Overall project impacts are minimal, and involve land and access at the drilling site for the borehole, and also along right-of-ways of roads for acquisition of planned seismic surveys. Impact includes short-term surface disruption of 2 to 3 acres required to construct a drilling rig location site for the test borehole. Drilling operations are normally performed on a 24-hour basis, which shortens the overall duration of the project but incurs some impact to the surface lands. Expectations are that up to 50 days on the site will be required for geologic assessment from start to finish, and between two and three weeks to perform seismic line data gathering along town or county road right-of-ways. During the drilling process, diesel-powered drilling equipment will not exceed 100 decibels – about the same level of noise one would hear standing next to a running snowmobile or motorcycle. Noise levels drop as distance from the noise source increases. For example, at 800 feet away, the noise from a drilling rig will be approximately 74 decibels, a little less than the noise from a telephone dial tone. The TriCarb team is working to select a drilling site that is far enough from homes and businesses to minimize noise impacts. Dense vegetation, site layout, topography and infrastructure, such as buildings, can also help minimize noise impacts.
A seismic survey is a technique used to develop images of the rock strata and structure. It is an important tool for characterizing a region for carbon storage because, combined with information from test borings, it helps researchers gain a better understanding of the thickness, depth, geometry, orientation and structural features of different rock layers. In conducting a seismic survey, scientists use a “seismic source” – in this case truck-mounted equipment – which sends vibrations into the earth for a few minutes at a time, then measures the travel time of the resulting pulses as they are reflected back to the surface. Scientists measure the differences in the amount of time it takes for sound waves to bounce off the rock layers and be detected by the geophones. Computers help calculate the thickness and other properties of the rock strata.