Long Beach sits at roughly 30 feet above sea level, with a population exceeding 450,000—the seventh-largest city in California. The 1933 Long Beach earthquake, a magnitude 6.4 event centered just offshore, reshaped local building codes forever. Today, every foundation design in the area must reckon with the complex alluvial and estuarine soils beneath the surface. The Standard Penetration Test remains the backbone of that investigation: a direct method to log stratigraphy, retrieve disturbed samples, and measure blow counts that feed directly into bearing capacity and settlement calculations. For projects in the Alamitos Bay area or near the Port complex, we pair SPT data with liquefaction screening to flag potentially unstable sand layers before a single pile is driven.
In Long Beach, a 10-foot difference in boring location can mean the difference between dense alluvium and liquefiable channel fill—SPT spacing matters.
Common questions
What is the typical cost of an SPT boring in Long Beach?
Mobilization, drilling, sampling, and a summary log for a standard 30-foot SPT boring in the Long Beach area generally ranges from US$490 to US$660 per boring when scheduled as part of a multi-hole exploration program. Deeper borings, confined access, traffic control requirements near major corridors like Pacific Coast Highway, or expedited turnaround on reports can affect the final figure. We provide a fixed-price proposal after reviewing the site location and depth requirements.
How deep should SPT borings go for a typical commercial building in Long Beach?
For a two- to three-story commercial structure on spread footings, IBC generally requires borings to extend to a depth where the stress increase from the foundation is less than 10% of the existing effective overburden stress—commonly 30 to 40 feet in Long Beach's alluvial soils. If deep foundations are planned, borings must penetrate at least 20 feet below the anticipated pile tip elevation. The presence of liquefiable sand layers may push investigation depths to 50 feet or more beneath the groundwater table, which in coastal Long Beach is often encountered between 8 and 15 feet below grade.
How do you handle SPT refusal in Long Beach's coastal soils?
When refusal occurs—defined as 50 blows for less than 6 inches of penetration—we immediately stop the SPT and switch to a solid-stem auger or core barrel to advance the boring through the obstruction. The refusal depth and partial blow count are recorded on the log with a note indicating the sampler encountered refusal. The material causing refusal is recovered and classified. If refusal is widespread across the site, we typically recommend a cone penetration test (CPT) to profile the dense material continuously, or a larger-diameter bucket auger borehole to sample cobbles and verify whether the refusal represents a continuous competent layer or an isolated obstruction within a softer matrix.
