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refuse, as placed, may have contained finer grained or even clayey ' material or constituents with cementitious properties. A roughly horizontal layer of such material would result in an "aquitard" which would restrict downward flow of percolating water and force the water to flow horizontally. Two conditions found indicate the ' existence of a series of such aquitards: 1.) The seepage exiting from the slope above the bench at ' elevation 4880 as previously discussed. In order for such a condition to exist, there would need to be a roughly horizontal boundary exhibiting low enough ' permeability to force the water to the face of the slope. 2.) The fact that, in several instances, two or more piezometers located in the same vicinity show greatly ' differing piezometeic levels. This condition is difficult to explain in any other way than the existence of distinct aquifer zones separated by lower permeability ' horizontal boundaries. The piezometers may be indicating the pressures in separate zones or composite effects of several zones since they are not isolated at a particular ' depth. Not only is it suspected that the refuse pile material consists of a series of roughly horizontal aquifer zones, the ' piezometer measurements suggest that the natural material forming the foundation for the pile may comprise another distinct aquifer zone. Since it appears that the subsurface water flow in this area ' is significantly influenced by the conditions described above, it is difficult to draw any specific conclusions from measurements taken in the open wells which are used as piezometers. That is because the measured water levels may be influenced, to some ' degree, by any number of distinct aquifers through which the wells pass. ' Three underdrain zones were constructed beneath the refuse pile. These underdrains were apparently located along the alignment of existing draws or drainage depressions found in the ' foundation formation. The underdrains are identified as No. 1, No. 2 and No. 3, with No. 1 located under the southern portion of the pile and No. 3 the under the northern portion of the pile. Underdrain No. 2 discharges near the center of the pile footprint ' and forks at same point under the pile to extend some 500-feet under the pile in two directions. From review of previous reports the underdrains are constructed as an 8-foot diameter zone of river ' cobble and gravel (6-inch maximum particle size) surrounded by an envelope of geotextile filter material. The underdrains' exact configuration, with respect to construction materials, could not be ' determined during the inspection as the (visible) outfalls appear to be comprised of 2 to 3-foot diameter rip rap. At the time of the inspection drains No. 2 and No. 3 appeared dry. Drain No. 1 was flowing a small amount, estimated to be between 1 or 2 GPM. 3 1