Setbacks on a Small Lot with Fractured Limestone
A proposed well for a new rural home is staked 45 feet from the existing septic tank, 90 feet from the absorption field, 120 feet from a barnyard, 25 feet from the property line, and 40 feet from a road ditch. The lot slopes toward the well from the barnyard, and a 30-foot-deep abandoned hand-dug well lies 60 feet downslope. The owner wants the well on the downhill side because the drill rig has better access there and the house is closer. The county sanitarian notes that the area has fractured limestone at 35 feet and that the neighbor's well, 150 feet away, has had coliform detections after heavy rain. The driller proposes to 'make up for it' by drilling deeper and grouting the casing to 60 feet. The owner asks whether the county can simply issue a variance because the lot is small.
1. Which proposed setbacks fail Iowa's minimum isolation distances, and can deeper drilling or a longer grout seal substitute for relocating the well? Explain the decision.
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Under Iowa's well construction rules, the minimum separation from a septic tank is generally 50 feet and from an absorption field 100 feet; barnyard and feedlot separations are at least 100 feet, with larger distances for manure storage. The 45-foot septic tank distance and the 90-foot absorption field distance fail on their face. The 120-foot barnyard distance may meet the minimum but still needs evaluation because the lot slopes toward the proposed well. The 25-foot property line and 40-foot road ditch also require checking against local right-of-way and setback requirements. Deeper drilling and a longer grout seal improve protection but do not substitute for isolation; they cannot eliminate a source pathway that is already too close. The proper fix is to relocate the well upslope, at least 50 feet from the tank, 100 feet from the absorption field and barnyard, and away from the ditch and property line. If the lot truly cannot meet the distances, a variance must be sought from the DNR with site-specific hydrogeologic justification and alternative protection; the county cannot simply waive the rule.
2. What is the source-water risk from the 30-foot abandoned well and the fractured limestone, and what should be done before the new well is approved?
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The abandoned hand-dug well is a direct vertical conduit from the surface to shallow groundwater. If it is unsealed, surface runoff, animal waste, and septic effluent can move down its open borehole and then laterally through the fractured limestone. The neighbor's post-rain coliform detections are a warning that the limestone transmits contamination rapidly rather than filtering it. Before approving the new well, the abandoned well should be located, inspected, and plugged under Iowa's abandoned well requirements: remove debris, disinfect, and place a continuous low-permeability seal from the bottom to the surface, with special attention to the water-bearing zone. Surface drainage should be diverted away from both wells, and the new well should be upslope, cased and grouted through the weathered zone, and completed with a sanitary cap. A baseline water sample for bacteria and nitrate should be collected before the well is placed in service, and the owner should be told that the fractured limestone offers little natural protection.