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The U.S. Army Corps of Engineers is responsible for dredging the Cleveland shipping channel, but would prefer to use the sediment to cap a two-square mile mass of toxic sediment in Lake Erie rather than dispose of the sediment in a lakefront containment dike.

(Scott Shaw/Plain Dealer file photo)

CLEVELAND, Ohio -- The heads of the Ohio EPA and the Great Lakes Division of the U.S. Army Corps of Engineers have debated over the past week the source, significance, and urgency of a mass of toxic sediment located in Lake Erie, offshore from Cleveland.

EPA Director Craig Butler said the two-square mile polluted expanse, known as Area 1, contains dangerously high levels of PCBs and PAHs, and has been migrating over the past four decades to within five miles of a water intake site for the Cleveland Water Department.

Brigadier General Richard Kaiser responded in a news release and letter to Butler this week denying that the toxic sediment in Area 1 was migrating or that it posed any threat to the city's water intake site. He said the EPA's testing methods and reports were "critically flawed."

Kaiser said the polluted mass of sediment is the EPA's responsibility. Butler said the Army Corps placed the dredged sediment there in the years prior to the passage of the Clean Water Act in 1972, and it's the corps' duty to clean it up.

Both agencies have tested the sediment in the toxic site and both found elevated levels of PCBs and PAHs much higher than elsewhere in Lake Erie, an EPA official said.

The Army Corps has proposed "capping" Area 1 this year with freshly dredged sediment from the Cleveland shipping channel that it has said is clean enough for open-lake disposal.

To sort through the facts and theories behind that argument, The Plain Dealer gathered information from both sides on some of the key questions.

Q: What evidence says that the toxic field is moving?

Butler: "Based on the sampling the EPA conducted in 2014 and 2015, we think the data clearly shows a migration of contaminated sediment outside the original boundaries that the Army Corps had presented as Area 1."

Kaiser: "No credible scientific evidence supports the hypothesis that a 'toxic blob' is migrating towards Cleveland's water intakes.... Based on our thorough evaluation of sediment data and the location and characteristics of Area 1, we firmly believe that the lake bottom sediment in this area is not migrating nor does it pose a risk to Cleveland's drinking water now, or in the future."

Kaiser also acknowledged that the EPA had found elevated levels of contaminants "adjacent to" the original dumping ground.

Butler said the EPA knows of no possible source for that contamination other than previous dumping by the Corps. He added that the Corps, on its own web site, cites areas where they disposed of dredged material as being "disbursive in nature."

Q: What is the risk of the contaminants moving toward the city's water intake?

Kaiser: "Area 1 is an area two-square miles in size, and is located nine miles from the shoreline, in about 60 feet of water and is miles downstream of, and in much deeper water than Cleveland's water intakes."

Butler: "The water intake at risk is shallower than where the sediment is. But the Army Corps is trying to make an argument that the sediment would have to move uphill to reach the intake. We believe it's going to move wherever the storms or the currents move it... The lake is this dynamic system with currents, wave action and storms. It is our belief that it is fair to expect sediment to move in a dynamic lake environment."

Kaiser's scientists have assured him that waves cannot influence the sediment at 60 feet, the depth of Area 1, except during extreme storm events. Even then, the water current is not strong enough to meaningfully move the sediment.

Q: What concerns do you have about contaminants actually polluting the city's drinking water?

Butler: Tests show the city's raw water and treated water is safe and clean. If the contaminated sediment were to reach the intake, Cleveland has a treatment process designed to remove these types of contaminants with filters and larger amounts of chemicals. This would impose additional costs on the water system, but it would effectively filter out the contaminants.

Kaiser: "It is important to know that there is no credible scientific evidence concluding that it has ever posed a danger to Cleveland's drinking water."

Kaiser cites his own experts who reviewed the EPA report on Area 1 and found it to be critically flawed. The report failed to take into account sediment erosion, deposition and density, and other conditions specific to this area of Lake Erie, his experts said.

Q: If the toxic mass is migrating toward the city's water intake, how soon might this happen?

Butler: "That is the precise question we need answered. We have time to come up with a remedy and we need to work together. The Army Corps owes it to Ohio and the citizens of Cleveland to go find out. And not say, 'It's on your bottom of the lake and it's not our problem.'"

Kaiser: "While the Army Corps will not characterize and address contaminants of unknown sources in the entire lake bottom, it will support as appropriate any efforts by the Ohio EPA, as the owner of the lake bottom, to investigate the source of the contaminants and build a science-based understanding of their impacts."

Q: What are your primary concerns here?

Butler: "Public safety and the safety of the drinking water. It is our belief this material was placed there by the Army Corps before the Clean Water Act regulations existed. But that does not relieve the Army Corps of their responsibility to clean it up."

Kaiser: "On Saturday, April 30, 2016, The Cleveland Plain Dealer published an article titled 'Cleveland's water supply at risk as toxic blob creeps across Lake Erie, Ohio EPA says.' The U.S. Army Corps of Engineers is fully committed to working with the Ohio EPA and other state and federal agencies to ensure that headline never becomes a reality."

Q: What is going to happen next?

Butler: "This is a long-term concern. It can't wait. We need to do it now. My intention is to reach out to our partners with U.S. EPA to go out and do more testing. Whether the Army Corps wants to join us is up to them. We're not going to wait."

Kaiser: "As per previous correspondence from the U.S. Army Corps of Engineers on March 10 and 21, 2016, we continue to advocate for a collaborative, science-based discussion with the Ohio EPA."