ASTM D6913 and D7928 define the standard for particle size distribution, and in Fresno those standards matter more than most people realize. The alluvial soils of the San Joaquin Valley shift from coarse channel deposits to fine silty clays over short distances, often within a single lot. A project off Herndon Avenue might hit sandy loam at five feet and fat clay at twelve. Without a complete grain size curve — including the hydrometer fraction passing the No. 200 sieve — you're guessing on drainage behavior, frost susceptibility, and how the material will compact under load. Our lab runs the full combined analysis because partial data leads to expensive surprises during grading and foundation inspection.
The silt and clay fraction — what passes the No. 200 sieve — often controls Fresno foundation performance, not the sand and gravel everyone can see.
