|Looking even better
|The most important stage of the installation of the
Barra da Tijuca Marine Sewage Outfall is about to
begin: laying pipe for the outfall line. The project
will clean up Rio de Janeiro’s Marapendi Lagoon
|Written by Eliane Salles
Photos by Carlos Júnior & Ricardo Gomes
Residents of Rio de Janeiro, particularly people living in the districts of Barra da Tijuca, Recreio dos Bandeirantes and Jacarepaguá, are about to seen a long-held dream come true: the cleanup of Marapendi Lagoon. An important part of the Barra da Tijuca Sanitation Program (Portuguese initials: PSBT), which aims to prevent sewage from polluting the area’s lagoons, beaches and waterways, is nearing completion – the Barra da Tijuca Marine Sewage Outfall. This project is being built by Barra Nova, a joint venture of two contracting companies: Construtora Norberto Odebrecht, Carioca Christiani-Nielsen Engenharia. An initiative of the Rio de Janeiro state water and sewage company, CEDAE, construction of the outfall has reached the critical stage: laying the pipe for the outfall line.
Expectations are that by the end of this year the outfall will be discharging 900 liters per second of treated sewage well away from the coastline – 5,200 meters from shore, far from the rich water resources of one of the loveliest and most valuable areas of Rio de Janeiro. Sewage from the districts of Barra da Tijuca, Recreio dos Bandeirantes and Jacarepaguá is currently treated by apartment buildings with over 40 units and deposited in Marapendi Lagoon. Smaller buildings do not treat their waste at all, and dump raw sewage into the same lagoon.
These districts, which lie in the West Zone of the city, constitute the fastest-growing part of Rio. Their population has grown four-fold in the last 20 years. Today, they are home to over 600,000 people. This demographic explosion has taken its toll on the environment, and despite the fact that cleanup programs have been high on the agenda of residents, politicians and environmentalists since the 1980s, their demands are only now being met with action.
The insidious impacts of water pollution are innumerable, ranging from damage to people’s health, destruction of local plant and animal life, and economic losses. Sportspeople, fishers, ecotourists, regular tourists and merchants all shy away from the area’s lagoons when seeking places for work and recreation. “Now that the cleanup program is underway, the health sector will feel the benefits immediately and directly. The program will also add value to business ventures and help protect our water sources,” explains Roberto Cumplido, Odebrecht Contract Director for Sanitation Projects in Rio de Janeiro State.
The PSBT also includes construction of sewage collection and interception facilities and a treatment plant. The State Environmental Conservation and Human Development Fund (FECAM), whose resources come from royalties generated by the Campos Basin oil fields, is financing the entire program.
When this stage of project is completed, the outfall will discharge up to 2.8 cubic meters per second. “During the second stage, it will discharge 5.6 cu. m., which will be enough to handle the area’s sewage output up until 2020. We have built two sections in the surf zone so we won’t have to build a new structure to install another section in the future,” says CEDAE’s Alduir Melquíades, who heads the Guanabara Bay Cleanup Program and is also responsible for the PSBT.
Scheduled for completion by June, the outfall will be the first PSBT project delivered, and is certainly the most complex. It is made up of two pipelines. The first, which is 5,180-m long, will begin operations this year. Another 518-m section will be closed until needed to meet increased demand.
To build the project, the joint venture acquired cutting-edge materials and technologies and international expertise. The joint venture’s teams devised and developed some innovations themselves. They decided to sideline iron and steel, once the materials of choice where pipe was concerned. Instead, high-density polyethylene (HDPE) pipe has come into play. Because HDPE cannot rust or rot, it does not pollute the environment. It has an average useful life of 50 years, and neither sea plants nor shellfish can attach themselves to it. Due to the size of each of the sections – 518 meters in length, an internal diameter of 1.4 meters and an external diameter of 1.5 m – they were manufactured by the Portuguese branch of the Finnish firm KWH Pipe. The biggest pipe made in Brazil is one meter in diameter. Pipe that is over 2 meters in diameter is not available on the world market, because it is still undergoing tests. All told, the joint-venture contractor purchased 11 sections of pipe, which were towed across the Atlantic in two stages.
The outfall starts at the oceanfront, where it will be connected to a treatment plant now under construction. It was precisely at this point that the joint-venture contractor’s experts met their greatest challenge. First, the initial 300 meters of the pipeline had to be installed underground because that section ran through a recreational area that is popular with beachgoers. To install the pipe, the contractor’s teams had to build a temporary pier – a structure that was 300 m long and 12 m wide and weighed roughly 2,300 tonnes.
Then another challenge arose. When construction of the pier was starting to move forward, the team hit sandstone, a sedimentary rock consisting of sand consolidated with some cement (clay or quartz etc.). The sandstone occupied 180 meters of the area where the pipeline was supposed to be installed underground. The solution was to blast through the rock, and once again, the team came up with the best way to do it. They developed a system involving equipment installed above the pier to drill holes in the rock, place the explosives and remove an average of 55 cu. m. of sandstone daily.
“The blasting had no environmental impact whatsoever. We hired the National Waterway Research Institute (INPH) to carry out a study and submitted it to the State Environmental Engineering Foundation (FEEMA) for its approval. FEEMA gave us a special permit to remove the sandstone,” says Odebrecht’s José Lauro Contrucci Larica, the joint venture’s Operational Manager.
The next challenge they faced was clearing up the blasted rock. To stay on schedule, it had to be removed in two shifts using a crane with a 9-tonne clamshell bucket to remove the material from the trench and place it into a vehicle equipped with several buckets, which unloaded it on the beach.
Meanwhile, the pipe was being made ready for installation in another part of town, in the Caju district, part of Rio de Janeiro’s docklands. Because the project’s plans called for 300 meters of pipe to be installed underground in the surf zone, the remainder was to be laid directly on the seafloor, so counterweights were needed to prevent the pipeline from floating. As a result, a concrete counterweight was attached every 5 meters. All told, the joint venture made 1,306 counterweights weighing 7.5 tonnes apiece. “We developed equipment specially designed to install the counterweights,” says Production Manager Marco Guerreiro, from Carioca Christiani-Nielsen.
Construction of the Barra da Tijuca Marine Outfall began in April 2001, halted for nearly a year due to a lack of funds, and was only able to resume in January 2003. It required over two years of hard work, and for some periods, the teams took turns working day and night shifts to stay on schedule and get ready to install the pipe when the “sea window” arrived. This phenomenon, which calms the waters and furnishes the ideal conditions for laying pipe in the surf zone, generally occurs between December and February. However, Rio de Janeiro had unusual weather that summer, so the joint venture was forced to wait until the end of March and early April.
Meteorologists at the Universidade Federal do Rio de Janeiro Marine and Atmospheric Process Modeling Laboratory monitored the phenomenon to determine the exact time when it would occur. This is because many preparations had to be made just before the “window” opened. The pipe, which was still in Caju, had to travel 29.5 nautical miles (53 km) to the construction site in Barra da Tijuca. As a result, the joint venture needed the help of the Brazilian Navy (Rio de Janeiro Port Authority) and even the boats that ferry passengers between the cities of Rio de Janeiro and Niterói, which had to stop when the pipeline crossed their paths.
Another important point was that sand is replaced very quickly in the surf zone, where the trench is located. ”We had to build highly productive equipment that could dredge the trench in two days, maximum,” recalls José Lauro Contrucci Larica.
A dredging specialist, engineer Marco Nicolette, was brought in to help with this task. With his aid, the joint-venture team put a dredger into operation. When coupled to the pier, it removed the fine sand that the waves brought in. The joint venture hired another specialist, Belgian engineer Yan Larsen, to help with the installation of the pipeline. An expert in that area who has taken part in 46 similar operations, he did all the calculations and developed the procedures for sinking the pipeline, making sure that this delicate operation went off without a hitch. “You work for two or three years to prepare for a task that takes a single day. That requires careful planning, including a risk matrix, which involves mapping and quantifying risks and finding solutions, in case you need to implement them. On the day, things are very tense, and several teams are working on many different fronts at the same time. Everything has to be very well planned in extensive detail,” explains Engineering Manager Evando Barros Júnior, from Odebrecht.
The pipe left the Caju worksite on March 30 at 12:40 pm and reached its destination at 4 am the next day, when it was anchored 1 km from the pier. Twelve tugboats with Brazilian Navy escorts towed and positioned the pipe, while the operation was monitored from two helicopters and two motor launches. The installation procedure, per se, began at 8:30 am. The first closed stretch of pipe was towed using a 20-tonne crane and placed between the supporting piles of the pier. Then, it was depressurized and gradually filled with water until it sank to the bottom. After that, pre-cast pieces were used to hold it in place. The teams used reinforced-concrete “handles” attached at 5-meter intervals along the pipe, in an excavated area with depths ranging from 3 to 8 meters. Once it was depressurized, the pipeline sank in approximately 20 minutes. The operation was marked by careful maneuvers from the tugboats, with the help of divers and people on jet-skis.
The installation of the first pipeline ended at around 3 pm that same day. The second section was installed two days later. The remainder – three 1,554-meter pipelines connected to the first – will be installed underwater in April. Because these sections will lie directly on the seabed, ideal ocean conditions will not be necessary to put them in place, but that job will also require good weather.