Managing post-conflict demolition wastes in Gaza Strip: a case study on May 2021 conflict

Gaza Strip is considered as one of the armed conflicts prone areas in Middle East. Several intensive conflicts occurred in Gaza Strip in 2008, 2012, 2014 and 2021. These conflicts caused massive destroying the infrastructures, facilities, and buildings, which affected all services and activities in Gaza Strip. One of the major post-conflict issues in Gaza strip is the management of resulted demolition waste including its removal, sorting, recycling, and material recovery. In May 2021, over than 370,000 tons of demolition waste composed of rubbles and debris was generated during 11 days of armed conflict. The accumulated previous experience of rubbles and debris removal and recycling in Gaza Strip supported to perform a quick management approach for safe removal of the post-conflict demolition waste and reuse/recycle the resulted waste materials in various applications. The sorting and transporting process of concreate and non-concreate rubble elements of the waste were carried out in cooperation between local and international agencies as emergency recovery-funded projects. The most proportion of rubbles are concrete aggregates, thus, the material recovery was conducted through crushing process for concrete rubbles and then reusing it for road rehabilitation or producing concrete building blocks. The large concrete blocks reused to be placed for shoreline protection for specific area along Gaza beach. The recycling of post-conflict demolition waste management projects in Gaza Strip brought economic and social benefits through the reuse and recycle of resources and creation of job opportunities. In conclusion, although the post-conflict demolition waste management is quite different from municipal/industrial waste management in Gaza Strip, it is conducted through applying similar techniques of disaster waste management in waste removal, and those of construction and demolition (C&D) waste management in sorting, crushing, and sieving for recycling.


Introduction
The Gaza Strip is located in the Middle East, along the eastern coast of the Mediterranean Sea, bordering Egypt on the southwest and Israel on east and north and, together with the West Bank is part of the Palestinian Territories. The Strip is 40 km long and 6-12 km wide and covers an area of 365 km 2 . With a population of more than 2.16 million inhabitants, it is one of the highest densely populated areas in the word [1]. Gaza Strip is divided into 5 governorates: Northern Gaza, Gaza, Deir Al Balah, Khan Yunis, and Rafah.
The Palestinian Territories in general, specifically Gaza Strip is considered as one of armed conflicts prone areas in Middle East. Concerning the sensitive political situations in this hot spot area, several military attacks conducted by Israeli authorities during the last 15 years over Gaza strip, intensive conflicts occurred in 2008, 2012, 2014 and 2021. The Israeli force attacked on Gaza caused massive destroying the infrastructures, facilities and buildings, which affected all services and activities in Gaza. Furthermore, as blockade and isolations have been applied on Gaza Strip since 2007 that lead deteriorated economic conditions of Gaza Strip as most of infrastructure facilities became inadequate to the function. The blockade and the armed conflicts, together, prevented or delayed the implementation of many development projects, and that Gaza Strip currently is still heavily dependent on the international humanitarian support [2].
One of the major post-conflict issues in Gaza Strip is the appropriate management of massive amounts of demolitions wastes composed of debris and rubbles, which were resulted from damaged infrastructure, housing, commercial buildings, governmental buildings, and others. Reportedly, an amount of 600,000 tons of rubbles generated from 2008/2009 conflict in Gaza [3], while it is estimated that 2 million tons of debris resulted in Gaza as a consequences of 2014 conflict, as this conflict lasted for 51-day [4]. The most recent conflict record, which occurred in May 2021 revealed that approximately over than 370,000 tons of rubbles, resulted from 11 days of military operation [5]. In addition to that, unexploded ordinances (UXOs) have been reported at the main post-conflict demolition waste disposal sites and in the rubble of destroyed buildings, which pose potential risks [6].
The main concern following each conflict is how and where to dispose this massive volume of concrete rubble taking into consideration the fact of oversaturation of existing landfills. Accordingly, several post emergencies and recovery projects in Gaza Strip undertook the immediate removal of the rubble and debris that were accumulated as result of the military operation and transfer it to a safe place for further processing. The major of these projects were implemented by the United Nations Development Programme-Programme of Assistance to the Palestinian People (UNDP-PAPP) [7] to manage of resulted post-conflict demolition wastes in Gaza Strip including rubble removal, sorting, recycling and material recovery though divert funds from several donors, notably Government of Japan, under the overall supervision of local government ministries. The main activity components of these project are to (i) Unexploded Ordnance (UXOs) clearance, safe disposal and (ii) Removal of post-conflict demolition waste from destroyed sites, and (iii) Crushing, sorting and recycling of collected rubble and debris [8].
Management of post-conflict demolition waste presents a significantly different aspect from general (municipal and industrial) solid waste management. General solid waste is generated in a certain amount on a daily or weekly basis and is collected, transported, and disposed in predetermined place. However post-conflict waste is suddenly generated debris and rubbles at an unpredictable time and place, in which a large amount of waste is generated all at once and blocks/damages roads that are used for waste collection and transportation activities. Therefore, in the operation of post-conflict demolition waste management, at first, it is necessary to secure the access to piles of the post-conflict debris/rubbles for collection and transportation and to establish soon an emergency treatment and disposal system. On the other hand, since post-conflict demolition waste is mostly composed of debris and rubbles, there are aspects similar to construction and demolition (C&D) waste treatment methods that target these types of materials [26]. Moreover, at the generation stage, it has characteristics similar to those of disaster waste.
In the light of above, this article aims to present the overview of post-conflict demolition waste management in Gaza Strip with surveying the data on destination of rubble recycling caused by most recent conflict occurred in May 2021, including describing the on-ground actions. It is also included summary of collaborative efforts implemented by different agencies involved in rubble removal and recycling activities in the Gaza Strip.

Materials and methods
Interviews and records are applied for the purpose of data collection from the concerned authorities and agencies in charge of conflict debris removal and recycling involved in rubble and debris management projects in Gaza strip, the data for 11-day, May 2021 conflict attack on Gaza Strip. Primary data collection has been performed through interviews with focal persons in charge with such projects in the Ministry of Public Works and Housing (MoPWH) and UNDP-PAPP during the period January to May 2022. Furthermore, collective information has been considered from attending stakeholder meetings and workshops concerning the rubbles removal projects progress, achievements, and challenges organized by UNDP-PAPP in Gaza Strip in June 2022 [17]. The gathered data included overall of rubbles management approaches, quantities of debris removed and recycled, materials recovery, compositions of demolitions wastes and destination of treated demotions wastes.
It is worth to mention that part of efforts of rubbles removal and recycling under different projects are still ongoing, up to this reporting period. However, many records are obtained from the damage assessments reports and the announced bidding documents of relevant projects, which implemented/or still implementing by UNDP-PAPP and relevant ministries.

Infrastructure damage assessment in Gaza 2021
Mentioning the infrastructure damage resulting from the attack on Gaza on May 2021, the on-ground survey revealed that the housing sector has experienced the largest proportion of damages. The assessment recorded 11,894 housing units as partially damaged distributed among 8,241 buildings in which 88% of them are concreate buildings [9]. While 664 housing units were totally damaged included within 164 buildings, where 78.2% were concrete buildings and thus resulting of more than 80,000 square meters totally damaged. Gaza and North Gaza governorates have the highest numbers of totally damaged buildings, with 56% in Gaza and 25% in the North of Gaza. As of October 2021, and according to the latest United Nations Office for the Coordination of Humanitarian Affairs (OCHA) Situation Report, about 8,250 internally displaced people (IDPs) across the Gaza Strip [9]. Figures 1 and Fig. 2 show location maps of housing sectors damages in Gaza Strip during May 2021 conflict distributed geographically in terms of totally and partially damage level respectfully, which were produced by UNDP-PAPP. In addition, United Nations Satellite Centre (UNOSAT) provides satellite images for damaged infrastructures in Gaza Strip up to 28th May 2021 [10].
At the same context of assessing other damaged infrastructure, 77 of public buildings were partially and totally damaged, in which 58% of the totally damaged buildings were used for public services. Also, it has been recorded that around 273 educational buildings, 35 health facilities, 239 energy locations, 240 roads, 76 WASH (Water, Sanitation, and Hygiene) facilities and total 116.6 km length of water and wastewater networks, 107 workshops, 38 municipal machinery and 2528 private sector facilities were affected at varying degrees ranging from severe to moderate. The cost estimated for reconstruction efforts to cover entire affected infrastructure were over than 108 million USD [9].

Institutional arrangements for conducting post-conflict demolition waste management in Gaza
Based on experience and lessons learned from previous confliction event occurred in Gaza Strip, a common protocol has been established joining all involved actors for better to coordinate and supervise the operations of managing the post-conflict demolition waste, debris and rubbles, in Gaza Strip. The Ministry of Public Works and Housing (MoPWH) is the leading government agency for such sector starting from the damage assessment to the final recycling of the debris.
As aforementioned, the rubbles removal and recycling in Gaza depends on international agencies' interventions, as UNDP is the primary agency that considered the rubble management during emergencies in Gaza Strip. At the same context, other international agencies were involved for rubbles removal in Gaza after May 2021 attack, such as Egyptian Committee for Gaza Reconstruction and others [5]. In same context, a coordination channels established between Environmental Quality Authority (EQA), Ministry of Local Government (MoLG), Joint Service Councils for Solid Waste Management (JSCs) and municipalities for setting up the required planning response interventions towards all aspects of post-conflict solid waste issues.
United Nations Mine Action Service (UNMAS) is involved for related risks regarding the clearance and safe destruction of UXOs for remove explosive items and undertake destruction, assist stakeholders in the rubble removal operations and providing site-specific risk assessments [4] [8].

Management process and rubbles destinations
Regarding solid waste management operations during conflict emergencies, the waste management service providers such as municipalities and JSCs defined special action measures concerning the accessibility to waste disposal sites and waste accumulation, re-organization of waste collection fleet management and collection operations on-ground and use emergency sites to take the immediate response actions. In regards to post-conflict debris/rubbles management issue during the conflicts time in Gaza strip, the immediate actions taken for the priority of saving people life's once buildings targeted by attacks, through securing heavy machines for specific response actions towards recuse people. Furthermore, some fleets assigned to remove partial of debris/ rubbles scattered amounts, which locked the streets for the purpose of roads movements' facilitation and/or transferring them to specific emergency sites. However, generally the solid waste management service providers possess insufficient number of heavy machineries for the removal of postconflict debris/rubbles, and the need to coordinate with the MoPWH for deploying emergency its heavy machineries. Many of waste management fleets also engage the operation of heavy machineries such as wheel loader and trucks during the emergencies for the post-conflict debris/rubbles removal.Posteriorly, the process of the recovery of debris/ rubbles resulting from conflict in Gaza strip follow common procedures starting from damage assessments, debris/rubbles removal and material recovery. Generally, the process of debris removal and recovery carried out through private sector contractors who have a certain capacity for machines and transporters used for such process. The final disposal sites for debris/rubbles were selected in coordination with relevant authorities, and usually located in landfills sites. The Juhr AlDeek landfill have been selected for the process of placing the transferred post-conflict debris/rubbles and for the process of crushing and recovery rubbles in May, 2021 conflict.
The recovery of debris resulting from May 2021 conflict in Gaza strip follows specific procedures as per following subsections. Figure 3 shows different field pictures for managing post-conflict demolitions wastes in Gaza Strip starting from removal process to the final reuse of debris, which adopted in May, 2021 conflict.

Collecting damage information and its assessments
The process starts with collecting damage information and conducting its assessment to identify on-ground damages resulting related to infrastructure and classifying such damage to levels of severity, which allow rehabilitation, reconstruction, and recovery interventions.
As the process of the damage assessment, it is not only targeted the fully damaged building but also some of partially damaged building. Evaluating such issue covered detailed engineered and economic assessment regarding the recovery to the state it was before the damages, and recovery of damaged buildings towards a better physical construction [9].
The UNDP granted a fund from the Government of Japan to conduct detailed assessment of infrastructure damages resulting from the conflictions on the Gaza Strip from 11 to 21 May 2021 with full coordination with relevant ministries/entities [11]. In particular, UNDP coordinated with MOPWH to receive a list of buildings that proposed to be removed through the recovery interventions.
In the same line, a quality assessments were carried out which include identification of asbestos and other hazardous components, and identification of UXOs possible locations [12]. After the 2009 conflict, the quality assessment for rubbles' hazardous components was carried out by UNEP [13]. Risk Assessment reports prepared by UNMAS for each building before commencement of the demolition activity of damaged buildings. In May 2021 conflict, 30 risk assessments were identified for urgent removal of Explosive Remnants of War (ERW) during the period of conflict by UNMAS [6] during the period of conflict. Afterwards in post-conflict period, UNMAS, an integral component of the UNDP-PAPP Rubble Removal project, conducted 291 risk assessments as requested during damage assessment stage. Based on the assessment results, UNMAS in coordination with local partners carried out the operation of direct explosive ordnance disposal (EOD) at designated sites. On the other hand, EQA assessment report reveals that enormous amount of agricultural hazardous waste, in particular chemical wastes of pesticides and fertilizers are resulted from direct targeting a fertilizer factory in North Gaza [14]. Urgent removal actions were considered for an amount of 886 tons of hazardous wastes though UNDP intervention in c Resulted crushed materials to be reused for roads rehabilitation [17]. d Removed reinforced concreate foundations and large concreate blocks from damaged buildings. e Reusing the rubble foundation blocks for shoreline protection at Gaza beach [17] full coordination with relevant ministries, in particular EQA and Joint Service Council in Gaza and North Governorates (JSC-GNG) [15]. Safety measures were taken amid implementing the removal, transport and stockpiling the collected hazard waste to the special cell at the Juhr Aldeek landfill.

Removal of concrete rubble and non-concrete debris
The major quantities of rubbles removed either by the citizens themselves through contracting with a private sector, or by UNDP and other agencies. Table 1 describe the amount of rubbles, which have been generated in Gaza Strip during the May 2021 conflict and that have been assigned for removal and processing of recovery with relation to its number of damaged buildings. In addition, Table 1 linked the amounts of removed rubbles to the different responsible agencies involved with rubbles removal projects in Gaza strip. Therefore, the citizens and UNDP handled 75% of rubbles removal. The amount of rubbles have been reported according to MoPWH internal reports of removal rubbles progressing up to beginning of January 2022. Exact amounts records have been reported for UNDP-PAPP rubbles removal project in Gaza Strip.
Regarding the rubble removal and recycling project conducted by UNDP, the demolition process were defined through classify the type of rubbles to concrete and non-concrete elements in regards to the level of damaged buildings heightens as per followings; (i) Demolishing of buildings with height less than 12 m and (ii) Demolishing of buildings with height more than 12 m. A set of specific instructions regarding the safety measurements were defined for the contractors carried out the demolition and rubbles removals for buildings with high height as towers [16] [17]. Figure 3a shows an example demolition activity for a damage building from May, 2021 conflict [17].
The demolishing, sorting and transporting process of concreate materials for rubbles have specific producers prior the recycling process; according to instructions reported, the major components instructions for this activity is to; excavation for rubbles, cutting concreate elements to small parts (maximum 50 cm × 50 cm × 50 cm), extracting and cutting reinforced concreate bars, demolishing damage building and walls, loading, transporting and unloading of concrete rubble to final location for further recycling process. While the large reinforced concrete foundations are only extracted from damage buildings to be reused after that without cutting into small parts. On the other hand, the non-concrete materials were demolished and sorted such as wood, aluminum, steel, and any other items from existing damaged structures and rubble stockpiles [16] [17].
Considering a lack of fleet capacity and equipment for implementing such activities through Local Government Units (LGU's) or ministries, the local private sector (contactors) carried out demolition of destroyed buildings, the transportation of the debris to the crushing site and crushing the material though contracting with the UNDP or MoPWH.

Material recovery for concrete debris/rubble aggregates
The process of recycling the concrete debris/rubbles as per following steps; (1) Preparation of crushing site including leveling works and laying of polythene sheets, (2) Crushing transported concrete materials, (3) Stockpiling of crushed concrete materials at the prepared area at the crushing site, and (4) Lab tests for the crushed concrete materials [17].
The UNDP-PAPP project provided a crushing equipment, through contractor, at Juhr Alddek landfill (Fig. 3b). The total rubble transported to crushing site were 122,525 tons of rubble resulted from May 2021 conflict and assigned for UNDP intervention, in which around 111,621 tons were crushed by this equipment (Fig. 3c) [17]. Similarly, the citizens and other organization were involved in rubbles removal, and contacted other private sector conducted crushing at the sites in Gaza for further recycling the removed rubbles. International Labour Organization (ILO) in 2012, estimated that 30-50 small rubble crusher were available in Gaza, while about 200 to 300 people were involved in the collection of rubbles and blocks from destroyed buildings [18].
The test for the crushed materials revealed some size differences in some types of granules after conducting Sieve Analysis test. In same context, the California Bearing Ratio of Soil (CBR) also applied for testing the strength of aggregated resulting from the crushing, a range from 80 to 120% were reported. The labs results varied due to many factors; as way of mixing crushed materials, differences in type of crushed materials, and variation in soil surrounded the demolition buildings [17]. These results were performed for assessing the applicability of using crushing debris for paving roads. Based on the projects data for rubbles removals, it has been noticed that concrete elements represent around 88% of the total rubbles removed, while 8.6% are non-concrete elements. Reinforced concrete foundations blocks represent 3.4%.

Reusing recovered concreate demolition wastes
A part of crushed materials was used to paving agricultural roads though laying of crushed materials as subgrade replacement. Total of 72,400 tons of crushed materials were used for paving 50 road in Gaza Strip, for an over than 26,000 m length though the funds of Swedish International Development Cooperation Agency (Sida) and Government of Japan [17]. It is worth to mention that several local universities researchers and international agencies verified the opportunities for using crushed rubbles in the road rehabilitation and construction industry in general [19]. For Gaza Strip context, several tests were performed to ensure possibility and potential of producing recycled aggregates from the construction and demolition wastes and concrete rubbles through laboratory tests and the results revealed the applicability of reusing the crushed materials in construction industry and for road subbases [12] [20] [21].
In addition, one of the very important useful applications for reusing the demolitions wastes in Gaza Strip is utilizing the reinforced foundation blocks resulting from rubbles (Fig. 3d) for shoreline protection. The current situation indicated that the coast of Gaza is suffering from sand erosion problems and sedimentation pattern and building roads adjacent to the shoreline raising a serious stability problem in some locations on Gaza Beach area [19] Accordingly, a proximately of 4000 tons were placed to protect the shoreline in Rafah, Al-Zahra, and Gaza (Fig. 3e). The process of this reusing technique is to lay the big concrete elements horizontally and/or in inclined way according to site investigation [17].
Regarding to steel bars extracted from rubble reinforced concrete items, as columns, slabs. etc., it is important to mention that such steel bars modified and/or adjusted to be reused for only non-major constructions elements and secondary concrete elements because it lose a significant percentage of its tensile strength. For example, the reused bars can be utilized in door shoulders, infills and lintels. In either case, engineering tests shall be considered to assess the applicability of reusing any extracted items from rubbles.
Furthermore, when citizens (house owners) managed to remove the rubbles, they sell the concreate materials to private sector crushing sites to produce small aggregate for building blocks industry. The sands materials utilized for leveling matters. Figure 4 shows a schematic overview diagram for the entire management process for post-conflict rubbles and debris in Gaza war during May 2021.

Cost description for rubbles removal and recycling
The average cost was determined based on the previous experience of the entire rubbles management processes. The cost might have small variations among the conflicts occurrence years. However, according to latest bids of rubbles removal and recycling in Gaza Strip during 2021 conflict, the operation cost of demolishing, sorting and transporting activities is approx. 12 USD/ton, while the crushing process costs were about 7 USD/ton.

Overall post-conflict demolition waste management observed in Gaza Strip
For the technical side, some on-ground field challenges were observed during the removal and recycling process of rubbles from the damages buildings; such as (but not limited): (i) uncertainty of the damages levelness from the physical investigation, thus, further engineered exploration were needed, in which lead to delay the rubbles removal process. For example; damage can be observed at the structure of partial damaged buildings, but more observations needed for the its infrastructure (ii) limitations of reusing the recycled items from rubbles concreate materials in which that its physical parameters is changed or modified; e.g. reused steel reinforcements shall be for secondary concrete elements that should not be addressed to stresses. Furthermore, and the reuse of crushed concreate material as base course is not recommended in roads with high slope that need specific levelness of tensile strength which cannot be achieved by the properties of reused crushed materials [17].
On the other side, the consequences experience of the demolition wastes projects in Gaza Strip confirms its socioeconomic feasibility, thus, it opens more widen eyes towards the demolition wastes value through compensating the shortage of construction materials that are not available on the local market, providing new job opportunities and encouraging the public private partnership companies.
From the institutional setting side, it is obvious that most of protocols, measures, contingency plans, operational producers for demolitions wastes removal and recycling have been set as a result of accumulated experience of governmental and international institutions for these types of projects since 2005 in Gaza strip. The activities of removal and recycling of debris were optimized according to Gaza context. The relevant ministries, international agencies and other local partners experienced formulating technical and management committees for dealing the sector of disaster waste at the time of crisis and recovery period [22]. While there is a gap of formulating such kind of national regulations for rubbles management and recycling resulting from conflicts/wars. However, it worth to mention about the availability of experience, technical capability and financial support (though international funds) in Gaza Strip for war recovery programs.
The current fleet and equipment capacity of concerned ministries, LGUs and JSCs for handling the removal and recycling process is very limited, even not exists, thus, managing the post demolition wastes implemented through international support under the supervision and coordination with local authorities.

Conclusions
The post-conflict demolition waste management procedures is well established in Gaza Strip through the different national and international agencies, where rubbles can be managed applying similar techniques of disaster waste management [23] in contingency planning, identifying harmful materials, and emergency waste removal, and those of construction and demolition (C&D) waste management [24], such as sorting, crushing, and sieving for recycling. The accumulated experience of armed conflicts in Gaza Strip revealed good dealing with rubble and debris removal including the unexploded ordnance clearance, safe disposal, and crushing and reuse of collected rubble for various applications under close coordination with relevant local and international agencies. Concrete debris were removed and recycled in Gaza mostly by buildings owners and recovery by international projects but also other supports from local and international organizations.
The rubble concrete materials represent the most proportion of debris, which removed according to specific engineering instructions, and then it crushed to produce recycled aggregates used for paving specific types of roads, or it transported to private crushing sites for produce buildings blocks. The rubbles foundations blocks were reused to be placed for shoreline protections in specific areas in Gaza Strip.
Although the post-conflict demolition waste management is different from the management of municipal and industrial wastes, both share common points of view: urgent collection and transport, appropriate treatment, proper disposal, and recovery and recycling of as many resource materials as possible in the process. the manuscript. The views expressed in this article are given under the responsibility of authors and do not necessarily represent the official positions of institutions to which they belong.
Author contributions All authors jointly carried out the study; HA collected data and drafted/finalized the paper; WAB collected data, SAM supervised, and MY reviewed and revised the paper.

Data availability
The data that supported the findings of this study are available from the corresponding author, upon reasonable request.

Conflict of interest
The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The Publication cost (APC) for this article was financially supported by Japan International Cooperation Agency, Tokyo, Japan.
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