Information about design and construction of earth sheltered homes and a journal of my own progress

Drilling a Well

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Posted on October 2, 2014 by

The Video:

I thought this video was more interesting than some of the recent ones.  Hopefully you enjoy it also.

The Story:

I got there a bit early and got to sweeping off my newly poured concrete, but I was really doing some last minute thinking about where the well should go.  Factors to consider range from ease of hookup now, to constructing around it and eventually living with it.

The well drilling crew from Cribley Well Drilling arrived and we settled on a location they could access.  They actually wanted to put it about 10 or 15 feet out from the house, but it would have made it difficult later as I tried to get equipment and trucks around my house…  I had originally wanted it further around the side of the house (which is why the camera angle had been set up that way), but they didn’t think they could drive the truck over there because of the soft sand, and if they did, the well would have been too far from the building and in the way later.  Eventually, they agreed to get it as close as they could to the front of the house.  The main constraint was needing room for the large drill fluid recycling tank behind the well head.  The final location will end up behind a retaining wall, out of the way.

I dug to level the ground for this tank and they filled it with water from the second truck.

tri-cone-00The drill bit was a 9 inch tricone bit.  As an engineer, I have worked on computer simulations for these for my companies “oil and gas” clients, so I know that these are designed for crushing rock and stone.  As the bit turns, the three roller “cones” rotate to break-up and scrape away rock.  Water is pumped in thru the shaft, both to cool the bit and to push the debris out the hole.  You can find an animation here…  It was definitely overkill for drilling in my soft sand, but it got the job done.

They started things off without water, just to locate the hole…  But then they pulled the bit up again and added a spout collar to direct the drill fluid (water with a bit of bentonite clay mixed in) into the recycle tank.  Sand and gravel settles out in the first section of the tank and the cleaner water/clay mixture flows over to the other end of the tank where a hose sucks it back into the truck and thru the drill shaft and down into the well again.  If they didn’t recycle the water, it would take a large swimming pool worth and would make a huge mess.  Every now and then they would need to dig (or dump) the sediment out of the tank.

Versa-drill Rig

After they drill the first piece (with the bit on the end) in to the ground, it is time to add an extension to the shaft.  The $600,000 Versa-Drill rig is designed and built for streamlining this task.

It comes equipped with two hydraulically activated wrenches.  First, the one at the bottom comes out of the back of the truck to hold the lower portion of the shaft still.  The operator runs the drill backwards for a moment to loosen the end piece and then pulls back the “wrench”.

Then they raise the drill up to the top of the mast.  The rig also has a carousel with 15 extensions (capable of drilling 300 ft with what they brought, but they can bring additional shafts if necessary). The carousel rotates the next 20ft shaft section into position and the rig screws its self in loosely.  The second hydraulically operated “wrench” moves into place to hold the new shaft section still while the drill tightens into it.  Then the new shaft is moved into place above the previous piece.

The lower end is threaded in with the shaft below it held in place by the lower hydraulic wrench… and the rig can drill the next 20 ft down.  This process was repeated 20ft at a time, over and over. See the video.

On my site, it was nothing but sand for the first 116 ft.   Then they hit gravel and it made a lot of noise…  Enough to bring me out of my mobile office to see what was going on.  That layer only lasted about 4 ft and they were back to sand.  My neighbor, who lives higher on the hill, came to check it out and told us that he hit water after only 117 ft.  Actually, the same guy who drilled my well had also done the neighbors, but with an older version of the drill rig.  He said that the water table is definitely not flat.

My well didn’t reach “water bearing fines” until about 185 ft…  At nearly 16$ per ft, just for drilling, that difference adds up. The guys from Cribley joked that they wanted to drill further to help pay off their new six hundred thousand dollar rig (yes, he mentioned that price several times and that Obama was letting him write it all off in one year)…  But they stopped at 186ft.

Cleaning out the well

The Versa-Drill V-100NG drilling rig comes equipped with 500/200 air, 3×4 centrifugal mud pump, 15 rod carousel (3½” x 20″, 9GPM water injection, built in 2″ Bowie grouter, 12K winches with job booms, hose reel, and mounted on a 2014 Peterbilt 340 6×6.

 

With the water table reached, they began the process of pulling out the drill, piece by piece, back on to the carousel.  It was pretty much the inverse of the previous process, but went much more quickly.

The next step was inserting PVC casing into the well to keep it from collapsing.  The first piece, the well intake, was special with perforations to let the water in…  The rest were just 6” PVC tubes.  They glued one into the next and lowered it down, repeat.

Well Casing

Since the 6 inch tubes were dropped into a 9 inch hole, there was still some space around the outside.  Leaving this open would let sand fall down the gap and clog the well tip.  To prevent this, they inserted a flexible 1” white tube into that space.  Like before, they put down 20′ at a time and just pushed (without glue) one section into the next.  They pushed it down to just above the water bearing layer.  Actually, they did it so fast, the time-lapse camera didn’t really catch it.  Once it was ready to go, they started mixing bentonite clay into a slurry and pumping it down into the well (at 35$ per bag, you can count them in the video, I didn’t want to).  As they did so, they pulled up the white tube.  This effectively filled the gap around the pipe with clay that would hold the pipe in place without letting water flow around it or sand get down into the water bearing fines…

Mixing Bentonite slurry

Done drilling, it was time to clean up the equipment and pack up…

Overall, they ended up digging nearly 40% deeper than the 135ft that I had estimated.  That increased my cost a couple thousand dollars over the initial estimate (but they have not set the bill yet and it has been over a month). On the plus side, they estimated my well was producing about 50 gallons per minute, which is quite a bit more than the 18 g/m pump that I planned to install.  That means I will have more water than I need, which is a good thing.  Pumping well water is also much cheaper than city water.  At current electric rates, I will pay about 25¢ per 1000 gallons.  My current rate for city water/sewer is about ~8$/thousand gallons.  If we used the 400 gallons per day that the standard American family uses, the well drilling should pay itself off in a little over 5 years.  That swells to 16 years if I include paying off the septic field (which also went about 30% over budget).

 

They will send a different crew to dig a trench and run water pipes to my mechanical room.  A third crew will eventually install the pump and pressure tank after my mechanical room floor is poured. That will need to wait for spring.

The Mistakes:

I don’t know if I made any here yet.  It probably helped that I had experts do the actual work.  But if I find out about any later, I will come back and add it here.  ;^)

The only think I can think of was that after the job was over, there was a lot of bentonite laying on the ground in the area…  It holds the water well and stayed annoyingly squishy for days after the rain passed.  I knew it would be a drainage barrier, so I didn’t want to bury it in place…  Instead I decided to spread it out (with the skid-steer), thinking that might even improve the properties of my surrounding sand…  However, a little of that stuff goes a long way and even spread out, it just made the sand squishy and more difficult to deal with.  I should have just scooped it all up and saved it for later.

Pouring the Footings

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Posted on September 29, 2014 by

The Video:

The Story:

These things usually start early in the morning…  This morning, we were all ready to get these footings poured without any of the usual last minute running around.  Three concrete mixing trucks were waiting at the bottom of the drive way as a dozen guys from Dysert Concrete arrived.  The concrete pump truck arrived and while it setup, the guys were walking around and scratching their heads about my strange layout.  Some were even taking pictures with their cell phones.

I showed some of the guys where the garage formwork had been done incorrectly and they started figuring out what to do.  I was nervous because the first few guys clearly had no idea how to mount the groove form…  But then a guy showed up who clearly knew what he was doing and took over organizing that work while some of the other guys got to filling the other forms with concrete.

The concrete mixer trucks dump their concrete into the back of the pump truck.  The pump truck comes equipped with powerful pumps that can push the heavy concrete thru its 135 ft boom.  The operator has a remote control box and walks around with a few of the of the concrete guys to control the movement of the boom and the flow rate of the concrete while they guide the end of the pipe along the form. It is quite something to hear that concrete falling down thru the pipe.   For a big job like this, the pump truck really is worth the money.  The alternative would have been trying to position the mix trucks around the site and push or wheelbarrow the concrete to the inner parts of the forms…

Initially, they overfilled the forms.  The thin lap siding formwork was not strong enough and started to give way and lean out.   I guess there were not enough stakes in the soft sand to hold back that much pressure.  And after that, they filled the forms only half way and gave it some time to stiffen up a bit before coming back for a second pass.  After the forms are filled up, they simply screed them off.  It was amazing how the weight of the concrete pushed out even the 2×12 boards.

2014-09-29_Footing

Meanwhile, the larger group were still working to properly finish the groove forms for the garage.

2014-09-29_FootingsGarage

By the time the form for the garage was ready, they had already finished pouring the footings for the rest of the house.  They started by filling the perimeter of the garage footing.  They gave that a little bit of time to stiffen up because this was 18 inches thick and even more likely to blow out.  While they waited, they pushed in vertical pieces of rebar along the middle of the floor to mark the floor slope.

Eventually, they started filling up the slab area, but quickly ran out of concrete.  Another whole truck arrived and they dumped it out, but it didn’t go too far either.  Along the way, they were screeding off the surface with long poles and leveling the concrete against the side of the forms and the rebar pegs in the middle.  On the right side of the below picture, you can see the power screed that they used.

2014-09-29_FootingsGaragePour1

I noticed a slight bulge were my radiant floor pex tubes went under the concrete.  I pointed it out and they said that it must be floating up.  They said I should have tied it down every 8 inches…  I thought that they (as experienced professionals) should probably have checked that before starting.  Anyway, since we were waiting for the next concrete delivery to come anyway, they just gave the concrete a little time to stiffen and then pushed the pipe under (using long sticks) and pulled concrete (screeded) over it.  I was still very nervous that it was still too close to the surface, but they told me it would be fine.  I didn’t think until later that I could have put a piece of that 6×6 inch welded Wire reinforcement over the pex pipe to make sure that it stayed down…

Another truck load of concrete arrived and was pumped out.  This time my concern was that the 6×6 WWR (Welded Wire Reinforcement) had been stamped down too much, especially at the front of the garage.  Like the rebar, this welded wire reinforcement needs to be fully encased within the concrete to do its job.  It doesn’t do much if it is trampled down under the concrete.  I had been pestering the guys to try to pull up WWR elsewhere, and they made some halfhearted attempts upon each request, but at the front of the garage, where the slab sloped to the full 18 inches thick, it was so trampled down that I concluded it would be hopeless to ask them to pull it up…  Instead, I waited until they got the got concrete in, and then I brought over two more big pieces of WWR and laid them on top before they guys had a chance to screed things over…  Hopefully,  these additional pieces stayed within a few inches of the surface where they could do their jobs.

With only one little corner left to go, they sent the pump truck home and we waited for the last concrete mixer truck.  Most of the crew left also, except for two guys who were going to hang around and do the finish work on the slab.

2014-09-29_PowerTrowel

After the last couple yards of concrete were in place, the senior guy used a power trowel to work the surface.  The younger guy got busy working on removing the wood that held the groove form in place.  Since things were now setting up quickly, my family and I rushed to press our hands into the stiffening concrete.

They took the power trowel over the surface 4 separate times and did a pretty good job there and on visible edges of the slab.

All in all, the footings and garage floor took 78 yards of concrete.  The guys put down about 1300 lbs of rebar in the footings and I added another 530 lbs in the slab floor.  That is just shy of a full ton, not including the fourteen 16×8 sheets of 6×6” WWR.

They came back the next day to remove the forms and cut grooves in the concrete…  However, they didn’t want to cut up in the area where the radiant pex tubing had floated near the surface.

Mistakes:

On the whole, the footings turned out pretty well, and I appreciate that Dysert concrete was even willing to take on this job (many other companies didn’t even call me back after seeing the plans).

However, as a first time General Contractor, I made some mistakes here (just like every other phase of construction).

  • I should have checked those forms better. As the rule of thumb goes, “put as many stakes as you think you need, and then add a couple more.”   We didn’t have enough stakes in many places, especially on the bedroom side where the sand is softest.  The bulges are a bit ugly, and they wasted concrete (more volume than needed).  In one spot where the form leaned out, it actually affected the surface level of the footing and may give me a bit of a headache later…  Oh well, at least these footings will be buried and never seen again.  They don’t need to be pretty to do their jobs well.
  • I did ask one or two guys if the pex tube that I placed looked right, and they just gave me a nod and a grunt… I should have got someone to check my work more closely.  Then they would have seen my mistake (not tying them often enough).  Things would have been more secure and I could have properly cut the slab to prevent cracks…  As it is, I have 3 long (thin) cracks across the uncut portion of my slab…
  • I should have complained about the level for the grove form.  I saw that the east side sagged a bit in the middle, but I thought it would float up or be taken care of some other way…  I didn’t say anything and now I need to deal with water pooling in that area.  It won’t matter when I am finished the Quonset and grout the groove, but in the meantime, it is annoying.  If that water freezes, it could cause damage.  It could also rust the bottom of the Quonset steel before it is grouted…

 

Generally speaking, you need to speak up about concerns and get them addressed before the concrete gets poured… It is too easy to get swept up in the frenzy when there are so many things happening on the site.

Prepping the garage slab

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Posted on September 27, 2014 by

The Video:

My time-lapse camera is pretty basic and has a manual focus.  I had it set to 8ft instead of ∞.  Easy mistake ;^).  But here is the slightly out of focus video anyway.

The Story:

I was not able to be on site when the crew setup the formwork and rebar for the garage slab.  When I did see it, I realized it would need to be redone.  Engineering had been done by 2 different engineers…  The first was the engineer that I had hired to do the entire project.  He specified rebar every 24 inches across the slab.  The engineer from SteelMaster specified 6×6 WWR (welded wire reinforcement).  I decided to do both.  The guys who assembled the footings were only looking at one of the drawings, so they just put down the WWR. In addition to adding rebar, I wanted to add a vapor barrier, rigid insulation and radiant floor pex also…

First, I waited for the plumbers to come and do their work roughing in the garage bathroom.  While they were working, I removed the large sheets of welded wire reinforcing and bent 40 peices of repar to put into place.  After the plumbers were done their work, I tried laying it all out myself.  However, I soon realized that positioning 16×8 ft sheets of welded wire is really a two man job.  I decided to phone a friend.  Aaron was willing to give me a hand early Saturday morning.

We started by excavating away a couple inches of sand in the areas where we planned to place the rigid insulation.  At nearly 27$ per sheet, I didn’t want to insulate the whole slab, but I did want warmer feet in the bathroom and workshop areas.

We cut and laid the insulation carefully around the plumbing for the bathroom. And then in an “L” shape where my workbench would be…

Then we unrolled a 20ft wide sheet of 6mil poly to use as a vapor barrier under the slab and under the footing all the way around.  Here, we are lifting the rebar in the footing to get the plastic underneath it.

The poly sheet was 20’ wide, so we had to do this in two overlapping pieces… Which Aaron taped together.

Initially, we had rebar chairs down the middle, but they were too tall so we had to remove them later.

I measured out and marked the 24 inch intervals for the rebar using surveyors paint.

Then we laid the rebar, using small bits of insulation as spacers.  We put the 6×6 WWR on top of that.

Lastly, I brought out some pex pipe for future radiant floor heating…  The pex was much longer than I needed for the bathroom, so I made a last minute decision to swing a loop out past my workbench…  I secured it to the Welded Wire Reinforcement ever few feet.

The last thing that needed fixing was the wooden board that had been put in place as a keyway for the quonset hut.  It had been installed too shallow and had been put in the wrong place (even though I had clearly marked where it should go).  We decided to let the experts fix that mistake on the day of the pour.

The Mistakes

  • Perhaps I should have excavated a bit more before placing the rigid insulation. It seemed OK at the time, but after adding spacers, rebar, WWR and radiant tubing, I wished I had it an inch deeper.
  • I may regret adding the pex loop thru the shop… It may end up making it difficult for me to heat that bathroom adequately without also wasting heat in the shop.
  • I only tied off the pex every few feet. But later, when we added the concrete, many sections floated to the surface.  The crew pushed it back down again, but then later they didn’t want to cross cut the back half of the shop.  Of course, cracks formed along  where the PEX tube was too close to the surface.
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