If you are buying or selling a home in Washington D.C. this is just something you must know.
Now, your agent will provide it for you, BUT, if by chance they don't or you feel their data is out of date, this link will have the most recent information for you to make a well informed decision.
Their blurb: Web Soil Survey (WSS) provides soil data and information produced by the National Cooperative Soil Survey. It is operated by the USDA Natural Resources Conservation Service (NRCS) and provides access to the largest natural resource information system in the world. NRCS has soil maps and data available online for more than 95 percent of the nation’s counties and anticipates having 100 percent in the near future. The site is updated and maintained online as the single authoritative source of soil survey information.