The Washington State Department of Ecology is revising the air quality thresholds for toxic air pollutants (TAPs; WAC 173-460), based on best available science. These proposed changes have some significant effects for landfill owners looking to keep air quality good, protective of human health and the environment, and doing so cost effectively. The key proposed changes are:
The last flare this landfill in Port Angeles will ever need. When the gas is no longer combustible, reliable treatment will be provided by biofilter technology – made easier by recent updates in air quality criteria.
Two of the most conservative constituents commonly found in landfill gas, benzene and vinyl chloride, will have higher thresholds (by factors of 3.7 and 8.9, respectively).
The threshold for hydrogen sulfide – a common driver for odor control in landfill gas – did not change. However, biofilter technology is showing promise as an economic and reliable method for polishing treatment.
The threshold for trichloroethene went down by a factor of 0.4. This constituent has also been commonly found in landfill gas, and the new threshold may or may not change our clients’ treatment obligations.
What this means for landfill owners is that air quality compliance should be easier to demonstrate. This means:
Downscaling treatment at older landfills can focus on odor control instead of destruction efficiency for volatile organic compounds (VOCs) as TAPs.
The costs associated with flaring landfill gas can be re-directed to biofilter technology for polishing treatment for odor control.
The schedule for ending or minimizing post-closure obligations associated with landfill gas treatment can be accelerated.
Next Steps
This rule-making process is on-going, and details of the process are provided at Ecology’s website: https://ecology.wa.gov/460rulemaking.
A hearing on the re-calculated air quality thresholds is planned for July 16, 2019, and comments are due be July 23, 2019.
Barring delays, the new rule on air quality thresholds becomes effective in late October 2019.
For more information on what the implication of these changes for landfill owners and managers, contact Associate Engineer Peter Bannister at (206) 780-7728 and pbannister@aspectconsulting.com.