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Utah 13L~i Stunt ('shin 3D Seismic Survey F:nvironnttntal Assessnunt Page 3 of 17 The proposed seismic survey operations would not impact either the tar sand deposits or hydrocarbon production m this area. Dulling depths of 50 to 60 feet would not intercept the substantial Sunnyside tar sand depose in the Project Area as the main part of Ih~s deposit is found at greater depths In the Green River Formation than the 50- to 60•foot depths noted above Ground vibrations generated by seismic survey operations associated with the Proposed Action, due to their localized limdations and non-seismically reactive tar sands, would also not have an impact on the tar•sand or hydrocarbon resources. The aclivrty Thal could occur within the two WSAS would be done in such a manner that no negative impacts to the wilderness character of the respective area would be evident following cessation of activities, Q_portion of Pressed Action activities would take place near sleep slopes and vortical cliffs. These activities -- _ _ `NQ1LId iRC1(ld~ll~!~9.-SrJtZS(~d?Ce-del0n2lion pf gxplos!vCS. ~ncllpr t)uyyy vibrator ground vil~raugll. Puislrl(ir3L in~acts from ground vibrations generated by these activities would include rock falls from exposed rock faces and rock movemenlrroltiny down slope from re.lalwely unslabie posiions on steep slajies. In irflhl of this, source points have been located with consideration of sta6lily of nearby slopes if louse rock or rock falls wore observed, source points would be relocated to spots more distant from the ciifl laces ~lddional natural factors moy I~kely contribute to rock mstabi6ty and falls. ~/ana6ons in temperature, humidly, and_. Yvind have been shown to produce nquwalent vibration velocities greater than 0.75 inches per second in structures D Sislpnd (2000) surrunarires r!ara for a) temperature, where a change o~ ten degrees Fahrenhol_ produced a range of vibrction actual rue.+sured ve'nclu~s from 0 5 to 3 2 inches per sec nil in a stnrcture, b) hunudly, where a ten percent chancdr producers a r u,gr; of measured veloc;iies of 1 0 to~.4 inches per second, and c) wrnd, where a wrnd vebcity of 20 miles per Hour produced a range of measured veloafies of 0 6 to 2.5 Inches per second and a wind velocity of 50 Halos per hour produced a range of 1 T To ri 7 inches per second. - - - About 700 earthquakes ocau in the Ulah region each year (UUSS 2003). In ground motion studies conducted by Abrabasz et al (2002), potential for earthquakes rn the Wasatch Plateau-Book Cliffs area, which includes the Protect Area, were proteclecf for ono every ton years wlh a magnitude of 4 or greater; one every year with a magnlude of three or greater: ono BO per year with a magnlude of two or greater. Veloaties at about 0.06 mtle from the earthquake event would be about 94, 11, and 2 inches per second for magnitudes of 4. 3, and 2. respecfively Orslances from the earthquake event at which point the 0 75 inches per second threshold would not be exceeded are 2.4, 0.5, and 0.14 miles. The high level of natural seismic activity both ~n the past and anticipated m the v~cmity of the Profecl Area indicates earthquake events have tikety occurred wdhm or ground vibrations have passed through the Protect Area. Quake•produced ground vibrations have undoubtedly afiecled the Protect Area and rock stability. Ground vibrations from earthquake events have also undoubtedly exceeded and will 4kely exceed the 0.75 inches per second threshed in the Project Area Ground vibration generation by detonation of explosives a[ depth rn shot holes would produce less ground motion than natural sources everywhere except m the ~mmed~ale vicinity of the source location, which by necessity are sited in stable locations (held observation by Rrchard Bell, O8G Environmental Consulting). Forces of nature are more probable sources of future rock falls and other forms of rock movement Than the proposed geophysical -- seismic source generation projecE_ _ ' A possible ~mpacl of causing a more substantial mass or slope movement such as a landslide is not reasonably foreseeable. Only one small landslide has been mapped m the Project Area (Harty 1991), and the north trending, gently-sloping consolidated beds of the Green River Formation appear to be resistant to more massive slumping and landslides (field observation by Richard Bell, O&G Environmental Consulting). Vibrator buggy operations would generate ground vibrations such that at a distance of 50 feet from the buggy, the maximum particle velocity would not exceed 0.35 inches per second (Vibra•Tech 1986), which is well below the BLM's 0, 75 inches per second threshold cntenon noted above. At 220 feet, ground vibration would not exceed 0.1 inches per second, again well below the BLM's reported threshold value Impacts from vibrator buggy shaking al distances of 50 tool or more would most Okely not increase the potential for structure or rock failure based on this data. However, the BLM (H•3150, Illustration 10) recommends a distance of 300 feet. under normal operating cond~hons, to ensure that the 0,75 inches per second threshold will not be exceeded. As previously mentioned, a wind of 50 mph causes a peak particle velocly or vibration more Than two times as intense as the charge or vibrator buggy would generate A normal person standing 50 Feet from the detonation of a 20•pound charge at a depth of 60 feel would sense the vibration; however, at 100 feet the vibration would be undetectable. http:,ne~aw.tit.bint.guv ,tuncrrhut:'1':\fcltaptcr3a.hhn C,j; 200(i