Question 1 of 10: Two False Statements — Hazardous Waste Identification and TCLP

Question 1: Two False Statements — Hazardous Waste Identification and TCLP (5 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Statement (a) — listing is only ONE of two independent routes to a hazardous-waste determination. Ontario Regulation 347's F, K, P, U and S schedules (mirroring the RCRA F/K/P/U listed-waste categories) list specific processes and discarded commercial chemical products that are hazardous by definition, regardless of how they test. But every jurisdiction's hazardous-waste rule also has a second, entirely independent pathway: a waste that exhibits one or more of the four hazard characteristics — ignitability, corrosivity, reactivity, or toxicity (the last determined by TCLP, Question 1(b) below) — is hazardous even though it appears on no list at all. A used solvent blend that is not a named F/K/P/U waste but has a flash point below 60°C is still hazardous by the ignitability characteristic; a plating rinse water containing no listed chemical but with a TCLP-leachable cadmium concentration above the regulatory limit (Question 4 below) is still hazardous by the toxicity characteristic. Absence from a list therefore proves nothing on its own — the generator must ALSO screen the substance against the four characteristic tests before it can be certified non-hazardous. The statement conflates one sufficient condition (listing) with a necessary one, which it is not.

Statement (b) — a 0.4% solids sample never reaches the shred/dry/extraction-fluid stage of TCLP at all. EPA Method 1311 (Toxicity Characteristic Leaching Procedure) begins by determining the sample's percent dry solids by filtration, and that single number decides which of two entirely different procedures follows:

1. Route 1 — percent solids ≥ 0.5%. The liquid and solid phases are separated; the solid phase, if its particles do not already pass a 9.5 mm (≈3/8 in, <1 cm) sieve, is size-reduced to increase its exposed surface area, and is then agitated with an appropriate extraction fluid (a pH 4.93 buffered acetic-acid/NaOH fluid, or a pH 2.88 acetic-acid-only fluid for low-alkalinity wastes) at a 20:1 liquid-to-solid ratio for 18±2 hours in a rotary extractor. This is the sequence Statement (b) describes.
2. Route 2 — percent solids < 0.5%. The sample is essentially all liquid, so after filtration the filtrate itself IS defined, by the method, as the TCLP extract — no extraction fluid is added, no particle-size reduction is performed, and no 20:1 dilution is applied, because there is effectively no solid fraction left to extract from.

Substance B's solid content is 0.4%, which is below the 0.5% threshold, so it falls squarely under Route 2: the correct procedure is to filter it and analyze the filtrate directly as the TCLP extract. Shredding it to <1 cm, drying it, and mixing it with acetic acid at a 20:1 ratio is the Route 1 procedure for a ≥0.5%-solids sample and is simply the wrong protocol for a sample this dilute — drying a nominally-liquid waste before testing would also drive off any volatile organic hazardous constituents, defeating the purpose of the test.