You guys are not alone.... it happens everywhere and not just in our industry. This topic is Major when our industry gatherings occur. As much as this hurts to hear... alot of this can be avoided in the interview process (assuming they show up for the interview)... we extol the benefits we offer, the career goals that they can achieve if they stick around, the fact that we are agressively growing and that opportunities abound for them if they stick it out.
Unfortunately, the turnover still persists, although at the foreman level that turnover is dramatically reduced (at least in our operation), although with foreman status comes increased benefits.
Front line turnover is still high... we don't have the answer's you seek, but we too are working at it.