The on-site investigation for new construction can generally be approached in one of two ways. The first is a more limited investigation and is typically for those who have not yet purchased a lot and have a location under consideration. This investigation is more limited in scope, generally more cost effective, and basically used strictly for the decision making process. The second investigation is a more detailed investigation and is generally more applicable for those who have a location purchased and are moving forward with construction. The second investigation provides much more detail on site development, mitigation of unsuitable soils, foundation design and design considerations for long term performance. These two scopes can also be used in conjunction where a limited investigation can be initially performed to evaluate the potential risks, then if the location is pursued the second investigation can be completed to supplement the initial investigation in order to provide more detail for development. Each type of investigation is expanded upon below.
Site Characterization Soil Borings
This consists of drilling a soil boring or soil borings at an existing residence or on individual vacant residential lot to discern the general subsurface conditions at the location. The objective is to utilize the soil boring information to gain a basic understanding of the subgrade conditions at the potential home site or existing house, and apply that knowledge to evaluate potential risk in the decision making process. Typically the soil boring(s) extends to a depth of about 10 feet. The primary intent of this type of investigation is to discover and document the presence of shallow expansive clay or other unsuitable soils. The soil boring(s) can be a visually boring or a data boring. The visual soil boring log consists of visual classification of the soils encountered to establish a basic description of the stratigraphy. The data soil boring log incorporates the collection of
samples and execution of laboratory soil testing to provide a more specific
and accurate characterization of the soil subgrade.
Detailed Geotechnical Investigations
This is performed to utilize soil boring information to evaluate the subsurface conditions at the potential home site and discern the need for any special considerations when constructing the foundation for a new house. The investigation is predominately geared toward discovering the presence of organic soils, expansive clay, soft soils, or generally any subsurface conditions that could negatively impact the home's foundation performance. The typical geotechnical investigation consists of drilling two or more soil borings (dependent upon the home's footprint, a rule of
thumb is generally 1 boring per 1,000 square feet of conditioned on the ground floor space) to about 10 to 12 feet during which disturbed soil samples are collected from the soil borings for transportation to our laboratory for soil testing. Prior to the soil boring
excavations, field soil testing is generally performed at the location toestablish the strength profile of the upper soils. The collected samples are tested to determine the physical and engineering properties of the soil such as moisture content, plasticity (the presence and amount of clay), and shrink/swell potential. This information is then used
to evaluate the suitability of the subsurface for construction. The geotechnical report includes copies of the soil boring logs, all field and laboratory soil testing information collected as well as information addressing earthwork construction of the lot, mitigation of any potentially problematic soil conditions, basic information associated with foundation design, and considerations for maintenance of the foundation to help with long term