4.9 General Design Considerations
a. General Requirements.
1) All general requirements are per City Sewer Master Plan
2) Sanitary sewer systems shall be designed and constructed to achieve total containment of sanitary wastes and maximum exclusion of infiltration and inflow.
3) Sewers shall be designed to convey the peak instantaneous wet weather flows anticipated over the design period without surcharging.
4) Where possible, all sanitary sewers shall be designed to flow by gravity to an existing or new sewer without sewage lift stations.
5) As a condition of sewer service, all developments will be required to provide public sewers to serve adjacent upstream parcels in order to provide for the orderly development of the drainage area, as well as connection (to the new system) of existing sewer lines or laterals crossed or intercepted by the new sewer lines, at locations as required by the Director (see also PWDS 1.6.e). This shall include the extension of sewer mains in easements across the property to adjoining properties and across the street frontage of the property to adjoining properties when the main is located in the street right-of way. This shall include extension to the far side of streets fronting or adjacent to the development as required to avoid work within or under these streets in the future. This shall include trunk sewers which are oversized to provide capacity for upstream development.
6) Storm water, including street, roof or footing drainage, shall not be discharged into the sanitary sewer system but shall be removed by a storm drainage system separate from the sanitary sewer system.
7) Unpolluted (noncontact) cooling waters shall not be discharged into sanitary sewers.
8) Public sewers within easements will be permitted only upon a showing that services cannot be provided from a line within a right-of-way. Minimum easement widths shall be as outlined herein, but in no cases shall easements narrower than 15 feet be considered.
b. Design Factors.
1) The following factors as a minimum shall be addressed in the design of sanitary sewers and determination of design flows.
a) Drainage basin to be served.
b) Topography of the area
c) Depth of excavation
d) Service lateral elevations
e) Soils conditions
f) Land use within the area to be served.
g) Projected population within the area to be served at build-out.
h) Per capita sewage flow.
i) Flows from commercial, industrial or institutional users.
j) Infiltration and Inflow
(1) Infiltration allowance for new facilities.
(2) Infiltration and inflow from existing facilities.
k) Maximum hourly and peak instantaneous flows
l) Condition and size of existing sewers
m) Location of WWTP
n) Pumping requirements
o) Maintenance, including accessibility for cleaning and inspection personnel and equipment.