A Tampa man portrayed by prosecutors as an incorrigible polluter was sentenced yesterday to 13 years in the slammer, the longest sentence ever given out in a federal environmental crimes case. Gary Benkovitz, 62, owner of a company that cleans and resells 55-gallon drums, has been convicted of deliberately releasing more than 4 million gallons of contaminated water and more that 630,000 pounds of toxic sludge into the city’s sewer system and waterways. Benkovitz continued to pollute even after pleading guilty to similar charges in 1997. U.S. District Judge Richard Lazzara called his crimes “environmental homicide.”