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Marijuana Grow Operations

Assessment and Cleanup


When does the municipality get involved?

Muncipalities become involved in marijuana grow operation (MGO) investigations once Police notify a municipality of an MGO in their jurisdiction. A municipality has a legal responsibility to do an inspection where an MGO has been found.

Investigations are only done on properties identified as MGOs after December 12, 2006.

The role of Peel Public Health in an investigation

Peel Public Health ensures that unacceptable public health hazards from a property identified as an MGO are assessed and cleaned up. Peel Public Health does not assess structural or other physical hazards. However, the municipality oversees the assessment of these hazards.

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The investigation process

In Brampton and Mississauga, once a property has been identified as an MGO by Peel Police, the area municipality is notified. Brampton or Mississauga staff then notify Peel Public Health.

In the Town of Caledon, Ontario Provincial Police inform the town of properties identified as marijuana grow operations. Addresses of properties found to be MGOs and information on their cleanup can be found on the Town of Caledon’s Grow Ops & Clandestine Labs List or you can call 905-584-2272 (toll free at 1-888-CALEDON).


Who is responsible for choosing a qualified remediation (cleanup) individual or company?

It is the responsibility of the homeowner or landlord to select an individual or company to remediate a marijuana grow operation. ‘Remediation’ refers to the clean up of a property formerly used as a marijuana grow op.

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Qualifications of a remediation individual or company

The selected remediation individual or company is required to:

  • have a current and active membership in a related professional organization or certifying body of expertise (e.g., Environmental Health or Indoor Air Quality) prior to the start of any work on the premises.
  • demonstrate current and active membership in a related professional organization or certifying body of expertise to Peel Public Health.

Peel Public Health strongly recommends that the individual or company that is chosen carries environmental liability insurance of at least one million dollars and qualifies for Professional Errors and Omissions coverage.

The laboratory selected by the individual or company to do the microbial analysis (testing for mould) should be:

  • certified by the American Industrial Hygiene Association as an Environmental Microbiology Accredited Laboratory with expertise in moulds; or have other comparable accreditation; or
  • able to demonstrate regular participation and acceptable performance in an Environmental Microbiology Proficiency Analytical Testing (PAT) program for both culturable and direct examination determination of fungi, or have other comparable accreditation.

Documentation of accreditation must be provided to Peel Public Health.

Regulation of remediation companies or individuals

Neither the Region of Peel nor the Province of Ontario licenses or certifies companies to investigate, remediate or test environmental conditions within former marijuana grow operations.

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The Indoor Air Quality Assessment Report

When an MGO is found, it is very likely that an air quality assessment will be required. The air quality assessment must be done by a professionally qualified individual or organization, who will complete an Indoor Air Quality Assessment Report.

The Indoor Air Quality Assessment Report evaluates the:

  • extent of water damage.
  • indoor moisture problems and associated mould.
  • levels of pollutants (pesticides, fertilizer, etc) and compounds present in the air.

The report is comprised of three parts:

  • a detailed assessment of the unit before cleanup
  • a description of the proposed cleanup
  • a final evaluation report.

The initial assessment should include invasive testing into hidden spaces (i.e., behind drywall, etc.).

The following should be documented in the Indoor Air Quality Assessment Report:

  • air temperature
  • relative humidity
  • carbon dioxide levels
  • carbon monoxide levels
  • measurement of volatile organic compounds (VOCs)
  • the presence of mould (including air and swipe tests)
  • a description of the state of the ventilation system.

Recommended procedures for testing will be provided to the owner of the MGO.

When is the investigation complete?

An air quality remediation is complete when Peel Public Health is satisfied with the remediation and/or the Indoor Air Quality Assessment Report and no longer objects to re-occupancy.

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Identifying and Reporting an MGO | Information About MGOs | Health and Safety Concerns
Assessment and Cleanup of an MGO | Resources

Revised: Wednesday February 29 2012

Revised: Friday July 09 2010


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