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Dentistry: Guide to New Dental Amalgam Rule

Dentistry: Guide to New Dental Amalgam Rule

Effective July 14, 2017, the Federal Environmental Protection Agency (EPA) put into effect new effluent guidelines for dental facilities that discharge wastewater associated with the placement or removal of mercury containing amalgam (40 CFR Part 441).  Dental facilities that place or remove mercury-containing amalgam, in or from patients, must submit a certification to the control authority certifying that specific Best Management Practices (BMPs) are being followed.  The federally mandated BMPs necessitate the installation, operation, and maintenance of best available technology amalgam separators, to reduce the discharge of mercury-containing solids to the City of Tacoma’s (City) Publicly-Owned Treatment Works (POTW).  The City has been delegated authority from the Washington State Department of Ecology to ensure that dental facilities who discharge to the City of Tacoma comply with the required Best Management Practices.


If your facility discharges to the service area of the City of Tacoma POTW, your control authority and reporting responsibility is also to the City of Tacoma. This includes facilities located in the surrounding areas of the Cities of Fife, Fircrest, and Ruston. If your dental facility is in a contributing jurisdiction and you receive a notice, your location has been identified by a sewer mapping database as a discharger to the City of Tacoma POTW. These facilities will be required to submit compliance certification materials to the City of Tacoma.



Dental amalgam — typically referred to as a "silver filling" — is made of two nearly equal parts; liquid mercury, and a powder containing a mixture of silver, tin, copper, zinc, and other metals. The pollutant of concern in this alloy is the heavy metal mercury, which can have a bio accumulative toxic effect that persists when introduced into the environment, especially in aquatic ecosystems. Amalgam discharged to City of Tacoma POTW has the potential to enter local waterways through discharge to the Puget Sound and Puyallup River. Controlling amalgam discharges benefits the health of our local ecosystems.


Who is Affected by this Rule?

This rule applies to dental dischargers, including large dental institutions and clinics, where dentistry is practiced, who emplace or remove amalgam and who discharge to City POTW. Facilities that are affected by this rule will be required to submit a one-time compliance report/certification by October 12, 2020. To determine if this rule applies to your facility, see 40 CFR Part 441.10 (applicability).


New Facilities and Offices

New facilities that begin discharging to a publicly owned treatment plant on or after the effective date of July 14, 2017, are expected to comply immediately. Within 30 days of opening, these businesses must submit a signed Compliance Certification and include proof of installation of an amalgam separator that removes 95% of solids in accordance with ISO 11143 at the new facility to DentalAmalgam@cityoftacoma.org. If emailing a signed scanned document, keep the original onsite. Keep any maintenance logs, and records of amalgam waste disposal from a period of up to three years. The City of Tacoma may conduct site inspections to verify compliance with the rule. Change in ownership at a facility is considered a new source and the new owner must submit the compliance certification within 30 days. 


Existing Facilities and Offices

Facilities in business before the effective date of July 14, 2017, will have three years from the effective date to retrofit their offices with the required equipment. Existing facilities will be required to submit Compliance Certifications by October 2020.

Who is Exempt from this Rule?

This rule does not apply to mobile units or offices where the practice of dentistry consists only of the following dental specialties: oral pathology, oral and maxillofacial radiology, oral and maxillofacial surgery, orthodontics, periodontics, or prosthodontics. Also excluded are dental offices that do not place or remove amalgam except in limited, emergency or unplanned, unanticipated circumstances. However, these types of facilities will need to submit a one-time self-Certification Compliance form.



Forms Related links and resources


Tacoma's Dental Self Certification Compliance Form



Tacoma requires dental offices to meet requirements of this new rule. BMPs to be followed by all facilities affected by the rule include:

  • Treat all amalgam wastewater through properly-sized amalgam separator(s), certified to remove at least 95% of total amalgam solids, in accordance with ISO 11143.
  • Inspect the amalgam separator(s), at a minimum, once per month to ensure proper operation and confirm that there is no bypass of the treatment system (441.30(a)(2)(v)).
  • Repair or replace defective amalgam removal equipment/components in accordance to the manufacturer’s instructions (441.30(a)(2)(vi)).
  • Regularly maintain the amalgam separator(s) by replacing retaining cartridges, separator canisters, filters, and/or other treatment units annually, or whenever the unit reaches the manufacturer’s design capacity, whichever comes first.
  • The use of oxidizing or acidic cleaners to flush dental unit water lines is prohibited.
  • Collect scrap amalgam from chair-side traps, screens, vacuum pump filters, dental tools, and/or other collection devices for off-site disposal. Scrap amalgam must not be flushed down the drain.

All dental facilities are required to fill out an initial compliance report.


Record Retention

Compliance Certification: The dental facility or an agent or representative of the dental facility must maintain this Compliance Report and make it available for inspection in either physical or electronic form.


Other Records: The Dental facility subject to this rule must maintain documents and make available for inspection in either physical or electronic form for a minimum of three years, including receipts and manifests.

  • Documents related to inspection of amalgam separators and follow-up actions.
  • Documentation of amalgam retaining container or replacement, including date, if applicable.
  • Documents related to dental amalgam pickup or shipment for proper disposal by a licensed storage or disposal facility.
  • Documentation of any repair or replacement of an amalgam separator or device.
  • Manufacturer’s current operating manual for the device in place.


Contact Us

For questions or to submit compliance forms:

email us


Or mail to:

City of Tacoma
Environmental Compliance
Attn: Dental Amalgam
2201 Portland Ave. #P-1
Tacoma, WA 98421