EVALUATION OF NATURAL VULNERABILITY TO CONTAMINANTS APPLYING DRASTIC INDICES
Abstract
The characterization of environmental susceptibility to pollution is fundamental for decision making on
land use and occupation. The vulnerability indices constitute useful tools to help protecting the quality of the groundwater,
given the technical and economic limitations to remediate the existing contamination. The DRASTIC index was used here to
evaluate the natural vulnerability of aquifer constituted by the weathered basaltic rocks of the Serra Geral Formation. The
DRASTIC method was chosen in this evaluation for its simplicity, low cost, easy application and because it has been widely
used for analysis of the natural vulnerability. The weathered layers of basalt consist of silt-clay, providing aquifer protection.
However, a large number of wells crosses extremely fractured weathered basalts (saprolite), favoring groundwater flow.
Hydraulic conductivity obtained from slug tests range from 213,4 to 25,6 m/d, averaging 110,4 m/d. In general, the
vulnerability of the studied area can be classified as moderate, while that in the water divide region and in the vicinity of
ribeirão Lindóia are ranked low and high, respectively.