Connecting Site Design With Subsurface Conditions

But there is an important question that has to be answered along the way:

What is actually underneath the site, and can it support what is being designed above it?

That is where the relationship between the Civil Engineer and Geotechnical Engineer becomes important.

Just as importantly, understanding these conditions early can have a significant impact on the cost of developing and building on the property.

The Civil Engineer Develops the Site

Civil Engineers play a major role in transforming a piece of property into a buildable site. Working with the developer, architect, surveyor, and other project professionals, the Civil Engineer typically addresses elements such as:

• Site layout and grading
• Roadways, parking areas, and access
• Stormwater management and drainage
• Water and sewer infrastructure
• Erosion and sediment control
• Utility coordination
• Site permitting and regulatory requirements

For a residential development, that could mean laying out an entire neighborhood, including roads, lots, utilities, stormwater facilities, and grading.

For a commercial project, it might involve determining how a building, parking areas, utilities, loading areas, and stormwater infrastructure will fit and function on the property.

But many of those decisions are affected by conditions below the surface.

That’s Where the Geotechnical Engineer Comes In

A Civil Engineering firm will often retain a Geotechnical Engineering company such as Ingram Engineering Services to investigate the subsurface conditions of the property.

Our job is essentially to help answer an important question:

How will the ground interact with what the project team plans to build?

Ingram can deploy field personnel and equipment to investigate soil and subsurface conditions at strategic locations across the site. Depending on the project, this can include soil borings, test pits, Dynamic Cone Penetrometer (DCP) testing, groundwater observations, soil sampling, and laboratory testing.

The resulting information helps our Geotechnical Engineers evaluate characteristics such as soil type, density, bearing capacity, moisture conditions, fill materials, groundwater, and other conditions that may affect construction.

Geotechnical Decisions Can Become Financial Decisions

This is where geotechnical engineering moves beyond simply determining whether the soil can support a structure.

Subsurface conditions can influence how a site is graded, how foundations are designed, where structures are positioned, and even how a finished building relates to the surrounding grade. Small changes repeated across a large development can have significant financial consequences.

Consider a residential development where the builder intends to offer basements.

The relationship between groundwater, existing soils, proposed grades, foundation depths, and drainage can influence how high the structure needs to sit relative to the surrounding grade. That, in turn, can affect the elevation of the first floor.

A few inches can matter.

If a house needs to sit higher, the builder may need additional exterior steps, longer railings or handrails, additional foundation materials, changes to grading, or modifications to walkways and entrances.

One change on one house may be manageable. Multiply that change across 50, 100, or 200 homes, and a seemingly small engineering detail can become a substantial development cost.

Early coordination between the Civil and Geotechnical Engineers gives the project team an opportunity to understand these conditions while there is still flexibility to make economical decisions.

Turning Soil Data Into Engineering Recommendations

The value of geotechnical engineering isn’t simply identifying what type of soil is present. It is determining what those conditions mean for the project.

Ingram provides the project team with practical engineering recommendations that can influence:

• Foundation design and allowable bearing capacity
• Site preparation and grading
• Excavation and unsuitable soil removal
• Fill placement and compaction
• Settlement considerations
• Pavement design
• Retaining structures
• Groundwater management
• Soil stabilization or remediation

If challenging conditions are discovered, solutions might include undercutting and replacing unsuitable material, improving compaction, modifying foundation designs, or using techniques such as compaction grouting or other ground improvement methods.

The earlier these conditions are identified, the more options the project team generally has to evaluate the most practical and economical solution.

Finding the same condition after roads, utilities, foundations, or buildings are already under construction can be a very different conversation.

The Cost of Finding Problems Later

Proper geotechnical due diligence is also an important part of managing long-term project risk.

Soil movement, settlement, drainage problems, unsuitable fill, or groundwater conditions that were not adequately understood during design can become significantly more expensive to address after construction.

Instead of modifying a design on paper, the solution may now involve removing completed work, underpinning or repairing foundations, improving drainage, stabilizing soils, replacing pavement, repairing utilities, or performing other remediation.

There can also be indirect costs. Construction delays affect schedules, subcontractors, equipment, financing, and ultimately the delivery of homes or commercial space.

If problems develop after a project is complete, documentation of the original investigation, engineering recommendations, testing, inspections, and construction procedures can also become important in understanding what occurred and determining the appropriate corrective action.

Geotechnical investigation cannot predict every condition that may exist across a property. But appropriate investigation, testing, documentation, and engineering analysis provide the project team with better information and demonstrate that subsurface conditions were considered as part of the project’s due diligence.

It is almost always easier and less expensive to solve a problem while it is still represented by lines on a plan than after it has been built.

A Collaborative Process

Civil and Geotechnical Engineering aren’t isolated steps. On a well-coordinated project, information moves back and forth between the disciplines.

The Civil Engineer provides the Geotechnical Engineer with information about the proposed development, including site plans, anticipated building locations, proposed grades, roads, stormwater facilities, and other planned improvements.

The Geotechnical Engineer investigates the property and provides recommendations based on actual subsurface conditions.

Those findings can then help the Civil Engineer refine grading, pavement sections, stormwater features, and other portions of the site design. They can also provide critical information to the Structural Engineer designing the building and its foundations.

Sometimes the investigation confirms that the proposed approach is appropriate. Other times, it identifies a condition that should be addressed before the project moves forward.

Either result is valuable because it replaces assumptions about the ground with engineering data.

From Undeveloped Land to Construction

Consider a developer planning a new residential neighborhood.

The Civil Engineer may begin developing the overall site plan while Ingram performs the geotechnical investigation. Our team evaluates subsurface conditions across areas planned for homes, roads, stormwater facilities, and other improvements.

The results go back to the project team so that site preparation, grading, foundations, pavement, and other construction details can account for the conditions that are actually present.

As construction begins, Ingram’s involvement can continue.

Our field technicians can provide construction materials testing and inspections, including soil compaction testing, concrete testing, bearing capacity verification, and other services that help confirm construction is proceeding in accordance with the project’s plans and specifications.

Our AASHTO-accredited laboratory also gives our team the ability to perform required materials and soil testing without sending that work outside the company.

That continuity is important. The same engineering team that helped evaluate the ground before construction can remain involved as the project moves from design into the field.

Better Information Makes for Better Projects

Civil Engineers, Geotechnical Engineers, Structural Engineers, architects, surveyors, developers, and builders each see a project from a slightly different perspective.

The best projects connect those perspectives early.

At Ingram Engineering Services, we regularly work directly with Civil Engineering firms throughout Pennsylvania, Delaware, New Jersey, and Maryland, providing the geotechnical expertise and field data they need to move projects forward.

We also work closely with partner Civil Engineers and Surveyors when a client needs additional disciplines, creating a more coordinated, turnkey approach from initial site evaluation through design and construction.