Migration of Pollutants in a Glacial Outwash Environment

A test drilling program was conducted in a drain field area of the Spokane Valley, Washington, to study the movement of pollutants in glacial outwash deposits when they are subjected to extreme pollutant loads. Contrary to what might be expected, very dry soils were found at depth beneath the drain field, and it is concluded that most of the waters are being dispersed laterally by capillary mechanisms. Much of the systemic water may ultimately be returned to the atmosphere by evapotranspiration. Moisture conditions in the drain field system strongly indicate that ground‐water recharge through incident precipitation in this part of the Valley would be highly improbable. Chemical pollutants are found to travel with moisture fronts, but fine materials are determined to be very effective in filtering bacteria within a relatively few feet of the leach bed.