The Basin is Complete

Contractor Kevin Anderson and his crew were here bright and early this morning to remove the forms from the concrete.  With that, the concrete work is officially finished.

Now it will be up to me to build the removable deck and hook up the pump and the plumbing.  But Kevin has advised me to let the concrete cure for a week before doing any work on it.

Pouring Concrete

This is the big day.  They are pouring the concrete for my catch basin.  Contractor Kevin Anderson has ordered the concrete.  The big truck on the right has the material, not yet mixed.  There are separate compartments for cement, sand, and water.  The material is mixed as it is dispensed from the truck. This avoids the ticking clock of a ready mix truck, which absolutely MUST dispense its wet concrete before it hardens.

The smaller truck on the left has brought a concrete pump.  They will use this to pump the freshly mixed wet cement to the work site in the back yard.

The concrete delivery truck is set up to dispense freshly mixed wet concrete into the pump.

Here is the hose from the pump, delivering wet concrete into the form.  Kevin makes sure that the concrete fills the space in the form, leaving no voids.

Here again, wet concrete is being pumped into the form.

Kevin finishes the top of the walls while more concrete is being pumped into the bottom area.

The finished product.  It took the crew about an hour to pour and finish the concrete.

A lot of things can go wrong when you are working with concrete.  None of them did.  I was glad to have professionals doing the work.

They used three and one half cubic yards of concrete, or about 14175 pounds.  According to my calculations the basin will displace about 175 cubic feet, or 10,472 pounds of water.  This means that it would not float.  More importantly, it should not pop out of the ground if it is empty and the surrounding ground is saturated with water.

The Forms are In Place

I have delegated the concrete work to Kevin Anderson, a contractor who has done several projects for me previously, including an addition to the house.  Kevin arrived at about 8:00 this morning to build the forms, along with two helpers.

There was a cubic yard of crushed concrete base material in the back of this truck.  Kevin and his crew covered the bottom of the hole with the base material, to a depth of six inches or so and packed it down with a tamper.  In the foreground below is the rebar that they will use to reinforce the concrete. This will have to be cut, and some of it bent into an L shape.  Then it will be placed on the bottom and inside the walls of the forms.

Cutting the plywood for the forms.  This is 3/4 inch exterior plywood.

The outside walls of the forms in place.

Rebar in place on the bottom.  The rebar is supported by bricks and tied together with stiff wire.

The completed forms.  You can't see much of it in this picture, but there is a lattice of rebar between the inner and outer walls of the forms, similar what you see on the bottom in the picture above.  There are also L shaped pieces of rebar with a vertical part inside the form and a horizontal part in the bottom.  These will help support the concrete walls against lateral pressure from the surrounding dirt.

The outer walls of the form rest on the base material at the bottom of the hole.  The inner walls are suspended from the 2 by 4s across the top, about four inches above the base material, so that the walls and the bottom will be a continuous piece of concrete.

Ready to pour!

The Hole Is Complete

The digging part of the project is finished. The hole is complete to spec: 4' wide by 15' long.  The depth goes from 4' 2.5" closest to the house to 4' 4.5" at the opposite end.

Next comes the really crucial part of the project, building the concrete basin.  I have decided to leave the basin open on the top and cover it with a removable wood deck. Maintenance will be a lot more convenient  with the top open.  

The original plan was to have a concrete top and replace the pavers above it, restoring the patio to its original appearance, and provide an access hole at the end.  The basin will be large enough that I could easily crawl through it in order to work on the pump or do any other maintenance that might be required.  But then I started thinking about what the inside of the basin will be like after it has been used for a while.  Dark and wet, with muck on the bottom and spiders and stuff throughout.  Who knows what else?  Rats, snakes?  Having it completely open at the top is much more appealing.

I have read enough about concrete work to be afraid to try it myself.  The consequences of mistakes are just too devastating.  And when have I ever done anything like this for the first time without mistakes?  So now the problem becomes finding a contractor to do the concrete work.

The Saga of the Hole Continues

After a long run of hot and rainy days, the weather is now great for digging.  I have made a lot of progress in the last few days, digging for an hour or two each day.  The digging part of the project is getting close to completion, and I am eager to start work on the concrete.

It is four feet deep and four feet wide at the end closest to the house, and 15 feet long. When finished it will be 4'x4' for the entire length. I still have to make it wider and deeper at the end away from the house.

You can get a better appreciation for the size of the hole from the pile of dirt that I have removed.

The pile got so high that it became difficult to shovel dirt onto it from the bottom of the hole.  I would toss a shovelfull of dirt up onto the pile, and it would land on the near side and slide back into the hole.  It finally occurred to me to build a ramp and use a wheel barrow to remove the dirt.

It's amazing how much you learn when you do something for the first time!