(A) Manhole excavation shall be kept free from water during construction. Space excavated below the depth required for the manhole base shall be refilled with compacted sand or crushed stone.
(B) Manhole floors shall be formed with concrete to a depth of one-half the incoming sewer size with the floor sloped to the sewer invert. Floors for “straight through” manholes shall be formed by laying the pipe straight through the manhole, pouring the concrete and then cutting out the top half of the pipe. Floors shall be constructed as the manhole is being built and this thickness is in addition to the eight-inch base required.
(C) Precast concrete risers and adjusting rings shall be used in such combination that the top of the concentric cone section, when installed, will be at proper elevation for the manhole frame. Concrete adjusting rings shall be allowed up to a maximum of 12 inches height adjustment. Manholes needing more than 12 inches adjustment shall have a concrete riser section installed to the proper elevation.
(D) Manhole frames shall be brought to grade, centered and embedded in a mastic bending course after the mortar bedding has set up. The inner face of this mortar joint shall be trowel finished.
(E) Steps shall be built into all manholes four feet in depth or greater and shall begin eight inches below the bottom of the chimney. Steps shall be installed at 16 inches on center maximum.
(F) Precast concrete risers and cone sections shall be installed so that the axis of the manhole is vertical. Gaskets for riser joints shall be installed in accordance with the manufacturer’s recommendations.
(G) Unless otherwise indicated, set castings for manholes at finish grade level.
(H) Remove all debris and excess soil from manhole after construction.
(Ord. 2002-5-1, passed 5-14-02; Am. Ord. 2013-3-1, passed 3-28-13)