October 20, 2026
This week’s photo is courtesy of- Roscoe Moss Company- Los Angeles, CA, USA.
Safety Focus
Part 2 of 4: Heat and Cold Stress
Yesterday set the stakes. Today is about catching trouble early, in yourself and in the hand next to you.
Cold illness. NIOSH lists the early signs of hypothermia as shivering, fatigue, loss of coordination, and confusion. Late signs include no shivering, blue skin, slowed pulse and breathing, and loss of consciousness. Because "no shivering" is on the late list, a worker who stops shivering in the cold may be getting worse, not better. Confusion is the dangerous one around a rig, because the confused worker is the last to notice it.
Cold does not need freezing temperatures to do damage. NIOSH says trench foot "can occur at temperatures as high as 60°F if the feet are constantly wet." Watch for reddened skin, numbness or tingling pain, swelling, and blisters. Chilblains come from "repeated exposure of skin to temperatures just above freezing to 60°F" and show up as redness, itching, and inflammation. Wet boots on a mud rotary job in November set up both. Frostbite gets its own two-part Health Focus on Friday and Saturday.
Heat illness. NIOSH lists heat exhaustion signs as headache, nausea, dizziness, weakness, irritability, thirst, heavy sweating, elevated body temperature, and decreased urine output. Heat stroke is the emergency: confusion or slurred speech, loss of consciousness, seizures, very high body temperature, and "hot, dry skin or profuse sweating." That last line matters. A heat stroke victim may still be sweating, so do not wait for dry skin. NIOSH’s first step is "Call 911."
Wind chill. The National Weather Service describes wind chill as how cold it feels outside, because wind pulls heat from exposed skin faster. Its chart shows how quickly skin can freeze at a given temperature and wind speed. Check it before you set up.
Key Takeaways
• A worker who stops shivering in the cold may be getting worse; no shivering is a late hypothermia sign (NIOSH).
• Trench foot can occur at up to 60°F when feet stay wet.
• A heat stroke victim may still be sweating. Confusion is the red flag; call 911.
Sources:
• NIOSH: Cold-related Illnesses
• NIOSH: Heat-related Illnesses
• National Weather Service: Wind Chill Chart
Knowledge Share
Part 2 of 4: Domain 1 Review
Formula Spotlight: Domain 1 on One Page
Formula | Gives you | Units | Watch out |
Darcy: Q = -K A (dh/dl); q = K i; v = K i / nₑ | Flow rate (Q); Darcy flux (q); average linear velocity (v) | Any consistent set (ft, day) | q is not travel speed; v needs effective porosity, nₑ |
T = K b | Transmissivity | ft²/day or gpd/ft | b is saturated thickness |
Specific capacity = Q / s | Well performance | gpm/ft | Includes well loss |
Thiem: Q = 2πT (h₂ - h₁) / ln(r₂/r₁) | T at steady state | Consistent units | Natural log; true steady state is rare |
Theis: s = (Q / 4πT) W(u); u = r²S / 4Tt | Transient drawdown | Consistent units | Do not mix gpd/ft with feet and days |
Cooper-Jacob: T = 264 Q / Δs; S = 0.3 T t₀ / r² | T and S from a semi-log plot | T gpd/ft; Q gpm; Δs ft per log cycle; t₀ days; r ft | Valid only when u is small |
Recovery: s′ = (264 Q / T) log(t/t′) | T from recovery data | Same as Cooper-Jacob; base-10 log | t = time since pumping started; t′ = time since it stopped |
Superposition | Well interference | ft | Drawdowns from separate wells add |
The math in these formulas is simple. The setup is where it goes wrong. Three traps:
• Units. Transmissivity comes in gallons per day per foot (gpd/ft) or square feet per day (ft²/day). Same quantity, different units: divide gpd/ft by 7.48 gallons per cubic foot to get ft²/day. The Theis equation needs one consistent set. The Cooper-Jacob constants, 264 and 0.3, are unit conversions built for gpd/ft, gpm, feet, and days.
• Logs. Thiem uses the natural log (ln). Cooper-Jacob and recovery use the base-10 log, because the plot is read per log cycle.
• Flux versus speed. Darcy’s law gives flux, q = Ki. Average linear velocity divides by effective porosity: v = Ki / nₑ. With an effective porosity of 0.25, water travels four times faster than the Darcy flux suggests.
One more: specific capacity describes the well, not just the aquifer, because the measured drawdown includes well loss.
What this means for your next design
• Convert every input to one unit system before you calculate.
• Know which log the formula wants.
• Do not read aquifer quality straight off a specific capacity number.
Sources:
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
Vendor Directory
Premium Vendors-
Become a Premium or Plus vendor and increase your exposure. Claim your company and upgrade or list your company at https://waterwellresource.com/become-a-listed-vendor/
Basic Vendors-
Work Hard. Work Smart. Stay Safe!
