Which Idaho counties have the widest gap between shallow and deep wells?
Shoshone County has the widest spread in Idaho: the middle 80% of its wells run 22 ft to 420 ft, a 19x range from 733 records. Jerome is the most predictable at 2.4x. A median tells you the typical cost; the spread tells you the risk.
The spread between the shallow and deep end of normal, ranked by county. The spread is the risk you carry when you make an offer.
By WellDepthPublished
Why the spread matters more than the median
A median tells you what a typical well cost. The spread tells you what you are risking. Two counties can share a median and offer completely different odds, because drilling is priced per foot and nobody knows which end of the range a particular parcel sits at until the rig is running.
This ranks every county by how far its 90th-percentile well is from its 10th — the ratio between the deep end and the shallow end of normal.
| # | County | 10th–90th percentile | Spread | Median | Records |
|---|---|---|---|---|---|
| 1 | Shoshone | 22–420 ft | 19.1x | 77 ft | 733 |
| 2 | Cassia | 60–700 ft | 11.7x | 234 ft | 4,458 |
| 3 | Minidoka | 34–385 ft | 11.3x | 168 ft | 3,389 |
| 4 | Owyhee | 62–675 ft | 10.9x | 215 ft | 2,276 |
| 5 | Elmore | 58–629 ft | 10.8x | 351 ft | 3,139 |
| 6 | Washington | 33–348 ft | 10.5x | 93.5 ft | 1,970 |
| 7 | Lemhi | 30–308 ft | 10.3x | 66 ft | 2,324 |
| 8 | Boundary | 58–555 ft | 9.6x | 240.5 ft | 1,230 |
| 9 | Bonner | 57–540 ft | 9.5x | 205 ft | 7,311 |
| 10 | Caribou | 38–344 ft | 9.1x | 145 ft | 1,814 |
| 11 | Bear Lake | 46–400 ft | 8.7x | 157 ft | 889 |
| 12 | Ada | 41–353 ft | 8.6x | 119 ft | 13,720 |
| 13 | Payette | 32–275 ft | 8.6x | 83 ft | 2,803 |
| 14 | Gem | 29–241 ft | 8.3x | 85 ft | 3,398 |
| 15 | Nez Perce | 103–800 ft | 7.8x | 300 ft | 976 |
| 16 | Valley | 42–305 ft | 7.3x | 109 ft | 5,411 |
| 17 | Custer | 42–300 ft | 7.1x | 100 ft | 1,846 |
| 18 | Blaine | 40–260 ft | 6.5x | 103 ft | 2,966 |
| 19 | Twin Falls | 75–470 ft | 6.3x | 180 ft | 7,139 |
| 20 | Butte | 60–365 ft | 6.1x | 140 ft | 1,012 |
| 21 | Franklin | 73–441 ft | 6x | 201 ft | 1,087 |
| 22 | Idaho | 100–600 ft | 6x | 275 ft | 2,757 |
| 23 | Oneida | 73–420 ft | 5.8x | 213 ft | 1,239 |
| 24 | Boise | 81–460 ft | 5.7x | 226 ft | 2,137 |
| 25 | Canyon | 60–324 ft | 5.4x | 140 ft | 14,209 |
| 26 | Lewis | 125–671 ft | 5.4x | 305 ft | 399 |
| 27 | Fremont | 75–400 ft | 5.3x | 180 ft | 3,923 |
| 28 | Clark | 100–527 ft | 5.3x | 256 ft | 332 |
| 29 | Clearwater | 120–619 ft | 5.2x | 305 ft | 882 |
| 30 | Teton | 84–420 ft | 5x | 185 ft | 2,928 |
| 31 | Adams | 85–425 ft | 5x | 201 ft | 1,417 |
| 32 | Kootenai | 145–684 ft | 4.7x | 380 ft | 5,626 |
| 33 | Bannock | 80–370 ft | 4.6x | 165 ft | 3,259 |
| 34 | Camas | 75–345 ft | 4.6x | 160 ft | 690 |
| 35 | Madison | 60–275 ft | 4.6x | 98 ft | 3,044 |
| 36 | Power | 105–455 ft | 4.3x | 230 ft | 1,122 |
| 37 | Jefferson | 62–260 ft | 4.2x | 120 ft | 6,557 |
| 38 | Latah | 125–500 ft | 4x | 298 ft | 1,933 |
| 39 | Bonneville | 100–398 ft | 4x | 200 ft | 4,502 |
| 40 | Benewah | 145–526 ft | 3.6x | 301.5 ft | 1,400 |
| 41 | Bingham | 65–228 ft | 3.5x | 119 ft | 6,511 |
| 42 | Gooding | 100–300 ft | 3x | 192 ft | 2,729 |
| 43 | Lincoln | 235–591 ft | 2.5x | 345 ft | 1,030 |
| 44 | Jerome | 179–430 ft | 2.4x | 270 ft | 3,231 |
Percentiles rather than extremes: a single mistyped record would otherwise define a county's range. 141,748 records report a depth.
The widest and the narrowest
Shoshone County is the least predictable in the state. Its middle 80% of wells run 22 ft to 420 ft — a 19x spread, from 733 records. At published rates that is the difference between $800–$1,300 and $14,700–$25,200 for the same job.
Jerome County is the most predictable: 179–430 ft, a 2.4x spread. A quote there is far more likely to resemble the final bill.
Neither fact makes a parcel good or bad. They tell you how much contingency to carry, and how hard to push for a fixed-price or capped quote before you commit.
What a county figure cannot tell you
A county median describes the wells people drilled and reported, not the ground under one parcel. Groundwater varies over short distances, and these records sit on other people’s property.
Use a county figure to know which questions to ask and roughly what to budget. Use the records near a specific point to know how much that budget could move. Neither is a substitute for a written quote from a licensed Idaho driller.
Sources
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