Mineral Resources Program Publication Index

California remained one of the largest producers of non-fuel minerals in the United States in 2020. This report discusses the commodities produced as well as production and trends for many commodities.

To obtain the full report, visit California's Non-Fuel Mineral Production web page.

by Greg D. Marquis

• Special Report 253 - Mineral Land Classification: Portland Cement Concrete Aggregate in the Western Ventura County and Simi Production-Consumption Regions
• Plate 1 - Mineral Resource Zone Map
• Plate 2 - Resource Sector Map

Summary of SR 253

SR 253 is the second update Mineral Land Classification (MLC) report for Portland cement concrete (PCC) aggregate in Ventura County. The original MLC report was published as SR 145 in 1981. The first update was published as Open-File Report 93-10 in 1993. SR 253 reevaluates PCC aggregate resources, permitted reserves, past production, and includes an updated 50-year projection (through the year 2067) of demand for PCC and all other grades of construction aggregate in the Western Ventura-Simi Production-Consumption Regions.

The following list summarizes some of the major findings and conclusions reached in this update report:

• Of the 27,179 acres of Designated Sectors in the WVS P-C Regions, 1,674 acres (6.2 percent) were lost due to land uses incompatible with mining.
• There are an estimated 5,593 million tons of PCC resources in the WVS P-C Regions. 118 million tons are currently permitted.
• The 118 million tons of permitted PCC aggregate reserves could last less than 23 years.
• The WVS P-C Regions PCC aggregate reserves are approximately 80 percent fine and 20 percent coarse.
• Approximately 25 percent of aggregate (coarse PCC aggregate) was imported to the WVS P-C Regions in 2017.
• Imports to the WVS P-C Regions are transported at least 40 miles, which increases costs and greenhouse gas emissions.
• Barriers to future mine permitting include housing, parks, environmental policies and land use decisions protecting wildlife habitat.

by Ronald K. Churchill, Joshua A. Goodwin, and Brenda L. Callen

This report summarizes indoor radon data available up to 2018 for each county in the state of California, using information provided by the California Department of Public Health through an interagency agreement. The report is available as a single PDF file, which can be viewed using Adobe Acrobat Reader. Follow this link to download Special Report 247.

NOTE: Clicking the link above will take you to our File Request system, where you will need to provide your email address; other than that the process is quick, and you receive a file link within five minutes of requesting it.

For more information about indoor radon in California, visit our Indoor Radon page.

by David Reioux, Benjamin Parrish, Brian J. Swanson, and Howard J. Brown

The California Geological Survey (CGS) released four new preliminary geologic maps, supported by the United States Geological Survey's (USGS) Earth Mapping Resource Initiative (Earth MRI) within the Mountain Pass Rare Earth Element Focus Area. The maps are:

• Preliminary geologic map of the Crescent Peak 7.5-minute quadrangle, New York Mountains, San Bernardino County, California
• Preliminary geologic map of the Castle Peaks 7.5-minute quadrangle, New York Mountains, San Bernardino County, California
• Preliminary geologic map of the Ivanpah 7.5-minute quadrangle, New York Mountains, San Bernardino County, California
• Preliminary geologic map of the Pinto Valley 7.5-minute quadrangle, New York Mountains, San Bernardino County, California

Project Background

In 2019, the CGS entered into a cooperative agreement with the USGS to conduct geologic mapping of the New York Mountains at 1:24,000 scale. This project is supported in part by funding from the USGS and occurs within the Mountain Pass Rare Earth Element Focus Area. The field area was selected due to its proximity to the world class, carbonatite-hosted, light rare earth deposit at Mountain Pass.

Rare earth elements are among 50 minerals listed as critical by the USGS. Critical minerals are defined as being essential for manufacturing products significantly important to the economy and national security and as having supply chains vulnerable to outside disruption. The Earth MRI Project aims to gather information to identify potential domestic sources of critical minerals.

Downloadable Files Related to this Release

The maps are available as PDF files, which can be viewed using Adobe Acrobat Reader. To download these maps, visit our Preliminary Geologic Maps page.

by Catherine Wesoloski, David Reioux, and Brenda Callen

• Special Report 254 - 2021 Update of the Mineral Land Classification for Portland Cement Concrete Aggregate Resources in the San Fernando Valley and Saugus-Newhall Production-Consumption Regions
• Plate 1 - Mineral Resource Zone Map
• Plate 2 - Resource Sector Map

Summary of SR 254

This report, Special Report (SR) 254, serves as an update to the findings presented in SR 143 parts I, II (Anderson and others, 1979), and V (Joseph and others, 1987) and Open-File Report (OFR) 94-14 (Miller, 1994). It includes: 1) a reevaluation of Portland cement concrete (PCC) aggregate resources within the San Fernando Valley and Saugus-Newhall Production-Consumption (P-C) Regions; 2) estimates for the quantity of resources as of December 2018; and, 3) a 50-year forecast of PCC aggregate demand within the San Fernando Valley and Saugus-Newhall P-C Regions from 2018 to 2068.

The major findings are:

• No new sectors were added; the four sectors classified in the San Fernando Valley P-C Region and the three sectors classified in the Saugus-Newhall P-C Region were maintained from SR 143 and OFR 94-14.
• The projected 50-year PCC aggregate demand on the San Fernando Valley P-C Region through the year 2068 is estimated to be 959 million tons.
• The projected 50-year PCC aggregate demand on the Saugus-Newhall P-C Region through the year 2068 is estimated to be 80 million tons.
• Reserves are proprietary but will be exhausted in less than 10 years in both regions if the current demand is sustained.
• Approximately 416 million tons of resources underlie the San Fernando Valley P-C Region.
• Approximately 10.5 billion tons of resources underlie the Saugus-Newhall P-C Region.
• If no additional reserves become available, both the San Fernando Valley and Saugus-Newhall P-C Regions will remain dependent on external sources of PCC aggregate.

by Greg Marquis

• Mineral Land Classification of the Teichert Shifler Property, Yolo County, California, for Portland Cement Concrete Aggregate (2.5 MB PDF)

Background of Special Report 255

Teichert Materials submitted a petition dated September 30, 2020 to the SMGB for classification of the Shifler Property, located approximately three miles west of the town of Woodland in Yolo County, just south of Cache Creek. The property consists of two parcels totaling 442 acres. The project area comprises 277 acres. The project area was most recently classified in CGS Special Report (SR) 245 in 2018. Portions of the project area were classified in SR 245 as not having significant mineral resources based on an analysis of surficial geologic mapping. Under the provisions of the Surface Mining and Reclamation Act of 1975 (SMARA; Public Resources Code § 2712 et seq.), the petitioner requested that the State Geologist reclassify the project area as MRZ-2 for PCC aggregate.

Summary of Special Report 255

The State Geologist investigated the area proposed for mining, and subsequently reclassified it as Mineral Resource Zone 2 (MRZ-2) for Portland cement concrete (PCC) aggregate. The petition contains drill logs that show the presence of construction aggregate at mineable depths throughout the project area. The petition also references a third-party laboratory that concluded the project area aggregate was suitable for use in PCC based on petrographic analysis. In addition to evidence provided in the petition, adjacent properties—also located off-channel from Cache Creek—are being or have been mined for PCC aggregate. The value of the aggregate resource in the project area exceeds the threshold for a significant deposit of construction materials for the purpose of classification.

by Benjamin Parrish

• Special Report 252 - 2021 Update of the Mineral Land Classification for Concrete Aggregate Resources of Merced County, California
• Plate 1 - Mineral Resource Zone Map
• Plate 2 - Resource Sector Map

Clicking the links above will take you to our File Request system, where you can request high-quality PDF versions of the documents. You will need to provide your email address, but other than that the process is quick, and you receive a file link within five minutes of requesting it.

by Erica Key

• Special Report 251 - 2021 Update of the Mineral Land Classification for Construction Aggregate Resources in the Monterey Bay Production-Consumption Region
• Plate 1 - Mineral Resource Zone Map
• Plate 2A - Resource Sector Map 1 of 2
• Plate 2B - Resource Sector Map 2 of 2

Clicking the links above will take you to our File Request system, where you can request high-quality PDF versions of the documents. You will need to provide your email address, but other than that the process is quick, and you receive a file link within five minutes of requesting it.

by Joshua A. Goodwin, Matt D. O’Neal, and Ronald K. Churchill

• Radon Potential in Western Placer County, California (3.6 MB PDF)
• Plate 1 - Radon Potential Zone Map for Western Placer County, California (4.7 MB PDF)

Background of Special Report 246

Radon is a naturally occurring odorless and colorless radioactive gas. It forms from the radioactive decay of small amounts of uranium naturally present in rocks and soils. Given the right circumstances, radon can move from the subsurface and concentrate in overlying homes and buildings. Breathing air with elevated radon gas increases one’s risk of developing lung cancer. While not everyone exposed to radon will develop lung cancer, the U.S. Environmental Protection Agency (U.S. EPA) estimates that 21,000 people in the United States die annually from lung cancer attributed to radon exposure. Indoor-radon concentrations are related to the uranium contents of local soils and rocks, soil permeability, climate, and building design, condition, and usage. Uranium data for rocks and soils provide information on where radon concentrations in the subsurface are higher or lower. Soil permeability data provide information on pathway availability for radon to move from the subsurface to a building’s foundation. Indoor-radon data represent the combined result of these factors at a specific location and can be used to develop radon potential maps. Radon potential maps identify areas where homes and other buildings are more likely, or less likely, to exceed the U.S. EPA’s recommended radon action level of 4 picocuries per liter (4 pCi/L). Radon potential maps may be used with population data to estimate the number of individuals exposed to 4 pCi/L or higher radon levels within the area of map coverage. In California, radon potential maps are informational, not regulatory.

Summary of Special Report 246

The Department of Conservation, California Geological Survey (CGS) has completed a radon potential map and report for Western Placer County, California. The map identifies areas more likely, and areas less likely, to have indoor-radon measurements exceeding the U.S. EPA recommended action level of 4 pCi/L. The map also identifies areas where more data are needed to determine the radon potential. All radon potential areas, high, moderate, or low, contain some indoor-radon measurements above the U.S. EPA recommended action level and some below. This map cannot be used for determining the indoor-radon level of a particular building. Testing for radon is the only way to determine a building’s radon level, no matter where it is located. The Western Placer County radon potential map was developed using indoor-radon test data, geologic unit information from several geologic maps, uranium geochemistry data, and soil permeability data. Details about these data and maps, and the procedures used to develop the radon potential map, are included in the accompanying report. The report also estimates the number of Western Placer County residents potentially exposed to indoor-radon levels at or above the U.S. EPA recommended action level.

Availability of Special Report 246

Special Report 246 and its associated plate (map) are available as free downloads or as printed products; there is a charge for the printed version. (NOTE: Plate 1 measures 36 inches by 30 inches.) To purchase printed copies, contact our Publications Sales Desk or visit the California Geological Survey Library in Sacramento.

by Ronald K. Churchill

• Radon Potential in Western Santa Clara County, California (4.7 MB PDF)
• Plate 1 - Radon Potential Zone Map for Western Santa Clara County, California (8.1 MB PDF)

Background of Special Report 244

Radon is a naturally occurring odorless and colorless radioactive gas. It forms from the radioactive decay of small amounts of uranium naturally present in rocks and soils. Given the right circumstances, radon can move from the subsurface and concentrate in overlying homes and buildings. Breathing air with elevated radon gas increases one’s risk of developing lung cancer. While not everyone exposed to radon will develop lung cancer, the U.S. Environmental Protection Agency (U.S. EPA) estimates that 21,000 people in the United States die annually from lung cancer attributed to radon exposure. Indoor-radon concentrations are related to the uranium contents of local soils and rocks, soil permeability, climate, and building design, condition, and usage. Uranium data for rocks and soils provide information on where radon concentrations in the subsurface are higher or lower. Soil permeability data provide information on pathway availability for radon to move from the subsurface to a building’s foundation. Indoor-radon data represent the combined result of these factors at a specific location and can be used to develop radon potential maps. Radon potential maps identify areas where homes and other buildings are more likely, or less likely, to exceed the U.S. EPA’s recommended radon action level of 4 picocuries per liter (4 pCi/L). Radon potential maps may be used with population data to estimate the number of individuals exposed to 4 pCi/L or higher radon levels within the area of map coverage. In California, radon potential maps are informational, not regulatory.

Summary of Special Report 244

The Department of Conservation, California Geological Survey (CGS) has completed a radon potential map and report for Western Santa Clara County, California. The map identifies areas more likely, and areas less likely, to have indoor-radon measurements exceeding the U.S. EPA recommended action level of 4 pCi/L. The map also identifies areas where more data are needed to determine the radon potential. All radon potential areas, high, moderate, or low, contain some indoor-radon measurements above the U.S. EPA recommended action level and some below. This map cannot be used for determining the indoor-radon level of a particular building. Testing for radon is the only way to determine a building’s radon level, no matter where it is located. The Western Santa Clara County radon potential map was developed using indoor-radon test data, geologic unit information from several geologic maps, uranium geochemistry data, and soil permeability data. Details about these data and maps, and the procedures used to develop the radon potential map, are included in the accompanying report. The report also estimates the number of Western Santa Clara County residents potentially exposed to indoor-radon levels at or above the U.S. EPA recommended action level.

Availability of Special Report 244

Special Report 244 and its associated plate (map) are available as free downloads or as printed products; prints are $52 each, plus $8 to cover shipping. (NOTE: Plate 1 measures 38 inches by 36 inches.) To purchase printed copies, contact our Publications Sales Desk or visit the California Geological Survey Library in Sacramento.

by Ronald K. Churchill

• Radon Potential in Amador, Calaveras, and Tuolumne Counties, California (8.5 MB PDF)
• Plate 1 - Radon Potential Zone Map for Amador, Calaveras, and Tuolumne Counties, California (15 MB PDF)

Background of Special Report 242

Radon is a naturally occurring odorless and colorless radioactive gas. It forms from the radioactive decay of small amounts of uranium naturally present in rocks and soils. Given the right circumstances, radon can move from the subsurface and concentrate in overlying homes and buildings. Breathing air with elevated radon gas increases one’s risk of developing lung cancer. While not everyone exposed to radon will develop lung cancer, the U.S. Environmental Protection Agency (U.S. EPA) estimates that 21,000 people in the United States die annually from lung cancer attributed to radon exposure. Indoor-radon concentrations are related to the uranium contents of local soils and rocks, soil permeability, climate, and building design, condition, and usage. Uranium data for rocks and soils provide information on where radon concentrations in the subsurface are higher or lower. Soil permeability data provide information on pathway availability for radon to move from the subsurface to a building’s foundation. Indoor-radon data represent the combined result of these factors at a specific location and can be used to develop radon potential maps. Radon potential maps identify areas where homes and other buildings are more likely, or less likely, to exceed the U.S. EPA’s recommended radon action level of 4 picocuries per liter (4 pCi/L). Radon potential maps may be used with population data to estimate the number of individuals exposed to 4 pCi/L or higher radon levels within the area of map coverage. In California, radon potential maps are informational, not regulatory.

Summary of Special Report 242

The Department of Conservation, California Geological Survey (CGS) has completed a radon potential map and report for Amador, Calaveras, and Tuolumne Counties, California. The map identifies areas more likely, and areas less likely, to have indoor-radon measurements exceeding the U.S. EPA recommended action level of 4 pCi/L. The map also identifies areas where more data are needed to determine the radon potential. All radon potential areas, high, moderate, or low, contain some indoor-radon measurements above the U.S. EPA recommended action level and some below. This map cannot be used for determining the indoor-radon level of a particular building. Testing for radon is the only way to determine a building’s radon level, no matter where it is located. The Amador, Calaveras, and Tuolumne Counties radon potential map was developed using indoor-radon test data, geologic unit information from several geologic maps, uranium geochemistry data, and soil permeability data. Details about these data and maps, and the procedures used to develop the radon potential map, are included in the accompanying report. The report also estimates the number of Amador, Calaveras, and Tuolumne County residents potentially exposed to indoor-radon levels at or above the U.S. EPA recommended action level.

Availability of Special Report 242

Special Report 242 and its associated plate (map) are available as free downloads or as printed products; prints are $35 each, plus $8 to cover shipping. (NOTE: Plate 1 measures 42 inches by 50 inches.) To purchase printed copies, contact our Publications Sales Desk or visit the California Geological Survey Library in Sacramento.

by Matt D. O'Neal and Fred W. Gius

• Special Report 245: Mineral Land Classification: Concrete Aggregate in the Greater Sacramento Area Production-Consumption Region 2018 (2.6 MB PDF)
• Plate 1: Mineral Land Classification Map (23 MB PDF)
• Plate 2A: Resource Sector Map 1 of 2 (13 MB PDF)
• Plate 2B: Resource Sector Map 2 of 2 (19 MB PDF)

Background of Special Report 245

California's Surface Mining and Reclamation Act of 1975 (SMARA) requires the State Geologist to classify land into Mineral Resource Zones (MRZs), based on the known or inferred mineral resource potential of that land. The process is based solely on geology, without regard to existing land use or land ownership. The primary goal of mineral land classification (MLC) is to help ensure, through appropriate local lead agency policies and procedures, that mineral resources will be available when needed and do not become inaccessible because of inadequate information during the land-use decision‑making process.

Summary of Special Report 245

This report is the first MLC study of concrete aggregate resources to cover all lands within the newly defined Greater Sacramento Area Production-Consumption (P-C) Region. The region is 6,080 square miles in area, of which 2,580 square miles were classified for a variety of mineral commodities for different purposes between 1975 and 2010. The remaining 3,500 square miles of the P-C Region are newly classified for concrete aggregate resources in the present report.

Urban expansion in the P-C Region threatens to preclude mineral resource extraction. At present, the P-C Region contains sufficient concrete aggregate resources to meet the projected 50-year demand. However, there is a substantial and important disparity between the geographic distribution of mineral resources and population centers. Only a minor proportion of resources are located near population centers. Utilization of more distant resources results in a significant increase in cost to the aggregate consumer, road wear and tear, traffic congestion, greenhouse gas emissions, and air pollution. For example, each additional mile of aggregate transport costs 15 cents per ton, and one mile of a six-lane highway consumes more than 110,000 tons of aggregate.

In this update report, the following conclusions are reached:

• The 10 historic reports identified 85 concrete aggregate resource sectors, with a total area of 42,033 acres (66 square miles).
• Of this area, 2,417 acres (about 6 percent) have become lost due to changing land use, resource depletion, or re-evaluation based on new data.
• The remaining 39,616 acres host a total of 3,565 million tons of concrete aggregate resources.
• This report identifies an additional nine concrete aggregate resource sectors with a total area of 3,880 acres.
• These newly identified sectors host a total of 769 million tons of concrete aggregate resources.
• An estimated 4,334 million tons of resources are identified in the P-C Region.
• The projected demand of construction aggregate in the P-C Region for the next 50 years (through the year 2066) is 1,367 million tons. Of this total, 889 million tons will likely be used for concrete aggregate.
• The 1,446 million tons of currently permitted concrete aggregate reserves are projected to last beyond the year 2066.
• Presently, the P-C Region consumes approximately as much as it produces, with imports and exports estimated to account for less than 5% of consumption and production within the region.
• Land-use planners and decision-makers in the P-C Region are faced with balancing a wide variety of needs in planning for a sustainable future for their communities. These include the need to plan carefully for the use of lands containing construction aggregate resources, to consider the permitting of additional aggregate resources in the P-C Region, and to take into consideration the demands of neighboring areas, within the P-C Region, that are competing for resources.

Availability of Special Report 245

Special Report 245 and its associated plates (maps) are available as free downloads or as printed products. (NOTE: The plates measure 36 inches by 48 inches each.) To purchase printed copies, contact our Publications Sales Desk or visit the California Geological Survey Library in Sacramento.

by John P. Clinkenbeard and Fred W. Gius

Background of Map Sheet 52

Sand, gravel, and crushed stone are "construction materials." These materials, collectively referred to as aggregate, provide bulk and strength to portland cement concrete, asphaltic concrete, Class II base, and other aggregate commodities such as subbase, drain rock, and fill. Aggregate normally provides 80 to 100 percent of the material volume in these uses.

The building and paving industries in California consume large quantities of aggregate and future demand for this commodity is expected to increase throughout California. Aggregate materials are essential to modern society, both to maintain the existing infrastructure and to provide for new construction. Because aggregate is a low unit-value, high-bulk-weight commodity, it must be obtained from nearby sources to minimize economic and environmental costs associated with transportation. These factors make information about the availability and demand for aggregate valuable to land-use planners and decision makers charged with planning for a sustainable future for California’s citizens.

Aggregate reserves and projected aggregate demand shown on Map Sheet 52 are updated from mineral land classification reports published by CGS between 1979 and 2017. The reports were prepared in response to California’s Surface Mining and Reclamation Act of 1975 (SMARA) that requires the State Geologist to classify land based on the known or inferred mineral resource potential of that land. The primary goal of mineral land classification is to ensure that the mineral resource potential of lands is recognized and considered in land-use planning.

Although the statewide and regional information presented on the map and in the accompanying report may be useful to decision-makers, it should not be used as a basis for local land-use decisions. The more detailed information contained in each of the aggregate studies employed in the compilation of Map Sheet 52 should be used for local land-use and decision-making purposes.

Summary of Map Sheet 52

Map Sheet 52 is a statewide overview of projected future aggregate needs and currently permitted reserves. The purpose of the map is to compare projected aggregate demand for the next 50 years with currently permitted aggregate reserves in various regions of the state. The map also shows the projected years of permitted reserves remaining and highlights regions where less than 10 years of permitted aggregate supply remain. Map Sheet 52 was originally published in 2002 and subsequently updated in 2006 and 2012. Map Sheet 52 (2018) is an update of the version published in 2012. The estimates of permitted reserves, aggregate demand, and years of permitted reserves remaining are based on conditions as of January 1, 2017.

The report is divided into three parts:

Comparing regional needs to available reserves and resources demonstrates the important aggregate resource issues facing lead agencies in California. These issues include the need to plan carefully for the use of lands containing these resources and the need to consider the permitting of additional aggregate resources before currently permitted deposits are depleted.

The following conclusions can be drawn from Map Sheet 52 (2018) and the accompanying report:

• In the 30-year period from 1987 to 2016, Californians consumed an average of about 180 million tons of construction aggregate (all grades) per year or about 5.3 tons per person per year.
• In the next 50 years, the study areas identified on Map Sheet 52 will need approximately 11 billion tons of aggregate.
• The study areas currently have about 7.6 billion tons of permitted reserves, which is about 69 percent of the total projected 50-year aggregate demand identified for these study areas. This is about 10 percent of the total aggregate resources located within the study areas.
• One aggregate study area is projected to have 10 or fewer years of permitted aggregate reserves remaining as of January 2017 (San Fernando Valley / Saugus-Newhall area).
• Seven aggregate study areas have between 11 and 20 years of aggregate reserves remaining.
• Ten aggregate study areas have between 21 and 30 years of aggregate reserves remaining.
• Four aggregate study areas have between 31 and 40 years of aggregate reserves remaining.
• Two aggregate study areas have between 41 and 50 years of aggregate reserves remaining.
• Five aggregate study areas (Bakersfield, Fresno, Yuba City-Marysville, Nevada County, and Placer County) have more than 50 years of aggregate reserves remaining.

Availability of Map Sheet 52

Map Sheet 52 and its companion report are available as free downloads or as printed products; prints are $25 each, plus $8 to cover shipping. (NOTE: the map measures 36 inches by 42 inches.) To purchase printed copies, contact our Publications Sales Desk.

• Map Sheet 52: Aggregate Sustainability in California (4 MB PDF)
• Map Sheet 52 companion report (270 KB PDF)

by Fred W. Gius, Lawrence L. Busch, and Russell V. Miller.

This report updates the mineral land classification of western San Diego County, reevaluates the region's PCC-grade aggregate resources, and includes an updated 50‑year projection of construction aggregate demand for the P-C Region through the year 2065.

Background of Special Report 240

California’s Surface Mining and Reclamation Act of 1975 (SMARA) requires the State Geologist to classify land into Mineral Resource Zones (MRZs), based on the known or inferred mineral resource potential of that land. The process is based solely on geology, without regard to existing land use or land ownership. The primary goal of mineral land classification is to help ensure, through appropriate local lead agency policies and procedures, that mineral resources will be available when needed and do not become inaccessible because of inadequate information during the land-use decision-making process.

Summary of Special Report 240

This report is the third in a series of regional mineral land classification reports for portland cement concrete (PCC)-grade aggregate for the Western San Diego County Production-Consumption Region (P-C Region). The original mineral land classification was published as Special Report (SR) 153 in 1982. The first update was published in 1996 as Open-File Report (OFR) 96-04. This current report updates the mineral land classification of the region, reevaluates the region’s PCC-grade aggregate resources, and includes an updated 50-year projection of construction aggregate demand for the P-C Region through the year 2065. This update report reevaluated the PCC-grade aggregate resources in areas originally designated by the State Mining and Geology Board and new areas identified in subsequent mineral land classification reports including this update report. This update report does not replace SR 153 or OFR 96-04.

Since the mid-1990s, local aggregate production has not been sufficient to meet local demand in the P-C Region. This shortfall has been met by importing construction aggregate, predominately sand, from neighboring aggregate producing regions. At various times, construction aggregate has been imported into the P-C Region from mines in Los Angeles, San Bernardino, Riverside, and Imperial counties, and Baja California, Mexico.

In this update report, the following conclusions are reached:

• Since the designation of 50,982 acres in 1985, 14,436 acres have been lost to urbanization or other incompatible land uses. The remaining 36,546 acres contain 5,700 million tons of PCC-grade aggregate resources.
• This update report identifies an additional 1,461 acres of undesignated land containing an estimated 282 million tons of PCC-grade aggregate resources.
• An estimated 5,982 million tons of PCC-grade aggregate resources, both designated and non-designated, are identified in the P-C Region.
• The projected demand of construction aggregate in the P-C Region for the next 50 years (through the year 2065) is estimated to be 760 million tons. Of this total, 380 million tons will likely be used for PCC.
• The 271 million tons of currently permitted PCC-grade aggregate reserves are projected to last to the year 2035.
• Presently, the P-C Region consumes more PCC-grade aggregate than it produces; the balance of the Region’s demand is imported from adjacent regions.
• Land-use planners and decision-makers in the P-C Region are faced with balancing a wide variety of needs in planning for a sustainable future for their communities. These include the need to plan carefully for the use of lands containing construction aggregate resources, to consider the permitting of additional aggregate resources in the P-C Region, and to take into consideration the demands of neighboring regions that are competing for the resources being imported into the San Diego area.

Availability of Special Report 240

Special Report 240 and its associated plates (maps) are available as free downloads or as printed products; prints are $128 each, plus $8 to cover shipping. NOTE: Plate 1 measures 36 inches by 42 inches; Plates 2A and 2B measure 42 inches by 46 inches each. To purchase printed copies, contact our Publications Sales Desk or visit the California Geological Survey Library in Sacramento.

• Special Report 240: 2017 Update of Mineral Land Classification: Portland Cement Concrete-Grade Aggregate in the Western San Diego County Production-Consumption Region of California (1.3 MB PDF)
• SR 240 Plate 1: Updated Mineral Land Classification Map for Portland Cement Concrete-Grade Aggregate in the Western San Diego County Production-Consumption Region, California (2.4 MB PDF)
• SR 240 Plate 2A: Updated Aggregate Resource Sector Map [Northern Part] for Portland Cement Concrete-Grade Aggregate in the Western San Diego County Production-Consumption Region, California (4.8 MB PDF)
• SR 240 Plate 2B: Updated Aggregate Resource Sector Map [Southern Part] for Portland Cement Concrete-Grade Aggregate in the Western San Diego County Production-Consumption Region, California (5.6 MB PDF)