Refining the site conceptual model at a former uranium mill site in Riverton, Wyoming, USA

Dam, William L.; Campbell, Sam; Johnson, Raymond H.; Looney, Brian B.; Denham, Miles E.; Eddy-Dilek, Carol A.; Babits, Steven J.

doi:10.1007/s12665-015-4706-y

Table 1 Summary of new activities to refine the CSM

From: Refining the site conceptual model at a former uranium mill site in Riverton, Wyoming, USA

Original CSM deficiency	Refined CSM need	New activities
Plume source area: elevated contaminant concentrations in groundwater still remain at the former mill site (source area)	Enhanced delineation of groundwater plumes and soils in the source area	Install additional monitoring wells; collect additional groundwater and soil samples
Stagnation of groundwater plumes: high concentrations in the vicinity of the Little Wind River as a result of groundwater flow conditions	Groundwater flow direction and groundwater gradient near the river	Collect discrete and continuous groundwater-level data; install stilling wells, measure river elevations; model groundwater flow
Stagnation of groundwater plumes: high concentrations in the vicinity of the Little Wind River as a result of geochemical influences	Better definition of geochemical influences on plume stagnation near the Little Wind River	Install and sample well points adjacent to the river; collect soil samples from borings to characterize organic-rich sediments; perform column tests and geochemical modeling
Secondary contaminant distribution: spikes in concentrations were measured after flood events	Contaminant distribution and concentrations in soil and aquifer materials	Collect samples from borings to characterize organic-rich sediments and evaporite layers; perform laboratory testing and analyses
K_d approach to contaminant transport did not account for additional geochemical processes, including contaminant concentration increases after a flood event	Characterization of the solid phase to better understand the geochemical processes that control contaminant transport	Collect soil samples from borings; perform laboratory testing and analysis of soil samples; perform geochemical and reactive transport modeling
Surface water infiltration and the effect on groundwater flow and contaminant plume configurations	Account for all surface water infiltration	Measure flows in ditches, canals, and fields; measure groundwater levels continuously; survey Wind River elevations north of the site; use USGS Wind River gaging station data; model groundwater flow

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