That’s a very broad question so let’s break it down a bit.
First,  while BC (like most provinces) does have its own provincial TDG enforcement infrastructure and accident/emissions reporting requirements, it basically follows federal TDG rules as far as substantive safety issues. That includes rules for containers, which are set out in Part 5 of the federal TDG Regulations, Means of Containment. So that’s where you should look first. Here’s the link, http://www.tc.gc.ca/eng/tdg/clear-part5-300.htm
I was also able to find some federal TDG guidance from Transport Canada on reuse of drums that were previously used to contain dangerous goods. https://www.tc.gc.ca/eng/tdg/moc-smoc-faqdrumreconditioning-280.html Some of the key points:

• Steel drums with a capacity greater than or equal to 150 L may not be reused to transport liquid dangerous goods in classes 3, 4, 5, 6.1, 8 or 9 unless the drums are reconditioned in accordance with the requirements of Part II of CGSB-43.126 before reuse;
• Plastic drums with a capacity greater than or equal to 150 L may not be reused to transport liquid dangerous goods in classes 3, 4, 5, 6.1, 8 or 9 unless the drums are reconditioned in accordance with the requirements of  Part III of CGSB-43.126 before reuse;
• The requirements for reconditioning are set out in Part II (for steel drums) and Part III (for plastic drums) of CGSB-43.126, but not limited to:
  • interior and exterior washing
  • interior and exterior inspection
  • chime straightening (for steel drums only)
  • leak testing
  • replacement of all non-integral gaskets
  • marking

There are also separate rules for drum remanufacturing–which I presume don’t apply to your situation. Hope this helps.
Glenn Demby, 203 354-4532