LAS VEGAS (AP) — A year after hundreds of Las Vegas Rock ‘n’ Roll Marathon and Half-Marathon runners reported symptoms of stomach illness, organizers on Monday promised changes that include strict sanitation rules and the hiring of a contractor to supply water to runners.

Revisions for Sunday’s event include the use of closed 125-gallon tanks with spigot hoses at water stations along the courses, officials said. Water will be trucked in, instead of drawn from fire hydrants.