permost underground layers, the study of which made it possible to propose a system for rehabilitating a layer by pumping out contaminated water. Such measures are necessary because the alluvial layer drains into and possibly contaminated the Cheptsa River. The magnitude of seepage losses from the tailings repository was calculated, broken down by elements of the water balance and including three calculation stages: (1) calculation of initial data, (2) calculation of balance inputs, and (3) calculation of balance outputs. The maximum level of seepage losses from the tailings repository totaled approximately 300,000 m3 per year.
The overall approach to rehabilitating the water-bearing alluvial layer is to prevent this layer from soaking up contaminated solutions caused by seepage from the tailings repository and subsequently to pump the contaminated water out of the area of its distribution and return it to the tailings repository. Various options for capturing the contaminated water were considered: installation of an antiseepage “wall-in-the-ground” barrier around the perimeter of the tailings repository and the pumping off of contaminated water; installation of an impenetrable barrier around the tailings repository (using the Sergeev method, Moscow State University); and reconstruction of the existing horizontal drainage system. All of these measures are aimed at limiting the influx of water from the tailings repository into the alluvial layer, but they do not address matters of how to clean the contaminated layer drained by the Cheptsa River or how to handle the contaminated water that is pumped out.
Based on these models, a capture drainage system was designed, including boreholes down to the alluvial layer located near the tailings repository dam (option 1) and over the area of the alluvial layer (option 2). According to preliminary assessments, this technology is the most effective and the least costly.
Under option 1, approximately 900 m3 per day (about 330,000 m3 per year) would be pumped out and transferred to an existing deep repository (storage site) for isolation in a collection layer located at a depth of 1,435-1,600 m. The total volume of industrial wastewater removed from operational production facilities and of water pumped out of the underground layer being rehabilitated will not exceed the designed processing capacity of the storage site, 2,500 m3 per hour.
Under option 2, which is the more effective, the volume of water pumped out is 2-2.5 times greater, which exceeds the designed processing capacity of the existing storage site. To reduce the volume of water being transferred into storage, plans call for using an ENERGO-70,-45–type reverse osmosis unit. Using such units makes it possible to obtain purified water meeting household consumption or technical use standards for reuse, as well as concentrated solutions (which make up 35 percent of the purified water), which will be transferred to the tailings repository and then pumped through boreholes into the collector layer.
Design work is under way on a technological system for rehabilitating the water-bearing layer according to option 1.
A similar system for cleaning near-surface groundwater layers may be considered for the Mayak enterprise. To bury the water pumped out, which is con-