U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2011–1119

Aggregate Resource Availability in the Conterminous United 

States, Including Suggestions for Addressing Shortages, 

Quality, and Environmental Concerns
Aggregate Resource Availability in the Conterminous 

United States, Including Suggestions for Addressing 

Shortages, Quality, and Environmental Concerns

By William H. Langer

Open-File Report 2011–1119

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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Suggested citation:

Langer, W.H., 2011, Aggregate resource availability in the conterminous United States, including suggestions for 

addressing shortages, quality, and environmental concerns: U.S. Geological Survey Open-File Report 2011–1119, 87 p.
Contents

Abstract...........................................................................................................................................................5

Purpose and Scope .......................................................................................................................................6

Introduction.....................................................................................................................................................7

Presentation Outline....................................................................................................................................11

Where Aggregate Occurs ..........................................................................................................................12

Sand & Gravel......................................................................................................................................12

Crushed stone......................................................................................................................................13

Limestone.............................................................................................................................................14

Granite ..................................................................................................................................................15

Trap........................................................................................................................................................16

Other......................................................................................................................................................17

Where Aggregate is in Limited Occurrence ...........................................................................................18

High Plains, Nebraska........................................................................................................................19

Colorado Plateau and Wyoming Basin, Northeastern Arizona...................................................25

Non-Glaciated Northern Plains, Northeastern Wyoming............................................................33

Glaciated Midwest, Iowa ..................................................................................................................38

Coastal Plain & Mississippi Embayment, Louisiana .....................................................................42

Quality, Societal, and Environmental Issues Limiting Aggregate Availability ...................................46

Quality Issues – Agua Fria River, Phoenix, Arizona.......................................................................47

Quality Issues – South Platte River, Denver, Colorado.................................................................52

Quality Issues – Florida......................................................................................................................59

Environmental Issues – Southwest Indiana...................................................................................65

Societal Issues – Permitting – Southern California ......................................................................68

Quality Issues – Minneapolis/St. Paul, Minnesota .......................................................................75

Societal Issues – Encroachment – Minneapolis/St. Paul, Minnesota.......................................77

Summary........................................................................................................................................................81

References Cited..........................................................................................................................................83
Abstract

One-third of America‘s major roads are in poor or mediocre condition, and over 

one-quarter of the bridges are either structurally deficient or functionally 

obsolete. A 70-percent increase in annual aggregate production may be 

required to upgrade the transportation infrastructure. Natural aggregate is 

widespread throughout the conterminous United States, but the location of 

aggregate is determined by geology and is non-negotiable. Natural aggregate is 

in short supply in the Coastal Plain and Mississippi embayment, Colorado 

Plateau and Wyoming Basin, glaciated Midwest, High Plains, and the nonglaciated Northern Plains. A variety of techniques have been used to overcome 

local shortages, such as the use of substitute materials, recycling, and importing 

high-quality aggregates from more distant locations.

Although potential sources of aggregate are widespread throughout the United 

States, many sources may not meet certain physical property requirements, 

such as soundness, hardness, strength, porosity, and specific gravity, or they 

may contain contaminants or deleterious materials that render them unusable. 

Encroachment by conflicting land uses, permitting considerations, environmental 

issues, and societal pressures can prevent or limit development of otherwise

5
suitable aggregate. The use of sustainable aggregate resource management 

(SARM) can help ensure an economically viable supply of aggregate. SARM 

techniques that have successfully been used include (1) protecting potential

resources from encroachment; (2) using marginal-quality local aggregate for 

applications that do not demand a high-quality resource; (3) using substitute 

materials such as clinker, scoria, and recycled asphalt and concrete; and (4) 

using rail and water to transport aggregates from remote sources.

Purpose and Scope

This report discusses the types of aggregate, describes the occurrence of goodquality aggregate, and points out where good-quality aggregate is limited. 

Societal and environmental issues that limit aggregate development also are 

discussed. Example plans for growth and development are presented. 

A similar version of this slide show was given as two separate presentations at the Transportation 

Research Board 2011 Annual Meeting Workshop 102 on Aggregate Sources Depletion and Future Supply, 

Washington, D.C., January 23, 2011

6
According to the American Society of Civil Engineers 2009 Report Card (2009): 

1) one-third of America‘s major roads are in poor or mediocre condition; 2) 

nearly half of the major urban highways are congested; 3) over one quarter of 

the Nation‘s bridges are either structurally deficient or functionally obsolete; 4) 

capital investments in airports are inadequate; and 5) almost all of the locks on 

the Nation‘s inland waterway have exceeded their design life by 20 percent. 

7
The American Society of Civil Engineers (2009) estimates that nearly $186 

billion annually is needed for 5 years to substantially improve conditions of the 

Nation‘s roads and bridges, with an additional $40 billion needed per year for the 

remainder of the transportation infrastructure (aviation, rail, and inland 

waterways). 

With aggregates representing 5 to 10 percent of total project costs, those 

projects would require about $11.3 to $22.6 billion worth of aggregate. Assuming 

aggregate is valued at about $10 per ton, from 1.1 to 2.3 billion tons of 

aggregate per year may be required for upgrading and repairing the Nation‘s 

transportation infrastructure. This amounts to an increase in aggregate 

production of about 35 to 75 percent over 2006 levels.

8
Tepordei (1995) reported that the total cost of materials for Federal Highway Aid 

contracts from 1980 to 1989 represented between 44 and 48 percent of the total 

cost. He calculated the put-in-place cost of aggregates to be between 9.6 and

15 percent of the materials used in highway construction, with the cost of 

aggregates representing 4.6 to 7.2 percent of the overall cost of highway 

construction. The California Department of Transportation (2007) estimated that 

aggregates account for 8 to 10 percent of total project costs.

9
Because aggregate is a high-bulk, low-unit-value commodity, transporting 

aggregate to the point of use can add significantly to the final cost of the 

product. Over 90 percent of aggregate transport is by truck. Generally, 

transporting aggregate to the end-user at truck haul distances of 30 to 50 miles 

can double the cost of the aggregate (Robinson and Brown, 2002). 

Consequently, it is most economical to have aggregate operations located as 

close to the final point of use as possible. 

10
This presentation addresses where aggregate occurs, or conversely where 

aggregate is non-existent or occurs in limited supplies; and how quality, societal, 

and environmental issues can limit access to good-quality potential sources of

aggregate. The presentation uses case studies to demonstrate methods to 

address issues that limit aggregate supply and how to overcome shortages of 

supply.

11
The aggregate industry commonly refers to two general groups of aggregates; 

sand and gravel (s&g), and crushed stone. Sand and gravel make up about 42 

percent of the total United States aggregate production. Sand and gravel is 

produced in every state (Bolen, 2008). Most sand and gravel produced in the 

United States is of glaciofluvial or alluvial origin. Glaciofluvial deposits are 

restricted to northern latitudes and high altitudes, and commonly make excellent 

sources of aggregate. Alluvial fans are typical of arid and semiarid regions and 

occur primarily in the Great Basin of the western United States. These materials 

tend to be poorly sorted and require significant processing before use as 

aggregate. Alluvial (river or stream) deposits are widespread. Their properties 

are highly variable and depend in large part on the parent material from which 

they are derived and the distance from the bedrock source area. Those parts of 

the United States that have sources of good-quality bedrock also commonly 

have good quality alluvial gravels. The amount of gravel-sized particles in 

alluvial deposits commonly decreases the more distant the deposits are from the 

source area. 

12
Crushed stone is the product resulting from the artificial crushing of rock. 

Crushed stone makes up about 58 percent of total United States aggregate 

production.

American Society for Testing and Materials (ASTM, 2011) Descriptive 

Nomenclature for Constituents of Concrete Aggregates C 294 provides brief 

descriptions of some of the more common rock types that comprise mineral 

aggregates as they occur in nature. Nevertheless, crushed stone commonly is 

divided into four general groups that are loosely tied to common petrological

classifications—limestone, granite, trap rock, and other rocks. 

13
 ̳Limestone‘ consists of carbonate rocks including limestone, dolomite, and 

marble, and makes up about 68 percent of crushed stone production (Willett, 

2008) or 39 percent of the total aggregate production. These carbonate rocks 

are widely distributed throughout the United States and they are produced in 

every state except North Dakota and Delaware. Their suitability for crushed 

stone varies greatly from location to location. 

Carbonate rocks occur in the mid-continent from the Great Plains states 

eastward to the west flank of the Appalachian Mountains; the Coastal Plains of 

Florida, Mississippi, Alabama, Georgia and South Carolina; the Balcones 

Escarpment in Texas; the Black Hills of South Dakota and Wyoming; all of the 

far western States; and in parts of Alaska and Hawaii.

14
Granite refers to coarse-grained igneous or metamorphic rocks including true 

granite as well as other light colored rocks such as syenite, gneiss, and darkcolored gabbro. These make up about 16 percent of the crushed stone

production (Willett, 2008) or 9 percent of the total aggregate production. Granite 

usually makes excellent crushed stone; however, some granitic-type rocks are 

too porous or too weak to make good aggregate or contain certain forms of silica 

that may react with alkali when used as concrete aggregate. 

Granite-type rocks are widely distributed. They occur in the Appalachian and 

Adirondack Mountains, northern Minnesota and Wisconsin, the Black Hills of 

South Dakota and Wyoming, southeastern Missouri, central Arkansas, southern 

Oklahoma, central and southwestern Texas, all the western states, including the 

Rocky Mountains and areas to the west, and Alaska.

15
Trap is dark-colored, fine-grained, volcanic rock, and makes up about 9 percent 

of the crushed stone production (Willett, 2008) or 5 percent of the total 

aggregate production. Basalt and diabase are generally referred to as traprock

and commonly make excellent crushed stone. Most other light-colored volcanic 

rocks contain certain forms of silica that may react with alkali when used as 

concrete aggregate, have vugs that contain deleterious minerals, or have 

physical properties that make them unsuitable for general use as aggregate.

Extensive amounts of trap rock occur in the western United States from the 

eastern flanks of the Rocky Mountains to the west coast. In the east, trap rock 

generally is restricted to the Triassic-Jurassic basins in the Piedmont 

Physiographic Province, primarily in the Connecticut River Valley of Connecticut 

and Massachusetts; the Palisades of New Jersey and New York; the Triassic 

Lowlands Section of Pennsylvania, Maryland, and northern Virginia; and in

Georgia and Alabama.

16
Other unclassified rocks include quartzite, sandstone, cinders, shell, and other 

rocks not widely used as aggregate. These rocks make up about 7 percent of 

the crushed stone production or 4 percent of the total aggregate production.

17
Although potential sources of crushed stone or sand and gravel are distributed 

across most of the conterminous United States, they occur in limited quantities 

in some regions. The colored and ruled areas on this slide show where sources

of aggregate, especially crushed stone, occur in very limited supply. The areas 

include the Coastal Plain and Mississippi embayment, Colorado Plateau and 

Wyoming Basin, glaciated Midwest, High Plains, and the non-glaciated Northern 

Plains. The areas conform to boundaries of Fenneman and Johnson (1946). 

18
The High Plains of Nebraska is selected as an example of the High Plains (tan 

ruled area) for this presentation.

19
The High Plains is an area of large, relatively flat, gently sloping plains. 

Significant topographic features in Nebraska include an extensive area of sand 

dunes in western Nebraska, and broad valleys of braided streams that originate

in the Rocky Mountains and flow eastward across the plains. 

20
Sand and gravel is generally confined to the Platte River floodplain and terraces, 

and to its larger tributaries. Most of the alluvial deposits attributable to the Platte 

River are fine sand in the river channel and sandy silt on the terraces 

(Huntzinger and Ellis, 1993), and are deficient in coarse sizes. Gravels may 

have chemical or physical problems that limit their use as aggregate (Langer 

and Glanzman, 1993). The small orange dots show active sand and gravel 

operations, as described by the Nebraska Conservation and Survey Division 

(NCSD).

Much of the area is underlain by soft, semi-consolidated, Miocene sediments, 

almost all of which are unsuitable for use as crushed stone. The eastern part of 

the cross-hatched area (High Plains province) is underlain by Cretaceous 

limestones, most of which typically are also too soft for use as aggregate. 

Sandstone in the western panhandle can be used for some applications such as 

roadstone. Active crushed sandstone operations are noted by the large brown 

dots. 

21
Permian limestones (280-248 million years) occur in eastern Nebraska (outside 

of the High Plains). These limestones generally make suitable quality crushed 

stone aggregate. To accommodate the demand for coarse aggregate, crushed 

limestone is transported to western and central Nebraska from quarries in the 

eastern portion of the state (shown by dark pink dots) or from quarries in 

Wyoming or Colorado to the west. 

22
During the late 1940s to the early 1950s, the construction of Harlan County Dam 

near McCook, Nebraska, required aggregate with special quality requirements 

not satisfied by limestone. The Rogers Brothers quarry in Golden, Colorado, 

over 350 miles to the southwest, provided aggregate for the dam. The quarry, 

which was started in 1925, was enlarged in 1949 to meet the new demand 

(Langer and Tucker, 2003).

23
A fortuitous situation in Nebraska helps reduce the cost of shipping some 

aggregate from Colorado to Nebraska. Large amounts of corn are grown in 

Nebraska, and some of that corn is shipped via truck to feedlots in eastern 

Colorado. To offset the cost of returning empty, some trucks return to Nebraska 

with granitic rocks quarried near Denver. Backhauling, in turn, offsets the cost of 

transporting aggregate.

Photograph from the Federal Highway Administration.

24
The Colorado Plateau and Wyoming Basin have similar characteristics regarding 

the availability of aggregate. The Colorado Plateau in northeastern Arizona is 

selected as an example for this presentation.

25
The Colorado Plateau consists of the high desert and buttes bordered by steep 

cliffs. The erosion on the cliff face in the right-hand photograph demonstrates the 

weakness of the rocks.

26
The area is generally underlain by poorly consolidated to consolidated Mesozoic 

sandstone, shale, and limestone, with the sandstone and shale being most 

prevalent. The soft sandstone and shale tend to yield poor-quality crushed

stone. Sand and gravel occurs in limited supplies, and when weathered or when 

derived from the erosion of soft sandstone or shale, tends to be of poor quality 

(Langer and Glanzman, 1993). The black dots indicate material sources that 

have completed the Arizona Department of Transportation (ADOT) 

Environmental Analysis process and do not necessarily represent an active 

aggregate operation.

27
There are very limited resources in the northwestern part of Arizona. Crushed 

stone is imported from north of Flagstaff and from near Show Low.

28
As one approaches Flagstaff from the east or north a large number of cinder 

cones are encountered in an area referred to as the San Francisco volcanic 

field. Some of those cinder cones are quarried for aggregate. 

29
Cinders tend to be a marginal aggregate but are used in some applications such 

as road base and as a surface for low-volume roads. Cinders can also be used 

as a high-quality, light-weight aggregate in certain applications.

30
Most of the cinders used in the Phoenix area come from quarries near Flagstaff. 

Trucks that haul the cinders to Phoenix commonly return to Flagstaff with normal 

weight aggregate that is used near Flagstaff and areas to the east.

31
Even though the cost to transport aggregate in mountainous areas can be three 

to four times as expensive as for open-highway transportation (Achterman and 

others, 2005; Hull, 2001), it is still economical to backhaul aggregate from 

Phoenix to Flagstaff.

32
Northeastern Wyoming is selected as an example of the non-glaciated Northern 

Plains (shown by the blue ruled area) for this presentation.

33
The non-glaciated Northern Plains consist of a variety of landforms, including 

gently rolling to steep dissected plains, flat-topped buttes, and steeply sloping 

badlands. 

34
Most of the region is underlain by sedimentary rocks consisting of sandstone, 

shale, conglomerate, and scattered limestone. These rocks are generally poor 

sources of aggregate. Stream channel and terrace deposits are the source of

sand and gravel, but the quality and clast size of the gravel is highly variable.

The black and yellow dots indicate active aggregate operations according to the 

Wyoming Geological Survey (Harris, 2004). There are no operations quarrying 

limestone, granite, or trap in the non-glaciated plains of Wyoming.

35
In the portion of northeastern Wyoming, encompassed by the non-glaciated 

Northern Plains, traditional sources of aggregate are extremely limited. To avoid 

large transportation costs, clinker (the red areas highlighted by the red ovals) is

often used as a substitute for gravel and crushed stone. 

Clinker, also referred to as scoria, porcellanite, and red dog, is hardened 

claystone, siltstone, and sandstone that was baked by the natural burning of 

coal beds. The process is similar to firing clay to form brick. Claystone and 

siltstone near the burning coal are altered to a brick-like material, and sandstone 

is hardened by the heat (Hoffman, 1996).

36
Clinker makes up over one-third of the crushed stone produced in Wyoming 

(U.S. Geological Survey, 2007); the principal use is for surfacing roads.

37
Iowa is selected as an example of the Glaciated Midwest (shown by the green 

ruled area) for this presentation.

38
The glaciated Midwest is an area of loess hills in the western part of the state, 

and flat plains, rolling hills, and low rounded hills in the rest of the state. Much of 

Iowa is covered with thick unconsolidated material.

39
The cross-hatched pattern on this slide shows areas where the bedrock is 

overlain by overburden greater than 150 feet thick. The amount of overburden 

that a producer is willing to extract to access the underlying rock depends on a 

number of factors, including the mineable thickness of the underlying rock, the 

quality of the underlying rock, and the proximity to market area. In general, 

overburden of 150 feet or more will make crushed stone quarrying 

uneconomical.

Bedrock in the northwestern part of Iowa consists primarily of sandstone and 

shale that do not make good-quality aggregate. Much of the eastern part of the 

state is underlain with potentially suitable bedrock, more than half of which is 

covered with overburden too thick to allow economical extraction of the rock. 

Sand and gravel are abundant throughout the region, but in the northern part is 

commonly buried by fine-grained sediments. Aggregate from the Missouri River 

and tributaries may be contaminated with deleterious material from the 

underlying soft sandstone and shale bedrock (Langer and Glanzman, 1993).

The purple dots are Iowa Department of Transportation (IDOT) approved 

sources of aggregates and may not be active quarries or pits.

40
The Iowa DOT approved sources of aggregates occur, not only in Iowa, but also 

in nearby states. This allows for more access to aggregates with special 

characteristics (such as the Sioux quartzite) and allows for access to nearby 

mineable limestone resources located outside of the state.

41
Louisiana is selected as an example of the Coastal Plain and Mississippi 

Embayment (shown by the purple ruled area) for this presentation.

42
The topography of the Coastal Plain and Mississippi embayment in Louisiana 

includes nearly flat floodplains, swamps and marshes, and pine barrens. 

Photograph of floodplain from the U.S. Army Corps of Engineers.

Photograph of cypress tupelo swamp and pump-jack from the U.S. Geological 

Survey.

43
Louisiana is located primarily in the Mississippi embayment, a geologic trough 

where, as sea level has risen and fallen over geologic time, late Tertiary period 

and Quaternary period sediments have accumulated to a thickness of about 

40,000 ft. These sediments consist almost entirely of unconsolidated sand, silt, 

clay, and organic matter (Saucier and Snowden, 2008), none of which can be 

used in their natural state as aggregate. 

Louisiana mines very little stone, the only source is anhydrite (dehydrated 

gypsum) that is mined in Winn Parish in the north-central part of the state. 

Anhydrite has been used quite extensively in the past by local and parish 

governments for aggregate surface courses on unpaved roads near the deposit. 

The Louisiana Department of Transportation and Development has used 

anhydrite for shoulder surface course in some rural highways.

Gravel is so limited in the area that shells dredged from the Gulf of Mexico are 

commonly substituted for gravel in low-specification applications. Louisiana 

imports almost all of its aggregate. The blue dots show ports that, according to 

the Army Corps of Engineers, receive aggregate.

44
The majority of aggregate used in Louisiana (in the red circle) is shipped via

barge from other states, including Arkansas, Illinois, Kentucky, and Missouri, and 

via freighter from Mexico. During 2006, over 11 million tons of limestone were

shipped to Louisiana by shallow draft barge (U.S. Army Corps of Engineers, 

2010). 

The blue dots show ports that, according to the Army Corps of Engineers, either 

ship or receive aggregate.

Photograph of barge from the U.S. Army Corps of Engineers

Photograph of freighter from the U.S Geological Survey

45
If potential sources of aggregate are present, they must meet certain quality 

parameters before they can be put to use. Those quality parameters are 

determined by the final application and can restrict the development of otherwise

high-quality aggregate. In general, aggregates must meet certain physical 

property requirements, including soundness, hardness, strength, porosity, and 

specific gravity, and they must not contain contaminants or deleterious 

materials. Societal issues, such as encroachment by conflicting land uses and 

permitting considerations, and environmental issues can prevent or limit 

development of otherwise suitable aggregate. 

The remainder of this presentation will describe techniques that have been used 

successfully in six geographic areas to address those societal and 

environmental issues. The green dots show the locations of case studies on 

quality, societal, and environmental issues that limit aggregate development.

46
The modern stream channel of the Agua Fria River west of Phoenix, Arizona, is 

mined and processed to provide aggregate to the greater Phoenix area. This 

example demonstrates how aggregate quality can change with depth and with 

weathering.

47
The alluvium in the lower reach of the Agua Fria River occurs as three distinct 

alluvial deposits. The ages of the deposits can be estimated through correlation 

with units described by Huckleberry (1995). The upper alluvial deposit correlates 

with Huckleberry‘s unit Y2 – the modern stream channel of the Agua Fria River 

(<0.5 thousand years old). The middle alluvial deposit correlates with deposits 

associated with Huckleberry‘s unit Y1 – Holocene alluvium located outside the 

modern stream channel of the Agua Fria River (<10 thousand years old). The 

lower alluvial deposit correlates with the deposits associated with Huckleberry‘s 

unit M2d – the lowest and youngest Pleistocene epoch stream terrace along the 

Agua Fria River (10-200 thousand years old).

48
Gravel from the Agua Fria was first divided by deposit (upper, middle, and lower 

alluvial deposits), then into three general rock types—igneous, metamorphic, 

and Tertiary volcanic rocks. Each rock type from each deposit was subjected to 

three engineering tests. In almost every case the quality decreased with 

increase in depth. It is noteworthy that the best values of rock property for the 

Tertiary volcanic rocks are almost always worse than the worst values of the 

igneous and metamorphic rocks (Langer and others, 2010). 

Photograph from the U.S. Geological Survey.

49
This photograph demonstrates that the Tertiary volcanic rocks (behind pencil) 

are so weak that they break apart rather than be plucked intact from the face of 

a pit when being excavated with earthmoving equipment. 

Photograph from the U.S. Geological Survey.

50
The upper alluvial deposit can easily be processed into material specification 

construction-grade aggregate. The middle alluvial deposit is generally lower 

quality than the overlying upper alluvial deposit. The middle alluvial deposit has 

more deleterious materials but commonly can be processed into specificationgrade aggregate with the use of impact crushers. The lower alluvial deposit is 

the lowest unit that could theoretically be extracted without extensive interburden removal (Langer and others, 2010). Waste factors in lower alluvial 

deposit are 14 percent higher than the upper alluvial deposit, and the deposit 

commonly does not make construction-grade aggregate with current processing 

equipment. Blending material from the upper and middle alluvial deposits may 

extend the aggregate supply in this area.

51
The stream channel and low terraces of the South Platte River north of Denver, 

Colorado, are mined and processed to provide aggregate to the greater Denver 

area. This example demonstrates how aggregate quality can change from one 

location to another.

52
Clear Creek flows eastward from the mountain front towards Denver, where it 

joins with the South Platte River, which flows northward toward Fort Lupton. 

Sand and gravel were mined along Clear Creek, but urbanization has shut off 

that area for most gravel mining. Most new gravel operations occur between 

Brighton and Fort Lupton.

Near the mountain front, the sand to gravel ratio in the Clear Creek alluvium is 

about 1:1. Downstream, between Brighton and Fort Lupton, the ratio is about 

3:1. Significantly more material near Fort Lupton needs to be mined and 

processed to obtain an equal amount of gravel as can be obtained near the 

mountain front.

53
This slide shows the area between Fort Lupton and Brighton in more detail. The 

next slide will show how the area will look in the future if all currently permitted 

sand and gravel operations are mined out and reclaimed as outlined in their 

permits (Langer, 2009).

54
Almost all of the sand and gravel operations are planned to be reclaimed as 

reservoirs to hold water appropriated from the South Platte River. 

55
One of the consequences of mining sand and gravel with a high sand-to-gravel 

ratio is that there are large piles of sand that remain after processing and 

marketing the gravel.

Photograph of reservoir from the Minerals Information Institute.

Photograph of sand piles from Amy Lilienfeld.

56
To avoid wasting the sand, some operators have ready-mix or asphalt plants 

located midway between their crushed stone operations near the mountains and 

their sand and gravel operations near Brighton.

57
Crushed stone and manufactured sand can be used for applications such as 

SuperPave, and natural sand and gravel can be used for types of concrete that 

require surface finishing.

Photograph of asphalt plant from Astec Inc.

Photograph of concrete from the Federal Highway Association.

58
Limestone in Florida is mined and processed to provide some of the aggregate 

for in-state use. This example demonstrates how aggregate quality can affect its 

use and how a sophisticated transportation system can address aggregate 

shortages.

59
The geologic processes that created the limestone in Florida produced rocks 

that are not uniform in hardness, durability, or chemical composition. The red 

dots on this map show aggregate sources approved by the Florida Department 

of Transportation (FDOT). FDOT also defines acceptable applications for 

crushed stone, based on its quality.

60
During 2006, about 120 million tons of aggregate was produced in Florida 

(Florida Department of Transportation, 2007). Aggregates for state projects 

must meet specifications prescribed by FDOT. The dark pink area on the map is 

underlain with limestone (Miami limestone) that generally is hard, durable, and 

acceptable for use as aggregates in the construction industry. Much of the 

limestone shown by light pink is soft and fails to meet specifications for 

engineered applications (Florida Department of Transportation, 2009). However, 

these softer rocks commonly can be used to create ―limerock,‖ a fill material that 

can be compacted into a durable base for roads and buildings. Low-quality 

limestone also can be used in parking lots and sidewalks. 

61
During 2006, about 8 million tons of aggregate was imported to Florida from 

other U.S. states. Much of this material was granite, which is imported for 

wearing surfaces on high-traffic pavements where durable aggregates are

needed to meet skid resistance and abrasion requirements. 

62
Florida imports granite from Canada and Honduras, and limestone from the 

Bahamas via freighter into facilities at the Port of Tampa, Port Manatee, Port 

Canaveral, and the Port of Jacksonville. 

63
About 10 million tons of aggregate used in Florida is recycled asphalt or 

concrete (Florida Department of Transportation, 2007).

64
Southwestern Indiana contains a large area that is underlain by potential 

sources of limestone. This example demonstrates how environmental issues 

can encumber access to aggregate resources.

65
Over 4 million acres of land in the area enclosed by the oval are underlain by 

potential sources of limestone (shown in dark pink). 

66
Managed lands, such as parks and conservation areas (shown by dark green), 

overlie about 0.14 million acres, or about 5 percent, of the limestone.

Karst, floodplains, and wetlands (shown by light green) overlie about 0.9 million 

acres, or about 30 percent of the limestone.

By employing best management practices, most environmental impacts can be 

controlled, mitigated, or kept at tolerable levels and can be restricted to the 

immediate vicinity of the aggregate operation. Nevertheless, some otherwise 

high-quality aggregate resources may not be developed because of 

environmental issues. 

67
California is a state that primarily uses sand and gravel as aggregate. Southern 

California can be used as an example of how permitting affects the availability of 

aggregate.

68
The State of California passed the Surface Mining and Reclamation Act 

(SMARA) in 1975. SMARA requires that counties have sufficient permitted 

aggregate resources to meet the demand for the next 50 years (Kohler, 2006). 

69
According to Kohler (2006, p. 6), ―Permitted aggregate resources (also called 

reserves) are aggregate deposits that have been determined to be acceptable 

for commercial use, exist within properties owned or leased by aggregate

producing companies, and have permits allowing mining of aggregate material. A 

 ̳permit‘ is a legal authorization or approval by a lead agency, the absence of 

which would preclude mining operations.‖

70
During 2002, the California Geological Survey published a map containing data 

on the availability of permitted aggregate resources in 31 study areas throughout 

the state (Kohler, 2002). The 50-year demand for aggregate in each study area

was estimated and compared with the amount of permitted aggregate at the 

time. 

The exercise was repeated in 2006 (Kohler, 2006). The results for 12 of the 

study areas that occur in southern California are plotted on this map.

The yellow triangles show production areas. The size of the triangles reflect the 

relative amount of production, ranging from the smallest triangle, which indicates 

production of less than 0.5 million tons per year, to the largest triangle, which 

indicates production of greater than 10 million tons per year.

The blue circles indicate, by size, the relative 50-year reserve requirement. The 

green inner circles indicate, by size, the amount of permitted reserves. 

71
In the entire state, 25 of 31 study areas have less than half of required reserves. 

In southern California, 9 (shown by the red dots) of the 12 study areas have less 

than half of the required reserves. 

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The data on the 2006 map were compared with the data on the 2002 map. Total 

permitted reserves in the state decreased from 6.848 billion tons to 4.343 billion 

tons, with a total loss of about 2.5 billion tons of aggregate reserves (Kohler, 

2006).

Eighteen of the 31 study areas shown on the 2006 map experienced a decrease 

in permitted aggregate reserves, including 8 (shown by the red dots) of 12 in 

southern California.

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Aggregate is being transported long distances to accommodate the shortfall in 

permitted aggregate resources, resulting in significant transportation coat 

increases. Most of the transport is by truck. Aggregate is hauled from 

southwestern Imperial County into downtown San Diego, a distance of about 90 

miles. Coarse aggregate from eastern Ventura County is hauled as far as 60 

miles to western Ventura County. Aggregate from Orange County is hauled over 

50 miles to northern San Diego County. Aggregate is transported over 30 miles 

among numerous production districts (Kohler, 2006).

In addition, between 1 million and 2 million tons of aggregate are annually 

shipped by rail nearly 150 miles from central Riverside County into Los Angeles 

County, and sand is being shipped by barge from Mexico into the San Diego Bay 

region (Kohler, 2006).

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This example from the Minneapolis/St. Paul metropolitan area demonstrates 

how aggregate quality can affect its use, how urban encroachment can limit its 

development, and how plans for growth and development can protect aggregate 

for future use.

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The Minnesota Department of Transportation (MDOT) Office of Materials & 

Road Research tested several aggregate sources for the potential alkali-silica 

reaction (ASR). Results from the 14-day expansion test are shown in this map. 

The smaller symbols indicate test results on aggregate. The larger, green circle 

indicates the 14-day test result when fly ash is used in the concrete mixture. All 

aggregates in the mapped area had test results of less than 0.15 percent 

expansion when used in concrete with fly ash. By understanding the quality of 

the aggregate in an area, the sources of aggregate can be matched to the 

application.

Data from Minnesota Department of Transportation, (2009).

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Nearly one-quarter of the potential sources of aggregate in the Minneapolis/St. 

Paul area have been covered by development, and are no longer available for 

use.

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A new development is planned in the southeastern metropolitan area.

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The University of Minnesota Outreach, Research and Education (UMore) Park is 

a University-owned 5,000-acre property located 25 miles southeast of the Twin 

Cities in Dakota County. The goal is to build a sustainable, University-founded 

community of 20,000 to 30,000 people over a period of 25 to 30 years.

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The plan allows for gravel extraction on approximately 1,722 acres on the 

western edge of the UMore Park property. A 40-year lease agreement has been 

signed whereby a local aggregate producer will conduct phased gravel mining at

UMore Park, with gravel mining limited to a total of 160 acres at any given time. 

The lease agreement generates royalties for the University that will be 

designated for long-term support of special academic pursuits not adequately 

funded by other sources. Following local approvals, mining activities will 

tentatively commence in late 2011.

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There is an indisputable need for an uninterrupted, large supply of aggregate for 

the restoration and rehabilitation of the infrastructure. Aggregate needs to be 

mined as close as possible to the projects that use it.

Natural aggregate is widespread through the conterminous United States, but is 

not universally available for consumptive use. Some areas are devoid of gravel, 

and potential sources of crushed stone may be covered with sufficient 

overburden to make surface mining impractical. The aggregate may not meet 

the strict quality requirements for its intended use. Encroachment by conflicting 

land uses and environmental restrictions may limit access to potential aggregate 

resources. 

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