Geothermal activities possibly responsible for tree death

New data from the United States Geological Survey (USGS) has shed light on the effects of Ormat Technologies’ geothermal power plant activities in the Long Valley, including the possibility that hot geothermal water is mixing with the non-geothermal water – otherwise known as Mammoth’s drinking water.

There is little new data concerning the tree kills associated with the geothermal extraction, because most of that information has already been published. The connection between the two has been documented since 2006. The findings of a 2015 USGS report found ground temperatures in and around proposed well sites for the Casa Diablo IV project to be 199 degrees Fahrenheit seven inches below the surface.

Geothermal water extraction and reinjection creates an imbalance in pressure between the hot, geothermal resource and cold water tables. The water in the resource then boils at a lower temperature and the steam rises to the surface, heating the ground and the roots of trees.

Bill Evans, Chemist Emeritus for the USGS, has been studying tree kills and geothermal activity in Long Valley since the early 1970s, and will be giving a presentation on the new chemistry data from the USGS report at the Long Valley Hydrological Advisory Committee meeting at 10 a.m., Wednesday, August 10 in the Town Conference Room above Giovanni’s Restaurant.

He told The Sheet on Tuesday, August 2 that he has seen steam coming out of the knot holes in trees.

Data supporting the correlation between tree kills and geothermal extraction was included in the Environmental Impact Report for the Casa Diablo IV project. The Bureau of Land Management, which oversees the land, has yet to give the project the final approval. However, the direct relationship was not considered an “adverse effect” in the EIR and so did not require a mitigation plan.

The connection between tree kills and geothermal extraction has been disputed, but, Evans said, most would agree that geothermal power production is causing trees to die. These tree kills are different from those around Horseshoe Lake, caused by tectonic activity and high concentrations of CO2 being emitted.

Click here for more