At McAlpine L & D, normal upper pool elevation is 420.0 feet (130.8 meters) MSL, equal to 12.0 feet (3.7 meters) on the upper gage. The vertical clearance at the Clark Memorial Highway bridge is 72.6 feet (22.1 meters) above normal pool. What is the clearance if the gage reads 10.6 feet (3.2 meters)?
• Relationship between gage reading and pool elevation • How a change in water level affects vertical bridge clearance • Using simple subtraction to adjust from normal conditions
• If the normal gage reading is 12.0 feet and the current gage reading is 10.6 feet, has the water level gone up or down, and by how much? • When the water level goes down by a certain amount, does the clearance between the water surface and the bridge increase or decrease? • How do you adjust the original 72.6-foot clearance using the change in water level to find the new clearance?
• Be clear whether the water is higher or lower than normal pool at 10.6 feet compared to 12.0 feet • Carefully compute the difference between the two gage readings before changing the clearance • After adjusting the clearance, compare your result to the answer choices and confirm it is reasonable (higher water level means less clearance; lower water level means more clearance)
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