What is the purpose of the fill? If the fill is for something important like an approach for a bridge or other such structure, and it is possible, abandon the existing line and lay a new one with a pipe designed to handle the new cover. You have no idea how that line was installed regardless...
The simple and conservative approach is to correctly select the motor. If as you say the pump requires a 40 to 50 bhp at design flow, I suspect you have figured out that "out on the right of its curve" the pump requires a higher brake horsepower. See if a 60 or 75 horsepower motor...
I only want to comment on the advanced degree issue as most of the responses above cover my thoughts in general. Civil Engineering as a profession has long understood the importance of practical work experience in what makes a good engineer. To become licensed in most states of the US one has...
JMH
Can you correlate the pressure spikes to pumps turning on or off? Valves opening or Closing and the like? If you can, this could be a classic example of water hammer.
I realize pumps come with thrust bearings to account for the axial thrust loads and radial bearings for radial load, I am just curious how one would calculate it. I also tend to agree with tsdead regarding the split case pumps in theory. However, it is always good practice to require thrust...
Does anyone have a quick and dirty method for calculating axial and radial thrust on a centrifugal pump shaft, or alternatively, recommend a good reference with such a discussion?