An underground storage vault is to be constructed to serve as a detention pond for a heavily urbanized area. The walls of the vault will be vertical, but the flow will be sloped along its length to promote drainage. In plan view, the vault is rectangular with a length of 75 feet and a width of 40 feet. The slope of the floor, along the 75ft dimension, is 2%. The invert of the lower end of the vault is at an elevation of 123ft.
Determine the elevation vs. surface area relationship for the vault and use this information to calculate and graph the elevation-storage relationship. Use the average end area method.