evaluate a potential site for the construction of a freshwater sh farm; select the type of pond best adapted to this site and to your needs; lay out your sh farm; build eahen ponds; and construct the various structures required for proper water control and transpo

1. 12.DETAILEDPLANNINGFORFISHFARMCONSTRUCTION
12.0Introduction
1.Inthepreviouschaptersyoulearnedhowto:
evaluateapotentialsitefortheconstructionofafreshwaterfishfarm;
selectthetypeofpondbestadaptedtothissiteandtoyourneeds;
layoutyourfishfarm;
buildearthenponds;and
constructthevariousstructuresrequiredforproperwatercontrolandtransport.
2. You have selected a good site both from the technical and economical
aspects (see Sections 2.2 and 2.3).You have surveyed this site in detail for
its topography and its soils. On these bases and according to your
requirements, you have laid out your fish farm and prepared a detailed
topographicalplanofit(seeSection2.6).
Theselectedsite
3.Nowhascomethetimetodecideonthefollowingimportantissues:
(a)When willtheconstructionbegin(seeSection12.1).
(b)Whowillconstructthefarm(seeSection12.2).
(c)How willtheconstructionbedone(seeSection12.3).
4.Thesedecisionsmayleadtofurtheractivities,allofwhicharelookedintointhischapter:
(a)Somemoredetailedplansanddrawings mayhavetobeprepared(seeSection12.4).

2. (b)Aseriesofspecificationsforthecontractormayhavetobeprepared(seeSection12.5).
(c)Adetailedscheduleofactivitiesmayhavetobedrawnup(seeSection12.6).
5.Finally,andinallcases,youwillwishtoknowinadvancehowmuchtheconstructionofthefishfarmwillcost (seeSection12.8).

3. 12.1Whentobuildthefishfarm
1.Beforedecidingatwhichtimeoftheyearyoushouldbuildyourfishfarm,youshouldaskthesequestions:

4. (a)Whenisthesite easilyaccessible?
(b)Whenisthesoil relativelydry,softandeasilyworkable?
(c)Willtherebewater availabletofillthepondshortlyafterbuildingit?
(d)Doesitneedtobepreparedforstockingwithfish ataparticulartime?
(e)Willtherebelabour,machineryandmaterialsavailableatthattime?
(f)ShouldIconsiderbuildingthefarminstages,overseveralseasons?
2. Accessibility to the site and workable conditions are particularly important if you plan to use machinery for the earthwork. Remember that for
materials and supplies such as sand, cement, gravel, wood and pipes, access to the site by vehicles may also be required. It is best to fill the
pond withwatershortlyafterconstructiontoavoidthegrowthofweeds.
3.Underextremeconditions,selecttheseasonforconstructionusingthefollowingguidelines;
swampyconditions:towardtheendofthedryseason;
heavyclaysoils:towardtheendoftherains;
harddryground:endofrainyseason.
4.Whenbuildingabarragepond,itisbesttoselecttheperiodwhentheflowofthestreamtobedammedisminimal.
12.2Whowillconstructthefishfarm?
1.Therearethreepossibilities:
eitheryouconstructthefarmentirelyyourself;or
youpayasmall,localcontractortodoit;or
youdoitpartlyyourselfandpartlyundercontract.
2.Youshouldconsiderconstructingallorpartofthefishfarmyourself,forexamplewhen:
thefishfarmtobebuiltisrathersmall,lessthan1ha,andyoucanrelyonsometechnicalassistancefromaspecializedextensionservice;
thereisnoqualifiedcontractoravailablelocally,andyouhavesomeoftherequiredexperience;
theinterestedcontractorsquotepricesmuchhigherthanyourownestimate;checkthelattercarefullyandquestionthecontractorsbeforetakingafinaldecision.
3.Ifyoudecidetoconstructalargerfarmyourself,beforestartingitsconstructionyoushould:
decidewhetheryouaregoingtoconstructitwithorwithoutmechanicalmeans(seeSection12.3);
preparethetechnicalspecificationsfortheearthworkandthestructures(seeSection12.5);

5. prepareascheduleofactivities(seeSection12.6);
plan for the necessary inputs such as labour, tools, supplies/materials and equipment by working out how much you will need, when you will need these inputs
andforhowlong.
4.If you decide to employ a contractor to do part or all of the construction work, it is simplest to discuss a direct contract with a known contractor
andtoagreewithhimonan all-inclusive price forthejob.Thiscontractorshouldnotonlyhavetherequiredtechnicalqualifications,butshould
alsohavereliablefinancialcredentials.
5. In this last case, you do not have to decide for yourself the best way in which to construct the fish farm according to your plans. This
should be done by the contractor. But first, you will have to prepare plans and drawings (see Section 12.4) and specifications for the contract (see
Section 12.5). The contractor will base the price of the contract on these plans, drawings and specifications. Compare this price with your own
estimate (seeSection12.8)andacceptitonly iftheydonotdiffertoomuch.
12.3Constructingthefishfarm
1.Ifyouhavedecidedtoconstructyourfishfarmyourself,youhavetwochoicesofwaystoproceed:
eitherusingmanuallabouronly;or
usingmachineryinpartandusingmanuallabourinpart.
2.Thechoicelargelydependsuponthe size of the farm tobebuiltandonthe availability of machinery.Verysmallfarmsupto1000m2 areusually
built using manual labour only. It is also important to have the farm constructed within a reasonable time to bring it into production and
reducethetimebeforeearningsaremadeonyourinvestment.
3. For manual construction you will need simple equipment such as picks,
hoes, shovels and wheelbarrows. It can be done by yourself and your
family, assisted by some friends if necessary. You can also contract
someone to dig the pond manually for a fixed price based on the
earthwork.Thesizeofindividualpondsgenerallydoesnotexceed400m2
.Fromthevolumeofearthworkrequired,youcanestimatehowlongitwill
take you to build each pond and, if necessary, how much it would cost
youtosubcontractitsconstruction(seeSection12.8).

6. 4. Mechanical construction is done with earth-moving machines such as
bulldozers and wheel loaders (see Section 4.8). Compaction equipment
can also be used. This construction method is much faster and not
necessarily more expensive than using manual labour only, but it requires
the selected site to be accessible to the machinery and to have adequate
soil conditions, It also requires skilled operators. The amount of earthwork
should be large enough to justify the costs of transporting equipment to
the site. One way of reducing these costs would be to join your neighbours
andbuildseveralfishfarmsinthesamearea,usingthesamemachinery.
5. Normally, you would hire the services of a contractor who owns the necessary equipment. This is usually done either with a price determined by
the nature and amount of workto be done or for a weekly, daily or hourly rate.While the latter could be cheaper, you should make sure that
theoperatorisskilled,andbecarefulifthereisariskofthemachinerybreakingdownorgettingstuckduringconstruction.Beforediscussing
the contract, it is best to estimate yourself the volume of earthworkto be done and, from this, the machinery time needed (see Section 12.7).
You can do similar calculations for other types of construction work, such as site preparation and dike compaction. Remember that it will
alwaysbenecessarytousemanuallabouraswell,particularlyforfinishingtheconstruction.
6. A mixed method is often the most advantageous way to construct medium-size fish farms. This only involves the use of earth-moving
equipment, for example an ox-drawn scoop or scraper or a small bulldozer, as discussed in Chapter 4, to speed up the main earth
movements.Allothertypesofworkaredonemanually.
12.4Makingdetailedplansanddrawings
1. At the beginning of this manual (see Section 2.6), you learned how to prepare a topographical plan showing the site elevations and the
proposedlayoutofthefishfarm,includingallitsstructures.
2. If the fish farm to be constructed is rather small (less than 5 000 m2) you will not usually need to prepare more detailed plans. It is usually
sufficient to markthe main dike boundaries and estimate the volumes of earth required.You will only need to use detailed calculations and markings
ifthegroundisveryirregular(seeSections6.4to6.8).Asdistancesarenotgreat,theplanningofearthmovementsisnotsoimportant.
3.Themostusefuladditionstotheexistingtopographicalplan arethefollowing:
elevationsofthetopsofthedikes;
elevationsofthepondbottoms;
elevationsofthefeederanddrainagecanals;
characteristicsofthedikes(sideslope,length,thickness);
characteristicsofthecanals(sideslope,bottomwidth);
characteristicsoftheroads(elevations,width);
positionsoftheotherstructuressuchasmainwaterintake,pondinlets/outlets,divisionboxesoncanals,spillways,etc.

7. Generallayoutforasmallfishfarm

8. 4. It may also be useful to prepare detailed drawings of the various structures as a basis for estimating their individual cost (see Section 12.8) and
fortheirconstruction.Elevationsshouldbeclearlyindicatedtoavoidanymistakeslater.
5. If the fish farm to be constructed is larger (greater than 5 000 m2), it is advisable to prepare more detailed work plans to be closely followed
duringconstruction.Foreachfishpondprepareatopographicalworkplaninthefollowingway:
(a)Surveythesitearea inmoredetail,eitherbyradiationorusingasquaregridasdiscussedinSections8.1and11.4,Topography,16.Thissurvey
is best done after partial clearing of the vegetation (see Sections 5.2 to 5.5), and it should provide you with accurate information on the
positionsandthelevelsofthepondsitearea.Atthisstageyouwillhavepeggedoutthepondarea.
(b)Startdrawingthetopographicalworkplan ofthepondarea,includingallsurveyedpoints.
(c)Determinethebestexcavationdepthtobalancecutandfillvolumes accordingtothetypeofpond(seeSections6.4to6.8).
(d) Make sure that these calculations tie in with the required feeder and drainage canal levels, and that localsoil conditions such as areas of rock,
permeablesoil,sourcesofclay,etc.aretakenintoaccount.
(e)Trytominimizethedistances youmoveearthwithinthepond,particularlyifyouplantobuildthepondbyhand.Asanapproximateguide,on
flat ground you should aim to transport the earth no more than about one quarter of the pond's width and on steeper slopes, no more than
two-thirdsofthepond'swidth.

9. (f)Makesurethataccessroadsortracks,feedercanalsanddrainsarelaidouttoservicethesiteefficientlyandwell.
Note: insomecases,particularlyforlargesiteswithmanyponds,itmaybenecessarytomoveearthfromoneareaofthesitetoanother.Allowfor
theextraearthvolumestakenawayorbroughtintothepond.Checkthattheearthvolumesbalanceoutoverthewholesite.
(g)Determinethekeyelevationsofthepond.
(h)Completethetopographicalworkplanofthepond byenteringthefollowinginformationonit:
theelevationsofthetopofthedikes;
thepositionsandelevationsoftheinletandoutlet;
thepositionsandelevationsofanyotherstructuretobebuiltinthepondarea;
thecharacteristicsofthedikes.
6. It is also better to prepare cross-section profiles of the site and the pondsin two perpendicular directions, especially if the site is sloping and if
thepondsaretobeconstructedatdifferentelevations.Indicateonthemthekeyelevationsofthepondsandotherstructures.
7.Addtotheexistingtopographicalplanofthefishfarm allinformationrelatingtothefeeder/drainagecanals,roadsystem,servicebuildings,etc.,
whichdonotappearontheworkplans.
8. Prepare detailed drawings of the various structures, indicating clearly their key elevations and giving a reference number to each kind of
structure.
Typicalstructuresforalargerfishfarm
Cross-section feedercanal Cross-sectionofafeedercanalwithdoubleinlet

10. Cross-section pondinlet
NOTES: Elevation measurements are
inmetres;allothermeasurementsare
incentimetres
Cross-sectionofapondoutletwithmonk

11. Generallayoutforalargerfishfarmof16pondsof0.25haor4hatotal

12. Typicalcross-sectionforalargerfishfarm
12.5Makingspecificationsforconstructioncontracts
1. Preparing the specifications for the construction of a larger fish farm can be a very complicated task, and this should be carried out by a
qualifiedtechnicianorengineer.However,ifyourfishfarmissmall (lessthan5000m2),youmayprefertopreparethespecificationsyourselffor
itsconstructionundercontract,preferablywithsomeassistancefromyourextensionagent.
2.Makeadetailedlistofthenon-technicalspecifications,underthefollowingheadings:
generaldescriptionofthesiteandworktobedone,includingnumberandsizeofponds,canalsandstructures;
descriptionofcontractor'sresponsibilitiesfortheconstructionsuntilcompletion,deliveryandacceptance;
descriptionofsupervisory,testingandacceptanceconditions;
descriptionofpaymentscheduleaccordingtoworkprogress;
time limits for delivery or completion, and possibilities for extension (for reasons beyond contractor's control) and penalties (for late delivery and loss of
production/andinterest).
3.Listthetechnicalspecificationsclearlyandindetail,referringtoavailabletopographicalplansanddetaileddrawings(seeSection12.4).These
specificationsshoulddealseparatelywiththeearthworkandthestructuresasfollows:
(a)Earthworkspecifications:

13. siteclearing,includingtotalremovalofstumpsandroots,handlingandplacingofclearedvegetation;
removaloftopsoil,includingdetailsofarea,thickness,storage;
constructionofdikes,includingtheoriginandqualityofthesoilanditscharacteristics,
compaction,coveringmaximumthicknessoflayers,soilmoisturecontent,typeofequipmenttobeused.
(b)Structurespecifications,listingtypeandqualityofmaterialstobeusedineachcase,suchas:
reinforcedconcrete,includingmixtype,slumptestlimits,reinforcementquality,curingprocess,forms;
wood,listingdetailsofspecies,treatment,relativehumidity,storageconditions;
bricksorconcreteblocks,notingquality,finish,type,weight,storageconditions-,
pipes,listingtype,material,storage,handling,laying;
mortarandplastermixes,additives,water,etc.;
paints,specifyingnumberofcoats,type.
4. To be able to give a price quotation for the construction contract, the contractor will require all the above specifications together with
topographicalplansanddetaileddrawings.
12.6Makingascheduleofactivities
1.Ifyouhavedecidedtoconstructthefishfarmyourself,youshouldpreparearealisticscheduleofactivitiestohelpyouplanfortherequired
inputs.
2.Beforestartingconstructionwork,inmostcasesitisnecessarytohaveapreparatoryphase inwhichyouwill:
stakeoutthepositionoftheponds,dikes,canals,etc.;
clearthevegetation;
removethesurfacesoilandstoreit;
establishtemporarybench-marks;
assembletheconstructionmaterialsrequiredonthesite;
stakeoutindetailthedikes,canals,pondbottom,etc.;
digtemporarydrainsforcarryingawayexcessseepageorrunoff;
digprotectioncanals(seeSection11.5).
3. Thetemporary bench-marks (TBMs) that you establish allow you to determine and check by levelling the elevations of the dikes, canals and
otherstructures(seeSection8.1,Topography,16).Themainpointstoconsiderarethat:
thenumberofTBMsrequiredincreaseswiththesizeofthefarm;
theseTBMsshouldhavethesamereferencelevelastheexistingtopographicalbenchmarks;
theTBMsshouldpreferablybesetaroundtheperimeterdike;
theTBMsshouldbewellfixedandprotectedduringthewholeconstructionperiod.

14. Stakeoutpondsandcanalsandestablishtemporarybench-marks
4. The construction of one or more ponds and structures can then be initiated, following a sequence which varies according to the type of
pond, as suggested in Table 50. Not all the steps are necessary in all cases, but depend on the farm design and the kind of structures to be
used.
TABLE50
Usualorderofpondconstructionphases
Constructionphase Sunkenponds
Barrageponds Diversion
ponds
Withoutdiversioncanal With
diversioncanal
Diversioncanal/mainfeedercanal - - 1 7
Temporarydiversionofstream - - 2 -

15. Pondinlet(s) - - 3 11
Secondaryfeedercanal(s) - - - 8
Mainwaterintake - - - 9
Barrageonstream - - - 10
Ponddike(s)
foundation 3 6 8 1
construction 4 7 9 6
forming 5 8 10 12
grassing 6 9 11 14
Pondbottomlevelling - - - 13
Pondoutlet(s)
excavationofpit(s) - 1 4 2
constructionofstructure(s) 1* 2 5 4
refilling/compactingpit(s) - 3 6 5
Spillway(s)
mechanicalspillway 2* 4 - -
emergencyspillway 7* 5 7* -
Drainagecanal(s) - - - 3
*Ifnecessary

16. 5.Youmayneedtochangetheorderofconstruction inparticularcircumstances.
(a)Underswampyconditionsorwheneverthefloodingofthesite istobeavoided,itisbesttobuildthedrainagesystemofthefarmfirst.
(b) Whenever the ground is flat (slope less than 0.5 percent), it may be easier to build the drainage canal first, then the inlet canal and then to
adjustthelevelsoftheponddikesandbottomaccordingly,atanintermediateelevation.
(c) For small artisanal ponds, it may be easier to finish building the dikes before building the pond outlet. Then you need to cut the dike, put in
placetheoutletstructure,andthenrebuildthedikeontop.
Sunkenpond Diversionpond
Barragepondwithoutdiversioncanal Barragepondwithdiversioncanal
6.Onthebasisofthisinformation,prepareascheduleofactivities showing:
alongacentralline,theorderinwhichtheindispensableactivitiesaretobeimplemented;and
alonglaterallines,thecomplementaryactivities,whichcanbeimplementedsimultaneouslywithsomeindispensableactivities.

17. Scheduleofactivities
7.Youcanimprovethisscheduleofactivities byaddingabackgroundtimescale (inweeksforexample)andbyshowingforeachactivity:
whenitisplannedtotakeplace;and
howlongitwilltake.
8.Todothis,usetheworkingstandards whicharegiveninthenextsectiontogetherwithyourearthworkestimatesandthelistofstructuresto
bebuilt.
Scheduleofactivitiesonaweekbasis
12.7Workingstandardsforplanningpurposes
1.Youwilluseworkingstandardsbothbeforeconstructionstartsandduringitsexecution,forexample:
toestimatethenumberoflabourersandhowlongyouwillneedthemforeachconstructionphase;

18. toselectthetypeofearth-movingequipmentandtoestimateforhowlongyouwillrequireit;
toestimatehowmuchtheconstructionwillcostyouand,ifnecessary,todiscusswithacontractorthepricebeingproposed.
2.Inthefollowingparagraphs,generalstandardsusefulforfishfarmconstructionareprovided.
Working standards for manual earthwork
3.Theseworkingstandardswillvarymainlywiththenatureofthesoil.The
harder the soil, the more difficult it is to work it and the lower the work
outputs. The presence of excess water also decreases outputs,
particularlyinheavyandstickyclays.
Manualearthwork
Example
Workinghoursformanualconstructionofruralponds
Farm1* Farm2** Farm3***
Mainwaterintakewithsmalldamonstream 130 266 130
Feedercanal (200m)50 (200m)50 (270m)70
Excavation/dikesconstruction (150m3)600 (400m3)1600 (950m3)3600
Inlet/outletpipes 5+ 4 90+

19. Totalworkingtime 785 1920 3890
*One400m2 diversionpond
**Two200m2 diversionponds
***Four400m2 diversionpondsandtwo100m2 diversionponds
+Includingconcrete
4. When planning earth movements, you should take into account that to
minimizecosts,distancesshouldbelimitedasfollows:
horizontaldistanceforthrowingearth:maximum4m;
verticalupwarddistanceforloadingearth:maximum1.60m;
obliquedistanceforloadingearth:maximum4m.
5. Working standards for earthwork with manual labour are given in Table 51. These are the average outputs to be expected from labourers of
averagestrengthworkingforeighthoursatdiggingandthrowingtheearth1maway.Theminimumvalues areforexcavatingandthrowing1m
awaybyhoe.Themaximumvalues refertotheuseofpickandshovelundersimilarconditions.Theseoutputsshouldbeslightlyreducedasthe
throwingdistanceincreases.
6.Forexcavatingandformingcanals,theoutputforatrainedlabourervariesfrom0.8to1.2m3/day.
TABLE51
Averageoutputofmanuallabourforexcavations
Natureofsoil Volumeexcavated/thrownaway(m3/8h)
Byhoe Bypick/shovel
Soft(alluvium,sandysoil) 2.5-3 3.5-4
Moderately hard (loam, light
clay) 1.5-2 2.5-3

20. Hard(heavierclay) 1 2-2.5
Lateritic,moderatelyhard* 0.5 1-1.5
Watersaturated 0.8-1.5 1.5-2
*SeeSection18,Soil,6.
7.Thenatureofthesoildeterminestheexcavationmethod.Ifthesoilissoft,itmaybepossibletoworkwithashovelonly.Ifthesoilisharder,it
is best to first use a pick to loosen the soil before shovelling it away. In this case, the following outputs can be expected for each team of
labourers:
Soil Labourandtools Output
(m3/hour/team)
Normal 2labourers=1pick+1shovel 0.8-1.0
Light 3labourers=1pick+2shovels 1.5-2.5
Heavy/wet 3labourers=2picks+1shovel 0.4-0.6
Working standards for transporting earth with wheelbarrows
8. A standard metal wheelbarrow can transport from 30 litres (0.03 m3) to 60 litres (0.06 m3) of earth. Preferably, you should limit the transport
distanceto30m atthemost.Forplanningpurposes,youcanthencalculatethefollowing:
(a)EstimatethenumberNofearthloads tobetransportedoverashortdistance perworkinghouras
N=60min� (loadingtime+transporttime)
where
loadingtime averages1.5minutesperload;and
transport time is based on the total distance to be covered and an average walking speed of 50 m/min on level ground or 40 to 45
m/minonslopinggroundcarryingthefullloaduphill.Downhillslopeswillsimilarlyincreasetransportspeed.
Note:itispossibletoreduceaverageloadingtimeandevenmakeitzerobyusingmanywheelbarrows.
Example

21. Youtransportearthonlevelgroundoveradistanceof20m.Perworkinghour,youwillbeabletomake:
N=60min� [1.5min+(40mat50m/min)]
=60min� (1.5min+0.80min)
=60min� 2.30min=26trips
(b)Estimatetheamountofexcavatedearthyoucanloadinonewheelbarrow,forexample0.045m3.
(c)Estimatehowmanyeffectiveworkinghours therewillbeforeachworkingday,takingintoaccountrestingperiods,whichnormallytotalabout
25percent.Forexample,eacheight-hourworkingdaymayprovidesixeffectiveworkinghours.
(d)Estimatetheearthworkvolume tobemoveddailyforeachwheelbarrowfromtheabovefigures.
Example
Numberoftripspereffectiveworkinghour=26
Effectiveworkinghoursperday=6
Excavatedearthworkperwheelbarrow=0.045m3
Earthworkvolumemoveddailyperwheelbarrow=26x6x0.045m3 =7.02m3 orabout7m3
(e)Toserviceeachwheelbarrowfortransportdistancesupto30m,youwillneedatleast:
oneworkertodigandfillthewheelbarrow;and
oneworkertopushthewheelbarrow.
(f)Youmightneedadditionalworkers atparticularspots:
atthedumpingsite,toassistemptyingthewheelbarrowcompletely;
alongthetransportroadatclimbingpoints,tohelpbringthewheelbarrowuptheslope.

22. Average output of various types of machinery
9. Working standards for the most commonly used earthworking machinery are given in Table 52. These machines are particularly useful if relatively
largeareasoflandareinvolved.
10. Bulldozers' output increases as the engine power increases, as shown in Table 53. These are approximate outputs for normal soil conditions
and for a maximum transport distance of 50 m by pushing. Lower outputs should be used as soil conditions worsen, for example in heavy/sticky
clays.
Example
Onecontractorcalculatedtheaveragetimenecessarytoconstructone2500m2 diversionpond,aspartofa5hacommercialfarmasgivenhere.
Item Machinery/labour Working
time(hours)
Ripping/removingtopsoil BulldozerD4 13
Excavation/dikes
construction BulldozerD8 56
Levellingdiketops BulldozerD4 8
Levellingpondbottom Grader 6
Compactionofdikes D4+roller 12
Finishingdikes 6men 32
Monkconstruction 4 men + concrete
mixer 32
Inletconstruction 4 men + concrete
mixer 32
TABLE52
Averageoutputofvariousmachineryperworkinghour

23. TABLE53
Approximateoutputofbulldozersforearthwork
Approx.power
rating(horsepower)
Approx.blade
capacity*(m3)
Excavation/transport**
(m3/h)
Spreadingloose
earth(m3/h)
40 1.2 13-17 18-24
70 2.5 22-29 30-39
90 3.6 32-40 42-54
130 4.0 46-71 60-76
*Whencompletelyfilled.Inpractice,fillingisusually30to60%ofthis,dependingonsiteconditions
**Excavationsbylayerslessthan0.5mthick.Transportover50matmost,ingoodsiteconditions

24. Bulldozer Wheelloader
Compactors
Working standards for construction of structures
11.To build a brick wall (half-stone pattern), you will require about 50 bricks per m2 .Agood mason can place at the most 600 to 800 bricks
pereight-hourday.Note,however,thatwallsshouldnotbebuiltupmorethanabout50cm/day.
12. To mix and cast concrete, the required labour varies from eight work-hours/m3 (without reinforcement) to ten work-hours/m3 (with
reinforcement).
Note: it is possible to estimate output by defining the time for each trip based on: excavation of blade load 0.5-1 min; pushing, 2 km/h;
returning 4-5 km/h; turning, positioning, gear change 0.5-1 min; allow a maximum of 50 minutes per hour utilization. These output figures
decreaseconsiderablyindifficultsiteconditionssuchasslopingground.
12.8Estimatingthecostofconstruction
1.Theconstructioncostsoffishfarmsvaryconsiderablyfromplacetoplace,dependingparticularlyonsuchfactorsas:
thetopographyofthesite:agentleslopecanreduceearthtransport;
thetypeofsoil:swampysitesarethemostexpensive-,
thekindofmaterialstobeused:concretecanbecheaperthanwood;
thefishfarmlayout:itischeapertobuildlargerponds;
thewayyouchoosetoconstruct:itmaybecheapertoorganizetheworkyourself;

25. therateatwhichyoudothework:itisusuallycheapertoplantheworkaccordingtothecapacityoflocallyavailableworkersandequipment.
2. By estimating the cost of several alternatives, you will be able to compare them and select the cheapest way. A good solution to reduce the
overall cost of the fish farm is to reduce the cost of its structures, for example by fitting the plan as well as possible to the local conditions,
choosingacheapermaterialandplanningforsmaller,betteradaptedstructures.Youcanalsoreducecostbydevelopingthefarmstage-by-stage,
sothatearningsfromearlyproductioncanhelptopayforlaterstagesofconstruction.Whiletryingtosaveonconstructioncosts,bewareof:
reducingthequalityofthestructures,whichshouldremaingoodinallcases;and
tryingtosavemoneyonthecostofthedikes,especiallyforabarragepond.
TABLE54
Usefullifeandrelativemaintenancecostsonfishfarms
Item Usefullife
(years)
Relativemaintenance
cost*
Earthenponds 25-50
Pondstructures
hard wood,
treated 10 (3)
masonry 20-25 (2)
concrete 20-25 (1)
Earthencanals 30-50
Well 15
Pump 10-15
Fueltank 20
Servicebuildings 20
*Thehigherthenumber,thegreaterthecost

26. 3.Whendecidingonwhichmaterialstouse,itisalsoimportanttotakeintoaccountthe useful life ofthestructures(Table 54).Astheusefullife
increases,theannualdepreciationcostoftheitem(originalcost� usefullife)decreases,(seeSection16.7,Management,21).
4. Maintenance costs can also vary according to the type of material used for the construction of a structure. They increase, for example, from
concretetomasonrytotreatedhardwood.
5. Major items of cost for the construction of a fish farm include site preparation, pond construction, water control structures and water
transport structures. Other costs may include detailed topographical and soil surveys, pegging of the construction works and miscellaneous
expensessuchasthesettlingbasin,protectioncanal,accessroads,fencingandservicebuildings.
6.Additionalstructurescanbeconstructedaccordingtotheneedsofthemanagementofthefishstockssuchasharvestingandfeeding.This
is discussed in detail in Management, 21. You should calculate the cost of each item separately. A first estimate of the total cost is obtained by
addingalltheseindividualcoststogether.Thefinalestimate isthisfirstestimateincreasedby10to15percentforcontingencies.
7. For manual construction only, the cost estimate is based on the working hours required and on the materials to be used. Whenever machinery is
involved,individualcostestimatesareobtainedasfollows:
(a)Sitepreparation:
site clearing: price is essentially based on the density of the vegetation cover and on the average size of the trees. If possible, the wood can be sold either
processed(e.g.charcoalorplanks)orunprocessed;
topsoilremoval/storage:priceisbasedonthedepthofexcavation,thesurfaceareaandthetransportdistance;
levelling:priceisbasedonthedepthofexcavationandsurfacearea.
(b)Pondconstruction,wherethedikes'volumeshouldbeequaltoexcavationvolume:
excavationvolume:priceperm3;
transportdistance:priceperm3 accordingtodistance(inm).
Note:averagetransportdistancedcanbeestimatedaccordingtothelocaltopographyandthepondwidthw,somewherebetweend=0.25w for
flatgroundandd =0.66w forsteepslopes.
compaction:priceeitherperm2 ofdikeorperm3 ofearthwork;
finishing:priceperm2 ofdike.
(c)Watercontrolstructures,wheretheindividualpriceisdeterminedaccordingtoquantity(length/weight/volume)ofmaterialsneededandunit
priceofeachmaterial,pluslabourcostforconstruction.
(d)Watertransportstructures,wherethepriceoftheexcavationandformingofwatercanalsiscalculatedaccordingtoexcavationvolume.

27. Example
Apaddypond20mx20m=400m2 istobeconstructedonaflatareaofland,withthedikes'cross-sectionbeing2.50m2 .Thevegetationcoverconsistsofclearedrain
forestandthetopsoiltoberemovedis0.20mdeep.Thestructuresare:
inlet=1mconcretepipewithdiameter0.15m;
outlet=concretemonk(1.50mhigh)onconcretefoundation;totalconcretevolume=0.34m3 ;concretepipelineis5mlongwith0.20mdiameter;
feedercanal:50mlongwith0.1m3 cross-section.
Constructioncostestimateforthis400m2 paddypondisobtainedasfollows:
Item Unit Numberofunits Costperunit(US$) Costofitem(US$)
Siteclearing m2 400 0.25 100.00
Topsoilremoval/storage(0.20m) m3 80 2.50 200.00
Earthwork
ponddikes(80mx2.50m2) m3 200 1.60 320.00
feedercanal(50mx0.10m2) m3 5 1.60 8.00
drainagecanal(20mx0.10m2) m3 2 1.60 3.20
transporton5maverage m3-m 1000 0.0012 1.20
compaction m3 200 1.00 200.00
finishing:forming/planting m2 160 0.50 80.00
Monktowerstructure m3 0.34 103.40 35.16
Monkpipeline m 5 1.70 8.50
Inletpipe m 1 1.40 1.40

28. Constructioncostofpond 957.46
Contingencies(approx.10%) 95.75
Totalcostestimate 1053.21