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Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries: Report and Symposium Proceedings PART II PROCEEDINGS OF THE SYMPOSIUM SEDIMENTATION CONTROL TO REDUCE MAINTENANCE DREDGING IN ESTUARIES
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Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries: Report and Symposium Proceedings OPENING REMARKS Ray B.Krone Symposium Chair Welcome to this symposium on sedimentation to reduce maintenance dredging in estuaries. Sedimentation in harbor facilities that are located in estuaries was a problem even before channels were deepened beyond their natural depth. In my own back yard, for example, in Humboldt Bay, California, in 1852, 1853, and 1854, lumber companies installed wharves out to the six ft water depth. Six feet was deep enough for the lumber schooners in those days. Sedimentation rates immediately increased, and the state legislature passed laws against dumping of ballast and sawdust to try to stop that sedimentation, to no avail. The presence of the ships themselves and of the piers built out into the bay exacerbated the sedimentation rates. Now we’re deepening harbors to provide for deeper draft ships. These activities can increase the rate of sedimentation, at least in those cases in which the entire supply of sediment isn’t already depositing. Increasingly severe restrictions on disposal of dredged sediment further add to the operational and monetary costs of maintenance dredging. The limited capacity of land disposal sites, recent reductions in available open-water disposal sites, and the prospects of long hauling distances to open disposal sites all intensify the need for reducing sedimentation rates in harbors and improving the efficiency of maintenance dredging. Our sponsor for this symposium is the United States Navy. The Navy’s new battle group home berthing program, its vital need to maintain constant readiness of naval port facilities, and the deeper drafts of the latest maritime weapons systems all accentuate the need to reduce its onerous and ongoing maintenance dredging. Reductions of operational and monetary maintenance costs for commercial facilities are also important to the United States economy, and the benefits of our efforts in this symposium should have widespread value. The United States could do without as much of its half billion dollar annual dredging cost as possible. This Committee was appointed by the National Research Council Marine Board to assemble the latest knowledge that can be brought to bear on these problems. The members of the Committee are the session chairs and myself. This Committee organized the agenda for this symposium, and each session chair solicited contributions from speakers
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Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries: Report and Symposium Proceedings who are highly qualified in their particular areas. We also invited participants whose special knowledge will contribute both to the areas that are formally identified and to areas that might have slipped between the cracks. This symposium is concerned with means for reducing the deposition of fine cohesive sediments in estuaries and estuary harbor facilities, means for reducing the cost of maintenance dredging in these facilities, and means of disposing of dredged sediment. We anticipate that the report of this symposium will include descriptions of the state of the art in each of these areas, will identify emerging technologies and management options that have the potential for reducing maintenance dredging and maintenance costs, and will indicate directions for productive research. The members of the Committee and I are delighted with the prospect of your participation in this symposium, and we look forward to the contribution from all of you here during the next two and a half days. Our keynote speaker is Rear Admiral John R.Ives, Civil Engineering Corps, United States Navy. Rear Admiral Ives graduated with honors from the United States Naval Academy in Annapolis in 1959. He continued his education at Rensselaer Polytechnic Institute, where he graduated with a bachelor’s degree in civil engineering, and at Stanford University, where he received a master’s degree in civil engineering and engineering economic planning in 1967. He later completed the Navy’s command and staff course at the Naval War College in Newport, Rhode Island. He has had a long and distinguished career in the United States Navy, and he is presently assigned as Deputy Commander for Planning and Facilities Acquisition, the Naval Facilities Engineering Command, Headquarters, Alexandria, Virginia.
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Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries: Report and Symposium Proceedings KEYNOTE ADDRESS Rear Admiral John R.Ives, USN Deputy Commander Naval Facilities Engineering Command When my old friend Marty Finerty extended this invitation, I was a bit awed at the idea of addressing a group like this. I think perhaps what I can best do is characterize for you the problem of sedimentation in harbor facilities as it affects the U.S. Navy, and identify some of our interests and some of our current thrusts. Since I’ve been allotted only ten minutes, that’s probably about all I can hope to do. Ten minutes is probably well advised, because I think in that time I could probably pretty much exhaust my total technical knowledge of the subject. I have brought with me some other people who will stay through the meeting and will use the results of the discussions as input to the Navy’s program. With me is Milan Essoglou from our research and development organization. Mr. Charlie Chern from design, and Dr. Jim Bailard from the Navy’s Civil Engineering Laboratory in California. Please direct all your piercing technical questions in their direction. Dr. Krone mentioned a very large figure for annual maintenance dredging costs—half a billion dollars a year. The Navy’s portion of that is currently running about $30 million per year, but it is rising sharply and we anticipate continued growth of that figure. Dredging is a serious problem for the Navy. It’s serious not only because of its budget implications, which in the days of Gramm-Rudman-Hollings get more and more serious as each year rolls by, but it’s also significant in terms of operational impact. We must take a berth or a channel out of service or undergo some operational interruption to accommodate the maintenance dredging that is necessary. Finding suitable sites for dredge material disposal is also becoming more difficult and more expensive, and environmental considerations are a significant problem. Additionally, actual damage to ships has resulted from siltation along piers—from either silt or marine organisms being picked up through saltwater intakes—and the cost of repairs is significant. The Navy’s dredging costs will go up sharply as the new development at Kings Bay, Georgia comes on line. The prospect for the long-term operations of that facility include significant maintenance dredging. One of the things that concerns us is that in our experience, sedimentation control is very, very site specific. By that I mean we must study in detail each site and the method best suited for that
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Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries: Report and Symposium Proceedings particular site. We can’t automatically assume that what works in one location is going to work in another. Thus, the Navy sees a need to study in quite some detail most of the sites of great interest to us, and that presents a problem because it represents a significant expense. Regettably, we can’t take some easy solutions from a few sites and extrapolate them to all the other sites. It is a more complex problem than that. Another problem is scaling: we can’t model all sites at full scale. We have to work on a reasonable scale in order to hold expenses down, and scaling up is a potential problem. The Navy plans to do modeling as appropriate. We make extensive use of the Waterways Experiment Station run by the Army. Modeling is a somewhat expensive approach and we’re investigating some systems and approaches to establish criteria within which models operate well. We will build on that experience to reduce the expense to the Navy of the modeling effort. These are some of the issues that the Navy is working on and some ideas about our approaches. To be a little more specific, we’re currently spending on the order of $500,000 to $600,000 a year for research and development. Money is spent on such things as concept validation, system and component testing, and development of criteria. We hope that the money spent in this area will lead to some promising systems, which we can then advance into engineering development and eventually deploy for specific sites. One of the locations that is of particular interest to us I’ve already mentioned—Kings Bay, Georgia. We are looking there for perhaps tidal current modification to reduce sedimentation rates. Another area of real interest is Mayport, Florida, where there is basin siltation. We have done some extensive model studies there and are looking at the possibility of a venting canal. Mare Island is another site that’s very active. In fact, Mare Island is sufficiently interesting that with our little bit of R&D money, we can’t quite keep up with their needs, and they contribute money of their own toward examination of some of the concepts which we’d like to try. Right now we’ve got a scour jet array system deployed at Mare Island that we’re monitoring. We’re looking in the future toward the possibility of a vortex foil array and perhaps a barrier curtain. Barrier curtains give us some uneasiness with regard to their operation, which might cause more of an impediment than we like. Cooper River, at Charleston, South Carolina is another area that’s of great interest because heavy siltation occurs between the piers there. Norfolk, Virginia has been a problem in the past, particularly aircraft carrier piers 10 and 12, which had problems with intake of microorganisms, hydroids, and some other unpronounceable things. Our approach at Norfolk was to develop a maintenance trench to catch the siltation before it entered the area alongside the piers. We did that about three years ago and it seems to be working rather well. We’ve also got the microorganism problem under control and haven’t been picking them up in the saltwater intakes.
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Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries: Report and Symposium Proceedings These are some of the issues that represent the Navy’s set of interests—the problem from our perspective, some of the directions of our research and development, and an idea of the size of our program. As I have indicated, as a result of the [Gramm-Rudman-Hollings] Deficit Reduction Act, it’s going to be more and more difficult to maintain current levels of R&D. We very much look forward to the ideas that will be generated by this board to guide our research and development into the most promising areas. The $30 million that we’re spending now, which is rising, doesn’t buy an awful lot in terms of national defense or in terms of adding to our fighting capability. Yet it is a necessary and relentless cost which must be borne. Anything that can be done to reduce the rate of increase of that figure—or perhaps even drive it down—would be very important to the Navy and the national defense. Thank you for your time and attention. I commend the board for its efforts in this important area and look forward to very productive results of the next several days.
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