Manhole Repair and Rehabilitation

Manhole Repair and Rehabilitation,

(Applies to wet wells and pump stations and similar structures.)

The UK has a wide range off manhole types, mainly concrete and brick
construction, installed over the years.
Manholes can be found in all type of infrastructure, Sewers and drains, surface
water control, industrial plants of all types, chemical plants, foods processing
plants, breweries, refineries etc. etc.
Older manholes were made from engineering and vitrified brick that have
excellent resistance to chemicals and in particular sulphuric acid, formed from
the H2S gas generated by microbiological activity in sewage. These
bricks were excellent when first used in the construction of manholes.
Unfortunately the sand / cement mortar mix used to bond the
bricks together has poor resistance to H2S (resulting in sulphuric acid) and
chemical attack, the mortar joints are attacked by the chemicals and
the mortar can be significantly reduced in strength and consequently affecting
the bonding of the bricks and the structural integrity of the manhole.
Similarly chemical and H2S attacks on unprotected concrete manholes reacts in
the same way, attacking the cement in the concrete and reducing its strength,
dissolving the bond between the aggregate, sand and cement mix resulting in the
eroding the surface and exposing rebar in some extreme cases.
The symptoms of this type of damage to manholes are displayed as infiltration
issues (through brick joints, concrete ring joints, penetrations) causing
overcharging of the downstream treatment plants, exfiltration leading to
pollution and environmental issues, structural failure, damage or complete
destruction to the concrete benching and pipe connections, wash out of backfill
and surrounding ground subsidence.
We have solutions for all aspects of dealing with manhole, pumps station and
wet well problems.
We visit site, survey and examine the problem, (all our operatives are confined
spaces certified), we will recommend and quote for a solution to the problems
identified that can include;
Leak sealing.
Preparation and cleaning of the manhole surfaces.
Repair of benching, mortar joints, replace missing concrete, repair and restore
and protect re-bar.
Application of protective coating.
Check and sign off and issue guarantee for completed work.

CASE STUDY – Concrete Manholes in Brisbane

Case Study – Concrete Manholes in Brisbane

Substrate

1 x Concrete Manhole used in Trunk Line Sewer, Size = 1050 dia x 2.7m deep + biscuit

Condition

 The manhole was in need of repair due to severe high levels of H2S attack and erosion.

Preparation

The chamber was vented above and below the chamber on the sewer line and then an air mover was used to increase the ventilation and airflow. A high pressure power wash was followed by acid etch, wash down and then dried using the air mover.
Spray ApplicationSpraying took 1.5 hours including the preparation. 1 coat of Epoxy was applied at 6mm using approx 40 gallons of Epoxy resin

Outcome

 Redlands Shire Council were impressed with the outcome, more work followed.
Concrete-Manhole-1

Before; – with the temporary pipe to protect the epoxy spray from live sewer.

 

Concrete-Manhole-1

Condition before spraying

 

Concrete-Manhole-1

Preparation finished and spraying commences

Concrete-Manhole-1

Complete Spray

CASE STUDY: Brick Manhole Chambers

Case Study – Brick Manhole Chambers

Substrate10 x Brick Manhole Chambers
SizeManholes all approx 600mm x 600mm at various depths, ranging from .75m to 2m deep
PurposeDrainage system on chemical plant
ConditionVarious, ranging from a very severe build up of mineral deposits to oil and grease residue and had previously been coated with an unknown material plus minor structural defects.
Repair detailsChemicals were leaking into the water table causing pollution issues with EA. A sealed system was required because the drains had recently been re-lined because a sealed system was required
PreparationWhere required the manhole was isolated using inflatable drain plugs and then high pressure power washed. Previous coating was removed using a scabbler. Mineral build up was removed using a CP9 and scabbler. The oil/grease residue was removed using acetone.
Spray1 coat at 6mm applied
Time Scaleapprox 7 days

 

Brick-Manhole-Chambers-Before

Before

 

Brick-Manhole-Chambers-After

After