Latrine+Plans



ENGR 330 Final Report Andrew Combs

1. Introduction

One of the main objectives of the partnership with the school in Peltan, Haiti is to help the Haitians complete the construction of projects which will accommodate the physical needs of the students and faculty. This allows them to devote more of their physical and mental efforts to education.

Mr. Wells and Mr. Huff have obtained a list of projects from Richard, the director of the school. Ricahrd thinks that the most important project is the construction of a latrine for the school. There are several motivations for this. First and foremost is the safety of the children. Poor sanitation puts people at risk for a variety of diseases that are spread through fecal matter. The second issue is the continued operation of the school. Haiti does not have high assurance of property rights, and Haiti’s government officials are susceptible to corruption. By building a latrine for the school, the legitimacy of the school will be increased. This will give the government less pretext to close the school. All of these concerns have been magnified by the recent outbreak of cholera in the country. Since poor sanitation assists the spread of cholera, the risks associated with poor sanitation facilities are now more severe.

2. Task Purpose

Due to the recent outbreak of cholera in Haiti, it is necessary to begin construction of the latrine as soon as possible. Waiting six months to go to Haiti is not viable. This means that the project changed to designing a latrine that school officials would be able to easily build with provided designs and funds. It is important to note that school officials are perfectly able to build a latrine on their own if the construction costs are covered. The project is thusly centered on improvements that they could make to their plans that may not be immediately apparent to someone designing from scratch.

The primary design considerations were the resources and preferences of the partners. The first consideration was the basis for rejecting any latrines that involve flush mechanisms or offsite transportation of the waste. The second consideration led to the rejection of any designs that required composting and removal of waste. In light of the current cholera pandemic, the Haitians do not want to deal with the waste in any way. This is a very understandable desire! They also want a very large, deep pit so that the latrine will last a long time. For these reasons, it was decided that the design should be a VIP latrine. This design is similar to the simple pit latrine that the Haitians were already planning to build; however, it includes a ventilation pipe that will help alleviate flies and odors.

The primary risk in the project is giving suggestions which will undermine the structural integrity of the project. If given enough money for materials, the Haitians will build a toilet that is structurally sound. The original toilet used at the school collapsed because they did not have enough money for rebar or a good concrete mix. It was not due to any mistakes by the builders. What we don’t want is for the toilet to collapse again because they are implementing our “improvements” and making the toilet less sound as a result.

3. Task Accomplished

A full design for the latrine has been completed. The document contains general instructions for the construction of the specific items of the latrine. It also has pictures and diagrams to assist the Haitians in visualizing the design.

A major structural concern was the size of the pit. The design suggests that the Haitians narrow the size of the pit that they are planning to dig. Richard’s original plans were for a 6m long x 3m wide x 5m deep pit. The design calls for the width to be narrowed to 2 m. This is based on instructions for latrines found online such as this: []. The design for the latrine on this website is quite different from ours; however, the general principles are the same. These designs have a circular pit and call for a diameter of 1.8 m and warn that larger diameters could make the building less stable. We suggest increasing the length of the pit to 8 m in order to make up for the lost volume.

Another decision was the diameter of the of the ventilation pipes. Circulation would best be served by putting one ventilation pipe next to each toilet hole. The building contains four stalls. This means that there would be four pipes, and each pipe would provide the ventilation for each stall. Proper ventilation occurs when the air in the stall is changed out a few times every hour. The flow rate of air is, of course, directly proportional to the area of the pipe. The main source of information for making this decision was this table from the World Bank. Using this table, the proper size can be approximated.



If it is assumed that each of the stalls is made around 2.5 m high, then each stall would be about 10 m3 of volume. This high volume means that a 200 mm PVC pipe should be used. This would allow the air in the latrines to circulate approximately 5 times every hour. This might be less due to the dense woods surrounding the construction site. These pipes will also be enough for proper fly prevention because there would be one pipe next to each toilet hole. These would obviously constitute the only possible exits from the pit.

It was also important to determine whether to put the pipes outside or inside the building. It was decided to put the pipes outside the building in order to avoid the difficulties of having to seal up the roof around the pipes.

3. Future Work

At this point the task is near completion. The goal is to finish the designs and send them to Peltan before the end of the semester. Some modifications need to be made. The current drawings depict one of the long sides of the building resting only on the concrete platform over the pit. This is a structurally sub-optimal. The design needs to be modified to allow both long sides of the structure to rest over the ground. It may be that the decision to place the pipes outside the building needs to be reversed. Other useful modifications might come from the final class meeting. Once these decisions have been made, the drawings will be modified and sent to Haiti. I plan to spend Thursday afternoon implementing the final changes before leaving for home.

4. Conclusion

Advancing the schedule on building a latrine has in many ways been an improvement. The school children will be able to use the new sanitation facilities much sooner than if we had waited until summer to begin construction. Also, since this project will be carried out solely by the Haitians, it will in many ways be a project that they have done for themselves. We have provided the funding and overall design for the toilet; however, the Haitians will provide the labor and the masonry skill. This will prove to be the beginning of a successful partnership.