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Renate Spaeth1

1 Ministry for Environment, Regional Planning and Agriculture of Land Nordrhein-Westfalen, Schwannstraße 3, 40476 Düsseldorf, Germany.

Authors of the research: Gero Becker, Uwe Barge and Johannes Ressmann, University of Göttingen, Institut für Forstbenutzung, Büsgenweg 4, 37077 Göttingen.


The Land Nordrhein-Westfalen (NRW) is one of the 16 states of the Federal Republic of Germany. Almost 18 million inhabitants live within 34 000 m2. Forests cover 26 percent (or 880 000 ha) of the surface, that means an average of 527 m2 of forest per inhabitant.

Growing pressure on forests for recreational activities results in increased involvement of the general public and demands for a forestry road network able to handle the multiple uses of forests in a highly industrialised and densely populated country.

The apparently inappropriate use of industrial waste material for surfacing forest roads in the recent past led to public debates.

The forestry administration therefore decided to do research on environmentally sound forest road construction. The research, done by the University of Göttingen, made suggestions and recommendations about different aspects of forest roads:

1. With the exception of small-scale private woodlands, forest road networks in NRW have reached a state of completion.

2. Road improvements and maintenance are due on a far larger scale in order to bring the system in line with increased operating and public demands.

3. New road construction should be avoided altogether in "specially protected biotopes" and sensitive woodland areas.

4. Each new road construction project should be re-examined with a view to abandoning it in favour of other technical means.

5. If the decision is made to proceed with new construction, alignment, design and choice of materials should be determined according to ecological principles.

6. If less foreign materials are used for road construction and maintenance, the adverse ecological impact can be minimized. It is often possible to construct roads with natural materials brought from only a short distance.

7. If suitable construction material cannot be extracted from the immediate vicinity, specific criteria should be observed when obtaining materials from external sources.

8. Employment of recycled building materials and industrial by-products is only viable for environmentally compatible forestry road construction if at least the same material compatibility standards are applied as for public highway construction under current laws and subsequent regulations. This automatically rules out the employment of residual materials that have not been processed under stringent conditions of quality control.

Introduction to Nordrhein-Westfalen (NRW)

The Land Nordrhein-Westfalen is one of the 16 states of the Federal Republic of Germany. Situated in the west of Germany, it borders with Belgium and the Netherlands. Well-known large cities such as Cologne, Düsseldorf, Aachen, Duisburg and Münster are situated here. One of Europe's most important rivers, the Rhine, flows through Nordrhein-Westfalen and there is the highest density transportation network in the whole of Europe with 20 000 km of motorway.

Almost 18 million inhabitants live within 34 000 km2, that is nearly 25 percent of Germany's total population.

The traditional concentration of industry and trade around the rivers Rhine and Ruhr causes numerous environmental problems.

Nordrhein-Westfalen has responded to the need to conserve and restore the natural fundamental basics of life for its inhabitants by:

· laws and regulations to protect the environment;
· rigorous monitoring of water, ground and air;
· intensive research;
· introduction of the most up-to-date environmental technology.

Although the Land is an economic and cultural centre for western Europe, 80 percent of it consists of open cultivated land from the lowland plain to the foothills of the mountains, with fields and meadows, forests, rivers and lakes.

Forests in Nordrhein-Westfalen

Twenty-six percent (or 880 000 ha) of the surface is covered by forests, that means an average of 527 m2 of forest per inhabitant (the Federal average is 1 200 m2).

Forest ownership is as follows:

· state-owned


· corporate ownership


· private ownership


· owned by the Federal Government


In a highly industrialized and densely populated state, forests are multifunctional. They have to produce timber as well as to protect water, air and soil. They are recreation areas for people living in big cities as well as habitats for animals and plants.

Foresters in Nordrhein-Westfalen are trying to balance these different demands.

At the basic level of forest administration there are 35 forest offices, responsible for forests of all ownership categories within a given district (Figure 1).

The forest offices are coordinated and controlled by two intermediate Forestry Authorities (Rheinland and Westfalen-Lippe).

Within the State government of Nordrhein-Westfalen the Ministry for Environment, Regional Planning and Agriculture is also responsible for forestry, wood industry and forest ecology. This upper level of forest administration works within the same division as Conservation of Nature and Species, Landscape Conservation and Hunting.

Forest road construction and environment

Within the last few years forest road construction and use was one of the problems the forest administration had to deal with. It was therefore decided to carry out research on the issue of environmentally sound forest road construction in Nordrhein-Westfalen.

This survey was done by the Forest Department of the University of Göttingen. The following pages contain the most important conclusions of the research.

1. Environmentally sound forest roads

1.1 Introduction and highlights of the topic

Woodlands and forests form a significant and extensive element of the Central European cultural landscape. Although, or even because, they have been intensively cultivated and used. They perform today an ecological balancing function, ensuring effective protection of water, soil, climate and species to a far greater extent than any other type of land use. Their importance thereby increases proportionately to the growing pressures of civilization on the landscape. Proper forestry management methods whose objective is to conserve and utilize forests are linked to the existence of an adequate network of forest roads. Growing pressure on forests for recreational activities also results in increased involvement of the general public and demands for a forestry access road network able to handle these multiple uses. At the same time, construction of roads and their use for forestry as well as public access have inevitable consequences on the forest's regenerative balance and its ecosystem. The general public's sensitivity toward such encroachments keeps pace with the increasingly significant role of the forest as a creator of ecological equilibrium. Greater appreciation and experience of qualitative and quantitative repercussions have resulted in a growth in environmental-political relevance, and thus public concern of the complex of questions relating to the ecological evaluation of forestry access roads. They also coincide with an increased potential of conflict when determining the appropriate balance between public and commercial use demands.

Even if large expanses, in particular of the state-owned forest of Nordrhein-Westfalen, may be deemed to be developed adequately, from a forestry point of view there is still a need to upgrade the forest road system, especially in the case of corporate and private woodlands. Road improvement and maintenance are needed on a far larger scale in order to bring the system in line with increased operating and public demands. In both areas, projects and proposals which were evidently not optimally planned and constructed have led to public debates in the recent past, one of the main objections being the apparently inappropriate use of waste material (building rubble) for surfacing roads, resulting in disproportionate environmental impact. In the course of, and as a consequence of, the recent amendment to the State Forestry Act, this prompted the lawmakers to extend their field of vision to the need for regulations and action in the sphere of forest road construction. In doing so it quickly became obvious that there were numerous questions to be answered before the problems addressed could be clarified and evaluated from a legal and practical point of view.

1.2 Relevance of forest roads for leisure and recreation

Forest roads are a part of the operational infrastructure, whose primary purpose is forest management. Decisions within the framework of general development planning (road network density, routing) and road standards (cross-sectional design, dimensioning) are initially determined from a technical, economic and individual operational point of view. The legal character of these roads, which are regarded as private rights of way belonging to the respective landowner, is in keeping with this and clearly underscores it.

On the other hand, forest roads have become increasingly popular with the general public for recreational purposes. In NRW they are available to a resident population of 18 million as well as visitors from outside the region. The type of usage is regulated and restricted by the Forestry Act, and must be tolerated by the landowner as it falls within the scope of the social contribution of forest property. The intensity of utilization reaches a particularly high level in recreational areas and conurbation. The multitude of different recreational uses (nature watching, hiking, strolling, cycling, horseback riding, mountain biking) leads to additional conflicts and their aggregate impact occasionally results in an overtaxation of the common usage rights of forest access.

As a consequence, the objective of environmentally compatible and ecologically sound forest development should be striven for recognizing and ranking the conflict of interests between forestry on the one hand and nature conservancy and ecology on the other. However, the fact that in many cases these roads play a significant role in enabling public access for increased recreational usage must also be taken into account.

2. Suggestions and recommendations

2.1 Appropriate level of development for NRW

A stipulation or a generalized, numeric statement of an appropriate access road grid density for NRW appears problematic, because the factor "network density" is a mathematical mean. Difficult topographical conditions (steep slopes, wet areas) or complicated ownership patterns often rule out a meaningful stipulation of this figure, which in any case makes no qualitative statement nor an indication of the need for additional access roads.

With the exception of small-scale private woodlands, access road networks in NRW have for the main part reached a state of completion. New construction is usually only necessary for optimizing outdated access road systems. As the example of road system re-optimization by a private forest management has shown, this can even result in a reduction in density of the grid whilst at the same time maintaining the standard of access (Becker et al. 1995). Besides this, there is still a need for access roads in the smallest categories of private woodland, whereby it appears expedient to combine several small woodland ownership into one development unit (usually according to topographical criteria). Despite integrated planning and high-level development, without doubt necessary on a regional scale, it should not be assumed that every parcel of woodland could be provided with an access road. However, in each individual case the type of construction and development standard must be assessed and determined.

2.2 Recommended planning density

Planning density depends mainly on:

· difficulty of terrain;
· type of access (vehicular access - logging trails);
· construction standard (contractors usually require detailed plans);
· experience of the planner; and
· sensitivity of the landscape.

Since May 1995 road construction in NRW requires notification to the forestry authorities under §6b of the State Forestry Act (Landesforstgesetz). In the case of new road construction it would appear expedient to require that the notification of proposals be accompanied by a topographical map on a scale of 1:5000 or 1:10000 showing the horizontal alignment of the road. Furthermore, the reasons for selecting the alignment should be explained in a brief written description, and a technical report on the design of critical parameters of the planned road (width, type of surfacing) should be included. The proposed course of the road should also be made visible on site before construction work begins. In this way a minimum planning standard will be assured. More precise planning documents, such as earth mass calculations, are only required by the forest authorities in special instances, e.g. in connection with the crossing of watercourses, construction of large-scale embankments, steep sloping sites and proposals in the vicinity of important biotopes ( §62 LG).

It can thereby be assumed that the above-described "minimum standards", as required in a letter of notification - made, if necessary, with the assistance of a forestry official - are within the realm of capability of a forest landowner who is familiar with his property. Any more detailed planning documents require the consultation of expert planners and incur expenses which may run counter to the apparently "low profile" intentions of the law (only notification, no requirement for official approval).

2.3 Recommended dimensioning and layout of roads

Longitudinal section: Gradients in the longitudinal section of the road should be kept at a minimum, but should be in excess of 2 percent. A maximum of 8 percent is desirable. In exceptional cases gradients of up to 12 percent are acceptable for short distances, if this permits substantial savings in the overall segment length.

Site plan: The horizontal alignment in the site plan should be as close as possible to the course of the centre line. Curves should have a minimum radius of 20 m. Centre-line and contour-sensitive alignments are preferable to "streamlined" construction.

Cross-sections: The upbrow should be within as small a width as possible (as a rule on the uphill side 1 m wider than the road with embankment, on the valley side approximately road and embankment width). The roadway width should be approximately 3.5 m with a soft shoulder of about 0.5 m, in adverse topographical conditions (steep slope) approximately 3 m. The roadway should as far as possible be inclined on both sides (watch-glass section) with a camber of about 2 percent in its centre section, increasing to 8-12 percent at its edges, accompanied by a trench on its uphill side on sloping terrain. In order to prevent surface water from collecting, a sufficient number of cross-channels should be incorporated. Diverted water should be allowed to repercolate into the forest floor.

Embankments: The natural angle of incline must be observed in the construction of embankments. Man-made grassing (using indigenous seeds and plants) should be considered only in the case of acute risk of erosion or if rapid natural plant coverage on extremely exposed surfaces is not to be anticipated.

Turning circles and passing points: depend on the individual situation and should be designed according to demand. Turning areas require a large amount of space; culs-de-sac are thus to be avoided as far as possible.

Storage areas: should be constructed as soft shoulders alongside the road (in sloping terrain on the valley side only). The width of these perimeter storage areas should not exceed the Jib length of a truck-mounted crane (approximately 8 m) if used for longitudinal storage. As far as the terrain permits, these perimeter storage areas should be continuous. Storage areas should have a capacity of at least a half truckload of timber.

2.4 Standard surfacing for forest access roads

For technical, ecological and economic reasons water-permeable base and surface courses have become the norm in forestry road construction. For the design of the cross-section, and particularly for lateral run-off of water, it is important that the subgrade and base course are prepared with a camber and not as a flat surface. In the long-term, the so-called watch-glass (arc) or grader sections with varying transverse slopes, increasing gradually to 8-12 percent at the perimeter, and side ditches lend themselves to low-cost motor grader maintenance with minimal ecological disturbance. A diagram of a cross-section is shown in the following figure.

Figure 1. Modern grader or watch-glass section (schematic)

2.5 Recommendations for environmentally compatible road construction1

1 See also "Forest Development and Nature Conservancy" Study Group 1988.

· Excavators - together with bulldozers if necessary - are preferable on construction sites with slopes exceeding 50 percent and in ecologically sensitive areas where the roadway must be kept as narrow as possible.

· Blasting is to be avoided if possible. Hydraulic chisel hammers should be used instead.

· Construction equipment should be supplied with biologically degradable hydraulic fluids, oil binders and suitable tools for sealing leaks. If contractors are used, this stipulation should be made at the tendering stage (this also applies to the following items).

· Only machines should be used which are well maintained and do not lose any significant amounts of fuel or lubricant. It will thereby be necessary to rely on the scrutiny of the contractor, since the vast majority of road construction machines are not subject to compulsory independent inspection (TUV). Machines should be checked daily for leakage of mineral oils.

· Transport of fuels must conform with the Ordinance pertaining to Transport of Hazardous Materials on Roads or exceptions to the same.

· Consideration should be given to incorporating a bonus system into the contractual stipulations for the exemplary execution of construction work, and alternatively for making deductions for shortfalls in goal achievement.

· Contractors whose standard of performance has been exceptional should be especially recommended. Conversely, poor performers should be excluded from future tendering procedures.

· A flexible schedule should be drawn up containing a broad outline of seasonal construction projects. Special consideration should thereby be given to humidity conditions, the growth of vegetation and possible resulting delays in the progress of construction work.

· New road construction should be avoided altogether in "specially protected biotopes" according to the Landscape Act (§62 LG) and existing roads should be examined with a view to reducing their width or closing them completely. The same applies to construction in forest types represented by a very limited overall surface area (Iycopod-beech, lunaria-ravine woodland).

· In sensitive woodland areas, road construction work should be executed in a particularly cautious manner, for instance when cutting into steep inclines, crossing running water or skirting on damp areas with standing water.

· Each new road construction project should be re-examined with a view to abandoning it in favour of other technical means. If the decision is made to proceed with new construction, alignment, design and choice of materials should be determined according to ecological principles. Possible subsidies should also be oriented toward this.

2.6 Suggestions for choice of materials and surfacing

If less foreign materials are used for road construction, the adverse ecological impact can be minimized. Before commencing a new construction project or comprehensive maintenance work, an appraisal should thus be made of the suitability of natural materials already available on site and the extent to which they permit the striven for construction standards to be attained. It is often possible to construct roads with natural materials brought from only a short horizontal distance or to obtain materials by the soil exchange process.

The potential of employing the soil exchange process to obtain suitable material for a load-bearing subgrade or base course is probably considerably greater than presently exploited. The process has been employed with success not only in Triassic formations (shell limestone and variegated sandstone) but also in clay shale, Iydite, porphyry and new red conglomerate in the eastern Harz Mountains (Thuringia). Further experimentation with the process, in particular for Devonian shales, which occur extensively in Nordrhein-Westfalen, is to be welcomed.

After a succession of negative experiences, the practice of excavation can only be recommended when the open cut produces materials of a quality similar to that expected from a quarry (grading curve, material hardness) and when quality control is possible. In addition, there should not be the slightest risk of contaminants or harmful substances (recognized as being of safe origin according to LAGA guidelines).

If suitable construction material cannot be extracted from the immediate vicinity by the above-described process, the following criteria should be observed when obtaining materials from external sources:

1. Mineral material can be obtained inexpensively as pre-screened material. In this case technical expertise and practical experience are essential for continuous quality inspection.

2. Increased quality approaching the level of quality-controlled material with an almost even grading curve usually permits a reduction in the necessary course thickness, but results in increased costs. This increase in quality and price is accompanied by a reduction in inspection requirements and an improvement in the safety margins important for insurance purposes.

3. Transport of materials over long distances causes substantial environmental problems. In the practice of forest access road construction, hauling distances of up to 100 km are not uncommon. In terms of overall ecosystem compatibility, a "sensible" decision on choice of material must include suitable weighting for the hauling distance factor. A disproportionately long hauling distance for mineral construction material should swing the decision, for example, in favour of a local, environmentally compatible and quality-controlled, recycled construction material, or alternatively, limited local excavation of materials in the form of a small-scale quarry for road construction purposes. The latter does not fall under the encroachment rules of the Landscape Act.

4. Materials whose presence can impact the surrounding area (dust generation, lateral conveyance of nutrients in water), as experienced with surfaces comprising cinders and limestone or basalt, should be avoided at all costs in the acidic soils of important biotopes and in florally sensitive zones. This should be taken into account when selecting materials.

5. Because of their tendency to generate a strong microclimate in the vicinity of the forest floor, dark materials intensify the barrier effect for small animals. This should be borne in mind particularly in areas with pronounced amphibian migration.

2.7 Suggestions for use of RCL (Recycling) materials and industrial by-products

1. Employment of recycled building materials and industrial by-products is only viable for environmentally compatible forestry road construction if at least the same material compatibility standards are applied as for public highway construction under current laws and subsequent regulations. This automatically rules out the employment of residual materials that have not been processed under stringent conditions of quality control. Such materials, such as unsorted building rubble, fall under the category of waste and are not to be considered as construction material.

2. For the purposes of forest road construction in the State of Nordrhein-Westfalen, only the analogous application of the ordinance outlined in Chapter 5.3.1, which relegates residual materials to limited applications in road construction outside of hydrogeologically sensitive areas - and obviously outside of ground water preservation zones I and II - can be recommended as a basis.

3. Furthermore, for precautionary and technical reasons:

a) If residual materials are used, the minimum distance from the subgrade to the highest groundwater level should be > 1 m.

b) Unsealed surface courses should be understood as "permeable" and not as "semi-permeable" for the purposes of the ordinance.

4. After a detailed examination of the regulations to determine the suitability of construction materials for forest road construction in NRW, only quality controlled slags and steel mill sand, as well as the recycled construction material RCL II, merit consideration, and then only in the forms as shown in the matrix (summary of the matrices displayed in the ordinance).

5. Before employing quality-controlled residual materials for this purpose, documentation should be assembled, to include a precise definition of the material, a certificate of quality control and a plan showing the area in which it is to be employed (scale 1:25000 or 1:10000), indicating its hydrogeological implications. The basis for this is provided by the map of water table formations in NRW and the regional soil maps as referred to in the notes on the ordinance. This material description and cartographic representation are to become a constituent part of the notification under §6b of the State Forestry Act. (A proposal not covered by this regulation would otherwise necessitate a complex individual consent under the laws pertaining to the protection of water resources, incurring an effort which is completely out of proportion to the generally small-scale forest road construction projects, so that this type of procedure cannot be recommended.)

6. In addition to the requirements relating to the protection of water resources, to ensure that the greatest possible importance is attached to the specific ecological requirements placed on forest road construction (ecological weighting and sensitivity to the surrounding forest vegetation as a natural environment), the use of residual materials which produce a distinct alkaline reaction in aqueous solutions must be warned against in areas or instances where lateral water run-off is likely to carry away nutrients and result in a transformation of the surrounding area. The same applies to the employment of residual materials for surface courses in areas where dust generation from the basic material could cause an undesirable change in the roadside flora. This type of impact will be felt most in the alkaline soils of important biotopes or in nature reserves and should be avoided.

7. To simplify and accelerate the issue of a water authority permit under §7 of the Water Resources Act (WHG), the water authority's approval process for forest road construction can also be facilitated (as currently practised for road improvements by public highway departments). This can either be in the form of a declaration by the applicant that the legal stipulations laid out in Chapter 5.3.1 will be observed to their fullest extent, or a verification of quality assessment from the supplier of the residual material.

8. For the verification of quality assessment, in addition to the certificate of suitability, the seller or supplier of the material must provide the results of monitoring studies carried out by himself or by a third party. Furthermore, it is recommended that for every truckload delivered a confirmation of material characteristics and origin be required in the form of an individual delivery note signed by the driver.

9. When the use of residual materials is under consideration, thought should always be given to the cost of verification of quality assessment and of the simplified water authority permit, as well as to the hard-to-define residual risk with regard to the content of potentially harmful, but hitherto unknown or unidentified substances.

10. A "sensible" choice of materials that harmonize with the integral ecosystem must include appropriate weighting of the hauling distance factor. A disproportionately high cost for hauling mineral construction materials to the site can be a substantial argument in favour of using locally available, approved and suitable residual materials.

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