Categorical Exclusion Determination
Office of NEPA Policy and Compliance
November 30, 2016
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The U.S. Geological Survey (USGS) needs geologic, stratigraphic, and hydraulic data for the purpose of characterizing groundwater flow and water quality in the eastern Snake River Plain aquifer. Monitoring wells are constructed to obtain the needed data, and the USGS has identified the need for an additional monitoring well. The proposed well is needed to provide coverage for information gaps related to regional geologic stratigraphy and groundwater flow by providing water quality and water level information near the west central section of the Idaho National Laboratory (INL). The proposed action would continuously core geotechnical borehole USGS-145 to a depth of about 1,000 ft below land surface. After coring, USGS-145 would be constructed as a monitor well and used to measure and collect aquifer data. Borehole USGS-145 is sited about 5 miles north of the Radioactive Waste Management Complex (RWMC) and about 7 miles northwest of Central Facilities Area (CFA) off of highway 20/26 (Figure 1), and will serve as a new downgradient regional monitoring well of the Naval Reactors Facility (NRF) and Advanced Test Reactor (ATR) Complex facilities.