Abandoning a Flowing Artesian Irrigation Well with Corroded Casing
A 1950s irrigation well on a Georgia coastal plain farm is 240 ft deep with 12-inch steel casing to 65 ft and an 8-inch gravel-packed screen from 65 to 100 ft. It flows at about 40 gpm at land surface and has done so for years. The casing is corroded and the top is 18 inches below grade in a fenced equipment area. The landowner wants to abandon it because a new well is planned 200 ft away. The site is 100 ft from a drainage ditch and 300 ft from a wetland. The well penetrates an artesian sand at 180 ft. Abandonment must prevent cross-connection and uncontrolled flow; Georgia requires a licensed driller and a report.
1. Outline the abandonment procedure, including how to control the flow while placing grout and how to address the corroded casing.
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First, notify the landowner and EPD as required, confirm the well is not needed, and remove the pump, wiring, and any obstructions. Measure the depth and verify the casing condition. Because the well flows at 40 gpm, grout cannot simply be poured; install a packer or a temporary cap and use a tremie or a grout injection line to place heavy grout from the bottom upward. If the artesian head is strong, a packer set below the flowing interval can hold the grout in place until it sets, or the driller can use a pressure-grouting setup with a blowout preventer. The corroded upper casing must not be relied on as a seal; if it is perforated or holed, overdrill or clean the annulus and grout the casing-to-formation space as well, or remove the upper casing and grout the full borehole. Fill from 240 ft to land surface with a cement-bentonite or neat cement grout, then cut off the casing below grade and cap it. Verify the fill by sounding and top off if the grout settles.
2. Estimate the grout volume needed and explain what could make the actual volume much larger than the calculation.
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Using nominal diameters: 12-inch casing from 0-65 ft gives 0.785 ft² × 65 = 51 ft³; 8-inch screen from 65-100 ft gives 0.349 ft² × 35 = 12.2 ft³; assume a 10-inch open hole from 100-240 ft gives 0.545 ft² × 140 = 76.3 ft³. Total is about 140 ft³, or about 1,050 gal; at 1.18 ft³ per sack, that is roughly 118 sacks, before excess. Add 25-50 percent for the gravel pack, corrosion voids, and losses to the artesian sand, so 150-220 sacks and 1,300-1,600 gal is a realistic planning range. Actual volume can be much larger if the gravel pack is continuous and takes grout, if the corroded casing has holes that let grout escape into the formation, or if the screen interval is longer than assumed. The driller should track volume continuously and not stop merely because the calculated amount has been pumped; the acceptance criterion is grout at land surface and a verified full column.
3. What safety and regulatory issues are specific to this flowing well and its location near a ditch and wetland?
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The flowing well is a confined-space and drowning hazard; never enter the casing, and keep the area fenced and signed until abandonment is complete. The 40-gpm flow can erode the ground around the casing, undermine the pad, and carry sediment to the ditch, so divert the flow to a settling area before it reaches the drainage ditch. Grout and cement are caustic; contain returns so they do not enter the wetland, and have a spill kit on site. Because the well penetrates an artesian sand at 180 ft, a failed abandonment can create a permanent cross-connection between the artesian aquifer and shallow groundwater, so the packer and grout placement must be verified, not assumed. File the state abandonment report with the well identification, method, grout volume, and verification. Keep the new well 200 ft away from the old borehole until the old well is sealed, and check that the new well's grout program does not intersect the old gravel pack.