The Septic Tank

 Here is what the backyard of the house in Crofton looked like when we took possession.

Backyard from the MLS listing

Note the concrete ' pad' on the left and an old oil tank on its side beyond this. The edge of the garage is just in frame to the right. That concrete pad turned out to be the top portion of a septic tank - a fact I discovered by excavating the sewer pipe from the house and part of the perimeter of the tank. We had an initial scare when we discovered that the cast iron sewer pipe coming from the house still entered the tank. Fortunately, it carried right on out the other side and joined into plastic pipe connected to the city sewer.

The septic tank is about 6 feet by 4 feet when viewed from above. We excavated one edge to more than a foot so knew it was fairly deep,

I probably should have just lived with this tank in place and maybe used it as a base for a patio or deck. The cast iron pipe seemed to be in OK condition although various sources give its life expectancy at 50-100 years and we were at 70. Anyway... I picked up a borescope on Amazon that is a tiny camera on the end of a flexible line. I drilled a hole in the tank to put down the borescope to see if it had been decommissioned properly. I learned that it had been filled with dirt. Naively I bought a diamond concrete cutting blade for my Makita skilsaw and set to to cut and break the tank apart. The concrete turned out to be 6 inches thick and my blade that cuts maybe 2-3 inches was no match for this task. A frustrating morning of cutting and sledge hammering only opened up the much thinner top. 

Tank with broken lid and the resulting concrete bits

Ed - an elder in the church next door walked by the yard while I was hammering away and gave me the name and contact info for a couple of local guys who do excavation. After chatting with them we decided we needed to use the big excavator to get the tank out. I dug out the sewer lines and cut the cast iron near the house and the plastic just past where it joined the iron.

Before we get into the destruction, here is a nice picture of what our backyard used to look like...

What a nice green looking yard. The oil tank was emptied of its load of garbage (2 trailer loads to the dump) and then recycled. The garage is looking better with its new roof and paint.

The excavator was difficult to bring into the yard. It slid sideways off the trailer and nearly pancaked the garage. We plan to take down some fence wire on the other boundary to get it out.

Chris Vale arrived this morning at 9 and set to work turning the yard into something resembling a battle scene from the first world war. I will let the pictures speak for themselves. Chris is very very experienced having operated that machine for more than 20,000 hours over the last 20 years.

Chris Began by digging a hole into which he will put the tank once it is pulled out.

The pile will be used to level the yard so it slopes away from the house, filling a depression left by previous perimeter drain work

Next he turned to the tank and dug down 4 feet on one side. The tank did not budge.

After excavating 6 feet deep on the side toward the backhoe, Chris was able to pull the tank free. It took several goes and for a while all he accomplished was dragging the excavator across the lawn towards the tank.

The tank is free and upside down. It is six feet deep and has no concrete bottom - it was made of wood!

The tank must have been poured in two pieces because it split evenly when lifted.

One half is out and ready to bury. Chris dropped the other half a couple of times and it splashed into the water filled pit covering half the house with mud.

Overview from the back window - not much greenery left! The tank is buried in a shallow grave just behind the excavator. Note the mud splashed windows

New sewer line hooked up with flexible couplings to both the house cast iron and the plastic running to the city, which turned out to be a thinner walled pipe than modern ABS sewer pipe.

The destruction took only two hours and I spent the rest of the day installing the new sewer pipe and moving clay and rock around to fill in holes and cover the pipe. The pit where the septic tank is buried will serve as a rock pit to drain water runoff from the alley and neighboring uphill lot. I will bring in topsoil and level and seed the yard in the spring.