the depth necessary to reach sound undisturbed earth.
2. Precast reinforced concrete sections shall be set vertical and with sections in true
alignment.
3. Butyl rubber joint sealant shall be installed between each concrete section. Catch
basin sections do not require joint sealant if so indicated on the drawings.
4. All holes in sections used for handling the sections shall be thoroughly plugged with
mortar. Mortar shall be one part cement to 1-1/2 parts sand, mixed slightly damp to
the touch (just short of "balling"), hammered into the holes until it is dense and an
excess of paste appears on the surface, and then finished smooth and flush with the
adjoining surfaces.
B. BRICK WORK:
1. Bricks shall be moistened by suitable means, as directed, until they are neither so dry
as to absorb water from the mortar nor so wet as to be slippery when laid.
2. Each brick shall be laid as a header in a full bed and joint of mortar without requiring
subsequent grouting, flushing or filling, and shall be thoroughly bonded as directed.
3. The brick inverts shall conform accurately to the size of the adjoining pipes. Side
inverts shall be curved and main inverts (where direction changes) shall be laid out in
smooth curves of the longest possible radius which is tangent to the centerlines of
adjoining pipe.
C. CASTINGS:
1. Cast iron frames, grates and covers shall be as specified. The frames and covers
shall be set by the Contractor to conform accurately to the grade of the finished
pavement, existing ground surface, or as indicated on the drawings. Frames shall be
adjusted to meet the street surface.
2. Cast iron manhole frames and covers not located in paved areas shall be set 6-inches
above finished grade, at a height as directed by the Engineer, or as indicated on the
drawings. The top of the cone shall be built up with a minimum of 1 course and a
maximum of 5 courses of brick and mortar used as headers for adjustment to final
grade.
3. Frames shall be set concentric with the top of the concrete section and in a full bed of
mortar so that the space between the top of the concrete section or brick headers and
the bottom flange of the frame shall be completely filled and made watertight. A
thick ring of mortar extending to the outer edge of the concrete shall be placed all
around the bottom flange. The mortar shall be smoothly finished to be flush with the top
of the flange and have a slight slope to shed water away from the frame.
2019 Sewer Replacement Project Precast Manholes and Catch Basins
Nashua, NH 02631-6
