Arlington County, Virginia, population 207,627 (2010), lies across the Potomac River from Washington DC. In 2006, Arlington County adopted a TDR ordinance allowing sending sites to be proposed throughout the county that provides open space, historic preservation, affordable housing, community recreation or facilities. Unused sending site development capacity can be transferred to receiving sites using a special exception site plan process in which the county board determines whether or not the proposed transfer is consistent with land use plans, policies and ordinances. TDRs from residential sending sites can be converted to non-residential floor area at the rate of 3,000 square feet per foregone single family dwelling unit and 1,500 square feet per foregone multiple-family unit. The county subsequently adopted specific TDR zoning regulations with designated receiving sites for the Clarendon, Columbia Pike, and Fort Myers Heights districts aimed at affordable housing, historic preservation, green buildings, open space and other extraordinary benefits. To date, the county has approved at least four developments using TDR for historic preservation as well as the provision of open space and community/recreational facilities.