A Special Town Meeting is being held in Bethel tonight on water main upgrades.  Residents are being called onto vote on the 998-thousand dollar plan.  Upgrades would be made to water mains on Mansfield Street, Pleasant Street, Grassy Plain Terrace. Highview Terrace and Oakland Heights. If there's room in the budget, water mains on Maple Lane will be replaced as well.  Bethel water customers will repay the loans.  Tonight's meeting is at 6:30pm.