These babies weren't buried. They were literally flushed down the toilet.
If you look at Catherine Corless statements, her claims are based entirely on speculation that there MIGHT be human remains in a septic tank where the orphanage used to be, but the septic tank hasnt even been excavated to see if theres anything down there. She has also admitted that it isnt large enough to hold the 800 skeletons which she has speculated might be in there.
The only reason she thinks there are any skeletons in there at all is because:
These remains (if they existed at all) were apparently never exhumed nor examined to determine whether they are human or animal, or what historical time period they date from (a century ago? Two centuries? A thousand years ? Youd need to carbon date them).
They havent been able to find these bones that were supposedly there, somewhere. Hence there is absolutely no credible basis for the claim of a mass grave which the media keeps on repeating.
And it gets even smellier. If you follow the stated sources in these media articles, you can trace the information back to a tabloid called the Irish Mail, which looks and reads like the National Enquirer and is seemingly no more credible. Worse, many of these news articles have been running the grossly misleading headline 800 babies found in a mass grave while usually admitting (near the end of the same articles) that the septic tank hasnt been excavated yet.
A few articles admit that many of the locals thought the bones dated from the time of the great famines in Ireland, in which case they would have nothing to do with the orphanage; some articles also admit that the recorded deaths at the orphanage were in the same proportion as overall childhood deaths in the general population at that time, due to diseases that couldnt be cured yet.
Even Corless hasnt accused the nuns of deliberately starving children to death, despite all the lurid, sensational headlines. In short, the medias own articles often contradict their own headlines and scandal mongering; and the actual quotes from Corless and other people involved indicate that there is virtually nothing behind these claims at all. This is the definition of a smear campaign, helped along by people who have little interest in evidence as long as there are Long-dead charitable Christian women who need a good bashing.