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HomeMy WebLinkAboutABANDONED WELLS_LITERATURECost - sharing and Sealing Wells WHAT ARE ABANDONED WELLS? Abandoned water wells are wells that: o are no longer in use; or • are in such a state of disrepair that they can- not be fused. WHY SHOULD AN ABANDONED WELL BE SEALED? Abandoned wells are frequently loosely covered or uncovered holes in the ground. They may pose a serious threat to the safety of animals and humans, especially small children. Unsealed abandoned wells also may act as drains for run -off, to allow contaminated water and near - surface water to migrate avectly into an aquifer (water - bearing soil or rock). Water from a contaminated aquifer may flow through an abandoned well and pollute another aquifer that is normally protected from pollution by an impervious layer. Thus an abandoned well can contaminate a well that is providing drinking water. Burying an abandoned well will not solve the problem and is illegal. Unfortunately, a buried well may be out of sight but still serve as a pathway for pollution. Sealing an abandoned well by filling it with clay or cement prevents accidents and preserves the valuable drinking water resource. WHEN MUST ABANDONED WELLS BESEALED? A well must be sealed by a lice..:.ed well driller when it is imp - operly located, constructed, or maintained or when it becomes a safety hazard or a threat to groundwater quality. i well has been improperly sealed, arrangements must be made to re -seal the well properly. Well sealing must be done in accordance with the well construction code of the Minnesota Department of Health. WHO ! S LSPONSIBLE FOR SEALING AN ABANDONED WELL? The owner of the land on which the well is located is responsible for - Paling the abandoned well. WHEN "STATE ISSUE WELL Si UNDS? The 1989 Minnesota Legislature passed legislation providing limited state funding for a well - sealing program. The program will be administered by the Board of Water and Soil Resources (BWSR). The Department of Health, which administers the well construction program, and counties will assist in developing guidelines and procedures. A timetable for implementing the well sealing program has been established. July 1989 —June 1990 — The DeveloptxntYear. An interagency work group will be established by BWSR to oversee the development of guidelines and procedures. Guidelines will be developed for determining well sealing priorities and the selection of counties to participate in the cost -share grant program. Several state agencies and local units of government, including counties and soil and water conservation districts, will be involved in this work group. July 1990 —June 1991 —The Cost - Sharing Year. Approximately $400,000 will be available to counties for cost -share grants. This will be enough money to seal only a few hundred wells. Counties most consult with local health boards, soil and water conservation districts, planning and zoning departments and other local units during program administration. The county may also contract with a local unit of government to administer the well sealing program. July 1991 until program ends in June 1995: Current legislative funding expires June 30, 1991. The legislature may appropriate funds for the period July 1, 1991 until the mandated end of the program on June 30, 1995. Beginning July 1, 1991 well sealing cost -share funds will be available only in those counties that have identified the sealing of abandoned wells as a priority in their comprehensive local water plans. WHICH WELLS WILL RECEIVE COST-SHARE FUNDS? BWSR will choose the counties to receive well sealing cost -share funds in consultation with the Department of Natural Resources, Pollution Control Agency, Department of Health, and Minnesota Geological Survey. Wells will be prioritized for receiving cost -share grants by BWSR and the commissioner of Health In consultation with the local water planning Officials based on the following criteria: • well construction, depth and condition; • importance of the aquifer as a water source; •proximity to known or potential contamina- tion sources; • current contamination of the well or aquifer; • aquifer susceptibility to contamination byun- sealed wells; *availability of alternative drinking water sources; • anticipated changes in land or water use; •conditions such as construction, rehabilita- tion, or demolition; • potential use of the well as a monitoring well; and • danger of humans and animals failing into the well. The county will be responsible for providing much of this information to the BWSR and the Department of Health. HOW WILL PROPERTY OWNERS RECEIVE ASSISTANCE? The law provides that landowners who need financial assistance to seal abandoned wells have two options: • Beginning July, 1990, cost-sharing can be re- quested from the county or other local unit administering the program on behalf of the county (cost - sharing is limited to 75 percent of the total cost, not to exceed $2,000 per well); or, • Beginning July, 1990, financial assistance can be requested directly from BWSR (this is not a cost - sharing program -- if the BWSR provides well sealing funds directly to a land- owner, 100 percent of the cost will be recoveredeither bya lien on the real property where the well is located or by assessments on property taxes). After a well is sealed by a licensed contractor, certification forms must be completed. Information about well sealing certification is available from the Minnesota Department of Health. Since 1974, well code regulations have required abandoned wells to be sealed, so lack of well scaling cost -share grants cannot be used as a defense to avoid sealing a well. WHAT ARE THE LIABILITIES OF UNSEALED WELLS? The greatest risks posed by unsealed wells are accidents and ground water contamination, which could result in legal and financial liabilities. State law requires a properly owner who is selling property to provide information to the prospective buyer on all wells known to be on the properly. The well information must be on a certificate that is signed by the seller and provided to the buyer at the time of the closing of the sale. A seller who fails to report the existence of a well on the property will be liable to the buyer for costs and reasonable attorney fees relating to the sealing of the wen for six years following the date of purchase. Well owners may take action for civil damages against a person whose action or inaction caused contamination of their well within a period of six years after discovering the contamination of the wells. FOR FURTHER INFORMATION, CONTACT Minnesota Department of Health, Well Management Unit (on technical issues) (612) 623 -5376 Board of Water and Soil Resouaes state office (on cast -sham issues) (612) 296-3767 or the BWSR administrative region for your area: Northwest, 1819 Bemidji Avenue, BEMIDJI 56601 (218) 755 -3962 Northeast, 320 West Second Street, B 603, DULUTH 55802 (218) 7274752 Southwest, 1400 East Lyon Street, Bas III, MARS14ALL56M (507)537.72W South Central, Dos 756, NEW ULM 56073 (507) 354.2196 Southeast, 12M South Dmadway, ROCIIESIL-R55904 (507) 285.7458 Ease Central, 155 Sr,uth Wabasha, 0 104, SP.PAULS5107 (612) 297.1894 Wen Central, 303 Washinglon stmet, BRAINERD 36258 (218)V44692 ..... i r� M; %4; COST-SHARING AND SEALING WELLS MINNESOTA BOARD OF WATER AND SOIL RESOURCES MINNESOTA DEPARTMENT OF HMTH Sep tuber 1989 Abandoned Wells I CTI Minnesota Department of Health SEALING ABANDONED YELLS Magnitude of the Problem Abandoned wells are water wells whose use has been discontinued or which are in such disrepair that continued use is impractical or may be a health hazard. Abandoned unsealed wells can act as conduits or channels for contamination to reach the groundwater. The threat of open holes serving as passageways for surface or near - surface contamination poses a major problem to the ground- water, particularly in contaminated areas. The magnitude of the problem was demonstrated by a pilot study conducted by the Minnesota Department of Health in 1973. The pilot study located abandoned wells in five southeastern Minnesota townships in Winona, Fillmore, Wabasha and Houston Counties. The study revealed a surprisingly large number of aban- doned wells with estimates ranging from 1,200 to 2,050 abandoned wells for the five townships or about one abandoned well for every five active wells in operation. Later ir+s•mation from the University of Minnesota, School of Public Health's abardcned well survey indicated that there may be as many as one to four abandoned wells for eery active well. The total number of abandoned wells can be visualized when it is realized that approximately 100,000- 400,000 active wells are estimated to exist in the state. Based on the abandoned well survey, this means that approximately 100,000 - 1,600,000 abandoned wells are present throughout the state threatening the quality of the groundwater. Adverse Effects of Abandoned Wells Properly constructed water wells are not normally sources of groundwater con- tamination. But when the wells are in a state of disuse or disrepair, or if they are buried or casings are damaged and begin to deteriorate, then the wells can become conduits through which contamination can travel vertically through boreholes. Since 1974, when the Minnesota Water Well Construction Code came into effect, water wells have been drilled so that they do not pose a threat to the ground- water if properly maintained. In some instances today, an aquifer must be sealed off and special well construction employed, for example, in geolog- ically sensitive areas underlain by limestone. The Code may require casing and grouting of the limestone. An abandoned well's potential for adversely affecting groundwater quality will depend on its original use, the local geology, land use, the hydraulic characteristics of the subsurface fluids, and the type of well construction. When a well is improperly sealed, it is often simply covered by a board or a sheet of metal in an unsuccessful attempt to insure that the well does not become a hazard. Unfortunately, such procedures fail to take into account the fact that the mere existence of an unsealed, abandoned well represents a great -1- hazard to groundwater quality either as a direct conduit for surface contamination to enter the groundwater or for inter- aquifer exchange, that is, flow between two aquifers having different heads. The natural 4uality of groundwater tends to be degraded by the activities of man. Wastes, which are not discharged into lakes and streams are deposited on or below the land and from there may migrate downward to contaminate the groundwater. The problem is compounded t- _ groundwater contamination and the effects of contamination are not usually recognized until groundwater quality is seriously impaired. Reasons for Sealing Abandoned Wells Unsealed abandoned wells constitute a hazard to publ =�; health and a danger to groundwater supplies. In Minnesota approximately two- t.r ;rd: of the state's population (2.6 million people) consume groundwater. Such a valuable resource must be protected from unwarranted neglect in allowing degradation from abandoned wells. The principal dangers of an abandoned well are that it may transfer surface or near - surface contamination through the well bore or through the unsealed annular space between the casing and hole or between two casings or from a contaminated aquifer to an uncontaminated aquifer. Many abandoned wells are buried below the ground surface and may transfer contamination directly into the groundwater. Groundwater normally moves very slowly, from a few feet to tens of feet per year, and in the process is filtered and cleaned up or attenuated before it moves into the lower water - bearing zones. An abandoned well will cause the natural clean -up process to be circumvented and transfers large 'mounts of contaminated water to be concentrated at one point. The ability of a well to transfer large amounts of water back into the ground- water system has been documented on many occasions. Such an example occurred a number of years ago when a recharge well in the Twin Cities was used to dis- pose of storm water before the practice was halted by the state. The well drained a storm sewer holding pond into the underlying groundwater at the rate of 2,000 gallons per minute. The well was reported to be completed in the highly fractured Shakopee limestone, a formation known to yield and accept large volumes of water. A summary of the types of abandoned or unsafe wells that may transfer contami- nation into the groundwater may be classified as follows: (1) buried wells in which contamination may enter the well through the buried top of the casing; (2) wells in which the casing has been corroded and surface or near - surface water may run into the well; (3) improperly constructed wells in which the annular space around the outside of the casing is not sealed and acts as a channel; (4) improperly constructed wells in which an unsealed inner casing allows the transfer of water between formations; (6) open hole wells in which the borehole interconnects aquifers. -2- Priorities for Sealing Abandoned Wells The abandoned well program has been one of the target projects for extra effort by the Minnesota Department of Health because of the recognition of the importance in protecting groundwater. Recognizing that a large number of abandoned wells exist with varing hazards, an abandonment priority has been developed: 1. Abandoned wells located in areas of major pollutant discharge or where wells intercept contamination plumes include wells located near spills of industrial chemicals or petroleum products, waste sites, processing facilities and landfills. 2. Developments with private wells annexed by and connected to municipal water systems. A cross - connection hazard exists between the water systems. 3. Demolition, rehabilitation or construction areas or where there are problems of scheduling proper sealing while access is available. 4. Wells improperly constructed, located or maintained. Wells with faulty seals or casings, multi- aquifer wells, "recharge" or disposal wells, wells near contamination sources such as septic systems. 5. Wells in geologically sensitive areas, wells completed in or through carbonates (limestone). 6. All other abandoned wells. Sealing Procedures Seal ing•of.abandoned wells may be classified as temporary or permanent. A temporary seal or temporary removal of a well from service requires written approval from the Minnesota Department of Health. In addition to placing a watertight cap or cover on the casing, the well must be maintained so that it is not a source or channel of contamination when not in service. A permanently abandoned well requires that it be disconnected from the system and the hole completely filled. The statutory authorization for the sealing of abandoned wells is vested in Minnesota Statutes, Chapter 156A. Under this statute the Minnesota Department of Health, through the Commissioner of Health, has been granted strong regulatory power. The Commissioner may order the owner of a well to take remedial measures including making repairs, reconstruction or sealing of a well. The order may be issued if the Commissioner determines, based upon inspection of the well and site or analysis of the water. from the well, that any of the following conditions exist: 1. The well is contaminated. 2. The well has not been sealed and abandoned properly. -3- 3. The well is in such a state of disrepair that its continued existence endangers the quality of the ground water. 4. The well is located in such a place or constructed in such a manner that its continued use or existence endangers the quality of the groundwater. The law (Chapter 156A) specifies that no contractor shall drill, construct, repair or seal and abandon a water well unless in the possession of a valid license issued by the State Commissioner of Health. Location and Inspection Location of abandoned wells is the first step in proper sealing. While some wells are easily located, others may be buried or otherwise concealed. Location of abandoned wells may be through contact with the present or past owners, neighbors, or water well contractors. Regulatory officials may have information. Historic documents may be used such as aerial photo and plat maps, insurance company maps or photographs. Metal detectors may be of value in locating buried casings. The procedure for sealing abandoned wells starts with obtaining information on the well's construction and condition. This information is best obtained from water well drilling records. Historical well records are filed with the Minnesota Geological Survey. Water well records for wells drilled after 1974 may be obtained from the Minnesota Department of Health. When written water well record information is lacking, interviews with the owners or well driller may provide information. A downhole TV camera survey can provide valuable information and can also verify the current well depth, condition and construction. In specific circumstances, the Minnesota Department of Health may conduct a camera survey. After information is obtained about the well's construction, a site inspection will be necessary to ascertain the condition of the well and to note if the well is accessible, located in a pit, or buried, if the pump has been removed or if the well is currently operating. Inspection should also note if the well has been damaged or obstructed. When the well has been damaged, it is usually very expensive and time consuming to seal it. Sam lip The policy of the Minnesota Department of Health is to require water samples from abandoned wells in industrial or commercial areas or where contamination is present or suspected. The water analysis is usually tailored to the specific constituents suspected, but a complete analysis may be run where a broad range of chemicals are suspected. The owner is responsible for the cost of sealing an abandoned well including sampling costs. A complete laboratory analysis can consist of the following parameters: 1. 20 inorganic chemicals - sodium chloride, nitrate, etc. -4- 2. 10 metals - lead, mercury, etc. 3., 12 volatile non - halogenated organic chemicals, such as benzene, toluene, etc. 4. 42 volatile halogenated organic chemicals - trichloroethylene, etc. The sampling protocol is to pump the well until a water sample is obtained that is clear of debris, and sediment. Once the water is "clear" the usual procedure is to pump the well three to five times the calculated volume of water in the well bore to obtain a representative sample. The object is to purge the well of water that has been "standing" in the casing. Water samples taken for anlaysis at the Minnesota Department of Health are only taken in clean, specialized sample bottles provided by the Minnesota Department of Health laboratory. Remedial Action - Clearing the Well Sealing of abandoned wells starts with removing the pumping equipment and clearing any obstacles or debris that may have entered into the well. When the well is obstructed and pumps or other equipment have been dropped down the well, the debris will have to be removed or "fished" out before the well can be sealed. A variety of fishing tools are used to remove obstructions. Threaded taps on the end of a drill rod may be run into the hole in an attempt to screw into the top df a pump or drop pipe. Other types of equipment used are over shots. (a casing with inner teeth that is run over the obstacle to be removed , corkscrews, and spears used to hook the obstacle for removal. In some instances the driller may ,:hop or grind up the obstacle in an attempt to clear the well. Debris or other materials such as rock, sand clay, stones, wood, etc., is usually drilled -but or washed out of the hole. Fishing material out of a borehole is very difficult and the success of the operation is dependent on the experience and ability of the driller, but also somewhat subject to luck. Casing Removal Multiple strings of casing in a well increase the difficulty of sealing the well. To properly seal a well a non - grouted inner c must be: (1) removed, or (2) perforated or ripped to insure that the annular space is sealed throughout its length, or (3) in rare instances a tremie line may be installed between the casings to grout up the annular space. in older wells the rnnular space is often too small to grout by use of a tremie line between the casings. Whenever possible, the Minnesota Department of Health recommends €hat the - casings be removed. On shallower wells, particularly sartdpo #nt wells, the casing can usually be removed. 'Often the cost of casing raw- ' and its negligible salvage value will lead to leaving the casing tin place. -S- Sealing Upon clearing of the well bore, the well is ready for sealing. The preferred method of sealing is to pump neat cement through a tremie pipe from the bottom of the well to within two feet of the surface in one continuous operation. The casing should be cut off two feet below the surface and the hole backfilled with native material. Permanent sealing of an ac2i unobstructed well will usually require the simple process of removing the pumping equipment, inserting the tremie line and pumping grout into the well. Care must be taken at this time that the grout line does not become buried too deeply in the cement so that it cannot be pulled out. Usually the driller will use "feel" to determine if the grout level is rising on the tremie line, and remove one or more sections at a time, keeping the lowest section of the tremie pipe submerged in grout. Usually a tremie line of 1- or 1h -inch diameter galvanized steel or plastic pipe is used to install the grout to the bottom of the well. Larger diameter pipes may be used for larger diameter wells. Grout and sealing materials other than neat cement may be used to seal a well in some instances, but the filling material should be selected so as to restore natural conditions as nearly as possible. 1. Unconsolidated deposits such as glacial drift may be sealed with a mixture of clean sand and puddled clay or neat cement grout or concrete grout (above the static water level) to provide a permeability no greater than the natural condition. 2. Cavernous or creviced rock such as cavernous limestone, basalt, creviced granite, etc., may be sealed with alternate layers of neat cement or concrete with gravel or stone aggregrate. When alternative materials are placed in the well they shall be installed so that consideration is taken to seal the hole. For example, a large diameter well constructed through several aquifers separated by confining beds must have cement grout placed so that the confining beds are isolated or sealed off from the aquifers. Thus when large diameter wells are sealed, the filling material will be selected so that the water- bearing zones are isolated. 3. A blasted and bailel hole in which a large cavern was created may be filled with clean sand equivalent in permeability to the aquifer. The Well Code requires that concrete grout, cement grout, and bentonite must be installed through a tremie line to insure the proper placement of the grout from the bottom to the top of the well. It should be noted that a tremie line is used because it (1) insures that grout is placed in the bottom of the hole, (2) insures a proper cement /water ratio, which affects the Strength and Permeability of the grout, (3) insures that the sand and cement in a concrete mix do not segregate. -6- Zones of lost Circulation Zones of lost circulation are commonly encountered when sealing wells completed through cavernous rock. Such zones may be badly fractured rock that has large caverns or solution channels in which large volumes of grout maybe lost. The Minnesota Department of Health recommends that whenever lost circulation zones are encountered, the grout should be pumped until it is certain that cement is being lost. Grouting should then stop and the cement be allowed to set up. Generally three hours is sufficient time for the grout to set, after which grouting can be resumed. If upon resuming the grouting operation the grout continues to be lost, 3/8- to 1/2 -inch diameter "pea rock" may be inserted very judiciously from the surface in an attempt to plug the zones of lost circulation while simultaneously inserting grout through the tremie pipe. The "pea rock" is used to plug the cracks and crevices as it floats on the top of the cement and acts as a plug or restriction to the cement flow through fractures or broken rock in the zones of lost circulation. In all well abandonment operations, no matter what types of filling material are used, the top 10 feet must be sealed with cement or concrete grout. Types of Grout Grout used to seal wells may be classified as follows: 1. Neat Cement Grout - A mixture of one bag (94 pounds of Portland cement (ASTM C150 -69A)) to not more than 6 gallons of clean water. Bentonite up to 2% by weight of cement may be added to reduce shrinkage or other admix- tures (ASTM C457 -69) to reduce permeability and /or control set time below the water level in the well. It should be noted that one bag of cement to 6 gallons of water is a very fluid mixture, but the mixture will set up like concrete after it hardens. Cement grout may be used as grout for wells constructed in all geologic formations. Concrete Grout - A mixture of cement, sand and water in the proportion of one bag of Portland cement (94 pounds) (ASTM C150 -69a) and an equal volume of dry sand to not more than 5 gallons of clear water. Where large volumes are required to fill openings, gravel not larger than Is-inch diameter may be added. Concrete grout shall not be used below the water level. Concrete grout may be used in all geologic formations such as drift, sand- stone, metamorphic rock, and igneous rock but must not be placed below the water level. Heavy Drilling Fluid or Heavy Bentonite - Heavy bentonite is a mixture containing a minimum of 10% bentonite by weight added to clean water or approximately 5% bentonite added to drilling mud. The fluid must be of -7- sufficient viscosity to require a time of at least 70 seconds to discharge one quart of grout through an API (American Petroleum Institute) Marsh funnel viscometer (See picture on page C -21). This funnel can be obtained from companies that sell drilling muds or from petroleum drilling supply dealers. Heavy drilling fluid or heavy bentonite may be used as grout for glacial drift formations comprised of sands, clays, tills, etc. Grout Pump and Grouting Procedures Grout is inserted under pressure by means of a grout pump. These pumps are typically screw, rotor, piston, or diaphram -type pumps usually run by a gas engine or an air compressor. A Moyno pump is typical of the screw -type pump. Other common types are the Wilden diaphram and piston pumps typically called "contractor's" pumps. a pumps are usually capable of developing 100 -125 psi or greater pressure. Aii pumps will clog with aggregate or bad cement. To avoid this problem contractors will usually screen the cement before it is run through the pump. Pumps will not allow large -sized aggregate to pass through. A diaphram pump will usually allow aggregate not larger than one -third the throat size to pass. The throats are usually 1/4- to 3/8 -inch in diameter. Particles larger than sand size will often clog typical pumps. Licensed water well contractors seldom use the drilling equipment mud pump for grouting with cement because of the difficulty in cleaning and fear of clogging the mud pump. A separate pump is generally dedicated for grouting use. Abandoned Well Report The final step in sealing an abandoned well is the submission of an abandoned well report by the licensed water well contractor. The report is the official documentation that the well has been sealed and no longer constitutes a real or potential pathway for contamination to enter the groundwater. The abandoned well report should be reported to the Minnesota Department of Health on a water well Work Copy (the water well form that does not have a" Unique Well Number printed on the upper righthand corner). The information given should include all data that is known about the well including such information as depth, diameter, static water level, casing schedule,, geology, method of sealing, volume and type of grout used. -13- TABLE 1 CAPACITIES OF - Vff CASING Cubic Yard of Diameter of Gallons Per Sacks of Cement Linear Feet Per Grout To Fill Holes - Inches Linear Foot Per Linear Foot Sack of Cement 100' of Hole 14" 0.064 0.007 137.8 .03 2" 0.163 0.020 50.2 .08 3" 0.367 0.031 32.1 .18 4" 0.653 0.079 12.6 .32 5" 1.020 0.124 8.0 .50 6" 1.468 0.178 5.6 .73 8" 2.611 0.337 3.2 1.3 10" 4.080 0.496 2.0 2.0 12" 5.875 0.714 1.4 2.9. 14" 7.996 .972 1.03 4.0 16" 10.448 1.270 0.78 5.2 18" 13.219 1.606 0.62 6.5 20" 16.320 1.983 0.50 8.1 24" 23.501 2.856 0.36 11.6 30 36.720 4.462 0.22 18.2 36 52.877 6.426 0.15 26.2 *One sack cement 1.1 foot TABLE 2 Typical Quantity of Grout Found Necessary to Fill Wells in the Seven County Metropolitan Area Wells Completed in Volume (Does not include blasted Geologic Formation and bailed sections of wells.) Drift 1 x Calculated Borehole Volume x Depth Platteville Limestone 3 x Calculated Borehole Volume x Depth St. Peter Sandstone 1.2 to 1.3 x Calculated Borehole Volume x Depth Shakopee Dolomite 2.5 x Calculated Borehole Volume x Depth Jordan Sandstone 1.2 x Calculated Borehole Volume x Depth Useful Formula o Gallons per 100' - 4.08 x (Inside Hole or Casing Diameter) o Cubic feet of grout per 100 feet - .55 x (Inside Hole or Casing Diameter)2 o 7.48 gallons - 1 cubic foot o 202.0 gallons - 1 cubic yard _S_