Some comments on drawholes:

• Valley angles do not exist at the surface of live material draw-downs. Observation  will show that no matter the shape of the actual draw point, the live depression is usually circular. To provide compensation for this effect we chose to use inscribed arcs at the ends of rectangular holes, which is closer to the natural than strict slopes up from the edge of rectangular holes.
• Use circular holes for preliminary work. A circle is easier for the user to enter than a rectangle with its added dimensions and orientation. Fewer key strokes means quicker results. We recommend using circles for preliminary work with relatively square rectangular holes. It is simpler to key in the data and gives virtually the same results.
• 1% accuracy. We have chosen a reasonable, easy to enter approach to defining drawholes that will provide better than 1% accuracy

Why did you not include an inverted cone as in some bin bottoms? This might be done, but the effort did not seem worth the little use envisioned.
Same with height and width limited walls, which was the initial intent. The infinite walls are much easier for the user to input and little is lost by doing it that way.

To handle cone bottoms:

1. Divide the bin in two sections parting at the cone joint. 
2. Let PileV calculate the total live volume of both parts using the full height of the bin. 
3. Record the live volume. Then let PileV calculate the upper section. 
4. Record the total volume of this section. Then hand calculate the dead storage from the drawhole to the cone joint, if any, and add it to the total storage.

Unlike an inverted cone, an inverted pyramid with four sloping walls is possible to calculate by entering the bin bottom as walls. Then it must be determined that the infinite extension of the walls causes no errors. The conical bottom alone can be examined by using level limits, (See the Run Calc tab).

Multiple drawholes may be contained at the bottom of the walls. For multiple pyramid bottoms, use a procedure similar to the cone bottoms above.

Large storage structures with multiple regularly spaced drawholes can be calculated by isolating typical drawholes with imaginary walls placed between drawholes and then adding the results. See the sample calculation records that are included.

  Used for testing purposes, these methods can be used for short-cuts in some instances.

• Straight wall 2 point data can be entered into the text boxes without typing. Depress and hold the left mouse button on the drawing and drag it to the desired location of one point. Release the button and the coordinate data will be entered. The right mouse button used similarly will enter the other point.
• Drawhole location data can be entered likewise. A drawhole must already have been entered to establish elevations and obtain a properly scaled location drawing. This method is very useful for leach piles with sloping bottoms. Dragging across the drawing at the edge of the pile will find the low point of the bottom, the ideal point for the calculation axis.