INJECTION WELLSAn Introduction to Their Use,

Operation, and Regulation

~Dedicated to protecting the nation’s ground water~

A publication of the

INTRODUCTION

What is a way to safely dispose of millions of gallons of liquid waste per year from many manufacturingsites? In what way can millions of gallons of municipal sewage-derived liquid waste be disposed ofwithout impacts to lakes, rivers or oceans? How can we dispose of, or even better, use billions ofgallons of fluids from oil and natural gas production to help produce more oil? How can valuableminerals be mined without constructing large, deep mines? What method can coastal communitiesuse to slow down salt water migration into fresh drinking water?

The answer to all of these questions can be summed up in two words: underground injection.

Water that is located in the subsurface is called groundwater. To understand underground injection, a briefdiscussion of ground water and some geologic terms isessential, so let’s begin.

Water is essential to life. Whether your drinking watercomes from a public water supply or a private well orspring, your very existence depends upon having safewater. The average American household usesapproximately 146,000 gallons of fresh water annually.Americans drink 1 billion glasses of tap water per day.Many homes and businesses use ground water. Thiswater is located in small spaces in sand or rock, calledpores, that are interconnected. The interconnected poresallow the water to move and be pumped out, or the watermay flow out naturally, such as from an artesian well. Theamount of water that infiltrates the subsurface varieswidely, depending on land use, the type of soil present,and the amount of precipitation that falls.

Ground water is stored beneath the land surface of ourlocal communities in formations of saturated rock, sand,gravel, and soil. Unlike surface water, ground water doesnot flow in a series of lakes and rivers. Instead, theprecipitation that seeps into our soil continues itsdownward journey and eventually fills the pores of thesesubsurface formations. Ground water can also be

replaced or recharged when rock formations come intocontact with surface water bodies such as lakes and rivers.

Formations that contain large enough amounts of water tofeed springs or wells are called aquifers. Two factorsdetermine the amount of water that aquifers can provide:porosity and permeability. Porosity is a measure of theamount of pore space, or holes, present in a rock. The morepores present, the greater the rock’s ability to hold water. Arock with many pores has high porosity. Permeability refersto the degree to which the pores in the rock are connected,providing the ground water in the pores and cracks a way tomove in the formation.

Ground water is found in rock, sand, gravel, and soil at awide variety of depths. Ground water is essential to our publicwater supply systems, economic growth, national agriculturalproduction, and the overall quality of life that we all sharewhether or not we are personally dependent on it for drinkingwater.

Estimates place the volume of nationally-usable groundwater at 100 quadrillion gallons. However, a problem exists:the potential for ground water contamination. Once a groundwater resource has been contaminated, cleaning it up tomake it usable again can be extremely difficult, costly, andis sometimes not feasible at all.

Ground water can be extremely susceptible to contaminationfrom a variety of common sources, including septic tanks,feed lots, fertilizer, highway de-icing salt, industrialprocesses, landfills, and underground storage tanks. It isimportant that these and other potential sources ofcontamination be

Ground Water

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handled in ways that protect ground water. Some wastesare generated by industrial processes that are difficult orimpossible to treat to levels that are safe for discharge atthe surface. These materials may contaminate ground waterresources if not kept away from them. Some of these wastes,in liquid form, can be pumped into formations deep belowthe earth’s surface and permanently isolated from usablewater resources.

Sandstone, a highly porous rock, generally allows water tomove through its pores easily. Some rock formations,including many shales and clays, have very low verticalpermeability and act as confining layers to fluid movement.Think of a sponge in between two thick layers of childrensclay. This is a simple version of how rock units in thesubsurface can exist – a water filled formation with tightconfining layers above and below that keep the fluid withinthe water-bearing layer. If liquid wastes are pumped into thesandy layer, represented by the sponge, the shale layers,represented by the clay, will keep the wastes trapped in thesandy layer and isolated from drinking water sources. Thereare approximately 190,000 wells in the United States that

MOST AMERICANS ARE SURPRISED TO LEARN:

• 77 billion gallons of ground water are used in America each day, compared to 34 billion in 1950.

• 40% of the nation’s drinking water and 92% of our total fresh water supply comes from ground water.

• 75% of our cities derive all or part of their water from underground sources.

• 99% of the rural population supply their own water from their own wells, using ground water.

store or dispose of fluids in underground rock formationstrapped by shale layers, keeping the fluids away fromunderground sources of drinking water.

Ground water quality generally deteriorates with increaseddepth. Fresh water—that is, water with lower salinities andmineral content—is usually located nearer the earth’ssurface. Deeper rock formations contain water of limitedquality or use, with high dissolved mineral content. Waterwith high salinity is not considered a potential source ofdrinking water. This is why these deep formations are usedfor disposal or injection of liquids.

Since the passage of several legislative acts in the 1970’sthat regulate waste disposal into water, air, and landfills,underground injection has grown in importance. In thepetroleum industry alone, over two billion gallons of salt waterare brought to the surface along with about two hundredmillion gallons of oil. The water is then separated, and re-injected deep underground each day. When disposed of atthe surface, many of these fluids pose a risk of contaminatingsurface waters or ground water.

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Underground injection is the placement of fluids into thesubsurface through a well bore. Many of the wells used forinjection are “high tech” in their construction, as discussedin this brochure. However, some are very simple, includingdug wells, certain septic systems, and other shallow, simplyconstructed, subsurface fluid distribution systems. Thepractice of underground injection has become essential tomany of today’s industries, including the petroleum industry,chemical industry, food and product manufacturingcompanies, geothermal energy development, and many localsmall specialty plants and retail establishments. To disposeof fluids safely, the wells need to be in the right kind ofgeologic setting, properly constructed, operated, maintained,and checked through different kinds of monitoring.

In the late 1960’s, the realization that subsurface injectioncould contaminate ground water if wells were not properlylocated and operated prompted many states to developprograms and methods to protect underground sources ofusable water. Additionally, to increase ground waterprotection, a federal Underground Injection Control (UIC)

Underground Injection WellsProgram was established under the authority and standardsof the federal Safe Drinking Water Act (SDWA) of 1974.This federal program establishes minimum requirementsfor effective state UIC Programs. Since ground water is amajor source of drinking water in the United States, theUIC Program requirements were designed to preventcontamination of Underground Sources of DrinkingWater (USDW) resulting from the operation of injectionwells. A USDW is defined as an “aquifer or its portion whichsupplies any public water system or contains a sufficientquantity of ground water to supply a public water system,and either currently supplies a public water system, orcontains less than 10,000 milligrams per liter of totaldissolved solids and is not an exempted aquifer.” Mostground water used as drinking water today contains lessthan 3,000 milligrams per liter of total dissolved solids (tds).However, the UIC Program protects waters with muchhigher mineral concentrations to ensure that all water withthe potential to be treated and used as drinking water inthe future is protected now. Since the passage of the SafeDrinking Water Act, state and federal regulatory agencieshave modified existing programs or developed newstrategies to protect ground water by establishing evenmore effective regulations to control the permitting,construction, operation, maintenance, monitoring, andclosure of injection wells.

Injection Well Relationship to USDWs(Underground Sources of Drinking Water)

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Injection wells are divided into five different classes. Theclasses are generally based on the kind of fluid injectedand the depth of the fluid injection compared with the depthof the lowermost USDW. Class I wells are used to injectindustrial or municipal waste to a depth beneath thelowermost USDW. Class II wells are used to dispose offluids associated with the production of oil and natural gas.Class III wells are used to inject fluids to aid in the extractionof minerals. Class IV wells were used to dispose ofhazardous or radioactive wastes into or above a USDW,but have been banned in all 50 states, unless they arepart of a contaminated site cleanup. Though Class IVhazardous and radioactive waste disposal wells have beenbanned for many years, some are still periodicallydiscovered and must be cleaned up and closed. Class Vwells are all wells not included in Classes I-IV that areused to inject or dispose of non-hazardous waste into orabove a USDW.

The United States Environmental Protection Agency(USEPA) has given primary enforcement authority, calledPrimacy, over underground injection wells to those stateagencies that have shown they are able to implement aUIC Program that meets USEPA’s legal requirements.These requirements are in Sections 1422 and 1425 ofthe SDWA, and the Federal Register (40 Code of FederalRegulations Sections 144 through 147), the publicationthat includes all of the federal regulations. The states thatUSEPA has determined have regulations, laws, andresources in place that meet the federal requirements andare authorized to run the UIC Program are referred to as

1Source: GWPC Class I Inventory of the United States prepared by Texas World Operations, Inc., June 2005. Disposing of 9 billiongallons of waste per year2Disposing of about 730 billion gallons of brine per year (Based on an average water vs oil production ratio of 10:1)3Source: GWPC Class III Well Inventory prepared by Subsurface Technology, Inc., January 20044This number is based on a state by state estimate of Class V wells and is expected to increase when an inventory is conducted.

ACTIVE INVENTORY

4841

170,0002

19,9253

540

1,500,0004

EPA CLASSIFICATION

CLASS I

CLASS II

CLASS III

CLASS IV

CLASS V

Injection Well Classification Chart

INJECTION WELL DESCRIPTION

Wells used to inject waste beneath the lowermost USDW

Wells used to dispose of fluids associated with the production of oil and natural gas

Wells used to inject fluids for the extraction of minerals

Wells used to dispose of hazardous or radioactive wastes into or above a USDW

Wells not included in the other classes generally used to inject non–hazardous waste

Primacy States. In many states, more than one stateagency has Primacy for one or more classes of injectionwells. For instance, one agency may have authority overClass II wells, and another agency have authority over ClassI and Class V wells. In states that have not received primaryresponsibility for the UIC Program, USEPA remains theresponsible regulatory agency. These states are referredto as Direct Implementation (or DI) States, becauseUSEPA directly implements the federal UIC regulations inthese states. Some states share responsibility with theUSEPA, with authority over some well classes residing atthe state level, and other well classes being regulated byUSEPA. For instance, in the map below, the State ofMontana has primacy for Class II wells, while USEPAregulates other well classes.

Regulatory Responsibility by State

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Some waste is an unavoidable byproduct of a myriad ofmanufacturing processes that create thousands of theproducts we use in the course of everyday living. Productssuch as steel, plastics, pharmaceuticals, and many otherscannot be made without generating certain fluid wastes.While industry continues to research and implement waysto reduce waste by recycling and improving manufacturingprocesses, wastes are still generated that require disposal.There are many acceptable ways to do this job, includingincineration, biological or chemical treatment, and landfillsin properly located and constructed sites. Additionally, manymillions of gallons of liquid wastes are generated in largemunicipalities from treated sewage. While some areas haverivers or other water bodies at the surface that can receivethis treated water stream, others have very sensitive watersthat make disposal of this wastewater unsafe and/orimpractical. An environmentally acceptable way to deal withall of these wastes in many parts of the United States isdisposal through injection wells. Injection wells penetratethousands of feet below the earth’s surface into rockformations where the waste is isolated from undergroundsources of drinking water. Class I wells typically injectanywhere from 1,700 to over 10,000 feet beneath the earth’ssurface. Most geologic formations containing potentialdrinking water sources are much shallower, within a fewhundred feet of the ground surface.

The suitability of this disposal method depends on theavailability of appropriate underground rock formationcombinations that have the natural ability to accept, yetconfine, the wastes. It is this long term confinement thatmakes deep well disposal an environmentally sound wastedisposal method. The ability of some rock formations toaccept but confine liquids injected into them is the samecharacteristic that has held naturally occurring oil and gas

Class I Injection Wells:Injection Wells Used for Disposal of Hazardous, Industrial Non–Hazardous,

and Municipal Wastewater Below USDWs

Hazardous Class I Injection Wells

Hazardous wastes are those industrial wastes that arespecifically defined as hazardous in federal law andrules (40 CFR Part 261.3 under Section 3001, of SubtitleC of the Solid Waste Disposal Act, as amended by the1976 Resource Conservation and Recovery Act, orRCRA). As seen in the figure to the left, very few stateshave Hazardous Class I injection wells. Many of thesewells are located along the Texas–Louisiana Gulf Coast.This area has a large number of waste generators suchas refineries and chemical plants as well as deepgeologic formations that are ideal for the injection ofwastes.

deposits for millions of years without allowing them toescape.

Because these wells inject waste below the deepestpossible USDW, there is little chance of any negative effectson potentially usable ground water. In fact, in its March2001 Study of Class I wells, the USEPA said that “theprobability of loss of waste confinement due to Class Iinjection has been demonstrated to be low” and “existingClass I regulatory controls are strong, adequately protective,and provide an extremely low-risk option in managing thewastewaters of concern.” In other words, the deep geologicformations that receive the waste (called the injectionzone), the related confining layers above the injection zone,and the many layers of protection required in theconstruction, operating, and monitoring of wells, providemany safeguards against upward fluid movement,effectively protecting USDWs.

Class I wells can be subdivided by the types of wasteinjected: hazardous, non–hazardous, and municipalwaste water. There are 291 active Class I injection facilitiesin 19 states; which have a total of 484 wells. Of these, 122wells are listed as hazardous, 251 are non-hazardous and111 are municipal waste. (“Class I Inventory of the UnitedStates”, June 2005, Texas World Operations, Inc. forGWPC) The greatest concentrations of Class I wells arelocated in the Gulf Coast, Great Lakes, and the Floridapeninsular regions. A facility owner is required to apply forand receive a permit from the state or USEPA beforeconstructing or operating any type of Class I well.

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Municipal wastes, which are not specifically defined infederal regulations, are wastes associated with sewageeffluent that has received treatment. Disposal of municipalwaste through injection wells is currently practiced only inFlorida. In Florida, this waste disposal practice is oftenchosen due to a shortage of available land, strict surfacewater discharge limitations, extremely permeable injectionzones, and cost effectiveness.

Site selection for a Class I disposal well is dependent upongeologic and hydrogeologic conditions, and only certainareas are suitable. Most of the favorable locations aregenerally in the mid–continent, Gulf Coast, and Great Lakesregions of the country, though some other areas are alsosafe for Class I well sites.

The process of selecting a site for a Class I disposal wellinvolves evaluating many factors. Paramount in theconsideration is the determination that the undergroundformations possess the natural ability to contain and isolatethe injected waste. One important part of this determinationis the evaluation of the history of earthquake activity. If alocation shows this type of instability in the subsurface, itmay mean that fluids will not stay contained in the injectionzone, indicating the well should not be located in thatparticular location. A second important factor is determiningif any improperly abandoned wells, mineral resources thatprovide economic reserves, or underground sources ofdrinking water are identified in the area. These resourcesare evaluated to ensure that the injection well will not causenegative impacts. Abandoned wells of any type—oil, gas,water, or injection that penetrate the proposed injection zoneare investigated within a specified radius of the injectionwell to ensure that they were properly plugged. If they werenot, they must be properly plugged to prevent them frombecoming a means for the fluids injected into the Class I

Municipal Class I Injection Wells

well to escape upward, potentially contaminating groundwater.

A detailed study is conducted to determine the suitability ofthe underground formations for disposal and confinement.The receiving formation must be far below any usable groundwater and be separated from them by confining layers ofrock, which prevent fluid migration upward. The injectionzone in the receiving formation must be of sufficient size(both over a large area and thickness) and have sufficientporosity and permeability to accept and contain the injectedwastes. The region around the well should be geologicallystable, and the injection zone should not contain recoverablemineral resources such as ores, oil, coal, or gas.

Non–hazardous wastes are any other industrial wastes thatdo not meet the legal definition of hazardous wastes andcan include a wide variety of fluids, such as those fromfood processing. Texas and Kansas have the greatestnumber of wells in this category because these states havespecific industries that generate large quantities of non–hazardous, liquid wastes. Non–hazardous industrial ClassI wells are located in 19 states.

Non–Hazardous IndustrialClass I Injection Wells

Site Selection and Distribution

The primary concern in the construction of a Class Iinjection well is the protection of ground water by assuringcontainment of the injected wastesthrough a multilayer protectionsystem. A Class I injection well isconstructed in stages, the firststage being the drilling of a hole toa depth below the lowermostUSDW. A steel casing or surfacepipe (usually between 6.5 and 15inches outside diameter) isinstalled the full length of the borehole and cement is placed outsideof the casing from the bottom tothe top of the hole. This providesa barrier of steel and cement thatprotects the ground water.

The second phase is to continuedrilling below the surface casingdown through the intendedinjection zone. After drilling iscomplete, a second, smaller,(generally between 4.5 and 10inches outside diameter)protective pipe called injectioncasing is installed from the surfacedown to the injection zone and iscemented in place from bottom totop. An injection packer, which islike a drain plug with a hole in themiddle, is located inside the longstring casing above the injectionzone by placing it on an evensmaller protective pipe (about 2.5to 7 inches in diameter), known asinjection tubing, which is placedinside the long string. The space

Construction Requirements

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The operating conditions for the well are closely studiedand are limited in the permit to make sure that the pressureat which the fluids will be pumped into the subsurface issafe, that the rock units can safely receive the volume offluids to be disposed of, and that the waste stream iscompatible with all the well construction components andthe natural characteristics of the rocks into which the fluidswill be injected.

Class I injection wells are continuously monitored andcontrolled, usually with sophisticated computers and digitalequipment. Thousands of data points about the pumpingpressure for fluid disposal, the pressure in the annulusbetween the injection tubing and the well casing (that showsthere are no leaks in the well), and data on the fluid beingdisposed of, such as its temperature and flow rate, aremonitored and recorded each day. Alarms are connectedto sound if anything out of the ordinary happens, and ifunusual pressures are sensed by the monitoring equipment,the well automatically shuts off. Disposal in the well doesnot resume until the cause of the unusual event isinvestigated, and the people responsible for operating thewell and the regulatory agencies both are sure that noenvironmental harm has been or will be done by welloperations. The wells are also tested regularly, usingspecial tools that are inserted into the well to record dataabout the well and surrounding rock formations. Thesetest results tell a geologist or engineer a great deal aboutconditions down in the well where we cannot otherwise see.

Regulators review all the data about the well operations,monitoring and testing frequently, and inspecting the wellsite to make sure everything is operating according to therequirements put in place to protect drinking water sources.

When a Class I well is taken out of service, the injectiontubing is taken out and the well is plugged to prevent anywaste movement. Often, a combination of mechanicalplugs and cement are used to seal the wells, which areconsidered to be permanently secured—not abandoned.The large column of cement in the well ensures that nothingcan move up or down in the well, protecting the groundwater resources that could otherwise be affected. Properlylocated, designed, constructed, operated, and monitoredClass I wells have proven through years of use and manystudies to be an environmentally and technically-soundmethod of permanent liquid waste disposal.

Construction Requirements Operating Requirements

Monitoring Requirements

between the long string and the injection tubing, calledthe annulus, is filled with a corrosion inhibiting fluid. Whenthe seal on the outside of the injection packer is inflatedtightly against the sides of the injection casing it forms aseal which keeps the annulus fluid in and the injectionfluid out of the space above the packer. The pressure inthis annular space is constantly monitored so that anychange, indicating a failure of safety systems, would causethe well to be shut down for repairs before possiblecontamination of a USDW. The diagram below illustratesthe basic components of a Class I well in a cutaway view.

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NOT TO SCALE

Class II injection wells have been used in oil field relatedactivities since the 1930’s. Today there are approximately170,000 Class II injection wells located in 31 states. AllClass II injection wells are regulated by either a state agencywhich has been granted regulatory authority over theprogram, or by USEPA. Class II wells are subject to aregulatory process which requires a technical review toassure adequate protection of drinking water and anadministrative review defining operational guidelines. Theevaluation of the site suitability for a Class II injection wellis very similar to that for a Class I nonhazardous wasteinjection well. The site’s subsurface conditions areevaluated to make sure the formations will keep the fluidsout of drinking water sources. The wells must beconstructed to protect USDWs, and wells are tested andmonitored periodically to ensure no drinking water is beingnegatively impacted by the operations.

Class II wells are categorized into three subclasses: saltwater disposal wells, enhanced oil recovery (EOR)wells, and hydrocarbon storage wells.

As oil and natural gas are brought to the surface, theygenerally are mixed with salt water. On a national average,approximately 10 barrels of salt water are produced withevery barrel of crude oil. Geologic formations are selectedto receive the produced waters, which are reinjected throughdisposal wells and enhanced recovery wells. These wellshave been used as a standard practice in the oil and gasindustry for many decades and are subject to authorizationby regulatory agencies.

Enhanced Oil Recovery (EOR) injection wells are used toincrease production and prolong the life of oil-producingfields. Secondary recovery is an EOR process commonlyreferred to as water–flooding. In this process, salt waterthat was co–produced with oil and gas is reinjected intothe oil-producing formation to drive oil into pumping wells,resulting in the recovery of additional oil. Tertiary recoveryis an EOR process that is used after secondary recoverymethods become inefficient or uneconomical. Tertiaryrecovery methods include the injection of gas, water withspecial additives, and steam to maintain and extend oilproduction. These methods allow the maximum amount ofthe oil to be retrieved out of the subsurface. Approximately60% of the salt water produced with oil and gas onshore inthe United States is injected into EOR wells.

Hydrocarbon storage wells are generally used for theunderground storage of crude oil and liquid hydrocarbons*in naturally occurring salt or rock formations. The wells aredesigned for both injection and removal of the storedhydrocarbons. The hydrocarbons are injected into theformation for storage and later pumped back out forprocessing and use.

* Hydrocarbons fit this classification if they are liquid at standardtemperature and pressure (75 degrees Fahrenheit at 14.7 pounds persquare inch).

Salt Water Disposal Wells

Enhanced Oil Recovery Wells

Class II Injection Wells:Injection Wells Related to Oil and Gas Activity

Hydrocarbon Storage Wells

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Typically, oil, gas, and salt water are separated at the oiland gas production facilities. The salt water is then eitherpiped or trucked to the injection site for disposal or EORoperations. There, the salt water is transferred to holdingtanks and pumped down the injection well. For EOR, thesalt water may be treated or augmented with other fluidsprior to injection. In some EOR cases, fresh water, or freshwater converted to steam, is injected to maximize oilrecovery.

Injection well operations are regulated in ways to preventthe contamination of USDWs and to ensure fluid placementand confinement within the authorized injection zone. Thisincludes limitations on factors such as the pressure that canbe used to pump the water or steam into the well, or thevolume of the injectate. Primacy states have adoptedregulations which have been approved by USEPA asprotective of USDWs for Class II injection well operations.These regulations address injection pressures, well testing,pressure monitoring, and reporting. Direct implementationstates must meet operational guidelines developed directlyby USEPA.

After placing Class II injection wells in service, ground waterprotection is assured by testing and monitoring the wells.Injection pressures and volumes are monitored as avaluable indicator of well performance. Effective monitoringis important since it can identify problems below ground inthe well so that corrective action can be taken quickly toprevent endangerment of USDWs.

Tests that evaluate the conditions of the various wellcomponents and the formations in the subsurface arerequired prior to initial injection and no less than once everyfive years afterward. However, in some cases, morefrequent testing may be requiredby regulatory authorities, ifneeded. All tests and testmethods are rigorously reviewedby the State and/or USEPA. Testdata, as well as data on thevolume and characteristics of thefluids injected into the well, areregularly evaluated by regulatoryagencies to make sure USDWsare protected by the operationand maintenance of the wells.

Operations

Testing and Monitoring

Construction of Class II injection wells must adequatelyconfine injected fluids to the authorized injection zone toprevent the migration of fluids into USDWs. Through thepermitting process, site specific requirements are imposedto address any unusual circumstances.

These injection wells are drilled and constructed using thesame techniques as those for Class I wells, with steel pipe(called casing) cemented in place to prevent the migrationof fluids into USDWs. Surface casing in conventionallyconstructed wells is cemented from below the lowermostUSDW up to the surface to prevent fluid movement. Cementis also placed behind the injection casing at critical sectionsto confine injected fluids to the authorized zone of injection.A typical salt water injection well also has the injection tubingthat was described earlier, through which the fluids arepumped from the surface down into the receiving geologicformations. As described in the section on Class I wells, apacker is commonly used to isolate the injection zone fromthe space between the tubing and injectioncasing abovethe packer, called the annulus. In some cases, multiplewells will be constructed under one permit, to manage thefluids in an entire oil or natural gas production field. Theoverall well system for injection is then evaluated byregulators to make sure all the components are properlyconstructed.

Construction Requirements

Closure of Class II wells mustbe conducted in a mannerprotective of USDWs. Althoughregulations vary slightly fromstate to state, a cement plug iscommonly required to be placedin the well across the injectionzone, with additional plugsplaced across the base of thelowermost USDW and near thesurface.

Closure

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Class III injection wells are found in 18 states. Every ClassIII injection well, whether located in a Primacy or DirectImplementation state, must be permitted through theauthorized regulatory agency. The operating permitrequires that a well meet any regulations the state hasadopted to ensure the protection of USDWs. The permitsmay include specific requirements for well construction,monitoring, mechanical integrity testing, maximumallowable injection pressure, and reporting. Proper closureor plugging of all Class III injection wells must be conductedin a manner to protect USDWs from potentialcontamination.

The techniques these wells use for mineral extraction maybe divided into two basic categories: solution mining ofsalts and sulfur, and in situ leaching (in place leaching)for various minerals such as copper, gold, or uranium.

Solution mining techniques are used primarily for theextraction of salts and sulfur. For common salt, the solutionmining process involves injection of relatively fresh water,which then dissolves the underground salt formation. Theresulting brine solution is pumped to the surface, eitherthrough the space between the tubing and the casing inthe injection well, or through separate production wells.

The technique for solution mining of sulfur is known as theFrasch process. This process consists of injectingsuperheated water down the space between the tubing andthe casings of the injection well and into the sulfur–bearingformations to melt the sulfur. The molten sulfur is extractedfrom the subsurface through the tubing in the injection well,with the aid of compressed air, which mixes with the liquidsulfur and airlifts it to the surface.

Solution Mining

Class III Injection Wells:Injection Wells Related to Mineral Extraction

In situ leaching is commonly used to extract copper, gold,and uranium. Uranium is the predominant mineral minedby this technique. The uranium in situ leaching processinvolves injection of a neutral water solution containingnontoxic chemicals (e.g., oxygen and carbon dioxide) downthe well. This fortified water is circulated through anunderground ore body or mineral zone to dissolve theuranium particles that coat the sand grains of the ore body.The resulting uranium–rich solution is then pumped to thesurface, where the uranium is extracted from the solutionand the leaching solution is recycled back into the ore bodythrough the injection well. This same general technology

is employed for in situ leaching of other minerals, the onlydifference being the type of fluid used in the process.

The typical life of an in situ leaching well is less than fiveyears. At the end of the in situ leaching operations, UICregulations require restoration of the mined zone to itsoriginal quality. Given the purpose of Class III wells andtheir life span, Class III UIC projects often include manywells that are authorized through one permit, called an areapermit. The standards in the permit apply to all of the wellsin the project area.

Construction standards for Class III injection wells aredesigned to confine injected fluids to the authorized injectionzone to prevent migration of these fluids into USDWs. ClassIII injection wells are drilled intomineralized rock formations andare cased with pipe which iscemented in place to preventfluid migration into USDWs.Construction materials andtechniques vary and depend uponthe mineral extracted and thenature of the injected fluids.

Tests are required before initialoperation of Class III injectionwells to evaluate conditions of thewell construction materials andthe rock formations. Severaldifferent tests have beenapproved for this purpose. Thetests are required to determinethat there are no leaks in thetubing, casing, or packer andthere is no fluid movement into aUSDW. In situ leaching wells alsorequire that the ore body besurrounded by monitoring wells todetect horizontal migration of themining solutions. Additionally,overlying and underlying aquifersmust be monitored to detect anyvertical migration of these samefluids. This entire network closelymonitors the mining activityperformed through Class III wellsto protect USDWs.

In Situ Leaching

Construction and Testing

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Class IV Injection Wells:Injection Wells Used for Hazardous and Radioactive

Wastewater Disposal Into or Above USDWs

Class IV wells have been identified by USEPA as asignificant threat to human health and the environmentsince these wells introduce very dangerous wastes into orabove a potential drinking water source. USEPA has bannedthe use of these wells for many years. However, due toboth accidents and illegal intentional acts, Class IV wellsare still periodically found at various locations. As thesewells are identified by state and federal UIC regulatoryagencies, their closure is a high priority for the UIC Program.Regulators evaluate site conditions, determine what actionsneed to be taken to clean up the well and surrounding area,and permanently close the well so additional hazardouswastes cannot enter the subsurface through the well. Thiswell class may include storm drains where spills ofhazardous wastes enter the ground or septic systems wherehazardous waste streams are combined with sanitarywaste. When these wells are found, the UIC Program staffusually coordinates with the state or USEPA hazardouswaste program staff to oversee actions required at the siteto remove the contamination and protect USDWs.

Although otherwise banned, there is one instance whereClass IV wells are allowed. In these cases the wells areused to help clean up existing contamination. Sites exist

across the United States where hazardous wastes haveentered aquifers due to spills, leaks or similar releases intothe subsurface. Under two separate federal laws, theResource Conservation and Recovery Act (RCRA) and theComprehensive Environmental Response, Compensation,and Liability Act (CERCLA), regulators require and overseethe clean up of these contaminated sites. Some remediationtechnologies require the contaminated ground water to bepumped out of the subsurface, treated at the surface toremove certain contaminants, then pumped back into thecontaminated formation. The process essentially createsa big treatment loop for the ground water. However, thewater can still have contaminants at levels that meet thedefinition of hazardous waste when it is injected back intothe subsurface, until the treatment process has time toremove more contaminants. Thus, these wells that aretreating and cleaning up ground water technically are stillClass IV wells. USEPA recognized that these site cleanups need to occur, and that the ban of Class IV wells washindering the process. Since these wells are helping theenvironment, the agency changed the regulations to allowthese wells to be used, as long as they are part of anapproved regulatory clean up of the site. This is the onlyexemption to the ban on Class IV wells.

The ban on Class IV wellsprevents ground water

contamination byprohibiting the shallowinjection of hazardouswaste except as part of

authorized cleanupactivities.

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Class V Wells:Injection Wells Not Included in the Other Classes

If a well does not fit into one of the first four classes ofinjection wells, but still meets the definition of an injectionwell, it is considered a Class V well. Class V injectionpractices recognized by USEPA include several individualtypes of wells, which range in complexity from simplecesspools that are barely deeper than they are wide, tosophisticated geothermal reinjection wells that may bethousands of feet deep. However, the number of shallow,relatively simple Class V wells is large, and thesophisticated, deep Class V wells are quite rare incomparison. Remember that injection wells are classifiedbased on the type of waste disposed of and the depth ofthe disposal zone compared with the deepest USDW. Insome parts of the country, USDWs can exist at great depths.Because injection above the USDW does not meet thedefinition of a Class I well, such wells are classified as ClassV wells. Also, if the fluids injected are NOT:1. Class I: Hazardous waste and non hazardous industrialor municipal waste injected below the lowermost USDW;or2. Class II: From oil and natural gas activities; or3. Class III: Related to mineral production; or

4. Class IV: Hazardous or radioactive wastes injected intoor above a USDW, the well defaults to the Class V category.

Class V injection wells can be located anywhere, but theyare especially likely to exist in areas that do not havesewers. These unsewered areas are often the same areaswhere people are most likely to depend on ground waterfor their drinking water source, typically from private wellsthat do not undergo treatment at a public water supplysystem. The variety of Class V wells includes but is notlimited to agricultural drainage wells, storm water drainagewells, large capacity septic systems, mine backfill wells,aquifer remediation wells, heat pump/air conditioning returnflow wells, aquifer recharge wells, aquifer storage andrecovery, saltwater intrusion barrier wells, subsidencecontrol wells, and industrial disposal wells.

Not all Class V wells are used for disposal. Examples ofClass V practices which are not disposal related include:aquifer recharge, aquifer storage and recovery, andsaltwater intrusion control.

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Class V Disposal Wells andYour Drinking Water

Class V wells injecting below the lowermost USDW havethe least potential for contaminating ground water. Class Vinjection directly into USDWs has a greater potential to causeharm to water quality than discharges above the water table.Discharges above the water table may allow somecontaminants to be removed from the waste throughabsorption by soils, and by degrading or otherwise changingas they move through shallow soils and some rockformations. However, some rock formations and soil types,such as sand, can allow fluids injected above USDWs tomove very quickly without very much change. In thesecases, the effect can be similar to injecting directly into theUSDW.

Based on numbers obtained through a survey of the states,it is estimated that there are at least 1,500,000 Class Vinjection wells in the United States and its territories. Thesurvey also suggests that about 83 percent of all Class Vwells belong to two categories: drainage wells (approx. 57percent) and sewage-related wells (approx. 26 percent).

USEPA has developed rules and a strategy for regulatingClass V injection wells. Involvement by state and localgovernment and the public in implementing the strategy isessential to its success. Many states have adoptedregulations and ordinances for oversight of certain Class Vwells. USEPA targeted those Class V wells which pose thegreatest environmental risks as candidates for regulatorydevelopment, education and outreach, and enforcementwhen necessary.

Two groups of particular concern are large capacitycesspools and automotive waste disposal wells. Largecapacity cesspools are any residential cesspools used bymultiple dwellings, businesses, or other facilities that arenot individual homes (such as schools and churches). Thespecific definition of a large capacity cesspool can varyslightly from state to state, and environmental regulatorscan help a facility determine if their cesspool is “largecapacity.” Large capacity cesspools dispose of untreatedsewage into or above a drinking water source, creatingsignificant risk for bacteria and viruses being introduced intodrinking water. Automotive waste disposal wells are thoseused by motor vehicle repair or maintenance shops, cardealers, or any operation that disposes of fluids from vehicles(including trucks, boats, trains, planes, tractors,snowmobiles, and similar types of vehicles). Motor vehiclewaste disposal wells have a high potential to receive dropsand spills of vehicle fluids, such as oil, transmission fluid,antifreeze, solvents and degreasers, and other toxic

materials. As these fluids enter ground water, they cancreate a serious health risk if consumed in drinking water.

These two types of Class V wells were the subject ofadditional rulemaking due to the high risk they pose toUSDWs. In 1999, USEPA finalized the UndergroundInjection Control Regulations for Class V Injection Wells,Revisions, known as the Class V Rule, Phase I, whichestablishes minimum federal standards for these two kindsof Class V wells. Some of the protective requirements ofthe Class V Rule, Phase I include a ban on new largecapacity cesspools and the closure of all existing largecapacity cesspools by 2005. New motor vehicle wastedisposal wells are also banned, while existing wells in groundwater protection areas and other designated sensitiveground water areas must either be permanently closed orpermitted by the primacy state or USEPA to continueoperating under the ban. Some UIC primacy states havemade the requirements for existing motor vehicle wastedisposal wells apply in the entire state, rather than limitingthem to specific sensitive ground water areas. The owneror operator of a large capacity cesspool or motor vehiclewaste disposal well is required to send a notice to the stateor USEPA at least 30 days before beginning to close one ofthese wells. USEPA developed a special guide for ownersand operators of motor vehicle waste disposal wells, toprovide additional information about how the rule affectsthem. The document, entitled Small Entity ComplianceGuide: How the New Motor Vehicle Waste Disposal WellRule Affects Your Business, is USEPA publication number816-R-00-018, November 2000, and is available bycontacting USEPA’s Small Business Division at (800) 368-5888. Additional information about large capacity cesspools,motor vehicle waste disposal wells, and other Class V wellsis also available on the Internet at www.epa.gov/safewater/uic/. A video describing the regulation and closure of motorvehicle waste disposal wells is available in the UIC sectionof the GWPC website at www.gwpc.org.

In June 2002, USEPA announced its final determination that,at that time, additional federal requirements were not neededfor the remaining types of Class V wells (other than themotor vehicle waste disposal wells and large capacitycesspools). The determination also noted that the use andenforcement of existing federal UIC regulations areadequate to prevent Class V wells from endangeringUSDWs. This determination was made after completion ofa national Class V study, a proposed determination, receiptof public comments and additional information received inresponse to the proposed determination, and a finalassessment of all the data and information provided by thepublic and by various state UIC programs.

This determination certainly does not mean that Class V

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wells are not regulated. In fact, the only Class V wells thatare operating legally are those whose owners havesubmitted inventory information to the State or USEPA asrequired by regulation and are operating their wells in away that does not endanger USDWs. The requiredinventory information is simple to prepare and submit, andeach Regional USEPA office or primacy state has a formthat an owner or operator of a Class V well should complete.If the state or USEPA office decides that additionalinformation is necessary to ensure USDWs are notthreatened by the operation of a well, the owner or operatorwill be asked for that information. There are cases in whicha well that is not a large capacity cesspool or motor vehicledisposal well will be required to be subject to a permit orrequired to be permanently closed. This could occur withvirtually any type of Class V well, due to local or stateregulations that include additional requirements beyond thefederal standards, or based on data that indicate the wellposes a risk of contamination to nearby undergrounddrinking water sources.

The June 2002 determination by USEPA included adiscussion of how the agency will continue to prioritize ClassV program actions to ensure that these wells areconstructed, operated, and maintained to protect USDWs.These actions include continuing to implement the longstanding UIC regulations as well as the 1999 Class V, PhaseI Rule, educating and assisting Class V well operators onbest management practices and compliance tools,exploring non-regulatory approaches for voluntary Class Vwell standards and practices, and coordinating with otherUSEPA programs to educate and inform the maximumpossible number of UIC well facilities. USEPA also willevaluate new information as it becomes available, and ifnew information illustrates additional needs in the Class VUIC Program, the agency will still be able to take additionalsteps, including developing additional federal regulations.

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Public Awareness:The Key to Protecting Drinking Water

As you can tell from all the information in this brochure, protecting drinking water is a responsibilitythat everyone needs to take seriously. Being aware of your drinking water source is the first step.You then can actively participate in protecting it. This could include working with your localcommunity in developing or helping implement an existing program to protect drinking watersources, known as Source Water Protection. While Class I, II, and III wells are heavily regulated,your community may have unidentified Class IV or Class V injection wells. Even though there arefederal, state, or local regulations affecting a wide variety of potential ground water contaminantsources, each of us should learn how our community might be affected by any of them and, if weare, what we can do about it. Perhaps you will be the key to unlocking the information necessaryto help your community identify these potential contaminant sources and protect your drinkingwater!

If you would like any additional information about a specific class of injection well, or the UICProgram in general, you may contact the Ground Water Protection Council at www.gwpc.org or at(405)516-4972. You can find more federal UIC information at www.epa.gov/safewater, or bycontacting USEPA’s Drinking Water Hotline at 1-800-426-4791 or by email at hotline-sdwa@epa.gov.

OUR MISSION:The Ground Water Protection Council is a national association of state ground waterand underground injection control agencies whose mission is to promote the protectionand conservation of ground water resources for all beneficial uses, recognizing groundwater as a critical component of the ecosystem.

The Ground Water Protection Council provides a forum for stakeholder communicationand research in order to improve governments’ role in the protection and conservation ofground water.