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18-Env-A6 Solid Waste Engineering and Management · May 2014

Question 15 of 22: Importance of Hydraulic Conductivity of Compacted Wastes

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Notes on this paper

National Examination, May 2014 — 04-Env-A6 / 18-Env-A6, Solid Waste Engineering and Management. 3 hours duration, closed book, no calculator, one letter-sized aid sheet permitted. All 22 questions constitute a complete paper (100 marks total).

Reference texts: Tchobanoglous, Theisen & Vigil, Integrated Solid Waste Management: Engineering Principles and Management Issues; Vesilind, Worrell & Reinhart, Solid Waste Engineering; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); CCME, Guidance Document on Landfill Gas Management; Canadian Environmental Protection Act, 1999.

Question 15: Importance of Hydraulic Conductivity of Compacted Wastes (2 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.

The hydraulic conductivity of the compacted refuse mass governs how quickly infiltrated water (and leachate) moves through the waste toward the collection system at the base, which is needed to (1) design the leachate collection system's capacity so it can keep pace with the actual rate leachate arrives, and (2) predict how long it takes moisture to reach the refuse's field capacity and begin producing leachate at all. If the waste's hydraulic conductivity is too low relative to the inflow rate, water can perch and build up within the waste mass (the "bathtub effect"), raising internal pore pressure and slope-stability risk, rather than draining efficiently to the collection layer.