Soil Remediation is First Step
By Gary Niemi
As we’re on the cusp of starting site work at Cooper Elementary School, we felt that further information on the site investigations that have been done would be beneficial. The soil testing on the site consisted of 25 soil borings to determine the basic subsoil characteristics and bearing capacity.
Because a few of the results showed some softer clay, we did four consolidation tests on subsoil samples under the building footprint which were used to calculate the anticipated settlement over the life of the building. This calculated settlement was larger than acceptable.
In order to reduce the total building settlement to acceptable levels, we are excavating the topsoil and old fill that was placed on the site. We are then adding 7+ feet of sand over this area. The top of this fill will be the bottom of the floor slabs for the new building.
This work will result in the new building first floor being about three feet higher than that of the current site.
By adding this sand fill now, the clay beneath the building will have three months this winter to consolidate, which reduces the calculated settlement to acceptable levels.
An additional benefit of this compacted sand fill is that the new footings will be founded on this fill, and we will not have to overly disturb the existing clay subsoil.
Our plan to pre-consolidate the clay subsoil was the least costly method to provide an adequate foundation for the new school. Other alternatives we considered included geopiers or piling in order to provide adequate support for the building. However, those options were much more expensive to construct.
We chose this path because it works and saves referendum funds that are better spent on the educational areas of the building. The start of site preparation will begin on November 30th with this earthwork, and we will commence with building construction in April of 2017.
I encourage you to watch the video below which provides a great eye-in-the-sky view of the current school, and includes an overhead site plan for the new school. That image also appears below the video and the dotted lines show the current school’s footprint, along with the location of the new school at the northern end of the site.
We will work on the new building throughout the 2016-2017 and 2017-2018 school years, with the goal of having the new school open to students and educators by September of 2018. Demolition of the current school will take place over the summer of 2018, which will allow for construction of new parking lots and sporting fields.
Thanks again to the voters of the School District of Superior for approving the referendum last April. This gives us the opportunity to improve our school and insure that our children have the opportunity to get the best education we can provide them here in Superior.
Updated site plan of Cooper Elementary from the City Planning Commission meeting, note dotted line showing location of current school. The footprint of the new school is shown at the top of the image.
