2000 TOWER ST ARTS AND SCIENCES BLDG 2018-01-02 MF Import

After completing the proofrolling, the subgrade areas should be recompacted to a firm and unyielding condition, if possible. The degree of compaction that can be ach eved will depend on when the Iconstruction is performed. If the work is performed during dry weathcr conditions, we recommend that all subgrade areas be recompacted to at least 95 percent of the maximum dry density (MDD) in accordance with tie American Society for Testing and Materials (ASTM) D 1557 test procedure (modified Proctor). If the work is performed during wet weathcr conditions, it may not be possible to recompact the subgrade to 95 percent of the MDD. In this case, we recommend that the subgrade be compacted to the extent possible without causing undue weaving or pumpi.ig of the subgrade soils. Subgrade disturbance or deterioration could occur if the subgrade is wet and can not be dried. If the subgade deteriorates during proofrolling or compaction, it may become necessary to modify the proofrolling or compaction criteria or methods. Working Pad If construction of the building occurs during the wet weather months, generally October through May, routing of equipment on the glacial subgrade soils will be difficult and the subgrade will likely become disturbed and softened. In addition, a significant amount of mud can be produced. Therefore, to protect the subgrade soils and to provide an adequate working surface for the contractor's equipment and labor, we recommend that a working pad layer be placed over the exposed subgrade soils. The working pad layer should be about 12 inches thick and should consist of I'/: -inch minus clean crushed gravel with negligible sand or tilt. The working pad layer can be placed in one lift and should be compacted to at least 95 percent of the MDD (per ASTM D 1557). If a working pad layer is used, and if relatively clean immediately prior to construction of the slab -on -grad,!, it may be used to replace the 6-inch capillary break layer. However, if the working pad becomes contaminated with soil, the contaminated areas should be overexcavated to a depth of 6 inches for placement of ;he capillary break gravel prior !o constructing slabs -on -grade. Structural Fill All fill, whether existing on -site glacial till soil or imported soil, that will support floor slabs, p ivement areas or foundations, or be placed against retaining walls or in utility trenches should generally meet the criteria for structural fill presented below. The suitability of soil for use as structural fill depends on its gradation and moisture content. Materials. Materials used to construct building pads, embankments and surface parking areas are classified as structural fill for the purpose of this report. Structural fill material quality varies depending upon its use as described below: 1. Structural fill placed to construct emban'cment and parking areas, to backfill utility trenches and to support building and floor slabs may consist of on -site glacial till provided that the soils are conditioned for the required compaction. On -site till soils will be suitable for use as structural fill during dry weather conditions in areas needing 95 percent compaction. If structural fill is placed during wet weather, the structural till should consist of imported gravel borrow as described in clz_� 6 e o E n g i n c e r s 6 File No. 5816-002-00/0402O4