September 22, 2026
This week’s photo is courtesy of- K.P. Ventures Drilling and Pump - Camp Verde, AZ, USA.
Safety Focus
Part 2 of 4: Confined Space Entry: Spot It
OSHA's definition of a confined space has three parts, and a space must meet all three. It is large enough to get your body into. Entry and exit are limited. And it is not designed for continuous occupancy. A pump vault meets all three. So does a water tank, a manhole, a wet well.
A permit-required confined space is the one the standard takes seriously. It is any confined space with one of four features: it contains or could contain a hazardous atmosphere; it holds material that could engulf an entrant; its walls converge inward or its floor slopes to a smaller cross-section so an entrant could be trapped; or it contains any other recognized serious hazard.
OSHA does not leave you guessing. The note to 1926.1201(a) lists pump and valve pits, sewer and utility manholes, water tanks, water mains, drilled shafts, lift stations and transformer vaults.
Recognition is not a one-time call. NIOSH investigated two deaths in a Minnesota manure pit. A 27-year-old went down to free a clogged pump, having told a coworker he had been in it before without trouble. His uncle was warned, was physically restrained, and went down ten minutes later. Both died of hydrogen sulfide. Investigators tested the pit weeks later, on a cool day, and found it clean. Safe last time is no evidence about this time.
Here is where people go wrong. Which standard applies depends on the work you are doing, not what the space is called. Construction sits at 29 CFR 1926 Subpart AA, general industry at 1910.146. Subpart AA carries three carve-outs: it does not cover work under Subpart P (Excavations), Subpart S (Underground Construction, Caissons, Cofferdams and Compressed Air), or Subpart Y (Diving). Where another OSHA standard also addresses a confined space hazard, 1926.1201(c) says comply with both. On mine property, MSHA governs. The OSHA and MSHA interagency agreement is explicit: Section 3(d) of the Mine Act defines operator to include independent contractors performing services or construction at a mine.
Under 1926.1203(a), a competent person identifies all confined spaces before work begins, and which are permit spaces. Not once somebody is standing over an open lid.
The field detail that separates knowing from doing: entry occurs the moment any part of your body breaks the plane of an opening. Leaning in to look counts.
Key Takeaways
• A confined space meets three tests: you can bodily enter it, entry and exit are limited, and it is not designed for continuous occupancy.
• A permit-required space adds at least one of four hazards, starting with an actual or potential hazardous atmosphere.
• Construction work runs under 1926 Subpart AA, general industry under 1910.146, and Subpart AA excludes work under Subparts P, S and Y. On mine property, MSHA governs.
• Entry starts the instant any part of your body breaks the plane of the opening.
Sources:
• CDC, Morbidity and Mortality Weekly Report: Fatalities Attributed to Entering Manure Waste Pits, Minnesota, 1992, with NIOSH confined space surveillance data
Knowledge Share
Part 2 of 4: Pump Test Interpretation: Understand It
A step-drawdown test pumps the well at several increasing rates, holding each for a set period and recording drawdown through each step. It tells you about the well: how drawdown grows as you push more water through it, where efficiency falls off, and what rate is reasonable for a longer test. It is a well test, not an aquifer test.
A constant-rate test pumps at one steady rate for an extended period. This is the aquifer test. The steady rate is what makes the analytical methods usable, because Theis, Cooper-Jacob and Thiem all assume constant discharge.
The normal sequence is step test first, then a rest while water levels recover, then the constant-rate test at a rate the step test says the well can hold.
An observation well gives you a known distance from the pumping well to the point of measurement, and it reads aquifer response without the pumping well's own losses mixed in. With one, both transmissivity and storativity come out of the analysis.
Placement is a judgment, and it is a trade. Too close and you pick up partial penetration effects and the pumping well's own hydraulics. Too far and the drawdown is too small to separate from natural water level noise. The right distance depends on expected transmissivity, on whether the aquifer is confined or unconfined, and on how long the test runs.
There is a catch worth naming. One observation well gives you numbers. Two or three, set on different bearings, give you something better: whether the aquifer behaves the same in every direction, and whether there is a boundary out there. A stream that recharges you, or a fault that cuts you off, shows up as a departure from the expected curve. With one observation well you cannot tell which direction it came from.
Test Design at a Glance
| Step-Drawdown Test | Constant-Rate Test |
Rate | Several increasing rates, each held for a set period | One rate, held steady throughout |
What it measures | Well performance and efficiency | Aquifer response |
Primary output | A defensible rate for the longer test | Transmissivity, plus storativity if an observation well is used |
Observation wells | Not required | At least one, at a known distance |
Order | Runs first, followed by full recovery | Runs after recovery from the step test |
What this means for your next design: Decide whether you need well performance or aquifer properties. If the answer is both, budget for a step test, a recovery period, and a constant-rate test with at least one observation well at a known distance. If all you have is the pumping well, say so in the report and label storativity as not determined rather than estimated.
Sources:
• U.S. Geological Survey: Aquifer-Test Design, Observation, and Data Analysis (TWRI 3-B1)
Recommended Print References:
• Hydraulics of Wells: American Society of Civil Engineers
• Handbook of Ground Water Development- Roscoe Moss Company
• Groundwater & Wells, Third Edition- Edited by Robert J. Sterrett, Johnson Screens
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