The U.S. Environmental Protection Agency (EPA) has released its “First Five-Year Review Report” of the “Onondaga Lake Bottom Subsite of the Onondaga Lake Superfund Site.”
“Implementation of the remedy is progressing as expected,” according to the EPA report. The report went on to say, “Several process enhancements and modifications were implemented to improve overall dredge system performance and production capabilities. As a result, dredging of the Lake and three adjacent shoreline areas, which included removal of approximately 2.2 million cubic yards of sediments, was completed within three years instead of four years as anticipated in the design. Capping operations from 2012 through 2014 were consistent with design projected volumes and capping is projected to be completed within five years as originally planned.”
Based upon the results of this first five-year review, EPA concluded that:
- “Concentrations of dissolved mercury are significantly lower in surface water samples collected between 2008 and 2014 relative to samples collected during the RI (Remedial Investigation). This is likely attributable to reductions in mercury loading to the Lake from external sources such as tributaries and groundwater. Further reductions in dissolved mercury are expected from the implementation of the selected remedy.”
- “As a result of METRO (Metropolitan Syracuse Wastewater Treatment Plant) upgrades and adding diluted calcium nitrate near the sediment/water interface in the deep water portions of the Lake since 2011, MeHg concentrations in Lake water and in zooplankton have declined dramatically. Lower MeHg exposures from the water column and through the food chain are expected to contribute to lower mercury concentrations in fish.” [MeHg is methlymercury, which is a form of mercury that accumulates in fish and organisms. It forms during the summer months, in the deep water portions of the lake, when oxygen is not present.]
- “The combination of lower than projected concentrations of mercury in surface sediment and settling sediments, and higher average annual sedimentation rates than the rate assumed in the Final Design indicate that natural recovery in the Lake is progressing faster than predicted.”
- “Due to the scheduling of various aspects of the remedial program and the nature of biological systems, it is premature in this first five-year review to determine whether the remediation has achieved the goals for mercury in fish tissue identified in the ROD (Record of Decision).”
- “Future five-year reviews will have the opportunity to review data over sufficiently long time frames to determine the extent of compliance with the goals in the ROD.”
The EPA also reported that air monitoring results showed levels did not exceed government criteria for total volatile organic compounds, mercury or sulfides. EPA states, “No exceedances of work perimeter limits or action levels occurred for total VOCs, mercury, hydrogen sulfide or noise.” The report also says, “One 1-hour work perimeter limit exceedance for dust occurred at one station in 2012 due to evening shift change traffic by the air monitoring station. Levels for dust dropped to within limits immediately after the shift change and roads were watered the following morning. There were no other additional exceedances for dust.”
To view the complete report, click here.
For more information on the Onondaga Lake cleanup, please visit www.lakecleanup.com.