Practice Question: Construction site layout and control

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Solution

Answer: C) 428.4 ft

Refer to PE Civil Reference Handbook Section 2.1.3 for Site Layout and Control.

We are given:

Benchmark: \(BM = 422'\)

Backsight 1: \(BS_1 = 4.4'\)

Backsight 2: \(BS_2 = 5.4'\)

Foresight 1: \(FS_1 = 1.3'\)

Foresight 2: \(FS_2 = 2.1'\)

We can relate elevations as follows:
\[\text{Elevation of BM+BS=HI}\\\]
\[\text{Elevation of TP = HI - FS}\\\]Therefore, we can find the Height of Instrument:
\[HI_1 = BM+BS_{1} = 422+4.4=426.4\ ft \\\]Turning Point 1 Elevation:
\[TP_{1}  = HI_{1}-FS_{1}=426.4-1.3=425.1\ ft \\\]Turning Point 2 Elevation:
\[TP_{2}=TP_{1}+BS_{2}-FS_{2} = 425.1+5.4-2.1 =428.4\ ft \\\]

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