When installing a culvert, what is the slope when the conduit is installed at 1.40%?

A slope of 1.40% indicates a rise of 1.40 units for every 100 units of horizontal distance. This percentage means that for every 100 feet of horizontal run, the pipe rises or falls by 1.40 inches. Therefore, the correct answer is indeed that the slope corresponds to a rise of 1.40 inches over 100 feet.

To contextualize this, in practical terms, hydraulic structures like culverts need to be installed at specific slopes to ensure proper drainage and prevent issues such as water pooling or backflow. A 1.40% slope is quite gentle, which is typically suitable for culverts to facilitate smooth flow while minimizing turbulence and erosion.

The other choices do not accurately convert the percentage slope into meaningful units for this application. Options that indicate more aggressive slopes—like inches per 10 inches or a larger measure across a lesser distance, such as 1000 inches—would imply a steeper incline than what a 1.40% slope actually represents. Understanding percentages in terms of rise over run is crucial in highway construction to ensure correct installation and functionality of drainage systems.