This would also identify water table depth, soil liquefaction, soil expansivity (soil that expands or shrinks), or soil chemical content.

No heavy chemicals should go down the drain.

You cannot occupy the property on a DSCR loan, im not sure about hard money loans but to be honest I'm not sure why you would want to take on the harsh terms of a hard money loan for a house hack.These are investment loans, and for DSCR loans the terms are based on projected rental income and the lenders are calculating their risk based on how certain they are that the property will produce enough income to pay back the loan.

I sent them a link with a non-chemical alternative method to use a less harmful way to get rid of them, and suggested they take one to a nursery to see if they actually ARE dangerous, advised to supervise their child and dogs, just like they would in a local park, but I'm not about to run back and forth to the property everytime a naturally-occuring plant pops up on the lawn.   

During my research, I've been focusing on the potential risks associated with the use of laundry chemicals and their potential impact on the surrounding areas, particularly on the upper floors. 

And even if it is a year long with time left, it is impossible to perform (the tenant is dead) so  I would send them a letter ending it with no liability (and if you are looking for the vacancy days from a dead guy that was there 27 years, that is a looking  a bit harsh) and forward all the mail.

How much of this operation do you foresee having to rely on Governmental handouts to make a go of it.Do you have cleared farmable land that has been off chemical fertilizer for enough time to be "Organic", or are you waiting for the time to expire on the land still?

If the released chemical does not constitute as a reportable event it wont become public. 

I think the letter is a little harsh and threatening and could be reworded but I see your point too. 

You may also want to consider an environmental test to make sure there's no rusted, buried drums of chemicals hiding somewhere.