Once an engineer completes the design for a building and a developer places a building order, the ground must be prepared to support the building. Excavation remains the phase in the construction process that takes a raw site and shapes it into a viable and safe foundation by controlling moisture, loading, and shifting of future utility locations. For prospective developers in the construction process, knowing how the process works during this phase is useful for managing budgets, scheduling, and minimizing risks.

What Is Excavation Exactly?

Excavation is the controlled removal and movement of soil and rock to specified design elevations, followed by shaping and compacting the site to keep it performing as intended. Excavation crews will first survey stakeouts, install erosion controls, and recommended routes of access, and will then execute grading by cutting (i.e. digging down) and filling (thereby bringing in material) to establish pads, roads, and trenches. Proper moisture conditioning and compaction are needed to minimize settlement to support the structure for decades.

Click here https://www.ccohs.ca/oshanswers/hsprograms/trenching_excavation.html  to learn more.

During this phase, determining short-term site layouts of clearing trees, stumps, and surface obstructions is likewise beneficial for safe and efficient work area around the site. For remediations, very minimal demolition work might be required to tear down sheds or slabs that may exist on the property interfering with the new grade elevations. Excavated spoils would either be hauled away or reused, as required by engineering specs, and temporary means of stormwater drainage and management for controlling stormwater flows will be implemented and functional throughout the progress of the construction phase.

How Soil Conditions Affect Projects

Every site has unique behaviors, and not all sites are treated alike. The dimensions and density of clay that holds water, shifting sands, clayey matrix fill that was undocumented debris left over from demolition geologically will affect the process. A geotechnical investigation of the site can scope this unique soil profile, the groundwater level, and to simple understand if there is engineering scope on whether the subgrade is dense enough to carry loads the design specifies. With that report, the team can make decisions that make sense in the context of cost and performance.

Some soil related decisions developers generally encounter are:

• • Moisture management and compaction. The prescribed densities (e.g. Proctor values) were designed to limit the settlement below foundations, pavements, and utilities. Crews can add water or let soils dry and ultimately help achieve the compaction window.

• • Undercut and replacement. Removing soft organics or unsuitable fill and replacing with engineered material i.e. aggregate; may, in short, get a better base.

• • Slope stability and shoring. On deeper cuts, temporary slope or shoring is again done to protect workers and adjacent property.

• • Drainage layers and capillary breaks. Using granular or geotextile layers to prevent water from getting into the foundation.

• • Value engineering with an excavation contractor. Given, we realize the knowledge and experience with site partners, they can be used to change cut/fill ratios, reuse soils locally on site (if they meet the specifications), and limit the additional specific amounts of material imported from other sites.

Utility Checks Before Digging

By this point, underground utilities need to be located and preserved. Your professional team will coordinate with “call before you dig” services (e.g. 811 in the U.S.) and private locating services to reduce the chance of outages, injury, and delays to project schedules and budgets. Plans and as-builts are verified in the field by paint marks and flags. In cases where lines are uncertain, vac excavation with soft digging can expose lines without damaging them. A construction company King of Prussia may schedule utility coordination at least a few weeks out when they can effectively coordinate the route and depths of trenching based on civil drawings to limit conflict.

 

Public agencies typically require permits for utility work in the right-of-way, traffic control plans, and inspections prior to backfilling. Trench safety (shielding or sloping), use of bedding material, and warning tapes are the norm. After placement, utilities are pressure tested or video inspected, and then backfilled and compacted in controlled lifts to ensure protection of the pipe or conduit.

Grading vs. Leveling Explained

Leveling can be straightforward on occasion, but most sites do not remain absolutely flat (and they should not). Grading is the alteration of the earth into a design which controls where the water goes, keeps the foundation intact, and allows for access per roadway and building codes. The grading plan will define finished floor elevations, give the elevations where the driveway will tie-in, and define surface drainage patterns to help drain stormwater away from buildings, neighbors, and parking lots.

There are a few basic grading terms that developers will probably hear about:

• • Positive Drainage: grades should fall between 2–5 percent from the building so that rainwater does not back up and flow into basements.

• • Swales and Berms: Swales are small channels and berms are small, raised areas that act as interceptors and routing methods of stormwater runoff to inlets or bio-retention areas.

• • Building Pads and Tolerances: pads are graded as tight as possible, to allow concrete crews to form & pour all forms (i.e. walkways, paving slabs, etc.) as quickly and productively as they can.

• • Rough Grading and Final Grading: Rough grading shows where the utilities and buildings will be located. Final grading fine-tunes surfaces to receive paving, planting, and/or final inspections.

Environmental Considerations

Excavation in today’s world works to mitigate air, water, and habitat on site and still stay on schedule. Erosion and sediment controls—and employer responsibilities—are in play including silt fence, inlet protection, stabilized construction entrances, etc., and retain sediment on the site through rain events. If wetlands floodplains, or protected trees exist on the worksite, permits and protection buffers like limits-of-disturbance fencing exist to limit equipment and activities encroaching on sensitive areas.

Material Management is key as well. Clean soils can be reused, thereby reducing hauling and emissions, while contaminated soils must be profiled and disposed of as approved. Concrete, asphalt, and metals that are excavated should be recycled where possible and junk removal planning should also address piles of waste that may become hazardous materials. After the bulk of the work is complete, a complete cleaning on debris and street cleaning before a safe inspection of the site.

Finally, useful documentation (daily reports, compaction test results, as-builts, stormwater logs) proves you are compliant and limits your liability. If developers plan excavation, grading, and environmental controls together from day one, this gives them a predictable basis for everything that is completed next, from footings to finishes.