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Pennsylvania State Sen. Andy Dinniman, a longtime Chester County Democrat and one of the most prominent critics of the Mariner East pipeline system, will not seek reelection this year, his office has announced.

Dinniman, 75, revealed his plans to retire shortly after his wife, Margo, underwent surgery.

“For nearly 30 years, as your Chester County commissioner and state senator, I have had the privilege of building a close relationship with the people of Chester County," he said in a statement late last week. “This was a very tough decision, especially knowing just how many of you have faithfully and tirelessly supported my work over the years. However, as I sit at Penn Presbyterian Medical Center with my wife, Margo, who is now recovering from surgery, we both came to the sudden realization this was not the time to run again.”

Dinniman was elected to the State Senate in 2006 and serves as the ranking Democrat on the Education Committee. But he’s best known lately for his criticism of Sunoco’s Mariner East pipelines, which run through his county.

In the legislature, Dinniman has introduced bills to change pipeline safety regulations. He also brought a formal complaint and emergency petition before the state Public Utility Commission, which halted operation and construction of Mariner pipelines in 2018. A Commonwealth Court panel later ruled Dinniman didn’t have standing to bring the challenge and allowed pipeline construction to resume.

“It’s Sunoco’s own faulty practices that have caused harm to the whole pipeline process," Dinniman said in a 2018 statement. “They’ve amassed more than 200 violations in Pennsylvania, putting the whole pipeline industry in such a position.”

The FBI is probing how Gov. Tom Wolf’s administration issued permits for the Mariner East project. Wolf has denied knowledge of any wrongdoing. The Chester County district attorney is also leading a probe and in December filed criminal charges against pipeline security personnel.

Dinniman joins more than a dozen other state lawmakers who have announced their retirements from the General Assembly in recent months, most notably House Speaker Mike Turzai (R., Allegheny). Dinniman endorsed Don Vymazal, his director of government relations and policy, to succeed him in the heavily Democratic district.

Before he was a state senator, Dinniman served for 15 years as a Chester County commissioner. He founded an emergency housing shelter and created a program that works with local farms to redistribute surplus produce. He also served on the Downingtown Area school board and taught at West Chester University.

“Please know that I will continue to work hard for you until the very last day of my term,” he said in the statement.

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