Figure 4-39.Typical manholes.
noncorrosive wire. If a sewer connection cannot be
made, there should be a hole in the manhole floor so
that water can drain out. A pocket under the manhole
filled with broken rock will promote effective
Before entering any manhole, the vault must
be ventilated to remove all toxic or explosive
gases and ensure adequate oxygen for
survival. Forced air ventilation, respiratory
Figure 4-40.Elliptical type of manhole.
Figure 4-41.Rectangular type of manhole.