In the early 1960's, Washington Gas carved out a cavern near Accotink to store liquid propane
Source: Washington Gas, Growing with Washington, Part 2 - A History of Washington Gas 1948-2012
In 1962, Washington Gas excavated an underground cavern in Fairfax County to store 13 million gallons of Liquefied Petroleum Gas (LPG). The Ravensworth Station reservoir was carved out of the nearly 500-million year old Occoquan granite bedrock west of Lake Accotink Park. The cavern was constructed first by drilling a 42-inch wide hole down 400 feet, then lowering one man to the bottom to start the excavation. The underground hole was gradually widened enough for pieces of equipment less than 42-inchs wide to be lowered down through the pipe. The cavern has a 25-foot high ceiling, with pillars of granite left at different spots to support the roof.
In the early 1960's, Washington Gas carved out a cavern near Accotink to store liquid propane
Source: Washington Gas, Growing with Washington, Part 2 - A History of Washington Gas 1948-2012
The Southern Railway delivered over 400 tanker cars to a siding near Springfield for the initial filling of the cavern. There is little indication of the natural gas storage facility on the surface, other than the compressors which mix air into the propane to create a mixture with the appropriate burning characteristics.17
liquid propane is stored in a cavern excavated by Washington Gas in Fairfax County
Source: ESRI, ArcGIS Online
A geologist who managed the site noted that during excavation, workers wore raincoats due to water leaking into the cavern. That provided a clear indication that the bedrock was fractured, but the walls were not sealed with cement of any kind. To keep the propane (compressed into its liquid state) in the cavern, Washington Gas relies upon a water cap to maintain geostatic pressure.
Washington Gas selected the Occoquan Granite for its Ravensworth Station propane storage cavern in Fairfax
Source: US Geological Survey, Geologic map of the Annandale quadrangle, Fairfax and Arlington Counties, and Alexandria City, Virginia (1986)
Water that leaks into the cavern is constantly extracted and injected into the soil, and the company ensures the soil stays saturated even in a drought. Propane does not dissolve easily in water so nearly all of the Liquefied Petroleum Gas stays trapped in the cavern. Traces of propane have been identified in the soil after a nearby resident notices the smell of "swamp gas" in an area without a swamp, and tiny bubbles may escape into Accotink Creek. Most likely, that propane was brought to the surface with water pumped out of the cavern, and there is not a series of cracks in the granite stretching 400 feet up to the surface.18
Washington Gas excavated the Ravensworth Station propane storage cavern in Fairfax County where the Southern Railroad could deliver propane in tanker cars
Source: US Geological Survey, Annandale 1:24,000-scale quadrangle map (1965)
17. "Gas Firm Completes $5.6 Million Project," Washington Post, November 14, 1963, p.C7; "Natural Gas Shipment," Southern Railfan, 1963, http://southern.railfan.net/ties/1963/63-10/gas.html; Richard P. Tollo (ed.), From Rodinia to Pangea: The Lithotectonic Record of the Appalachian Region, Geological Society of America, 2010, p.649, https://books.google.com/books?id=CQoeMsyDNPYC; "'Entering the
Big Leagues' - Chapter II 1960�1969," Growing with Washington. Washington Gas, https://www.washingtongas.com/-/media/d2067877df1e446991e9bece0a1749da.pdf; "Washington Gas Calls Up Reserves from the Midwest," Washington Post, https://www.washingtonpost.com/archive/business/1977/02/05/washington-gas-calls-up-reserves-from-the-midwest/554c0485-2c54-40cf-a7b2-a67e10b23246/ (last checked May 9, 2017)
18. "Propane Trace Found in Soil of Fairfax Area," Washington Post, October 19, 1973, p.C6, personal communication, Washington Gas geologist, April 20, 2017