South Coast Botanic Garden
The site was operated as an open pit mine from 1929 until 1956, producing over one million tons of crude diatomite. With declining production, the land was sold in 1957 to the County of Los Angeles for a sanitary landfill, which was in use until 1965. Starting in 1961, an experiment in land reclamation began when County Board of Supervisors approved a motion establishing the site as the South Coast Botanic Garden, which was landscaped over 3.5 million tons of refuse, in an example of land recycling. The Sanitation District in cooperation with other County agencies carried out initial planning, grading and contouring. Operating responsibilities were given to the Los Angeles County Department of Arboreta and Botanic Gardens. In April 1961, the first large-scale planting took place on completed fill overlooking Rolling Hills Road, with over 40,000 plants donated by individuals, nurseries and the County Arboretum.
The site presents unusual difficulties in gardening. First, its soil is composed almost entirely of diatomaceous earth. Second, because of the diverse nature and thickness of the fill, settling rates vary throughout the garden resulting in frequent irrigation system breakage. Third, heat is caused by decomposition of organic matter below the soil surface, and it is accompanied by the production of gases, primarily carbon dioxide and methane.