Domestic Well Too Close to Septic System With Incomplete Annular Seal
A driller completes a 6-inch PVC domestic well on a 0.4-acre lot. Total depth is 140 ft, static water level is 25 ft, and the pump is set at 130 ft. The surface casing is 20 ft of PVC, and the annular space was grouted only from 0 to 10 ft because the hole caved below that point. The homeowner's septic tank is 35 ft from the well, and the drainfield is 80 ft away. The property line is 12 ft from the casing. The client wants 15 gpm for household use and a small garden. The driller has not filed the well report or attached the well identification tag, and the county sanitarian has not inspected the site. The driller asks whether the well can be accepted as-is and what must happen before the pump is started.
1. Evaluate the setback and casing/grout compliance issues. What are the driller's realistic options before completing the well?
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The setbacks are a problem. Using Oregon's typical separation standards, a well should be at least 50 ft from a septic tank and 100 ft from a drainfield; this well is 35 ft from the tank and 80 ft from the drainfield. The 12-ft property-line distance may also violate local setback rules. The driller should not pump the well and call it complete. Options are to relocate the well, relocate the septic components, or seek a variance from the local health authority or OWRD if the rules allow one. The annular seal is also inadequate: 20 ft of surface casing may be too shallow in caved material, and grout only to 10 ft leaves a vertical pathway behind the casing. The driller should ream or wash the annular space and place a continuous grout seal from the casing shoe to land surface, using a tremie or pressure grouting if needed. If the hole cannot be sealed, the well should not be accepted.
2. The driller proposes to grout only the top 10 ft and rely on a clay layer at 30 ft as a natural seal. Is that acceptable? Explain.
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No. A clay layer is not a substitute for a properly placed annular seal. The grout must be continuous around the casing and must prevent water and contaminants from moving vertically along the borehole. Relying on a clay layer assumes the clay is intact, laterally continuous, and unaffected by drilling, which the driller cannot verify from this information. The top 10 ft of grout also does not protect the casing shoe or the space below it. If caving prevented grout from reaching the shoe, the driller should treat that as a construction defect: ream the hole, use a larger diameter or temporary casing, and pressure-grout the annulus. The well report should show the actual grout depth and any corrective work, not an assumed seal.
3. What reporting and tag actions are required, and what are the consequences of starting the pump before the compliance issues are resolved?
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The driller must file the well report within the required period after completion and attach the well identification tag to the well. Starting the pump before the annular seal is corrected risks damaging the seal, washing out grout, and creating a contamination pathway. It also makes the as-built report inaccurate if the driller records a completed well that is not actually compliant. The driller should stop, correct the seal, document the grout placement, attach the tag, and file a truthful report showing the final casing depth, grout interval, static water level, and any variance or relocation. If the setback cannot be resolved, the well may need to be decommissioned by a licensed driller and a new well drilled at a compliant location.