A contractor grading a pad off Ironwood Avenue got surprised by fines content that didn’t show up in the initial visual log. The silt fraction pushed the soil into an ML classification under ASTM D2487. That changed the compaction spec and the foundation drain design. We ran the full grain size analysis—sieve stack plus hydrometer—and delivered the curve in 48 hours. In Moreno Valley, where alluvial fans from Box Springs Mountain mix coarse gravel with wind-deposited fines, skipping the hydrometer portion is a gamble. A sand cone density test confirms field compaction, and Atterberg limits pin down the plasticity of the fine fraction.
A single hydrometer test often changes the USCS classification from sand to silt—and that changes the entire earthwork specification.
Our approach and scope
Moreno Valley sits on Quaternary alluvium eroded from the Perris Block. Particle size jumps from cobbles to clay within the same terrace. Our ASTM D422 procedure covers the full range: washed No. 200 separation, sieve stack from 3-inch to No. 200, and hydrometer readings at 15, 30, 60, 240, and 1440 minutes. We report percent gravel, sand, silt, and clay plus D10, D30, D60 for the coefficient of uniformity and curvature. The lab holds ISO 17025 accreditation. For projects near the San Jacinto fault zone, the gradation curve feeds directly into liquefaction susceptibility screening. A well-graded gravel behaves differently than a uniform fine sand under cyclic loading. We run the hydrometer in a temperature-controlled bath and apply meniscus and dispersant corrections per ASTM D422. The report includes the zero-air-voids curve and the grain size distribution plot ready for earthwork submittals.
