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I <br /> ( adjaccnt pavcmcnt and slab arcas. Onh hand-operaicd mechanical �'ihralors shnuld hc uscd for <br /> compaclion���ithin 5 fcc�horizontally of ihc hack of thc N�alls. <br /> ( The ouh��ash sands arc hiehly erosivc. Thcrefore, if�hc �•auh bonom is dcsigned lo hc opcn, <br /> I thcn the iloor of the vault should be pmiccted. �1'e recommend that a minimum Idoot lavcr of <br /> I 'G-minus clean crushed gravcl (with neglicible sand and silq be placed over the sand and across <br /> Ithe bonom of the�•aulL Additional scour pmtection may hc necded�ehcre inlct pipes arc planned. <br /> 4.7 PAVEMENT RECOMMENDATIONS AND SUBGRADE PREPARATION <br /> f 4.7.1 Subgrade Preparetion <br /> � Parking arca and access dri�e pavetnent suhgrades should be prcpared as descrihed prcviously <br /> � in the Eanhwor!: scction of[his rcport. In addition to thcse requiremans, H•c recommend thai ihe <br /> preparcd subgraae be proofrolled thoroughh•prior to pavine to locate any sofl or pumping soils. If <br /> proofrolling is noi practical.GeoEngineers should evaluate the prepared subgrade with a hand probc <br /> Irod. If soft or pumping soils are encountered, such unsuitable subgrade soils should be <br /> orereacavated and replaced. The depth of overcxcavation shcc;d be deterniined by GeoEngineers. <br /> � It may be possible to limit ilie depth of overexcavation of unsuitable subgrade soils by placing a <br /> gcotcatile reinforccment fabric such as Mirafi SOOX (or approved equi��alent)on the overexcavated <br /> subgrade and covering the geote�tile wiih base course material or rock spalls. The geote�tilc will <br /> � proride additional support b�� bridging over tLe soft material, and will help reduce fines <br /> contaminatio;. into the gravel or rock spalls. 'Ilie combination of geotcatile and gravcl or rock <br /> should provide a stable base on �chich to place and compact other pavement base course materials. <br /> ' 4.7.2 Portland Cement Concrete Pavement <br /> I \4c recommend that these pavements consist of at least 6 inches of portland cement concrete <br /> over 6 inches of crushed surfacing base course. A thicker concrete section may be needed based on <br /> the actual traffic data. lf lhe concrete pavement will have doweled joints, we recommend that the <br /> 1 concrete thickness be increased by an amount equal to the diameter of the dowels. The base course <br /> 6 should be compacted to at least 95 percent 1�4DD. <br /> � VJe recommend that porttand cement concrcte pavements incorporate construction joints and/or <br /> crack convol joints that are spaced maximum distances of 12 feet apart,cemer-tacenter, in both the <br /> longitudinal and transverse directions. Crack convol joints may be created by placing an insen or <br /> Igroove into Ihe fresh concrete surface during rnishing, or by sawcutting the ^oncrete after it has <br /> initially set-up. We recommend that the depths of the crack control joinu be approximately '/. the <br /> ihickness of the concrcte; or about 1'/: inches deep for the recommended concrcte thickness of 6 <br /> iinches. We also recommend that the crack control joinu be sealed with an appropriate sealant to <br /> help rcsVict water infiltration into thejoints. <br /> l4.7.3 Asphalt Concrete Pavement <br /> In automobi!e parking areas, we recommend a minimum pavement section consisting of <br /> I2 inches of Class II asphnit concrete (AC) over a 4-inch thicGness of densely compacted cruslied <br /> rock base course. In truck traffic areas,we recommend a rninimum pa��ement section consisting of <br /> � <br /> G e o Ii n g i n c c r s ]� filehn. itgy.ppz-OD-1130\050101 '-y�C <br /> � / / <br />