The city walls of San Juan, Puerto Rico are a part of the San Juan World Heritage Site. The walls were begun in the 1630s with construction continuing for the next 150 years. They average 42 feet in height and are also about 42 feet thick at their base. The National Park Service began cleaning the walls with D/2 Biological Solution more than 8 years ago. The current project includes two distinct sections of the wall known as the Santa Elena and the San Augustin. Together they extend 2,600 feet.
National Park Service
During its restoration of the 168 Benjamin Latrobe designed sandstone cenotaphs, the National Park Service chose D/2 to do the cleaning.
The National Park Services trusts D/2 to keep America's iconic White House looking white.
The National Cemetery Administration now uses D/2. Quote: "The NCA entered into an agreement with the National Center for Preservation Technology and Training, NPS, to evaluate marble cleaners in an effort to minimize damage to historic headstones. The 3-phase study began in 2004 and was completed in 2011. The best - practice recommendations resulted in NCA's determination to use the preferred cleaner, D/2 Biological Solution…" (Page 3)
From Presidential Executive Order 13287, Preserve America FY 2011 Triennial Report Department of Veteran Affairs.
Researchers studied five different cleaners on stones located in five different climates at locations across the United States. Microbiologists at Harvard University evaluated samples for regrowth of microorganisms including bacteria, fungi, and algae. D/2's quaternary ammonium solution came out on top!
A six-person preservation team with the National Park Service has been working its way around the Chickamauga and Chattanooga National Military Park giving its Civil War monuments a spring cleaning. The crew, which works out of Frederick, Md., and travels the country to clean monuments, will work at the park for about three months. The group uses the environment friendly cleaner D/2 to clean the structures.