Studies of environment of a road project

The code of the environment, created in 2000, defines rules which are essential on the projects of road infrastructures, and gathers a whole of legislative texts.

The impact study

An obligation beyond 1,8 M€

In France, any realization or modernization of an infrastructure whose cost of project is higher than 1,8 M€ must be the subject of an impact study. One can note that this financial threshold is not ecologically coherent: an inexpensive project concerning a medium of great value escapes this obligation. It is moreover interdict to cut out a road great project ( by “saucissonnage” ) in several individually treated sub-projects, making it possible the whole of the project to escape a public survey with impact study.

Its contents

To carry out the impact study, all the sets of themes directly dependant on the environment (water, air, fauna, flora), but also on the environment of the human being must be approached.
In addition, an European directive imposes on the great projects and programs a EIE (evaluation of the incidences on the Environment), as well as a consultation of the population before granting or not the authorization of construction of the project. In the same way any already made EIE must be brought up to date if the project undergoes changes likely to modify considerably its total incidence compared to the preliminary draft.

The obligation of an evaluation of the impact of the project on the human Santé was imposed by the Loi on the air and the rational use of energy. This one aims rationalizing the energy utilization and at laying down a public policy integrating the air as regards urban development. She recognizes in particular with each one the right to breathe an air which does not harm its health. It is necessary for each studied topic, to define a coherent and relevant perimeter. The space effects are indeed different according to the parameter considered (infrasonic vibrations, vibrations, noise, air pollution, harmful effects luminous, etc)

The perimeter of the zones of influence could be defined according to the boundary conditions (biogeographic unit, or area catchment for the terrestrial environment. It can also depend on the functional relations between medium, for better taking into account the impacts differed from the project in space and time. In the case of the 1% Landscape of the Highway A 16, the principle selected was that of the zone of “Co-visibility” , which does not have an ecological direction.

Thus for each perimeter the characteristics in the beginning, and the impacts of the project for each solution considered will be defined.

Its mode of realization

The realization of these studies is entrusted to specialized research departments which gather the competences proven (university qualifications) in the studied fields. But their work is sometimes made difficult by the lack of available data or state-zero .

The superintendent of project defines the schedule of conditions of these studies. He must thus have a minimum of competences in the field. For this reason, it can force the methods of investigation to be implemented. These last cover the shape of the biological inventories (i.e. parameter lists to be evaluated), the stations to be measured, the time interval between measurements, the mining methods of the data, and presentation of the results forms it.

Water

The law on water reinforced the obligations of building precaution the owner protection of this resource, which one measures the value more and more.

Need

On the road infrastructures, the surface waters take care of contributions coming from exhaust fumes, of the wear of the roadways and the parts of the vehicles (brake pads, tires for example).

As example the annual throughputs on a two-track road supporting a traffic of 10.000 vehicles per day rise with:

Suspended matter: 200 to 1200 kg/km
chemical Demande oxygenates of it: 230 to 400 kg/km
Lead: 0,9 to 1,3 kg/km
Zinc: 1,5 to 2,5 kg/km
Hydrocarbons: 5 kg/km

It is thus necessary to envisage devices of recovery of surface waters coming from a road platform.

Constraints of installation

The importance of the equipment to be installed depends on the sensitivity of the receiving medium. They for example are limited when the grounds surrounding the place of discharge system are impermeable. With contrario, they must be sophisticated for zones very permeable and located at the top of a Nappe of subterranean water. In the cases extrèmes, it is thus necessary to completely waterproof the influence of the road, including the Accotement S. In this case it is even necessary to implement devices preventing the inversion of the vehicles except influence (ground slope for example).

It is necessary to take into account constraints of exploitation of the infrastructure. It is the winter viability which is most significant at this stage. The pollutants are in the case in general the Sodium chloride, but also sometimes the Calcium chloride and the Chlorure of magnesium. The latter are effective fluxes at temperatures lower than -5°C.

Another data to be taken into account is accidental pollution, related to the accidents. The accused matters are in this case mainly the Hydrocarbure S. not being miscible in water, they have a very important capacity polluting. Protection against this kind of pollution is carried out by separating basins which make it possible to isolate hydrocarbons from water, very often by walls siphoïdes.

Fauna, flora, ecosystems

The impact on the natural environments must be appreciated on the whole of a coherent Biotope or an ecological zone, since the project affects ecological balance, the functionalities of the ecosystems and balances fauna-flora. The hot areas are more and more delimited and protected by classifications regulating the realizable uses and equipment with their access. They are ZNIEFF (natural zone of faunistic and floristic ecological interest), ZICO (important zone for the conservation of the birds) and maintaining protected areas within the framework of the European directive on the habitat of the natural species (Natura 2000).
The Wetlands, whose Marsh and Banks, constitutes biotopes rich in flora and fauna, of high interest and in regression. These zones are biologically very rich. Moreover they contribute to the absorption of the carbonic gas emitted by transport in the air, their production vegetable is the first element on the one hand major of the terrestrial food chain (invertebrates, birds, mammals.).

Study must also to relate to impacts in term of Fragmentation ecological, and on corridors of migration of animals, including night S (Environment night has often be forgotten by impact studies, whereas the road projects take part in the phenomenon known as of luminous Pollution, which in many countries increases by 4 to 5% per annum, of the years 1995 to 2005). These aspects will be studied with the objectives to propose devices to be implemented to maintain these migrations, while guaranteeing the safety of the road users, for example by means of écoduc S who can strongly limit the Roadkill

Impact on health

The constraints of protection of health are essential now on the routiers18 projects. This set of themes must be developed in the impact studies, and the compensatory measures or preventive must be implemented by the building owner.

The shutter health of the impact study must in particular evaluate the initial state in term of mortality and morbidity on a zone of relevant study. It must then evaluate the incidence of installation on these data.
Thus zones of passage could be completely condemned so protection measures are not realizable. Extreme example, the passage of main road 1 in Paris (completely covered passage).

Noise

The law on the noise of December 31st, 1992 and the decree on enforcement of a law of May 5th, 1995 seriously modified the preceding regulations. These texts in particular took into account the night noises and the use which is made buildings.
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The measuring unit of the noise or noise level, is the decibel has dBa, the index has means that the various frequencies present in the aural signal are the subject of a weighting. The noise level at a given time is insufficient to give an account of noise pollution to which can be subjected the residents of an transport infrastructure.

More representative indicators were elaborate. They are the equivalent noise levels for a certain period (Leq (A) or Laeq measured in dB (A).

The evolution of the legislation leads to a retreat of approximately 100 m of the source of noise to pass from the isophone 65 dBa to the isophone 60 dBa. The studies of noise must from now on take into account a certain number of new parameters which have a great influence on the transmission of the noise, in particular the weather conditions.

The difference in measured noise with 200m can vary from 15 dBa according to whether the conditions are favorable or not. The most favorable conditions take place the night with the inversion of the temperatures and by bearing wind.

The road noise comes from the noise of the engines and bearing. The legislation also modified the noise levels maximum of a vehicle.

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The lawful and technical evolutions made it possible to decrease the noises of the engines considerably.

The noise related to the bearing became the primary source emitted by the vehicles for high speeds to 50 km/h and starting from 70 km/h for the PL. Two factors are obviously at the origin of this noise: the road coating and the tire. The progress made in the field of the bituminous mix made it possible to decrease this noise: particularly for the bituminous mix with low granulometry (0/6).

The means to fight against the noise in a road project can take several forms:

Reduction speed,
establishment of the way compared to the built-up areas (average noise level decreases by 3 dB each time the distance is doubled),
construction of ground hillocks,
longitudinally lowers profile compared to the original ground,
anti-noise walls,
insulation of the buildings.

Studies of town planning

The studies of town planning are fundamental for the study of an transport infrastructure in zone agglomerated or perished agglomerated.

These studies will highlight the assignment of the zones inside the perimeter of study (zone of economic activities, retail parks, zones of habitat by distinguishing collective habitat, individual habitat population density…). It will be taken into account the development projects registered in the various documents of planning like SCOT, the RAINED, the particular ZAC, but also development projects.

Information making it possible to feed the reflection is available in the town halls, the communities of agglomeration or communes, the DDE, the chambers of commerce….

It will be then necessary to define the needs for exchange of these zones between them, but also with the communes, the areas close. These data will feed also the studies of circulation. They will also make it possible to position the terminal points and their nature.

As we indicated for the other sets of themes and as soon as the project is defined, it will be also necessary to study the impact of the infrastructure on the development of the zones concerned.

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