Jay, so sorry to hear about the problems you're having with the pool. So far, the PB is responding, which is great, but that means there is no immediate legal action to be taken. You could press for a new plaster job, but at this point I'd say that might be premature, because we don't yet know if the pool is going to continue to move. Here's some things to think about or do.
- As Kim suggested, all communication should be in writing. Email is OK, certified letters are better.
- If verbal communications take place, follow them up immediately with an email that summarizes what was said or agreed to. Ask the PB to confirm receipt of the email with a reply. This in essence gets him to confirm the conversation took place and what was said. If he neglects to confirm such an email, especially after being asked to a second time, you should assume that is intentional. So at that point all verbal communication should stop, and only written communications after that. Personally, I don't rely on email for that, I use certified mail. A proper paper trail might be essential. Which brings me to the next point:
- The fix could cost anywhere between $0 to what you paid for the pool plus removing the existing one (worst case scenario). That could be high-five-figures, and quite possibly into six-figures. Treat every piece of your evidence as a commodity worth six-figures. That means duplicate everything and keep it safe, offsite (like at a friends house). Print every email and letter, two copies, one for on-site, one off-site. Store all digital data carefully and store backups offsite: pictures, saved emails, etc, everything. Copy the plans. Copy the contract. Everything duplicated offsite. You have to be very diligent about this, and keep the backups up to date. You never know what piece of paper or snapshot could make a difference should this end up in court.
- Other posters' thoughts about getting second opinions is fine, you can start to gather those if/when you need to. But be very careful NOT to initiate ANY repairs yourself. Right now the PB is responding. He's doing so as he sees fit. That is his obligation and right. You cannot initiate any repairs yourself without giving him a demand letter and then a reasonable amount of time to respond and take action. So far, he's not doing anything wrong, so you can't either.
- Now, here's the tricky part. You need to be aware of the statute of limitations for the contractor's liablitity for this discovered construction defect. The length of your warranty will come into play, but that might not be your only or best recourse. There are a slew of possible deadlines: 2, 3, 4, 10 years, and when the clock starts is also a difficult thing for us laymen to nail down. This is what you might seek a lawyer to help you determine. At 2.5 years, you may or may not have a deadline looming. And certainly now that the defect has been discovered, and the PB has been notified, the clock is ticking. And it's possible the clock started ticking when the pool was finaled. What you need to protect is that the PB doesn't limp along with semi-fixes long enough for the statute of limitations to expire, and then the pool cracks after that, and then that'll very likely be on you.
The worst worst case is if this current fix, or the next one, outlasts the statute of limitations and then the defect reappears. You would have a much weaker case, and possibly a much shorter statute of limitations, because the defect revealed itself while you could have demanded the fix. It's a catch-22 situation.
Best case, and what you should be seeking, is that the PB hires an engineer to ascertain the nature or cause of the problem, and then applies the fix. If he refuses, and claims the plaster fix is all that is needed, then you will have to determine if you want to risk the crack coming back later, and if not, then you might have to seek a third party to inspect the pool and soil, etc, to prove to yourself and the PB that more of a fix is needed.
Because the deadlines are tricky, and a little bit hard to sort out, I would not go too much longer without consulting an attorney, at least to help you find out if the statute of limitations clock is running and when does it stop. If you are going to resist or procrastinate on that advice, then I can share how to prepare a proper demand letter, which is among the first things you must do if you feel the contractor is not performing.
I haven't even mentioned this here yet, because I had a self-imposed gag order in place so that I didn't inadvertently blow my recently won judgement (I've been waiting out the appeal period). But I got the settlement check last week, so I guess it's officially over. I sued a CA contractor for a construction defect he refused to fix, and the Statute of Repose (limitation) of 10 years came into play. I spotted it just before the Statute expired and I proceeded to court and bombarded the judge with a 1" thick stack of evidence (pictures and documents, which I had protected as I advised). The defendant didn't stand a chance. Point being: (1) I practice what I preach, and (2) it is possible to sue a CA contractor up to 10 years after he finishes a build, even though his warranty was only for one year. But my home's defect was hidden, yours is not (any longer). The catch for you is to find out how long you have, and make your PB apply a satisfactory fix before then.
If he won't, then we can later talk about how to use the CA Contractors State License Board (CSLB). That's how I won a previous case against a PB. I don't think I have any worse luck with contractors than anyone else, but if crossed, I just don't accept it.
www.troublefreepool.com
I am so glad to hear you got THE check!!! 
