COMISIÓN EJECUTIVA PORTUARIA AUTONOMA REPUBLIC OF EL SALVADOR
FINAL REPORT FOR SPECIAL TECHNICAL ASSISTANCE FOR MAINTENANCE DREDGING OF THE PORT OF LA UNIÓN IN THE REPUBLIC OF EL SALVADOR
June 2014
JAPAN INTERNATIONAL COOPERATION AGENCY
ECOH CORPORATION
EI JR 14-018
COMISIÓN EJECUTIVA PORTUARIA AUTONOMA REPUBLIC OF EL SALVADOR
FINAL REPORT FOR SPECIAL TECHNICAL ASSISTANCE FOR MAINTENANCE DREDGING OF THE PORT OF LA UNIÓN IN THE REPUBLIC OF EL SALVADOR
June 2014
JAPAN INTERNATIONAL COOPERATION AGENCY
ECOH CORPORATION
Abbreviations Table ALMOB Automatic Light Mixture Overboard C.D.L. Chart Datum Level CA4 Four Central American countries:El Salvador, Guatemala, Honduras and Nicaragua CA5 Five Central American countries:El Salvador, Guatemala, Honduras, Nicaragua and Costa Rica CEPA Comisión Ejecutiva Portuaria Autónoma or Executive Autonomous Port Commission of the Republic of El Salvador CNR National Registration Center of the Republic of El Salvador COCATRAM Comisión Centroamericana de Transporte Marítimo (The Central American Commission on Maritime Transport) CPN Comision Portuaria Nacional Guatemala (Guatemala National Port Commission) D.L. Datum Level ECOH Environmental Consultants for Ocean and Human EPN Empresa Portuaria Nacional (Nicaragua National Port Company) EPQ Empresa Portuaria Quetzal (Quetzal Port Company) GPS Global Positioning System GVD Geodetic Vertical Datum JBIC Japan Bank for International Cooperation JICA Japan International Cooperation Agency JSCE Japan Society of Civil Engineers LMOB Lean Mixture Overboard LOA Length overall MLIT Ministry of Land, Infrastructure, Transport and Tourism MLLW Mean Low Low Water MLW Mean Low Water MSL Mean Sea Level NAD27 North American Datum of 1927 NOAA National Oceanic and Atmospheric Administration United States Department of Commerce OCDI The Overseas Coastal area Development Institute OD Origin-Destination PIANC World Association of Waterborne Transport Infrastructure SAPI Study on Special Assistance for Project Implementation SIECA La Secretaría de Integración Económica Centroamericana (The Secretariat of Central American Economic Integration) TDS Tons Dry Solid TOR Terms of Reference TSHD Trailing Suction Hopper Dredger TSS Total Suspension Solid UNCTAD United Nations Conference on Trade and Development USA United States of America USDA U.S. Department of Agriculture VBA Visual Basic for Applications WGS84 World Geodetic System 1984 WID Water Injection Dredging
Executive Summary
Executive Summary
Chapter 1 Introduction The Republic of El Salvador decided to develop the new port in the Department of La Union, and requested the Japanese Government to prepare a master plan for the port construction and to carry out a feasibility study. The latter responded to the request by executing the feasibility study of La Union Port through JICA during October 1997 to December 1998. Following the feasibility study, the detailed design was made during July 2001 to January 2003. The project of constructing La Union Port began in April 2005, and construction of the civil engineering works was completed in December 2008 (see Figure 1.1).
While capital dredging of the access channel of 22.3 km long was progressing in 2007, it was observed a large quantity of siltation in the Inner and Outer channels and the harbor basin. Because the siltation might endanger the smooth operation of the port, the government of El Salvador and Japan discussed on the necessity of study on the fast siltation in July, 2008, and they agreed upon to start the Special Assistance for Project Implementation for La union Port Development Project (hereinafter referred to as “SAPI”). The SAPI Study was undertaken by JICA and executed during November 2008 to November 2009 (see Figure 1.1).
The SAPI Study clarified that the siltation is caused by slow movement of fluid mud toward a deeper seabed. Owing to the limited quantity of bathymetric time-series data and a relatively short duration of the study, however, it was difficult to predict the siltation volume with a high accuracy for making reliable estimate of the volume of maintenance dredging.
Figure 1.1 History of La Union Port
To make the port function properly as a deep sea port, dredging method as well as cost is a vital issue in financial viability and a key factor for successful terminal operation. Hence, CEPA again requested JICA to provide an effective and efficient maintenance dredging plan. According to a result of discussion between JICA and CEPA, JICA commenced the 1st Term Study in January 2011 and conducted a series of bathymetric survey and analysis for about one year and four months up to May 2012.
The survey and analysis have proved that detailed analysis of future shipping service, detailed demand forecast, and the data of trial dredging are inevitable for making valid maintenance dredging plan. Hence, JICA and CEPA discussed again and agreed to revise the TOR of Special Technical Assistance for Maintenance Dredging of the Port of La Union before the
1 commencement of the 2nd Term Study. In the 2nd Term Study, not only the engineering issue but also the economic issue is included in the study scope to analyze technically/financially and economically optimum channel depths at present and in the future. After about one year suspension of study, the 2nd Term Study resumed on April, 2013.
The 1st Term Study and the 2nd Term Study have the following three purposes: (1) To prepare data, information and analysis utilized by CEPA to formulate an effective and efficient maintenance dredging plan of the Port. (2) To transfer technology to cope with the siltation in the channel and basin. (3) To assist CEPA to prepare dredging plan based on the collected data and analysis.
The 2nd Term Study Team consists of two sub-teams, that is to say, the Engineering Team and the Economic Team. In order to properly implement the 2nd Term Study, the Project Support Domestic Committee has been established in JICA Headquarters to support and give advices to the Engineering Team from an academic and technical view point.
Chapter 2 Technology Transfer
In the 1st Term Study, the technical training of CEPA personals was carried out in Japan from 21 November to 9 December, 2011. Two trainees participated in the training program and studied on operation and management of dredging works, methodology of bathymetric survey and astronomical tide prediction, and so on.
In the 2nd Term Study, the Engineering Team has transferred the technology to the counterparts and participants through the twelve times of lectures, exercises, discussion and on-the-job training. The technology transferred contains the matters concerning the bathymetric survey, the prediction of tide level, the tide level correction, the mechanism and the processes of siltation, the rake-dredging, the empirical prediction models for siltation, the monitoring plan of siltation, the influence of the Semicircular Island and the types of dredging vessel, and so on.
The Economic Team has transferred the technology to the counterparts and participants through sixteen lectures and discussions. The technology transferred includes matters concerning the Vessel Calling Model, the present state of container shipping in Central America, the tariff of La Union port and neighboring countries, the expected ship waiting time by tidal change in La Union port, the navigable time of the channel by using tidal advantage, the connection between industrial development of the region surrounding the port and port planning and promotion, and so on.
The workshop on “Special Technical Assistance for Maintenance Dredging of the Port of La Union in the Republic of El Salvador” was held in CEPA Headquarter on 27 August, 2013. Numbers of participants were 17 from the El Salvador (CEPA) side, 4 from the Japanese side, 7 from the JICA Study Team and 4 from the JICA El Salvador Office.
Chapter 3 Field Survey and Results
The field survey such as bathymetric survey and mud sampling were conducted in the 1st Term Study.
The bathymetric survey was repeated three times in February 2011, August 2011 and January 2012. A preliminary analysis was made with the data obtained. La Union Port has an access channel with total length of 22.3 km and had been dredged to a depth of D.L.-14 m. At present,
2 however, the entire passage has been filled to almost the original elevation and the depth when it was completed has not been maintained.
From the analysis of mud sampled at about two years after capital dredging, it is confirmed that fluid mud layer, the wet density of which is less than 1,200 kg/m3, is formed with the height of about 0.5m in Outer channel and about 1.0 m in Inner channel.
The fluid mud layer in the channel continues in existence for relatively long period. This indicates a possibility to reduce maintenance dredging volume by making a maintenance dredging plan taking the fluid mud layer into account.
Judging from the Team’s experience in the field, it is considered that the echo sounder of 200 kHz in frequency detects the top surface of the fluid mud layer. Therefore, the depth navigable for vessels is considered to be deeper than the depth measured by the echo sounder of 200 kHz, due to the thickness of the fluid mud layer.
Chapter 4 Analysis of Siltation Process and Prediction Models
At first, an empirical prediction model is formulated with an exponential function based on the bathymetric data.
Next, a process and a mechanism of siltation in the channel are revealed through the analysis of bathymetric data. According to the result of analysis, the original exponential model has been improved to be a new model, which is named as a modified Exponential Model.
Moreover, it is shown that a rapid siltation occurs just after the dredging within several months. By taking into account a possibility that the rapid siltation does not occur during a period of maintenance dredging, a second prediction model has been newly established, which is called a Linear Model.
At present, there is a discrepancy in the volumes of siltation predicted by the modified Exponential Model and the Linear Model. The volume of siltation predicted by the former is usually equal or greater than that of the latter. Since the latter model is formulated based on a unverified hypothesis, we must refrain from the use of it until the hypothesis is verified with the bathymetric data.
Chapter 5 Estimation of Dredging Volume and Cost
By using two prediction models formulated in Chapter 4, the volume of maintenance dredging will be estimated in Chapter 5.
At present, the harbor basin, Inner channel and Outer channel have been filled to almost the original elevation. The basin and channel need to be re-dredged at first. The total volume of the re-dredging for six target navigation depths of 9 to 14 m varying by 1 m is estimated based on the latest survey result in July 2013. The estimated re-dredging volume by depths is summarized in Table 5.1.
Table 5.1 Estimated re-dredging volume (units: 1000 m3) Depth (m) Outer Ch. Inner Ch. Basin Total 9.0 0 895 0 895 10.0 25 1,535 59 1,619
3 11.0 404 2,215 344 2,964 12.0 1,161 2,936 798 4,895 13.0 2,284 3,696 1,471 7,452 14.0 3,882 4,496 2,186 10,565
The maintenance dredging volume is calculated for six levels of the target depth: i.e., 9, 10, 11, 12, 13, and 14 m. The cycle time, or the time interval of successive maintenance dredging, is set at 3, 4, 6, or 12 months. The volume of maintenance dredging at a specified cycle time and a target depth is estimated by applying the modified Exponential Model and the Linear Model. In the calculation, the fluid mud thickness is taken into account. The result of estimation is shown in Figure 5.7.
Figure 5.7 Maintenance Dredging Volume by Depths
TSHD (Trailing Suction Hopper Dredger) is regarded appropriate for the re-dredging and the maintenance dredging in La Union Port, because TSHD has the lowest impact on “other vessels traffic” with the highest “productivity” and “cost efficiency” among four types of dredger.
The dredging cost by own dredger is estimated smaller than contract base because the indirect cost is estimated cheaper than by contract base while direct costs are similar. Indirect cost of contract base includes mobilization cost, insurance cost, costs related with contingency and so on. On the contrary, indirect cost of dredging by own dredger include only mobilization, insurance cost and contingency as other cost is difficult to estimate. However, it is not appropriate to discuss about the dredging framework only with a comparison of dredging costs by contract base and own dredger, for the following reasons.
4 If CEPA owns a dredger, CEPA would have to bear considerable cost more than the cost estimation. And, dredging works could not be functioned without long experience and the accumulation of know-how. Aside from the cost, CEPA would have to handle training and education for dredger’s crew.
Furthermore, accurate prediction of the siltation volume is necessary to design the size or capacity of the dredger before its procurement. But prediction models of siltation volume developed in this report is not reliable enough and necessary to be revised through monitoring of channel siltation for a certain period.
In addition to above, in case of change of target channel depth, the flexible response is extremely difficult if CEPA owns its dredger. This problem will remain unchanged for future as well.
Judging from the above all, “dredging by contract base” for the channel maintenance dredging for a certain period is strongly recommended.
Chapter 6 Proposal of Monitoring Plan
The two models established in Chapter 4 are based on the bathymetric data which is not necessarily enough in quality and quantity. More the Linear Model is standing on the unverified hypothesis. The monitoring of the channel depth by bathymetric survey is the only method for improving the precision of prediction and for enhancing the applicability of the Linear Model to the maintenance dredging. This is the first purpose of monitoring. The second one is to confirm the phenomenon of rapid siltation just after the dredging.
The monitoring plan is set up, subject to the condition that the bathymetric survey will be conducted by CEPA themselves with their own equipment.
For the first purpose, the bathymetric survey should be conducted immediately before and just after the re-dredging in the basin and the access channel. After that, the bathymetric survey shall be repeated with the time interval of two months, or one month if possible. For the second purpose, the bathymetric survey must be conducted just after the re-dredging. After that, it is recommended that the survey is repeated at an interval of two weeks for several months. The bathymetric survey must be usually conducted with the two acoustic signals of 38 kHz and 200 kHz to have the data on the thickness of fluid mud.
The record of dredging and the record of vessels which enter into and leave from the port must be collected at the same time.
Chapter 7 Reviews of Demand Forecast Model and Market Allocation Model developed by CEPA
In this chapter, the calculation method for projecting the growth rate of container volume from CA4 (El Salvador, Guatemala, Honduras and Nicaragua) and developing the market allocation model is shown. “Port demand Study of La Union” carried out by CEPA consists of three parts: 1. Projected growth rate of container volume to and from CA4 2. Development of market allocation model 3. Projected market allocation for La Union Port
5 Chapter 8 Vessel Calling Model
The main purpose of Chapter 8 is to describe the vessel calling model which will be used to conduct the financial and economic analysis of La Union Port.
For that purpose, the current status of Salvadoran ports (8.1) as well as other major ports in other Central American countries (8.2) is summarized. The main focus is put on economic aspects because they are key for underpinning the model development, but the physical condition of each port is also described because it affects the capacity of cargo handling. In particular, the physical condition of Acajutla Port is crucial because the present and future limitation of its handling capacity is considered to directly influence the future container cargo throughput in La Union Port.
The strategy of maritime container shipping companies in the Pacific Coast of Central America is also examined prior to establishing the model ( 8.3). It is examined by two approaches; the first approach is to develop the liner shipping network of each company from the containership movement database. The second approach is to conduct interviews with shipping companies and other stakeholders.
The latter part of this chapter focuses on the vessel calling model. First, an outline of the model is described (8.4). After that, each component of the model is described; i.e., behavior of shipping companies, container cargo assignment model, and input data for the vessel calling model.
The maritime container shipping network of regular services operated by each company is vital to understanding the behavior of shipping companies ( 8.5). It is structured from the containership movement database by extracting 28 worldwide and local companies and 163 ports of the world.
The container cargo assignment model is the core element of the vessel calling model (8.6). The container cargo assignment model is an application of stochastic network assignment model on the intermodal shipping network of international container cargo, based on the generalized cost including both monetary cost and shipping time.
Preparing the input data is also important for the vessel calling model (8.7). Container cargo shipping demand (container cargo OD) between each port or region of the world is one of the most important data items. It is estimated from container cargo OD between countries and various statistics and information on regional economy, trade, and cargo handling in ports. The other necessary data is information on the shipping network including physical distance and shipping cost in the land, port, and maritime links. The information on the cost and time in border-crossing on land is also included.
The last section ( 8.8) of Chapter 8 summarizes the calculation results of the container cargo assignment model. After the description of the calculation procedure and unknown parameter estimation, the calculation results are examined from the viewpoint of the model reproducibility by several benchmarks such as container cargo throughput, share by partner countries, export and import port in CA4 countries, shares by shipping company, and estimated volume shipped by each liner service. Also, the sensitivity of the model to estimated unknown parameters is also examined.
As a result, the container cargo assignment model well describes the actual container cargo shipping market in CA4 countries and reasonably behaves against the change of the model input.
6 Chapter 9 Vessel Calls to La Union Port and Economic Analysis
Chapter 9 mainly focuses on the output of the vessel calling model.
The first part of the chapter describes the present status of navigation channel and rules in La Union Port, followed by a proposal for a new navigation rule (9.1). The “expected waiting time” is calculated based on the new rule as well as on the existing rule. It is found that the existing rule may be effective under the current situation that a small ship navigates a shallow channel, but when the channel is deepened and ships of various sizes are expected to call the new rule needs to be introduced.
Many calculation scenarios on the future liner shipping network are prepared for each channel depth in La Union Port in 2020 and 2030, and several feasible scenarios for each depth in both years are selected based on certain criteria (9.2). Figure 9.12 and Figure 9.13 show the container cargo throughput in La Union Port in 2020 and 2030, estimated by the vessel calling model based on each feasible scenario with the depth of navigation channel. In the figure, the results in both 1) modification scenarios of existing feeder and way-port service network with -9m to -12m channel depth and 2) additional vessel-calling scenarios as a transshipment hub with -12m to -14m channel depth are shown. The figures show that the container cargo throughput in La Union Port increases as the depth of navigation channel increases.
Figure 9.12 & 9.13 Container cargo throughput for each feasible scenario in port of La Union in 2020 and 2030
Based on the container cargo throughput and other outputs estimated in the model, net income (which is acquired by subtracting the expected revenue from port and handling charges by expenditure such as container operation cost except for the dredging cost) from container business of La Union Port, net income from container business of Salvadoran port sector (sum of Acajutla and La Union Port), and net benefit for Salvadoran economy of the dredging project in La Union Port (difference of the sum of the net incomes of the ports of La Union and Acajutla and shipping cost of Salvadoran import/export cargo for dredging scenarios from those of the no-dredging scenario) are estimated and compared with the dredging cost by channel depth (9.3). From the financial aspect for La Union Port, if the tariff of La Union Port is kept at the present level, the net income will be always less than the dredging cost for each channel depth (see Figure 9.18 and Figure 9.19).
However, if the tariff of La Union Port is increased, the net income (except for the dredging cost) may be larger than the dredging cost in the scenario that the expected net income is maximized by channel depth (9.4, see Figure 9.24 and Figure 9.25). It implies a need to increase the tariff in
7 La Union Port to keep a sound financial condition. However, this could weaken the competitiveness of the port against neighboring ports resulting in a decrease in the amount of containers handled. The level of the tariff will be a crucial issue when the shipping market becomes more liberalized such as when the barriers at national borders are removed (9.2.3(3)).
Figure 9.18 & 9.19 Estimated net income and dredging cost by channel depth in La Union Port (left: 2020; right: 2030)
Figure 9.24 & 9.25 Estimated net income in case of the tariff increase and dredging cost by channel depth in La Union Port (left: 2020; right: 2030)
The other important point in the simulations of the chapter is that the scenarios on the future liner shipping network are prepared not only for modification of the existing feeder and way-port network, but also for calling by vessels of the trunk route. Some of these “transshipment hub” scenarios for La Union Port are considered to be feasible as already shown in Figure 9.12 and Figure 9.13; in addition, if the transshipment hub is realized, it will be very beneficial to the economy of El Salvador. However, an important point to keep in mind is that simply deepening the channel by dredging does not guarantee that the port will become a transshipment hub. To become a transshipment hub, considerable efforts to attract the vessels of the trunk line would need to be made.
The last finding is that regional development in the eastern El Salvador would contribute to increasing the amount of container cargo as well as the revenue in La Union Port (9.2.3(3)2) and 9.4.4). As originally planned, the integrated development of La Union Port with the hinterland in the eastern area of El Salvador is also one of important keys for the future development of La Union Port.
8 Chapter 10 Optimal Dredging Plan Considering Time-Series Changes on Demand and Costs
In Chapter 10, a methodology of the time series analysis considering each year’s income, benefit and dredging cost is introduced.
Also, example results of calculation are shown in order to contribute to the discussion on the timing of investment for dredging. The calculation results on optimal year and net benefit for each combination of target depth after the first and second re-dredging and each type of dredging after increasing the tariff in La Union Port are shown. The calculation is based on many assumptions (e.g., re-dredging is allowed only twice and the second re-dredging must be carried out precisely ten years after the first dredging); in addition, a limited number of example results are shown based on the liner service network to generate the expected maximum net benefit in each channel depth is considered.
The example results imply that the best strategy to maximize the net benefit is to purchase a dredger for annual maintenance dredging within a few years and maintain a channel depth of around -12m or -13m, although there is a significant risk because this strategy will only be successful if the transshipment hub” scenario is realized. On the other hand, the second best strategy with relatively smaller risk is that the first re-dredging for a depth of around -10m is conducted with a contracted dredger and the second re-dredging for a depth of -13m. This kind of “step-wise” strategy is very useful for avoiding huge financial risks.
Chapter 11 Conclusions and Recommendations
Major findings of the study and recommendations are summarized on the following items;
11.1 Conclusions (1) Present state of siltation in the access channel (2) Thickness of fluid mud layer (3) Mechanism of siltation and prediction models foe water depth in the channel (4) Volume of re-dredging (5) Volume of maintenance dredging (6) Appropriate dredging method (7) Vessel calling model (8) Financial and economic analysis of La Union Port and policy simulation (9) Optimal dredging plan considering time-series changes (10) Navigation rule of access channel
11.2 Recommendations (1) Applicability of a empirically formulated prediction model (2) Applicability of the Linear Model (3) Appropriate dredging framework (4) Necessity of monitoring channel depth (5) Use of dual frequencies of echo sounder (6) Tariff setting (7) Transshipment hub scenario (8) Regional development in eastern El Salvador (9) Importance of step-wise investment plan for dredging to avoid huge financial risks (10) Necessity of new navigation rules for access channel of La Union Port
9
THE REPUBLIC OF EL SALVADOR: SPECIAL TECHNICAL ASSISTANCE FOR MAINTENANCE DREDGING OF THE PORT OF LA UNIÓN
Abbreviations Table Executive Summary
Table of Contents
Chapter 1 Introduction ...... 1-1 1.1 Overview of Development of La Union Port ...... 1-1 1.1.1 Development of La Union Port ...... 1-1 1.1.2 Harbor Facilities of La Union Port ...... 1-2 1.2 Recognition of Siltation Problem in La Union Port and Commencement of SAPI Study ...... 1-3 1.3 Result of SAPI Study ...... 1-4 1.3.1 The Gulf of Fonseca and Feeder Rivers ...... 1-5 1.3.2 Sediment classification and mechanism of siltation ...... 1-6 1.3.3 Establishment of prediction formulae for siltation speed and channel depth ...... 1-7 1.4 Objectives and Major Works of this Study ...... 1-8 1.5 Engineers concerned and Chronologies of Study ...... 1-9 1.5.1 Engineers concerned ...... 1-9 1.5.2 Chronologies of Study ...... 1-12 1.6 Composition and Abstract of Chapters in the Report ...... 1-13 Chapter 2 Technology Transfer ...... 2-1 2.1 Execution for Technical Training of CEPA Personals in Japan ...... 2-1 2.2 Technology Transfer to Counterparts ...... 2-2 2.2.1 Technology Transfer in the Field of Engineering ...... 2-2 2.2.2 Technology Transfer in the Field of Economic ...... 2-7 2.3 Workshop ...... 2-13 Chapter 3 Field Survey and Results ...... 3-1 3.1 Bathymetric Survey ...... 3-1 3.1.1 Survey lines of bathymetric survey ...... 3-1 3.1.2 Longitudinal depth profile of access channel ...... 3-3 3.1.3 Transversal depth profiles of harbor basin and access channel ...... 3-3 3.1.4 Mean depth of access channel and harbor basin ...... 3-13 3.1.5 Difference between depth measurements with 38 and 200 kHz sonic waves ...... 3-16 3.2 Seabed Mud Conditions ...... 3-18 3.2.1 Sites and methodology of mud sampling ...... 3-18 3.2.2 Description of sampled mud and vertical density profile of mud layer ...... 3-20 3.2.3 Physical properties of sampled mud ...... 3-22 3.2.4 Numerical prediction of density profile change by means of mud consolidation process ...... 3-24
i 3.2.5 Assessment of thickness of fluid mud layer for definition of nautical bottom ..... 3-29 3.3 Main Results of the Field Survey ...... 3-30 Chapter 4 Analysis of Siltation Process and Prediction Models ...... 4-1 4.1 Collected Data ...... 4-1 4.2 Siltation Speed and Depth Difference in the Channel (Exponential model) ...... 4-2 4.3 Analyses of Siltation Processes in Channel ...... 4-6 4.3.1 Siltation in Inner Channel ...... 4-6 4.3.2 Siltation in Outer Channel ...... 4-11 4.3.3 Physical consideration for rapid siltation just after dredging ...... 4-14 4.4 Siltation Prediction Models for Channel ...... 4-19 4.4.1 Modifications of original Exponential Model ...... 4-19 4.4.2 Linear model ...... 4-24 4.4.3 Applicability of two models ...... 4-26 4.5 Siltation Prediction model for Harbor Basin and Port Channel ...... 4-26 Chapter 5 Estimation of Dredging Volume and Cost ...... 5-1 5.1 Re-Dredging volume ...... 5-1 5.2 Maintenance dredging volume ...... 5-4 5.2.1 Navigable depth ...... 5-4 5.2.2 Estimation method of maintenance dredging volume ...... 5-4 5.2.3 Maintenance dredging volume by depths ...... 5-6 5.2.4 Maintenance dredging volume and over dredging depth by segments ...... 5-12 5.3 Examination of Dredging Methods and Dredger Capacity ...... 5-17 5.3.1 Types of dredger ...... 5-17 5.3.2 Appropriate dredging method ...... 5-22 5.3.3 Required capacity of dredger ...... 5-25 5.4 Cost Estimation of Dredging ...... 5-30 5.4.1 Consideration on cost estimation of dredging ...... 5-32 5.4.2 Cost for re-dredging ...... 5-41 5.4.3 Cost for maintenance dredging ...... 5-41 5.4.4 Observations on re-dredging cost ...... 5-43 5.4.5 Effect of decreasing cycle time (Case study on target channel depth of 12 m) .... 5-44 5.4.6 Recommendation on dredging framework ...... 5-46 Chapter 6 Proposal of Monitoring Plan after Re-dredging ...... 6-1 6.1 Purposes of Monitoring ...... 6-1 6.2 Verification on appropriateness of the predicted siltation volume ...... 6-1 6.3 Confirmation of rapid siltation just after the dredging ...... 6-3 6.4 Tide Correction of Bathymetric Data ...... 6-7 6.4.1 Improvement of tide correction of bathymetric survey data ...... 6-7 6.4.2 Datum level of La Union Port ...... 6-13 Chapter 7 Reviews of Demand Forecast Model and Market Allocation Model developed by CEPA ...... 7-1 7.1 Outline of Demand Forecast Model and Market Allocation Model developed by CEPA ...... 7-1 7.2 Projected the growth rate of container volume to and from CA4...... 7-1 7.3 Development of Market Allocation Model ...... 7-4 7.4 Projected market allocation for La Union Port ...... 7-8
ii Chapter 8 Vessel Calling Model ...... 8-1 8.1 Ports of El Salvador ...... 8-1 8.1.1 Outline of El Salvador ...... 8-1 8.1.2 Outline of ports of El Salvador ...... 8-1 8.1.3 Major facilities of ports ...... 8-1 8.1.4 Cargo volume by type ...... 8-1 8.1.5 Acajutla Port ...... 8-2 8.1.6 La Union Port ...... 8-24 8.2 Ports on the Pacific Coast of CA5 countries ...... 8-28 8.2.1 Basic indicator ...... 8-28 8.2.2 Locational conditions ...... 8-28 8.2.3 Physical conditions ...... 8-28 8.2.4 Port management and operation ...... 8-29 8.2.5 Characteristics of ports ...... 8-29 8.2.6 Characteristics of handling containers ...... 8-30 8.2.7 Future development and improvement ...... 8-30 8.3 Container Activities of Central American region ...... 8-38 8.3.1 Container throughput of ports of Central America ...... 8-38 8.3.2 Containership movement in the Central American region ...... 8-41 8.3.3 Views of shipping operators ...... 8-47 8.4 Outline of Vessel Calling Model ...... 8-51 8.5 Behavior of Shipping Companies ...... 8-53 8.5.1 Liner shipping network ...... 8-53 8.5.2 Shipping company ...... 8-53 8.5.3 Port ...... 8-55 8.6 Container Cargo Assignment Model ...... 8-59 8.6.1 Whole model structure ...... 8-59 8.6.2 Formulation of container cargo assignment model ...... 8-59 8.6.3 Maritime shipping submodel ...... 8-60 8.6.4 Ocean freight charge ...... 8-60 8.6.5 Land shipping time and freight charge ...... 8-61 8.7 Input Data ...... 8-63 8.7.1 Container cargo OD (container cargo shipping demand) ...... 8-63 8.7.2 Level of service in each port ...... 8-68 8.7.3 Maritime shipping network ...... 8-68 8.7.4 Land shipping network ...... 8-68 8.8 Calculation Results of the Container Cargo Assignment Model ...... 8-71 8.8.1 Calculation procedure of the model ...... 8-71 8.8.2 Unknown parameter estimation ...... 8-72 8.8.3 Model reproducibility ...... 8-72 8.8.4 Sensitivity of the model output ...... 8-77 8.9 Conclusion of Chapter 8 ...... 8-80 Chapter 9 Vessel Calls to La Union Port and Economic Analysis ...... 9-1 9.1 Present Navigation of La Union Port ...... 9-1 9.1.1 Present status of navigation channel and navigation rule ...... 9-1 9.1.2 Tidal conditions ...... 9-7 9.1.3 Navigable condition by depth of channel ...... 9-9 9.2 Vessel Calling Model Calculation and Results ...... 9-18 9.2.1 Simulation of calling at La Union Port at the present moment (as of 2010) using the
iii model developed ...... 9-18 9.2.2 Scenario setting for future simulation (2020 and 2030) ...... 9-19 9.2.3 Model calculation results ...... 9-26 9.3 Economic and Financial Analysis in the Original Model ...... 9-36 9.3.1 Definition and methodology ...... 9-36 9.3.2 Net income from container business of La Union Port and dredging cost by channel depth ...... 9-38 9.3.3 Net income from container business of Salvadoran port sector and dredging cost by channel depth ...... 9-41 9.3.4 Economic benefit of El Salvador by container handling at La Union Port ...... 9-44 9.4 Economic and Financial Analysis on Policy Simulation ...... 9-47 9.4.1 Net income from container business of La Union Port (in case of the tariff increase) and dredging cost by channel depth ...... 9-47 9.4.2 Net income from container business of Salvadoran port sector (in case of the tariff increase in La Union Port) and dredging cost by channel depth ...... 9-50 9.4.3 Economic benefit of El Salvador by container handling at La Union Port in case of tariff increase ...... 9-53 9.4.4 Net income from container business of La Union Port (in case of the advancement of regional development in the eastern El Salvador) and dredging cost by channel depth 9-56 9.5 Conclusion of Chapter 9 ...... 9-58 Chapter 10 Optimal Dredging Plan Considering Time-Series Changes on Demand and Costs ...... 10-1 10.1 Concept ...... 10-1 10.2 Dredging Cost ...... 10-1 10.2.1 Re-dredging cost ...... 10-2 10.2.2 Mobilization cost for re-dredging ...... 10-2 10.2.3 Cost for purchasing dredger (in case of own-basis dredging) ...... 10-2 10.2.4 Mobilization cost for maintenance dredger ...... 10-3 10.2.5 Regular cost for maintenance dredging ...... 10-3 10.3 Time-series estimation of container cargo throughput, net income and benefit, and dredging cost considering the timing of the dredging ...... 10-4 10.3.1 Time-series estimation of container cargo throughput, net income and benefit ... 10-4 10.3.2 Time-series dredging cost including the timing of the re-dredging...... 10-7 10.4 Methodology and example results of time-series financial and economic analysis considering the timing of the dredging ...... 10-10 10.4.1 Making a calculation sheet for time-series estimation ...... 10-10 10.4.2 Obtaining the optimal timing of re-dredging and combination of target depth .. 10-12 10.5 Conclusion of Chapter 10 ...... 10-15 Chapter 11 Conclusions and Recommendations ...... 11-1 11.1 Conclusions ...... 11-1 11.2 Recommendations ...... 11-4
iv
ANNEXES
ANNEX A MINUTES OF MEETING ON EXECUTION OF THE PROJECT ...... A-1 ANNEX B MINUTES OF MEETING BETWEEN CEPA AND STUDY TEAM ...... B-1 ANNEX C TOPICS RELATED TO CHANNEL SEDIMENTATION IN LA UNION PORT ...... C-1 C.1 SIDE SLOPE STABILITY ...... C-2 C.2 POSSIBILITY OF CANNEL RELOCATION ...... C-7 C.3 RAKE-DREDGING ...... C-9 C.4 COMMENTS ON CEPA’S PLAN ...... C-18 C.5 DREDGING METHD ...... C-28 C.6 OVERDREDGING DEOTH AND VOLUME BY SECTIONS ...... C-46 C.7 WESTWARD OVER-DREDGING IN OUTER CHANNEL ...... C-58 C.8 RE-DREDGING VOLUME CALCULATION ...... C-61
ANNEX D TOPICS RELATED TO ECONOMIC STUDY FOR LA UNION PORT ...... D-1 D.1 A PORTS IN NEIGHBORING COUNTRIES ...... D-2 D.2 DETAIL OF MARITIME SHIPPING SUBMODEL ...... D-34 D.3 INTERVIEW AND SURVEY TOGATHER WITH CEPA ECONOMIC TEAM MEMBERS ...... D-48 D.4 COMPUTER OPERATION MANUAL OF THE VESSEL CALLING MODEL ...... D-59
v List of Tables
Table 1.1 Volume of siltation deposited from April 2007 to January 2008 in comparison . 1-3 Table 1.2 List of members of Project Support Domestic Committee in Japan ...... 1-9 Table 1.3 Members of the first term Study Team ...... 1-10 Table 1.4 Members of the second term Study Team ...... 1-10 Table 1.5 Counterparts in the first term Study ...... 1-10 Table 1.6 Counterparts in the second term Study ...... 1-11 Table 1.7 JICA Experts dispatched to CEPA ...... 1-11 Table 1.8 Others relevant person of CEPA in the first term Study ...... 1-11 Table 1.9 Relevant person of CEPA in the second term Study ...... 1-11 Table 1.10 Chronology of First Term Study ...... 1-12 Table 1.11 Chronology of Second Term Study ...... 1-12 Table 2.1 Itinerary of technical training in Japan ...... 2-2 Table 2.2 Participants (1) ...... 2-3 Table 2.3 Participants (2) ...... 2-3 Table 2.4 Participants (3) ...... 2-4 Table 2.5 Participants (4) ...... 2-4 Table 2.6 Participants (5) ...... 2-4 Table 2.7 Participants (6) ...... 2-5 Table 2.8 Participants (7) ...... 2-5 Table 2.9 Participants (8) ...... 2-5 Table 2.10 Participants (9) ...... 2-6 Table 2.11 Participants (10) ...... 2-6 Table 2.12 Participants (11) ...... 2-6 Table 2.13 Participants (12) ...... 2-7 Table 2.14 Participants (1) ...... 2-8 Table 2.15 Participants (2) ...... 2-8 Table 2.16 Participants (3) ...... 2-8 Table 2.17 Participants (4) ...... 2-9 Table 2.18 Participants (5) ...... 2-9 Table 2.19 Participants (6) ...... 2-10 Table 2.20 Participants (7) ...... 2-10 Table 2.21 Participants (8) ...... 2-10 Table 2.22 Participants (9) ...... 2-11 Table 2.23 Participants (10) ...... 2-11 Table 2.24 Participants (10) ...... 2-11 Table 2.25 Participants (12) ...... 2-12 Table 2.26 Participants (13) ...... 2-12 Table 2.27 Participants (14) ...... 2-12 Table 2.28 Participants (15) ...... 2-13 Table 2.29 Participants (16) ...... 2-13 Table 2.30 Program of workshop, titles of presentations and presenters ...... 2-14 Table 2.31 List of participants and presenters ...... 2-14 Table 3.1 Location of bathymetric survey lines ...... 3-1 Table 3.2 Mean depth of access channel and harbor basin in February 2011 ...... 3-14 Table 3.3 Mean depth of access channel and harbor basin in August 2011 ...... 3-14 Table 3.4 Mean depth of access channel and harbor basin in January 2012 ...... 3-14 Table 3.5 Approximate range of fluid mud thickness at respective transverse lines (SAPI,
vi 2009) ...... 3-17 Table 3.6 Locations of mud sampling sites...... 3-18 Table 3.7 Soil characteristics at five sampling sites ...... 3-23 Table 4.1 Periods of implementation of dredging ...... 4-1 Table 4.2 Parameters of the final depth difference in Port channel and Harbor basin ...... 4-28 Table 5.1 Estimated re-dredging volume (units: 1000 m3) ...... 5-2 Table 5.2 Estimated TDS (Tons Dry Solid) of re-dredging (units: 1000 t) ...... 5-2 Table 5.3 Siltation prediction models to estimate maintenance dredging volume ...... 5-4 Table 5.4 Maintenance dredging volume by the Modified Exponential Model ...... 5-7 Table 5.5 Maintenance dredging volume calculated by the Linear Model ...... 5-8 Table 5.6 Height and Volume of maintenance dredging (over dredging) estimated by Mod. Exp. Model for Target depth of 14 m ...... 5-16 Table 5.7 Applicability of dredging methods to La Union Port ...... 5-24 Table 5.8 Calculation example of working hours ...... 5-27 Table 5.9 Necessary dredger capacity for re-dredging (m3) ...... 5-28 Table 5.10 Necessary dredger capacity for maintenance dredging (m3), in the case of Modified Exponential Model ...... 5-29 Table 5.11 Necessary dredger capacity for maintenance dredging (m3) in the case of Linear Model ...... 5-29 Table 5.12 Building price of dredgers studied by CEPA ...... 5-32 Table 5.13 Building price of dredgers in Japan (Actual base) ...... 5-32 Table 5.14 Equipment cost of TSHD by capacity ...... 5-34 Table 5.15 Breakdown of engine power by TSHD capacity (pump power and propulsion power) ...... 5-37 Table 5.16 Number of high class crew and common crew and labor unit cost (excluding fringe benefit and other expenses) ...... 5-37 Table 5.17 Annual crew cost by each category ...... 5-38 Table 5.18 Crew cost in case of dredging by own dredger (CEPA’s unit cost including fringe benefit and other expenses) ...... 5-38 Table 5.19 Initial mobilization cost by dredger capacity and annual cost ...... 5-39 Table 5.20 Mobilization cost by dredger capacity for inspection (round trip from/to Balboa) ...... 5-40 Table 5.21 Insurance cost and contingency estimated by CEPA ...... 5-41 Table 5.22 Dredging cost by target water depth ...... 5-41 Table 5.23 Dredging cost by Modified Exponential Model ...... 5-42 Table 5.24 Dredging cost by Linear Model ...... 5-42 Table 5.25 Breakdown of indirect cost of dredging by contract base (cost that CEPA considers are described in red letters) ...... 5-48 Table 6.1 Vertical reference levels for El Salvador provided by CNR...... 6-14 Table 7.1 Real GDP Growth Rate of CA4 ...... 7-2 Table 7.2 Estimated Container Volume to CA4 ...... 7-2 Table 7.3 GDP Elasticity of Container Volume to/from CA4 ...... 7-3 Table 7.4 GDP Elasticity ...... 7-3 Table 7.5 Container Growth Rate (2010=100) ...... 7-4 Table 7.6 Container Volumeof each port in 2010 ...... 7-5 Table 7.7 Container Volume of each country in 2010 (TEU) ...... 7-5 Table 7.8 Hinterland transport matrix (2010) ...... 7-7 Table 7.9 Referencing the following locations: ...... 7-9 Table 7.10 Transportation Cost per TEU in 2010 (USD) ...... 7-9 Table 7.11 Transit Time in 2010 (Days) ...... 7-9
vii Table 7.12 Hinterland transport matrix(with La Union) ...... 7-10 Table 7.13 Hinterland transport matrix (with La Union) in 2020 (Scenario1) ...... 7-13 Table 7.14 Hinterland transport matrix (with La Union) in 2030(Scenario 1) ...... 7-14 Table 7.15 Projected market allocation for La Union Port in 2020,2030(Scenario 1) ...... 7-15 Table 7.16 Hinterland transport matrix with La Union in 2020 (Scenario 2) ...... 7-15 Table 7.17 Hinterland transport matrix with La Union in 2030 (Scenario 2) ...... 7-17 Table 7.18 Projected market allocation for La Union Port in 2020,2030(Scenario 2) ...... 7-18 Table 8.1 Tendency of ship calls and handling cargo of main ports of El Salvador ...... 8-2 Table 8.2 Dimension of the pier ...... 8-4 Table 8.3 Major facilities of Acajutla Port ...... 8-4 Table 8.4 Transition of total cargo volume in the last 10 years ...... 8-5 Table 8.5 Cargo handling by type and pier ...... 8-6 Table 8.6 Transition of container cargo in the last 10 years ...... 8-6 Table 8.7 Origin countries of import container by commodities in 2012 ...... 8-7 Table 8.8 Destination countries of export container by commodities in 2012 ...... 8-7 Table 8.9 Ship calls by type in 2012 ...... 8-8 Table 8.10 Monthly container ship calls by shipping line in 2012 ...... 8-8 Table 8.11 Berth assignment of pier by commodity category in 2012 ...... 8-9 Table 8.12 Berth assignment of pier by commodity in 2012 ...... 8-10 Table 8.13 Expected berthing/working time and container increase ...... 8-11 Table 8.14 Container handling capacity ...... 8-12 Table 8.15 Port facilities and present status in Acajutla Port ...... 8-14 Table 8.16 Test results by Schmidt hammer ...... 8-18 Table 8.17 Survey result of visual and hammering inspection for diagnosis survey of deterioration degree of the ...... 8-19 Table 8.18 Appraisal of the Remaining Service Life based on the Survey Results of the Acajutla Port Facility ...... 8-20 Table 8.19 Major facility of La Union Port ...... 8-24 Table 8.20 Cargo throughput of La Union Port ...... 8-25 Table 8.21 Container throughput of La Union Port ...... 8-26 Table 8.22 Ship calling at La Union Port on 2012 ...... 8-26 Table 8.23 Economic situations of CA5 countries ...... 8-32 Table 8.24 Locational conditions of ports on the Pacific Coast on CA5 ...... 8-33 Table 8.25 Physical conditions of ports on the Pacific Coast on CA5 (revised) ...... 8-34 Table 8.26 Port management and operation ...... 8-35 Table 8.27 Characteristics of ports on the Pacific Coast of CA5 from type of calling vessel and handling cargo (2012) ...... 8-36 Table 8.28 Characteristics of handling containers of ports on the Pacific Coast of CA5 (2012) ...... 8-37 Table 8.29 Container throughput of the ports in the Central American region ...... 8-39 Table 8.30 Standard value of dimensions of container vessels ...... 8-41 Table 8.31 Changes in number of container services calling at ports ...... 8-46 Table 8.32 Example of MDS containership database (source: MDS containership databank) ...... 8-53 Table 8.33 28 container shipping companies in the model (source: JICA Study Team) ... 8-54 Table 8.34 Central American ports included in the model and their throughput ...... 8-56 Table 8.35 Shares (cover rates) in terms of TEU capacity that containerships called at the ports included in the shipping network of the model ...... 8-57 Table 8.36 Breakdown of cargo by partner regions handled in two Guatemalan ports (2010) ...... 8-64
viii Table 8.37 Share of each coast by partner region for laden container cargo from/to Central America (in TEU basis, 2010) ...... 8-65 Table 8.38 Share of each zone by partner regions (export and import) ...... 8-65 Table 8.39 Settings of level of service in each port ...... 8-68 Table 8.40 Driving time and cost between zone representatives (O and D node) and ports ...... 8-70 Table 8.41 Border-crossing time and cost between zone representatives (O and D node) and ports ...... 8-70 Table 8.42 Estimated amount and share of containers by partner country/region of trade from/to CA4 ports (Source: JICA Study Team’s estimation) ...... 8-74 Table 8.43 Estimation results of export and import port of containers from/into CA4 countries (TEU) ...... 8-74 Table 8.44 Actual and estimated share of shipping companies in Acajutla port (2010) .... 8-75 Table 9.1 Navigation rule of La Union Port ...... 9-3 Table 9.2 Tide Levels of La Union Port provided by CNR ...... 9-7 Table 9.3 PIANC Suggestions on allowance of gross under-keel clearance by case ...... 9-10 Table 9.4 Calculation results of navigable time in the channel ...... 9-11 Table 9.5 Calculation results of average daily navigable time ...... 9-12 Table 9.6 Result of calculation for expected waiting time ...... 9-14 Table 9.7 Estimation result of container cargo throughput in CA4 ports (TEU) considering a liner service to call at La Union Port ...... 9-19 Table 9.8 Future settings of level of service in each port ...... 9-20 Table 9.9 Existing liner shipping service call at Acajutla Port as of May 2010 ...... 9-21 Table 9.10 Existing liner shipping service call at La Union Port as on February 2012 .... 9-21 Table 9.11 Possible alternatives in the level of liner service to be changed from the initial level by shipping company which call at Salvadoran ports at present ...... 9-22 Table 9.12 Possible alternatives to be added as a transshipment service into La Union Port ...... 9-23 Table 9.13 Example of scenario on maritime shipping network for model input (in case of -12m depth) ...... 9-24 Table 9.14 Example of hinterland distribution of Salvadoran ports estimated from the model ...... 9-29 Table 9.15 Example of hinterland distribution of La Union Port estimated from the model (in case of tariff increase) ...... 9-33 Table 9.16 Example of hinterland distribution of La Union Port after the tariff increase (in case of Scenario S30-5-5(14m) with -14m channel depth in 2030) ...... 9-34 Table 9.17 Revenue and expenditure of container business in La Union Port ...... 9-36 Table 9.18 Tariff of La Union Port (related to containers) ...... 9-36 Table 9.19 Container terminal operation cost ...... 9-36 Table 9.20 Revenue and expenditure of container business in the Salvadoran port sector 9-37 Table 9.21 Tariff of Acajutla Port (related to containers) ...... 9-37 Table 9.22 Economic benefit and cost of dredging project of the channel in La Union Port (comparison to the “no-dredging” scenario) ...... 9-37 Table 9.23 Estimated container throughput and ship calls in La Union Port (2020) ...... 9-38 Table 9.24 Estimated container throughput and ship calls in La Union Port (2030) ...... 9-38 Table 9.25 Dredging cost by channel depth and model ...... 9-39 Table 9.26 Maximum net income from container business in La Union Port (2020) ...... 9-40 Table 9.27 Maximum net income from container business in La Union Port (2030) ...... 9-40 Table 9.28 Maximum difference between net income and dredging cost by channel depth in La Union Port (2020) ...... 9-40
ix Table 9.29 Maximum difference between net income and dredging cost by channel depth in La Union Port (2030) ...... 9-40 Table 9.30 Container throughput and ship calls in Acajutla Port and La Union Port (2020) ...... 9-41 Table 9.31 Container throughput and ship calls in Acajutla Port and the La Union Port (2030) ...... 9-41 Table 9.32 Maximum net income from container business in Acajutla Port and La Union Port(2020) ...... 9-43 Table 9.33 Maximum net income from container business in the Acajutla Port and the La Union Port(2030) ...... 9-43 Table 9.34 Maximum difference between net income for Salvadoran port sector and dredging cost by channel depth in La Union Port (2020) ...... 9-43 Table 9.35 Maximum difference between net income for Salvadoran port sector and dredging cost by channel depth in La Union Port (2030) ...... 9-44 Table 9.36 Maximum net benefit of dredging project for Salvadoran economy by channel depth(2020) ...... 9-46 Table 9.37 Maximum net benefit of dredging project for Salvadoran economy by channel depth(2030) ...... 9-46 Table 9.38 Maximum economic benefit of dredging project for Salvadoran economy by channel depth (2020) ...... 9-46 Table 9.39 Maximum economic benefit of dredging project for Salvadoran economy by channel depth (2030) ...... 9-46 Table 9.40 New tariff set in La Union Port...... 9-47 Table 9.41 Estimated container throughput and ship calls in La Union Port in case of the tariff increase (2020) ...... 9-47 Table 9.42 Estimated container throughput and ship calls in La Union Port in case of the tariff increase (2030) ...... 9-47 Table 9.43 Maximum net income from container business in La Union Port in case of the tariff increase (2020) ...... 9-49 Table 9.44 Maximum net income from container business in La Union Port in case of the tariff increase (2030) ...... 9-49 Table 9.45 Maximum difference between net income in case of the tariff increase and dredging cost by channel depth in La Union Port (2020) ...... 9-49 Table 9.46 Maximum difference between net income in case of the tariff increase and dredging cost by channel depth in La Union Port (2030) ...... 9-49 Table 9.47 Container throughput and ship calls in Acajutla Port and La Union Port in case of the tariff increase in La Union Port (2020) ...... 9-50 Table 9.48 Container throughput and ship calls in Acajutla Port and La Union Port in case of the tariff increase in La Union Port (2030) ...... 9-50 Table 9.49 Maximum net income from container business in Acajutla Port and La Union Port in case of the tariff increase in La Union Port (2020) ...... 9-52 Table 9.50 Maximum net income from container business in Acajutla Port and La Union Port in case of the tariff increase in La Union Port (2030) ...... 9-52 Table 9.51 Maximum difference between net income for Salvadoran port sector in case of the tariff increase and dredging cost by channel depth in La Union Port (2020) ... 9-52 Table 9.52 Maximum difference between net income for Salvadoran port sector in case of the tariff increase and dredging cost by channel depth in La Union Port (2030) ... 9-52 Table 9.53 Maximum net benefit of dredging project for Salvadoran economy by channel depth in case of the tariff increase (2020) ...... 9-55 Table 9.54 Maximum net benefit of dredging project for Salvadoran economy by channel
x depth in case of the tariff increase (2030) ...... 9-55 Table 9.55 Maximum economic benefit of dredging project for Salvadoran economy by channel depth in case of the tariff increase (2020) ...... 9-55 Table 9.56 Maximum economic benefit of dredging project for Salvadoran economy by channel depth in case of the tariff increase (2030) ...... 9-55 Table 9.57 Estimated container throughput and ship calls in La Union Port in case of the advancement of regional development in the eastern El Salvador (2020) ...... 9-56 Table 9.58 Maximum net income from container business in La Union Port in case of the advancement of regional development in the eastern El Salvador (2020) ...... 9-57 Table 9.59 Maximum difference between net income in case of the advancement of regional development in the eastern El Salvador and dredging cost by channel depth in La Union Port (2020) ...... 9-57 Table 10.1 Items of dredging cost summarized in terms of the timing when it is needed 10-1 Table 10.2 Re-dredging cost (US$) estimated for each combination of existing and target depth ...... 10-2 Table 10.3 Mobilization cost (US$) of re-dredging for each combination of existing and target depth ...... 10-2 Table 10.4 Cost for purchasing dredger (US$) by target depth for both models to predict the change of water depth after the initial dredging ...... 10-3 Table 10.5 Mobilization cost for maintenance dredger (US$) estimated for each target depth ...... 10-3 Table 10.6 Regular cost for maintenance dredging (US$/year) for each target depth ...... 10-3 Table 10.7 Estimated container cargo throughput and other revenue/cost for each channel depth in 2010 ...... 10-4 Table 10.8 Example of a representative result on container cargo throughput and other revenue/cost for each channel depth in 2020 and 2030 ...... 10-5 Table 10.9 Example of calculation result on optimal year and net benefit for each combination of target depth after the first and second re-dredging and each type of dredging (before increasing the tariff in La Union Port) ...... 10-13 Table 10.10 Example of calculation result on optimal year and net benefit for each combination of target depth after the first and second re-dredging and each type of dredging (after increasing the tariff in La Union Port) ...... 10-14
xi List of Figures
Figure 1.1 History of La Union Port ...... 1-2 Figure 1.2 Changes of the sea bottom in the Inner channel ...... 1-3 Figure 1.3 Changes of the sea bottom in the Outer channel ...... 1-4 Figure 1.4 Bathymetry of Gulf of Fonseca reproduced from Chart 21521 of US NGIA .... 1-5 Figure 1.5 Satellite photograph of Gulf of Fonseca reproduced from ...... 1-5 Figure 1.6 Sediment classification and median diameter around the Inner channel ...... 1-6 Figure 1.7 Sediment classification and median diameter around the Outer channel ...... 1-7 Figure 3.1 Bathymetric survey lines of access channel ...... 3-2 Figure 3.2 Bathymetric survey lines in harbor basin ...... 3-2 Figure 3.3 Longitudinal depth variation along the centerline of access channel ...... 3-3 Figure 3.4 Transversal depth profiles of Outer Channel with the planned channel profile (L1, L2, and L3) ...... 3-4 Figure 3.5 Transversal depth profiles of Outer Channel with the planned channel profile . 3-5 Figure 3.6 Transversal Depth profiles of Outer Channel with the planned channel profile 3-6 Figure 3.7 Transversal depth profiles of Outer Channel with the planned channel profile . 3-7 Figure 3.8 Transversal depth profiles of Inner Channel with the planned channel profile . 3-8 Figure 3.9 Transversal depth profiles of Inner Channel with the planned channel profile . 3-9 Figure 3.10 Depth profiles of Turning Basin on the lines perpendicular to the wharf...... 3-10 Figure 3.11 Depth profiles of Turning Basin on the lines perpendicular to the wharf...... 3-11 Figure 3.12 Depth profiles of Turning Basin on the lines parallel to the wharf...... 3-12 Figure 3.13 Variation of mean depth of the access channel ...... 3-15 Figure 3.14 Variation of mean depth of the inner access channel and harbor basin ...... 3-15 Figure 3.15 Transversal channel profiles with the acoustic signals of 38 kHz and 200 kHz at L18 to L20 (SAPI, 2009) ...... 3-16 Figure 3.16 Location of sampling sites ...... 3-18 Figure 3.17 Lifting of sampling tube at Site E (a) and Sampling tube at Site E (b) ...... 3-19 Figure 3.18 Cutting a sampling pipe into sections of 0.3 m long ...... 3-20 Figure 3.19 Photographs of mud sample with its density ...... 3-21 Figure 3.20 Vertical profile of mud wet density outside the access channel ...... 3-22 Figure 3.21 Vertical profile of mud wet density inside the access channel ...... 3-22 Figure 3.22 Relationship between moisture content and wed density of mud samples .... 3-23 Figure 3.23 Deposition speed employed in calibration of mud consolidation analysis .... 3-25 Figure 3.24 Time evolution of (a) channel mean depth and (b) mud wet density profile at Site D ...... 3-26 Figure 3.25 Time evolution of (a) channel mean depth and (b) mud wet density profile at Site E ...... 3-26 Figure 3.26 Deposition speed employed in prediction of mud deposition after maintenance dredging ...... 3-27 Figure 3.27 Time evolution of (a) siltation height and (b) bottom mud wet density after maintenance dredging ...... 3-28 Figure 3.28 Time evolution of bottom mud wet density versus siltation height after maintenance dredging...... 3-28 Figure 3.29 Time evolution of mud wet density profile. (a) h = 3.0 m and (b) h = 4.5 m ...... 3-28 Figure 3.30 Time evolution of mud wet density profile. (a) h0 = 6.0 m and (b) h0= 7.5 m ...... 3-29 Figure 4.1 Period of dredging and times of bathymetric surveys ...... 4-1
xii Figure 4.2 Changes of water depth in the Inner and the Outer channel ...... 4-2 Figure 4.3 Bathymetric survey lines of access channel ...... 4-3 Figure 4.4 Siltation speed versus the depth difference inside and outside the access channel...... 4-3 Figure 4.5 Definition of water depths ...... 4-4 Figure 4.6 Comparison of predicted and measured channel depths for selected survey lines ...... 4-5 Figure 4.7 Changes of water depth on the reference lines from L21 to L18 in Inner channel ...... 4-6 Figure 4.8 Superposition of cross section along L21 ...... 4-7 Figure 4.9 Superposition of cross section along L20~L18 ...... 4-8 Figure 4.10 Superposition of cross sections after shifting, for L21 (Cross section in December, 2008 is shifted by 0.6m upward) ...... 4-8 Figure 4.11 Superposition of cross section along the reference lines of L20 to L18, after shifting date obtained in December, 2008 upward ...... 4-9 Figure 4.12 Corrections of depth data in Inner channel ...... 4-10 Figure 4.13 Locations of reference lines in Outer channel ...... 4-11 Figure 4.14 Changes of water depth on the reference lines from L08 to L05 in Outer channel ...... 4-12 Figure 4.15 Periods of dredging in the Outer channel and the bathymetric data utilized for consideration ...... 4-13 Figure 4.16 Situation of full-sedimentation along L08~L05 in Outer channel ...... 4-13 Figure 4.17 Conceptual diagram of dynamic equilibrium condition before dredging ...... 4-15 Figure 4.18 Conceptual diagram of siltation in Outer channel ...... 4-15 Figure 4.19 Superposition of cross sections along L07and L06 ...... 4-16 Figure 4.20 Spatial distribution of sediment ...... 4-16 Figure 4.21 Superposition of cross sections just after the second dredging, (Surveyed on 28 April and 5 May, 2008) ...... 4-17 Figure 4.22 Superposition of cross sections, 11 August, 2008, about 3 and half months after the dredging ...... 4-18 Figure 4.23 Spatial distribution of sedimentation ...... 4-18 Figure 4.24 Gap of cross section, on reference line L21(Inner channel) (Reproduce from Figure 4.8) ...... 4-19 Figure 4.25 Siltation speed versus the depth difference in the Inner channel, after the correction of data ...... 4-20 Figure 4.26 Comparison of original and modified Exponential Model with the actual depth ( for Inner c) ...... 4-21 Figure 4.27 Modification of Exponential Model by introducing a concept of final depth ( for Outer channel) ...... 4-22
Figure 4.28 Longitudinal profile of final depth he of Outer channel ...... 4-22 Figure 4.29 Comparison of original and modified Exponential model with the actual depth (for Outer channel) ...... 4-23 Figure 4.30 Time variations of channel depth for Inner and Outer channels ...... 4-24 Figure 4.31 Representative siltation speed for Inner and Outer channel ...... 4-25 Figure 4.32 Connection of Linear Model to Modified Exponential Model ...... 4-25 Figure 4.33 Coordinate system in harbor basin ...... 4-27 Figure 4.34 Cross sections along the line of x=200m, perpendicular to the wharf ...... 4-27 Figure 4.35 Bottom profiles along the line of Y=-400m, parallel to the wharf ...... 4-28 Figure 4.36 Cross sections along the line of L22, perpendicular to wharf ...... 4-28
xiii Figure 4.37 Comparisons between the predicted and the measured relative siltation height ...... 4-29 Figure 5.1 Longitudinal profile on the centerline of the access channel surveyed at July 2013 ...... 5-1 Figure 5.2 Channel Shape for re-dredging volume calculation ...... 5-2 Figure 5.3 Definition of overbreak in channel dredging ...... 5-3 Figure 5.4 Definition of the navigable depth and the measured depth ...... 5-4 Figure 5.5 Sketch of rise of channel bottom between maintenance dredging...... 5-5 Figure 5.6 Maintenance dredging volume (plotted by a fixed vertical scale) ...... 5-9 Figure 5.7 Maintenance dredging volume (plotted on different vertical scales) ...... 5-10 Figure 5.8 Maintenance dredging volume by Depths ...... 5-11 Figure 5.9 Definition of height of dredging and over dredging height below the target depth ...... 5-12 Figure 5.10 Over dredging depths estimated by Mod. Exp. Model ...... 5-13 Figure 5.11 Over dredging depths estimated by Linear Model ...... 5-14 Figure 5.12 Correspondence between over dredging depth and annual dredging volume 5-15 Figure 5.13 Conceptual drawing of Cutter Suction Dredger (Source: “Dredging; A handbook for engineers” R N Bray et al., 1998) ...... 5-17 Figure 5.14 Conceptual drawing of TSHD (Source: “Dredging; A handbook for engineers” R N Bray et al.,1998) ...... 5-18 Figure 5.15 Conceptual drawing of Grab Hopper Dredger ...... 5-19 Figure 5.16 Photo and Conceptual drawing of Grab Dredger (pontoon type) ...... 5-20 Figure 5.17 Conceptual drawing of Backhoe Dredger (Source: “Mimar Sinan” Jan De Nul Group) ...... 5-21 Figure 5.18 Location of dumping site ...... 5-26 Figure 5.19 Necessary time for dredging work ...... 5-28 Figure 5.20 Necessary dredger capacity for maintenance dredging (m3) in the case of Modified Exponential Model ...... 5-30 Figure 5.21 Necessary dredger capacity for maintenance dredging (m3) in the case of Linear Model ...... 5-30 Figure 5.22 Cost estimation items of dredging by contract base ...... 5-31 Figure 5.23 Cost estimation items of dredging by own dredger intended by CEPA ...... 5-31 Figure 5.24 Building price of TSHD by capacity ...... 5-33 Figure 5.25 Relation with TSHD capacity and total engine power ...... 5-36 Figure 5.26 Relation with TSHD capacity and pump power ...... 5-36 Figure 5.27 Dredging cost of dredging by contract base (Cost comparison between Modified Exponential Model and Linear Model) ...... 5-43 Figure 5.28 Dredging cost of dredging by own dredger (Cost comparison between Modified Exponential Model and Linear Model) ...... 5-43 Figure 5.29 Structure for costs of re-dredging and maintenance dredging ...... 5-44 Figure 5.30 Relation between cycle time and annual volume of maintenance dredging .. 5-44 Figure 5.31 Relation between cycle time and working ratio in cases of ...... 5-45 Figure 5.32 Relation between cycle time and working ratio for necessary dredger capacities ...... 5-46 Figure 5.33 Relation between cycle time and annual dredging cost ...... 5-46 Figure 5.34 Dredging cost comparison between dredging by contract base and by own dredger ...... 5-47 Figure 5.35 Comparison of direct and indirect cost by contract base and own dredger (12m target depth of Modified Exponential Model with 3 months cycle) ...... 5-48 Figure 5.36 Dredging cost and dredger capacity by water depth ...... 5-49
xiv Figure 6.1 Survey lines for Inner channel with the transversal length of 500 m and the longitudinal pitch of 1 km...... 6-4 Figure 6.2 Survey lines for Inner channel with the transversal length of 500 m and the longitudinal pitch of 1 km ...... 6-5 Figure 6.3 Survey lines for Port area (basin) with the pitch length of 200 m ...... 6-6 Figure 6.4 Equipment of the bathymetric survey mounted by CEPA staffs ...... 6-7 Figure 6.5 Relation between measured and corrected water depth ...... 6-8 Figure 6.6 Variation of tide level of April 19, 2013 ...... 6-8 Figure 6.7 Tidal correction parameters related to the locations of the channel (from SAPI’s report) ...... 6-9 Figure 6.8 Screenshot of the geodetic converter which CEPA staffs use ...... 6-10 Figure 6.9 Post-processing tools coded by Excel/VBA ...... 6-11 Figure 6.10 Example of the post-processed data ...... 6-12 Figure 6.11 Vertical reference employed by CNR ...... 6-15 Figure 6.12 Vertical reference employed by DD-Report (CUT-9 is a benchmark located on the south-eastern corner of the port of La Union) ...... 6-15 Figure 6.13 Variation of water depth along the access channel before depth correction. . 6-17 Figure 6.14 Variation of water depth along the access channel after depth correction. .... 6-17 Figure 8.1 Cargo volume of main ports of El Salvador ...... 8-2 Figure 8.2 Location of Acajutla Port ...... 8-2 Figure 8.3 Port layout ...... 8-3 Figure 8.4 Transition of import / export cargo volume by category ...... 8-5 Figure 8.5 Transition of container cargo ...... 8-6 Figure 8.6 Container yard layouts ...... 8-12 Figure 8.7 Location of each berth ...... 8-13 Figure 8.8 General plan view of A berth ...... 8-13 Figure 8.9 Cross section of B berth ...... 8-14 Figure 8.10 Cross section of C berth ...... 8-14 Figure 8.11 Continuous red-orange colored rust on steel sheet piles in A berth ...... 8-15 Figure 8.12 Situation of steel pipe piles in B berth ...... 8-15 Figure 8.13 Peeled off concrete in A berth ...... 8-16 Figure 8.14 Concrete wall facing to outer sea in C berth ...... 8-16 Figure 8.15 Hammer inspection on steel sheet piles in A berth...... 8-16 Figure 8.16 Test points performed by Schmidt hammer ...... 8-17 Figure 8.17 Position of Schmidt hammer ...... 8-17 Figure 8.18 Position of Schmidt hammer for A berth ...... 8-17 Figure 8.19 Position of Schmidt hammer for B berth ...... 8-18 Figure 8.20 Planned electric power plant ...... 8-23 Figure 8.21 Road network from / to Acajutla Port ...... 8-23 Figure 8.22 Location of La Union Port ...... 8-24 Figure 8.23 Plan of La Union Port ...... 8-25 Figure 8.24 Development plan of La Union Port ...... 8-27 Figure 8.25 Container ports in the Central American region...... 8-38 Figure 8.26 Container ports on the Pacific Coast of CA5 ...... 8-40 Figure 8.27 Distribution of capacity of deployed vessels ...... 8-40 Figure 8.28 Containership movement of each shipping company ...... 8-45 Figure 8.29 Whole structure of the vessel calling model (source: JICA Study Team) ...... 8-52 Figure 8.30 Location of ports in Central America (added ports in this model are shown in red letter) (source: JICA Study Team) ...... 8-56 Figure 8.31 All ports dealt in the model (source: JICA Study Team) ...... 8-57
xv Figure 8.32 Shipping network considered in the container cargo assignment model ...... 8-59 Figure 8.33 Land shipping network considered in this project ...... 8-69 Figure 8.34 Container cargo throughput reproduced by the developed model compared with the actual throughput (Source: JICA Study Team’s estimation) ...... 8-73 Figure 8.35 Example of estimated container flow by liner service (Maersk, 2010) ...... 8-76 Figure 8.36 Sensitivity of unknown parameters [1] value of time for shippers vt and container cargo throughput by each CA4 port (Source: JICA Study Team’s estimation) ...... 8-77 Figure 8.37 Sensitivity of unknown parameters [2] distribution parameter θ and container cargo throughput by each CA4 port (Source: JICA Study Team’s estimation) ...... 8-78 Figure 8.38 Sensitivity of unknown parameters [3] adjustment parameter on bonded transportation α and container cargo throughput by each CA4 port ...... 8-79 Figure 9.1 Navigation channel of La Union Port ...... 9-2 Figure 9.2 Vertical level reference ...... 9-7 Figure 9.3 Tide level of La Union Port in 2013 ...... 9-8 Figure 9.4 Definition of under-keel clearances ...... 9-10 Figure 9.5 Concept for calculation of expected waiting time ...... 9-13 Figure 9.6 Calculation results of expected waiting time by channel depth ...... 9-15 Figure 9.7 Relationships between draft and container loading capacity in TEUs ...... 9-15 Figure 9.8 Output tool of navigable time range ...... 9-16 Figure 9.9 Calculation result of expected waiting time according to the current navigation rule ...... 9-17 Figure 9.10 Service route operated by APL and Hamburg-Sud in 2012 ...... 9-18 Figure 9.11 Base and example case of maritime shipping network (displayed only services to call at Acajutla Port or La Union Port) ...... 9-25 Figure 9.12 Container cargo throughput for each feasible scenario in La Union Port (above) and Acajutla Port (below) in 2020 ...... 9-27 Figure 9.13 Container cargo throughput for each feasible scenario in La Union Port (above) and Acajutla Port (below) in 2030 ...... 9-28 Figure 9.14 Container cargo throughput for each feasible scenario in La Union Port (above) and Acajutla Port (below) in 2020 (in case of tariff increase in La Union Port) ...... 9-31 Figure 9.15 Container cargo throughput for each feasible scenario in La Union Port (above) and Acajutla Port (below) in 2030 (in case of tariff increase in La Union Port) ...... 9-32 Figure 9.16 Difference of impact of tariff increase on container cargo throughput: current border barrier (above) and case that any border barrier is removed (below) ...... 9-33 Figure 9.17 Container cargo throughput for each feasible scenario in La Union Port (above) and Acajutla Port (below) in 2020 (in case of regional development in Eastern El Salvador) ...... 9-35 Figure 9.18 Estimated net income and dredging cost by channel depth in La Union Port (2020) ...... 9-39 Figure 9.19 Estimated net income and dredging cost by channel depth in La Union Port (2030) ...... 9-39 Figure 9.20 Estimated net income for Salvadoran port sector (sum of Acajutla Port and La Union Port) and dredging cost by channel depth in La Union Port (2020) ...... 9-42 Figure 9.21 Estimated net income for Salvadoran port sector (sum of Acajutla Port and La Union Port) and dredging cost by channel depth in La Union Port (2030) ...... 9-42 Figure 9.22 Estimated net benefit of dredging project for Salvadoran economy and dredging cost by channel depth (2020) ...... 9-45 Figure 9.23 Estimated net benefit of dredging project for Salvadoran economy and dredging cost by channel depth (2030) ...... 9-45
xvi Figure 9.24 Estimated net income in case of the tariff increase and dredging cost by channel depth in La Union Port (2020) ...... 9-48 Figure 9.25 Estimated net income in case of the tariff increase and dredging cost by channel depth in La Union Port (2030) ...... 9-48 Figure 9.26 Estimated net income for Salvadoran port sector (sum of Acajutla Port and La Union Port) in case of the tariff increase and dredging cost by channel depth in La Union Port (2020) ...... 9-51 Figure 9.27 Estimated net income for Salvadoran port sector (sum of Acajutla Port and La Union Port) in case of the tariff increase and dredging cost by channel depth in La Union Port (2030) ...... 9-51 Figure 9.28 Estimated net benefit of dredging project for Salvadoran economy in case of the tariff increase and dredging cost by channel depth (2020) ...... 9-54 Figure 9.29 Estimated net benefit of dredging project for Salvadoran economy in case of the tariff increase and dredging cost by channel depth (2030) ...... 9-54 Figure 9.30 Estimated net income in case of the advancement of regional development in the eastern El Salvador and dredging cost by channel depth in La Union Port (2020) ...... 9-56 Figure 10.1 Typical example on framework of time-series income-cost calculation (in case of contract-basis dredging for the first ten years) ...... 10-7 Figure 10.2 Typical example on framework of time-series income-cost calculation (in case of own-basis dredging) ...... 10-9 Figure 10.3 Typical example on framework of time-series income-cost calculation (in case of own-basis dredging without second re-dredging) ...... 10-9 Figure 10.4 Example of a calculation sheet (in an excel-basis) for time-series estimation of net income and benefit including container cargo throughput, revenue of both Acajutla Port and La Union Port, dredging and other cost ...... 10-11
xvii
Chapter 1 Introduction
Chapter 1 Introduction
1.1 Overview of Development of La Union Port
1.1.1 Development of La Union Port The economic structure of the Republic of El Salvador depends strongly on foreign trade, and a major of its freight distribution is a marine transportation, which plays a significant role on the development of the country. However, Acajutla Port which is only one international trade port in the country is directly exposed to the full energy of the Pacific Ocean. Because of this natural condition, there is a limit on the capacity of freight handling, especially for containers. There was no enough facility in El Salvador which could manage the increasing of seaborne traffic and a global trend of containerizing freight transportation.
The Department of La Union, which is the easternmost Department of Republic of El Salvador, is bordered with Honduras and Nicaragua across the Gulf of Fonseca. A port named Cutuco had been developed at the western waterfront of the Gulf of Fonseca at the distance of about 25 km from the entrance of the Gulf. The port handled 236 thousands ton of cargo in 1975, but the trade dwindled considerably during the civil war time late 1980s and early 1990s. The Department of La Union had been lagging in economy in comparison with other departments.
After the cease of the civil war, the Republic of El Salvador decided to develop the new port in the Department of La Union, which had an objective of stimulating economical and industrial development through the port activity in the Department of La Union. And also the new port is expected to function as a hub port of container ships along the Pacific coast of the Central American continent.
The Government of El Salvador requested the Japanese Government to prepare a master plan for the port expansion and to carry out a feasibility study for the short-term facility installation plan. The latter responded to the request by executing the feasibility study of La Union Port through Japan International Cooperation Agency (hereinafter referred to as “JICA”) during October 1997 to December 1998 and presenting the final report. Following the feasibility study, the detailed design was made during July 2001 to January 2003. The name of port was changed from Cutuco to La Union with a slight location shift of the wharf area.
The project of constructing La Union Port began in April 2005 with a total cost of about 21,400 million Japanese yen among which 11,233 million Japanese yen was provided by the Japan Bank for International Cooperation (hereinafter referred to as “JBIC”) as the low-interest loan, and construction of the civil engineering works was completed in December 2008.
The history of La Union Port mentioned above is shown in Figure 1.1.
1-1
Figure 1.1 History of La Union Port
1.1.2 Harbor Facilities of La Union Port La Union Port has been designed for Post-Panamax container ships, bulk carriers of 50,000 DWT, and passenger ships of 25,000 DWT classes. The channel had been dredged to a depth of 14 m, but the entire passage has been filled in by siltation, and the depth when it was completed has not been maintained.
The port has one container berth with a length of 340 m and a depth of 15.0 m, one multi-purpose berth with a length of 220 m and a depth of 14.0 m, and a passenger berth with a length of 240 m and a depth of 9.5 m. However, the water depth at every facility becomes shallower due to siltation. The yard areas are built by reclamation with a fill volume of 3.0 million m3.
The turning basin has a diameter of 600 m and had the depth of 14 m. Also in this area, the water depth becomes shallower due to siltation. The total area of the harbor basin with the berth area and the turning basin is measured as 65.7 ha.
The access channel of 22.3 km long is divided into the inner and outer parts by the narrow waterway between Cape Chiquirin and Zacatillo Island. The Inner channel is about 5.0 km long and the Outer channel is 17.3 km long. When the dredging works completed in 2008, the Inner channel had the width of 140 m at the bottom and the water depth of 14m, while the Outer channel had the width of 137 m and the water depth of 14.5m. About 4.5 km of the Inner channel were cut through the water area shallower than 10 m with the shallowest portion of about 6 m. The length of the outer channel pass through the area shallower than 10 m is about 1.5 km; the shallowest depth is about 9 m. The side slope is designed with a gradient of 1 on 5.
1-2 1.2 Recognition of Siltation Problem in La Union Port and Commencement of SAPI Study
When La Union Port was under construction toward its completion at the end of November 2008, it was observed a large quantity of siltation in the Inner and Outer channels and the harbor basin, based on the bathymetric surveys performed during the execution of the dredging works (see Figure 1.1).
Bathymetric surveys around the harbor basin and access channel have been conducted before and during the construction works by using an echo sounder equipped with 210 kHz frequency acoustic signals. When the reflection of the 210 kHz frequency waves is regarded to the presence/detection of the sea bottom, the volume of siltation from April 2007 up to January 2008 is calculated as listed in Table 1.1. The volume of sedimentation in the harbor basin and access channel had been predicted in the Detailed Design Report, which was submitted by Nippon Koei Ltd in 2002, and they are also listed in Table 1.1. The prediction was done by a numerical computer simulation by Hydraulic Research (HR) Wallingford, U.K. under commission. Actual siltation was 4 to 8 times the prediction as of early 2008.
Table 1.1 Volume of siltation deposited from April 2007 to January 2008 in comparison with prediction at the time of Detailed Design Study in 2002 Name Area Vo l u me ( m 3) (m2) Obs. Pred. Harbor basin 657,000 158,000 478,000 Inner channel 626,000 1,973,000 453,000 Outer channel 1,660,000 2,389,000 312,000 Total 2,943,000 4,521,000 1,243,000
Examples of the temporal progress of siltation are shown in Figure 1.2 and Figure 1.3 at three locations of the access channel at the distance of 2.78, 16.0, and 17.0 km from the harbor basin. As seen in these figures, the interface observed with a 210 kHz frequency waves rose by about 3 m in these locations in ten months from April 2007 to January 2008.
Figure 1.2 Changes of the sea bottom in the Inner channel
1-3
Figure 1.3 Changes of the sea bottom in the Outer channel
During the dredging works of the project, unexpectedly fast siltation in the channel had been observed, which might endanger the smooth operation of the port when it opens. Since the cause of such phenomenon was not identified, it was not possible to estimate the future siltation volume, nor to find an adequate measure. Then, a scrutiny of fast siltation became an acute task.
The JBIC and the Comisión Ejecutive Portuaria Autónoma (hereinafter referred to as “CEPA”) discussed on the necessity of study on the fast siltation in July, 2008, and they agreed upon to start the Special Assistance for Project Implementation for La Union Port Development Project (hereinafter referred to as “SAPI”).
The objectives of the SAPI Study are itemized as in the following: i) Clarify the present situation of the siltation in La Union Port, ii) Estimate the volume of future siltation in case of no countermeasures, iii) Propose and recommend the appropriate countermeasures against siltation, iv) Clarify the environmental conditions such as tide, currents, waves, soil, and others, through data collection, field survey, and numerical simulations. Under these objectives, the following works had been conducted:
A. Survey of the Policy and Practice of Harbor Maintenance with Nautical Bottom Concept in World Ports B. Collection and Analysis of Environmental Condition C. Estimation of Present and Future Siltation Volume D. Examination of Countermeasures against Siltation
The SAPI Study was undertaken by JICA** and executed during November 2008 to November 2009 (see Figure 1.1).
** Note: On 1st October, 2008, the Overseas Economic Cooperation Operation of JBIC has been merged with JICA.
1.3 Result of SAPI Study
The major results concerning with the siltation problem are cited from the Report of SAPI.
1-4 1.3.1 The Gulf of Fonseca and Feeder Rivers The Gulf of Fonseca is about 65 km wide and 45 km long, having an area of about 3,200 km2(see Figure 1.4). Figure 1.5 is a satellite photograph of the Gulf of Fonseca, which has three embayments. From the west to the east, they are the Bay of La Union, Bay of Chismuyo (Honduras), and Bay of San Lorenzo (Honduras). As indicated with dark green color in Figure 1.5, the periphery of the Gulf is occupied by wide stretches of mangrove forests. The total area of mangrove forests is estimated at about 780 km2. Five major rivers flow into the Gulf : Goascoran, Nacaome, Choluteca, Negro, and Estero Real from the west to the east. These rivers are discernible in Figure 1.5 with indigo color, together with many creeks and inlets that penetrate deep into mangrove swamps. Many small rivers flow directly into the Gulf; they collecting rainwater falling on open fields around the Gulf. Mud in the Gulf of Fonseca has come from the suspended sediments during floods from many rivers. Sediments of bed load are mostly caught by mangrove swamps at the head of the Gulf. Suspended sediments of silt and clay are diffused with flood discharge and uniformly spread over the whole bay areas with a thickness of 0.2 to 1.2m.
Figure 1.4 Bathymetry of Gulf of Fonseca reproduced from Chart 21521 of US NGIA
Figure 1.5 Satellite photograph of Gulf of Fonseca reproduced from
1-5
1.3.2 Sediment classification and mechanism of siltation Figure 1.6 and Figure 1.7 show the sediment content and the median diameter of the samples around the Inner and Outer channels, respectively.
In the area north of Cape El Chiquirin, most of the seabed is covered with silt and mud except for a few locations such as Stations 9, 12, 24, and 26, where local supply of fine sand seems to be available. The median diameter varies from 0.013 to 0.034 mm excluding the sites with local fine sand.
Figure 1.6 Sediment classification and median diameter around the Inner channel
In the area south of Cape El Chiquirin, the stations outside the Outer channel indicate the fine sand content of 30% to 50% except for Station 20 at the outcrop near Conchanguita Island.
Within the channel, however, sand content is few with a median diameter of 0.02 to 0.04 mm. Little sand content along the outer channel as exhibited at Stations 1 to 6 indicates that sand does not move into the channel, but silt and mud are brought into the channel. That is to say, siltation in the channel is caused by the movement of silt and clay, while fine sand remain in its original position. This supports the concept on siltation mechanism that a thin layer of fluid mud on the
1-6 sea bottom creeps down into a deeper section by gravity.
What is happening in La Union Port is the movement of fluid mud layer as a density current. Wherever there is the elevation difference on the seabed such as across a dredged channel, fluid mud flows into the lower elevation by gravity. Movement continues as long as there is an elevation difference on the surface of fluid mud between the seabed inside and outside the channel.
Figure 1.7 Sediment classification and median diameter around the Outer channel
1.3.3 Establishment of prediction formulae for siltation speed and channel depth The most reliable data for the analysis of siltation problem is the records of bathymetric surveys of the access channel since June 2006 when the capital dredging started.
A trend analysis of the temporal variation of the mean channel depth at traverse survey lines has
1-7 enabled to establish an empirical prediction formula for siltation speed as a function of difference in the depths inside and outside the channel, and the time elapsed from completion of capital dredging.
Another prediction formula for estimation of channel depth in future has also been derived from the siltation speed formula. The channel depth prediction formula has been validated with the records of previous bathymetric survey results.
1.4 Objectives and Major Works of this Study
The SAPI Study clarified that the siltation is caused by slow movement of fluid mud toward a deeper seabed. Based on the analysis of bathymetric survey data during and after the dredging works, the prediction formulae for siltation were established. By utilizing the formula for estimation of channel depth, it was predicted that the siltation volume in the access channel with the depth of 14 m would be 10 million cubic meters per year.
Owing to the limited quantity of bathymetric time-series data and a relatively short duration of the study, however, the accuracy of the predicted siltation volume was not high enough to make reliable estimate of the volume of maintenance dredging. The variation of nautical depth, which is dependent on the speed of mud consolidation, also remained as not clarified enough. Thus, it is currently recognized that a definitive plan for maintenance dredging including location, frequency and method for elaboration of dredging cost and financial analysis is difficult to be provided.
To make the port function properly as a deep sea port, dredging method as well as cost is a vital issue in financial viability and a key factor for successful terminal operation either in the contingent stage of operation or in the stage of concession. Hence, CEPA requested JICA to provide an effective and efficient maintenance dredging plan.
According to a result of discussion between JICA and CEPA, Minutes of Meeting on 28 April, 2010 (see Annex A), JICA commenced the 1st Term Study in January 2011 and conducted a series of bathymetric survey and analysis for about one year and four months up to May 2012. The 1st Term Study had the following two purposes as stated in the Minutes of Meeting:
(1) To prepare an effective and efficient channel maintenance plan to make La Union Port function properly as a deep sea port. (2) To transfer technology to cope with the siltation in the channel and basin and to assist CEPA to review/revise the prepared dredging plan based on the bathymetric monitoring data.
The survey and analysis have proved that detailed analysis of future shipping service, detailed demand forecast, and the data of trial dredging are inevitable for making valid maintenance dredging plan. Hence, JICA and CEPA discussed and agreed to revise the TOR of Special Technical Assistance for Maintenance Dredging of the Port of La Union before the commencement of the 2nd Term Study, which has done on 31 October, 2012 (see Annex A). In the 2nd Term Study, not only the engineering issue but also the economic issue is included in the study scope to analyze technically/financially and economically optimum channel depths at present and in the future.
The 2nd Term Study has the following three purposes as stated in the Minutes of Meeting between JICA and CEPA on 31 October, 2012 (see Annex A):
1-8 (1) To prepare data, information and analysis utilized by CEPA to formulate an effective and efficient maintenance dredging plan of the Port. (2) To transfer technology to cope with the siltation in the channel and basin. (3) To assist CEPA to prepare dredging plan based on the collected data and analysis.
1.5 Engineers concerned and Chronologies of Study
1.5.1 Engineers concerned (1) Project Support Committee in Japan In order to properly implement the project on “Special Technical Assistance for Maintenance Dredging of the Port of La Union in the Republic of El Salvador”, the Project Support Domestic Committee has been established in the Economic Infrastructure Department, JICA Headquarters. Table 1.2 is the list of committee members. The Committee evaluates items with respect to the following issues and gives advice to the director of department, from an academic and technical view point.
1. Issues related to siltation in the channel 1) Analysis of present situation 2) Analyses of siltation volume and speed in the whole stretch of access channel including the basin 3) Collection and Analysis of the rake-dredging data and study on the dredging method 4) Estimation of dredging cost by the target navigation depth of channel 5) Suggestion about countermeasures against channel siltation 2. Any other necessary issues
Table 1.2 List of members of Project Support Domestic Committee in Japan Name Specialism Affiliation Chairman Dr. Kazuo Siltation in General and Emeritus professor, MURAKAMI Countermeasures for Tokyo City University Channel Siltation Member Dr. Yasuyuki Coastal and Estuary Team Leader of Coastal and NAKAGAWA Sediment Dynamics Estuary Sediment Dynamics Research Group, Port and Airport Research Institute Member Mr. Tsuyoshi Administration on Operation Chief of International NAKASAKI and Maintenance of Port Policy Planning Office, Facilities Ports and Harbors Bureau Member Mr. Masanori Dredging Method Expert Adviser, Japan KURODA Dredging and Reclamation Engineering Association
(2) Study Team The first term Study Team consists of engineers mainly from ECOH Corporation as listed in Table 1.3.
Members of the second term Study Team are listed in Table 1.4. The second term Study Team can be divided into two sub-teams, that is to say, the engineering team and the economic team. The former consists of engineers mainly from ECOH Corporation, which is in charge of siltation
1-9 problem and dredging plan in the channel. The latter is consists of engineers from OCDI, which is in charge of demand forecast and economic analysis of the port.
Table 1.3 Members of the first term Study Team Name Field in Charge Affiliation Dr. Yoshimi GODA Leader, Siltation Analysis ECOH Co. Dr. Nobuyuki ONO Sub Leader, Siltation Analysis ECOH Co. Mr. Takahisa AOYAMA Dredging Works and Planning ECOH Co. Mr. Yoshimasa ITO Oceanographic Survey ECOH Co. Mr. Anuratoshimitsu Bathymetric Survey Ocean MATSUMOTO Engineering Co.
Table 1.4 Members of the second term Study Team Name Field in Charge Affiliation Dr. Kazumasa Leader, Siltation Analysis ECOH Co. KATO Dr. Nobuyuki Prediction of Siltation ECOH Co. ONO Engineering Mr. Takahisa Channel dredging works and ECOH Co. Team AOYAMA Cost Estimation Mr. Shinji Channel dredging planning DRAM SAKURAI Engineering Mr. Tatsuyuki Maritime Economics OCDI SHISHIDO Dr. Ryuichi Demand Forecast OCDI SHIBASAKI Economic Mr. Takayuki Economic Analysis OCDI Team IIJIMA Mr. Tadahiko Port Planning OCDI KAWADA
(3) Counterparts For two counterparts in the first term Study listed in Table 1.5, the technical training was carried out in Japan.
In the second term Study, CEPA named 11 engineers as the counterparts, being 3 for the engineering team and 8 for the economic team, which are listed in Table 1.6.
Table 1.5 Counterparts in the first term Study Name Affiliation Mr. Mario Orantes Navigation Aids Mr. Abelino Cruz Chief of Maintenance Department
1-10 Table 1.6 Counterparts in the second term Study Name Affiliation Mr. Andrés Abelino Cruz Maintenance Manager, Engineering La Union Port Team Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Economic Mr. Carlos Federico Paredes Concessions Department, Advisor to Team the President Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Ms. Andrea Castillo Presidency Mr. Alan Castillo Concessions Department Mr. Juan Carlos Martinez Concessions Department Mr. Damian Reyes Market Analysis Division
(4) JICA Experts dispatched to CEPA JICA experts dispatched to CEPA are listed in Table 1.7.
Table 1.7 JICA Experts dispatched to CEPA Name Period Dr. Hidefumi IKEDA In the first term Study Mr. Takashi KADONO In the second term Study
(5) Relevant person of CEPA Those who were not the counter parts but participants in the meetings and the seminars of technology transfer are also listed in Table 1.8 and in Table 1.9.
Table 1.8 Others relevant person of CEPA in the first term Study Name Affiliation Mr. Luis Enrique Córdova Macías President Mr. Alberto Arene President Mr. Milton Lacayo Director of La Union Port Mr. Salvador Villalobos Brizuela General Manager Mr. Rolando Alberto Díaz Concession Manager Mr. Juan Caros Martíinez Concession Department Mr. Alberto Jiménez Manager of La Union Port Mr.Carlos R. Cornejo Maintenance Engineer Mr. Amilto Orellana Administration Manager Ms. Karen Martínez Mr. Miguel Martíinez Operation Mr. Osman Montoya IT Manager
Table 1.9 Relevant person of CEPA in the second term Study Name Affiliation Mr. Alberto Arene President Mr. Milton Lacayo Director of La Union Port Mr. Andrées Abelino Cruz Maintenance Manager, La Union Port
1-11 Mr. Marcos Vásquez Concession Department Mr. Juan Carlos Martínez Concession Department Mr. Rolando Díaz CEPA Consultant
1.5.2 Chronologies of Study Table 1.10 and Table 1.11 show Chronologies of the first and the second term Studies, respectively.
Table 1.10 Chronology of First Term Study 2010 28 April Minutes of Meetings (by Miyake) 2011 7 January JICA made the contract with the Team for the first term Study 25 January to 21 February First On-site Works Submission of Inception Report 1 31 January to 2 February Bathymetric Survey 7 to 9 February Mud Sampling 15 August to 6 September Second On-site Works Submission of Interim Report 1 19 to 22 August Bathymetric Survey 2012 15 January to 6 February Third On-site Works Submission of Interim Report2 19 January to 21 January Bathymetric Survey
Table 1.11 Chronology of Second Term Study 2012 31 October Minutes of Meetings (by Kawakami) 2013 29 March JICA made the contract with the Team for the second term Study 1 April First Project Support Domestic Committee 10 April to 5 May First On-site Works Submission of Inception Report 14 May Report Meeting in JICA HQ on the First On-site Works 09 August Second PSDC 11 August to 1 September Second On-site Works Submission of Interim Report 27 August Workshop on “Special Technical Assistance for Maintenance Dredging of the Port of La Union in the Republic of El Salvador” 11 September Report Meeting in JICA HQ on the Second On-site Works 31 October Prior Explanation on DF/R to JICA HQ and Office in TV Meeting 19 November Third PSDC 04 to 16 December Third On-site Works Submission of Draft Final Report 10 and 11 December Explanation on DF/R to CEPA 24 December Report Meeting in JICA HQ on the Third On-site Works
1-12 2014 20 January Deadline of comments on DF/R 31 March Submission of Final Report
1.6 Composition and Abstract of Chapters in the Report
In Chapter 2, the technical training of two counterparts in Japan, contents of technology transfer in the second term Study and a workshop held on 27 August, 2013 are explained.
In Chapter 3, the field survey such as bathymetric survey and mud sampling conducted in the first term Study is explained with its results.
In Chapter 4, at first, an empirical prediction model was formulated with an exponential function based on the bathymetric data. Next, a process and a mechanism of siltation in the channel are revealed through the analysis of bathymetric data. According to the result of analysis, the original exponential model has been improved to be a new model, which is named as a modified Exponential Model. Moreover, it is shown that a rapid siltation occurs just after the dredging within several months. By taking into account a possibility that the rapid siltation does not occur during a period of maintenance dredging, a second prediction model has been newly established, which is called a Linear Model. The applicability of these models is discussed.
In Chapter 5, the volumes of re-dredging and a maintenance dredging are estimated. The volume of maintenance dredging is estimated for each target depth by two prediction models formulated in Chapter 4. In a consideration for dredging method, a Self-propelling Trailing Suction Hopper Dredger (TSHD) is selected after the comparison of four types of dredging method. The dredging cost of re-dredging is estimated for the dredging of contract base, and those of maintenance dredging are estimated for both the contract base and the own dredger by CEPA.
In Chapter 6, contents and a method of monitoring on siltation in the channel and the basin are examined, which will be carried out just after the re-dredging and during the maintenance dredging. The purpose of monitoring are to verify an appropriateness of siltation volumes predicted by two models and to confirm the phenomenon of rapid siltation just after the re-dredging.
In Chapter 7, a review of the model developed by CEPA are shown including the estimation of the growth rate of container cargo shipping demand to/from CA4 countries (El Salvador, Guatemala, Honduras and Nicaragua) and the market allocation model.
The main purpose of Chapter 8 is to describe a vessel calling model for financial and economic analysis of La Union Port. After the outline of the model is described, every component of the model including behavior of shipping companies, container cargo assignment model, and input data are stated. The calculation results of the container cargo assignment model are examined from the viewpoint of the model reproducibility by several benchmarks. The sensitivity of the model to the estimated unknown parameters is also examined.
Chapter 9 mainly focuses on the output of the vessel calling model. However, the first part of the chapter describes the present status of navigation channel and rule in La Union Port, followed by a proposal of new navigation rule. After that, according to a lot of scenarios on the future liner shipping network which are prepared for each channel depth in La Union Port, the vessel calling model is calculated to estimate the future container cargo throughput and other outputs. From the
1-13 model output, net income (except for the dredging cost) from container business of La Union Port, net income from container business of Salvadoran port sector (sum of Acajutla Port and La Union Port), and net benefit for Salvadoran economy of the dredging project in La Union Port are estimated and compared with the dredging cost by channel depth. The model calculation as well as financial and economic analysis as mentioned above is also conducted in the cases that each related policy such as tariff increase of La Union Port, regional development in the eastern El Salvador, and decrease of the barrier at national border is implemented.
Chapter 10 shows a methodology of the time series analysis considering each year’s income, benefit and dredging cost. Also, example results of calculation are shown, in order to contribute to the discussion on the timing of investment for dredging.
In Chapter 11, major findings of the study and recommendation are summarized.
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Chapter 2 Technology Transfer
Chapter 2 Technology Transfer
2.1 Execution for Technical Training of CEPA Personals in Japan
The technical training of CEPA personals was carried out in Japan from 21 November to 9 December, 2011. Two trainees participated in the training program and studied on operation and management of dredging works, methodology of bathymetric survey and astronomical tide prediction, and so on (see Photo 2.1 and Photo 2.2). The itinerary of the training program is shown in Table 2.1.
Participants Mr. Cruz Fuentes Andrés Abelino Mr. Orantes Montiagudo Mario René
Photo 2.1 Exercise on MLIT’s survey boat, COSMO
Photo 2.2 Exercise on MLIT’s dredger, Kaisho Maru
2-1 Table 2.1 Itinerary of technical training in Japan CEPA Trainee JICA Day Date Mr. Cruz Fuentes Andres Abelino Mr. Orantes Montiagudo Mario Rene Interpriter Stay in a day of a week day of
1 11/21 Mon San Salvador -> Miami Miami
2 11/22 Tue Miami→Chicago frying overnight
3 11/23 Wed Chicago→Narita Tokyo
4 11/24 Thu Courtesy call on JICA, Orientation with Trainee Tokyo
Exercise on Shin-Tokyo Maru 5 11/25 Fri with Trainee Tokyo Seminor on Dredging at ECOH
6 11/26 Sat documentation with Trainee Tokyo
7 11/27 Sun documentation with Trainee Tokyo
8 11/28 Mon Excursion to HORS, Hasaki, Ibaraki with Trainee Tokyo Tokyo → Fukuoka 9 11/29 Tue with Trainee Kitakyushu Inspection of Hakata Port Hakata → Kitakyushu 10 11/30 Wed Exercise on MLITT's dredger, Kaisho Maru with Trainee Kitakyushu Exercise in Sounding Survey on Survey Boat Inspection of Construction site at Shinwakato Tunnel and Kanda Port 11 12/1 Thu with Trainee Tokyo Kitakyushu → Tokyo
12 12/2 Fri Seminar in Astronomical tide prediction at PARI with Trainee Tokyo
13 12/3 Sat documentation with Trainee Tokyo
14 12/4 Sun documentation with Trainee Tokyo
15 12/5 Mon Seminar in Astronomical tide prediction program at ECOH with Trainee Tokyo
16 12/6 Tue Exercise on Astronomical tide prediction program at ECOH with Trainee Tokyo
17 12/7 Wed 15:00 Assesment of the training with Trainee Tokyo
18 12/8 Thu Narita→Los Angeles Los Angeles
19 12/9 Fri Los Angeles→San Salvador
2.2 Technology Transfer to Counterparts
2.2.1 Technology Transfer in the Field of Engineering (1) Explanation of the Inception Report in the Second Term Study on 16 April, 2013 The Inception Report which contains the purposes and methods of the second term Study was explained to the participants in La Union Port. They understood the contents well. The participants are listed in Table 2.2.
2-2 Table 2.2 Participants (1) Name Affiliation Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Cornejo Maintenance Engineer, La Union Port Mr. Marcos Vásquez Concessions Department Mr. Osman Montoya Navigation Aids, La Union Port Mr. Roque Machado IT Technician, La Union Port
(2) Inspection of rake-dredging and confirmation of CEPA’s tide correction, on 17 April, 2013 The Engineering Team got the information about the rake-dredging through the interview and the discussion with the participants. The counterpart explained about their method of tide correction. The team pointed out that their method was not appropriate. The participants are listed in Table 2.3.
Table 2.3 Participants (2) Name Affiliation Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Cornejo Maintenance Engineer, La Union Port Mr. Marcos Vásquez Concessions department Mr. Osman Montoya Navigation Aids, La Union Port Mr. Roque Machado IT Technician, La Union Port
(3) Joint bathymetric survey practice on 19 April, 2013 In the field, the participants explained the Team on the items related to the bathymetric survey such as an installation of echo sounder, a calibration of measured water depth, operation of surveying vessel, a recording of sounding data and so on (see Photo 2.3). It was confirmed that their method of bathymetric surveying was correct and appropriate, and their skill has been good. The participants are listed in Table 2.4.
Photo 2.3 Setting of recording device for bathymetric survey
2-3 Table 2.4 Participants (3) Name Affiliation Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Cornejo Maintenance Engineer, La Union Port Mr. Marcos Vásquez Concessions department Mr. Osman Montoya Navigation Aids, La Union Port Mr. Roque Machado IT Technician, La Union Port
(4) Explanation on the Soft-ware program for the prediction of tide level in La Union Port, on 22 April, 2013 A basic concept of tide correction was transferred to the participants. And also, a soft-ware program for the prediction of tide level in La Union Port, which is absolutely necessary for tide correction, has been provided to them with a detailed explanation. The participants are listed in Table 2.5.
Table 2.5 Participants (4) Name Affiliation Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Cornejo Maintenance Engineer, La Union Port Mr. Marcos Vásquez CEPA Concessions Department Mr. Osman Montoya Navigation Aids, La Union Port Mr. Roque Machado IT Technician, La Union Port
(5) Joint bathymetric survey and a practice of tide correction on 21 August, 2013 The Joint Bathymetric survey of the engineering Team and counterparts was carried out. The bathymetric data obtained was used for practice of tide correction, in which the provided soft-ware program was effectively utilized. The participants are listed in Table 2.6.
Table 2.6 Participants (5) Name Affiliation Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Cornejo Maintenance Engineer, La Union Port Mr. Osman Montoya Navigation Aids, La Union Port Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz Port of La Union Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Roque Machado IT Technician, La Union Port
(6) Explanation of siltation process in the channel on 22 August, 2013 A result of analysis on the siltation process in the access channel of La Union Port was explained to the counterparts. The Team and the counterparts discussed on the phenomena of siltation, which gave a basic knowledge to the counterparts for understanding the prediction models of siltation. The participants are listed in Table 2.7.
2-4 Table 2.7 Participants (6) Name Affiliation Mr. Carlos Cornejo Maintenance Engineer, La Union Port Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port
(7) Joint bathymetric survey on 23 August, 2013 In the Inner channel, a longitudinal bathymetric survey was conducted under the joint of the Team and counterpart. The participants are listed in Table 2.8.
Table 2.8 Participants (7) Name Affiliation Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Roque Machado IT Technician, La Union Port
(8) Modification of prediction model for siltation in La Union Port, on 6 December, 2013 The engineering Team explained to the counterparts about the modified Exponential Model and newly formulated Linear Model. The counterparts could understand the applicability of these models. The participants are listed in Table 2.9.
Table 2.9 Participants (8) Name Affiliation Mr. Milton Lacayo Port Manager, La Union Port Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Mmarcos Vásquez Concession Department
(9) Explanation of the Monitoring plan on siltation after re-dredging, on 6 December, 2013 As a result of technology transfer, the counterparts deepened their understanding of the importance of monitoring for improving the prediction model. The participants are listed in Table 2.10.
2-5 Table 2.10 Participants (9) Name Affiliation Mr. Milton Lacayo Port Manager, La Union Port Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Marcos Vásquez Concession Department
(10) On the influence of Semicircle Island to the environment around it, on 9 December, 2013 CEPA has a plan to construct the Semicircular Island in order to reduce the volume of siltation. The effects of semicircular Island they expect are an alternate dumping site for dredged mud and reduction of siltation volume. The team explained a result of consideration concerning to this issue. The participants are listed in Table 2.11.
Table 2.11 Participants (10) Name Affiliation Mr. Milton Lacayo Port Manager, La Union Port Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Marcos Vásquez Concession Department
(11) Calculation method of siltation volume and Nautical depth of navigation, on 10 December, 2013 The counterparts understood the calculation method of siltation volume by applying two prediction models. The participants are listed in Table 2.12.
Table 2.12 Participants (11) Name Affiliation Mr. Milton Lacayo Port Manager, La Union Port Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Marcos Vásquez Concession Department
(12) Introduction of various dredgers, on 12 December, 2013 Various types of dredger were introduced (see Photo 2.4). The participants are listed in Table 2.13.
2-6
Photo 2.4 Atmosphere of presentation
Table 2.13 Participants (12) Name Affiliation Mr. Carlos Federico Paredes Concessions Manager Mr. Milton Lacayo Port Manager, La Union Port Mr. Amilto Orellana Administrative Department Manager, La Union Port Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Mr. Rafael Antonio Hernández Engineering Department Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port Mr. Juan Carlos Martínez Concession Department Mr. Julio Alberto Romero Concessions Management Technician Mejía Ms. Patricia Callejas Concessions Management Technician Ms. Eugenia Luna Concessions Management Technician Ms. Andrea Castillo President's Assistant Mr. Damián Reyes Economical Financial Analyst
2.2.2 Technology Transfer in the Field of Economic (1) Explanation of the Inception Report in the Second Term Study on 16 April, 2013 At the beginning of the second term Study, the JICA economic team explained the Inception Report. CEPA economic team was able to deepen their understanding of the central aim of this survey. The participants from the counterparts are listed in Table 2.14.
2-7 Table 2.14 Participants (1) Name Affiliation Mr. Carlos Federico Paredes Concessions Department, Advisor to the President Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Ms. Andrea Castillo Presidency Mr. Alan Castillo Concessions Department Mr. Juan Carlos Martinez Concessions Department
(2) Method of calculating CEPA model, on 26 April, 2013 The JICA economic team confirmed the methodology used in the future demand forecast and market allocation conducted by CEPA. The participants are listed in Table 2.15.
Table 2.15 Participants (2) Name Affiliation Mr. Carlos Federico Paredes Concessions Department, Advisor to the President Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Juan Carlos Martinez Concessions Department Mr. Alan Castillo Concessions Department
Photo 2.5 Presentation by a member of the economic team
(3) Vessel Calling Model [1]: Outline of the model and explanation of the maritime shipping submodel on 11 July, 2013 (by Skype meeting) The JICA economic team presented an outline of the Vessel Calling Model. In particular, the team focused on the abstract and estimated results of the maritime shipping submodel. CEPA economic team confirmed the result and was able to deepen their understanding of the model. The participants are listed in Table 2.16.
Table 2.16 Participants (3) Name Affiliation Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Juan Carlos Martinez Concessions Department Mr. Alan Castillo Concessions Department
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Photo 2.6 Skype meeting
(4) Vessel Calling Model [2]: Estimated results of the container cargo assignment model on 18 July, 2013 (by Skype meeting) The JICA economic team gave an outline of the container cargo assignment model including not only the maritime shipping submodel but also the land shipping network. The estimated results were discussed among JICA and CEPA economic team. The participants are listed in Table 2.17.
Table 2.17 Participants (4) Name Affiliation Mr. Juan Carlos Martinez Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Alan Castillo Concessions Department
(5) Vessel Calling Model [3]: Confirmation of the revised results on 9 August, 2013 (by Skype meeting). The revised calculation results based on the discussion in previous meetings and new information were confirmed. The participants are listed in Table 2.18.
Table 2.18 Participants (5) Name Affiliation Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damián Reyes Market Analysis Division
(6) Vessel Calling Model [4]: Review of the model and discussion on the future scenarios for model simulation on 12 August, 2013 The JICA economic team reviewed the whole structure of the model which had been explained in the Skype meetings with high-level staff of CEPA. The discussion mainly focused on the possible future scenarios for the model simulation. The participants are listed in Table 2.19.
2-9 Table 2.19 Participants (6) Name Affiliation Mr. Carlos Federico Paredes Concessions Department, Advisor to the President Mr. Milton Lacayo Port Manager,La Union Port Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Ms. Andrea Castillo Presidency Mr. Damian Reyes Market Analysis Division
(7) Basics of traffic assignment model on 15 August, 2013 The JICA economic team explained the traffic assignment model which is one of the fundamental components of the Vessel Calling Model. CEPA economic team practiced using the model, and was able to deepen their understanding of the model. The participants are listed in Table 2.20.
Table 2.20 Participants (7) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damián Reyes Market Analysis Division
(8) Container Service along Pacific Coast on CA5 on 16 August, 2013 The JICA economic team explained the present state of container shipping along the Pacific Coast in CA5. CEPA economic team was able to understand that the routes and frequency of container service could change depending on the strategy of shipping companies in Central America. The participants are listed in Table 2.21.
Table 2.21 Participants (8) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damian Reyes Markey Analysis Division
2-10 Photo 2.7 Participants of CEPA economic team
(9) Tariff of La Union port, on 25 August, 2013 The JICA economic team explained the tariff of La Union port and neighboring countries. CEPA economic team was able to deepen their understanding of the tariff. The participants are listed in Table 2.22.
Table 2.22 Participants (9) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damián Reyes Market Analysis Division
(10) Vessel Calling Model [5]: Improvement of the model (consideration of ocean freight charge) on 27 August, 2013 Before the workshop which was held on the afternoon of that day, improvements to the model were explained to CEPA economic team. The participants are listed in Table 2.23.
Table 2.23 Participants (10) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damián Reyes Market Analysis Division
(11) Estimated an expecting ship waiting time in La Union Port, on 28 August, 2013 The JICA economic team explained the estimation methodology of the expected ship waiting time by tidal change in La Union port. CEPA economic team was able to understand that the navigable time of the channel could be expanded by using tidal advantage. The participants are listed in Table 2.24.
Table 2.24 Participants (10) Name Affiliation Mr. Julio Romero Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damián Reyes Market Analysis Division
(12) Vessel Calling Model [6]: Validation of the model, simulation results, and execution of the program on 29 August, 2013 Of the contents which were presented at the workshop held on August 27, detailed results including the validation on the reproducibility of the model and simulation for the vessel-calling to the La Union Port were explained to the CEPA economic team. In addition, the calculation programs were distributed to the participants and executed. The participants learned how to execute the program on the computer. The participants are listed in Table 2.25.
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Table 2.25 Participants (12) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damián Reyes Market Analysis Division
Photo 2.8 Presentation by a member of the economic team
(13) Channel Navigation by using Tidal Advantage, on 6 December, 2013 The JICA economic team explained the navigable time of the channel by using tidal advantage. CEPA economic team was able to deepen their understanding of the method used to calculate navigable time. The participants are listed in Table 2.26.
Table 2.26 Participants (13) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Mr. Damián Reyes Market Analysis Division
(14) Regional/Industrial Development and Port Planning and Promotion, on 9 December, 2013 The JICA economic team explained the connection between industrial development of the region surrounding the port and port planning and promotion. CEPA economic team was able to deepen the understanding of the significance of port policy. The participants are listed in Table 2.27.
Table 2.27 Participants (14) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Ms. Andrea Castillo Presidency Mr. Damián Reyes Market Analysis Division
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(15) Summary of Draft Final Report [1]: Explanation of the final version of the Vessel Calling Model on 11 December, 2013 Of the contents included in the Draft Final Report, the final version of the Vessel Calling Model and its estimation results were explained by the JICA economic team. In addition, how to derive a logit model which is one of fundamental models of the stochastic assignment model was explained. The participants confirmed the final version of the model and its output as well as learned how to derive a logit model. The participants are listed in Table 2.28.
Table 2.28 Participants (15) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Ms. Andrea Castillo Presidency Mr. Damián Reyes Market Analysis Division
(16) Summary of Draft Final Report [2]: Method of calculating Financial & Economic analysis and on 12 December, 2013 The JICA economic team explained the method of financial and economic analysis, which is included in the Draft Final Report. CEPA economic team was able to deepen the understanding about the analysis and how to use an excel file for the time-series analysis. The participants are listed in in Table 2.29.
Table 2.29 Participants (16) Name Affiliation Mr. Julio Romero Concessions Department Ms. Patricia Callejas Concessions Department Ms. Marta Eugenia Canales Concessions Department Ms. Andrea Castillo Presidency Mr. Damian Reyes Market Analysis Division
2.3 Workshop
The workshop on “Special Technical Assistance for Maintenance Dredging of the Port of La Union in the Republic of El Salvador” was held in the Seminar Room on the top floor of CEPA Headquarter on 27 August, 2013. The workshop started while participants were taking the lunch which was invited by CEPA. The program of workshop, titles of presentations and presenters are listed in Table 2.30. Among them, Dr. K. Murakami and Dr. Y. Nakagawa are the members of Project Support Domestic Committee established in JICA Headquarters, Japan. Photo 2.9 shows an atmosphere of workshop, in which persons in CEPA side were occupying on the left side as one faces the screen of projector. The participants and presenters are listed in Table 2.31.
2-13 Table 2.30 Program of workshop, titles of presentations and presenters START 12:00 0. Lunch Invited by CEPA in order to enhance awareness of participants and presenters 12:00-12:30 1. Welcome Speech By Mr. A. ARENE, President of CEPA 12:30-12-35 2. Opening Address By Mr. T. KAWAKAMI, JICA HQ 12:35-12:40 3. Interim Report on Engineering Issues By Dr. N.ONO, ECOH 12:40-13:20 4. Interim Report on Economic Issues By Dr. R.SHIBASAKI, OCDI 13:20-14:00 5. Port Promotion examples in Japan By Mr. M.KIHARA, MLIT 14:00-14:30
Photo 2.9 Workshop held in CEPA Headquarters
Table 2.31 List of participants and presenters Name Affiliation El Salvador Side Mr. Alberto Arene President Mr. Carlos Federico Paredes President Advisor Castillo Mr. Milton Lacayo Port Manager, La Union Port Mr. Padre Amilto Orellqana Financial Manager, La Union Port Mr. Andrés Abelino Cruz Maintenance Manager, La Union Port Ms. Marta Eugenia Canales Administrator Data Base, La Union Port Ms. Andrea Castillo Assistant President Ms. Patricia Callejas Financial Assistant Mr. Carlos Alejandro Molina Bathymetry and Dredging Specialist, Paz La Union Port
2-14 Ms. Egly Tatiana Chacón Bathymetry and Dredging Specialist, La Union Port Mr. Rafael Antonio Engineering Department Hernández Mr. Damián Reyes Marketing Analyst Mr. Jaime Flores Financial Technician Mr. Marcos Vásquez Concession Department Mr. Juan Carlos Martínez Concession Department Mr. Julio Alberto Romero Concession Department Mejía Mr. Takashi Kadono JICA Expert Japanese Side Mr. Taiji Kawakami Executive Technical Advisor, Economic Infrastructure Department, JICA Headquarter Dr. Kazuo Murakami Emeritus professor, Tokyo City University Dr. Yasuyuki Nakagawa Team Leader of Coastal and Estuary Sediment Dynamics Research Group, Port and Airport Research Institute Mr. Masatomo Hihara Director for International Policy, Ports and Harbors Bureau JICA Study Team Dr. Kazumasa Kato Leader, Siltation Analysis, ECOH Dr. Nobuyuki Ono Siltation Analysis and Prediction, ECOH Mr. Takahisa Aoyama Channel Dredging works and Planning, ECOH Mr. Tatsuyuki Shishido Maritime Economics, OCDI Dr. Ryuichi Shibasaki Demand Forecast, OCDI Mr. Takayuki Iijima Economic Analysis, OCDI Mr. Tadahiko Kawada Port Planning, OCDI JICA El Salvador Office Mr. Shinji Sato Adjunct President Representative Mr. Yuichiro Inoue Director of Reimbursable Financial Cooperation Ms. Miwako Kamimura Project Formulation Adviser Ms. Gabriela Alfaro Program Officer
2-15
Chapter 3 Field Survey and Results
Chapter 3 Field Survey and Results
3.1 Bathymetric Survey
3.1.1 Survey lines of bathymetric survey The bathymetric survey was conducted along one longitudinal line along the access channel, 22 transversal lines across the access channel, 7 lines in the harbor basin perpendicular to the wharf, and 3 lines in the harbor basin parallel to the wharf. The locations of the transversal lines across the access channel are shown in Figure 3.1 with their distances from the base point listed in Table 3.1, which provides the conversion relationship between the line number and KP coordinate. The line numbers L1 to L22 correspond to the lines shown in Figure 3.1. The locations of survey lines within the basin are shown in Figure 3.2. The line numbers x+0 to x+1200 are set nearly perpendicular to the wharf, while the line numbers y-200 and y-400 are set parallel to the channel centerline. The column of extension indicates approximate lengths of survey lines.
Table 3.1 Location of bathymetric survey lines KP Extension KP Extension KP Extension No No No (km) (m) (km) (m) (km) (m) L1 21.91 600 L12 10.90 400 x+1200 1.20 700 L2 20.90 600 L13 9.91 400 x+1000 1.00 700 L3 19.90 600 L14 8.90 400 L22 0.92 700 L4 18.91 600 L15 7.91 400 x+800 0.80 700 L5 17.90 600 L16 6.92 400 x+600 0.60 700 L6 16.90 600 L17 5.93 400 x+400 0.40 700 L7 15.91 600 L18 4.93 400 x+200 0.20 700 L8 14.91 600 L19 3.92 400 x+0 0.00 800 L9 13.91 600 L20 2.92 400 y -0 - 800 L10 12.91 600 L21 1.92 400 y -200 - 1300 L11 11.89 400 y -400 - 1300
3-1 KP0
Figure 3.1 Bathymetric survey lines of access channel
Survey lines in harbor basin Longitudinal L22 KP0
y
x
Figure 3.2 Bathymetric survey lines in harbor basin
3-2 3.1.2 Longitudinal depth profile of access channel Figure 3.3 shows the longitudinal depth variation along the centerline of the access channel as surveyed during the period from 31 January to 2 February 2011, that from 19 to 22 August 2011, and that from 19 to 21 January 2012. The upper diagram shows the whole longitudinal profile of the access channel, while the lower diagram shows the portion of profile shallower than 15 m. The shallowest location of the Outer channel is around KP16.000 with the depth of 10.2 m, while the Inner channel is shallowest around KP3.500 with the depth of 7.4 m.
Distance(KP) ‐1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 5.0 10.0 15.0 (m) 20.0 2012_01
Depth 25.0 2011_08 30.0 2011_02 35.0 Distance(KP) ‐1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 6.0 7.0 2012_01 8.0 2011_08 9.0 2011_02 (m)
10.0 11.0
Depth 12.0 13.0 14.0 15.0
Figure 3.3 Longitudinal depth variation along the centerline of access channel
3.1.3 Transversal depth profiles of harbor basin and access channel Figure 3.4 to Figure 3.9 exhibit the profile changes of the cross-sections of the access channel from L01 (KP21.91) to L22 (KP0.92) at the interval of 1 km; five survey results in December 2008, June 2009, February 2011, August 2011, and January 2012 are shown with the plan shape of the channel. In each figure, the origin of the distance is set on the channel centerline and positive eastward.
Figure 3.10 and Figure 3.11 show the cross-sections of the harbor basin at the interval of 0.2 km; four survey results in December 2008, February 2011, August 2011 and January 2012 are shown. The water depths at completion of capital dredging in December 2008 are also shown in the figures.
Figure 3.12 are the depth profiles of the harbor basin along the lines of y = 0, -200, and -400 m, which are parallel to the centerline of the access channel. The distance is measured southward from the northern end of the basin as indicated in Figure 3.2.
3-3 L01 = KP21.91 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 Jan/20122012_01 10.0 A2011_08ug/2011
(m) Feb/20112011_02 11.0 12.0 Jun/20092009_06 Depth 13.0 Dec/20082008_12 14.0 PLAN 15.0 L02 = KP20.90 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 Jan/20122012_01 9.0 A2011_0ug/20118 10.0 Feb/20112011_02 (m)
11.0 Jun/20092009_06 12.0 Dec/20082008_12 Depth 13.0 PLAN 14.0 15.0 L03 = KP19.90 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 Jan/20122012_01 Aug/2011 10.0 2011_08 Feb/20112011_02 (m) 11.0 Jun/20092009_06 12.0 Dec/20082008_12
Depth 13.0 PLAN 14.0 15.0
Figure 3.4 Transversal depth profiles of Outer Channel with the planned channel profile (L1, L2, and L3)
3-4 L04 = KP18.91 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 10.0 (m)
11.0 12.0 Jan/20122012_01 A2011_08ug/2011 Depth 13.0 Feb/20112011_02 14.0 Jun/20092009_06 15.0 Dec/20082008_12 PLAN
L05 = KP17.90 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 10.0 (m)
11.0 Jan/20122012_01 12.0 A2011_08ug/2011
Depth 13.0 Feb/20112011_02 Jun/20092009_06 14.0 Dec/20082008_12 15.0 PLAN
L06 = KP16.90 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 10.0 (m) 11.0 Jan/20122012_01 12.0 A2011_08ug/2011
Depth Feb/2011 13.0 2011_02 Jun/20092009_06 14.0 Dec/20082008_12 15.0 PLAN
Figure 3.5 Transversal depth profiles of Outer Channel with the planned channel profile (L4, L5, and L6)
3-5 L07= KP15.91 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 10.0 (m)
11.0 2012_01Jan/2012 12.0 2011_08Aug/2011
Depth 13.0 2011_02Feb/2011 2009_06Jun/2009 14.0 2008_12Dec/2008 15.0 PLAN
L08= KP14.91 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 10.0 (m)
11.0 2012_01Jan/2012 12.0 2011_08Aug/2011 Depth 13.0 2011_02Feb/2011 14.0 2009_06Jun/2009 2008_12Dec/2008 15.0 PLAN
L09= KP13.91 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 Jan/20122012_01 9.0 A2011_08ug/2011 10.0 Feb/20112011_02 (m)
11.0 Jun/20092009_06 12.0
Depth Dec/2008 13.0 2008_12 14.0 PLAN 15.0
Figure 3.6 Transversal Depth profiles of Outer Channel with the planned channel profile (L7, L8, and L9)
3-6
L10= KP12.91 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 Jan/20122012_01 9.0 A2011_08ug/2011 10.0 Feb/20112011_02 (m)
11.0 Jun/20092009_06 12.0 Dec/2008 Depth 13.0 2008_12 14.0 PLAN 15.0
L11= KP11.89 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 Jan/20122012_01 9.0 A2011_08ug/2011 10.0 Feb/20112011_02 (m)
11.0 Jun/20092009_06 12.0 Dec/2008 Depth 13.0 2008_12 14.0 PLAN 15.0 L12= KP10.90 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 8.0 9.0 Jan/20122012_01 A2011_08ug/2011 10.0 Feb/20112011_02 (m) 11.0 Jun/20092009_06 12.0 Dec/20082008_12
Depth 13.0 PLAN 14.0 15.0
Figure 3.7 Transversal depth profiles of Outer Channel with the planned channel profile (L10, L11, and L12)
3-7 L17= KP5.93 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 11.0 12.0 Jan/20122012_01 13.0 A2011_08ug/2011 14.0 Feb/20112011_02
(m) 15.0 Jun/20092009_06
16.0 Dec/20082008_12 17.0 PLAN Depth 18.0 19.0 20.0 21.0 L18= KP4.93 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 6.0 7.0 8.0 9.0 Jan/20122012_01
(m) 10.0 11.0 A2011_08ug/2011 12.0 Feb/20112011_02
Depth 13.0 Jun/20092008_12 14.0 Dec/20082008_12 15.0 PLAN 16.0
L19= KP3.92 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 6.0 7.0 8.0 9.0 Jan/20122012_01
(m) 10.0 11.0 A2011_08ug/2011 12.0 Feb/20112011_02
Depth 13.0 Jun/20092009_06 14.0 Dec/20082008_12 15.0 PLAN 16.0
Figure 3.8 Transversal depth profiles of Inner Channel with the planned channel profile (L17, L18, and L19)
3-8 L20= KP2.92 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 6.0 7.0 8.0 9.0 Jan/2012 (m) 10.0 2012_01 11.0 A2011_08ug/2011 12.0 Feb/20112011_02
Depth 13.0 Jun/20092009_06 14.0 Dec/20082008_12 15.0 PLAN 16.0 L21= KP1.92 (200kHz) Distance(m) ‐200 ‐150 ‐100 ‐50 0 50 100 150 200 6.0 7.0 8.0 9.0
(m) 10.0 2012_01Jan/2012 11.0 2011_08Aug/2011 12.0 2011_02Feb/2011 Depth 13.0 2009_06Jun/2009 14.0 2008_12Dec/2008 15.0 PLAN 16.0 L22= KP0.92 (200kHz) Distance(m) ‐500 ‐400 ‐300 ‐200 ‐100 0 100 200 6.0 7.0 8.0 9.0
(m) 10.0 11.0 Jan/20122012_01 12.0 A2011_08ug/2011
Depth 13.0 Feb/20112011_02 14.0 Jun/20092009_06 15.0 Dec/20082008_12 16.0 PLAN
Figure 3.9 Transversal depth profiles of Inner Channel with the planned channel profile (L20, L21, and L22)
3-9 X=1200KP 1.200 (200kHz) Distance(m) ‐700 ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 100 200 300 6.0 7.0 8.0 9.0
(m) 10.0 11.0 12.0 Jan/20122012_01 Depth 13.0 A2011_08ug/2011 14.0 Feb/20112011_02 15.0 Dec/20082008_12 16.0
X=1000KP 1.000 (200kHz) Distance(m) ‐700 ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 100 200 300 6.0 7.0 8.0 9.0
(m) 10.0 11.0 Jan/20122012_01 12.0 Aug/2011 Depth 13.0 2011_08 14.0 Feb/20112011_02 15.0 Dec/20082008_12 16.0
X=800KP 0.800 (200kHz) Distance(m) ‐700 ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 100 200 300 6.0 7.0 8.0 9.0
(m) 10.0
11.0 Jan/20122012_01 12.0 Aug/2011 Depth 13.0 2011_08 14.0 Feb/20112011_02 15.0 Dec/20082008_12 16.0
Figure 3.10 Depth profiles of Turning Basin on the lines perpendicular to the wharf.
3-10 KPX=600 0.600 (200kHz) Distance(m) ‐700 ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 100 200 300 6.0 7.0 Jan/20122012_01 8.0 A2011_08ug/2011 9.0 Feb/20112011_02
(m) 10.0
11.0 Dec/20082008_12 12.0
Depth 13.0 14.0 15.0 16.0
KPX=400 0.400 (200kHz) Distance(m) ‐700 ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 100 200 300 6.0 7.0 Jan/20122012_01 8.0 A2011_08ug/2011 9.0 Feb/20112011_02
(m) 10.0 11.0 Dec/20082008_12 12.0
Depth 13.0 14.0 15.0 16.0 KPX=200 0.200 (200kHz) Distance(m) ‐700 ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 100 200 300 6.0 7.0 Jan/20122012_01 8.0 A2011_08ug/2011 9.0 Feb/20112011_02
(m) 10.0 11.0 Dec/20082008_12 12.0
Depth 13.0 14.0 15.0 16.0
Figure 3.11 Depth profiles of Turning Basin on the lines perpendicular to the wharf.
3-11
Y = 0 (200kHz) Distance(m)
7.0 8.0 9.0 10.0 (m) 11.0 12.0 Jan/20122012_01
Depth 13.0 A2011_08ug/2011 14.0 Feb/20112011_02 15.0 Dec/20082008_12 16.0
Y = ‐ 200 (200kHz) Distance(m)
8.0 9.0 Jan/20122012_01 10.0 A2011_08ug/2011 11.0 Feb/20112011_02 (m) 12.0 Dec/20082008_12 13.0
Depth 14.0 15.0 16.0 17.0
Y = ‐ 400 (200kHz) Distance(m)
7.0 8.0 2012_01Jan/2012 9.0 Aug/2011 10.0 2011_08
(m) Feb/2011 11.0 2011_02 12.0 2008_12Dec/2008
Depth 13.0 14.0 15.0 16.0
Figure 3.12 Depth profiles of Turning Basin on the lines parallel to the wharf.
3-12
3.1.4 Mean depth of access channel and harbor basin The surveyed water depths over the bottom width of navigation channel (about 140 m) were averaged to yield the mean channel depth. The mean depth is listed in Table 3.2 to Table 3.4.
Figure 3.13 shows the variation of the mean water depth along the harbor basin and access channel, listed in Table 3.2 to Table 3.4, in comparison with the previous survey results which were obtained in August 2008, December 2008, and June 2009. Figure 3.14 shows an expanded plot of Figure 3.13 for the portion of Inner channel and harbor basin. The mean depth at the completion of capital dredging is also shown with the marks of black closed circles. The mean depths just after capital dredging are measured in April 2008 for the Outer channel and in December 2008 for the Inner channel and harbor basin.
In the Outer channel, siltation since June 2009 is slight and locally depression is also seen in KP13 and KP14. On the other hand, siltation in the Inner channel is heavy and the channel depth at the locations of KP3.00 to KP4.00 is about 7.5 m. The harbor basin has the mean channel depth of about 12.2 m. Though the mean depths of the survey lines of x+200 and x+400 are about 12.7 m, the mean depth just in front of the wharf is -9 to -11 m, indicating localized siltation there.
The mean water depths in the harbor basin obtained from 1st to 3rd On-site Works have changed little and indicates that siltation at the present situation seem to have almost finished because the channel has almost filled with sediments.
3-13
Table 3.2 Mean depth of access channel and harbor basin in February 2011 KP Mean depth KP Mean depth KP Mean depth (m) No No No (km) Channel (m) (km) Channel (m) (km) Channel Basin L1 21.91 -13.70 L11 11.89 -13.25 L21 1.92 -8.80 - L2 20.90 -13.03 L12 10.90 -13.54 x+1200 1.20 -10.71 - L3 19.90 -12.36 L13 9.91 -16.16 x+1000 1.00 -10.93 -11.47 L4 18.91 -11.70 L14 8.90 -22.14 L22 0.92 -11.06 -11.52 L5 17.91 -11.17 L15 7.91 -33.33 x+800 0.80 -11.34 -12.04 L6 16.91 -10.94 L16 6.92 -29.68 x+600 0.60 -11.57 -12.64 L7 15.91 -10.96 L17 5.93 -17.75 x+400 0.40 -11.69 -12.47 L8 14.91 -11.60 L18 4.93 -8.19 x+200 0.20 -10.85 -13.03 L9 13.91 -12.57 L19 3.92 -7.70 x+0 0 L10 12.91 -12.97 L20 2.92 -7.74
Table 3.3 Mean depth of access channel and harbor basin in August 2011 KP Mean depth KP Mean depth KP Mean depth (m) No No No (km) Channel (m) (km) Channel (m) (km) Channel Basin L1 21.91 -13.68 L11 11.89 -12.08 L21 1.92 -8.76 - L2 20.90 -12.94 L12 10.90 -13.96 x+1200 1.20 -10.72 - L3 19.90 -12.06 L13 9.91 -16.23 x+1000 1.00 -10.94 -11.51 L4 18.91 -11.54 L14 8.90 -22.42 L22 0.92 -11.02 -11.42 L5 17.91 -11.15 L15 7.91 -33.42 x+800 0.80 -11.23 -11.91 L6 16.91 -10.81 L16 6.92 -29.78 x+600 0.60 -11.39 -12.35 L7 15.91 -10.75 L17 5.93 -18.12 x+400 0.40 -11.63 -12.87 L8 14.91 -11.32 L18 4.93 -7.89 x+200 0.20 -10.78 -13.09 L9 13.91 -12.24 L19 3.92 -7.55 x+0 0 L10 12.91 -12.54 L20 2.92 -7.50
Table 3.4 Mean depth of access channel and harbor basin in January 2012 KP Mean depth KP Mean depth KP Mean depth (m) No No No (km) Channel (m) (km) Channel (m) (km) Channel Basin L1 21.91 -13.77 L11 11.89 -12.38 L21 1.92 -8.55 - L2 20.90 -13.25 L12 10.90 -13.91 x+1200 1.20 -10.50 - L3 19.90 -12.38 L13 9.91 -15.92 x+1000 1.00 -11.02 -11.37 L4 18.91 -11.67 L14 8.90 -22.63 L22 0.92 -10.91 -11.52 L5 17.91 -10.81 L15 7.91 -33.35 x+800 0.80 -11.35 -11.90 L6 16.91 -10.38 L16 6.92 -25.08 x+600 0.60 -11.66 -12.00 L7 15.91 -10.14 L17 5.93 -18.08 x+400 0.40 -11.61 -12.79 L8 14.91 -10.92 L18 4.93 -7.67 x+200 0.20 -10.78 -13.16 L9 13.91 -11.96 L19 3.92 -7.44 x+0 0 L10 12.91 -12.52 L20 2.92 -7.48
3-14
-6 Cap. Dredg. (Apr.08) -7 Aug. 08 Dec. 08 -8 Jun. 09 -9 Feb. 11 -10 Aug. 11 -11 Jan. 12 -12 East B. (Feb. 11) -13 East B. (Aug. 11) -14 East B. (Jan. 12) -15
Channel Channel mean depth (m) -16 -17 -18 -19 -20 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0
Distance (KP) Figure 3.13 Variation of mean depth of the access channel
-6 Cap. Dredg.(Apr.08) -7 Aug. 08 -8 Dec. 08 -9 Jun. 09 -10 Feb. 11 -11 Aug. 11 Jan. 12 -12 East B. (Feb. 11) -13 East B. (Aug. 11) -14 East B. (Jan. 12) -15 basin (Feb. 11) -16
Channel (m) mean depth basin (Aug.11) -17 basin (Jan.12) -18 -19 -20 0.0 1.0 2.0 3.0 4.0 5.0 6.0
Distance (KP) Figure 3.14 Variation of mean depth of the Inner channel and harbor basin
3-15
3.1.5 Difference between depth measurements with 38 and 200 kHz sonic waves The dual frequency bathymetric survey in June 2009 during the SAPI Study indicated a certain difference between the water depth measured with the sonic waves of 38 kHz and 200 kHz, as shown in Figure 3.15, which are reproduced from the Final Report of SAPI Study (2009).
Figure 3.15 Transversal channel profiles with the acoustic signals of 38 kHz and 200 kHz at L18 to L20 (SAPI, 2009) The lower frequency waves of 38 kHz yielded the water depth greater than the one measured with those of 200 kHz. The difference varied from location to location in the range of 0 to 1.2 m as listed in Table 3.5 (from the Final Report SAPI Study, 2009). The depth difference was regarded as representative of fluid mud layer which had not been consolidated yet after the completion of capital dredging in late December 2008.
3-16
Table 3.5 Approximate range of fluid mud thickness at respective transverse lines (SAPI, 2009)
There have been many arguments on the acoustic response of fluid mud layer to the low and high frequency sonic waves, but no quantitative conclusion has been obtained yet. Vertical mud sampling conducted in the First On-site Works indicates the surface density of fluid mud layer is around 1.05 g/cm3. Judging from the Team’s experience in the SAPI and the present Project, the threshold density for activating the response of 38 kHz sonic waves seems to be around 1.05 g/cm3, while the threshold density for the 200 kHz sonic waves seems to be around 1.03 g/cm3 which is just above the seawater density with inclusion of turbid mud particles.
When maintenance dredging is undertaken, siltation process will take place immediately. During the early stage of siltation, there may be some difference in the acoustic response of the seabed with the sonic waves of 38 kHz and 200 kHz.
3-17
3.2 Seabed Mud Conditions
3.2.1 Sites and methodology of mud sampling During the First On-site Works, mud sampling was made at five locations listed in Table 3.6. The sites A and B are located outside the basin and channel, while the sites C, D, and E are located inside the basin and channel. The site locations are shown in Figure 3.16.
Table 3.6 Locations of mud sampling sites. Approx. depth of mud No KP (km) y (m) surface layer (m) Remarks As meas. Ref. to DL A 0.20 +200 -8.7 -8.5 Outside basin B 2.92 +200 -6.9 -6.7 Outside channel C 0.20 0 -13.7 -13.5 Inside basin D 2.92 0 -7.8 -7.6 Inside channel E 15.91 0 -11.6 -11.4 Inside channel
A C B D
E
Figure 3.16 Location of sampling sites
At each site, a pair of 1ong polyvinyl-chloride pipe (1.5 m) and a short polyvinyl-chloride pipe (0.5 m) was vertically inserted into the mud layer by a pair of divers. The pipes had the inner diameter of 50 mm. Short pipes were inserted into mud for full length, while long pipes were inserted by 1.2 m. The elevation of the top of each short pipe was monitored by a diver’s computer and later converted to the water depth relative to the port datum level. The pipes were sealed at the top and bottom with caps while drawing out from the mud layer, and they were brought to the survey boat (see Figure 3.17). The depth reported by the divers is approximately equal to the water depth measured by the sonic waves of 200 kHz. Thus, the water depth measured by the echo sounder is judged to represent the depth of the surface of fluid mud layer.
3-18
Visibility of seawater was almost zero near the seabed. The divers reported that they could not recognize the surface of mud layer by eyes. They sat on top of the mud layer and identified it by touch with their hands.
The short pipes were intended to catch the surface layer of fluid mud. Because of no visibility around the seabed, the divers seem to have inserted the short pipes somewhat deeper than the fluid mud surface. The long and short pipes were brought to the office and the weights of a pipe with and without mud content were measured using a digital scale. The wet density of fluid mud was calculated with the weight of mud contained in the pipe by dividing it by the pipe’s capacity.
Figure 3.17 Lifting of sampling tube at Site E (a) and Sampling tube at Site E (b)
The long pipes were supposed to be inserted into the seabed by the length of 1.2 m, leaving the top 0.3 m above the mud layer. At certain locations, a diver could not drive the pipe more than 0.9 m or so, because of large resistance of hard mud there. The pipes were cut into sections of 0.3 m long on board (see Figure 3.18). The top section contained seawater only. The second section usually contained mud dispersed in water. After a long pipe was brought on the boat, the settlement process of mud particles started and an interface between water and fluid mud appeared in a few minutes. The interface height was measured, and it was employed to estimate the elevation of the fluid mud surface.
3-19
(a) Cutting off the 0th and (b) Splitting the 2nd and 3rd (c) Splitting the 3rd and 4th 1st sections. sections. sections.
Figure 3.18 Cutting a sampling pipe into sections of 0.3 m long
3.2.2 Description of sampled mud and vertical density profile of mud layer The mud content in each section was measured for its wet density, and then it was poured into a plastic bag with tight sealing (Ziplock) for later shipment to Japan. Mud samples from long polyvinyl-chloride pipes are counted as 40. Each sample of mud weighed about 1 kg. The pictures of mud samples placed in plastic bags are shown in Figure 3.19.
When the mud wet density is less than 1.1 g/cm3 as shown in Figure 3.19 (a), mud is just like liquid. As the density increase, mud gains plasticity like soft clay. When a mud sample is placed into a bag from a polyvinyl-chloride pipe section, the sample maintains a cylindrical shape for a while. When the mud wet density exceeds 1.2 g/cm3, a mud sample looks like a mass of clay as shown in Figure 3.19 (d).
The measured wet density of mud layer is plotted against the mean depth of sampled layer below the seabed in Figure 3.20 and Figure 3.21 for outside and inside the channel, respectively. To indicate the trend of wet density variation, a linear regression line is drawn for each measurement site. Mud on the bank outside the channel has been left undisturbed for many years and well consolidated by its own weight and loading by wave pressure and shear stress of tidal currents. A rapid increase of the wet density with the increase of layer depth from the seabed shown in Figure 3.20 is an evidence of the well consolidated state of mud. Measured data of mud wet density show some scatter probably due to sampling variability, but the trend of density change indicated with the regression lines suggests that the mud wet density will exceed 1.4 g/cm3 at the level of 0.7 m below the seabed.
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3 t = 1.12 g/cm 3 t = 1.08 g/cm
(a) Mud sample from Site D (b) Mud sample from Site D th (2nd Section) (4 Section)
3 3 t = 1.27 g/cm t = 1.17 g/cm
(c) Mud sample from Site B (d) Mud sample from Site B (2nd Section) (4th Section)
Figure 3.19 Photographs of mud sample with its density
Compared with the mud wet density on the bank outside the channel, the density of mud deposited inside the channel is low and its increase with depth is slow, as shown in Figure 3.21. The site D at the location of KP2.9 has a silted mud layer of about 7 m as indicated in Figure
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3.14. The mud layer has been deposited in the past 2 years and it is still under the process of consolidation. The depth of threshold density (1.2 g/cm3) would be nearly 2 m below the seabed.
Around the site C at the location of KP0.20, the thickness of silted mud layer is about 4.5 m as seen in Figure 3.14. Around the site E at the location of KP15.91, the thickness of silted mud layer is also about 4.5 m, but the deposition since June 2009 is only 0.5 m thick. The thinner mud layer in the sites C and E than the site D may be the reason of the increase of mud wet density with the depth faster than that in the latter.
0 Outside A: Meas. Outside A: Linear (m)
‐0.2 Outside B: Meas. Outside B: Linear
seabed ‐0.4
from ‐0.6 depth
‐0.8 Layer
‐1 1.0 1.1 1.2 1.3 1.4 1.5 Density (g/cm3) Figure 3.20 Vertical profile of mud wet density outside the access channel
0 Inside C: Meas. Inside c: Linear (m) ‐0.2 Inside D: Meas. ‐0.4 Inside D: Linear seabed
Inside E: Meas. ‐0.6 Inside E: Linear from
‐0.8 depth
‐1 Layer
‐1.2 1.0 1.1 1.2 1.3 1.4 1.5 Density (g/cm3) Figure 3.21 Vertical profile of mud wet density inside the access channel
3.2.3 Physical properties of sampled mud The 40 mud samples were transported to Japan and detailed soil tests were commissioned to OYO CORPORATION. The wet density and moisture content were measured for all the samples, but other soil characteristics were investigated for the vertically mixed samples at respective sites because the mud properties are considered invariant to the depth.
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The wet density (t) satisfied the theoretical relationship with the moisture content as expressed by Eq. (3.1). /1 w st %100 (3.1) wt 1/ where w and s denote the density of water and soil grains, respectively. Figure 3.22 shows comparison between the measured data and theoretical prediction, in which the water density is 3 3 taken at w = 1.00 g/cm and the soil density at s = 2.65 g/cm . 500
Meas. 400 Theory (%)
300 content
200 Moisture 100
0 1.10 1.20 1.30 1.40 1.50 Wet density (g/cm3) Figure 3.22 Relationship between moisture content and wed density of mud samples
It should be commented that the wet density tested in laboratory in Tokyo was greater than the density measured at La Unión up to 0.1 g/cm3. Mud samples were sealed in Ziplock bags, which were placed in sealed plastic bottles. Nevertheless, a lapse of two months from the time of sealing in La Unión to that of opening in Tokyo might have caused small evaporation of water content in mud samples and increased the wet density. Thus, the wet density measured immediately after sampling from the seabed is employed as representative of in-situ density and shown in Figure 3.20 and Figure 3.21.
The test results of the soil characteristics of vertically-mixed samples are listed in Table 3.7. Because these five samples represent the mud on the surface layer of 1.0 m below the seabed, they have more clay content than those analyzed in the SAPI Study. The sample from the site D has the grain diameter much smaller than those at other sites and the higher plasticity index. It might have been caused by rapid inflow of fluid mud owing to a large depth difference there between the inside and outside of the access channel.
Table 3.7 Soil characteristics at five sampling sites Sampl Soil grain Median 75% upper Liquid Plastic Plasticity Organic Ignition ing density diameter diameter limit limit index content loss 3 site s (g/cm ) d50 (mm) d75 (mm) wL (%) wL (%) IP c0 (%) Li (%) A 2.640 0.002 0.014 111.6 33.9 77.7 4.69 13.4 B 2.648 0.006 0.042 103.7 34.0 69.7 5.20 12.9 C 2.672 0.003 0.040 105.7 33.0 72.7 4.39 13.2 D 2.626 0.001 0.008 132.4 39.0 93.4 5.14 15.1 E 2.636 0.005 0.028 113.3 34.3 79.0 4.78 14.0
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3.2.4 Numerical prediction of density profile change by means of mud consolidation process (1) Methodology of mud consolidation prediction Fluid mud deposited in the basin and channel is a mixture of fine mud particles and sea water. Its initial density is somewhere between 1.05 to 1.10 g/cm3. As time elapses, mud particles congregate together and their contact builds a 3D skeleton structure of mud particles. The weight of individual mud particles works as the load to the skeleton and squeezes out the water contained within the skeleton. Then the mud particle skeleton shrinks and the fluid mud wet density increases. This is the initial stage of mud consolidation. Fluid mud of low density gradually becomes very soft mud and then soft mud.
The key parameters of mud consolidation are the compressibility and permeability of mud. They are investigated through a mud settlement test and a low pressure consolidation test. The former employs a settlement tube of 0.2 m in diameter and 2 m in height. A mixture of mud and water with the moisture content of 1000 to 3000% is poured in the settlement tube. Immediately after pouring, mud particles begin to settle and there appears an interface between water and fluid mud. The interface settles down as time elapses and the settlement of interface is monitored over a certain period. For the mud samples taken from five locations of A to E were subjected to the settlement test for 60 days. The mud deposited at the bottom of the settlement tube was then subjected to the low pressure consolidation test. Through these tests, the compressibility and permeability parameters were estimated. Because samples from the five locations yielded similar values of the parameters, their average values were adopted in the consolidation analysis.
Computation of mud consolidation process is made by solving the consolidation equation of one dimension along the vertical axis. The weight of mud layer is the sole load activating consolidation. External loading such as the wave pressure is not taken into account. Numerical computation of mud consolidation has been executed by Dr. Masaki Kobayashi of Kobayashi SoftTech Co. Ltd..
Consolidation is computed by increasing mud layer continuously with a reducing deposition speed. A newly deposited mud is reduced in height by consolidation and the deposition speed is enhanced from the continuous siltation. The rate of enhancement is set by the try and error method. Mud consolidation was analyzed with 180 steps. During the first step, a single top-most mud layer is dealt with. During the second step, a second mud layer is added upon the first layer. The process is repeated to the 180th step, and thus the thickness and density of 180 layers are calculated. The results on 180 layers are summarized into 10 layers, each of which represents the average of 18 steps at respective depths.
Two series of mud consolidation computation have been undertaken. One series aimed at simulating the process of siltation that took place at the locations D and E in Table 3.6 and Figure 3.16 for the purpose of calibrating the consolidation prediction method. The other series simulated the siltation process in the access channel within 12 months after execution of maintenance dredging. Four levels of the depth difference between the inside and outside of the channel are employed for representing a possible range of depth difference from 3.0 to 7.5 m. The results of computation are described in the subsequent sections.
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(2) Calibration of consolidation analysis with In-situ data The site D in Table 3.6 and Figure 3.16 is located at the distance KP 2.92 (L20). The vertical profiles of mud wet density near the seabed are shown in Figure 3.21. The depth change with time and the density profile are the target of calibration of consolidation analysis.
When the capital dredging was completed at the site D in the end of December 2008, the depth difference between the inside and outside of the access channel was 7.8 m. According to the bathymetric survey results, the siltation speed was v = 0.87 m/month in early January 2009 and v = 0.25 m/month in early February 2011. In the case of the site E where the capital dredging was completed in the end April 2008 with the depth difference of 5.9 m, the siltation speed was estimated at v = 0.66 m/month in early May 2009 and 0.08 m/month in early February 2011.
In consideration of consolidation of deposited mud, the deposition speed was set faster than the siltation speed measured by bathymetric survey results. Several trials of consolidation computation with different deposition speeds were made, and those shown in Figure 3.23 were selected for the calibration test.
1.2 Inside D (Dh = 7.0 m) 1.0 Inside E (Dh = 5.9 m)
(m/month) 0.8 v
0.6 speed,
0.4
0.2
Deposition 0.0 0 6 12 18 24 30 36 Elapsed time, t (month) Figure 3.23 Deposition speed employed in calibration of mud consolidation analysis
3 The density of fluid mud creeping into the channel was assumed to be s = 1.100 g/cm against 3 the surrounding seawater with w = 1.025 g/cm . The computed thickness of deposited mud was employed to calculate the variation of channel mean depth with the lapse of time. Figure 3.24 (a) shows the predicted channel mean depth in comparison with the bathymetric survey results at the site D. The calculated depth was deeper than the actual depth, indicating the assumed deposition of fluid mud at the site D was not sufficient enough to simulate the actual bathymetric change. Nevertheless this was the best case among several trial simulations. Though there remains a difference of some 1 m on average between the calculation and the bathymetry, the trend of calculated depth change agrees with the bathymetric data.
Evolution of mud wet density profile at the site D is shown in Figure 3.24 (b). The ordinate is the height of silted mud layer above the channel bottom. The silted height corresponding to the density of 1.100 g/cm3 represents the total mud thickness at respective date. The mud wet density shown in this figure is the density at each level of silted height. For example, the mud wet density at the height of 2.0 m above the channel bottom was 1.13 g/cm3 in July 2009, and then increased to 1.21 g/cm3.in January 2010, 1.24 g/cm3 in July 2010, and 1.26 g/cm3 in January 2011. As the time elapses, the mud wet density profile shifts upward with little change,
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indicating the density profile measured from the surface of mud layer remains the same and the lower part of mud layer gradually gains higher density.
(a) Time evolution of channel mean depth (b) Time evolution of mud wet density at Site D. profile at Site D.
Figure 3.24 Time evolution of (a) channel mean depth and (b) mud wet density profile at Site D
(a) Time evolution of channel mean depth (b) Time evolution of mud wet density at Site E. profile at Site E.
Figure 3.25 Time evolution of (a) channel mean depth and (b) mud wet density profile at Site E
Comparison of the calculated consolidation and the in-situ data at the site E is shown in Figure 3.25(a) for the channel mean depth and in Figure 3.25(b) for the mud wet density profile. The calculated rise of the channel depth in Figure 3.25(a) was slower than the in-situ data up to 18 months after the start of siltation, but the calculation gave the final depth same as the bathymetric survey result.
The evolution of mud wet density profile at the site E shown in Figure 3.25(b) is similar with that at the site D shown in Figure 3.24 (b), but the mud wet density at the channel bottom at the site E is slightly larger than that at the site D, because of a long deposition period of 33 months in comparison with 25 months at the site D. The high mud wet density above 1.2 g/cm3 near the seabed measured in situ could not be simulated by the mud consolidation analysis. The discrepancy is thought to have been caused by the additional loading by the underwater pressure by the swell persistent along the Outer channel.
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Although the results shown in Figure 3.24 and Figure 3.25 exhibit some difference between the calculation by the consolidation analysis and the in-situ data, it can be said that the consolidation analysis does clarify the process of siltation with evolution of mud wet density increase.
(3) Prediction of mud deposition and density change after maintenance dredging With confirmation of the capability of simulating mud siltation process presented in Sec. (2), prediction of the process of mud deposition and the evolution of mud wet density after maintenance dredging has been carried out. The density of fluid mud creeping down into the channel is assumed to be 1.100 g/cm3 against the seawater density of 1.025 g/cm3. In consideration of several dredging depths, the depth difference between the dredged channel and the outside bank is set at four levels of h = 3.0, 4.5, 6.0, and 7.5 m. Figure 3.26 shows the deposition speed employed in the consolidation analysis.
1.6 Del_h = 7.5 m 1.4 Del_h = 6.0 m 1.2 Del_h = 4.5 m Del_h = 3.0 m
(m/month) 1.0 v
0.8
0.6 speed,
0.4
0.2
Deposition 0.0 036912 Elapsed time, t (month) Figure 3.26 Deposition speed employed in prediction of mud deposition after maintenance dredging
The predicted siltation height with the lapse of time is shown in Figure 3.27(a). According to Eq. (5.2), the siltation height is estimated as h = 2.2, 3.3, 4.4, and 5.5 m at 12 months after dredging for the initial depth difference of h0 = 3.0, 4.5, 6.0, and 7.5 m, respectively. The predicted siltation height is slightly lower than the estimated height, but the difference may be regarded as allowable for examination of time evolution of mud wet density.
The time evolution of mud wet density at the channel bottom is shown in Figure 3.27(b). The increase of bottom mud wet density is fast at the first three months and the effect of initial depth difference is small. The increase of bottom mud wet density with time is shown in Figure 3.28 against the siltation height. It is a combination of the data plotted in Figure 3.27(a) and (b). Four curves corresponds to the four levels of initial depth difference, and four symbols indicate the data of density and height at the lapse of 3, 4, 6, and 12 months after maintenance dredging. 3 Figure 3.27(b) indicates that the threshold density of s = 1.20 g/cm for nautical bottom will be reached in 3 to 4 months after dredging with the thickness of 1 to 2 m.
The time evolution of mud wet density profile is shown in Figure 3.29 and Figure 3.30 for the initial depth difference of h = 3.0, 4.5, 6.0, and 7.5 m, respectively. The pattern of density profile evolution is almost the same regardless of the initial depth difference.
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(a) Time evolution of siltation height after (b) Time evolution of bottom mud wet density maintenance dredging. after maintenance dredging.
Figure 3.27 Time evolution of (a) siltation height and (b) bottom mud wet density after maintenance dredging
Figure 3.28 Time evolution of bottom mud wet density versus siltation height after maintenance dredging.
(a) Time evolution of mud wet density (b) Time evolution of mud wet density profile withh = 3.0 m. profile withh = 4.5 m. 0 0 Figure 3.29 Time evolution of mud wet density profile. (a) h = 3.0 m and (b) h = 4.5 m
3-28
(a) Time evolution of mud wet density (b) Time evolution of mud wet density profile with h = 7.5 m. profile withh0 = 6.0 m. 0
Figure 3.30 Time evolution of mud wet density profile. (a) h0 = 6.0 m and (b) h0= 7.5 m
3.2.5 Assessment of thickness of fluid mud layer for definition of nautical bottom The main objective of mud consolidation analysis is to make assessment of the thickness of fluid 3 3 mud layer with the density below s = 1.20 g/cm = 1,200 kg/m , which is taken as the threshold density for defining the nautical bottom.
Outside the channel, the mud wet density exceeds the threshold value at the depth of 0.4 m below the seabed at the sites A and B as shown in Figure 3.20. Inside the Inner channel, the threshold density is exceeded at the depth of 0.5 m and more than 1.0 m at the sites C and D, respectively, as shown in Figure 3.21. Inside the Outer channel at the site E, the depth to the threshold density is 0.4 m.
Compared with the in-situ density data, the consolidation analysis predicts slow increase of mud wet density with the depth above the seabed. The result of comparison shown in Figure 3.25 (b) is an example. One reason is the absence of additional loading such as shear stress by tidal currents and underwater pressure by wave actions.
3 For the assessment of fluid mud layer thickness with the density below s = 1,200 kg/m , it would be safe to assume the thickness of 0.5 m for the Outer channel in consideration of additional loading by swell action. For the Inner channel, it is taken as h = 1.0 m on the safe side in consideration of the in-situ data at the site C, even though the consolidation analysis suggests larger depth up to 2.0 m.
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3.3 Main Results of the Field Survey
In this Chapter, results of bathymetric surveys and analysis of mud property have been summarized. Main findings from the surveys are as follows:
From the bathymetry survey results, it is confirmed that both the Inner channel and the Outer channel have already filled with the sediment and the channel depth is presently the almost same level as the outside depth of the channel.
Judging from the Team’s experience in the field, it is considered that the echo sounder of 200 kHz in frequency detects the top surface of the fluid mud layer. The depth navigable for vessels is considered to be deeper than the depth measured by the echo sounder of 200 kHz, due to the thickness of the fluid mud layer.
The fluid mud layer in the channel continues in existence for relatively long period. This indicates a possibility to reduce maintenance dredging volume by making a maintenance dredging plan taking the fluid mud layer into account.
From the analysis of mud sampled at about two years after capital dredging, it is confirmed that fluid mud layer, the wet density of which is less than 1,200 kg/m3, is formed with the thickness of about 0.5 m in the Outer channel and about 1.0 m in the Inner channel.
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Chapter 4 Analysis of Siltation Process and Prediction Models
Chapter 4 Analysis of Siltation Process and Prediction Models
4.1 Collected Data
The data collected for analyses of siltation processes are the bathymetric data and the records of dredging.
Figure 4.1 shows the periods of dredging and the times of bathymetric surveying by distinguishing the areas of the harbor basin, the Inner channel and the Outer channel. In Table 4.1, periods of dredging are listed. The data were selected for analyses from these bathymetric data by taking into account the dredging period and times of surveying.
Newly obtained bathymetric data, July, 2013, is partly included in the analyses.
Figure 4.1 Period of dredging and times of bathymetric surveys
Table 4.1 Periods of implementation of dredging Location of dredging Period of dredging Harbor Basin 16 ~22 June, 2006 25 April~11 May, 2007 25 November~10 December, 2008 Inner channel 17 November~21 December, 2005 22 June~17 July, 2006 13 ~22 August, 2006 25 September~6 October, 2006 12 January~10 March, 2007 5~15 May, 2008 25 November~10 December, 2008 Outer channel 17July~12 August, 2006 23 August~24 September, 2006 30 January~4 May, 2008
4-1 4.2 Siltation Speed and Depth Difference in the Channel (Exponential model)
Figure 4.2 shows the changes of water depth at representative reference lines (Figure 4.3) in the Inner and the Outer channels, in which a brown line is the mean water depth in the channel, a blue and a green line are the depths at the western and eastern banks of the channel, respectively. The periods of dredging are indicated by the gray belts for the Inner channel and orange belts for the Outer channel. The bathymetric survey was repeated irregularly and the dredging was conducted also irregularly. From this data, it is easily understood that the siltation occurred after the dredging.
Figure 4.2 Changes of water depth in the Inner and the Outer channel
As the first trial, an empirical prediction model of siltation is considered based on the bathymetric data obtained after the last dredging. The formulation makes use of the data only after completion of capital dredging operations. For the Outer channel, seven sets of survey data in April ’08, August ’08, December ’08, June ’09, February ’11, August ’11, and January ‘12 are employed. For the Inner channel, five sets of survey data in December ’08, June ’09, February ’11, August ’11 and January ‘12 are utilized.
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Figure 4.3 Bathymetric survey lines of access channel
Figure 4.4 shows the relationship between the siltation speed of the access channel and the mean depth difference h (m) between the inside and outside channel depths. The definition of water depths is shown in Figure 4.5. The siltation speed v in the units of m/month is calculated as the amount of the rise of the mean channel depth during two successive surveys being divided by the period between the two surveys. The mean depth difference h is in the units of meter. The water depth outside the channel is defined as the average depth of the western and eastern banks. The water depth inside the channel is taken as the average of two successive surveys. The legend such as “Outer: Dt = 4” denotes the data of Outer channel with the lapse of 4 months after the capital dredging, i.e., the survey data in August ’08. The Outer channel includes the data of L01 to L12, while the Inner channel includes the data of L18 to L21.
0.8 Whole Channel Outer: Dt = 4 Outer: Dt = 8 0.7 Outer: Dt = 14 0.6 Outer: Dt = 33
(m/month) 0.5 Outer: Dt= 39 v Outer. Dt=44 0.4 Inner: Dt = 6 speed,
0.3 Inner: Dt = 25 0.2 Inner: Dt= 31
Siltation Inner. Dt=36 0.1 Linear Approx. 0 Linear (outer) ‐0.1 Linear (inner) ‐101234567 Mean depth difference, h (m)
Figure 4.4 Siltation speed versus the depth difference inside and outside the access channel.
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Figure 4.5 Definition of water depths Although the scatter of data is large, a linear regression line is tentatively drawn for the Inner and Outer channel as follows:
hd v .0 109 : hhhh : Access channel (4.1) dt in out The coefficient of determination is R2 = 0.6503.
The empirical formula of Eq.(4.1) is easily integrated for derivation of a prediction formula of the depth difference h as in the following:
exp[ tahh ] (4.2) 0 where a is assigned the value of 0.109 for the access channel. This value is determined taking all available data into account.
Use of Eq.(4.2) enables to predict the change of mean water depth in the access channel. Figure 4.6 compares the predicted and measured mean channel depth for selected sections of the Inner and Outer channel. The prediction formula produces better agreement with measured depth data. In case of the Outer channel in Figure 4.6 (b), the predictions for the sections at KP16 (L07) and KP17 (L06) overestimate the measured results.
4-4 ‐6 ‐7
(m) ‐8 in
h ‐9 , KP2_pred ‐10 KP2_meas depth ‐11 KP3_pred ‐12 KP3_meas
mean ‐13 KP4_pred KP4_meas ‐14 KP5_pred Channel ‐15 KP5_meas ‐16 0 6 12 18 24 30 36 42 48 Elapsed time, t (month)
(a) Depth change prediction and measurement for the Inner channel
‐9
‐10 (m)
in ‐11 h , ‐12 KP20_pred depth
‐13 KP20_meas KP17_pred ‐14 mean KP17_meas KP16_pred ‐15 KP16_meas ‐16 KP15_pred Channel KP15_meas ‐17 0 6 12 18 24 30 36 42 48 Elapsed time, t (month)
(b) Depth change prediction and measurement for the Outer channel Figure 4.6 Comparison of predicted and measured channel depths for selected survey lines
4-5 4.3 Analyses of Siltation Processes in Channel
In Chapter 4.2, as the first step to predict the siltation the empirical model (Eq.(4.2)) is formulated, which is the exponential function (hereinafter referred to as “ the original Exponential Model” ). In order to improve this model, CEPA tried to conduct the spot re-dredging by using the rake. However, the data which is necessary for improving the original Exponential Model have not been obtained yet as explained (see Annex C.3).
Then, there is nothing else to do, an existing bathymetric data has been analyzed to understand the siltation processes, and also to look for the possibility of improving the model.
4.3.1 Siltation in Inner Channel Figure 4.7 shows the changes of water depths on the reference lines from L21 to L18, in which a brown line is the mean water depth in the Inner channel, a blue line and a green line are the depth at the western and eastern banks of the Inner channel, respectively. The periods of dredging are indicated by the gray belts. Among these bathymetric data, those in the Term A and in the Term B were selected for analyses because the dredging work was suspended in these two terms.
Figure 4.7 Changes of water depth on the reference lines from L21 to L18 in Inner channel
4-6 In Figure 4.7, paying attention to the Term A, the water depth linearly changed on all reference lines. That is, the speed of sedimentation was constant. On the other hand, the water depth in the Term B became shallower with relatively high speed just after the dredging and the speed became slower with a decreasing of water depth. In short, the water depth changed exponentially. The tendency of exponential change of water depth in the Term B is recognized on every reference line in Figure 4.7.
The reason why the water depth changed exponentially in the Term B is examined. The speed of sedimentation was faster just after the dredging, which is denoted by a red arrow for the data on the reference line L21 as an example in Figure 4.7. In order to check the situation in detail, three cross sections are superimposed in Figure 4.8 for the reference line L21. They are the cross section before the dredging in August, 2008 (which is denoted by “a” in Figure 4.7), that of December, 2008 just after the dredging (“b”) and that of 6 months after dredging in June, 2009 (“c”).
The cross section “a” (August, 2008) and “c” (June, 2009) are very similar to each other. However, the cross section “b” (December, 2008) is different from them in two points. First point of difference is the channel depth, which was due to the dredging of course. The second point is elevation of the tops of slope which is surrounded by red broken lines in Figure 4.8. The elevation of the tops of slope just after the dredging (“b”) is about 60cm lower than those of remains, which is undoubtedly unnatural.
Aug. 2008 Dec. 2008 Jun. 2009 abc 6 L21 7 8 9 10 11 12 13 14 15 16 -300 -200 -100 0 100 200 300
Figure 4.8 Superposition of cross section along L21
Figure 4.9 shows the similar superposition of the cross sections along the remaining reference lines of L20 to L18. The unnaturalness at the tops of slopes which is pointed out in Figure 4.8 is recognized on every reference line.
Seeing Figure 4.7 again, it is understood that the water depth at the eastern bank and the western bank were stable during 6 years from 2005 to 2011, except one case in December 2008, of which data are shifted downward. Therefore, it is probably due to some systematic error such as an inappropriate correction for the tide level or a mistaken of datum level.
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Figure 4.9 Superposition of cross section along L20~L18 In Figure 4.10, the cross section just after the dredging (“b” in Figure 4.7) along the reference line L21 has been shifted by 60cm upward by way of trial so that three cross sections are well overlapped. As a result, the consistency of cross sections as the whole is improved well. This correction is considered to be well adequate.
Aug. 2008 Dec. 2008 Jun. 2009
6 L21 7 8 9 10 11 ↑ 0.6m 12 13 14 15 -300 -200 -100 0 100 200 300
Figure 4.10 Superposition of cross sections after shifting, for L21 (Cross section in December, 2008 is shifted by 0.6m upward)
4-8
Figure 4.11 Superposition of cross section along the reference lines of L20 to L18, after shifting date obtained in December, 2008 upward In Figure 4.11, the cross sections along the reference lines of L20 to L18 are superimposed in the same way, by shifting the bathymetric data obtained in December, 2008 upward. An amount of shifting is written for each reference line in Figure 4.11. As a result, the consistency of cross sections as the whole are improved well, too. The tide level correction may be inappropriate for the bathymetric data obtained in December, 2008.
Next, the mean water depth measured in January, 2011 is examined, which is denoted by “d” in Figure 4.7. The water depth inside the Inner channel agrees approximately with that of outside. Therefore, there are two possible interpretation concerning to this data “d”.
a. The channel was full of sediments in January, 2011.
b. The channel had been already full of sediments in January, 2011.
In the latter case, it is necessary to identify the date when the channel was full of sediments, which should be some day between “c” and “d” in Figure 4.7. However, it is nearly impossible to identify the date of full sedimentation because there is no more data and information at present. It is strongly desired to resume and continue the monitoring on sedimentation.
In Figure 4.12, the data are corrected by way of trial, in which the water depth in December, 2008 (“b”) is shifted upward and time of full-sedimentation is backed from January, 2011 (“d”) to some day between (“c”) and (“d”) in Figure 4.12. An amount of shifting upward is depending
4-9 on the result of consideration in Figure 4.10 and Figure 4.11, while there is no evidence which supports an amount of going back to the past indicated in Figure 4.12. The purpose of preparing Figure 4.12 is to show the possibility that the change of water depth is constant, or speed of sedimentation is constant also in the Term B. If so, the characteristics of sedimentation in two Terms of A and B do not contradict each other.
The hypothesis that the speed of sedimentation is constant without depending on the water depth in the channel will have significantly important meanings. In short, even if the target of maintenance depth of channel increases, only the volume of initial dredging increases but the volume of maintenance dredging does not increase. In order to confirm a validity of this hypothesis, it is basically important to resume and continue the monitoring of sedimentation in the channel.
B
Figure 4.12 Corrections of depth data in Inner channel
4-10 4.3.2 Siltation in Outer Channel Figure 4.13 shows the locations of the reference lines in the Outer channel.
Figure 4.14 shows the changes of water depths on the reference lines from L08 to L05, in which a brown line is the mean water depth in the Outer channel, a blue line and a green line are the depth at the western and eastern banks of the Outer channel, respectively. The periods of dredging are also indicated by the orange belts.
Figure 4.13 Locations of reference lines in Outer channel
As all of water depth changes at the reference lines from L08 to L05 have nearly the same features, then that of L07 will be explained as a representative example. The mean depth in the Outer channel became deeper due to the dredging. Just after the dredging, the water depth in the Outer channel rapidly became shallow and it gradually became shallower with time in the following period. These two processes, which are rapid and slow siltation processes, have been considered simultaneously in the original Exponential Prediction Model.
The depth of full-sedimentation in the Outer channel predicted by utilizing the original Exponential Model in the Outer channel is nearly 1 meter shallower than the actual depth. Then the cause of discrepancy between the predicted depth and the actual one is examined.
As seen in Figure 4.14, in June, 2006, before the dredging, three kinds of water depth, which are the mean water depth in the Outer channel, the water depth of the western and the eastern banks outside the channel, were of equal. At the outside of the Outer channel, the water depth was kept almost constant on the western bank, while it increased, became deeper, gradually on the eastern bank. The water depth in the channel became shallower with time due to the siltation up to the same elevation as the eastern bank, which is lower than its original elevation before dredging in 2006.
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Figure 4.14 Changes of water depth on the reference lines from L08 to L05 in Outer channel
Next, the feature of cross section in full-sedimentation is examined on the reference lines of L08 to L05 in the Outer channel. The dredging periods in the Outer channel and the dates of bathymetric data which are utilized for consideration are shown in Figure 4.15. The three kinds of the bathymetric data are utilized, that is,
Data①(surveyed on 10 June, 2006); before the first dredging,
Data②(on 18 January, 2008); about 1 year and 4 months after the first dredging in 2006,
Data③(on 01 February, 2011); about 2 years and 8 months after the re-dredging in 2008.
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Figure 4.15 Periods of dredging in the Outer channel and the bathymetric data utilized for consideration
Figure 4.16 shows the superposition of three cross sections along the reference lines of L08 to L05. A black line is a planned channel section, toward which the dredging were conducted in 2006 and in 2008. It seems that the full-sedimentation occurred two times at all the reference lines, and there features are qualitatively same. Then, the feature of sedimentation along the reference line L07 will be explained as a representative example.
Figure 4.16 Situation of full-sedimentation along L08~L05 in Outer channel
4-13 Along the reference line L07, the sea bottom was flat in June, 2006, which was a situation before dredging. The first stage dredging was completed by 24 September, 2006. In January, 2008, which was about 1 year and 4 months after the dredging, the Outer channel was almost full with sediments. The volume of sedimentation was larger in the western area than in the eastern area of the channel. The sediments deposited asymmetrically inside the channel. Outside the channel, the change of the sea bottom topography was also asymmetrical. The sea bottom did not changed, being stable, in the western area from a point of -100 meters, while in the eastern area the sea bottom was eroded by January, 2008 and further by February, 2011. These features are also recognized in the cross sections along the remaining reference lines. It is the most important and interesting situation that the water depth in the channel is usually equal to or deeper than that of eastern bank on the every reference line. This condition should be taken into the original Exponential Model.
In addition, as the sedimentation occurred from the west, which made the width of channel narrow, an extra dredging in the westward direction may be required to widen the channel width in a future dredging.
4.3.3 Physical consideration for rapid siltation just after dredging Let’s move on to the next topic of rapid sedimentation. As already explained, just after the dredging, the water depth in the Outer channel rapidly became shallower. However, in the following period, that is to say in the Term A and in the Term B in Figure 4.14, the water depths became gradually shallower with a constant speed as approximated by the straight broken lines. The approximate straight line has the same gradient for every reference line in the Term A, and the approximate line in the Term B has another gradient which is the same for every reference line in the Term B.
By taking this situation into consideration, a new prediction model of siltation speed can be developed, which is a so-called linear prediction model of constant siltation speed. However, there is a hard barrier which refuses the introduction of the new model. If the approximate lines in the Term A and the Term B are extrapolated back to the past of just completing of dredging, there are large gaps between the extrapolated lines and the measured depths, which are indicated by red arrows in Figure 4.14. The measured depths are deeper. Then, there is a danger that the linear model underestimates the siltation speed just after the dredging.
Before discussing the process of rapid siltation, the slow siltation with a constant speed is examined. Based on the feature of sedimentation seen in Figure 4.16, the process of sedimentation can be conceptually explained as follows.
Figure 4.17 shows the sea bottom topography before excavating the channel. It is assumed that the sea bottom is flat and the sediment is transported from the left to the right. In the control segment B, if the volume of sediment transported into the control segment B is equal to that of going out from the segment B, the sea bottom does not change. In short, it is in the dynamic equilibrium condition. The same situation is established in the control segments A and C.
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Figure 4.17 Conceptual diagram of dynamic equilibrium condition before dredging
Let’s consider the condition that the channel is built in the control segment B, which is shown in Figure 4.18. The volumes of sediment going out and in the control segment A are the same as before. The dynamic equilibrium condition is still kept in the control segment A and the sea bottom does not change. The sediment transported into the control segment B deposits in the channel, then the volume of sediment going out decreases. As a result, the volume of sediment transported into the segment C becomes small. The volume of sediment going out from the control segment C is the same as before. The budget balance is lost, and the sea bottom is eroded in the control segment C.
Figure 4.18 Conceptual diagram of siltation in Outer channel
Figure 4.19 shows the superposition of cross sections along the reference lines of L07 and L06. During a period from October, 2006 to January, 2008, the dredging work was suspended. From the changes of cross sections, it can be seen the process of sediment accumulation from the west bank and the evolution of erosion in the east bank. A new knowledge we can obtain from Figure 4.19 is a situation that the accumulation continued with rising of the flat and horizontal bed in the east side in the channel which is surrounded by red broken lines. This is considered to be due to the deposition of sediment having high fluidity, e.g. fluid mud, in the east side in the channel.
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Figure 4.19 Superposition of cross sections along L07and L06
By taking these situations into account, it is inferred that the characteristics of sediment deposited during the second slow siltation in the Outer channel is as shown in Figure 4.20. In short, on the western side-slope the coarse material having the high falling velocity accumulated, while the sediment having the high fluidity such as the fluid mud deposited in the east side in the channel.
Figure 4.20 Spatial distribution of sediment
At last, the rapid siltation is examined. Let’s see Figure 4.14 again. The rapid siltation occurred two times, just after the first dredging and the second dredging. In the former rapid siltation
4-16 occurred between the depth of 12 and 13 meters, while in the latter it occurred around the depth of 14 meters. Then an occurrence of rapid siltation does not depend on the water depth, but depends on the timing of just after the dredging.
Figure 4.21 shows the superposition of cross sections along the reference lines from L08 to L05, which were surveyed on 24 April and 5 May, 2008, just after the completion of second dredging in 2008. Although there are small leaving parts of unexcavated earth in the cross sections on reference lines L08 and L07, the channel was dredged almost more than planned cross section.
Figure 4.22 shows the cross sections at the time of about 3 and half months after the dredging, 11 August, 2008, in which it can be seen that the rapid siltation occurred with the embedding thickness of 1.5 to 2 meters during this period. As accumulations were horizontal in the full width of channel on all reference lines, and there is no deposition on the side slope, it is inferred that high fluidity material, e.g. fluid mud, deposited in the channel. In short, just after the dredging, it is within the bounds of possibility that the rapid siltation occurred due to the inflow of high fluidity sediment which existed in the area surrounding the channel before dredging.
Figure 4.21 Superposition of cross sections just after the second dredging, (Surveyed on 28 April and 5 May, 2008)
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Figure 4.22 Superposition of cross sections, 11 August, 2008, about 3 and half months after the dredging
The siltation process in the Outer channel can be divided into two successive stages, that is to say, the rapid siltation in a few months just after the dredging and the slow siltation in the following period. In the first stage, the accumulation with high fluidity sediment were horizontal in the full width of channel, while in the second stage of slow siltation, as explained in Figure 4.18 and Figure 4.20, the deposition of coarse material on the western side-slope and the sea bottom erosion on the eastern bank, and the siltation of high fluidity sediment such as fluid mud occurred simultaneously. By taking these situations into account, it is inferred that the characteristics of sediment deposited in the Outer channel is as shown in Figure 4.23. In short, during a period just after the dredging, high fluidity material such as the fluid mud rapidly flowed into the channel and deposited horizontally there. After that, on the western side-slope the coarse material having the high falling velocity accumulated, while the sediment having the high fluidity such as the fluid mud deposited in the east side in the channel.
Figure 4.23 Spatial distribution of sedimentation
As explained in Figure 4.14, the rapid siltation just after the dredging does not depend on the channel depth, but on the timing of dredging. Then, the rapid siltation just after the dredging is also considered to be due to inflow of very movable sediment which existed surrounding the channel before excavation. If so, the rapid siltation may be the bound phenomenon only once in the channel newly excavated, and it does not occur in the case that the maintenance dredging is continuously conducted.
4-18 4.4 Siltation Prediction Models for Channel
4.4.1 Modifications of original Exponential Model In section 4.2, the prediction model for the depth change in the channel has been formulated empirically. However, a close examination on the siltation process based on the bathymetric data gives us two concerns. In the Inner channel, the bathymetric data obtained in December, 2008, just after the second dredging, is unnaturally shifted downward. In the Outer channel, the water depth in the channel did not become shallower than that of the eastern bank. By taking these concerns into consideration, the original Exponential Model is modified.
(1) Modification for Inner Channel The water depth in December, 2008, just after the second dredging, was deepest in the Inner channel during a period from 2006 to 2011. As the corresponding data was shifted downward, as shown in Figure 4.24 by example, it has been corrected by shifting upward. The results of correction to the reference lines L21 to L18 are shown in Figure 4.25, in which the original data in the Inner channel reproduced from Figure 4.4 are denoted by the symbol ○ and the corrected data are plotted by the symbol ●. As the whole data of cross section are shifted upward, the depth difference between inside and outside of channel does not change on an abscissa, while the siltation speed decreases on an ordinate.
Aug. 2008 Dec. 2008 Jun. 2009 abc 6 L21 8
10
12
14
16 -300 -200 -100 0 100 200 300
Figure 4.24 Gap of cross section, on reference line L21(Inner channel) (Reproduce from Figure 4.8)
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Figure 4.25 Siltation speed versus the depth difference in the Inner channel, after the correction of data
As seen in Figure 4.25, the slope of linear relation between the siltation speed and the depth difference decreases from a=0.109 to
a=0.089, (4.3) which is introduced into Eq. (4.2) for the Inner channel.
Figure 4.26 shows a comparison of the predicted curves by the original Exponential Model in the upper and by the modified one in the lower with the actual water depth in the Inner channel. The depth data corresponding to correction are surrounded by the red broken lines. After the modification of the original Exponential Model, in the lower figure, the slope of predicted curve around the depth from 9 to 14 meters becomes a little bit gentler than that of the original one, which means a decrease of siltation speed.
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Figure 4.26 Comparison of original and modified Exponential Model with the actual depth ( for Inner c)
(2) Modification for Outer Channel In the Outer channel, a shoaling of water depth due to siltation approaches asymptotically to the elevation of the eastern bank. Because the eastern bank is eroded after dredging, the water depth is deeper than that of before dredging. If the channel is left further without a maintenance dredging, the water depth will recover to the original depth before long, which is the same depth as that of the western bank. It is, however, considered that the depth of eastern bank is usually deeper than that of western bank when a maintenance dredging is conducted continuously.
The simplest method for taking the effect of eastern bank is shown in Figure 4.27. The water depth outside the channel, hout , and the depth difference between inside and outside the channel,
h0 , in the original Exponential Model are replaced with he and h0e respectively, which are defined in Figure 4.27. The water depth at the east bank, he , is called “final depth” hereinafter. The coefficient is fixed without change, being a =0.109.
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Figure 4.27 Modification of Exponential Model by introducing a concept of final depth ( for Outer channel)
Figure 4.28 Longitudinal profile of final depth he of Outer channel
Figure 4.28 shows a longitudinal profile of final depth, he , which is adopted in the calculation. A black line is the longitudinal profile of sea bottom before the first dredging, June 2006, and a blue line is the longitudinal profile of the Outer channel when it was in full-siltation, which is the mean profile of three data, that is February and August 2011, January 2012. The final depth on each reference line is determined so that it agrees with the mean profile. Figure 4.29 shows a comparison of the predicted curves by the original Exponential Model in the upper and by the modified one in the lower with the actual water depth in the Outer channel. By introducing the final depth in the model, the predicted curve and the actual water depth become to almost agree in the shallow area surrounded by a red dotted line. Furthermore, paying attention to the points denoted by red arrows in the figure, concerning to the reference lines of L07 and L06, it takes 12 months to shoal up to the depth of 11meters in the original model while it takes 18 months in the modified model. In short, the modification for the Outer channel also makes the siltation speed slow.
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Figure 4.29 Comparison of original and modified Exponential model with the actual depth (for Outer channel)
4-23 4.4.2 Linear model In section 4.2, it is explained that the siltation process in the Outer channel can be divided into two successive stages, that is to say, the rapid siltation just after the dredging and the slow siltation in the following period. The rapid siltation might be the bound phenomenon only once in the newly excavated channel. If this be so, the rapid siltation does not occur in the case that the maintenance dredging is continuously conducted. This hypothesis must be verified with the data. However, there is no more suitable data for it at present. In the second stage of slow siltation, the speed of siltation is constant without depending on the water depth in the channel. Therefore, as for a trial, a tentative linear model is formulated by picking up only the convenient data, which are the data such as that lying on the dotted lines in Figure 4.30.
Figure 4.30 Time variations of channel depth for Inner and Outer channels
In Figure 4.31, the mean siltation speed at each reference line is plotted. The mean siltation speed for Inner channel is 0.39 m/month in average, and that for Outer channel is 0.14 m/month.
dh .0 39 (Inner channel) v (4.4) dt .0 14 (Outer channel)
By integrating Eq.( 4.5), the water depth in the channel is obtained as the linear expression of the elapsed time,