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1 <br /> -- June 6,2008 <br /> Serenity Meadows <br /> ' L&A Job No. 8A017 <br /> Page 10 <br /> Permanent fill embankments, required to support structural or traffic load should be constructed <br /> ' with compacted structural fill placed over undisturbed, compacted proof-rolled weathered soils <br /> or the underlying dense to very-dense, fresh, advance outwash and/or till soils after the surficial <br /> ' unsuitable soils are completely stripped. Permanent fill placed over sloping ground steeper than <br /> 20% grade should be structurally supported. Sloping ground steeper than 15% grade should be <br /> 111 benched with vertical steps not exceeding 4 feet tall after stripping of the surficial unsuitable <br /> soils and prior to constructing permanent fill embankment. The slope of permanent fill <br /> embankments should be no steeper than 2H:1V. Upon completion,the sloping face of permanent <br /> fill embankments should be thoroughly compacted to a non-yielding state with a hoe-pack. <br /> I The above recommended cut and fill slopes are under the assumption that groundwater seepage <br /> would not be encountered during construction. If groundwater seepage is encountered, the <br /> construction should be immediately halted and the slope stability re-evaluated. The slopes may <br /> have to be flattened and other measures taken to stabilize the slopes. Surface runoff should not <br /> be allowed to flow uncontrolled over the top of cut or fill slopes. Permanent cut slopes or fill <br /> embankments should be vegetated as soon as possible for erosion protection and long-term <br /> stability, and should be covered with clear plastic sheets, as required, to protect them from <br /> stormwater until the vegetation is fully established. <br /> GRADING OVER UNSTABLE SOILS <br /> ' Thick, loose, unstable bog sediment and organic soils may exist along the fringe of the wetland <br /> buffer zone. For grading in this area, such unstable soils, if encountered, should be over- <br /> excavated down to firm bearing soils wherever feasible. Unsuitable soils cannot be completely <br /> excavated and removed due to high groundwater table, if encountered, should be removed as <br /> much as practicable. Rock spalls of 4 to 6 inches in particle size should then be spread over the <br /> excavated areas and pounded into exposed soils with a hoe-pack until the rocks are in firm <br /> contact with the underlying firm bearing soils. This compacted crush rock base should be <br /> LIU & ASSOCIATES, INC. <br />