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Lutzky Associates Development. LP - Geotechnical Investigation <br />MACTEC Project 4953-03-2631 <br />September 18. 2003 <br />Backfill <br />All required backfill should be mechanically compacted in layers; flooding should not be <br />permitted. Proper compaction of backfill will be necessary to reduce settlement of the backfill and <br />to reduce settlement of overlying slabs and paving. Backfill should be compacted to at least 90% <br />of the maximum dry density obtainable by the ASTM Designation Dl 557-00 method of <br />compaction. The on-site soils can be used in the compacted backfill. However, the on-site clay <br />soils are expansive and will be difficult to compact and should not be used within the upper 2 feet <br />of the backfill beneath concrete walks and slabs. The exterior grades should be sloped to drain <br />away from the foundations to prevent ponding of water. <br />Material for Fill <br />The on-site soils, less any debris or organic matter, can be used in required fills. However, <br />because of their expansive characteristics, the on-site clayey soils should not be used within 2 feet <br />of the subgrade for floor slabs, walks, and other slabs. Cobbles larger than 4 inches in diameter <br />should not be used in the fill. Any required import material should consist of relatively <br />non-expansive soils with an expansion index of less than 35. The import materials should contain <br />sufficient fines (binder material) so as to be relatively impermeable and result in a stable subgrade <br />when compacted. All proposed import materials should be reviewed by our personnel prior to <br />being placed at the site. <br />6.12 GEOTECHNICAL OBSERVATION <br />The reworking of the upper soils and the compaction of all required fill should be observed and <br />tested during placement by a representative of our firm. This representative should perform at <br />least the following duties: <br />• Observe the clearing and grubbing operations for proper removal of all <br />unsuitable materials; <br />• Observe the exposed subgrade in areas to receive fill and in areas where <br />excavation has resulted in the desired finished subgrade; <br />• Observe proof-rolling and delineation of areas requiring over-excavation; <br />• Evaluate the suitability of on-site and import soils for fill placement; <br />32