Tudor Thomas Davies, a senior EPA scientist and executive whose work led to protections for the Chesapeake Bay, has died.

Davies died of pancreatic cancer Nov. 27 at his home in suburban Washington. He was 65.

Davies joined the then-nascent environmental agency in 1972. For the next three decades, he served as director of the water and science program offices and as acting assistant administrator.

His water-quality research would form the basis for efforts to protect local, national and international waters from pollutants. In the late 1970s and early 1980s, he led the EPA’s multiyear study of the Chesapeake which led to the creation of the Chesapeake Bay Program in in 1983.

Davies retired in January 2001 at the end of the Clinton administration. Then-Administrator Carol M. Browner had just nominated him for a Distinguished Career Award. “His achievements, dedication and high standards exemplify the very best of the federal civil service,” an assistant administrator wrote in the fall of 2000.

Friends and colleagues said Davies, a native of Wales, pursued his efforts with a work ethic that emphasized hard science and a spirit of gentlemanly collaboration.

His first assignment at EPA in 1972 was a three-year research project on the Great Lakes that led to national restrictions on phosphates in laundry detergent. Next, he focused on the impact of toxic chemicals on aquatic plants and animals, work that shaped the agency’s handling of insecticide discharges in the James River.

Davies also directed research at a laboratory he opened in Rhode Island in 1982 that included the effect of New York and New Jersey cities’ dumping of sewage sludge in coastal waters. He later took part in agreements to restrict such practices.

“He knew that environmental research was only a means to an end: applying the lessons learned and the tools to improve the environment,” said his widow, Elaine Fitzback Davies. “He knew also that the environment did not stop at the border…and had an uncanny knack for pulling people together.”

Davies was awarded the Presidential Meritorious Rank Award and gold medals for creating the National Estuarine program and for forging an agreement in San Francisco that raised drinking water standards for millions of people in northern California.