Summary of Issue
Things to Consider
Hydro excavation is becoming increasingly popular in Ontario municipalities for small public works activities where there are existing buried utilities, constrained site conditions or unsafe environments. The technology allows for quick and precise excavations which require less backfill, less labour with a lower excavation footprint than conventional drilling methods. High-pressure water is used to loosen the soil and dig a hole. The wet, muddy excavated material is then suctioned into a tank that is mounted on a hydro excavator truck and carried offsite. The slurry is often commonly referred to as “liquid soil”, and liquid soil is manageable under the Excess Soil Regulation, if key criteria are met; hydro excavated slurry may not be manageable based on the Excess Soil Regulation if it is made up of such materials as wastewater and/or materials associated with higher-risk activities. Excavated dry and liquid soil (e.g. excavation necessary to repair a watermain) is generally regulated under the Excess Soil Regulation; materials such as sewage from a catch-basin cleanout are not.
The difficulty with hydrovac excavation is finding an approved site that can process the liquid soil and convert it to dry soil that can then be beneficially reused. Currently, there are not many municipalities that have the proper infrastructure (at public works sites) or approved processing sites, to deal with the liquid slurry that is produced from the hydrovac process.
Liquid soil collected by hydrovac trucks is also challenging because the vehicles typically collect slurry from multiple sites, and if one of those sites contains some contaminated soil, the entire truck load could be deemed contaminated. Some of the best practices for managing these issues include:
Permitting soil management sites (for temporary storage or processing) to receive and process liquid soil
Require haulers to use detectors for VOCs and other means to check for contaminants in the soil at each location
Build special containment areas on public works lands to receive and treat the liquid soil extracted from municipal work sites.
Short Form References
This page makes reference to:
The “Excess Soil Regulation” which is the short form for the Ontario Regulation 406/19 On-Site and Excess Soil Management made under the Environmental Protection Act.
The “Rules document” which is the short form the reference document to the regulation entitled Rules for Soil Management and Excess Soil Quality Standards
Key Takeaways
The Excess Soil Regulation has a range of requirements that affect hydro-excavation, including but not limited to:
When liquid soil can be accepted at a reuse site
Liquid soil can be accepted at a reuse site only if a site-specific instrument (e.g. a by-law) authorizes the liquid excess soil to be deposited at the reuse site; this is to ensure appropriate on-site management of the liquid soil.
See Section 3(2)3 of the Excess Soil Regulation. From the perspective of municipal by-laws this is a key provision, as the municipal by-law can permit the receiving of excess soil at a reuse site, in accordance with Sections 3-5 of the Excess Soil Regulation.
This can include liquid soil from vac-trucks, provided regulatory requirements are followed (e.g. the material is excess soil and not hauled sewage or other material not included).
There are general storage rules in Part I, Section C of the Rules document that would apply (though the by-law or related permitting process can create alternate storage rules).
When local waste transfer facilities can be used, without an ECA, for such activities as passive dewatering (Section 25)
If there is a hydro-vac operation that is operating outside of what would be considered a local waste transfer facility, then this kind of site would require an ECA for waste (and would be considered a Class 1 soil management site).
Liquid Soil is defined in the Excess Soil Regulation as: soil that has a slump of more than 150 millimetres using the Test Method for the determination of “Liquid Waste” (slump test) set out in Schedule 9 to Regulation 347;
A local waste transfer facility is defined in Regulation 347 (General – Waste Management). Local waste transfer facilities can be utilized for the same temporary storage and processing of excess soil as source sites/project areas well as temporary storage and specified low risk processing of liquid soil (e.g., dewatering of liquid soil) with an ECA for waste, provided requirements and rules in the Excess Soil Regulation and the Rules document are met.
Local waste transfer facilities must be either owned by a public body or by a project leader in respect of an undertaking related to infrastructure. The Soil Rules document provides additional requirements for different types of temporary sites, including local waste transfer facilities. There are storage rules that apply to all sites in the Rules document; however a by-law or related permitting process can set its own alternate storage rules.
Like other haulers of excess soil, it should be noted that a hydro-vac truck is required to carry a hauling record when transporting excess soil or liquid soil.
For more information, see factsheets on the MECP’s Excess Soil main page (Handling excess soil | Ontario.ca):
Also, for more information on hauling of excess soil, including from hydro-vac trucks see Best Practices for Hauling for Consideration with O. Reg. 406/19: On-site and Excess Soil Management in Ontario from the Ontario Environmental Industry Association.
By-Law Sections
Requirements for Issuance of a Permit
Things to Consider
The Town of Whitchurch-Stouffville has developed an approach in their by-law to help the municipality deal with the increase of hydrovac trucks, and to discourage the illegal dumping that occurs.
Sample Language
“No Person shall import any Fill onto any Property with the use of a Hydro Excavation Truck, except where approval has been given by Council.”[1]
“Prior to Site Alteration Permit closure, Large Site Alterations, and Hydro Excavation Truck Sites will be required to complete a Record of Site Condition in accordance with The Brownfields Regulation, as amended, and provide to the Town a completed final topographic survey confirming that the Final Grade matches the Approved Grades.”[2]