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iec. <br />commonly cncountcred in thc glacial deposits. Over-size materials and hard drilling conditions can be <br />expected and should be anticipated by the contractor. The foundation-drilling contractor should be <br />prepared to case the excavation to prevent caving and raveling o: the pier shatt sidcwall. Groundwater <br />was not encountered at this site during drilling. Depending on lhe required depth of pier penetration, we <br />do not anticipate dcwatering of thc drilled shaft wi11 be required in advance of construclion. Should <br />unanticipated heavy groundwater inllow be encountercd during drilling, it may be necessary to pump the <br />accumulated groundwatcr prior to pier concretc placcment. Altemativcly, the use of bentonite slcrry <br />could be utilized to stabilize the drillcd pier excavation. <br />The drilling contractor should bc prepared to clean out the bottom of the pier excavation if loose soil is <br />observed or suspectcd, with or without the presence of slurry or groundwater. As a minimum, we <br />rccommend that thc drilling contractor havc a cleanout bucket on site to remove loose soils anNor mud <br />f'rom thc bottom oC the pier. If groundwater is present and abundant within the pier hole, we recommend <br />that thc foundation concrete be tremied from thc bottom of the hole to displace the water and minimize <br />thc risk of contaminating the concrete mix. Thc Drilled Shaft Manual published by the Federal Highway <br />Administration recommends that concretc he placed by tremie methods if more than 3 inches of watcr has <br />accumulatcd in thc cxcavation. <br />Srructurnl Fif! <br />The following commcnts, recommendations, and conclusions regarding structural fill are provided for <br />dcsign and construction purposes: <br />Materials: Structural fill includes any fill materials placed under footings, pavemcnu, drivcways, and <br />other such structures. Typical matcrials used for shvctural fill include: cican, well-graded sand and <br />gravel (pit-run); clean sand; crushed rock; controllcd-density Gll (CDP); lcan-mix concrete; and various <br />soil mixtures of silt, sand, and gravcl. Recycled concrete, asphalt, and glass, derived from pulverized <br />parent matcrials may also bc uscd as strvctural till. <br />I'lacement and Compaction: Gencrally, CDP, and lean-mix concrete do not require special placemcnt and <br />compaction proccdures. In contrasi, pit-run, sand, crushed rock, soil mixtures, and recycled materials <br />should be placed in horizontal litis not eaceeding 8 inches in loose thiclrness, and each lift should be <br />thuroughty compacted with a mechanical c�mpactor. Using the modificd Ptoctor maximum dry density <br />(ASTM: D-1557) as a standard, wc recommend that structural fill used for various on-site applications be <br />compacted to the following minimum densitics: <br />�i11 Apnlication <br />S1abiFooting subgrade <br />Gravel drive subgrade (upper 1 foot) <br />Gravel drive subgrade (below 1 foot) <br />Minimum CompacHon <br />90 percent <br />95 percent <br />90 perccnt <br />May I8, 20IX1 <br />\'oiccStrcam Wirelcss Page 8 <br />ADaPT ProjcctNo. WA00�40}4 <br />