Infrastructure resources are the basic physical materials needed to support the development, maintenance, and growth of a society. Natural aggregate for construction, energy for fuel, and water for domestic and commercial use are primary infrastructure resources. Indeed, wherever people live, work, and travel in the United States, infrastructure resources are critical ingredients for sustaining a thriving society and maintaining a high quality of life.
In 1996, the Director of the U.S. Geological Survey (USGS) initiated a 5-year study to develop methods for assessing infrastructure resources and to characterize the location, distribution, and quality of the infrastructure resources of a part of the Colorado Front Range urban corridor between Denver and Fort Collins, Colo. (fig. 1). The Front Range Infrastructure Resources Project has completed its primary task and has gone on to identify geosocietal and environmental factors that influence the availability of these resources as well.
Figure 1. Index map of Front Range Infrastructure Resources Project (FRIRP) area. Area consists of 45 USGS 1:24,000-scale (7.5 minute) topographic quadrangles along the Denver-Greeley-Fort Collins section of the Front Range urban corridor. Most of the area is in the Great Plains but includes the foothills of the Colorado Front Range at its western edge.
The Colorado Front Range urban corridor between Denver and Fort Collins is a prime example of a region that has been shaped by its natural resources. The region has evolved through a series of booms and busts — beaver furs, gold and silver, cattle, coal, oil and gas — and now treasures perhaps its most precious commodity, the "Colorado lifestyle." In Colorado's early years, its beauty and natural resources must have seemed inexhaustible. These qualities have drawn people to Colorado, and the Front Range urban corridor in particular, which is now being threatened by its rapidly growing population.
As population centers grow outward and become interconnected, infrastructure resources may become fragmented, depleted, or precluded from use, while natural vegetation, open spaces, wetlands, and wildlife habitat are lost. Political, social, and economic considerations strongly influence whether land is used to supply resources or is put to other uses such as parks and recreational facilities, residential and commercial development, open space, or agriculture. Planners, decisionmakers, and the public face difficult choices, some of which may be irreversible.
The Front Range Infrastructure Resources Project has created a legacy of technical information, most of it in digital (electronic) format, on the location, distribution, and quality of natural aggregate, oil, natural gas, coal, and water resources in the project area. These types of data are required if planning is to consider the availability and cost of the infrastructure resources necessary to support and maintain the expanding society of this part of the Colorado Front Range urban corridor.
The steady increase in aggregate production and use that has occurred in the Front Range urban corridor since the 1950's is expected to continue due to projected population growth and demand for infrastructure improvements and maintenance (fig. 2). Whether local producers can meet future aggregate demand is a growing concern. Although there is an abundance of potential aggregate resources in the project area, many of them are no longer accessible for extraction. Expanding population centers have built out and gradually encroached on existing deposits, thus rendering many nearby resources inaccessible. Zoning restrictions, land use conflicts, environmental concerns, and public opposition to mining are also making acquisition, permitting, and development of nearby aggregate resources increasingly difficult.
Figure 2. Colorado aggregate production and population growth for 1951 through 1997. Larger version of chart.
The tonnage of aggregate being locally permitted for extraction has steadily decreased over time, and the area has been producing more aggregate than it has been permitting new resources since 1994. The result has been a net decrease in available reserves. Consequently, recoverable resources are being hauled from greater distances as local resources become depleted or inaccessible. If this trend continues, aggregate operators may be forced to move to resource areas even farther away from local markets and transportation costs will increase. Increased costs for this aggregate would be passed along to the State or counties as higher construction bids, to the contractor as higher supply costs, and ultimately to the consumer in the form of higher taxes, user fees, and purchase prices.
Significant volumes of oil, gas, and coal remain in the rocks of the Denver Basin. Current estimates for the life of production from wells in the greater Wattenberg area (fig. 3) are at least 30 years, and much of the greater Wattenberg area has a moderate to high potential for additional drilling to exploit remaining oil and gas. In contrast, future production of coal or lignite within the project area is unlikely. The value of the coal beds may, instead, rest in its potential for economic concentrations of natural gas as coal-bed methane rather than for the coal itself.
Figure 3. Location of the Wattenberg oil and natural gas producing area and the Boulder-Weld coal field and Foothills district coal producing areas relative to the Front Range Infrastructure Resources Project area.
Although oil and gas resources remain in the ground for exploitation, continued growth in the Front Range region may limit future development of additional energy resources and, in fact, may curtail ongoing resource development. Even though oil and gas operators, as owners or lessees of the mineral rights, have legal access to the land surface for exploration and production, State statutes and city and county regulations prevent or limit exploration and production activity where development has already occurred. Thus, some portion of the petroleum resource base has already been excluded from production. There will probably be increased competition for use of the land surface between surface owners and owners or lessees of the underlying mineral rights.
Urban areas commonly rely on ground water for at least part of their municipal water supply. As population increases, urban areas expand and require larger volumes of water. However, the very same growth that demands more water may ultimately decrease its availability, and human activities in expanding urban areas can introduce ground-water contaminants that degrade its quality, and thereby limit its use.
Because shallow aquifers in the project area are easily recharged, water levels generally have not been greatly affected by the development of urban areas. Water levels decline and rise from year to year owing to climatic fluctuations and changes in withdrawal rates, but long-term average water levels do not change significantly in spite of increased development. However, the shallow depths and generally high permeability of the shallow aquifers cause them to be particularly susceptible to contamination. Pollution from sources such as underground fuel storage tanks, chemical spills, landfills, and fertilizers and pesticides applied to crops and lawns can easily infiltrate shallow aquifers and can degrade the quality of their water. Thus, although water in the shallow aquifers is easily renewable, it may not be suitable for some uses.
In contrast, water levels in the bedrock aquifers are more sensitive to increases in urban development because they are less permeable and have limited outcrop areas where they can receive recharge from precipitation and surface water. Although some wells in the bedrock aquifers have recorded drawdowns of more than 250 feet between 1991 and 2000, the water level in the wells is still above the top of the aquifers. Thus, the aquifers still contain a large volume of water, but, because they are very slow to recharge (perhaps taking thousands of years), water that is withdrawn from the aquifers may be, in effect, nonrenewable by natural means.
Reclamation of resource production areas
Mining reclamation involves altering the landscape from one produced by resource extraction to one that promotes a new land use. Production of oil and natural gas in the project area has a minimal effect on the land surface. Shallow underground coal mining practices and subsequent coal mine fires initiate land subsidence over old mines that is difficult or impossible to address by current reclamation technology. Where the development of water resources involves landscape modification, it is usually construction of permanent structures (dams, tunnels, reservoirs) rather than a temporary land usage that will eventually require reclamation. Production of aggregate resources, however, requires the removal of large volumes of material from the surface, which creates pits and quarries that are obvious intrusions to the surrounding landscape. Reclamation is the process of converting these holes in the ground to a new land use.
Reclamation of exhausted aggregate mine sites is an essential activity that can have a positive impact on a region. The Colorado Mined Land Reclamation Act and the Colorado Land Reclamation Act for the Extraction of Construction Materials require an approved mining permit and reclamation plan before mining begins. Permit applications and reclamation plans must consider a variety of site characteristics, including hydrology, geology, geochemical and geological hazards, land use and zoning, air quality, archeological, historical, and scenic features, vegetation, and wildlife habitat, as well as potential operational impacts such as noise, dust, truck traffic, and blasting effects. The promise of a reclamation project that will produce a land use that is viewed as necessary to the community or highly beneficial and desirable to the public may help to soften opposition and ensure continued availability of aggregate resources. An important role for the aggregate industry is to implement creative reclamation designs that integrate sound scientific practices with aesthetic and socioeconomic values of the public.
Factors in resource availability
Many factors affect the availability of infrastructure resources like aggregate, energy, and water as well as all other natural resources including the land itself. Overall, there is a general lack of awareness that access to resources will be the source of some of the most intense conflicts of the future. Most people take for granted that when they want to repave a road, add an addition to their home, water their lawn, or hike in the local open space, the resources that make it possible will always be there at a reasonable price. That may no longer be the case in the near future. In fact, not too long ago the construction boom along the Front Range produced a shortage in the raw materials needed to make concrete, an incident that went largely unnoticed except by people whose home improvements were put on hold for several months while the needs of commercial customers were met.
However, factors affecting resource availability are not as simple as whether or not a resource is physically available. As urban areas expand, planners and policymakers must balance multiple, often conflicting demands being placed on the land. A local change in land use in one city can have ripple effects throughout the larger region. As urban density increases and spreads across a region, so does interdependence on the entire region for resources.
Valuable resources on the land may be lost forever through resource sterilization. Resource sterilization occurs when the development of resources is precluded by either an existing land use or the development of another resource. For example, a housing development or shopping center prevents extraction of the gravel underneath. Roads, parking lots, and other impervious surfaces may sterilize aquifer recharge areas and ultimately reduce the amount of water available in wells many miles away.
A resource conflict can occur when two or more resources exist within the same geographic area. The conflict arises when there are differences of opinion as to whether resources should be developed at all, which resource should be developed first, or how development of one resource affects the development of another. Resources can be any kind -- aggregate, energy, water, biological, agricultural, minerals, scenic, historical, and so forth. Selecting a single use from among the various possibilities would be to the detriment of each of the remaining interests, and no matter which use prevails, resources are lost to society. In addition, zoning, existing long-range plans, mineral rights, and other legal issues may create other conflicts that further complicate the situation.
For example, developing oil and gas resources creates a conflict with developing aggregate resources. Some of the oil and gas production areas overlap areas containing near-surface aggregate deposits. Colorado statute requires aggregate operators to leave a buffer of undisturbed land around man-made structures such as oil and gas well sites, access roads, pipelines, and tank batteries. In some instances, more than 300,000 tons of aggregate may remain in the ground owing to the presence of a single well along with its associated production infrastructure. Unless wells are abandoned prior to or during aggregate mining, the aggregate resource around them will likely never be mined.
The Colorado Front Range region will be required to address difficult questions that affect the future availability of local infrastructure resources. Planning the best short-term and long-term uses of the land will involve a delicate balance between maintaining a certain quality of life, while ensuring continued economic integrity of the region. The Front Range Infrastructure Resources Project has created an archive of technical information, mostly in digital format, on the location, distribution, and quality of natural aggregate, oil, natural gas, coal, and water resources in the project area. These types of data will be necessary if planning is to consider the availablilty and cost of the infrastructure resources necessary to support and maintain the growing population in the region.