Well Construction and Compliance
Well Construction and Compliance
This domain tests how Oregon well constructors build wells that protect groundwater and meet OAR Chapter 690, Division 200 standards. Expect questions on casing, annular seals, grouting, wellhead protection, screens, and abandonment-plus how those choices appear in compliance documents.
Core standards
- Casing must be sound, watertight, and extend above finished grade so surface water cannot enter; the wellhead must be capped and protected from flooding and tampering.
- The annular space between the borehole and casing must be sealed with approved grout, usually from the bottom up, to isolate aquifers and prevent surface contamination. Shallow unconfined sand/gravel wells need a seal that extends below the uppermost confining layer where present.
- Screens and gravel packs must match formation grain size; oversized openings cause sand production, undersized openings reduce yield.
- Abandonment requires filling or grouting the borehole so it cannot transmit water between aquifers, and reporting it to OWRD.
Worked example
A well uses 6-inch casing in a 10-inch borehole, with an 80-foot annular seal. Ignoring washouts, annular volume = π/4 × [(10/12)^2 − (6/12)^2] × 80 = 0.349 ft² × 80 = 27.9 ft³. Add 10–15% for irregular borehole and lost grout: about 31–32 ft³. Ordering grout by casing volume alone would under-grout the seal.
Traps
Using casing diameter instead of borehole diameter; failing to document grout depth and method on the well report; leaving casing too low in a flood-prone area; and assuming a bentonite chip seal is equal to a pumped grout seal.