Tunisia - Greater Tunis Sewerage Project : environmental assessment summary

RJPUBLIC OF TUNISIA GREATER TUWIS SEWERAGE PROJECT ENVRONMENTAL ASSESSMENT SUMMARY TABLE OF CONTENTS 1. The Project Scope .................... ... . 2. The Project Description ....................... 3. The Project Cost Estimates .............. ...ii 4. The Environmental Review and Assessment ... ................ .......... .ii 5. Summary or Environmental and Social Impacts . ..... iii 6. Mfitigation Plan. ..... ............................ .. . iv The Tunis West Treatment Plant . . . v The Sud Miliane Treatment Plant . .... vi 7. The Reuse of Treated Waste Water . . . ........ vii P. Conclusions ...... ..... viii LIST OF ANNEXES 1. MAP: IIBRD No.27729 2. MAP: IBRD No.27730 /1 J f f  REPUIBLIC OF TUNISIA GREATER TUNIS SEWERAGE PROJECT ENVIRONMENTAL ASSESSMENT SUMMARY 1. Proiect Scone. 1.1 The proposed project covers the reorganization, expansion and rehabilitation of the Greater Tunis Seweraee System in order to cope with the growing demand for sewerage up to the year 2011. By then the population is expected to have grown from the present 1.8 million to 2.5 million. The service level is expected to increase from the present 75% to 95% of the population being hooked up to the sewer svstem by then. As the expansion of the greater Tunis urban area will be mostly to the west, it will be necessary to create a new western sub-basin, subdividing the city in four sub-basins. The new westem basin will have its own sewage treatment plant, situated at Attar, outside the city limnits and within the area where treated sewage could be used for irrigation. The other three basins, the southern, central and northem ones, are in need of expansion and rehabilitation only. The project will be executed by ONAS (the National Sewerage Agency). 2. Proiect Description 2.1 The proposed project includes: i. The construction of a waste water treatment plant (WWTP) for the western basin of Tunis. The WWTP, of the activated sludge system, will have a capacity to treat the sewage of 700,000 population equivalent. The main complex is situated at Attar, just after the divide with the Mornag basin. A sewage collection center, with a pre-treatment consisting out of sand and grit removal facilities and a pumping station will be situated at a low site on the shore of the Lac Sedjoumi. A double pressure main will transpon the sewage from the collection center to the WWIP; ii. The expansion and rehabilitation of the 'Sud-Maliane" sewage treatment plant in the southern basin of Tunis. The capacity will be increased from 300,000 to 600,000 population equivalent, applying the same extended aeration treatment procedure; iii. The restructuring of the western Tunis sewage collection system, in order to divert part of the sewage to the new Western Tunis treatment plant;  iv. The strengthening of the southern Tunis sewage collection system and the connection of the village of Mornag to the "Sud-Meliane" treatment plant; v. The extension of the northern Tunis sewage collection system and a liaison conduit of 4 km between the northern Tunis and 'Cherguia" treatment plants, replacing an open canal that obstructs groundwater drainage of the Soukra plain in the Ariana lake; vi. The rehabilitation and resizing of the sewage collection networks of central Tunis and northern Tunis (La Goulette and Le Kram), to prevent salty groundwater intrusion; vii. The strengthening of all secondary sewer systems; viii. The construction of seven pumping stations; ix. The construction of a pilot project for ground water recharge with purified sewage after tertiary treatnent; x. The acquisition of miscellaneous sewer maintenance equipment; xi. The acquisition of a mobile laboratory type of sewage treatment plant; and xii. Miscellaneous studies and research work. 3. Proiect Cost Estimates 3.1 Total project cost (including the costing of the mnitigation plan) is estimated at DT 154 million (USS 144 million), with a direct and indirect foreign exchange component of DT 93 million (US$ 87 million). Identifiable taxes and duties amount to about 11% of total cost. 4. The Environmental Review and Assessment 4.1 The proposed project has been reviewed, screened, and proposed for Category A, consistent with the provisions of Operational Directive 4.01, Annex E, "Environmental Assessment." Preparation for this project was comprehensive, encompassing a Sector Environmental Assessment (SEA) and Project Specific Assessment (PSA) for each of the WWTPs proposed for the Greater Tunis area. The Enviromnental Assessment was carried out by a consortium of foreign and Tunisian consultants, financed under a Japanese (PBRD) Grant. The studies, which were done in close cooperation with the Tunisian Authorities and the World Bank, were carried out in two phases. The first phase , the SEA provided a qualitative framework on the situation of waste water management and GREATER TUNIS SEWERAGE PROJEC ENVIRONMENTAL ASSE5SMENT SUMMARY DALILA TADJEROUNI DECEIER 5.1996  iii disposal and how it could be improved for future investments in the field. The second phase covered the specific assessments related to the proposed project. These assessments were based on studies, field work, and public consultation with the different concerned population groups and with the many institutions involved. In addition, ONAS is required by law to undertake an Environmental Impact Assessment in conformity with the requirements of the ANPE ( the National Agency for Environmental Protection). 4.2 Both the SEA and PSAs showed that numerous positive impacts will arise from this project, ranging from those related to public health to those directly affecting the economy. Such effects are generally associated with the provision of sewage treatment facilities to a sizable part of a capital city, with coverage of more than a million inhabitants equivalent; an increase of 30,000 connections to the sewer network; and protection of vulnerable receiving waters from polluting discharges. Other substantial benefits concern the agriculture sector, since the proposed project will include the reuse of treated waste water for irrieation and other purposes related to the protection and preservation of groundwater resources. Few negative impacts associated with the project have been studied. These are related to the construction and operation of the treatment facilities and the rehabilitation of the sewerage system. Detailed environmental analysis along with a plan to mnitigate the identified negative impacts were discussed and approved by the Government of Tunisia. These mitigation measures will be made part of the enviromnental strengthening and educational program to be developed within the scope of this project. The project will not cause any resettlement due to construction of proposed facilities. S. Summan of Environmental and Social Impacts 5.1 The proposed project will improve the quality of sanitation services, reduce envirommental pollution and mitigate health hazards from waste water discharges in the national capital region through the facilities described above. The most significant positive and negative impacts that the project will generate are summarized below. 5.2 Positive mnRacts: The construction of the tetment faciities will have a strong positive effect on the overall environment at each proposed location. It will prevent the intense negative impacts on hman health and urban nuisances associated with the discharge of untreated sewage directly into the environment from the sewage colector system at discharge points and, hence, decrease the exposure to waste water related diseases (e.g., gastro- intestinal) of the affected urban population. The rehabilitation and construction of new sewers will enhance firther the quality of life in the urban areas, especially for those settlements with insufficient ifrastucture networks and higher housing density. More than 150,000 low income population are expected to directly benefit from the project. 5.3 There will also be improvement of the water quality in the streams that flow throughout the city. A major benefit is the protection ofthe groundwater resources frorn GREATER TUNIS SEWERAGE PROECr ENVIRONMENTAL ASSESSMENT SUMMARY DAULATAD3EROUNI DECES,M 5. 1996  iv contamination by untreated sewage and the preservation of the marine environment and other vulnerable water bodies (agoons, oueds and sebkhas) frcm further eutrophization. As a result, economic benefit wil occur in terms of increased water volume of good quality, and increased fisheries and tourism activities along the coast near Tunis. 5.4 Furthermore, the treatment facilities will provide an opportunity to improve the control of the industrial discharges through pretreatment and connection to ONAS sewers, as required by the tunisian law. For the Sud Meliane plant, potential industries with non- compliant waste waters have already been identified. Whin the framework of the FODEP activity, these industfies will benefit from a program which has materialized in the construction of an industrial pretreatment unit that will be connected to the proposed plant. 5.5 Finally, it is worth noting that the enviromental aspect lays at the heart of the whole conception process of this project. It has, iteratively, influenced the design of the WWIP's, their site locations and the quality and use of their by-products. Two major elements around which this process has revolved are the protection of the environment and the valorization of the scarce water resources through the reuse of the treated water. Indeed, in the case of Tunis West' WWTP the flow of the eising sewerage system, for a sizable part of the covered area, will be reverted to the newly identified westem basin where it will be treated in the proposed WWTP. This, on the one hand, prevents the efuent from being discharged into the Gulf of Tunis, the sea and other vulnerable RWB. On the other hand, it offers the advantage of using this effluent for irrigation or recharge of the groundwater resources. Hence, generating significant economic and social benefits. 5.6 ieeative Inpacts: During the construction and rehabilitation of the sewer network and the construction of the treatment facilities, impacts of minor importance and magnitude a- -. uected to occur. These impacts are tempomry and will include: disruption of traffic pattem in.; - ,viced areas of the city, interference with other urban infastructures, disrupted access to residential or/and other buildings, change in the landscape Ooss of vegetation), noise mnisances and air pollution due to dust formation. The project activities do not require any involuntary resettlement. During operation of the treatment plants, some of these minor physical imnpacts will continue to occur. It is, actually, the case for odor and gas emissions and noise. 6. Miti2ation Plan 6.1 A detailed Mitigation Plan was presented and approved by ONAS, the Ministry of Environment and ANPE. The Plan contains a list of al the possible impacts that could occur in this project during the diff-rent phases of the project inplemernation cycle, comprising: (a) rehabilitation and construction phase of the sewer networks; (b) the construction phase of the treatment facilities; and (c) the operation phase of the plants. For each ofthe possible source of impacts or type of project activity, the nature of the impact is descibed and actions for remedy are listed. The responsibiliifes for these actions are defined and the concemed agencies identified. An enronmental management plan is also proposed. GREATER TUNIS SEWERAGE PROJECT ENVIRONMENTAL ASSESSMNT SUMMARY DALILATADJEROUNI DEMBR 5,1996  v 6.2 A monitoring program is recommended for the sewer networks and the treatment plants. In addition to what is currently done by ONAS, through its laboratories, specific monitoring of the properties of both the influent and effluent will be performed and assessed against the norms for agriculture reuse. The use of the sludge as fertilizer is strongly recommended. The monitoring program will also continue to evaluate all possible other impacts on the environment including ambient air, soils and vegetation, and the RWBs dow%nstream effluents. 6.3 A program for institutional strengthening of ONAS' technical, organizational and managerial capacities is also foreseen. It will cover the regional departments and will include a Geographic Infornation System component. Furthermnore, reinforcement of the existing institutional machinery is recommended along the lines of the SEA!s findings. 6.4 The main impacts and related mitigation measures for the treatment plants are sumnarized below: The Tunis West Treatment Plant E-mission of polluted water: The proposed project will prevent emission of raxv waste water in the served areas from currently overcharged plants to a very important extent and, hence improve considerably the sanitation of a sizable part of the capital urban areas. It wil also relieve Sebkha Sejouni from tne curent discharges and possible flooding of its banks. However, it may present some risks. The major one remains the discharge of the effluent into the environment if the reuse option is not pursued. The plant is designed to produce a disinfected effluent with a quality to meet the standards for irrigation. lt will however, contain high nutrient concentrations which will contribute to the ongoing accumulation of nutrients ir. the Gulf of Tunis. The latter, being highy vulnerable to eutrophization, this will cause further deterioration of the sea grass fields and bloom of algae. The effluent will also affect the Mejerda but to a lesser extent than the Gulf of Tunis. It is estimated that the effluent will increase by 1% the flow ofthis section of the Mejerda adding to its already rich load of nutrients. MitiLation: The nutrients will be removed, by means of tertiauy treatnent, if the effluent is to be discharged into the oueds and, in final stage, into the Gulf Altematively, other destinations ofthe effluent will be examined. Emission of waste: The plant will also produce an estimated 90 m3 per day of stabilized, dried sewage sludge that will be sold to farmers or else transported to a controlled dumping site. Construction of a solid waste treatment plant under study is proposed for the close vicinity of El Attar site. Mtigation: The sludge produced so far by ONAS' eisting treatment plants has been of good quality and has been in high demand by farmers. However, irregular emissions into the sewer systems could drastically change its quality as well as the quality of the GREATER TUNIS SEWERAGE PROJECT ENVIRONMENAL ASSESSMENr SUMMARY DALILATADJEROUN DECEMBE, S.1996  vi effluent, which in tum will be damaging to the environment and public health. ONAS monitors carefully sewage coLected at each of its operating WWTP's, through on-site laboratories and a sophisticated central laboratory. Emissions into the air: The waste water treatment plant wrill also have local impacts in the forTn of odor and gas emissions into the ambient air as well as noise. At El Attar, odor will be emitted be the sedimentation basins causing nuisance up to 500 meters beyond the plant's limits. The methane-driven generator for aeration wil cause emission of NO, et CO2. A torch (5 m height) uill be needed too for flaring rmetane surplus. Mfitlation: At the Sejouni plant, odor emissions will be controlled by covering the equipment and treating the air in a biofilter. In El attar, the site is isolated and there are no houses in the close vicinity. Urban Plannin Aspect: In addition to the already existing urban settlements in the vicirnity of the plant at Sejoumi, the area is planned, according to the provisions of the Master Plan , to be fiuther developed into a residential quarter wuffi average to high density. Mitigation: It is foreseen to install a buffer zone of no less than 500 meters around the site to prevent any negative impacts to the health of the inabitants of the planned residential development. Within the scope of this project, the Department of Urban Planning will be notified in order to makle provision for such measure into the Master Plan, currently under study. The Sud Meliane Treatment Plant Emission of poluted effluent: The effluent will be discharged into the Oued Meliane and then into the sea. It will have an adverse effect on the marine ecosystern if the nutients are not removed. Mitization: Additional treatment is needed if the reuse program does not mateialz and the sea outfalls are unjustifiable. Emission of waste: It is estimated that the production of sludge will reach 38 m3 per day. In this area of Tunis south, the sludge currently produced is being used entirely by fmers. Mitigation: If unused, the sludge wil be dumped into controlled landfiDls. Emission of other nuisance: The plant will produce regular emission of odor into the air and noise. Mitigation: The odor emission will be unacceptable with the doubling of plant capacity in highly urbanized area. In addition the international sport complex will be GREATER TUNIS SEWERAGE PROJEC ENVONMETAL ASSESSMNT SUMMARY DALILATADJEROUN!l DECMBER 5.1996  vii located just in front of the plant, across the road. Simple measures such as covering, evacuating and treating the air uith biofilters will be used. 6.5 Public Hearing and Communications: During September and October 1996, ONIAS, in coordination uith the Ministry of Environment and ANPE, organized a public infornation procedure in harmony with legal rules. A seninar was held where all the partics were invited including community groups, professional associations, and non governmental organizations. The appraisal mission will assess the results of this procedure. The fill environmtal assessments reports are available in the Public Information Center. 7. The Reuse of Treated Waste Water 7.1 Reuse Potential in Tunis West: El Attar is located just over the water separation of the Mejerda river basin with a large area of land suitable for irrigation, located on the sides of the hills overlooking the Chaffrou valley. This land (6,000 to 8,000 ha) is suitable for cultivation of fruit trees. Consultation with the agriculturc department proved that there are no technicaL socioeconomic or cultural obstacles for effluent irrigation in this area. The activated sludge treannent process coupled with disinfecton will produce an effluent with a suitable quality for irrigation. 7.2 To be able to use the effluent, construction of a storage basin and distribution works will be required. These should be the responsibility of the agricultre sector. Preliminary studies have located a suitable site for a storage basin close to the plant. Increased storage capacity, using the natural depressions of the land nearby the site of the ,plant could also be achieved at minimum cost. It is sought to make the effluent available for non-restrictive irnigation wher. the recon=nended changes in legislation are made. In the meantime, only restrictive irrigation will be allowed- The fiu debit could be reused by 2011, creating up to 8,000 ha and possibly extending to the neighboring zone. 7.3 Reuse Potential in Sud Meliane: For the existing plant of Sud Meliane, the reuse has currently attained 40 percent of the identified irrigable land (fruit and olive trees), counting 1000 ha and located in the close vicinity of the site. This low percentage is due to the defective state of the irrigation irastructure in place. Investments need to be done to renew and/or rehabilitate this infrastructure. This could result in an increase in the present potential of reuse to a higher percentage and open up the possibility of extending the current irrigation area by another 400 ha, that have already been identified. 7.4 Based on the results of this first experience, though promising conclusions on the potential of the reuse practice in this area could not yet be drawn. A study needs to be conducted to shed some light on this matter. The discussions with the Agriculture Department regarding the potential for the whole project (existing and extension) suggest that the area is rather sensitive and confirm the need for fiuiher study to explore the possibilities. The economic feasibility of reuse in this area has also to be established. As the cost of irrigation water from the Canal Cap Bon, used in this area, could prove to be a serious competitor to treated water. GRATER TUn SEWERAGE PROJECr ENVIONM ENTAL ASSESME SU "Y ALATAD=OU DEE 5.1996  viii S. Conclusions 8.1 The environmental review concludes that the proposed project will generate overwhelmingly positive emironmental, social and economic impacts. With its mitigation measures, the project does not present negative environmental consequences. The mitigation plans stress the importance of project planning during the different implementation phases, institutional strenghening and technical performance. ONAS, ANPE and the M,inistry of Agriculture will oversee and evaluate, for their respective part, the compliance and the effect of these plans. They will also ensure proper coordination during implementation of these plans. GREATER TUNIS SEWERAGE PROJECT ENVtONMENTAL ASSESSMENT SUMMARY DALIA TADJEROUNI DECELME 5. 1996  -~~~~~~~~~~~~~~~~~~ . - lsmo ~ ~ ~ ~ ~ ~ a 'V s;CNr S- J gi'6l!:s'''SV;'~~~~s a,l