San Bernardino’s development arc—from a small Mormon colony in 1851 to a major logistics hub crisscrossed by I-10 and I-215—has always been shaped by what lies beneath the surface. The city sits on the San Bernardino Valley floor, where Pleistocene alluvial fans from the San Bernardino Mountains have deposited thick sequences of interbedded sands, silts, and cobbles. These deposits can shift dramatically within a 50-foot lateral span. When a grading plan or shallow foundation design needs ground truth, an exploratory test pit provides the direct visual evidence that borings sometimes miss. Our team logs stratigraphy in-situ, collects bulk samples for grain size analysis, and documents the presence of oversize particles that would destroy a split spoon—all while working within the city’s setback and trench safety requirements. For projects near the Santa Ana River wash or in the older downtown grid, this visual verification is often the difference between a straightforward permit and months of redesign.
A 14-foot pit in San Bernardino alluvium can reveal more about foundation performance than 100 feet of SPT borings in the same formation.
How we work
The semi-arid climate of San Bernardino—averaging just 16 inches of rain annually but subject to intense Santa Ana wind events—creates a near-surface crust that can mislead a shallow drilling log. A test pit cuts through that crust and exposes the true moisture profile and soil structure. In the Verdemont and North Park areas, we frequently encounter cemented alluvium layers that require an excavator with ripper teeth, yet just a few hundred feet south the material transitions to loose, collapsible silty sand. Observing this directly lets us take undisturbed block samples for triaxial testing, giving the structural engineer a real strength envelope rather than a conservative textbook value. Our pits typically reach 12 to 15 feet, with stepped benching as required by Cal/OSHA. We log according to the Unified Soil Classification System (ASTM D2487), photograph the sidewalls, and measure in-situ density with a nuclear gauge when the client needs compaction correlation data for fill placement specifications.
Site-specific factors
A Caterpillar 320 excavator with a 42-inch cleanout bucket is our standard tool for San Bernardino test pits—powerful enough to break through the caliche lenses common in the Cajon Pass outflow deposits, yet precise enough to expose a utility line without damaging it. The real risk on these sites isn’t always the soil; it’s the unknown. The city’s underground service alert (USA North 811) clears public utilities, but private laterals, abandoned septic tanks, and old agricultural wells from the citrus-growing era appear on no map. Before the bucket breaks ground, we walk the site with a private utility locator and review historical aerial photos. In the Hospitality Lane corridor, we have uncovered buried construction debris from the 1970s boom that made conventional footing bearing assumptions invalid. A single day of pit exploration can prevent a stop-work order and a six-figure change order.
Questions and answers
How much does an exploratory test pit cost in San Bernardino?
A standard single test pit to 12 feet depth in San Bernardino, including a written log, photographs, and bulk sampling, typically ranges from US$440 to US$900. The final figure depends on access constraints, the need for private utility locating, and the number of samples collected for laboratory testing.
How many test pits do I need for my San Bernardino project?
For a single-family residential lot under 0.5 acres, two pits placed at opposite corners of the proposed building footprint usually satisfy the city’s minimum requirement. Commercial pads and larger grading projects need a pit spacing that captures the lateral variability of the alluvial deposits—often one pit per 5,000 square feet of building area.
What is the advantage of a test pit over a boring in San Bernardino alluvium?
San Bernardino alluvium frequently contains cobbles and boulders that deflect or stop a hollow-stem auger, leaving gaps in the boring log. A test pit exposes these materials directly, letting us measure particle size, assess matrix packing, and observe the actual contact between colluvial and alluvial units—details a 2-inch split spoon sample cannot capture.
How do you handle groundwater in a test pit?
In many parts of San Bernardino, groundwater is deep—often below 100 feet—so most pits stay dry. When we do encounter seepage in shallower areas near the Santa Ana River or Lytle Creek channels, we measure the inflow rate, note the depth of first water, and if necessary, use a trash pump to keep the working face clear for logging and sampling.
What safety protocols do you follow during pit excavation?
We comply with Cal/OSHA Title 8 regulations for all excavations. Up to 5 feet depth, vertical walls may be used in competent soil. Between 5 and 15 feet, we step-bench the walls or install hydraulic shoring. A designated competent person inspects the pit at the start of each shift and after any rain or vibration event.
