Which of the following is the depth of a sanitary sewer force main crossing at a right below the surface of an equal tangent 600 foot vertical curve, given the pipe elevation at Station 10+00 is 100 feet, the PVI at Station 13+85 is 109.0 feet, and the initial and final grades are +1.2% and -1.06%?

Question

Quizplus · Accepted Answer

The depth of the sanitary sewer force main below the surface of the given vertical curve is 12.1 feet.
Solution:
Step 1: Use the offset formula (distance between curve and tangent)
Y = [G/ (200*L)]*x2
Given G = | 1.2-(-1.06)| = 1.26
L = 600 feet
x = 385 feet
Therefore,
Y = [1.26/ (200*300)]*3852 = 1.5 feet
Step 2: Determine PVC elevation
109.0 feet - (6/2 stations x 1.2 feet/station) = 105.4 feet
Step 3: Determine initial tangent above pipe
109.0 + (3.85 stations x 1.2 feet/station) = 113.6 feet
Step 4: Determine curve elevation at pipe crossing (initial tangent - offset)
113.6 - 1.5 = 112.1 feet
Step 5: Determine distance between curve elevation and top of pipe
112.1 - 100.0 = 12.1 feet

Which of the Following Is the Depth of a Sanitary