In 17th of 1970 was opened one of the main engeneering works of Chile: Lo Prado Tunnel. This was the longest underground highway duct built until then in our country and it decreased the path between the capital and its main port, Valparaíso.In a ceremony performed by President Eduardo Frei Montalva, traffic was opened through the mountain of San Francisco, specifying a long-term aspiration for national progress.
Almost two centuries before its opening, the governor of Chile, Ambrosio O’Higgins, charted the way between Santiago and Valparaíso, drawing a line that connected the slope of Lo Prado . Although this old aspiration, the route that finally joined the center litoral with the capital passed through Barriga slope, a road with steep slopes and 92 curves that made the trip long and exhausting.
The development of mechanized transportation generated the necessity of better roads, and safer layouts. Barriga slope meant a lot of time and fuel expenditure, it was a problem not the solution for a quick and safe transportation, because of its slopes and curves, that is why an alternative layout was being planned.
On January 4th of 1937, the engineers Alfonso Díaz, Oscar Jiménez and Juan González included in the register of intelectual property a Project which contemplated a variant of the road, passing by the tunnel through San Francisco mountain . All the project proposals insisted in decreasing the distance between the capital and Valparaíso . In 1964 there was a call on public proposals and the 17th of December that year, through n°3098 decrete, the proposition was accepted and presented as “Devés, Del Río y Torreti Ltda”. The project worth a total of 54 million escudos (chilean currency of that time), about 80 million dollars, expectin a 20% return rate for the opening year . With the removal of the curves and the shortening of the distance, it was expected an economic growth estimated in 50%, and it was though this meant not justa an economic benefit but a substancial improvement in the quality of life.
On Thursday 13th in January of 1966, the President commanded the first blasting, commencing the construction of the modern engeneering work. Frei Montalva was accompanied by the Minister of Public Works, Edmundo Pérez Zujovic, the engineers in charge and other authorities. In his speech, Sergio Torreti, one of the partners of the building company, indicated this was one of the greatest works of civil engineering made in Chile, and that represented the “culmination of the effort that for 30 years was made by countless generations of engineers” . After the first blasting, Cardinal Raúl Silva Henríquez effected the blessing of the future works. President Frei, on his part, expressed this work was the product of the national effort and tha joined every chilean in pursuit of social and economic progress.
It was expected the executing of the work take four years y was finished at mid 1969, but the process took longer and was opened in September of 1970. During the period of its construction the tax inspection counted on the counceling of diverse public and private entities as the Institute of Geological Research and the Institute of Research and Materials Testing of Universidad de Chile, the Office of Calculations and Stability of Santiago Arias, the Technical Office of Miguel Menadovich del Río, the Laboratory of de Department of Construction of Highways and also the support of Norwegian technicians with great experience in tunneling.
The excavation work must be suspended temporarily to began new reasearch because of the rocks’s bad quality . This stopping caused controversy since it was accused the new research was made just to improve the profits of the building company, which was unnecessary and technical terms . Despite this, the work was took up at the end of 1967, gaining a vas pace of work.
In June of 1968 the mechanical equipment purchased for the works arrived to Valparaíso. The next year it was development the final excavation, with typical issues of works of this kind: landslides, thrusts, wáter, slides, floods, among others . In its building was used more than 50,000 cubic metres of concrete coating, 3,420 tons of steel in reinforcements and supports, among other materials . Its characteristics became it in one of the most modernt road work built in Chile. Among the elements that were remarked was the innovative ventilation system which allowed a complete inner air renewal each 3.7 minutes. The design also contemplates the installation of a closed-circuit televisión, which permitted the inner control of the air. The lighting and mosaic coating were though and installed thus the drivers had a sense of not being inside a long concrete tuve. It was also applied a modern traffic control system, emergency telephones inside and fire alarms. Those systems allowed the operators knowing what happened inside the tunneñ and having the means to control the traffic night and day.
The classic tri- colour ribbon was cut on September 17th on 1970, opening the traffic through the mountain of San Francisco in the midst of the joy of workers, employees, authorities and personalities that participated in its construction. This engineering work constituted a pride for all the country. With its opening ended part of a vast highway agenda, becoming the Lo Prado Tunnel in a symbol of progress and modernity, being corollary of an administration that stood out by a huge rise in public work and communication routes which were conceived by the government of Eduardo Frei Montalva as a mean to boost the economic and social development of the country. It was blessed by Curacaví’s priest, Benjamín Ulloa, and after its opening was travelled complete by the President and his entourage.
At the beginning, the tunnel was used solely between 8 am to 8 pm o’clock, because there was some remaining work to do . It shortened the travel from Santiago to Valparaíso that much that in the first week of operation experienced traffic jams. For this reason, the following weekend since the opening, were problems and the tunnel must be closed. There was no technical failure or accident, but the traffic overload due to the initial enthusiasm of the people of Valparaíso and Santiago who wished to know the new work, forced the authorities to take this action. Everyone wanted to pass through the longest tunnel of Chile at that time.