Open wells and “Mota layer” (foundation stratum) Pick the <em>incorrect</em> statement regarding the Mota layer and well terminology used in field practice.

Introduction / Context:In many practical hydrogeology and well-construction contexts, “Mota layer” refers to a hard, relatively impervious stratum encountered below the water table. Understanding its role helps in correct siting and sinking of open wells.

Given Data / Assumptions:

• Mota layer is hard/impervious, offering bearing support.
• Open (dug) wells are constructed to intercept water-bearing strata, not to seat screens in impervious layers.

Concept / Approach:Open wells are typically sunk through overburden until they rest on or are seated within a competent stratum for stability. Yield is obtained from surrounding permeable horizons (aquifers), not from the impervious “Mota” layer. Therefore, drilling into an impervious layer to “increase yield” is illogical.

Step-by-Step Solution:

Verification / Alternative check:Site logs show yields are associated with permeable strata (sands, gravels, fractured rock); impervious layers are used for support or act as confining beds.

Why Other Options Are Wrong:

• (a) and (e) are consistent with well-sinking practice (support/bearing).
• (c) is tautologically correct.
• (d) “None of these” is false because (b) is indeed incorrect.

Common Pitfalls:Assuming that harder strata always give more water; in fact, permeability governs yield.

Final Answer:For deep wells, a borehole is generally drilled into the Mota layer to increase yield.