<< Back January 2006

Avenida Grau Leads Straight to the Past
By C.J. Schexnayder

A massive transportation upgrade in the center of Lima is providing historians a rare opportunity to look at the engineering techniques of another age. The excavation for the Miguel Grau Freeway project has uncovered a wealth of public works that date back to Lima's colonial period, including sewage systems and the city's original wall.

“One of the most important things we are learning is exactly where this and other works were located exactly,” said Guillermo Cock Carrasco, the director general of ConsultPatCu E.I.R.L. who is overseeing the archeological aspects of the project. “Formerly we had an idea but couldn't tell for sure.”

The public works projects that followed the razing of the city wall in the late 19th century required the pre-Columbian water canals to be covered. .

Last January, Lima began an $18.5 million upgrade of Avenida Grau in the center of the Peruvian capital. When completed, the new 3.5 kilometer Miguel Grau Freeway will be a lynchpin for four arteries that extend out from the heart of Lima.

“Currently, [Av.] Grau supports about 80 percent of the public transportation in the city, and is located next to the center of Lima,” said José Justiniano head of engineering department for EMAPE, Lima's public works agency. “It is the point of entry for several highways that converge on the center of Lima that lead to the most populated districts of the metropolis, zones that have grown tremendously in the last ten to fifteen years.”

That uncertainty of where historically significant items were going to be found created headaches for the construction of the new freeway. The stop-start process that followed has delayed the completion of the road for several months, said Armando Molina, the project manager for the City of Lima.

Every construction project in Peru requires an environmental assessment that includes an archeological portion. In recent years, a number of private companies like Cock's have begun to capitalize on the growing number of projects in the country by offering services to perform archeological impact studies and handle the excavation once the project progresses.

Typically, this is aimed at understanding if there will be any effect on the country's rich pre-Spanish heritage but, in the case of the Grau Freeway, it is the history of the city that is being uncovered, Cock explained.

The bulk of their work on the Grau project has been the excavation of ceramics. The old city wall was Lima's de-facto dump and, to date, Cock's group has excavated more than 30,000 metric tons of ceramic pieces, providing a wealth of information about the city's late colonial and early republican period.

“This is a by-product of the disasters that have struck the city through the centuries,” Cock said. “Lima is known for its earthquakes and one of the things that earthquakes tend to be rough on is ceramics.”

The biggest surprise has been the discovery of portions of the base from the outer protective wall that had been built during the colonial period to protect the city against attacks by pirates.

The foundation of the adobe wall built during the colonial period to protect Lima from pirates.

An adobe wall that was built in 1687 and stood for almost two centuries protected colonial Lima. The foundation of the wall was constructed with large rounded stones held in place with a clay mortar. The individual bricks were made of adobe and placed on the base stones to create a protective wall that surrounded the city.

In the second half of the 19th century, Peru was reaping the rewards of the guano age. The sale of the bird droppings that covered the islands off the coast brought in many millions of dollars and led to a population boom.

An American entrepreneur, Henry Miggs, was hired by the city in 1872 to demolish the wall to make way for a flood of public works that were made possible by the sudden largess and necessity, due to the rapidly increasing population. The original Av. Grau was constructed over the layout of the original wall.

Another key part of the original city infrastructure being uncovered is the water and sewage system. Until the 1870s, this was made up of a series of crude canals that pre-dated the Spanish and were originally used to irrigate the crops grown in the region. The largest, known as Canal Guatca, ran directly through Lima.

The public works projects that followed the razing of the city wall required the canals to be covered, so engineers decided to create a series of three tunnels in the existing waterway. The channel bottom was filled with stones and then brick walls were built that divided the channel into three portions. Each was covered with an arch.

While stone sections were held together with the traditional clay mortar, the brick mortar was calicanto, a mix of lime, sand, stone and bird eggs the last being readily available from the millions of birds that inhabited the guano islands.

The brick and mortar channel portions of which are still in use today has ceramic piping from the turn of the 20th century connected to it. These in turn have metal piping from the 1940s. These are connected to PVC pipe that began to be used in the late 1970s.

“It is really incredible when you stop to think about what you are actually looking at,” Cock said. “Basically, you can see the entire history of the city when you uncover these things.”

<< Back