[Solved] Removing Permanent Ink from Mylar
Most of us have gone through this process on our own work. Is it safe to presume that the record of survey is something that your office/department/organization prepared? If so, it is probably proper for you to alter it and some of the above will work. I suggest that you contact the oldest drafter or PLS around and have them help. If not, contact the original surveyor and have them print a replacement and enter it into the record with a note as to why. If you are trying to alter someone else's work, I cannot help.
Electric eraser as above but with a solvent impregnated eraser; they were blue green if I'm recalling correctly.
If you can find them, the soft yellow eraser sticks were the best, but at the price on Amazon you can reprint a lot of mylar.
WD40 should work
Most permanent marker will come off skin and other surfaces by using some oil based product like skin cream.
Then it is necessary to clean that oily substance off the mylar.
Too much electric erasing can scorch the mylar.
UPDATE: After a surprisingly enjoyable science experiment, we discovered that both acetone and WD-40 worked wonders for removing the permanent markers our office uses! We're going to go with acetone in the unlikely event this happens again - applying with a q-tip made it easier to contain what was erased.
Thanks for all your suggestions! 👍