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Hydrogeologic characterization report for the Rocky Flats environmental technology site

Conference ·
OSTI ID:474022
;  [1];  [2]
  1. S.M. Stoller Corp., Boulder, CO (United States)
  2. RMRS, Golden, CO (United States); and others
The Denver groundwater basin encompasses approximately 6,700 square miles, extending east from the Front Range of the Rocky Mountains. This structural basin contains four Cretaceous bedrock aquifers overlain by a regional Quaternary alluvial aquifer. The Rocky Flats Site is located on the northwest margin of the basin. The shallow groundwater system at the Rocky Flats Site is divided into upper and lower hydrostratigraphic units (UHSU and LHSU, respectively). The UHSU at the Rocky Flats site comprises Quaternary alluvium, colluvium, valley-fill alluvium, artificial fill, weathered bedrock of the undifferentiated Arapahoe and Laramie formations and all sandstones that are hydraulically connected with overlying surficial groundwater. The LHSU comprises unweathered claystone with interbedded siltstones and sandstones of the undifferentiated Arapahoe and Laramie formations. The contact separating the UHSU and LHSU is identified as the base of the weathered zone. The separation of hydrostratigraphic units is supported by the contrasting permeabilities of the units comprising the UHSU and LHSU, well hydrograph data indicating that the units respond differently to seasonal recharge events, and geochemical data reflecting distinct major ion chemistries in the groundwaters of the UHSU and LHSU. Surface-water/groundwater interactions at the Rocky Flats site generally respond to seasonal fluctuations in precipitation, recharge, groundwater storage, and stream and ditch flow. Effluent conditions are dominant in the spring along western stream segments and influent conditions are common in the late summer and fall along most stream reaches.
OSTI ID:
474022
Report Number(s):
CONF-960804--Vol.2
Country of Publication:
United States
Language:
English

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