My usual workflow for special ditch grades is to have a P-DCH-R plan element collinear with the baseline that the corridor follows. P-DCH-R has its own profile. I attach it to the corridor. The template has an end condition that targets the feature definition in the vertical aspect. My problem is that this special ditch grade is attached to a corridor that loops, and the part of the opposite side of the loop is picking up the special ditch grade as well.
The workaround that I had first considered was to limit the horizontal aspect to 90 feet, just so it doesn't search too far off. That doesn't work, since P-DCH-R never shows up in that horizontal range, so it wouldn't be located. After a quick trial, I found this to be true.
The next workaround that came to mind was to add a vertical line starting at the baseline to target P-DCH-R, the lower end of which is to set the elevation of the ditch line. Whether I specify the lower end of this null EC so that the end condition is or is not infinite, it affects both parts of the loop, which is undesirable.
So I suppose the final solution is to offset the main P-DCH-R element to place it in the range where it will be within the horizontal limits of the end condition element. And now trying that, I'm seeing difficulties there too.