CPWM Landfill Design and Operations 4 — Questions and Answers
Question 1: What is the design life requirement for post-closure care at a municipal solid waste landfill under federal regulations?
- 10 years
- 20 years
- 30 years (Correct answer)
- 50 years
Correct answer: 30 years
RCRA Subtitle D requires a minimum 30-year post-closure care period, though states may require longer periods based on site-specific conditions.
Question 2: Which of the following is NOT a required component of a landfill's post-closure care plan?
- Maintenance of the final cover system
- Groundwater monitoring continuation
- Leachate management system maintenance
- Resumption of waste acceptance for beneficial reuse (Correct answer)
Correct answer: Resumption of waste acceptance for beneficial reuse
Post-closure care includes cover maintenance, groundwater monitoring, and leachate management, but waste acceptance is permanently prohibited once closure is certified.
Question 3: What type of financial assurance mechanism allows a landfill owner to self-fund closure costs by depositing funds into a dedicated trust over the life of the facility?
- Surety bond
- Letter of credit
- Closure trust fund (Correct answer)
- Liability insurance policy
Correct answer: Closure trust fund
A closure trust fund requires annual contributions so that, at the time of closure, sufficient funds are available to complete closure and post-closure activities without reliance on external credit.
Question 4: Bioreactor landfills differ from conventional MSW landfills primarily because they:
- Use only geomembrane liners without clay components
- Deliberately recirculate leachate to accelerate waste decomposition (Correct answer)
- Prohibit all gas collection infrastructure
- Operate under negative pressure to prevent gas escape
Correct answer: Deliberately recirculate leachate to accelerate waste decomposition
Bioreactor landfills intentionally recirculate leachate (and sometimes add liquids) to maintain optimal moisture for microbial activity, accelerating waste stabilization and gas generation.
Question 5: What is the minimum thickness of low-permeability soil required in the final cover barrier layer under 40 CFR Part 258?
- 6 inches
- 12 inches
- 18 inches (Correct answer)
- 24 inches
Correct answer: 18 inches
The final cover barrier layer must be at least 18 inches of compacted soil with hydraulic conductivity ≤1×10⁻⁷ cm/s, or an equivalent geomembrane alternative.
Question 6: A landfill is located within 10,000 feet of an airport used by turbojet aircraft. What operational restriction applies?
- Enhanced leachate monitoring is required
- The landfill must demonstrate it will not increase bird hazards to aircraft (Correct answer)
- Landfill gas flares must be extinguished during flight operations
- Waste must be covered more frequently to reduce odors
Correct answer: The landfill must demonstrate it will not increase bird hazards to aircraft
Federal regulations prohibit siting or operating MSW landfills within 10,000 feet of airports serving turbojet aircraft unless the owner demonstrates the site won't pose a bird-strike hazard.
Question 7: Which analytical parameter is most indicative of fresh leachate contamination in downgradient groundwater monitoring wells at a young MSW landfill?
- Total dissolved solids and chloride (Correct answer)
- Arsenic and lead concentrations
- Dissolved oxygen levels
- pH values above 9.0
Correct answer: Total dissolved solids and chloride
High total dissolved solids (TDS) and chloride are conservative tracers commonly used to detect fresh leachate in groundwater because they are mobile and do not readily attenuate.
CPWM Landfill Design and Operations 4
What is the design life requirement for post-closure care at a municipal solid waste landfill under federal regulations?