Phosphate fertilizers were in use as early as the late 1700's in South Carolina, as deposits of mineable phosphate ore were discovered in many areas in the Low Country. During the mid-1800's, it was discovered that mixing the raw phosphate ore with sulfuric acid produced a "super-phosphate" fertilizer that was water soluble for better absorption by crops. Also, it could be produced in a fine, dry powder state which could be more easily transported and applied to the fields.
During the late 1800's and early 1900's, super-phosphate fertilizer production was a huge industry in South Carolina, due to the considerable phosphate deposits that were mined from our low-country. At one point, the industry accounted for over 20% of the state's economy. Several of these former plants were among the largest in the world during their peak. Do to the operational processes, which included the necessity to make sulfuric on site and the need for vast amounts of lead-lined chambers and vats to contain the corrosive acid, the sites left behind significant problems most notably with lead and arsenic contamination of soil and groundwater.
In the mid-1990's, DHEC Site Assessment staff began working with USEPA to identify all super-phosphate sites within SC. The initial focus was on the Charleston neck area, which was home to many of the largest super-phosphate producers. However, plants were discovered across the state.
A key historical resource is the existence of Sanborn insurance maps. These maps were originally produced for the fire insurance industry. Sanborn maps were produced beginning in 1867, and generally included industrialized towns and areas of the state. Access to Sanborn maps was generally available only at libraries; however, around 2000 the Charleston County Library put its collection on-line. SCDHEC Site Assessment staff downloaded the entire collection of this valuable resource and scanned through hundreds of maps in an effort to locate every super-phosphate fertilizer plant that existed within South Carolina. As it turns out, one map page that was missing from the Charleston County Library's collection was the page with the recently discovered Royster Guano Fertilizer in the Rosewood area of Columbia.
As the sites were discovered, it was determined that under the Superfund liability scheme, Exxon-Mobil and Conoco-Phillips were responsible parties for many of the former operations. USEPA negotiated consent agreements with these corporations to fund the necessary investigation and remediation at the sites. It is estimated that well over $100M has been spent to date remediating these sites in SC by these two corporations alone.
DHEC has identified 38 former super phosphate sites to date. Thirty of these sites included sulfuric acid production on-site. Five sites purchased their sulfuric acid and did not make their own. The remaining three sites have no evidence of acid production or use.
All of these former sites have received at least initial screening assessments. Thirteen sites have received cleanups under EPA direction from the Emergency Response and Removal Branch.