With around 631,000 inhabitants, Cochabamba is Bolivia’s fourth largest city and capital of the Department of Cochabamba and also home to a university. It is an ancient city with numerous ruins from the pre-Inca and Inca periods, located in the eastern Andes at 2,560m above sea level. The first Europeans settled here in 1542 and re-founded the city of Cochabamba. Only after independence from Spanish colonial rule and the founding of Bolivia in 1825 did Cochabamba become the capital of the new department of the same name.
Today Cochabamba is a modern city with numerous parks and gardens, being also called Ciudad Jardin (Garden City). The city’s public drinking water supply and sewage disposal utility SEMAPA is equally modern described as ‘a decentralised municipal company designed to meet the needs of the population in the regulatory area of the province of Cercado in the department of Cochabamba and the field of drinking water supply, sewage collection and treatment. It also contributes to the improvement of living conditions and the general protection of the environment with its services.’
New Construction
As part of the urgent rehabilitation (complete renewal) of a 33 km long, extremely outdated drinking water network in the 10th district, which is the inner city, the house connection pipes are and were also rehabilitated, also through complete new construction. A total of 2,758 house connections were affected and had to be re-installed, as was the case in the Avenida Ayacucho. Here, as in numerous areas of the inner-city district, the street is relatively narrow with high-density population and housing. Semapa acted professionally and true to its own definition ‘to improve living conditions and protect the environment’, decided to install the house connections in this section of Avenida Ayacucho, with a trenchless installation technology, in this case with the soil displacement method. SEMAPA commissioned Sur Energy S.R.L. & Asociados, which has the necessary experience and machinery for trenchless construction. The company leases its machines from PLASTIFORTE, a TRACTO representative in Bolivia.
Soil displacement hammers
Due to its accuracy and penetration power, even in stony soils, TRACTO’s GRUNDOMAT soil displacement hammer is ideal for fast and economical underground installation of house connections. The people in charge decided to use the 45 mm diameter model from the new generation, equipped with a stepped head for universal use in all displaceable soils. The installation lengths of the new house connection pipes to be installed varied, between 7 and 10 m, due to each different location and distance of the houses from the main drinking water pipeline.
After excavating the necessary small starting and target pits (one on each side of the road), measuring the precise bore path and placing the machine in a stable position, the pneumatically driven GRUNDOMAT 45 soil displacement hammer (2-gear control unit plus reverse gear) worked its way, with a high target precision, stable, reliably and effectively at a depth of around 0.6 m along each pre-determined bore path underneath the road. The soil, comprising clay with sandy components and the occasional groundwater horizon, did not cause any problems during the bore process. The soil was displaced outwards, step by step, without any problems. Even existing old drinking water and sewage pipes, as well as communication and gas pipes in the area were crossed beneath without causing any damage.
The installation time for each house connection took between 1 to 1½ hours. The advance rate was middle range, at 5 to 7 m/h. The new HDPE drinking water pipes with 25 to 32 mm diameter for each relevant house connection were pulled in with a second working process.
Good For the City and the Citizens
As a result, in the large rehabilitation project, around 1,000 house connections were and are still being re-constructed with the GRUNDOMAT 45 soil displacement hammer and the need to dig trenches for an open-cut installation has been completely avoided. The city can be proud of this environmentally-friendly renewal, as the new installations mean no further problems with water losses for many years to come and also a vast improvement of the living conditions for the citizens.
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