STUDY NUMBER : 10.8 



ORGANIZATION ; University of Montana (UM), Department of Geology 



TITLE OF STUDY ; Geochemical Responses of Sediments and Ground- 

 water to the Draining of the Reservoir at Milltown, Montana 



CONTACT ( S ) ; Anne Udaloy, Department of Geology - 728-3495 



Johnny Moore, Department of Geology - 243-2141 



OBJECTIVES ; 1) Determine how the chemical behavior of metals 

 in reservoir sediments and groundwater are affected by changes 

 in redox environments caused by draining and refilling the reser- 

 voir, 2) determine the factors affecting the mobilization of 

 metals and where they migrate. The investigation is focused 

 on arsenic, copper, iron, manganese, sulfur and zinc. 



CURRENT STATUS ; Existing wells and sandpoints from previous 

 water quality studies are utilized, plus shallow wells at two 

 additional sites, to establish a six-point sampling grid. The 

 wells are constructed as piezometer nests or as multilevel sam- 

 plers. A lysimeter is established at each site at the level 

 of the June, 1986 water table. 



A sediment core sample equal in length to the deepest well 

 at that point is used to define the local stratigraphic sequence 

 of the sediments. The water table is recorded on a biweekly 

 schedule and at the same time samples for water quality analysis 

 are taken from the study grid wells. 



On a monthly schedule, 3 ten centimeter sediment cores are 

 taken at each grid point from the same levels as the water quality 

 Scimples. Sediment analysis includes separation of chemical com- 

 ponents into crystalline particles, organic or metal hydroxide 

 coatings and absorbed or exchangeable ions. Sediment extracts, 

 ground water and pore water are analyzed using an inductively 

 coupled plasma spectrophometer and atomic absorption spectorphoto- 

 meter. 



PUBLICATIONS AND REPORTS 



The investigation is the basis of a Master of Science thesis 

 investigation . 



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