02-17-1987 Planning Packet - Laserfiche WebLink

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'*>3PM r ?^jr ^ : *■ - filled based on the total marsh area included in Area A is seven (7) percent. GROUNDWATER ANALYSIS Groundwater levels in the landfill area are reflected by the presence of surface water in the adjacent lakes, ponds, and marshes. The topographic maps show that the landfill will be an extension southward of a small relatively high area along Highway 12 which is actually an island surrounded by water at or near the ground surface. 3 Seepage from this ''island'* will be both downward and laterally. Hickok indicates that this is a recharge area for the Jordan Sandstone formation, the uppermost bedrock formation. Therefore groundwater will move down ward to the deeper layers. Lateral seepage from the "island" including the proposed landfill will occur if infiltration at the surface exceeds the deep seepage rate. Because the depth of glacial tills should be considerable and the materials have low permeabilities, the downward seepage rate will be low and there should be some lateral seepage to the adjacent marsh areas. It is unlikely that seepage from the landfill will reach any areas north of U. S. Highway 12. Closer seepage outlets are available in the adjacent marsh areas. Because the present and proposed landfill area is underlain by up to 35 feet of organic soils, it would seem that free seepage paths would be available through the poorly consolidated materials. This is not the case. Peat and muc’x when surcharged will consolidate. We calculated that the organic soils will settle as much as 10 to 15 feet when the proposed fill is constructed. Figure 3 shows a section through the' landfill and indicates the probable settlements. This settlement will result in a decrease in the permeability of the organic soils. MacFarlane^ indicates that peat consolidated under fills similar to the proposed landfill will have permeabilities similar to clays. In summary, the groundwater movement at the site should be both downward to the bedrock aquifers and laterally to the marshes south of Highway 12. Infiltration rates will be low due to the heavy soils used for cover and the grading of the site (see Wm. K. McKie s site plans). However some lateral seepage will likely result. - 6 -