September 9, 2026
This week’s photo is courtesy of White Mountain Operating, LLC- Pinedale, WY, USA
Safety Focus
Part 3 of 4: Manual Materials Handling: Control It
The NIOSH Lifting Equation is the federal research tool for sizing up a two-handed lifting task and redesigning it. It starts from a load constant of 51 pounds (about 23 kilograms), the most nearly all healthy workers can handle under ideal conditions. Then it shrinks that number for every bad factor, reach, low or high position, vertical travel, twisting, frequency, and poor grip, down to a Recommended Weight Limit, or RWL. It covers two-handed lifts, not carrying, one-handed, or seated work.
The check is simple. Divide the actual weight by the RWL to get the Lifting Index, or LI. NIOSH says keep the LI at or below 1.0. Above that, risk climbs. The point for the field: 50 pounds held close, at waist height, with no twist is one lift. The same 50 pounds at arm's length off the floor with a twist scores far higher on the same scale and belongs on a machine.
Control it two ways. First, fix the lift: get the load close, keep it between waist and shoulder height, turn your feet instead of twisting your spine, and clear the path before you pick it up. Second, and better, take your back out of it. Use a hoist, cathead, tugger, hand truck, cart, or forklift wherever you can.
When it has to be done by hand, make it a team lift with one person calling the move so everyone lifts and sets down together.
Key Takeaways
• The RNLE starts from a 51-pound load constant under ideal conditions, and the recommended weight drops fast for reach, height, twist, frequency, and grip.
• Keep the Lifting Index (actual weight divided by the RWL) at or below 1.0.
• Mechanical aids and team lifts beat willpower every time; get the load close and never twist your spine under it.
Sources:
• CDC / NIOSH: Revised NIOSH Lifting Equation (RWL and Lifting Index)
Knowledge Share
Part 3 of 4: Steady Rate Flow: Apply It
The real payoff of the Thiem equation is running it backward. If you pump a well at a steady rate and read the drawdown in two observation wells at known distances, you can solve for transmissivity right in the field, no lab required. Rearranged for T, it looks like this:
T = Q ln (r₂ / r₁) / [ 2 π (s₁ − s₂) ]
Here s1 and s2 are the drawdowns in the two wells. The head difference between the two points equals the difference in their drawdowns, so drawdown readings are all you need. Keep the units consistent.
A quick example. You pump at 300 gallons per minute (gpm). At 50 feet the drawdown is 8 feet; at 200 feet it is 3 feet. First, put Q in the same units: 300 gpm is about 57,750 cubic feet per day. Then ln(200 divided by 50) is ln(4), about 1.386, and the drawdown difference is 5 feet. Put it together: T equals 57,750 times 1.386, divided by (2 pi times 5). That gives T of about 2,550 square feet per day, which is roughly 19,000 gallons per day per foot. That is a workable field estimate of how well the formation moves water.
One field detail that separates knowing from doing. The two observation wells must be far enough apart to read a real difference in drawdown, and the readings should be taken after drawdown has effectively leveled off. Two wells too close together, or read too early, will hand you a number you cannot trust.
What this means for your next design:
Two observation wells and a steady pumping rate turn a pumping test into a transmissivity estimate. Build them into the test plan when the number matters.
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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