Arsenic and Boron in the Tongonan Environment

Abstract

Arsenic and boron occur in higher concentrations in Tongonan hydrothermal fluids than in those of most other geothermal projects, and are the elements most likely to cause problems in the local environment. Mercury levels are low, and H2S is unlikely to have adverse effect in view of local geography and rainfall. Streams in the steam field join rivers flowing though a rice irrigation scheme and out to sea in an area which is intensively fished, hence the clear necessity to minimize environmental damage. Studies during project development led to the proposal of site specific concentration limits for As and B, with subsequent monitoring to assess their validity. Well testing is programmed to take account of these limits in conjunction with expected flow rates and chemical characteristics of the separated fluids. Injection wells are or will be provided to accept all effluents except those from isolated exploration wells in distant parts of the field.