annex a9 - environmental resources management (erm) · pdf fileenvironment and the esia...

Annex A9

Project Presentation

The world’s leading sustainability consultancy

Kariba Dam Rehabilitation: Environmental & Social Impact Assessment (ESIA)


Introduction Who is the ZRA?

The Zambezi River Authority was established in 1987.

It is a statutory body jointly and equally owned by the Governments of Zambia and Zimbabwe.

It is responsible for overseeing the development of the Zambezi River.

The Environmental Resources Management (ERM) is the consulting firm appointed to undertake the project ESIA

International environmental consultancy with 3,600 staff in 130 offices in 40 countries around the world

Working with Oliver Manjengwa (Zimbabwe); Felix Chisha (Zambia)


Purpose of this Presentation

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To provide stakeholders with information about the proposed project, the project environment and the ESIA process;

To gather information from the project area that can be used to inform project planning;

To assist in the identification of concerns and issues regarding the proposed project and the ESIA process;

To capture stakeholder comments and suggestions on alternatives;

To confirm issues identified in the public domain and ensure that where relevant these are investigated further through technical studies;

To report back on the findings of the ESIA and proposed management measures; and

To meet legislative requirements regarding stakeholder engagement.


The Proposed Project and Rationale

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Dam Safety concerns = motivation

Kariba Dam was constructed between 1956 and 1959

It supplies water to two underground hydropower plants located on the north (left) bank in Zambia and on the south (right) bank in Zimbabwe.

Jointly, the power stations have the capacity of 1,830 MW, once the new turbines have been installed in SB an addition 300MW will be produced =2,130MW

The dam and associated infrastructure are over 50 years old as such needs an upgrade of some essential hydro-electrical equipment.

The ZRA is proposing the reshaping and enlargement of the plunge pool and rehabilitation of the spillway gates

The world’s leading sustainability consultancydi t i bilit lt

General Layout of Dam & Power Stations

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Tailrace OutletsIntakes

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Normal TWL without spillage :depending on powerstationsactivity

Deepest section is short

The more general case is

30 m

50 m

80 m

Maintenance works area

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Plunge Pool Features

Foundation Loads

Erosion

1962

1972

1981 to date


Results from Multi-beam Bathymetric Survey of the Plunge Pool

7 (March 2011)


Physical model: Testing in progress

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Reshaped Geometry

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The world’s leading sustainability consultancy10

Normal TWL without spillage :depending on powerstationsactivity

Deepest section is short

The more general case is

30 m

50 m

80 m

Maintenance works area

Plunge Pool Reshaping (With upstream strengthening of

fault zone)

Strengthening works on upstream face of pool

Anchors

Stepped excavation of rock on downstream, North & South banks


Reshaping to be done in the dry with a Cofferdam down stream of

pool

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Cofferdamlocation

Stepped excavation of rock on downstream, North & South banks111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111


Plunge Pool Works

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Temporary Decommissioning of the Project Works. The cofferdam and access road to the plunge pool will be removed from the riverbed

TTTTemporary

Step 6

TDgWcatwfr

TTTTConcrete works and Reinforcement of weak area

CCConcrette

Step 5

CwRo

CCCExcavation and on-going pumping of water out of the plunge pool

EEExcava itition

Step 4

Eapwtp

EEEPumping out of water in the Plunge Pool & Excavation

PPPumpiiing outtt

Step 3PoP&

PPPInstallation of the Cofferdam Downstream of the Plunge Pool

IIIn ttst llallllatitition offf

Step 2

tDoP

Rehabilitation & Constriction of Access Roads

RRehhabibililittatition

Step 1

Enlargement = excavation of 300,000 m3 of bedrock

Construction of Secondary Roads

Assemble and installation of cofferdam downstream – Plunge Pool

Construction timeframe 5 years – non-spillage (7 months =May-November)

2


PP Reshaping

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Method of works:Controlled open air Blasting: cautiously

planned sequence of works to damage to the surrounding infrastructure

Monitoring: seismograph, dam and bankmovements, ground water levels

Associated infrastructure:secondary roads, cofferdam, & waste rock dump site.


SPILLWAY REFURBISHMENT

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Essential Steps to arrive at Solution Design, fabrication and supply of cofferdam for upstream sluice closure

replacement of secondary concrete and Built-in-Parts in stopbeam slots (in the dry) requirescofferdam

design, fabrication and supply of emergency gate

design, fabrication and supply of new gantry

modification of crest civil works to support new gantry

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Spillway video

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•Site installations, construction of spillway and temporary roads

Step 1

•Construction of the floating cofferdams and cofferdam for sluice 2

Construction ofth fl ti

Step 2 •Refurbishment of the Sluices and BIPs; &Installation of the emergency gatethe emergencygateteeeteeeeeeeeeeeeeeeeeeeeeeteeeeteeeeetteetttteetttettteeettte

Step 3

•Rehabilitation of the grooves, sills, and lintels and associated BIPs

Rehabilitation ofth ill

Step 4 •Installation of the new gantry runway

Step 5

•Installation of new stopbeams– andcommissioning

Installation of

Step 6


Emergency Gate and Gantry

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Safety Concerns (emergency sluice closure)

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Safety Concern

Effect Prescribed Remedial Measures

2b General agingof the dam concrete:• Inability to close

sluice upstream in the event of gate failure (ieno emergency sluice closure)

Uncontrolledrelease of water Loss of power generation due to emptying of reservoir.

Spillway refurbishment Design, fabrication and installation of Emergency Gate, Gantry and Associated Works


Emergency Gate

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Total weight : 160 T

5 elements of approximately 32 T each

Assembled with 16 bars and bolts

4 days to assemble it


RISK OF INACTION (Consequences of Dam Failure)

Loss of power generation at Cahora Bassa andpossible loss of dam.

Failure of Cahora Bassa would compound the problem. Worst case scenario will be failure of Kariba and CahoraBassa when run off is at its peak with the river at peak.

Loss of wildlife and wildlife habitat in Lower Zambeziin Mozambique, Zambia and Zimbabwe (Mana Pools is a UNESCO world heritage site)

Loss of socio-economic activities on the lake (fisheries, tourism etc)

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THANK YOU

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OPEN DISCUSSION

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