| 摘要 |
A manhole assembly for below ground liquid storage tanks, such as fuel storage tanks, that includes securing the upper region of the below-grade manhole to the at-grade manhole so that lowering of the below-grade manhole bottom due to tank settling or stepping on the hatch cover will not lower the below-grade rim relative to the at-grade ring. Riser pipe extenders can be added without interfering with hatch cover closure and sealing of the below-grade manhole. One embodiment includes adjustable length bolts tying the at-grade ring to the below-grade ring. The assembly can be factory assembled, delivered to the site, and installed on the riser pipe then height adjusted before pea gravel, backfill, and concrete are poured. Bellows and bucket manholes can be used.
|
