Casey's confrontational letter represents the latest salvo between public officials, union representatives, and the companies over the decisions to sell or shut down the refineries in Philadelphia, Marcus Hook, and Trainer.
The three plants process about 700,000 barrels of crude oil a day, more than half the refining capacity in the Northeast. Sunoco's Marcus Hook refinery and ConocoPhillips' Trainer plant are already idled. Sunoco says it will close its Philadelphia plant in June if a buyer is not found.
In the letter, Casey said he is concerned the sellers are placing restrictions on the sales of the facilities that could deter buyers, including those who might convert the plants to process natural gas by-products from Pennsylvania's Marcellus Shale region.
"Shuttering these facilities is not an acceptable outcome," Casey wrote. "There are many strong potential reuses, including uses that would bolster the Commonwealth's growing Marcellus Shale industry, that need to be considered."
Thomas P. Golembeski, Sunoco's spokesman, said the company has been in contact with public officials and conveyed their offers of support to potential buyers.
"We are acutely aware of and concerned about the impact this change may have on employees and the local communities, so we are working diligently on the sales process," he said in an e-mail.
Read Casey's letter at www.philly.com/caseyletter.
Contact staff writer Andrew Maykuth at 215-854-2947, @Maykuth on Twitter or email@example.com.