27 July 2015 – for immediate release
Contact: Michael Conway (Michael.conway@azgs.az.gov); 520.209.4146

The Arizona Geological Survey has released its first geologic map database for aggregate resource assessment in the Phoenix metropolitan area. This map product will provide the basis for local and county planning and zoning authorities to make informed decisions regarding conservation and management of aggregate resources.

Sand, gravel and crushed stone, collectively referred to as aggregate, are the basic ingredients for constructing buildings, homes and infrastructure. In rapidly urbanizing areas, aggregate resources, which frequent river channels and floodplains, are threatened by urbanization and zoning that prevents their development.
The Aggregate Protection section of the Regulatory Bill of Rights, SB 1598, of 2011 requires that counties and municipalities revise their general plans to identify aggregate in their jurisdiction, and implement policies to preserve aggregate resources for future use by avoiding incompatible land use.

This new report, map graphic, and GIS (geographic information system) data shows the distribution of unconsolidated sediments (sands and gravels) from Phoenix’s five major rivers systems – Salt, Gila, Verde, Agua Fria and Hassayampa – and their tributaries. These channel deposits make the highest quality and most desirable aggregate resources.
Rapid population expansion in the Phoenix area and elsewhere in Arizona threatens to bury aggregate resources beneath urban growth, housing additions and infrastructure. As aggregate sites near communities are reduced or become off limits to quarrying, aggregate resources must be trucked in from ever more distant quarries.

Harvesting aggregate resources locally greatly reduces transportation costs – a major component of the aggregate cost. Using local sources also reduces road wear and diesel fuel consumption, thereby greatly reducing the emission of CO, NOx, particulate matter 10 micrometers, SOx, and volatile organic compounds.

The July Arizona Mining Review e-Video Magazine includes an interview with Arizona Rock Products Association Executive Director Steve Trussell and Dr. Phil Pearthree (AZGS – Environmental Geology section) by Dr. Lee Allison (AZGS Director) regarding the application of this report to managing and conserving aggregate resources. The interview will be available at AZGS’s YouTube channel after 10:30 a.m. on Wednesday, 29 July.

Background. Rivers of the Phoenix area drain large watersheds with diverse types of bedrock, and bed load that has been deposited in the Valley of the Sun. Commonly, this rock has been transported for tens of miles or more providing a natural filtering that removes less resistant rock and results in a high-quality rock product for use in various types of aggregate. This map product depicts the deposits associated with each of these rivers and reflects variations in rock type and gravel size.

Citation: Pearthree, P.A., Gootee, B.F., Richard, S.M. and Spencer, J.E., 2015, Geologic Map Database for Aggregate Resource Assessment in the Phoenix Metropolitan Area and Surrounding Regions, Arizona. Arizona Geological Survey Digital Information DI-43, 11 p., map sheet, Shapefiles, ArcGIS Map Packages, polygons and geologic features.