APPENDIX 3 Report K. Rainer Massarsch

Considerations Regarding Management of Environmental Risks

Contents

1 Introduction ....................................................................................................................... 2

2 Identification of Environmental Risks ............................................................................ 2

3 Implementation of Environmental Risk Management .................................................. 3

3.1 Contractual Requirements ........................................................................................... 3

3.2 Building Conditions Survey ........................................................................................ 3

3.3 Control of Residual Risks ............................................................................................ 4

3.4 Full-scale Test.............................................................................................................. 4

4 References .......................................................................................................................... 4

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Considerations Regarding Management of Environmental Risks

1 Introduction "I have made my greatest engineering contributions not by solving difficult problems but by

avoiding them", Conlon 1989.

The main objective of environmental risk management for tunnelling projects is to identify

risks at an early stage of the project, which makes it possible to avoid future problems. During

the construction phase or thereafter it is often difficult and time-consuming to resolve such

problems, which can result in negative environmental effects, project delays and increased

costs. Environmental risk management shall therefore be an integral part of environmental

impact assessment.

Risk management is widely adopted to control risks in construction projects, especially when

assessing environmental aspects of a project, safety of workers and the public and financial

and other project risks. Codes and technical guidance documents have been published on

safety in tunnelling and risk management of tunnel works, for example the Code of Practice

by the ITIG (2006).

The most important aspect of environmental risk management and the observational method

is the identification of hazards and associated risks and the preparation of remedial and/or

mitigation measures.

2 Identification of Environmental Risks A multi-disciplinary approach shall be used to update the identification of the initial risks and

to keep under control the residual risks by:

Collecting, analysing, and processing the monitoring data relating to the previously

excavated section, (TBM data, retaining wall movements).

Collecting, analysing, and processing new data that can affect the local geological /

hydrogeological reference model.

Collecting, analysing and processing the piezometric data.

Collecting, analysing and processing data related to noise and vibration monitoring.

Reviewing the results of recent condition surveys of buildings and pre-existing

information on buildings and their foundations.

Reviewing the results of the building assessments including the sensitivity to potential

variations.

Defining mitigation and contingency measures.

Reviewing the need for monitoring instruments or the frequency of the readings, and

reviewing the requirements in terms of the on-going construction works.

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3 Implementation of Environmental Risk Management The PPP Contractor in cooperation with the Applicant shall manage the risks during

construction of the tunnels and underground works and operation of the scheme in

compliance with the requirements given and ensure that the residual environmental risks

associated with these works after the application of any mitigation measures shall comply

with the Environmental Risk Assessment (ERA). The environmental risk management

process, to be managed by the Applicant and implemented by the contractor, should include

the following activities:

Implement an integrated organisation to manage environmental movement risks,

including ground movements, ground water flow, vibrations and groundborne noise.

Implement a database and geographic information system (GIS) to provide a common

means of storing, accessing and interpreting the all relevant information, including

buildings, tunnel construction and monitoring data.

Carry out building/structural surveys as required for any buildings/structures that may

be affected by the works.

Carry out predictions of settlement/movement from the works.

Carry out predictions of vibrations and groundborne noise from the works.

Asses the initial risks induced by the predicted settlement/movement and assess the

vulnerability of buildings and other structures to damage.

Identify buildings and other structures at risk and requiring extended monitoring

and/or protection or other mitigation measures.

Design the appropriate mitigation measures to ensure that building damage as defined

under the terms of the EIA will not occur.

Reassess the impact to buildings and other structures as well as installations in the

ground, taking into account mitigation measures to be implemented.

Document that damage as defined under the terms of the EIA will not occur.

Design and implement appropriate monitoring systems.

Develop secondary mitigation measures to be implemented if movement thresholds

are reached.

3.1 Contractual Requirements The contractor shall integrate the real time monitoring with other project information so that

the works are tightly controlled, any behaviour outside the predicted range is immediately

observed and the appropriate remedial measures are taken. The sensitivity of ground

movement estimates and the consequent structural damage assessments shall be considered as

part of the building assessments. The assessments shall take into account potential variations

in the ground conditions together with a range of parameters for the soil and for the volume

loss from the tunnelling. These assessments shall incorporate sensitivity analyses covering the

“worst credible” parameters together with the “most likely” parameters.

3.2 Building Conditions Survey The information obtained during the building condition surveys including, drawings, building

construction and condition, photographs foundation information and building assessment

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reports shall be entered into the database system and be accessible via the GIS system. The

assessment process shall include a detailed documentation, indicating that damage will not

occur, taking into account both the mitigation measures to be implemented, and the “worst

credible” parameters. During the execution of the works the building assessments shall be

updated in accordance with the experience gained and amended as necessary. In that respect,

trigger levels shall be identified which indicate that critical conditions (which may lead to

potential damage) are reached.

3.3 Control of Residual Risks The basic concepts and objectives employed by environmental risk management are in close

agreement with the objectives of the observational method of geotechnical design and

monitoring of the construction process, (CIRIA, 1989). When applying the Observational

Method, emphasis is placed on prototype testing, field monitoring and on-going analysis of

obtained information regarding the construction process and ground response, (EN 1997-1,

2004).

The contractor shall for each station and shaft and for each section of the tunnel drives

(between adjacent stations or shafts) and for each underground structure through application

of the Observational Method (“active design”) collect all relevant information for that part of

the works.

3.4 Full-scale Test Full-scale tests are an important part of any design based on the Observational Method and

should be specified in the construction process. Full-scale tests shall be employed to

determine geotechnical and other construction risks as well as risks related to vibrations and

groundborne noise. Such full-scale tests shall be carried out at the initial phase of sensitive

works and carefully monitored (e.g. ground movements, groundwater, vibrations and

groundborne noise etc.). Based on the results of initial construction monitoring or information

obtained from ground and building response measurements, the construction method and

equipment to be employed may have to be altered or adapted to the prevailing environmental

conditions in order to control and minimise residual environmental risks.

4 References CIRIA (1989). The observational method in ground engineering: principles and applications.

CIRIA Report 185.

EN 1997-1 (2004). Eurocode 7 Part 1, General Rules CEN/TC 250/SC7. European

Committee for Standardization, Brussels.

ITIG. (2006). A Code of Practice for Risk Management of Tunnel works. Prepared by the The

International Tunnelling Insurance Group. 28 p.