FYI It is estimated that from 1961 through 1981, more than 60 billion gallons of industrial wastes were disposed of in underground injection wells in Texas. (Source: Texas Department of Water Resources, Underground Injection Operations in Texas, 3-11).

Injection wells, where pressurized liquid wastes or other fluids are injected into aquifers, are a major method of disposal for industrial and hazardous wastes. Injection wells are also used to help recover oil, gas, and minerals. Uranium and sulfur are often mined by injecting hot water into formations to loosen up these materials.

The Railroad Commission of Texas has jurisdiction over injection wells used to inject oil and gas wastes -- mainly saltwater -- injection wells to be used for secondary recovery and those used to store hydrocarbons underground. As of December of 2002, the Railroad Commission reported that it had permitted 51,338 so-called Class II injection wells, 33,026 of which were active. The vast majority of these consisted of secondary-recovery wells (about 25,000), while there were about 8,000 saltwater disposal wells and some 500 active hydrocarbon and gas storage wells ^* Two confirmed cases of groundwater contamination resulting from injection wells have been documented in the past few years, though both have since been cleaned up.^*

EXAMPLE OF A URANIUM MINE AND INDUSTRIAL WASTE DISPOSAL WELL Source: Texas Natural Resource Conservation Commission

Injection wells have been involved in a number of controversial lawsuits and permit battles, as well as high-profile groundwater contamination cases, usually resulting from improper handling of the waste at the surface prior to injection (see Industrial Waste chapter). According to the TCEQ, there have been no confirmed cases of groundwater contamination from the injection of hazardous and other industrial wastes in the past few years. However, in the case of injection wells used for mining, the movement of mining fluids into groundwater is not considered a case of groundwater contamination so long as the facility cleans up the water and ensures that it does not spread beyond the boundaries of the mining area. All groundwater contamination resulting from these activities has been cleaned up.

Currently, there are 102 Class I injection wells permitted and operating in Texas, with about half injecting only "non-hazardous waste" and the other half authorized to inject both non-hazardous and hazardous industrial waste.^* Most are located in the coastal area and dispose of wastes associated with the petrochemical industry. While most are only authorized to dispose of on-site generated waste, there are presently 10 commercial facilities which are pemitted to inject off-site generated waste. While the federal Land Disposal Restriction (LDR) regulations generally prohibit the injection of most hazardous waste unless the waste is treated to meet or exceed LDR standards, and exemption can be obtained if the operator can demonstrate that the waste will not migrate from the injection zone. Most hazardous waste injection facilities have sought and received this exemption from the LDR regulations, allowing them to inject wastes without further treatment.

Another class of injection wells --Class III wells -- are those used for uranium or sulfur mining or for the recovery of brine (subsurface salt deposits). While sulfur and underground uranium mines are regulated by the TCEQ, brine mining (and surface uranium mining) is regulated by the Railroad Commission. These wells can contribute to the contamination of groundwater by increasing its salinity or by moving naturally occurring radioactive material.

UNDERGROUND INJECTIONS IN TEXAS TYPE OF UNDERGROUND INJECTION SOURCE Industrial and hazardous waste Manufacturing industry Oil and gas waste, oil and gas recovery, oil and gas storage Oil and gas exploration, development, and recovery Superheated water Brine mining, sulfur and sodium, sulfate mining, uranium mining Sewage disposal Municipalities, individuals Agricultural drainage Agriculture, particularly citrus production Source: Texas Department of Water Resources, Underground Injection Wells in Texas (1984).

Currently 70 brine mining injection facilities -- with a total of 86 injection wells -- are operating in Texas. Most of these are located in the High Plains and Trans-Pecos regions. Most of these require a monitoring well which monthly sampled the amount of electrical conductance to determine contamination.*. Since 1975, 34 sites have permitted for in-situ uranium mining, six for Frasch sulfur mining and three for sodium sulfate mining, all in South Texas. All of the sulfur and sodium sulfate sites have been closed due to poor economic conditions, while only five "in-situ" (subsurface) uranium mines are presently in operation due to low demand for uranium. Uranium mines take background levels before mining begins, and mine operators are expected to return any affected groundwater to background or pre-mining levels.^* In general, injection wells used in mining are not as deep as those used for injection of wastes. They are thus more likely to impact near-surface water used for drinking, which is the reason they are monitored more extensively. There are currently no confirmed cases of groundwater contamination -- meaning outside the boundaries of the mining area --  from these injection mining activities*.

Finally, Class V wells include agricultural drainage wells, domestic wastewater disposal wells, aquifer storage and retrieval wells, aquifer remediation wells when waters are contaminated, and closed-loop wells for air conditioning and heating. These wells -- also regulated by the TCEQ -- are generally authorized by rule, not permit, although they must submit inventory information and obtain written approval before construction. In December of 2002, the TCEQ reported it had inventoried over 20,000 Class V wells, the vast majority associated with aquifer remediation in Leaking Petroeum Storage Tanks.*.The Lower Rio Grande Valley is the major area of Texas where agricultural drainage wells are used. These wells help eliminate excess water from agricultural production. Because this part of the state is flat and has clay soils and high water tables, surface drainage is limited. Agricultural drainage wells collect near-surface waters and drain them into subsurface formations. They dispose of waters containing nitrates, dissolved solids, and pesticides, all of which have a high potential for contamination of groundwater. These wells are used mainly in citrus production, which has been rapidly declining in the Valley.^* Some 108 wells have been located in the Lower Rio Grande Valley counties of Hidalgo and Starr and in south-central Runnels County. Other agricultural drainage wells are located in Oldham County, where they could impact the Ogallala Aquifer.^*

CONTAMINATION POTENTIAL OF MISCELLANEOUS INJECTION WELLS WELL TYPE CONTAMINATION POTENTIAL POTENTIAL CONTAMINANTS Agricultural Drainage High Pesticides, fertilizers, pathogens, metals via soil sediments, salts. Storm Water Drainage Moderate Heavy metals (Cu, Pb, Zn), organics, coliform bacteria, contaminants from streets, pesticides. Industrial Drainage High-Moderate Organic solvents, acids, pesticides and various other storm drainage wells. Heat Pump/Air Conditioning Return Flow Low Potable Waters (90o to 110o F) may contain scale or corrosion inhibitors. Sewage Disposal (septic tanks) High-Low Suspended solids, nitrates, chlorides, sulfates, sodium, calcium, fecal coliform. Mine Backfill Moderate Acidic waters. Automobile Service Station High Heavy metals, solvents, cleaners, used oil and fluids, detergents, organic compounds. Artificial Recharge High-Low Variable, sediments, pesticides, fertilizers. Water is generally of good quality. Abandoned Water Moderate Potentially any fluid, saline waters, hazardous chemicals, fertilizers, sewage, sediments. Others Unknown Variable. Source: Texas Department of Water Resources, Underground Injection Wells in Texas (1984).

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