The Shoppes at Wyomissing’s 14-plus acre site near Reading, Pa., was riddled with site challenges requiring 100,000 cubic yards of mass excavation, 40,000 cubic yards of soil to be exported, 52,000 cubic yards of rock drilling and blasting, and 30,000 cubic yards of rock to be processed. The Keystone Chapter of Associated Builders and Contractors honored High Construction with the Award of Excellence for this project.

There’s an old saying that ‘what you don’t know can hurt you’. That’s particularly true when it comes to site excavation for your construction project.

“The biggest risk to owners in a construction project is often in the site work, because you can’t see what’s below the ground,” says Michel Gibeault, High Construction’s vice president of business development.

How large the risk is and who winds up taking that risk are among the most important questions you will tackle.

‘Classified’ vs. ‘Unclassified’

A project owner will encounter two important terms at the outset: “classified” and “unclassified” excavation.

Classified excavation defines the soil conditions that are expected to be encountered and makes provisions for measurement and payment of any rock encountered at an agreed upon unit price. This method places the rock payment responsibility onto the owner.

Conversely, unclassified excavation stipulates that all rock or other unexpected materials encountered in the site work will be the responsibility of the contractor at no change in contract cost.

“An unclassified excavation is similar to purchasing an insurance policy, where the owner pays a flat fee for removal, regardless of what is unearthed,” says Deron Henise director of estimating for High Construction. “It may be more costly than the actual excavation costs, or it could prove to be a lifesaver from unforeseen conditions.”

“More and more we’re finding that the owners want to pass the risk along to the general contractor or the site contractor,” Henise notes. He adds that owners should be especially mindful in specifying if a site will be unclassified for rock only, or also for unsuitable soils.

Common Subsurface Problems

Rock is the most common subsurface problem. Drilling and blasting are the preferred and least expensive solutions, but not always an option, especially if it’s an urban project.

“Pinnacle rock”—rock that juts up toward the surface in irregular points—may need to be mechanically removed with a ripper or breaker. Mechanical removal is the most expensive solution.

Unsuitable soil is another common problem. This category includes wet soils, topsoil with too much organic material that won’t compact properly, and too much clay.

During the right time of year, when the weather is dry and moderate, wet soils can be “toothed up” and aerated or dried with applications of lime. Topsoil needs to be removed.

Sinkholes can occur where limestone is prevalent. Old mine tunnels can even pose a risk. Then there’s the possibility of a site that has been contaminated by some sort of chemical or hazardous material.

“You can have a vast number of conditions,” says Brad Clubb, president of Flyway Excavating in Lititz. Pa.

A shopping center project that High Construction worked on recently, the Shoppes at Wyomissing, near Reading, Pa., is a case in point. It turned out the site had been used as a dump for a highway construction project. There was a lot of rock to begin with. There was also trash, cast-off appliances, and pieces of old concrete and rebar in the ground. The cost of excavating the site ran to 40 percent of the overall project cost.

Investigate in Advance

No matter who ends up with the risk, Gibeault recommends getting a geotechnical report on the site ahead of time on every project.

“You can’t tell just by going out and looking. Our job is to find out what is underground—soil, rock, or groundwater—and how it will affect your building,” says Jon Raab, a geotechnical engineer and principal with the York office of Geo-Technology Associates. “You can identify a million-dollar problem with a $10,000 study. It’s that order of magnitude.”

The site investigation can be done several ways—by analyzing aerial photos, by digging test pits, or, as in most cases, by drilling and taking core borings.

The field work can take as little as a day or as long as week. With technical analysis thrown in, the process can take two weeks to a month to produce a complete report.

For example, Raab’s firm was called in on a project that was just a month away from construction. The investigation revealed 20 feet of buried topsoil where the building pad was supposed to go. The topsoil had to be removed, as it would have caused anywhere from three inches to a foot of settling. “It was very significant in terms of additional cost and schedule delays,” Raab says.

Cover All the Bases

Gibeault cautions that even geotechnical reports won’t necessarily discover everything in advance.

He says it’s imperative for owners to make sure they’ve covered all contingencies in their contract and have a clear understanding—before the digging starts—of what the costs will be if adverse conditions have to be overcome.

When the site work is bid, the owner should get unit prices—by the cubic yard or by the truckload, for example—for the different ways rock might need to be removed. The contract should even cover who measures removed rock and by what method.

The cost can run from as low as $10 to $15 per cubic yard for rock removal to as high as $200 per cubic yard if a hydraulic breaker is needed.

Typically, site excavation runs 5 to 15 percent of the overall project cost.

It Comes Down to Fairness

In the end, the owner’s decision to opt for classified or unclassified excavation is a judgment call—hopefully an informed one.

Gibeault says the owner should sit down with the builder and excavation contractor and jointly review the geotechnical reports as part of the decision-making process.

Rick Jackson, principal in charge of land planning and landscape architecture for the Lititz, Pa., office of the ELA Group, believes fairness to all parties is essential.

“If we recommend to a client that the project be classified, then we should help the client identify what risk is involved in getting an earthwork contract that has a rock clause that will be in addition to normal and customary earthwork and that risk identification should be based on a thorough geotechnical report,” he says.

“If the project is unclassified, meaning the contractor is taking all the risk, then the earthwork contractor should be provided with the geotechnical report so as to make a reasonable bid/estimate.”

Jackson adds, “It really does not serve a great purpose to have people at odds. Let’s figure out the best way to go based on the conditions on the site, so everybody is treated fairly.”