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D.C. Municipal Regulations (Last Updated: September 13, 2017) |
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Title 21. WATER AND SANITATION |
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Chapter 21-18. WELL CONSTRUCTION, MAINTENANCE, AND ABANDONMENT STANDARDS |
Section 21-1831. WELL ABANDONMENT PROCEDURES
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1831.1A person abandoning a well shall, if feasible, remove all obstructions that may interfere with the effective sealing operations by cleaning out the borehole or re-drilling.
1831.2A person abandoning a well shall remove all well upper terminus completion structures and well casing.
1831.3If the removal of the well casing or obstructions is not feasible, the following shall be performed to ensure that the well casing and annulus or voids are filled with sealing or fill materials:
(a)Rip or perforate the well casing below ground surface;
(b)Over-drill the well casing for removal; or
(c)Submit an alternate abandonment procedure to the Department for approval in accordance with §§ 1803.10 and 1803.11.
1831.4The abandoned well shall be completely filled and sealed in such a manner that vertical fluid migration within the well, including the annulus surrounding the well casing, is effectively and permanently prevented.
1831.5The following materials shall be used for filling and sealing a well for abandonment:
(a)A sodium-based bentonite slurry; or
(b)Hydrated, medium size, sodium-based bentonite chips or pellets, if:
(1)The diameter of the well casing is less than one and one-quarter inches (1.25 in.) and the well is not over-drilled for abandonment; or
(2)The well is no more than ten (10) feet below ground surface; and
(i)The terminus of the well does not intersect the water table; and
(ii)The well is sited greater than twenty-five feet (25 ft.) from the mean high watermark of a waters of the District or waters of the United States of America and twenty-five feet (25 ft.) from a wetland.
1831.6In the event the diameter of a well does not allow for a slurry mixture to be emplaced using a tremie pipe, sodium-based chips or pellets shall be used in accordance with § 1818.
1831.7Clay, silt, sand, gravel, crushed stone, and mixtures of these materials are considered fill material, and shall only be used under the following conditions:
(a)In soil borings in areas where no known or suspected, historic or current, groundwater or soil contamination exists;
(b)In a manner that shall mimic the original, stratigraphic layering of geologic units;
(c)In a manner that shall not create a conduit between aquifers;
(d)In a manner that shall not cause negative impacts to groundwater quantity or quality; and
(e)With prior written approval of the Department in accordance with §§ 1803.10 and 1803.11 or 1830.1.
1831.8A well shall be abandoned by filling it with the appropriate sealing materials introduced at the bottom of the well by using a tremie pipe and placed progressively upward to at least two feet (2 ft.) below ground surface.
1831.9The abandoned well shall be furnished with suitable materials to create a final cover similar to that of the surrounding area, such as a cold patch, or a non-coal tar based hot patch, or native soils or a combination of these materials.
1831.10All abandonment sealing material shall be placed in one continuous operation using methods that prevent free fall, bridging, dilution, or separation of aggregates from cementing materials, unless otherwise approved by the Department.
1831.11A well in a consolidated formation shall be filled by placing gravel in the water producing zones, and cement or cement-grout in accordance with § 1818.14 in the non-water producing zones to the ground surface. A suitable packer shall be placed between the gravel and the sealing material.
1831.12A well penetrating a confined and multiple aquifer formation shall be abandoned by placing sealing materials throughout the confining horizon and water producing zone(s).
1831.13In a well penetrating a consolidated formation where known contaminants exist, only cement or cement-grout in accordance with § 1818.14 shall be used to seal and abandon a well.
1831.14In a multiple aquifer well, the well shall be filled and sealed in such a way that exchange of water from one aquifer to another is prevented and all fluids are permanently confined to the specific strata in which they were first encountered.
1831.15A person abandoning a closed-loop ground source heat pump well or ground freeze well shall comply with the following procedure:
(a)Pressure test the closed-loop system including the well and header piping, to identify any leaks and isolate and seal them with high solids, low-permeability grout equal to or less than 1 x 10-7 cm/s;
(b)Capture any circulation fluids and flush the loop piping with potable water to remove all contaminants in non-leaky piping systems;
(c)Conduct a laboratory analysis of the final flush (abandonment solution) and submit the results to the Department;
(d)After pressure testing and flushing the system, fill the loops with potable water;
(e)Cut off the piping in the well at least five feet (5 ft.) below the ground surface and seal it with a permanent fusion cap;
(f)If gaps are found in the annulus grout seal during the decommissioning process, pump grout into the deficient borehole annulus in a continuous operation until undiluted grout returns to the surface;
(g)If there is visual evidence of subsidence greater than one foot (1 ft.) at a well, excavate the ground to the top of the well, and grout the open well using a tremie pipe or by surface methods consistent with the requirements of § 1818;
(h)If a previously decommissioned closed-loop ground source heat pump system is breached and no known contaminant is present, reseal the system using a permanent fusion cap; and
(i)If contaminants are known or suspected to have entered a damaged pipe, purge the pipe again, fill it with potable water, and reseal.