sewer conduits shall be extra-strength vitrified clay pipe conforming to ASTM Designation C 200, with plastisol, or equal, compression joints, or polyvinyl chloride (PVC) sewer pipe with a maximum DR of 35, conforming to ASTM Designations D 2784 and D 3034, with flexible elastomeric seals conforming to ASTM Designation D 3212.
In new sewer line construction, wyes to tees for house service connections shall be complete fittings. Saddle type connections will not be permitted.
2. Size. The minimum sanitary sewer size shall be eight (8) inches in diameter except that six (6) inch pipe may be used in the last run in residential areas on cul- de-sacs and in locations where no future extensions of the main are intended.
No sewer pipe shall have a diameter less than that of the pipe immediately upstream from it.
3. Slope. Slope will be controlled by physical conditions and velocity criteria. Abrupt changes in slope are undesirable and should be avoided wherever possible.
4. Velocity. The minimum velocity shall be 1.8 fps when the pipe is flowing full and/or half-full.
5. Head and Head Losses. Sanitary sewers shall be designed to pass the design flow with a free water surface. Proper consideration shall be given to minor head losses.
6. Alignment. Alignment will be straight between manholes with no bends except that curved alignment with a minimum radius of 500 feet may be used in special cases.
7. Location. The location of sanitary sewers relative to roadway centerline shall be in accordance with the improvement standards. Care should be taken that sanitary sewers and other underground facilities do not conflict with each other.
8. Depth. Minimum sewer depth shall be four and one-half (4.5) feet from flowline to finish grade. For unimproved streets where street grades have not been set, the minimum depth shall be five (5) feet from the flowline to existing grade.
D. Manholes.
1. Type. The type of manholes to be utilized shall be as set forth in the improvement standards.
2. Location. Manholes shall be placed:
a. Where two or more sewer mains join;
b. Where the conduit changes in size;
c. At angle points;
d. At points where a change of slope in the conduit occurs.
3. Spacing. Manholes shall be spaced no farther than 350 feet apart.
4. Grade. The crowns of all conduits intersecting at a manhole shall match.
E. Flushing Holes. Flushing holes shall be of the type shown in the improvement standards and shall be placed in accordance with the improvement standards. They shall not be used except in cul-de-sacs or at temporary ends of lines if the end of line does not occur at a manhole. Flushing holes shall be placed no more than 150 feet from a manhole.
F. Laterals.
1. Size. Minimum lateral size for single-family dwellings shall be four (4) inches in diameter. All others will require special design, and design calculations shall be submitted for approval.
2. Slope. Laterals shall have a minimum slope of two (2) percent.
3. Location. Laterals shall be provided for every lot and shall generally be centered on each lot. They shall be at right angles or radial to the sanitary sewer main.
Laterals shall be installed to a point at least five (5) feet into the property prior to other utility installation, pressure testing and subsequent connection to the effluent source.
4. Depth. Laterals shall have a three (3) foot minimum cover at the back of the sidewalk. Where the sewer main is ten (10) feet or greater in depth, deep sewer risers shall be installed.
G. Temporary Pumping Plants. The subdivider’s engineer shall design any needed pumping plants subject to the approval of the director. Each design will be considered on an individual basis.
(Res. No. 9 77-78 (part), Res. No. 87 86-87 §1, Res. No. 86 87-88, Res. No. 113-07, Res. No. 19-13)