CAMBODIA LAO PDR THAILAND VIETNAM REVIEW ON DAM

CAMBODIA LAO PDR THAILAND VIETNAM REVIEW ON DAM SAFETY, AND NAVIGATION FIRST DRAFT OF THE TECHNICAL REVIEW REPORT FOR SANAKHAM HYDROPOWER PROJECT’S PRIOR CONSULTATION PROCESS THE 10 TH MRC REGIONAL STAKEHOLDER FORUM – REGIONAL CONSULTATION ON THE PRIOR CONSULTATION PROCESS FOR SANAKHAM HYDROPOWER PROJECT 24 NOVEMBER 2020, PAKSE, LAO PDR, VIA VIDEO CONFERENCE Prepared by the MRC Secretariat Presented by Ms. Ton Nu Thi Thanh Yen, Navigation Operations Specialist, Planning Division

DAM SAFETY

Background / Scope of the Review The Sanakham HPP is located approx. 2 km upstream of the Lao/Thai border. Safety is important! The TRR provides an assessment of the Sanakham HPP Engineering Status Report (October 2018) + Additional documents with respect to Dam Safety requirements. This section of the final TRR will address; • Overall content of the SNHPP documents for dam safety measures; • Comprehensive dam safety reviews; • Emergency preparedness plan; and • Other information on the safety of dams. MEETING THE NEEDS Methodologies for review • To review the safety design of dam as well as observation during field visit (TBC) and discussion with Developer/Go. L • To provide recommendations on actions that could help to improve the design and operations; and • To identify and provide recommendations related to any other issues requiring follow-up KEEPING THE BALANCE

Main review findings – Geology / Seismicity ► ► The proposed dam site is located at a sharp lefthand bend in the river. The processes of erosion and deposition on this bend will be reduced upstream once the reservoir is impounded but will continue downstream. The Engineering Status report does not comment on the potential long-term significance of these processes. Historic earthquake activity in the project area is assessed to be low. However, much more extreme events should be considered for the design to comply to the relevant standards; PDG, ICOLD, LEPTS 2018. MEETING THE NEEDS KEEPING THE BALANCE

Main review findings – Design and Operational Parameters ► ► The SNHPP will be classed as an extreme risk structure under the LEPTS 2018. This requires the adoption of the Probable Maximum Flood (PMF) as the Inflow Design Flood and not the 10, 000 yr event proposed as the check flood. Return Peak Condition Period Discharge (year) (m 3/s) Design 2, 000 34, 700 All gates operational Check 10, 000 38, 800 2 gates out of operation* A physical model investigation, covering the entire powerhouse and spillway structures has been undertaken, but must be repeated with a wider range of flows up to the PMF. Physical model of SNHPP MEETING THE NEEDS KEEPING THE BALANCE

Main review findings – Stability ► ► ► The proposed design standard for stability is Engineering Manual 1110 -2 -2200 published by the US Army Corps of Engineers Not fully comply with LEPTS which requires higher factors of safety for sliding stability. The final proposed design standard is therefore not clear but compliance with LEPTS remains mandatory for projects in Lao PDR. Stability studies do not cover all load cases or consider potential failure planes in the foundation rock mass and should be updated, checked and verified by the Dam Safety Review Panel as envisaged by World Bank Operational Policy 4. 37. MEETING THE NEEDS KEEPING THE BALANCE

Main review findings – Transboundary Impacts ► ► SNHPP ► Since project is located close to the Lao/Thai border, study is required to determine the impact of the project on downstream discharge rates and water levels during construction and during operation (Operating rules are required). Survey of population and property at risk under the full range of possible events is required during the following events including comparison with the pre-project condition (Thai – Laos). Dam break studies and Contingency planning must be done together with the relevant Thai authorities. MEETING THE NEEDS KEEPING THE BALANCE

Compliance with PDG 2009 / Good Practice Requirement Compliance Comply with National Standards, WB OP 4. 37 & ICOLD Bulletins Design does not comply with LEPTS 2018 and relevant ICOLD Bulletins. Requirements of OP 4. 37 not implemented. Comply with all aspects of WB OP 4. 37 • Developer confirmed on 24 August 2020 that an independent panel will be appointed during design and construction. No Dam Safety Review Panel has been appointed during development phase. • Developer submitted details of dam breach studies on 24 August 2020. Studies are incomplete and do not form adequate basis for EPP. No reference to preparation of a construction stage EPP. Reflect ICOLD Bulletins in design and operation ICOLD Bulletins are referenced but no evidence of adopting recommendations Effective consultation with local communities No details have been provided of consultation with downstream communities or the Thai authorities. Dam safety budget details for Developer confirmed on 24 Aug 2020 that all dam safety costs are included in the project design and operation budget. No budget details have been submitted. MEETING THE NEEDS KEEPING THE BALANCE

Conclusions and Recommendations ► ► ► Seismic Hazzard Assessment has been undertaken but it is not clear if this provides a suitable basis for project design. Further reassessment is required and considered by the Dam Safety Review Panel. The physical model study has been undertaken but does not cover the required range of flood events. Further tests are required. Several of the dam safety requirements do not meet the requirements of the LEPTS 2018 and is therefore not consistent with the Lao PDR standards and needed to redesigned Consideration should be given to; ► Adopting radial gates in place of the proposed vertical lift gates for the spillway ► Cascade operation or reference to the upstream Xayaburi HPP already in operation ► Transboundary impacts resulting from changes to river flow and water level ► Appointment of an independent Dam Safety Review Panel (DSRP) as soon as possible Recommend that the Thai Authorities are consulted and preferably involved in the development of the Contingency Plans. MEETING THE NEEDS KEEPING THE BALANCE

NAVIGATION

Background / Scope of the Review To technically review the Sanakham HPP Feasibility Study Report with the following items: • Navigation structure design • Lock equipment • Upstream and downstream approach channels • Filling and Emptying system • Lock chamber and approach channels sedimentation • Operation, safety and maintenance. MEETING THE NEEDS Methodologies for review • Prepare the technical review on navigation; i. e. ship lock and its components + approach channels; • Identify any gaps or discrepancies and request any missing information; • Undertake a site visit and discuss with the Developer; • Provide a TRR recommendations related to the issues identified. KEEPING THE BALANCE

Main review findings (1/9) N AVIGATION L OCK C HAMBER • The design provides floor slab that is only 2 m thick. • All other ship locks on the mainstream have floor slabs of 9, 7, 5. 6 and 4 m, respectively for LP, PL, PB and XB. MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (2/9) Bridge above upper lockhead A IR C LEARANCE • The air clearance of upstream service bridge is only 8 m. • However along the Mekong mainstream between the Golden Triangle and the Khone Falls all bridges must have a minimum navigation air clearance of at least 10 m. MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (3/9) M AIN FEATURES • The effective length of the proposed lock chamber is only 113 m long (PDG: 120 m) F ILLING AND EMPTYING SYSTEM • The proposed design calculates the maximum hawser forces, from measures in the physical model, at 16 k. N, which is inconsistent with the PDG 2009 (10. 06 k. N) D ESIGN OF THE SECOND LOCK SYSTEM • The PDG 2009 requires that the 2 nd set of locks be parallel to the first, and that construction costs should be minimised. • Both ship locks will have to use the same approach channel. MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (4/9) The PDG 2009 requires that the 2 nd set of locks be parallel to the first, and that construction costs should be minimised MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (5/9) U PSTREAM AND DOWNSTREAM APPROACH CHANNELS • The upstream approach has a straight-line channel of only 220 m instead of 250 m straight-line channel recommends in PDG 2009; • The width of the downstream approach is insufficient since the mooring area for waiting vessels (12 or 13 m wide); • None of the mooring pillars (dolphins) offer access to the land through interconnected floating walkways; S HIP LOCK CHAMBER APPURTENANCES • There are not enough or not all the ladders, floating bitts, line hooks, steel slider wall protections or overhead rolling crane stretching the entire length of the lock chamber. MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (6/9) U PSTREAM AND DOWNSTREAM APPROACH CHANNELS SHOULD BE ADDED! MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (7/9) S HIP LOCK CHAMBER APPURTENANCES Water level gauges, wall armour, line hooks and floating mooring bitts should be provided. MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (8/9) S HIP LOCK CHAMBER APPURTENANCES Overhead rolling crane should be stretching the entire length of the lock chamber MEETING THE NEEDS KEEPING THE BALANCE

Main review findings (9/9) O PERATION, SAFETY AND MAINTENANCE • Emergency stoppage of the locking operation must be possible is not mentioned; • List of spare parts for the repairs should be available to make sure that unscheduled; • Maintenance plan is not mentioned such as regular dredging of areas identified; • Maintenance and other unexpected outages will not exceed 2 % of the operating time; N AVIGATION DURING CONSTRUCTION • The developer has indicated that the navigation lock system will be operational during the 2 nd phase of construction. However, it was not mentioned the solution for strong currents may be expected at the entry and exit of the approach channels due to the 13 spillway; • The developer has provided an explanation of navigation during construction but did not made special provision for the small fishing / family boats (At the other HPP these smaller boats are/will be put on a trailer and transported over land around the construction site). MEETING THE NEEDS KEEPING THE BALANCE

Compliance with PDG 2009/ Good Practices by draft PDG 2020 (1/2) • The proposed navigation infrastructure is not well aligned with the PDG 2009. • There are several areas where insufficient or illegible information has been provided (lost in translation) to confirm alignment. • Critical design flaws have been identified: some of the drawings/text show the contradictory information. • Others are related to the safety and reliability aspects of the facilities, including the need for spares, emergency access, overhead cranes etc. MEETING THE NEEDS KEEPING THE BALANCE

Compliance with PDG 2009/ Good Practices by draft PDG 2020 (2/2) MEETING THE NEEDS KEEPING THE BALANCE

Recommendations The developer is encouraged to: 1. Increase thickness to a uniform floor slab of 3. 50 m (not 2 meter). 2. Increase the effective length of the lock-chamber to 120 m (currently 113 m). 3. Enlarge to a channel width of the downstream approach channel of 40 m plus the width of the mooring area for waiting ships (of 12 or 13 meters). 4. Raise the upstream service bridge to an air clearance to 10 m (now only 8 m) 5. Make sure that the hawser forces is 10. 06 k. N (asked by PDG) instead of 16 k. N 6. Make sure that the straight line from the upstream approach should be 250 m 7. Provide access to land from the mooring pillars (dolphins). Line hooks and recessed ladders should be provided in both guidance walls…similar to the Xayaburi lock 8. Provide Operation, Maintenance Plans 9. Recommended that an area of 45 m x 220 m be reserved for the construction of a second ship lock directly next to the first one. 10. Clarify on Several discrepancies between the drawings MEETING THE NEEDS KEEPING THE BALANCE

THANK YOU One Mekong. One Spirit.