1                                            Introduction

1.1                                      Introduction

In May 2005, the Castle Peak Power Company Limited submitted an application for an Environmental Impact Assessment (EIA) study brief (No. ESB-126/2005) to be undertaken on a Liquefied Natural Gas (LNG) Terminal and Associated Facilities at South Soko Island, and a submarine natural gas pipeline between Black Point and South Soko (Figures 1.1 and 1.2).  As the proposed development involves marine works (see Part 2 – Section 3.2.1, 3.2.3, 3.2.4, 3.2.6, 3.3.3, 3.3.4 and 3.3.5 for details of marine works required), potential impact on marine archaeological resources would be a concern.  Thus, a Marine Archaeological Investigation (MAI), in accordance with Clause 3.7.8.2(ii) of the Study Brief, was required.  This report was prepared by Bill Jeffery, a qualified marine archaeologist, detailing the MAI findings.

 

Figure 1.1      LNG Layout Plan at South Soko

1.2                                      Objectives of the Marine Archaeological Investigation

The objectives of the MAI were to include a phased review/investigation of the Study Areas in accordance with the MAI Guidelines as stated in ESB-126/2005, which should include the following:

·       Baseline Review on known sources of archive data as stated in Section 1.2 of the MAI Guideline;

·       Review of Geophysical Survey Raw Data prepared by CAPCO’s Geophysical Contractor EGS (Asia) Limited (EGS);

·       Review of Magnetic Survey Data prepared by CAPCO’s Geophysical Contractor EGS (Asia) Limited (EGS);

·       Remote Operated Vehicle Survey prepared by CAPCO’s Geophysical Contractor EGS (Asia) Limited (EGS);

·       Establish Archaeological Potential;

·       Provide a Report on these aspects.

This report represents the MAI results.

1.3                                      Report Structure

Following this introductory section, the remainder of the report has been structured as follows:

Section 2    The legislative framework for the marine archaeological assessments in Hong Kong;

Section 3    The methodology used in this survey;

 

Section 4    The findings of the baseline conditions (desktop and geophysical surveys) for the Study Areas;

 

Section 5    Establish archaeological potential of the Study Areas; and

 

Section 6    Assessment of the impact on the archaeological resources and recommendations.

 

2                                            Legislative Requirements and Evaluation Criteria

The following legislation and guidelines are applicable to the assessment of marine archaeological sites in Hong Kong:

·      Environmental Impact Assessment Ordinance (Cap. 499) and the associated Technical Memorandum on the EIA Process (EIAO-TM);

·       Antiquities and Monuments Ordinance (Cap. 53)(AM Ordinance);

·       Land (Miscellaneous Provisions) Ordinance (Cap. 28);

·       Hong Kong Planning Standards and Guidelines; and

·       Guidelines for Marine Archaeological Investigation prepared by AMO.

2.1                                      Environmental Impact Assessment Ordinance Technical Memorandum on the EIA Process

The EIAO-TM outlines the approaches required in investigating and assessing the impacts on marine archaeological sites.  The following sections of the EIAO – TM are applicable:

Annex 19:  “There is no quantitative standard in deciding the relative importance of these sites, but in general, sites of unique archaeological, historical or architectural value will be considered as highly significant.  A baseline study shall be conducted: (a) to compile a comprehensive inventory of places, buildings, sites and structures of architectural, archaeological and historical value within the proposed project area; and (b) to identify possible threats of, and their physical extent, destruction in whole or in part of sites of cultural heritage arising from the proposed project.”

The EIAO – TM also outlines the criteria for assessment of impact on sites of cultural heritage as follows: 

Annex 10:  “The criteria for evaluating impact on sites of cultural heritage includes:  (a) The general presumption in favour of the protection and conservation of all sites of cultural heritage because they provide an essential, finite and irreplaceable link between the past and the future and are points of reference and identity for culture and tradition; (b) Adverse impacts on sites of cultural heritage shall be kept to the absolute minimum.”

The EIAO – TM also outlines the approach in regard to the preservation in totality; and in part to cultural resources:

Annex 19:  “Preservation in totality will be a beneficial impact and will enhance the cultural and socio-economical environment if suitable measures to integrate the sites of cultural heritage into the proposed project are carried out.  If, due to site constraints and other factors, only preservation in part is possible, this must be fully justified with alternative proposals or layout designs, which confirm the impracticability of total preservation.”

2.2                                      Antiquities and Monuments Ordinance, Cap. 53

The Antiquities and Monuments Ordinance (Cap. 53) (AM Ordinance) provides statutory protection against the threat of development on Declared Monuments, historical buildings and archaeological sites to enable their preservation for posterity.  The AM Ordinance also establishes the statutory procedures to be followed in making such a declaration.

“This Ordinance provides for the preservation of objects of historical, archaeological and palaeontological interest…”

The Ordinance defines an antiquity as a relic (a movable object made before 1800) and a place, building, site or structure erected, formed or built by human agency before the year 1800.  The Ordinance also states, amongst other things, that the discovery of an antiquity shall be reported to the Authority (Secretary for Home Affairs); that ownership of all relics discovered after 1976 shall be vested in the Government; that the Authority can declare a place, building, site or structure to be a monument, historical building or archaeological or palaeontological site or structure (and therefore introducing certain additional controls for these sites); and that licences and permits can be granted for excavation and for other work.

Over the years, surveys have been undertaken to identify archaeological sites in Hong Kong.  The AMO has established boundaries for the identified sites and a set of administrative procedures for the protection of the known archaeological sites.  However, the present record of archaeological sites is known to be incomplete as many areas have not yet been surveyed.  There is a need therefore to ensure that the procedures and mechanisms, which enable the preservation or formal notification of previously unknown archaeological resources that may be revealed or discovered during project assessment or construction, are identified and implemented at an early stage of the planning of a project.

Section 11 of the AM Ordinance requires any person who discovers an antiquity, or supposed antiquity, to report the discovery to the Antiquities Authority.  By implication, construction projects need to ensure that the Antiquities Authority, the Antiquities Advisory Board (AAB) ([1]), is formally notified of archaeological resource which are discovered during the assessment or construction of a project. 

2.3                                      Land (Miscellaneous Provisions) Ordinance (Cap. 28)

Under this Ordinance, it is required that a permit should be obtained for any excavation within the Government land prior to any excavation work commencing.

2.4                                      Hong Kong Planning Standards and Guidelines

The Chapter 10, Conservation, of the HKPSG provides general guidelines and measures for the conservation of historical buildings, archaeological sites and other antiquities.

2.5                                      Marine Archaeological Investigation (MAI) Guidelines 

Guidelines for MAI which detail the standard practice, procedures and methodology which must be undertaken in determining the marine archaeological potential, presence of archaeological artefacts and defining suitable mitigation measures can be found in Appendix D of the EIA Study Brief No. ESB-126/2005.  Baseline review, geophysical survey and establishing archaeological potential are considered the first stage of a MAI.  Subject to the results of the first stage MAI, further investigation may or may not be required.

 

3                                            Assessment Methodology & Scope of work

3.1                                      Methodology

The methodology used in this assessment followed the Guidelines for MAIs as prepared by AMO and experience from the marine archaeologist and comprised the following tasks.

3.1.1                                Establish Baseline Conditions

·      Implement Desktop Research, comprising a review of geotechnical survey data, historical documents and United Kingdom Hydrographic Office ‘Wreck’ files to establish the potential for marine archaeological sites in the Study Area (South Soko terminal, gas pipeline, watermain and submarine cable);

·      Examination of the seabed and below seabed information using the geophysical survey equipment, magnetic survey and remote operate video (ROV) for the preferred gas pipeline alignment in order to locate and define any sites of archaeological potential in the Study Areas.

3.1.2                                Establish Archaeological Potential

The synthesis and analysis of the baseline conditions were used to establish if there were any marine archaeological sites in the Study Areas.

3.1.3                                Impact Assessment

Based on the findings and analysis of the baseline conditions, an assessment was made of the potential impact of the project on the marine archaeological sites, and recommendations made to mitigate any impact.

 

4                                            Baseline Conditions

4.1                                      Desktop Research

The review of the historical documents and literature indicated that the general region was occupied and used by Chinese, then many other foreign traders for many years.  The islands of the region contain archaeological evidence of occupation from about 4,000 years ago, including evidence of the use of the sea, and material from the seabed, during that time.  They became important trading centres for trading vessels from Arabia, Persia, India, IndoChina, the East Indies, and the Portuguese.  They also became bases for the many Pirates, given the region’s many maritime activities and therefore potential for plunder.

4.1.1                                Geotechnical Data

Generally, the submarine deposits in the Hong Kong region are subdivided into two formations, Chek Lap Kok Formations and the overlying Hang Hau Formations.

The Chek Lap Kok Formations, the lowest part of the Quaternary succession are considered to be Middle to Late Pleistocene in age and consists of colluvium, alluvium and lacustrine sediments Fyfe, et.al., (2000).  The marine sediments on top of this formation are sediments related to the Holocene period (from about 13,000 BP to the present day) and referred to as the Hang Hau Formations consisting of clayey silt sediments and some sand.

The Sham Wat Formation, found between Chek Lap Kok Formations and Hang Hau Formations is considered to be the Eemian deposit with uncertain age and consists of soft to firm silty clays with yellowish mottling.  This formation is presently not widespread but only in subcrops beneath the Hang Hau Formation ([2]).

More modern sediments are related to the discharge from the Pearl River, (and which would have an effect on the project area, being located down stream from the mouth of the Pearl River) having a seasonal discharge of about 370,000 million cubic metres each year ([3]).  They consist of sand, mud and some gravel.

Fyfe ([4]) further explains the rate of sedimentation:

“In general, present day sedimentation rates in Hong Kong waters are low, though they were undoubtedly greater earlier in the Holocene when sea level was rising rapidly. … Without tidal flushing, the sediment entering Victoria Harbour from the Pearl River, sewage solids and losses from dredging and reclamation might be expected to raise the seabed level by 40mm per year.  However, comparison of Hydrographic charts of Victoria Harbour from 1903 to 1980 revealed no conclusive evidence of net sedimentation, implying that the seabed is a state of dynamic equilibrium.  Assuming that sedimentation in Hong Kong waters began about 8 000 years ago, deposition of the 10 to 20 m of marine mud must have occurred at an average sedimentation rate of between 1.25 and 2.5 mm per year.  Available evidence indicates that the rate of Holocene sedimentation has not been steady.  Radiocarbon dating suggests that the majority of sedimentation has taken place over the past 4 000 to 5 000 years.”

During the late Pleistocene period (18,000BP) sea levels began to rise until about 6,000 years BP to levels similar to the present day.  “The extent of the rise could be as great as perhaps 140 metres in parts” ([5]).

The sediments of the Late Holocene period, considered to be relatively homogenous very soft to soft silty clay and with high moisture content, offers the greatest potential to include well preserved remains associated with the occupation and use of the islands in Hong Kong waters.  This is in contrast to the surface of the seabed which is often found to have been disturbed by fishing and other shipping related activities.  These remains could include shipwrecks.

4.1.2                                Review of Historical Documents

There is lack of precise historical document in relation to the maritime activities associated with the Study Area.  However, literature review indicated that the water channel between South Soko and Guishan Islands, namely the Lantao Passage or Lantau Channel was a famous route for vessels visiting Canton during the northeast monsoon season since the 15th century.  A battery was built in 1717 on the southwest headland of Lantau island at Fan Lau Kok ([6]).  The Soko Islands waters were marked as an anchorage place in the Chart of The China Sea from the Island of Sanciam to Pedrabranca of 1780 ([7]).  This indicated that vessels might anchor at the Soko Islands as a stop in the 18th to 19th centuries, and the water channel between southwest Lantau Island and Soko Islands has been an important vessel route during the northeast monsoon period since the 17th century.  Based on these above findings, it is believed that the marine area of the Soko Islands is considered to have archaeological potential. 

Marine archaeology is still a new area in Hong Kong.  In 1998, a study was undertaken on the potential, assessment, management and preservation of maritime archaeological sites in Hong Kong and to explore all aspects of the subject to ensure that the scope of all future work is feasible.  Review of the report identified no shipwreck recorded within the proposed marine works areas([8]).

4.1.3                                United Kingdom Hydrographic Office ‘Wreck’ Files 

The United Kingdom Hydrographic Office (UKHO) in Taunton maintains a database of known shipwrecks in the HKSAR.  The aim of the UKHO in keeping the database is to maintain a list of shipwrecks/obstructions that could be navigation hazards, wrecks through deterioration/corrosion over time become less of a navigation hazard but still remain on their database and if not removed could potentially become significant archaeological sites.  The UKHO database is only one source of data, albeit an important source of historical data on shipwrecks, that combined with other historical sources on other types of sites (as well as some types of shipwrecks) and the geophysical surveys, it provides a significant contribution in ascertaining if a region encompasses submerged archaeological deposits.

Annex 12-D-A and Figure Annex A1 provide a list of these sites, which are summarised as follows.

A total of 24 shipwrecks were found to be in a very broad area that included the three Study Areas.  Twelve of them are still ‘live’ (i.e. exist) and the remaining have been ‘lifted’/’dead’ from the seabed and nothing remains of them on the pipeline route (see Figure 4.24).  For the ‘live’ (either chartered or unchartered but potentially still lying on the seabed) shipwrecks, only two of them (No. 46602 and 62931) were found to be within 1 km of the Centre Line (CL) of the pipeline route and the associated facilities.  No. 62931 located about 928 m east of the CL and at 2462177m N, 792754mE and No. 46602 located about 57 m east of the CL of the proposed pipeline at 2481409m N,  795912m E(UTM, WGS84). 

The UKHO records state that Wreck No. 46602 was a 3130 ton Japanese freighter Shirogane Maru that was sunk during World War II.  Its position was last verified by a diver on 20th October 1987.  Wreck No 62931 is referred to as an ‘obstruction’, its position is accurately known but no other details recorded – it is potentially not even a shipwreck.  The identity of wreck No. 46537 is also unknown apart from it being 14 m in length.

Chart No. HK1503 has an Obstruction marked (“Obstn”) at the location of Wreck No. 46602 and which is recorded as a Wreck on Chart 3026 (Dated 1990).  One of the other UKHO Wrecks (No. 62931) also appears on this chart.

The Hong Kong Marine Department could not provide any additional information beyond what was provided by the UKHO. The geophysical survey (which was very comprehensive, as outlined below) failed to locate either wrecks Nos. 46602 or 62931 and this would indicate that they have been salvaged/lifted or removed for unknown reasons.

Discussions were also carried out with the Hong Kong Marine Department about a wreck adjacent to Sha Chau/Lung Kwu Cha that had been lifted in March 2006 from a location about 700 m north of the pipeline CL.  The wreck is a Chinese engineering vessel mostly damaged and approximately 10 m x 3 m x 2 m in size.  It is estimated that the wreck was about 30 years old (see Figure 4.24 for location).  Shipwrecks/Obstructions are continually salvaged in Hong Kong waters and it is potentially what happened to the two ‘live’ wrecks on the UKHO Wrecks Database.

4.2                                      Geophysical Surveys

4.2.1                                Introduction

The objective of the geophysical survey was to define the areas/sites of greatest archaeological potential by establishing the depth and nature of the seabed sediments and mapping any seabed and sub-bottom anomalies, which may be archaeological material.  This information is provided below.

4.2.2                                Survey Scope

The survey scope (see Figure 4.1) of the Geophysical Survey covers the following:

·      Proposed Approach Channels, Turning Circles and Reclamation Areas at South Soko covering 715 km2 of seabed;

·      A 500 m wide corridor was surveyed, centred on the preferred option of the proposed gas pipeline route from South Soko to Black Point with route length of 39 km, a total of 1,145 km of line survey;

·      A 400 m wide corridor was surveyed, centred on the proposed power cable route survey from Shek Pik to South Soko with route length of 8 km, 140 km of line survey;

·      A 504 km line of geophysical records, in a corridor stretching from the north west of Lantau to close to the southern boundary of the Sha Chau and Lung Kwu Chau Marine Park; and

·      A 15km route length, 300-500 m wide corridor inshore of the area to the west of Lantau. 

4.2.3                                Survey Methodology

Geophyscial Surveys were undertaken by CAPCO contractor, EGS (Asia) Limited (EGS), between May and September 2005, February 2006, April to June 2006.  Side Scan Sonar and Boomer data was collected from 20 m tracks (along the length of the various routes).  These tracks, in the case of the Side Scan Sonar survey overlapped at least three other tracks, providing a comprehensive coverage of the area.  Cross traverses every 100 metres were also implemented.  A similar thorough Side Scan Sonar and Boomer survey was implemented at all the other impacted areas off Black Point and South Soko using similar distances between tracks and cross tracks.  The vessel track plot of the surveys are presented in Figures 4.2a and 4.2b, 4.3a to 4.3m and 4.4a to 4.4b.  These surveys allowed for a comprehensive investigation of the seabed, and below the seabed.

4.2.4                                Equipment Used

·      Multi-Beam Echo Sounder (Seabeam 1180 multi-beam system, 180 kHz transducer and cable, Anschutz Raytheon Gyrostar II gyrocompass, Seatronix MRU 5, Valeport Model 600 temperature/salinity profiler);

·      Single-Beam EchoSounder (Knudsen Model 320 survey echo sounder, Dual frequency transducer, Bar Check);

·      Navigation & Positioning (C-Nav DGPS System w/ 50m cables, C-Nav Antenna Stand, Navigation PC, Navigation Monitor, Marine Radio, Hand Held Radio Set w/ Charger);

·      Sub-bottom Profiler (C-Boom low voltage boomer system, EGS TVG Processor, C-Phone hydrophone system, 120/138 Waverley Recorder);

·      Side Scan Sonar System (Klein 3000 side scan sonar system);

·      Measurement of Currents (RD Instruments acoustic Doppler current profiler (ADCP));

·      Magnetometer (‘SeaSPY’, manufactured by Marine Magnetic Ltd); and

·      Other Computer facilities (C-View Logging System & monitors, C-View Int. System, Printers (B/W), UPS for computer systems).

4.2.5                                Review of Geophysical Survey Results

The geophysical survey data obtained by EGS were processed by in house geophysicists and reviewed by the marine archaeologist.  The geophysical surveys showed how the seabed in the different Survey Areas had been impacted by anchoring, trawling (Figure 4.5) and the dumping of materials (Figure 4.6).  Anchoring and trawling will reduce the archaeological potential of the seabed in these areas as will the dumping of materials, although this activity can also enhance the archaeological potential by providing a protective covering over sites (it can also interfere/damage sites through this activity).  It makes it very difficult, potentially impossible to assess the archaeological potential of these parts of the seabed.  Seismic records found the underlying sediments on the route close to Lantau have been worked and reworked, caused by scouring and deposition from the strong currents.  In addition, the surveys located a total of 255 Sonar Contacts([9]) comprising natural features, dumped materials, shipwrecks, linear debris, anchor marks and fishing devices.  Further review of the 255 Sonar Contacts identified 14 which are considered as wrecks, possible wrecks or sites of archaeological potential (Table 4.1 and Figure 4.7).

 

Figure 4.5       Geophysical Survey Showing How The Seabed Was Impacted By Anchoring & Trawling

Figure 4.6       Geophysical Survey Showing How The Seabed Was Impacted By The Dumping Of Materials


Table 4.1        List of the 14 Sonar Contacts

Contact number

Latitude

Longitude

Easting

Northing

KP

RPL offset

Dimensions (m)

Description

SC014

22° 24.389' N

113° 52.407' E

795836.0E

2480649.0N

34.039

198m E

6m x 1.3m x 0.3m

Possible wreck

SC020

22° 24.360' N

113° 52.354' E

795745.0E

2480594.0N

33.977

96m E

13m x 5m x 0.25m

Possible wreck

SC027

22° 21.253' N

113° 52.268' E

795708.0E

2474854.0N

28.227

33m E

39m x 6.5m x 2m

Wreck

SC028

22° 20.235' N

113° 52.237' E

795691.0E

2472974.0N

26.338

5m W

8m x 2m x 0.2m

Possible wreck

SC043

22° 12.320' N

113° 49.589' E

791415.0E

2458273.0N

10.491

176m W

6m x 2m x 0.5m

Possible wreck

SC044

22° 12.304' N

113° 49.628' E

791482.0E

2458244.0N

10.437

126 W

6m x 2m x 0.5m

Sites of Archaeological Potential

SC053

22° 10.885' N

113° 50.471' E

792981.0E

2455651.0N

7.384

743m SW

3m long

Linear Debris

SC055

22° 10.742' N

113° 51.264' E

794350.0E

2455413.0N

6.013

107m SW

14m long

Linear debris

SC067

22° 10.546' N

113° 51.276' E

794377.0E

2455052.0N

5.874

373m SW

12m x 3m x 0.5m

Sites of Archaeological Potential

SC072

22° 10.074' N

113° 53.422' E

798084.0E

2454250.0N

2.103

277m N

8m x 3m x nmh

Sites of Archaeological Potential

SC086 ([10])

22° 24.388' N

113° 54.072' E

798693.9E

2480702.4N

39.148

1572m SW

10.77m x 3.31m x 2.03m

Possible wreck

SC090

22° 9.876' N

113° 54.338' E

799667.0E

2453914.0N

0.440

19m N

5m x 2m x 0.2m

Sites of Archaeological Potential

SC091

22° 9.923' N

113° 54.411' E

799791.0E

2454003.0N

0.309

118m N

18m x 4m x 0.9m

Possible wreck

SC092

22° 9.991' N

113° 54.488' E

799921.0E

2454132.0N

0.168

236m N

9m x 2m x 0.5m

Wreck

The 241 Sonar Contacts discounted as wrecks, possible wrecks or sites of archaeological potential were based on a combination of factors, which included the interpretation and a comparison of the geophysical signatures with those signatures that were clearly wrecks (and possibly wrecks), debris and dumped materials.  Wrecks as seen in the side scan sonar images have identifiable relief (as seen in the shadows they develop on the side scan sonar images) and features that could be considered not-natural, such as straight lines delineating its boundaries.  In comparison, debris could show relief but it is characterised by natural, rounded features and boundaries.  Dumped materials and some debris were characterised by areas of a darker/black section of the seabed on the side scan sonar images consisting of coarser materials/sediments with little or no relief.  The assessment also included the context of the Sonar Contact with its surrounding seabed environment, where identifiable dumped materials/debris was found to be in the very near vicinity.  The raw data for all the Sonar Contacts was reviewed by the marine archaeologist using the above criteria and 14 contacts were interpreted as wrecks, possible wrecks, linear debris or sites of archaeological potential. Sonar Contacts 079 and SC082 , while initially identified as debris/wrecks , upon review of the side scan sonar images by the marine archaeologist using the above criteria were interpreted as debris/dumped materials and this is illustrated in the SC082 case (see Figure 4.7a).

Figure 4.7a     A Further Review and Interpretation of SC082 Was Based on Its Context with the Nearby Dumped Materials, Its Physical Appearance and Lack of Relief.

In some sections of the survey area, a small number of ‘masked zones’ are referred to.  This applied to some of the seismic data, where gas masking affected the interpretation of the sediments/formations but only below the Hang Hau Formations (the zone which most likely to contain archaeological deposits).  The side scan sonar data was not masked, so there were no gaps in the geophysical surveys from an archaeological perspective.

All of these 14 anomalies are sitting on the seabed.  A review of the boomer data failed to identify any sub-bottom anomalies.

Based on the side scan sonar results, six of the anomalies are problematic about their identity but were labeled as ‘linear debris’ or ‘sites of archaeological potential’ and worthy of further investigation, including  SC044 (Figure 4.8), SC053(Figure 4.9), SC055(Figure 4.10), SC067 (Figure 4.11), SC072(Figure 4.12) and SC091(Figure 4.13).  While it is quite likely that others, such as SC014 (Figure 4.14), SC020 (Figure 4.15), SC028 (Figure 4.16), SC043 (Figure 4.17), SC086 (Figure 4.18) and SC091 (Figure 4.19) are possibly shipwrecks, there was still a degree of doubt given the problematic side scan sonar survey images of these anomalies.  Some of the side scan sonar results revealed without doubt shipwrecks, e.g. SC027, (Figure 4.20) and SC092 (Figure 4.21). 

 

 

Figure 4.8       Site of Archaeological Potential (SC044)

 

Figure 4.9       Linear Debris (SC053)

Figure 4.10     Linear Debris (SC055)

 

 

Figure 4.11     Site of Archaeological Potential (SC067)

 

Figure 4.12     Site of Archaeological Potential (SC072)

 

 

Figure 4.13     Linear Debris (SC090)

Figure 4.14     Possible Wreck (SC014)

Figure 4.15     Possible Wreck (SC020)

Figure 4.16     Possible Wreck (SC028)

Figure 4.17     Possible Wreck (SC043)

Figure 4.18    Possible Wreck (SC091)

Figure 4.19     Possible Wreck (SC086)

Figure 4.20     Wreck (SC027)

Figure 4.21     Wreck (SC092)

It was this degree of doubt in some of the sites as well as the possibility that the recognisable shipwrecks could be modern sites, i.e., post-1800 (the date which AM Ordinance defines an antiquity as a relic) that prompted the recommendation that a Magnetic Survey was conducted of the above sites to ascertain how much ferrous material remains on the anomalies.  While pre-1800 ships would have carried ferrous equipment and used ferrous material in their construction, post-1800 ships, particularly the larger ships of the size of SC027 could potentially be modern ferrous barges that are used today in and around Hong Kong.  It was considered that the amount of ferrous material detected during a Magnetic Survey and in association with the site descriptions already obtained during the side scan sonar survey, an indication on the age (through the nature of the remains) of the sites could be obtained.  EGS had already performed a limited Magnetic Survey along the gas pipe route and cable route centre lines, but it was conducted from the point of view of identifying modern utility cables/pipelines along the pipeline centre line and around South Soko and on review it was found not to be useful in assisting in identifying ferrous equipped shipwrecks.

4.3                                      Magnetic Survey

For the purpose of the MAI, a Magnetic Survey covering the 14 Sonar Contacts as presented in Table 4.1 was undertaken by EGS from 2 to 4 September 2005([11]).

4.3.1                                Survey Scope and Methodology

Magnetometers have been used in maritime archaeology for about 40 years to locate and map shipwrecks, both iron shipwrecks and non-ferrous shipwrecks (Green, 2004: 62-73)[12].  Ferrous material (such as anchors, cannons, nails, chain, etc.) contained in a shipwreck will change the intensity of the earth’s magnetic field and this change in intensity can be measured with a magnetometer sensor towed behind a boat.  For a typical object (such as a shipwreck) the intensity of the magnetic anomaly varies as the inverse of the cube of the distance from the anomaly and the unit of measurements is known as a nano Tesla (nT). The SeaSPY magnetometer used in this survey can detect changes in intensity of less than 1 nT. A 5 nT change in intensity will detect a 10 tonne shipwreck at 45 metres, a 10kg cannon ball at 3 m and a 2 tonne cannon at 27 m (Green, 2004: 63). Conversely, a 10kg cannon ball will produce a change in intensity of c.2-3 nT at 5 m (distance from sensor to seabed in this survey) and a 2 tonne cannon will be produce a change in intensity of c.600 nT at 5 m.

When searching for shipwrecks, magnetometers use wide search lanes, perhaps 50, 100 or hundreds of metres depending on the size of the anomaly to provide an exact location, with little detailed information about the nature of the anomaly. In this survey, the SeaSPY magnetometer was used to implement close-plot surveys over small areas of a number of sites, using a maximum of 5 m search lanes and with the instrument capable of taking a reading every 0.25 second. This enabled detailed magnetic contour plans to be developed which in association with other surveys, such as other remote sensing surveys can assist in ascertaining the nature of a site. These accurate contour plans can help to locate discreet anomalies such as cannons, anchors, even iron fittings used in wooden hull construction.[13] Large intensity anomalies without many discreet anomalies could be single objects, such as a cannon, an anchor, an engine, dumped materials and the ship itself if constructed of ferrous material.

It is highly unlikely that timber vessels of any size from small sampans to large junks would not contain some ferrous material.  Iron nails have been found in use on Chinese ships dating back to 220BC, together with the use of iron adzes and chisels used in their construction and maintenance ([14]).  Some pieces of iron equipment in the form of anchors, grapnels, guns, machinery have also been used on Chinese junks for over 1000 years.  The quantity and distribution of the ferrous material (found through an analysis of the intensity of the anomaly and an examination of the close-plot contour plans) will in association with the other surveys help to identify the nature of the site and was the major objective of the magnetic survey.

The survey covered the 14 Sonar Contacts identified by the Marine Archaeologist as presented in Table 4.1.  For each of the Contacts, survey lines around 100m long were surveyed, with a line spacing of 5 m (see Figures 4.1 and 4.22a to 4.22i).   The 100 m line lengths were selected to allow time for the magnetic sensor to be deployed close to the seabed and moving smoothly at a fixed level by the time it passed across the feature.  The line interval of 5 m was selected as magnetic anomalies decay rapidly with distance from the ferrous material (usually an inverse cube relationship), and a wider spacing risked completely missing a magnetic anomaly.

Turbidity and Visibility Readings

For each of the surveyed areas of the 14 Sonar Contacts, a vertical profile of turbidity was recorded, with closely spaced readings close to the seabed and wider spacing close to the sea surface.  The turbidity sensor was attached to a Secchi disc, so that the greatest depth that visible objects could be seen from the survey boat was also recorded.

Magnetometer

The magnetometer was deployed 15 m behind the survey vessel, to separate the magnetometer sensor from the magnetic effect of the vessel’s steel engine.  In shallow water close to coastlines, in less than around 5 m of water, the sensor and cable were buoyed with floatation material to keep them close to the sea surface.  In deeper waters away from the shore, non magnetic (brass) weights were attached to the sensor so that it would sink down close to the seabed.  The position and quantity of these weights was adjusted until the pressure sensor attached to the magnetometer showed that the magnetometer sensor was within 5 m of the seabed, without striking the seabed.

The magnetic field strength measured in the sensor was transmitted up the towing cable to the survey vessel, where the values were logged together with the navigation information on a computer logging system.

Positioning and Navigation

Surface positioning was provided by GcGPS during all of the work: C-Nav provided primary positioning with a one sigma standard deviation of 0.5 m for this project.  A C-Nav antenna provides the GcGPS position of the vessel on a C-Nav decoder.  For each position update, an NMEA string (GGA, VTG) was sent from the C-Nav decoder directly to the computer logging the navigation and magnetometer information.

4.3.2                                Magnetic Survey Results

For each survey line, the regional gradient and diurnal variability was subtracted from the measured values using proprietary EGS software, leaving the background geological magnetic field; in Hong Kong, this is mostly around 44,500nT to 45,000nT.  The remaining magnetic anomalies associated with ferrous material at the seabed or buried at shallow depth were contoured and displayed in Figures 4.23a to 4.23k at a scale of 1:500.  These drawings also show the location of seabed features mapped from the earlier phase of the survey. 

Some of the anomalies have significant variations from the surrounding background which is associated with the features containing ferrous material.  Others had no noticeable magnetic variation beyond the level of natural variability expected in these readings, indicating little ferrous material around these locations.  The results are summarised below in the description of the magnetic surveys.

The vertical profile of turbidity measurements and the Secchi disc depths are presented in Annex 12-D-B.

The turbidity readings and Secchi disc depths suggest that visibility near the seabed will be less than 1 m for much of the route, so it is likely to be difficult for divers to make a visual inspection of these features.  The outcomes of the Magnetic Survey is presented in Table 4.2.

Table 4.2        Outcomes of the Magnetic Survey

Survey number

Sonar Contact

Intensity of anomaly

Conclusion

M01

SC092

500nT

Confirms presence of ferrous material

M02

SC091

>1,000nT

Confirms presence of ferrous material

M02

SC090

No change with surrounding environment

No ferrous material

M03

SC072

No change with surrounding environment

No ferrous material

M04

SC055

No change with surrounding environment

No ferrous material

M05

SC067

No change with surrounding environment

No ferrous material

M06    

SC053

No change with surrounding environment

No ferrous material

M07

SC043

>1,000nT

Confirms presence of ferrous material

M07

SC044

No change with surrounding environment

No ferrous material

M08

SC028

>1,000nT

Confirms presence of ferrous material

M09

SC027

700nT

Confirms presence of ferrous material

M10

SC020 and  SC014.

No change with surrounding environment

No ferrous material

M11

SC086

>1,000nT

Confirms presence of ferrous material

 

4.3.3                                Interpretation of the Magnetic Anomalies

Of the 14 Magnetic Anomalies part of M02 (SC090), M03(SC072), M04 (SC055), M05(SC067), M06 (SC053), part of M07 (SC044), M10 (SC014 & SC020) contained insufficient ferrous material for the magnetometer to record any magnetic anomaly.  The magnetic sensor was within 5 m of the seabed/sonar contact and only a 1-4 nT magnetic variation was detected around SC014, SC020, SC044, SC053, SC055, SC067, SC072 and SC090 and which could be explained as ‘background noise’, related to the movement of the cable or sensor during the magnetic survey, or the variability in the nature of the seabed([15]).  If these particular Sonar Contacts were timber vessels with no or little ferrous fastenings, equipment, stores or cargo then they may not produce any addition to the 1-4nT variation.  However, it is considered that a vessel of pre-1800 would contain some ferrous fittings, equipment, stores or cargo that would provide a significant change (greater than 1-4nT) in the earth’s magnetic field given the magnetic sensor was within 5 m of the Sonar Contact.  Another possibility is that these anomalies are very old, pre Iron Age vessels, but given their location, i.e., exposed on the seabed, this is not realistic. Coupled with their problematic Side Scan Sonar results it is concluded that Sonar Contacts 014, 020, 044, 053, 055, 067, 072 and 090 are natural features and or debris and not of archaeological potential. 

In association with the side scan sonar results, it is concluded that SC027, SC028, SC043, SC086, SC091 and SC092 are vessels or man-made structures of some sort and potentially pre-1800.  Given the size of the magnetic intensities at the distance of the magnetic sensor to the Sonar Contacts they are considered not to be solely made of iron, but are of a composite material, possibly timber and iron/steel. While they could be pre-1800, they could also be post-1800 as many composite vessels are from this era as well.  It also concluded that SC027 in particular has the potential, through its size and the Side Scan Sonar image to be a modern steel barge.  However, the 700nT magnetic intensity is far too low if this was the case and it is potentially an interesting archaeological site.

In summary, the magnetic survey results has eliminated 8 Sonar Contacts from those identified through the side scan sonar surveys and enhanced the potential of the remaining 6 and which require further investigation.

4.4                                      Remote Operated Video (ROV)

As mentioned above, six Sonar Contacts were identified as possible sites of archaeological potential (see Table 4.3 and Figure 4.24 for details).  In order to identify their nature and age, an inspection of the sites was undertaken on the 15th February 2006, carried out by EGS using their Remote Operated Vehicle (ROV) from their work-boat and employing EGS staff (six in total) to operate the ROV, the positioning equipment (DGPS) and boats.  The ROV is a small piece of equipment that contains a video with lights and is controlled by an operator on the boat.  It can be propelled (using a surface generator attached with a cable to the ROV) to move about in the water.  However this model (Titan) cannot operate against much current and needs to be used as a ‘drop camera’, i.e., to be simply dropped onto the site to be inspected and to be moved by operators with ropes from the surface (see Figures 4.25(i) & 4.25(ii)).  The ROV was dropped on some of the sites from the work-boat (Figure 4.25(iii)) and the sampan depending on current and site location (Figures 4.25(iv)).

Table 4.3        List of the Six Sites of Archaeological Potential

Contact number

Latitude

Longitude

Easting

Northing

KP

RPL offset

Dimensions (m)

Description

SC027

22° 21.253' N

113° 52.268' E

795708.0E

2474854.0N

28.227

33m E

39m x 6.5m x 2m

Wreck

SC028

22° 20.235' N

113° 52.237' E

795691.0E

2472974.0N

26.338

5m W

8m x 2m x 0.2m

Possible Wreck

SC043

22° 12.320' N

113° 49.589' E

791415.0E

2458273.0N

10.491

176m W

6m x 2m x 0.5m

Possible Wreck

SC086

22° 24.388' N

113° 54.072' E

798693.9E

2480702.4N

39.148

1572m SW

10.77m x 3.31m x 2.03m

Possible wreck

SC091

22° 9.923' N

113° 54.411' E

799791.0E

2454003.0N

0.309

118m N

18m x 4m x 0.9m

Possible Wreck

SC092

22° 9.991' N

113° 54.488' E

799921.0E

2454132.0N

0.168

236m N

9m x 2m x 0.5m

Wreck

Most videos will work in low lux (amount of luminosity) values of 5-15 lux (10 lux is early twilight or light from 60 watt bulb from 3 m away; 1 lux is late twilight; and 0.1 lux is light from a full moon).  It was anticipated that the water in the vicinity of the sites would be turbid (from suspended sediments) and most likely with a very low lux value.

Tides during the day were 0.5 m at 0505; 1.5 m at 1117; 1.0 m at 1607; and 2.1 m at 2239. The weather was overcast, either fog, pollution or a combination and which would have only contributed slightly to the gloomy underwater visibility.

4.4.1                                ROV Results

1.           SC092 (10:30am) (Figure 4.26(i))

This site is located adjacent to South Soko island in 4m of water and was not found during the ROV survey. Visibility was in the order 20-30cm. The seabed was flat silty-mud. Sea conditions were calm with little breeze. Given the same weather/seabed/visibility conditions were encountered on the adjacent site SC091, in which it was possible to discern the nature of the shipwreck, a further survey is recommended for SC092 as it may provide data to identify it.

2.           SC091 (12 noon)

This site is also located adjacent to South Soko island in 4m of water (about 100m south of SC092). The visibility was about 20-30cm. The seabed was flat silty-mud. Sea conditions were calm with little breeze. The site was found during the ROV survey and was characterised by a large number of coils of rope/rigging which was interpreted to mean the site is a recent shipwreck and not 206 years old (1800 and beyond is the date for which a site is defined as an archaeological site and should be protected) (see Figure 4.27 for the video clips record).  

Figure 4.27   Video Clips Showing SC091

3.           SC043 (1:40pm)

This site is located adjacent to western end of Lantau island in 23m of water and was not found during the ROV survey. Sea conditions were calm with little breeze. The visibility was zero, the water had a very muddy appearance on the surface, unlike SC091 and SC092 (see water colour in Figure 4.26(ii)). Some current (c. 1/2 knot) was experienced.

4.           SC028 (3:20pm)

This site is located adjacent to the existing marine park in 6-7 m of water and was not found during the ROV survey. Sea conditions were calm with little breeze. The visibility was zero, the water had a very muddy appearance on the surface. Some current (c. 1/2 knot) was experienced.

5.           SC027 (4:15pm)

This site is located adjacent to the existing Marine Park in 7 m of water and was not found during the ROV survey. A slight increase in wind was found on this site. The visibility was zero, the water had a very muddy appearance on the surface. Some current (c. 1/2 knot) was experienced. This is the largest site and nothing at all could be seen on the ROV video (Figure 4.26(ii) for the area around 027_028).

6.           SC086 (5:35pm) (Figure 4.26(iii))

This site is located about 20m from the rocks at Black Point in 7 m of water and was not found during the ROV survey. The visibility was zero, the water had a very muddy appearance on the surface, the same as SC043, SC028 and SC027. There was a slight breeze and given the busy shipping activity in the vicinity, there was at times a choppy sea. The ROV Video camera did show what was most likely rocks (or possibly wreckage) and the remains of some fishing nets (see Figure 4.28 for the clip of video record).

Figure 4.28   Video Clips Showing SC086

4.4.2                                ROV Conclusions

There are a number of issues to address in terms of the impact of the project on the sites.

SC91 was shown from the ROV to contain rope and due to its exposed condition would not be expected to be found on a site that was 206 years old in these waters, i.e. pre-1800.  A visual survey requires some visibility and the 20-30 cm visibility found on SC091 was adequate given the lights on the ROV.  It is considered that SC091 is of no or low archaeological potential, however, due to the poor visibility in the sea, the wreck cannot be clearly seen.  For the rest of the sites (SC027, SC028, SC043 and SC086), as there was a lack of visibility, the nature of the sites could not be determined.  For SC092, the site could not be located from the survey due to poor visibility.

Given the lack of visibility for most of the sites (and most likely to be encountered all the time on these sites) and low visibility of two sites, it was not possible to conduct a visual survey of these sites with the current ROV or divers.  The presence of fishing nets found on SC086 also makes diver surveys hazardous for this and the other sites that could contain nets, given their prominence on the seabed and the likelihood of trapping nets.

It was recommended that a more detailed remote sensing work incorporating multi beam sonar and side scan sonar data be undertaken for the sites so that the sonar data could be used to develop three dimensional models that could be rotated and viewed at different angles.  These very accurate virtual models are the closest thing to viewing the real site and are currently the best system that can be used in nil visibility situations.  In combination with more detailed side scan sonar surveys and the existing magnetometer data (or closer plot magnetometer survey data) it may be possible to identify rope or other modern artefact/equipment that will confirm the nature and age of the sites.

It is problematic if diver surveys would be more useful in determining the nature of the sites. The ROV with its low lux values can ‘see’ better than human eyes and while a diver can feel objects, he/she may not be able to produce objective results in the form of drawings as they would be reliant on their memory or the translation of their surface, diving supervisor when noting their descriptions. It was considered more useful to implement a multi beam survey which produces objective and recordable results and in combination with the other remote sensing surveys provides for more comprehensive and independent assessments.

4.5                                      Side Scan Sonar and Multi Beam Sonar Survey

Further to the ROV result, a further detailed Side Scan Sonar and Multi Beam Sonar Surveys was undertaken by EGS on the 6th and 7th April 2006 covering the six Sonar Contact numbers including SC027, SC028, SC043, SC086, SC91 and SC92.  Survey track plots are shown in Figures 4.29 to 4.34.  

4.5.1                                Survey Methodology

The main equipment used for the survey is shown in Table 4.3.

Table 4.3       Equipment Used for the Side Scan Sonar and Multi Beam Sonar Surveys

Survey System

Manufacturer

Model Number

Swath Bathymetry

Reson A.s.

400 kHz 8125

Side Scan Sonar

Klein Associates Inc

System 3000

Positioning

C&C Technologies Inc

C-Nav GcDGPS

Navigation

C-Products Ltd

C-View Nav

4.5.2                                Swath Bathymetry

The navigation receiver was placed vertically above the swath transducer mounted on the side of the survey vessel.  As the vessel travelled along the survey traverses, the system transmitted a fan of echo sounder beams down into the water column to map the shape of the sea bed in great detail.  The geometry is illustrated in Figure 4.35.

Figure 4.35   Illustrations of Swath Bathymetry Systems

At each location, the survey vessel sailed along four traverses around the artefact, “boxing in” and isonifying the sonar contact from each side. The measurements from each side were combined into a single image using the QinSys processing software supplied with the swath system.  The level of each sounding has been colour coded, using a spectrum of colours to represent the range of levels found at each location.  To give the impression of looking at the sonar contact from different directions, the image has been rotated in three dimensions before capturing the image. The images are presented in the results.

4.5.3                                Side Scan Sonar

At each location, the survey boat sailed along four traverses to box in the sonar contact and isonify it from each direction, as for the swath measurements. The side scan sonar fish was towed behind the survey vessel a few metres above the sea bed. As it travelled along the survey traverse, the transducers emitted sound pulses to either side and measured the echoes from features on the sea bed.  The arrangement is illustrated in Figure 4.36.

Figure 4.36   Schematic Illustration of Side Scan Sonar System Operation

A dual frequency (100 kHz and 500 kHz) system was used.  The echoes for each frequency were recorded separately using the C-View acquisition system.  Amplifier gains were applied to compensate for geometrical dispersion of the wave intensity with distance: no other processing was applied. 

The images for each pass were examined and the clearest images for each contact were selected for printing in the results.

4.5.4                                Side Scan Sonar and Multi Beam Sonar Surveys Findings

After EGS completed the Side Scan Sonar and Multi Beam Sonar Surveys, an analysis of this new data in context with the earlier survey work (side scan sonar survey and magnetometer data) was carried out by the marine archaeologist.  The results are presented below under each Sonar Contact.

SC027

The site was identified as a shipwreck and the most obvious of all the sites being about 39 m (length) x 6.5 m (breadth) x 2 m (height) as can be seen in the side scan image (see Figure 4.37), surveyed in 2005.

Figure 4.37     Side Scan Sonar Image of SC027

The magnetometer survey carried out between the 2nd to 4th September 2005 found the anomaly to contain about 700 Nanotesla (nt) more than the surrounding seabed/sub-bottom material.  This was estimated to be about 1-2 tons of iron/steel.  Given the relatively large size of the shipwreck, one ton of ferrous material is indicative of this shipwreck being a wooden vessel containing a number of ferrous fittings (perhaps fastenings, chain, water tank, etc.)

The further side scan sonar survey carried out on the 6th and 7th April 2006 failed to locate the anomaly.  This was not a result of poor navigation as grid coordinates within a few metres of the 2005 location were reproduced in the outcomes of this further survey (see Figure 4.38).  The shipwreck has either been intentionally removed or unintentionally moved (from storms/currents) as is verified by examining the side scan sonar image (see Figure 4.39); the multi beam sonar image (see Figure 4.40) and C-view bathymetric data (see Figure 4.38).  The disturbed area of seabed as seen in these images is a shallow depression of about ½ m, where it once had nearly 2m elevation.

Figure 4.38     Bathymetric Data of the Same Area (The Yellow Region is the Same Depression as in Figure 4.40 and Coloured Blue) and Showing the Coordinates of the Position; 795703E, 2474862N.

Figure 4.39  Showing Area where Shipwreck had been Located

Figure 4.40     Multi Beam Sonar Image with the Area in Darker Blue, Being a Depression of About 0.5m Deep and With Only a Very Small Fragment with Any Elevation in the Middle of the Image.

Conclusions

This shipwreck was moved prior to the April 2006 remote sensing surveys.  The ROV survey in February 2006 failed to locate this shipwreck and it was concluded at that time, that the nil visibility was the factor it could no be seen, but it is highly likely to have been moved before the date of this survey.  Its new location is unknown and a further survey undertake confirmed that it is not found in the proposed pipeline route. 

SC028

The side scan sonar survey implemented in 2005 found an anomaly located at 795691.10E, 2472975.41N. The site was identified as SC028 and had the dimensions, 8m x 2m x 0.2m as shown in Figure 4.41.  It had the appearance of some type of man-made object possibly a small sampan.

Figure 4.41     The Small Anomaly (Left of Centre in this Image)

The magnetometer survey found this anomaly to contain in excess of 1,000nt more that the surrounding area.  This was estimated to be about 2-3 tons of ferrous material and given the size of the anomaly, the Sonar Contact could be interpreted as a wooden vessel containing a reasonable amount of iron/steel, or some other type of man-made object, possible even some type of dumped materials consisting of ferrous materials.

During the side scan sonar survey of the 6th and 7th April 2006, no similar side scan image could be obtained (see Figure 4.42) suggesting that these remains have also been removed/moved and which was verified through the multi beam sonar survey which only showed a depression in the seabed (see Figure 4.43).

Figure 4.42  SC028 Remains in the Centre (under the text 30m) of this Image

Figure 4.43     A Multi Beam Sonar Survey Image of a Black Hole (Depression) which Indicates the Position of SC028.  A Small Sand Bar Lies Next to the Hole (White Mass to the Left of the Hole)

Conclusions

It also appears that this wreckage has been removed or moved.  The combination of the shadow (from something proud of the seabed) on the initial side scan sonar image and the 1000nt magnetic anomaly would tend to indicate something more than the present depression and small raised sand bar was located in this position.  While it is a possibility, from the sonar and magnetic data, that this shipwreck could be interpreted to be a small motor vessel similar to the one shown in SC086, it could also have been some other type of man-made object, possible even some type of dumped materials containing ferrous materials.

SC043

The side scan sonar survey implemented in 2005 found a 6m x 2m x 0.5m “possible wreck” at 791415E, 2458273N (see Figure 4.44).

Figure 4.44     The Initial Side Scan Sonar Image of SC043

The magnetometer survey found this anomaly to contain in excess of 1,000nt more that the surrounding area.  This was estimated to be about 2-3 tons of ferrous material and given the size of the anomaly, the possible wreck could be interpreted as a wooden vessel containing a reasonable amount of iron/steel or some other type of man-made object, possible even some type of dumped object consisting of ferrous materials.

During the 6th and 7th April side scan sonar and multi beam surveys, the anomaly was re-located.

Figure 4.45 is a high resolution scan but with slightly different orientations provide different and inconclusive results as to the nature of the anomaly.      

 

Figure 4.45  SC043 Image from two different angle (Left: in the Centre, Right: Centre )

The multi beam sonar survey also provided inconclusive results as to the nature of SC043 (see Figures 4.46 and 4.47).

Figure 4.46     Only a Small Section is Proud of the Seabed (Shown as Orange and the Square End is Suggestive of a Bow or Stern of a Small Sampan)                        

Figure 4.47     Another View of the Small Anomaly (SC043)

Conclusions

The relatively small physical size of the anomaly, the comparatively large amount of ferrous material and the possible sampan shape and collapsed nature is suggestive indicative of a small motorised wooden sampan.  On the other hand this anomaly could be some other type of man-made object, possibly even a dumped object.

SC086

In the side scan sonar survey in 2005, the following assessment was made of this anomaly.  A vessel of about 10.77m x 3.31m x 2.03m and located at 798694E, 2480702N (see Figure 4.48).

Figure 4.48     A Vessel Located in the Middle of the Image, Located close to the Rocks at Black Point

The magnetometer survey found this anomaly to contain in excess of 1,000nt more that the surrounding area. This was estimated to be about two to three tons of ferrous material and given the size of the anomaly, this site was interpreted as a wooden vessel containing a reasonable amount of iron/steel.

On the 6th and 7th April 2006 the area was surveyed with the multi beam sonar and the side scan sonar and better images of the vessel were obtained (See Figures 4.49 to 4.52.

Figure 4.49     Side Scan Sonar Image of SCO86 UNDERTAKEN in April 2006 (Centre)

Figure 4.50    General View of the Vessel by the Multi Beam Sonar

Figure 4.51     Sampan with What Looks Like a Hole Towards One End of the Vessel

Figure 4.52     Plan View of Sampan Confirming Damage in the Hull

Conclusions

The vessel and its location has all the appearances of a ‘recent’ motorised wooden sampan (see Figure 4.52).  Located close to the rocks at Black Point and effected by the swells breaking over it, and the continual sea traffic, the vessel could not be expected to maintain its integrity for very long (perhaps months or just a year or so).  Seats can be seen in the vessel and it shows damage to its hull which is considered to have been caused from its continual movement underwater and/or sinking.  A vessel of pre-1800 age would not be in this condition in this location but a modern vessel illustrated in Figure 4.53 could be. The Marine Department salvaged a similar looking sampan on the 22 March 2006 (see Figure 4.24 for its location and Figure 4.54) which they reported was about 30 years old.  SC086 is probably of a similar vintage.

Figure 4.53     A Motorised Sampan of about the Size of SC086

 

Figure 4.54     Recently Recovered (by Marine Department) Sampan with Dimensions very similar to SC086 (Source: Marine Department )

SC091

The side scan sonar survey of 2005 classified this sonar contact as a wreck of 18m x 4m x 0.9m and located at 799794E, 2454000N (see Figure 4.55).

Figure 4.55     Bottom Right Hand Corner of Image with ‘Shadow’ Providing the Height of the Vessel

The magnetometer survey found this anomaly to contain in excess of 1,000nt more than the surrounding area.  This was estimated to be 2-3 tons of ferrous material and given the size of the anomaly, this site was interpreted as a wooden vessel containing a reasonable amount of iron/steel.

On the 15th February 2006, the ROV video survey provided images of this vessel.  Coils of rope, or cable could be seen lying within the vessel and what could have been iron/steel fittings.

On the 6th and 7th April 2006 the area was surveyed with the multi beam sonar and the side scan sonar and better images of the vessel were obtained (See Figures 4.56 to 4.58).

Figure 4.56     Side Scan Sonar Image of Vessel and Debris Field

Figure 4.57    Modern Work Vessel and Scattered Debris

Figure 4.58     A Possible Propeller Shaft and Propeller Located a the Lower Right End of the Image/Boat

Conclusions

The shape and nature of this vessel is indicative of a modern working vessel. It appears to contain an engine (as shown by the propeller) and the size of the magnetic anomaly is also indicative of this.  The rope/rigging that was seen during the ROV survey is indicative of a vessel of only a few years in age, rather than something that is pre 1800.

SC092

The side scan sonar survey of 2005 concluded this sonar contact to be a wreck of about 13m x 1.1m x 0.6m and located at 799910E, 2454136N (see Figure 4.59). In another side scan sonar view of the site the dimensions were provided as: 9m x 2m x 0.5m.

Figure 4.59    The Sampan Looking Vessel Designated SC092

The magnetometer survey found this anomaly to contain about 500nt more that the surrounding area. This was estimated to be about one ton of ferrous material and given the size of the anomaly, the wreck was interpreted as a wooden vessel containing a reasonable amount of iron/steel.

On the 6th and 7th April 2006 the area was surveyed with the multi beam sonar and the side scan sonar and further images of the vessel were obtained (See Figures 4.60 to 4.63).

Figure 4.60    Side Scan Sonar View of the Sampan undertaken in April 2006

Figure 4.61  The Raised and Squared Bow or Stern

Figure 4.62    The Site is Possibly Another Sampan of Poor Condition

Figure 4.63    The Anchor Scar Adjacent to the Site

Conclusions

The vessel appears in April 2006 to be in much the same condition as in the 2005 side scan sonar survey.  It is similar in size and shape (although narrower, from one set of measurements) to the sampan at Black Point (SC086) and in slightly worse condition. The nature of the remains is suggestive of a more modern vessel and not something that is pre 1800.

If the larger length/narrow beam set of measurements are more accurate and given the narrow breadth (beam) of the vessel, it is possible that the boat is a dragon boat. Dragon boats can vary in size, an International Racing Standard Dragon Boat is 12.5m (length) x 1.16m (breadth). The other possibility is that the vessel is something like the longer vessel shown in see Figure 4.64.  Either of these possibilities don’t fit well with the amount of ferrous material found on the site as they would possibly not have contained much iron or steel.

Figure 4.64     Model of a Vessel Used in Hong Kong Waters, Similar in Size to SC092 (Macau Maritime Museum)

The 2006 survey shows a line (scar) on the seabed adjacent to the vessel which was not apparent in 2005.  It is most likely this is from an anchor being dragged along the seabed, indicating an anchor was dropped nearby and dragged away from the site, or an anchor was dragged adjacent to the site and then raised.  There is the likelihood that the vessel has been damaged in this process.  It is also possible that the scar is the result of the vessel being dragged to its present location.

4.5.5                                Further Side Scan Sonar and Multi Beam Sonar Surveys Findings for SC027 and SC028

As SC027 and SC028 were not identified from the April 2006 survey, if the two wrecks are still surviving within the proposed gas pipeline route, potential impact on these two contacts due to the installation of the gas pipeline would be a concern.  Marine Department was consulted to check if any vessels had been removed recently adjacent to SC027 and SC28.  It is confirmed that apart from the vessel recovered in March 2006 (see Figure 4.54), no other vessels were recovered by the Marine Department.   Therefore, it is considered necessary to undertake further survey to confirm if they are still within the proposed gas pipeline route.    On the 2nd June 2006, EGS implemented a further survey of a more extensive area surrounding the original locations of SC027 and SC028 and within the pipeline route.  Using the same multi beam sonar and side scan sonar equipment and processes as in the 6th and 7th April surveys, four vessel tracks spaced 20 m apart covered an area of 4,300m x 100m (Figures 4.1 and 4.65).

The surveys confirmed the disappearance of SCO27 finding a large shallow depression where the shipwreck was once located (see Figure 4.66).

Figure 4.66     Side Scan Sonar View of SC027

The surveys also confirmed a depression containing different sediments in the original location of SC028, but no feature containing any elevation indicative of a shipwreck sitting proud of the seabed, as was originally found (see Figure 4.67).

Figure 4.67     Side Scan Sonar View of Original Location of SC028

The surveys failed to locate any feature that could be construed to be either SC027 or SC028.

 

5                                            Impact Assessment

Review of the UKHO data identified two ‘live’ shipwrecks within 1 km of the centre line of the pipeline route and the associated facilities (nos. 46602 and 62931).  The comprehensive Geophysical Surveys undertaken for this study covering the area where shipwreck nos. 46602 and 62931 indicated no such shipwrecks exist within the marine area of the proposed development where seabed disturbance may occur.  Since the geophysical survey covered comprehensively the potential impacted area, the shipwrecks may have been removed for unknown reasons.  The geophysical survey data (which included magnetometer data along the CL) covering the locations of these two shipwrecks were thoroughly checked.  Wreck no. 46602 (which is within 20 m of the CL) was a 3130 ton Japanese frighter (length 318 m x beam 45 m x draught 24m) and with a superstructure of many more meters in height.  The depth of water for its location is 4-5 m.  If it was still in the location recorded by the UKHO at the time of the geophysical surveys, it would not have been unobserved.  It must have been removed – it could not have deteriorated to an extent where is is not evident.  The only other possibility is that its location is incorrect, but a similar coordiate location is recorded in the UKHO files for several years and it is the only “obstruction” recorded in this location.  Therefore, its incorrect location is not a possibity for being unobserved in the survey data. 

While no information is available about wreck no. 62931 that would assist in its interpretation (apart from it being recorded by the UKHO as an obstruction, and therefore it is possible that it is not a shipwreck).  It was not observed during the review of the geophysical data.  The most obvious conclusions to be drawn from it not appearing on the survey data, is that it has been removed or it was of a nature that could have deteriorated to such an extent that makes it unobservable in the survey data.

Nevertheless, the Geophysical Survey and Magnetic Survey identified six Sonar Contacts comprising SC027, SC028, SC043, SC086, SC91 and SC92 to have marine archaeological potential.  They were considered to be possible wrecks.  In order to investigate their nature and age, further surveys comprising a Remote Operated Video Survey and a further detailed side scan sonar survey and multi beam sonar survey were undertaken. 

The results indicate that SC043 was some type of man-made object, possibly the remains of a motorised sampan and even a recently dumped object. The combination of its physical size and shape (from the multi beam and side scan sonar surveys) and its magnetic intensity does suggest a site of post-1800 in origin. It is not suggestive of a cannon or anchor related to a pre-1800 site given its physical size, shape and magnetic intensity. Sonar Contacts 086 and 092 were concluded to be motorised sampans and SC091 was concluded to be a motorised work boat. In the context with the Antiquities and Monuments Ordinance (Cap. 53), these four sites are not considered an antiquity or relic and of no archaeological value.  Thus, due to the lack of archaeological value of the sites, impact to them is considered acceptable.

Sonar Contacts 027 and 028 could not be re-located with the subsequent detailed side scan sonar survey and multi beam survey. Further investigative surveys to confirm their whereabouts failed to relocate them within the immediate surrounds.  It is therefore concluded that SC027 and 028 have been intentionally or unintentionally moved out of the pipeline route and the pipeline poses no threat to these sites.

 

 

6                                            Conclusions and Recommendations

Review of the UKHO shipwreck record identified two shipwrecks (no. 46602 and no. 62931) adjacent to the proposed pipeline route and the associated facilities.  However, the comprehensive Geophysical Surveys undertaken for the study indicated that these shipwrecks no longer exist within the marine area of the proposed development where seabed disturbance may occur.  It is highly likely that these shipwrecks/obstructions may have been removed for unknown reasons.  Nevertheless, Geophysical Survey, Magnetic Survey, Remote Operated Video Survey and a further detailed side scan sonar survey and multi beam sonar survey were undertaken to identify marine archaeological potential sites within the marine area of the proposed development where seabed disturbance may occur. 

Six sites considered to be shipwrecks were identified from the survey. It is concluded that three of them are motorised sampans or work boats and another possibly the remains of a sampan or possible some other type of recent man-made object.  They are not considered to be an antiquity or relic in the context of the AM Ordinance. 

Two other sites, while initially located in the pipeline route were removed before subsequent surveys and the opportunity to provide a more comprehensive assessment. Further surveys failed to relocate these shipwrecks in the pipeline route it is concluded that the pipeline project poses no threat to these sites.



([1])      The Antiquities and Monuments Office is the entry point to pass information to the AAB.   The AAB is a statutory body consisting of expertise in relevant fields to advise on any matters relating to antiquities and monuments.

([2])     Fyfe, J.A., R. Shaw and et al. 2002. The Quaternary Geology of Hong Kong, Hong Kong: Civil Engineering Department.

([3])     Ibid.

([4])     Ibid.

([5])     Fyfe, J.A., R. Shaw and et al. 2002. The Quaternary Geology of Hong Kong, Hong Kong: Civil Engineering Department .

([6])     Siu, K.K. 1997 Fort and Batteries: Coastal Deference in Guangdong during the Ming and Qing Dynasties, Hong Kong, Hong Kong Museum of History.

([7])     Empson, H 1992 Mapping Hong Kong: A Historical Atlas, Hong Kong: Government. Printer.

([8]) Ali, Sarah 1998 Study on the Potential, Assessment, Management and Preservation of Maritime Archaeological Sites in Hong Kong. Hong Kong: Lord Wilson Heritage Trust

([9]) One of the Sonar Contact is located within the Black Point terminal.

([10])       This is located within the Black Point terminal over 1km from the proposed submarine gas pipeline.

([11]) The numbering in the plans do not reflect the numbers shown in the above table

([12])       Green, J.G., 2004, Maritime Archaeology: A Technical Handbook Elsevier Academic Press California

([13])       See Green, 2004:159-162 for details of a close-plot survey of the Dutch shipwreck Amsterdam and which provides, amongst other things a good outline of the timber hull shape.

([14]) Maitland, D., 1981, Setting Sails. A tribute to the Chinese Junks. South China Morning Post. Hong Kong

[15]         EGS geophysicists concluded that the 1-2nT was ‘natural variability expected in these readings’