IL Well Driller common mistakes
IL Well Driller · Understand the traps and how to avoid them.
Treating the Illinois minimum setback distances as one blanket number (for example, applying a single 50-foot rule to every potential contamination source) instead of recalling each source-specific distance separately.
Candidates memorize a single '50 feet from everything' figure because it appears repeatedly in study summaries, then apply it to sources that actually carry larger or differently measured requirements. The setbacks are source-specific and measured from different reference points, so a blanket figure produces wrong answers on several items.
What to do instead
Build a one-page table with a row per contamination source (sewage disposal, privies, animal pens, fuel storage, chemical storage, surface water, property lines, buildings) and a column for the required distance and the point from which it is measured. Rehearse the table until you can state each distance without cues, then practice items that mix sources so you must select the correct specific value rather than a default.
Confusing the required grout/seal annular space depth and method with the casing depth or the screen setting, so answers describe sealing the wrong interval or using the wrong material for the annular space.
Casing length, grout column, and screen interval are taught together in construction sequences, and candidates collapse them into a single 'depth' concept. The exam tests them as separate requirements, so a merged mental model yields answers that are internally consistent but wrong.
What to do instead
Draw a vertical cross-section for each common well type and label four independent dimensions: total depth, casing length, grout/seal interval, and screen/open-hole interval. For each, write the governing requirement and the acceptable materials. Then answer practice items by pointing to the specific labeled dimension before choosing an option.
Selecting a drilling method based only on formation type while ignoring the contamination risk, casing/grout requirements, and site access constraints that the method imposes.
Method selection is studied as a geology-matching exercise (sand and gravel versus bedrock, unconsolidated versus consolidated), so candidates pick the method that 'fits the material' and overlook that some methods make proper annular sealing difficult or require different equipment and space.
What to do instead
For each method (rotary, cable tool, auger, air rotary, etc.), write a short profile covering formations suited, typical depth range, casing and grout implications, and site/logistics needs. Practice scenario items by first identifying the formation, then checking the sealing and access constraints before committing to a method.
Treating well development as a single fixed step (for example, 'surging until clear') rather than selecting development intensity and endpoint based on formation, screen type, and the drilling method used.
Development is often summarized as one procedure with one stopping rule, so candidates answer items with a memorized sequence and miss that the appropriate technique and the criteria for completion vary with the well design and the damage introduced during drilling.
What to do instead
Create a matrix of development methods (surging, jetting, air lifting, overpumping, mechanical brushing) against formation and screen type, and note the acceptance criteria for each (sand content, turbidity, specific capacity stabilization). Practice items that ask what to do next given a described condition rather than what development is in general.
Describing disinfection as 'add chlorine and wait' without specifying concentration, contact time, or the requirement to disinfect before the bacteriological sample is collected.
Disinfection questions feel familiar, so candidates answer at the level of general practice and skip the numeric parameters and sequencing that the exam actually tests. They also forget that sampling too soon after chlorination produces a false result.
What to do instead
Memorize the chlorine concentration, contact time, and the required waiting period before sampling as a small set of numbers, and write the full sequence (develop, disinfect, purge, wait, sample) as an ordered list. Answer practice items by locating where in that sequence the question sits before choosing.
Answering abandonment items by describing plugging the well from the bottom up with a single material, without addressing removal of obstructions, sealing of the full interval, and the documentation/reporting obligation.
Abandonment is studied last and briefly, so it reduces to 'fill it with grout.' Candidates then miss items about wellhead removal, casing perforation or removal to ensure the seal is continuous, and the requirement to submit a record of the abandonment.
What to do instead
Write an abandonment checklist in order: remove obstructions and pumps, decide whether casing is pulled or perforated, place sealing material across the full interval with no bridging, restore the surface, and file the required record. Practice items by asking which step is missing from a described procedure.
Confusing the roles of the licensing authority, the construction code, and the local health department, and attributing a requirement to the wrong body.
The three appear together in the regulatory framework, and candidates learn 'the state requires it' without sorting which entity issues licenses, which adopts the construction code, and which issues permits or inspects locally. Items testing jurisdiction then fail.
What to do instead
Make a three-column chart (licensing body, code authority, local health department) and place each requirement, permit, inspection, and reporting duty in exactly one column. For each practice item, name the responsible entity before reading the options.
Ignoring the distinction between a well contractor's license and the individual driller's credential, and answering as though one covers the other.
Both are called 'licensing' in ordinary speech, and study material often discusses them in the same paragraph. Candidates then answer items about who may perform work, who is responsible for supervision, and what must be displayed or carried as if the two were interchangeable.
What to do instead
Write two short definitions side by side: what the contractor license authorizes and what the individual credential authorizes, including supervision and responsibility. Then answer practice items by asking 'is this about the firm or the person?' before selecting.
Designing the setback layout from the wellhead only, forgetting that some distances are measured from the property line, right-of-way, or the nearest source rather than the borehole center.
Well siting is visualized from the well, so candidates anchor every measurement at the wellhead. Items that specify a source near a property line or a road then produce answers that are off by the distance to the actual reference point.
What to do instead
For every setback in your table, add a column naming the reference point (wellhead, property line, right-of-way, source). Practice with simple sketch problems where the source sits between the well and the property line, so you must compute from the correct origin.
Answering public health protection items by naming the hazard (bacteria, nitrate, arsenic) without linking it to the specific construction or siting control that prevents it.
Health-risk topics are memorable on their own, so candidates stop at identifying the contaminant and never connect it to the annular seal, casing height above grade, backflow prevention, or setback that the question is really testing.
What to do instead
Build a hazard-to-control map: for each contaminant or risk (surface water intrusion, shallow groundwater, backflow, cross-connection, animal waste), write the construction or siting measure that addresses it. Answer practice items by naming the control, not the hazard, before reading options.