Condominial Sewerage Systems Planning & Design of Sanitation Systems and Technologies Klaus Neder, CAESB Welcome to this module of the MOOC on condominial sewers and the approach employed in their design and implementation. My name is Klaus Neder. I am an engineer at CAESB, the Water and Sanitation Utility of the Federal District in Brasília, Brazil, where I have led CAESB’s efforts to roll out condominial sewers and appropriate wastewater treatment to the whole of the Federal District region over the past twenty years. Nowadays serving about 1.5 million people, the metropolitan area of Brasilia is one of the most extensive examples of the use of the condominial sewers in the world. In this module, you will learn, what are condominial sewers and how do they differ from conventional sewer systems. What are the advantages of condominial sewers over conventional sewers and in which circumstances are they particularly beneficial. What are the implications of condominial sewers for a utility company? Prior to adopting the condominal sewerage approach in Brasilia, CAESB found that conventional sewers were being built but, households would not connect to them. It was quite common that less than 50 percent of the neighborhood was effectively connecting to the new sewer systems. Consequently, the large amounts of funds invested in the trunk sewer infrastructure and in the wastewater treatment plants would not realize their expected public health and environmental benefits. Some of the major factors for this failure were, a lack of dialogue between the utility and the households regarding the sewerage solutions to be designed and installed. The high capital costs of conventional sewers that utilities, and by extension their customers, had to cover. We found that the major reason that caused users not to connect to sewers included, a lack of funds in the household to allow them to make the piped connection to the sewers. No adequate internal toilet/plumbing installations in the household. The local topography, including situations where internal installations are located lower than the sewer lines. An existing solution, such as septic tanks, already in use. Where connecting would require the breaking of floors and walls or where the wastewater was already connected to some kind of drainage requiring its separation. Soon we realized that conventional approaches to implement sewers are generally rigid and not flexible or adaptable enough to take into account the specific requirements of the target population and of the local situation, such as those mentioned. As a result, it is often difficult to roll out conventional sewerage systems to which households actually connect, especially in informal, densely populated, unplanned settlements. When CAESB first introduced condominial sewers in Brasilia, we adopted an approach in which we did not expect the client to come after the sewerage project but, instead, through which we would actively pursue the client. In fact, following the condominial philosophy, we start our work and our analysis from the upstream source of the sewage, this means at the household, with a focus on each individual household connection, and then follow a downstream path through the trunk sewers to the wastewater treatment plant. Such an approach is in the marked contrast to conventional sewerage projects in which the household connection is the last concern or sometimes is not a concern at all. Providing adequate, effective, and affordable connection to the sewer network is thus a main objective of condominial sewer. The following slide will show the key characteristics of the condominial model, which has been developed and refined in Brazil, generally, and in Brasília with CAESB, in particular, over a number of decades. The Condominial approach features several key characteristics that distinguishes it from the implementation of conventional sewerage interventions. One key difference is the participatory approach adopted during the design and implementation of condominial sewers and, sometimes, during their operation and maintenance as well. Households are mobilized even before engineering designs are commenced and are fully encouraged to engage in the design and the works phases of the implementation of the local sewers. The community is a major decision maker regarding the design and implementation of the sewer system, and becomes the owner of the ‘condominial branch’, which will be described more fully later. An important factor of condominial sewers is the reduction in capital costs that can be achieved when compared to conventional sewers through the optimization of the condominal network in regards to branch routing, pipe extension, pipe depths, pipe diameter, and the optimized use of inspection boxes. One outcome of this optimization is that condominial sewerage networks can typically be 50 percent of the length of conventional ones. The condominial approach to implementing sewers provides us with the tools to depart from conventional thinking on the design principles of sewers. It thus allows us to design sewer system that can be successfully implemented in densely populated, unplanned, informal areas, such as in slums. One of the guiding principles of the condominial approach is to achieve 100 percent connection rate of households, whether they are located in rapidly expanding poor informal settlements or in middle class or rich areas of the city. Technical details for the implementation and maintenance agreement of the condominial branch are the result of a discussion and a joint decision of the utility and the targeted community, and result after consideration of all viable solutions. Households are not forced into certain solutions, but the technical and other alternatives are discussed with them so that an agreed optimal position is reached. In many cases, however, the local topography and the elevation of existing household sanitary installations are the determining factors for locating the household connection and for routing the condominial branch. The sequence of development and execution of condominial works is different from that of the traditional sewerage system. After the utility has concluded a survey, a preliminary sewer design is used to define the ‘condominiums’. These are the units of service which will be each having a single, shared condominial branch sewer. Both the social and the technical teams of the utility will work with the Condominium members to define the type and routing of the condominial branch that will serve them as well as the terms that will be applied to the construction and subsequent operation of the sewer branch. An essential part of the implementation of a condominial program is the dialogue and collaboration of the utility with the Condominium members. A close relationship between the two parties is required to successfully design, construct and operate the condominial sewerage system. Since such participatory approaches are relatively new to traditional sanitation, CAESB deploys “social teams” together with their “technical teams” to facilitate the approach and to thus help successfully arrive at the necessary joint agreements between the utility and the community. The final engineering design related to the collector networks are only undertaken after agreement has first been reached between the utility and the condominiums on the lay out of the condominial branch. This process of finalizing the design of the collector networks is carried out during the execution of the corresponding sewer civil works themselves, we call it in the field "final design". Let us take a closer look at the possible layout of a condominial sewerage network and the different elements made up by it. As we just heard, a condominium is a newly formed service unit with a single, collective connection point. All households in one condomium will connect to a shared branch that discharges into a secondary sewer network. Instead of service laterals directly connecting households to a sewer main under the street, the condominial system uses one single pipe that connects to each household in the block. This is called the “condominial branch”. There are different types of branches, depending on their location. However, irrespectively of whether the branches are internal or are at the sidewalk, they are considered the responsibility of the household, as a sewer connection would be under traditional sewerage projects. The illustration shows how the extension of the pipe network can be reduced through optimized routing of the condominial branch. Together with the shallower depth of the branches, smaller pipe diameters, and the use of simple inspection boxes instead of manholes, capital costs can be consequently reduced. Besides the optimized network layout introduced when using the condominial approach, there are other design aspects of condominial sewerage that help optimize the costs of installation. Pipe diameters in condominial branches are generally minimized. Hydraulic conditions permit a diameter of 100 milimeters. Shallower depths of pipes can be used when sewers are laid in front or in the backyard or under the sidewalks, thus avoiding traffic-bearing sites so to get as little as 60 cm, reducing the amount of excavation required. In condominial sewerage system, the number of costly manholes is reduced and they are replaced by simplified forms called inspection chambers. These factors not only reduce the cost of the sewers, but can also prove beneficial during maintenance and repairs. When condominial branches are located in household yards and in sidewalks, access for repair and maintenance is possible without the need for the utility to break up roads and interrupt traffic. The condominium members jointly agree on the location of the condominial branch. If the utility is to maintain the branch, the sidewalk is the preferred branch location. However, in informal, densely populated, unplanned settlements, or in other circumstances such as where the sanitary facilities are located at the back of the house, the back-of-the-lot branch is sometimes the only feasible option. It is in these circumstances where the condominial approach is especially beneficial, as it can provide solutions in situations where conventional sewers would not be feasible. Costs savings of condominial sewerage systems usually range between 30 and 40 percent of those of conventional systems. Furthermore, given that construction costs of the condominial branches, which are considered the private part of the sewerage network and are generally covered by the household, this arrangement represents a significant reduction in the financial burden assumed by the utility. Even though the households are responsible for the cost of construction of the condominial branch, in most cases it is executed by the utility. These construction costs are covered by the condominium members in the form of a connection fee, and are in accordance with the agreement signed by each household and the utility. A service fee for operation of the condominial sewer is usually based on the household’s monthly water consumption. In situations where users opt to maintain their branch themselves, they qualify for a reduced service fee. The condominial approach involves the targeted households and their community as a fundamental part of the sewerage solution and thus creates ownership among the users, which is an important factor in the sustainable operation of the sewers. The condominial approach is based upon the full participation of the community in the engineering design and construction of the local sewerage system. This requires that the utility employs social outreach specialists as well as technical/engineering specialists to work in conjunction on the design and implementation phases. This participation throughout the project cycle leads to high levels of connection by households to the sewer network, often reaching 100 percent. Given the optimization of the local sewer layout, the smaller sewer diameters, the shallower depths and the greater distances between the inspection chambers, the costs of the condominial sewer civil works can be reduced by some 30 to 40 percent of the costs of a corresponding conventional sewerage solution. The adaptability of the condominial approach to local conditions enables the provision of sewerage service where conventional solutions would not be possible, for example in informal, densely populated, unplanned, peri-urban settlements. However, the condominial approach can be equally applied to formally urbanized areas. In the district of Brazil where CAESB works, condominial sewers have been successfully implemented in all types of urban settings, poor and rich alike.
