Using the vacuum guzzler to remove contamination
In the spring of 2000, the Lab’s Peconic River cleanup project team faced a significant decision. Over the previous five years, the team had conducted several rounds of sampling and analysis to define the extent of mercury contamination found in river sediment. The team commissioned a study of potential health impacts and developed various cleanup strategies.
When the Lab and the Department of Energy (DOE) released a proposed plan for comment, the plan recommended excavation of the sediments, including some located in sensitive wetland areas that supported thriving ecosystems. The plan also recommended cleaning up certain areas in Suffolk County parkland adjacent to the BNL site.
The Lab’s Community Advisory Council (CAC), and the wider community, voiced great concern about the plan. They recommended moving forward with cleaning up BNL’s sewage treatment plant, the original source of the contamination, and recommended investigating less-disruptive technologies that could be used in the river. DOE, the Lab, and regulatory agencies agreed with this two-pronged approach.
The alternative technologies that the Lab explored included phytoremediation (using plants to remove contaminants from sediment), vacuum guzzling (removing pockets of contamination using a large vacuum device), and electrochemical remediation (using an electrical current to concentrate contaminants for removal).
The Lab also conducted a pilot study that excavated and replanted a small stretch of the river to determine whether it would be successful. Of the four technologies studied, the pilot excavation was the most successful. The Lab also conducted additional sampling to better delineate the extent of mercury contamination and its potential impact on the environment and human health.
“Threatened” banded sunfish returned to the river
In the end, a plan was developed that addressed the concerns of regulators as well as the community. The plan included targeting specific areas within the river where contaminants were concentrated, as well as conducting the cleanup using low-impact conventional construction equipment. “Haul paths,” constructed using large plastic mats, enabled access to the river while minimizing the removal of vegetation and the impact of the sediment-excavation vehicles on the paths. After the project was completed, the plastic mats were removed and the haul paths have largely recovered. To the maximum extent possible, the Lab also agreed not to bring in topsoil to replace removed sediment. Instead, soil was taken from designated “open water” areas of the river to complete the restoration process following confirmatory sampling. The Laboratory also monitored and removed invasive wetland plants in remediated sections of the river for three years following the cleanup. Prior to the remediation work, banded sunfish, a New York State “threatened” species, were removed from the river and kept in a holding pond. Once the project was complete, some of the fish were returned to the river while some are still being monitored in the holding pond.
The CAC closely followed all of the activities related to the river project. When the second plan was put out for public comment in 2004, they, along with many others in the community, supported it.
DOE and the Lab worked closely with the Parks Department, Suffolk County Legislature, the Pine Barrens Commission, and many other key agencies to clean up the portion of the river in the Suffolk County parkland. All of this planning and coordination was imperative before DOE and the Lab could negotiate crucial access agreements with property owners.
In 2005, the cleanup of both the on- and off-site portions of the river was completed, and the river was replanted with native Peconic River wetland plants. Prior to the cleanup, approximately 47,000 wetland plants were gathered from the Peconic, potted, and kept in a natural nursery until they were replanted following the cleanup. In 2007, the New York State Department of Environmental Conservation inspected the restored wetlands and determined that the restoration project had met all of their expectations.
While it will take some time for the river to fully recover, improvements can already be seen, and both aquatic and terrestrial local wildlife have returned. The Lab’s long-term monitoring program will continue to monitor the Peconic River surface water, sediment, and fish through at least 2011 and the data will continue to be shared with both the regulators and the community.
Sewage Treatment Plant
In 1997, the Lab upgraded its sewage treatment plant from primary (one-stage) to tertiary (three-stage) treatment. The treatment process now includes nitrogen and organic material removal and ultraviolet disinfection (replacing chlorine treatment). Today, the sewage treatment plant is considered a state-of-the-art facility.
Although the facility was upgraded, the Laboratory needed to clean the sand filter beds and berms of the sewage treatment plant to remove low levels of chemical and radiological contaminants. In 2002 and 2003, the Lab removed soils containing mercury and cesium-137 that were at concentrations above the U.S. Environmental Protection Agency and New York State acceptable levels. The former sludge drying beds, sand filter berms, and sewer lines were also remediated to remove low-levels of these contaminants. Low levels of tricholoroethene (TCE) and tritium found east of the sewage treatment plant were investigated. The TCE was found to be below the depth of typical residential wells and the tritium was well below the drinking water standard. It was determined that there was no need for active treatment, however, the Lab continues to monitor groundwater in this area.