SCIENTIFIC RESEARCH, DEVELOPMENT AND TRAINING: Any structure wherein the primary use is the administration and conduct of investigation, examination, experimentation or training aimed at the discovery and interpretation of facts and/or the practical application of the above to products or processes. Establishments for scientific research, development and training shall include one or more of the following principal facilities and/or activities: laboratory facilities; pilot plants; prototype production; and/or the assembly, integration and testing of goods and products. An establishment for scientific research, development and training shall not be deemed an office.

SCREENING: Landscaping and/or physical barriers that are erected to mitigate potential incompatibilities between different types of land uses.

SEAWALL: A vertical structure or partition, usually running parallel to the shoreline, for the purpose of retaining upland soils while providing protection from severe wave action. Seawalls are often concrete structures poured in place.

SECONDARY SYSTEM: Non Interstate and non Primary roads in Virginia with route numbers of 600 or greater, generally serving only individual counties.

SHARED HOUSING: See Homesharing.

SHOULDER TREATMENT: Various design standards for the edges of roadways to accommodate stormwater runoff and mitigate safety problems.

SHRINK SWELL CLAY SOILS: High clay content soils characterized by swelling when moistened and shrinking when dried. These soils have low load bearing values for foundation support.

SINGLE FAMILY DETACHED DWELLING: A single family dwelling unit which is entirely surrounded by open space or yards on the same lot.

SINGLE FAMILY RESIDENTIAL: Units designed to house one family per unit. Includes detached single family homes as well as townhouses.

SLIPPAGE SOILS: Marine or silty clay deposits that are plastic in nature with a high shrink swell potential are generally unstable, particularly on steep slopes. Soil movement may result in damage to structures built on these deposits.

SPECIAL EXCEPTION/SPECIAL PERMIT USES: Uses, which by their nature, can have an undue impact upon or can be incompatible with other uses. Such uses may be allowed to locate within given designated zoning districts only under special controls and limitations, and regulations.

STREAM VALLEY: An aggregation of features, produced by the physical action of flowing water, which includes intermittent or perennial streams, 100 year frequency flood plains, and adjacent slopes.

SUB REGIONAL PLANNING PROCESS: A planning effort initiated by the Commonwealth of Virginia to address the overall transportation system in Northern Virginia from a regional perspective.

SUBURBAN CENTERS: The Land Classification System category for Centers that contain a complementary mixture of office, retail, residential uses and parks (including Urban Parks and active recreation facilities) in a cohesive, moderate intensity setting.

SUBURBAN NEIGHBORHOODS: The Land Classification System category for areas that comprise the majority of land in the County devoted primarily to residential use. In addition to the predominantly residential use, this category includes the community serving retail, service and office uses required by residents, as well as associated institutional and public facility uses such as churches, schools, parks and libraries.