If it were me, I'd drain half the water and refill. You can also drain 1/4 of the water and refill--your CYA should come to 80 then.

Aylad lives 'way down South and she finds she needs to run her CYA at 80. Otherwise the sunshine and other stuff eats her residual chlorine too fast. So by running 80ppm and her FC in the 8-10ppm range for normal swimming, she doesn't have to keep adding excessive chlorine.

OTOH, she has to test to a higher level, but that trade-off works for her. I'm in a cooler climate and the sun is less intense so I prefer to run CYA in the 30-50 range, no higher.