|A Training Manual in Conducting a Workshop in the Design, Construction, Operation, Maintenance and Repair of Hydrams (Peace Corps, 1981, 216 p.)|
Session 17, Handout 17D
After the siting of the components for the hydram system has been completed, it becomes necessary to design the components in detail. This session will discuss how to develop them and will allow for a better estimation of the money, labor and time needed.
The components of the system that are of concern here are the takeoff from the source, the hydram, the storage facility, and all necessary piping. Variations for developing the components and factors that influence their design will be presented. The attachments to this session will give further guide lines and will give references for those topics that will not be covered in this manual/workshop.
TAKE-OFF FROM THE SOURCE
As was mentioned before, the water for a hydram system is not taken directly from the stream; a take-off component must be installed. Its purposes are to protect the system from the potential damage by floods, to keep sand and debris out of the system and to make maintenance of the system easier. The two basic parts to the takeoff area are a settling basin and a transmission channel from the stream to the basin.
The size of the basin has to be just large enough to insure an uninterrupted flow of water to the hydram while trapping sediment, sand, and debris. If the hydram system is small - that is, it uses a 2" drive pipe or smaller, a 55 gallon drum or small tank may be used. If the soil at this site has a good clay content, a small pond can be constructed to serve as the basin. A rough way to determine the size of the basin is to determine the volume of water contained in the drive pipe at any point in time and have the basin be large enough to allow 34 times that volume of water standing above the drive pipe, e.g., if the drive pipe contains 10 gallons (area of the inside diameter of the drive pipe times its length), then a basin with 30-40 gallons above the drive pipe inlet will be sufficient. The inlet of the drive pipe should be positioned at least 1/3 of the way up from the bottom of the basin. A fine mesh screen must cover the inlet of the drive pipe (keeps frogs, etc. out).
The second part to the take-off is the channel or pipe that takes the water from the source and directs it to the basin. If a drum or tank is used as a basin, a pipe is more suitable as the inlet channel in that the pipe lends itself to an easier attachment to the drum/tank. If a pond is used, a dug channel can be used. The channel however, may need to be lined with clay to minimize seepage loses through the soil. The channel or pipe should be placed well into the stream to be able to pick up sufficient water during the dry season. The pipe needs to be anchored to the streambed for protection from being swept away by raging waters during the rainy season. A channel also will need to be protected. In both cases, large rocks placed on each side of the channel/pipe should be sufficient.
The channel will need more regular maintenance than a pipe to keep the sediment and weeds from blocking the passage. The pipe will need a trash rack in front of it's stream opening to keep debris, fish, etc. out of it.
The channel/pipe will need to have a slight negative slope to it 1% or so to allow the water to naturally feed into the basin. Both the channel and the pipe should have some means of blocking the flow of water to the system when that becomes necessary. If a plastic pipe is used, it will have to be covered to protect it from the sun; the ultraviolet rays of the sun will eventually destroy the plastic.
One last note: if the stream under consideration has excellent year round flow rates, but not an adequate head to run the hydram, a small dam may need to be constructed. This is a costly undertaking in terms of money, time, skill and labor. This manual/workshop cannot provide the necessary information for working with a dam. You will need more information to help decide if further consideration of the project is worthwhile.
The hydram component consists of the drive pipe, the hydram itself, the delivery pipe and a protection box/foundation for the hydram. Details about development and construction of the hydram are covered in this manual.
The drive pipe needs to be made of metal to withstand the pressures and pounding that develops in running the system. It should be positioned in the settling basin about 1/3 the way up from the bottom. The pipe should be well supported along its length and protected from outside disturbances. If stakes can be driven into the ground, the pipe can be anchored to them; this will help minimize vibrations and keep it from being bumped off its supports. The pipe should transverse as straight a course as possible. In no case should sharp bends (90°) be used; 45° bends or less should be used. If they are used, support must be provided at each bend to keep the side-way thrusts that will develop inside the pipe at that point from destroying the line.
The delivery pipe can be made of plastic. The same care in supporting, anchoring and protecting the drive pipe should be applied also to the delivery pipe. The course of the pipe should be as straight as possible, avoiding all sharp bends. An additional concern with plastic pipe is protection from the ultraviolet rays of the sun. The pipe needs to be covered. One way to do this is to bury it. However, if this is done, the channel should not be covered up until the system is working and the pipe checked for leaks.
The delivery pipe, because of its length, may raise additional concerns. It must be adequately protected any place it has to cross a trail or road, or in other ways is subject to possibly being run over by a cart or vehicle. If it crosses cultivated land, it's course must be adequately marked so that it is not accidentally damaged during cultivation operations.
The hydram itself must be well supported and protected from accidental disturbances. In addition the waste water needs to be directed away from the support foundation. The best way to provide this protection is to build a concrete foundation with drain outlet and a concrete or cement block box around it. The box should be large enough to allow enough room for a workman (or two) to comfortably move around the hydram. If a concrete hydram is used, the accumulator and/or the body may weigh a couple of hundred pounds. If it has to be removed for some reason, there must be enough room in the box to allow workers to get in there and lift it out.
The final part to the box should be some type of cover that can be locked; this offers protection from vandals or people tampering with the hydram out of curiosity. A final note on the construction of the box: the foundation should be poured and the hydram installed. After the hydram is working like it should, the walls to the box should be constructed and the cover installed.
The Storage Facility
The construction design of this component of the system is dictated by its size, the available materials, and physical characteristics of the site. A few examples may highlight some design considerations for the storage facility:
Let's say your calculations for the system indicate that 1000 gallons of water a day needs to be delivered. To store this amount of water, the facility will need to be about 12 feet on a side and 12 foot high. (1 cubic foot of water equals 7.48 gallons) If you want to have a 3-day supply of water (1 day's use and 2 days in reserve) the facility will need to he at least 12' x 12' x 3'. It may be economically reasonable to construct this out of concrete and block.
Now let's say the system will be used for irrigation and will need to store 100,000 gals and use it every 8 days. The size of this facility will need to be approximately 40 feet on a side and 3 feet high. To construct this structure out of concrete may be too costly; a pond would have to be constructed. (Incidentally, a system needing 2100,000 gallons every 8 days will need to pump about 10 gals a minute, all day, every day. 100,000/8 days/24 hours/60 minutes.)
This manual/workshop can not go into all the details and procedures necessary to construct these storage facilities. However, some reference materials are listed in the attachments that can assist in this work. In addition, assistance can be obtained from the agriculture department and technical donor groups/agencies.
Irrespective of the design of the facility, there are basic concerns for the protection of the system and for safety to the individuals using it. A pond almost assuredly will have to have a fence around it to keep animals and little children out of it. The walls of a tank will have to be reinforced with metal bars and the inside of the tank plastered with cement and painted to prevent leaks.
Cost and Labor Considerations
The labor for and the costs of this system can be quite a burden for the rural farmer or village; this is why the siting and the design of the system are so important. When both are done with care and skill, the costs for a completed system will be as low as possible. It should be obvious that with ample free/cheap labor and proper soil available the system can be kept within reasonable limits. It should also be obvious that the amount of labor needed and the length of time to do it all can be extensive.
It may be useful to take an example and see what a system might cost. Prices for everything are different everywhere, hut for the sake of this example, let's say:
· Cement costs $7/bag - 1 bag
can make 20 blocks 16" x 8" x 8"; can plaster 50 sq. ft. of surface can bond 35
blocks together; can produce 6 cu. ft. of concrete
· Reinforcing bars for the total system costs $75
· Metal pipe costs $8/foot
· Additional plumbing parts $75.
· hydram can be built for $100
· Plastic pipe costs $4/foot
· 55 gal drum costs $10
· welding work on drum costs $15 e Pipe lengths are: inlet line to drum 20' Drive pipe 40', delivery pipe 200', supply pipe 300' e Hydram box needs to be 6' x 5' and 4 courses high foundation ½ foot thick
· Storage facility needs to be 15' x 15' x 4' foundation - 1 foot thick
· Paint $50
· standpipe and faucet at final use point $100
· Transportation costs $200
· no labor costs
What will this system cost? (round off fractions to next highest whole number.)
If the storage facility will be a pond with no material costs, what will the system cost? (Transportation costs are cut in half; no reinforcing bar is needed.)
If, in addition, the supply line isn't needed, what will the system cost?