^{Figure 1. The area around Barcelona Airport}

In 2018, Barcelona airport registered the record figure of 50,172,457 passengers (6.1% more than the previous year) and 335,651 operations and 172,940 tonnes of cargo. The airport is open 24 hours a day and can handle 90 operations per hour. Together with its two terminals, the airport can handle 55 million PAX/year. The airport is operated by AENA, the world's leading airport operator (by the number of passengers).

During its lifetime, the airport was continuously expanding, and with its third great transformation, which took place in 2004, the third runway was brought into service (see Figure 1 "New Runway").

Noise regulations

EU Directive 2002/49/CE in 2002 and its subsequent transposition to Spanish legislation in the form of the Noise Law 37/2003 and its partial implementing regulations outlined in Royal Decree 1513/2005. A process was introduced, which resulted in the production of strategic noise maps and the subsequent elaboration of major airports' action plans.

The Royal Decree 1367/2007 developed the Law 37/2003 and determined the acoustic quality objectives applicable to acoustic areas (both for outdoor and indoor places) as well as the methods and processes for the evaluation of acoustic indices. It contains a chapter about mandatory prevention and correction plans and an important chapter about inspection and fines. In legal terms, the previous process and the Environmental Impact Assessment for the new runway has been done properly, and the noise was under the legal limits.

This case study focuses on the operational procedures implemented to solve the social crisis generated after the new runway's inauguration and explains how the potential solutions were discussed and approved.

Additionally, the institution of the Commission for Environmental Monitoring of the Airport Expansion Works (CSAAB), which aims to monitor and control the compliance of the preventive, corrective and off-setting measures, developed during the construction and operation phase of the airport's expansion. The affected communities were the main drivers in creating the Technical Working Group of Noise (GTTR), dependent on the aforementioned CSAAB. All the potential solutions to the situation were discussed inside this technical group with all the stakeholders involved.

Objective

Barcelona airport was an infrastructure close to the sea and therefore didn't have significant noise problems. When the new runway started operating, an avalanche of complaints came from some unexpected areas. Firstly, residents in those areas had never had an aircraft overflying this area before the new runway's operation. Secondly, it was a non-preferred configuration and, consequently, noise insulation programs had not been established there.

This case study's objective was to find a solution for this unexpected situation in areas under, but very close to the noise limits (annual average).

Approach

The approach of this case study was to find a solution by discussing many ideas in the Technical Working Group of Noise (GTTR) and studying the potential solutions from various points of view, technical/constructive, operational, capacity, environmental/sustainability and cost/benefit, to agree on the better solution for the majority of the communities around the airport. The process involved all the stakeholders needed around the same table, including local communities and authorities.

1. On October 2004, after a few days of operations on the new runway in the direction approved by the Environmental Impact Assessment process (illustrated in Figure 2), the airport had received a high number of noise complaints from the residents annoyed by aircraft noise (mainly from Gavá Mar community);

^{Figure 2. West and East configurations at the Barcelona Airport}

2. The affected communities were the main drivers in creating the Technical Working Group of Noise (GTTR) dependent on the aforementioned Commission for Environmental Monitoring of the Airport Expansion Works (CSAAB). GTTR was a technical forum where different interest groups could present technical proposals and studies to minimise noise impact;

3. Part of the final solution was presented by airline pilots and air traffic controllers from Gavá and Castelldefels – switching each runway's role during the day. The longest runway should be used for departures and the shortest for landings (for safety reasons). The GTTR studied the new role using the shortest runway for take-offs and the longest runway for landings and some take-offs that required more length (depending on the kind of the aircraft) (see Figure 3);

^{Figure 3. Day time configurations}

4. The previous cross runway (02-20) was avoided by introducing night configuration change, and the runway was used during night periods and on East configuration with less capacity. West configuration during the night period was permanently limited during the night (see Figure 4);

^{Figure 4. Night-time configurations}

5. To support this solution, technical, constructive studies were required, as well as operational, capacity and environmental/sustainability studies. The technical part had to assess cost and benefit, safety and time frame matters. Additionally, emissions and noise studies were performed, and the number of overflights in the different points of populated areas were calculated. All of them were presented and discussed inside the GTTR;

6. At least 11 options of the solution were rejected because of a ground capacity study, technical issues, or air capacity studies. Eventually, three options (which were compared to the reference option approved in the Environmental Noise Assessment process) were presented to the CSAAB, which selected one because of the environmental outcomes presented;

7. In 2005, after months of working hand in hand, GTTR received the approval from the CSAAB to implement the idea provisionally, for the period of four years. The implementation of the solution took almost one year, and it was a complete success;

8. Regarding transparency, CSAAB published a press release before the implementation of the solution. Together with the rest of the stakeholders, local authorities also disseminated the information, each one about its competences. New information was published after the implementation. All the noise measurements were accessible to the public;

9. The GTTR continued working and after new studies, new safety systems, new regulatory frameworks and hard technical work and new developments, in 2010, the GTTR presented it to CSAAB asking for approval for the extension of the solution, which was approved in 2005. They asked to extend it until the next Master Plan of the airport would be prepared (in 2020-2025);

10. The GTTR continues to search for a permanent solution and is meeting four times a year. They must study each proposal or initiative on possible actions aimed at improving noise exposure around the airport.

This case study showed that a collaborative group of technicians and stakeholders was the best way to find a solution to the problem. Additionally, the airport should be aware of the noise situation even under non-preferential configurations, where the people are not compensated for the noise. Those people are forced to hear aircraft noise for a few hours per day or even for a few days and they will definitely be annoyed.

Also, this study confirms that L_den is a good indicator to see the global annoyance throughout the years and to compare different noise from different sources, but it is not enough for being aware of the annoyance. For studying annoyance, L_den should be studied with other daily indicators per configuration and a noise event (L_Amax) analysis.

Finally, this case study showcased that lack of transparency and information makes people feel ignored – reliable communication and control sources are needed to increase people's trust.