Report on Trial of Scavenging Floating Refuse by Net Trawling
This report documents a trial scheme of using a traditional fishing vessel to scavenge floating refuse.
Background 2. Prompted by the launching of Government’s Clean Hong Kong programme in December 2000 a public spirited citizen Captain Gijs Lock approached Marine Department with an idea of using modified second hand fishing nets to clean the harbour. Gijs formerly served as an officer in the Dutch merchant navy which honed his seamanship skills and now works in Asia for Philips Electronics. 3. On 31 March 2001 the Civic Exchange, a non-profit think tank, launched the Clean Environment Campaign as a private sector initiative to complement the Government’s Clean Hong Kong programme. An opportunity of public/private sector collaboration to test the innovative idea by Gijs Lock was identified.
Objective of the Trial 4.
The following objectives for the trial were set – (a)
To evaluate the usefulness of using trawl nets to collect floating refuse.
(b)
To raise public awareness of the floating refuse problem.
Partnership Roles 5.
The main parties involved in the trial were –
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(a)
Civic Exchange, through which funding from private citizens was secured. It also arranged a number of interns to be present on the fishing vessel to supervise, observe and video tape/photograph the operations, and to check the amount of floating refuse collected.
(b)
Captain Lock, who provided technical advice on physical arrangements and rig-up of the nets.
(c)
The boat owner, nominated through the Hong Kong and Kowloon Floating Fishermen Welfare Promotion Association, Mr. Leung Sing, who provided and operated the boat and carried out the net trawling operations during the trial.
(d)
Marine Department, which served an overall co-ordination role, provided logistic support and monitored the trial scheme.
Trial Arrangements 6. The boat involved was provided on a hire basis, at a daily rental of $7,000. Its manning included a combined master/engineer and three crew members. The boat is licensed as a fishing vessel, licence number M63391A. Its length is 11 metres and breadth 4.15 metres, and is fitted with a 80.5-Kilowatt propulsion engine. 7. The trial was for a total of 15 working days. Operations were carried out from Monday to Friday during the period 27 June to 19 July 2001, except on 6 July 2001 when No. 8 signal was hoisted because of tropical cyclone Utor. 8. The sea areas chosen for the trial operations was generally south of Hong Kong Island, including Sandy Bay, Deep Water Bay, Repulse Bay, around Middle Island, South Bay, near Chung Hom Kok, Stanley Bay, Tai Tam Bay and near Lamma Island. These areas are less congested than typhoon shelters and are comparatively calmer than the main fairways and anchorages. In order to assess the performance in congested water area, some trials were also done inside the Aberdeen Typhoon Shelter.
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9. To give identity to the trial scheme the boat owner refreshed the bright orange colour paintwork of the boat’s decking and housing. Civic Exchange arranged to supply a large yellow colour banner with blue lettering “Clean Environment Campaign 碧水藍天運動” to be conspicuously displayed on the boat. 10. The trial was officially launched on 27 June and a small sending-off ceremony was held. Representatives of the involved parties, including Ms. Christine Loh, CEO of Civic Exchange and Mrs. Wendy Kwok, patron of the “Clean Environment Campaign” were present. Participants and media reporters were arranged to observe the trial operation on board Marine Department’s launches. A press release (Annex I) was issued.
Methodology – Net Trawling Arrangements 11. There are booms fitted on both sides of the boat for fish trawling use. These booms can be raised/lowered manually or by power winch. For the trial scheme heavy duty purse nets rigged at the booms were used, one net on each side. The opening of the nets measured about 3 metres wide (i.e. outreach horizontally from the side of the boat) and 1.5m high (i.e. vertically). The depth of the nets (i.e. from the opening to the apex) is about 2 metres. 12. During operations, the booms were lowered. The bottom boom kept the lower edge of the net opening submerged below sea level and the top boom kept the upper edge of the net above sea level. When the nets are towed through the water floating refuse would be trapped inside the nets. After a considerable amount of refuse is collected the nets would be hoisted on board for emptying the collected refuse into storage containers. 13. There is a working area of about 12 square metres on the boat’s deck. The boat was equipped with containers with a total storage capacity of 4.5 cubic metres. 14. Prior to the official launching of the trial scheme, on 15 June, Captain Lock carried out some basic testing of the methodology with Mr. Leung Sing on
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his fishing boat. The basic testings were to adapt the conceptual arrangements to the physical layout of the boat, to determine the optimum size and placement of the nets and to ensure that Mr. Leung Sing was fully conversant with the underlying thinking behind the methodology.
Implementation 15. The net trawling operations were carried out in various locations according to a plan drawn up by the Marine Department. 16. Photographs and video recording of the daily activities were taken during the operations. A number of the photographs are shown in Annex II. In addition the Civil Exchange interns also kept a record of the daily operations using a data sheet (Annex III). Before the interns were sent on board the boat a briefing had been given by Marine Department staff to them on safety when working on board the boat, essential observations to be made, and assessment requirements. Also a Marine Inspector was assigned to carry out daily inspection of the trial. 17. Other staff members of the Civic Exchange and Marine Department also visited the boat to observe the trial at various times. 18. With a view to stimulate commercial interest in the methodology being tested Marine Department organised an observation tour for all the existing marine refuse cleansing contractors to see the trial operation. The observation tour took place on 9 July 2001.
Observations 19. From the experience gained through the trial period and analysis of the collected data a number of observations can be made. The methodology of using trawl nets to collect floating refuse has both strengths and weaknesses. 20.
Strengths of the method : (a)
The strengths are listed below –
The fishing trawler has good manoeuvrability, particularly in
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more open waters. Provided the water is deep enough for her draft she is able to trawl close to the shore.
21.
(b)
The fishing trawler can change directions easily to reach floating refuse when seen.
(c)
Using two nets with openings of a total length of about 6 metres wide, the boat can cover quite a wide area as she moves forward.
(d)
Floating refuse is trapped into the nets easily, once inside the net the refuse generally stay therein. The chance of losing the catch due to wave or wind is small.
(e)
The nets can work effectively in collecting small size floating refuse (e.g. plastic bags, plastic bottles, styrofoam pieces) that are larger than the mesh of the net.
(f)
The method is very effective when used in areas with dense concentration of small size floating refuse, such as tidal lines in open waters or pockets close to the shore.
(g)
Using containers to temporarily stow the collected refuse on the boat, instead of keeping the refuse on the deck, facilitates easy transfer of the refuse for final disposal.
Weaknesses of the method :
The weaknesses are listed below -
(a)
Being relatively small in size, the boat rolls and pitches rather drastically when the sea condition is less than calm. Drastic movement of the boat causes the rigging booms and the nets to become unstable and makes the floating refuse collection process very difficult.
(b)
It is very difficult to use net trawling to collect large size, heavy or bulky floating refuse, such as wooden boards, long pieces of timber, large styrofoam boxes, rubber tyres, liquified petroleum gas bottles and animal corpses.
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(c)
After the net is hoisted on board it is quite difficult to transfer the refuse in the net into receptacles on the boat. During the trial this difficulty was overcome by emptying the nets on to the boat’s deck and then used a shovel to scope them into the containers.
(d)
A considerable amount of refuse (e.g. plastic bags, small tree branches, pieces of rope, timber pieces) tend to be entangled/stuck on the net. During the trial the crew cleared them by hand. This process is obnoxious and can be dangerous when there are things like timber with nails sticking out.
(e)
Handling the nets on the boat’s deck when they are full requires an adequate working area. There is only limited working space available on a normal fishing boat. Insufficient working space can endanger the crew in addition to hindering the refuse handling process.
(f)
The boat cannot trawl floating refuse accumulated close to vertical seawalls or similar structures, as the boom may be easily damaged due to slight misjudgement in steering the boat.
(g)
In congested water areas, such as inside Aberdeen Typhoon Shelter, the trawling method cannot be used. Other than being unable to maneouvre between closely moored vessels the refuse collection boat with booms extending from the sides causes obstruction to normal traffic/activities when traveling along the fairway.
(h)
When working in a relatively large area with sparse amount of floating refuse widely scattered the net trawling method is not efficient because of the boat’s slow speed.
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Civic Exchange Report 22.
A report prepared by the Civic Exchange is at Annex IV for reference.
Comparison of Cleansing Methods 23. A comparison of the trawling method is made with Marine Department’s purpose-built scavenging vessels and contractor’s manual cleansing vessels. The comparison is shown in Annex V. It can be seen that during the trial the fishing vessel was able to achieve a productivity (0.95 tonnes/day) that compares well with the Marine Department vessel’s (0.72 tonnes/day) and the contractor vessels (0.45 tonnes/day). 24. Although it is necessary to point out that the Marine Department’s vessels are large and fast steel vessels. They are purpose-built to be able to withstand the usual rough conditions in open sea areas. Also these vessels are assigned to cover a very wide area. In addition to consider the amount of refuse collected, their efficiency should be measured taking into account the large areas covered by the vessels daily. 25. Annex VI shows a comparison of the average cost for collecting a tonne of floating refuse by the different methods. It can be seen that the cost of using net trawling is considerably more expensive than the existing contractor’s manual scavenging method.
Conclusion 26. Using trawl nets to collect floating refuse is a potentially effective system, however, compared with the current contractor’s service using this method is more expensive.
Achievements 27. The attention of the existing marine refuse cleansing contractors has been drawn to the net trawling technology. Marine Department will endeavour
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to encourage them to consider the application of the technique in areas of suitable conditions. Should there be any interest to pursue the technique all possible assistance will be rendered to facilitate further development of the net trawling method. 28. The experience of this trial provides a good example of postive result reached through private and public sector collaboration. The involvement of Gijs, the funder, Civic Exchange, the fishermen, the student interns, the fishermen association and the Marine Department in this projected has demonstrated that people from all walks of life can work together and do a good job to help clean the environment. 29. There has been good media coverage of the trial. In addition, the conspicuous appearance of the trial boat has also attracted much attention. The trial was carried out in full view of hundreds of fishing boats sheltering for the close fishing period in Aberdeen and the residents in Southern and Islands Districts. The trial has fully achieved its objective of raising public awareness of the floating refuse problem.
Pollution Control Unit Marine Department August 2001 PA/S 930/7/28
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Annex I - 1/4
Attn: Local News / Environment / Features Desks
Press Release For Immediate Release
‘Clean Environment Campaign’and Marine Department launch pilot project to clean up local waters (Hong Kong – June 27, 2001) The “Clean Environment Campaign”, a private sector initiative launched in March, bolstered government efforts to clean up Hong Kong and reduce visual blight today with a 3-week trial of an innovative system for collecting floating marine rubbish. This has focused government, business, and community attention to an environmental problem that has nearly doubled in magnitude since 1996. The Marine Department processed over 8,700 tons of rubbish dumped at sea last year. Non-profit think-tank Civic Exchange, the Marine Department, a Dutch sea captain, the Fisherman’s Association, and an Aberdeen fisherman have teamed up to support this new method of refuse trawling, which uses adapted fishing nets with floating devices to enable capture on and below the surface. Gijs Lock, an industrial auditor and consultant with Philips Electronics Hong Kong, former Merchant Marine Officer, and long-time sailing enthusiast, observed from his Hung Hom residence that conventional government methods of scavenging floating refuse at sea could be further enhanced for better efficiency. Specially-designed refuse scavenging vessels invariably lost a portion of the garbage harvested in choppy waters before being able to discharge their catch into supporting boats and containers. He contacted the Marine Department in January with an innovative idea to supplement their efforts. Over the last several months, Marine Department general manager Szeto Lok-Ki, Aberdeen fisherman Leung Sing, and Lock have been collaborating in developing this method, finetuning and conducting small-scale testing. “I’m looking forward to a successful trial-run, as we are supportive of testing this on a larger scale,” said Szeto. “The rubbish flow directly into the nets will substantially reduce the amount that gets washed way by the waves as the scavenger vessels bring it in. With Mr. Lock’s idea, we’ve now perfected the net release mechanism to more easily discharge refuse to supporting boats for disposal. Ordinary fishing boats can easily be outfitted with this system, enabling us to expand our efforts and work with a lot more enthusiastic fisherman like Mr. Leung.” Leung Sing, who has painted his boat bright orange and installed a large yellow banner to call attention to the pilot project, added: “It wasn’t necessary to modify my boat at all. Traditional, heavy-duty fishing nets 6 feet long and 7 feet deep are adapted to trawl rubbish, Visit us at: www.civic-exchange.org HOSEINEE HOUSE, ROOM 601 69 WYNDHAM STREET CENTRAL, HONG KONG TEL: (852) 2893-0213 FAX: (852) 2575-8430 E-MAIL: CLOH @C IVIC -EXCHANGE.ORG OR LISAH @C IVIC -EXCHANGE.ORG
Annex I - 2/4 and can hold 1.5 tons before needing to be emptied. And they’re about $1000 cheaper than regular fishing nets. I think this is really a good idea!” The Marine Department is responsible for refuse cleaning of Hong Kong waters, collecting garbage from ocean-going ships and smaller boats inside typhoon shelters, and disposing of the waste at landfill sites. This year, the department has a fleet of 10 specialized scavenging vessels, the replacement cost of which ranges between $2 to $6.6 million each. It employs 9 outside contractors to supplement the fleet with 59 additional vessels. Over 11,300 tons of garbage were collected in 2000 – 77% of it having been dumped at sea. This represents a 93% increase in the amount collected just since 1996, when there were a total of 44 refuse cleansing vessels in use. The Marine Department prosecuted 113 cases of marine littering in 2000. Gijs Lock said from Nanjing today: “I have only good words to say about co-operation with the Marine Department. I found them stimulating and constructive in trying to solve the floating rubbish problem. They desperately need the support of the public at large to work more on preventing pollution. The visual water pollution in Victoria Harbour and Aberdeen is an issue that hopefully bothers a growing number of Hong Kong citizens. It surely doesn’t go unnoticed by the many tourists who contribute so much to the local economy.” Christine Loh, CEO of Civic Exchange and strategic planner of the “Clean Environment Campaign” and this latest project, pointed out, “This effort involves R&D which enabled the adaptation of traditional Chinese fishing techniques for new usage. It saves money, and it’s efficient. This project is an ideal cooperation between government, business, and the community.” Summer interns from Civic Exchange will help the Marine Department to monitor the trial project throughout. Mr. Roger Tupper, Assistant Director of the Marine Department, said that all efforts to work with the department to clean-up Hong Kong waters were appreciated and needed. Mrs. Wendy Kwok, patron of the “Clean Environment Campaign”, urged heightened public awareness in preventing the marine pollution problem from getting worse. - End For further information, please contact: Christine Loh Tel: 9802-8888 E-mail: cloh@civic-exchange.org
Visit us at: www.civic-exchange.org HOSEINEE HOUSE, ROOM 601 69 WYNDHAM STREET CENTRAL, HONG KONG TEL: (852) 2893-0213 FAX: (852) 2575-8430 E-MAIL: CLOH @C IVIC -EXCHANGE.ORG OR LISAH @C IVIC -EXCHANGE.ORG
Annex I - 3/4 致﹕港聞/環保/評論版編輯 新聞稿 立即發放
「碧水藍天運動」和海事處合作展開 一個清潔本港水域的試驗計劃 （香港 -- 2001 年 6 月 27 日）「碧水藍天運動」是一項由私人機構在本年三月展開的計
劃，它的目的是支持政府清潔香港的工作和減少垃圾帶來的視覺污染。「碧水藍天運 動」今天會開始利用三個星期的時間去測試一個創新的收集海上漂浮垃圾方法。這測 試集合政府、商業機構和民間組織的力量去對付海上漂浮垃圾這個環保問題。自一九 九六年起，海上垃圾的問題便開始變得雙倍嚴重，海事處單在去年就已經收集到 8,700 噸的海上垃圾。
非牟利的思匯政策研究所、海事處、一名荷蘭裔船長、漁民組織及一名香港仔漁民合 作推動採用這種新的收集海上垃圾方法。這種新方法是透過在傳統魚網加上漂浮裝 置，令魚網能有效地收集海面上及水底的垃圾。 現職香港飛利浦公司工業技術顧問的羅克海先生是一名前海員及長期航海愛好者。他從紅磡的 住所觀察政府現時的收集海上垃圾方法，認為是可以加以改良以提高效率。專門用作收集海上 垃圾的船隻在把垃圾卸下到其他輔助船隻或貨櫃時，部份的垃圾無可避免地跌回海中。羅克海 先生在今年一月聯絡海事處把他嶄新的收集海上垃圾方法介紹給他們，企望可幫助海事處收集 海上垃圾的工作。 在過去幾個多月，海事處海事處總經理司徒洛基先生、香港仔漁民梁勝先生和羅克海先生一同 合作改良及小規模地測試此收集海上垃圾的新方法。 司徒洛基先生說：「海事處支持今次進行較大規模的測試，我希望這次新的收集海上垃圾方法 測試能夠成功。垃圾直接流到漁網中，這會大量減少當垃圾收集船隻在卸下垃圾時被海浪沖走 的垃圾數量。我們已根據羅克海先生的提議去改良漁網的卸下垃圾技術，令漁網更容易把垃圾 卸下到負責運走垃圾的支援船隻中。普通漁船很容易便能安裝這系統，這令我們能擴展我們的 工作，以及和更多像梁勝先生的熱心漁民合作。」 梁勝先生剛在自己漁船的船身，噴上閃耀的橙色油漆及掛上一幅很大的黃色橫額，希望讓更多 人留意到這個試驗計劃。他說：「這新方法完全不需要改裝我的船隻。把六呎長七呎深的重型 捕魚網改良作收集垃圾用途，魚網能在收集 1.5 噸垃圾後才需要卸下垃圾。這些魚網比常規魚 網便宜港幣一千元。我覺得這是一個很好的新方法！」 Visit us at: www.civic-exchange.org HOSEINEE HOUSE, ROOM 601 69 WYNDHAM STREET CENTRAL, HONG KONG TEL: (852) 2893-0213 FAX: (852) 2575-8430 E-MAIL: CLOH @C IVIC -EXCHANGE.ORG OR LISAH @C IVIC -EXCHANGE.ORG
Annex I - 4/4
海事處是負責清潔香港水域的垃圾和從遠洋船及避風塘內的小船隻收集垃圾，最後將 垃圾棄置在堆填區內。今年海事處有十艘專門用作收集海上垃圾的船隻，每艘船隻的 更新費用是二百萬至六百六十萬港元。海事處亦額外僱用九個承辦商共五十九艘船隻 去清潔海上垃圾。海事處在二零零零年收集了 11,300 公噸的垃圾，其中的 77%是被棄置 在海上的。這數字比一九九六年增加了 93%，而當時總共有四十四艘船隻負責收集海上垃 圾的工作。海事處在二零零零年共檢控了一百一十三宗海上棄置拉圾事件。 羅克海今天在南京表示：「我對和海事處的合作感到非常滿意。我覺得他們在嘗試解決
海上漂浮垃圾的問題上表現得十分有創意和具建設性。海事處極需要更多公眾人士的 支持去防止環境緩污染。我希望有更多的香港市民關注維多利亞港及香港仔的海上污 染問題，這問題一定已被很多遊客所察覺，這些遊客對本港經濟有很大的貢獻。」 思匯政策研究所行政總裁、「碧水藍天運動」策劃人及此計劃的籌辦者陸恭蕙說： 「這項合作計劃讓傳統捕漁的方法有嶄新的用途。這新方法既節省金錢，又十分有 效。這是一次政府、商業機構及民間組織難得的合作機會。」思匯政策研究所的暑期實習 生將會協助海事處監察整個試驗計劃的過程。 海事處助理署長 Mr. Roger Tupper 說海事處感謝所有和他們合作清潔香港水域的努力，而這 些合作是需要的。「碧水藍天運動」的贊助人郭李天穎敦促政府提高公眾對防止海洋污染問題 的關注，以避免問題愈趨惡化。 - 完結 查詢請電﹕ 陸恭蕙 電話: 9802-8888
電郵：cloh@civic-exchange.org
Visit us at: www.civic-exchange.org HOSEINEE HOUSE, ROOM 601 69 WYNDHAM STREET CENTRAL, HONG KONG TEL: (852) 2893-0213 FAX: (852) 2575-8430 E-MAIL: CLOH @C IVIC -EXCHANGE.ORG OR LISAH @C IVIC -EXCHANGE.ORG
Annex II (Photo 1) Trawler M63391A
(Photo 2) Rigging the trawling net
(Photo 3) Sweeping floating refuse
(Photo 4) Refuse collected by the net
(Photo 5) Recovery of refuse of medium size
(Photo 6) Recovery of timber log
(Photo 7) Recovery of refuse
(Photo 8) Recovery of refuse
(Photo 9) Dumping the recovered refuse aboard
(Photo 10) Sorting and packing of recovered refuse
(Photo 11) Transfer the packed refuse to Marine Refuse Collection Vessel for disposal
(Photo 12) Transfer the packed refuse to Marine Refuse Collection Vessel for disposal
(Photo 13) Scavenging work at Aberdeen Typhoon Shelter
(Photo 14) Scavenging work at Aberdeen Typhoon Shelter
Daily Record of Net Trawling Floating Refuse Trial at Hong Kong South Date : Time From To
Weather : Location
Sea State : Activity
Manning: Remarks
Total time spent in recovering of floating refuse: ____________________ Total time spent in unloading collected refuse: ______________________ Total Downtime: ______________________________________________
Annex III - 1/2
Summary:Total Refuse Collected : ___________________________ m続 Total time spent in travelling : ________________________ Total time spent in preparation: _______________________
Wind : Amount of Refuse Collected (m続) Foam Box Timber Bulky Others Refuse
Comments 1) Manoeuvrability under different weather conditions and sea states:____________________________________________________________ __________________________________________________________________________________________________________________ __________________________________________________________________________________________________________________ 2) Ability in recovering floating refuse in different areas:______________________________________________________________________ __________________________________________________________________________________________________________________ __________________________________________________________________________________________________________________ 3) Ability in recovering different types of floating refuse:______________________________________________________________________ __________________________________________________________________________________________________________________ __________________________________________________________________________________________________________________ 4) Ability in recovering floating refuse by different methods:___________________________________________________________________ __________________________________________________________________________________________________________________ __________________________________________________________________________________________________________________ 5) Difficulties of recovery refuse from the net to the boat:______________________________________________________________________ __________________________________________________________________________________________________________________ __________________________________________________________________________________________________________________ 6) The strength and the weakness in the whole process:________________________________________________________________________ __________________________________________________________________________________________________________________ __________________________________________________________________________________________________________________
Annex III - 2/2
Recorded by __________________________________________
Annex IV - 1/3 REPORT Net Trawling Floating Refuse Trial By: Christine Dobridge Between the 27th June and the 19th July 2001, Civic Exchange, the Marine Department, a Dutch sea captain and an Aberdeen fishing crew collaborated to design and test a new refuse trawling method for cleaning up Hong Kong marine waters. The method adapted traditional fishing nets to capture floating refuse above and below the surface. A local fishing crew carried out daily trials around southern Hong Kong Island and the following report si a compilation of the daily observations recorded by Civic Exchange interns and the fishermen during the trial. Strengths of the method •
The nets were very effective at collecting small floating refuse, like plastic bags, plastic containers and small Styrofoam pieces. The rubbish flowed directly into the nets and none of it was washed away. The method was particularly effective at trawling for refuse in areas where the refuse had collected in pockets near the shore or in lines in the open water. In those areas, the nets picked up a large amount of refuse in a short amount of time.
•
Putting the plastic bags in the fishing buckets and then filling up the bags was an effective way of getting the trash into the bags.
•
The boat was able to trawl close to the shore.
•
The small vessel was highly maneuverable and could change directions easily to reach the refuse.
•
Using the mechanized pulley to lift the full nets out of the water was effective and easier for the fishermen than manually pulling the nets out of the water.
Weaknesses of the method •
The refuse was difficult to remove from the net. The fishermen had to transfer it from the nets to the bags and bucket by dumping the refuse on deck and transferring it by hand. The process was very dirty and could be dangerous (there were often loose nails sticking out of pieces of timber, for example). There was only one shovel on the boat to transfer the refuse from the deck to the bags. Another shovel would have helped.
•
It was difficult to collect heavy, bulky refuse. The fisherman used a combination of hand nets, ropes, a long hook, the mechanized pulley and manpower to hoist large pieces of refuse including tree trunks, large pieces of timber, large foam boxes and gasoline jugs onto the boat. The process was time consuming and could be dangerous.
•
In choppy seas, the small vessel is hard to maneuver. Choppy seas also made the recovery process more dangerous.
•
Storage space on the boat was limited. When the deck was congested it was difficult and a little dangerous for the fishermen to work around them.
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Annex IV - 2/3
•
The method was not very effective at collecting in heavily congested areas like the Aberdeen Typhoon shelter because most of the floating refuse was close to the moored boats where the fishing boat could not maneuver.
•
The small fishing boat was not very effective at collecting refuse in open water (unless the fisherman found streams of refuse) because the span of the nets was quite small and it took a long time to collect a substantial amount of refuse.
•
Small pieces of plastic and timber stuck in the nets.
Conclusions
The very nature of rubbish collection is labor, time and energy intensive, whether at sea or on land. Four people appear to be an optimum number for a vessel of the size used for the trails. The fact that it took a team of four to clean marine refuse should not be seen as a fault of the method. Using adapted fishing nets to collect floating refuse is potentially an excellent method for cleaning up Hong Kong waters and reducing the visible blight of marine rubbish. Much of the visible blight is due to small pieces of floating plastic and timber and using nets is an excellent method for collecting that type of refuse. The nets can collect a substantial amount of refuse in a short amount of time and very little of the catch is lost before it can be transferred to bags for disposal. Before the technique can be utilized by the Marine Department on a large scale to clean up Hong Kong waters, however, the weaknesses in the process must be addressed and the technique should be adapted for use under different conditions. The difficulty of transferring rubbish from the nets to the trash bags is the main weakness of the system and modifications should be made and safety should be a priority at all times. The use of nets to collect rubbish can also be expanded beyond sending out one fishing boat at a time. Mr. Gijs Lock’s ideas for expanding the netting techniques include: 1) sending out two or three fishing boats to trawl side by side so that they can collect a wider span of rubbish, and 2) stringing nets between two tugboats to trawl a larger area or an area with choppier conditions than a fishing boat can handle, like Victoria Harbour. Adapted fishing nets could be effectively integrated into the Marine Department’s current program for collecting marine refuse. The netting technique is not very effective for collecting bulky pieces of rubbish but is good at collecting small pieces. Marine Department vessels that use mechanized scoops for collecting refuse are very effective at collecting and disposing of bulky pieces of rubbish, but not effective at collecting small pieces. Marine Department vessels invariably lose a portion of the refuse collected in choppy waters before being able to dispose of it. Neither the larger Marine Department vessels or the netting technique are effective at collecting floating refuse in highly congested areas like the typhoon shelter; a very small vessel and hand nets are necessary for this. All things considered, the combination of netting techniques and current Marine Department techniques for collecting refuse has the potential to facilitate and expedite the clean up of Hong Kong waters. 20 July 2001
52) 2893-0213
FAX: (852) 2575-8430
Annex IV -
Approximate Amounts of Refuse Collected buckets of rubbish m^3 of refuse (foam box, timber, (1 bucket = ~ weight of large other) .15 m^3) timber pieces Location Pok Fu Lam, Sandy Bay, Ap Lei Pai 27/6/01
21 buckets other
3.15
Deep Water Bay, Chey Hom 28/6/01 Wan, Pok Ful Lam, Wah Fu
14 buckets other
2.35
3/3
Remarks
Date
S. Bay, Round Island, Ap Lei Chau, Ocean Park 29/6/01
-
most refuse is plastic bags or containers with some small timber and foam pieces
most refuse is plastic bags or containers -
13 buckets 'other'
1.95
-
several large pieces of timber found, most of the floating refuse is plastic bags and small timber pieces
3/7/01
Southern Horizon, Sandy Bay, Ocean Park
3 buckets of timber, foam, 8 buckets other
1.65
100 lbs timber
"other" = bottles, plastic bags
4/7/01
Luk Chau Wan, Picnic Bay
6 buckets timber, 12 buckets other
2.7
-
"other" = plastic bags
5/7/01
27 buckets
4.05
200 lbs timber
9/7/01
? Sandy Bay, Wah Fu Estate, Souther Horizon
42-45 buckets total
6.3-6.75
1200 lbs timber
10/7/01
Repulse Bay and Chung Hom Kok
15 buckets timber, 30 buckets other
6.75
-
11/7/01
Stanley, Repulse Bay and Sandy Bay
5 buckets timber, 13 buckets other
2.7
300lbs timber
12/7/01
Tai Tam, Stanley, Repulse Bay, Deep Water Bay and Ocean Park
13 buckets other
1.98
150 lbs timber
13/7/01
Luk Chau, Hok Kwu Wan, Repulse Bay, South Bay
6 buckets timber, 26 buckets other
4.8
600 lbs timber
16/7/01
Sok Kwu Wan, Repulse Bay, Ocean Park
5 buckets timber, 27 buckets other
2.8
300 lbs timber
17/7/01
Yung Shu Wan, Typhoon Shelter, Ocean Park
12 buckets timber, 23 buckets other
5.25
300 lbs timber
18/7/01
Causeway Bay, Clear Water Bay, Ocean Park
11 buckets timber, 35 buckets other
5.25
500 lbs timber
19/7/01
Yung Shu Wan, Lamma Island, Ocean Park
30 buckets total
4.5
100 lbs timber
2 large Styrofoam blocks, plastic jugs, tires, other = plastic bags, containers, small timber pieces
most refuse is plastic bags and bottles, several large timber pieces, one large rope
Annex V - 1/1
Floating Refuse Collected 27 June 2001 to 19 July 2001
Refuse collected by Fish Trawler “M63391A” (in tonnes)
Marine Department Scavenging Vessel (in tonnes)
Contractor’s Cleansing Vessel (in tonnes)
0.79
0.20
0.38
0.59
0.20
0.40
0.49
0.55
0.38
0.41
0.40
0.35
0.68
0.70
0.40
1.01
0.50
0.50
1.69
1.80
0.50
1.69
0.70
1.00
0.68
1.10
0.33
0.50
0.80
0.30
1.20
0.50
0.38
0.70
0.80
0.38
1.31
0.80
0.63
1.31
0.60
0.38
1.13
1.10
0.45
Total
14.18
10.75
6.76
Daily Average
0.95
0.72
0.45
Date
27.6.01 (Wed) 28.6.01 (Thur) 29.6.01 (Fri) 3.7.01 (Tue) 4.7.01 (Wed) 5.7.01 (Thur) 9.7.01 (Mon) 10.7.01 (Tue) 11.7.01 (Wed) 12.7.01 (Thur) 13.7.01 (Fri) 16.7.01 (Mon) 17.7.01 (Tue) 18.7.01 (Wed) 19.7.01 (Thur)
[RNTFRT(Annex)]
Annex VI - 1/1
Comparison of Recovery Cost of Floating Refuse
Vessel Fish Trawler
Marine Department Scavenging Vessel
Average Daily Operating Cost
HK$7,000
HK$7,920
HK$1,000
Average Daily Amount of Refuse Collected
0.95 tonnes
0.72 tonnes
0.45 tonnes
Estimated Recovery Cost of Floating Refuse (per tonne)
HK$7,368
HK$11,000
HK$2,222
[RNTFRT(Annex)]
Contractor’s Cleansing Vessel