Award of Merit: Water Structures Category
Deep Drainage System Evaluation and Rehabilitation
Submitted by BASF Corporation
Sistema de Aguas de la Ciudad de México
Intituto de Ingenieria UNAM
Mexico City, Mexico
Lombardo Construcciones SA
The Drenaje Profundo of Mexico City (Deep Central Drainage) is a tunnel with a depth of 164 ft (50 m) and a diameter of 21.3 ft (6.5 m) that began operation in 1975. This system was designed for the removal of sewage and rainwater in Mexico City, which includes integrated Interceptors Center West, Central, and East with an overall length of 103 miles (166 km).
In 2006, the staff of the Water Authority of Mexico City carried out inspections inside tunnels that had an inadequate hydraulic performance. These examinations revealed deterioration of the tunnel coating and exposure of reinforcing steel with resulting steel corrosion and loss of section. The concrete inside the pipeline was heavily damaged by the hydrogen sulfide gas caused by decomposition of organic matter in the wastewater—mostly in the crown of the tunnel—and damage in the bottom of the tunnel caused by the scour of solids.
A method was developed to repair the deterioration using a system that provided chemical resistance to this type of hydrogen sulfide attack. The surface was prepared and mortar was pneumatically applied. The final surface was given a two-part chemical-resistant coating. The rehab- ilitation following this procedure was made in 0.9 miles
(1.5 km) of tunnel.