Cross-connection control

All wells discharging to sources of contamination, such as livestock watering tanks, must be provided with an approved backflow prevention device or an airgap to prevent the backflow or siphonage of contaminants into the well. The airgap should provide a minimum vertical distance between the potable water pipe outlet and the water surface of not less than twice the diameter of the outlet pipe. Greater distances are preferable. Overflow lines from stock watering tanks or other sources of contamination may not discharge to the well. Please consult the North Dakota state plumbing code for details. APPENDIX I. WELL DISINFECTION. A. General. Immediately after construction or repair, always disinfect with a strong chlorine solution of fifty to one hundred milligrams per liter. Materials used in construction or repair of a well are contaminated with dirt and bacteria and the water from a well is considered safe to drink only when laboratory tests show that no harmful bacteria are present. B. Procedure. 1. Determine the amount of water in the well by referring to the table. 2. Add the amount of chlorine compound necessary to give a dosage of fifty milligrams per liter as indicated on the table, into the opening between the casing and the drop pipe. On new well construction, the chlorine should be added just before installation of the pumping equipment. a. Chlorine tablets may be dropped in the top of the well and allowed to settle to the bottom. b. Deep wells with high water levels may require that chlorine solutions be added through a hose inserted down the well casing to ensure proper diffusion of the chlorine. Chlorine can destroy only the bacteria with which it comes in contact. Agitation of the water in the well may be required to assure thorough mixing. After adding the chlorine, start the pump and operate until the odor of chlorine is detected at the pump discharge. 3. The storage and distribution system should be disinfected along with the well. Open the house faucets and let the water run until the odor of chlorine is apparent. 4. Allow the chlorine solution to remain in the well and distribution system for a period of twenty-four hours. Pump the well and flush the distribution system to remove all traces of chlorine. 5. After pumping, collect a water sample and submit to a laboratory for a bacteriological analysis to assure the safety of the water supply. If contamination is shown to be still present in the water supply, the chlorination procedure should be repeated. 6. When time does not permit well disinfection by the procedure previously described, apply to the entire depth of the well a total volume of 50 mg/l chlorine solution at least four times greater than the volume of water in the well. Allow the chlorine solution to remain in the well for a period of at least two hours. Pump the well and flush the distribution system to remove all traces of chlorine. QUANTITY OF DISINFECTANT REQUIRED TO GIVE A DOSE OF 50 MILLIGRAMS PER LITER CHLORINE Diameter of Well, Spring, or Pipe, in Inches Gallons of Water Per Foot of Water Depth Ounces of Disinfectant Per 10-Ft. Depth of Water 65% Calcium Hypochlorite 5 1/4% Sodium Hypochlorite* 2 0.16 0.02 0.21 3 0.37 0.04 0.47 4 0.65 0.07 0.83 5 1.00 0.10 1.30 6 1.47 0.15 1.87 8 2.61 0.27 3.32 10 4.08 0.31 5.19 12 5.88 0.60 7.47 18 13.22 1.36 16.80 24 23.50 2.41 29.87 36 52.88 5.43 67.20 48 94.01 9.65 119.47 *Sodium Hypochlorite, also known as Bleach, Clorox, etc., can be purchased at most drug and grocery stores. One heaping tablespoon of 65% calcium hypochlorite = approximately 1/2 oz. Six (6) 65% calcium hypochlorite tablets = approximately 1 oz. Heavy concentrations of chlorine on or near the well screen with waters very high in iron and/or iron bacteria may result in oxidation of iron on the well screen. Efficiency of the well screen and well output could be reduced under such conditions. II. LABORATORY SERVICE. Chemical and microbiological laboratory service is provided by the department of environmental quality laboratory located at 1205 Avenue A West, Bismarck, North Dakota. Mailing address is: Department of Environmental Quality Division of Laboratory Services P.O. Box 937 Bismarck, ND 58502 Microbiological laboratory service is available from: First District Health Unit 801 11th Avenue SW P.O. Box 1268 Minot, ND 58702-1268 Southwestern District Health Unit 2869 Third Avenue West Dickinson, ND 58601 Fargo Cass Public Health Environmental Laboratory 435 14th Avenue South Fargo, ND 58103 Grand Forks Environmental Laboratory 503 South Fourth Street Grand Forks, ND 58201 III. RECOMMENDED PROCEDURES. A. Plumbness and Alignment. Every public water well, before being officially accepted, should be tested for plumbness and alignment. The test method to be followed should be clearly stated in the specifications. As a minimum, a forty-foot [12.19-meter] section of pipe, or rigid dummy of the same length, having an outside diameter not more than one-half inch [12.7 millimeters] smaller than the diameter of the casing or hole being tested, shall move freely throughout the length of the casing or hole to the lowest anticipated pump setting. The well should not vary from the vertical in excess of two-thirds of the smallest inside diameter of that part of the well being tested, per one hundred feet [30.48 meters] of depth. B. Abandoned Wells. For detailed procedures for abandoning wells, see Section A1-13, Sealing Abandoned Wells, AWWA Standards for Deep Wells, A100-66 or later amendments prepared by the American Water Works Association and the National Water Well Association. C. Springs. Springs should be considered as a water supply only when it is not possible to develop an acceptable well. Springs shall be protected from entry of surface water and should be housed in a permanent structure. Continuous chlorination of springs is recommended to assure the bacterial purity of the water supply. D. Continuous Chlorination of Public Well Water Supplies. Continuous chlorination is recommended for the safeguarding of public well water supplies. Chlorination not only assists in maintaining the bacterial purity of the water, but also eliminates the growth of taste-and-odor-producing nuisance organisms. E. Livestock Wells. A check valve on the pump discharge line is not required on nonpressurized wells for livestock use that would be damaged by freezing. The pump discharge line shall have a minimum airgap equal to twice the effective diameter of the discharge line to prevent backflow or siphonage into the well to prevent contamination of the well. IV. MEASUREMENT OF WATER WELL DRAWDOWN AND SPECIFIC CAPACITY. Pumping tests of water supply wells can serve many purposes. Properly planned and conducted tests will reveal information about the performance and efficiency of the well being pumped. In addition, from the data obtained, calculations can be made which interpret ground water aquifer performance. Measuring each well for pump and well yield, depth to water level, drawdown, and specific capacity should be done on a routine basis. These test results should be compared with previous tests to estimate current well and/or aquifer conditions. A. Terminology. It is important to understand the meaning of the terms used relating to the pumping test. Some of these terms are as follows: 1. Static Water Level. This is the level at which water stands in the well when no water is being pumped. It is generally expressed as the distance in feet from the ground surface to the water level in the well. 2. Pumping Level. This is the level at which water stands in the well when pumping is in progress. The pumping level may also be referred to as the dynamic water level. 3. Drawdown. When a well is pumped, the water level in the vicinity of the well will be lowered. Drawdown is the difference, measured in feet, between the static water level and the pumping level. 4. Well Yield. The well yield is the volume of water per unit of time discharged from a well either by pumping or by free flow. 5. Specific Capacity. Specific capacity of the well is its yield per unit of drawdown, usually expressed as gallons per minute (gpm) per foot of drawdown. B. Determination of Depth to Water Level. 1. Wetted Tape Method. The wetted tape method will accurately measure the depth to water in a well and can be used for depths up to one hundred feet [30.5 meters] or more. Attach a lead weight to the end of a steel measuring tape, if needed. Wipe dry the lower three or four feet [.91 or 1.22 meters] of the tape and coat with carpenter's chalk. Lower the tape into the well through the air vent or other opening until part of the chalked section is below water. Continue to lower the tape until the next even foot mark can be held exactly at a reference point and record the number of feet indicated. The tape is then removed from the well and note is made of the footage of chalked section washed away by the water. Subtract this reading from the reading obtained at the top reference point. The difference in these readings is the depth from the reference point to the water level. 2. Air Line Method. The air line method measures depth to water level by determining the air pressure required to push all of the water out of a submerged tube of known length. The air line consists of a one-fourth inch [6.35 millimeters] pipe, copper or plastic tubing, extending from the top of the well to a point several feet below the lowest anticipated water level. To avoid turbulence near the intake of the pump, the lower end of the air line should be at least five feet [1.52 meters] above or below the point where water enters the pump. The exact length of the air line must be known or should be measured as it is placed in the well. Make all joints airtight with white lead or piping compound. The upper end of the tube is fitted with suitable connections for an air gauge, a tire valve, and an air pump. Pump the air into the line until the gauge pressure is constant. This indicates that all of the water has been expelled from the tube. The gauge reading shows the pressure necessary to support a column of water of a height equal to the depth the tube was submerged. If the gauge indicates feet of water, then it shows directly the submerged length of the line in feet. Subtracting the submerged length from the total length of the air line gives the depth to static water level. Gauges calibrated in pounds per square inch (psi) may be converted to feet of water by multiplying by 2.31. C. Determination of Drawdown. Example: Depth to water before pumping = 100 feet Depth to water after pumping = 125 feet Drawdown = Depth after pumping - depth before pumping = 125 feet - 100 feet = 25 feet First, determine the static water level. Second, after the well has achieved a constant pumping rate or yield, measure the depth to the water level. The difference of these readings before and after pumping the well at a specific rate is measured in feet and recorded as feet of drawdown. D. Determination of Specific Capacity. Example: Yield of well = 160 gpm Drawdown = 20 feet Specific capacity = 160/20 = 8 gpm per foot of drawdown Specific capacity is calculated by dividing the yield of the well in gallons per minute by the drawdown. Both measurements shall be taken at the same time. E. Interpretation of Water Well Problems. With proper records of water well tests, well problems can be interpreted. Some rules to follow are: 1. If the output of the well (gpm) drops, the drawdown decreases, and the specific capacity remains the same, the problem is most likely the pump. 2. If the output of the well (gpm) drops, the static water level remains the same, the drawdown increases and the specific capacity decreases, the well may be plugging. Acid clean the well when the specific capacity drops about twenty-five percent. 3. If the output of the well (gpm) drops and the static water level is declining, the aquifer may be depleting. V. GENERAL POLICY - GEOTHERMAL ENERGY. Geothermal energy is the renewable thermal energy of the earth or ground water. Using this form of energy for heating and cooling purposes has become increasingly popular for both commercial and residential purposes. Geothermal regulations are administered by the North Dakota Geological Survey, and require a permit from the State Geologist prior to the installation of a geothermal system. All construction of geothermal energy systems must comply with the rules contained in chapter 43-02-07, Geothermal Energy Production. These regulations cover both vertical-loop and horizontal-loop systems. Installers should contact the North Dakota Geological Survey for more information regarding installation of geothermal energy systems. Because of the potential for contamination of drinking water systems and aquifers, and the pollution of surface waters, the department provides the following guidance for users of geothermal energy. This policy relates primarily to private individual systems. Commercial and industrial projects should be constructed only after consultation with the department regarding water supply and disposal requirements and the North Dakota Geological Survey regarding construction permitting requirements. 1. The department encourages the conservation of ground water resources, therefore, closed-loop geothermal systems are recommended. Closed-loop systems also have fewer maintenance problems. If an open-loop system is constructed, whenever possible, the water should be reinjected into the supply aquifer or used for other beneficial purposes such as irrigation or stock watering. 2. Users of open-loop geothermal energy systems must be aware of the scale-forming or corrosive nature of some of the highly mineralized water in North Dakota. Some ground water supplies may require treatment prior to use, or serious problems with operation of the heat exchange system can develop. Chemicals used for cleaning the heat exchange system, and the material removed through cleaning, may not be suitable for discharge to the storm sewer system. Problems with the development of scale will often reduce the volume of water that can be disposed into injection wells. 3. All supply and disposal wells shall be constructed to comply with department rules, chapter 33-18-01, "Water Well Construction and Water Well Pump Installation". The geothermal system should be constructed to eliminate all sources of contamination to the water supply system and the ground water aquifer. 4. If municipal water supply systems are to be used as a source of geothermal energy, an approved backflow prevention device shall be used to separate the geothermal energy from the public water supply system. 5. To protect the drinking water supply, heat exchangers, unless otherwise permitted under the North Dakota state plumbing code, shall be of double-wall construction with a space between the two walls which is vented to the atmosphere. 6. Geothermal energy systems shall not discharge water to either municipal drinking water or sanitary sewer systems. Discharge to the municipal drinking water system is a cross-connection and could result in chemical and/or microbiological contamination of the system. Nearly all cities in the state have sewer use ordinances specifically prohibiting the connection of clear water discharges to the sewer system. 7. Geothermal energy systems may discharge to municipal storm sewer systems with approval of the municipality, and if the discharge water is compatible with the waters of the receiving stream. Degradation of surface waters by discharges from geothermal energy systems will not be allowed. 8. If water is to be reinjected into the ground water system, the discharge should be made to a similar or inferior quality aquifer. 9. Highly mineralized or saline waters, such as from the Dakota formation, should be returned to those aquifers if secondary use is not possible. 10. Evaporation ponds, which do not discharge, may be used as a means of disposal where other methods of disposal are not feasible. 11. Disposal permits under the Underground Injection Control Program or the National Pollutant Discharge Elimination System Regulations may be required. Users of geothermal energy systems should contact the department to determine whether a permit is required for their installation. VI. ABANDONMENT OF TEST HOLES, PARTIALLY COMPLETED WELLS, AND COMPLETED WELLS. Reprinted from AWWA Standard for Water Wells, A100-84, by permission. Copyright © 1984, American Water Works Association. Section 1.1 - General The recommendations contained in this appendix pertain to wells and test holes in consolidated and unconsolidated formations. Each sealing job should be considered as an individual problem, and methods and materials should be determined only after carefully considering the objectives outlined in the standard. Section 1.2 - Wells in Unconsolidated Formations Normally, abandoned wells extending only into consolidated formations near the surface and containing water under water-table conditions can be adequately sealed by filling with concrete, grout, neat cement, clay, or clay and sand. In the event that the water-bearing formation consists of coarse gravel and producing wells are located nearby, care must be taken to select sealing materials that will not affect the producing wells. Concrete may be used if the producing wells can be shut down for a sufficient time to allow the concrete to set. Clean, disinfected sand or gravel may also be used as fill material opposite the water-bearing formation. The remainder of the well, especially the upper portion, should be filled with clay, concrete, grout, or neat cement to exclude surface water. The latter method, using clay as the upper sealing material, is especially applicable to large-diameter abandoned wells. In gravel-packed, gravel-envelope, or other wells in which coarse material has been added around the inner casing to within twenty to thirty feet [6.1 to 9.1 meters] of the surface, sealing outside the casing is very important. Sometimes this sealing may require removal of the gravel or perforation of the casing. Section 1.4 - Wells in Noncreviced Rock Formations Abandoned wells encountering noncreviced sandstone or other water-bearing consolidated formations below the surface deposits may be satisfactorily sealed by filling the entire depth with clay, provided there is no movement of water in the well. Clean sand, disinfected if other producing wells are nearby, may also be used through the sandstone up to a point ten to twenty feet [3.0 to 6.1 meters] below the bottom of the casing. The upper portion of this type of well should be filled with concrete, neat cement, grout, or clay to provide an effective seal against entrance of surface water. If there is an appreciable amount of upward flow, pressure cementing or mudding may be advisable. Section 1.5 - Multiple Aquifer Wells Some special problems may develop in sealing wells extending into more than one aquifer. These wells should be filled and sealed in such a way that exchange of water from one aquifer to another is prevented. If no appreciable movement of water is encountered, filling with concrete, neat cement, grout, or alternate layers of these materials and sand will prove satisfactory. When velocities are high, the procedures outlined in section 1.6 are recommended. If alternate concrete plugs or bridges are used, they should be placed in known nonproducing horizons or, if locations of the nonproducing horizons are not known, at frequent intervals. Sometimes when the casing is not grouted or the formation is nocaving, it may be necessary to break, slit, or perforate the casing to fill any annular space on the outside. Section 1.6 - Wells With Artesian Flow The sealing of abandoned wells that have a movement of water between aquifers or to the surface requires special attention. Frequently the movements of water may be sufficient to make sealing by gravity placement of concrete, cement grout, neat cement, clay, or sand impractical. In such flow, if preshaped or precast plugs are used, they should be several times longer than the diameter of the well, to prevent tilting. Since it is very important in wells of this type to prevent circulation between formations or loss of water to the surface or to the annular space outside the casing, it is recommended that pressure cementing, using the minimum quantity of water that will permit handling, be used. The use of wells, large stone aggregate (not more than one-third of the diameter of the hole), lead wool, steel shavings, a well packer, or a wood or cast-lead plug or bridge will be needed to restrict the flow and thereby permit the gravity placement of sealing material above the formation producing the pressure mudding instead of this process if sometimes permissible. In wells which the hydrostatic head producing flow to the surface is low, the movement of water may be arrested by extending the well casing to an elevation above the artesian-pressure surface. Previously described sealing methods suitable to the geologic conditions can then be used. Section 1.7 - Sealing Materials A number of materials that can be used for sealing wells satisfactorily, including concrete, cement grout, neat cement, clay, sand, or combinations of these materials, are mentioned in this appendix. Each material has certain characteristics and distinctive properties; therefore, one material may be especially suited for doing a particular job. The selection of the material must be based on the construction of the well, the nature of the formations penetrated, the material and equipment available, the location of the well with respect to possible sources of contamination, and the cost of doing the work. Concrete is generally used for filling the upper part of the well or water-bearing formations, for plugging short sections of casings, or for filling large-diameter wells. Its use is cheaper than neat cement or grout, and it makes a stronger plug or seal. However, concrete will not penetrate seams, crevices, or interstices. Furthermore, if not properly placed, the aggregate is likely to separate from the cement. Cement grout or neat cement and water are far superior for sealing small openings, for penetrating any annular space outside of casings, and for filling voids in the surrounding formation. When applied under pressure, they are strongly favored for sealing wells under artesian pressure or those encountering more than one aquifer. Neat cement is generally preferred to grout because it does not separate. Clay, as a heavy mud-laden or special clay fluid applied under pressure, has most of the advantages of cement grout. Its use is preferred by some competent authorities, particularly for sealing artesian wells. Others feel that it may, under some conditions, eventually be carried away into the surrounding formations. Clay in a relatively dry state, clay and sand, or sand alone may be used advantageously as sealing materials, particularly under water-table conditions where diameters are large, depths are great, formations are caving, and there is no need for achieving penetration of openings in casings, liners, or formations, or for obtaining a watertight seal at any given spot. Frequently combinations of these materials are necessary. The more expensive materials are used when strength, penetration, or watertightness are needed. The less expensive materials are used for the remainder of the well. Cement grout or neat cement is now being mixed with bentonite clays and various aggregates. Superior results and lower cost are claimed for such mixtures. ASTM STANDARD A 53* Welded and Seamless Steel Pipe Schedule 40 - Standard Weight Nominal Size (Inches) External Diameter (Inches) Internal Diameter (Inches) Wall Thickness (Inches) Weight Per Foot (lb) Plain End Threads and Couplings 1 1/4 1.660 1.380 0.140 2.27 2.28 1 1/2 1.900 1.610 0.145 2.72 2.73 2 2.375 2.067 0.154 3.65 3.68 2 1/2 2.875 2.469 0.203 5.79 5.82 3 3.500 3.068 0.216 7.58 7.62 3 1/2 4.000 3.568 0.226 9.11 9.20 4 4.500 4.026 0.237 10.79 10.89 5 5.563 5.047 0.258 14.62 14.81 6 6.625 6.065 0.280 18.97 19.18 8 8.625 7.981 0.322 28.55 29.35 10 10.750 10.020 0.365 40.48 41.85 12 12.750 12.000 0.375 49.56 51.15 14 14.000 13.250 0.375 54.57 57.00 16 16.000 15.250 0.375 62.58 65.30 18 18.000 17.250 0.375 70.59 73.00 20 20.000 19.250 0.375 78.60 81.00 22 22.000 21.000 0.500 114.81 24 24.000 23.000 0.500 125.49 26 26.000 25.000 0.500 136.17 28 28.000 27.000 0.500 146.85 30 30.000 29.000 0.500 157.53 32 32.000 31.000 0.500 168.21 34 34.000 33.000 0.500 178.89 36 36.000 35.000 0.500 189.57 ASTM STANDARD A 589* Water-Well Reamed and Drifted Pipe Nominal Size (Inches) External Diameter (Inches) Internal Diameter (Inches) Wall Thickness (Inches) Weight Per Foot (lb) Plain End Threads and Couplings 1 1/4 1.660 1.380 0.140 2.27 2.30 1 1/2 1.900 1.610 0.145 2.72 2.75 2 2.375 2.067 0.154 3.65 3.75 2 1/2 2.875 2.469 0.203 5.79 5.90 3 3.500 3.068 0.216 7.58 7.70 3 1/2 4.000 3.548 0.226 9.11 9.25 4 4.500 4.026 0.237 10.79 11.00 5 5.563 5.047 0.258 14.62 15.00 6 6.625 6.065 0.280 18.97 19.45 8 8.625 7.981 0.322 28.55 29.35 10 10.750 10.020 0.365 40.48 41.85 12 12.750 12.000 0.375 49.56 51.15 *From "1973 Annual Book of ASTM Standards"