Thirty years ago, Thomas Petty was a young employee at Chevron when he heard about a blood drive the company was hosting and encouraging its workers to participate in.

"They had regular blood drives so I started giving here and there," said Petty, a 55-year-old Livermore resident who now operates a digital marketing agency. "I've been a longtime volunteer since I was a teenager and so that was one way of giving back."

Petty would meet his wife Joanne at Chevron, and she also took part in the blood drives. But upon retiring, she realized she no longer had a go-to place to donate.

"That was when I said, 'Why don't we start our own (blood drive)?'" Petty recalled.

And so in December 2002, the Pettys held the inaugural Asbury United Methodist Church blood drive, collecting around 25 units of blood.

Just over 15 years later, the Livermore church's blood drive has become a monthly event that typically nets around 50 units of blood each time. Petty estimates a little over 5,800 units of blood have been collected all told.

Earlier this month which is National Blood Donor Month the American Red Cross recognized Petty for his work and his own contributions to the cause. At the Asbury UMC blood drive on Jan. 12, Petty arrived to a festive atmosphere with cake and balloons. It was his 100th time giving blood, meaning he has donated approximately 12.5 gallons.

Reaching the milestone "gets me ready to gear up to get to 200," Petty said. He estimates getting there will take him nearly 17 years.

"It makes me feel good that my donations are going to people who are sick or injured," Petty said. "In the Bay Area we don't have enough blood donors, so the Red Cross actually has to import blood from other parts of the country."

"And with all the snowstorms out east, they've canceled hundreds of blood drives, so there's a shortage on the shelf," he added.

Severe winter weather has led to the cancellation of more than 550 blood drives this month alone, causing over 16,500 blood and platelet donations to go uncollected through last week, Red Cross officials said in issuing an urgent call for donations.

"Blood and platelet donations are currently being distributed to hospitals faster than they are coming in," Red Cross Blood Services senior vice president Clifford Numark said in a statement. "Donors are critically needed to restock the shelves for patients in their community as well as areas where donors are unable to give due to inclement weather."

With a lack of donors in the Bay Area and the nationwide blood shortage, Petty encourages people to give blood if they can.

"Bay Area hospitals need over 300 units of blood every single day, and we don't have enough people donating," he said.

To schedule an appointment to give blood, visit redcrossblood.org, use the Blood Donor App or call 1-800-RED-CROSS.