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accidental pollution

Accidental pollution is the result of the discharging of polluting substances in case of an accident in which vehicles transporting toxic or dangerous substances are involved.

Polluting substances are those substances that constitute danger both from the point of view of the security and the public hygiene when they are transported. Here belong: liquid hydrocarbons, chemical products transported in tanks, the gas from gas cylinders or tanks, packed chemical products, bitumen, explosives, radio-active materials.

The risk of accidental pollutions grows with the traffic, so does the impact upon the environment factors: surface and subsoil water layers, soil (depending on the vulnerability of the area and the quantity and nature of the discharged product).

1. water

1.1. Sources of pollution

When serious car accidents take place, liquid hydrocarbons, construction materials and other toxic or corrosive products can be discharged on the platform of the motorway or on the neighboring fields.

Most of these accidents are caused by the inadequate signs or inadequate speed to the road conditions (wet surface, glaze, ice, holes, etc.). The risk of accidental pollution grows with the traffic.

Statistics show that 80% of the accidents happen rather in crowded areas than on motorways.

1.2. the impact upon environment

The probability of the discharging of dangerous materials can be estimated by the annual average number of accidents involving dangerous materials and by the national traffic with such products. It is supposed that the accident is a random phenomena that abides by Poissons law:

Prob (K) = e-K * mK/K! the probability to have K annual spreading on a chosen sector,

where: m annual average number of spreading/ Km

The information provided by the SETRA Study regarding the Water Protection against Traffic Pollution   have been considered as hypothesis and data for the estimation of the probability of unloading dangerous materials on a reference route.

The simplifying hypotheses that have been taken into account are the following:

an annual average number of accidents involving dangerous substances of about 25/an;

cool traffic with dangerous substances: 12 x 109 t / km / year;

average daily traffic heavy vehicles: N (VF/day);

average weight for a heavy vehicle: 15 t;

transport of dangerous materials: about 13% of the transported weight (national average).

Tp cool traffic of dangerous substances (t / Km / year):

Tp = N (VF/day) x 15 t / vehicle x 13% x 300 days / year

m annual average number of spreading / km, it has been considered that one of two accidents generates an overflow of dangerous substances:

m = (250 / 12 x 109) x Tp x 0,5

The calculation has been made for the traffic anticipation of the year 2025.

Table nr. 1.2. 1 Annual average number of spreading - Km


N (VF/day)

Tp (t / Km / year)


Bucharest Snagov

Snagov Dumbrava

Dumbrava Ploiesti

Ploiesti Belt road - Buda

Ploiesti Banesti

Banesti Comarnic

Comarnic Sinaia

Sinaia Predeal

Predeal Codlea

The effects upon the receiver depend on the discharged product and the nature of the receiver.

Special studies classify dangerous materials in three categories:

Category A - substances that generate changes of the waters pH (acid or basic),

Category B low toxicity substances but which make water impossible to drink by modifying its organoleptic properties,

Category C high toxicity products.

The effect of accidental pollution manifests by a rapid dispersion of the dangerous materials that are transported into the atmosphere. The impact is felt at the level of the acquiferous layers, lakes, ponds or running waters in the area. The impact depends on the quantity of the substances that have been discharged and reached the receiver and its self-filtering capacity.

The effects upon the subsoil water layers

If the accident took place in the area where the subsoil water layer is cantoned in alluvial soils, the advancing time of the water is long enough to avoid the risk of distribution of the polluted water. Cleaning is difficult but the polluted areas can be settled.

If the accident took place in an area where the ground is fissured (the case of limestone), the polluting substance advances rapidly through the gaps, the risk of the distribution of the polluted water is high and the cleaning and the settling are impossible because the circulation of the water is little known.

The effects of toxic or dangerous substances overflow upon the subsoil water layers depend on:

the level of the subsoil water layer,

the general flow direction of the stream,

the filtering degree.

The levels of the water layer vary along the motorway, where the polluting substances accumulate easier, between 2,5 3,0 m in the valley areas and 15 20 m. Generally, the quality of the water in the subsoil water layer is not drinkable because of the agricultural activities and the overflows from the industrial plants.

Pollution phenomena of the subsoil water layer have been seen in the area of Ploiesti City, respectively the area of the oil distilleries. In these areas the accidental polluting phenomena may constitute a supplementary factor of aggression.

In Brasov, in the area of the Codlea locality, the acquiferous layer is polluted because of the overflows generated by the industrial plants. In these areas the accidental polluting phenomena may constitute a supplementary factor of aggression.

The effects upon the surface water layers

A total or partial destruction of the flora and fauna can happen on a tens of km section, depending on the down-stream confluences, as a result of a sudden overflow into a water course the dissolution capacity of which is incompatible with it.

If the product is soluble or miscible with the water, the effects are still important but short; the polluting substance is transported down-stream and thus the organisms will be able to progressively colonize the area again.

If the overflow takes place into a still water then all the polluting forms are harmful and the process of recovery of the quality of the water is slow. This is the case of the Snagov and Caldarusani lakes where special attention needs to be paid in order to avoid the polluting substances overflow as a result of accidental pollution.

1.3. Environment protection measures

The measures that need to be taken in order to limit the negative impact in case of accidents are the following:

v    the local interruption of the ditches,

v    the traffic deviation,

v    the cleaning of the ditches and of the land, if necessary.

The project suggests the realization of some constructions for the filtering of the meteoric water that washes the platform of the motorway before being discharged into an emissary or on the neighboring fields.

2. soil

2.1. Sources of pollution

The sources of pollution for the soil are the same as for the surface and subsoil water layers namely the overflow of toxic or dangerous substances as a result of a car crash involving vehicles which transport them.

2.2. The impact upon soil

The impact upon the soil caused by the accidental overflow of toxic or dangerous substances depends on the vulnerability of the area and the type and quantity of the discharged product.

According to the special literature the following elements should be taken into account:

there are no soils impermeable to hydrocarbons; their penetration and migration can only be limited;

in the case of the soils with interstitial porosity the speed of the oily phase depends on its thickness: being lighter than the water the hydrocarbons accumulate at the surface of the acquiferous layer where the superficial tension created when the two liquids meet stops the displacement of the water-oil complex.

The effects upon the soil depend on its type; the alluvial type soils have the property to render the filtering process of the polluting substances towards the deeper layers more difficult.

The sodium is rapidly fixed within the superficial layers and the accumulated quantity depends on the type of the soil.

2.3.Environment protection measures

We can enumerate some of the protection measures with a general and preventive character:

v     in case of accident the driver has to inform regarding the nature of the transported product;

v     the existence of a prevention and intervention plan in case of an accidental pollution;

v     the limiting of the speed for the vehicles which transport toxic or dangerous substances, in order to avoid accidents;

v     the vehicles which transport dangerous materials should be provided with protection systems;

v     the identification of the sensitive areas (soil, surface and subsoil water layers).

The existence of an adequate signal and marking system on the motorway generates a lowering of the risk of accidents.

The urgent announcement of the special services such as The Environment Protection Inspectorates, the Fire Department, the Civil Defense and the Police should be done in case of accidental pollution. The suggested measures for the surface and subsoil water layers protection regarding the blocking of the water in the ditches, traffic deviation, the cleaning of the ditches and land, if necessary are compulsory measures for the soil protection.

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