Comments on Dauphin Island Erosion

Information provided by Glen Coffee. Mobile Bay Chapter.

COL Sebastien P. Joly, District Commander
U.S. Army Corps of Engineers, Mobile District
P.O. Box 2288
Mobile, AL 36628-0001
or via email: MobileHarborGRR@usace.army.mil

Comments on Dauphin Island Erosion

The Draft GRR/SEIS does not fully comply with §1508.25 of CEQ’s NEPA Regulations because of Corps’ practice of “segmenting” Mobile Harbor Project by preparing multiple separate NEPA documents.  The Corps needs to develop a Master Plan and associated Environmental Impact Statement that would identify all work required to expand and maintain Mobile Harbor for at least the next 20 years.  Such a plan should include all existing, recommended, and proposed future disposal sites so the complete impact of the Mobile Harbor project is disclosed to the public as required by NEPA.

The original 1980 report/EIS that originally recommended the ship channel be deepened was deficient because it completely ignored Dauphin Island’s erosion problem.  The GRR/SEIS is supposed to update the original 1980 report/EIS by analyzing changed conditions.  The tremendous amount of erosion of the Sand/Pelican Island complex and Dauphin Island that has occurred since the 1980 report represents a significant “changed condition” in not only the Study Area, but also the immediate Project Area since the Sand Island Beneficial Use Area (SIBUA) is the Corps’ only designated disposal area to maintain the Bar Channel and is intended to bypass littoral drift sands to the west side of the channel to nourish Dauphin Island.  Despite numerous public inquiries during the planning process, the Corps has never explained its refusal to address the enormous amount of erosion that has occurred to these islands.  Instead, the Corps has chosen to ignore the 38 years of past shoreline erosion impacts that have produced today’s significantly weakened Dauphin Island.  The GRR/SEIS MUST address the 38 years of erosion that has occurred since 1980.

The public does not accept the results of the Corps numerical modeling study results that allege maintenance of the Bar Channel does not contribute to the erosion of Dauphin Island.  The rejection is based on the clear fact the model results do not match with the actual observed shoreline losses that have occurred since the early 1970s.  The Corps admitted at the February 22, 2018 public meeting that the use of the Sand Island Beneficial Use Area (SIBUA) was preventing at least half of the sands that would naturally been carried to Dauphin Island from reaching the island.  In addition, Corps dredging records also indicate that as much as 72% of the sands dredged from the Bar Channel since 1980 have been lost from the nearshore littoral drift system because the Corps practice of disposing of the valuable beach sands in deeper Gulf waters.  These facts indicate the loss of millions of cubic yards of beach quality sands due to unwise channel disposal practices has and continues to adversely affected Dauphin Island.

The 2009 Settlement Agreement that ended the Dauphin Island POA erosion lawsuit required the Corps to begin disposing of dredged sands in the Sand Island Beneficial Use Area (SIBUA).  However, the Corps knew even as early as 2009 that sands were accumulating in the SIBUA instead of moving toward Dauphin Island as promised.  Until the Corps can provide substantive proof the proposed SIBUA expansion will allow most of the placed sands to return to the littoral drift system to nourish Dauphin Island, the Corps could be violating the spirit and intent of the terms of the Settlement Agreement.  Thus, one or more of the 1,700 Class members may be within their rights to challenge the Corps in court for failing to comply with the terms of the 2009 Lawsuit Settlement Agreement since the Corps failed to disclose to the Class that it knew in advance about the sand accumulation problem in the SIBUA.

The public is withholding support for the proposed Sand Island Beneficial Use Area (SIBUA) expansion to the northwest until the Corps provides conclusive information assuring upwards to 100% of the littoral drift sands intercepted by channel dredging and placed in the SIBUA expansion area will return to the littoral drift system to nourish Dauphin Island.  After 20 years of use, the Corps’ promises about the beneficial functioning of the existing SIBUA have all been proven to be wrong while Dauphin Island continued to erode.  The public will no longer accept the Corps’ verbal promises alone that the new site will function as suggested without being provided substantiated proof to support the promise.  Figure 8 on page ES-17 should be modified to clearly show water depths within the proposed SIBUA expansion.  Also, the report should state that all dredged sands placed in the SIBUA expansion will be deposited at water depths much shallower than 15 feet MHW (mean high water).  If the Corps is unwilling to make that disposal commitment, it is unlikely the outcome of use of the proposed expansion will be any different than the original SIBUA in countering the erosion problem.  Because of that concern, a detailed risk and uncertainty analyses of the Corps projections about the effectiveness of the proposed SIBUA expansion should be conducted by an independent third party to assess the effectiveness of the new site to accomplish its intended purpose.

The impacts of shoreline erosion on sea turtle nesting should be discussed.  Section 5.9.1 should be expanded to acknowledge that a consequence of the progressive erosion of Dauphin Island’s Gulf Shoreline is the low success rate of sea turtle nesting on the island.  The low percentage of successful nests on Dauphin Island compared to Baldwin County’s beaches is believed to be associated with the deteriorated shoreline conditions attributable to erosion.  This issue warrants coverage in the report because of the Endangered Species Act connection and because Dauphin Island provides a substantial portion of Alabama’s total Gulf shoreline used for nesting by sea turtles.  It is possible that a “taking” type situation may exist as an indirect impact of the Bar Channel maintenance program and the Mobile Harbor project’s role in contributing to the erosion of Dauphin Island and the lowered turtle nest success rates compared to other northern Gulf beaches.

Comments on Other Topics

The failure of the Draft GRR/SEIS to sufficiently identify the availability of maintenance disposal capacity for the Tentatively Selected Plan (TSP) for the next 50 years is a major concern.  Since the report does not adequately analyze the disposal capacity deficit issue, the future environmental impacts resulting from maintaining the channel also cannot be adequately identified and evaluated.  Therefore, the Supplemental Environmental Impact Statement component of the report does not fully comply with the National Environmental Policy Act for the full 50-year period of analysis identified in the report.

Erosion of Mobile Bay’s western shoreline is a serious continuing issue.  Long-term bayfront property owners have repeatedly stated they have observed large waves created by passing ships.  Instead of giving credence to the validity of landowner statements, the Corps has relied entirely upon in the results of computerized modeling to conclude ship wakes do not represent a serious issue.  Because of the public’s concern over ship generated waves the Corps, Coast Guard, and Port Authority should evaluate imposing speed limits on the larger deep draft ships, particularly if fully loaded, to reduce the magnitude of bow waves from passing vessels.

Why has the Corps and EPA found it necessary to pursue a massive expansion of the Ocean Dredged material Disposal Site (ODMDS) in the Gulf of Mexico?  Figure 4-7 shows the proposed expansion would increase the size of the ODMDS by 500%, from the current 4,017 acres to the proposed 20,341acres.  The report should explain why it is necessary to expand the ODMDS by 500% since the Corps plans to use the existing open water thin layer disposal sites as much as possible to receive future maintenance material.

The report states the Tentatively Selected Plan (TSP) has a Benefit-to-Cost Ratio of 3.0 and will annually produce over $34.5 million of Excess Benefits over Costs.  A portion of the Excess Benefits should be directed to beneficially use dredged material to pursue various restoration projects.  Example projects could include improving Mobile Bay’s oyster resources and pursuing measures to prepare other important environmental resources (such as marsh areas) to better withstand the future effects of Sea Level Rise.

Thin layer disposal of material dredged from the Bay Channel affects thousands of acres of Mobile Bay bottoms each year.  The report’s Tentatively Selected Plan (TSP) to deepen the channel recommends the additional maintenance dredged material also be disposed in the bay over the next 50 years.  But the report provides no adequate scientific information to support the Corps contention that thin layer disposal benefits Mobile Bay’s environment.  Instead, it appears open water disposal within the bay is really being driven by the intent to reduce project costs by no longer having to transport the material offshore for disposal in the Gulf.  The entire return to thin layer disposal in the bay is based upon two unsubstantiated, extremely sketchy statements contained in the July 2014 Environmental Assessment entitled “Modification to Mobile Harbor Operations and Maintenance Addition of a Long-Term Open Bay Thin-Layer Disposal Option”.  Detailed information from independent studies and literature to validate the Corps allegation that thin layer disposal is beneficial for Mobile Bay must be added to the report.

Oysters are a major “indicator species” of the overall health of Mobile Bay.  Historical NOAA catch data for Alabama from 1950 through 2016 show the total annual oyster harvests from Alabama waters have experienced a significant continuing decline during the last 10 years.  To provide a true representation of the existing quality of oyster resources within the Study Area, the report should clarify that the recent four years (2013, 2014, 2015, and 2016) selected to develop the Study Baseline represents a significant low point in both oyster production and reef condition over the past 66 years.  It is worth noting that the decline in oyster production, which is centered around Mobile Bay, coincides with the Corps return to open water disposal of dredged material in the bay in 2014.  The report should devote more discussion to the current deteriorated condition of Mobile Bay’s oyster resources, including additional modeling work dealing spat movements, effects on salinity regimes, predation, etc.

The primary reason given for filling the relic shell mining holes located in the midportion of Mobile Bay is that these areas experience periods of low oxygen.  However, during periods of extreme winter cold, when portions of the bay have been known to freeze and cause winter fish kills, these deep areas also provide temperature refugia that benefit fish fleeing the lethal colder shallow waters.  However, the document does not address the potential refugia benefit that would be foregone if the areas are filled with dredged sediments.

The report should explain how dredged material disposal capacity needs for the Tentatively Selected Plan (TSP) will be satisfied over the entire 50-year economic life of the project.  Table 4-5 shows the remaining annual disposal capacity for the open water thin layer disposal sites in Mobile Bay (Figure 4-6) to be 59,594,000 cy after 20 years of use.  Assuming the average annual dredging volume for the Bay Channel TSP consistently remains at 4,500,000 cy/year during the final 30 years of the project’s 50-year economic life, a total of 135,000,000 cy will have to be dredged.  Subtracting the remaining disposal site capacity of 59,594,000 cy from the projected total dredging requirement of 135,000,000 for the final 30-year period shows the Bay Channel segment will suffer from a disposal capacity deficit of 75,406,000 cy that will become increasingly more difficult to overcome and will likely increase the future cost of the maintenance program.  The report provides no information as to how the Corps and the Alabama State Port Authority plan to satisfy the future dredged material disposal needs of the TSP after the initial 20 years of maintenance.  The potential adverse impacts to Mobile Bay from future dredged material disposal practices are too significant for the report to ignore the significant importance of the dredged material disposal capacity deficit problem the TSP will experience over the total 50-year period of analysis.

Figure 4-9 must be revised to include the 1,200-acre dredged material disposal island planned for the Upper Bay south of the Causeway.  The island project was approved for funding on December 9, 2015 by the federal Gulf Coast Ecosystem Restoration Council at a cost of $2.5 million.  Initiation of the study has now been delayed 2-3/4 years, without any explanation being provided.  The Corps and the Alabama State Port Authority were actively pursuing the proposed island project until the public began asking questions about the proposal and whether it would truly represent a beneficial use of dredged material.  By failing to include the 1,200-acre island on Figure 4-9 and discussing it in the report, it appears the Corps is attempting to prevent the public from being made more aware of the proposal to construct the island.  The public is concerned the Corps is simply delaying starting the dredged material island study until after the current report to deepen the ship channel is finalized.

The water quality modeling analysis must be reconsidered to evaluate a multi-year drought condition to adequately determine if the Tentatively Selected Plan (TSP) will alter salinity regimes within Mobile Bay to the point that oysters, submerged aquatic vegetation, and other specific environmental resources could be adversely affected.  The greatest prolonged changes in salinity in Mobile Bay occur during periods of sustained low flow that are experienced during multi-year drought events affecting significant portions of the Mobile Drainage Basin.  The water quality model must be rerun to generate the projected “worst case” salinity regimes that could reasonably be expected to occur in the foreseeable future under the TSP during a multi-year drought.  That approach is necessary if the potential effects of the TSP on salinity levels, SAV, oyster drills, oysters, and other key environmental resources in Mobile Bay are to be adequately disclosed in the report.

The report does not explain why disposing of maintenance dredged material in open water over thousands of acres of Mobile Bay bottoms over extended periods of time during dredging operations will not increase turbidity values (i.e., a measure of how muddy the water is) above ambient levels.  On page 5-14, the statement is made that “…there would be no expected increase in the concentrations of the turbidity as a result of the implementation of the TSP.”  Given the magnitude of the annual maintenance dredging operations and the fine-grained nature of the sediments dredged, this impact statement does not make sense.  The report should be expanded to better explain why turbidity levels in Mobile Bay will not be increased during sustained periods of open water disposal of dredged material.