UPDATED SAND AND GRAVEL RESOURCES OF MCHENRY COUNTY, ILLINOIS

McHenry County, in northeastern Illinois, contains extensive deposits of sand and gravel, which were deposited mostly by glacial meltwater streams of the recent geological past. The geological origins and landforms associated with these deposits were classified and their occurrences have been described. However, the thickness and depth of burial of these deposits, two of the important factors for the aggregate industry, are not documented well. Fortunately, surficial mapping and 3D mapping by the ISGS and state universities at a variety of scales have provided important new data in the last two decades.

Potential sand and gravel resources are presented in two ways. First, stratigraphic drilling sites are shown and labeled with 4 numbers related to the sand and gravel layers at the site. The labels indicate total thickness of sand and gravel, number of layers, maximum thickness. and depth of burial of the single thickest layer. In addition, we reclassify McHenry County map of NRCS Soil Survey Geographic (SSURGO) Database: the lowermost soil texture. For example, “warm” colors such as red, tan, and yellow represent relatively coarse-grained materials such as gravel, sand and gravel, and sand, respectively. Alternatively, units symbolized with “cool” colors such as blue and green represent relatively fine-grained materials such as clay and clay loam.

This representation of soil texture data coupled with detailed stratigraphic drilling data shows a more detailed distribution of possible aggregate-grade sand and gravel deposits than previous studies. Good agreement between shallow soil texture and the deep borehole sand and gravel thickness gives confidence on the attempts to use soil data to assess sand and gravel resources. Thus, the methodology used in our study can be applied to other counties in Illinois and elsewhere.

As the Chicago metropolitan area population continues to grow, a better understanding of the distribution of sand and gravel deposits in McHenry County and nearby counties will be increasingly important for land use, environmental planning, and ground water resource decisions. In addition, this type of map can certainly help constituents in the sand and gravel industry with implications for aggregate quality, transportation and economic feasibility.