02-27-2002 Council Agenda - Laserfiche WebLink

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FEB 14 '02 05 :33PM BRAUN INTERTEC Drywall Supply, Inc. BBXX -02 -O 10A January 29, 2002 Page 9 (generally 1/2- to 1 -foot) with a stabilizing aggregate. Where organic soils are exposed or are present within 2 feet below the utility, we recommend the organic soils be partially removed (subexcavated to a depth of 2 feet) and replaced with compacted fill or a stabilizing aggregate. P.13/24 C.5.b. Baekfrlling and Compaction. Backfill placed over utilities may consist of available on -site (excluding organic soils) or imported soils that can be adequately compacted. For ease of compaction, however, sands are preferred. Silt and clay soils will be more difficult to compact, particularly if wet. For uniformity, utility backfill placed within 1 -foot of floor slabs, and 2 feet of pavements should consist of sand having less than 15 percent of the particles by weight passing a 200 sieve. In areas that will support pavements, we recommend backfill below 3 feet be compacted to 95 percent standard Proctor density (ASTM D 698) and 100 percent in the top 3 feet. C.6. Pavement Support +C.6.a. Subgrude Preparation. The borings encountered existing fill soil at the surface consisting of a mixture of silty sand, clayey sand, and in some cases, silt. Before placing new pavements, we recommend that all existing pavements within the new pavement areas be removed and backfilled with compacted fill. To help provide uniformity we recommend the exposed subgrade soils be scarf fed to a depth of 8- inches, dried or moistened to a moisture content near optimum, and then be recompacted to a minimum of 100 percent of the standard Proctor maximum dry density. The purpose of scarifying the soils is to provide a uniform soil blend and disrupt potential seepage paths present within the upper 6 inches of the subgrade. As a final check before placing the aggregate base, we reconunend that all pavement subgrades be proofrolled. This precautionary measure will assist in detecting localized soft spots. Any soft spots noted during the proofrolling process may require additional subcuts. A qualified geotechnical engineer should observe the proofrolling process to make a final evaluation of the subgrade.