Social Democracia: Airport construction: materials use and geomorphic change

Informação científica retirada da ScienceDirect, editado.

Journal of Air Transport Management
Volume 9, Issue 3, May 2003, Pages 177-185

Aviation and sustainability
Ian Douglas and Nigel Lawson
School of Geography, University of Manchester, Oxford Road, Manchester M13 9PL, UK

Abstract

As airport construction competes for land, more and more new developments involve major landform changes, from the channel modifications on the River Bollin at Manchester Airport to the seaward expansion of runways at Sydney and Beirut and the enlargement or total creation of islands at Chek Lap Kok Airport, Hong Kong and Kansai International Airport in Osaka Bay, Japan. The quantities of material involved are large, 307 Mm³ of material being moved for Chep Lap Kok Airport and 13 Mm³ will be needed to fill the area required for a new runway at Seattle-Tacoma International Airport. Both the landform changes and the excavation and filling of materials produce profound geomorphic changes. In some cases the new configurations are unstable and may need to be rectified by further engineering work. Greater sustainability is achieved when recycled material is used for filling, such as the use of some 2 Mm³ of material dredged as a part of normal navigation channel maintenance from the Delaware River in the construction of a new commuter airline runway at Philadelphia International Airport.

Author Keywords: Airport; Materials flow; Geomorphology; Land reclamation; Sustainability

1. Introduction

Environmental concerns are now widely recognised in air transport, especially in Europe (Morell and Lu, 2000). Many see the negative social and environmental impacts of large airports being concentrated around the airports themselves, because the impacts of air pollution, noise and traffic occur there ( Janic, 1999; Nero and Black, 1998). However, the environmental impacts of transport are not only due to vehicle use, but are also due to the production, maintenance and ultimate disposal of these vehicles. Other impacts of transport arise from the production of building materials, construction, maintenance and dismantling of the infrastructure ( Van Ierland et al., 2000). We can thus distinguish the direct impacts of aviation operation from the indirect impacts due to the construction of facilities and the supply of materials for aviation operations ( Table 1). The indirect impact occurs both locally and over the areas where raw materials and energy are sources, where manufacturing takes place and where wastes are disposed. Airports also use valuable flat land close to major urban centres. In Europe alone, airports and military airfields occupy over 1500 km² (European Environment Agency, 2000).

Table 1. Environmental problems/impacts associated with aviation (based on and expanded from Janic, 1999)

When the use of energy and materials in transport is considered, the quantities and substances involved are much more than the fossil fuels consumed in operating the vehicles. The air transport industry relies on a wide range of goods and services from many industrial sectors, such as the construction of runways, terminal buildings, ground transportation links and other infrastructure as well as all the materials in daily use to operate the airports and aircraft. The use of energy and materials at all stages of these operations has to be considered in any analysis of the sustainability of aviation.

The direct use of energy in ground vehicles and aircraft and the associated greenhouse gas emissions can be seen as the consequences of direct needs (Lenzen, 1999). Whilst technological innovations and increasing occupancy rates have resulted in significant improvements in the energy efficiency of air transport over the last 30 years, the energy costs of air passenger travel remain high. Energy use per passenger-km by air in 1995 was nearly double that for cars and more than three times that used for travel by rail and bus ( European Environment Agency, 2000).

In addition to this direct energy use, the indirect energy expenditure incurred during the extraction, refinement, storage and distribution of these fuels as well as those embodied in goods and services necessary for the operation of transport has to be assessed. This becomes a broad issue when the requirements of energy and materials for the machinery used to quarry stone, dig the aggregates, and manufacture the concrete used for runways and terminal buildings are considered. These total requirements can be assessed using input–output analysis (Lenzen, 1998). Such indirect requirements of energy and materials have to be taken into account when considering the sustainability of aviation operations, especially in terms of fossil fuel depletion and climate change ( Lenzen, 1999).

Many studies of the environmental impact of transport through energy use do not examine all the energy embodied in goods and services. Studying energy use in Australian transport, for example, Lawlor and Brown (1980) suggested that indirect energy for transport was 160 PJ, with 28% being used in vehicle manufacture, maintenance and repair, 63% in fuel manufacture and delivery; and 9% in the construction and maintenance of infrastructure.

1.1. Environmental impact assessment

Among the methodologies developed to help decision makers and planners assess the impacts of proposed transportation developments on the natural and social environment is the Evaluation Framework of Environmental impacts and Costs of Transport (EFFECT) (Tsamboulis and Mikroudis, 2000). This procedure combines multi-criteria analysis (MCA) with cost–benefit analysis (CBA) to make a complete assessment of both spatial and temporal aspects of transportation schemes. The various environmental criteria are weighted and then combined with monetary values to form a decision tree that helps in the evaluation of alternative proposals.

1.2. Life cycle analysis

A well-established way of ascertaining the total environmental impact of transport is to do a life cycle analysis (LCA). The indirect effects of transport that ought to be considered in an LCA include soil and water pollution; landscape damage; claims on land use, and fragmentation of ecosystem (Van Ierland et al., 2000). Marheineke et al. (1998) estimated the greenhouse gas requirements of a German road freight task, including the complete life cycle of the truck and the road.

1.3. Material flow accounting

Material flow accounting (MFA) refers to accounts in physical units (usually as mass expressed in tonnes) comprising the extraction, production, transformation, use, recycling and disposal of materials. It considers flows of substances, raw materials, base materials, products, manufactured goods, wastes and also emissions to air. MFA can help us to understand how changes in land use, industrialisation, consumption and population affect the land surface and alter the natural circulations of chemical elements in the environment (biogeochemical cycles).

1.4. Geomorphic impacts and their earth science implications

The use of materials is increasing, especially of construction materials, as people per household in industrialised economies decline and thus more dwellings are required, each in turn filled with more possessions. In the rapidly industrializing countries, urban and industrial building and the construction of roads, harbours and airports are proceeding apace. For example, in China, the production of aggregates and associated hidden flows more than doubled in 7 years, rising from 2313 Mt in 1989 to 5403 Mt in 1996 (Chen and Qiao, 2000).

The impacts of such rapid transfers of materials from the natural environment to the urban, industrial and transportation built environment are two-fold, a removal of material from the earth's surface (a change in geomorphology) and the accumulation of a stock of concrete and other materials elsewhere in cities and industrial zones (a change in urban morphology). Currently, in many places, waste flows also lead to morphological change as landfills occupy old quarries or parts of river floodplains, or develop new hills as land raise builds them higher than the surrounding land. Thus the metabolism of industries transforms natural landscapes and industrial activity has to be considered as a highly efficient geological and geomorphological agent in comparison with the rates at which rivers and water running over the ground change the landscape (Douglas and Lawson, 2000).

In order to appreciate the position of the flows of concern to industrial ecology within the spatial and temporal scales of geological processes, we have to consider people's urban, industrial and transportation infrastructure activity as one of the sets of actions by organisms that contribute to the earth surface component of the rock cycle. Students of industrial ecology, such as Guinée et al. (1999) correctly recognise that people also exploit biogeochemical cycles when they exploit substance stocks in the lithosphere and the environment and create stocks in the economy, through the materials flows involved in industrial, agricultural, urban and transportation activities, such as building airports. They incorrectly assume stocks in the lithosphere to be immobile: that natural earth surface features can be regarded as immobile. In many places changes to landforms are indeed imperceptible over the timescale of human lives. However, elsewhere, such as around the Pacific Rim, lithospheric processes are highly active, with volcanic eruptions and earthquakes frequently causing disruptions to human activity.

At a less dramatic scale, the earth surface changes through the action of water, wind, waves and ice. Where the pathways of material moved by such processes are disrupted, such as by the re-routing of rivers for runway extensions, or by building airports in areas prone to sand drift, care has to be taken to avoid the creation of large-scale risks of natural disruptions of airport activity, or of activities downwind or downstream of aviation installations. Part of the sustainability of aviation relates to successfully designing with nature to avoid damage and increased costs due to events such as flooding, subsidence, sand storms and storm surges over low-lying coastal installations.

2. The quantities of material moved for airport construction

The growth of air travel is inevitably accompanied by the expansion of ground facilities, from car parks to terminal buildings and runways. The construction of new runways and the extension of existing ones account for much the largest portion of the materials moved and land area taken in airport development and expansion. Since 1998, some 27 projects involving the building of at least one new runway have been completed, are under construction, or have been commissioned (Table 2).

Table 2. New major civil runway projects completed, under construction, or commissioned 1998–2001

Nevertheless, the amounts of material moved for the construction of individual runways are dwarfed by the mass of materials shifted during the construction of some of the biggest new airports (Table 3).

Table 3. Representative quantities of materials involved in airport construction projects

2.1. Hong Kong's Chek Lap Kok Airport

This project was one of the largest earth-moving and dredging operations ever undertaken. Originally, the granite island's area was only 302 ha, but in just 31 months, 938 ha of new land were wrested from the sea and the shoreline was moved 5 km further west. A 13 km-long seawall surrounds the levelled airport island, with blocks of granite weighing from 1 to 5 t apiece forming the protective seawall. They were blasted out of the island's rock to the seawall specifications, and made to interlock tightly with one another in open fashion to dissipate the wave action of the sea.

The marine component of the works required the removal of 69 million m³ of marine mud from the reclamation area and the deposition of 76 million m³ of sand extracted from offshore borrow pits. Dredging of marine mud and alluvial clay at the borrow pits involved the movement of a further 40 million m³ of material. Some 55 million m³ of all this moved material had to be re-handled, with the carriage of marine materials between the borrow pits, the airport site and the dumping areas involving over 2.04 million km of dredger journeys. The earthworks operations on land entailed the excavation of 122 million m³ of rock. 108 million m³ were dug out and shifted on Chek Lap Kok, with nearly 14 million m³ being extracted from quarries on Brothers Island and Tsing Yi (Plant et al., 1998) ( Fig. 1 and Table 3).

Display Full Size version of this image (60K)
Fig. 1. Pattern and volume of marine materials movement for the construction of the Chep Lap Kok airport island platform in Hong Kong (based on data in Plant et al., 1998).

A 2-m thick finishing layer of crushed granite aggregate and sea sand was spread over the whole of the island's surface. Seven million m² of a special geotextile separates this 2-m thick drainage layer from the much coarser landfill substrate (Hong Kong Airport Authority, 1999). In addition to the construction of the airport itself, the movement of materials to provide road and rail access has to be considered. The rock excavation for the anchorages of the double-deck Tsing Ma Suspension Bridge carrying the road and railway to the airport required the removal of nearly 1,000,000 m³ of material.

2.2. Kansai International Airport (KIX)

Kansai airport, serving Osaka, Japan, was the world's first 24-h airport to be constructed on an artificial island. The island, some 510 ha in extent, is bounded by 11 km perimeter wall and carries a single 3500 m runway and a 1680 m long terminal building. It was expensive to build, the total construction costs of approximately US $12.5 billion (Edgington, 2000) making it difficult for the airport to show a profit. Costs of maintenance and development of new technologies were greater than originally anticipated ( Wensveen, 1999).

Reclamation work for the island caused settlement of the seabed. The additional weight of the material dumped compressed the underlying alluvial clay. Piles were driven through the clay to increase the stability. The pattern of dumping dredged sand was strictly controlled. Ensuring the stability of the large terminal building required the installation of hydraulic jacks into all its supporting columns so that they could be adjusted to cope with any uneven settlement.

Work on a second runway began in 1999 and is scheduled for completion in 2007. However, the new reclamation area is farther from the coast and in deeper water. The problems of subsidence are expected to be more severe than in the first runway, with a prediction that after 50 years subsidence will have been 18 m compared to 11 m for the first stage (Kansai Airport Authority, 2000). Detailed analyses have been made of the way landing aircraft cause small temporary depressions in the runway that in turn affect the drag on aircraft moving along the runway ( Endo, 2000).

2.3. Singapore Changi Airport

The construction of Changi Airport in the late 1970s involved the reclamation of about 700 ha of land from the sea. Some 40 million m³ of sand were extracted from two seabed areas by cutter-section dredgers and were pumped ashore along 4 km of pipelines (Wong, 1992). Further reclamation work at Changi East for an extension of the airport in the 1990s involved an additional 170 million m³ of sand fill (Choa, 1994).

2.4. Incheon International Airport

Construction of the new Incheon International Airport, begun in 1992, has necessitated the building of 17.3 km of sea dykes around 5615 ha of reclaimed tidal land between Youngijong and Yongyu Islands, 53 km west of Seoul. Two 4000 m runways are being completed on land originally covered by water to an average depth of 1 m. The main terminal building has required the removal of 2.25 Mt (million tonnes) of earth, 0.18 Mt of steel and reinforcing bars and 252,000 m³ of ready mixed concrete. To provide access a 4.4 km long suspension bridge, a 40.2 km 6–8 lane highway and a new 53.7 km double track railway, to downtown Seoul via Kimpo International Airport, have been built (Lee, 1998; Incheon International Airport, 2001).

2.5. The new runway at Funchal, Madeira

The growth of tourist traffic and the need to accommodate larger aircraft has forced the airport on this popular, mountainous island, to expand. The project has entailed the construction of a kilometre long embankment along the coast on 180 concrete pillars, each 3 m in diameter, rising 70 m above sea level with a further 60 m of foundation below ground level. Although modest in scale compared with the foregoing examples, it illustrates the expensive engineering solutions required to adapt some environments for growing air traffic (Anon., 1998; Madeira-web, 2001).

3. The possibilities of using recycled materials in airport construction and maintenance

Much attention has been given to the use of recycled materials for the reconstruction of airport runway pavements. It may now be argued that such use of recycled materials is no more costly than the use of primary materials and in some cases yields superior pavements at lower cost.

A reconstituted base procedure using recycled old asphalt pavements as a base for new bituminous concrete surfacing has been widely used at small airports such as Martha's Vineyard, New Hampshire, Rockland, Maine, and at Beverly Municipal Airport near Boston in the New England region of the USA (Aikman, 1984). At the Jacksonville International Airport in Florida, the existing runway pavement was recycled to produce a 15 cm crushed concrete filter course and a 15 cm econocrete base by breaking out the existing concrete, processing it through a crusher to produce a maximum size aggregate of about 37 mm, and running it through a central mix plant to produce a mix with about 143 kg of cement per cubic metre of concrete. This recycling technique substantially reduced costs by using the material readily available on site.

At Rostraver Airport the fill used in the expansion of a safety zone around a runway extension was a low permeability cementitious material (LPC) made by the Duquesne Light Company by mixing coal combustion by-products (fly ash and flue gas desulphurisation sludge) with lime (Buckley, 1998). Manufactured fill material made by mixing dredged matter, coal ash and lime kiln dust has been used as a sub-base in an airport runway extension at Boston, MA. Fly ash mixed with bitumen (tarcoal) in the ratio of 70:30 at about 80–90°C creates a strong tensile material considered suitable for airport runway construction ( Wasay, 1992).

A major use of recycled material occurred when the City of Philadelphia dredged approximately 2.5 million m³ of material from the Delaware River federal navigation channel and used that material to construct a new commuter airline runway, formally opened in December 1999. As the planned expansion of runway 8–26 would affect federally regulated waters and wetlands, the Corps of Engineers had to give approval. The Corps tied the approval to its ongoing Delaware River channel maintenance dredging program so that the city could use the nearby, high-quality river material instead of traditional upland sources for the runway embankment fill. The City of Philadelphia and its taxpayers benefited because $7 million in savings resulted by using the less costly Delaware River fill material instead of upland sources. There were also considerable environmental benefits. By using the Delaware River dredged material as the primary source of fill for the runway construction, mining and trucking of fill from traditional sources were not necessary. This eliminated environmental impacts related to mining activities and the associated noise and air pollution, traffic congestion and roadway wear that come with trucking the 1,900,000 m³ of fill needed for the new runway. Furthermore, the beneficial use of the Delaware River dredged material conserved dredge disposal capacity. This will reap future economic savings and reduced environmental and social impacts as the Corps of Engineers continues its ongoing maintenance of the Delaware River navigation channel.

4. The Earth science components of aviation sustainability

4.1. Subsidence problems

In addition to Kansai International Airport, many airports suffer risks of subsidence, some due to abstraction of fluids from beneath the ground, others to tectonic activity, especially earthquakes. Among the severe subsidence problems due to oil or groundwater abstraction are those at Long Beach Airport, CA (Jet Propulsion Laboratory, 1999) and at Lakefront Airport near New Orleans ( Hart, 1994). Airports built on limestone substrates, where sinkhole development and subterranean karst cave collapse can occur, may also suffer subsidence, as at Liangjiang International Airport Guilin, in the famous tower karst area of Guangxi Province, China. To avoid such subsidence risks, grouting with cement was used to fill potential sinkholes at the Huntsville Airport on karstic terrain in Alabama ( La Moreaux, 1967).

The risk of settlement may be greatly reduced by pre-compaction of the substrate before runways are built. Dynamic compaction involving the controlled dropping of a heavy weight, or tamper, from a crawler crane on a predetermined grid pattern was carried out over 575,000 m² for the new terminal building at Dubai International Airport. The treatment enforced settlement in the ground by reducing void spaces between constituent soil particles. This improved the geotechnical properties of the uppermost 5 m of the substrate, thereby greatly reducing the likelihood of further settlement after construction.

4.2. Shrink-swell (cracking clay) foundation problems

Many parts of the world, especially in mid-latitudes and the sub-tropics have surface clay deposits containing montmorillonite clay minerals that swell when wet and shrink when dry. These clays can severely affect the foundations of buildings through movements in extremely wet periods or times of drought. Often the movements lead to severe cracking of structures. Precautions have to be taken in the design of airport runways and terminal and ancillary buildings in such circumstances.

The new Denver International Airport is built on clays with swell potentials as high as 15 per cent and averaging 8 per cent. These potentials had to be taken into account in the design of the terminal, parking garages and airport office building as well as the airfield pavements themselves. Consideration had to be given to the effects of heavy aircraft landing on the runways and the compaction and compression effects this would produce on the underlying clays.

4.3. Flood damage to airfields

Flooding disrupts aviation activity and may destabilise runways. Sherman US Army Airfield, located on the Missouri River floodplain was inundated to a depth of 1.8–3 ms during the exceptional floods of 1993. The ingress of water destabilised the pavement, reducing its stiffness. In this case however, the strength of the pavement structure improved rapidly as the water drained away and full operational capability was restored more easily than expected. Greater difficulties occur where the post-flood drainage is not as efficient.

Flood risks may be high at many airports built on toe slopes of alluvial fans in arid regions. At Eilat, Israel, the airport runway runs for 3 km along the toe of a fan slope, parallel to its contours, only a few metres above sea level (Schick et al., 1999). The streets of Eilat run downslope and would act as floodways carrying water towards the runway. The protective flood drain along the runway is only big enough to intercept small flows. Such flows could escape through some drainage tunnels under the runway, but these tunnels would be filled by sediment during a major storm event. At adjacent ‘Aqaba, the local airport is similarly at flood risk. Much of the area between the airport and the northern suburbs of ‘Aqaba itself is occupied by a customs-free zone whose compound has to be protected from floods ( Schick et al., 1999).

4.4. Groundwater contamination problems

The new 13 km² main airport at Gardermoen, Norway is sited above a 100-km² sand and gravel groundwater aquifer where the water table is 3–20 m below the ground surface (Kaarø, 1994). The behaviour of the groundwater body will be considerably affected by the construction of the airport. The railway tunnel to the main terminal is so deep that it will effectively divide the groundwater system into two. 50 per cent of the rainfall that reaches the surfaces of the new airport will eventually enter the groundwater body. A key issue is the maintenance of both the quality and quantity of the groundwater resource. De-icing of aircraft during the winter will potentially cause chemicals to runoff and infiltrate into the groundwater body, as could any escape of petroleum product residues and other liquid wastes into drainage systems and onto vegetated surfaces. In many cases, groundwater contamination has been discovered only as airports close ( Johnson and Pedoe, 1996).

4.5. Sand drift problems

The movement of sand and dust by wind poses serious problems in drylands, extensive control measures being necessary to avoid incursion of sand on to airfields and other transportation infrastructure (Cooke and Doornkamp, 1990). Sand blasting may cause serious damage to equipment, motors and telecommunications installations. Visibility linked to dust storms is a major hazard for flights into and out of airports in desert regions such as Sharjah and Bahrain in the Persian Gulf ( Houseman, 1961). Blowing dust can create a skidding risk on airport runways.

Movement of dunes can be aggravated through disturbance of vegetated areas during the construction of airport facilities, such as new access roads, car parks and hotels. Accelerated dune movement can result in sand build-up on the edges of airfields, which may add to natural sources of blown sand and dust. Sustainable airport management requires that these impacts on geomorphic processes are considered, controlled and minimised in order to involve the creation of unnecessary costs for the airport, its users and for adjacent landholders and residents.

5. Conclusions

The sustainability of aviation is more than operating airports and aircraft with a view to minimising their direct environmental impacts. The indirect effects, not only on the immediate vicinity of airports and transportation routes, but also on the areas from which the materials for airport construction and operation are obtained, need to be considered. The changes to earth surface systems caused by land reclamation for major airports, especially those for runways built on artificial islands or peninsulas are significant. Serious feedbacks from the earth surface system may occur, as in the case of subsidence at the Kansai International Airport. Even on the ground surface, airport construction often increases the risks of disruption from geophysical hazards, such those due to flooding and siltation where runways are sited on low-angle alluvial fans, or those of dust and sand storms where airport development accelerates natural movements of dune sand.

The sustainability of ecosystems and earth surface systems adjacent to airports can be greatly reduced by runoff of chemicals, groundwater contamination, airborne emissions, and all the complex disturbance of land surfaces and vegetation communities through the peripheral urban and industrial activity associated with provision of access and services from airport users and air freight movement. Increasingly aviation facilities act as a magnet for related commercial and industrial developments. While these developments are not part of the aviation industry itself, they would not be there if the associated airport did not exist. This paper has emphasised materials use and geomorphic change associated with airport construction and has indicated that when the full indirect impacts of airport construction are considered, the materials flows involved are of geological significance in terms of mass moved per unit of time. Some of the material flows could be reduced by the use of recycled materials in runway construction maintenance, terminal construction and related facets of airport development. The earth science, geomorphic elements of land surface change for aviation are important, both for possible future high cost remedial engineering works for the industry itself, and for the long-term stability of earth-surface systems.

Social Democracia

2007-12-21

Airport construction: materials use and geomorphic change