AGGREGATE RESOURCE MAPPING IN WASHINGTON STATE

Sand, gravel, and bedrock may be mined or quarried to produce raw materials known as aggregate. Aggregate resources are the building blocks of our communities as they are used in the manufacturing of critical materials for roads, bridges, and development. Although sometimes thought of as ubiquitous, aggregate resources are nonrenewable resources found only in specific geologic areas and their quality and quantity can vary significantly. Effective planning for the needs and uses of aggregate resources faces several challenges such as nonuniform distribution throughout Washington, resource sterilization by development, time and fuel costs for transportation, and increased greenhouse gas emissions for long-distance hauling. For these reasons, identifying and protecting sources of aggregate is critical to promoting sustainable economic development and ensuring the health, safety, and high quality of life enjoyed by people in Washington State.

To meet the goals of Washington Administrative Code (WAC) 365-190-070 related to the Growth Management Act, the Washington Geological Survey (WGS) is now regularly producing new county-scale aggregate resource inventory maps with the goal to have full state coverage. These publications are intended to aid planners and other local officials with land-use planning decisions related to identifying aggre­gate resources of long-term significance. Our projects include outreach and coordination with local planners to promote the integration of our data into land use decisions. WGS is prioritizing mapping counties that lack aggregate-resource data and have an upcoming comprehensive plan update scheduled, among other factors.

Our aggregate resource maps identify potential sources of aggregate (sand, gravel, and bedrock) using a combination of surficial and bedrock geologic mapping, subsurface information from boreholes and water wells, aggregate testing data, and records of current and historical mining activity. Our aggregate resource classification scheme assesses both the quality and quantity of potential resources, and communicates that assessment using four classifications: Demonstrated, Inferred, Speculative, and Not a Resource. We also report volume and tonnage estimates, a developed-lands analysis, and proximity-to-market network analyses.