Application of Geotechnical Criteria for the Occurrence of Earth Flows (Avalanches) on the Right of Way of Pipeline Transportation System of Camisea in the Coast Zone of Peru
Authors: Oliveros Francisco , Hernández Emilio , Soto Guillermo 
Published: October 2017

The Camisea’s Pipeline Transportation System (PTS) in Peru, owned by Transportadora de Gas del Perú (TgP) and operated by Compañía Operadora de Gas del Amazonas (COGA), stars in the Amazon rainforest, crosses the Andes Mountain (4850masl) and descends finally towards the coast of the Pacific. The PTS has more than 10 years of operation and it has two pipelines: one transports Natural Gas (NG) and the other Natural Gas Liquids (NGL) pipelines. The NG pipeline has a length of 864km including a Loop pipeline of 135km. The NGL pipeline has a length of 557km.

Because of particular physiographic conditions of each geographic sector that cross the right-of-way (ROW), the integrity of the PTS acquires a level of significant susceptibility to the occurrence of geohazard, which are the product of natural erosive processes and mass movements.

In the coast sector, one of the most representative processes of geotechnical instability is the soil or debris flow (mass movements of soils). The occurrence of this type of flow has a greater incidence in the torrential creek, which generate transport of large volumes of sediments during rainy seasons. The flow has destructive effects and therefore, it is necessary to analyze the geomorphological, geological and hydrological aspects of the main creek and rivers that crosses the ROW with the objective of maintaining the integrity of the pipelines. In Peru, the flows are associated and known as Huayco or Huaico.

As an additional component, it is highlight that the Peruvian coast is located within the area of interaction between the South American Continental Plate and the Nazca Plate, where there is evidence of seismic activity with different magnitude that influence on the occurrence of geo-dynamic processes with certain periods of frequency that could change the terrane’s morphology.

The current article describes technical aspects of identification, intervention, monitoring, and geotechnical control in sub-fluvial crossings with levels of potential damage to the geohazard defined as huayco in the integrity management program of PTS. This activity include 63 main sub-fluvial crosses, approximately 30% are of the seasonal flow regime, located in the coast zone; at the same time, these are tributary to main rivers of constant flow as is the case of the Pisco, Cañete and Mala rivers. In this paper, it is place a special emphasis on the fourth crossing of the Huáncano creek, because it is a place of potential impact in the occurrence of soil flows.

Within the annual geotechnical maintenance of the sub-fluvial crosses, in the part of the Peruvian coast, for the operation of the PTS of TgP, bed and banks protection some works are implemented, such as: Check dams, re-channeling, levees and stone riprap (Stone armour). Likewise, a program of evaluation and technical inspection is develop: it includes the analysis of the expected levels of undermining and performance condition of the existing works, which allow defining the geotechnical intervention in a term according to the identified risk level. All in all framed within a process of permanent geotechnical monitoring of the right of way.

Finally, it is highlighted that to date the application of the process described above has been continued, which has facilitated the development and continuous assessment of the risk condition by huaycos in the PTS of TgP. This program has maintained an operation with an acceptable level of risk in the areas of interest and avoiding problems and consequences of great impact to communities, the environment and the operation of the system.