Section 7 1 C. Manholes
SECTION 7 SANITARY SEWER GRAVITY COLLECTION SYSTEM
1. New manholes shall be precast. Cast-in-place concrete or brick masonry manholes may be used only if approved by the City Engineer. Precast manholes shall conform to ASTM C478, with Type II acid resistant cement. All manholes shall have 48″ minimum inside diameter and shall have monolithically poured base.
2. Concrete in precast manholes shall maintain a minimum compressive strength of 4000 psi in 28 days, and all reinforcing bars shall be ASTM A615 grade 60 steel with minimum of 3 inches cover.
3. Manhole built-in sections shall be joined with a mastic compound or a round compression ring of neoprene material set in annular spaces cast into the spigot end of a bell and spigot type joint. The mastic compound or ring shall be uniformly compressed between the positioned sections so as to form a watertight joint. After the sections are assembled, the remaining space in the joint shall be pointed up and filled with dense cement mortar and finished so as to make a smooth, continuous surface inside and outside the wall sections.
4. Shallow manholes may have an eight inch (8″) precast reinforced concrete slab on the top in-lieu of the conical sections. Slabs shall have a twenty-four inch (24″) minimum diameter access hole centered in the slab.
5. Precast manhole cones or slabs shall terminate at such elevations as will permit laying up a minimum of three (3) courses and maximum of (5) courses of clay brick under the manhole frame to make allowance for future street adjustment and/or settlement.