New Scientist seems to be inventing a controversy here:

ALEXANDER wasn't quite so great after all. Sure, he conquered most of the world known to the ancient Greeks, but he didn't found the Egyptian city of Alexandria - he just rebranded it. It now seems that this part of the Nile has been settled for at least 4500 years, pre-dating Alexander's arrival by a good two millennia.

Alain Véron from the Paul Cézanne University in Aix-en-Provence, France, and colleagues made the discovery by measuring the variations in lead concentration in a mud core from Alexandria's ancient harbour. They determined how lead levels had changed over time by carbon-dating seashells found in the core.

Clear pulses of lead contamination occurred between 2686 and 2181 BC and then again from 1000 to 800 BC. The researchers conclude that these peaks were associated with human activities such as plumbing, fishing, building and ship-building. This is supported by ancient texts, which mention a settlement named Rhakotis (Geophysical Research Letters, DOI: 10.1029/2006GL025824).

Lead levels rocketed around 330 BC when Alexander the Great arrived, and got higher by the time of the Roman empire about 400 years later. The work should settle a long-running debate over the founding of the city based on literary evidence.

... folks will want to check out the excellent article in Al-Ahram from a few years ago on the subject of 'pre Alexander Alexandria' (although I'm not sure about the claims of a library are warranted) ...