i'll throw in my two cents. first of all, the 61.5+/- for estimated pile length means "the data indicates that 61.5' might work. it could be 50' or 70' but 61.5' is the best estimate we can give you". from a geotechnical standpoint, the +/- means to whatever depth needed for bearing but from a contractual standpoint, the +/- means "give me an estimate based on this assumed depth and we'll go from there". now personally, i wouldn't estimate a pile length to the 1/2 foot anyway...i'd round (probably up) to the nearest 5' or so unless you've already got boring data at each/most pile locations. i've seen owners try similar tactics with skimpy geotech data...but if the owner would've spent the appropriate monies during the exploration phase, they would not have been so surprised by the variance. or maybe the necessary exploration was performed and this is just one of those oddball scenarios that happens when you really get in to it...since you never really know until you actually do the work. as always though, contractors will play their games too. secondly, i would hope the contract wasn't so exactly written that the pile contractor couldn't get paid for the additional footage (assuming the total footage was much higher than the 3075'). if the contractor agreed to a lump sum of $xxxx regardless of the bearing depth, they might be at the mercy of the owner. likewise, if all the piles went to 50', then the owner should not pay for the leftover footage. but if the contract said that the owner would pay $xxxx regardless of the bearing depth, then the owner would be at the mercy of the contractor.
i would hope that both sides would use "reasonable" judgement when confronted with this issue. there's a lot of if's in this scenario and perhaps there's more to the story since it's difficult to fully explain both sides of the issue via internet.