That's high, but not as crazy as our water here.
Calcium 2.96 ppm
Magnesium 0.7 ppm
Bicarbonate 459 ppm
Sodium 200 ppm
Chloride 54 ppm
Sulfate 9 ppm
Now
that's out of whack!! Almost no calcium or magnesium to balance out the insanely high bicarbonates.
Have you checked out
Palmer's spreadsheet or nomographs on water corrections? See
here. Highly recommended!
Here's what I've been doing. I add about 1/2 - 3/4 of the amount of lactic acid required to get the residual alkalinity into the range needed for the beer's SRM. Then I add the 5.2 pH buffer and let that lock the pH in where it needs to be. I still have horrible efficiency, but my beers taste great. Another local brewer said he strictly uses lactic acid and has had good results. I like the idea of the buffer since the levels probably fluctuate throughout the year. It takes the guess work out.