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                            LOW COST DEVELOPMENT OF
                               WATER POWER SITES
                                 HANS W. HAMM
                       1600 Wilson Boulevard, Suite 500
                         Arlington, Virginia 22209 USA
                     Tel: 703/276-1800 . Fax 703/243-1865
                            LOW COST DEVELOPMENT OF
                            SMALL WATER POWER SITES
                                       HANS W. HAMM
                                  a VITA publication
             Overshot Water-Wheel: Design and Construction Manual
                         Small Michell (Banki) Turbine
                                 Hydraulic Ram
               Environmentally Sound Small-Scale Water Projects:
                            Guidelines for Planning
              Environmentally Sound Small-Scale Energy Projects:
                            Guidelines for Planning
For free catalogue of these and other VITA publications, write
                          VITA Publications Services
                      Volunteers in Technical Assistance
                       1600 Wilson Boulevard, Suite 500
                          Arlington, Virginia 22209 USA
                                  ABOUT VITA
                Volunteers in Technical Assistance (VITA) is a
                private, nonprofit,international development
                organization. It makes available to individuals
                and groups in developing countries a variety of
                information and technical resources aimed at
                fostering self-sufficiency--needs assessment and
                program development support; by-mail and on-site
                consulting services; information systems training.
                Vita promotes the use of appropriate small-scale
                technologies, especially in the area of
                renewable energy. VITA's extensive documentation
                center and worlwide roster of volunteer technical
                experts enable it to respond to thousands of technical
                inquiries each year. It also publishes a
                quarterly newsletter and a variety of technical
                manuals and bulletins.
                                      IN TECHNICAL
ISBN 0-86619-014-7
                               TABLE OF CONTENTS
I.           Introduction
II.          Basic Data
III.         Power
IV.          Measuring Gross Head
V.           Measuring Flow Rate
VI.          Measuring Head Losses
VII.         Small Dams
VIII.        Water Turbines
IX.          Water Wheels
X.           Example
I            Flow Value
II           Maximum Velocity & Friction Coefficient
1.           Availability of Manufactured Turbines
2.           Conversion Tables
3.           Bibliography
4.           The Author and Reviewers
5.           Data Sheet
6.           Decision Making Work Sheet
7.           Record Keeping Work Sheet
    During the last several years of answering individual requests from
Peace Corps and other community development workers, VITA has come to
realize the great need for a manual on small hydroelectric power development.
    VITA is an international association of more than 5,000 scientists,
engineers, businessmen and educators who volunteer their talent and
spare time to help people in developing areas with their technical
problems.  The Volunteers are from the United States and 100 other
    The difficulty of communication has proved extreme in answering requests
concerning the feasibility of a small hydro plant as a source of
power, as compared with a diesel.   The value of a manual written in simple
terms is readily apparent.
    The present manual has been prepared to fill this need.  It should
enable the reader to assess the possibility and desirability of installing
a small hydroelectric power plant, select the type of machinery most
suitable for installation, and order turbine and generating equipment.
It should also serve as a guide in actual construction and installation.
When further guidance is needed.   VITA can put the reader in touch with
expert VITA Volunteers.
    The manual begins by describing in simple language the steps necessary
to measure the head (the height of a body of water, considered as causing
pressure) and flow of the water supply, and gives data for computing the
amount of power available.  Next it describes the construction of a small
dam and points out safety precautions necessary in designing and building
such structures.  Following this is a discussion of turbines and water
wheels.  Guide lines are given for making the right choice for a particular
site.  In this connection, ready-made units are available from
such reliable manufacturers as James Leffel & Company in the United States
and Ossberger-Turbinenfabrik in Germany.   Both companies give excellent
service in advising prospective purchasers.
    This section of the manual also describes in detail how to make a
Michell (or Banki) turbine in a small machine shop with welding facilities,
from usually available pipe and other stock material.   However,
the hazards accompanying the manufacture of so delicate a machine by
do-it-yourself methods, and the difficulty of achieving high efficiency
Should warn the ambitious amateur to consider the obvious alternative
of securing advice from a reliable manufacturer before attempting to
build his own.  Table 3 gives information on the availability of manufactured
units.  Electric generator equipment is standardized and
readily available.
    Appendix 1 gives detailed information on manufacturers of turbines.
Appendix 2 is a chart for converting English units of measure to metric
units.  English units are used in the text.
    Finally, for those who are interested in pursuing the subject further
and who have the engineering background to understand technical treatises,
a bibliography in Appendix 2 describes textbooks and handbooks available
in English in the United States and England.
                                                 Harry Wiersema
                            I. INTRODUCTION
A. Alternatives
   Flowing water tends to generate automatically a picture of "free"
   power in the eyes of the observer.  But there is always a cost to
   producing power from water sources.  The cost of developing low-output
   water power sites should be checked against available alternatives,
   such as:
   1. Electric Utility - wherever transmission lines can furnish unlimited
      amounts of reasonably priced electric current, it is
      usually uneconomical to develop small and medium-sized sites.
   2. Generators - diesel engines and internal-combusion engines may
      use a variety of fuels, for example, oil, gasoline, or wood.  In
      general, the capital expenditure for this type of power plant is
      low compared to a hydro-electric plant.  Operating costs, on the
      other hand, are very low for hydro-electricity and high for
      generated power.
   3. Solar Heat - extensive experimental work has been done on the
      utilization of solar heat.  Equipment now available may be less
      costly than water power development in regions with long hours
      of intense sunshine.
B. Evaluation
   For isolated communities in countries where the cost of coal and oil
   is high and access to transmission lines is limited or non-existent,
   development of even the smallest water power site may be worthwhile.
   Particularly favorable is the situation where the head (the height of
   a body of water, considered as causing pressure) is relatively high,
   and for this reason a fairly inexpensive turbine can be used (note
   Figure 1).   Water power is also very economical where a dam can be

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   built into a small river with a relatively short (less than 100 feet)(1)
   conduit (penstock) for conducting water to the water wheel (note
   Figure 10).   Development cost can be fairly high when such a dam and

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   pipeline can provide a head of only 20 feet or less.  Cost factors which
   must be considered are:
   1. Capital Expenditures
      a. Design cost - can be relatively high for small plants.
      b. Cost of Head Plants.
         High for low-head plants where a dam and reservoir have to
         be created.
         Small for high-head plants with only an intake, a pipeline
         and shed for machinery.
(1) A table for converting English units to metric units is given in
    Appendix 2.
      c. Riparian Rights - the rights of those whose property borders
         on a body of water must be respected.
      d. Construction Cost - including civil works and machinery.
      e. Electrical Equipment - transformers, transmission lines, and
   2. Operating Expenditures
      a. Amortization charges and interest on capital expenditures.
      b. Depreciation - for machinery, about 4% a year.
                              - for buildings, it can be as low as 1% a year.
      c. Labor - operation and maintenance.
      d. Repairs.
      e. Taxes, insurance, and administration.
      The safest method of evaluating and developing a small site is to
      be guided by the following instructions for determining available
      head, flow, and, therefore, power.
      A Note of Caution: flow should be measured at a time when it is at
      a minimum, i.e., during the dry season.  Otherwise the plant will be
     The data obtained can be submitted through VITA to several manufacturers
of small turbines for preliminary quotations and recommendations.  Turbine
manufacturers will furnish considerable advice and usually an outline drawing
of the entire project.  Government publications for designing civil
works such as a dam are available from:
        U.S. Government Printing Office                 Her Majesty's Stationery Office
        Washington, D.C. 20402           and    London, England
These agencies will supply a list of publications on the subject.
                                II. BASIC DATA
A. Minimum flow in cubic feet or cubic meters per second.
B. Maximum flow to be utilized.
C. Available head in feet or meters.
D. Pipe line length required for obtaining desired head.
E. Site sketch with elevations, or topographical map with site sketched in.
F. Water condition, whether clear, muddy, sandy, acid, etc.
F. Soil condition, the velocity of the water and the size of the ditch or
   channel for carrying it to the works depends on soil condition.
H. Minimum tailwater elevation at the powerhouse site must be given to
   determine the turbine setting and type.
I. Air temperature, minimum and maximum.
                                  III. POWER
     The amount of power desired (useful power) should be determined in
advance.  Power way be expressed in terms of horsepower or kilowatts.   One
horsepower is equal to 0.7455 kilowatts.   One kilowatt is about one and a
third horsepower.  The required amount of power (gross power) is equal to
the useful power plus the losses inherent in any power scheme.  It is
usually safe to assume that the net or useful power in the case of small
power installations will only be half of the available gross power due to
water transmission losses and the turbine and generator efficiencies.  Some
power is lost when it is transmitted from the generator switchboard to
the place of application.
The GROSS POWER, the power available from the water, is determined by the
following formula:
     In English Units:
     Gross Power (horsepower)
         Minimum Water Flow (cubic feet/second) X Gross Head(feet)
     In Metric Units:
     Gross Power (Metric horsepower) = 1,000 Flow (cubic meters/second)
                                       -----          X Head(meters)
The NET POWER available at the turbine shaft is:
     In English Units:
     Net Power = Minimum Water Flow X Net Head X Turbine Efficiency (English)
     In Metric Units:
     Net Power = Minimum Water Flow X Net Head X Turbine Efficiency (Metric)
     The NET HEAD is obtained by deducting the energy losses from the gross
head.  These losses are discussed in section VI.  A good assumption for
turbine efficiency, when it is not known, is 80%.
                           IV. MEASURING GROSS HEAD
                                (Either Method)
A. Method No. 1
   1. Equipment
      a. Surveyor's leveling instrument - consists of a spirit level
         fastened parallel to a telescopic sight (note Figure 2).

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      b. Scale - use wooden board approximately 12 feet in length
         (note Figure 3).

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   2. Procedure (note Figure 1)

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      a. Surveyor's level on a tripod is placed down stream from the
         power reservoir dam on which the headwater level is marked.
      b. After taking a reading, the level is turned 180[degrees] in a
         horizontal circle.  The scale is placed downstream from it
         at a suitable distance and a second reading is taken.   This
         process is repeated until the tailwater level is reached.
B. Method No. 2
   This method is fully reliable, but is more tedious than Method No. 1
   and need only be used when a surveyor's level is not available.
   1. Equipment
      a. Scale (note Figure 3).
      b. Board and wooden plug (note Figures 4 and 6).

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      c. Ordinary carpenter's level (note Figure 5).

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   2. Procedure (note Figure 6)

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      a. Place board horizontally at headwater level and place level
         on top of it for accurate leveling.  At the downstream end
         of the horizontal board, the distance to a wooden plug set
         into the ground is measured with a scale.
      b. The process is repeated step wise until the tailwater level
         is reached.
                            V. MEASURING FLOW RATE
     For power purposes, measurements should take place at the season of
lowest flow in order to guarantee full power at all times.  Investigate
the stream flow history to ascertain that the minimum required flow is
that which has occurred for as many years as it is possible to determine.
An obvious point that has, nevertheless, been overlooked in the past is
this: if there have been years of drought in which flow rate was reduced
below the minimum required, other streams or sources of power may offer a
better solution.
     A. Method No. 1
        For small streams with a capacity of less than one cubic foot per
        second, build a temporary dam in the stream, or use a "swimming
        hole" created by a natural dam.  Channel the water into a pipe and
        catch it in a bucket of known capacity.  Determine the stream flow
        by measuring the time it takes to fill the bucket.
        Stream Flow (cubic feet per second) = Volume of Bucket (cubic feet)/Filling Time (seconds)
     B. Method No. 2
        For medium streams with a capacity of more than one cubic foot per
        second, the weir method can be used.  The weir (see Figures 7 & 8)

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        is made from boards, logs or scrap lumber.  Cut a rectangular
        opening in the center.  Seal the seams of the boards and the sides
        built into the banks with clay or sod to prevent leakage.  Saw the
        edges of the opening on a slant to produce sharp edges on the upstream
        side.   A small pond is formed upstream from the weir.  When
        there is no leakage and all water is flowing through the weir opening,
        (1) place a board across the stream and (2) place another narrow board
        level (use a carpenter's level) and perpendicular to the first.   Measure
        the depth of the water above the bottom edge of the weir with the help
        of a stick on which a scale has been marked.  Determine the flow from
        Table I.
                                    Table I
                      FLOW VALUE (Cubic Feet per Second)
                                             Weir Width
Overflow Height   3 feet   4 feet    5 feet   6 feet    7 feet   8 feet   9 feet
   1.0 inch          .24       .32      .40       .48      .56      .64       .72
   2    inches        .67      .89      1.06     1.34     1.56      1.8      2.0
   4    inches      1.9       2.5      3.2      3.8       4.5      5.0      5.7
   6    inches      3.5      4.7       5.9      7.0      8.2       9.4     10.5
   8    inches      5.4      7.3       9.0     10.8     12.4      14.6     16.2
  10    inches      7.6     10.0      12.7     15.2     17.7      20.0     22.8
  12    inches     10.0     13.3      16.7     20.0     23.3      26.6     30.0
     C. Method No. 3
        The float method (Figure 9) is used for larger streams.  Although it

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        is not as accurate as the previous two methods, it is adequate for
        practical purposes.  Choose a point in the stream where the bed is
        smooth and the cross section is fairly uniform for a length of at
        least 30 feet.  Measure water velocity by throwing pieces of wood into
        the water and measuring the time of travel between two fixed points,
        30 feet or more apart.  Erect posts on each bank at these points.
        Connect the 2 upstream posts by a level wire rope (use a carpenter's
        level).   Follow the same procedure with the down stream posts.  Divide
        the stream into equal sections along the wires and measure the water
        depth for each section.  In this way, the cross-sectional area of
        the stream is determined.  Use the following formula to calculate the
        Stream Flow (cubic feet per second) = Average Cross-Sectional Flow
             Area(square feet) X Velocity (feet per second)
                           VI. MEASURING HEAD LOSSES
     As noted in Section III, the "Net Power" is a function of the "Net
Head".  The "Net Head" is the "Gross Head" less the "Head Losses".
Figure 10 shows a typical small water power installation.  The head losses

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are the open-channel losses plus the friction loss from flow through the
   A. Open Channel Head Losses
      The headrace and the tailrace in Figure 11 are open channels for

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      transporting water at low velocities.  The walls of channels made of
      timber, masonry, concrete, or rock, should be constructed
      perpendicularly. Design them so that the water level height is one half of
      the width.   Earth walls should be built at a 45[degrees] angle.  Design them so
      that the water level height is one half of the channel width at the
      bottom.   At the water level the width is twice that of the bottom.
    The head loss in open channels is given in the nomograph in Figure 12.

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The friction effect of the material of construction is called "n".  Various
values of "n" and the maximum water velocity, below which the walls of a
channel will not erode are given in Table II.
                                   Table II
                                Maximum Allowable
                                Water Velocity
Material of Channel Wall          (feet/second)             Value of "n"
Fine grained sand                      0.6                      0.030
Coarse sand                            1.2                      0.030
Small stones                           2.4                      0.030
Coarse stones                          4.0                      0.030
Rock                                  25.0       (Smooth)       0.033 (Jagged) 0.045
Concrete with sandy water             10.0                      0.016
Concrete with clean water             20.0                      0.016
Sandy loam, 40% clay                   1.8                      0.030
Loamy soil, 65% clay                   3.0                      0.030
Clay loam, 85% clay                    4.8                      0.030
Soil loam, 95% clay                    6.2                      0.030
100% clay                              7.3                      0.030
Wood                                                           0.015
Earth bottom with rubble sides                                 0.033
    The hydraulic radius is equal to a quarter of the channel width, except
for earth-walled channels where it is 0.31 times the width at the bottom.
    To use the nomograph, a straight line is drawn from the value of "n"
through the flow velocity to the reference line.   The point on the reference
line is connected to the hydraulic radius and this line is extended
to the head-loss scale which also determines the required slope of the
    B.   Pipe Head loss and Penstock Intake
        The trashrack in Figure 13 is a weldment consisting of a number of

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        vertical bars held together by an angle at the top and a bar at the
        bottom.   The vertical bars must be spaced in such a way that the
        teeth of a rake can penetrate the rack for removing leaves, grass
        and trash which might clog up the intake.  Such a trashrack can
        easily be manufactured in the field or in a small welding shop.
        Downstream from the trashrack, a slot is provided in the concrete
        into which a timber gate can be inserted for shutting off the flow
        of water to the turbine.
        The penstock can be constructed from commercial pipe.  The pipe
        must be large enough to keep the head loss small.  From the nomograph
        (Figure 14) the required pipe size is determined.  A straight line

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        drawn through the water velocity and flow rate scales gives the
        required pipe size and pipe head-loss.  Head loss is given for a
        100-foot pipe length.  For longer or shorter penstocks, the actual
        head loss is the head loss from the chart multiplied by the actual
        length divided by 100.  If commercial pipe is too expensive, it is
        possible to make pipe from native material; for example, concrete
        and ceramic pipe or hollowed logs.  The choice of pipe material
        and the method of making the pipe depend on the cost and availability
        of labor and the availability of material.  VITA can provide the
        needed technical information.
                               VII.   SMALL DAMS
    A dam is necessary in most cases to direct the water into the channel
intake or to get a higher head than the stream naturally affords.  A dam
is not required if there is enough water to cover the intake of a pipe or
channel at the head of the stream where the dam would be placed.
    A dam may be made of earth, wood, concrete or stone.  In building any
kind of a dam, all mud, vegetable matter and loose material must be removed
from the bed of the stream where the dam is to be placed.  This usually is
not difficult since most small streams will cut their beds down close to
bed rock, hard clay or other stable formation.
A.  Earth Dams
    An earth dam may be desirable where concrete is expensive and timber
    scarce.   It must be provided with a separate spillway of sufficient
    size to carry off excess water because water can never be allowed to
    flow over the crest of an earth dam.  If it does the dam will-erode and
    be destroyed.   A spillway must be lined with boards or with concrete
    to prevent seepage and erosion.  Still water is held satisfactorily by
    earth but moving water is not.  The earth will be worn away by it.
    Figures 15 and 16 show a spillway and an earth dam.  The crest of the

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    a roadway, with a bridge placed across the spillway.
    NOTE: Building a dam will cause important environmental changes
    both upstream and downstream. In addition, even a small dam creates
    a potential flooding hazard once it is filled with water. CONSULT
    The greatest difficulty in earth-dam construction occurs in places where
    the dam rests on solid rock.  It is hard to keep the water from seeping
    between the dam and the earth and finally undermining the dam.  One way
    of preventing seepage is to blast and clean out a series of ditches in
    the rock, with each ditch about a foot deep and two feet wide extending
    under the length of the dam.  Each ditch should be filled with three
    or four inches of wet clay compacted by stamping it.  More layers of
    wet clay can then be added and the compacting process repeated each
    time until the clay is several inches higher than bedrock.  The upstream
    half of the dam, as shown in Figure 16 should be of clay or heavy clay

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    soil, which compacts well and is impervious to water.  The downstream
    side should consist of lighter and more porous soil, which drains out
    quickly and thus makes the dam more stable than if it were made
    entirely of clay.
B.  Crib Dams
    The crib dam is very economical in timber country as it requires only
    rough tree trunks, cut planking and stones.  Four- to six-inch tree
    trunks are placed two to three feet apart and spiked to others placed
    across them at right angles.  Stones fill the spaces between timbers.
    The upstream side (face) of the dam, and sometimes the downstream side,
    is covered with planks (see Figure 17).  The face is sealed with clay

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    to prevent leakage.  Downstream planks are used as an apron to guide
    the water which overflows the dam back into the stream bed.  The dam
    itself serves as a spillway in this case.  The water coming over the
    apron falls rapidly and it is necessary to line the bed below with
    stones in order to prevent erosion.  A section of a crib dam without
    downstream planking is illustrated in Figure 18.  The apron consists

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    of a series of steps for slowing the water gradually.
    Crib dams, as well as other types, must be embedded well into the
    embankments and packed with impervious material such as clay or
    heavy earth and stones in order to anchor them and to prevent
    leakage.   At the heel as well as at the toe of crib dams, longitudinal
    rows of planks are driven into the stream bed.  These are priming
    planks which prevent water from seeping under the dam, and the also
    anchor it.   If the dam rests on rock, priming planks cannot and need
    not be driven; but where the dam does not rest on rock they make it
    more stable and watertight.  These priming planks should be driven as
    deep as possible and then spiked to the timber of the crib dam.  The
    lower ends of the priming planks are pointed as shown in Figure 19,

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    and they must be placed one after the other as shown.  Thus each
    successive plank is forced, by the act of driving it, closer against
    the preceding plank resulting in a solid wall.  Any rough lumber may
    be used. Chestnut and oak are considered to be the best material. The
    lumber must be free from sap, and its size should be approximately
    two inches by six inches.  In order to drive the priming planks and
    also the sheet piling of Figure 16, considerable force may be required.

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    A simple pile driver as shown in Figure 20 will serve the

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C.  Concrete and Masonry Dams
    Concrete and masonry dams more than 12 feet high should not be built
    without the advice of a competent engineer with experience in this
    special field.  Dams of less height require knowledge of the soil
    condition and bearing capacity as well as of the structure itself.
    Figure 21 shows a stone dam which also serves as a spillway.  It can

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    be up to ten feet in height.  It is made of rough stones.  The layers
    should be bound by concrete.  The dam must be built down to a solid
    and permanent footing to prevent leakage and shifting.  The base of
    the dam should have the same dimension as its height to give it
    Small concrete dams (Figure 22) should have a base with a thickness

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    50% greater than height.  The apron is designed to turn the flow
    slightly upwards to dissipate the energy of the water and protect
    the downstream bed from eroding.
                             VIII.  WATER TURBINES
    The manufacturers of hydraulic turbines for small plants can usually
quote on a complete packaged unit, including the generator, governor and
switch gear.  Water turbines for small power developments may be purchased
(see Table III) or made in the field, if a small machine and weld shop is
    A centrifugal pump may be used as a turbine wherever it is technically
possible.  Its cost is about one-third the cost of a hydraulic turbine.   But
it may be poor economics to use a centrifugal pump because it is less
efficient than a turbine and will have other disadvantages.
    A water power unit can produce either direct current (D.C.) or
alternating current (A.C.) electricity.
    Two factors to consider in deciding whether to install an A.C. or D.C.
power unit are (1) the cost of regulating the flow of water into the turbine
for A.C. and (2) the cost of converting motors to use D.C. electricity.
Flow Regulation
    The demand for power will vary from time to time during the day.   With
a constant flow of water into the turbine, the power output will sometimes
be greater than the demand for power.   Therefore, either excess power must
be stored or the flow of water into the turbine must be regulated according
to the demand for power.
    In producing A.C., the flow of water must be regulated because A.C.
cannot be stored.  Flow regulation requires governors and complex valve-type
shut-off devices.  This equipment is expensive; in a small water
power site, the regulating equipment would cost more than a turbine and
generator combined.  Furthermore, the equipment for any turbine used for
A.C. must be built by experienced water-turbine manufacturers and serviced
by competent consulting engineers.
    The flow of water to a D.C. producing turbine, however, does not
have to be regulated.  Excess power can be stored in a storage battery.
Direct-current generators and storage batteries are low in cost because
they are mass-produced.
    To summarize:  In producing A.C., the flow of water into the turbine
must be regulated; this requires costly and complex equipment.  In producing
D.C., regulation is not necessary, but storage batteries must be
Converting Motors for D.C.
    D.C. power is just as good as A.C. for producing electric light and
heat.  But for electrical appliances, from farm machinery to household
appliances, the use of D.C. power can involve some expense.   When such
appliances have A.C. motors, D.C. motors must be installed.  The cost of
doing this must be weighed against the cost of flow regulation needed for
producing A.C.
                                   Table III
                       Small Hydraulic Turbines
                         Impulse               Michell            Centrifugal Pump
                            or                   or                     Used as
                         Pelton                Banki                    Turbine
Head Range               50 to 1000            3 to 650               Available  
Flow Range               0.1 to   10            0.5 to 250
(cubic feet per second)                                                   any
Application              high head             medium head             desired
Power                    1 to 500               1 to 1000               condition
Cost per Kilowatt        low                   low                        low
Manufacturers            James Leffel & Co.    Ossberger-           Any reputable
                         Springfield, Ohio      Turbinenfabrik        dealer or   
                         U.S.A. 45501          8832 Weissenbura     manufacturer
                         Drees & Co.           Bayern, Germany      
                         Werl. Germany         Can be do-it-your-   
                         Officine Buhler       self project if small
                         Taverne, Switzerland  weld and machine
                                               shops are available
A.  Impulse Turbines
    Impulse turbines are used for high heads and low flow rates.  They
    are the most economical turbine because the high head gives them high
    speed and their size and weight per horsepower is small.  Construction
    costs of intake and power house are also small.  A very simplified
    version is shown in Figures 23 and 24.

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   The Michell (or Banki) turbine is simple in construction and may be
   the only type of water turbine which can be locally built.  Welding
    equipment and a small machine Shop like those often used to repair
   farm machinery and automotive parts are all that is necessary.
   The two main parts of the Michell turbine are the runner and the
   nozzle.   Both are welded from plate steel and require some machining.
Figures 25 and 26 show the arrangement of a turbine of this type for

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generator with a belt drive.   Because the construction can be a DO-IT-YOURSELF
project, formulas and design details are given for a runner of
12" outside diameter.  This size is the smallest which is easy to
fabricate and weld.  It has a wide range of application for all small
power developments with head and flow suitable for the Michell turbine.
Different heads result in different rotational speeds.   The proper belt-drive
ratio gives the correct generator speed.   Various amounts of water
determine the width of the nozzle ([B.sub.1], Figure 26) and the width of the

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runner ([B.sub.2], Figure 26).   These widths may vary from 2 inches to 14 inches.
No other turbine is adaptable to as large a range of flow.
The water passes through the runner twice in a narrow jet before discharge
into the tailrace.  The runner consists of two side plates, each 1/4"
thick with hubs for the shaft attached by welding, and from 20 to 24
blades.  Each blade is 0.237" thick and cut from 4" standard pipe.
Steel pipe of this type is available virtually everywhere.  A pipe of
suitable length produces four blades.   Each blade is a circular segment
with a center angle of 72 degrees.   The runner design, with dimensions
for a foot-long runner, is shown in Figure 27; and Figure 28 gives the

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for other size runners.  Upstream from the nozzle discharge
opening of 1 1/4", the shape of the nozzle can be made to suit penstock
pipe conditions.
To calculate the principal turbine dimension:
[B.sub.1] = Nozzle Width (inches) = 210 X Flow (cubic feet per second)
                                    Runner Outside Diameter (inches) X [square root]Head (feet)
[B.sub.2] = Runner Width between Discs = [B.sub.1] + 1/2 to 1"
Rotational Speed (revolutions per minute) = 73.1 X [square root] Head (feet)
                                            Runner Outside Diameter (feet)
The efficiency of the Michell turbine is 80% or greater and therefore
suitable for small power installations.   Flow regulation and governor,
control of the flow can be effected by using a center-body nozzle
regulator (a closing mechanism in the shape of a gate in the nozzle).
This is expensive because of governor costs.   It is, however, needed
for running an alternating-current generator.
The application of Figures 25 and 26 is a typical example.  For high
heads the Michell turbine is connected to a penstock with a turbine
inlet valve.  This requires a different type of arrangement from the
one shown here.  As mentioned before, the Michell turbine is unique
because its [B.sub.1] and [B.sub.2] widths can be altered to suit power-site traits
of flow rate and head.  This, besides simplicity and low cost, makes
it the most suitable of all water turbines for small power developments.
C. Centrifugal Pumps and Propeller-Type Pumps
   The use of centrifugal pumps or propeller-type pumps as turbines
   should be explored before all other alternatives, provided that
   direct-current electricity can be used (See Figures 29 and 30).

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   cost and are available in many sizes.  Manufacturers can quote
   the proper unit if head and flow are given.
   They can be used to produce alternating current also, but with increased
   cost.   In this case, a butterfly valve is used as the turbine-inlet
   valve; and the valve can be regulated by a small water-turbine
    The help of an engineer should be sought in modifying these pumps for
   use as turbines.
                           IX. WATER WHEELS
    Water wheels date back to biblical times but are far from obsolete.
They have certain advantages which should not be overlooked.  They are
more economical for small power requirements than water turbines in some
cases.  It is possible to make a water wheel for power requirements up to
10 horsepower in places where there are no elaborate manufacturing
     Water wheels are attractive especially where fluctuations in flow rate
are large.  Speed regulation is not practical -- therefore, water wheels are
used primarily to drive machinery which can take large fluctuations in
rotational speed.  They operate between 2 and 12 revolutions per minute
and require gearing and belting (with inherent friction loss) to run most
machines.  Thus, they are most useful for slow-speed applications, e.g.,
flour mills, some agricultural equipment, and some pumping operations.
    A water wheel, because of its rugged design, requires less care than
a turbine does.  It is self-cleaning, and, therefore, need not be protected
from debris (leaves, grass and stones).   The two main types of
water wheels are the overshot and the undershot.
A. Overshot Water Wheel
   The overshot water wheel way be used with heads of 10 to 30 feet, and
   flow rates from one to 30 cubic feet per second.
   The water is guided to the wheel in a timber or metal flume at a
   water velocity of approximately 3 feet per second.  A gate at the
   end of the flume controls the flow to the wheel and the jet velocity,
   which should be from 6 to 10 feet per second.  To obtain this velocity,
   the head ([H.sub.1] in Figure 31) should be one to two feet.   Wheel width

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   depends on he amount of water to be used.  The discharge will be one
   to two cubic feet per-second for a flume width of one foot.  Wheel
   width must exceed flume width by about one foot because of jet
   expansion.   The efficiency of a well-constructed overshot water wheel
   can be 60% to 80%.
B. Undershot Water Wheel
   The undershot water wheel (Figure 32) should be used with heads of 1.5

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   to 10 feet and flow rates from 10 to 100 cubic feet per second.   Wheel
   diameter should be 3 to 4 times the head -- wheel diameters between 6
   and 30 feet.   Rotational speed should be 2 to 12 revolutions per minute,
   with the higher speed applying to the smaller wheels.  For each foot
   of wheel width, the flow rate should be between 3 and 10 cubic feet
   per second.   The wheel dips from one to three feet into the water.
   Efficiency is in the range of 60% to 75%.
                              X. EXAMPLES
Mission Hospital
1. Requirements:  10 kilowatt light and power plant.
2. 10 kilowatts is 13 1/3 horsepower.
3. The gross power required is then about 27 horsepower.
4. A stream in hilly territory can be dammed up and the water
   channeled through a ditch 112 mile long to the power plant site.
5. A penstock 250 feet long will take the water to the turbine.
6. The total difference in elevation is 140 feet.
7. Available minimum flow rate: 1.8 cubic feet/second.
8. The soil in which the ditch is to be dug permits a water velocity
   of 1.2 feet per second.
9. Table II, Section VI gives n= 0.030
10. Area of flow in the ditch = 1.8/1.2 = 1.5 square feet.
11. Bottom width = 1.5 feet.
12. Hydraulic radius = 0.31 X 1.5 = 0.46 feet.
13. Figure 8 shows that this results in a fall and head loss of 1.7 feet

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    for 1,000 feet.   The total for the half-mile (2,64C feet) ditch is
    4.5 feet.
14. The fall that is left through the penstock is then: 140-4.5 = 135.5
    feet.   Figure 10 gives 5.7 inches as the required penstock diameter

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    for 1.8 cubic feet per second flow at 10 feet per second velocity.
15. Head loss in the penstock is 10 feet for 100 feet of length and
    25 feet for the total length of 250 feet.
16. For the water tubine:
    Net Head = 135.5-25 = 110.5 feet
17. Power produced by the turbine at 80% efficiency:
    Net Power = Minimum water flow X net head/8.8 X Turbine Efficiency
              =1.8 X 110.5/8.8 X .80 = 18 horsepower
18. Consult Table III.  The cost of a pump or turbine for a particular
    situation can only be learned by writing to the various manufacturers.
    VITA engineers can step in here, lay out the physical
    arrangement and compile a list of necessary mechanical and
    electrical components to the best advantage of the field worker.
                                  Appendix 1
    Small hydraulic turbines and even more the governors for regulating
these turbines are difficult to obtain because the demand for these products
has diminished to a considerable extent in the last twenty years.  And
manufactured water wheels are completely off the market.  Of the remaining
number of manufacturers of small turbines and governors only one exists in
the United States, and two are known by the author to exist in Europe.
    The James Leffel & Company is located in Springfield, Ohio.  Their
booklet, Leffel Pamphlet "A".   Hints on the Development of Small Water
Power, is available on request.   It is a very useful supplement to the
information in this manual.  Its description of Leffel's small vertical
Samson turbine is very complete.   This turbine is available in sizes from
3 to 29 horsepower.  The company maintains an engineering department
which stands ready to assist in planning and design of the entire installation.
    This company also manufactures a complete unit called Hoppes Hydroelectric
Unit, which is useful in isolated locations where the demand is
small.  It comes in sizes of I to 10 kilowatts.  A Leffel bulletin
describing this unit gives complete instructions on submitting the
information necessary for ordering it.
    The Michell (or Banki) turbine is manufactured exclusively by the
Ossberger-Turbinenfabrik of Weissenburg, Bavaria, Germany.  This turbine
is made in sizes ranging from 1 to 1000 horsepower.   The company has an
impressive record of installations, many in less-developed countries.
Ossberger-Turbinenfabrik is very responsive to requests for information.
It furnishes without charge a considerable amount of data, translated
into English.  The simple design of the Michell turbine makes it a
favorite for remote regions and is priced lower than corresponding
Francis and impulse type turbines.   Its governor, developed by Ossberger,
is also very reasonably priced.
    A third company which manufactures turbines and governors for turbines
but does not sell packaged units, including the electrical equipment, is
the Officine Buehler, Taverne.   Canton Ticino.  Switzerland.  They are in
the small turbine field, and they manufacture all types except Michell.
Their workmanship is of the highest quality, and their engineering is
superb.  Like the other companies, they assist prospective customers in
planning their installations.
                                  Appendix 2
                              CONVERSION TABLES
Units of Length
     1 Mile                      = 1760 Yards              = 5280 Feet
     1 Kilometer                 = 1000 Meters             = 0.6214 Mile
     1 Mile                      = 1.607 Kilometers
     1 Foot                      = 0.3048 Meter
     1 Meter                     = 3.2808 Feet             = 39.37 Inches
     1 Inch                      = 2.54 Centimeters
     1 Centimeter               = 0.3937 Inch
Units of Area
     1 Square Mile              = 640 Acres               = 2.5899 Square Kilometers
     1 Square Kilometer         = 1,000.000 Sq. Meters   = 0.3861 Square Mile
     1 Acre                      = 43.560 Square Feet
     1 Square Foot              = 144 Square Inches      = 0.0929 Square Meter
     1 Square Inch              = 6.452 Square Centimeters
     1 Square Meter             = 10.764 Square Feet
     1 Square Centimeter        = 0.155 Square Inch
Units of Volume
     1.0 Cubic Foot             = 1728 Cubic Inches      = 7.48 U.S. Gallons
     1.0 British Imperial Gallon = 1.2 U.S. Gallons
     1.0 Cubic Meter            = 35.314 Cubic Feet      = 264.2 U.S. Gallons
     1.0 Liter                   = 1000 Cubic Centimeters = 0.2642 U.S. Gallons
Units of Weight
     1.0 Metric Ton             = 1000 Kilograms         = 2204.6 Pounds
     1.0 Kilogram               = 1000 Grams              = 2.2046 Pounds
     1.0 Short Ton              = 2000 Pounds
                   CONVERSION TABLES
Units of Pressure
     1.0 Pound per square inch            = 144 Pound per square foot
     1.0 Pound per square inch            = 27.7 Inches of Water(*)
     1.0 Pound per square inch            = 2.31 Feet of Water(*)
     1.0 Pound per square inch            = 2.042 Inches of Mercury(*)
     1.0 Atmosphere                        = 14.7 Pounds per square inch (PSI)
     1.0 Atmosphere                       = 33.95 Feet of Water(*)
     1.0 Foot of Water = 0.433 PSI        = 62.355 Pounds per square foot
     1.0 Kilogram per square centimeter   = 14.223 pounds per square inch
     1.0 pound per square inch            = 0.0703 kilogram per square centimeter
(*) at 62 degrees Fahrenheit (16.6 degrees Celsius)
Units of Power
     1.0 Horsepower (English)             = 746 Watt     = 0.746 Kilowatt (KW)
     1.0 Horsepower (English)             = 550 foot pounds per second
     1.0 Horsepower (English)             = 33,000 foot pounds per minute
     1.0 Kilowatt (KW) = 1000 Watt        = 1.34 Horsepower (HP) English
     1.0 Horsepower (English)             = 1.0139 Metric Horsepower (cheval-vapeur)
     1.0 Metric Horsepower                = 75 Meter X Kilogram/Second
     1.0 Metric Horsepower                = 0.736 Kilowatt  = 736 Watt
                                 Appendix 3
                         General Texts and Handbooks
Brown, J. Guthrie ed, Hydro Electric Engineering Practice.  New York:
   Gordon & Breach, 1958; London:  Blackie and Sons, Ltd., 1958.  A
   very complete treatise covering the entire field of hydroelectric
   engineering.   Three volumes.   v. 1 Civil Engineering $50.00 U.S.
   v. 2 Mechanical and Electrical Engineering $30.00 U.S.
   v. 3 Economics, Operation and Maintenance ($25.00 U.S.)
Creager, W. P. and Justin, J. D.   Hydro Electric Handbook.  2d ed.
   New York:   John Wiley and Son, 1950.   A most complete handbook
   covering the entire field.  Especially good for reference.
   ($18.50 U.S.)
Davis, Calvin V.  Handbook of Applied Hydraulics.  2d ed. New York:
   McGraw-Hill, 1952.  A comprehensive handbook covering all phases
   of applied hydraulics.  Several chapters are devoted to hydroelectric
   application.   ($23.50 U.S.)
Paton, T. A. L.  Power from Water.  London:   Leonard Hill, 1961.   A
   concise general survey of hydroelectric practice in abridged form.
   ($8.50 U.S.)
Zerban, A. H. and Nye, E.P.  Power Plants. 2d ed.  Scranton, Penn.:
   International Text Book Co., 1952.  Chapter 12 gives a concise
   presentation of hydraulic power plants.  ($8.00 U.S.)
                         The Banki Turbine
Haimerl, L. A., "The Cross Flow Turbine," Water Power (London), January
   1960.   Reprints available from Ossberger Turbinenfabrik, 8832 Weissenburg,
   Bayern, Germany.  This article describes a type of water turbine
   which is being used extensively in small power stations, especially
   in Germany.
Mockmore, C. A. and Merryfield, F., The Banki Water Turbine.  Corvallis,
   Ore.:   Oregon State College Engineering Experiment Station Bulletin
   No. 25, February 1949.  40c.   A translation of a paper by Donat Banki.
   A highly technical description of this turbine, originally invented
   by Michell, together with the results of tests.
Small Michell (Banki) Turbine. Arlington, Virginia:   Volunteers in
   Technical Assistance (VITA), 1979.
                             Appendix 4
                     THE AUTHOR AND REVIEWERS
  Hans W. Hamm, a VITA Volunteer, was a consultant on small water
power developments for twenty years with a Pennsylvania manufacturer
of water wheels and small turbines.   He earned a degree in mechanical
engineering from the State Technical University of Braunschweig in his
native Germany.  He retired in 1966 from the York, Pennsylvania, works
of Allis-Chalmers.
  Other VITA Volunteers have helped in producing this manual:   Morton
Rosenstein, public relations and market research manager at Ionics, Inc.,
Watertown, Massachusetts, edited the entire manual.
  Harry Wiersoma, consulting engineer of Knoxville, Tennessee, made
many helpful suggestions based on more than fifty years' experience in
hydraulic engineering.  He also wrote the preface for the manual and
prepared the bibliography.
  Dr. John J. Cassidy, associate professor of civil engineering,
University of Mitsouri, and Robert H. Emerick, consulting engineer
of Charleston, South Carolina, both reviewed the manual for technical
  Ian D. Burnet, projects officer of the Department of Trade and
Industry, Port Moresby, Papua, New Guinea, reviewed the book from the
point of view of the eventual user, the community development leader.
  The manual was also reviewed by Jeffrey Ashe and John Brandi,
Peace Corps Volunteers who were working on a project to develop a small
water power site in Loja, Ecuador, by Ossberger Turbinenfabrik,
Weissenburg (Bayern), Germany and by James Leffel & Company,
Springfield, Ohio.
                                 Appendix 5
                                 DATA SHEET
  This form is given as a guide to help you collect the
information a VITA engineer would need to help you plan a small
water power site.
TO:  Volunteers in Technical Assistance
       1600 Wilson Boulevard, Suite 500
          Arlington, Virginia 22209 USA
 1. Minimum flow of water available in cubic feet per second
    (or cubic meters) per second.                 __________________
 2. Maximum flow of water available in cubic feet per second
    (or cubic meters) per second.                 __________________
 3. Head or fall of water in feet (or meters)     __________________
 4. Length of pipe line in feet (or meters) needed to get the
    required head.                                __________________
 5. Describe water condition (clear, muddy, sandy, acid)
 6. Describe soil condition (see Table II)        __________________
 7. Minimum tailwater elevation in feet (or meters)_________________
 8. Approximate area of pond above dam in acres (or square
    kilometers).                                   __________________
 9. Approximate depth of the pond in feet (or meters)_______________
10. Distance from power plant to where electricity will be
    used in feet (or meters).                     __________________
11. Approximate distance from dam to power plant   __________________
12. Minimum air temperature.                       __________________
13. Maximum air temperature.                       __________________
14. Estimate power to be used.                     __________________
Date_______________              Name__________________ _____________
                                Address_______________ _____________
See reverse for guide in                _______________ _____________
collecting further helpful              _____________________________
                             DATA SHEET - 2
  The following questions cover information which, although
not necessary in starting to plan a water power site, will
usually be needed later.  If it can possibly be given early in
the project, this will save time later.
1. Give the type, power and speed of the machinery to be
   driven and indicate whether direct, belt or gear drive is
   desired or acceptable.
2. For electric current, indicate whether direct current is
   acceptable or alternating current is required.  Give the
   desired voltage, number of phases and frequency
3. Say whether manual flow regulation can be used (with D.C.
   and very small A.C. plants) or if regulation by an automatic
   governor is needed.
                                 Appendix 6
                         DECISION MAKING WORK SHEET
If you are using this guide in a development effort, collect as
much information as possible and if you need assistance with the
project, write VITA.  A report on your experiences and the uses of
this manual will help VITA both improve the book and aid other
similar efforts.
                   Volunteers in Technical Assistance
                     1600 wilson Boulevard, Suite 500
                        Arlington, Virginia 22209, USA
o Describe current agricultural and domestic practices that rely
  on water.   What are the sources of water and how are they used?
o What water power sources are available? Are they small but
  fast-flowing? Large but slow-flowing? Other characteristics?
o What is water used for traditionally?
o Is water harnessed to provide power for any purpose? If so,
  what and with what positive or negative results?
o Are there dams already built in the area? If so, what have been
  the effects of the damming? Note particularly any evidence of
  sediment carried by the water--too much sediment can create a
o If water resources are not harnessed, what seem to be the
  limiting factors? Does cost seem prohibitive? Does the lack of
  knowledge of water power potential limit its use?
o Based on current agricultural and domestic practices, what
  seems to be the area of greatest need? Is power needed to run
  simple machines such as grinders, saws, pumps?
o Given available water power sources, which ones seem to be
  available and most useful? For example, one stream that runs
  quickly year around and is located near the center of agricultural
  activity may be the only feasible source to tap for
o Define water power sites in terms of their inherent potential
  for power generation.
o Are materials for constructing water power technologies available
  locally? Are local skills sufficient? Some water power
  applications demand a rather high degree of construction skill.
o How much skilled labor is necessary for construction and
  maintenance? What kinds of skills are available locally? Can
  you meet the need? Do you need to train people?
o Some aspects of turbine construction require someone with
  experience in metalworking and/or welding.  Is this skill
o Waterwheel construction may require woodworkers.   Are they
o Is help available for dam building? Surveying? Determining
  environmental impacts?
o Do a cost estimate of the labor, parts, and materials needed.
o How will the project be funded?
o What is your schedule? Are you aware of holidays and planting
  or harvesting seasons, which may affect timing?
o How will you arrange to spread information on and promote use
  of the technology?
o Is more than one water power technology applicable? Remember to
  look at all the costs.  While one technology appears to be much
  more expensive in the beginning, it could work out to be less
  expensive after all costs are weighed.
o Are there choices to be made between a waterwheel and a
  windmill, for example, to provide power for grinding grain?
  Again weigh all the costs:  economics of tools and labor, operation
  and maintenance, social and cultural dilemmas.
o Are there local skilled resources to introduce water power
  technology? Dam building and turbine construction should be
  considered carefully before beginning work.  Besides the higher
  degree of skill required in turbine manufacture (as opposed to
  waterwheel construction), these water power installations tend
  to be more expensive.
o Where the need is sufficient and resources are available, consider
  a manufactured turbine and a group effort to build the
  dam and install the turbine.
o Is there a possibility of providing a basis for small business
o How was the final decision reached to go ahead--or not go
  ahead--with this project? Why?
                             Appendix 7
                    RECORD KEEPING WORK SHEET
Detailed records of project implementation are helpful to ongoing
project management and to other people who may be involved in
similar efforts elsewhere.
Photographs of the construction and installation process, as well
as the finished result, are helpful.   They add interest and detail
that might be overlooked in the narrative.
A report on the construction process should include much very
specific information.  This kind of detail can often be monitored
most easily in charts (such as the one below). <see report 1>

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Some other things to record include:
o Specification of materials used in construction.
o Adaptations or changes made in design to fit local conditions.
o Equipment costs.
o Time spent in construction--include volunteer time as well as
  paid labor; full- or part-time.
o Problems--labor shortage, work stoppage, training difficulties,
  materials shortage, terrain, transport.
Keep log of operations for at least the first six weeks, then
periodically for several days every few months.   This log will
vary with the technology, but should include full requirements,
outputs, duration of operation, training of operators, etc.
Include special problems that may come up--a damper that won't
close, gear that won't catch, procedures that don't seem to make
sense to workers, etc.
Maintenance records enable keeping track of where breakdowns
occur most frequently and may suggest areas for improvement or
strengthening weakness in the design.   Furthermore, these records
will give a good idea of how well the project is working out by
accurately recording how much of the time it is working and how
often it breaks down.  Routine maintenance records should be kept
for a minimum of six months to one year after the project goes
into operation. <see report 2>

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This category includes damage caused by weather, natural disasters,
vandalism, etc.  Pattern the records after the routine
maintenance records.  Describe for each separate incident:
o Cause and extent of damage.
o Labor costs of repair (like maintenance account).
o Material costs of repair (like maintenance account).
o Measures taken to prevent recurrence.