Minnesota Aggregate Resource Study: Volume II: Report

In 1979, the Minnesota Department of Transportation (Mn/DOT) felt that the aggregate supply would become critical in about 20 years. Hence, in December 1979, Mn/DOT acting as an agent of the Local Road Research Board, requested Ernest K. Lehmann & Associates of Minneapolis to study the aggregate supply problem in four selected areas of the state. The objectives of the study were (1) to determine permitted reserves, and the rate and causes of aggregate depletion in Polk County and vicinity, St. Cloud and vicinity, Hennepin County, and Rochester and vicinity; and 2) to determine methods used at the local, state and national levels to conserve, and enhance aggregate supplies.

Aggregate reserves within permitted properties in the four pilot areas were determined through interviews with pit and quarry operators and with government personnel. Demand for aggregate was obtained by analyzing the construction activity, both public and private, and by applying aggregate-content factors to the construction dollar estimates. Review of conservation methods being used by other states and in Canada suggest several methods for conserving and enhancing aggregate supplies in Minnesota.


The remaining years of supply from permitted properties in the four pilot areas range from 9 to 22 years. Land use regulations are the single most important determinant of future aggregate availability, especially in metropolitan areas. Model legislation termed "The Aggregate-Land Protection Act" is suggested for the conservation and orderly development of aggregate lands. Other supply enhancement measures suggested in the report are the recycling of aggregate in pavement and buildings, increased use of substitutes such as flyash and boiler slag, maximizing the use of pit-run materials by improving processing techniques, and underground mining of limestone.