In preparing the physical layout of the infrastructure and buildings on the site, having a topographical survey available will reduce surprises during construction and reduce those costly change orders. You can have a field run topographical survey on the property typically on a 200’ grid for large parcels, 100’ grid for smaller ones, and 10’ grid for very small parcels. Alternatively, you can obtain the US Geological Survey (USGS) for your area and overlay it on your parcel. It is a matter as to how precise you need to be. USGS surveys are updated periodically, where as a commissioned field run survey will be the most accurate.
The lines represent points that have a common elevation. Subject to the survey scale, these lines typically denote 10’ elevation differences. Blue lines represent water. Burnt red lines represent an elevation. In interpreting the lines, the further apart the lines are, the flatter the area is. Lines that are very close together represent inclines. Though buildable, it costs much more for foundation work on an incline than it does on flat land.
Now knowing the elevation challenges your site presents, next you need to know what’s below grade. That is referred to as a sub-surface geological report, the subject of another blog entry to come.
