The following technical provisions shall be used in the design
of sewers connected to or a part of the city sewage system. For facilities
for which specific requirements are not provided, the city engineer
shall determine the design parameters:
1. Sizing
of all sewers shall be based upon a complete drainage study of the
present proposal as well as all existing and potential up-stream contributing
areas. Minimum main size is six inch diameter.
2. Sewers
shall be designed to handle a per capita average flow of one hundred
gallons per day for residential areas.
3. Commercial
and industrial areas will require the design of sewers to handle the
quantities discharged as determined by the applicant's engineer with
the approval of the city engineer.
4. Design
of the sewer lines will be based upon peak flows in accordance with
the standard practice adopted by the American Society of Civil Engineers
in their manual on Engineering Practice No. 37 latest revision.
5. All
sewers shall be designed to flow two-thirds full under peak design
conditions.
6. The
minimum size of a lateral sewer shall be four inch diameter. The minimum
slope of a lateral sewer shall be a minimum five tenths foot per one
hundred feet and the minimum cover shall be twenty-four inches unless
a variance from these standards is given in writing by the city engineer.
7. Sewer
Slopes. The minimum slopes of pipe are as follows:
Size of Pipe
|
Minimum Slope
|
---|
6 inch
|
.0034
|
8 inch
|
.0024
|
10 inch
|
.0020
|
12 inch
|
.0014
|
15 inch
|
.0012
|
8. All
sewer mains and laterals shall be vitrified clay pipe. This pipe shall
be rubber gasket, wedge lock, band seal or equal.
9. Manholes
shall be used to make all turns.
10. Manholes
on straight sewer lines shall be placed a maximum of four hundred
feet center to center.
11. Sewer
mains in curved streets shall be a minimum of twenty feet from the
nearest property line and shall be on a minimum two hundred foot radius.
Manholes between tangents shall not be closer than twenty-four feet
to the nearest property line.
12. Manhole
covers in undeveloped areas will be set one foot above existing grade.
13. All
manhole stubs shall be shown on the plans by size.
14. Clean-out
or manhole shall be used on dead-end lines.
15. All
sewer mains in the street shall be in a location designated by the
city engineer.
16. All
sewer laterals shall be extended to the property line and shall be
a minimum four inch diameter but in no case shall the sewer lateral
on public property be smaller than the lateral on private property.
17. The
lateral invert at the curbline shall be three feet below the curb
flowline grade.
18. Lift
stations shall be avoided where possible. However, it is recognized
that they may have to be used and the following design requirements
are to be adhered to in their design:
a. Pumps
or ejector units shall be provided in duplicate arranged for positive
priming.
b. Capacity
shall be provided to handle ultimate peak flow from the tributary
area. When the tributary area exceeds three hundred acres the capacity
shall be provided to handle the peak ultimate flow with the largest
pump out of service. Staged installation of pumps is allowed providing
space is provided for future installation.
c. Access
shall be provided to the site for removal and repair of equipment.
d. A
means of dewatering force mains shall be provided.
e. An
overflow device will be provided if possible as approved by the city
engineer.
f. Forcemains
shall be designed so as to be able to pass the peak flows without
excessive pressures, and the materials shall be corrosive resistant
to the type of sewage being delivered through them. Force mains shall
be designed as to obtain a minimum of three feet per second velocity
during the pumping period.
19. New
sewers shall have a maximum allowable infiltration/exfiltration rate
of two hundred gallons per day per inch diameter of sewer per mile.