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<br /> <br /> <br />t <br />1 <br /> <br />1 <br />1 <br />1 <br />1 <br /> <br /> <br />EXHIBIT D (Cont'd) <br />I^ a dredge operation the material is excavated along <br />the banks creating a nearly vertical face. In time, the <br />vertical face sloughs off to about 1'~ to 1, the slope of <br />stability for this particular material. In order to achieve <br />a slope of 3 to 1, it is necessary to stop mining one and <br />one-half times the depth back from the setback line (see <br />sketch). For example, if the depth of material is 20 feet, <br />mining will be discontinued 30 feet from the setback line, <br />a.c. .~.~ icc~ ii v~~~ ~i~c ~i vl~cl ~.y iii~c. <br />~- 55' <br />I--30' ~I <br />T / A yexcavation line <br />25' ~ <br />property setback /.~~slope 3:1 when <br />line 20' A material moved <br />depth I~ B to B <br /> An exception to these figures occurs when depth exceeds <br />' approximately 27 feet and the leave line is 40 feet out <br /> from the setback line. Then it is no longer necessary to <br /> i <br />th <br />l <br />b <br />h <br />d <br /> ncrease <br />eave area <br />e <br />ecause t <br />e overbur <br />en available <br />' for use in sloping can be used to make up shortages in <br /> the remaining materials. <br />' The sand and gravel below the overburden on the affected <br /> land varies in thickness from four feet to 50 feet (see map <br />' Exhibit C-3) as found in exploratory holes drilled in <br />' September 1972 by Walter Doeringsfeld, Jr. and in October <br /> 1975 by Commercial Testing Laboratories. <br /> <br /> 11 <br />1 <br />