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Resources, Conservation and Recycling 69 (2012) 100– 108

Contents lists available at SciVerse ScienceDirect

Resources, Conservation and Recycling

journa l h o me pag e: www.elsev ier .com/ locate / resconrec

ff-site sorting of construction waste: What can we learn from Hong Kong?

u Weishenga,∗, Yuan Hongpingb

Department of Real Estate and Construction, The University of Hong Kong, Hong KongSchool of Economics and Management, Southwest Jiaotong University, Chengdu, Sichuan 610031, China

r t i c l e i n f o

rticle history:eceived 9 June 2012eceived in revised form5 September 2012ccepted 18 September 2012

eywords:onstruction wasteaste sorting

egulationong Kong

a b s t r a c t

To tackle the large amount of solid waste generated from construction activities, Hong Kong has issueda series of construction waste management policies in the last twenty years. One of the most significantpolicies is the launch of an off-site construction waste sorting (CWS) program. Since its implementa-tion in 2006, the off-site CWS program has contributed greatly to construction waste minimization byhitherto separating 5.11 million tons of construction waste in total. This paper aims at carrying out a thor-ough investigation into the off-site CWS program in Hong Kong. Both successful experience and existentshortcomings in relation to the CWS program are discussed in detail. Data on which the analysis and dis-cussions are based are mainly obtained from two channels. One is from literature review and examinationon government regulations and statistics, while the other is from two empirical case studies carried outat the Tuen Mun construction waste sorting facility. The findings reveal that the success of the off-site

CWS program is mainly attributed to ‘sustaining policy support from the Hong Kong government’, ‘goodpolicy execution’, ‘encouraging off-site CWS through higher disposal charges’ and ‘implementation of thetrip-ticket system’. Suggestions for further enhancing the effectiveness of the off-site CWS program arealso proposed. The study is not only useful for decision makers to further improve the overall effective-ness of this practice, but also provides valuable references for other countries or regions in minimizing

gh of

construction waste throu

. Introduction

How to minimize construction waste effectively and efficientlyas long been a challenging issue that has received worldwidettention (Skoyles, 1976; Bossink and Brouwers, 1996; Craighillnd Powell, 1999; Poon et al., 2001a; Tam, 2008; Lu et al., 2011;uan et al., 2011). It is commonly found that people have widelymbraced four major clusters of construction waste countermea-ures ranging from reduction, reuse, recycling, which are known as3R’, to disposal (Yuan and Shen, 2011). Reduction is perceived ashe most environmentally friendly, as it can prevent constructionaste from generation in the first place. Typical waste reduction

pproaches include design out waste and optimal constructionaterial management. After construction waste is inevitably gen-

rated, the other three measures (i.e. reuse, recycling and disposal)an be successively applied.

Among the various construction waste minimization meas-res, sorting construction waste into its constituent parts before

eing dumped in landfills or public fill reception facilities is often

ntroduced as a good practice. In many cases, the constructionaste is a mixture of inert and non-inert construction materials

∗ Corresponding author.E-mail addresses: wilsonlu@hku.hk (W. Lu), yuan@home.swjtu.edu.cn (H. Yuan).

921-3449/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.resconrec.2012.09.007

f-site waste sorting program.© 2012 Elsevier B.V. All rights reserved.

(Poon et al., 2001b). In Hong Kong, for example, the inert materials,which comprise mainly sand, bricks and concrete, is deposited atpublic fill reception facilities for land reclamation, while the non-inert portion, consisting of materials such as bamboo, plastics, glass,wood, paper, vegetation and other organic materials, is dumped atlandfills as solid waste. They should be properly sorted instead ofbeing buried as a whole. Sorting can thus increase the efficiencyof construction waste reuse and recycling, and in turn extend thelifespan of landfills (Poon et al., 2001b; Hao et al., 2008).

On-site and off-site construction waste sorting (CWS) are thetwo favorable options. Poon et al. (2001b) investigated the feasi-bility of carrying out on-site CWS by taking into consideration thecharacter of building related construction waste generated in HongKong. The investigation found that building construction partici-pants are mostly reluctant to conduct on-site sorting although ithas various advantages as compared with CWS centrally carriedout at a designated off-site area. As a matter of fact, on-site CWShad not been popular in Hong Kong, and the prevailing practicewas still that contractors sent the construction waste directly tolandfills or public fill reception facilities for disposal.

Things have changed when the Hong Kong government imple-

mented a Waste Charging Scheme (WCS) in 2006 based on the“polluter pays principle”. In line with the WCS (Ref. Cap. 354N),a construction contractor will be imposed a levy of HK$125(1US$ = 7.76HK$) for every ton of construction waste it disposes

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W. Lu, H. Yuan / Resources, Conserv

f at landfills; it will be levied HK$100 per ton if the construc-ion waste was accepted by off-site sorting facilities while it wille charged only HK$27 per ton if the waste consists entirely of

nert materials accepted by public fill reception facilities. The priceiscriminations reflect the different environmental impacts causedy different forms of construction waste. It is also anticipated thathe charge will be channeled back to construction contractors toncourage more active construction waste management activities,uch as reduction, reuse, and recycling. An off-site CWS programas introduced and two off-site waste sorting facilities were setp against this backdrop.

According to the statistics provided by the Hong Kong Civil Engi-eering and Development Department (CEDD), the two off-siteWS facilities have successfully handled a total amount of 5.11 mil-

ion tons of construction waste by February 2012 since its operationn 2006. It comes to an opportune time to examine the off-site CWSrogram with a view to assimilating the successful experiences or

mproving its potential weaknesses in the future. Therefore, thisaper mainly aims at examining the off-site CWS practices in Hongong by drawing upon practical experiences of implementing theff-site CWS program.

This remainder of this paper is organized as follows. Firstly, theesearch methodology adopted is introduced. Secondly, the off-siteWS program in Hong Kong is reviewed. Thirdly, a blow-by-blowccount of major experiences and shortcomings regarding imple-entation of the off-site CWS program in Hong Kong is presented.

articularly, major regulative, economical, and managerial factorsontributing to the effectiveness of the practice are abstracted andnalyzed in detail. Finally, the paper concludes by summarizing theessons learned from the off-site CWS practices in Hong Kong. It isxpected that the findings derived from this study could not onlydentify the strengths and weaknesses residing in the Hong Kongff-site CWS program for further improvements, but also shed lightn its successful experience on which other similar economies canase to better develop their own programs of such kind.

. Research methodology

A hybrid research methodology is adopted in this study, involv-ng literature review, a site survey, and several rounds of interviews.he review of literature helps in constructing a solid understandingbout construction waste management in Hong Kong, in particularts off-site CWS program. Also, related government regulations andtatistic reports are reviewed to filter information that is highly

elated to CWS. A site survey was conducted in February 2012n one of the two off-site CWS facilities, which is located at theuen Mun Area 38 in Hong Kong. Six researchers from the researcheam participated in the site survey, encompassing two senior

Fig. 1. Solid waste disposed of at

ource: HKEPD (2011).

and Recycling 69 (2012) 100– 108 101

researchers and four graduate students. The site survey was led bytwo government staff members: one is from the CEDD head officeand the other is a full-time inspector working at the Tuen Mun CWSfacility. The two staff members are also responsible for answeringquestions raised in the interviews in parallel with the site survey.The results of the interviews afford useful supporting materialsfor the authors to carry out in-depth analyses of the off-site CWSpractices.

3. Off-site CWS in Hong Kong

3.1. Introduction of the off-site CWS program

Fig. 1 shows the amount of solid waste (including constructionwaste) which has been disposed of at Hong Kong landfills over thetime span of 1991 and 2010. It is obvious that the amount of solidwaste dumped at landfills is grave, although a general trend ofdecreasing is observed, particularly after 2002. The large volumeof waste disposal has cost the capacity of the three strategic land-fills in Hong Kong in a relatively quick speed. In contrast, there isgrievous scarceness of land space for planning and constructingnew landfills or extension of existing landfills, if the current wastedisposal scale henceforth cannot be diminished. To maximize theefficacy of exiting landfills and prolong their serving span, an opti-mal strategy under the government’s consideration is to enhancethe effectiveness of solid waste minimization at source.

Also, it is notable from Fig. 1 that the construction waste inHong Kong makes up a prodigious portion of the total solid wasteprocessed by landfills, touching as high as 68% in 1991 and even thelowest reaching 23% in 2007–2009. In a sense, the effectiveness ofsolid waste minimization at source relies highly on how the con-struction waste was reduced at the first place. Corresponding tothe increased desire to reduce construction waste, the Hong KongLegislative Council (LegCo) launched an amendment to the WasteDisposal Ordinance in 2004, a key intention of which is to chargeconstruction waste dumped at designated construction waste dis-posal facilities on the one hand and to enhance control on illegalconstruction waste dumping behavior on the other (HKEPD, 2012).

According to the Waste Disposal Ordinance (HKEPD, 2012),project stakeholders, mainly referring to construction contractorshere, will have to pay HK$100 per ton for their construction wastecontaining more than 50% by weight of inert materials if it is sortedby off-site CWS facilities. If sorting is conducted before the con-struction waste is transported to the off-site sorting facilities, the

inert materials can be dumped in designated public fill recep-tion facilities directly at a much lower charge of HK$27 per ton.Construction waste containing less than 50% by weight of inertmaterials can be disposed of directly at landfills at a higher charge of

landfills from 1991 to 2010.

102 W. Lu, H. Yuan / Resources, Conservation and Recycling 69 (2012) 100– 108

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Similarly, the screen is bestrewn with hollows of radii from 50 mmto 150 mm. The 50–150 mm separated waste will further be han-dled by a density separator, handpicking and air blower to sortnon-inert materials. Finally the residual construction waste from

Table 1The criteria for construction waste to be accepted at the sorting facility.

Fig. 2. The two construction wote: This figure is provided by the Hong Kong CEDD.

K$125 per ton. In accordance to the Ordinance, two CWS facilitiesere successively built and operated in 2006 (see Fig. 2). The design

apacities of the two waste sorting facilities (i.e. Tseung Kwan Orea 137 and Tuen Mun Area 38 CWS facilities) are 2800 tons peray and 700 tons per day, respectively.

.2. The off-site CWS practices in Hong Kong

Based on the information provided by the staff members fromhe CEDD, together with the analyses of our site survey and inter-iews, a flowchart is developed to describe the circumstantialccount of the entire off-site CWS process in Hong Kong (Fig. 3).t is clear from the flowchart that central purpose of the practice iso sort the mixed construction waste received at the off-site CWSacilities into inert and non-inert waste, which would otherwise beumped directly in mixture at landfills and consequently place aeavy burden on existing landfill capacity. The detailed operationalrocedures are described as follows.

Owing to the price difference, contractors certainly tend to sendll the waste to these off-site CWS facilities (charging HK$ 100 peron) if not the public fill reception facilities (charging HK$ 27 peron). The first challenge is thus to make sure that the mixed con-truction waste received at the off-site CWS facilities is acceptableor sorting. There are generally applied criteria drawing from rule-f-thumb for determining whether the construction waste receiveds acceptable. The off-site sorting facilities only accept construction

aste containing more than 50% by weight of inert materials inrder to maximize its service efficiency (HKEPD, 2008a). In its cur-ent practice, two specific indicators, namely, weight ratio and depthf waste, are used. They are calculated based on the following for-ulas: (1) Weight ratio equals to results of dividing ‘net weight of

onstruction waste’ by ‘permitted gross vehicular weight’; and (2)epth of waste equals to ‘height of waste’ minus ‘height of loading

latform’. The acceptance criteria and main indicators for justify-

ng whether the construction waste received contains more than0% by weight of inert materials are tabulated in Table 1 (HKEPD,008b). Once the waste meets the criteria, it can be accepted

orting facilities in Hong Kong.

for further processing. It is worth mentioning that besides thequantitative measurements, a preliminary visual inspection of theconstruction waste by experienced management staff will also beconducted. The main purpose is to ensure that the constructionwaste received does not contain an evident proportion of non-inert materials, which should go to landfills. The construction wastecontaining obviously perceptible non-inert components will berejected outright by the management staff, though it may meetthe quantitative criteria as afore-mentioned.

The qualified construction waste will then enter the first pro-cess of sorting (named Process 1), which is performed by using aVibratory Grizzly Feeder (VGF). In this process, the waste whichhas a radius greater than 250 mm will be segregated. Two meansare adopted: one is by mobile plant to separate inert materials andthe other is by handpicking mainly for non-inert materials separa-tion. After that, the residual construction waste of Process 1 will behandled to remove the metallic waste with the aid of a MagneticSeparator, which is called Process 2.

In the next process (Process 3), the construction waste has topass through a Heavy Duty Scalping Screen. The screen is full ofholes with the radius of 150 mm. With this screening process, theconstruction waste with radii ranging from 150 mm to 250 mmcan be separated. The 150–250 mm separated waste will further beprocessed through handpicking and air blower to remove non-inertmaterials.

The construction waste with radii less than 150 mm will enterProcess 4, in which the waste is filtered by a Rotary Trommel Screen.

Indicators Demountable trucks Non-demountable trucks

Weight ratio >0.25 >0.20Depth of waste <1 m <1.5 m

W. Lu, H. Yuan / Resources, Conservation and Recycling 69 (2012) 100– 108 103

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rocess 4 will pass through a conveyor belt so that non-inert mate-ials can be sorted out by handpicking.

It should be highlighted that after going through all the sortingrocesses, the mixed construction waste can be eventually sorted

nto two piles, namely, inert materials and non-inert materials.s indicated in the flowchart (Fig. 3), the inert materials will beent to the public fill reception facilities while the non-inert onesandfilled.

.3. Contribution of off-site CWS to construction waste reduction

As discussed previously, the off-site CWS program is imple-ented by Hong Kong with a primary purpose of minimizing

onstruction waste both on-site and off-site. Fig. 4 illustrates theuantities of construction waste received at the public fill receptionacilities and landfills respectively during the period of 1991–2010.enerally, the total amount of construction waste processed by the

wo kinds of facilities has increased quickly by the end of 2005. Inhe period of 2006–2008, the amount of construction waste has aramatic decrease. Although later, in 2009, the quantity began to

ncrease again, the average annual amount of construction waste

on waste sorting in Hong Kong.facility visit.

over the period of 2006–2010 is much less compared with that in2005.

If we examine the ratio of construction waste disposed of atlandfills to the total waste dumped, it is clear from Fig. 4 that theratio has decreased sharply from 0.77 in 1991 to 0.09 in 2010. Par-ticularly, the ratio has decreased from 0.14 in 2006 to 0.09 in 2010.This demonstrates evidently that increasing proportion of inertmaterials has been separated from the mixed construction wasteand sent to public fill reception facilities, which in turn is helpfulin relieving the burden on the existing landfill capacities. These arepartly contributed by the off-site CWS program implemented.

To further investigate the effectiveness of the off-site CWS pro-gram in Hong Kong, data regarding amounts of construction wastesorted by the CWS facilities are plotted and shown in Fig. 5. It isseen that every year a significant amount of construction wastehas been handled by the CWS facilities. Meanwhile, both the abso-lute amount of construction waste sorted by the CWS facilities and

the proportion of sorted construction waste to the total construc-tion waste disposed exhibit a general trend of decline. This mayimply that after implementing the off-site CWS program for a fewyears, construction contractors may have been convinced to carry

104 W. Lu, H. Yuan / Resources, Conservation and Recycling 69 (2012) 100– 108

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ut waste sorting on-site proactively instead of sending the wasteirectly to the CWS facilities. Nonetheless, this needs to be substan-iated by further research on on-site CWS.

. Potential areas for improving the off-site CWS program

.1. Properly siting the off-site CWS facilities

As shown in Fig. 2, the current two off-site CWS facilities inong Kong are located in Tuen Mun (in west Hong Kong) andsung Kwan O (in south Hong Kong), respectively. By comparinghem with Fig. 6, it can be seen that the off-site CWS facilitiesave been deliberately located next to the landfills. Their locationsre largely different from the three strategic construction wasteandfills, which are situated in west, south and north east Newerritories, respectively. The three landfills are distributed like a

riangle and thereby can largely cover all areas around Hong Kongith reasonable radii. Therefore, it is somehow costly if construc-

ion waste is transported to the two CWS facilities from either eastr north Hong Kong. According to the site survey, it is unclear

Fig. 5. Construction waste sorted bote: The data were provided by the staff from the Hong Kong CEDD.

on waste in 1991–2010.

whether the two locations were investigated thoroughly prior tobeing selected for building the waste sorting facilities. Given thatconstruction waste can be sent from construction sites in anyplacearound Hong Kong, it will be better to investigate and plan locationsof CWS facilities in advance so that transportation routes could beoptimized and transportation costs reduced.

4.2. Effective measurements of the proportion of inert materials

It has been introduced in Table 2 that there is only a ‘weightratio’ indicator applied for measuring the proportion of inert mate-rials in each load of construction waste received when the off-siteCWS program was originally implemented. After December 2010,a ‘depth of waste’ indicator was added to the measurement crite-ria for enhancing the accuracy of the measurement. According tothe survey, it is found that there are two issues needing to be

addressed. The first issue is that how the two existing indicators(i.e. weight ratio and depth of waste) are calculated and deter-mined. None of the regulations but the rule of thumb explainsthe rationale behind using the two indicators for quantitatively

y the off-site CWS facilities.

W. Lu, H. Yuan / Resources, Conservation and Recycling 69 (2012) 100– 108 105

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ig. 6. Location of existing strategic landfills in Hong Kong. NENT:North East New Tandfill.

ource: HKEPD (2012).

etermining whether the construction waste received containsore than 50% by weight of inert materials. The second is that

n its current practice, non-inert materials will be very difficulto be spotted if they are concealed at the bottom of the vehicle.t present the inspector only visually glances at the top of theehicles to confirm whether it contains significant non-inert mate-ials. In this regard, the inspector has to follow the entire tracks ofhe vehicles to make sure the construction waste accepted meetselated mandatory requirements. Thus, if the program was adaptedy other economics, a method to determine components of theonstruction waste received in the first place is needed.

.3. Prevention of noise and dust at the CWS sites

The current off-site CWS program affects environment in aaradoxical way. Firstly, it positively contributes to constructionaste reduction and thereby saving natural resources. This has

een clearly proved by the factual data as exhibited in Fig. 5.nauthorized construction waste dumping occurred at inappro-riate areas has also been largely prevented, although concreteata demonstrating its effectiveness is hard to obtain. Nevertheless,

able 2hanges in the construction waste acceptance criteria at sorting facilities.

Effective date Construction waste accepted Waste acc

Before December 29, 2010 Construction waste containing more than50% by weight of inert waste

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ies Landfill; SENT:South East New Territories Landfill; WENT:West New Territories

paradoxically, a major adverse effect of the off-site CWS programlies in its impacts on the surroundings where the facilities weresited. During the site survey, each of the participants must wear asafety helmet and a mask. It is observed that when the mechanicalwaste sorting process starts, there will be a lot of noise and dustwhich are very harmful to the surroundings as well as people on-site. This is probably a primary reason resulting in the two wastesorting facilities to be located at the suburban areas in the NewTerritory of Hong Kong, as it can be seen from Fig. 2.

There are two groups of on-site workers involved in CWS activ-ities, including the inspectors responsible for site observing andvisual scanning at the construction waste transportation vehicles,and the workers undertaking the handpicking work in differentCWS processes. It is found in the study that when waste sortingstarts, there will be a lot of noise and dust which are very harm-ful to the health of on-site workers irrespective of being equippedwith masks and safety helmet throughout the processes. The noise

and dust caused by CWS activities can also affect the surround-ings. Currently, the CWS is carried out on outdoor sites withoutlittle noise or dust prevention measures. In a sense, the originalintention of implementing off-site CWS is to reduce construction

eptance criteria

of construction waste not consisting entirely of bamboo, plywood or timberby a vehicle, the weight of the waste divided by the permitted gross vehiclethe vehicle must be greater than 0.25 for goods vehicle with demountable skipr other types of vehicle.

of construction waste consisting entirely of bamboo, timber or plywoodby a vehicle, the load is regarded as construction waste containing not morey weight of inert construction waste.

of construction waste not consisting entirely of bamboo, plywood or timberby a vehicle: (1) the weight of the waste divided by the permitted gross vehiclethe vehicle must be greater than 0.25 for goods vehicle with demountable skipr other types of vehicle; and (2) the depth of the waste must not be greater thanods vehicle with demountable skip and 1.5 m for any other types of vehicle.

of construction waste consisting entirely of bamboo, timber or plywoodby a vehicle, the load is regarded as construction waste containing not morey weight of inert construction waste.

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aste being landfilled so as to contribute to sustainable develop-ent. However, the off-site CWS activities themselves can cause

lot of adverse effects on environment and society. Therefore, toaximize the overall effectiveness of the off-site CWS program,

dverse effects resulted from the off-site CWS processes should benvestigated and corresponding mitigation measures ought to beaken in the future.

.4. Recycling recyclable materials rather than disposal

In its current practices, construction waste is divided into tworoups (i.e. inert and non-inert) in each of the sorting processes.t the end, inert and non-inert materials will be collected to twoiles. Prior to the final disposal, both the inert and non-inert mate-ials have to be smashed to pieces by hammers so that they coulde well handled at landfills or public fill reception facilities. In theurvey, it is observed that some separated waste materials are suit-ble for recycling or reuse, such as timber. However, the staff tolds that all sorted materials entering the waste sorting facilities wille smashed to pieces directly and dumped at landfills or public filleception facilities. Thus, it is suggested that in future the recy-lable material can be preserved to maximize its residual valuenstead of being smashed or dumped. To some extent, recyclinguch materials provides a new stream of incentive for the CWS con-ractors. It has been noticed that in some other economies (e.g. USA,ustralia and Taiwan), the facilities were called waste recyclinglants. This is apparently a new philosophy although the prosperityf the practice is largely dependent on how well a material recyclingarket is developed.

. Lessons learnt from the off-site CWS program in Hongong

While there are areas for potential improvement, the off-siteWS program in Hong Kong is largely effective and efficient. Var-

ous lessons can be analyzed and summarized from its practicesith a view to providing valuable references to other economies

rying to stimulate construction waste minimization through CWS.

.1. Developing a set of supporting and interlocking policies

Government policies always play a key role in promoting the off-ite CWS practice, which will ultimately impact the environments a public good. In December 2005, the Hong Kong governmentntroduced the Waste Disposal Charging Scheme to ensure that finalisposal of construction waste is properly differentiated and priced.he waste charging scheme is promulgated not only to serve as anconomic tool for construction waste reduction at source but alsoo promote construction waste reuse and recycling thereby sus-aining the landfills and public fill reception facilities (Hao et al.,008). The off-site CWS program is subsequently launched as a keyupporting policy of the waste charging scheme. Under the pro-ram, mixed construction waste that contains more than 50% byeight of inert materials can be further processed to separate theon-inert portions prior to its final dumping. In so doing, the inertaterials will be transported to public fill reception facilities rather

han handled by landfills.In January 2006, the construction waste sorting facilities and

heir supportive infrastructure were completed in Tseung Kwan Ond Tuen Mun respectively. Table 2 tabulates the detailed crite-ia for accepting construction waste received at the designated

WS facilities. It can be easily observed that there is a distinctifference in the major criterion for determining whether theonstruction waste received at the sorting facilities meets theandatory requirements – ‘waste should contain more than 50%

and Recycling 69 (2012) 100– 108

by weight of inert materials’. Before December 29, 2010, it is deter-mined through measuring the weight ratio indicator, whereas fromthat time onward, the criterion has been extended to include a depthindicator as explained in Table 2. The interviewees in the studyreflected that the new criterion has resulted in increased percent-age of inert materials among the construction waste accepted at thesorting facilities. This in a sense proves that stricter waste accep-tance criteria do channel contractors and developers to carry outsome basic processing on construction sites before the constructionwaste is sent to the off-site sorting facilities.

Another interlocking policy that supports the implementationof the off-site CWS program is a trip-ticket system (TTS), which wasimplemented by the Hong Kong government in 1999 and enhancedsubsequently in 2004 (HKDB, 2010). It has been anticipated thatunauthorized construction waste dumping will increase given thewaste charge. Nonetheless, under the TTS, construction contrac-tors must fill in a standard trip-ticket form containing particularsof the transportation vehicle, type and approximate volume of con-struction waste, and the designated disposal facilities which havebeen approved by the Public Fill Committee or the Director of EPD.Once the construction waste is accepted by the designated facili-ties, a receipt will be issued to the vehicle operator for returningto the project engineer for verification of the contractors’ compli-ance with related policies. The contractors are also charged basedon their receipts. The system is used to ensure that all constructionwaste generated by public construction works is properly disposedof through tracking the waste destination.

Also, the TTS is applied throughout the off-site CWS program toprevent unauthorized construction waste dumping. Upon receivingthe construction waste, a receipt with essential project particulars,which is issued by the EPD, will be passed by the construction wastetransporter to the sorting facility staff responsible for visual inspec-tion and recording. Whenever the construction waste received isaccepted or rejected by the sorting facility, the information will berecorded on the receipt and returned to the transporter. Eventually,the transporter will hand in the returned receipt to the contractorwho is in authority. The receipts are essential documents for finalacceptance of construction works in Hong Kong. In this way, theTTS contributes to recording and tracking construction waste in areal-time way and prevents the waste being dumped improperly.

Implementation of the TTS is a strong enhancement resultingin an improved effectiveness of the off-site CWS program. Accord-ing to conversations with the staff from the CEDD and the on-siteinspector, if the off-site CWS program is solely adopted to encour-age secondary separation and sorting of the construction wastebefore it is dumped, some project stakeholders would dump thegenerated construction waste directly at some unauthorized areasrather than sending it to designated landfills or public fill receptionfacilities. This would reduce the effectiveness of the off-site CWSprogram a lot, as well as diminish the overall effect of guiding con-struction waste dumping choices by the Waste Disposal ChargingScheme. With the TTS, any construction waste sent out from con-struction sites could be well tracked and recorded. As a result, majorproject stakeholders concerned will have to dispose of their con-struction waste properly. Otherwise, they would have to be subjectto a high penalty for their inappropriate waste dumping behavior asregulated by related regulations. In summary, the implementationof the TTS has positive effects on the off-site CWS program.

5.2. Aiming at good policy execution

Without good policy execution, the off-site CWS program can-

not be well implemented irrespective that all details of the CWSprogram have been well regulated and documented. Due to thelimited land space and constantly active construction activitiesthroughout the region, the Hong Kong government has been

ation and Recycling 69 (2012) 100– 108 107

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aking a strong and continuous commitment to improving its con-truction waste management situation for more than two decades.

ith such a commitment, all construction waste management reg-lations issued have been strictly followed and well executed.

.3. Improving environment attitudes among project stakeholders

Many studies have found that human related factors are impor-ant in affecting the overall effectiveness of construction waste

anagement (Teo and Loosemore, 2001). It is also found that manyroject stakeholders will be involved in the entire constructionaste management process. Their attitudes are at the core of the

uccess or failure of a construction waste management processYuan and Shen, 2011; Teo and Loosemore, 2001). This is alsopplicable to the off-site CWS practice in Hong Kong. Here thetakeholders can be sketchily divided into three groups: (a) staffrom the CEDD, (b) inspectors and recording staff at the CWS facili-ies, and (c) workers involved in the mechanical sorting processes.

Staff members from the CEDD are in charge of promulgatingegulations for the off-site CWS program. They have two roles tolay in the whole program. First, they have to specify and reallynforce the related regulations that have been passed by the Hongong LegCo or the EPD in practice. Second, as the principal gover-or of the off-site CWS program, they will supervise and monitorhe implementation of the program, and enhance its effectivenesshen necessary.

The inspectors and recording staff working at the waste sortingacility are also critical to the success of the off-site CWS program.ormally the inspectors are responsible for inspection and super-ision of in- and out-vehicles and the construction waste acceptedo ensure that they are in line with the criteria as shown in Table 1.lso, they can audit recording staff’s work if it is necessary. Forxample, a typical work of the inspectors is to visually observehether the construction waste received at the checking point

ontains more than 50% by weight of inert materials. If they spot significant proportion of non-inert materials, the constructionaste will be rejected for further processing by the waste sorting

acilities, although it might meet requirements of the weight rationd depth indicators. This enhances the effectiveness of the off-siteWS program, because under strict check, contractors and deve-

opers are expected to carry out a careful pre-sorting of waste ononstruction sites so as to avoid increased transportation and laborosts. Similarly, the recording staff members are also responsibleor scanning the waste at the checking point to make sure compo-ents and quality of the construction waste accepted is consonantith the waste acceptance criteria. The only difference is that the

ecording staff’s judgments rely much more on the quantitativeeasurement results of the construction waste, including its weight

atio and depth indicators.The third group of stakeholders concerns workers carrying out

he handpicking job throughout the mechanical waste sorting pro-esses. It is evident from Fig. 3 that handpicking is conducted inach of the mechanical waste sorting processes. The handpickings especially useful for sorting lighter non-inert materials that can-ot be effectively and fully done by the mechanical sorting plants.s shown in Fig. 7, workers equipped with essential safeguards aretanding along either side of the conveyor belt to pick out non-inertonstruction materials before they were conveyed to the next sor-ing process. Since these workers undertake the handpicking work,heir attitudes and behavior toward CWS will be much importanto the overall efficiency of waste sorting.

.4. Economic feasibility is also essential

Despite the increasing environment awareness, the construc-ion waste disposal charges as regulated in the Waste Disposal

Fig. 7. A snapshot of construction waste handpicking.Note: This figure is provided by the CEDD.

Charging Scheme is an effective vehicle in stimulating on-siteand off-site CWS. As afore-introduced, the disposal charges forconstruction waste either entering landfills or being accepted byoff-site waste sorting facilities will be higher than that received bypublic fill reception facilities. Through this way, significant amountsof construction materials could be saved for reuse or recycling.Therefore, the discriminative price system for construction wasteaccepted by the off-site CWS facilities is helpful in bettering theoff-site CWS program.

From its commencement in January 2006 to February 2012when the survey was conducted, the two off-site CWS facilities havesuccessfully accepted and dealt with a total volume of 5.11 milliontons of construction waste. The latest daily average intake of TseungKwan O and Tuen Mun waste sorting facilities is 780 tons and 380tons, respectively. In line with its current practices, the governmentoutsourced the two waste sorting facilities to qualified contrac-tors following a public competitive tendering procedure. Now itis within the second contract (contract number: CV/2010/05) ran-ging from the period between December 22, 2010 and December26, 2013. The total winning price of the bid was HK$128 millionfor operating the two waste sorting facilities during the period.Because of ‘commercial secrete’, in this site survey, the authorscould not obtain the economic feasibility data, such as operationcosts of various mechanical plants, labor costs, and costs of trans-porting the sorted waste to landfills or public fill reception facilities.However, given that the off-site CWS program in Hong Kong hassustained for a relatively long period from its implementation in2006 and at present entered its second contract, it is reasonableto assume that the program is economically feasible, both for theCEDD and the contractors.

5.5. Promoting environment awareness among the whole societyas a long-term strategy

Societal factors also contribute to the implementation of theoff-site CWS program. The Hong Kong government has launcheda series of regulations for promoting its construction waste man-agement since 1980s. By executing those regulations, the society’sawareness toward construction waste management have beensignificantly promoted and enhanced. This forms a favorableinstitutional framework for cultivating better construction wastemanagement culture. For example, the waste charge scheme aswell as the off-site CWS program is not introduced overnight with-

out confrontations. Rather, it has gone through a relatively longperiod before these regulations are accepted by the stakeholdersconcerned. Elimination of loopholes in these regulations is one con-tributor, while the increasingly improved societal environment, in

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articular the environment awareness, is another factor that cannote ignored.

. Conclusions

The Hong Kong government launched the off-site CWS programnd built two CWS facilities in Tuen Mun area and Tuseng Kwan

area respectively in 2006 for separating and sorting constructionaste before its final disposal. Since its implementation, significant

mount of construction waste has been handled by the two wasteorting facilities, thereby alleviating the depreciation of existingandfills for receiving and processing construction waste to a largextent. Based on implementation practices of the off-site CWS pro-ram in the past years, this paper carried out a detailed analysis ofhe off-site CWS program for understanding its successful expe-ience and potential shortcomings. Besides data collected fromiterature review, government regulations and statistic reports, aase study on the Tuen Mun CWS facility was conducted for acquir-ng data to support the analysis and discussions.

It is found from this study that a total amount of 5.11 mil-ion tons of construction waste has been separated and sortedince implementation of the off-site CWS program. This contributesignificantly to reducing the amount of construction waste han-led by landfills. The success of the off-site CWS program isainly attributable to four aspects, including ‘sustaining policy

upport from the Hong Kong government’, ‘good policy execution’,encouraging off-site CWS through higher disposal charges’, andimplementation of the TTS’. While acknowledging the off-site CWSrogram’s success, there are some suggestions that can be usedo further improve the program in the future, which are ‘properocation of the off-site CWS facilities’, ‘effective measurements ofhe proportion of inert materials’, ‘prevention of noise and dustt the CWS sites’, and ‘recycling recyclable materials rather thanisposal’.

Drawing upon Hong Kong’s off-site CWS practices, the suc-essful experience identified in the present study can be valuableeferences for other territories aiming at better managing con-truction waste through implementation of off-site CWS. On thether hand, the suggestions provided can be used by the Hongong government when they consider improving the effectiveness

f its current off-site CWS program. Also, it is worth highlight-ng that the findings are presented in the particular context ofong Kong, they should be adjusted accordingly if applied to other

egions.

and Recycling 69 (2012) 100– 108

Acknowledgements

The work is jointly supported by the Hong Kong Research GrantsCouncil (RGC), Public Policy Research (PPR) Scheme project (RGCRef. HKU7016-PPR-11) and the National Science Foundation ofChina (NSFC) project (No.: 71273219) led by the first author, andthe NSFC Project (No.: 71203184) by the second author. Apprecia-tions go to Ms. Ruth TSO and the Inspector from CEDD Hong Kongfor organizing the case study. Special thanks are given to Dr. SarahLiao, who was the former Secretary for the Environment, Trans-port and Works of Hong Kong, for her insightful suggestions to thisresearch project.

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