Proof rolling is where a pad tells the truth. A loaded water truck or scraper crosses the subgrade, the inspector watches the surface, and any spot that ruts, pumps or springs shows up in a way no boring log could have predicted. Over-excavation and recompaction is what we do about those spots, and about the larger zones the geotechnical engineer has already flagged: cut out the weak or movement-prone soil, replace it with material that will hold, and compact it until the numbers say it is ready to carry a building.
The decision to over-excavate is rarely easy, because the work adds cost and days. But the alternative is a slab on soil that moves, and in Texas that is expensive in a different way. The earlier the soft or reactive zone is found, the cheaper it is to remove. We would rather dig out two feet of bad clay during site work than chase a cracked floor two years after the owner has moved in.
Why Texas soils get cut out and replaced
Expansive clay is the main reason. A University of Texas at Austin research report prepared with TxDOT and the Federal Highway Administration on characterizing expansive clays in Texas includes training material on three ways to calculate the Potential Vertical Rise of an expansive soil: TxDOT's Tex-124-E, which correlates plasticity index with swelling, and two university methods that use centrifuge swell tests, one drawn from a database of central Texas clays and one from project-specific tests. The point for a builder is that the movement can be calculated, and when the number is too high for the slab, the usual answer is to remove some of the reactive soil and replace it with a non-expansive fill.
Water is the other cause. The National Weather Service reports that Hurricane Harvey brought widespread storm total rainfall over 40 inches to Jefferson County, flooding over 64,000 homes, with the northeast side of Beaumont among the hardest hit areas. A pad prepared in that region has to be built to shed water and to dry out after saturation, and subgrade that has been soaked and then covered can hide a pumping layer. We often over-excavate just to get below the wet zone and start fresh.
The steps from cut to retested fill
The excavation limits are set by the geotechnical report and confirmed in the field. We remove the soil to the specified depth and a margin beyond the building line, and we keep the bottom of the cut level and clean so that the new fill has a uniform base. The bottom is proof rolled, and if it is soft we go deeper or stabilize it before any replacement is placed.
Replacement material is placed in lifts, moisture conditioned, compacted and tested. Engineered fill may be select clay, crushed stone, flexible base or a lime or cement treated soil, depending on the report. The specification usually sets a minimum density and a moisture range relative to optimum, and every lift is tested before the next is placed. The finished pad is surveyed and handed to the fine grading crew for the final trim.
Testing, documentation and who signs off
Over-excavation is a documented process. The geotechnical engineer or an independent testing lab observes the work, records the depth of removal, the material used and each density test, and issues a report that the structural engineer and the building official may ask for. We keep daily records as well, including survey shots at the bottom of the cut, so that the extent of the work is clear if the pad is ever questioned.
For commercial buildings in Texas, the governing code edition and local amendments differ from city to city, so the geotechnical recommendations in the project documents drive what we do. That is also true of accessibility: projects with a total estimated cost of $50,000 or more are registered with the state for plan review, but the soil work behind them is controlled by the soils engineer. Where the plan involves lime treatment, we coordinate with the lime and cement soil treatment scope so the two operations do not undo each other.
Drought, heat and the dry-down window
Weather shapes the schedule more than machines do. Long drought spells shrink clay and crack the ground, and they open fissures that let the next heavy rain penetrate deeply. Reference accounts of Wichita Falls describe a persistent drought from 2010 to 2013, including 100 days at or above 100 F in 2011, and soils in the region that behave that way can be hard to dig, then hard to compact because they will not take moisture evenly.
In dry spells we pre-wet the cut and the fill, in wet ones we scarify and dry, and in both we try to avoid leaving a cut open longer than a few days. A pad finished in a drought and left uncovered can slake and crack, and one finished in a wet spring can pump under the first loaded truck. We plan the over-excavation so the replacement fill and the base rock go in without a long gap, and we protect the finished surface with a seal coat of rolled soil when the forecast changes.
Working in deep cuts and next to structures
Over-excavation can be deep, and deep cuts near existing footings or utilities are a hazard. We slope the sides, or shore them where space does not allow a slope, and we support or protect adjacent structures. Machine traffic on the lip has to be controlled, and haul roads into the cut need to be graded and kept clear so trucks do not slide.
Dust and mud are a constant companion. Water trucks and track-out controls keep the haul road safe and the street clean, and where the cut reaches groundwater we bring in pumps before we start. The excavation crews we coordinate run these cuts with a competent person on site at all times.
How this connects to the rest of the pad
Over-excavation sits at the beginning of the pad sequence and sets up everything after it. The replacement fill is part of the engineered fill and soil stabilization scope, and the finished pad is the base for the slab. For tilt wall buildings, where panels and slab edges carry concentrated loads, the quality of the pad is checked even more closely.
Owners who are developing several buildings on a large site can ask us to carry the work across all of them under one plan, which keeps the testing consistent and the schedule predictable for industrial and manufacturing owners.
Show us the proof roll
If your pad failed a proof roll, or the soils report calls for removal and replacement, send it over. We will confirm the limits, price the work by the yard, and keep the records the engineer needs.
Early calls save money, because every week a soft spot stays unfound is a week of schedule it will cost later.
Common Questions
How deep do you usually have to dig out?
It depends on the report. Two to four feet of replacement is common under a slab on expansive clay, and some sites need more. The engineer sets the depth from the borings and the movement calculation, and we verify it in the field.
Can we reuse the soil we remove?
Sometimes. If the soil is simply wet, we can dry and recompact it. If it is highly plastic clay or organic, it usually cannot be used as structural fill and is either moved to a non-structural area or hauled off.
Who decides when more over-excavation is needed?
The geotechnical engineer or the testing agency observing the work. If proof rolling shows a soft area, or density tests fail, they direct additional removal. We keep records of the extent and report quantities so the owner understands the change.
What is the difference between recompaction and stabilization?
Recompaction takes the same soil, conditions the moisture and compacts it again. Stabilization changes the soil by adding lime, cement or another binder. Over-excavation may use either, depending on the soil and the design.
How do you control cost when quantities change?
We bid unit prices for removal and replacement, so the owner pays for the measured volume. Daily records and survey checks keep the numbers visible, and we flag potential overruns early.