An online journal documenting the planning and building process of our modern home from start to finish. It is intended to share our experiences throughout this project with all those interested in modern design.

Geotechnical Evaluation

We received the Geotechnical Report from CVT on December 30th. Overall, it was good news to know that competent bedrock was between 12' to 17' deep. To summarize, There is about 3-4' feet of brown silty clay under the topsoil, then around 2-4' of light brown silt, then some 4-11' of orange fine graded sand, then orange/yellow/white standstone. The boring logs can be found here. Here is a map showing the clearing and the approximate boring log locations:

Recommendation is to remove the topsoil, clay, and silt and to anchor the foundation into the sandstone in areas closer to 50' from the top of the slope. Looks like we can build the house, the question is what kind of foundation will be needed.


In November, the architect asked about the subsurface condition to ensure where the house could be placed (how far away from the top of the slope) and to determine an appropriate foundation design. After asking my sister, Karen (who is a structural engineering that works on bridges out of Eau Claire, WI) what geotechnical engineering firms were located in the area that she would recommend, we contacted a few consultants. After receiving a nicely summarized proposal and having a good conversation with one of the geotechnical engineers, we decided to hire Chosen Valley Testing to do the subsurface investigation and slope stability analysis. We scheduled the drilling for December 11 and I got some plane tickets to come home for a long weekend to watch the drilling and meet the geotechnical engineer at the site.

In the week leading up to the drilling, we kept checking the weather report as snow storms and bitterly cold temperatures were forecast. On December 8 and 9, the area received over a foot of snow! My Dad hired a guy to plow the dirt access road to make sure the drill rig could make it up the hill. The plowing was to take place the day before the drilling, on the tenth. I was also flying that same day, with my flight leaving on the morning of December 10. On the way to the airport, I talked to the geotechnical engineer, Jay, and he confirmed that it wasn’t too cold to drill and as long as the road was plowed, the rig should make it up the hill. I arrived at my Mom and Dad’s place at 11:45 pm. It was -9° F. When I got in the house, I discovered my Dad wasn’t there. He had gone back out to the site to help the guy plowing the road because he blew out a hydraulic line on his bobcat and his truck had gotten stuck in the hole at the very top of the hill.

Long story short, the guy worked on plowing the road from 1:30 pm to past midnight. The next morning, the drillers showed up, put on chains, and made it up the hill no problem. That was a big relief! I think my Dad was convinced the rig wouldn’t make it. It ended up being a beautiful day. It was 5-10° the next day, but fortunately there was hardly any wind. We drilled three holes along the conceptual placement of the home. Under the topsoil, there was around two feet of dark gray clay, then around two feet of dark gray silt, then around four to ten feet of orange/yellow fine grained sand, then yellow/white sandstone. Jay said the stone looked pretty strong and his preliminary assessment was as long as the clay was removed, which we would do anyway, it should be OK. I was sure happy to hear that!