2001 Geotechnical Evaluation Report

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RVC Homes Project BABX-01-0124 April 12, 2001 Page 9 After the piles have been driven to adequate bearing and cut-off at design elevations, the inside of each pipe should be inspected to evaluate any damage and also to document the plumbness of the pile. Should the piles be damaged during driving,or should they be driven at an angle outside the plumbness specification,their load bearing capacities should be reviewed by the geotechnical engineer and the structural engineer. Contingencies should be included in the project budget for additional piles and additional pile length below the estimated"tip elevations. If the piles are not damaged during driving, and the piles have been driven within the plumbness specifications, they should then be filled with concrete. D.4. Backfills Fill should be placed in lifts not exceeding 4 to 12 inches in thickness, depending upon the material and size of the compactor used. Below slabs and pavement each lift should be compacted to a minimum of 95 percent of its standard Proctor maximum dry density. Other backfill can be compacted to a minimum of 90 percent of its standard Proctor maximum dry density. D.S. Backfill Compaction Testing We recommend density tests of backfills and fills placed beneath slabs and pavements. Samples of proposed backfill and fill materials should be submitted to our testing laboratory at least three days prior to placement for evaluation of their suitability and determination of their optimum moisture contents and maximum dry densities. D.5.a. Floor Subgrade. If floor coverings or coatings less permeable than the concrete slab will be used, or if moisture is a concern, we recommend a vapor retarder be placed beneath the slab. (Some coverings, coatings or situations may require a vapor barrier, i.e., a membrane with a permeance less than 0.3 perms.) Industry standards generally recommend burying the vapor retarder or barrier beneath a laver of sand to reduce curling and shrinkage of the concrete, but this practice risks trapping water between the slab and vapor retarder or barrier. We recommend the vapor retarder or barrier be placed directly below the slab, making sure care is taken to prevent damage during concrete placement. and quality concrete and placement practices are used for construction. D.5.b. Seepage Control. If water percolates down alongside the walls, it may enter the basement through shrinkage cracks in the concrete or masonry block. Collecting run-off and discharging it well away from the foundations and sloping the ground surface down and away from the basement walls are two common methods of reducing infiltration and percolation.