Sydney Mine Sludge Ponds

• Site Profile
• Administrative Record Index (PDF): OU1 (20 pp., 801K)
• Potential Reuse Fact Sheet (PDF, 1 pp., 150K)
• Additional Site Documents including Five Year Reviews, Records of Decisions (ROD) and Explanation of Significant Differences (ESD).
• For documents not available on the website, please contact the Region 4 Freedom of Information Office (http://www.epa.gov/region4/foiapgs/submit.htm).

Site Background:
The Sydney Mine Sludge Ponds Site is a 9.5 acre former liquid waste disposal site that was strip-mined for phosphate ore from the 1930s through the 1950s. Starting in late 1973, Hillsborough County leased a small portion of the tract and operated a liquid waste disposal facility until 1981. Approximately 16 million gallons of liquid waste, including sludge, grease trappings, cutting oil, etc. were hauled to and disposed of at the site. As a result of this disposal, contaminants, principally volatile organic compounds, have migrated vertically and laterally, and are being detected in the limestone of the Hawthorn aquifer, locally the principal potable water source of groundwater.

Site Responsibility: This site has been addressed through responsible party actions.

Threats and Contaminants
Groundwater contamination by volatile organic compounds is the principal threat.   

Cleanup Approach
Twelve thousand cubic yards of contaminated soil from the sludge ponds were excavated and incinerated in the mid-1980s. Subsequent to this, the County constructed a slurry wall around the ponds, believing that this would prevent the migration of contaminants. In the late 1980s the County constructed a recovery and treatment system in order the remediate the surficial aquifer. In 1989, EPA issued a Record of Decision, requiring the County-constructed Groundwater recovery and treatment system be optimized.  Working under a Unilateral Administrative Order in the early 1990s, the potentially responsible parties modified the surficial aquifer system, in an effort to improve the performance of the system. While this work was going on, it became apparent that two additional water-bearing units had also become contaminated. At EPA's request additional recovery wells were installed in the intermediate aquifer system. This system was put into operation in early 1995.

Late in 1996, the potentially responsible parties submitted a plan to evaluate the effectiveness of intrinsic bioremediation, rather than active pumping and treating, as a way of ultimately achieving cleanup goals. Groundwater quality data over the years indicate that remediation through pumping and treating will take a very long time.  EPA evaluated this proposal, keeping in mind Tampa Bay's growth along the corridor that the site is located. The same reason that attracted disposal of the liquid wastes into the clays of the former phosphate mine makes remediation of the groundwater to State of Florida standards problematic.

In late 1997, the first round of data collection to determine whether intrinsic bioremediation is a viable option for the site's surficial and intermediate aquifers was conducted. The report on the second and final phase was submitted for EPA and FDEP review in mid-June 2000.

Response Action Status

During late 2001 and early 2002, the groundwater pump-and-treat system was decommissioned. Long-term groundwater monitoring continues.  The most recent groundwater data available is from January 2009 sampling.  Negotiations for a Restrictive Covenant have finished.  EPA is awaiting (March 2009) concurrence from the State of Florida on the draft Restrictive Covenant.

The site’s second Five Year Review Report was concluded in September 2006.  The link to the Report is: http://www.epa.gov/superfund/sites/fiveyear/f2006040001070.pdf.

Site Repository
Tampa-Hillsborough Public Library, 619 Vanderburg Dr., Brandon FL 33511
EPA Region IV Superfund Records Center, 66 Forsyth Street, Atlanta,  GA 30303