Stormwater management ponds (SWM ponds) capture runoff and accumulate sediment over time. Appropriate management, and disposal, of SWM pond sediments removed during cleaning or decommissioning requires an understanding of the environmental quality of those sediments. Ontario Regulation 406/19 and the accompanying soil rules have specific regulatory requirements for managing excess sediment from all SWM ponds (i.e., where that sediment cannot be managed on-site).
What contaminants are expected?
O.Reg. 406/19 sets out minimum sampling and analysis requirements sufficient for SWM pond projects. However, although a formal “Assessment of Past Uses” is not required to support the excavation of sediment (or soil) from a SWM pond, your Qualified Person (QP) may recommend completion of this step if your pond is in a commercial/industrial area.
- Action: For commercial/industrial sites, interview facility operators and review historic records to get an idea of what potential contaminants may exist in the pond’s sediment.
- Benefit: This will help reduce the potential for surprises later in the process.
- Checkpoint: Have potential beneficial Reuse Sites been identified? The characteristics of the Reuse Site(s) will help determine what quality standards will apply to the SWM sediment.
Characterization of SWM Pond sediments can be challenging
Based on the SWM pond physical characteristics, the volume of sediment and potential contaminants of concern, the QP will set out a plan (i.e., Sampling and Analysis Plan) for assessing the environmental quality of the sediment.
An initial in-situ sampling program can help determine the quantity of sediment needing removal and identify potential problem areas. It can also help identify suitable Reuse Sites earlier. More sampling and analysis can be done, including mandatory leachate testing, once the sediment has been dredged and dewatered.
- Action step: Consider characterizing the quality of the sediment following a staged approach, incorporating both in-situ and ex-situ sampling.
- Benefit: The QP will be able to respond effectively if there is a need to revise the sampling and analysis plan, maybe to confirm earlier findings or point to new information.
- Checkpoint: Were any surprises found in the sampling and testing program? If so, the QP should review the site history and consider modifying the sampling plan.
Communicate the results of sampling and testing
One of the requirements of O.Reg 406/19 is formal documentation of the sampling and analysis carried out for the SWM pond sediments (i.e., a Soil Characterization Report). These findings are expected to be presented by the QP in a narrative format, supported by data tables, site plans and laboratory certificates of analysis.
- Action step: Consider what additional information potential receivers of the sediments may require prior to accepting the material, such as any nutrient information for agricultural applications.
- Benefit: Recognizing, in advance, that suitable Reuse Site(s) may have considerations other than just the geochemical quality of the sediment should help prevent last minute delays in gaining acceptance of the material.
- Checkpoint: Does the quality of the excess soil/sediment meet the specific criteria for each of the proposed reuse/disposal site(s)?
Reuse of SWM Pond sediment can be problematic
Due to the physical properties of SWM pond sediment (primarily high-water and organic content), beneficial reuse opportunities may be limited. SWM Pond sediment may need management steps similar to those for soil from Brownfields . This may be the case even if the material meets the applicable Excess Soil Quality Standards.
O.Reg. 406/19, and the accompanying soil rules, outline specific requirements relating to dewatering or solidifying liquid soils (i.e., including, but not limited to, sediment). Many soil conditioning processes are now permitted under O.Reg. 406/19, offering opportunities to improve the sediment properties so that they are suitable for a wider range of beneficial reuses. Soil conditioning is now permitted in the Project Area or at some Temporary Storage Sites, offering greater flexibility and more opportunity to avoid costly disposal wherever possible.
Assuming that the dredged sediment does not warrant disposal as a waste, before the Reuse Site agrees to accept the sediment, you will need to document that the material meets the specific requirements of the Reuse Site (e.g., through an Excess Soil Destination Assessment Report).
- Action step: Engage with potential reuse and/or disposal sites early in the planning process.
- Benefit: Starting this planning exercise earlier in your project will help find a beneficial reuse of the sediment and may even help get earlier commitments from potential sites to accept the material.
- Checkpoint: Does the owner/operator of the Reuse Site understand their own regulatory obligations? A collaborative approach will help reduce the potential for project upset at the “last minute”.
Plan transport and document delivery
Implementation of a tracking system is the final component required to demonstrate compliance with O.Reg. 406/19. It must be robust enough to readily provide information regarding the origin of each load of soil (sediment) and its approved destination.
- Action step: Start developing a tracking system early in the process, that is suitable for the volume of soil involved.
- Benefit: Fewer challenges from regulators, fewer project delays, satisfied recipients of your Excess Soil.
- Checkpoint: Is the tracking system suitable for the complexity of your project? Do staff or contractors need training?
Management of SWM pond sediment requires special planning and care. Following the steps required by O.Reg. 406/19 will provide reasonable reassurance for yourself (and your legal team) that the sediment does not carry liabilities with it when it leaves your site. Becoming familiar with the process will give you an edge in working with properties that include SWM ponds.
Carl Schroeder Member Name
Senior Environmental Engineer
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- Reg. 406/19: On-site and Excess Soil Management
Carl Schroeder (M.A.Sc., P.Eng.) is a professional engineer in Ontario with over twenty (20) years of experience as an environmental consultant with Golder. Carl is a Qualified Person under Ontario Regulation 153/04 and has assisted numerous clients with Environmental Site Assessments (ESAs) and site remediation for general due diligence and in support of Record of Site Conditions in this role. As a generalist environmental engineer, over the course of his career Carl has undertaken or managed hundreds of environmental projects for large and small clients, including the provision of strategic, regulatory and practical advice to clients on managing their environmental risk relating to property transactions, management of excess soil material, demolition, decommissioning and infrastructure (culvert) management.