February 10, 1998
by Edmund Tsang
When asked to comment on the recent Environmental Protection Agency (EPA) report listing Mobile Bay as one of 96 watersheds in U.S. that "contain areas of probable concern" because of contaminated sediments, Mike Dardeau of the Dauphin Island Sea Lab and a co-chair of the Technical Advisory Committee (TAC) of Mobile Bay National Estuary Program (NEP), said, "It's hard to say without seeing the report." Concerning the characterization of Mobile Bay, Dardeau told The Harbinger in a telephone interview last week that "I don't think all the data are in. We have to wait and see the information we are gathering through our contractors."
The Mobile Bay NEP program is partly funded by EPA to develop a plan to protect the estuarine system of Mobile Bay. One of the tasks of the Mobile Bay NEP program in its first year is to collect and organize the scientific and technical data to characterize the current state of estuarine system, and to identify data gaps, Dardeau explained. "The first draft of a report on water quality is due in a month," Dardeau added.
Danny Calametti, a community coordinator for the Mobile Bay NEP program, told The Harbinger last week that he had no comment "because I have not seen the report." Calametti then added: "We know that sediments are a problem, but we don't know the extent of the problem and the make-up. We don't have characterization [of Mobile Bay] completed yet," Calametti said, but the study will be completed by this summer or early Fall. "They [the issues of Mobile Bay] will be addressed, no matter where we rank on that [EPA] list."
One of the sub-contractors who will be submitting a report to NEP on Mobile Bay's characterization is Dr. Wayne Isphording of the University of South Alabama, who is an expert on Mobile Bay's sediments. A 1991 report to the U.S. Geological Survey authored by Dr. Isphording, titled "Organic And Heavy Metal Chemistry Of Mobile Bay Sediments," concluded that the results of the study "indicate that (1) significant increase in heavy metals and certain organic compounds occur toward the head of Mobile Bay, (2) partitioning data indicate that, unlike some other estuaries in the northern Gulf of Mexico, most metals are held in Mobile bottom sediments in forms that allow not only their release back into the water column, but also their extraction by bottom feeding organisms, and (3) excessively high concentration of zinc (and copper) are present in oysters living in the northern part of Mobile Bay."
The levels of heavy metals in the sediment in 1991 were much lower than those measured in 1979 and 1988, according to Dr. Isphording's 1991 report, much of it due to the "scouring action of Hurricane Frederick." In a 1990 report that Dr. Isphording co-authored with Dr. George Lamb, they wrote: "because the sediments most susceptible to resuspension and removal by the anti-clockwise winds of hurricanes are those of smallest particle size (or least specific gravity), it is not surprising that the loss of large volumes of clay-sized sediments (and organic material) resulted in a decrease in the average heavy metal content of the sediments." In the 1991 study, Dr. Isphording reported that "subsequent deposition that continues to take place in the bay, has acted to restore heavy metals in the bottom sediments of the bay to more acceptable levels."
Data in Dr. Isphording's 1991 report indicate a slightly higher concentration of ten heavy metals in Mobile Bay's sediments than the values in EPA's January, 1998 report, and a slightly lower concentration in one metal, nickel.
Because "substantial increases in a number of heavy metal species and three organic compounds were observed toward the head of the bay," Dr. Isphording's 1991 report concluded the result "suggests that even higher levels are present in the Mobile Delta. This area is the largest contiguous wetland region in the State and is the habitat for a diverse biota. Additional work is needed to assess the extent of the heavy metal and organic contamination in the delta region."
The Harbinger asked Dr. Isphording last week about the follow-up work to his 1991 study on characterizing the upper delta of Mobile Bay. Dr. Isphording said he has just completed the task of organizing the raw data provided to him by various agencies on the chemical characteristics of sediments, and he will begin statistical analysis of that data soon. Dr. Isphording said this study is part of the NEP characterization program and he will submit a report in March, 1998.
The January, 1998 EPA report identifies dredging as one of four goals in managing contaminated sediments because of the potential to release the contaminants. The Fact Sheet in EPA's web site on the report states this goal: "Ensure that sediment dredging and dredged material disposal are managed in an environmentally sound manner." For this goal, the fact sheet outlines the following action plans: "Release new guidance on improved testing standards for dredging and disposal of contaminated material in state waters." and "Establish a national stakeholder group to review procedures for dredged material management in ocean waters."
Dr. Susan Rees of the Mobile office of the U.S. Army Corp of Engineers and a former interim director of Mobile Bay NEP, told The Harbinger in a telephone interview last week that while she has not read it, "I don't think we agree with the EPA report" because it is making "broad statements based on only a few samples." Dr. Rees said the Corp of Engineers has been "routinely monitoring" the dredging operation of the Mobile Bay ship channel since 1970's. "The samples we take from the channel do not indicate" contamination of concern. As to the high levels of heavy metals and organic compounds published in the EPA report, Dr. Rees said the EPA sampling locations are "not near the area where we dredge," and sampling might have been chosen in "areas with high contamination."
"There are chemicals in the dredged material of course, some above natural background value and some at the background value," Dr. Rees explained. "We learned in Dr. Isphording's study that most of the contaminants are bound in the sediments in a form so they are not available to aquatic animals. The sediments are serving like a bank vault to store the metals." "If you take things into context, you will see that Mobile Bay is getting cleaner over time," Dr. Rees said. "If you look at contaminants with a long life, for example DDT, which was banned but we still found it in the sediments, the level of DDT is declining. Furthermore, we are seeing more of the degradation by- products of DDT such as DDE, but DDE is still considered a contaminant by EPA."
Calametti of Mobile Bay NEP program said the issue of dredging and the potential to release contaminants from sediments should be addressed from the standpoint of "a long-term strategy" of managing the assets of Mobile Bay. "Many people benefit from dredging. We can't look at it in isolation, and the solution will involve trade-off and balance," he added.