Wednesday, January 13, 2010

Excavation

On Monday, January 4, excavation began.  We opted for a partial basement to save a little money and because rock is known to be a problem in Carlisle.  While full basements are common in this area, we figured the less digging we do, the better our chances of not running into a significant rock problem.  The plan was to dig down about nine feet for the basement area and about three feet along the perimeter of the garage and the rest of the house.  The basement/foundation walls were due to arrive on Friday, January 8 so the excavation needed to be finished by then.

Back in December, we did some test digging and ran into no rock whatsoever.  But when the lot was prepped, we ran into a rock vein at the top of the driveway.  So we had no idea what we would run into when the real digging began.  Initially, everything was going very nicely and it looked like we'd be done in no time at all.


Easy digging. (Click image for more photos.)

But then reality set in.  They started scraping against some rock on one side of the basement hole when they still had another six inches to go.  As they continued digging around the rock, the rock just got bigger and bigger until it was clear we had a problem.  Initially, they brought in a jack-hammer to try to break up the rock but that didn't work at all.  Then they brought in a small rock chipper that fits onto the little dozer.  That was making some progress, but it was painfully slow.  After exchanging the small chipper for another one, things went a little faster but still quite slow.  At this point, it was clear that the basement/foundation wall delivery would have to be postponed.  We were lucky to be able to reschedule for Tuesday, January 12 (sometimes you can't reschedule for quite some time).

Finally, they decided to bring in a big chipper than fits onto the backhoe.  This thing was impressive to watch.  It would pound away for 30 seconds or so and then boom, huge rock fragments would chip off.  They continued chipping away with this monster for the better part of a day before they got through everything.  Thankfully, it was only in one small section of the basement hole and only the last six inches or so.  I don't know what we would have done if we had run into rock like that in the first foot or so.


Lots of rock (Click image for more photos.)

Once the basement hole was dug, they dug a three-foot-deep trench around the perimeter of the garage and where the concrete slab will go.  They also started adding crushed stone everywhere as this will form the footer for the basement/foundation walls.  A french drain was also added around the basement to help prevent water from entering the basement (this provides a low-resistance path for water and guides it into a sump so that it can be pumped away).  Also, because of the cold weather, it was important to prevent the ground/crushed stone from freezing overnight, so a layer of Styrofoam insulation and a tarp was placed over the stone.  Work continued over the weekend as it was important not to postpone the delivery of the basement/foundation walls again.  When it was all done, things looked nice and "clean" - or about as clean as a big dirt hole can look anyway.


All finished (Click image for more photos.)

2 comments:

Kevin said...

Go go backhoe!

Judy said...

There are so many houses in Carlisle which have huge boulders in the basement -- essentially the houses are built around the boulders. It seems to work, as the houses I'm thinking of have been standing for over 100 years. Next time you're here, I'll show you ours.

You probably could have managed that; glad it wasn't necessary.

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