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One of the highest potentials for cost overruns, according to RV Anderson, is dealing with the unknown quantities of rock. When blasting rock with a deep soil overburden, the trench walls either have to be gradually sloped, to avoid cave-ins (which would destroy much of the Franktown Road), or a trench box (like that above) would have to be used, to minimize damage to the paved road. Both methods are very costly. |
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