Batey Cinco Casas – Septic System Project


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Assessment 2011: Preparing For The Septic System

In order to properly prepare for construction over the summer of 2011, RHIT-EWB sent a small team of students in late February to the village in the Dominican Republic to gather vital information for the project, the design and construction of a septic tank and pipe network.Things such as land elevation for gravity-powered piping, measurements of the building to determine the amount of materials needed, soil permeability to decide what type of filtration system to use, and the overall feasibility of this phase of the project were determined. The team of students returned with their findings and shared them with the rest of EWB-RHIT, so that design and planning for construction could begin.

Implementation 2011: Phase 2 – A Septic System Behind Us

After months of design work, and redesign work, technical reports and presentations, and then more redesign work throughout the summer, we were finally ready to begin implementation of the septic system.

Septic System PictureWhile this might seem easier than constructing a roof, there was a whole different aspect here of physical labor. Instead of pounding in thousands of nails in every day, we dug, and dug, and dug some more… until it rained… and then we bailed, and bailed, and bailed, and… until we finally found a pump, although sometimes faulty, to rent (a few days later). But that obviously isn’t where we started… or where we ended (read our blog – Entry 1Entry 2Entry 3 – for more information).

After disembarking our plane and driving to Monte Plata in central Dominican Republic, we began to prepare for the next day where our designs would become reality. Reviewing the site the first day, we found the pipe network drawn out with lime (cal) and wooden stakes set up to measure the slope of the pipes so that they could drain just by the force – due to gravity. Some of our Dominican compatriots had already begun the back-breaking work of pick-axing through the dry (soon to be drenched) clay and shoveling out the dirt. We soon joined in, and for the next couple of days, this is what we would be doing. It then began to rain in the afternoon (as we soon saw it did every day), and so began bailing the septic tank pit (which was to be over 8 feet deep) as it filled up with water fast. We created a fire-line and some-what efficiently (any failure was most likely due to our lack of strength) displaced the water. We ended up giving up and going home as it continued to rain, coming back to the next day and hearing that it had taken 3 hours to bail out the pit – dios mio.

Finally after we began finishing excavations for the trenches of the pipe network, we began using a rod with pen marks to flatten the bottom so that the pipe (PVC) would have the same slope all the way across (this was much easier thank using a measuring tape because 1) it didn’t bend, 2) we didn’t have to remember a number to look for and 3) we didn’t have to squint too closely to make sure that the string was between the right millimeter lines [we only had a 3 millimeter range]). After sloping the ground correctly, we laid a bedding of sand, then remeasured the slope, laid the pipe, and then remeasured the slope, put bedding on the sides, and then remeasured the slope again, before finally covering the pipe with a few inches of sand and then backfilling parts of it in with clay so that it wouldn’t shift during the rain.

By the time we had finished the pipe network, hurricane Irene hit, and knocked out 3 work days (although it didn’t hit us too hard, just lots of rain and a little wind). The BRA had to finish the work we couldn’t complete during our 2 week stay. After getting back to work, the concrete tops and bottoms of the junction boxes were laid and then the blocks forming the wall were placed. These were for any corner, or every 40 meters, in the pipe network so that there wouldn’t be pressure problems with corner PVC pieces and it would also be easy to access certain pipes to fix any issues. We then backfilled these in, and finally, the “swimming” pit was also ready to start being prepared for the septic tank.

During the past weekend, we had already bent the necessary rebar for the bottom slab, so this skeleton was placed and tied together so that the bottom slab could be laid. After allowing it some time to cure, we started constructing the block walls around the edges, placing the necessary vertical and horizontal rebar in the blocks, and also making sure that the pipes would enter, exit, go between the correct blocks (there were 3 groups of pipes: influent, effluent, and a transfer pipe through the baffle wall [a wall that stopped solids settling on the bottom from passing through to the other compartment of the tank]). About this time, we had to leave. The BRA, with the help of Angel Rojas, a local civil engineer, was able to complete this project and hooked it up to the filtration system (reinjection well) so that when the add bathrooms to the new clinic building, everything will be ready for the patients.

The final few days, we toured around some of the surrounding communities since we were supposed to start assessing the next phase of the project. It looks like the main options are a cafeteria for the clinic, an incinerator for clinic, expanding the piping network of the clinic so that it would reach the cafeteria and other future buildings, or latrine and housing construction in the surrounding communities. We will be returning in the fall or winter to take our formal assessment trip after deciding which project would most benefit the community but still fall within our ability level and monetary limitations.

Part 3: Latrines