Question 5 of 16: Common Landfill Design Problems

Question 5: Common Landfill Design Problems (8 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.

(1) Leachate generation and containment — infiltrating precipitation percolates through the refuse and must be intercepted by a composite liner/collection system before it can reach groundwater; liner integrity and long-term leachate management (including post-closure, once active collection may cease) are a central design risk. (2) Landfill gas generation, migration and control — anaerobic decomposition produces methane (explosion hazard if it migrates laterally into buildings) and is a potent greenhouse gas if released uncontrolled, requiring an active or passive gas collection system. (3) Differential settlement — refuse compresses non-uniformly as it decomposes and consolidates over years to decades, which can crack the final cap (compromising its barrier function) and damage gas/leachate infrastructure; design must anticipate and accommodate this movement. (4) Siting and slope/geotechnical stability — suitable geology (low-permeability native soils, adequate separation from groundwater and sensitive receptors), sufficient capacity/life, and stable side-slope geometry for both the waste mass and the liner system are all difficult constraints that shrink the pool of viable sites and often meet strong community opposition.