Mehaffey leads the Irish Women’s Open Stroke Play Championship by six shots from Jessica Ross (Donaghadee) and Chloe Williams (Wales).
A flawless front nine included three birdies and six pars.
One dropped shot on the 11th was made up for when she carded an eagle at the 18th.
“I played really steady today and if I got in trouble I recovered well. Kevin LeBlanc, caddied for me so he was a great help,” said Olivia.
Asked about her eagle three on 18 she added; “I hit driver and then three wood to 12 feet and holed the putt so that was a nice way to finish.”
Mehaffey’s closest Irish competitors include Jessica Ross (Donaghadee) on 75 and Mairead Martin (Killarney) and Chloe Ryan (Castletroy) with scores of 77’s.
There will be a cut to 50 players (+ ties) after 36 holes.