AASHTO: American Association of State Highway and Transportation Officials.

ACCESSORY DWELLING UNIT (OR APARTMENT): A secondary dwelling unit established in conjunction with and clearly subordinate to an existing single family detached dwelling unit.

AFFORDABLE DWELLING UNITS (ADU): Sale or rental housing units to serve households with incomes up to 70 percent of the Area Median Income (AMI) for the Washington Metropolitan Statistical Area (MSA) which are required to be included in certain housing developments of 50 or more units pursuant to Article 2, Part 8 of the Fairfax County Zoning Ordinance. In return for provision of this housing, additional development density is granted. Eligible occupancy, sales prices and rents of ADUs are controlled for a certain period of years. The FCRHA or nonprofit housing groups have a right to purchase a portion of the ADUs in a development.

AFFORDABLE HOUSING:For purposes of the Policy Plan, housing that is affordable to households with incomes that are 120 percent or less of the Area Median Income (AMI) for the Washington Metropolitan Statistical Area (MSA). Affordable housing includes units created under the Affordable Dwelling Unit (ADU) program that are affordable to households with incomes that are 70 percent or less of the AMI. Affordable housing also includes units produced through the Workforce Housing initiative, which is designed to encourage proffers of rental and for sale units that are affordable to households at various income limits up to 120 percent of the AMI. Affordable housing may also include other units produced through federal, state or local programs by the private, non-profit and/or public sectors. The Area Median Income for the Washington Metropolitan Statistical Area is determined periodically by the U.S. Department of Housing and Urban Development.

ASSISTED LIVING: Assisted living is an industry term for multifamily housing with congregate and personal care services. Assisted living goes by many names, including personal care, residential care, congregate care and in some areas, board and care. The services offered vary widely, but frequently include as core services, meals, housekeeping and transportation and often some assistance with laundry, grooming, medication management and other functions of daily living. Special care units in some facilities care for individuals with cognitive impairment and respiratory assistance needs. Unless an assisted living facility is a component of a continuing care or "life-care" community, it does not offer the health care services of a nursing facility.

ASSISTED LIVING FACILITIES: Facilities that provide three meals a day, supervision of medications, weekly housekeeping, and around the clock supervision.

BEST MANAGEMENT PRACTICES (BMPs): A practice, or combination of practices, that is determined to be the most effective, practicable means of preventing or reducing the amount of pollution generated by nonpoint sources to a level compatible with water quality goals.

BETTER SITE DESIGN: Site and subdivision design techniques that minimize impacts to the natural environment, including topography, hydrology, vegetation, natural habitat, groundwater recharge, and stormwater runoff. Such a design respects these natural systems by employing practices that minimize impacts to these systems both on and off site.

BMP: See Best Management Practices.

BREAKWATER: A fixed or floating structure usually constructed parallel to the shoreline to protect the shoreline from erosion by dissipating wave energy before it reaches the shore. Typically, in order to address erosion over a reach of shoreline, a series of breakwaters are constructed.

BUFFERING: The area of open land which serves to mitigate potential conflicts between different types of land uses. Buffer zones are most commonly employed between different types of uses but, in certain circumstances, it may be appropriate to provide a buffer between high and low density residential uses.

BULKHEAD: A vertical structure or partition, placed on a bank or bluff and usually running parallel to the shoreline, for the purpose of retaining upland soils while providing protection of the inland area from wave action. Bulkheads are generally smaller than seawall structures and are designed to retain upland soils while providing protection from minimal wave action.