Lakefront Lot With Two Possible Well Sites
A 1.5-acre lakefront parcel has a 1972 septic system with a 1,000-gallon tank and a drain field, an abandoned 20-foot hand-dug well at the rear of the lot, and a seasonal wetland that reaches within 30 feet of the proposed building pad. The homeowner wants a new 4-inch well for a heat pump and domestic supply. Two sites are available. Site A is a gravel driveway shoulder 52 feet from the drain field, 12 feet from the property line, and 8 feet above the wetland. Site B is a grassy area 45 feet downslope from the drain field, 60 feet from the lake, and 25 feet from the old dug well; the water table there is 8 feet deep. The local health department enforces Part 127 setbacks and requires a permit before construction. Soil logs show sandy loam to 30 feet over silty clay. The driller must pick a site, justify it, and specify how the upper 30 feet will be sealed.
1. Which site should the driller select, and what conditions could still disqualify that site? Explain using the separation distances, slope, and contamination-pathway logic.
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Site A is the better choice, but only conditionally.
Why Site B fails:
- It is 45 feet from the drain field, below the 50-foot separation the local health department is applying. That alone is a permit defect.
- It is downslope, so shallow groundwater and surface runoff move from the septic system toward the well head.
- It is only 25 feet from an abandoned hand-dug well. Old dug wells are often unsealed vertical conduits; the new well could draw water that has passed through the old well or the septic area.
- The water table is 8 feet deep, giving little unsaturated soil to filter pathogens.
Why Site A is better:
- It meets the stated 50-foot drain-field separation at 52 feet, though the margin is thin. The driller should verify the actual edge of the absorption area, not just the tank, because the setback is measured from the pollution source.
- It is 8 feet above the wetland, which reduces flooding risk, but the well still needs a raised, graded grout pad and a sanitary cap.
- The driveway shoulder creates a vehicle and spill risk. The driller should install protective bollards and divert runoff away from the casing.
The property-line distance of 12 feet is the weak point. Property-line setbacks are often set by local ordinance rather than by the health-based isolation table, so the driller must confirm the local requirement. If the local rule is 10 feet, Site A passes; if it is 25 feet, Site A fails and the driller must find a third location or seek a variance. The driller should not treat the 52-foot separation as permanent until the drain-field boundary is staked.
2. Specify the casing and annular seal for the selected site from the surface through the sandy loam and into the clay. Include depth, materials, grout placement, and verification of a continuous seal.
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The design should seal the sandy loam and seat the casing in the silty clay so that surface water cannot travel down the annulus.
Casing:
- Drill an 8-inch borehole to about 40 feet.
- Set 6-inch casing with a drive shoe to about 38 to 40 feet, at least 8 to 10 feet into the silty clay that begins at 30 feet.
- Leave the casing 18 to 24 inches above finished grade, fit a sanitary well cap, and slope the grout pad away from the casing.
Annular seal:
- Use neat cement or a high-solids bentonite grout placed by tremie from the bottom of the annular space to the surface. Do not pour grout from the top; it will bridge, dilute, and leave voids in the sandy loam.
- Use a positive-displacement grout pump and keep the tremie end submerged in grout as it is raised.
- For a 10-inch hole and 6.625-inch casing over 40 feet: annular area = 0.7854 x (10^2 - 6.625^2) = 44.1 square inches = 0.306 square feet. Volume = 0.306 x 40 = 12.2 cubic feet, or about 91 gallons. Order at least 20 percent excess, about 110 gallons, because the sandy loam may take extra grout.
Verification:
- Require grout returns at the surface before stopping.
- Compare actual volume pumped with the calculated volume; a large loss means a void or a fractured zone and must be investigated, not ignored.
- After the grout sets, top off any settlement and document the final seal. A continuous seal is demonstrated by returns, volume, and a full annular space, not by the appearance of the surface alone.
3. What must happen to the old dug well and the wetland before the new well is placed in service, and who is responsible?
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The old dug well cannot be left as-is. It is an abandoned well and a direct pathway for surface water and shallow groundwater to reach the aquifer. Under Part 127, an abandoned well must be plugged by a registered well driller using an approved method: remove the pump, piping, and debris; disinfect; fill the well from the bottom up with an impermeable material such as neat cement, sand-cement, or bentonite; and seal the top. If the old well has a casing, the casing should be removed or perforated as required so that the plug is continuous. The driller must file the required abandonment record with the state and local health department. Filling it with stones, gravel, or debris is not a plug and does not remove the pathway.
The wetland is a separate constraint. The driller should not use the wetland for drilling-fluid disposal, should divert runoff around the well pad, and should avoid disturbing the wetland without checking whether a state or local wetland permit is needed. The new well should be cased and grouted so that it does not act as a drain between the wetland and the aquifer.
Responsibility is shared: the driller is responsible for the well construction and the old-well plugging under Part 127; the homeowner is responsible for authorizing the work and protecting the site; the local health department is responsible for the permit and final approval. The new well should not be placed in service until the old well is plugged, the grout has set, disinfection is complete, and the required water samples are satisfactory.