1. Introduction2. Landslide Impacts

• Service and cost Impact Landslide• Indirect Impacts / Costs• Funded Capital Projects• Current practice of managing landslide

impact3. Identification of Land Slide

• General• Select to the Hazard Area

4. Mitigation• Stabilization• Protection• Avoidance• Maintenance and Monitoring

5. Conclusion• Complicating factors for landslide reduction• Future Plan

Contents

1. INTRODUCTION:Sarulla Geothermal Power Plant Project is a geothermal power plant to be built on the northern part of

Sumatra Island. There are 1 plant commissioning and 2 plants under construction - Silangkitang (“SIL”) power

plant and Namora-I-Langit (“NIL”) -1 and 2 plants with total capacity of 330MW. The construction period is

from March 2014 to March 2018.

1. INTRODUCTION:

A. SIL Site

Capacity: 1 plant (110MW)

Well Pad: 3 well pad

Access Road: 1.75km

Pipeline: 4.1km

B. NIL Site

Capacity: 2 plants (110MW x2)

Well Pad: 5 well pads

Access Road: 8.7km

Pipeline: 6.1km

LANDSLIDE EVENTS AT SARULLA GEOTHERMAL POWER PLANT

2. LANDSLIDE IMPACT

A. Service and cost Impact Landslide• Direct costs of landslide such as repair, replacement or maintenance. Those will include

capital improvement projects and maintenance costs, for example debris cleanup anddisposal, repair of property. Direct cost also include like, loss of property values, loss ofcommercial productivity.

Blocked Access Blockade Access, andDisturb Operation

Damage of Property

B. Indirect Impacts / Costs• Cost to the local communities include direct loss property, devaluation of property , higher

insurance cost, Landowner cost repairs and prevention, compensation for disturbancecommunity field.

Debris cover communitypaddy field

Repair LandownerProperty

C. Funded Capital Projects• Additional cost to identify, design, construct slope stabilization improvements. Which is the

cost will be take from capital project.

D. Current practice of managing landslide impact• Routinely inspects and maintains the slopes, ditches, retaining structures to minimize impact

operation when landslide occur. Inspection and monitoring during the rainy season. Investedby installing catchment pit, widening ditches to contain the landslide debris and stabilize theslopes.

Catchment Pit Ditches at Bench

3. IDENTIFICATION OF LAND SLIDE:A. GeneralFlowchart of protection land slide (Construction Phase)

3. IDENTIFICATION OF LAND SLIDE:

Technical SpecificationTechnical Specification of Slope Protection for Sarulla project as below.

Cut Slope:All cut slopes shall be based on a slope of 1V:1.5H with allowance for a 4m berm each 10m of

vertical cut, giving an approximate overall batter of 1V:2H.

Embankment and fill Slope:All embankment slopes shall be set at 1V:2H.All fill placed onto sloping ground shall be benched in.In the fill slopes, berms with a width of 2 m should be installed at every 5 m in vertical height.

If slopes are not achieve above specification, we select that slopes to Hazard Area. The indication of slope sliding under the construction phase. And others

(1) Select to Potential of Hazard Area

B. Select to the Hazard Area

3. IDENTIFICATION OF LAND SLIDE:(2) Slope Stability Analysis

Slope Stability Analysis based on data below,

Boring Log at Hazard Slope (Including underground water level) Laboratory Test result (Soil parameter) Actual Site Topographic Survey Data CLIMATIC (e.g. Rainfall log data and Storm Water Analysis)

Perform the Slope Stability analysis and check the criteria as below, Normal Condition FS > 1.5 Rainfall Condition FS > 1.2 Seismic Condition FS > 1.0

We will perform slope reinforcement if analysis result isnot achieved our criteria. And also re-analysis.

2. IDENTIFICATION OF LAND SLIDE• ANALISYS DESIGN

• MODELING BY FINITE ELEMENT ANALYSIS SOFTWARE FOR SOIL NAIL

• MODELING STORM WATER ANALYSISThis purposes to know flow water runoff occurs when precipitation from rain flow over the land surface.Cessation of adverse flow water line by diverting storm water away from steep slopes.

A. Stabilizationwe performed Stabilization work below to Sarulla Project site,

• Grading unstable portion of the slope to lower gradient• Construction of rock buttresses• Retaining walls and Gabion• Drainage Improvements• Reinforcement of high tensile steel wire mesh (Shotcrete) and secured with patterned ground

anchors (Soil Nail)• BORED PILES• Re-vegetation (Hydro Seeding and Sodding)

4. MITIGATION

• GRADING UNSTABLE PORTION OF THE SLOPE TO LOWER GRADIENT

• RETAINING WALLS and GABION

• DRAINAGE IMPROVEMENTS

• SOIL NAIL and SHORTCRETE

• BORED PILES

Drilled bore holes by insert H-Beam piles with concrete to reinforce steeply slope

• RE-VEGETATION (HYDRO SEEDING and SODDING)

B. Protection

• Protection measures for landslide primarily focus on containment and diversion of the movingdebris. Measures include walls, berms, ditches and catchment basins, which can be low tomoderate in cost. However considering long-term maintenance costs are often associated withthese measures to clean out and dispose of accumulated debris.

Debris Containment Wall

C. Avoidance

• Avoidance measures constitute a permanent solution to a landslide hazard. Measures include re-alignment away from the slope, relocation of the facility, and elevated structures that allowpassage of debris underneath the facility.

D. Maintenance and Monitoring

• Maintenance and monitoring measures include proactive cleanout of available catchment area.• Routine observation and assessment of slope conditions, land-slide warning (slide), monitoring slope.

- Equipment: INCLINOMETER- Frequency:1 time/week and After Heavy rain and Earthquake

• Provide weather instrumentation to prevent closures- These measures are relatively low cost and can be highly effective to reducing exposure to slide risk.

SYSTEM MONITORING• INCLINOMETER

• Deployment inclinometer in vertical holes, drilled over the hill surface (Bench)• Using Instrumentation data logger to measure the inclination• Maximum allowable deflection is 60 mm

Developing a plan that measurably reduces landslide complicated by the following:• Land Ownership – Some of the landslides on private property are outside SARULLA control or

responsibility. Some of the landslide area partially due to poor slope management by adjacentlandowners.

• Limited of Right of Way (ROW)-Construction of slope stabilization measures generally requireswork outside of SARULLA Right of Way.

• Funding – There is no long-term source of SARULLA’s funds for capital.• Permitting – Permitting Process and timelines. Due to some of SARULLA’s area within forestry

area with limited leasehold permit.

5. ConclusionA. COMPLICATING FACTORS FOR LANDSLIDE REDUCTION

B. Future PlanWe will share of the knowledge for slope protection from Construction Team to Operation Team :• Land slide log (Location, Impact Area, Reason and others)• Hazard Area of Land Slide• Check points of slopes for maintenance