• Fill Materials: The Good, the Bad and the Ugly – Part 1

  • By: Bill Leedham, P. Geo., CESA

    Recently there has been a lot of discussion about fill, especially with proposed new Ontario regulations for excess construction fill and requirements for Soil Management Plans (SMP) to be completed by a Qualified Person. I thought this would be a good time to talk about the subject of fill materials as they relate to Environmental Site Assessments. I will leave the issues of excess construction fill and SMP for a future blog, and instead discuss what constitutes fill, why it can be a potential environmental concern, and how to identify possible fill in Phase 1 ESA research and distinguish fill materials in the field.

    What is Fill?
    Fill definitions may refer generally to any type of material that can be deposited or removed from lands, or list example materials which may constitute fill. According to the Ontario Ministry of the Environment (MOE), under their Proposed Excess Soil Policy Framework - “‘Fill’ means topsoil, Soil, rock, stone, clean concrete without coating, free of rebar and free from contamination, sod or turf, either singularly or in combination, and scientifically demonstrated inert material”; and “‘Waste’ means any material that is not Fill.” Regulation 347 under the Ontario Environmental Protection Act (Waste Management – General) designates “inert fill” as a waste and then goes on to exempt “inert fill” from the waste management requirements under Part V of the EPA. “Inert fill” is defined as “earth or rock fill or waste of a similar nature that contains no putrescible materials or soluble or decomposable chemical substances.”

    Why is Fill a potential environmental concern?
    Fill materials on a property can present problems for many reasons, including: potential environmental concerns due to soil and groundwater impacts from contaminated fill to and/or methane generation when high organic content soils or putrescible materials (garbage) are buried; geotechnical concerns related to poor soil bearing capacity and structural settlement; and financial concerns due to excavation and disposal and/or increased construction costs. The Canadian Council of Ministers of the Environment (CCME) notes that historical filling with waste soils may result in dispersed and approximately random “pockets” of contamination of varying size. In Ontario, the MOE has defined “Importation of Fill Material of Unknown Quality” as a Potentially Contaminating Activity (PCA), and the presence of such material on-site would trigger a mandatory Phase Two ESA for the purposes of obtaining a Record of Site Condition.
    When people say ‘Clean Fill Wanted’ they usually mean soil that is free from organic matter, vegetation, debris or other deleterious or un-compactible materials; and little thought is given to the source of these materials nor their chemical composition, especially for historic fill placement. Fill materials of unknown origin or quality may have been imported to a property for rough or bulk site grading; levelling or filling in localized low spots, ravines or depressions; and for backfilling of buildings, excavations, or below floor slabs and pavement structures. If such material were to originate from an industrial property or other (potentially) contaminated site, those source property contaminants could also be imported to the receiving property. Field indicators of potential soil contamination may include the presence of site features such as tanks, drums, burn pits, lagoons, etc., as well as the presence of odorous, discolored or stained soils, the presence of non-native materials such as fill, stockpiles, or debris, and the presence of distressed vegetation, or contaminant tolerant plant species.

    About the Author:

    Bill Leedham, P. Geo., CESA
    Bill is the Head Instructor and Course Developer for the Associated Environmental Site Assessors of Canada (
    www.aesac.ca); and the founder and President of Down 2 Earth Environmental Services Inc. You can contact Bill at info@down2earthenvironmental.ca