Vertical Variation in Groundwater Chemistry Inferred from Fluid Specific-Conductance Well Logging of the Snake River Plain Basalt Aquifer, Idaho National Engineering Laboratory, Southeastern Idaho

Authors

Spencer H. Wood, Geosciences, Boise State UniversityFollow
William Bennecke, Geosciences, Boise State University

Document Type

Conference Proceeding

Publication Date

1994

Abstract

Well logging of electrical fluid specific conductance (C_s) shows that permeable zones yielding ground water to intrawell flows and the water columns in some wells at INEL have highly different chemistry, with as much as a two-fold variation in C_s). This suggests that dedicated pump sampling of ground water in the aquifer may not be representative of the chemistry of the waste plumes migrating southwest of the nuclear facilities. Natural background C_s in basalt-aquifer ground water of this part of the Snake River Plain aquifer is less than 325µS/cm (microSiemans/cm), and total dissolved solids in mg/L units, (TDS) ≈ 0.6C_s). This relationship underestimates IDS for waters with chemical waste. when C_s) is above 800 µS/cm.

At well 59 near the ICPP water of 1115 µS/cm (≈670+ mg/L TDS) enters the well from a permeable zone between 521 and 537 ft depth; the zone being 60 ft below the water level and water of 550 µS/cm. At the time of logging (9/14/93) the 1115µS/cm water was flowing down the well, mixing with less concentrated waters and exiting at 600 or 624-ft depth. Waste water disposed of down the injection well at ICPP until 1984 was estimated to have a C_s) of 1140 µS/cm, identical to the water detected in logging.

At well OW2, the highest C_s) water (760µS/cm) is in the upper 30 feet of the water column: water from two flow zones below have different chemistry with lower values of C_s. The Site 14 well and USGS 83 show uniform values throughout the water column. The water column in Site 14 is dominated by a downward flow of 50 gal/min probably entering between 475 and 500 ft depth and exiting near the bottom of the well at 700 ft depth.

Impeller flowmeter and precision temperature logging are used to define and quantify temperature variations and intrawell flows. At well 59 (depth=657 ft) and OW2 (depth=996 ft), are downward decreasing temperatures in the bottom zones of no flow, suggesting that major flow zones lie beneath the deepest parts of these wells.

Publication Information

Wood, Spencer H. and Bennecke, William. (1994). "Vertical Variation in Groundwater Chemistry Inferred from Fluid Specific-Conductance Well Logging of the Snake River Plain Basalt Aquifer, Idaho National Engineering Laboratory, Southeastern Idaho". Hydrogeology, Waste Disposal, Science and Politics Proceedings 30th Symposium Engineering Geology and Geotechnical Engineering, 267-283.