I work full time as a chemical engineer and have become very interested in real estate.

They were manufacturing it in the garage with oxygen and acetylene tanks and dozens of other flammable chemicals.

Sand, or chemicals?

Leaves and debris not being cleaned out jam up pumps, chemical balances are a constant annoyance, possible plumbing issues, extra water costs.

There are many solutions that you can do yourself.There are some that you never want to do yourself.The EPA guidance on mold issues is here:  http://epa.gov/mold/moldguide.htmlThe digital copy of the same information is here: http://epa.gov/mold/pdfs/moldguide.pdfThis document does not help you estimate costs for repairs, but does help you see through the "smoke screen" that many remediation companies will put up when talking about mold in homes.In spite of what John D. recommended in his response above, the use of a chemical or biocide that kills organisms such as mold (chlorine bleach, for example) is not recommended as a routine practice during mold cleanup.  

You are looking more of the large manufacturing facility or chemical company type place.

I own several businesses, from the chemical industry to govtech and consumer products.

Those chemicals are obviously a deadly serious hazard & I would rather put my life & health in my own hands rather than a corporation that is only concerned with getting it clean enough to be able to legally sign off on it.

Outside of my interest in REI, I'm just a sales guy with a chemical engineering background.

PB has been found to have its structural integrity reduced compared to other materials because of the way many chemicals in public water supplies react to it, breaking it down and causing small cracks over a long period of time.