The Orlando Sentinel is mostly responsible for a plume of ink solvent that may be leaching into the city's water supply. Sentinel Communications, owned by the Tribune Co., agreed to clean up the mess and several years ago the state approved a pumping system to do it. But the state may have been too hasty to please a big corporation, and the pumps may not work. Jeff Lockwood, a state environmental engineer, says in a 141-page deposition that the Sentinel's system may not be cleaning the spill at its source. The deposition is part of a lawsuit filed by downtown land owners against the paper.