Environment

To build the three new deep stations, it will be necessary to occupy large construction sites in the heart of Istanbul. Traffic diversions will be put in place, but congestion problems will occur at times.

When constructing the third track and when upgrading the existing tracks, it will be necessary to limit or even close down the existing commuter rail service at certain periods. Alternative means of transport will be provided in the form of bus services serving the affected areas. These services, when combined with traffic diversions around the affected station areas, may create congestion problems during these periods.

The Contractors will have to use the road systems near the deep stations for the transport of materials to and from the construction sites using large trucks and this activity will from time to time overload the capacity of the road systems.

It will not be possible to avoid disruption completely, but careful planning combined with comprehensive information to the public and support from the relevant authorities will limit the adverse impacts.

Construction activities required for the Marmaray Project are noisy activities. In particular, the activities required to construct the deep stations will produce loud and continuous daily noise over the duration of the construction period.

The underground works will normally not create noise in the city. However, the tunnel boring machines (TBMs) will create a low-frequency vibration of the soil surrounding the TBM. This may create a rumbling type of noise in the properties nearby, and this noise will persist 24 hours a day, but should not affect any one area for more than a few weeks.

To avoid closing down the existing commuter rail service for longer than is absolutely necessary, some of the work will be carried out at night. It can be expected that the activities that will take place during these periods will be quite noisy and may from time to time exceed the limitations normally acceptable for such works.

It will not be possible to avoid noise disturbance completely, but extensive requirements have been imposed on the Contractors to do what is possible to limit the noise level caused by the construction activities.

Construction activities will result in dust in the air and mud and soil on the roads around the construction sites. This will also occur on the Marmaray Project.

Although it will not be possible to avoid these problems altogether, in general much can and will be done to reduce their impact - for example, watering the roads and paved areas and cleaning the vehicles and the roads.

Before construction works start, all known utilities will be identified and diverted as necessary. However, many of the existing utilities will not be positioned exactly where they are supposed to be, and there will be utilities no-one even knows about. Therefore it is not possible to avoid disruption from time to time of the power supply, water supply, sewer systems, and communication systems such as telephone and data cables.

Whilst it may not be possible to avoid such disruption completely, careful planning combined with comprehensive information to the public and support from the relevant authorities will limit the adverse impacts.

The investigations already carried out in the Istanbul Strait have documented that contaminated material exists on the seabed where the Golden Horn meets the Istanbul Strait. The amount of contaminated material that has to be removed is of the order of 125,000 mｳ.

DLH has requested the Contractors to use proven and internationally recognised techniques to take the material out from the seabed and bring it to a Confined Disposal Facility (CDF). Such facilities will typically be an on-shore confined and controlled area that will be sealed with clean material, or it may be a confined pit in the seabed covered by clean protective material.

Contamination problems can be eliminated completely if the correct methods and equipment are used for the operations. Furthermore the cleaning of a substantial area of the seabed of contaminated materials will have a positive effect on the marine environment.

It will be necessary to dredge more than 1,000,000 mｳ of soil from the bottom of the Istanbul Strait to prepare the trench for the immersed tunnel. It is unavoidable that this operation will release natural sediments in the water and thereby increase turbidity. This may have adverse effects on fish migration in the Istanbul Strait.

During spring, fish migrate northwards near the bottom of the Istanbul Strait where the current flows towards the Black Sea, and during autumn they migrate southwards in the upper layers where the current flows towards the Sea of Marmara.

However, because these contra-flowing currents are relatively stable and coexist, it is expected that the plume of increased turbidity that is created will be relatively narrow - most likely of the order of 100 to 150 metres. This has been the experience in other similar projects, for example the Oeresund immersed tube tunnel between Denmark and Sweden.

If the width of the plume generated is less than say 200 metres, it is not likely to have significant effects on fish migration because there will be good opportunities for the migrating fish to find paths in the Istanbul Strait where the turbidity is not increased.

It will be possible to avoid these adverse effects on the fish almost entirely, and the mitigation measure will simply be to restrict the Contractors' options regarding the timing of the dredging operations. They will therefore not be allowed to perform dredging in the deep parts of the Istanbul Strait in the spring migration period, and they will only be allowed to perform dredging in not more than 50% of the width of the Istanbul Strait during the autumn migration.

There will be a period lasting about three years when a substantial amount of marine activities related to the construction of the immersed tunnel will take place in the Istanbul Strait. Most of these activities can be performed in parallel with the normal marine traffic passing through the Istanbul Strait, but there will be periods when constraints will be put on the traffic, and there may even be shorter periods when the traffic has to be completely stopped.

Mitigation will be to ensure careful and timely planning of all the marine activities in close cooperation with the Harbour Master and other authorities. Furthermore, all possibilities of utilising the modern Vessel Traffic monitoring Systems (VTS) will be explored and initiated.

When heavy marine operations are ongoing, there will always be a risk of accidents that may cause pollution problems. Typically, such accidents will be the spillage of limited amounts of oil or gasoline in the waterway of the Istanbul Strait or the Marmaray Sea.

The risk can not be fully eliminated, but the Contractors will have to adhere to strict and internationally well proven standards and maintain a readiness to deal with such situations to limit or neutralise the impacts on the environment.