STAMFORD — A former general manager of a Springdale ice skating facility has pleaded guilty in federal court to bilking nearly a half million dollars from the business. Mark Zito, of Shelton, faces up to 20 years in prison after pleading guilty this week in New Haven federal court to one count of wire fraud. Stamford police financial crimes investigator Heather Bozenkto said Zito had been stealing the money from the owners of Stamford Twin Rinks for 15 years. The scheme involved Zito collecting commissions for the advertising dollars that he generated for the rink, Bozenkto said.