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 drainage.

WARNING

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.