Envirocare owner Khosrow B. Semnani pleaded guilty Friday to a misdemeanor tax charge and promised to cooperate in the continuing investigation of the state's former radiation waste regulator.

In an arraignment before U.S. District Senior Judge David K. Winder, Semnani admitted he paid $40,000 in cash to Larry F. Anderson in 1993 knowing Anderson would not report it as income on his tax return."You knew what you were doing was wrong?" Winder asked.

"Yes, sir," Semnani answered.

However, Semnani has consistently maintained he paid Anderson the $40,000 plus another $560,000 in real estate, coins and cash out of fear of economic and regulatory reprisal. In other words, he considered it extortion.

Under terms of a plea and cooperation agreement signed Friday by Semnani and federal prosecutors, Semnani will pay the maximum $100,000 fine and assist investigators unconditionally.

He promised to provide the U.S. Attorney's Office and the Internal Revenue Service with "truthful and complete information, evidence and assistance in the investigation of others who have violated the criminal laws of the United States."

Also, he agreed to appear before grand juries, testify as a government witness in any court proceeding and, if asked, submit to a polygraph examination.

For their part, prosecutors agreed to bring no further charges against Semnani in connection with the payments he made to Anderson between 1987 and 1994 and to recommend he not receive the maximum one-year prison term.

While stressing he was not bound by the agreement, Winder accepted Semnani's guilty plea and postponed sentencing until Nov. 30 to give prosecutors ample time to fully assess the degree of his cooperation.

A graduate of Westminster College and the University of Utah, the 51-year-old Semnani told Winder he fully understood and accepted the terms and risks of the plea agreement.

The Envirocare investigation was launched in 1996 after Anderson filed a civil lawsuit asserting a "consulting arrangement" that called for Semnani to pay him $5 million in fees beyond the $600,000 he had already received.

The claim immediately raised eyebrows because Anderson headed the state radiation regulatory agency during the decade that Semnani was establishing his Tooele County facility as the third largest low-level radiation waste dump in the nation.

At a press conference last month, Semnani told reporters, "I, of course, regret this entire matter regarding Larry Anderson's demands for money. . . . As I have previously stated, I believe I was a victim of extortion."