Site Selection - Part 1

My next few blogs will discuss the process and some of the components for site selection for new school facilities. As the recession wanes and school districts find themselves growing again, the need to acquire school sites has come to focus for many districts. 

If you are evaluating several sites, as you narrow the list to the top one or two sites, we recommend that you have a geo technical study done for each site. The geo tech study is performed by qualified engineers that will take soil samples from various locations on the site to determine the characteristics of the soil. Typically the test holes are drilled 25' to 50' depths at various locations where the building is anticipated to be located. This is important information that can be used by the  architect and contractor in estimating what the cost of the foundation system will be. 

For example, site 1 may have soil that has a large clay content versus site 2 with a sandy type soil. Sandy soils are typically more stable to build on and require less work to prepare the building pad, therefore are less expensive than building on clay soils. You may also find that site 2 has a layer of rock at a shallower depth than site 1 meaning that the piers for the foundation system are shorter in length, therefore less expensive than at site 1. 

Another factor to look for in the geo tech report would be if the soil tests show encountering any underground water. If excessive underground water is found in the test holes it may mean that the piers will need to cased. Casing piers is a process that involves first drilling the pier hole then inserting a steel casing in the hole to keep water from collapsing the hole. The reinforcing steel is placed and then the concrete is poured into the hole. The steel casing is then extracted upon completion of the pour. This process is tedious and increases the cost of the foundation system. There are other methods to drill piers in locations that have underground water, but it is safe to say anytime you encounter this situation, you will be spending more money.

The cost for having a geo tech study performed is several thousand dollars, however this is a very small cost in the total budget of a new building and could potentially save your district tens of thousands of dollars by making an informed decision on choosing one site over another by knowing the type of soil that is present.

Michael D. King AIA