Homework 6

Department of Earth Science |Northeastern Illinois University

PRINCIPLES OF HYDROGEOLOGY
ESCI 337
Spring, 2004

Homework #6: Cross Section of the Project Area Dr. Sanders
Due Thursday, April 8, 2004

The Assignment: Construct a cross section of the project area using well boring data provided by the ISGS. Each student should construct one cross section.

Each group will focus on one of the two Montgomery water supply wells. Draw your cross section in such a way that it includes your water supply well.

How to Begin: The materials you will need are in Room S-130. There you will find gridded paper in a roll that is wrapped in an orange plastic sleeve, the TopoTool rulers you can use use in plotting latitude and longitude, as well as the topographic maps of the study area.

Download and open the Excel files that give 1) the boring locations, and 2) the boring logs themselves. (One copy of each of these was already distributed to each group.)

Each boring has its own unique "API number", and you'll need to match the numbers to match the boring locations with the boring logs. Use the final five digits of the API number as the ID number for each well.

In the file that gives boring locations, change the latitude and longitude from decimal degrees to degrees, minutes, and seconds (you might want to figure out how to have Excel calculate this for you!) Using a location (given in degrees, minutes, and seconds) and the TopoTool, plot the location of a boring. Now, using data from the other file, you can see what geologic formations are present at that location. (Note: this file tells the depth to the top of each formation. Depth is not the same as elevation!)

Select boring logs and locations that are most useful to you. This means that the borings are in good locations, and it also means that the logs themselves are useful! Not every log is a good log, so make your selections carefully.

Make your cross section run in a crooked line that extends from boring to boring, rather than trying to make a straight line. Use a vertical exaggeration of 100x--in other words, your vertical scale should be 100 times your horizontal scale. The horizontal scale should equal the scale on the topographic map: 1:24,000.

Within each group, one person should construct a roughly north-south trending cross section, and one person should construct a roughly east-west trending cross section. The third and/or fourth person should construct cross sections that extend in some other direction; you might wish to get a rough idea of the subsurface geology and where the borings are located before you determine where the third/fourth cross sections will be placed. Remember, the goal here is to delineate the boundaries (constant head, no-flow, or water table boundaries) of a hydrogeologic system, so let the geology of the system be your guide as you determine where to draw your cross sections.

Draw your cross section in pencil! You will have to make changes, so consider this a draft. (Eventually, after you have worked out all the problems, and just before you hand in the final product at the end of the semester, you will go over your pencil lines in ink.) Please cooperate with your group members to try to give all of your cross sections a similar format.

Be sure to include the horizontal and vertical scales, show the position of each boring that you used to plot the cross section (label it with the 5-digit well ID number), label the rivers/lakes, and give the cross section a title. Make sure your name is on it, in small letters in an inconspicuous place.

What to Hand In: Hand in the cross sections together as a group. In addition, each group should provide a single copy of the topographic map showing the lines of the cross section.