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<br />~I <br />1 <br /> <br />1 <br />1 <br /> <br />indication of the existence of such reservoirs is that the vertical <br />extent of zones controlled by a single piezometric level increases <br />further into the pile. The model which seems to best fit the <br />obser•rations is described below: <br />1.) As precipitation falls on the pile and infiltrates, it <br />percolates generally downward until a horizontal boundary <br />is encountered. When downward moisture movement is <br />impeded by a boundary, the water would be expected tc <br />build up on the boundary filling permeable zones and <br />creating a subsurface reservoir comprised of a system of <br />such zones. <br />2.) As the head increases in this reservoir or dome, latera'_ <br />movement of the stored water wculd be expected to occur, <br />with the water spreading out through the networ'.: of <br />permeable channels but generally remaining above the an_; <br />horizontal boundaries. Piezometric levels would decrease <br />further from the source reservoir. <br />3.) Any discontinuities in a low permeability boundary ;cculd <br />result in a relatively sudden decrease in pressures at <br />the same elevation. <br />1 <br />4.) The piezometers which measure zones further frcm the face <br />of the pile and which appear to be controlled by <br />horizontal boundaries, also appear tc be relatively <br />erratic and substantially less stable than those closer <br />to the slope. Far example piezometers 302, 303, 3C4 and <br />305 have shown sudden changes, either increasing .,_ <br />decreasing. During the same period of time that these <br />piezometers were changing, the opposite effect was seen <br />in deeper pie2ometers 306, 307 and 104. In other words, <br />while 3C2 through 305 were dropping, 306, 307 and 104 <br />were rising. Similar variations have been observed in <br />piezometers 402 and 403 which are believed to be <br />controlled by horizontal boundaries. This data has been <br />evaluated to determine if drilling and piezome`_er <br />installation may have had some influence cn the erratic <br />data. The conclusion was that the instruments a_e <br />measuring pressures generated by actual subsurface f'_ow <br />ccnditicns. If that is the case, then the subsurface <br />flow regime and corresponding pressures can be epected <br />to vary frequently and substantially. These wi'_d <br />variations are likely the result of the characterist_cs <br />of the refuse material. Wherever open graded materia'_ <br />such as hard crushed rock are placed adjacent to `_iaer <br />grained materials, the potential exists for movement of <br />the firer material through the more coarse zones due tc <br />seepage forces. It appears that, in some areas there -,a1 <br />be as much as 30-feet of head or. a low permeability <br />beundary. It is conceivable that heads of this magnitude <br />could generate sufficiently high seepage forces to result <br />17 <br />