Fiberglass Manholes for Foot Traffic Locations

Most fiberglass manholes are installed in locations where neither foot or vehicular traffic is present. For those applications a fiberglass domes top is provided to aid in operator access. But what do you do when the manhole has to be placed where foot traffic will be present?

One approach is to use a standard grade ring / frame / cover system. This is a tried and true method but which has operator access issues. Now Openchannelflow’s H-20 reducer opening sized at a generous 31 ¾-inches diameter - which provides twice as much open area as the 22 ½ opening H-20 reducer you might be used to (about 790 square inches of access), but for even greater access, Openchannelflow offers foot traffic rated aluminum covers.

fiberglass manholes with aluminum covers for use in foot traffic pedestrian areas

Openchannelflow's aluminum tops are split to provide clear access to 2/3 of the manhole’s opening:

On a 48-inch diameter manhole, the open access is 1280 square inches (62% greater than a 31 ¾-inch H-20 reducer).
On a 60-inch diameter manhole, the open access is 2002 square inches (153% greater than a 31 ¾-inch H-20 reducer).
On a 72-inch diameter manhole, the open access is 2882 square inches (300% greater than a 31 ¾-inch H-20 reducer).

As you can see, as the manhole diameter gets larger, the aluminum top’s advantage in open access increases dramatically over that of even Openchannelflow’s oversized H-20 reducer.

A further advantage is that the ladder for the aluminum top manhole extends up to the underside of the aluminum top – essentially up to surface grade. In contrast, H-20 reducers are sized so that the shoulder of the reducer is about 12-inches below grade to provide space for grade rings to bring the frame and cover up to surface grade. This unfortuntately puts the first rung of the ladder at least 14-inches below surface grade - making it awkward to get into and out of the safely.

Note that the standard aluminum manhole cover is not watertight. While a gasket is provided between the cover and the mounting flange that it is bolted to on the manhole, some water can enter through the standard aluminum top.

For foot traffic applications where the cover must be watertight (or gastight), an optional cover is available. The optional cover mounts a rectangular watertight hatch in an aluminum diamond plate surround. Note that changing from a spit cover to a rectangular hatch does reduce the amount of open area for the operator to enter / exit the manhole.

fiberglass manhole with optional aluminum hatch top

Keep in mind, that while robust, Openchannelflow aluminum manhole covers are NOT intended for use in traffic areas. If there is a chance that vehicles may run over the cover, the cover should be protected by bollards or the manhole should be supplied with a H-20 reducer top instead.