CIPP used to rehab more than 2,000 feet of pipe in one of the first major trenchless projects south of the border.
The U.S. and Canada have successfully used CIPP for years to rehab deteriorating pipe. South of the border, however, the process is just beginning to flex its underground infrastructure mending muscle.
Take Mexico City. A population in excess of 20 million is tough on all the city’s infrastructure through the sheer volume of use. Add the burden of assets aging out, plus constant heavy traffic loading and sewer gas corrosion, and you already have a major maintenance headache. Pile on another layer of punishment from a substantial 1985 earthquake that shifted, cracked and even fully separated large sections of sanitary sewer lines, and that headache reaches migraine status.
Now imagine you must deal with the immediate repair of a 2,625-foot section of this system, just 7 miles from the most congested area of the city. What do you do?
It wasn’t a rhetorical question for Ramon Aguirre, general director of the Mexico City Water Authority.
Before trenchless made its debut, rehabilitating a deteriorated sewer pipe under a busy street meant closing it for weeks — if not months — at a time for a traditional open-dig project. Businesses and residents were significantly impacted. No functional sewer line meant Aguirre and his team had to consider and implement alternate waste disposal processes, re-route traffic (which affected sales for businesses), adjust parking and create safety barriers around a huge work site. Aguirre was wide open to new alternatives that would limit these negative impacts.
In 2014, the Sistema de Aguas de la Ciudad de Mexico (SACMEX) requested proposals for rehabilitation of a 2,625-foot section of concrete sewer line, directly off a main artery in the Colonia Roma district of Mexico City. Minimizing disruption for people in the area was a major point called out in the request, so traditional methods were not an option.
The project consisted of five residential and industrial gravity 60-inch-diameter sewer lines with manhole access running beneath existing roadways. Their flow was being slowed by sand, dirt and stormwater infiltrating through cracks and broken or missing sections. Friction from H2S-roughened pipe walls compounded the problem.
INBODE, previously solely an equipment distributor, chose the project to bid on for actual implementation of the new CIPP technology in Mexico. The company saw it as a perfect proving ground for CIPP south of the border.
“We knew it would minimize discomfort and the consequences of social and economic impact to the street’s businesses and residents,” says Angel Amaya, an assistant technician at INBODE.
Thorough Pre-Installation Cleaning
Before the CIPP process could begin, a comprehensive cleaning and inspection was needed. Flow was blocked with a pneumatic plug and a Thompson brand pump provided power to re-route it through a bypass. The work area was cordoned off with road marking and vehicular traffic control personnel.
INBODE is the exclusive distributor of Vacall combination sewer cleaner equipment in Mexico and maintains a fleet of these vehicles to serve both public and private entities. Pre-inspection cleaning was achieved using a Vacall AllJetVac (AJV) P series model 1215 combination sewer truck from Gradall Industries Inc. Operators employed storm and torpedo type nozzles to blast away accumulated debris so CCTV inspectors could come in to survey the pipe’s condition.
Visualizing Needed Work
INBODE is also the Mexican distributor for R.S. Technical Services Inc. CCTV video inspection equipment. The company chose an R.S. Technical vehicle-mounted system for this project. Running a TrakSTAR pan-and-tilt zoom camera on a Steerable Storm Drain Tractor capable of televising pipes up to 200-inch diameter, the video feed was streamed back to the truck’s computer using POSM software.
“As in the United States, much of Mexico’s extensive sewer infrastructure has reached or exceeded its service life and will soon need attention. Our success in the structural recovery of these systems depends heavily on the work of video inspection,” says Amaya. “We chose R.S. Technical equipment for its versatility and performance, which allows real-time visualization of the physical/structural condition of the inside of the pipe, the input of information about diagnosis of obstructions and failures, and pipeline construction design.”
Since cleaning had left the pipe relatively free of debris, the video inspection work took place without problems over a 72-hour period. This included three separate camera passes — one before the process of introducing the liner sleeve, to ensure all debris and blockages had been removed and to identify service connections and current pipe conditions; a second during the CIPP process to monitor proper sleeve installation and curing; and a final one after the last pipe rehabilitation, to provide proof of effective rehabilitation without defects.
While televising took place, technicians began setting up the CIPP equipment, which consisted of a conveyor belt system for the wet-out process, a bulk storage tank to hold the resin, the static mixer to accurately combine and dispense the two-part resin/initiator impregnation material, and heaters and pumps for the process water.
INBODE performed “over-the-hole” (OTH) wet-out and installation of the resin-impregnated felt liner. Conducting on-site resin impregnation reduced the risk of contamination or mishandling during transportation of the impregnated felt liner from wet-out to the cure site. Also, the busy nature of the area precluded work that would take too long. The shorter OTH method execution time minimized operation downtime in each section and the impact on street users.
What stood in the way of getting started was the lack of availability, in Mexico, of all resin initiators typically used in the process. Usually, American and Canadian contractors use Trigonox C liquid and Perkadox 16 powder, but the Perkadox was not available at the time in Mexico.
INBODE worked with Interplastic Corp. out of St. Paul, Minnesota, to construct a resin specifically designed to cure with the only applicable initiator available in Mexico City: Trigonox 121 liquid.
Another challenge was providing the significant amount of water required for the CIPP liner inversion and curing, since the streets lacked fire hydrants. INBODE trucked the water in using tankers, which had to be strategically scheduled and staged to reach the site as needed, within a fixed open working time before the resin cured. Careful planning was critical, and during the most intensive phase, a dozen or more tankers were lined up along side streets, waiting to be called for off-load.
Scheduling was also crucial to deliver product and perform any needed work within the constraints of Mexico City’s strict regulations, which are intended to keep things moving among the huge population and constant traffic congestion.
The Big Show
The first section — about 510 feet of 22.5 mm thick and 60-inch-diameter liner — was installed on a Friday afternoon. The two-component mix was measured and dispensed into it on the conveyor belt one slug at a time. The wetted-out tube was inverted and fed into the host pipe through the access box. This inversion was achieved through pressure from a shot of cold water, its head pressure calculated according to the size and weight of the wet-out liner.
Once it was completely inverted into the pipe, the water was heated using a boiler truck to about 180 degrees F, where it remained for eight to 12 hours until the resin cured and the liner became rigid. Then the water was cooled for four to eight hours to below 100 degrees F, after which the ends were cut out, curing water flowed out downstream, and service laterals were restored.
The project was completed on Monday, and the new pipe-within-a-pipe is expected to last at least 50 years.