New hydrogeochemical data from Kosova and southern Siberia agree with previous studies from Botswana and Moldova in suggesting that high densities of pit latrines (and other domestic pollution sources) in rural villages can result in contamination of potable groundwater supplies by microbes and nitrate. Concentrations in excess of 100 mg/l nitrate have been recorded in each of these areas, at which levels small children may be endangered by methaemoglobinaemia. The sanitation and water-supply conditions are believed to be typical of large areas of Eastern Europe and the former Soviet Union. It is likely that poor sanitation and conflict with potable-water supplies are among the main sources of environmental risk to populations in these areas, rather than the industrial and military contamination upon which so many international collaborative programmes have focused.

The San Jos6 Mine is a mothballed Ag-Sn mine near Oruro on the Bolivian Altiplano. A groundwater risk assessment has been carried out considering: (i) the current mine water pumping operation; (ii) potential future mine flooding; and (iii) mine waste leachate, at risk sources. Mine flooding rates have been simulated using two models (MIFIM and MODFLOW), with input data based on the observed water inflow distribution and calculated mine volumes. Mine water chemistry has been characterized by field analyses. Transport of contaminants in groundwater in the Quaternary sedimentary aquifer complex surrounding the mine has been assessed by empirical data and hydraulic-geochemical modelling using MODFLOW and MPATH. Empirical and modelled data suggest that no risk is (or will be) posed to Oruro's public water supply wellfields at Challapampa. Continued pumping and discharge of mine water poses a potential risk to surface water recipients and private groundwater abstractions located alongside these.

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This report has been reproduced directly from the best availattie copy.Available to DOE and DOE contractors . . ( H 2 0 2 ) , if applied at sufficient loadings to contaminated soils, can effectively oxidize trichloroethylene (TCE) and perchloroethylene (PGE). Between the two oxidants, KMn04 is more stable and may result in a higher rate of TCE degradation. LIST OF TABLESIn 1996, researchers at Oak Ridge National Laboratory ( O N ) proposed an oxidant delivery technique involving injection and recirculation of the oxidant solution into a contaminated aquifer through multiple horizontal and vertical wells. This technique would be applicable to saturated, hydraulically conductive formations. In the spring of 1997, the Department of Energy (DOE) at the Portsmouth Gaseous Diffusion Plant (PORTS) agreed to collaborate with the DOES Subsurface Contaminants Focus Area to conduct a field-scale treatability study using in situ chemical oxidation through recirculation (ISCOR). PORTS agreed to support the demonstration at the X-701B site where the technology can potentially be used to remediate TCE-contaminated groundwater and sediments. The ISCOR field demonstration took advantage of existing infrastructure and extensive site characterization data generated from previous field demonstrations at X-701B. The field test was implemented using a pair of previously installed horizontal wells that transect an area of DNAPL contamination. Groundwater was extracted from one horizontal well, pumped to an existing pump and treat facility, dosed with KMnO4, and re-injected into a parallel horizontal well approximately 90 ft away. The field demonstration lasted approximately one month. Treatment effectiveness was determined by comparing contaminant levels in pre-treatment, during, and post-treatment groundwater samples and preand post-treatment soil samples Analytical results from the field demonstration indicate that ISCOR is effective at oxidizing TCE in the saturated zone. Lateral and vertical heterogeneities within the Gallia impacted the ability to deliver oxidant solution uniformly throughout the area between the horizontal wells. Furthermore, TCE in the neighboring low-permeability formations (the Sunbury and Minford layers) was not affected by oxidant recirculation through the G a l l i a . The oxidant may not have had time to diffuse from the Gallia into the Sunbury or Minford formations given the short duration of this test. However, in general, TCE was not detected where oxidant was present in samples collected from Gallia monitoring wells within the test region. Reduction of the TCE mass within the more conductive Gallia formation will lead to an overall reduction of TCE mobility within the X-701B area. Long-term groundwater monitoring will be required to fully assess the impact of this demonstration on the ISCOR test region.. vi ACKNOWLEDGMENTSThe planning and execution of the full-scale demonstration required the efforts of many individuals. The contributions of the following are recognized and appreciated.