Foundation & Sewer

Trabajo en el suelo:  Cimientos  y Drenaje   Onward and downward to the below-ground portions of our house renovations. Our plans called for a new addition, to be built in the grass-covered area between the dining area  in the southwest corner of the house, and the outlying laundry or cuarto de servicio in the SW corner of the lot. This area measures about four by three meters, and the new construction would create a full bathroom for the ground floor and a back entrance hall, and a second story flat roof terraza opening off the master bedroom.  Like most new structure construction projects here, one has to start at the bottom.  This meant excavation and foundation/footings.

Locating a new bathroom meant that we had to come up with a drenaje (drainage) plan.  The existing laundry drained into a registro, a concrete collector box sunk into the driveway/sidewalk outside the large gate at the northwest corner of the lot.  Prying up the cover of the registro, we discovered that the laundry drain was only a 2" PVC line, and the line exiting the box connecting to the city sewer was also this size.  Obviously a new, larger line had to drain the new bathroom.  Running the waste lines the other direction, to the calle on the southeast corner of the house where all the other existing house plumbing drained, was off the table.  It would have meant digging thru the interior floors, with no guarantee that a line buried there could be sufficiently sloped to drain the toilet connection in the floor of the new bathroom.

Dan asked our nextdoor neighbor (a renter), Valentín, if he knew where the sewer line ran down the avenida in front of his house, but he had no idea where his waste lines ran.  This meant the first of many trips to the CASF (Comision de Agua y Saneamiento, Water and Sanitation Commission) to locate and arrange for our new sewer connection. The fellows from CASF visited several times, after consulting city maps and even talking to retired employees who might have some ideas.  This was a long process, and ultimately involved the engineering and design department.  It was determined that there was no city line in the avenida, connecting to a branch of the city sewer, but apparently when each house had been built lines had been laid independently.

It came down to three choices for us:  (1) run a new line from a new, enlarged registro at the cormer of our property, at a depth of about three feet, west down the avenida to a city line buried under Calle 9, a distance of about 80 meters; (2) run a new line east to the city sewer line under Calle 11, a shorter distance of only 20 meters, but we'd have to connect at a depth of over 10 feet; or (3) tie into the existing 4" pipe just west of Valentín's registro, from which the sewage would be drained into the creek at the bottom of the hill.

Wanting to be ecologically responsible, we rejected option three and were all set to go for the second choice, and had the CASF architect figure out the route and slope required for the connection.  Then the CASF project engineer, who would actually oversee the work, revealed that whichever choice we made, the sewage outfall would be into a streambed arroyo, either close to us or a bit south where the lines in the calles ended.  A master sewage plan for the city, with a treatment plant at the south end of town has been planned for years, but lacking funding, won't happen anytime soon (years and years, maybe never).  He advised using option three (the cheapest option, about US$300 we'd have to pay for the city to do the job),  and which in truth is how all the homes above us on the stream have connected.

This still doesn't sit well with us, and we have resolved to use that toilet infrequently, use the minimum amount of toilet paper, and investigate composting alternatives.  We actually won't have to use that bathroom exclusively until we are too infirm to manage the stairs and have moved our sleeping quarters to downstairs.  The actual city work to connect our registro to the line in the street (digging up the roadside gutter and driveway of our neighbor, digging and burying the line, concreting over everything) didn't take place until almost three months after the rest of the renovation was completed.  We showed up at the CASF offices every week, received assurances that the job would be done right away, this week, etc until it finally happened in late August.

In late January 2013, the roof repairs complete, our crew moved on to the below-ground  work, the work on our cimientos (foundation or footings). Luís made estimates and Dan ordered all the brick, block, steel, cement, gravel, sand, and the work commenced.  Straight-sided ditches underneath the positions of the bearing walls were dug, and pieces of larger construction rubble  and rock were placed and tamped there at the bottom of the trenches. Part of the crew cut and bent 3/8" varilla (rebar) and alambrón (1/4" smooth rod) formed into stirrups and ties, for horizontal reinforcement and the vertical castillos (posts situated at the corners/ends of the new walls).  The vertical reinforcing is bedded in the footings, will be secured in the roof, and stands there as a skeleton until the walls are laid.

This rough footing was was capped with a leveling course of concrete. Our crew of abañiles (masons) laid up the rest of the foundation for the bathroom walls, with a stemwall of two rows of blocks (bringing things to ground level), topped with a reinforced cadena (beam) bonding the stemwall together.  Dan decided the best next task was to get all the white PVC waste pipes in the ground and covered, permitting all the rest of the work to take place on flat ground. The crew started removing the paving blocks in the backyard, and opening the ditches we'll need to run from the new bath area to the sidewalk. 

Since the city sanitation fellows assured us that, ultimately, a sewer connection could be made from the location of our existing registro, we were now ready to lay down our new larger lines. The PVC main lines run diagonally from the location of the toilet in the southeast corner of the new bath, past the shower and into the backyard, then turn 45º and aim toward the registro location.  It was not necessary to disturb the existing 2" line running from the laundry (under the bbq) so both lines dump into the registro independently.

Our living room floor looked like a child has been playing with his building blocks, as Dan had all the plumbing fittings for the drain lines set out to make sure everything would connect as he envisioned.. The old registro that took the 2” drain line from the laundry was broken out Luís and Alfonso continued ditching in the addition's floor area, cut all the PVC pipe and dry fitted it all together. Dan looked it over and approved the layout, and the guys proceeded to glue up everything, and then backfill.  Two vertical PVC lines were set inside castillos.  A large 4" line went up to the terraza level, which would serve as a floor drain to deal with rain falling there, and a 2" vent went up in  the castillo in the corner of the wall behind the toilet.  It would serve as a wet vent (a drain line for a small handsink planned for the terraza level), continuing up the party wall an additional story high to vent the fixtures below.  Vents are almost non-existent in waste plumning here south of the border, but are essential at keeping sewer smells out of the house.

Luís, agreeing with comments from the city engineer, directed work on reconstructing the registro.  The old one was broken out and re-made large enough for input from the new 4" PVC line.  A new lid was cast and put in place by the back gate.

Next:   New Walls