Survey Vessels

12.8.17 A Class III commercially licensed survey vessel was used to carry out the offshore survey. As the water depth is very shallow over the inshore part of the survey area, a motorised sampan was used for the survey. During the survey period carried out by this motorised sampan, the Class III commercially licensed survey vessel was in attendance to comply with Marine Department regulations.

Coverage

12.8.18 Survey lines were run as illustrated on the Hydrophone Track Plots. The presence of an Oyster bed, approximately from 814210E 836650N to 814455E 836325N within the survey corridor prevented complete adherence to the survey plan.

Echo Sounding, Seismic Profiling and Side Scan Sonar

12.8.19 The seismic profiling and side scan sonar surveys were carried out simultaneously with the echo sounding survey. A swell filter was used to minimise the effects of surface waves from the seismic records. The side scan sonar was towed from the stern of the survey waves at a depth of 5 to 15m below the sea surface. Data was recorded digitally throughout the seismic survey. The echo sounder was calibrated using the 'bar check' method at the start and end of every survey period.

Land Based Magnetic Survey

12.8.20 The land based, GSM-19 magnetometer was set up at Chung Hom Kok prior to the commencement of the survey. The magnetic field base readings from 15:46:32 on the 7th January 2002 to 11:11:41 on the 11th January 2002 were averaged to generate a background value of 44850.2nT. The base and survey magnetometer crystal controlled clocks were synchronised with reference to the GPS time at the commencement of the survey and compared for relative drifts at the completion.

Marine Magnetic Survey

12.8.21 The depth sensor inside the marine magnetometer was calibrated at the commencement of the survey. The recording parameters for the survey were listed as follows:

Vessel Speed : 2.0 - 3.0 m/sec
Fix Interval : 10 seconds
Fish Depth : 2m
Sampling Rate : 1 reading per second (Marine Magnetometer)
Sampling Rate : 1 reading per 3 seconds (Chung Hom Kok Base station)

Site Safety

12.8.22 Safety was generally in accordance with the 'Marine Geophysical Operations Safety Manual' (International Association of Geophysical Contractors, Eighth Edition, 1996).

12.9 Results - Baseline Review

Physical Setting

12.9.1 Located in the northwest New Territories near the market town of Yuen Long, the shores of Deep Bay were historically one of the major agricultural areas of the north-western New Territories. The shallow soils surrounding Deep Bay in the salt-marches close to the sea produced a form of brackish-water paddy crop in the late summer. This rice was considered somewhat inferior to better quality rice produced from more fertile inland valleys such as Lam Tsuen and Shatin (Ng, 1983).

12.9.2 In Deep Bay, the coastal area comprises low-lying mud flats and brackish back swamps. Mangroves fringe the shoreline and the mud flats are a refuge for a wide variety of crustaceans and other fauna. This is the most important mangrove habitat in the HKSAR (Pitman & Peck, 1979). Figure 12.7 presents a photograph of the Study Area. Accretion of sediment around the roots of the mangroves had led to a seaward extension of the mud flats and consequently of the coastline. To the south and around the southern coast of the western New Territories, the granite of the Castle Peak area forms a shoreline of low relief.

12.9.3 The English name, Deep Bay, is a complete misnomer as the water depth nowhere exceeds 5m. The bay is a sheltered inlet on the eastern margin of the Pearl River estuary with a relatively large catchment. Inter-tidal channels occur along the eastern margin of the bay where the Sham Chun and Shan Pui rivers discharge fresh water into the bay. Both the northern and southern shores of Deep Bay comprise mud flats with mangroves. Prior to reclamation and the creation of ponds in the last century, the mudflats were more extensive and tidal influences extended further inland.

Fisheries and Oyster Production

12.9.4 Fishing and oyster gathering were major local activities since the mid-eighteenth centuries. Both were undertaken mainly by boat-dwelling Tanka and Hoklo people. Later there was considerable Punti participation in the oyster industry. Land-dwellers were also involved in coastal fisheries, either as part-time stake-net operators along the coastline or full-time as brackish or fresh-water pond-fish farmers. There were two thousand six hundred and ninety eight mu of fishponds registered in what was then Sun On County in 1898; many of them were in the Deep Bay area of the county (Ng, 1983). Fish-ponds were a major source of revenue in the Deep Bay area until the late 1980s, when many were filled in to provide building land.

Rural Reclamation Work

12.9.5 Gei-wai or salt-paddy reclamation is the process of reclaiming small piecemeal areas of land from shallow tidal areas by means of small weirs. These are flushed out over a period of several years with fresh water and then planted with varieties of salt-resistant paddy. The land gradually silts up and raises slightly above sea level. This process was undertaken in slow phases by local farmers for generations along the shores of Deep Bay and work was done on a more extensive basis in the 1920s and 1930s.

12.9.6 The shoreline of Deep Bay has, as a direct result of gei-wai reclamation, moved steadily northwards over the past century. Yuen Long's Tin Hau Temple, which dates in parts from the mid-eighteenth century, was once located on or very near the Deep Bay coastlines. It is now over 2 kilometres inland. From this, we can infer that any archaeological resources that may have once been in its vicinity are both deep underground and very far from the sea.

European Contacts in the Vicinity of Deep Bay

12.9.7 Reference has been made in numerous works to the early Portuguese presence at Lintin and Tuen Mun, both in the immediate vicinity of Deep Bay. Castle Peak and the Deep Bay are clearly marked in O Livro de Francisso Rodrigues, (Translated by Armando Cortesão as The Suma Oriental of Tomé Pires and The Book of Francisco Rodrigues, originally written in 1514). Rodrigues was a very early Portuguese pilot, cartographer and captain who sailed in these waters in the early sixteenth century. Rodrigues was one of the commanders of Alvares' flotilla during the voyage from Malacca to China in 1517-18 (Braga, 1955). His book contains the earliest maps of the region drawn by a European based on actual observation and by men who were familiar with the places depicted. Maps tended to be approximations drawn from the oral accounts of professional pilots, usually Malay or Arab.

12.9.8 The first European navigator known to have reached the China coast, a Portuguese named Jorge Alvares, made his landfall in 1513. Alvares commenced his mission in Malacca, now in Malaysia, that the Portuguese had captured in 1511. Merchandise brought from China, especially porcelain, fetched extremely high prices, with good quality ceramics fetching twice their own weight in silver when re-sold at Goa. Instead of relying on Chinese traders, the Portuguese intended to establish a sea-route to China, and purchase for themselves at source.

12.9.9 Most of Alvares' time was spent at Lintin, the island known as "Solitary Nail" in Chinese due to its sharply-pointed shape. The Portuguese named it Tamão - an approximation of the Cantonese pronunciation of Tune Mun - and the name appears on many old maps of the Pearl River Delta.

12.9.10 The local mandarinate at Tuen Mun anchorage, headquartered at nearby Nam Tau, received the Portuguese in a friendly manner and trade commenced. A padrão or stone carved with the Portuguese cross and crest was erected by Alvares at Lintin, though nothing of it now survives. These stones functioned more a marker of passage for later seafares than as a territorial claim, and were erected wherever the Portuguese mariners sailed, from Mombasa and Ormuz to western India and the Moluccas. They are still to be seen in some of these places today. Alvares' young son accompanied him on the voyage from Malacca, but he died at Lintin and was buried at the base of the padrão erected by his father.

12.9.11 Alvares' flotilla remained at Tuen Mun for ten months, only returning to Malacca when the south-west moonsoon winds permitted them to sail. While not given much freedom of movement, traders visiting Lin Tin were not as closely confined by the Chinese authorises as in later centuries, and while it is not recorded, it is highly likely that Alvares and his men visited the nearby mainland.

12.9.12 Jorge Alvares made two more voyages to China, in 1519 and again in 1521. On what was his last voyage to the China coast, he died on 8th July 1521 and was buried beneath the padrão in the same spot at his son (Braga, 1955). No trace reamins today of the padrão. Ming Dynasty gazetteers record that in 1516 the Portuguese came again, but the Chinese under Naval Commander Wang Hong defeated them (Ng, 1983).

12.9.13 Later the Portuguese navigator Simao Peres de Andrade built a fort in the neighbourhood of Deep Bay without receiving permission from the Chinese to do so; in 1521 a Chinese naval force attacked the Portuguese in the vicinity and defeated them (Ng; 1983).

Shipwreck Data

12.9.14 Practically nothing is known about the archaeological potential of the seabed deposits in Hong Kong. The only marine archaeological discovery was that of a later Sung/early Ming Dynasty boat exposed during construction of the High Island Reservoir, near Sai Kung (Frost, 1974). Since then, no other historic shipwreck has been found. However, this is probably because there were no dedicated marine archaeological surveys until the introduction of the 1998 EIA Ordinance. Marine archaeology is therefore a new area of study in Hong Kong with very little baseline data to draw upon.

12.9.15 Formation of archaeological sites underwater is mainly due to shipwrecks (Muckelroy, 1978). Since these are random and haphazard events it is difficult to predict their exact location if no written references survive. A combination of geophysical and diver survey is the most efficient method for accurately assessing the archaeological potential of the seabed.

12.10 Results - Archieve Research

12.10.1 The UK Hydrographic Office (UKHO) holds a database of surveyed shipwrecks in Hong Kong, including those not shown on Admiralty Chart. There are no records of shipwrecks within the study area.
12.10.2 The UKHO holds navigation charts of the study area dating from 1899 (Figure 12.9) and 1966 (Figure 12.10). These charts are particularly useful as they may show wrecks which have been subsequently buried or broken up. A 1905-1909 British War Office Map (Figure 12.11) is also of interest as it shows the lack of development in the study area.

12.11 Geophysical Survey

Sounding Data

12.11.1 The influence of wave action was corrected in real time by the motion compensator. The smoothed sounding data was then digitized and reduced to levels below Principal Datum using the measured tidal data.
Interpretation of Side Scan Sonar Records

12.11.2 Processing was carried out as follows by EGS:

· The features in the side scan sonar data were interpreted and marked on the original records.
· The marked features were digitised and plotted.
· The plotted seabed features were checked by reconciling them with the original raw side scan records, and making final adjustments accordingly.

12.11.3 The side scan sonar records collected over this area are characterised by the following features:
· Extensive areas of oyster beds (Figure 12.12)
· Man made navigation channel
· Trawl marks (Figure 12.13)
· 5 Unidentified Features (Figures 12.14 to 12.17)

12.11.4 All of the features listed above are drawn onto the Seabed Features Charts. Figure 12.18 shows the distribution of the 5 Unidentified Features. There are no magnetic anomalies associated with the Unidentified Targest.

Interpretation of Seismic Profiler Records

12.11.5 Record quality was slightly affected over parts of the survey area by masking within and close to the base of the Marine Deposits: such masking is probably caused by the anaerobic decomposition of organic plant material trapped during a recent inundation. The gas bubbles so generated absorb the seismic energy, thereby preventing reflections from deeper horizons (Permchitt et al, 1992). In this case, such masking was both patchy and variable, enabling the identification of deeper horizons on th seismic records in many of the affected areas.

12.11.6 Processing was carried out as follows by EGS:

· Seismic horizons were selected for interpretation and highlighted on copies of the seismic records during preliminary interpretation.
· All traverse crossing points were then calculated and marked on the seismic records.
· The records were then physically correlated at all of these points.
· The correlated horizons were digitized, plotted and contoured.
Seabed Stratigraphy

12.11.7 Geophysical survey data enables (1) establishment of the marine geology and (2) the archaeological preservation potential of the marine sediments. The survey data will be discussed in terms of its relevance to the marine archaeological investigation; it is not appropriate to provide full geological analysis of the study area.

12.11.8 The following general succession applied to this area:

-------------------------------------------------------------------- Sea Bed

RECENT DEPOSITS

(soft silty CLAY or clayer SILT)

-------------------------------------------------------------------- Base of Recent Deposits

MARINE DEPOSITS (Hang Hau)

(Soft Silty CLAY, or clayer SILT, sometimes

Sandy at the base and close to the shorelines)

-------------------------------------------------------------------- Base of Marine Deposits

ALLUVIUM (Chek Lap Kok)

Silty, Sandy CLAY or fine to medium

Silty SANG

--------------------------------------------------------------------- Top of Grade V Rock

DECOMPOSED ROCK

Silty fine/coarse SAND, fine sandy SILT

--------------------------------------------------------------------- Top of Grades III Rock

GRADE III ROCK

Pink, grey coarse grained granite

---------------------------------------------------------------------

12.11.9 Based on data from numerous borehole records and seismic surveys of the territory, the Hong Kong Geological Survey has mapped the offshore surficial deposits (e.g. Strange & Shaw, 1986; Langford et al, 1989; Strange et el, 1990). The subdivided the submarine deposits into two formations: the pleistocene Chek Lap Kok Formations (alluvial/estuarine deposits) and the overlying Holocene Hang Hau Formation (marine muds). Recently, the stratigraphy has been refined Fyfe et al., (1997; 1999), and the Sham Wat (~130-85 ky.) and/or Waglan (~85-10 ky.) Formations (both shallow marine units) are sometimes positioned between the Chek Lap Kok and Hang Hau Formations.

The Hang Hau Formation

12.11.10 From an archaeological perspective, the marine sediments assigned to the Hang Hau Formation have the greatest archaeological potential.

12.11.11 The formation consists of relatively homogenous very soft to soft, greenish grey silty clay (Fyfe et al., 1997) and has a high moisture content. Therefore, the Hang Hau Formation sediments potentially provide an excellent substrate for the preservation of archaeological material. Additionally, the soft nature of the sediments would make it possible for archaeological material to be buried within the formation, where it would have greater protection than if it were exposed on the seabed.

12.11.12 Throughout the study area the Hang Hau formation is more than 2m thick.

Sham Wat and Chek Lap Kok Formations
12.11.13 The (pre-Holocene) sedimentary formations beneath the Hang Hau Formation in the study area are considered to offer limited to negligible archaeological potential. The original land surface that would have existed at the top of these deposits would have been planned-off during the Holocene marine transgression (Fyfe, 1997). Thus, any evidence of late Pleistocene human land activity in the study area would almost certainly have been removed. In the area of Deep Bay the sedimentary character of the Chek Lap Kok Formation has been controlled by the outflow of the Shenzhen River, a tributary of what is now the Fanshi Channel of the Pearl River Estuary.

12.11.14 There was a cluster of diffraction hyperbole on the northern edge of the navigation channels. After cross referencing them with the Seismic Profiler data it was concluded that these were caused by the presence of coarser seabed sediments rather than buried objects.

Marine Magnetic Data

12.11.15 Corrections were made to the magnetic data to compensate for the influences of diurnal magnetic drift. The natural diurnal variations of the magnetic data were recorded continuously throughout the survey periods by a static magnetometer base station established at a quiet place in Chung Hum Kok.

12.11.16 Base station records were subjected to a de-spiking filter process to remove any spurious transients from the data sequence and the temporal variations of the earth's magnetic field were expressed relative to a base datum level of 44000nT. Those variations were subtracted from the survey recorded data a eliminate or minimize the component of diurnal variation in the survey data values.

Sounding Plan

12.11.17 The seabed is extremely shallow within the survey area with depths ranging from 0m PD and -2m PD. A small channel was mapped during the survey and it was detected by both the echo sounding and side scan sonar surveys.

12.12 Barging Point

12.12.1 A barging point is proposed at Lung Kwu Sheung Tan (see Figure 6.3) for batching plant and storage. It was discussed and agreed with AMO that the piece of land on reclamation area could be used for works activities involved piling work. Details of the piling works should be sent to AMO for comment prior to works commencement.

12.13 Conclusion

12.13.1 The study area is exceptionally shallow with water depths ranging from 0m - 2m PD. The geophysical survey revealed that significant areas of the seabed are covered with oyster beds. These serve to cover the natural seabed and prevented archaeological investigation. A navigation channel has been dredged across the northern section of the study area.

12.13.2 The side scan sonar data also revealed that the seabed within the study area has been extensively trawled. This is indicated by the presence of a large number of deeply incised linear scars on the seabed. The trawling activities may have served to destroy or redistribute archaeological material, if present, thereby reducing the archaeological potential of the study area.

12.13.3 There are five Unidentified Targets within the southern section of the study area and it is not possible to assess their archaeological significance until without a diver inspection. All the five targets are found to locate outside the 100m EIA Study zone (refer Figure 12.19) as stipulated in the EIA Study Brief Clause 3.4.8.3. The proposed works limit is at 50m from both edges of the SWC footpath and therefore there will be no physical disturbance due to the proposed marine works of the project to the seabed of the 5 sites. Therefore, diving inspection is not recommended for all the five unidentified objects.

12.13.4 Diver inspection is required to cover the area with no data due to extremely shallow water or oyster beds within the strip of land directly beneath SWC footprint, refer Figure 12.20. The visual inspection of the archaeological investigation area found no visible features or objects of archaeological interest. This may be result of the high sedimentation rates in the area and the extensive disturbance to the seabed from fishing and oyster cultivation or the absence of archaeological features. Due to the proximity of the archaeological investigation area to the coastal archaeological site, Ngau Hom Shek, the potential for such resources cannot be ruled out. However, based on the visual inspection and review of the site conditions, the archaeological potential is classified, as very low and further investigation is not recommended.

12.13.5 It was proposed that a batching plant may be required at Lung Kwu Sheung Tan barging point. The contractor shall submit the proposal to AMO for agreement prior to any works commencement.

12.14 References

Braga, J. M 1995. China Landfall 1513. Jorge Alvares Voyage to China. A complilation of some relevant material. Macao. Imprensa Nacional.
Cortesao, A. 1994. The Suma Oriental of Tome Pires and The Book of Francisco Rodrigues. London. Hakluyt Society.
Davis, D. W., Sewell, R. J. & Campbell, S. D. G. 1997. U-Pb dating of Mesozoic igneous rock from Hong Kong. Journal of the Geological Society of London, 154: 1067-1076.
Davis, S. G. 1949. Hong Kong in its Geographical Setting. London. Collins.
Frost, R. J. 1974. Sha Tsui, Hing Island. Journal of the Hong Kong Archaeological Society, 5: 23-30.
Fyfe, J. A., Shaw, R. 1997. The Offshore Geology of Hong Kong. Hong Kong Geological Survey Memoir. Geotechnical Engineering Office, Hong Kong.
Hong Kong Environmental Protection Department. 1997. Technical Memorandum on Environmental Impact Assessment Ordinance Process (EIA Ordinance, CAP. 499, S16). Hong Kong Government Press.
Landford, R. I., Lai, K. W., Arthurton, R. S. & Shaw, R. 1989. Geology of the Western New Territories, 1:20000 Sheets, 2, 5 & 6. Hong Kong Geological Survey Memoir No. 3. Hong Kong Government Printer.
Lo, H. L. 1963. Hong Kong and its External Communications Before 1942. Institute of Chinese Culture, Hong Kong.
Muckelroy, K. 1978. Maritime Archaeology. Cambridge University Press.
Ng, P. Y. L. 1983. New Peace County: A Chinese Gazetteer of the Hong Kong Region. Hong Kong. Hong Kong University Press.
Pickman, J. & Peck, R. 1979. The physical nature of the Hong Kong seashore. In: B. Morton (ed) The Future of the Hong Kong Seashore. Oxford University Press, Hong Kong.
Premchitt, J., Rad., N. S., To, P., Shaw, R. & James, J. W. C. 1992. A Study of Gas in Marine Sediments in Hong Kong. Continental Shelf Research, 12: 1251-1264.
Sayer, G. R. 1975. Hong Kong 1862-1919. University Press, Hong Kong.
Strange, P. J. & Shaw, R. 1986. Geology of Hong Kong Island and Kowloon. Hong Kong Geology Survey Memoir, No. 2. Geotechnical Control Office.
United States Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region. 1991. Requirements for Archaeological Resource Field Surveys.