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Wellpoint Dewatering Radius of Influence Calculator (Sichardt)

Estimate the radius of influence for a dewatering wellpoint system using the Sichardt empirical formula.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Estimated radius of influence

295.28 ft

Low confidence

The Sichardt formula is a widely-used but approximate empirical estimate — it's most useful for early planning and tends to underestimate the true radius of influence compared to more rigorous pump-test-based methods. Verify with an observation well or pump test once dewatering begins, especially near property lines or sensitive structures.

Running these inputs gives 90 as the estimated radius of influence. Note that hydraulic conductivity (k, m/s) sits at the low end of the range this calculator was checked against, so treat the output as indicative rather than settled. Low confidence on these inputs, so use the number to plan rather than to order. Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Sichardt's empirical formula (unconfined conditions): R ≈ 3000 x s x sqrt(k), where R is the radius of influence in meters, s is the drawdown in meters, and k is the soil's hydraulic conductivity in m/s. Widely used as a first-pass planning estimate, though it's known to be approximate and typically most reliable for early-stage (first few days) dewatering planning.

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Frequently asked questions

What is 'radius of influence' used for?
It estimates how far from a dewatering well the groundwater drawdown effect extends — used to check for interference with adjacent wells, potential settlement risk to nearby structures, and whether dewatering could affect neighboring properties.
Why is this formula called a 'first-pass' estimate?
It only uses two simple parameters (drawdown and permeability) and ignores factors like aquifer boundaries, pumping duration, and recharge — real dewatering systems are typically monitored and adjusted using observation wells rather than relying on the formula alone.
Does higher permeability mean a larger or smaller radius of influence?
Larger — more permeable soil transmits the drawdown effect further from the well, which is why coarse sand/gravel sites need wider well spacing (or more wells) than silty or clayey sites for the same target drawdown.