Whenever I find an environmental concern (REC or not), I'll discuss with client before issuing my report just to make sure we're all on the same page with sensitivities and recommendations.  Also prior reports often magically appear that address the concern.

I would say "A", but I would not use the word "Muddle".  Any good EP wouldn't think twice about researching a potential issue; it's what we do.  In today's electronic world information too accessible to not research a concern.  

Interesting comments, everyone; thanks!

For future reference, there are a few publications that are particularly helpful in understanding historical industrial processes and their possible impacts on the environment.  These include:

• NPDES effluent guidelines development documents (by industry)
• Shreve's Chemical Process Industries (McGraw-Hill)
• Perry's Chemical Engineers' Handbook
• Kent and Riegel's Handbook of Industrial Chemistry and Biotechnology

Research through these (including older editions if you can find them) will help the environmental professional to better understand the processes used by the industry in question, which in turn will provide guidance as to where one should look for problems, and what the nature of those problems may be.  As Stones points out, Google and Wikipedia can also help, but for older facilities the available information may not have been updated in online sources.

Good luck to all when encountering a "new" industry to study.

I'd do it myself, really.  I can learn enough about an industry in a couple days to satisfy my needs for a Phase I.

I like the EPA notebook thing, especially the printers and dry cleaners ones.  You can also get quite a lot from history books, or even How It's Made or Dirty Jobs.  If it was a large or long-lived company, someone may have done a company history.

Your usual COCs for tanneries are metals (most commonly arsenic and chromium, but others too).  If it's not in an urban area, there may be burial pits on the site in which they disposed of wastes.  Acids and caustics were used pretty intensely to defat and depilate the hides, but those aren't usually persistent in the environment.  Dyes were usually vegetable-based prior to the anilines becoming common in the early 1900s.

Different types of leather involved slightly different processes.... e.g. saddle leather vs. patent leather (black and shiny, with a lacquer coating).

Random trivia-- the "soft, Cornithian" leather used in the first model years of the 1970s Chrysler Cordoba was apparently prone to giving people rashes because it was treated with large amounts of chromium and nickel.  Thank you, Ricardo Montalban.