Environmental Engineering Reference
In-Depth Information
Ecological Resources
Most impacts on ecological resources (vegetation, wildlife, aquatic biota, special sta-
tus species, and their habitats) would be low to moderate and localized during explo-
ration and drilling (although impacts due to noise could be high). Activities such as
site clearing and grading, road construction, well drilling, ancillary facility construc-
tion, and vehicle traffic have the potential to affect ecological resources by disturbing
habitat, increasing erosion and runoff, and creating noise at the project site. Impacts
on vegetation include the loss of native species and species diversity, increased risk of
invasive species, increased risk of topsoil erosion and seed bank depletion, increased
risk of fire, and alteration of water and seed dispersal. Exploration and drilling activi-
ties have the potential to destroy or injure wildlife (especially species with limited
mobility); disrupt the breeding, migration, and foraging behavior of wildlife; reduce
habitat quality and species diversity; disturb habitat (e.g., causing loss of cover or
food source); and reduce the reproductive success of some species (e.g., amphibians).
Accidental spills could be toxic to fish and wildlife. The noise from seismic surveys
and drilling has a high potential to disturb wildlife and affect breeding, foraging, and
migrating behavior. If not fenced or covered in netting, sump pits containing high
concentrations of minerals and chemicals from drilling fluids could adversely impact
animals (e.g., birds, wild horses and burrows, grazing livestock). Surveys conducted
during this phase to evaluate the presence and significance of ecological resources
in the area would assist developers in locating sensitive resources and siting project
facilities in such a way as to avoid or minimize impact to these resources.
Water Resources
Impacts on water resources during the exploration and drilling phase would range
from low to high. Survey activities would have little or no impact on surface water or
groundwater. Exploration drilling would involve some ground-disturbing activities
that could lead to increased erosions and surface runoff. Drilling into the reservoir
can create pathways for geothermal fluids (which are under high pressure) to rise and
mix with shallower groundwater. Impacts of these pathways may include alteration
of the natural circulation of geothermal fluids and the usefulness of the resource.
Geothermal fluids may also degrade the quality of shallow aquifers. Best manage-
ment practices based on stormwater pollution prevention requirements and other
industry guidelines would ensure that soil erosion and surface runoff are controlled.
Proper drilling practices and closure and capping of wells can reduce the potential
for drilling-related impacts.
Temporary impacts on surface water may also occur as a result of the release of geo-
thermal fluids during any testing, if they are not contained. Geothermal fluids are hot
and highly mineralized and, if released to surface water, could cause thermal changes
and changes in water quality. Accidental spills of geothermal fluids could occur due
to well blowouts during drilling, leaks in piping or well heads, or overflow from sump
pits. Proper well casing and drilling techniques would minimize these risks.
Extracting geothermal fluids could also cause drawdowns in connected shallower
aquifers, potentially affecting connected springs or streams. The potential for these
types of adverse effects is moderate to high, but may be reduced through extensive
