ESTIMATING VACUUM EXCAVATOR OPERATING COSTS CAN HELP IMPROVE EFFICIENCIES

Sep 30, 2019

 

Do you have a good handle on what potholing is costing you? More importantly, do you know the different factors to consider when you’re estimating the operational costs of running vacuum excavators?

 

If you’re hesitant about the answers to those questions, read on. Understanding operational costs is essential for project bidding and keeping your company efficient.

 

Mitigating your risks

The first thing to get out of the way is a reason why your company should be employing a vacuum excavator. The answer to that question is easy — it’s all about helping mitigate the risks of striking a utility line. While your crew may already have a mini excavator onsite and shovels in the truck, these tools of the trade can put you at a higher risk of damaging the utility being potholed. Costs can add up when that happens, and you may put the well-being of your crew members, as well as bystanders, at risk.

 

Using vacuum excavators is an efficient way to daylight utilities because you’re using high-pressure water around underground infrastructure. However, material excavated with a traditional vacuum excavator can’t merely be piled up near the hole and filled back in. On most jobs, spoils need to be transported to designated disposal sites, and the effort and costs to do so can vary significantly. So, it’s a good idea to get your hands around the costs and potential savings that could come with operating a vacuum excavator.

 

Areas of consideration

According to Adam Bates, product manager at Vermeer, utility contractors should consider the costs associated with daylighting existing utilities during the bid process, but he said doing so can be a real challenge. “To estimate potholing expenses, contractors need to have a general understanding of what utilities their crews will encounter near the proposed drill path,” he explained. “The number of holes and depths need to be considered, as well as the site’s proximity to water and a disposal site. Depending on the customer, getting that information isn’t always easy, which makes estimating a bit of a moving target.”

 

Calculating excavated material

To get a rough estimate of operating costs, Bates recommends starting with a hole count. “Each hole will usually be about 1’ (30.5 cm) in diameter, but depths can vary,” he said. “Depending on ground conditions and climate, crews should be able to determine the approximate depth of each utility. So, if they need to excavate to a depth of 5’ (152.4 cm) on average, they are removing around 4 ft3 (113,267 cm3) of material for each hole. However, the volume of liquid being suctioned into the spoil tank also needs to be accounted for. Fluid volume can vary depending on the type of soil conditions, but crews can usually expect it to be a 1-to-1 ratio.”

 

The formula for estimating operating costs is shown below:

·         A 1’ diameter hole at a depth of 5’ = 3.9 ft3 or 0.15 yd3 (30.5 cm wide at 152.4 cm deep = 110,436 cm3 or 0.11 m3)

And since the volume of water is 1-to-1, you need to double it.

·         3.9 ft3 x 2 = 7.8 ft3 or 0.3 yd3 (110,436 cm3 x 2 = 220,872 cm3 or 0.22 m3)

 

Now, all you need to do is multiply that total by the number of holes you need to excavate. So, 10 holes would produce 3 yd3 (2.3 m3) or 606 gal (2,294 L) of spoil. If your crew is running an 800 gallon (3,028.3 L) vac, you can excavate around 13 holes before needing to dump the spoils.

 

Impact of variables

Calculating the volume of excavated material is pretty straightforward, but other considerations may not be.

 

“Over-the-road drive times and disposal costs for vacuum excavators can be all over the board,” said Bates. “In urban areas, a round trip from the jobsite to disposal facility may take from 30 minutes up to two hours depending on the time of day. That additional time doesn’t just compound the labor costs for the potholing crew. It can also have an impact on the productivity of the drill crew working behind them. It’s certainly not uncommon for HDD crews to be shut down for hours at a time because they are waiting for a vac stuck in traffic.”

 

Bates also said many communities regulate where spoils and slurry can be disposed, which has reduced the number of facilities. “I’ve heard from contractors working in large cities that their crews often have to drive to a location outside of city limits, and they pay substantially more than they used to just a few years ago. It’s a real issue,” he explained.

 

Longer drive times, project delays and higher disposal costs aren’t the only variables you need to consider, though. You also need to think about the transport weight of your truck and trailer vacs.As you can see, accounting for all of these variables can be a real challenge. Experience and staying on top of all the moving pieces can help. Bates recommends calculating the distance to disposal sites, researching dump costs and studying DOT weight regulations during the bid process. “After a project is completed, contractors should compare the estimated operational cost with actual expenses,” he added. “Going through this process will help them dial things in for future projects. Also, in some instances, investing in a way to take some of the variability out of a project is a better approach.”

 

Managing variables

Bates and the rest of the product specialist team at Vermeer have been talking to utility contractors for several years about their concerns regarding the rising costs of fluid management. In recent years, Vermeer has introduced several sizes of reclaimers to allow horizontal directional drill (HDD) crews to recycle drilling fluids, which helps reduce the amount of slurry they will need to dispose of. 

 

For drilling and potholing crews, Vermeer began selling the MUD Hub solidification system. With this system, contractors can establish a centralized dumpsite for vacs to feed the MUD Hub used liquids. A solidification agent is then added to the wet material to absorb the moisture. Now, you can have stackable material that can be transported by a regular dump truck, and possibly be disposed of at a regular landfill or reused in a variety of applications.

 

Vermeer has also introduced the XR2 vacuum excavator for utility contractors who do a lot of potholing or hydro-trenching. The truck has a self-leveling shaker deck that separates solids from the liquids. Used water gets pumped into onboard holding tanks for later disposal, and the separated solid material can be offloaded to a truck or stacked on site.

 

“With the XR2, crews can bring up to 1,500 gal (5,678.1 L) of fresh water to the job and leave with a similar amount of used fluids,” said Bates. “This setup gives the operator maximized wand time, which helps them stay on the job longer.

 

If you want to explore any of the fluid management solutions Vermeer offers, contact your local Vermeer dealer or visit Vermeer.com.

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Vermeer Corporation reserves the right to make changes in engineering, design and specifications; add improvements; or discontinue manufacturing at any time without notice or obligation. Equipment shown is for illustrative purposes only and may display optional accessories or components specific to their global region. Please contact your local Vermeer dealer for more information on machine specifications. Vermeer, the Vermeer logo and ROVER are trademarks of Vermeer Manufacturing Company in the U.S. and/or other countries. © 2019 Vermeer Corporation. All Rights Reserved.

 

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