VIDEO - Geological Field Work / by federico trevia

The presence of arsenic in the groundwater is dependent on the geology of the area. The aim of the Geo-Team (Tiemen Wegman and Bart Veenings) is to find a suitable location for a future water treatment unit in Harian. Finding a water source with low arsenic concentration would reduce the effort and the costs of a new filter. 

In order to study the geology, will perform three drillings in total. One drilling takes places in an area where the groundwater is severely contaminated with arsenic, one drilling in a medium arsenic contaminated area and the last drilling in a arsenic safe area. A method that is normally used for the installation of tube wells has been used for the drillings. Every 5 feet a soil sample has been taken. As a result of the drilling technique that is used the samples are disturbed, the samples give however still a good indication of what is down there.

Immediately after extraction of the sample a physical inspection and classification of the soil will be done. That means that the grains size, mineralogy, texture and colour of the soil is noted down. After classification of the samples, all samples are placed after each other to get a soil profile. We hope to see a difference in the sand layers between the different drillings. Theoretically the sand that is encountered in the arsenic contaminated area should black or dark grey, while in the arsenic safe area it is expected to be reddish.

The drilling shown in the video was located in an arsenic contaminated area. The aquifers that are encountered during the drilling contained rather dark coloured sand. This is an indicator of arsenic in the groundwater. The maximum depth that was reached is 170 feet (51 metres). A stiff clay layer was encountered at this depth, the drillers where not able to drill through the hard layer and had to stop the drilling.Many villagers were really interested in our Geo research and they all helped us with their knowledge  of the soil and the area.