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t <br /> � � i <br /> , <br /> Ial Icasi 4 inchcs of Class 13 asphah concrcic (AC) ovcr an F-inch �6ickncss of dcnsclr compncicd <br /> crushed rock hasc rnursc. ilic hasc coursc should he contpacicd io ;u Ic:�st 95 perccnl of Ihc <br /> I tnaxitnum dry densih (AST11 D 15571. 'fhickcr asphah scciions ma� hc nccdcd hascd on Ihc <br /> actual traffic data. <br /> I4.7.4 Asphalt-Treated Base <br /> Because paccinents tnsy be couslnictcd during the �ccl scasons, considcra�ion ma� he gi�cn �o <br /> I covering the areas to bc paved�cith asphalt-trcated basc(Al'D)for protection. 1'arking:�rcas should F <br /> bc surfaced H�it!: 3 inchcs of ATd, and Wck drivc��•a�•s for matcrials dcli��cry should bc surfaccd �� <br /> ���ith 6 inches of ATD. Prior to placcmcnt of the final pa�cmcnt sections. �re recommcnd that arcas <br /> Iof ATB pavement failurc be rcmoved and the subgrade rcpaircd. If AT[3 is uscd and is scrvircable 1 <br /> whcn final pavements are conswc�cd,the crushed surfacing base course can bc climinated,and Aic � <br /> I desiFn portland cement concrctc or asphah concre�e pavcmcni thickness can bc placcd dircctly m cr <br /> the Al'B. <br /> r 4.8 SEISMICITY <br /> � 4.8.1 General <br /> The Puget Sound area is a seismically activc rcgion a•;,; has e�pericnced thousands of <br /> ( earthquakes in historical time. Seismiciry in this rcgion i; anr:buted primarily to �he inicraction <br /> between the Pacific,Juan de Fuca and North American plates. Tlie Ji�nn de Fuca plate is subductin� <br /> beneath the North American Plate. Each year I,000 to 2.000 eaM1hruakes occur in Oregon and <br /> ' Washin�Ron. However, fc�r of thcse are hPically felt becausc the :^a ority of thc earthquakcs arc <br /> relatively minor,smallcr than Richter magnitude 3. <br /> � ln recent years, thrce laree eanhquakes occurred �rhich rcsulted in some liquefaction in loosc <br /> alluvial deposiu and significant damage to some shucWres. Tltese u•cre a 1949 carthquakc with a <br /> Richter magnitude of 7.1 that occurred in [he Olympia arca; a 19G5 carthquake with a Richter <br /> fmagnitude of 6.5 that ocwrred roughly half way bet�veen Senttle and Tacoma; and recently the <br /> � February 28, 2001 Nisquall�• earthquake ���iih a Richter macnitude of 6.8 that occurred north of <br /> � Olympia. <br /> Potential seismic hazards from earthquakes include Fround shaking, liquefaction, ground � <br /> rupturc from Iateral spreadine and surface fault rupture,and landslides. Our opinions regarding the <br /> ilikelihood of these scismic hazards occurring at the site usine thc desicn earthquake are presentcd i <br /> � below. <br /> ( 4.8.2 Ground Shaking � <br /> There is a risk of earthquake induced ground shaking at the site, as with all sites in the Puget <br /> I Sound mgion, and the intensiry of the ground shaking could be severe. Tlie severity of ground <br /> � shaking will be mostly a function of the earthquake magnitude and proximity to the site. In our <br /> opinion, strong gound shaking should be considered in thc design of the structures and <br /> fimprovemenu at this sitc. <br /> l <br /> G e o E n g i n e c r s ]$ FilcNo. 75R4-002-0(1-I130i050101 22�r <br /> I ` <br /> � <br />