Water Quality Improvement

The slow percolation of contaminated runoff into the pavement through a porous aggregate layer to an outlet substantially slows water movements, provides the possibility of filtration and allows water to pass by a large surface area of stone. By these means the water drops the suspended, fine, solids that it is carrying into the pore space of the pavement layers. The contaminants tend to adhere to the surfaces of the porous material’s particles — particularly to the fine fraction as it provides the largest area of fines. Hydrocarbon contaminants also tend to be sorbed to the solids. For these reasons the water that leaves the pavement is substantially

Hardness

Conductivity

Copper

Zinc

Motor oil

(mg CaCO3)

(pmhos/cm)

(Pg/l)

(Pg/l)

(mg/l)

Infiltration

Table 13.3 Mean concentrations of detected constituents in water running off or through 5 exper­imental pavements (from Brattebo & Booth, 2002)

Plastic grid filled with sand. Grassed

23.4

48

1.29 (6)

10.8(2)

<detection

Plastic grid filled with sand

14.7

38

<detection

14.3

<detection

60% open concrete blocks filled with gravel. Grassed

47.6

114

1.88(4)

12.2 (3)

<detection

90% solid concrete with gravel

49.8

Surface run-off

113

1.7(7)

8.6 (3)

<detection

Asphalt

7.91

14.1

9.07

22.2

0.183(1)

The water from 9 storms was measured. The number in parentheses indicates the number of sam­ples in which contamination was at less than the detection limit.

Updated: 24 ноября, 2015 — 11:59 пп