URBAN PLANNING AND DEVELOPMENT

The New Underground Planning Map of the Netherlands: a Feasibility Study of the Possibilities of the Use of Underground Space

R. A. H. Monnikhof, J. Edelenbos, F. van der Hoeven and R. A. A. van der Krogt

Abstract --In 1998 a study was conducted in the Netherlands into the possibilities of a more large-scale and systematic use of the underground in the western part of the country, the so-called ~Randstad". It was intended to be a more focused sequel on a study conducted on the possible role that use of the underground coald play for the whole of the Netherlands, the "Strategic Study on the utilization of underground space". The study examined the possibilities of improving an idealized model of the future spatial development of the Randstad, that was preferred by the provinces comprising this Randstad, by using more extensively he underground space. Improvement meant an enlargement of the efficiency of the use of space and maintenance or enlargement of the spatial quality of the area. Societal, cost, groundwater and policy aspects were investigated. The study showed some remarkable results. Gains in available space up to 50% in specific areas seemed possible and, when costs of working and maintenance were taken into account, underground construction for several facilities was no more expensive than above ground construction, which contradicts a widely held belief in the Netherlands. © 1999 Published by Elsevier Science Ltd. All rights reserved.

1. Introduction

T his paper deals with a study conducted on behalf of the "Randstad Spatial Planning Group ~ (abbrevi- ated in Dutch ~o RORO), the Centre for Under-

ground Construction and the Ministry of Housing, Spatial Development and Environmental Control. This study was intended to show the possibilities for using the under- ground to achieve a mere spatially efficient and greener development of the so-called "Randstad ' , the western par t of the Netherlands. I t was a more focused and in-depth sequel of a study conducted on the possible role that use of the underground could play for the whole of the Nether- lands until 2030, the "Strategic Study on the utilization of underground space" (see Horvat and van der Krogt 1997, Edelenbos et al. 1998).

Section 2 outlines the inducement to the study, which lies in the presentation of an overall map of all spatial plans in the Netherlands. Section 3 describes the spatial model that formed the normative start ing point for the study, followed by a sketch of the topics dealt with in the study in Section 4, as well as a short description of how the

Present address: Rend A.tt. Monnikhof, Jurrien Edelenbos, and Frank van der Hoeven, Research Assistants, Faculty of Architscture, DelR University of Technology, P.O. Box 5043, 2600 GA Delft, The Netherlands; Rob van der Krogt, Consultant, DHV Environment and Infrastructure, P.O. Box 1076, 3800 BB Amersfoort, The Netherlands.

study was conducted. In Section 5, three basic motives for going underground are outlined. Section 6 deals with safety, liveability and user aspects of going underground, followed by the effects on spatial efficiency in Section 7. The always important cost aspects are dealt with in Sec- tion 8. The effects of use of underground space on ground water, a topic which has been neglected in policy delibera- tions in the Netherlands until now, will be discussed in Section 9. Section 10 covers the policy recommendations that were made regarding the role provinces could play in a better use of the underground in spatial policy making. Finally, Section 11 presents some key conclusions of the study.

2. The New Map of the Netherlands and the "Randstad"

In 1997 a document called the "New Map of the Nether- lands" (Stichting de Nieuwe Kaar t van Nederland 1998) was published, showing all the spatial plans in the Nether- lands on one map. I t sent shock waves through the spatial planning and policy community in the Netherlands, be- muse it showed a future country full with new roads, railroads, urban sprawl etc .--a country that would use up its scarce green areas at high speed in the coming decades.

In particular, the area referred to as the"Randstad" was shown to be an area where future spatial claims would clash vehemently. A significant portion of the (spatial) problems in the Netherlands are concentrated in this western par t of the country, where the larger cities are situated (Amsterdam, Rotterdam, The Hague and Utrecht).

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Although this area covers only 13% of the area of the Netherlands (5335 ha of a total of 40,575 ha), it houses 36% of the population (approximately 5,4 million of a total of 15 million). It is the economic heart of the Netherlands and is densely populated by Dutch standards (a little more than 10 persons per hectare). This has led to a shortage of green areas, and those that still exist are under continuous pressure from the growing need for new housing and infrastructure. Especially famous here is the so-called "Green Heart", a larger green area in the centre of the Randstad. Protect ion of this area aga ins t fu r ther urbanisation has been a main topic for consecutive genera- tions of national and provincial policy makers. In addition, congestion problems on the existing infrastructure are considerable, as is the nuisance caused by this infrastruc- ture in existing urban areas. The plans shown on the New Map would aggrevate these problems.

Therefore the four provinces comprising the Randstad (organized in the so-called "Randstad Spatial Planning Group", abbreviated in Dutch to RORO) decided to initiate a study to investigate the possibilities of a more large-scale and systematic use of the underground in the Randstad. The intention of this study was to show the flaws in the image which the New Map had shown of the future of the

Figure 1. The Randstad area of The Netherlands is considered the economic heart of the Netherlands. In addition, it houses the so-called "Green Heart ~ area in its centre. Protection of this area against further urbanisation has been a main topic for consecutive generations of national and provincial policy makers.

Randstad, and to give it a greener and more "spatially efficient" turn. Other initiators were the Centre for Under- ground Construction and the Ministry of Housing, Spatial Development and Environmental Control.

3. Spatial Scenarios for the Randstad The study, which started from an idealized model of the

future spatial development of the Randstad that was preferred by RORO, examined the possibilities ofimprev- ing this model by a more extensive use of the underground space. "Improvement" here meant an enlargement of the efficiency of the use of space and maintenance or enlarge- ment of the spatial quality of the area.

RORO itself had already in 1995 drawn up five scenarios to assess the consequences of current policy goals and their possible alternatives. These scenarios differed in the amount of government involvement versus determination by the market in spatial developments, in the value attached to keeping present nature and landscape intact, in the ap- preach choosen towards mobility, etc. None of these sce- narios alone proved to be wholly desirable in its effects. Therefore, a synthesis of the two '%est" scenarios was made, which gave a so-called "preference model".

This preference modelis charactsrisod by a number of very densely built-up urban areas, around which are several public transport oriented intermediaire zones and transition areas between city and country, and more suburban areas in the periphery of the Randstad. Within this preference model, RORO discerned nine different types of areas: Central Busi- ness District, City Environment, Strate- gic Zone, Pedestrian Pocket, Condensa- tion Growth Nucleus, Municipal Balcony, High Quality Business Area, Low Qual- ity Business Area, Infrastructure Zone. These were used for part of the assess- ment in the study.

4. Structure of the Study The study investigated several as-

pects of a more extensive use of the underground, as follows:

Researchers developed a classifica- tion of underground spaces by shape and function and some profiles of exem- plary combinations of functions above - and underground. • The "societal aspects" of using the

underground were considered, with a focus on the difference in effects on users of and people living nearby a facility of put t ing that facility aboveground or underground.

• The possible "gain in space" that could be achieved by more use of the underground was estimated for sev- eral different kinds of (urban) envi- ronments and recommendations were made for the use that could be made of that space.

• The costs of underground construc- tion for different types of facilities and different kinds of (soil) situa- tions were dealt with.

• The effects on ground water in the area were considered and the limit- ing conditions that these put on the possibilities for using the under- ground.

342 TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY Volume 14, Number 3, 1999

• Policy measures that provinces could take to help a more extensive use of the underground come about, and so improve their spatial planning, were investi- gated and recommendations made.

To perform the study, an existing qualitative methodol- ogy was used (see Monnikhof et al. 1998). To this basic methodology, several typologies were added. As for a typol- ogy of areas, for assessing the effects on safety, liveability, users and the efficiency of use of space, the area typologies of RORO were used, partically combined to seven types of areas (Central Business District, City Environment, Stra- tegic Zone, Compact Living Area, High Quality Business Area, Low Quality Business Area, Infrastructure Zone). For the assessment of the ground water effects, a typologie of areas with different ground water situations was developed and used. And, finally, for assessing the cost aspects no typology of areas was used; this of course makes the assess- ment valid for only rather abstract, average circumstances.

Safety, liveability ~md user aspects were assessed by comparing the area typologies with the characteristics of five different functions, in a qualitative analysis. A quanti- tative estimate (percentage) of the possible gain in space by using the underground was achieved by matching the area types with the same five functions.

With the cost analysis quantitative results were achieved for average situations for three types of buildings (high quality commercial and industrial building, low quality commercial and industrial building, residences), whereas the qualitative analysis with regard to ground water effects discerned between lineshaped and blockshaped objects (an example ofa lineshaped object is a tunnel for infrastructure, examples of bleckshaped objects are for instance cellars, storage rooms, or part~3 of underground office space).

5. Why Go Undergn)und? In the study, three basic motives for going underground

were identified: 1. To strengthen the quality of the living environment.

By constructing certain functions underground, nui- sance and hazard can be limited. Disturbing effects such as sound, stench and emissions are isolated and safety risks for people living or working nearby the function can be diminished.

2. To achieve more efficient use of space. More building volume can be realised on the same ground area. Also, the use of underground space makes combina- tion (piling) of several functions possible.

3. To strengthen the spatial-functional structure. By constructing certain facilities underground valuable areas and functions can be spared. The character of historal centres or nature areas, for instance, can be saved by underground construction of infrastructure and also barr iers can be prevented. Furthermore, underground construction offers possibilities to com- bine mutual ly reinforcing functions into a more effec- tive functional s tructure (for example, the combina- tion of retail, storage and parking).

6. Safety, Liveability and User Aspects of Going Underground

For assessing safety, liveability and user aspects of going underground, the first and third criteria were di- vided in two. Safety was divided into internal safety, the safety within a facility, and external safety (safety for people living or working near a facility). User aspects were divided into experiental aspects and functional aspects, meaning aspects like controllability of production pro- cesses, ease of maintenance, etcetera. With the aid of these criteria, it was possible to analyse whether five different functions (distribution, industry, knowledge services, park-

ing and road- and rail infrastructure) would be better placed above ground or below ground in the types of areas identified by RORO.

Based on this analysis, it was concluded that an under- ground execution of the function distribution (transport and storage of goods) seemed most promising in most areas, whereas putting knowledge services underground seemed not to offer much promise. For the other three functions, conclusions differed considerably between the different types of area, with city centres and other city areas offering most promise for putting functions underground. A conclu- sion with regard to these three functions was that when they would be put underground, careful attention for inter- nal safety and experiental aspects would be needed.

7. Spatial Efficiency Aspects of Going Underground

Use of the underground space can lead to, as mentioned in Section 5, a higher spatial effiency. Three situations were identified:

1. Proportional gain in space. A proportional gain in space will mainly be the case in an environment where there are no special quality demands (with regards to green areas, open space etcetera), so that the space directly above the underground construc- tion can be used for other buildings.

2. More than proportional gain in space. In some situa- tions, functions that are brought underground nor- really cause considerable disturbance in their envi- ronment, e.g., highways or storage facilities for dan- gerous substances. Normally, either there would be no building in large noisy zones and/or there would be safety zones around these functions. Constructing the function underground therefore not only releases the space that such a function would take in itself, but also (a part of) the space of those disturbance zones. A more than proportional gain in space could also be realised when using the underground space allows new types of building and parcelling out.

3. Less than proportional gain in space, on behalf of spatial quality. In certain cases the use of the under- ground can be aimed mainly at achieving more spatial quality. The space above ground thus released is then not wholly used for building again, but is left (par- tially) free, to create, for example, more green, light and space in an area that is densely built up.

Start ing from the possibilities for using the under- ground for the different functions and the three forms of gaining space described above, an estimate was made of the maximum possible gain in space per type of area, when leaving the quality of the inner and outer space still at an acceptable level. Most of the time, the use of underground space was seen as complementary, meaning tha t not the whole of a building or facility should be put underground, but part of it. Because of the large uncertainties the possible gain in space was expressed in a percentage range. This leads to est imates of possible gains in space ranging from 5-15% for city environments, to up to 100% for infrastructure areas.

8. Cost Aspects of Going Underground For assessing the costs of underground construction in

the Randstad, three types of construction were considered: • High-quality commercial and industrial building,

characterised by representativeness, expensive fronts, good isolation and a solid construction. Examples are offices, hospitals and cinemas.

• Low-quality commercial and industrial building, characterised by a light construction, simple materi-

Volume 14, Number 3, 1999 TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY 343

als and low isolation. Examples include production halls and storage buildings.

• Residences.

The costs were calculated for hypothetical average situ- ations, based on distinctive numbers and experience. In reality, of course, the concrete situation with its specific local circumstances has a large impact on the actual costs.

The costs of buildings are determined by construction costs, the costs of land and exploitation costs. This last category is made up of costs for maintenance and use of energy. They are made during the whole duration of life of a building, in contrast to the construction costs and costs of land that have to be covered directly at construction. There- fore, use was made of a net present value calculation to be able to include exploitation costs in the cost comparison. Starting points were a duration of life of 50 years and a real interest of 5%.

Table 1 provides an overview of the relative difference in costs between construction costs, costs of acquiring land and exploitation costs (net present value) of a building constructed above ground in comparison to a building partially underground. For each type of building, the starting point was the maximum of use of the underground that under "average" circumstances would still be realistic (presented as the percentage of the building constructed underground).

The table shows that underground construction has consequences for costs. In all cases, higher investments are

needed for construction, but these can be (partially) recov- ered by savings on the costs of land and exploitation costs. Less surface is needed for the same amount of building, and less maintenance is needed for outer walls and roofs. Also, the use of energy for heating and cooling is lower (but the use of energy for lighting is higher). Underground construction can also be favourable for security and other costs, but these were not included in the calculations.

On the basis of the calculations of construction costs, costs of land and exploitation costs, Table 2 gives a com- parative overview of the total costs. When one takes the integral cost into account not only construction costs but also the costs of using a building and of the area that it covers, Table 2 yields the following results:

• The price of land is a relatively minor part of the integral costs.

• Low quality commercial and industrial building is structurally more expensive when built underground

• Partially underground residences and high quality company buildings are eventually not or hardly more expensive than comparable above-ground structures.

Research was not done on the cost of building infrastructure underground. It is well known that on average, building infrastructure underground in the Ne ther lands is m a n y t imes more expensive than constructing it above ground. Cost considerations therefore will never be an argument for constructing infrastructure

Table 1. Comparative overview of construction costs, land costs and exploitation costs (relatiw

Type of Building

High-quality commercial and Industrial building:

• City centre, low"

• City centre, high ~

• Outskirts, low"

• Outskirts, high b

Low-quality commercial end Industrial building:

• 1 storey underground

• 2 s~reys unde~round

Residences:

• Low-rise

• High-rise

Percentsge UndeP ground

33%

17%

20%

20%

50%

67%

25%

13%

Construction Costs

Above Below ground ground

100 113

100 107

100 110

100 110

100 170

100 193

100 113

100 112

Land Costs

Above Below ground ground

100 67

100 83

100 64

100 60

100 50

100 33

100 75

100 87

per square meter).

Exploitation Costs

Above Below ground ground

100 86

100 93

100 91

100 91

100 81

100 74

100 94

100 97

' refers to predominantly Iow-dse buildings b refers to predominantly high-rise buildings

344 TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY Volume 14, Number 3, 1999

Table 2. Comparative overview o f total costs (relative, per square meter).

Type of Building

High-quality commercial and Industrial building:

• City centre, low"

• City centre, high b

• Outskirts, low"

• Outskirts, high b

Low-quality commercial and Industrlal building:

• 1 storey underground

• 2 storeys unde~round

Resldences:

• Low-dse

• High-dse

Percentage Under- ground

Share of construction costa, land costa and axploitation costa in total costa (%)

Above ground Below ground

co la ex co la ex

33% 61 8 31 68 6 26

17% 64 5 31 68 3 29

20% 54 14 32 61 9 30

20% 57 10 33 64 6 30

50% 48 24 28 70 11 19

67% 48 24 28 76 7 17

25% 37 25 38 44 19 37

13% 43 14 43 48 10 42

Total Costa (construction costs, land costa and

exploltaUon costa)

= refers to predominantly low-rise buildings b refers to predominantly high-rise buildings

Above ground

100

100

100

100

100

100

100

100

Below ground

101

101

98

99

116

122

96

101

underground in the Netherlands (although newer methods of (micro-)tunneling miight bring down this cost difference between aboveground and underground construction of infrastructure).

9. Groundwater Aspects of Going Underground Because building structures underground can have large

and lasting effects on groundwater, these effects were taken into consideration. Groundwater has a number of essential functions, related to:

• Ecology. Groundwater determines the water balance in the soil on which the natural environment depends strongly. Quality and quantity of groundwater per- form an important role in this.

• Public water supply. Ttwo-thirds of the groundwater. in the Netherlands is used for drinking water and industrial uses. ~.["nerefore a high quality of ground water is necessary.

• Feeding o f agricul tural crops. For every type of crop, there is an optimal ground water level. Changes in the ground water level can lead to losses in yield.

• Recreation. Changes in the water mark influence vegetation and access to recreational areas and the possibilities for using recreational waters.

• Bui ld ing and infrastructure. For buildings on wooden pile foundations and for roads, dikes and networks of pipes, a more or less constant level of groundwater is desirable to avoid damage through subsidence.

To preserve these essential functions, it is recommended that the original ground water situation be left intact as much as possible. However, some smaller or larger changes in the ground water situation will always occur if an underground structure is built. For a general understand- ing of these effects the following ground water aspects are important:

• Infiltration: vertical downward flow of ground water, for example the entry of rainwater from the surface into the soil.

• Upward seepage (welD: vertical upward flow of ground water.

• Groundwater system: a (more or less) closed circuit of ground water flows within a defined area where (rain)water infiltrates, flows horizontally and wells upward again.

Underground construction will not cause too many problems for the groundwater situation if the conditions mentioned in Table 3 are taken care of.

Volume 14, Number 3, 1999 TUNNSLLING AND UNDERGROUND SPACE TECHNOLOGY 345

10. Provincial Steering Models for Stimulating the Use of Underground Space

Since the study was initiated by, among others, the provinces comprising the Randstad, a request had been to indicate how these provinces could help a bet ter use of the underground space come about. In this regard, five pos- sible roles were discerned in the study:

1. Normsetting role. In this role, the province could make the granting of permits dependent on the question of whether an underground option had been seriously considered. Further, the province has the legal possi- bility to assign several areas a special status with regard to soil protection. In these areas, the province could set more specific rules with regard to the use of the soil. Finally, when the province is the designated authority for a project for which an environmental impact assessment is deemed necessary, it could stipu- late that in this assessment, use of the underground space is to be explicitly considered.

2. Norm testing role. In this role, provinces could make their approval of municipal spatial plans dependent on the question of whether it also has a "three- dimensional" aspect, meaning that the use of the underground is also covered by it.

3. Informing and advising role. In addition to using their legal powers, provinces could also use the "softer" means of informing municipalities and companies about all the possibilities there are for use of the underground, when carrying out their plans. For this, of course, the provinces themselves need to keep in touch of the latest developments in the field. More specifically, a province could draw up guide-

4.

5.

lines or a basic model for underground use in the provincial spatial plan, to support municipalities with the filling in of the underground part of the municipal spatial plan. In addition to performing an advising role, provinces could also actively educate local administrators and consult with them about the possibilities of under- ground construction.

Stimulating role. Provinces could "show the way" by paying attention to the use of the underground in their own spatial plans and other policy plans. Fur- ther, provinces could make available funding for executing exemplary projects. And, finally, in this role provinces could contribute financially to the extra costs of innovative underground solutions.

Initiating role. When a province is the iniater, or one of the initiators, of a project, it could bring the possible underground construction of (parts of) the project under atttention on its own.

11. Conclusions The study showed some remarkable results. For one

thing, gains in available space up to 50% in specific areas of the Randstad seemed possible (even one 100% for infra- structure areas). For another, when costs of energy and maintenance were taken into account, underground con- struction for offices, hospitals and parts of houses was no more expensive than above-ground construction, which contradicts a widely held belief in the Netherlands. Espe- cially for commercial services, underground construction seems a viable option. Finally, once again the high potential of putting the distribution function underground was con-

Table 3. Conditions set by groundwater considerations for using the underground.

Urban area None, the natural ground water situation is on average already seriously disturbed

Infiltration area

Areas independent of upward seepage

Areas dependent of upward seepage

Drinking water areas

Preferably in large groundwater systems, possibly in small systems (dependent on the relationship between the size of the system and the size of the disturbance)

• Preferably in large groundwater systems, possibly in small systems

• Lineshaped constructions (infrastructure) preferably in the aquitar

• In aquifers: either parallel to the direction of the ground water flow or blocking no more than 50% of the height of the aquifer.

• Not in small groundwatersystems, unless when there is only a limited depth necessary for construction

• Lineshaped constructions preferably in the aquitar

• Lineshaped elements in aquifers: either parallel to the direction of the ground water flow or blocking no more than 50% of the height of the aquifer

No underground construction

346 TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY Volume 14, Number 3, 1999

Table 4. An example of a possible basic model for an underground spatial plan.

0-3

3-15

Below 15

Cellars, cables, tubes, pipes, sewers, etcetera

Cellarconstructions with and without superstructure, tunnels with a diameter smaller than 3 to 4 m, shallow city tunnels for metro, train and road traffic

Boring tunnels with a diameter larger than 3 to 4 m, cellarconstructions with special permits, for instance for oil storage

All depths Weighted priority for foundations, ecologically relevant groundwater

f i rmed (compare Horva t e t al. 1997 and Edelenbos et al. 1998)

The s tudy was "inserted" into the policy process. Since pol icy-making in the Ne the r l ands is a slow process, no rea l decisions on a more extens ive use of the underground have been taken , bu t extens ive fu r the r r e sea rch into for ins tance the pa r t unde rg round goods t r a n s p o r t could p l ay is being conducted.

References American Society of Civil Engineers (ASCE). 1973. Need for

National Policy for the Use of Underground Space. Proceedings, Engineering Foundation Conference Need for National Policy for the Use of Underground Space. South Berwick: Berwick Academy.

Baker, R.F. et al. 1972. The Use of Underground Space to Achieve National Goals. Report of the American Society of Civil Engineers. New York: ASCE.

Carmody, J. and Sterling, R. 1993. Underground Space Design: a guide to subsurface utilization and design for people in underground spaces. New York: Reinhold.

Edelenbos, J. and Monnikhof, R.A.H. 1997. Is there a future for the use of underground space in the Netherlands? An integral assessment method for strategic decisionmaking on spatial development. Proceedings, ACUUS 7th International Conference, Underground Space: Indoor Cities of Tomorrow. Montreal: ACUUS.

Edelenbos, J., Monnikhof, R.A.H., Haasnoot, J., Hoeven, F. van der, Horvat, E. and Krogt, R.A.A. van der. 1998. Strategic Study on the Utilization of Underground Space in the Netherlands. Tunnelling and Underground Space Technology 13:159-165

Haasnoot, J.K., Edelenbos, J. and Monnikhof, R.A.H. 1997. Potential obstructions for the use of underground space in the Nether lands . Proceedings, ACUUS 7th International Conference, Underground Space: Indoor Cities of Tomorrow. Montreal: ACUUS.

Hoeven, F. van der, Heusden, T. van, Hofstee, J., Edelenbos, J., Monnikhof, R.A.H. and Pries, F. 1997. De Nieuwe Kaart Verdiept: een verkenning naar de toepassingsmogelijkheden van ondergronds ruimtegebruik in de Randstad (The New Underground Map: a feasibility study of the possibilities for using underground construction in the "Randstad", in Dutch). Gouda: Cen t rum Ondergronds Bouwen (Centre for Underground Construction).

Horvat, E., and Krogt, R.A.A. van der (eds.). 1997. Strategic Study on the utilization of underground space. Summary and Conclusions. Gouda: Centrum Ondergronds Bouwen (Centre for Underground Construction).

Maurenbrecher, P.M. 1992. Evaluation of the opportunities for the use of underground space in the Netherlands. Proceedings, ICUSESS '92, 5th International Conference on Underground Space and Earth Sheltered Structures, 432-441. Delft: Delft University Press.

Monnikhof, R.A.H., and Edelenbos, J. 1998. The use of underground space in the Netherlands in a strategic perspective. Proceedings, Tunnels and Metropolises. World Tunnel Congress "98, Vol. 1, 23-28. Rotterdam: Balkema

Monnikhof, R.A.H., Edelenbos, J. and Krogt, R.A.A. van der. 1998. How to Determine the Necessity for Using Underground Space: an integral assessment method for strategic decision- making. Tunnelling and Underground Space Technology 13:167-172.

Stichting de Nieuwe Kaart van Nederland, De Nieuwe Kaart van Nederland (The New Map of the Netherlands). 1998. NIROV, The Hague.

Volume 14, N u m b e r 3, 1999 TUNN~LLINO AND UNDERGROUND SPACE TECHNOLOGY 347