Environmental impact assessment for the proposed multi-storey building at M. Odeon, Plot no: 263, Malé City, Maldives

Abstract

This report discusses the findings of an Environmental Impact Assessment (EIA) carried out for the proposed 12-storey building including at H. Odeon, Malé. The project is proposed by the Ministry of Housing & Infrastructure. EIA is required for buildings with more than 10 floors and foundations that are laid below 1.8m from the ground, as per the EIA Regulations of the Maldives and all amendments to it up to date. The main objective of the EIA is to identify potential impacts of excavation, construction of foundation and dewatering and consider mitigation measures that may be adopted. In addition, the EIA would also consider other construction phase and operational phase activities such as waste management, energy and water supply although they are not directly related to the scope of the EIA. Demolition of the existing single storey building has been completed, and demolition impacts have not been covered in the EIA in detail. The project is to commence as soon as the EIA is approved and the duration of the project will not be more than 36 months. Substructure works, which is considered to be the most sensitive component (socially and environmentally), is expected to be completed within two months. The critical elements of excavation and dewatering are expected to be completed within three to four weeks. Therefore, the project has a critical impact timeframe of less than 2 months. Environmental assessment for building construction in Malé City was enforced following incidents of cracks in neighbouring buildings and vibration and noise-related inconveniences which occurred when deep piling was undertaken for the construction of the 15-storey building in Athireege-aage. Based on this incident, deep piling is considered unsuitable for congested Malé. Therefore, the most commonly adopted method of raft foundation will be adopted in the construction of the proposed multi-storey building at H. Odeon. This method distributes the load from a structure over a large area, minimizing the pressure on the base. This method of foundation is ideal for loose soils with low bearing capacity. However, since the soil of Malé with well-compacted heterogeneous material provides very good base for such foundations, there would be minimal disruption to adjoining structures. Since Odeon is on the original land of Malé close to the original shoreline, therefore, the foundation will be the on the original seabed and the same conditions would prevail. The area is also of compact nature as this is close to the rim reef of the island and material is well compacted. The proposed depth of the foundation for M. Odeon is at about 2.8m below the existing ground level or road level. This depth, which is greater than that of a typical building, is due to the size of the plot and height of the building. The ground floor will have retail space and parking areas. Parking is becoming an important requirement due to the parking difficulties in Malé. The main concern in excavating to this depth is the safety of the adjacent structures, most of which are old and do not have a proper sub-structure. Therefore, appropriate protection measures have been considered during the excavation, dewatering and foundation works. It is usual practice to provide a retention structure to prevent the foundation of other buildings from collapsing during excavation and the same methodology is proposed for this project. For dewatering, the current practice is for Malé Water and Sewerage Company (MWSC) to install a purpose built catch pit connecting to the main sewerage network and for the Contractor to pump effluent from the dewatering process into this catchpit using multiple pumps at designated locations. Since dewatering is required throughout the process of laying the foundation, it will be continuous and irrespective of tide. In fact, tidal influence on the groundwater table has been seen to be very little or negligible in most of the larger islands. Heavy machineries that will be used in the construction include excavator and lorry for demolition and excavation including demolition and excavation waste disposal and concrete machine and large crane for concrete works on top floors. During excavation, excavators and lorries will work inside Odeon plot except for some minor works on the roadside. Soil that is well segregated and free from debris and contaminants will be used in backfilling. Demolition has been completed quite some time ago and is not within the scope of this EIA. The plot is empty and grass has grown at the back of the plot indicating that the plot has been vacant for quite some time. Cement dust during concrete works is expected to be less of an issue compared to demolition dust and dust during sanding of walls. All these dust-prone activities is expected to be carried out with caution to minimize dust levels in the area. During concrete works, concrete machine and mobile telescopic crane will work from the road and appropriate road blocks, safety and traffic diversion measures will be implemented according to the requirements/recommendations of Malé City Council and Traffic Police. Safety measures within and outside the premises will be ensured during demolition of existing building until the end of construction phase. The project location is congested with mainly multi-storey buildings and a few single storey buildings of less than 5 storeys. There is hardly any vegetation in the area except for a mango tree on the west of the plot and a couple of Burmese rosewood (ofi eley) on the road side. Due to the congested nature of Malé and the area surrounding the project site, the condition of neighbouring houses were considered including condition of the structures, condition of groundwater (if groundwater is used) and living conditions to some extent. It has been identified that most of the buildings are old, single-storey or two-storey buildings and have several cracks due to ageing and settlement (mainly on the ground floor in high rise buildings) but could not have been subjected to vibration impacts in the past. There is little or no structural damage in the existing multi-storey buildings. Traffic in the area was considered important and was assessed to be similar to other areas of Malé. Traffic and pedestrian numbers increases in the evening after 1600hrs because people are usually out during the evening to cool off, especially for use of recreational facilities near Odeon. The roads in the vicinity of the project area are main roads majeedheemagu with heavy traffic, thus diversions during the construction phase have to be carried out with precaution. All parking spaces are nearly full throughout the day mostly with parked motor cycles. Private cars are becoming increasingly common in Malé today, therefore, getting parking space on the road is also becoming increasingly difficult. In terms of living conditions in the vicinity of the project site, most of the houses have congested living conditions except for some multi-storey buildings. Groundwater is still quite commonly used in households for washing, flushing and other nonpotable uses. Noise levels in the area are much higher than expected and average noise levels during day time as well as night time surpasses acceptable international standards for residential areas. There are also constant noise sources in the vicinity such as the STELCO powerhouse which add to the background noise levels of the area. The primary objective of the development is to enhance the income of the plot owner while improving quality of housing provided in Malé and improve living conditions in Malé. The living environment in Malé is in grave condition with building after building without any space except public spaces and roads. Most of the single storey houses and some of the multistorey buildings have congested living spaces. With a population density of 18,000persons/square kilometer of land area, and thousands of vehicles, Malé needs vertical growth and with increasing land value multi-storey buildings with adequate parking spaces in the building is an important aspect of development in Malé. The overall environmental and social impacts of the projects have been assessed and impacts are considered to be low magnitude and of minor significance. The negative environmental and social impacts of the development are also mainly short-term while the positive socioeconomic impacts of the project are long-term. Therefore, the overall impact of the proposed projects is greatly positive resulting mainly from improved living spaces and economic benefits, both direct and indirect. There would also be direct and indirect employment opportunities in the planning/design phase, construction phase as well as operational phase of the project. The socio-economic benefits of the project can be considered to outweigh the negative impacts of the project. The main potential impact of the project is possible damage to neighbouring structures due to vibration and weakness to substructure caused by soil movement due to deep excavation and dewatering. Disturbances to neighbours is an inevitable impact that will have to be minimized by taking appropriate measures to minimize nuisances such as noise and controlling dust and taking safety precautions. The construction staff needs to know about the importance of minimizing noise and dust and neighbours shall be made aware of the nature of works and potential disturbances. A grievance redress mechanism would have to be in place and made known to neighbours. Such a mechanism has been proposed in the report. Protection to neighbouring structures is an aspect that needs to be carefully looked at. Details of such protection are discussed in the report. Boundary walls of neigbouring structures would have to be protected prior to excavation. Impacts due to dewatering may be felt on adjacent buildings as well as neighbouring wells. Impacts of excavation and dewatering include loosening of subsoil and reduction in bearing capacity of the soil. This would generally occur in loose soil but not in compact sandy soil, as found in the project site, which is part of the original island of Malé. Sand particles have irregular shapes and sizes, therefore, it is well locked in place giving it a good load bearing capacity. Since the excavation is not too deep (about 3m from the ground surface), excavation would not have major impacts on the adjoining structures/buildings. The drawdown caused by dewatering on the water table is not expected to cause any loosening of subsoil in the area, since dewatering occurs at a shallow depth from the water table. However, the superficial groundwater lens will become saline due to drawdown. The current practice of using several small pumps instead of small number of large pumps minimizes such drawdown and there would be minimal impact on neighbours’ use of groundwater. However, this has to be monitored for the adjoining wells and provisions made to compensate for any drawdown effects. There is a mango tree on the west of the plot, which may be adversely affected due to salinization of the water lens. Appropriate mitigation of the impact by watering the tree regularly during the course of the dewatering works has been recommended. Atmospheric pollution due to concrete mixing works on site, cutting tiles, grinding and sanding of walls and timber works are of concern. Often only interior walls undergo smoothing by sanding and this process occurs within confined space. Carpentry works on site would be limited. Yet, it is often the case in Malé that interior finishing works are undertaken at night and with current regulations allowing noisy operations until midnight, there are certain disturbances that has to be minimized, especially given that the project happens in a residential area. In addition to foundation protection measures, the main mitigation measures for the proposed project would be to design for maximum natural ventilation and light, design for optimal efficiency of building while minimizing on losses such as excess concrete as in some of the recent buildings, minimizing and taking care in dusty operations, taking heed of noise during school hours and prayer times as well as night time and keeping the work areas safe and clean. The overall impacts of the proposed project are largely positive with some minor negative impacts. Yet, environmental monitoring has been proposed in order to ensure the effectiveness of the proposed impact management and mitigation measures. The proposed monitoring programme considers engineering inspection during foundation works, groundwater quality changes and availability during dewatering, dust and noise during construction, complaints/grievances, waste management measures including removal of excavated sand and demolition debris, measures to minimize falling of objects/materials during demolition, provision of personal protective equipment and so on. In conclusion, it appears justified from a socio-economic and environmental point of view, to carry out the proposed project.