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Oral presentation in WOC 3 Committee Session 3.2

GEOTECHNICAL STABILIZATION OF A PIPELINES SYS TEM IN MOUNTAIN AND TROPICAL SOILS

Ing. Fernando Adolfo Velásquez Martínez Geotechnical Chief, Compañía Operadora de Gas del Amazonas, Coga. Perú

Geol. Gustavo Martínez Sánchez

Operations Manager, Compañía Operadora de Gas del Amazonas, Coga. Peru

1. Planning 2. Prevention 3. Stabilizing 4. Monitoring 5. Risk

ABSTRAC The present abstract shows the development of the geotechnical stability process in the Camisea NG and NGL Pipelines System in Peru.

CAMISEA

LIMA

32”24”18”

729.3 km

COAST MOUNTAIN JUNGLE

NGL PIPELINE

PISCO

14 ”10”557.3 kmPRS #3

PS#4

223.9 km

PS#3

207.7 km

PS#2

107.9 km

PS#1

0 km

PRS #2 PRS #1

NG PIPELINE

CAMISEA

The Camisea Transportation System consists of two buried pipelines: 1) a 730Km Natural Gas (NG) pipeline, which runs from the upstream facilities at Malvinas to a terminal station at Lurin, at the southern edge of Lima; and 2) a 560 Km Natural Gas Liquid (NGL) pipeline, which transports the liquid condensates from Malvinas to a fractionation plant near Pisco, on the coast of Peru south of Lima. The two pipelines share a common Right -of-Way (ROW) that traverses the Peruvian jungle, climbs over the Andes M ountains (highest point in the latitude arrives to the 4,860 meters over the sea level) and descends steeply toward the Pacific coast. The geographical, geologic and climatic characteristics of the Peruvian territory for which crosses: Forest, Mountain and Cost differentiate the Camisea Transportation System, in comple xity respect to others pipelines in the world. The main threat to the Camisea Transportation System, - especially in the rainforest section -, are the risks associate to the geotechnical instability, where in the history of the Camisea Pipelines operation four incidents related with geotechnical factors have taken place. The first 180 Km of the RoW represent the biggest challenge for the operation, they are characterized by residual soils, slopes greater than 45°, rainfall levels that exceed the 6.000 mm per year; besides the logistical difficulty of not having vehicular access for personnel's transportation, and materials, where the maintena nce works are supported by helicopters.

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This p aper seeks to illustrate the diversity of geotechnical scenarios in this Peruvian geography; and the early identification of risks likewise through the handling cycle and control of geotechnical risks, which can be summarize in the following stages:

• System for Identification of Threats: Includes the process of continuous surveillance of the Right of Way where the geotechnical issues - detonated mainly by the rains - are identified.

• Valuation of the Risk: Use of a geotechnical risk matrix, elaborated with base in the denominated Security Ratio, assimilating the parameters of calculation of the Security Factor used in the analysis of stability of banks which allows to establish risk levels.

• Design of Works: In accordance with the level of risk is carried out to prioritize and elaboration of the

corresponding engineering to establish the design, using the processes of the geotechni cal engineering such as: underground exploration, labo ratory tests, mathematical modeling and instrumentation.

• Execution of Works: The execution of the works of geotechnical stabilization is carried out in the dry season, between the months of April and October of every year.

• Monitoring and Surveillance: By the end of the dry season and having built the stabilization works,

during the rain season (November-April) a continuous monitoring is developed through permanent inspections, topographical monitoring and instrumentation in sensitive places with inclinomete rs, piezometers and strain gauges.

The development and application of these analytical and control techniques in the geographical, geologic and climatic characteristics of the Peruvian territory, have significantly reduced the geotechnical risk on the Camisea NG and NGL Transportation System. INTRODUCTION The pipelines are designed to support low longitudinal tensions that emerge due to the pressures and movements induced by the thermal effect. These tensions approach and rarely exceed the limits established by Regulations ASME B31.4 and ASME B31.8 of 54 percent of the Specified Minimum Yield Strength , (SMYS) for longitudinal tension. Additionally, the slight elastic curvature imposed by installing a duct in an impe rfect ditch rarely causes concern. In stable area s of the soil and in absence of external thermal cycles, these “common” longitudinal tensions are not a problem. On the other hand, in areas where significant movement or sinking of the soil may occur, the imposed tensions may become h igh enough to cause pipeline failure. In such areas, it must be necessary to carry out constant surveil lance of pipeline behavior in order to prevent failures. In most cases, as we gain knowledge, intelligence and experien ce on the diverse types of soils that make up the Right of Way (RoW) and its characteristics, we can foresee and perform early interventions through a strong and persistent task of supervision, technical studies, and behavioral analysis on these soils; and thus prevent and avoid the geote chnical problems, or failures. Even thus, in terrains of complex geographical and geological characteristics, extraordinary and unexpected events can occur which generate failures in ducts. This is the case of the Camisea (Peru) Duct Transport System. From the point of view of the integrity of the duct, the soil movement may cause deformations and strains that could lead to the collapse of the pipeline. When the main risk of a duct system is related to the movement of soils, special attention must be placed; and a control strategy must be designed; the analysis of which will allow the minimization of said risk. This work seeks to illustrate a method ology to reduce and control the risks in a mountain duct system in tropical soil.

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1 TOPOGRAPHICAL, GEOLOGICAL, AND GEOTECHNICAL FEATURES OF THE CAMISEA DUCT TRANSPORT SYSTEM (DTS)

From a topographical point of view the geography that the Camisea Transport System runs through can be divided in three zones:

1.1 JUNGLE ZONE: Comprises the first 180 km of the system – KP 0.00 to KP 180.00

1.1.1 Topography: This stretch is characterized by:

• Terrain of soft to medium slopes: wavy plains, dissected alluvial terraces, wavy low hills, wavy medium slope hills, and rounded hills.

• Medium slope Terrain : Slopes of medium steepne ss, wide slopes, low dissected and scarped hills,

alluvi al valleys, (rivers of streams in “V”). • Terrain of high and vey high steepness: Slopes of high steepness, colluvial slopes (slope deposits), high

and scarped slopes, high, elongated and slim hills, elongated and scarped peak lines, and jagged slopes. These forms of terrain cover 75% of the remaining corridor.

Within the described topographical medium, in which high slopes prevail, we locate the alignment of the project in the Jungle stretch. The high slopes standout because they impose the greatest degree of difficulty in the “elongated, and scarped peak lines”, and in the “high, elongated and slim hills”.

1.1.2 Geological and geotechnical features

From a geological point of view, practically the entirety of the Jungle stretch is made up of Soft Rocks which in the Mechanics of Rocks of tropical terrain correspond to materials of low durability , or high degradability.

The mentioned durability characteristics refer to the behavior of rocks in face of the actions of weathering agents, or factors, and especially, before the humidification or saturation, and drying cycles typical of the alternation of the tropical climatic periods of high precipitation and dry seasons. Once exposed to the atmosphere as in a construction process, these materials easily degrade; they lose resistance to cut, or separate from the stratification planes and joint system (discontinuities in the rock mass), they fragment and may finally crumble.

The rock coverage present in the Jungle stretch is predomina ntly constituted by mixtures of low density mud, sand, and gravel. These materials are easily erodible to a high degree, depending on the steepness, which is generally high, as has been previously stated.

In the Jungle sector, it is important to point out the presence of a great amount of lateral joints where fine and cohesive soils are predominant, and which determine the mechanical behavior, and are therefore susceptible to destabilization due to the saturation they suffer from the humidity in this ecosystem.

1.2 MOUNTAIN ZONE: In this stretch the Duct Transport System (DTS) crosses the Andes mountain range and therefore a great diversity of materials with various geological origins. The fill of the RoW is composed by clays, muds, and sands with gravel -size fragments of predominantly igneous rock, both intrusive and volcanic; but there are also sedimentary and metamorphic rocks. There are also volcano-sedimentary deposits with a presence of ash and lapilli. Occasion ally conglomera te and limestone fragments are present. In the high part of the Sierra there are glacial and glaciofluvial deposits, with a predominance of a mud matrix; additionally, wetlands and moraine s; the latter with blocks and gravel of volcanic rock (lava).

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1.3 COASTAL ZONE: On the RoW there are predominantly sandy refills: medium thickness grain sands, of medium to low density, with angular gravel of igneous rock, both intrusive and volcanic. Occasionally there are conglomerates, colluvi ums, and alluvial deposits (huaycos) originating in the drainage that descends from the Andes toward the Pacific Ocean. The RoW is covered by medium grain, rounded, well selected, loose, sand dunes with the potential to liquate in zones where the water level is high. In the Camisea DTS, due to its constructive process, the majority of the materials present in the RoW correspond to refill, product of the conformation of the terrain. These materials originate from the cuts and excavations performed during the opening of the track and the ditching, respectively. In turn, there is a direct relation between the geology of the terrain and the diverse material present in the RoW refill, and in the cut slopes of the terrain. To facilitate the description of the material, we have followed the general subdivision of the system as of the three physiographical regions which it crosses. The Jungle sector comprises the first 180 Km, the Sierra Sector from Km 180 to Km 420 and the Co astal Sector runs from Km 420 to Kp Km 730.

2 PRECIPITATION REGIME Peru, due to its particular geographic location in the South American continent, tropical and subtropical position, and its long coastal zone on the Pacific Ocean, has a wide range of different types of precipita tion regimes. From north to south and from east to west of the country, we find a great variety of climates with various regional features, with well differentiated ecological classifications. The regions of Peru are influenced by tropical systems of medium latitudes, with two defined seasons which are summer and winter, predominantly in the coastal zone. The Peru Amazon, on the other hand, presents a rainy climate between Novembe r and April, while in the dry months; precipitatio n is at a lower scale. In th e Peruvian Andes the precipitation behavior is similar but with lower intensity. In the coastal region, precipitation is scarce or null, as corresponds to a tropical desert climate. The DTS in the jungle sector is found in the Peruvian Amazon having in this trajectory annual precipitation that reaches 6.000 mm; and during the rainy months of November to April there are monthly precipitations of up to 1.200 mm having intense rains of 12 hours recorded, that have reached 270 mm. In this way the rain in the sector becomes the main trigger of the various processes of mass removal that take place in the Jungle Sector. Graphic 2-1 shows the behavior of rainfall in the zones with higher rainfall risk of the DTS.

0250500750

1,0001,2501,5001,7502,0002,2502,5002,7503,0003,2503,5003,7504,0004,2504,5004,7505,0005,2505,5005,7506,000

Ene Feb Mar Abr May Jun Jul Ago Sep Oct Nov Dic

mm

meses

CAMISEA - ZONE KP 30 TO KP 50 JUNGLE SECTOR

2,006 2,007 2,008 2,009 acc. 2006 acc. 2007 acc. 2008 acc. 2009

Graphic 2-2 – Histogram of annual rainfall from 2006 to June, 2009.

Camisea Duct Transport System – Jungle Zone Kp 30 to Kp 50

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3 CHARACTERISTIC GEOTECHNICAL PROBLEMS OF THE CAMISEA DTS

Within the identification of the mass removal movements, typical of the subsoil, the various geo-forms of the terrain have vital importance. In this sense, there is a special meaning to distinguish along a slope or embankmen t, depressions or concaves followed by protuberances or bulges of the terrain, scarps or scars that are formed mainly due to the saturation of the soils, since the force of gravity and the saturation of soils are the main factors that act on the mentioned geo-forms, because the saturation allows the soil to lose resistance to cuts and to increase its volume and weight, and the soils become more susceptible to slides. Due to the previously stated, geotechnical engineering in the maintenance stage of the DTS, aside from the dedication to the control of surface runoff, gives way to the identification and remedy of mass removal moveme nts such as slides, (rotation al, translational, multiple, and complex), and land flows, amongst others. In this respect, it is applied in the Movement Classification System of Slope Failures of D.J. Varnes (1978), compleme nted for the clarity of the identification and description of the cases with the Skempton and Hutchinson System, (1969). Said classification process is performed as of the detailed visual inspection of the entire RoW; to this end, continuous vigilance groups were implemented which run through the stretch during the rainy season. Figure 3-1 and Figur e 3-2 illustrate the main types of landslides of the two mentioned systems.

Figure 3-3 - Frequent Types of Movements of Slope Failures. (Varnes, 1978) (Drafted based on : Varnes, David J.

1978 “ Slope Movement Types and Processes”, Chap. 2, S chuster R. L. and Krizek R. J., editors, 1978, “L andslides Analysis and Control” Special Report 176, Transportation Research Board. National Academy of Sciences,

Washington, D.C

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Figure 3-4 - Classification of simple and complex landslides (Taken from Skempton and Hutchinson 1969: “Stability of Natural Slopes and Embankment Foundations”, VII International Congress of Soil Mechanics

and Foundation Engineering. SIMSIF, México.

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Within the main causes for the generation of said processes of mass removal in DTS we find: • The rugged terrain representative of the Andean mountain system. • Soils with permanent activity of rearrangement of particles, product of the seismic activity. • Presence of supply of material simply placed originating from cuts performed during the DTS

construction period . • Due to the previously stated, they are soils with low parameters of resistance to cuts. • Geologi cally recent tropical soils, of easy degradati on in contact with exogenous agents such as water

and seism, adding to it the loss of vegetation coverage, which is a fundamental condition of stability of such erodible soils.

• In the Jungle Zone there i s mainly a high intensity of concentrated precipitation in a short period of time (November to April) which accelerate s the activation processes.

• There are rock masses in place with various degrees of alteration and weathering. • Change of hydraulic behavior of the micro basins due to a change in morphology due to the RoW and

the change if runoff ratio due to loss of native vegetation and change due to grasses. When the duct is embedded in a mass removal movement, in occasions it is submitted to combined stresses that produce material strains in the pipe which exceed the fluency limit, leading on occasions to rupture. It is therefore of vital importance to identify and construct geotechnical works that may anticipate mass movement or removal. The characteristic processes that are identified in the various DTS sectors are :

3.1 Mass Removal Process es in the Jungle Sector • Rotational Slides: Characterized by affecting the topographical profile and geotechnical section at a

considerable depth, on and/or close to the NG & NGL ducts axes upwards through the surface of concave failure. This phenomenon mainly occurs in zones of material joints that generally were located in the DTS construction stage in over-widths adjacent to the RoW and/or sectors where they lay on excessive caps product of final rearrangements.

Figure 3-5 - Rotational Slide . (Jaime Suarez, 2009) Chapter 1 Slide Nomenclature. Slides-Geotechnical Analysis.

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Photograph 3-1- Rotational Slide in lateral joint of jungle sector

• Translational Slides: Due to the origin of soil types, the failure surfaces of these types of slides generally coincide with the zones of change to cut resistance due to weathering effects and in lithological contacts. They are generally quick and may end in material flows. Regularly, and in the DTS, the crown of this type of movements affect the areas closest to the axes of the NG & NGL ducts.

Figure 3-6– Translational Slides. (Jaime Suarez, 2009) Chapter 1 Slide Nomenclature. Slides-Geotechnical Analysis .

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Photograph 3-2- Longitudinal Translational Slide to the Jungle Sector RoW

• Land flows: Generated in the sectors where there are materials of liquid consistency and particle size composition with over 50% fine composition. The initiation presents itself in the form of a rotational or translational slide in the high parts, and from there the material flows down the slope or embankment. Depending on the steepness of the sector, the gradation, and humidity of the soils, the flows are either quick or slow. In some cases, the NG and NGL duct axes were very close to the body of the land flows that occurred.

• Mud flows: due to the direct effect of water, the material (generally the detritus and the slightly altered)

suffers softening until it reaches high fluidity and a viscosity level which when concentrated and initiating a movement rate (depending of the topographical slope, and duration and intensity of rains), may reach high speeds. In some cases the RoW was affected by this type of processes (within the morphological units which define it: Sinking, neck, and dejection cone.)

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Figure 3-7 - Land flow / Muds. (Va rnes, 1978) (drafted based on: Varnes, David J. 1978 “ Slope Movement Types

and Processes”, Chap. 2 of Schuster R. L. and Krizek R. J., editors, 1978, “Landslides Analysis and Control” Special Report 176, Transportation Research Board. National Academy of Sciences, Washington, D.C

Photograph 3-3 - Land Flows in lateral joints in the jungle sector

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• Detritus flows: Generally, they are defined processes in the cut embankment that define the RoW, extremely quick and composed of thick materials with lower than 50% fine composition. Its activation is sudden and it is mainly due to the occurrence of intense rainfall. In most cases, the deposit zone of the movemen t involves the RoW, especially when these flows originate in the scarps formed by the cut embankments.

Figure 3-8 - Detritus flow. (Jaime Suarez, 2009) Chapter 1, Chapter 1 Slide Nomenclature. Slides-Geotechnical

Analysis .

Photograph 3-4 - Detritus Flow in cut embankment adjacent to the RoW. The deposit zone of the material is the RoW.

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• Creep: Is a slow to very slow process that may precede a flow and/or a translational slide. It has no defined surface failure and is evidenced by the formation of steps and/or “cattle paths” and the inclinations of posts and trees. In some zones the RoW is part of this type of movement and a planned follow up is performed with topographical monitors and monitoring of the strain status in the ducts through Strain Gauges.

Figure 3-7 - Creep. (Jaime Suarez, 2009) , Chapter 1 Slide Nomenclature . Slides -Geotechni cal Analysis.

Trees leaning

Photograph 3-5 - Creep on RoW in the Jungle sector.

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• Undermining of beds and margins of subfluvial crossings: During the rainy and extraordinary events season the subfluvial crossings may be affecte d by the erosion of the river bed and river banks. COGA continuously performs inspection and monitoring of the bottom of the more representative crosses with bathymetry studies, which quantifies amongst other data, the stream and the undermining, and topographical maps to identify the hydraulic sections of the crossing, the size of the basin, and the changes in the course of the currents.

Photograph 3-6 - Undermining of bed in brook that crosses the RoW in the Jungle Sector. We can see the bare spines of the NG and NGL ducts.

• Complex movements: They are identifiable by their great magnitude and high affectation level that place the DTS at ri sk. They can also be combinations of the processes previously described which alter typical geotechnical behavior and impede a quick definition of models which may allow the taking of decision to intervene and mitigate the risk.

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River Manugaly

Crack

NGLNG

Photograph 3-7 - Complex slide in the Jungle sector. Compromises the RoW and great adjacent wooded zone .

3.2 Mass Removal Proces ses in the Mountain Sector • Mud, detritus, and material flows (hua ycos): They occur mainly in the zones of jungle brow and in the

zone of initiation of the sierra sector and have the same morphologi cal and geotechnical characteristics previously defined.

Figure 3-9 - Mud, detritus, and material flows (Huaycos) . (Jaime Suarez, 2009), Chapter 1 Slide Nomenclature .

Slides-Geotechnical Analysis .

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Photograph 3-8 - Mud, detritus, and material flows (Huayco s) in the Jungle Brow sector. The deposit zone of one of the Huaycos is the RoW.

Soliflucti on: Occurs in the highest peaks of the mountain systems, where, due to low temperature, the freezing point is reached. It i s a creeping that is generated from the more superficial materials and the unfreezing of the water in the pores and empty spaces. It is produced unde r cold climatic conditions, where the icing and deicing processes continuously occur and it consists in the sliding of a viscous ma ss of material of soil saturated with water on an impermeable surface. It generally occurs in slopes of scarce steepne ss.

3.3 Mass Removal Process es in the Coastal Sector • Dropping of Block: In some stretches we identify detachment of rocks and/or blocks of slopes defined

and altered due to plane failures or wedge failures. It occurs in cut slopes or in slopes adjacent to the area that limits the RoW.

• Dumping of massifs: In some opportunitie s it occurs due to the forward rotation of the units and/or blocks under a same turning point . It occurs in some cut slopes which limit the area that defines the RoW.

• Aeolian Erosion : Due to the direct action of the wind. In Occasions we lose coverage of axis in the NG &

NGL ducts in the dunes that define the context of the coastal strip parallel to the Pacific Ocean. In the cases where it occurs we maintain monitoring of loss of coverage through Sand Markers.

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Photograph 3-5 - Aeolian Erosion in Dunes – Coastal Sector.

• Quick material flows (huayco s): Simi lar to those previously described , but are originated in the high part

of the Andes mountain range, however, the erosive power is greater because it occurs in the lower zones of the basins and the percentage of granular material that comprises the mobilized mass is quite considerable .

Photograph 3-6 - Huayco Transversal to RoW – Coastal Sector.

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4 MANAGEMENT SYSTEM FOR THE SECURING OF GEOTECHNICAL STABILITY In order to ensure the geotechnical stability of the ducts and the RoW, we have developed a management system with which we identify the geotechnical problems and we implement the measures relevant to performing the repairs, maintenance, and monitoring with the objective of foreseeing problems and attacking them in their early phase; decreasing their criticality. The main elements of the system are: Identification of geotechnical threa ts, risk assessment, works design, performance of remediation work, maintenance and monitoring works .

4.1 Threat Identification System In order to identify geotechnical problems in the RoW in the early phase, we maintain a continuous inspection in the jungle sector and jungle brow during the rainy season (Nov ember-Ap ril), this continuous vigilan ce consists in maintaining 9 groups that are distributed along the length of the first 210 kilometers of the RoW, which are the most susceptible to instability processes. Each group is composed of a Geo-technician with experience in identification of instability processes, a foreman of geotechnical engineering construction works, a nurse and an assistant. Each group lives in a strategically located camp in order to daily inspect a stretch of the RoW, taking invent ory of all instability details such as: fissures in the RoW, bulbs in the terrain, scarps, obstruction of drainages as observed by a decrease in the exit stream, dislocation of current cutters, (water collection gutters located transversally) and longitudinal canals, increase in erosive processes in the outlets of gutters, and undermining processes in river crossings, amongst other indicators of geotechnical instability . The personnel of the Continuous Vigilance Groups (CVG) have been trained in practical geotechnical engineering, first aid, safety and health; in order to facilitate their work in the field. The CVG daily send their report to the main base, through the Internet and maintain telephone communication daily to report recent events. In the first 210 km we do not count on terrestrial access and the only transportation means is the helicopter. The information sent by the CVG is classified and organized to conform a pack of activities to be performed, which begins by prior studies such as exploration of the subsoil and topographical relief, in order to obtain the geo -integrity paramet ers and so be able to perform the risk assessment. On the other hand, this information is very valuable and useful to understand how the works carried out in previous seasons have been behaving.

4.2 Risk Assessment When situations of geotechnical instability present themselves in the vicinity of the NG and NGL pipelines on the RoW, we proceed according to the techniques of conventional geotechnical engineering: Exploration of the subsoil, in situ geotechnical trials, laboratory trials to establish index properties and geo -mechanical properties, mathemati cal modeling to establish Safety Factors (which implies detailed topographical mapping of the influence area) and the drafting of a work Plan which includes detailed designs. Performing this detailed activity for each of the sites identified by the CVG which might be more than 100 in each season. The condition of access to the sites is only of the aerial type (helicopters), and places us in a situation that must be resolved through the programming of works, defining priorities and establishing Risk levels. To resolve the dilemma of where to begin the geotechnical remediation activities, we apply, as a first order tool; the Risk Matrix through which the risk assessment is performed and the geotechnical works organized by the levels of risk for each of the geotechnical instabilities. Transportadora de Gas del Peru (TGP), through it operator, Compañía Operadora de Gas del Amazonas (Coga), in association with Exponent, consulting firm of the Inter-American Development Bank (BID), developed an evaluation method to establish the criticality of the possible geotechnical failures that may place at risk the integrity of the Camisea duct transport system . The method consists of evaluating the geo-integrity parameters, evaluatin g the likelihood of failure using field analysis, characterizing the severity of the failures which may occur and finally evaluating semi-quantitatively the failure risk.

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4.2.1 Geo-Integrit y Parameters Geo-Integrity Parameters are those elements to be classified and that have a direct relationship with the stability of the RoW (Likel ihood) or with the social and environmental conditions (Severity) in which each evaluated site is located in relation to the population centers, difficulty of access, closeness to rivers, (in the event of a spill) and volume and potential of spills. In order to evaluate each site a preliminary subsoil exploration is performed, or through the as-built maps of the project we seek the elements that are not obtained or considered in the field. All the geo-integrity parameters have been developed based on the knowledge that is held on the project, amongst these: the geology, the specific geotechnical conditions, and the experience produced by the 4 NGL line ruptures associated to geotechnical causes. In Table Tabla 4-1 and Tabla 4-2 we find the geo -integrity parameters for Likelihood and Severity.

Tabla 4-1 -

Paramet er 1 2 3 4 5

L1 Pipe Foundation Fill

Soft ground Colluvium

Firm ground Rock with adverse bedding, foliation or joints

Highly weathered rock

Moderately weathered rock

Competent rock

L2 Plasticity Index >35% 20- 30% 20- 15% 15- 10% <10% L3 Slope Inclination

to ROW (Right of way)

<10° 10 to 19° 20 to 24° 25 to 29 ° >=30°

L4 Distance to Side Fill interface

d <= 0 m 0<d<=2 m 2<d<=5 m 5<d<=10 m d>10 m

L5 Slope inclination parallel to ROW <10° 10 to 19° 20 to 24° 25 to 29 ° >=30°

L6 Slope Height Parallel to ROW

<=7m 7<H<=15m 15<H<=20 20<H<=25 m >25 m

L7 Surface Drainage Control

Good handling; Works of control of erosion in operation

Erosion contr ol works, with maintenanc e required

No erosion control works, but suitable natural drainage

Evidence of pondiing and guillies

Large gullies and saturation of the land; significant water ponding

L8 Average Annual Rainfall

<500 mm/year 500 to 2000 mm/year

2000 to 2500 mm/year

2500 to 4000 mm/year

4000 to 6000 mm/year

L9 Ground water Depth

>10 m o no groundwater

5 to 10 m 2 to 5 m 1 to 2 m 0 to 1 m

L10 Gabion Wall Stabilization

No gabion walls

Gabion walls installed befote May 2006

New gabion stabilization walls founded in competent soil

New gabion stabilization walls founded in weathered rock

New gabion stabilization walls founded in rock

Tabla 4-2 -

Para meter 1 2 3 4 5 S1 Proximity to

Populate d Centr es >3000 m 1500 to 3000 m 1000 to 1500 m 500 to 1000 m < 500 m

S2 Difficulty of Access to Locati on

Road access within 200 m of the site

Road access between 200 to 500 m of the site

Road access between 500 to 2000 m of the site

Aerial access with sporadic meteorologi cal limitations

Aerial Acces with meteorolog ical limitations

S3 Proximity to Rivers >3000 m 1500 to 3000 m 1000 to 1500 m 500 to 1000 m <500 m S4 Spillag e Potenti al <50 m3 50 to 250 m3 250 to 1000 m3 1000 to 3000 m3 >3000 m3

4.2.2 Evalua tion of Likelihood of Failure

For the likelih ood evaluation the following steps were taken :

a. Estimate of the Safety Ratio (SR) calculated in function of the geo-integrity parameters for each failure mode .

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b. Qualitative evaluation of the risk divided into four categories of likelihood levels (LL) using the calculation of the Safety Ratio (SR) for each failure mode.

The failure modes used for the method were : (i) rotational slide (ii) wedge slide or failure and (iii) translational slide . In this methodology we do not include failure by undermining and permanent deformation of the terrain by seism. The evaluation of the failure likelihood does not pretend to replace the engineering methods that calculate the safety factor; on the contrary, they are used as a tool that in a preliminary way will allow the establishment of a risk condition in function of a more qualitative than quantitative analysis that is within the semi-quanti tative methods of failure analysis. The calculation of the Safety Ratio (SR) is conservative in respect to the calculations of the Safety Factor (SF) and these latter never stop being necessary. In fact, once the Safety Factor is calculated within the conventional geo-technical process (slope and/or emban kment stability analysis) the SR calculation is no longer used. In this way the SR is one of the main componen ts of the Risk Matrix. In the calculation process of the SR we will use comparisons with the SF in a permanent manner, considering always that the Safety Factor (SF ) by definition corresponds to the ratio between the Resistant Forces and the Acting Forces in the slope. In this way, when we have values higher than 1.0, mathematically we are in a condition of stability and in a condition of instability for values lower than 1.0. However, the SF uses values greater than 1.3 to establish acceptable stability conditions. In Table 4-3 we find the assignation ranges for the (SR).

Table 4-3 -

Likelihood Level (LL) Safety Ratio (SR) Notes

IV SR <1.1 High suscepti bility

III 1.1<=SR < 1.25 Moderately high susceptibi lity

II 1.25<=SR<1.5 Moderately low susceptib ility

I SR >=1.5 Low susceptibi lity

4.2.3 Severity Evaluation The Severity Levels (SL) are characterized using 4 ranges, with high levels for great consequences, however, we have used consequence classification by categories: environmental, property, health, and safety. The damage to property has been categorized consequently considering the conditions of difficulty of access, presence and absence of facilities (for example, pumping stations, reduction stations, blocking valves) and the failure mode. The consequences to health have considered the proximity to population centers, the existence of towns, and rivers that can be affected by a possible spill, and lastly, consequences to safety are influenced by proximity to population centers in the face of possible po tential spills. In all cases, the experience of who applies the parameters is necessary due to the required knowledge of the project.

4.2.4 Qualitative Evalua tion of Total Risk Both the levels of likelihood and Severity calculated above are used to assign a risk category; which are:

I. Risk category 1 – Low Risk Level II. Risk category 2 – Moderate R isk Level, which is acceptable III. Risk category 3 – Medium Risk Level, which can be mitigated IV. Risk category 4 – High Risk Level, which must be mitigated with high priority V. Risk category 5 – Very High Risk Level, which requires immediate action

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All sections of the RoW with risk categories of 3, 4, and 5 require remedi ation works or measures based on engineering analysis to reduce the risk to a lower level. In Error! Not a valid bookmark self-reference. we find the interaction in Severity and Likelihood, where we reach the risk level.

VI. VII. Tabl e 4-4 -

Likelihood

1 2 3 4

1 1 1 2 2

2 1 2 2 3

3 2 2 3 4 Seve

rity

4 2 3 4 5

4.3 Design of Geotechnical Engineering Works Except for the stretches where we can consider that the two pipelines of the Camisea DTS were installed in hard or durable rocks (hard, quartzous or cemented sandstone, limestone, massive phyllites), the gas duct was located in soft rock formations and formations of existing and prevailing soil deposits in the Jungle, Mountain, and Coastal regions, in the alteration conditions imposed by the tectonics (and seismics) and the natural weathering processes intimately associated with climatic and topographical factors. It is understood that the natural medium in which the ducts were install ed is composed in essence by elements or material masses that are far from being rigid and should be considered more as materials of certain flexibility. In the case of soils in slopes we know they are in a creeping process of extremely slow flow that elapses at rates between 1.0 and 6.0 cm/year in warm regions, such as those of the northern hemisphere, and between 1.0 and 10.0 cm/year in regions with influence of the tropical weathering processes such as the Camisea gas duct . Within the described medium, rarely do rigid structures, such as contention walls of reinforced concrete, last in service, without cracking or toppling and therefore one must recur to gabion walls or castled counterweights which allow a certain range of greater deformations. Both the refill of the gabion walls and the castled counterweig hts are frequently replaced by sacks fill ed with soil-cement due to the lack of available hard and durable rocks in the generality of the project. These structures are flexible and admit considerable deformatio ns, compatible with the thrusts and deforma tions of the terrain in which they find support or the terrain they contain. In these conditions, imposed by the environment in which the Camisea DTS was constructed and operates, the essential design criteria in respect to maximum terrain thrusts or displa cements are those of achieving minimum terrain displacem ent which will only induce tolerable strains and deformations on the part of the ducts with adequate safety margins. To comply with these criteria, works such as the following are put into practice : • Surface drainage . We include in this category the filters that are made with synthetic geo -drains, t he

depth of which is performed from 2.0 to 3.0 m, or at least to the height of the lower part of the tubes. In reference to deep drainage, we have introduced draining trenches, dug with mechanical trench hoes, which can be taken to depths of up to 4.0 and 5.0 m, in any case deeper than 3.0 or 3.5 m. In places where piezometers have been installed, the trenches are installed at a depth determined by the groundwater levels read with this instrumentatio n.

• Surface drainage systems: current cutters, collection canals, outlets, canaliza tion of stream currents of natural waters.

• Energy dissipation systems in torrential streams that cross the area or are located in the lower part of the area.

• Sheet erosion is controlled with structures such as transversal dikes or dams made of wood, sacks filled with soil -cement, or rocks dams.

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• Deepening of streams located across the RoW or that constitute the natural drainage of the critical zone. This has a favorable effect, at times surprising, due to the discouragement of the groundwater level that it imposes at a medium term. During the constructive process of the DTS, many of these minor streams were obstructed and its bottom height was alte red. Today they are recovered through especially directed excavation processes and are provided protection with rock beds that work in a manner similar to their original state.

• Limit to the maximum the possible soil slides through discharge terracing at the crown of rotational slides, and the installation of drainage systems and multiple contentions in translational slides.

• Construction of counterweigh t joints at the foot of slopes that have previously presented rotational failure surfaces .

• Reduce the over load caused by notable refill thicknesses that produce consolidations of soil of soft foundations (and the subsequent settlement of the RoW that could lead to vertical deformation of the pipes), through the removal of appropriate or practical thicknesses o f material. These thicknesses depend on the calculated magnitude of necessary relief of pressur e s, of the topography of the sector , of the density of the soils, and the availability of areas for permanent disposition of these surplus material s.

• Diverse types of contention structures such as gabion walls in soil -cement, walls of reinforced earth, gabion walls with deep foundations on pillars that are supported in competent stratums.

• Re-vegetation of slopes through natural mediums and helped with the use geo-synthetics and bio -covers.

To carry out the design of the described works once the works which are going to be carried out according to the prioritization and the application of the risk matrix have been decided, a normal process of geotechnical engineering is performed with some important variations, given the complexities of the solutions that must be adopted, as to the logistics to carry out the works.

4.3.1 Risk Verification and Geotechnical Inspection Before initiating the performance of the designs, a detailed geotechnical inspection is carried out by the group of COGA geo-technicians, and in the cases of greater complexity (Risk Level 5) they count on a consultant group with proven international experience, which drafts an inspection file card. The next step is to perform a final risk evaluation of the site through the risk matrix; checking the da ta initially recorded.

4.3.2 Subsoil Topography and Exploration The topographical mapping is carried out not only with the objective of revealing cracks, scarps, and other indicators of geotechnical instability but also because according to the characterization of the movement we define that the moving soil mass has in volved the lines (NGL and/or NG), or that there is no certainty that they have not been reached by this movement. Within the work we locate the pipes in the terrain taking as a basis the information recorded in the As-built map or the construction records. Then we carry out exploratory trial pits to verify the true location of the pipelines and their depth. We contrast the field information against the construction records and apply precision criteria that have been established for the Camisea Gas Duct, we conclude the displacement of the pipeline or pipelines or the lack thereof . In case of displacement we proceed to perform a complete analysis of integrity and amongst the measures that can be adopted we find the performance of “strain relief” through excavation by surface layers and in a very careful manner; both in the RoW and in the ditch, to leave the ducts viewable or uncovered and thus return to their original position or the position of least strain . Simultaneou sly we carry out subsoil exploration through the trial of SPT (Standard Penetration Testing) and BST (Borehole Shear Test) where samples of soils are taken and analyzed in the soil mechanics laboratory which is available in the COGA base in the jungle sector. The Pluviometric regime is a very important factor in the definition of hydraulic works, especially those that manage the runoff waters: canals, current cutters, and outlets. In this item the application of collection, conduction, and discharge parameters is very important in relation to the type of materials that must be used. These three factors are intimately related and the functionality of the works is based on their proper interaction.

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4.3.3 Mathematical Modeling of the Design With the laboratory trials and the SPT data, the resistance paramet ers of the identified soils are calculated (angle of internal friction and cohesion), the representative and more critical sections are taken in respect to steepness and thickness of soft materials to cali brate and define the mathematical models and obtain the safety factors of the slopes with designed works, for which various modeling scenarios are made in the Slide v.5.0 program of Rocscience and the best design is taken for its execution. For the stabil ity analyses, the maximum and minimum values of the cut resistance parameters are considered and taken into account by making random combinations of cohesion and friction data pairs assuming a uniform variation of parameters. Although it is true that the parameter values concentrate at the middle, showing in most cases a normal distribution, by assuming a uniform distribution of the resistance parameters we guarantee to take into account the extreme values of said materials which are the parameter with whic h we obtain the most critical safety factors. Said modeling is performed for both the conditions that the slope shows at the time of analysis, and the conditions projected with the execution of the works.

4.3.4 The Work Plan Once the work to be performed is defined, a complete document is drafted where all the information analysis and the calculation that originated the designs is presented. In this document we also describe the constructive method, the resources necessary for its execution, and the environmental, industrial safety, and social considerations that must be taken into account. We also include the numeric support of the design of works to be performed through known geotechnical methods.

4.4 Execution of Geotechnic al Remediation and Maintenance Works

For the execution of geotechnical remediation works we have crews that execute this work, preferably during the dry season (April to October). These crews can reach a peak of 600 people, who jointly with the other resources, are distribute d and prioritized within a Master Plan, which involves the execution of all designed Work Plans, and a great deployment of logistics which includes the construction of temporary camps of brigades, close to the works on the RoW, and contracting a fleet of helicopters for the transfer of personnel, provisions, material, machinery, and other elements necessary for the development of the works. This great operation is carried out in the dry season and must end before the beginn ing of a new rainy season . Simultaneou sly we also have geotechnical maintenance groups that are in charge of carrying out repairs to the surface erosion control works on the RoW and the repair and/or maintenance of the temporary remedi ation works construct ed in previous seasons.

4.5 Monitoring of Performed Works

Once the window for the performance of geotechnical remediation and maintenance works has closed in November, we begin monitoring of the works performed during previous years in order to verify their proper function and the integrity of the duct in these sites. This monitoring is performed not only through the continuous vigilance groups, but in the points catalogued as critical, (Levels IV and V) in the risk matrix and other places of high sensibility such as some river crossings. This monitoring is performed through topographical points, installation of inclinometers, piezometers, and Strain Gauges.

4.5.1 Topographical Monitoring This monitoring is performed for constructed works through the placement of topographical points (Monuments) placed on the constructed structures and/or points on the terrain itself. The measurement is performed with a periodicity no greater than 1 month, controlling these placed points with previously established fixed and known points that have no movement. Through these comparisons we establish if there is movement in the structures and/or terrain and based on these results we take action measures such as continuing with monitoring or we initiate more detailed integrity studies. Some of the final products of this monitoring are maps of slopes, movement vectors, and threat zoning.

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4.5.2 Inclinometers and Piezometers This instrumentation is placed in sites where works have been performed and or sites with complex geotechnical movements in order to monitor and/or know the depths of the surface failures and groundwater levels; respectively. The readin g of these instruments is performed with two week periodici ty and as of the results the necessary measures are taken to maintain the geotechnic al integrity of the RoW. These decisions may include the construction of complementary works.

4.5.3 Strain Gages The stress of main interest on soil movement areas is the longitudinal stress. That is why the Strain Gages are installed parallel to the pipeline axis. We used an array of three sensors separate d 120 degrees from one another (at 4, 8 and 12 o’clock). These sensors reveal information only in the place where they are installed and they only measure the strain variations from t he installation onward. A stress monitoring requires a periodic consulting of Strain gages measures. We confront a disadvantage because generally our concern areas are not as accessible as we need, so this task generally involves a lot of planning and lo gistic resources. We implement in some areas an automatic system which collects the data at specific time with more frequency. Our Strain Gages sensors give us frequency values (hertz) which are equivale nt to certain level of strain. To make this equivalen cy we use a formula which is function of the square of the frequency measured. For that reason these sensors has a high grade of sensitivity because a little change in frequency means a reasonable change in strain. We express the strain in microstrains. Strain has no units of measure but the values are often very small. To manage these values much easier we multiply them by 10E6. That is a microstrain, the strain multiplied by 10E6, or in other words strain expressed in parts per million. The strain we obtain is a longitudinal strain that correspond to a longitudinal stress. According to the variation of strain and the position of the sensor we can relate the tensional state with the possible movements of the pipeline.

5 CONCLUSIONS • The combination of the geographical, geological, and geotechnical characteristics in tropical zones with

a high to high precipitation regime, may generate mass removal processes such as: landslides, flows, creeps, and various erosive processes, generati ng a high potential risk to the integ rity of the ducts, as well as to the RoW, being able to generate impacts of environmental, and community type, as well as the interruption of the gas or liquids supply to the productive mechanisms of the country and home consumption.

• Early identification of the mass removal processes allows a considerable reduction in potential risks, allowing the implementation of strategies and actions that will allow us to prevent and safeguard the security of the DTS. This is the reason why maintaining a continuous vigilance and geotechnical inspection group during the rainy season is very important.

• The implementation of a geotechnical risks appraisal system all ows us to be efficien t when prioritizing the interventions and distributing the resources in a planned manner, taking into account the logistic difficulties that the environment offers.

• Based on the information obtained from the vigilance groups, the complementary geotechnical studies, and our experience, we draft the best design for each type of problem, the application of mathematical modeling techniques for slope stability is important in this stage.

• The work performance stage requires precise and efficient planning, taking into account the logistic difficultie s of the jungle sector, without terrestrial access, where all resources must be transported by air. For example, we count on heavy machinery that has been adapted to be transported by this medium. Another no -less -important difficulty is the limited amount of time in which the performance of the work can be carried out, since it is only possible to carry out the works in the season with lo wer rainfall.

• The continuous monitoring of the potentially unstable zones and of the sites works have been performed is carried out with advanced technology and in many cases with on-line information, through remote sensors. This monitoring includes the reading and follow up of meteorological stations, strain gauges, inclinometers, and piezometers amongst others, allowing us to obtain greater knowledge and make decisions with this information that will allow us to ensure the integrity of the DTS from the geotechnical point of view.

• The high quality policy is supported in the prevention or mitigation of the environmental impacts, preventi on of occupational injury and illness in our activities, processes and services; as well as the

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compliance with the applicable legal requirements and other voluntaril y subscribed commitments related with these aspects.

6 REFERENCES

Ingeciencia, 2009 . Geotechnical Zonification of the Camisea Gas Duct, Jungle Stretch . (Document Draft). Senamhi, 2007 . Ministry of Defense, Peru 's National Meteorological Service, Corporative Studies of Rainfall in the rainforest of the Camisea gas pipeline and historical files of Senamhi. Coga, 2007 . Rainfall Data of the pluviometric seasons located along the Camisea gas pipeline for 2006. Compañía Operadora de Gas del Amazonas. Varnes, D.J. (1978) “Slope Movement Types and Processes”. In: Schuster R.L. and Krizek R.J. Editors, “LANDSLIDES -Analysis and Control”. Special Report 176, Transportation Research Board. National Academy of Sciences, Washington D.C. Suarez Jaime (2009). Book - Sli des - Geotechnical Analysis. Deere and Patton, 1971 . Slope Stability in residual Soils. Fourth Panamerican Congress in Soil Mechanics and Foundation Engineering, Vol I, Puerto Rico, U.S.A. 1971. Exponent, 2006 . Appendix C Hybrid Risk Technical Memoran dum, Draft Interim Report of the Camisea Pipe Lines in Peru. December 20, 2006. Golder Associates Study – Ingetec