Evidence will be filed with the Surface Transportation Board in May as part of Pennsylvania Power & Light Co.'s pending rate case against three railroads: Conrail, CSX Transportation Co. and Norfolk Southern Corp.

About two weeks after giving PP&L the go-ahead to challenge origin-to-destination rates for shipments from central Appalachian coal mines, the board issued a procedural schedule for the case.

"PP&L was hopeful that the board would issue a procedural schedule as quickly as it did," said Michael W. Snovitch, PP&L's manager of fossil fuel supply. "We're ready to pursue the case, and we anticipate a ruling around the end of 1997."

A favorable ruling will enable PP&L to buy low-sulfur coal required to meet federal Clean Air Act emissions requirements.

The closest sources of significant amounts of low-sulfur coal are mines in West Virginia and Kentucky served by either CSX or Norfolk Southern. To reach PP&L power plants, the coal must be transferred to the Conrail system near the Pennsylvania border.

Opening evidence in the case will be filed with the Surface Transportation Board May 15. Replies are due July 14. Rebuttal must be filed Aug. 13. The case will be tried on the basis of the written filings; there will be no public hearings.