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Fall 2007 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />('rack numh~r -t n1ne. ~.I) inches (t~~~1 ~ra~k~ ~~ith ~~idths ~1f.~.11 and ?.(1 inrhrs) (f=i~urr ~~) <br />('rack numh~r ~ iun~. ,.l) in.:lic; (f~i~~ur~ ~hj <br />:,;;- .- <br />C <br />• <br /> ^'v ~ 7 i <br /> <br />Jf.~~~ V T <br />~ <br />' ' - <br />-.. <br />~ y . <br />~ <br />f <br />. <br />~ <br />1 .ti. ~. sAl.~\~i. <br />r <br />j ~ ~ {ry •~ <br />- <br />~ <br />~ ~"~~a .~ <br />~` <br /> ~ <br />.; .. <br />L Ay:: _ 1. , <br />.• <br />~' . : P. ~ ~.. <br />_ <br />Tf <br />~ <br />~ <br />~ .~ . ~. ~ .r f h.. - , <br /> <br />7 <br />,sue' ~si~ ~.. '4~ <br />* Y <br />`i~~~:. ~a r. ~F7 ~ c . .~ V <br />< <br />. <br />1, ~. -..1N <br />0 <br />1 <br />~~ h '' <br />~~~ ,~ ~ _ f`S~'~`.~....~ <br />R` '! <br />i' <br />. r <br />Figure 36. Crack number 5 zone at Apache Rocks. The crack, which <br />has a maximum width of 3.0 inches (foreground), is locally covered <br />with colluvium and soil. Another crack, out of view and as much 0.5- <br />inch wide, is located in the sandstone (upper left) about 12 feet south <br />of this crack. <br />The total horizontal strain (maximum extension) over the 280-foul area during both the spring <br />and fall 2007 tield visits is 16.0 inches, or 1.33 feet. 'vlaximum calculated cumulative strain over <br />the area is therefore 1.33 feet divided by 280 feet, which equals 0.00475 (or 0.48 percent). The <br />range of maximum horizontal strain measured in 2000 was 0.75 to 1.5 feet across a crack area <br />totaling 320 feet (or 0.23 to 0.47 percent). <br />831-032.780 Wright Water Engineers, Inc. Page 49 <br />November 2007 <br />