So, you’ve landed a job as a Geotechnical Engineer. What now? We all know that before performing any site investigation it is prudent to gather as much information that you can about the project site. There are so many resources out there that can help us get an idea of what the subsurface conditions are so that we can select the appropriate subsurface exploration techniques.
Below is a list of extremely useful sites that can help you gain some indication as to what the subsurface conditions are before planning the subsurface exploration program.
- Google Earth Software. Need to quickly get an idea of how a site looks likes? Google has got you covered. I am by no means suggesting that this tool can replace a site visit (we all know how invaluable these trips can be), but rather suggesting that this is a great way to see a site during proposal preparation or even to get a preliminary idea of site access and features. This software has the capability of providing latitude and longitude coordinates, which can be used to locate test sites. Also, the software has historical images, which can save the hassle of going to your local Public Works Department to obtain such images.
- United States Department of Agriculture (USDA) soil survey maps. This is a great website that provides a plethora of information regarding soil/rocks at a given site. This is an interactive map which provides information such as soil type, composition, general classification, depth to bedrock, color, precipitation, flooding frequency, general discussion on history of deposits, groundwater depth and more. Site information can be given in the form of an address or coordinates. In addition, it provides Township, Range and Section for your site. These soil surveys are, however, geared more toward agricultural applications. Nevertheless, you can still find very useful reports and nice aerial maps to give you an indication of what soil types your site may have. The web application generates professional reports and aerial maps for your use.
- United States Geological Survey (USGS) Geological State Maps. USGS provides Keyhole Markup Language (KML) files for each U.S. State which contains a GIS database of geologic units and structural features, with lithology, age, and data structure. Simply load the KML file and click on the area where the project site is to get information about the subsurface geology. The drawback with this file is that it only provides the uppermost geologic formation.
- USGS Topographic Maps. This is an interactive web application that provides topographic maps. A street address or coordinates can be used to locate a project site. This application generates topographic and aerial maps of any site in the United States. You can download your map or order a professional looking image from their site.
- State Geological Survey Website. Your State Geological Survey department has tons of useful information that they have gathered over the years. They provide local description of soil and rock types, groundwater data, hydrogeology information, geologic hazards, local geologic maps, and more. An extremely useful bit of information I found that these websites have are well log information. They tend to keep detailed information regarding subsurface conditions encountered at various well sites they have drilled in the State. Data such as groundwater elevation as well as geological formation description, type and depth are relevant information in these logs. For example, the Florida Geological Survey website has well log info (in the form of a DOS program) for every county in the state. Also, they provide several publications discussing local geological hazards (i.e. sinkholes), photographs of local rocks/minerals, subsurface profiles, boring records, and much more. Search online for your State Geological Survey website and find out what type of information they have. You’ll be surprised!
- USGS Active Groundwater Network. This website provides KML files for each U.S. State that you can import into the Google Earth software to see active groundwater wells that the USGS is monitoring. The groundwater wells appear plotted on the Google Earth map and each one provides a link to the USGS site that contains groundwater table information. You can get historical groundwater elevations including date measured, average value, and how the current reading compares to historical values. I use this information on a daily basis to compare groundwater table readings obtained from the field to historical values. This also provides an invaluable tool to try to estimate the dreaded Seasonal High Groundwater Table Elevation. This KML file also comes with a topographic image database.
- USGS Real-Time Water Data. This website from the USGS provides real-time groundwater data for your state. Information such as current and historical groundwater table readings is available. Also, this site provides water quality data (if you’re into that sort of thing.)
- FEMA Flood Maps. These maps provide indication as to whether your site is within a flood zone. In South Florida, this is extremely useful. You can view the site by providing an address. The map provides the base flood elevation along with a professional looking map. You can download a customized map for your area.
These are just some of the many tools you can use to get preliminary information regarding your project site. This shall by no means replace input from a Geologist nor a thorough field investigation supervised by a Professional Geotechnical/Geological Engineer.
About the Author
Mr. Rey Villa is a registered professional engineer in the State of Florida who obtained a Master’s Degree from the Missouri University of Science and Technology. His practice involves mainly transportation related projects, particularly design-build contracts. He is the web developer responsible for Geotech-Apps.com , which is a site that provides geotechnical web apps for use in foundation and retaining wall analyses and design. You can find him on Google+.