Reuse of Solid Waste from the Clearing of Road Basins and Ditches in Civil Engineering: Environmental Characterization, Ways of Treatment and Their Efficiency - Highway and Urban Environment - page 177

Table 1 MTE average and maximum contents in ditches sediments
Element Average Maximum

Cadmium 0.43 1.5

Lead 79 550

Zinc 190 1620

Chrome 43 210

Copper 74 1800

Nickel 28 115

3 000

VCI

2 500

2 000

1 500

1 000

In ert waste

VNF to u t u s a ge

500

0

0 10 000 20 000 30 000 40 000 50 000 60 000 70 000 80 000 90 000 100 000

(mg/kg)

AADT (veh ./day)

Fig. 2 Variation of sediment hydrocarbons contents with daily traffic

We observed that these pollutants are likely to exceed threshold values for traffic
above 20,000 vehicles/day. Fig. 2 presents the observed results for lead and
hydrocarbons.

Road basin: Studied parameters concerning road basins are: traffic, size of
carriageway, cleaning out frequency. No link could be established on carriageway
size parameter: this result seems pertinent as it has been established in a former
document [3] that pollutions gathered in runoffs depend more on traffic than on
carriageway size. Cleaning out frequency seems to point out that MTE concentration
increases with the last cleaning out date: this result seems to be coherent with a
renewing car fleer which emits less pollutants (Fig. 3 ).
Likewise, safety barriers, the main zinc source, tend to emit less zinc over
the course of some years [4] . These results are however to interpret prudently:
the number of basins where the last cleaning out date is known is limited, and the
collected data deals with a short cleaning out duration.