How have we never written about this before?
We like to consider ourselves the #wellprotection people, but we know that well protection isn’t as interesting as sexy to everybody else as lets say, a new 2021 Mobiledrill B37 rig.
However, well protection is still one of the most important aspects of geotechnical drilling, and is still one of the most overlooked.
While we’re confident that we’ve engineered a superior product, and feel that we’re changing the well protection standard in the industry, we still see our products installed incorrectly from time to time.
And that’s not a bad thing – drilling and installation techniques differ all across the world. What’s the standard in Texas, USA, might be a significantly different process than a well installed in Manchester, England.
We’ll try to keep all that in mind while walking you through the correct way to install your Alucast manhole cover.
A concrete surface pad must be installed around the well at the same time as the manhole cover is being installed. The surface pad should be formed around the outer ring of the manhole cover. Concrete should be placed into the pad forms and into the borehole (on top of the grout) in one operation making a contiguous unit.
Concrete Pad Size Variations
The size of the concrete surface pad is dependent on the well casing size. If the monitoring well casing is 2 inches in diameter, the pad should be 3 feet x 3 feet x 4 inches ( varies in all countries). If the monitoring well casing is 4 inches in diameter, the pad should be 4 feet x 4 feet x 6 inches. Round concrete surface pads are also acceptable in many countries. The finished pad should be slightly sloped so that drainage will flow away from the protective casing and off of the pad. A minimum of one inch of the finished pad should be below grade to prevent washing and undermining by soil erosion.
The Monument protective casing, when positioned and grouted, should extend above the ground surface a minimum of 2.5 feet (in most countries). The outer protective casing should be of aluminum or steel construction with a hinged, locking cover.
Typically, the monument protective casings used over 2-inch monitoring well pipe are 4 inches square by 4 or 5 feet long. Similarly, protective casings used over 4-inch well casings are 6 inches square and 5 feet long.
Grout & Bentonite
Before installing the monument protective casing, the bentonite grout in the borehole should be at a depth of approximately two feet from surface. The protective casing is installed by pouring concrete into the borehole on top of the grout. The protective casing is then pushed (by hand and not your rig) into the wet concrete and borehole a minimum of 2 feet.
Have any questions about installing our manhole covers? Let us know!
As always, thanks for reading and here’s where you can stay up to date for everything related to Alucast!
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