ioJa Ministry of Environment and Energy Water Wells And Groundwater Supplies Recommended Methods For Plugging Abandoned Water Wells INTRODUCTION Unplugged,abandoned water wellsniayconstitute Themainreasons for plugginga well areto: a hazard topublichealthand safety. Theplugging ofthese wellswill eliminate the hazard and pre- eUminatethephysical hazard; serveand protectourgroundwaterresources. Abandoned dugand bored wellsthatmayhavede- preventgroundwatercontamination; teriorated graduallyover theyearsareofparticular concern becauseof theirlargediameter. conservetheyield and maintain waterlevelsin OntarioRegulation903places legal responsibil- theaquifers*; ity for thepluggingofabandoned wellsontothe well owner. Section 21 states: "Whena well is tobe preventinterminglingbetweendesirableand un- abandoned, itshall beplugged withconcreteor desirablequality waters toensure thatoriginal othersuitablematerial soastopreclude thevertical subsurfaceconditionsare restored. movementofwaterorgasin thewell betweenaqui- fersorbetween anaquiferand theground surface." Toensure that theplugging iseffective, theuse Theconditionsunder whicha well ownermust erfsuitablematerialsisrequired. The placementof abandon and pluga wellare: thesematerialsmustbeappropriate to the local well and groundconditions. The purposeof thisarticle a new well which isdry; istoprovideguidancein theselectionand place- mentofpluggingmaterialsrelativeto varioustypes a well whichisnotbeingusedormaintained for ofwellsindifferentgeologicalandhydrologicalcon- futureuse; ditions. a well whichisproducingsalty,sulphurousor mineralized waterorwater thatis undrinkable. * Anaquiferisa water-bearing, saturated geo- TheregulationsalsoauthorizetheMinistryof logicalunitorformation thatwillyield waterto Environmentand Energy toordera well tobe wells. Aquifersmayoccur in theoverburdenorin plugged ifitencountersnaturalgas,orifitwascon- thebedrock. A looselypackedgravel isa good aq- structed incontraventionofanyoftheprovisionsof uifer,a siltora veryfinesand isapooraquiferand theregulationsincludingimproperspacingfrom fractured rock maybea good orapooraquifer. sourcesofpollution. ® Ontario PIBS603B Whetheryou plugyourown wellorwhether * Bentoniteisa commerciallyavailablecolloidal you hirea licensed well contractor, you should be clay in powderor granular form. Itcanbe used aware that thepluggingof some wells will bediffi- in thickeningdrillingmuds, asanadditive toce- cult because of thedepthof the well, the hydorstatic ment slurriesand asa sealantbecauseofitsspe- head conditions (e.g. flowingwell)or thecomplex cialgel-formingand swellingpropertieswhen nature of the geological fgoramtions. In these mixed with water. circumstatnccsitmaybeadvisable tohirea well contractor whowould have the properequipment The mostsuitable fill material toplaceopposite and thenecessary knowledgeofconstruction a water-bearing formation (see Figure 1) isa clean, thecniquesand local geologicalconditions. Theim- disinfected sand orgravel. A bored well will most properuseofa placementtechniquescould result likelyhavegravel in the wellbore, placed thereby in fialure toachieve thepluggingobjectives. the well contractorduring well construction. These Your regional groundwaterevaluatoror water materils should extendinto thecased portionofthe well inspector may alsobecontacted foradviceand well and becapped with a clay slurry,bentoniteor informationon well constructionand local ground concreteplug. The remainder ofthecased well n\ay conditions. (Addressesofregional offices arelisted beentirelyfilled to thesurface withcement, con- at thebackof thisfactsheet.) They maybeable crete,bentonite,clay,or with alternatingplugsof able to provideyou with a copyofthewater well sand and gravel and cementorclay. Removal of the record for the well you plan to seal. Thisrecord upperportionofthe well casingandbackfillingis will provide a descriptionof theconstructionde- good practiceand isrecommended (Figure 1). A tailsofthewell and will beofassistance toyou or cappingdevice maybe attached to the topofthe to the well contractoryou selectindeterminng the casing asanadded protection. These procedures best method to seal your well. Records for most will prevent the vertical movementofwaters within wellsdrilled since 1949areon file in the regional of- thecased portionof the well. ficesofthe ministry. Ifthe well'sformation seal isnotadequate,com- pletelyremove the well casing. Thiswillensurethe outward progressionofthepluggingmaterialsinto SEALING WELLS IN UNCONSOLIDATED theadjacent formations, thereby providinga better FORMATION seal and effectively preventing the vertical move- A well completed in a sand orgravel aquiferin the mentof water. Itisnotalwayspossible to remove thecasing,and theonly practical solutionin this overburdenand havinga satisfactory formation caseis toexcavatearound thecasing and cutoffthe seal on theoutsideof thecasingcanbeadequately casinga safedistance below ground surfaceor, in sealed bybackfilling thecased portionofthe well thecaseofa bored well, removesufficient tiles. witha sequenceofplugsconsistingofcement Next, placea clay slurry,bentoniteorconcreteplug grout, concrete,bentonite,clayand sand and gravel atthebaseoftheexcavation, sealing the topofthe asshownin Figure 1. cased portionofthe well and anyopeningoutside If there areotherproducing wellslocated thewellcasing. Backfill theremainderoftheexca- nearby in the same water-bearing formation,care vation with overburden materials toground level, mustbetaken in the selection and placementof but onlydo thisafter thelowerportionof the well sealingmaterialsso thattheywill not move laterally hasbeenadequatelysealed. Clayisespecially suit- outward through theaquiferand affect the water able for sealingthe upperportion oflarge-diameter qualityof these wells (i.e. cause themtoproduce wells. cloudy water). Theuseofcementorconcrete in the aquifierisdiscouraged for this reason. NOTE: In thispublication: SEALING WELLS IN ROCK FORMATION Wellsthatpenetratelimestoneorotherfractured * Cement is amixtureofportland cementand wa- rock formationsshould be filled withconcreteorce- ter. ment toensure the permanenceofthe seal. Theuse ofclayor sand in the uncaged portionofsuch wells * Concreteisa mixtureofwater, portland cement isnotadvised because fine-grained fill material may and sand orgravel. bedisplaced by theflowofgroundwater through crevicesor fractures. Alternateplugsofcoarsesand andgravel andcon- drillingofanother well maybenecessary torelieve crete maybe used indecj.) wellsor in wellswhere the pressurein the aquiferand to reduce the water the vertical movementof waterbetween fractures tobelow ground level, therebyallowingplugging to within the wellbore will notaffectthequalityor proceed normally. Control over the flow from a quantityofwaterinnearby producing wells. Itmay "well may sometimesbegained through the useof be necessary toseta clayora finesand seal ahead plugs, well packers, heavydrilling mud orbyex- oftheconcrete, asin thecaseofwells in tending the well casingaboveground level and unconsoHdated formations, toincreasetheeffective- abovetheartesianhead in the well. Pumpinga high nessofthe seal material. Wheneverpossible,avoid densitycement slurry through a groutpipe placed placingcementorconcreteoppositea water-pro- near thebottomofthecasing maybalance thearte- ducinghorizon. sianhead so thatcontrol ofthe well canberegained. Fill theupperthree tosixmetresofboreholein Control oftheflowcanonlybemaintained where the rock,justbelow thebottomofthe well casing, thereisaneffective formationsealbetween the well with cementorconcrete toprovideaneffectiveplug casingand the wellbore, otherwisea "breakout" or orseal against thepossible vertical movementof theleakageofgroundwateraround theoutsideof surface watersinto thebedrock. Cement,concrete, thecasingmayoccur, with seriousconsequences. bentonite,clay,orsand and gravel withoccasional Itisimportant torememberin thecontrol of cementorclay plugsmaybeused tofill thecased flowing wells toprevent: portionofthewell. groundwatermovementbetween formations, SEALING WELLS WHICH OBTAIN WATER FROM since thiscould resultin thepressuris^ation of shallowerwater-bearingzones; MORE THAN ONE AQUIFER IN THE BEDROCK Special measures need tobe taken in tftesealingof surface flow ofwaterfrom the well casingor wellsencountering more thanoneaquifer. These fromaround theoutsideofthe well casing. wellsshould besealed to preventthemovementof groundwaterbetweenaquifers (seeFigure2). WELL ABANDONMENT RECORDS If thereare no water-bearingzones withinanex- tensiveportionofthe wellbore, fillingitwithce- Before thepluggingequipment isremoved fromthe ment, concreteoralternate layersofthesenwterials site, theexactlocation oftheabandoned well orhole and coarsesand and gravel issatisfactory. Concrete shouldbeaccuratelyestablished using fixed refer- and cementare preferablebecause they will pen- encepoints,suchasa building, so that the property etrateand fill the voidsand fracturesin the wallof ownerwillhaveapermanentrecord ofthe location. theborehole,and provide themosteffectiveseal The materialsused toplugthewell and thedetails againstmoving water. Ifalternatingcementorcon- ofthepluggingprocedureshould alsoberecorded. creteplugsand sand and gravelareneeded tocon- This record will providea good referenceshould trol thegroundwatermovement, theconcreteplugs problemsoccurin thefuture. A WaterWell Record mustbeplaced in knownnon-producing,competent detailing theproceduresofthe wellabandonment horizons. If thelocationofthe non-producinghori- (pluggingmaterialsused,depthofpluggingmateri- zons isnotknown,placethe plugsat sufficiently als,casing removal,etc.)isrequired tobesubmitted frequentintervals toensureaneffectiveseal. to: MinistryofEnvironmentand Energy Environmental Monitoringand Reporting PLUGGING WELLS WITH ARTESIAN FLOW Branch The sealingofflowingwellsorwellsthathavea WestWing, 125 ResourcesRoad movementof waterbetweenaquifers requiresspe- Etobicoke,C>ntario cial techniquesand anexp>erienced well contractor M9P3V6 because therateofflow and pressureheadsof (416)314-4156 groundwatermaymakenormal sealingtechniques impractical. In thecaseofan uncontrolled flow,the EnvironmentOntarioregional office staff will WestCentral Region be pleased toansweranyquestionson well plug- 119 KingSt. W., 12th Floor gingand canbecontacted at thelocations listed be- Hamilton,Ontario L8N3Z9 low: (416)521-7702 Northern Region .435JamesSt. S., 3rd Floor Central Region Thunder Bay,Ontario 7Overlea Blvd.,4th Floor P7C5G6 Toronto, Ontario (807)475-1205 M4H 1A8 (416)424-3000 Mid-OntarioRegion 199 Larch St., 11th Floor SoutheasternRegion Sudbury,Ontario 133 Dalton Ave. P3E5P9 Kingston,Ontario (705)675-4501 K7L4X6 (613)549-4000 SouthwesternRegion 985 AdelaideSt.S. London,Ontario N6E 1V3 (519)661-2200 Sand andCra\«i Aquifer . VMell Screen a) PLUGGED DUG OR BORED b) PLUGGEDWELLWITH WELL SCREEN FIGURE SEAUNG OVERBURDEN WELLS 1. Wfell Bore W^ter-Bearing __, Fracture T Non VV^ter-Bearing Zone Limestone ConcreteCement f-tÂ^j-j ^:::::?Clean sandorgra\«i FIGURE 2. SEALING OPEN HOLE IN BEDROCK — 'vi-t-r 2 Tubagedu puitscoupé c tubagesoudée (facultative) Aquifèredesable etdegravier Crépinedupuits a) FERMETUREDTJN PUITSORDINAIREOU FORE b) FERMETURE DTJN PUITSÀCRÉPINE ÀLATARIÈRE FIGURE OBTURATION DE PUITS DANS LA COUVERTURE 1. Foragedu puits Bouchondebéton Fissureaquifère Calcaire Bétonouciment '•"•'•'•''ASableou gravierpropre FIGURE 2. OBTURATION DE LA PARTIE NON TUBÉE DTJN PUFTS DANS LA ROCHE-MÈRE Ministère de l'Environnement et de l'Énergie Les puits et les réserves d'eau souterraine Méthodes recommandées pour Tobturation des abandonnés puits INTRODUCTION Voici lesquatreprincipalesraisonspourobturer un puits : Lespuitsabandonnésnonobturéspeuvent constituer undangerpourla santéetla sécurité publiques. Leurobturation permetd'éliminerce éliminerundangerphysique; risqueetcentrisueà protégerleseaux souterraines. empêcherlacontaminationdeseaux Lespuitsordinaireset lespuits forésà la tarière, souterraines; qui peuvent s'êtredétérioréau fil desans,causent leplusd'inquiétudeen raisondeleurgrand préserverlerendementdespuitsvoisinset diamètre. maintenirleniveau d'eaudanslesaquifères"*; Aux termesdu Règlement 903de l'Ontario, la responsabilitélégaledel'obturationdespuits prévenirlemélange d'uneeau indésirableà abandonnés incombeà leurpropriétaire. Aux l'eau potable,demanièreà rétablirlesous-sol termesde l'article 21, un puitsabandonnédoitêtre dansl'étatou il se trouvaitavantle forage. obturéavecdu bétonou un autre nriatériau approprié pourempêcherle mouvementvertical Pourquel'obturationd'un puitssoiteffectuée d'eauou degazentrelesaquifèresou entre un correctement,il faututiliserdesmatériaux aquifèreet la surfacedu sol. Ondoitabandonneret appropriéset les mettreenplaceen respjectant obturer: l'emplacementdu puitsetl'étatdu sol. Le présent documentaidera lepropriétaireàdétenninerles un nouveaupuitsasséché; matériauxqui conviennentà l'obuturationdeson puitsetla façon de lesutiliserdansdesconditions un puits inutiliséou nonentretenu pourun géologiquesethydrologiquesdifférentes. usage ultérieur; un puitsqui tireuneeau salée,sulfureuse, * Unaquifèreestla masseou formation minéraliséeou nonpotable. géologiquesaturéed'eau qui alimentelepuits. Il peutse trouverdanslacouvertureou la roche-mère. Leministèredel'Environmentetdel'Energie Une massedegravierfiltrenon tasséconstitue un peutégalementordonnerl'obturationd'unpuitssi bonaquifère tandisquelelimonou lesable trèsfin onydécouvredu gaznaturel ou s'il a étéconstruit diffuse mal l'eau. Uneformationrocheusefissurée sans tenircomptedes règlementsdu peutou non laisserfiltrer l'eau. gouvernement,en particuliers'il n'estpasassez éloignédessourcesdepollution. Ontario PIBS603B Que vousayez l'intentiond'obturervous-même votre puitsou d'engager un entrepreneur titulaire Parbéton,on entend un mélanged'eau, de d'un permis, vousdevriezsavoirque l'obturation ciment Portland etde sableou degravier. decertains puitsest difficileà réaliseren raison de leur profondeur, de la pression hydrostatique Parbentonite,on entend uneargilecolloïdale (p. ex. dansun puitsjaillissant),ou de la nature commercialeofferteen poudreouengranules. œmplexedes formationsgéologiques. Dansde tels Elle peutêtreutilisée pourépaissirdesbouesde cas, il vaut mieuxengagerunentrepreneurqui forage, commeadditifau laitierdeciment et possède l'équipementappropriéetconnaîtbien les commeagentd'étanchéité,carellesegélifieet se techniques deconstruction etlescaractéristiques gonflelorsquemélangéeà l'eau. géologiqueslocales. Si vous n'employezpasles bonnes techniquesd'obturation, vousn'obtiendrez Du sableou du gravierpropreetdésinfecté pas le résultatvoulu. donnera les meilleurs résultatsprèsd'unaquifère L'évaluateurdeseaux souterrainesou (voirla figure 1). Un puitsforé à la tarière l'inspecteurdespuitsdelarégionpeut renseigner contiendra probablementdu gravierplacépar etconseillerla population surla constructiondes l'entrepreneurlors delaconstruction. Ces puitsetl'étatdu sol. Il possèdeégalement une matériaux devraient remplirle puitsjusqu à lapartie copiedu registredes puitsqu'on désireobturer. Ce tubéeet êtrerecouvertsd'unbouchon decoulis registredécritdefaçon détailléela façon dontle d'argile, debentoniteou debéton. Le restedu peut puitsestconstruitetaidera l'intéresséou êtreentièrementrempli,jusqu'à la surface,de l'entrepreneurà choisirla meilleure méthode ciment, debéton,debentonite,d'argileoude d'obturation. On trouvera le registrede la plupart couchesalternéesdesableetdegravieretdeciment despuitsconstruits depuis 1949 auxbureaux ou d'argile. Il estpréférablede retirerla partie régionaux du Ministère,dontl'adresse figureàla supérieuredu tubageetderemblayer (figure 1). findu présentdocument. Fixerunetêtede tubageà l'extrémitésupérieuredu puitsrendra l'ensembleencoreplussur. Toutesces OBTURATION DE PUITS DANS DES étapesempêcherontla montéedeseaux souterraines FORMATIONS NON CONSOLIDÉES dans la partietubée. Fauted'unobturateurdeformationadéquat, Pour obturerconvenablementun puitsdont retirerle tubageau complet pourquelesmatériaux l'aquifère a unecouverturede sableou degravieret progressentversl'extérieur,endirectiondes forma- dontlecuvelagese termineparunobturateurde tions voisines,cequi permetd'obtenirunemeilleure formation satisfaisant,oncomblela partie tubée obturationetd'empêcherque l'eau ne monte. Si cela avecune sériedebouchonsdecoulisdeciment,de estimpossible,la seule solutionconsisteàcreuser béton, debentonite,d'argileou desableetgravier autourdu tubageetà lecouperà unedistance (figure!). appropriée sousla surfacedu sol,ouà enlever Si d'autrespuits producteurs sontsitués à suffisammentdecarreauxdans lecasd'un puits foré proximitédans la même formation aquifère, il faut à la tarière. Unbouchon en coulisd'argile, en veillerà bien choisirlesmatériauxd'obturationetà bentoniteou enbétonà labasedel'excavation les mettreen place de façonà cequ'ilsne se obturera l'extrémité supérieuredela partietubéeet déplacent paslatéralement versl'extérieurde toutespace annulaire ouvertà l'extérieurdu tubage. l'aquifèreet ne nuisentpasà l'eau desautrespuits Ensuite,on remblayerala cavitéavecdesmatériaux (p. ex. en rendanteau trouble). Dansde telscas,on decouverturejusqu'au niveau du sol. Ce travail ne conseilled'obturerl'aquifèreà l'aidedecimentou peutcependantse fairequ'une fois la partie debéton. inférieuredu puitsconvenablementobturée. REMARQUE : Termesutilsésdansla présente pub- L'argileconvientparticulièrementbienà l'obturation lication dela partiesupérieuredes puitsdegrand diamètre. : Parciment,on entend unmélangedeciment Portland etd'eau.