Not completing boot up after power outage

While working on my iMac the power shut down in the entire house. When it came back on I restarted the Mac and the same thing happened. Power went down again. This happened four times in like 10 mins. Now when I power up the Mac it chimes and goes to the start up screen showing the Apple logo with the progress bar moving left to right. I can hear the HD chugging along but then the bar stops about a third of the way and just stays there. Any ides?

Thanks!