Montevideo: historical development of sewer and drainage systems

Transcription

1 Montevideo: historical development of sewer and drainage systems J. Alsina and M. Mena* Servicio de Estudios y Proyectos de Saneamiento, Intendencia de Montevideo, Avda. 18 de Julio1360, tel , Montevideo, Uruguay [email protected] ABSTRACT The present paper describes the historical development of the urban sewer and drainage system in the city of Montevideo. The department of Montevideo has inhabitants (INE, 2004), 96% of which dwells in the urban area. This population represents 41% of the total population of the country. The City Council of Montevideo (IM) provides sewerage and drainage services to the community. In the begging of the sanitation worldwide, the city of Montevideo undertakes the task in a pioneer form, but it then had ups and downs in terms of development. In this paper we present an overview of the historical development of the sewerage works of the city and the design criteria applied at every stage as well as changes in the management of the system over time. Montevideo today is in a privileged position from the standpoint of environmental quality like coverage of the Department and the sanitation sector is prepared to face future challenges Finally the conclusions resume what did work, what didn t work as well as lessons learned and plans forward. KEYWORDS sewerage, drainage, historical, development. HISTORICAL DEVELOPEMENT Early years: Arteaga s sewerage network Montevideo was the first city in South America with a sewerage network. The construction of this network was granted to Mr. Juan José de Arteaga s private company, under a concession contract. The record of this contract goes back to 1852, just four years after the studies for London s drainage were began, and five years before Brooklyn s network design started.(fair, Geyer, Okun, 1968) This first network had main pipes that formed a combined sewage gravity system, constructed without defined dimensional criteria and with an outline of an egg-shaped looped network. The network construction is done without any planning, according to customer demand and the shortest topographic path. The design criteria are quite empirical. Hygienist approach prevails, where the conveying system consists of large conduits in every street in order to ensure the rapid removal of the source of contamination at source far away to the bay J. Alsina and M. Mena 1

2 Transition period: Maggiolo s Plan This period had as an outstanding characteristic the rapid and planned expansion of the new systems. It began with the formulation of a General Plan of Building Works of the City of Montevideo (Maggiolo, 1922), that established the first effort in the planning of the sewerage system of the city and was not updated until 70 years after its approval. Even though the combined sewer system is still used efforts are made in order to minimize the discharge points and minimize the outfalls so as to optimize the performance of the network. No application of mechanized elements such as pumping stations, mechanized grades or other are incorporated to the system. Efforts were made in order to use the formulations available to calculate sewerage dimensions. The application of formulas for the calculation of storm flows depending on the basins surface, slope, and its urban characteristics became a standard. The intensity of rainfall was updated with over the years. While the forecast horizon of the Maggiolo Plan was 30 years ( ) population growth projections were exceeded broad mind ahead of schedule, both in quantity and spatial distribution. Provided some of the interceptors were not built for economic reasons this result in a multiplication of the sewage outfalls and contamination of urban waterways and beaches to a greater extent than expected. The fact that land use forecasts were outdated and that the formulation applied to the calculation of the flow depended heavily on this factor implies that works built in this stage is nowadays far exceeded in its transport capacity. Although the network in the Maggiolo area have already been depreciated and far exceeded its service life, these are the only structures available for collection and conveyance of storm water. Thus, in these areas are now serious flooding problems. In these dense and consolidated urban areas the solution to drainage problems becomes now very difficult and expensive. A pause: the crisis period It can be identified by the changes in the design criteria (separate sewers instead of combined systems) and the decline of the country s economical situation, which is reflected in several characteristics of the network. The following graph shows the slowdown in the works in these years Montevideo: historical development of sewer and drainage systems

3 The first designs of separative sewage systems were based on bibliographic data to estimate domestic flows and then speed criteria for pipes. With respect to the calculation criteria for stormwater networks the Rational Methods is applied indiscriminately but without unanimity in the intensity formulation. This implies that the works planned at this time have very different behavior with regard to extreme events. Studies conducted by Ing. Capandeguy indicates that for return period of 10 years, the intensity may vary between 20 and 60% according to the methods used in this years. The figure below shows the areas with sanitation coverage for the three periods mentioned above. Programs: the Plans of Urban Sewerage. Despite the fact that Montevideo was founded as a port city, its beaches turned out to be a major attraction, with 77 km of coastline over the La Plata River, 20 of which are sandy beaches. The coast with its beaches is one of the most precious asset of the city. So much so that according to the Gallup surveys, "The summer tourism in the summer of , 79% of tourists entering the country did it first attracted by the beaches. But the increasing deterioration of the environmental quality of the coast waters, bays and beaches, accentuated by the lack of development of the sanitation system, produces a severe affectation of the coasts uses because of its unacceptable condition, with a noticeable diminution of the concurrence to the beaches and the arrival of tourists. In the mid 80's the population was convinced that the beaches were unhealthy and therefore attendance dropped dramatically. Even family doctors recommend not taking children to the beaches. The results of the analysis carried out then for thermotolerant coliforms showed values of over cfu/ml and cfu/ml for dry and wet days respectively For these reasons the problem is considered of national importance and of maximal priority to the Government. Therefore, in 1972, technical studies were conducted in order to look for solutions and the Plan of Urban Sewerage of the City of Montevideo (PSU) was defined. Its execution was divided in stages that are carried out with the partial financing of the IDB since 1981 Today 3 Plans named PSUI, PSUII and PSUIII have been completed. Works include extension of sewer and drainage network, rehabilitation of existing networks and management improvement programs. The figure below shows schematically the works associated with these plans. J. Alsina and M. Mena 3

4 PSU I PSU II PSU III As these pictures show the three plans achieved to extend sanitation coverage significantly and particularly final disposal is provided to the east of Montevideo in PSUI by a marine outfall that serves almost half of the system. The main objectives of the Plans are the improvement of the environmental quality and the increment of the efficiency and quality of the service In this period new technologies were incorporated and special attention was paid to water quality aspects as well as new design criteria Strategic plans: the Sewerage Master Plan of Montevideo: PDSDM (Sogreah-Seureca- GKW -CSI, ) PDSM is a strategic plan, based in a tendency and scenarios analysis, allowed to define the main activities, with a time horizon of 2035, as well as the means to obtain the necessary resources to carry them out. There was made an important effort by the Plan to adopt new tools and methods in order to optimize the use of the existing network as well as the future one. Uniform criteria are established for the development of projects according to the state of the art techniques at that time. The Plan applies for the first time in Montevideo software for the analysis of phenomena such as quality of water courses, modeling of the sewerage and drainage hydraulics and coastal water quality. An important contribution is made in regard to the processing of available information and its application to the design area. With respect to the expansion of the sewer and drainage systems the PDSM scheduled the extensions of the separative system. Electromechanical elements such as pumping stations, mechanized grades, controlled weirs, remote control systems and other are incorporated to the system resulting in a very complex network. Land Use Master Plan and the Solid Waste Master Plan are indicated as a great priority for the City Council to address. The Plan also proposes institutional strengthening plans that result in separate accounting for the sanitation sector. Current situation: PDSDUM and CCLIP. Once the PSUIII was still under construction the IM noticed that the PDSM (1994) needed an update. There were several reasons for this: 4 Montevideo: historical development of sewer and drainage systems

5 Deviations in the population scenario. Economic difficulties to carry out works. New plans that affect the occupation and development of the city. Once the environmental quality of the Department had been improved by increasing sanitation coverage, people began to demand the resolution of other long-neglected problems: urban flooding in both consolidated areas with poor drainage as well as new drainage systems in areas of recent occupation. That is why the IM is advancing in the elaboration of the Master Plan of Sewerage and Urban Drainage of Montevideo: PDSDUM (IM, 2006) incorporating with more emphasis the urban drainage component. Today the IM continues with the implementation of plans for urban sanitation in the context of joint financing between the IDB and the IM. The PSUIV is being executed and its main objectives are to increase coverage of sewer and drainage systems, construction of the western submarine outfall, family re settlements in the areas provided for construction and improvement of commercial and institutional management. As presented in the figure below the PSUIV will construct a submarine outfall that will serve the western side of the city. With this infrastructure the complete sewerage system will have proper final disposal in the La Plata River. A Conditional Credit Line for Investment Projects (CCLIP) has been approved until the year 2022, which will allow the execution of the necessary works to achieve a 100 % of urban area with sanitation and the adequate final disposal. The IM is moving in the application of tools to help design new projects. It aims to generate the know-how for the technical personnel necessary to implement the models and perform alternative studies both at planning and budgeting and project management. The IM has also incorporated into the solutions, the concept of sustainable urban water cycle and complement the classical solutions for the disposal and transport of urban water with detention and retention facilities. In present the city council has begun to incorporate nonstructural management measures depending on the land use and zoning ordinances in order to provide lower impact development. J. Alsina and M. Mena 5

6 CONCLUSIONS In the begging of the development of sanitation worldwide, the city of Montevideo undertakes the task in a pioneer form. It can be noticed that in the first decades of the past century the city s growth was accompanied by the sewerage system expansion, until the crisis of the middle of the century. This has implied that in the implementation of the three stages defined by Desbordes of the historical development of sewer systems (sanitary, rational designs and finally integrated and sustainable sanitation solutions and management) the city was left behind by the first world in the last two stages. Once undertaken the path of strategic planning and the plans of sewerage a vast effort has been made in order to incorporate the new concepts to the phases of planning, execution and operation of the systems. During over more than 100 years of experience, and despite of the ups and downs in the development of the sewerage and drainage system, there has been an important effort made by the city council in order to update the design criteria, use more modern and up to date tools as well as to incorporate the new technology and modernize institutional aspects of the organization as far as possible considering the distinctive features of a developing country. What did work As a conclusion of the recent years sewerage and drainage management, it can be emphasized that: The department's environmental quality is good, the beaches are recovered and the process of recovery of the Bay has begun. Montevideo is the first city to be certified ISO for environmental management in its 5 most popular beaches. Coverage of sewerage reaches 91% of households including the informal city. Major investments have been accompanied by management changes and institutional updates. The city of Montevideo has been able to prioritize a global and integrated country strategy against purely sectorial interests. This sustained long-term effort has become a state policy. As a result of this, the FEMSA Foundation and the IDB granted the 2009 award for innovation in water and sewer services to the city of Montevideo. What didn't work Management systems still needs to be improved. 6 Montevideo: historical development of sewer and drainage systems

7 Interdisciplinary coordination between plans and their integration has begun but needs more efforts to be made. The area of sanitation of the IM is very vulnerable to corporate environment which hampers the implementation of sector-specific policies. Network extensions has often not been accompanied by a similar increase in house connections. Health education and communication with the population has started but is still insufficient. Lessons learned. Planning, dynamism, flexibility. Strategic planning is an indispensable tool. An irreversible process has begun and the sanitation sector has its own Master Plan as guide. However the plans must have sufficient dynamism and flexibility in order to accompany unexpected changes and adjust to new realities. There for it is particularly important that the knowledge is in the hands of the technicians of the IM. Management commitments. Its very important to define indicators to assess progress of activities aligned with the achievement of goals. Institutional strengthening and human resources. The management changes were necessarily accompanied by institutional strengthening and technical training. It is essential to continue in this path to accompany the development of the sanitation sector. International financing. The good relationship with the IDB has assured the international funding in order to assure the IM the founds to achive 100% coverage of sanitation and drainage in urban areas and proper disposal of 100% of domestic effluent. Plans forward Complete the update of the Plan. Accompany the paradigm shift in urban drainage, incorporating the concept of zero hydrological change, sustainable water cycle and incorporate non-structural measures. Seeking to be an engine and inter-sectorial and inter-institutional relationships. REFERENCES Instituto Nacional de Estadística, Censo Nacional de Población y Vivienda. Fair, Geyer, Okun, Abastecimiento de agua y remoción de aguas residuales. Maggiolo, General Plan of Building Works of the City of Montevideo SOGREAH-SEURECA-GKW-CSI, Plan Director de Saneamiento de Montevideo, PDSM. IMM, Plan Director de Saneamiento y Drenaje Urbano de Montevideo. DESBORDES, Contribution à l'analyse et à la modélisation des mecanismes hydrologiques en milieu urbain, Montpellier: Académie de Montpellier, Thèse. J. Alsina and M. Mena 7