Forgotten People
Residential Water System
with Temporary Storage Tank
Rita Sebastian
The Capacity Building Initiative
Heller School for Social Policy
Brandeis University
For
Forgotten People CDC
(928) 401-1777
forgottenpeoplecdc@
September 25, 2009
Engineering Consultants:
Ronald Tohannie
William Sebastian
Abstract
This paper presents the design of the temporary water systems that were developed and installed as part of the Black Falls Water Project. The project was a collaboration that began in July, 2008, between the US EPA and a coalition of families in the Black Falls region of the Navajo Nation. The coalition was organized and supported by Forgotten People CDC (FP CDC), a community organization based in Tuba City, AZ, with guidance from an academic partner, which was the Capacity Building Initiative at the Heller School for Social Policy, Brandeis University. The project was primarily funded from a grant from the EPA Environmental Justice Small Grants Program.
During the Black Falls water project, local residents designed and deployed a temporary water storage system using an elevated external water storage tank and kitchen sink. The tank provides high-capacity storage as needed to support efficient water delivery services and replaces the unsafe system of buckets currently in widespread use. The system can provide an immediate and low cost means to provide safe access to drinking water to a large population. Minimal training is needed to perform the on-site work, so that rapid up-scaling can be achieved using local labor. Deployment of the systems links the people into the provider network for health care, water delivery, and other related services. The system design is well suited for deployment via a community cooperative approach, which can reduce cost and improve sustainability. The long-term plan was to install solar-powered cisterns, after which the materials from the temporary external tanks could be reused at other locations.
This document includes detailed plans, parts lists, and other details as needed to support the replication of these systems in other communities.
1. Summary
The temporary water system provides an immediate and low cost way to transition families away from unsafe water sources. Provision of these systems can be the entry point to connecting families to the full range of health care and sanitation services. The findings from Black Falls include:
• Support water delivery services: A large on-site tank reduces the cost of operating a delivery service, as fewer trips to each home are required. The recommended design for replication uses a 405 gallon tank, which can hold more than the monthly consumption of most of the families at Black Falls.
• Replaces unsafe storage systems: The system provides a closed storage and distribution system, which eliminates the bacterial and chemical contamination associated with the buckets and improvised containers.
• Fast installation with limited training: The system was designed for quick on-site installation. If a stockpile of parts and preassembled kitchen units is available, a house can be brought on line in a few hours. Minimal training is needed to perform the on-site work, so that rapid up-scaling can be achieved using local labor.
• Efficient replacement: When a family subsequently obtains a cistern or access to piped water, the storage system can be moved to another home, while the sink/counter can be used with the hot water and pressurized system with few adjustments.
• Service Networking: The deployment of the home system gets the families involved with the service delivery system, so that they learn about safe use of water, obtain access to health and other services, and become proactively involved with the agencies providing water and sanitation systems
2. Construction details
The storage tank was mounted on a platform built from 4x4 timbers on top of concrete block pillars. The platform elevates the tank so that the bottom is at least 8" above the sink faucet. The key advantages of the design is that the platforms can be assembled and the tanks installed in less than two hours using low-cost parts that can be 100% re-used at another site when a permanent cistern is installed. This allows systems to be deployed as rapidly as qualified beneficiaries can be identified. The Black Falls project used 210 gallon white water transportation tanks. These should not be used during replication for two reasons:
• black tanks should be used to prevent algae growth. The use of white tanks in Black Falls required the tanks to be wrapped in black plastic, which creates a maintenance problem.
• tanks designed for fixed storage are cheaper than transport tanks and a larger tank can be provided at less cost.
For replication, a recommended tank would be a 405 gallon tank which is 52" diameter and 48" tall. This size stores more than a one month supply for the families in Black Falls, which reduces the number of roundtrips for a tank truck. Larger tanks in this class tend to be significantly taller, which complicates refilling since the base of the tank is already 4 feet above the ground.
The black tanks are large enough so that freezing during winter is not an issue unless the tanks are nearly empty. 2" pipes are used outside the home to reduce susceptibility to freezing, and the exterior plumbing is doubly wrapped in pipe insulation.
The Black Falls project used a 72" counter on a 60" sink base for the in-home distribution system. While some cheaper options were available, the extra cost of using these attractive units was not large and increased the level of involvement of the families in the project. The counters were prefabricated and the sinks mounted at a central location to reduce the need for experienced carpenters on each site.
The standard sink plumbing fixtures, such as 3/8' feeds to the faucets, do not work well for low pressure, so extra work was required to increase the pipe diameters to the faucet intakes. Even with these customizations, the sink assemblies can be added installed and plumbed in a couple of hours. The temporary system does not include a pump or hot water heater - those would be added as part of the permanent sanitation system.
The temporary system does not include sanitation. The water from the sink is typically piped directly to the outside, and the pipe exits at a height sufficient to place a 5 gallon bucket underneath. The families then either dispose of the water or recycle it for irrigation.
3. Lessons Learned from Deployment:
The installation of the temporary water systems at 10 homes in Black Falls was completed in February, 2009. In the subsequent months, the experiences of the families with the system have led to improvements in the design and a greater understanding of the issues involved.
The first issue that arose was lack of water pressure. The system pressure was unacceptable to the families initially. In most installations, the bottom of the tank was less than one foot above the height of the kitchen faucet. Water pressure increases at a rate of 0.4 psi for every foot of elevation, so that when the tank was less than 1/2 full, the water pressure was less than 1 psi. Water pressure in most residential systems is from 30-80 psi. The standard faucets and tubing were designed to reduce pressure. Removing constrictors in the faucet head and replacing the 3/8" braided tubing with larger piping produced an acceptable flow at the faucet.
The water pressure is now adequate for most uses of the kitchen sink. Higher water pressure is not necessarily beneficial - it can also promote waste and inefficiency. However, the low pressure can prevent the use of devices such as carbon filters and hot water heaters. One family is experimenting with a solar-powered pump, which supports pressures over 15 psi. With a pump, the tank does not have to be elevated, but if the pumping system fails, the family will have problems. If the pump is used in conjunction with the elevated tank, water could still flow if the pump is disabled. The pump would support the installation of a water heater or a shower prior to the installation of the full sanitation system. Whether this is worthwhile depends on the length of time between the deployment of the temporary water system and its replacement with the full sanitation system.
A second issue was the use of black plastic to wrap the tanks, which was needed to prevent algae growth. The region was periodically subject to high (>50 mph) winds which required repair work after each storm. Future systems should only use opaque black tanks to prevent this problem. The families were also provided with white tarps to reduce the tank temperature in the summer, which were placed over the black plastic. The white tarps will be provided to the families for this purpose. They have less of an issue with high winds, as it is not a major problem if they come off temporarily or do not cover 100% of the tank.
A third issue was the need for a screen water filter to prevent the small pipes from getting clogged if debris gets into the tank. These have been retrofitted into the Black Falls systems and added to the design for replication.
A final issue was water quality. When the Black Falls Church pipeline access was first deployed, the water had problems with clarity and taste. Once the people were assured that the water was safe, they experimented with the use of pitcher filters. These were found to help, and units are being provided to the families. The use should be temporary - the problem should go away after the pipeline has been in service longer.
4. System Cost Summary:
The parts list is provided in Appendix E, where the totals come to:
Parts cost:
Platform & exterior plumbing $ 536.98
Sink/counter & interior plumbing $ 363.25
Total unit cost $ 900.23
The kitchen counters quoted in the parts list require prefabrication to add the end caps on the counter top and to cut out for the sink and mount it in the hardware. The wood for the platform is pre-cut, so that no power tools are required on site except possibly for the drill that might used to for the hole through the external wall. No extra budget is required for transportation to the site as the materials for one home can be transported in one pickup truck load and brought on site by the installation crew. The installation crew typical consists of a trained foreman, an apprentice being trained for further replication, and at least one member of the family or local community to help with general labor.
Labor costs:
Skilled In-Training General labor & support
Prefabrication (off-site) 2.0 hours 2.0 hours --
Platform (on-site) 1.5 hours 1.5 hours 1.5 hours
Counter installation 2.0 hours 2.0 hours 2.0 hours
Transportation to/from site 1.0 hours 1.0 hours --
Total time 6.5 hours 6.5 hours 3.5 hours
Hourly rate (include benefits, etc) $35 $25 (in-kind contribution)
Total labor 227.50 + 162.50 = $ 390
Estimated program costs:
Parts $ 900.23
Labor $ 390.00
Subtotal $ 1,290.23
15% overhead $ 193.53
Total $ 1,483.76
These estimates are based on the costs for constructing 10 systems, and lower costs for both parts and labor could be achieved in higher volume production.
5. Parts List:
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6. Plans:
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