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1,?Yiu.' .��� i <br /> a <br /> ;:���� . ,� <br /> � �� � � <br /> ,� _ <br /> , ��� <br /> ��� � <br /> � , � <br /> � � <br /> � a i <br /> ��d Geo Engineeis <br /> QH� t# maximum dry density (['IDD) as determined by the ASTM D-1557 [est procedure. <br /> zyy H �� ` Fill placed in roadway areas at depths greater than 2 feet below the � <br /> r� � �a finished subgrade sliould be compacted [o at least 90 percent of hIDD; fill <br /> ��Cy�� � � placed within 'L feet of the subgrade should be compacted to at least j <br /> �.�Oa .x 95 percent of CIDD. These criteria also apply to utility trench backfill. <br /> , ��p ' Utility trenches outside of building or pavement areas should be compacted <br /> , � to a density relativel}� comparable to the natice soil adjacent to the • '� <br /> � �:�q trench. Strvctural fill placed on slopes steeper than 5:1 (horizontal to � <br /> . vertical) should be keyed into the native slope by means of horizontal � <br /> � I <br /> benches. The benches should be about 4 feet ninimum �:idch. <br /> � 4 <br /> . All structural fill material should be free of organics, debris and � <br /> ' � other deleCerious material with no individual particles larger than , <br /> i4 I <br /> 6 inches in diameter. As the amount of fines �that portion passing I <br /> � + No. 200 sieve) increases, the soil becomes increasingly sensitive to small <br /> � I <br /> / _,� changes in moisture content and adequate compaction becomes more difficult i <br /> F'�� � to achieve, particularly during wet weather. Generally, soils containing <br /> � } I, <br /> ;� more than about 5 percent fines by weight cannot be ptoperly compacte <br /> 1 f <br /> when the moisture content is more than a few percent [rom optimum, and ' <br /> �� i� � <br /> . i L= �� are consequently more difficult to work. I <br /> � We recommend Chat a representative from our firm observe placement of i <br /> � <br /> � � '� structural fill to evaluate if procedures used and results oUtained <br /> � �� � � conform with the inCent of this report and Che plans and specifi.�ationc. ; _ -. <br /> � � A representative number of in-place density Cests should be performed as <br /> . �� � part oi Lhis construction monitoring. � �� <br /> �� ��� . . . . . . <br /> I I � SuiCability ot On-Site Soils: The relatively high fines content of <br /> � <br /> � tLe till (estimated to be generally between 20 and 40 percent) indicates _ <br /> � �� w.�' ?� � V�� tliat tlie on-site soil will not be suitaUle for use as strucCural fill . <br /> i � <br /> � except during periods of exCended dry' weather. The moisture contents o I <br /> '�'� ,. _ the samples of the weathered Cill CesCed were in the ran�e of 11 to 24 . <br /> L py percen�'�c [lie moisCure contents oL Che unweatliered till samples were <br /> �- � generally in thc ran�e of 9 Co 12 percenl'. 'Phe optimum moisture content � <br /> ii <br /> � of glacial till soil is cypically between 8 and 10 percenC. The moisture <br /> I <br /> !� 7 L <br /> I + <br /> V <br /> � -_ _, _ _ <br /> .._. � ._.�-_. „'�"�#� <br /> � � <br />