Marathon has delayed a planned 27-day maintenance shutdown of the 60,000-barrel-per-day (BBL/d) Residual Hydrocracker Unit (RHU), and a 23-day shutdown of the 105,000-BBL/d Cat Feed Hydrotreating Unit, both from July 6 until July 12, at its 437,000-BBL/d Galveston Bay Refinery in Texas City, Texas.