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Gri#in Realry SA, Inc.-Geotechnical investigation <br />Law/Crandall Project 70131-7-0261.0001 <br />July 8, 1997 <br />Backfill <br />Any required soil backfill should be mechanically compacted, in layers not more than 8 inches in <br />thickness. to at least 90% of the maximum dry density obtainable by the ASTM Designation <br />Dl 557-91 method of compaction. The on-site soils may be used in the backfill. Flooding should <br />not be permitted. Proper compaction of backfill will be necessary to reduce settlement of the <br />backfill and to reduce settlement of overlying walks and paving. <br />Some settlement of the backfill should be anticipated, and any utilities supported therein should be <br />designed to accept differential settlement, particularly at the points of entry to the building. Also, <br />provisions should be made for some settlement of concrete walks on grade supported on backfill. <br />Drainage <br />Walls below grade and retaining walls should be designed to resist hydrostatic pressures or be <br />provided with drain pipes or weepholes. A drain pipe could consist of a 4-inch-diameter perforated <br />pipe placed with perforations down at the base of the wall. The pipe should be sloped at least 2 <br />inches in 100 feet and surrounded by filter gravel. The filter gravel should meet the requirements <br />of Class 2 Permeable Material as defined in the current State of California, Department of <br />Transportation, Standard Specifications. If Class 2 Permeable Material is not available, 4-inch <br />crushed rock or gravel separated from the on-site soils by an appropriate filter fabric, such as <br />Mirafi 140 or equivalent, can be used. The crushed rock or gravel should have less than 5% <br />passing a No. 200 sieve. For exterior retaining walls, drainage can be provided by weepholes <br />placed about 10 feet on center. <br />6.6 FLOOR SLAB SUPPORT <br />If the subgrade is prepared as recommended in the following section on grading, the building floor <br />slab can be supported on grade. Construction activities and exposure to the environment can cause <br />deterioration of the prepared subgrade. Therefore, we recommend that our field representative <br />observe the condition of the final subgrade soils immediately prior to slab-on-grade construction, <br />and, if necessary, perform further density and moisture content tests to determine the suitability of <br />the final prepared subgrade. <br />14