Unified Soil Classification System group symbol. For example, GW-GM corresponds to "well-graded gravel "with silt"." If the soil has more than 15% by weight retained on a #4 sieve (R > 15%), there is a significant amount of gravel, and the suffix "with gravel" may be added to the group name, but the group symbol does not change. For example, SP-SM could refer to "poorly graded SAND with silt" or "poorly graded SAND with silt and gravel." Unified Soil Classification System The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size
Campden Tunnel Gravel Pit Campden Tunnel Gravel Pit Campden Tunnel Gravel Pit () is a geological Site of Special Scientific Interest in Gloucestershire, notified in 1988. The site is listed in the 'Cotswold District' Local Plan 2001-2011 (on line). The site exposes a mixture of gravels, sands and silts which make up the Campden Tunnel Drift (Pleistocene period). These are glacial sediments which fill a deep channel. The melt water is considered to have run from the ice-filled valley of the River Avon (north) to the drainage system of the River Evenlode (south east). This links with the sequence of glacial deposits in the