Sanitary Sewer Design...
General Design Criteria...
Requirement for Sanitary Sewer...
All sanitary sewage of domestic and other water borne wastes shall be collected and conveyed in a sanitary sewer pipe
system to a point of discharge into an existing sanitary sewer system, City of Naperville interceptor, or sewage treatment
plant. No sanitary sewage shall be allowed to enter any storm sewer system or discharge onto the ground or into receiving
streams without first being treated in accordance with city, county, state and federal regulations.
Design Approval...
The Department of Public Utilities shall approve all designs and shall alter the following design requirements as
necessary to meet the City Utilities Master Plan. The Department of Public Utilities and the Transportation Engineering
and Development Business Group shall review and comment on all designs. Proposal of new sanitary sewer lift stations
requires approval from the Director of Public Utilities, prior to the design and review process. The City of Naperville’s
standard details, as currently adopted by the Department of Public Utilities, should be used in all construction plans.
Any modifications to these standard details require approval from the Director of Public Utilities.
IEPA Permit Required...
All public sanitary sewer mains require an IEPA Construction permit number and an Illinois Pollution Control Board
permit number, prior to construction. Some private extensions may require a permit, dependent upon the design population
equivalent.
Differentiation Between Public and Private Sanitary Sewers...
Those portions of the sanitary sewer system that are located within the public right-of-way are the responsibility of the
City. The City shall also maintain public mains, serving more than one customer. The maintenance and repair costs for the
sanitary sewer system located on private property, beyond the limits of the right-of-way, are the responsibility of the
property owner or property owner’s association depending on the associate’s covenants and guidelines. In such cases
where the City performs maintenance or repairs on the private sanitary sewer system, the City reserves the right to
charge the property owner for necessary work. All engineering plans shall clearly differentiate between public and
private sanitary sewers.
Easements...
All public sanitary sewers that are not located within a publicly dedicated right-of-way shall be placed in a public
utility and drainage easement, minimum 15 feet wide or as directed by the Department of Public Utilities, to the City of
Naperville. The easement shall be granted to the City either through a recorded plat of subdivision or a recorded plat of
easement. The City shall be granted access to these easements if not directly adjacent to public right-of-way. At the
discretion of the Director of Public Utilities, the City may require additional easements for future maintenance or repair
of sanitary sewers, even those sewers that may be located within the public right-of-way. For example, the City may have
an extra deep sanitary sewer located within the public right-of-way. However, the City may require a public utility and
drainage easement parallel to the edge of the right-of-way to accommodate future repair of the sanitary sewer if it ever
needs to be excavated and repaired.
Sanitary Sewers...
Sanitary Sewer Pipe Materials...
All sanitary sewer pipe materials and appurtenances shall be in conformance with Section 302 of the City of Naperville
Standard Specifications.
Location in the Public Right-Of-Way...
Sanitary sewers shall be located within the public right-of-way as directed by the City Engineer. In general, sanitary
sewers shall be located 7.5 feet inside the right-of-way on the south and east sides of the right-of-way.
Curvilinear Alignment of Sanitary Sewers...
Curvature of sanitary sewers is allowed for sewers 8 inches to 12 inches in diameter. Alignments must follow the general
alignment of streets. Only a simple curve design is acceptable. The minimum allowable radius of curvature is 300 feet.
Compression type pipe joints are required and manholes are required at the beginning and end of all curves. Maximum joint
deflection shall not exceed the manufacturer’s recommendations.
Sewer and Water Main Separation...
Sanitary sewers and services that are laid in the vicinity of pipelines designated to carry potable water shall meet the
conditions set forth in Section 5 of this manual.
Depth of Pipe Cover...
All pipe shall be laid to a minimum depth of 7 feet measured from the proposed ground surface to the top of the pipe,
unless specifically allowed otherwise in special circumstances by the Director of Public Utilities. If allowed, sanitary
sewer and services with ground cover less than 4 feet or more than 25 feet must be constructed of ductile iron class 50
pipe with polywrap. All sanitary sewers and services with less than 4 feet of cover shall be insulated with a 2- inch
exterior grade rigid insulation board. The insulation shall have a minimum R-value of R-9, and comply with ASTM C 578-92
Type 1X.
Overhead Sewers...
The City reserves the right to require overhead sewers, dependent upon the depth of the main and the loading.
Sanitary Sewer Sizing...
Sewer size shall be designed on the basis of a design average flow of not less that 100 gallons per capita per day and
provide a minimum of 2.0 feet per second velocity when flowing full. The Director of Public Utilities may increase sewer
size in accordance with Section 3.2.7 noted below. In no case shall a public sewer be sized less than 8 inches in diameter.
Oversizing and Extra Depth Requirements...
The Director of Public Utilities may request that sanitary sewers either be oversized or installed at an additional depth
in order to provide service to additional benefiting properties. Section 7-3-6 of the Municipal Code (City participation
in construction of public improvements) outlines the City’s policy relative to cost sharing for oversizing and extra depth
installation.
Sanitary Sewer Slopes...
All sanitary sewer slopes shall meet the requirements of the following sections :
Minimum Slopes...
Sanitary sewers shall be designed such that the minimum slopes are not less than the following :
Maximum Slopes...
Sanitary sewers shall be designed such that the slopes do not exceed a maximum of 12%. If the sanitary sewer system cannot
be designed without exceeding a slope of 12%, then drop manhole assemblies shall be utilized.
Last Run of Manhole Sets...
On last runs of all manhole sets, a minimum 1% slope needs to be provided in order to provide adequate flushing due to low
flows.
Limits of Installation...
At a minimum, sewers shall extend across the frontage of the property, at the developer’s cost, such that a connection can
be made with minimal disturbance in the future. In some cases, the City may require that the sanitary sewer be installed
from one corner to the diagonally opposite corner, at the developer’s cost.
Sanitary Sewer Manholes...
Manholes for sanitary sewers shall have a minimum inside diameter of 48 inches and shall be constructed of pre-cast
concrete units in accordance with ASTM C 478 and Section 32 of the "Standard Specifications for Water and Sewer Main
Construction in Illinois," and shall follow the City of Naperville sanitary sewer standards.
Manhole Location and Spacing...
Manholes shall be located at the junction of two sanitary sewer pipes or at any change in grade, alignment or size of pipe.
The maximum spacing of manholes shall be 500 feet, or as approved by the Director of Public Utilities. In general, the City
of Naperville prefers to minimize the number of manholes needed for a project. This will help reduce future operation and
maintenance costs.
Invert Elevations in Manholes...
Inverts of similar size pipe are to match other inverts. Where a smaller pipe intersects a larger pipe, the spring line or
top of pipe of both pipes shall be at the same elevation, unless otherwise directed by the Director of Public Utilities.
This is also to be done when tapping (core and boot required) into an existing manhole.
Drop Manholes...
Drop manhole assemblies shall be provided at the junction of sanitary sewers where the difference in grade is in excess
of 2 feet. The drop assembly shall follow Naperville Standards with filleted inverts. Drops are to be made outside of the
structure unless otherwise approved by the Naperville Department of Public Utilities. A minimum of 24 inches between the
inverts of the drop assembly must be provided. If the difference between the inverts is less than 24 inches, the inverts
must match. When pipe inverts in a manhole do not meet the requirements of section 3.3.2, a drop manhole assembly shall be
used.
Requirement for Inspection Manholes and Clean-Outs...
All commercial, office, institutional, industrial, and manufacturing buildings shall have an inspection manhole located
outside of the building that will allow the City to observe the discharge from the building into the public sanitary sewer
system. An inspection manhole is required for any multi- family building that has more than six (6) units. Additionally,
clean-outs shall be required on multi- family services serving between two (2) and six (6) units. A clean-out will also be
required for any service line over 90 feet in length which does not have an inspection manhole.
Grease / Oil / Sand Trap Manholes...
Grease/oil/sand trap manholes, as required by the Illinois Plumbing Code, shall be shown on the engineering plans.
Appurtenances...
Casing Pipes...
Manufactured non- metallic or non-corrosive casing spacers, adjustable runners, or cradles shall be used to support the
pipe in the casing. A minimum of two supports shall be used per pipe for lengths up to 12.5 feet, and a minimum of three
supports shall be used for lengths greater than 12.5 feet, or per manufacturer’s recommendation. The annular space shall
be filled with pea gravel or as required by permitting agency, and provisions shall be made so that no voids are left
to prevent flotation.
Casing Pipe Material...
The steel casing pipe shall be bituminous coated, a minimum of 30 mils thickness inside and out, and shall be of leak proof
construction, capable of withstand ing the anticipated loadings. The steel casing pipe shall have a minimum yield strength
of 35,000 psi and shall meet the requirements of ASTM A139, Grade B. Ring deflection shall not exceed 2% of the nominal
diameter. The steel casing pipe shall be delivered to the jobsite with beveled ends to facilitate field welding.
Sizing of Casing Pipes...
The diameter of the casing pipe shall be a minimum of 12 inches greater than the outside nominal diameter of the sewer.