N.M. Admin. Code § 19.27.4.30 - WELL DRILLING - NON-ARTESIAN (UNCONFINED) WELL REQUIREMENTS

A well driller shall ensure that the well drilling activities associated with the drilling of non-artesian wells are made in accordance with 19.27.4.29 NMAC and the following requirements:

A. Annular seal: All wells shall be constructed to prevent contaminants from entering the borehole from the ground surface by sealing the annular space around the outermost casing. If surface casing (outer casing) is used then there must be a seal between the surface casing and the production casing at the ground surface. When necessary, annular seals will be required to prevent inter-aquifer exchange of water, to prevent the loss of hydraulic head between hydrogeologic zones, and to prevent the flow of contaminated or low quality water. Sealing operations shall be made with an office of the state engineer approved sealant. Casings shall be centralized within the interval to be sealed so grout or sealing materials may be placed evenly around the casing.

(1) Annular space: The diameter of the borehole in which the annular seal is to be placed shall be at least four inches greater than the outside diameter of the outermost casing. The diameter of the borehole in which the annular seal is to be placed may be reduced to three inches greater than the outside diameter of the outermost casing if pressure grouting from the bottom up is used for grout placement and the well casing is centralized in the borehole. If surface casing is used, the inside diameter of the surface casing shall be at least three inches greater than the outside diameter of the production casing.

(2) Annular seal completed to ground surface: Annular seals shall extend from ground surface to at least 20 feet below ground surface.

(a) If a well is completed less than 20 feet below ground surface, the seal shall be placed from ground surface to the bottom of the blank casing used. However, if a monitoring well is completed less than 20 feet below ground surface, the seal shall be placed for the maximum length practical in order that the well is constructed to prevent contamination, to prevent inter-aquifer exchange of water, to prevent flood waters from contaminating the aquifer, and to prevent infiltration of surface water.

(b) The annular seal shall extend to ground surface unless a pitless adapter is installed. For wells completed with a pitless adapter, the top of the seal shall extend to one foot below the pitless adapter connection.

(c) All sealing materials placed deeper than 20 feet below ground surface shall be placed by tremie pipe or by pressure-grouting through the well casing and up the annulus.

(d) If in the event the water level in the annular space is less than 20 feet from surface, all sealing material shall be filled from the bottom upwards to ground surface using a tremie pipe. Time release bentonite pellets maybe used without a tremie pipe where standing water is above 20 feet.

(3) Annular seals to prevent inter-aquifer exchange of water or loss of hydraulic head between hydrogeologic units: Sufficient annular seal shall be placed to prevent inter-aquifer exchange of water and to prevent loss of hydraulic head between hydrogeologic units. Sufficient annular seal shall be placed to prevent loss of hydraulic head through the well annulus, through perforated or screened casing, or through an open bore interval.

(4) Annular seals to prevent the contamination of potable water: Wells which encounter non-potable, contaminated, or polluted water at any depth shall have the well annulus sealed and the well properly screened to prevent the commingling of the undesirable water with any potable or uncontaminated water. The use of salt-tolerant sealing materials may be required by the state engineer in wells that encounter highly mineralized water.

(5) Annular seal requirements for community water supply wells: Community water supply wells shall also be completed with annular seals in accordance with other regulatory agencies' applicable ordinances or rules. Well drillers may be subject to other applicable federal, state, or local regulations.

B. Well casing: The well casing shall have sufficient wall thickness to withstand formation and hydrostatic pressures placed on the casing during installation, well development, and well use.

C. Well plugging: A non-artesian well that is a permanently discontinued well or a well in a state of disrepair, a failed well drilling attempt, an improperly constructed or completed well, or a replaced well with a permit condition to plug shall be plugged. A well plugging plan of operations shall be approved by the state engineer prior to plugging unless the well is a replaced well with a permit condition to plug. The state engineer may require that the plugging process be witnessed by an authorized representative.

(1) Methods and materials: To plug a well, the entire well shall be filled from the bottom upwards to ground surface using a tremie pipe. The bottom of the tremie shall remain submerged in the sealant throughout the entire sealing process; other placement methods may be acceptable and approved by the state engineer. The well shall be plugged with an office of the state engineer approved sealant for use in the plugging of non-artesian wells. Wells that do not encounter a water bearing stratum shall at a minimum be plugged by filling the well with drill cuttings or clean native fill to within 10 feet of ground surface and by plugging the remaining 10 feet of the well to ground surface with a plug of the office of the state engineer approved sealant.

(2) Contamination indicated: Wells encountering contaminated water or soil may require coordination between the office of the state engineer and the New Mexico environment department (or other authorized agency or department) prior to the plugging of the well. Specialty plugging materials and plugging methods may be required.

(3) Plugging record: A well driller shall keep a record of each plugging activity as the work progresses. The well driller shall file a complete plugging record with the state engineer and the permit holder no later than 30 days after completion of the plugging. The plugging record shall be on a form prescribed by the state engineer and shall include the name and address of the well owner, the well driller's name and license number, the name of each drill rig supervisor that supervised the well plugging, the state engineer file number for the well, the location of the well (reported in latitude and longitude using a global positioning system (gps) receiver capable of five meters accuracy), the date when plugging began, the date when plugging concluded, the plugging material(s) used, the interval in which each plugging material was installed, the amount of plugging material installed, the depth of the well, the size and type of casing, the location of perforations, and any other information required by the state engineer.

Notes

N.M. Admin. Code § 19.27.4.30

19.27.4.30 NMAC - Rp, SE 66-1, Article 4-14, 8-31-2005, Adopted by New Mexico Register, Volume XXVIII, Issue 11, June 13, 2017, eff. 6/30/2017