Well Drilling (C-57) · Lesson 4 of 6

Wellhead Pad and Surface Seal: Sizing the Base and Sealing Openings

"Wellhead Pad and Surface Seal: Sizing the Base and Sealing Openings" is lesson 4 of 6 in the Well Drilling (C-57) Learning Hub. It opens with "Why the Wellhead Is Regulated" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. Why the Wellhead Is Regulated
  2. Seal Every Opening
  3. The Concrete Base
  4. Pitless Adapters, Vaults, and Enclosures
  5. Backflow, Blowoff, and Air Vents

The worked example in the course applies this lesson to a realistic job in 7 steps, starting with "Check the details. Slope the top away from the casing, and pour the pad before the cement seal sets so the contact is watertight".

What you'll be able to do

  • Explain the main idea of "Wellhead Pad and Surface Seal: Sizing the Base and Sealing Openings" in plain language you can use on the exam.
  • Apply this step with confidence: "The Concrete Base".
  • Apply this step with confidence: "Pitless Adapters, Vaults, and Enclosures".
  • Apply this step with confidence: "Backflow, Blowoff, and Air Vents".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Wellhead Pad and Surface SealSoilWatertight cap,removable plugVent: down-turned,screened U-bend4 in minslopes awayAnnular seal;pour pad beforeit sets2 ft2 ft10.6 inPad 4.89 ft minimum each wayWORKED EXAMPLE: 10.625-IN BORINGBoring = 10.625 / 12 = 0.885 ftPad side = 0.885 + 2 + 2 = 4.89 ftRound up: 5 ft x 5 ft, 4 in thick4 in = 0.3333 ftVolume = 5 x 5 x 0.3333 = 8.33 cu ft8.33 / 27 = 0.31 cu ydPitless monument pad (freezing areas):3 ft x 3 ft x 4 in = 3.0 cu ft3.0 / 27 = 0.11 cu ydTop of pad slopes away from the casingPad: 5 ft x 5 ft x 4 in, about 0.31 cu yd of concretePour before the seal sets; contact must be watertightSource: DWR Well Standards (Bulletin 74-90/74-81), Part II, Sec. 10.A (openings, bases), 9.A.4, 8.CCC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: Why the Wellhead Is Regulated

Section 10 (Surface Construction Features) of the DWR Well Standards (Bulletin 74-81 as supplemented by Bulletin 74-90, Part II) is about keeping surface water, pollutants, and foreign matter out of the well. The top of the casing must terminate above grade and above known levels of flooding caused by drainage or runoff (Section 8.C), and surface drainage near the well must be directed away from it. Every opening at the top of the well is either capped, plugged, or screened.

Step 2: Seal Every Opening

Access openings for measuring, chlorinating, or adding gravel must have watertight caps or plugs, and all other holes, crevices, and cracks must be sealed. Air or casing vents must end above ground and above known flood levels with down-turned and screened U-bends. A sounding tube, taphole with plug, or similar access for water-level measuring devices must be fixed to the casing of all wells. A pump set directly over the casing needs a watertight gasket or a well cap, and where the pump is offset or submersible, the opening around any pipes or cables must be closed by a watertight seal or well cap. If the pump is not installed right away, a watertight cover goes on the casing.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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