Eight Cisterns in Eight Weeks | Salitrillo Cistern Project

Wrapping Up   - 22nd Sept 2016

The cistern project in Salitrillo is well and truly underway. The Pilot cistern at the home of Señora Cecilia Luna Rosas is finished except for a curing period to set the concrete. 

Meanwhile the second cistern of eight which make up the first phase of the Salitrillo project is just about ready for its “gorro” or roof. At this point, the build team of seven women and two men are on their own except for weekly visits from Señor Abel, the technical advisor from CEDESA.

This year the Rotary San Miguel Midday Club working with the Rotary Action Group for Water and Sanitation (WASRAG) introduced an innovation in the cistern construction process: plastic wrap! 

As with any ferro-cement structure, cement must be allowed to cure slowly to prevent cracking and to attain its maximum structural strength. Normally ferro-cement structures are “watered”, sprayed down with water on a daily basis, for a period of days or weeks to make sure that the cement sets up slowly and remains crack-free. 

Needless to say this involves both careful attention to the watering schedule and the use of water which is then wasted. 

Hence, the use of plastic wrap. By wrapping the entire structure in a double layer of industrial sized plastic wrap (think kitchen plastic wrap on a grand scale), the cisterns wall and roof can undergo a slow curing period with much less care and feeding, and with virtually no wasted water.

Though it may seem modest, it’s important to place Salitrillo’s cistern project in perspective. The eight Salitrillo cisterns are among a total of 819 cisterns constructed since 2008. Each cistern collects 12,000 liters of rainwater when full. If you do the math, CEDESA and COCIRA, Project Beneficiaries and Rotary San Miguel Midday have created an amazing above ground reservoir capable of holding a whopping 9,828,000 liters of potable water storage. 

Think about that for a minute. 10 million liters is approximately 3 million gallons or roughly four Olympic sized swimming pools of water captured each year for the drinking and cooking needs of people living within the area of the Independencia aquifer.

When the current Global Grant is completed in the spring of 2017, a total of 1,092 cisterns will have been built representing an investment of over $10,000,000 pesos ($550,000 USD). Total rainwater collection capacity will top 13 million liters. And the geographic area serviced by the combined Rotary projects will include the communities surrounding San Miguel de Allende, San Diego de la Union, Dolores Hidalgo and San Luis de la Paz.

Guest post by Roger Brudno.

Ready for a Top Hat: Salitrillo Cistern Project

Day Three - 16th September 2016

It’s been two days since my last visit and I can’t believe the progress the build team has made. Not only has the concrete base of the cistern been set, but the walls of the cistern are up, and the metal work for the “gorro” or cap is laid out on the ground.

At this stage, you can see just how massive the finished cistern will be. Four workers are busy inside the cylinder applying the next-to-last coat of concrete. 

Cement is applied first in one direction (horizontal), then after a short period for layer-one cement to set up, a second layer is overlaid in the opposite direction (vertical). 

The bidirectional application makes for tough and water-tight walls. I am amazed to learn that, when full, the walls flex. Okay, the walls don’t actually bulge, but the ferro-cement expands dynamically under the weight of the water.

The “masa” or concrete mud for the gorro is mixed at a ratio of four parts cement to one-part sand, and significantly stiffer than the walls because the wet mix is applied directly to the metal mesh without the aid of plywood backing.

The gorro is equipped with an access door to permit maintenance on the interior of the cistern. 

And the exterior of the cistern is fitted with a clever, but commonsense water level gauge. A clear plastic hose will be connected between the water spigot at the bottom of the cistern and a narrow diameter pipe protruding from the top of the cistern. As the interior water level is drawn down, there is a corresponding drop in the water level in the transparent hose.

Recommended cistern maintenance consists of two primary elements: 1) yearly brushing of interior walls, and 2) if the catchment roof surface is of any material other than concrete or tin, then it must be repainted annually. 

Next stop, the final finish work.

Guest post by Roger Brudno.

Launched! Salitrillo Cistern Project

Day One - 13th September 2016

When Lee Carter and I arrive, the Salitrillo cistern build team had already laid out a base layer of chicken wire. As a first-time visitor to a cistern pilot, I’m excited to learn the basics of ferro-cement cistern construction.

Once completed, the cistern will hold 12,000 liters, harvesting enough water during one rainy season to serve all of the potable water needs, both drinking and cooking, for a family of 6-8 for a year.

It turns out that the metal structural elements of the cistern walls form a kind of layer cake—a layer of chicken wire folded over a layer of heavy-gauge iron mesh, then covered with a second layer of chicken wire all woven neatly together. Or rather, a layer cake that rolls up into a cylinder to create the walls of the cistern which are then set on a concrete base and lined with a temporary barrier of bendy plywood designed to support the application of an exterior coat of concrete until it dries.

Members of the community are hard at work weaving the chicken wire together under the watchful eye of Señor Abel, a technical expert from CEDESA in charge of teaching community members the basics of cistern construction. 

What stands out for me right away is the ratio of women to men in the work group: most of the team consists of women. And it’s obvious, that the team is already a well-oiled machine. Tasks are carried out with little discussion and a light-hearted atmosphere prevails.

This Salitrillo Pilot is cistern number 48 out of 319 cisterns funded by the Rotary Club’s recent Global Grant (GG1524911) and implemented in collaboration with CEDESA and COCIRA. 

It’s the first cistern for this little community of just 52 families. A total of eight cisterns are planned for Salitrillo. Once the core group is trained, they will cooperate to assist their neighbors with subsequent cisterns. Señor Abel from CEDESA will then make weekly visits to monitor progress and ensure quality-control.

Guest post by Roger Brudno.