Last month, the federal Mine Safety and Health Administration revealed evidence that Massey kept two sets of safety records, one for government inspectors and a more accurate, production-centered set for itself.

Before the blast, Massey had a reputation for putting profits before safety. Upper Big Branch alone was cited for 600 violations in less than a year and a half before the blast.

MSHA has drafted its final report but told victims' families it probably won't be delivered until October, in part because the agency needs more time to complete a list of violations that contributed to the disaster.

The UMW represents some miners in the investigation even though Upper Big Branch was a non-union operation. Although employees often contact the UMW, Smith said he is not aware of any active organizing campaign at Upper Big Branch.

But he pointed to a May research paper, funded by the National Institute for Occupational Safety and Health, that examined 15 years' worth of data and concluded that "unionization predicts a sizable and robust decline in both traumatic injuries and fatalities."

"I construe these results as evidence for a `real' union safety effect in U.S. underground coal mining," author Alison Morantz wrote in the Stanford Law School report.

In January, UMW President Cecil Roberts said that while it's not perfect, "Alpha's overall safety record is better than Massey's."

"It should come as no surprise to Alpha that we strongly believe both the company and the workers would be better off with a larger union presence at the company moving forward," he said, "and we are working toward that goal."

The union represents about 1,500 Alpha employees and thousands of retirees.

It reached a new contract agreement with Alpha last week for workers at the Cumberland and Emerald mines in Greene County, Pa., and affirmed it will continue to represent workers at the idled Wabash mine in Illinois if it reopens by the end of 2013.

The union knows about the memo that Virginia-based Alpha Natural Resources posted at the Upper Big Branch Mine, discouraging unionization on the day it bought Massey Energy, UMW spokesman Phil Smith said Tuesday.

Mine Safety and Health News, an independent newsletter, obtained the memo and posted the text online.

"Signing a Union Authorization Card is like signing a blank check. You will not know what it is going to cost you or your family in the future," the memo said, reminding workers of their legal right to refuse to sign.

"Unions are a business. They need monthly dues and assessments from employees to survive," it continued. "We believe you need to keep all of your take home pay and not share it with any union."

The memo also pledged management would listen to any worker with a complaint, concern or question.

"It's not uncommon for the mine management to post these policies so as to inform people of the rights they're entitled to under labor laws," said Alpha spokesman Ted Pile. "It's standard practice."

The UMW agrees.

"This is standard union-avoidance language straight out of a union-busting consultant's playbook," Smith said. "I suspect that something similar is posted at just about every one of the larger nonunion mines in America, no matter who owns it."

Still, he called the presence of such a notice at Upper Big Branch "sadly ironic," given the tragedy that occurred April 5, 2010, and a new study suggesting a correlation between union representation and a drop in coal mine injuries and fatalities.

Investigators have cited disregard for the industry's most basic safety standards as an underlying reason for the methane- and coal dust-fueled blast that ripped through Upper Big Branch in the deadliest mine disaster in four decades.

Last month, the federal Mine Safety and Health Administration revealed evidence that Massey kept two sets of safety records, one for government inspectors and a more accurate, production-centered set for itself.

Before the blast, Massey had a reputation for putting profits before safety. Upper Big Branch alone was cited for 600 violations in less than a year and a half before the blast.

MSHA has drafted its final report but told victims' families it probably won't be delivered until October, in part because the agency needs more time to complete a list of violations that contributed to the disaster.

The UMW represents some miners in the investigation even though Upper Big Branch was a non-union operation. Although employees often contact the UMW, Smith said he is not aware of any active organizing campaign at Upper Big Branch.

But he pointed to a May research paper, funded by the National Institute for Occupational Safety and Health, that examined 15 years' worth of data and concluded that "unionization predicts a sizable and robust decline in both traumatic injuries and fatalities."

"I construe these results as evidence for a `real' union safety effect in U.S. underground coal mining," author Alison Morantz wrote in the Stanford Law School report.

In January, UMW President Cecil Roberts said that while it's not perfect, "Alpha's overall safety record is better than Massey's."

"It should come as no surprise to Alpha that we strongly believe both the company and the workers would be better off with a larger union presence at the company moving forward," he said, "and we are working toward that goal."

The union represents about 1,500 Alpha employees and thousands of retirees.

It reached a new contract agreement with Alpha last week for workers at the Cumberland and Emerald mines in Greene County, Pa., and affirmed it will continue to represent workers at the idled Wabash mine in Illinois if it reopens by the end of 2013.