Marine Sand Resources off Kerala Coast visàvis Acute Shortage of Construction Sand in the State of...

DineshACetalMineralsandresourcesofKeralacoast

MarineSandResourcesoffKeralaCoastvisvisAcuteShortageofConstructionSandintheStateofKerala

ACDinesh1,PPraveenKumar2,NMShareef2&CJayaprakash3

Marine&CoastalSurveyDivision,GeologicalSurveyofIndia1Kolkata,2Mangalore,3BhubaneshwarEmail:[email protected]

Abstract. TheavailabilityofgoodqualityoffshoresandinthestateofKeralaisincreasinglybecominga rarityandtheconstructionindustryhasbeenfacingseriouschallengesduetothepaucityofsand.Theriver sandmininghas becomeunsustainable fromtheecological point of view. Thesystematic surveys by the Marine & Coastal Survey Division of the Geological Survey of India for construction grade sand have delineated five promisingareas in the offshore waters of Kerala; viz. Ponnani sector, Chavakkadsector, Alleppeysector,KollamNorthsectorandKollamSouthsector,withanestimatedresourceof 2030million tonsofmarinesandsuitableforuseinconstructionindustry.Thisresourcecansupporttherequirementof sandinKeralaforthenext50years.Thewidespreadsocietalconcernsaboutthesuitabilityofmarinesandfor constructionarealsoaddressed.

Introduction

ThoughseveraloffshoremineraldepositshavebeenidentifiedduringthecourseofsystematicoffshoresurveysbyGeologicalSurveyofIndia(GSI),utilizationoftheseresourcesisyettobeinitiatedinIndia.Reasonsforthisaremanifoldincludingthequestionofcommercialviability; but themost important reasonprobably is that therewasnopressingneedtoutilize theseresourcesuntilrecently.Inthecaseofconstructionsand,riversanddepositswhichareeasilyrecoverableandavailableonshorearebeingminedinstateslikeKerala.Theeaseofextraction, proximitytotheresourceandunprecedentedpaceofconstructionactivityinthestateofKeralaarethemajorfactorswhichresultedinoverexploitationoflandbasedsandresourceswithfarreachingenvironmental consequences. This has forced the Government of Kerala to imposerestrictionsonriversandminingandthatinturnhasresultedinacuteshortageofconstructiongradesandinthestate.Withafuturisticview,GSIhastakenupinvestigationforconstruction gradesandintheoffshoredomainsinasystematicmanner.TheGovernmentofKeralahasalsoevinced keen interest in finding alternate sand resources such as the ones in the outercontinentalshelfofftheStateshores.EconomicfeasibilityofoffshoresandmininghasalreadybeenprovedbymanycountrieslikeJapan,NewZealand,Netherlands,SriLankaetc.Dolageetal(2013).

Availabilityofconstructiongradesandintheterritorialwaters(TW)andbeyondoftheKeralaCoast

OccurrenceofrelictsandwithinandbeyondtheTW(TW:22.2km/12nauticalmilesfromtheshoreline)offtheWestCoastwasidentifiedbyGSIduringthecourseofroutineseabedmappingsurveys. These sand formations represent, in most cases, palaeostrandlines or buried riverchannels/estuaries formed during the past marine transgressionregression cycles, of lateQuaternary period. Preliminary investigation of sand resources by systematic widespacedsampling(5x5,5x4and4x4kmgrids)usinggrabsamplerandvibrocoreronboardRVSamudra Shaudikama at selected locations carried out by the Marine and Coastal SurveyDivision(M&CSD)ofGSIduringthelastfewyearshashelpedforfurtherdelineationofthesand

ShajiE&PradeepkumarAP(Eds)2014MineralResourcesofKeralaTrivandrum:DeptofGeologyUnivofKeralaISBN978819234490493


bodies.Thetargetareasfordetailedexplorationweredemarcatedbymoderatelyclosespacedvibrocoringon1x1and2x2kmgrids(Fig.1).

Fig.1StatusofsandinvestigationoffKeralaCoast

Based on the results, a fewpromising areas have been identified for detailed exploration.Resource estimation of sand is made for five sector viz., Ponnani sector (SD214&SD239cruises), Chavakkad Sector (SD214 & SD224 Cruises), Alleppey Sector (SD233 Cruise),KollamNorthsector(SD187&SD196Cruises)andKollamSouthsector(SD222Cruise).

ThispaperisaimedatprovidingconciseinformationontheexplorationforsandsofarcarriedoutinfivepromisingsectorsofftheKeralacoast.Thedatawillbeperiodicallyupdatedasandwhennewinformationcomesupwithfurtherdetailedexplorations,sothatthelatestdatawill bereadily available to all the concerned authorities as well as the stakeholders.Further, thesocietal concerns about usability of marine sandfor constructionpurposes andminingofoffshoresandresourcesisalsodealtinthepaper.

Sampling. Insandyareas,twotypesofsamplersarecommonlyused:thegrabandthevibrocorer.Thesamplescollectedusinggrabsamplergiveanideaaboutthesurfacedistributionofsandysedimentsbasedonwhichlocationsforvibrocoringaredecided.Vibrocoring(Fig.2)isthemostsuitablemethodemployedtoretrievecoresamplesfromsandyformations.BoththecoastalvesselsofGSIRVSamudraKaustubhandRVSamudraShaudikamahavethiscoring



facility,whereinelectricallyinducedvibrationbythevibratorymotor,(Fig.3)causesthebarrelwiththePVClinertoslowlypenetrateintosandysediments.Afterthevibrocorerunitishauledup,thePVClinercontainingthesampleisremovedandtheopenendsaresealedafterrecordingthenatureofthebottomandtopsediments.

Fig.2:Vibrocorerbeingloweredfrom Fig.3:electricalmotorof VibrocorertheaftdeckofRVSamudra

Shaudhikama

Thecoresamples are later split; (Fig.4) loggedandsubsampledat 50cmor 1mintervals dependingonthenatureofthesampleandobjectiveoftheproject.Thesubsamplesaresundriedandrepresentativesedimentsamplesweighingabout80100gmarecollectedbyconingandquarteringmethod.Thissampleisweighedandthenwashedafewtimestoremovesaltandmud(silt+clay).Thesampleisdriedandweighedagaintogettheweightofmud.Thesample, freeofmudandsalt,issubjectedtosievingat1phiinterval(using5,10,18,35,60,120and230ASTMsieves)(Table1).Theweightsofsamplesheldindifferentfractionsaredetermined.ThesievedfractionsarethentreatedwithdiluteHCltoremoveshellsandweighedagaintogettheweightofcarbonatefreefractions.Thepercentagesofgranule,carbonatesand,mudandcarbonatefreesandfractionsarethusdetermined.Drybulkdensityiscalculatedfollowingthenormalprocedure

Fig.4:Asplitcore(PVCliner)containingsandysediments

Asperthedefinitionoffineaggregate;itistheinertorchemicallyinactivematerial,mostofwhichpassesthrougha4.75mmISsieveandretainsat0.075mmsieveandcontainsnotmorethan5percentcoarsermaterial.AsperthebureauofIndianstandards(BIS)ofBritishStandard(BS),thecarbonatefraction(shells)lessthan5mmdoesnotaffect thestabilityofconcrete.Hence,thetermSANDisusedheretoincludeallfractions(carbonateandcarbonatefree)lessthanorequalto4mm(5ASTMsieve)andmorethan0.0625mm(230ASTMsieve).



Table1:SizesandterminologyoffractionsofSand

ASTM(meshsize)

Phi( ) mmTerminology(Udden,1914&Wentworth,1922)

510 2to1 42 Granule1018 1to0 21 Verycoarsesand1835 0to1 10.5 Coarsesand3560 1to2 0.50.25 Mediumsand60120 2to3 0.250.125 Finesand120230 3to4 0.1250.063 Veryfinesand

SandResources. Sandresourcesinthebelowmentionedfivesectorswereestimatedfortheavailable core length bycreating sand tonnageraster using sediment thickness raster, sandpercentraster,drybulkdensityandpixelareainArcGIS.TheresourcesestimatedforthefivesectorsaregiveninTable2inweightaswellasinvolume(Table1.2).Thesamplingintervalfor Ponnani,Chavakkad,AlleppeyandKollamSouthSectorsare2Kmx2KmwhereasforKollamNorthSector it is 1Kmx1Km.Theresourcesestimationcanbefurther refinedbydetailedexplorationbysamplingin250mx250mor500mx500mgrids.

Fig.5:Pointshapefileforsamplepoints

SandResourceestimation. Forsandresourceestimation, PointshapefileswerepreparedinArcGIS9.3.andprojectedtoUTM(Fig.5).Asedimentthicknessrastersurfaceiscreatedusingthecorelengthandshowninfig.6.Interpolationrasterswerecreatedforsedimentthickness,sandpercentageandsandtonnagefollowingIDW(InverseDistanceWeighted)method.Sandpercentageraster(Fig.7)wascreatedusingthesandpercentagewhichincludesallcarbonateandnoncarbonatefractionshavingthesizebetween4mmand0.0625mm.Rastersurfaceforsandtonnage(Fig.8)iscreatedusingtheformula:thicknessraster*sandpercentageraster/100*bulkdensity*cellsize.ThemapAlgebrawindowwiththeformulaforcreatingsandtonnagerasterisgiveninFig.8.Foruniformityandconsideringthesamplinginterval,acellsizeof50mx50mwasselectedforallthefivesectors.Hencetheareaofeachcellis2500sq.m.



Fig.6:Sedimentthicknessraster Fig.7:Sandpercentageraster

Fig.8:MapAlgebraexpressiontocreatesandtonnageraster Fig.9:SandtonnagerasterPonnaniSector.Sandtonnagevariesinaverywiderangefrom0to15600duetothepresenceofmuddominatedsedimentsalongtheperipheryofthesector.Thesandtonnageisobservedmaximumatthecentreofthesector(Fig.10).Astudyofthespatialdistributionofdifferenttypesofsediments inthesurfaceandbeyondandthedatainterpolatedaswell suggests thatthePonnani Sector could be a part of a palaeoestuary into which the palaeochannel ofBharathapuzhaRiverdebouchedandoccupiedthecentral part of thesector.ThetotalsandresourceestimatedinPonnaniSectoris597milliontons.

ChavakkadSector. Thesandpercentageismaximumintheeasternandwesternpartofthesector(Fig.11).Sandtonnagevariesinaverywiderangefrom0.1to12450duetothepresenceofmuddominatedsedimentsatthetopandbottomofthesector.Thespatialdistributionofthedifferent typesofsedimentsinthesurfaceandsubsurface,aswell astheinterpolateddatasuggeststhattheChavakkadSectorcouldbeapartofapalaeoestuaryintowhichthepalaeochannelofChetwaiRiverdebouchedandoccupiedthecentralpartoftheestuary.ThetotalsandresourceestimatedinChavakkadSectoris202milliontons.



Fig.10.EstimatedsandresourceinPonnaniSectorFig.11.EstimatedsandresourceinChavakkadSector

Fig.12.EstimatedsandresourceinAlleppeySector



AlleppeySector.Sandpercentageismorethan82%inmostoftheareaexceptafewpatches.Sandtonnagevariesinawiderangefrom557to12670(Fig.12).Maximumtonnageisobservedwherethesedimentthicknessismore.Thespatialdistributionofthesedimentsinthesurfaceandsubsurfaceinconjunctionwiththeinterpolateddata,theorientationanddispositionofthesand body suggests that Alleppey Sector could be a part of a palaeostrand body whichsubmerged under sea during the Holocene transgression. The sand resource estimated inAlleppeySectoris742milliontons.KollamNorthSector. Sandtonnagevaries inawiderangefrom1097to12886.Maximumtonnageisobservedwherethesedimentthicknessismore(Fig.13).Thespatialdistributionof thesediments in thesurfaceandsubsurface inconjunctionwiththe interpolateddata, theorientationanddispositionofthesandbodysuggeststhatKollamNorthSectorcouldbeapartofapalaeostrandbodylikeAlleppeySectorwhichsubmergedunderseaduringtheHolocenetransgression.ThesandresourceestimatedinKollamNorthSectoris343milliontons.

Fig.13.EstimatedsandresourceinKollamNorthSectorFig.14.EstimatedsandresourceinKollamSouthSector

KollamSouthSector.Sandpercentageismorethan92%inthecentralpartofthesector.Sandtonnagewasinterpolatedusingtheformulagiveninthe initialchapterandwasreclassified(Fig.14).Sandtonnagevariesinawiderangefrom550to5600.Maximumtonnageisobservedinthecentralpartofthesector.Thespatialdistributionofthesedimentsinthesurfaceandsubsurfaceinconjunctionwiththeinterpolateddata,theorientationanddispositionofthesandbodysuggeststhatKollamSouthSectorcouldbeapartofapalaeostrandbodylikethatof KollamNorthSectorwhichsubmergedunderseaduringtheHolocenetransgression.ThesandresourceestimatedinKollamNorthSectoris146milliontons.



Table2:SandResourcesEstimatedforFiveSectors

P.V.Sukumaranetal(2010)hasgivenapreliminaryassessmentofsandresourcesintheKeralaoffshore,viz.probablesandreservesof184milliontonnesoveranareaof180sqkmtoadepthof1.5mdownfromtheseafloorandlocated2540kmawayfromthecoastoffKollamand267milliontonnesoveranareaof500sqkmoffKannur1336milliontonnesoveranareaof543sqkmoffChavakkad.

SocioeconomicSignificanceofMarineSand.Sandandconstructionaggregates,whichincludecrushedrock,areclassifiedasminormineralandaresubjectedtoverylittle,miningregulationsbytheregulatoryauthoritiescomparedtootherminerals.Butthesandandaggregatesconstitutethelargestcommodityinminingindustryintheworldbyvolumeaswellasbyvalueamongthenonfuelminerals.So,forallpracticalpurposes,sandisthemajormineralamongthenonfuelmineralsintheworld.Inrecenttimes,constructionindustryhasbeenfacingseriouschallengesduetothepaucityofsand.Theunprecedentedboominconstructionindustryhasmaderiver sandminingunsustainable fromtheecological point of view. Unregulatedsandmininghasadverselyaffectedtheriversnotonlyfromanenvironmentalperspective,butaestheticallytoo.RivershavebeenthecradleofcivilisationssincetimeimmemorialandIndiahasaculturalandemotionalbondingwithmostofitsrivers. Theenvironmentalimpactcausedbytheunregulatedriversandmining,scarcityofsandandtheresultantpriceescalationetc.,areadverselyaffectingthesensitivesocioeconomicandenvironmental fabric and is increasingly felt bymanystates in India, especially Kerala. Theerosion of river banks leads to loss of valuable agricultural and commercial land, weakensstructureslikebridges,roads,buildingsetc.,posesseriouschallengetohumanlifeaswellastheeconomy.Groundwaterlevelsgetdrasticallyloweredandwaterqualitygetsaffectedduetosalt waterintrusionparticularlyincoastalareas.Italsoadverselyimpactstheriparianhabitat.Anoffshootofthehighdemandandconsequenthighcostofsandhasalreadybeenrecognisedasanissueleadingtoalawandorderprobleminmanypartsofthecountry. Many countries like England, France, Germany, Netherlands, and Switzerland havealreadybannedriversandminingandmanyothernationsoftheworldareimposingsevereregulations.InIndiatoo,theMinistryofEnvironment&ForestandNationalGreenTribunalhaveinitiatedplacingsevererestrictionsonsandmining.Recently,Msand,ormanufacturedsand produced by crushing of rocks has entered the market and is being considered as areplacementfornaturalsand.However,all thecrushedrockmaterialcannotbeusedintheconstructionindustry.Besides,largescalerockminingalsowillhaveaseriousimpactontheenvironmentapartfromtheairpollutionitcancreate.Fromanengineeringperspectivealso,theMsandisnotasensustrictoalternativetonaturalsandastheflakydustinthemcouldaffectthesuitabilityofmortarandthepresenceofchemicallyactivemineralscouldaffectthestrengthofconcrete. Hence, only those particles that meet the specifications will qualify as a fairreplacement for natural sand. But what is available in the market today, hardly meets thespecified standards. Natural sand is predominantly composed of quartz, which is inert orchemicallyinactiveandsoisamoststablemineral,whereasMsandcomprisesdifferentfelsicandmaficmineralsinvaryingproportionsandmanyarechemicallyactivetoo.Theirefficacyor


Sector EstimatedSandResources(inmilliontons) (inmillioncubicmeter)

Ponnani 597 346Chavakad 202 150Alleppey 742 431KollamNorth 343 250KollamSouth 146 116Total 2030 1293


otherwiseonstructuresinthelongrunisyettobeproven.Addedtothisistheveryhighcostof Msand which has multiplied the construction cost. This has its own ramifications ininfrastructureindustryandeconomyofthestateofKerala.ItisundersuchascenariothattheMarineSandDeposits withintheTerritorial Waters(TW)andtheExclusiveEconomicZone(EEZ) off Kerala coast needs to be considered for its availability and suitability in theconstructionindustry.Thereisawidespreadapprehensioninthesocietyabouttheusefulnessofmarinesandforconstructionpurposes.Anattempthasbeenmadeheretoallayallsuchfearswithscientificexplanation.

ConcernNo.1:EffectofsaltcontentinMarinesandanditssuitabilityforuseinconcrete.Chloridecontentinthetotalcementmixdeterminestheextentofcorrosioninconcrete.AspertheBritishStandard(BS882:1992),thechlorideioncontentpermissibleforreinforcedconcreteis0.05weight%,prestressedconcreteis0.01weight%(Table3).AconservativeestimateofthechloridecontentpermissibleinOrdinaryPortlandCement(OPC)foruseinconcreteis0.075weight%.

Table3.BritishStandardonChlorideionContent(wt%).

Permissiblechlorideinconcreteis0.3percentbyweightofcement.Cementtoohaschlorideupto0.05percent.So,offshoresandcanaffordtohavechlorideupto0.25percentwithoutanydeleteriousinfluence.EachcubicmetreofGrade25concretemixturecontains339kgofcementand837kgofsand. Hence, sandcanaffordtohavechlorideupto0.101percent(0.25x 339/837).ThechlorideinfreshoffshoresanddredgedfromcertainpartsofSriLankanoffshoreis0.04percentwhichisfarbelowtheacceptablelevelof0.101percent.Evenarainfallaslowas9.9mmcanreducethechloridecontent(rangefrom0.01to0.05)tolevelsfarbelowtheadmissiblelimit(0.101)whenexposedtorains.Rainfallsashighas581mmcouldwashawaychlorides almost completely(Dolageet al., 2013). Inastate likeKeralawhere theaverageannualrainfall ismorethan3000mm,dredgedmarinesandcanbestockpiledasshowninFig.15andwashthechloridesawaybyexposingtorain.


BRITISH STANDARD Chloride ion Content

(expressed as Mass % Aggregate)Pre stressed concrete / Heat cured ConcreteContaining embedded metal : 0.01

Concrete Containing embedded metal made with cement complying BS 4027 :0.03

Concrete Containing embedded metal made with cement complying BS 12BS 146, BS1370, BS 4246, BS6588, BS6610:0.05(Reinforced concrete)

Other Concrete : No Limit


Diasetal.,(2008)carriedoutacomprehensivestudybyusingoffshoresandsamplesobtainedfromastockpile,dredgedintheyear2002,justnorthofColombo,SriLanka,andconcludedthatoffshore sand is suitable for reinforced concreting work. Studies of Limeira and Etxeberria(2010)andLimeiraetal.,(2011)alsoshowthatdredgedmarinesedimentcanbesuccessfullyusedasafineaggregateforconcreteproduction.

Fig.15.EstuarineSandpileatPonnani(Kerala)harbournearBharathapuzharivermouth

ConcernNo.2:presenceofshellsfragmentsinmarinesandThe presence of shells and shell fragments is viewed by many as a deleterious factor inconstructionsand.Offshoresandmaycontainalargeamountofshellsandshellfragments.Butshellhasnoadverseeffectonstrengthbuttheworkabilityisreducediftheconcreteismadewithaggregatehavinglargeshellcontent,ChapmenandRoeder(1969). Withrespecttotheeffectofshellandotherimpurities,Limeiraeta.l(2011) statesthatthepresenceofsmall,normallyacceptablepercentagesofcoal,chalkorclayisunlikelytoaffectworkability.AspertheBritish Standard(BSEN1971:2011) specification for aggregates fromnatural resources inconcrete,publishedinSept.2011,sandasaggregateforuseinconcreteisthatforallwhosesizeiscoarserthan10mm,theshellcontentallowedismaximumof8%,forallaggregatesfinerthan10mmandcoarserthan5mm,theshellcontentpermissibleis20%andforaggregatesfinerthan5mm,thepresenceof shell fragments is immaterial (Table4). Theaverageshell content inKeralaoffshoresandis 510percent. As perBureauof Indianstandards(IS:2386(Part II)1963), the amount of deleterious substance in the form of soft/shell fragments in fineaggregates, is immaterial. This implies that thepresenceof shell fragments matters only inaggregatescoarserthan5mm,andforsandoffinersizewhichismainlyusedinconstructionindustry,theshellisconsideredaspartofthemineralgrainsinceitdoesnotaffectthestrengthordurabilityofthestructure. Themajortakeawayisthat,thelimitsonshell contentisnotapplicable to fine aggregate below 4.5mm i.e. for grains classified as SAND as per thespecificationgivenbyeitherBISorBS.



Table4.BritishStandardonLimitsonShellContent(wt%)

ConcernNo.3:StrengthofconcretemadeofmarinesandDolageetal.,(2013)presentedtheconcretemixdesignresults,togetherwithstrengthresults,forconcretesmadewithoffshoresandforgrade25concrete,thatbeingthemostwidelyusedstructuralconcrete.Thefreshoffshoresand,withoutbeingwashedandcleaned,wasusedfortheconcretemixdesignspecifiedinthepaper.Intheirstudy,freshlydredgedoffshoresandbroughttothesitewasusedwithaviewtocheckthestrengthofconcrete.Fromtheresultsobtainedforgrade25concreteitcanbeseenthatthestrengthofconcreteiswithinthespecifiedlimits.SimilarstudyonoffshoresandstockpiledatMuthurajawela(SriLanka)showsthatthecompressivestrengthiswithintherequiredlevel(Diasetal.,2008).

ConcernNo.4:EnvironmentalissuesofOffshoreSandMiningThemajorconcernsregardingtheeffectsofmarinesandminingonenvironmentare:

1. CoastalerosionandSlopeerosion2. Effectonmarinefloraandfauna

CoastalerosionandSlopestability.Thedistributionofmarinesand,identifiedintheoffshoreofKerala,iswidelyvaryingandisinfluencedbymanyfactors.TheminimumwaterdepthanddistancefromtheshoreineachsectorisgivenintheTable5.

Table5.MinimumwaterdepthanddistancefromshoreSector WaterDepth(m) Distance(Km)Ponnani 20 10Chavakad 25 13Alleppey 20 11KollamNorth 50 29KollamSouth 40 12

Sandminingisproposedtobecarriedoutbeyond20mwaterdepth.Sincethesedepthsaremuchbeyondthedepthofclosure,thereislittlechanceofminingaffectingthelittoralzoneor



theshoreline. Moreover, theseabedslopebeyondtheterritorial wateris negligiblylowlikeabout20mper10000m,i.e.theslopeangleis0.1.Therefore,thechanceofslopefailureduetominingattheminingsitesoratthedistantslopedoesnotexist.Sincetheproposedsandminingisbeyond20mwaterdepth,whichis,onanaverage,atleast10kmawayfromthepresentdayshoreline,anyminingactivityatsuchafaroffdistancefromtheshorewillhaveextremelylessimpactontheshorelinetotriggererosion.ThestudybyHobbs(2007)hasprovedthat changes in wave transformation resulting from modifying the bottom topography arerelativelysmalland,asthesandminingsitestendtobeinwatersgreaterthan10mdeepthe impactwillbeminimal.

Effect onmarine floraand fauna. Another apprehension amongthepublic, especially thefishermencommunity,relatestotheimpactofsandminingonthemarinefaunaincludingthefishes. They fear that marine sandmining candisrupt habitat anddisturb fishes andothermarineanimals.Themarineanimalslikelytoliveonsandybottomaredemersalfishes,starfish, seaurchin,crabs,shrimps,gastropods,squillaetc.StudiesbyCMFRI(CentralMarineFisheriesResearchInstitute)incollaborationwithM&CSD,MangaloreduringtheSD229cruiseshowthatthesandysedimentscollectedoffAlleppeyareoflowtomediumfertilityandwaterisofnormal quality. Further, copepod is dominant among zooplanktons. Field study testing the draftmonitoringprotocolwasconductedintheactive,sandminingregionofSandbridgeShoal,offVirginiaBeach,Virginia,USAbyHobbs(2007).Resultsindicatethatrepopulationofdredgedareas is enhancedby leavingpatchesof undisturbedbottomwithinthedredgedregion. Nonegativeimpactsonmacrobenthosordemersalfisheswerenoted. Whileallayingthefearsofgeneralpublicaswellaspolicymakersregardingthelikelyimpactofoffshoresandminingonthe marine habitat, it will be prudent to understand the impact monsoonwaves anddailytrawlingcreateontheseabottombychurningmudintosuspension.However,theadverseeffectofsandminingifany,onmarinefloraandfaunahastobestudiedindetail.

Conclusion

TheestimatedmarinesandresourcewithinthefivesectorsoffKeralacoastisabout2030milliontonnes.Thiswillbesufficienttomeetthesandrequirementofconstructionindustryinthestateforabout50years@40milliontonnesperyear.CentralWaterResourceDevelopmentandManagement(CWRDM)(1999)hasestimatedthat32milliontonnesperyearistheaverageconsumptionofsandinthefieldofconstruction.Studieshaveprovedbeyonddoubtthatmarinesandissuitableforconstructionpurposes.Theimpactofmarinesandminingontheseafloorcanbe controlled if it is exploited scientifically. A proper monitoring mechanism and strictcomplianceofmininglawswillenableustoutilizethishugenaturalresourceforthebenefitofsocietywithoutdegradingtheenvironment.Aresponsibleapproachwillensurethatresourcesareutilizedscientificallyandsustainably.

Acknowledgements

TheauthorswishtoexpresstheirsincerethankstoDr.S.K.Wadhawan,DirectorGeneral,GSIforpermittingtopublishthispaperaswellasforhisconstantencouragementforpublication.OursincethankstoDr.S.Kannan,DeputyDirectorGeneral,marineandCoastalSurveyDivision,GSIforscrutinyofthepaper, valuablecommentsandhelpprovided. TheauthorsexpresstheiroverwhelminggratitudetotheparticipantsofmarinescientificcruisesSD214,SD239,SD214,SD224,SD233Cruise,SD196andSD222whohavepainstakinglycollectedthesamplesandcarriedoutthelaboratoryanalysis.



References

BSEN1971:2011.Cement.Composition,specificationsandconformitycriteriaforcommoncements.BS882:1992.Specificationforaggregatefromnaturalsourcesforconcrete,BritishStandardsInstitute,London;1997ChapmenGP.RoederAR,Theeffectofseashellsinconcreteaggregates,ConcreteTransactions.July1969;25163CWRDM.,1999.SandMininginKeralawithspecialreferencetoPeriyar,CentreforWaterResourceDevelopmentand

Management,Kozhikode,61p.Dias M.G.S, Seneviratne GAPSN, Nanayakkara SMA., 2008. Offshore sand for reinforced concrete, Journal of

ConstructionandBuildingMaterials.22:13771384.Dolage.D.A.R., Dias M. G. S. 2 and Ariyawansa.C.T., 2013. Offshore Sand as a Fine Aggregate for Concrete

Production.BritishJournalofAppliedScience&Technology3(4):813825.Hobbs, C.H. ,2007. Considerations in Marine Sand Mining and Beach Nourishment OCEANS 2007 ,

10.1109/OCEANS.2007.4449120,Page(s):110LimeiraJ&EtxeberriaM.,2010.Dredgedmarinesandinconcrete:Anexperimentalsectionofnaharbourpavement.

JournalofConstructionandBuildingMaterials,24:863870.LimeiraJ,Etxeberria M,AgulloL, MolinaD., 2011.Mechanicalanddurability properties ofconcretemadewith

dredgedmarinesand.JournalofConstructionandBuildingMaterials,25:41654174.SukumaranP.V.Unnikrishnan,E.,Gangadharan,A.V.,Zaheer,B.,Abdulla,N.M.,Kumaran,K.,Ramachandran,K.V.,

Hegde,S.V.,Maran,N.,Bhat,K.K.,Rao,M.K.,Dinesh,A.C.,Jayaprakash,C.,PraveenKumar,P.,Shareef,N.M.,Gopalan,C.,2010,MarinesandresourcesinthesouthwestcontinentalshelfofIndia., indianJournalofMarineSciences,vol:39No.4.,PP:572578.

Udden,J.A.,1914."Mechanicalcompositionofclasticsediments",Bull.Geol.Soc.Am.25,655744.Wentworth,C.K.,1922."Ascaleofgradeandclasstermsforclasticsediments",J.GeologyV.30,377392.


Date post:	19-Oct-2015
Category:	Documents
Upload:	salec-knowle
View:	67 times
Download:	2 times

Marine Sand Resources off Kerala Coast visàvis Acute Shortage of Construction Sand in the State of...

Documents