Consideration about the Golden Horn metro crossing bridge impact assessment

Speaking like bridge designer people, we can say that design bridges means to make a typological research of work-environment and first of all socio-cultural relationship, recognizing in this, the first form of respect for the place. Today, the infrastructure project must ratify what has already been culturally confirmed: the infrastructure is part of the landscape, it is landscape, and has all the potential to define a place, according to its natural functional development, leading the user to recognize it in the trinomio identity-relation-history.

Keywords: mobility infrastructure, landscape, place, bridges, Istanbul, outstanding universal value, impact assessment.

The Golden Horn, placed in Turkey, is an inlet of the Bosphorus, which divides the Istanbul core, forming a natural historical harbour.
Considering the city as a place of exchanges and relations, the Golden Horn it is a paradigm, in its physical configuration and its geo-political location: this space has hosted the three great empires of history (Roman, Byzantine and Ottoman) that with the flow of time, has given rise to the unique and magnificent skyline of Istanbul through the construction of the most prestigious and important buildings of their time on the hills surrounding the Halic.
For these reasons in 1985 the Historic Areas of Istanbul were included in the WHL with the criteria (i), (ii), (iii) and (iv) permanently ratifying the importance of the area and the need for maintaining the Outstanding Universal Values enclosed in it (OUV).
Nowadays, the Hitoric Peninsula, the heart of these civilizations, is under the threat of the negative effects of globalization, which show the pressure of urban sprawl and increasing the chaotic traffic within the area.
In order to minimize the damages and to control these important development aspects, Metropolitan Municipality of Istanbul has prepared an implementation plan of public transport with the specific goal of reducing the traffic load by closing the circuit and connecting the two metropolitan Halic banks. The Golden Crossing Metro Bridge is the key to achieve the goal of this important strategic development plan.
The bridge, is a complex element technologically very advanced, is designed mainly as cable stayed bridge with a central span of 180 meters and two sides span of 90 m. On this main system are inserted a 70 m span swing bridge and two lateral approach viaducts for a total length of about 1 km.
The choice of this bridge typology was made after a range of considerations about environmental issues concerning the specific ecological conditions of the area, as well as the level of fracturing of the soil and the level of seismicity of the entire site.
Although the bridge is configured as a valid solution to the problems of city development, the UNESCO Committee, stressing the intangibility of the OUV, has requested the Municipality of Istanbul  to asses the impact of new “opera” by third parties and independent figures. In this sense, the Municipality has requested the advice of a group of independent international experts: Prof. Enzo Siviero, Prof. Jorg Schalich, Prof. René Walther and Prof. Marcus Binney.
The Siviero’s assessment report, in which Alessandro Stocco, Michele Culatti e Viviana Martini have collaborated, further the important contribution of Prof. T. Kirova, has been developed within the scientific and cultural PhD University of Nova Gorica field, “Economics and techniques for the Conservation of the Architectural and Environmental Heritage and Landscape”, in which Enzo Siviero built a working group focusing on the research of the particular field called ‘Landscape and Infrastructure’.
The undisputed universal value of Istanbul, which is clearly defined in the inclusion criteria incorporating the OUV, as well as the strategic and geographical importance of the area, center of a “natural” economic and social development system of the country, required an assessment from a methodological approach formed by highly interdisciplinary features. The analysis of sequential patterns has allowed the control of the interference level between the new infrastructure and its context, considering the fundamental respect for universal values, that have allowed the city to be included in the “World Heritage List”.
The methodology is built using certain parameters, coded in Italy, for the analysis of the impacts of new infrastructure on the landscape derived from “DPCM 12/12/2005” integrated with the recent “ICOMOS Heritage Guidance on Impact Assessment for Cultural World Heritage Properties “defining a system that can simultaneously evaluate aspects related to the integrity of OUV, ongoing changes and its effects, the possible benefits and of course the negative impacts and a possible mitigation or compensation.
In the end the results of the assessment have stressed that the metaphysical union, expressed by the actual role of the bridge, which is the functional connection of the line itself, should also be addressed to the “other user”, the bridge should assume its true role such as a transit portal, as a passage, a union, a connection between the two sides linked together not only because of the subway but also for its function as a pedestrian link in order to stress the importance of relational aspects that the bridge should take.
The results showed that it is necessary a design architectural review of the bridge, aimed to achieve a greater attention of pedestrian as observer, and as a member of a space that is configured as a place and then equipe it for that purpose. So not only related to the subway. This would bring the bridge to be able to take on the role of real link, able to reply at once to mere technical requirements and even more to those needs of perception of the space around in movement and stillness. It will thus have a right to express and to show the viewer the skyline of the beautiful Golden Horn the tangible sign of the renewed union of the two sides reflects the fact that cultural continuity.

BIO | Enzo Siviero
Full Professor at IUAV University in Venice, Vice President CUN, Engineer, Architect HC, Partner Progeest S.r.l. Padua, Italy.
Magisterial Laura Honorius Causa in Architecture from Bari Polytechnic.
Bridge Designer, specialised in their structural architectural design as related to the landscape.
Promoter of the exhibition “Il Tema del Ponte” and “Bridging” in sections of national and international exhibitions.
Author of numerous publications on the topic.
Supervisor for more than 600 architectural graduation theses, of which more than 300 on bridges.

BIO | Alessandro Stocco
Architect, Phd Student ETCAEH at University of Nova Gorica, Partner Progeest S.r.l. Padova, Italy.


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