B.
C.
I
J.
6. The date of manufacture and the name or trademark of the manufacturer shall be clearly
marked on the inside of each precast section.
7. Acceptance of the sections will be on the basis of material tests and inspection of the
completed product.
8. Circumferential steel reinforcement in walls and bases shall be a minimum of 0.12 sq.
in/lin. ft. for 4-foot diameter sections and 0.15 sq. in./lin. ft. for S- and 6-foot diameter
sections. Reinforcing shall extend into tongue and groove.
Conical reducing sections shall have a wall thickness not less than 5-inches at the bottom and wall
thickness of 8-inches at the top. Conical sections shall taper from a minimum of 48-inches
diameter to 30-inches diameter at the top, as shown on the drawings.
Except where insufficient depth of cover dictates the use of a shorter base, bases shall be a minimum
of 4 feet in height.
Slab top sections and flat riser sections (Grade Rings) shall conform to the contract
drawings, with particular attention focused upon the reinforcing steel and be designed to meet or
exceed an H-20 Loading requirement.
The tops of the bases shall be suitably shaped by means of accurate ring forms to receive the riser
sections.
Precast sections shall be manufactured to contain wall openings of the minimum size to receive
the ends of the pipes, such openings being accurately set to conform with line and grade of the sewer
or drain. Subsequent cutting or tampering in the field, for the purpose of creating new openings or
altering existing openings, will not be permitted except as directed by the Engineer.
"Drop-over" manholes shall be placed where indicated on the drawings. The Contractor shall
accurately measure the diameter of the existing outlet pipe and inform the manufacturer of
its size, so that the "Drop-over" type opening can be cut into the precast manhole base. The
bottom shall be precast; or cast in place by the Contractor as required by the Engineer. The
invert channel shall be formed of brick and mortar, as specified in this specifications section. The
sub-base shall be a compacted, level foundation of crushed stone, at least 6-inches thick, as
specified in Section 02300 EARTHWORK, but shall vary to the depth necessary to reach sound
undisturbed earth.
All manholes and catch basins shall be coated on the exterior with a bituminous damp-
proofing coating.
The Engineer reserves the right to reject any unsatisfactory precast section and the rejected unit shall
be tagged and removed from the job site immediately.
The Engineer may also require the testing of concrete sections as outlined under Physical
Requirements in ASTM C478 with the Contractor bearing all testing costs.
2022 Sewer Replacement Project Precast Manholes and Catch Basins
Nashua, NH 02631-3
