T2 7
4 8
2. Type Il cement shall be used except as otherwise approved.
3. Sections shall be steam cured and shall not be shipped until at least five days after
having been cast.
4. Minimum compressive strength of concrete shall be 4000 psi at 28 days.
5. No more than two lift holes may be cast or drilled in each section.
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 5- and 6-foot
diameter sections. Reinforcing shall extend into tongue and groove.
B. 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.
C. Except where insufficient depth of cover dictates the use of a shorter base, bases shall be a
minimum of 4 feet in height.
D. 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.
E. The tops of the bases shall be suitably shaped by means of accurate ring forms to receive the
riser sections.
F. 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.
G. —_"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
2019 Sewer Replacement Project Precast Manholes and Catch Basins
Nashua, NH 02631-3
