Manhole Rehabilitation Avoids Manhole Replacement

manhole rehabilitation

Once sewer systems went underground, the need for the manhole evolved. Now, many of these manholes need manhole rehabilitation to restore their structural stability.

Sewer systems, even though they are thought of as a modern invention, had their beginnings thousands of years ago.  Around 600 BC, the Romans built their eleven-foot-high stone vault, called the Cloaca Maxima (or Great Sewer) that emptied stormwater and wastewater from baths and latrines to the Tiber River, which ran beside the city.

Here in the U.S. and prior to the 1800s, if you lived in a city, untreated waste would most likely be dumped into the nearest stream of water to become somebody else’s problem downstream. The first full public sewer systems in the U.S. were built in Chicago and New York City in the 1850s.

Backups from sewer clogs

After many backups from sewer clogs, designers soon found the need to gain access to the underground sewer pipes which led to the addition of . . . the manhole.

Traditionally made of brick and mortar, modern manholes are now made of precast concrete or composite materials. Original brick sewer manholes still exist around the country. Many of these need manhole rehabilitation due to deterioration of the mortar joints between the bricks, allowing water to leak into the sewer system.

Sulfuric acid can eat away and weaken joints.

The deterioration process begins when hydrogen sulfide (H2S) gas, also known as sewer gas, created by bacteria in the sewage, combines with moisture on the walls of the manhole and oxygen gas from the air in the manhole, to form sulfuric acid (H2SO4). The effect of the sulfuric acid can eat away and weaken the joints between bricks and in severe cases can cause the manhole to collapse. Manhole rehabilitation can restore the manhole to prevent replacement.

Manholes are considered confined spaces

Blackwell’s, Inc. recently rehabilitated damaged sewer manholes. Since manholes are considered confined spaces, we provided trained associates with confined space protocols to do the repairs.

The manhole rehabilitation repairs included a polymer modified repair mortar applied to the weakened joints and a coating system specifically formulated for manhole rehabilitation and lining of sewer collection systems. This system is designed for high moisture tolerance and hydrogen sulfide (H2S) resistance. It also seals and protects the manhole from inflow and infiltration (I&I) of groundwater.

Initial pressure washing of manhole before repairs
manhole rehabilitation
After repairs and protective sewer lining
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