During its restoration of the 168 Benjamin Latrobe designed sandstone cenotaphs, the National Park Service chose D/2 to do the cleaning.
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. The Atlanta office of architects Lord Aeck Sargent have been retained by the NPS to write the cleaning specifications.