Stop Hauling Water: A Better Way to Manage Hydrovac Slurry

Your debris tank is full at 10 a.m.

The nearest receiving facility is 90 minutes away. There may be a line at the gate. The excavation is only half done, but the hydrovac truck is about to spend the next three hours driving there and back before waiting time and unloading are even counted.

For a contractor, that is the real slurry-management problem: an expensive, revenue-generating truck is hauling liquid instead of excavating.

The disposal fee matters. So do truck turns, billable hours, productive excavation time, truck utilization and the space required to store or process wet material. The business case for any alternative should be measured against those operating constraints.

The Cost Is the Disposal Cycle, Not Just the Disposal Fee

Hydrovac work is commonly priced by the hour, so every disposal run consumes time that could otherwise be spent on productive excavation. If the receiving facility is 90 minutes from the jobsite, the round trip alone is three hours. Add traffic, gate queues, discharge time and any processing delay, and one full debris tank can remove a large part of a shift from production.

That cost is easy to miss when it is split across fuel, labour, truck time and disposal invoices. A better operating measure is the full disposal cycle:

Then multiply that by the number of loads moved in a day or week. The same calculation can be used to compare a current wet-slurry workflow with an on-site solidification workflow.

One hydrovac project provides a concrete example. On that project, hydrovac trucks offloaded into a lined roll-off bin for on-site solidification. MetaFLO reported savings of approximately $2,000 per truck load and about $6,000 per day based on an average of three hydrovac loads per day. The project also reported that one hydrovac truck could remain focused on the daily excavation work rather than leaving the site to dispose of liquid soil. Those figures are project-specific, but they show why truck utilization can be as important as the disposal rate itself.

 

Why Wet Slurry Restricts the Operation

Hydrovac slurry contains soil, fines and water. While it remains flowable, it can require liquid-compatible containment, transport and receiving infrastructure. In Ontario, the regulatory definition of liquid soil is based on a slump of more than 150 mm under the prescribed test, not simply on the presence of free water.

Operationally, wet slurry can create four recurring constraints:

• Truck turns: the hydrovac truck leaves the excavation to haul its own debris tank.
• Receiving options: not every site is set up or authorized to receive liquid soil or slurry.
• Processing footprint: settling tanks, bins, drying areas or separation systems take space and handling time.
• Added material: conventional bulking methods can increase the amount of material that must ultimately be moved and managed.

Where On-Site Solidification Fits

Separation and solidification solve different problems. Separation removes or redirects water from the solids. Solidification changes how the slurry behaves by controlling free water and producing a more stable, non-flowable or stackable material. Some jobs use one approach; others combine both.

The advantage of moving solidification closer to the point of generation is operational: the hydrovac can offload and return to excavation while lower-cost material-handling equipment manages the next step, where site conditions and receiving requirements allow it.

What the Workflow Looks Like in the Field

The exact setup depends on site layout, slurry characteristics and the receiving destination. MetaFLO field applications show several practical configurations:

1. Offload into a contained mixing area. The hydrovac truck discharges into a lined roll-off bin, shale bin, containment cell or other approved receiving/mixing area instead of hauling the full debris tank directly to a remote liquid-receiving facility.
2. Add the selected reagent at the tested dose. Dosage is established for the actual material. MetaFLO hydrovac field cases include a 0.5% wt/wt addition rate at a utility operation and a 1% wt/wt dose on a pipeline integrity project.
3. Mix with available site equipment. Mixing can be performed with an excavator bucket or with existing facility infrastructure. On a pipeline integrity project, trucks discharged into two shale bins. Surface water was pumped to the second bin, the reagent was mixed into the heavier mud, and the separated water was returned to complete the mixing process.
4. Verify handling and receiving criteria. The target is not simply a drier appearance. The material must meet the handling, transport and receiving requirements applicable to the project. Bench testing is used to determine the appropriate formulation and dose before full-scale use.
5. Move the solidified material with the appropriate hauling system. Where allowed by the material classification, site plan and receiving facility, the solidified material can be loaded into dump trucks or transported in roll-off containers instead of tying up the hydrovac truck for the full disposal cycle.

Field Results: What Has Actually Been Measured

These results should not be treated as a universal performance guarantee. Soil type, moisture, fines and clay content, contaminants, site layout, mixing energy, receiving criteria and disposal route can all change the required formulation and the economics.

That is also why a fixed “one product, one dose” approach is not appropriate for every hydrovac slurry. The formulation and application method need to be matched to the material and the job.

How Solidification Compares with Dry Bulking

Sawdust and wood chips are used in some hydrovac waste-management workflows as dry bulking agents. In one of MetaFLO’s Hydrovac applications, a 1% reagent dose was used, requiring less added material than the amount of sawdust or wood chips that would have been needed for the same slurry. 

The practical difference is important: a bulking agent works partly by adding absorbent solids, so the quantity of material leaving the site can increase. A low-dose specialty reagent is intended to control free water with far less added mass. The actual comparison should be made using site-specific data rather than a generic percentage, because bulking requirements vary widely depending on the slurry and target consistency.

Regulatory and Receiving-Site Requirements Still Apply

Solidification changes the physical handling properties of the slurry; it does not remove contaminants or automatically change the material’s regulatory status.

In Ontario, O. Reg. 406/19 defines liquid soil using the prescribed slump test and sets requirements for the transportation and management of excess soil. The receiving or reuse destination, material characterization and any applicable approvals still determine where the material can go. In the United States, EPA Method 9095B (Paint Filter Liquids Test) is used in specific federal waste-management contexts to determine whether free liquids are present.

For contractors, the practical rule is simple: confirm the material characteristics, receiving criteria and jurisdictional requirements before changing the hauling or disposal route.

The Business Case: Keep the Hydrovac Producing

The strongest business case for on-site solidification is not “drying slurry.” It is recovering productive operating time.

If a hydrovac truck can discharge on site and return to excavation while another piece of equipment handles mixing and outbound transport, the contractor can potentially reduce non-productive hauling, improve truck utilization, use fewer hydrovac units for the same scope, reduce dependence on liquid-receiving facilities and lower transportation, processing and disposal costs.

Measure the opportunity with your own operating data:

• hours per disposal cycle;
• loads per day or week;
• hydrovac hourly rate and crew cost;
• fuel and mileage;
• receiving and processing fees;
• time and equipment used for settling, separation or bulking;
• space required for temporary storage or drying;
• added bulking material and the extra volume or weight it creates.

Those numbers will show whether hauling liquid is simply part of the job — or one of the largest avoidable costs in it.

Have a Challenging Hydrovac Slurry?

Send MetaFLO a representative sample for bench evaluation. The technical team can assess the material and help determine the appropriate reagent, dosage and mixing approach for the application before full-scale use.

MetaFLO Technologies · 1-888-862-4011 · [email protected] · metaflotech.com