IH-NTCO-X-04-252501-A0_Method Statement for Surge Shaft Excavation

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No:IH.NTCO.X.040*252501 Revision: A0 Date: 30 September 2004 Release/Amendment

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NISHIMATSU CONSTRUCTION CO.,LTD. Nam Theun 2 Hydroelectric Project

METHOD STATEMENT FOR

SURGE SHAFT CONSTRUCTION

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CONTENT

METHOD STATEMENT FOR SURGE SHAFT EXCAVATION

Page

1. General 3

2. Scope of Work 3

3. Reference Documents 3

4. Materials 4

5. Major Equipment and Tools 4 6. Work Procedure 4 7. Ventilation 13 8. Illumination/Lighting 13 9. Dewatering 14 10. Quality Assurance 14 11. Monitoring 14 12. Health and Safety 15 13. Environmental Management 19 14. Appendix 22

• Location Map • Reference Design Drawings • Typical Excavation Profiles for

Surge Shaft Excavation • Proposed Shotcrete Mix Design • Proposed Concrete Mix Design • Typical Drilling Pattern • Typical Rock Bolt Installation • Sedimentation Tank Drawing and

Details • Work Procedure Diagram • Inspection and Test Plan

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Method Statement For

Surge Shaft Excavation 1. General

Part of the underground waterways of the Nam Theun 2 Project, is the excavation of 2 shafts, the Surge shaft and the Vertical Pressure shaft. The surge shaft is situated on the left bank of the headrace tunnel. Its vertical axis (UW 5) is 14 meters from the axis of the headrace tunnel (UW 4). The surge shaft will dissipate pressure transients in the tunnel during start-up and load rejection operation of the power station. The vertical pressure shaft is 225 meters long extending from point UW 6 to UW 7, with a circular cross section, and an excavation diameter 9.7 meters. The lined diameter of the shaft is 8.8 meters.

2. Scope of Work The scope of work will be:

a. Rock excavation of the surge shaft. b. Installation of necessary ground support to excavation c. Concrete lining and grouting of the shaft excavation d. Installation of related civil structures and mechanical equipment e. Associated ventilation and lighting work.

3. Reference Documents

Document No : IH NTCO R 043 * 220001 A Description : Underground Works Surge Shaft General Arrangement Sections and Details Document No. : IH NTCO R 040 * 220003 A Description : Underground Works Typical Cross Sections

4. Major Materials and Supplies

Item Description Use 1 Steel Ribs HEB 200 Support from Portal (Sta. 0 + 000) to

Sta. 0 + 015 2 Rock bolt , Friction Type Rock support as applicable 3 Cement ASTM C150 Type I Shotcrete and concrete production 4 Sand Shotcrete and concrete production 5 Coarse Aggregate Shotcrete and concrete production 6 Steel Wire mesh Rock Support 7 Admixtures (Rheobuild 1000) Shotcrete and concrete Admixture (Meyco SA 160) Shotcrete Accelerator

8 NONEL Long Period Delay Detonators

Blasting

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Item Description Use 9 Emulsion dynamites 40 mm Ø x 300

mm. Blasting

10 Emulsion dynamite 25 mm Ø x 200 mm.

Blasting (smooth blasting)

11 ANFO Blasting 12 Detonating Cord, 60 – 80 g Blasting 13 Detonating Cord 12 g Blast Initiation 14 Electric Detonator Blast Initiation 15 Blasting Wire Blast Initiation

5. Major Equipment and Tools Item Description No. Activity

1 Hydraulic drill machine, 2 boom, crawler type

2 Drilling and rock bolting

2 Motor Compressor,75 kw, 12 m³/min.

2 Compressed air supply

3 Generator, 150 kva 1 Electrical power supply 4 Hydraulic breaker, 800 kg. 2 Scaling and Trimming 5 Hydraulic excavator,0.45 m³ 2 Mucking 6 Wheel Loader, 2.3 m³ side dump 2 Mucking 7 Dump Truck, 4 ton 4 Spoil Disposal 8 Dump Truck, 10 ton 3 Spoil Disposal 9 Shotcreting machine, robotic 2 Shotcrete application

10 Concrete Mixer Truck, 4.5 m³ 4 Shotcrete/Concrete Delivery 11 Boring Machine 2 Pilot Raise Boring 12 Ventilation Fan 4 Ventilation 13 Concrete Pump 2 Concreting 14 Accelerator Dosing pump 3 Shotcrete Application 15 Friction Bolt Pump 4 Rockbolting 16 ANFO Loader 2 Blasting 17 Blasting Machine 6 Blasting 18 Multi-Gas Detector 4 Air Quality determination 19 Sliding Form 1 Concrete lining 20 Shaft Elevator 1 Shaft Access 21 Scaffold set 1 Various shaft works 22 Hoist and accessories 1 Hoisting and lowering 23 Shaft Elevator 1 Shaft Access 24 Shaft Stairway/Ladderway 1 Shaft Access 22 Pick up 4x4 2 Service car

6. Work Procedure

6.1. Preparation Prior to starting the excavation and construction work, the necessary plant, equipment, materials and supplies needed to start the works will be at the site. The necessary temporary facilities will be laid out on site, proximate to the work area as possible.

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6.2. Survey and Setting out The shaft location, centerline and alignment, and elevation will be established by survey, in accordance with the design as indicated in the layout plan and typical cross sections of the reference drawings.

6.3. Shaft Excavation and Construction Construction of the shafts will be done in two stages. The first stage will be the drilling of a pilot raise bore, and the second stage will be the widening of the pilot bore to the designed excavation limit and casting the concrete lining. The pilot bore will have a final diameter of 1.5 meter. The pilot hole will be 250 mm. diameter. Prior to raise boring activities, the open excavation will be done from elevation 550 m. to 540 m. to prepare the staging area and platform for the shaft excavation. Corollary to this activity, the excavation of the shaft bottom from the Headrace tunnel will be done.

6.3.1. Raise Boring Preparation Work will involve the ground preparation and excavation work and the provision of the necessary facilities for the pilot raise bore drilling. The excavation of the Access adit to the position of the surge shaft bottom will be complete.

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Survey and Setting out Survey to set out and mark location, centerline, and elevation of the pilot raise bore, after which the boring machine will be set. The raise bore will be set along the axis of the shaft. Survey will establish and set the boring machine prior to drilling pilot hole. Drilling of Pilot Hole and Raise Boring Once the boring machine is set, drilling of the 270 mm. diameter pilot hole will commence. Drilling of the pilot hole will be done until breakthrough with the designed shaft bottom excavation. After breakthrough, the 270 mm. diameter pilot drilling bit will be replaced with the 1.5 meter diameter reamer bit after which widening the pilot hole by raise boring will be done. Cuttings from the reaming will be mucked out from the shaft bottom off the headrace tunnel using wheeled loader that will load the spoil to dump trucks for transport to designated disposal areas. After reaming, the boring equipment will be dismantled and removed from site. If during the pilot hole drilling and reaming of the raise bore it is determined that the raise will need support to maintain its integrity, a steel pipe will be installed to protect the walls of the raise bore from wearing. The void between the pipe and the walls of the pilot raise bore filled with mortar/sand. As the excavation advances, the pipe will be cut.

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6.3.2. Shaft Collaring The raise bore will be widened to the designed construction limits to a depth of 3 meters. After the initial excavation, collaring of the shaft will be done by applying the designed support system. Suitable hoisting equipment, and related accessories will be installed to transport machinery, equipment, supplies and personnel from the shaft collar to the work area. After advancing 15 meters, the sinking platform will be installed to facilitate the work of the shaft construction. The alternative access for workers (manways/ladders), shaft elevators will also be established and installed.

Typical Supply Arrangement for Surge Shaft Excavation

6.3.3. Excavation The raise bore will then be widened starting from the top and progressing downward. Main excavation will be by drill and blast method using hydraulic drilling machines. The depth of each drilling round will be in the range of 1.5 m. to 2.0 m. to preserve the integrity of the pilot raise bore. The explosives charge will be limited to ensure that the pilot raise bore is not deteriorated or damaged by the blasting operations. Another consideration in the design of the blasting pattern, type of explosives, and explosives charge will be the fragmentation after the blast to avoid “choking” of the pilot raise bore. The pilot raise bore will serve as “free face” for the blasting operation. Explosives charging and detonation will be carried out only by competent and authorized personnel. After blasting, the shaft will be defumed for at least 20 minutes before work will be allowed to resume.

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6.3.4. Mucking After each blast, broken rock is expected to drop to the shaft bottom through the pilot raise bore. The remaining spoil from the blasted area will be mucked to the raise bore using a hydraulic excavator or wheeled loader. When mucking at the shaft excavation is completed, the raise bore will be covered with a grizzly, and mucking at the shaft bottom will commence. The spoil at the bottom of the shaft will then be loaded by a wheeled loader into dump trucks that will transport the spoil to the spoil area through the access adit.

Mucking by Hydraulic Excavator at Shaft Excavation

“Mucking at the shaft bottom will commence after mucking in the shaft has been finished and coverage of raise bore”

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Mucking by Wheel loader at Shaft Bottom

6.3.5. Trimming and Scaling After each blast, trimming and scaling will be done by hydraulic breaker to scale loose rocks resulting from the blast, and to remove any under breaks to attain the designed excavation limit.

Trimming and Scaling by Hydraulic Breaker

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6.3.6. Primary Support Installation Shotcrete (First Layer) Once the excavation profiles are checked, an initial layer of shotcrete will be applied on the newly excavated walls of the shaft. The initial layer will be 3 – 5 cm. thick. Shotcrete application will be done by a robotic shotcrete machine. To ensure the correct thickness of shotcrete is attained, thickness guides will be installed in a 2 m. grid pattern. Rockbolting and Wiremesh Installation After the first layer of shotcrete is applied, drilling for rockbolts will be done using a hydraulic drilling jumbo. Rockbolt patterns and densities will be in accordance with the reference design and construction drawings. The rockbolt patterns and density may increase or decrease according to the actual ground conditions as determined by the geologist or geotechnical engineer. After drilling the holes for the rockbolts, they will be flushed to remove sludge or drill cuttings remaining inside the hole. When required, the wiremesh will be laid out along the shotcreted surface. The wiremesh will be fastened to the surface by steel pins to ensure the wiremesh is flush on the surface. Rockbolts will then be installed to further anchor the wiremesh to the surface.

Drilling for Rockbolts using Crawler Drill

Rockbolt Installation using Shaft Sinking Platform

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Shotcrete (Final Layer) Once the rockbolts and wiremesh are installed, a final layer of shotcrete will be applied. The thickness of the final layer will be 3 – 4 cm. or as determined by the geologist or geotechnical engineer. Again, thickness guides will be installed on a 2 meter grid pattern to ensure that the correct thickness of shotcrete is applied. Shotcreting will be done by a robotic shotcrete machine.

Shotcreting using Robotic Shotcrete Machine The procedures will be repeated until excavation of the shaft is completed.

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6.4. Concrete Lining After completion of the excavation, the shaft will be lined with concrete. Concrete lining will commence at the bend at the bottom of the shaft and progress upwards towards the shaft collar. Before concreting, the surface shall be thoroughly cleaned by purging to remove any soil, loose rock fragments, dust or fines adhering to the shotcrete surface. Once the lining of the bend is completed, the slipform shutter 8.8 meter diameter will be installed and concreting for the lining will commence. When reinforcement is required, the fixing of the reinforcements shall be in accordance with the relevant DTS and GTS. Also, before concreting is done, survey checks for the profile requirement will be carried out to ensure that the required internal clearance is achieved. As the concreting progress, the required civil and electromechanical structures will be installed (steel orifice, pressure keys, etc.) at the locations as specified in the reference design and construction drawings. When the lining for the 8.8 meter diameter span of the shaft from elevation 436.35 m. to elevation 490 m. is completed, the shutter will be modified for the concreting of the 13.9 meter diameter span from elevation 490 m. to elevation 540 m. During concrete lining, cast in pipes will be installed in preparation for grouting after the concrete lining. Slip forming and concreting will continue until the concrete lining is complete.

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6.5. Grouting Once the concrete has cured adequately and attained the required strength, grouting through cast in pipes will be done.

Contact and consolidation grouting will be done according to the predetermined patterns. If additional locations are required for grouting, these shall immediately be done.

7. Ventilation

An adequate ventilation system will be set-up. Axial fans will be used and fresh air will be conveyed to the working face by flexible ducting. Since mobile diesel equipment will be used in the shaft excavation, the ventilation system will provide a minimum of 50 l/s/hp according to the relevant GTS/DTS. Gasoline powered or stationary diesel equipment will not be used inside the shaft. Air quality determination will be done at the start of the work shift/s and after blasting, to check the concentration of noxious gases, before starting or resuming work.

8. Illumination/Lighting

As the shaft excavation progresses, lighting will be provided at the advancing shaft bottom and transit area as specified in the DTS/GTS. Mobile/movable spotlights, with minimum 40 lux illumination, will be used in the working area, so that they can be easily positioned, transferred or removed during blasting. In the transit area, fixed lighting with minimum of 10 lux illumination will be installed. The lighting will be installed along the perimeter of the shaft and spacing will be every 2 meters. Spacing between lighting rings will be maintained at 5 meters. Fixed lighting will be maintained 20 meters away from the advancing face.

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9. Dewatering Water from the shaft excavation activities will be drained thru the pilot raise bore down to the access adit. The drainage ditches and channels at the access adit will receive the water from the shaft and convey to the drainage system at the platform area. The discharge water will finally be conveyed by the drainage system to a sedimentation tank, to allow settling of silt and mud before further discharge of the water into natural drainage systems. The sedimentation tank will be regularly cleaned to ensure it’s functionality.

10. Quality Assurance Before and during the execution of works, materials testing will be performed by either on-site or off site laboratories, in Lao PDR or Thailand, as approved by the Employer’s Representative. Standard specifications and test methods will be in accordance with that described in the relevant GTS or DTS. Other specifications and test methods shall be approved and accepted by the Employer’s Representative on site before use. To ensure that the works are done in accordance with the relevant DTS and GTS, an Interim Test Plan covering the all phases or work procedures (Appendix

11. Monitoring

The integrity of the shaft during construction will be regularly monitored on short term and long term basis. Short Term Monitoring Systems:

1. Geological mapping and geotechnical data collection after excavation shall be done to ascertain and confirm the support system to be applied. The geologic data shall be interpreted and analyzed by the geologist and geotechnical engineer to be able to project the expected ground conditions for the next excavation round/s. or cycles.

2. During drilling for blasting and rockbolting, cuttings and sludge from drilling shall be observed to obtain information on the geology and rock type immediately after the face at certain length, and at the walls. If water ingress is encountered, flow rate shall be determined, and if necessary, pilot holes shall be drilled, to probe deeper into the rock face. Length of the pilot holes, diameter, etc. shall be determined by the geologist or geotechnical engineer. Excavation methods and procedures may be modified according to the results or findings of this procedure.

3. The applied shotcrete support shall be regularly checked for cracks and other abnormal conditions. Once these are observed, the appropriate measures to reinforce or repair the shotcrete shall be done immediately.

4. Probe holing drilling – When bad ground is expected or projected to be encountered, the geotechnical engineer or geologist will require probe hole drilling to confirm the geology condition and extent ahead of the advancing shaft bottom. The length and diameter of the probe hole will be determined by the geologist or geotechnical engineer and will be done before advancing the shaft. The results of the probe hole drilling will dictate any changes in methodology, support system, or preparatory works (consolidation grouting) in the shaft excavation.

5. Quality control of the works shall be done strictly following the Inspection and Test Plan. (Appendix 13)

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Long Term Monitoring Systems: Long term monitoring systems shall consist of procedures that are programmed to be periodically done to monitor the tunnel integrity during and after the construction phase. Convergence Monitoring

Convergence monitoring stations (5 points) will be established at intervals of 20 meters, one (1) week after excavation has passed. The monitoring stations shall be established by Tunnel profiler, a computer aided, state of the art survey instrument. No prisms, pins, steel rods are required for this, since the instrument has the software and can be programmed to automatically locate the convergence points, and make observation readings. The frequency of the monitoring will depend on the geology of the rock that is excavated and supported or as advised by the geologist or geotechnical engineer. If the monitoring shows movement, all measures shall be taken to reinforce the support systems at the particular location.

12. Health and Safety

a. Shaft Safety Excavation

1. Excavation will be done only within the boundaries of the profiles as set out and marked by survey in accordance with the layout, plans, and sections in the reference design and construction drawings.

2. Effort shall be taken to minimize or eliminate over break and over-excavation. When blasting is employed, the explosives charge schedule and powder factor shall be strictly followed. Explosives charging shall be properly supervised and executed only by authorized and experienced personnel. Prior to firing, the round shall be thoroughly checked by the Blaster. During blasting, all entrances and access to the blast area shall be barricaded or cordoned off and guarded.

3. All excavation done, either by blasting or hydraulic breaker, will be supported within 12 hours from the time of the blasting or excavation, to prevent deterioration or weathering of the rock when exposed to air. An initial layer of shotcrete, 3 -5 cm. shall be applied to cover the newly exposed rock resulting from blasting or mechanical excavation.

4. The excavations shall be regularly mapped by the geologist or geotechnical engineer to determine the type of rock, rock quality, geology, and other geotechnical information required, to be able to assess the type of support needed.

5. Before starting any work at the shaft excavation, the raise bore shall be covered with a removable grizzly or similar device to prevent workers, materials, or small equipment from falling into it.

6. Electrical equipment and machinery to be used in the tunnel shall be properly grounded, and electrical components provided with the protection required. Only authorized personnel shall be allowed to repair or work on the electrical components.

7. Lighting will be provided at the tunnel face, the minimum illumination shall be 100 lux. These shall be properly mounted on stands that can be easily moved around and positioned as required at the working face. The lighting fixtures shall be waterproof and maximum voltage for the fixtures shall be 240 volts.

8. Transit areas shall likewise be provided with lighting fixtures, and minimum illumination to be provided shall be 40 lux. The lighting fixtures shall be waterproof and shall have a maximum voltage of 240 volts.

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9. An alternative access for workers (shaft elevator, manway ladder or stairway) shall be provided.

10. When working above the shaft bottom, for repair or miscellaneous jobs, workers shall be equipped with the necessary safety harness and safety ropes.

Hoisting Equipment and Accessories

1. The hoisting equipment capacity shall be equivalent to heaviest load to be hoisted plus a safety factor of 20 percent. Hoisting equipment shall provided with the following safety devices:

a. Emergency stop switch b. Over travel tripping device c. Upper limit and lower limit tripping device d. Cable slack tripping device e. Indicator for location of sinking platform along the length of the shaft f. Signal system g. Communication system with the hoist operator

2. Hoisting equipment shall be operated only by qualified and competent personnel. The hoist operator shall be subjected to medical and psychometric tests every 6 months to confirm fitness for the job. Signal men shall be provided on the sinking platform to control the sinking platform and communicate with the hoist operator either directly or by signals. The signal men shall also be subjected to medical and psychometric tests to confirm fitness for the job.

3. After installation and commissioning, before the actual use of the hoisting equipment for shaft excavation, a load test shall be performed to check and confirm the load bearing capacity of the hoist and its accessories.

4. Cables shall be non-rotating steel wire rope, the diameter and number of strands shall be dependent on the required load capacity of the cable.

5. Cables shall be securely fastened to hoist drum and the cable properly wrapped in layers. No overlapping of the cable wrapping shall be tolerated. Once overlapping in the wrapping is observed, re-wrapping of the cable shall be immediately done.

6. Hoist inspection and servicing shall be done weekly. The emergency tripping devices of the hoist shall be checked for functionality and serviced. Controls, electrical and hydraulic system, and the braking system of the hoist shall also be checked and serviced.

7. Cable inspection and servicing shall also be done weekly. The cable shall be cleaned and the wire strands of the cable wire rope inspected at regular intervals to check for broken wire strands. If broken wire strands are observed, the corresponding course of action to correct the situation shall be done as determined by the mechanical engineer. Elongation of the cable shall also be checked. If re-wrapping of the cable to the hoist drum is required due to elongation, it shall be done.

8. The hoist shall never be operated and the sinking platform or equipment for hoisting or lowering in the shaft moved in an upward or downward motion unless the hoist operator confirms signals and communication given by the signal man.

9. During the lowering of equipment or supplies, the appropriate lifting equipment shall be used. Cable slings shall be of the appropriate size and number of legs shall at all times be four (4). Mobile equipment shall be properly lifted at the lifting points provided on the equipment. Cable slings shall be checked before each used of its integrity. If broken wire strands on each or any of the legs are observed, the sling shall be discarded and replaced.

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10. Once the sinking platform or equipment being hoisted or lowered are in motion, an audible warning sign shall be triggered to warn workers, and to stay clear of its path and the shaft bottom.

11. All personnel riding in the sinking platform shall be equipped with harness and lanyard fastened to the sinking platform.

Communications

Communication from the shaft bottom or anywhere along the shaft to the surface, (shaft collar platform, and hoist room) shall be done by suitable communication means or equipment for the purpose. The communication equipment will be installed at strategic intervals so that communication from the shaft to the surface (shaft collar area and hoist room) is maintained at all times. The communication equipment shall be laid out along the shaft ladder or stairway, and the shaft bottom.

b. Support Systems: 1. Rock bolt pattern and density will be installed in accordance with the typical plans,

layout, and sections of the reference design and construction drawings. 2. The geologist or geotechnical shall evaluate all geologic and geotechnical

information of the excavated area, and shall decide on the support system to be applied based on actual ground conditions (either the increase or decrease in rockbolt density and spacing between rockbolts, installation of wiremesh, use of steel ribs, increase in shotcrete thickness). The geologist shall inform the site engineer of his evaluation and recommendations regarding the support system. The site engineer and foremen shall ensure that the required support measures are applied.

3. When grouted rockbolts are employed, the whole length of the bolts shall be fully grouted. Grouting material shall be in accordance with the relevant DTS/GTS. Pre- grouting of the rock bolts shall be the preferred method. When friction bolts (Swellex) are used, the bolts shall be installed according to the manufacturer’s procedure and recommendations. The correct air and water pressure shall be applied to ensure that the friction bolt expands completely and creates the required anchorage of the rock.

4. All rockbolts face plates, conical washers, hemispherical nuts, lock nuts, and stick-out, shall be covered with shotcrete.

5. Shotcrete quality shall be regularly checked by QC procedures. Application procedure shall be in accordance with sound construction practice. Thickness guides shall be installed to ensure that the correct thickness of shotcrete is applied. Water ingress will be isolated and the rock surface to be sprayed, cleaned of loose rock fragments, soil, debris, etc.

c. Power, Compressed air, and Water supply systems

Power distribution lines, compressed air and water delivery pipes shall be properly laid out arranged in the tunnel. Power supply and distribution system The power lines shall be laid out separately from the air and water pipes and the necessary air circuit breakers (ACB) provided to automatically cut off power supply when abnormalities are detected. Electrically operated equipment and machinery shall be provided with circuit breakers and shall be properly grounded. Only authorized personnel shall be allowed to work on repairs or maintenance of the power lines and equipment.

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Power cables will be properly laid out and cable trays, hangers, racks provided and shall be securely fastened. Compressed air and water distribution system Air receiver tanks will be installed after the compressors prior to distribution to regulate the pressure in the delivery pipeline. The receiver shall be equipped with the necessary pressure release valves, pressure gauges, and drain valves. A main valve shall be installed after the air receiver tank to control or shut off compressed air supply in cases of repair or emergency. Isolation gate valves shall be installed at intervals of 50 meters also for repair and emergency purposes. Concrete Delivery Pipes

Concrete delivery pipes will be laid out along the shaft and securely fastened to walls. The pipes shall be cleaned after use.

d. Personnel Safety The safety of the workers shall be guaranteed at all times. Access to the Shaft Excavation Works Access to the surge shaft excavation area shall be restricted to authorized personnel only. A fence shall be constructed along the perimeter of the construction site and the area classified as ENTRY BY PERMIT ONLY. Authorized workers and personnel shall be issued Tunnel/Shaft Entry Pass or ID cards. Persons or workers without entry pass shall not be allowed entry into the construction site. Training and Information All personnel who will be assigned in the tunnel and related work shall undergo safety orientation before being allowed to work in the tunnel. Aside from this, tunnel workers shall be required to undergo the Basic First Aid training course (Red Cross Standard) during the duration of their employ. They shall also be required to attend refresher courses to be scheduled by the Safety department. Safety reminders in English and Lao language, shall be installed at strategic locations to keep the workers informed and remind them of safety rules, regulations, and procedures. Safety warning signs shall be installed whenever there is a hazard identified. All actions shall be taken to correct and eliminate the hazard at the soonest possible time.

Personal Protective Equipment (PPE) All personnel assigned in the tunnels shall be provided with the basic safety protective equipment. These shall consist of but are not limited to the following:

Safety Helmet (approved for underground use) – for head protection Dust mask or respirator – for respiratory protection Ear plugs - for noise protection Rubber Boots – foot protection Safety gloves - hand protection Safety goggles – eye protection Safety Harness and Lanyard – fall protection

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When the nature of work requires additional PPE, these shall be identified and provided to ensure worker protection and welfare. Worker compliance in the use of the PPE shall be ensured by the Site supervisors, foremen, in coordination with the safety personnel. Air Quality and Ventilation The minimum ventilation requirement of 300 l/s/m² shall be maintained at all times. Air quality tests shall be done at the start of the work shift and after blasting. After blasting operations, the blast area shall be defumed and air quality determination done before allowing work to resume. In cases where the ventilation system has stopped, work inside the tunnel shall be suspended and the workers evacuated to the portal until such that time that the ventilation system has been re-started and the work area ventilated for at least 20 minutes. No one shall be allowed to work in the tunnel without proper ventilation.

e. Emergency Response Procedures

The emergency response plans and procedures as set forth in the Site Safety Plan shall be strictly implemented. Information dissemination shall be done and incorporated in the safety induction program. A First aid station complete with a First Aid box containing essential medicine, equipment, medical supplies, shall be maintained at the platform area for administering first aid in case of accidents. The first aid station shall be regularly checked for supplies and equipment and provision or replenishment done. A telephone or suitable communication equipment shall be provided at the first aid station. The first aid station shall be manned by qualified and trained first personnel.

All other safety measures as stated in the Site Safety Plan will be implemented and compliance will be ensured.

13. Environmental Management

The Contractor’s Environmental Monitoring and Management Plan (EMMP) and the Site Specific Environmental Plans (SSEP) will be strictly followed and complied with to ensure mitigation of any impact the work may have on the environment. Clearing and Grubbing Once the open excavation and platform is completed, no additional clearing or grubbing is necessary for the duration of the works. Water from Tunnel Excavation The discharge water from the tunnel shall be isolated and diverted to the drainage network at the platform area. The discharge water from the shaft excavation shall be diverted or pumped if necessary, to pilot raise bore. From the pilot raise bore, the water shall be conveyed to the access adit platform drainage systems through the drainage channels in the access adit. At the access adit platform area, a sedimentation tank shall be constructed or provided, where silt, mud, and other impurities will be allowed to settle, before the water is discharged to natural drainage systems.

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Dust Generated during Blasting and Mucking Dust generated during blasting shall be dissipated from the tunnel by means of the ventilation system. Broken rock resulting from the blast shall be sprayed with water to eliminate dust generation during mucking.

Hazardous Materials (HAZMAT)

Storage and Handling Hazardous materials (oil, fuel, lubricants, explosives etc.) shall be stored in designated areas that are fenced out and provided with containment structures or facilities in case of accidental spill. The storage areas shall be clearly marked out and fenced off. The necessary spill response kits and equipment shall be made available. Handling of these materials shall be in accordance with the manufacturer’s recommendations. Explosives shall be stored in magazines provided with adequate ventilation and lighting to prevent premature deterioration of the explosives and explosives accessories. Detonators shall be stored separately from explosives. The explosives magazines shall be fenced off and secure, with access limited to authorized personnel. Earth barricades shall be proved around the magazines, and when necessary, lightning arresters will be installed. The necessary fire fighting equipment shall be provided for each magazine. The magazines shall be regularly checked and inspected. Brushing around the perimeter of the magazines shall also be done. Disposal Hazardous materials shall be disposed of according to the procedures stated in the EMMP. Temporary storage for waste shall be established to accommodate these materials until a permanent disposal area is designated. The temporary storage shall be provided with the necessary facilities to prevent contamination of the environment.

Non- Hazardous Materials Storage and Handling Non-hazardous materials shall be stored according to the manufacturer’s recommendations. Accidental spills shall be immediately treated and cleaned up according to procedures recommended by the manufacturer. Storage areas will likewise be fenced out and clearly marked out. Disposal Disposal of these materials shall be in accordance with the manufacturer’s recommendation and procedures as set forth in the EMMP and SSEP.

Garbage Generated All temporary facilities (workshops, offices, lunch rooms) shall be provided with garbage receptacles to receive garbage generated from these facilities. Garbage will be collected regularly and will be disposed in designated disposal areas and procedures as stated in the EMMP and SSEP.

Toilets

Toilets shall be provided at strategic locations within the platform area. The toilets shall be provided with a septic tank and continuous supply of water. The toilets shall be maintained for cleanliness and sanitation.

Spoil Disposal Areas

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Slopes of spoil disposal areas shall be maintained less than the determined angle of repose of the material to ensure stability. Coffer dams along the boundaries of the spoil disposal areas shall be constructed to ensure that the accumulated spoil is not washed away into natural drainage systems during heavy rains. Drainage shall be properly maintained to avoid saturation of the spoil material during rains and the necessary silt traps or ponds constructed along the drainage or discharge channels into natural drainage systems. The disposal areas shall be monitored regularly so that they are filled only to the designed capacity.

All other environmental plans and procedures as stated in the EMMP and SSEP shall be strictly complied with to mitigate any impact of the construction activity on the environment.

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APPENDIX

1. Location Map 2. Reference Design Drawings 3. Typical Excavation Profiles for Surge Shaft Excavation 4. Proposed Shotcrete Mix Design 5. Proposed Concrete Mix Design 6. Typical Drilling Pattern 7. Typical Rockbolt Installation 8. Sedimentation Tank Drawing and Details 9. Work Procedure Diagram 10. Inspection and Test Plan

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Appendix 1 LOCATION MAP

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LOCATION MAP

SURGE SHAFT EXCAVATION

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Appendix 2 REFERENCE DESIGN DRAWINGS

NOTES:

IHCW2

220001 * RNTCO 043

IHCW2

220003 * RNTCO 040

GENERAL NOTES:

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Appendix 3 Typical Excavation Profiles for Surge Shaft Excavation

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Appendix 4 Proposed Shotcrete Mix Design

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WET MIX SHOTCRETE

Reference Specifications: o Special Concretes : Section 6.5.7; GTS Civil Works Part 1 – Chapter 1

Section 8.3.2 Shotcrete : Section 6.6.3.1; DTS Article 8.3.2 BIS Shotcrete

o Aggregates : Section 6.5.7; GTS Civil Works Part 1 Section 1.1

: Section 6.6.3.1; DTS Article 1.1 BIS Aggregates

o Cement : Section 6.6.3.1; DTS Article 1.2 BIS Cement, Chapter 1.2.1.8 Cements for Other Conventional Concrete ASTM Type I

o Fly Ash : Section 6.5.7; GTS Civil Works Part 1-Chapter 1 Section

1.3.1 Fly Ash : Section 6.6.3.1; DTS Article 1.3.1 BIS Fly Ash

o Mixing Water : Section 6.5.7; GTS Civil Works Part 1 – Chapter 1

Section 1.4 : Section 6.6.3.1; DTS Article 1.4 BIS Mixing Water

o Admixtures : Section 6.6.3.8; DTS Article 8.2.1.2

o Mix Design : Section 6.6.3.8; DTS Article 8.2.1.1 BIS Nominal Formula, Type No. 5-Shotcrete

o Making Concrete : Section 6.6.3.8; DTS Article 8.2.2

Material and Design 1. Concrete Compressive Strength at 28 days 25 MPa 2. Water Cement Ratio 0.45 3. Cement Type 1 4. Maximum Size of Aggregate 9.5 mm. 5. Admixture (Super Plasticizer) Degussa - Rheobuild 1000 1000 cc/100 kg. cement 6. Specific Gravity of Cement 3.150 7. Specific Gravity of Fine Aggregate (Saturated Surface-Dry) 2.626 8. Specific Gravity of Coarse Aggregate (Saturated Surface-Dry) 2.739 9. Proportion of Fine Aggregate 55% 10. Design Slump 3-7 cm. 11. Admixture (Accelerator) Degussa - Meyco SA 160 12% by weight of cement

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Mix Proportion of Shotcrete / m³ NO Fly Ash

Cement Type I 400 kg. Water 180 kg. Fine Aggregate 947 kg. Coarse Aggregate 809 kg. Super Plasticizer 4 kg. Accelerator 48 kg. ========= Total Weight 2388 kg. Note: This design for trial mix and panel test prior to use on site

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Appendix 5 Proposed Concrete Mix Design

1.1 Type of Concrete : Type n° 3 bis Conc. fixing the high pressure tunnel not in direct contact with waterSection 6.6.3.8 DTS Article 8.2.1.1 bis: nominal formula .

1.2 Size Grading 0-12.5 mm1.3 Cement ≥ 310 kg/m3

1.4 Water : Cement Ratio ≤ 0.601.5 Compressive Strength (28 day) ≥ 30 MPa

2.1 Cement 380 kg2.2 Water : Cement Ratio 0.502.3 Water 380 x 0.5 190 kg2.4 Volume of dry rodded Coarse Aggregate 0.602.5 Unit Wt. of dry rodded Coarse Aggregate 1565 kg/m32.6 Wt. of Coarse Agg. In Concrete (Absorption of 0.74%) 946 kg2.7 Admixture Superplasticizer Rheobuild 561(0.80 litr. / 100 kg. of cement) 2.53 kg2.8 Specific Gravity

2.8.1 Cement 3.1502.8.2 Fine Aggregate (Sat. Sur. Dry) 2.6262.8.3 Coarse Aggregate (Sat. Sur. Dry) 2.7072.8.4 Admixture - superplasticizer (Rheobuild 561) 1.200

3.1 Cement 380 / 3.150 / 1000 = 0.1206 m3

3.2 Water 190 / 1.000 / 1000 = 0.1900 m3

3.4 Admixture - Superplasticizer (Rheobuild 561) 2.53 / 1.200 / 1000 = 0.0021 m3

3.5 Coarse Agg. 946 / 2.707 / 1000 = 0.3494 m3

= 0.6622 m3

3.6 Volume of AggregateFine Aggregate = 0.3378 m3

= 1.0000 m3

4.1 Cement 0.1206 x 3.150 x 1000 = 380 kg

4.2 Water = 190 kg

4.4 Admixture - Superplasticizer (Rheobuild 561) 0.0021 x 1.200 x 1000 = 2.53 kg

4.5 Aggregate

Fine Aggregate 0.3378 x 2.626 x 1000 = 887 kg

Coarse Aggregate (max 25 mm) 0.3494 x 2.707 x 1000 = 946 kg

= 2406 kg

IV. Calculation for Proportion of Mix by Weight

Total Weight (4.1 - 4.5)

II. Material Parameters

III. Calculation for Proportion of Mix by Volume

Total 3.1 - 3.5

Total Yield (3.1 - 3.5 & Volume of Fine Aggregate)

NAM THUEN 2 HYDROPOWER PROJECT (LAO PDR)

DESIGN MIX - Type n°3 bis (Concrete fixing the high pressure tunnel not in direct contact with water)

Concrete (without Fly Ash)

I. Reference Specifications

1.1 Type of Concrete : Type n° 3 Concrete fixing the high pressure tunnel in direct contact with waterSection 6.6.3.8 DTS Article 8.2.1.1 bis: nominal formula .

1.2 Size Grading 0-12.5 mm1.3 Cement ≥ 425 kg/m3

1.4 Water : Cement Ratio ≤ 0.451.5 Compressive Strength (28 day) ≥ 30 MPa

2.1 Cement 420 kg2.2 Water : Cement Ratio 0.452.3 Water 420 x 0.45 189 kg2.4 Volume of dry rodded Coarse Aggregate 0.602.5 Unit Wt. of dry rodded Coarse Aggregate 1565 kg/m32.6 Wt. of Coarse Agg. In Concrete (Absorption of 0.74%) 946 kg2.7 Admixture Superplasticizer Rheobuild 561(0.80 litr. / 100 kg. of cement) 2.8 kg2.8 Specific Gravity

2.8.1 Cement 3.1502.8.2 Fine Aggregate (Sat. Sur. Dry) 2.6262.8.3 Coarse Aggregate (Sat. Sur. Dry) 2.7072.8.4 Admixture - superplasticizer (Rheobuild 561) 1.200

3.1 Cement 420 / 3.150 / 1000 = 0.1333 m3

3.2 Water 189 / 1.000 / 1000 = 0.1890 m3

3.4 Admixture - Superplasticizer (Rheobuild 561) 2.8 / 1.200 / 1000 = 0.0023 m3

3.5 Coarse Agg. 946 / 2.707 / 1000 = 0.3494 m3

= 0.6741 m3

3.6 Volume of AggregateFine Aggregate = 0.3259 m3

= 1.0000 m3

4.1 Cement 0.1333 x 3.150 x 1000 = 420 kg

4.2 Water = 189 kg

4.4 Admixture - Superplasticizer (Rheobuild 561) 0.0023 x 1.200 x 1000 = 2.80 kg

4.5 Aggregate

Fine Aggregate 0.3259 x 2.626 x 1000 = 856 kg

Coarse Aggregate (max 25 mm) 0.3494 x 2.707 x 1000 = 946 kg

= 2414 kg

IV. Calculation for Proportion of Mix by Weight

Total Weight (4.1 - 4.5)

II. Material Parameters

III. Calculation for Proportion of Mix by Volume

Total 3.1 - 3.5

Total Yield (3.1 - 3.5 & Volume of Fine Aggregate)

NAM THUEN 2 HYDROPOWER PROJECT (LAO PDR)

DESIGN MIX - Type n°3 (Concrete fixing the high pressure tunnel in direct contact with water)

Concrete (without Fly Ash)

I. Reference Specifications

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Appendix 6 TYPICAL DRILLING PATTERN

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Appendix 7 TYPICAL ROCKBOLT INSTALLATION

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Appendix 8 SEDIMENTATION TANK DRAWING AND DETAILS

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Appendix 9 Work Procedure Diagram

For Surge Shaft Excavation Surge Shaft Excavation

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Work Procedure Diagram

Stage 1: Raise Boring

Surge Shaft Excavation

Setting of Machine

Remove Pilot hole bit and Install Reamer Bit

Install steel pipe and grout

Survey and setting out

Ream up pilot hole

Alignment of Boring Machine

Drill Pilot Hole to Breakthrough at Shaft Bottom

Widen Raise Bore (Slash Down)

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Work Cycle Chart

Stage 2: Widening of Raise Bore

Drill and Blast Excavation


Excavation by Drill and Blast

Shotcrete (First Layer)

Rockbolting and Wiremesh Installation

Shotcrete (Final Layer)

Repeat Cycle

Scaling and Trimming

Defuming

Mucking

Concrete lining and Grouting

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Appendix 10 INSPECTION AND TEST PLAN

NISHIMATSU CONSTRUCTION CO., LTD Rev. ________Project: CNamTheun 2 Hydroelectric Project For:

Civil Works Part II Date: 03/09/04Date:

CC (NCC/ITD)

Client Rep. / HC

Tools and Instrument

Acceptance Criteria

Verifying Document

Inspection checklist no.

1.0

1.1Before

Commencement of work

CC Approval by HC R PCA Order No. CW 2 - 09 & 10 n/a

2.0

2.1Before

commencement of work

CC

location map, design/reference

drawings, survey record

R

Dwg. Nos. IH NTCO R043 * 220001 A; IH NTCO R040 *

220003 A

n/a

3.0

3.1During setting

out of machine

CC survey instruments I / R 6.3.1 Method

Statement _

3.2 prior to final excavation CC

Specification and work procedure documents

I

6.6:DTS, Chap. 6.6.3.3

Earthworks, art. 3.2.1.3 bis Supports and Lining;

12.0: Health and Safety, Method

Statement

_

3.3

Before commenceme

nt of final excavation

CC

Specification and work procedure documents

I

6.6:DTS, Chap. 6.6.3.3

Earthworks, art. 3.2.1.3 bis Supports and Lining;

12.0: Health and Safety, Method

Statement

_

Legend: Copy to:CC: Construction Contractor I: Inspection n/a: not applicableHC: Head Contractor R: ReviewHP: Hold Point T: Test

Inspection and Test Plan Ref. No.:______________Surge Shaft Excavation Page: ____1___/___4___

Prepared by:_A. Morales_Approved by:__________

Activity No.

Construction Process Item to Inspect Frequency

Responsible Inspection Method Relevant DocumentsRemarks

Documents

Prepare Method Statement

Method Statement Approval

Commence work upon approval by HC

Site Preparation

Survey and setting out Control points, center line, elevation

Preliminary Excavation

Pilot Hole Drilling / Reaming Location, alignment

Pilot hole support

alignment, inhstallation support

and other safety concerns

Only if Necessary

platform and hoisting equipment installation,

access,safety concerns



CC (NCC/ITD)

Client Rep. / HC


Acceptance Criteria

Governing Specification


4.0

4.1Before every excavation

cycleCC

Design/reference drawings,

survey record, governing

specifications, blasting plan

R / I

Dwg. Nos. IH NTCO X043 *

220001 A; Drilling pattern

from MST

Inspection checklist before

blasting

4.2 after mucking CC

survey data, reference

drawing and specifications

I

DTS 6.6, Chap. 6.6.3.3

Earthworks, Art. 3.2.bis

Excavation; Dwg. Nos. IH NTCO R040 * 220003

Inspection checklist after

blasting

4.3 before shotcreting CC

Visual inspection, survey data

I / R

DTS 6.6, Chap. 6.6.3.3

Earthworks, Art. 3.2.bis

Excavation; Dwg. Nos. IH NTCO R040 * 220003

Inspection checklist for shotcreting

4.4before and

after shotcreting

CC

Laboratory equipment,

sample panels, Thickness guide

T / I

6.6:DTS, Chap. 3.8, Art. 8.3.2 BIS Shotcrete; Drwg. No. IH NTCO R040 *

220003 A

Inspection checklist for Shotcreting




Activity No.



Final Excavation


Control points, center line, tunnel limits, safety supports,

blasting equipment and accesorries, blast

hole locations

Excavation verification

excavation limits, blasting missfires,

ventilation, vibration data

Trimming and Scalingloose material debri, cleanliness of base

material, tunnel profile

Shotcreting (first layer)final excavation

profile, Shotcrete quality and thickness



CC (NCC/ITD)

Client Rep. / HC


Acceptance Criteria



4.5after first

layer shotcreting,

CC

survey data, visual and

actual measurements

I / R

DTS 6.6,Chap. 6.6.3.15 Rock

Anchor Bolts, Art. 5; 6.5:GTS, 6.5.7

Chap. 8, Art. 8.3.2 Shotcrete

Inspection checklist for Shotcreting

4.6

Before and after

spraying, after every excavation

cycle

CC

Laboratory equipment,

sample panels, Thickness

guide, survey check data

T / I

6.6:DTS, Chap. 3.8, Art. 8.3.2 BIS Shotcrete; Drwg. No. IH NTCO R040 *

220003 A

Inspection checklist for shotcreting

5.0

5.1

after installation,

before concreting

HP HC

actual measurements,

reference drawings

6.6.3.6:DTS, Chap. 6.1 BIS: Straightening, Bending, and Placement of

Reinforcing Bars for Concrete;

6.6:DTS, Part 3: Modification or

Additional Requirements to GTS, Chap. 3.7: Embedded Parts

in Concrete.

Inspection checklist for concreting

Copy to:Legend:

CC: Construction Contractor I: Inspection n/a: not applicableHC: Head Contractor R: ReviewHP: Hold Point T: Test



Activity No.



Installation of support

alignment, support dimensions, type of

support, location and installation, hole

dimension for rockbolt

Shotcreting (final layer)Shotcrete quality and

thickness, final shotcrete profile

Concreting

Reinforcement, embedments (pipes and

others)

type, grade, size and numbers installed;

concrete cover, bending, cutting,

shapes and installation; Test

results and certificates

only if required


Civil Works Part II Date: 03/09/04

CC (NCC/ITD)

Client Rep. / HC


Acceptance Criteria



5.2During and/or

after installation

HP HC

equipment data sheet,

maintenance record, safety

report confirmation

I / R

6.6.3.5:(DTS) Formworks and

Concrete Surface Finishing


5.3during

concrete pouring

CC

laboratory equipment, reference

specification and drawings

I / R / T

6.6:GTS, Chap. 3.8: Concrete

Design, Manufacturing

and Placement; 6.6.3.5:(DTS)

Formworks and Concrete Surface

Finishing


5.4 After concrete curing CC

Reference specification,

Method Statement procedure

R / I

6.6:DTS, 6.6.3.11: Grouting and Filling Mortar,

11.3 BIS Second Part-Grouting at

Site

Inspection checklist for consolidation



Prepared by:_A. Morales_

Activity No.



Formworks (slipform) installation

Alignment, quality of formwork material (anchors, jacking system, vibration

system)

Concrete pouring (slip formed section)

concrete type and quality, pouring sequence and

technique

Consolidation groutinggrouting material quality, grouting

sequence

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