Case Study: Environmental Impact

Marriott, B. (1997). Environmental impact assessment: A practical guide. New York, NY: McGraw-Hill.

11.1 Terminology

Energy is the capacity of a physical system to do work. We refer to energy resources predominantly as the fuels and methods used to pro- duce energy. Fuels may include oil, natural gas, coal, wood, radioactive materials, sunlight, or wind and water in the sense that rapid movement through turbines or windmills can generate electric energy. In this sense, energy is comparable to the term power.

The common measurement unit for energy consumption is the British thermal unit, abbreviated Btu. One Btu is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.

11.2 Proposed Project or Action Characteristics

The first step in the assessment of potential energy impacts is a thor- ough description of relevant features of the proposed project or action. The description should include the following:

All energy-consuming equipment and processes which will be used during construction and operation of the project

Consideration of the total lifetime of the project or action, if possible

Energy efficiency of required materials, fuels, or equipment

The potential of the project to generate trips, including the number of trips; mode of transportation (car, truck, bus, transit, or rail), length of trips, and use of fuel

Other possible secondary effects of the proposed project or action that may cause energy consumption, such as related facilities or population growth

Any energy conservation features, equipment, or incentives

• An estimate of the total energy requirements based on fuel consumption or other energy use

The Affected Environment section of the environmental document should identify suppliers of electricity, gas, and other energy fuels and sources, including capacities and related generating facilities.

11.3 Impact Analysis

Most all activities consume energy in some fonn or another. The goal of the environmental impact analyst is to determine the degree to which a particular proposed project or action consumes or conserves energy or fuels compared with a no-action, or no-build, alternative. The assessment may be no more than a paragraph or two, qualita- tively describing the expected impact of the project. A more detailed quantitative analysis may be required for more complex projects, or for projects or actions that directly involve the use or production of energy or energy resources, such as nuclear power plants, hydroelec- tric dams, coal mining, methane recovery, development of solar-pow- ered vehicles, windmill construction, and oil and gas drilling.

Consumption of energy can have a direct or an indirect impact on the proposed project or action. Energy consumption or conservation effects can be short-term or long-term and, if possible, should be cal- culated over the lifetime of a project or action. Energy use also is the type of impact included in the section of the environmental document related to irreversible and irretrievable commitments of resources. The discussion may include an assessment of how the project may preempt future energy development or future energy conservation. Impact assessment between no-action and proposed action condi- tions, and among various proposed alternatives, can be made by com- paring actual units of the particular resource, or by converting all energy resources to British thermal units. For example, the electricity use of various alternatives can be directly compared in units of kilo- watthours per day or gigawatthours per year. Natural gas consumption can be compared directly in thousands of therms per year. For alternatives involving differing energy source usage, conversion to Btu's permits a direct comparison. Conversion factors for kilo-watthours, therms, gallons of gasoline or diesel fuel, and gallons of crude oil are available from U.S. Department of Energy publications. For example, 1 kWh of electricity is equal to approximately 3414 Btu, and the heat of combustion of 1 gal of diesel fuel is equal to approxi- mately 147,600 Btu (LACMTA 1993). Selected proposed action alter- natives can thus be compared to each other and to the no-action alternative.

A light-rail transit project may use electricity to power the trains and at the stations, increasing the total consumption of that resource. The associated effect of possibly reducing trips in individual vehicles as riders are diverted to the transit system must then be entered into the assessment as an offsetting factor. Energy saved through fewer vehicle trips or better flow of traffic should be calculated by estimating corre- sponding reductions in consumption of gallons of gasoline or diesel fuel. If an all-bus alternative is being considered, the energy consump- tion of that alternative must be changed to Btu's from diesel fuel, or from compressed natural gas (CNG) if the system uses CNG buses.

Energy consumption of a no-action, or no-build, alternative may consist of existing conditions or calculations of future without-project conditions. The energy ramifications of not taking action or not pro- ceeding with a proposed project can frequently be overlooked, but should, in fact, be an important consideration in the overall analysis. A proposed action or project may provide improved energy or fuel use efficiency, less reliance on nonrenewable resources, or greater oppor- tunities for energy conservation than a no-action alternative.

To properly calculate energy use, the assumptions and information on the proposed project must be used. For example, to estimate the use of energy for a highway project first use information and/or as- sumptions on direct energy consumed by vehicle propulsion, including total vehicle miles traveled, mix of trucks and passenger cars, traffic volumes, speeds, delays at signals, distance traveled, and thermal value of the utilized fuel. Next, gallons of gasoline or diesel fuel con-sumed per mile of travel must be estimated. Finally, energy consumption for construction activities must be included.

A specific example of the calculation of energy consumption of a proposed highway project (U.S. DOT, FHWA, and PADOT 1993) uses the procedure summarized below.

Step 1. Calculate energy factors for automobiles, medium-weight trucks, and heavy trucks by multiplying the percentage of each ve- hicle type times a vehicle energy factor based on average assumed speed for each alternative and for the no-build alternative. Add the resultant three numbers and divide by 100 to get a composite vehi- cle energy factor. (It will be a number such as 4.034.)

Step 2. Multiply the composite vehicle energy factor from step 1 by the average daily traffic by the length of highway by 106, to get the total annual vehicle energy, in Btu's, for the year of completion and for the year of completion plus 20 years, such as 2001 and 2021, for the no-build alternative and each proposed build alterna- tive. (It will be a number such as 3.46 x 1010 Btu.)

Step 3. Multiply the construction energy factor (from known proj- ects) by the construction cost of each alternative by 104 , to get the total construction energy. (It will be a number such as 9.46 x 1010 Btu.)

Step 4. Add the 2001 and 2021 average daily traffic values, and divide by 2 to get an average for the 20-year period. Multiply that average by the composite vehicle energy factor by the number of miles saved, compared to the no-build alternative, by 106, to get the energy savings per year over the 20-year period for each build alter- native. (It will be a number such as 3.39 X 1010 Btu/yr.)

Step 5. Add the total annual vehicle energy for the year of comple- tion (2001) and the total construction energy, then divide by the en- ergy savings per year to determine the recovery period for each build alternative. (It will be a number such as 3.46 x 1010 plus 9.46 x 1010, divided by 3.39 x 1010, or 3.8 years.)

This example is given to illustrate the numerous steps in an energy analysis and the variety of required input factors.

The efficiency or wastefulness of project machinery, fuel use, in- duced transportation, or energy resource requirements should be dis- cussed in the environmental document. Related environmental effects of various energy uses also may be a consideration. Certain types of fuels are known to be more efficient and to produce less air pollution, or disturbance to natural resources, than other types of fuels. Whether the project uses renewable or nonrenewable energy, resources will be of interest to resource agencies and the public.

The ability of existing energy suppliers, such as local electric com- panies, to meet the needs of the proposed project or action can be de- termined through coordination with local utilities and comparison with existing capacities.

Results of an analysis of energy effects should comparatively evalu- ate all alternatives in terms of overall energy consumption, and in terms of reducing wasteful, inefficient, and unnecessary consumption of energy during project construction, operation, or maintenance. Criteria for assessing significance, or degree, of impact may include the following:

• Overall energy consumption

• Wastefulness or efficiency of energy use

• Consumption during construction or operation beyond capacity of energy suppliers to meet demands

• Need for construction of additional facilities for energy generation or distribution to meet increased demand.

11.4 Secondary and Cumulative Effects

The fact that changes in energy consumption often have ripple effects, or secondary ramifications, can lead to an estimated impact analysis at best. Many, many diversified energy resources and energy consump- tion uses can be indirectly related to a proposed change in use of one resource. Another consideration, especially for land-use and manage- ment plan assessments, is the potential for a proposed action to place limitations on energy and mineral exploration and development. The impact of such a restriction often cannot be quantitatively deter- mined.

11.5 Mitigation

The study should explore the feasibility of measures to reduce energy consumption, increase energy efficiency and conservation, reduce any associated environmental effects of energy use, and reduce dependency on nonrenewable resources. Mitigation measures may include these:

• Incorporation of energy-efficient equipment and practices into con- struction and operational procedures

• Reduction of wasteful, inefficient, and unnecessary consumption of energy

• Use of location, orientation, and design features to minimize energy consumption, including transportation energy

• Timing of energy use to not coincide with peak energy demand peri- ods

• Use of alternate fuels or energy systems

• Energy conservation through recycling

• Recovery and use of by-products or wastes of the process to produce energy, such as methane recovery from landfills

As with other areas of potential environmental effects, the assess- ment of possible energy impacts and mitigation measures should be based on an inquiring thought process that can include possibilities related to project design, operation, and conservation options. The awareness of energy as a resource, and the examples known from other projects or experiences, will lead to an appropriate considera- tion of possible energy effects of the proposed project or action.

In compliance with Section 106 of the National Historic Preservation Act (NHPA) of 1966, as amended, and other related legislation and regulations, the identification and impact evaluation related to his- toric and archaeological resources must follow a stringent, systemat- ic, timely procedure. This chapter examines what is commonly referred to as the Section 106 process. The goal here is to present a basic understanding of the requirements and the process. Several ex- cellent, more detailed, publications are available from the Advisory Council on Historic Preservation (ACHP), an independent reviewing agency established by the National Historic Preservation Act.

The environmental impact analyst should not become overwhelmed by the numerous individual laws and regulations related to historic and archaeological res(lurce protection. It is not necessary to be famil- iar with every statute. By following the direction given within the ACHP regulations, "Protection of Historic Properties" at 36 CFR Part 800, and other ACHP user-friendly publications, the analyst either will already be in compliance with pertinent other laws and regula- tions or will be referred to them as appropriate. This chapter refers only to those laws or Codes of Federal Regulation (CFR) which are generally in more common usage and should be familiar to even the nonhistorian environmental assessment analyst.

Although the laws and regulations are the same, the environmental impact analyst should be aware that requirements for Section 106 vary immensely from state to state. What may be an appropriate level of effort to meet requirements for surveys in one state, or even agency, may not be the "appropriate" level of effort in a different state or for a different agency. Required documentation in the form of spe- cific reports and forms for each step of the process also may vary sig- nificantly by state. The analyst should be aware that each state or agency sincerely believes that its way is not only the best approach, but the only appropriate approach. Many times there are legitimate reasons for these geographic or agency peculiarities.

This chapter points out some of the geographic and agency varia- tions that the author has experienced. The analyst, however, should become thoroughly familiar with the acceptable methodologies for his or her particular state, agency, or project being assessed.

As with other chapters in this text, this description of the require- ments of Section 106 procedures is not intended to replace the inclu- sion of a qualified local historian and archaeologist on the study team. Whereas evaluation of potential project effects may be conducted by more of a generalist, the identification and description of resources must be completed by qualified personnel with the appropriate educa- tional and experience backgrounds.

12.1 Comparison of Section 106 and Section 4(f)

Section 106 of the National Historic Preservation Act applies to feder- al, federally assisted, or federally licensed and permitted projects and actions. Its protection is afforded to properties listed on, or deter- mined eligible for, the National Register of Historic Places (NR). The National Register of Historic Places is contained within 36 CFR Part 60 and does not necessarily contain only properties or sites of nation- al significance, but also of state or local significance. The Section 106 process has two basic requirements: (1) The sponsoring agency must take into account the effect of the proposed undertaking on any dis- trict, site, building, structure, or object that is included in, or eligible for, the National Register of Historic Places. (2) The Advisory Council on Historic Preservation must be afforded a reasonable opportunity to comment.

Section 110 of the National Historic Preservation Act provides di- rection for historic preservation management within federal agencies for resources owned or controlled by the agencies. Section 110 also provides protection to National Historic Landmarks (so designated under the authority of the Historic Sites Act of 1935), as described in the ACHP regulations, "Protection of Historic Properties," 36 CFR Part 800. National Historic Landmarks are historic properties of out- standing national significance that have been specially designated by the Secretary of Interior. Under Section 110 of the National Historic Preservation Act, National Historic Landmarks require special treatment: Agencies must "to the maximum extent possible, undertake such planning and actions as may be necessary to minimize harm to any National Historic Landmark that may be directly and adversely affected by an undertaking." This special consideration applies in ad- dition to requirements of Section 106.

Section 4(f) of the DOT act of 1966 also applies to an adverse effect on a National Register listed or eligible historic or archaeological property, or a taking of that property, for federally funded transporta- tion projects (refer to Chap. 10). An exception is that Section 4(f) does not apply to archaeological resources significant for the recoverable data contained, but only to archaeological resources significant for preservation in place.

Of the two legislative requirements, Section 4(f) is the more restric- tive. Section 4(f) explicitly states that the transportation project can- not be approved unless there is no feasible or prudent alternative. Feasible and prudent do not mean just convenient, but that the avoid- ance alternative would have to cause impacts of an extreme magni- tude. For example, the taking of residential homes to avoid Section 4(f) involvement is often considered completely within the realm of feasible and prudent. Section 4(f) absolutely prohibits selection of an alternative involving Section 4(f) property, if another alternative is deemed to be feasible and prudent.

The Section 106 process does not require preservation of every his- toric property in every case. The Advisory Council on Historic Preservation does not have veto power over an agency's action. The sponsoring agency has the ultimate right to make the final decision, even if it disagrees with opinions of the State Historic Preservation Officer or the Advisory Council on Historic Preservation. Results of the Section 106 process can range from full preservation to unmitigat- ed destruction of a property. The process does ensure that an agency weighs preservation into the balance with the projected benefit of the completed undertaking, costs, and other factors.

12.2 Timing of Section 106 Activities

The Section 106 process includes numerous steps, as outlined in Fig. 12.1. Simplified, the three basic steps are as follows: (1) Identify resources; (2) assess impacts; and (3) if an adverse effect is identified, consult about ways to avoid, reduce, or mitigate the harm. These three steps are about the same as those undertaken for any area of potential environmental impact. Although the three basic steps are identification, assessment, and mitigation, there are numerous inter- mediate requirements within each basic step for compliance with the Section 106 process.

Although it is a separate legal requirement, Section 106 processing should be coordinated as much as possible with the environmental re- view process of NEP A. Because a public review period is required for the Section 106 process, it is extremely desirable to include the possi- ble project effects on historic and archaeological resources within the NEPA required Environmental Assessment or Draft Environmental Impact Statement. Because there are so many steps to the process prior to detennination of impacts, and many of these initial steps re- quire coordination with, and concurrence by, other agencies, it is im- perative that historic and archaeological studies begin immediately in the study process.

For example, concurrence of the State Historic Preservation Officer is required on the area of potential effect, the eligibility of potential re- sources for the National Register of Historic Places, and the results of application of the criteria of effect. All this needs to be accomplished if the Environmental Assessment or Draft Environmental Impact Statement is to include a description of impacts. The surveys needed just to gather the information required to initiate consultation for these concurrences can be extensive. If a review time of, say, 4 to 6 weeks is factored into the process for the State Historic Preservation Officer to respond, it is easy to understand how the Section 106 process can severely affect the schedule and progress of the draft envi- ronmental document.

Section 106 process documents can, however, be circulated for review separately from NEP A environmental documents, if it is not possible to include them within the Environmental Assessment or Draft Environmental Impact Statement. The final NEPA environmental doc- uments, however, should document the outcome of the Section 106 process. Because it is a separate legal requirement, Section 106 compli- ance is applicable to undertakings that do not require an Environmental Assessment or Environmental Impact Statement under NEPA. Section 106 prohibits expenditure of public funds on a project until the process is successfully completed.

Consideration of historic and archaeological resources must occur in the early stages of project planning so that preservation concerns can receive thorough consideration as a project or action is planned. Early preservation review also pennits modification to a project while such modifications are relatively easy to accomplish and reduces the potential for conflict and delay.

12.3 Area of Potential Effect

While in many states this early requirement of the Section 106 process is ignored, at least in the formal sense, in other states it is considered a major task. The task is to define the boundary of the possible impacts of the proposed project or action that may cause changes in the character or use of historic properties. This boundary then sets the geographic limits of subsequent historic and archaeolog- ical resource surveys.

The area ofpotential effect (APE) always includes all lands to be disturbed or cleared by the proposed project or otherwise affected by a proposed action. The APE also normally includes the area immediate- ly adjacent to the area to be physically disturbed. The definition of the APE must consider possible direct, indirect, secondary, and cumu- lative impacts for all proposed alternatives. It therefore does not nec- essarily need to be contiguous. For example, if alternatives include several different geographic sites, an APE can be established for each alternative site.

It is easy to recognize one of the inherent problems in integrating the Section 106 process into the NEPA process. Because of the exten- sive, and often time-consuming review requirements of Section 106, it is imperative that the process begin very early in the environmental impact studies. The definition of boundaries of the APE, however, must incorporate possible direct, indirect, and secondary effects of other dis- ciplinary studies, such as traffic, population changes, air quality, noise, or visual impacts. If the Section 106 process begins immediately upon study initiation, these other areas of impact analysis normally have not even begun, let alone have conclusive results available.

The APE should be defined as early in the environmental analysis process as possible. Coordination with and concurrence of the State Historic Preservation Officer (SHPO) and the state archaeologist on the boundaries of the area of potential effect are required. Local histo- rians, historical societies, and universities also should be consulted.

12.4 Description of Previously Identified Resources

The identification of resources within the area of potential effect will begin with examination of available material to determine the pres- ence of existing designated resources. Section 106 applies to proper- ties on, or eligible for inclusion on, the National Register of Historic Places. The National Register of Historic Places, published in the Federal Register, should be reviewed for the properties or sites within the area of potential effect. Information will include those properties listed on the National Register of Historic Places and a separate list of those properties determined eligible for the National Register of Historic Places but not actually on it.

The State Historic Preservation Officer will have valuable informa- tion on properties listed on the National Register of Historic Places and on previous surveys conducted in the state or project area. Other available sources of information include local governments, local histo- rians and historical societies, and books and surveys on the history and archaeology of the area. Local colleges and universities are always a good source of information. Any previously prepared Environmental Impact Statements for other projects or actions within the study area should always be reviewed for information related to historic and ar- chaeological resources, as well as other potential areas of impact.

The public participation and scoping process established for the proposed project or action should include opportunities for the identi- fication of sources of information and for individuals to express their concerns regarding historic properties early in the agency's planning process, so concerns can be considered in a timely manner.

Section 106 specifically requires consideration of special social and cultural values, particularly religious concerns, of Native American groups (American Indian Religious Freedom Act). The regulations re- quire that representatives of Native Americans be brought into the con- sultation process when historic properties of importance to them may be affected. If an APE includes lands owned by, or of interest to, Native Americans, local tribe leaders should be consulted for information.

A list of known designated resources should be prepared, noting the status of the resources, such as on or determined to be eligible for the National Register of Historic Places, identified as having value in local surveys, or designated as a National Historic Landmark.

After previously identified resources have been located and de- scribed, the area of potential effect must be surveyed for any un- known or unidentified resources. This requirement is rather unique in some ways to the Section 106 process. Section 106 protects proper- ties on the NR and identified as eligible for the NR, but also proper- ties not previously identified as eligible. It is the sponsoring agency's responsibility to determine if any previously unidentified eligible properties may exist within the area of potential effect.

This requirement is noted as somewhat unique because when com- pared with protective legislation and regulations in other areas of po- tential impacts, it is normally not the responsibility of the sponsoring agency to identifY previously unknown resources for protection under the law. Examples include the Endangered Species Act, wild and scenic rivers, or public parkland. In these cases, the agency is responsible for determining whether any designated resources exist within the project area, but not for conducting the required research to determine if, for example, a species should be listed as threatened or endangered, if a river should be included as wild and scenic, or if a park should be es- tablished. There are exceptions, of course, when information and public

or resource agency sentiment are extremely indicative of pressing for such incorporation of important, previously nondesignated species, rivers, or open space under the protection ofapplicable laws.

As opposed to endangered species and other examples listed above, the Section 106 process does place responsibility on the sponsoring agency to do the required research to determine if any previously unidentified resources exist within the APE and whether those resources meet the criteria of eligibility for the National Register of Historic Places.

12.5 Historic and Archaeological Resource Surveys

The objective of historic and archaeological resource surveys is to identify all properties that may be eligible for the National Register of Historic Places. The survey should be conducted by qualified histori- ans and archaeologists. Local knowledge of the area is useful to save time and to ensure that all resources are identified.

12.5.1 Eligibility for the National Register

National Register eligibility is determined through application of spe- cific criteria. The National Register of Historic Places is the official list of properties significant in U.S. history, architecture, archaeology, engineering, and culture. The criteria to evaluate significance used by the historic and archaeological teams to determine eligibility are con- tained within 36 CFR Part 60. As with other legislation and regula- tions, there are numerous helpful publications regarding application of the criteria. Basically, the criteria are as follows.

The quality of significance in U.S. history, architecture, archaeolo- gy, engineering, and culture is present in districts, sites, buildings, structures, and objects that possess integrity of location design, set- ting, materials, workmanship, feeling, and association and

• That are associated with events that have made a significant contri- bution to the broad patterns of U.S. history

• That are associated with the lives of persons significant in our past

• That embody the distinctive characteristics of a type, period, or method of construction, or that represent the work of a master, or that possess high artistic values, or that represent a significant and distin- guishable entity whose component may lack individual distinction

• That have yielded, or may be likely to yield, information important in prehistory or history

Ordinarily cemeteries, birthplaces, or graves of historical figures; properties owned by religious institutions or used for religious purpos- es; structures that have been moved from their original locations; re- constructed historic buildings; properties primarily commemorative in nature; and properties that have achieved significance within the past 50 years are not considered eligible for the National Register. Such properties can qualify, however, if they meet certain special criteria.

Specific guidelines are available to the historian or archaeologist in applying the criteria and in the definition of the terminology. The most helpful perhaps is published by the Department of the Interior, "How to Apply the National Register Criteria for Evaluation." These guidelines include the following.

Categories-how to define the categories of historic properties as districts, sites, buildings, structures, or objects.

Historical context-eligibility of a property depends on whether it represents a significant theme or pattern. Decisions on significance, thus, can reliably be made only within the context of an area's his- tory, and guidance is available on how to define historical context, a first step in designing a field survey.

Level ofsignificance-guidelines for classification of importance of a property as having local, state, or national significance.

Type of significance-application of the four specific criteria (A, B, C, or D) and determination of which applies within the context of identified relevant historical themes or patterns. Specific guidelines and examples of eligible and noneligible properties are given for each criterion.

Integrity-seven criteria that are listed and explained: location, de- sign, setting, materials, workmanship, feeling, and association. Guidelines are given with examples of eligible and noneligible prop- erties.

Criteria for properties normally not considered eligible-separate guidelines and criteria for religious properties, moved properties, birthplaces or graves, cemeteries, reconstructed properties, com- memorative properties, and properties less than 50 years old.

12.5.2 Historic resource surveys

The survey of aboveground resources often begins by the process of elimination of recent structures, or properties that normally are not considered eligible for the National Register of Historic Places. There is usually an agreement with the State Historic Preservation Officer of a particular state on the cutoff date for structures possibly eligible for the National Register of Historic Places. The acceptable age of structures is normally at least 50 years, but can be less if special cir- cumstances are involved which would give the resource exceptional historic value.

As noted earlier, each state will likely have its own required methodologies, forms, and documents for the conduct of surveys. Many states use the actual National Register of Historic Places nomination forms, even though the properties are not actually being nomi- nated for the listing.

The historian or historical architect surveys all aboveground struc- tures within the area of potential effect and prepares the appropriate forms for each property. The accompanying report normally separates properties thought not to be eligible, properties thought to be eligible, and properties for which eligibility is uncertain. It is the sponsoring agency's responsibility to determine National Register eligibility. The Determination of Eligibility report, or in some cases numerous re- ports of different titles, then facilitates coordination with the State Historic Preservation Officer for review and concurrence on the re- sults of the survey.

12.5.3 Archaeological surveys

The identification of prehistoric and historic archaeological resources begins with research of available information on the area within the APE and the context of the region. The state archaeologist should be consulted for appropriate known sites and previous surveys. 'lbpographical maps of the area can be reviewed for possible indication of resources.

Perhaps more than aboveground resources, appropriate methodolo- gies and formats of documentation for archaeological studies vary im- mensely from state to state. Because of this great flexibility in implementing field surveys, it is important that selection of tech- niques and level of effort be responsive to the specific goals of the re- sults. Surveys can range from simple "windshield" or walk-over surveys with very limited subsurface examination, often referred to as reconnaissance surveys, to extensive, subsurface investigation to determine precise information on the property, including significance, integrity, and boundaries sufficient to permit an evaluation under cri- teria of eligibility for the National Register of Historic Places.

The philosophy of archaeological resource preservation often differs from that of aboveground historic resources. Extremely oversimpli- fied, this philosophy involves the desirability of leaving archaeological resources intact for future generations, with better methods, to ex- plore. In other words, do not disturb what might be there just to find out in detail and recover what might be there. This philosophy is root- ed in past experiences when extremely sensitive and valuable archae- ological resources were extensively excavated with technology of the times; sites were thus destroyed for future technologies that would have yielded significantly more data.

In most cases, the minimum information necessary to evaluate properties against National Register of Historic Places criteria of eligibility should direct the extent of information-gathering activities. Resources should be evaluated within particular historical context and should be classified in terms of type and integrity. The location and physical extent of the property should be determined. It also is very important to detennine if the archaeological resource is valuable for the infonnation it may contain, as opposed to being significant for preservation in place.

The level of survey for archaeological resources should be deter- mined in consultation with the State Historic Preservation Officer and the state archaeologist. Most states have an established method- ology for survey types and techniques under various proposed project or action circumstances. AB with aboveground resources, archaeologi- cal resources survey infonnation is available in several helpful publi- cations from the Department of the Interior.

It is most important to remember that surveys should be appropri- ate in scale to the purpose of the evaluation. If the goal is to recover any discovered archaeological resources and artifacts from the site, then data recovery programs for the entire site may be conducted prior to any construction activities. On the other hand, an assumption of National Register eligibility may be agreed upon with minimum disturbance of a site, and the process continued directly to developing mitigation (Memorandum of Agreement) techniques to ensure re- sources are identified and recovered if found during actual construc- tion activities.

For example, a proposed new bridge will require excavation on river banks for construction of bridge abutments. Research and coordination with the State Historic Preservation Officer indicate a high probability of presence of significant archaeological resources in the location of the proposed bridge abutment. The State Historic Preservation Officer re- fuses, however, to agree to any unnecessary subsurface disturbance of the site to determine in detail what may be there and what the exact physical boundaries may be. The property is assumed eligible for the National Register of Historic Places, and the Section 106 process pro- ceeds to development of a mitigation plan. During construction within this particular area, a qualified archaeologist will be present to ob- serve the activities. Should any artifacts be found, the artifacts will be appropriately recovered, but the extent of disturbance will be kept to an absolute minimum.

12.5.4 Classes of historic properties

If a proposed undertaking will have possible effects that are extreme- ly difficult to define or that extend over a large geographic area, agen- cies may identify and consider classes of historic properties. Examples may include large reservoir projects, or housing projects where it may not be feasible to identify all individual properties possibly subject to effect, particularly secondary effect, prior to project approval. In these cases, it is acceptable to predict that the undertaking will affect cer- tain kinds of historic buildings or archaeological sites. Knowing such effects will occur will assist in developing programs to protect the sig- nificant characteristics of such properties. Thus, although it is not feasible to identify specific historic properties, the agency has met its responsibilities under Section 106.

12.5.5 Conclusion of identification and eligibility evaluation phase

Results of the identification of historic and archaeological resources within the area of potential effect and the evaluation of those re- sources for eligibility for the National Register of Historic Places are forwarded to the State Historic Preservation Officer for concurrence. The format for this documentation may be one report or several re- ports of very differing titles, depending on the state and/or agency in- volved in the project. The documentation should clearly indicate the sponsoring agency's opinion on whether each historic and archaeologi- cal resource or site is considered eligible for the National Register of Historic Places, or considered not eligible, and should make note of determinations which are not absolute and could be decided either way.

Ifthe State Historic Preservation Officer agrees with the agency, the process continues. If the SHPO fails to respond, concurrence is as- sumed. If the SHPO disagrees about eligibility, the agency must obtain a formal determination from the Keeper of the National Register in Washington, D.C.

If the SHPO concurs that no National Register-eligible historic and archaeological resources are located within the APE, interested parties must be notified and documentation must be made available to the public (within the Environmental Assessment or Draft Environmental Impact Statement if integrated into the NEP A process). Following such notification, the Section 106 process is completed.

12.5.6 Public disagreement

Now is a good time to emphasize the public's right to disagree with findings, even if the sponsoring agency and the State Historic Preservation Officer agree. At four basic points within the Section 106 process, any person, regardless of her or his formal involvement in the process, can request the Advisory Council's review of an agency's findings:

1. Identification of historic and archaeological properties

2. Evaluation of significance of properties

3. Finding that no historic properties are present

4. Finding no effect on historic properties

The council will complete its review within 30 days of the request. The request for review does not require the agency to suspend action on an undertaking. When an inquiry concerns an agency's judgment about National Register eligibility, the matter is referred to the Secretary of the Interior (who refers it to the Keeper of the National Register). There have been cases where the Keeper has overruled the opinions of the agency and State Historic Preservation Officer and has determined sites eligible for the National Register on behalf of a request from the public.

12.6 Impact Assessment

Criteria to determine potential impacts of a proposed project or action on historic and archaeological resources are contained in the Advisory Council's regulations, 36 CFR Part 800. There are two sets of criteria: criteria to determine whether there is any effect at all on the proper- ty, either beneficial or adverse; and criteria to determine whether there is an adverse effect on the property.

An effect occurs if the proposed project or action will in any way alter the characteristics of the property that qualifY it for inclusion in the National Register of Historic Places.

An adverse effect occurs if the proposed project or action may di- minish the integrity of the property's location, design, setting, materi- als, workmanship, feeling, or association.

Adverse effects include, but are not limited to: 1. Physical destruction, damage, or alteration of all or part of the property;

2. Isolation of the property from or alteration of the character of the property's setting when that character contributes to the property's qualification for the National Register;

3. Introduction of visual, audible, or atmospheric elements that are out of character with the property or alter its setting;

4. Neglect of a property resulting in its deterioration or destruction; and 5. Transfer, lease or sale of the property.

There are exceptions to the above criteria of adverse effect con- tained within 36 CFR Part 800; perhaps the most notable arises when the historic or archaeological property is of value only for its potential contribution to research and such research is conducted in accordance with applicable professional standards and guidelines.

One of the key factors in assessing whether a proposed project or action will have an effect or an adverse effect is the focus on the characteristics of the property that qualify it for the National Register. Eligibility of a particular property was based on its contri- bution to a theme or historical context. It may be eligible on the basis of architecture, engineering, ethnic heritage, art, agriculture, invention, or several other categories of significant themes. To prop- erly assess potential project impacts, it is essential to review the data on each property for the identified characteristics that qualified it for the National Register. Remember that to have an effect, the proposed project or action must cause changes in that particular characteristic.

Sometimes a proposed project or action changes the area surround- ing the actual building or structure, but does not alter the structure. Boundaries of sites as described on the National Register often coin- cide with property boundaries of the parcel of land, usually as a mat- ter of convenience. Again, the criterion regarding changes to setting applies in cases of isolation of character when that character con- tributes to the property's qualifications to be on the National Register. If the project being evaluated will produce physical changes near an eligible site, it is first necessary to examine how much of the sur- rounding setting actually contributes to the specific characteristics that qualify the property for the National Register. If the proposed project or action will produce changes within an area that actually do not contribute to the value of the resource, then a no-effect or no-ad- verse-effect determination is appropriate.

Results of the investigation of project effect will be one of three con- clusions: no effect, no adverse effect, or adverse effect. Results and supporting documentation are forwarded to the State Historic Preservation Officer for concurrence with the conclusions. For an agreement on a no-effect or no-adverse-effect determination, the Section 106 process is completed after notification to interested par- ties of its availability to the public (hopefully integrated into the draft NEPA environmental document). A no-adverse-effect finding must also be forwarded to the Advisory Council on Historic Preservation for a 30-day review. If the council disagrees with the no-adverse-effect finding, the effect is considered adverse. A public review period is re- quired, and this review is most efficiently accomplished within the Environmental Assessment or Draft Environmental Impact Statement. The environmental document must contain documenta- tion of agreement of the SHPO on the eligibility of resources and on findings of no effect or no adverse effect.

An adverse-effect finding requires continuation of the Section 106 process to the consultation, or mitigation, step.

12.7 Consultation and Mitigation

The consultation process for a determination of adverse effect is de- signed to reach agreement on how to avoid, mitigate, or accept the ad- verse effect. Consultation includes the agency; the State Historic Preservation Officer; the head of local government; owners of affected sites; a representative of an Indian tribe, if the undertaking will af- fect Indian lands; and other interested persons when deemed appro- priate by the agency and State Historic Preservation Officer.

The purpose of the consultation process is to accommodate the needs of the proposed project and the integrity of the historic property in a way that best serves the public interest. The first investigation is usually of alternatives that would avoid or reduce the impact while still accomplishing the agency's goals. Other mitigation measures may include the following:

• Limiting the magnitude of the project

• Modifying the design

• Rehabilitation of an historic property

• Preservation and maintenance operations for historic properties

• Documentation of buildings or structures that must be destroyed or substantially altered

• Relocation of historic properties • Salvage of archeological or architectural information and materials

In some cases, no alternatives or mitigation is feasible, and the pro- posed project's benefits in relation to the significance of the historic resource justify destruction of the resource as an acceptable loss. In most cases, however, measures to mitigate impacts are agreed upon; some examples follow.

• Specific design measures will be agreed upon to minimize impacts.

• If it is agreed to destroy an historic building or structure, the usual procedure is to fully document the resource through stringent, ac- ceptable documentation requirements.

• Many times historic buildings can be moved to locations where preservation can be maintained for future generations.

• In cases involving archaeological resources, data can be recovered prior to construction activities, or an archaeologist will observe con- struction activities and recover data if any artifacts are discovered.

• For the discovery of burials, the area is normally excavated and the remains are moved. If burials are of Native American heritage, an official of the tribe will most likely be present at the reburial for ap- propriate ceremony in keeping with tribal traditions.

If a site is to be destroyed because keeping it would result in the adverse-effect criterion of neglect, the site or property should be of- fered to the local historical society or government if it is willing t6 as- sume the cost of maintaining it. This situation often occurs with replacement of historic bridges when the new bridge is built adjacent to the old structure. The Department of Transportation cannot contin- ue ownership and maintenance of the old bridge, but can offer it to the local community.

Results of the consultation process are contained within a Memorandum of Agreement (MOA). The MOA is a legally binding doc- ument signed by the agency, State Historic Preservation Officer, and the Advisory Council on Historic Preservation. The signing of an MOA completes the Section 106 process. The public must be afforded an op- portunity to review and express its views on an executed MOA. Ifinte- grated into the NEPA process, the MOA is included in the final environmental document, either a Finding of No Significant Impact or a Final Environmental Impact Statement.

12.8 Programmatic Section 106 Agreements

In the early years of Section 106 review, the three steps of identifica- tion, assessment of effect, and mitigation were almost always applied on a project-by-project basis, and effects were considered for a partic- ular location or site. Under current regulations, agencies may obtain Advisory Council comment on a programmatic basis. As with pro- grammatic Section 4(f) agreements, the programmatic Section 106 agreement is not a waiver of responsibility under the law, but is used in cases where numerous projects are similar (such as replacing his- toric bridges), an activity covers a large geographic area, or effects cannot be fully determined prior to project approval. The particular proposed project or action must be shown to meet the specific condi- tions of the programmatic agreement or programmatic memorandum of agreement.

12.9 Summary

As with most regulations, there are exceptions to the process de- scribed in this chapter, especially if disagreement occurs at various steps. There are also special considerations not mentioned here, such as when an historic property is designated and discovered late in the project planning and design process. There also is a multitude of additional guidance and regulatory material on the specifics of applying the criteria of eligibility, criteria of effect, and documentation and mitigation techniques. This chapter, however, has presented an overview of the basic steps to a degree necessary for a general knowl- edge of the Section 106 process and the importance of appropriate timing and coordination during the process. The summary key to ac- tivities in Fig. 12.2 may be helpful in understanding and summariz- ing important steps in the process.

13.1 Inventory of Existing Resources

The description of the existing visual environment will depend on the type of project or action proposed. A site-specific project will require the description of the appearance of the site and surrounding area. Often this description may be divided into foreground, middle-ground, and background descriptions, depending on the characteristics of the site. All dominant elements of the visual environment should be de- scribed, including artificial and natural components.

A good beginning for the analyst is to just tell the reader what the area looks like. This may sound oversimplified, but the analyst must always remember that he or she is writing for the general public. Many of the readers of the environmental document will not have seen the site and, for starters, just need to know what it looks like. The description may begin with a general land-use definition, such as urban, rural, industrial, retail, residential, agricultural, or natural. Natural areas may continue to be described based on land cover, such as forest, woodlots, meadows, streams, mountains, desert, foothills, escarpments, or cliffs. Topography should be described, such as flat, rolling, steep, or mountainous.

Another factor in the description of the existing visual environment is the nature of the viewers. Viewer sensitivity usually relates to the activity taking place and is a measure of the degree of viewer interest in the scenic qualities of the landscape. A hiker in a National Forest will have a very different sensitivity from an urban commuter on the way to work on a congested freeway. The assessment should include an identification of the probable viewers and, in that relevance, the major dominant elements and any significant view sheds or vistas.

If the proposed project or action involves a very large area, such as a proposed community land-use plan, national park, or forest man- agement plan, or a resource recovery proposal over an extensive area, the description of visual resources will, by necessity, be more general. Such an overview should focus on dominant, or particularly signifi- cant, features, vistas, or view sheds. Notable visual resources from a regional perspective may already have been identified at a local, re- gional, or state level. Often these previously identified areas or sites will be noted within land-use, comprehensive, or management plans. Objectives for maintaining resources of significant visual quality also may be included in planning documents.

In an urban setting, the description of the visual environment will cover dominant features and perhaps place more emphasis on ele- ments of line, color, form, and texture. Continuity and contrast can be used to describe visual diversity and interest. Compatibility in archi- tecture, scale, materials, line, and form of urban structures may be important in defining contiguous visual units. Distinctive visual edges between relatively similar areas should be identified.

Many times, the best way to describe the existing visual environ- ment in an environmental document is with the support of drawings or photographs. The analyst should not try to be too subjective in defining visual quality, but rather should describe the components of the existing environment as objectively as possible and let the reader come to conclusions regarding the quality or value of the described environment.

13.2 Examples of Some Federal Agency Methodologies

The Bureau of Land Management (BLM) has a Visual Resources Management Program for the planning and design of the visual as- pects of multiple-use land management (U.S. Department of Interior, BLM 1984, 1986a, 1986b). Under the program, Visual Resource Management (VRM) classes of I to IV are assigned to all public lands to describe the acceptable level of change in the landscape and the as- sociated management goals and objectives. The resource management plan would include mapping of areas with each class designation and the total acres within each class. VRM class designations and related objectives are summarized below.

VRM class I has the highest visual resource sensitivity value, with a landscape that appears unaltered by humans. The goal is to pre- serve the existing landscape with only natural, ecological changes.

VRM class II objectives include maintaining the existing environ- ment with any changes blending into the natural surroundings by re- peating the basic elements of form, line, color, and texture found in the dominant elements of the landscape. Changes should not attract the attention of the casual observer.

VRM class III area has a low visual sensitivity resource value. The level of change in the characteristic landscape may be moderate. Management activities may attract attention, but should not domi- nate the view of the casual observer. Changes should repeat the basic elements found in the predominant natural features of the character- istic landscape.

VRM class IV visual quality objectives provide activities requiring major changes of the existing landscape. These activities may domi- nate the view and be the major focus of viewer attention (U.S. Department of Interior, BLM 1994).

The above example of the Bureau of Land Management system fur- nishes meaningful guidance for the analyst. The first lesson is to make full use of work already completed by others. Appropriate re- search or planning documents, previous Environmental Impact Statements or other studies, and coordination with local or regional officials may result in discovery that visual resources have previously been defined, at least to some degree. Not only does this save the ana- lyst time, but also it is normally a much better assessment than a short-term, project-oriented team could produce.

Second, the BLM system introduces meaningful descriptive termi- nology of the visual quality inventory and impact process. The objec- tives refer to lack of change as positive in areas of high visual quality; compatibility with, or a repeating of, the basic elements of form, line, color, and texture found in the dominant features of the landscape; and the ability to be noticed, or prominence of the change to the casu- al observer.

The USDA Forest Service has a similar system of visual resource management classification, with objectives related to acceptable al- teration of the characteristic landscape (USDA Forest Service 1992d). Five levels of visual quality objectives are preservation, retention, partial retention, modification, and maximum modification. The visu- al resource management objectives in the BLM and Forest Service programs are directly related to an accurate description of the visual quality of the existing landscape.

Use of the Federal Highway Administration's methodology for visu- al impact assessment, if deemed necessary and desirable based on po- tential project impact and anticipated degree of project controversy, requires significantly greater detail in describing the existing envi- ronment (U.S. Department of Transportation, FHWA 1986). The methodology takes several steps to define the existing visual environ- ment.

The FHWA methodology defines resources in the foreground, mid- dle ground, and background, but more specifically refers to these as level 1: internal aesthetics; level 2: relational aesthetics; and level 3: environmental aesthetics. The process begins with a thorough under- standing of the characteristics of the proposed project. The visual en- vironment is then described in terms of landscape components in the region and in the immediate project area, including land form, water, vegetation, and artificial development.

The methodology uses landscape units, either spatially enclosed or unenclosed, to define visual character. Major view sheds are defined and can be mapped. Visual resources within the view sheds are de- scribed both for roadway users (view from the road) and for roadway neighbors (view of the road). Viewers are characterized as to possible sensitivity.

Use of the FHW A technique results in numeric values for the visual character of the existing environment in four visual pattern elements (form, line, color, and texture) and four pattern characters (domi- nance, scale, diversity, and continuity) for each of the four landscape components Cland form, water form, vegetation, and development). Visual quality also is assigned numeric values by averaging the three criteria of vividness, intactness, and unity. Each criterion is evaluated in terms of several components and at each level (1, 2, and 3). The re- sultant tables of visual quality values serve as the baseline, or before- project, conditions upon which to compare the values obtained by calculating after-project conditions. The difference is the degree of vi- sual resource impact.

13.3 Impact Analysis

The impact on visual resources is defined by the changes produced by the proposed project or action. Before-project and after-project visual characters should be compared, keeping in mind that change is usual- ly, but not always, adverse. In natural areas, such as national forests or parks, change from a natural visual environment would be ad- verse, based on users' expectations. For example, if the view shed from a trail is changed from forested mountain slopes and streams to a coal mine or condominium complex, the change is considered adverse. If a proposed project or action includes regrading and replanti- ng a previously disturbed area, or removing vegetation to permit viewing of attractive vistas, the changes are beneficial.

In an urban area, more emphasis may be placed on the compatibili- ty with the architectural style and mass of the built setting including line, form, texture, and color. Construction of a modern, straight- lined, glass-and-steel tall building within a neighboring area of low- rise, Victorian, or art deco architectural buildings is certainly considered incompatible. A change in an urban area also may be ben- eficial, based on the urban resident viewers' expectations. For exam- ple, if an urban blighted area is replaced by new structures, plantings of vegetation, and attractive streetscape elements, the change consti- tutes a positive visual impact.

Another visual ingredient, particularly in an urban setting, but possibly also applicable to some rural environments, is the changes that may be produced in shade and shadow, or light, and glare. A pro- posed project or action that introduces shade, shadow, light, or glare may be considered visually intrusive and incompatible with before- project conditions.

The analyst should describe the changes as objectively as possible, without drawing personal conclusions concerning attractiveness and keeping in mind that not all viewers have the same values or sensi- tivity to visual landscape. 'lb a bridge engineer, an arching structure of steel or concrete over a chasm can be truly beautiful. To the trout fisher on the stream in the chasm, the same response may not be forthcoming.

In the same example, it is important to realize that individual de- sign elements can be used to lessen the impact on the visual environ- ment. Perhaps a massive, bulky, straight bridge design totally incompatible with the existing setting was dismissed from considera- tion in favor of a design that is more compatible. The bridge can be designed to be as harmonious as possible in line, form, color, and tex- ture with its surroundings and thus be as least visually obtrusive as possible.

Computer imaging can be extremely useful in presenting before and after photographs in the environmental document. Technology exists to superimpose a proposed project into a photograph of existing settings. Perspective drawings also can assist readers in visualizing the after-project visual settings. The study team should be cautioned that few persons attending a public meeting or workshop can look at engineers' or architects' drawings, or topographic mappings, and be able to realistically interpret these documents into a three-dimension- al image of the visual appearance of the after-project setting.

In cases where visual quality objectives have already been designated, as with the previously described federal management pro- grams or with local comprehensive plans, the evaluation of visual im- pacts will relate directly to compatibility with established goals and objectives. For example, the BLM uses a systematic contrast rating process to analyze potential impacts (U.S. Department of Interior, BLM 1986b). The degree of impact depends on the visual contrast cre- ated between the project and the existing landscape. The contrast is measured by comparing project features with the major features in the existing landscape through use of the basic design elements of form, color, line, and texture. The basis of the comparison is estab- lished by the designated VRM objectives.

Elaborate methodologies, such as that of the FHWA, should be used with caution and only if the project characteristics warrant such de- tailed analysis. A problem inherent in the use of numeric evaluation methodologies is that the resultant number values imply an objectivity that perhaps does not actually exist. The subjectivity in the methodolo- gy comes in the initial assignment of numeric values to various indi- vidual components in the early stages of the process. These subjective numeric values become incorporated into formulas and techniques that imply an objective result, when in fact the result may be just manipulated subjective values. Probably the most risky aspect of using these elaborate numeric methodologies is that the answer is understood by few. The public will usually relate better to a photograph and verbal description of an area's appearance than to a result of 2.5 or 4.6.

Construction-related activities, such as ground clearance and earth movement, can normally be considered to produce adverse visual ef- fects. The environmental document should describe the amount of earth to be disturbed and the duration of particular phases of con- struction activities. Mitigation measures can be used to shield adja- cent receptors and should be incorporated into project construction contract documents .

These are some of the major factors in the assessment of potential visual resource impacts of a proposed project or action:

Identify and describe visual changes.

Consider possible changes in light, glare, shade, and shadow.

Be objectively descriptive.

Consider foreground, middle-ground, and background vistas and view sheds.

Assess compatibility by comparing the form, line, color, and texture with those of the existing setting.

Compare dominant features before and after project implementa- tion in consistency of scale or mass.

• Make use of computer imaging, photographs, and perspective draw- ings.

• Consider viewer sensitivity in evaluating the degree of impact.

The content of the environmental document related to visual impacts may be a few paragraphs or several pages, depending on the identified appropriate scope of study. I f extremely detailed studies are warranted, data and analysis details should be contained within a technical report and summarized within the Environmental Assessment and FONSI or Draft and Final Environmental Impact Statement.

13.4 Cumulative and Secondary Impacts

Assessment of possible cumulative impacts should consider whether the proposed project or action will incrementally add adverse visual im- pacts in a particular area or view shed to a degree to cause a significant overall impact. Another type of cumulative impact may include prece- dent-setting or policy decision types of projects. By permitting one small project or action with minimal visual impact, is pressure then created for a continuation of additional such projects or actions that cu- mulatively would produce adverse effects on sensitive visual resources?

Secondary impacts also may occur in tenns of geographic separation or time separation. An example would be a project requiring fill materi- al. The area from which the fill earth is to be removed may not be near the project, but would create adverse visual effects on surrounding re- ceptors. An action permitting particular resource recovery may, in turn, promote the development of processing facilities for that resource.

13.5 Mitigation

The use of measures to reduce potential visual impacts is varied and often very project-specific. Visual buffers can obscure unsightly con- struction areas or land uses, such as automotive parts suppliers (junkyards). Design elements and architectural treatments can re- peat basic elements of form, line, color, and texture to reduce contrast and ensure compatibility in urban areas. Mine areas should be re- claimed into natural contours and vegetation. Limiting the clearance of land for timbering can blend edges and make cleared areas less ob- trusive. These examples are given to represent just a few of the many available techniques. It is important in designing mitigation mea- sures that the degree and severity of impact be properly identified and that suitable mitigation techniques be developed with a goal of reducing impacts to acceptable levels.

14.1 Legislation and Terminology

The Clean Air Act of 1970, as amended in 1990, establishes a man- date to reduce emissions of specific pollutants via uniform federal standards. Under the act, the Environmental Protection Agency is re- sponsible for standard-setting programs and for approval of individ- ual actions such as state implementation plans (SIPs) and specific permits.

14.1.1 Standards

Standard-setting programs under the act include the National Ambient Air Quality Standards (NAAQS), New Source Performance Standards (NSPS), National Emission Standards for Hazardous Air Pollutants (NESHAP), Acid Rain Program, Stratospheric Ozone Protection Program, and Standards for Control of Air Pollution from Motor Vehicles.

The National Ambient Air Quality Standards set maximum allow- able ambient concentrations for the following criteria air pollutants; ozone (03); nitrogen dioxide (N02); sulfur dioxide (S02); carbon monoxide (CO); particulate matter with aerodynamic diameter less than or equal to 10 micrometers (PMlO); and lead (Pb). Of these, ozone is not actually emitted directly from any source, but is formed in the presence of sunlight from two precursor pollutants that are emitted- oxides of nitrogen (NO) and reactive organic gases (ROGs), which are predominantly hydrocarbons (HCs). Primary standards are given to indicate levels necessary to protect public health; secondary stan- dards are given for levels to protect public welfare from any known or anticipated adverse effect of a pollutant. The act requires attainment of the primary standards within a target date. Each state must attain the secondary standards within a "reasonable time." The National Ambient Air Quality Standards are shown in Fig. 14.1. These stan- dards, and approved measurement techniques, are subject to revision over time. The analyst should use the most recent and applicable standards at the time of project assessment.

In addition to the National Ambient Air Quality Standards, many states have enacted air quality legislation with specific state stan- dards. In some states, such as California, the state standards are more stringent than the national standards, and more pollutants have been added.

14.1.2 Nonattainment and state implementation plans

Geographic areas that do not meet the primary NAAQS are termed nonattainment. Each state has been required to develop a plan to im- plement the Clean Air Act, called the state implementation plan (SIP), and to demonstrate how attainment of the primary NAAQS will be reached within a target date. Air quality regulatory jurisdic- tion normally falls within designated smaller geographic areas, called air basins, and managed by air quality management districts or air pollution control districts. These agencies must prepare air quality at- tainment plans containing specific measures to reduce criteria pollu- tant concentrations below federal and state standards.

The 1990 amendments defined five classes of increasing nonattain- ment: marginal, moderate, serious, severe, and extreme. The only area in the United States classified as extreme for any particular pol- lutant is the Southern California Air Quality Basin; the pollutant is ozone, the primary ingredient of smog.

The purpose of the state implementation plan is to eliminate or re- duce the severity and number of violations of the NAAQS and to achieve expeditious attainment of the standards. Federal activities may not cause or contribute to new violations of air quality stan- dards, exacerbate existing violations, or interfere with timely attain- ment or required interim emission reductions toward attainment.

Geographic regions previously designated nonattainment pursuant to the Clean Air Act Amendments of 1990 and subsequently redesig- nated to attainment are called maintenance areas and are subject to the requirement to develop a maintenance plan.

14.1.3 Conformity

New and modified projects proposed within nonattainment and main- tenance areas must be reviewed to determine conformity with the SIP. For stationary sources, any new emissions for a criteria pollutant or its precursors in a nonattainment area cannot be permitted with- out elimination of an equal or greater amount of the same pollutant through offsets. The offset required usually increases with the distance between the proposed and eliminated sources, but is never less than 1.0, to ensure that no net increase will occur.

The SIP outlines requirements for specific kinds of pollutants in each area of a state. The specific requirements are then applied to spe- cific sources (e.g., individual factories or plants) by incorporating them into operating permits for each source. The Clean Air Act gives to the Environmental Protection Agency the review and approval responsi- bility for state implementation plans and for new-source construction permits. The EPA also establishes New Source Performance Standards and National Emission Standards for Hazardous Air Pollutants.

For transportation projects, EPA regulations require the Department of Transportation (DOT) and the Metropolitan Planning Organization (MPO) to determine conformity with the SIP on regional metropolitan transportation plans before they are adopted. Highway and transit projects funded or approved by the Federal Highway Administration (FHWA) or the Federal Transit Administration must be found to conform before they are approved or funded by the DOT or the MPO. These regulations apply to transportation-related pollutants (ozone, carbon monoxide, nitrogen dioxide, and particulates) within areas designated nonattainment or subject to maintenance plans under the Clean Air Act. The EPA also establishes motor vehicle emis- sion standards.

The required analysis to demonstrate conformity can be quite com- plex and varies from state to state. Acceptable criteria for analysis methodologies and for concluding a project's conformance can be mod- ified over time.

14.1.4 PSD review

Within areas where the NAAQS are not violated, the Prevention of Significant Deterioration (PSD) program is aimed at maintaining air quality better than the NAAQS by controlling emissions from station- ary sources. Individual operating permits under PSD and new-source review (NSR) must be reviewed and approved by the Environmental Protection Agency. A PSD review for a proposed action is not required if emissions of each attainment pollutant from stationary sources would be less than a particular threshold rate.

14.1.5 Section 309 review

Another significant component of the Clean Air Act is that it estab- lishes, within Section 309, the authority of the Environmental Protection Agency to review and rate environmental legislation, regulations, and documents for all proposed federal actions. The EPA Office of Federal Activities and its ten regional administrators rate Draft Environmental Impact Statements based on a set of criteria and provide recommendations to the lead agency for improving the draft. EPA's criteria for Section 309 review of environmental docu- ments are shown in Fig. 14.2. If improvements are not made in the Final Environmental Impact Statement, the EPA may refer the Final Environmental Impact Statement to the Council on Environmental Quality. The council may issue findings and recommendations, may determine that the issue is not a matter of national importance, or may uphold the EPA's position. The EP A may identify a major federal action significantly affecting the environment even though the lead agency disagrees.

14.2 Determining Existing Air Quality

To effectively predict future air quality impacts of a proposed project or action, it is necessary to first describe the air resource characteris- tics within the region and study area. The description should include information on climatic conditions and on pollutant levels, both cur- rent and historic. Sources of pollutants exceeding the NAAQS should be explained, if possible.

14.2.1 Existing measured data

Climatic information includes temperature, precipitation, and typical wind velocity and direction. Sometimes a wind rose diagram, which graphically indicates the percentage of time that annual wind occurs at particular speeds and directions, is presented within the environ- mental document. Vertical mixing and dilution information includes the normal mixing height above ground level in summer. These inver- sion layer heights are normally given for the morning and the after- noon, and they reveal important information on whether specific emissions, such as of NO. and ROGs, are being dispersed or remain trapped. The project area or region should be reviewed for any topo- graphical constraints affecting air pollutant dispersion characteristics.

Regional air quality management districts, or control districts, are responsible for monitoring and reporting air pollutant characteristics within their area or region. The nearest established air quality moni- toring stations should be identified and presented on a map. Data from monitoring stations may need to be adjusted for the particular study area to reflect background air pollutant levels, after accounting for nearby sources of pollution.

Another source of air quality data can be previous monitoring pro· grams associated with permit applications or environmental docu- ments for other projects within the same, or comparable, region or area. For projects located in rural areas, assumed values sometimes can be used if they are conservative enough to be accepted by all in- terested and review agencies and the public.

If appropriate data is not available, an air quality monitoring pro- gram may be undertaken to provide recent, site-specific data on the existing air quality. A monitoring program must last for several months, often during specific months of the year determined to have the worst·case air pollution conditions. Therefore, a monitoring pro- gram should be undertaken only when the specific issues and scope of the proposed project or action warrant such intense effort, or when agreement on background levels of air pollutant using available data cannot be reached through coordination with the local air quality dis- trict, state air quality agency, and the EPA.

14.2.2 Modeled existing air quality

Computer models are used in the prediction of air pollutant concen- trations at specific project sites. Required input for the models nor- mally consists of "background" pollutant levels. Background means existing ambient air quality in areas relatively free of pollutants. Often background levels are measured in remote areas to ensure a true background not influenced by particular pollutant sources. When monitoring stations cannot be located in remote areas, resulting data may sometimes need to be adjusted (reduced) to eliminate nearby pol- lutant contributions. Because of this characteristic of background am- bient air quality, the analysis often will compute existing pollutant concentrations in the specific project area by adding the local pollu- tant sources to the background concentrations.

The presentation of two different existing air pollutant concentrations can be confusing to the public. There are usually a measured level of particular pollutants and a modeled level for the specific site character- istics. The modeled concentrations reflect the application of the comput- er air pollutant dispersion model, which uses the background concentrations, but then adds site-specific pollutant sources. An exam- ple would be a busy highway intersection or a large manufacturing plant. The measured background pollutant concentrations would ideal- ly not be monitored in such locations, because there is obviously the presence of local pollutant sources. Therefore, the background air quali- ty would represent the intersection or factory sites with no cars or man- ufacturing. Th get a true indication of existing pollutant concentrations, the traffic and factory emissions would be predicted with the computer model, resulting in a modeled existing description of air quality.

14.2.3 Sensitive receptors

Another activity in describing the existing air quality environment is the identification of sensitive receptors. Sensitive receptors may be residential areas, schools, parks, hospitals, or other sites for which there is a reasonable expectation of continuous human exposure dur- ing the period coinciding with peak pollutant concentrations. Air quality modeling sites for prediction of future-year pollutant concen- trations are located at representative sensitive receptors in the proj- ect area. Sensitive receptors should be shown on a map in the environmental document.

14.3 Predicting Air Quality Impacts

The air quality impact of any particular proposed project or action is the difference in future-year pollutant concentrations between a no- build alternative and the proposed project or action alternatives.

If conducted productively, the scoping process may limit or focus either the pollutants to be evaluated or the level of required analysis for air quality studies for a particular proposed project or action.

14.3.1 Methodology report

For proposed projects or actions requiring detailed air quality analy- sis, preparation of an air quality methodology report can ensure agreement on assumptions, appropriate models, and other input fac- tors prior to the expenditure of time and effort on the actual analysis and computer modeling. Here is an example of the many specific items which should receive agreement prior to analysis:

Background pollutant concentrations

Wind speed and direction

Atmospheric stability factor

Dispersion characteristics and mixing heights

Sensitive receptors and modeling sites

Traffic input and assumptions

Emission factors

Model to be used

Appropriate future analysis year

Future conditions and other projects to be incorporated (can be in- creased development projects, or perhaps a decrease, such as a mili- tary base closure)

Performance of various mitigation measures

Control measures already contained within the state implementa- tion plan or attainment plan

The proposed assumptions and methodologies should be described in detail, and the report should receive review and concurrence (in writing) from jurisdictional and interested agencies, such as the EPA, state air quality control boards, the metropolitan planning organiza- tion, and local planning officials.

14.3.2 Graphical solutions and dispersion models

For relatively simple projects, graphs can be used to predict future re- gional, and sometimes local, pollutant levels. Graphical calculations have been developed for use by incorporating typical emission factors of specific types of pollutant sources and general project and site features.

Results are often obtained in tons per year or pounds per year. This type of burden analysis is normally used at a regional level. Screening procedures also can be used at the project level. The procedure, for a transportation project, would use worst-case assumptions and consider project location, nearby receptors, traffic volumes and level of service, and air quality conditions for current and future analysis years.

For more detailed microscale studies, air pollutant dispersion mod- els are used to predict future pollutant concentrations with and with- out the proposed project or action. Input to the models is extensive and can include many features of the proposed project, area topogra- phy, distance to sensitive receptors, atmospheric and climatic data. The appropriate emission factors to be used can be based on research literature, data from similar facilities, test data on specific equip- ment, or, as is the case with transportation projects, mobile vehicle emission factors developed through calculations of a multitude of con- tributing featUres. With vehicles, such features would include the mix of car and truck traffic, the specific pollutant output of vehicles, the incorporation of pollutant-reducing engine features in new vehicles and the phasing out of old vehicles over time, and the existence of a mandatory state or local inspection and maintenance program for ve- hicles as a means to check for acceptable emission performance of the vehicle before issuing a registration.

The computer models used in predicting air pollutant concentrations vary by project type and characteristics and will not be discussed in detail in this text. Specific programs exist for transportation projects, and nonnally they predict carbon monoxide levels. Carbon monoxide (CO) is used as an indicator for transportation projects. Results are given in I-hour and 8-hour parts per million (ppm) concentrations to coincide ',vith the NAAQS for carbon monoxide. Increased CO levels are associated with congested traffic conditions and with any situation where cars are stationary and idling. Cold starts in geographic areas with cold winter weather also increases CO levels.

Results of the air quality analysis will be predicted future-year con- centrations of pollutants at sensitive receptor sites for both the no- build alternative and the various action alternatives. Impact adversity is determined by comparing future concentrations with the appropri- ate standards, and by discussing any increases over the values of no- action conditions.

The air quality analysis also should consider related impacts that may be distant from the proposed physical site of the project. For ex- ample, changes in traffic patterns due to a new facility may cause re- ductions of air pollutant emissions in other areas or on other transportation routes by diverting traffic to the new facility. However, location of a new major employer or construction of a particular transportation facility may cause motorists to use residential streets as shortcuts.

14.3.3 Hot-spot analysis

In addition to predicted CO concentrations along the proposed trans- portation corridor, pollutant concentrations must be considered for key intersections. Separate models and methodologies and air quality criteria (normally for CO and PMlO) exist for these hot-spot analyses. The quantitative particulates analysis is especially applicable to bus terminals, transfer points, and commuter rail terminals, which in- crease the number of diesel vehicles congregating at a single location.

As noted in Chap. 9 on traffic and transportation, obtaining reliable traffic volume and flow characteristics for existing and for future build and no-build conditions in the project area is the absolute basis for obtaining reliable predictions of future CO and other transporta- tion-related pollutant concentrations. For example, quantitative mod- eling hot-spot analysis is required for all intersections operating at the level ofservice D, E, or F or that will change to D, E, or F due to increased traffic volumes related to the proposed new project. The an- alyst also must model the top three intersections based on highest traffic volume and the top three based on worst level of service.

Particularly with transportation projects, for example, a new free- way or improved freeway access ramps, there may be an improvement in localized impacts at other locations. For example, if the existing freeway was so congested that motorists exited and sought alternate routes through residential neighborhoods or commercial arterial streets and the proposed improvement provides adequate capacity to permit efficient noncongested traffic flow, then the air quality impact on the previously used alternate routes will be improved.

14.3.4 Stationary sources

For other types of projects, such as factories or power plants, station- ary-source computer models are used. The analysis begins with an identification of project features that would be sources of air pollu- tion. Emission characteristics or factors are found in the literature or are developed specifically to suit the circumstances of the proposed project or action. Emissions are estimated from emission factors and characteristics of the emission device (for example, height, diameter, gas velocity) to create input information needed for the dispersion model, which is then used to compute air quality concentrations. Examples of currently used models are the EPA's Industrial Source Complex (lSC2) dispersion model and the updated industrial source complex short-term (ISCST3) dispersion model. These models compute concentrations at specific receptor points for criteria pollutants and for toxic air pollutants. Toxic air pollutant concentrations are used to compute carcinogenic, chronic, and acute health risks.

Criteria pollutants include nitrogen oxides (NO), reactive organic gases (RaGs), particulates (PMlO), oxides of sulfur (SOx), and carbon monoxide (CO). As noted previously, ozone (03) is not directly emitted from mobile or stationary sources, but is formed in the presence of sunlight from precursors of nitrogen oxides and RaGs. Depending on the wind characteristics and atmospheric mixing conditions, NOx and RaGs can be trapped at low levels in the atmosphere during night- time and then transformed to ozone during daylight hours.

As with NOx and RaGs, emission of sulfur dioxide can lead to other air quality impacts. Sulfate aerosols, which can originate by conversion of sulfur dioxide, account for a large percentage of visibility impairment in the desert southwest of the United States (EPA 1995). Sulfur dioxide emissions also contribute to the formation of acid rain and other sources of acidic deposition that can threaten wildlife and vegetation.

Models for calculation of toxic pollutants are based on assessing the risks due to sources of hazardous air pollutants. Toxic compounds can potentially cause three types of health risk: carcinogenic, chronic, and acute. Both carcinogenic and chronic risks are long-term and are based on the annual average ambient air quality concentrations, while acute risk is short-term and is based on 1-hour average concen- trations. A carcinogenic health risk is assumed significant if the prob- ability of toxics causing excess cancer over a lifetime at a receptor site where people reside exceeds 1 in 100,000. A chronic or acute risk is assumed significant if the hazard index for either type of risk exceeds 1.0 at a receptor site where people reside.

14.4 Cumulative and Secondary Impacts

Regional management plans help ensure that cumulative air quality effects are considered. All projects must be shown to conform with the state implementation plan and the attainment plan. As noted previ- ously, proposed projects or actions within attainment areas must un- dergo EPA review under the Prevention of Significant Deterioration (PSD) or New-Source Review (NSR) procedures. The PSD procedures establish increments of prescribed levels of air quality degradation that will be allowed in an area. New projects are not permitted to vio- late these PSD increments. The various legislative and regulatory standards, management plans, attainment plans, and permit require- ments ensure that no particular project or action will violate federal or state standards, contribute to an existing or projected violation of the standards, exacerbate the violation of a standard, contribute to a delay in attainment of standards, or be inconsistent with an approved air quality attainment plan.

The analysis of cumulative impacts must, of course, be sure to include other proposed projects within the region or area. Such inclusion is en- sured, for example, with the requirement that all proposed transporta- tion projects be included in the regional transportation improvement program at the time the entire program is analyzed for confonnity with the state implementation plan. If a particular project was not included when the latest analysis was completed, the entire system must be rerun with the incorporation of the proposed project to ensure that cu- mulative effects with other proposed projects are considered.

Potential secondary air pollution impacts must be investigated based on the characteristics of the particular project to ensure that no possible effects are overlooked. For example, a proposed landfill proj- ect must consider the air quality impact of transport of the wastes to the site, even to the point of assessing the possible impacts of vehicles waiting longer periods at particular at-grade rail crossings, and em- ployee trips to and from the facility. There would also be emissions of construction vehicles, particularly since a landfill type of operation basically requires continuous construction activities.

Secondary air quality impacts also may occur when the proposed project or action allows specific resources to be harvested, which in turn will be processed at other, sometimes distant, locations. This type of secondary impact, for example, was a particular issue for an EPA Environmental Impact Statement on a proposed permit for strip coal mining activities in Texas, near the Mexican border. The operator of the mine intended to sell the coal for use at a power plant complex about 20 miles away in Mexico. The power plant, although in Mexico, is a major source of existing and future air pollution emissions which impact a national park and other receptors on the U.S. side of the bor- der. Substantial technical, policy, and public controversy existed over the power plant, especially since the coal provided by the mine in Texas had a lower heat value than that of many other coals which could be burned. Therefore, use of the coal from the Texas mine would require a greater amount to be burned to supply the same heat output for electricity production and would produce a greater amount of sul- fur dioxide. A secondary secondary impact was that much of the power generated at the plant is in tum used at a steel mill not far from the power plant. This example illustrates how consideration of secondary and cumulative impacts is not always easy or straightforward.

Quantification of possible secondary impacts also is very difficult for sulfur dioxide emissions. Sulfur dioxide may convert to sulfate aerosols, which in turn can cause severe impairment of visibility. Reduced visibility, in tum, can produce other types of secondary impacts. Sulfur dioxide in the atmosphere can cause acid rain and other sources of acidic deposition. The resultant effects on water quality, vegetation, and wildlife are indeed secondary impacts of the emission of sulfur dioxide, but are extremely difficult to quantify or predict.

Regarding stationary sources, the emission of criteria pollutants by a particular source may consume much of the PSD increment desig- nated in the state implementation plan. The air pollutant emissions therefore could restrict future industrial growth, which in turn would affect employment and income to the region.

14.5 Mitigation

Mitigation of air quality impacts is not a new or recent area of study. Since the passage of the Clean Air Act in 1970, and even before that time, successful methods for reducing harmful emissions into the at- mosphere have been analyzed and developed. Results of these studies have produced numerous techniques, equipment, and measures for reducing potential air pollutant concentrations to within the NAAQS and to systematically improve air quality over time. This section can- not describe all available but will give examples of some types of measures in use.

14.5.1 Mobile-source pollutants

In many areas of the United States, transportation vehicles are the major cause of violations of the NAAQS. State implementation plans and air quality attainment plans contain methods to reduce mobile- source emissions to reach attainment within target dates. These transportation control measures can vary from very technical equip- ment changes, such as requiring engines to emit lower concentrations of particular pollutants, to public behavioral changes through educa- tion and encouragement to use carpools and mass transit systems. These are examples of some typical transportation control or manage- ment measures:

• Mandated vehicle emission reductions by particular target years • Use of clean fuels • Conversion of bus fleets from diesel to electric • Use of natural gas vehicles

• Construction of high-occupancy vehicle (HOV) lanes

• Construction of mass transit systems

• Appropriate spacing of freeway entrance and exit ramps to prevent congestion

Ramp meters during peak hours to regulate the flow of traffic

Improvements to intersection signalization and traffic flow charac- teristics

Incentives at the workplace to carpool or use mass transit

Installation of message signs on freeways to inform of congested areas

Provision of adequate shoulder areas for disabled vehicles

Implementation of call boxes and a full-time towing service to rapidly remove disabled vehicles

• Staggered work hours and flexible time for major employers

• Reduction in locomotive emissions or replacement of diesel engines with electrified systems

• Requirement of all proposed transportation projects to be included in the regional transportation plan found to conform with the state implementation plan

The analysis of possible mitigation measures for a particular pro- posed project or action must be sure not to take credit for any mea- sures already committed within an adopted attainment plan. The goal is to produce a net reduction of pollutant levels by implementing additional measures for the specific proposed project.

14.5.2 Stationary sources

Mitigation measures for stationary-source pollutants are very specific to the type of project. A regional landfill may incorporate liners to prevent the escape of landfill gas. A power plant will include scrub- bers to remove sulfur oxides and nitrogen oxides. Mitigation tech- niques are therefore very industry-oriented and should be developed for the specific characteristics and problem emissions of the proposed project or action.

In some circumstances, emissions of nonattainment pollutants and precursors can be mitigated by offsets ofequal or greater reductions of each emitted pollutant, such that no net increase occurs. The offset rate can vary; an example would be a need to offset 1.3 times the emis- sion rate. The proposed offset activity need not be within the jurisdic- tion of the project sponsor. An example is a proposed landfill project in rural California which proposes offsets related to a diversion of agri- cultural plant material from burning. The elimination of agricultural burning within the county, which is primarily a source of PM 10' RaGs, NO", and CO, was shown to offset the increases of nonattainment pol- lutants attributable to the landfill.

14.5.3 Mitigation assurance

In addition to avoiding double counting, or taking credit for measures already committed within an attainment plan analysis for future years, proposed project-specific mitigation (emission reductions) can be claimed only to the extent that implementation is ensured. Evidence should be provided for the commitment to implement. Such evidence should include

• An identification of responsible parties

• A schedule for implementation

• Evidence of availability of funding

• Procedures for monitoring and enforcing

Only if this evidence of assurance of implementation of proposed mitigation measures is established and in place at the time of the en- vironmental analysis can credit emission reduction be taken.

14.6 Contents of Environmental Document

The existing air quality environment should be described in the envi- ronmental document through the use of tables and graphics, with text to describe special characteristics or reasons for particular air pollu- tion events. Tables present available data on criteria pollutants rele- vant to the characteristics of the proposed project or action and compare the concentrations with the NAAQS and any state air quaJi- ty standards. Particularly, the discussion should focus on any nonat- tainment pollutants and possible sources.

Historic air quality trends can be compiled, showing number of days per year that a particular pollutant exceeded the standards and the highest concentration reached. A sample graphic of the type that may be used is shown in Fig. 14.3. Explanation of the violations of the standards should be given if possible, such as wind direction or other atmospheric conditions, particularly if the pollutant source is not in the project area. Often geographic areas of nonattainment are due not to pollution generation within that area, but to transport of pollu- tants from other, more populated areas.

The environmental document should describe the air quality plan- ning for the region and site. The plans contain target dates for attain- ment and specific control measures to be implemented to meet standards. Coordination with state, regional, and local air quality management agencies is absolutely essential throughout the air qual- ity study, including input on methodologies to be used for calculating existing and future air pollutant levels.

The preparer of the Environmental Assessment/FaNS! or the DraftlFinal Environmental Impact Statement must at all times re- member the audience for whom the document is written, that is, the public. Presentation of results of an air quality analysis should be di- rect, simple, and easy to understand. Details on existing data, moni- toring programs, model assumptions, and analysis of computer data should be contained in a separate technical supporting document or in the appendix of the environmental document.

The environmental document should contain tables showing future air pollutant levels with and without the proposed project or action. All proposed no-build and build alternatives should be equally as- sessed. The discussion should focus on which, if any, pollutant concen- trations will exceed the applicable standards. Conformity with the SIP and any proposed mitigation measures should be summarized. Remember to document all consultation and coordination efforts with EPA, state air resources boards, regional metropolitan planning orga- nizations, air quality districts, and local planning organizations. Opinions of these agencies should not be hidden or obscure in the doc- ument, even if a difference of opinion among agencies or the project sponsor occurs.

15.1 Terminology, Standards, and Criteria

Noise is defined as unwanted sound. Sound becomes noise when it in- terferes with normal everyday activities such as sleeping, reading, and conversation. Noise becomes a health hazard when it adversely affects hearing ability or causes psychological harm that could, in turn, lead to degradation of physical health.

15.1.1 Noise-level descriptors

Noise is expressed in decibels (dB), the basic unit for measurement of sound. Because the human ear has a different sensitivity to noise sources than a microphone, a logarithmic weighting curve, the A- weighted scale, has been developed for use in approximating the sen- sitivity of the average human ear perception of loudness. Therefore, noise levels related to human impacts are measured and expressed in terms of A-weighted decibels (dBA). Figure 15.1 indicates the approx- imate dBA noise levels for several common sounds.

Th assist in the assessment of noise levels most representative for particular noise sources and environments, various agencies and mu- nicipalities have developed measurement scales, or noise descriptors, for averaging, calculating, and representing noise levels. Time-vary- ing sound levels are often described in terms of an equivalent con- stant decibel level. Equivalent sound levels, denoted by Leq , are used to develop single-value descriptions of average noise exposure over various periods of time.

For example, the Federal Highway Administration (FHWA) uses this equivalent noise level, or Leq , by averaging the dBA noise levels measured over a specified time. A I-hour Leq, used by the FHWA in assessing highway noise levels, is the average of instantaneous dBA sound levels measured over 60 minutes. The actual noise level measured by sound meters during 1 hour may vary between 60 and 70 dBA, and the I-hour Leq may be calculated to be 66 dBA, depend- ing on the percentage of time the noise level was at the high or low end of the scale. The result is a single number that can be com- pared to federal and state noise criteria established for highway projects.

In some descriptors, average noise exposure values include addi- tional weighting factors for annoyance potential attributable to time of day or other considerations. A verage noise exposure over a 24-hour period is often presented as a day-night average sound level, denoted by Ldn . The Ldn values are calculated from hourly Leq values, with the Leq values for the nighttime period (10 p.m. to 7 a.m.) increased by 10 dB to reflect the greater disturbance potential from nighttime noises.

The community noise equivalent level (CNEL) also is used to char- acterize average noise levels over a 24-hour period, with weighting factors included for evening and nighttime noise levels. The Leq values for the evening period (7 p.m. to 10 p.m.) are increased by 5 dB, while the Leq values for the nighttime period (10 p.m. to 7 a.m.) are in- creased by 10 dB.

Infrequently occurring noise sources may be described just in terms of the maximum noise occurrence, without any averaging. Examples may include the use of a peak pass-by noise level for trains and peak short-term duration of noise emitted from construction equipment.

15.1.2 Comparison of descriptor use values

A peak hourly Leq value for traffic noise will differ from an associated Ldn value depending on the distribution of traffic over the 24-hour pe- riod. There is no precise way to convert a peak hourly Leq value to an Ldn value. In urban areas exposed to high traffic volumes, the peak hourly Leq value is typically 2 to 4 dBA lower than the daily Ldn value. The relationship will change with the degree of development to an equality in value, and, finally, to a peak hourly Leq value, 3 to 4 dBA greater than the daily Ldn value in rural areas with little nighttime traffic.

An Ldn value calculated at a site from a set of measurements taken . over a given 24-hour period will be slightly lower than the CNEL value calculated over the same period. Except in situations where unusually high evening noise levels occur, the CNEL value will be within 1 to 2 dBA of the Ldn value for the same set of noise measurements.

15.1.3 Characteristics of noise

Because noise-level scales are logarithmic, values cannot be directly added to each other to calculate a total combined noise level. Two noise sources producing equal sound levels at a given location will produce a composite sound level that is 3 dBA greater than either sound alone. When two values differ by 10 dBA, the composite noise level will be only 0.4 dBA greater than that of the louder noise source alone.

Human ear perception of change in noise level is generally accepted to be as follows:

• 3 dBA or less is barely perceptible, if at all.

• 5 dBA is clearly perceptible.

• 10 dBA is perceived as being twice (or half) as loud.

Because noise consists of sound waves traveling through air, levels decrease with the distance from the noise source. With no intervening obstruction, noise from a single source will decrease approximately 6 dBA for every doubling of distance away from the source. When the noise source is essentially a continuous line, such as vehicle traffic on a highway, noise levels generally will decrease about 3 dBA for every doubling of distance.

When intervening land or structural features are present within the distance between the noise source and the receptor, noise values can be affected by these features. If intervening ground is covered with noise absorption materials, such as grass, shrubs, and trees, the reduction in noise levels will be somewhat greater than the 3-dBA value noted above for traffic noise. Topographic features and structur- al barriers can cause sound waves to be absorbed or to bounce and re- flect in different directions, thereby affecting the value of noise at a particular receptor. Atmospheric conditions also can affect the degree to which sound is reduced over distance.

15.1.4 Guidelines and criteria·

Based on characteristics of noise sources and receptors, several feder- al agencies have developed guidelines for evaluating land-use compat- ibility for applicable noise-level ranges. The federal Noise Control Act of 1972 established a requirement that all federal agencies develop programs to promote an environment free of noise that jeopardizes public health or welfare. Although the Environmental Protection Agency has responsibility under the act, each federal agency has the authority to adopt noise regulations pertaining to that particular agency's activities. For example, the Occupational Safety and Health Administration sets workplace noise exposure standards, and the Federal Aviation Administration sets aircraft noise standards.

Under the federal Noise Control Act, the Environmental Protection Agency identified indoor and outdoor noise limits to protect public health and welfare (communication disruption, sleep disturbance, and hearing damage). The Federal Highway Administration has estab- lished noise criteria for evaluating impacts associated with federally funded transportation projects on the basis of justification of funding noise mitigation measures. The FHWA criteria are based on two as- sessments: absolute noise values and the increase over existing levels regardless of resultant absolute level. If the project causes noise levels exceeding the noise abatement criteria, then mitigation measures are incorporated into the project design. The Department of Housing and Urban Development has established guidelines for evaluating noise impacts on residential projects seeking financial support under vari- ous grant programs. Summaries of the basics of these agency stan- dards and criteria are given in Fig. 15.2 as examples of variations in guidance for different types of proposed projects or actions.

In other cases, noise criteria may be specifically developed based on the particular source or proposed project. The Federal Transit Administration uses a noise exposure (Leq) criterion consisting of a max- imum acceptable increase over existing levels. Criteria also have been developed specifically for transit and other types of periodically recur- ring noise, using a maximum pass-by descriptor Lmax. Even more specif- ic criteria have been developed, such as design goal criteria for substation noise or for vehicle noise. Examples of these industry-specific criteria are shown in Fig. 15.3. An important element of the federal Noise Control Act is that it directs all federal agencies to comply with applicable federal, state, interstate, and local noise control regulations. Many states have guide~ lines and standards for evaluation of noise impacts and the require- ment to incorporate mitigation measures into the proposed project or action. For example, the California Department of Health Services published guidelines for the noise element of local general plans that include a noise~level versus land-use compatibility chart. The chart categorizes various outdoor Ldn ranges into differing degrees of ac- ceptability based on land use. The California Department of Housing and Community Development has adopted noise insulation perfor- mance standards for new hotels, motels, and dwellings other than de- tached single-family structures. The standards set requirements for maximum indoor noise levels, from outdoor sources, for any habitable room with windows closed.

Municipalities also establish local noise guidelines, usually within the adopted general plan and through noise ordinances. The county of Los Angeles and the city of Los Angeles are used here as examples. The county of Los Angeles General Plan Noise Element establishes noise~related goals and policies and describes the general noise envi- ronment. The county also has a noise ordinance which recommends maximum expected ambient noise levels for four land-use categories: noise-sensitive, residential, commercial, and industrial areas. If, how- ever, a measured ambient noise level at a specific project location exceeds the expected levels outlined in the ordinance, the measured level may be used as the baseline noise level.

The county's exterior noise standards are described in terms of max- imum time duration for exceeding the baseline at particular increases in noise levels. For example, the baseline noise level plus 10 dBA may not be exceeded for more than 5 minutes in any I-hour period. Interior noise standards set maximum allowable noise levels and set time du- ration for any violation of these standards by specific increases over the allowable levels. The county also has separate restrictions for con- struction-related noise, based on time of day and maximum levels for various land uses. The construction standards also distinguish be- tween short-term and long-term construction projects.

The city of Los Angeles General Plan Noise Element gives a value for use in assuming the expected ambient noise level in residential areas during the day. The city's noise ordinance states that this ex- pected ambient noise level in a given area may not be increased by more than 5 dBA. If actual measured noise levels are above the stated expected ambient level, then the measured levels may be used as the baseline for determining whether there is a 5-dBA increase. The Leq noise descriptor is used for analysis, and the 5-dBA increase criterion applies to both noise generated by construction activities and long- term operation-generated noise.

The discussions and examples in this section should make clear to the environmental analyst the importance of researching the applicable noise standards and criteria for the project or action being proposed.

15.2 Methodology Report

As with air quality studies, it is often advantageous for projects re- quiring detailed noise assessments to prepare a separate noise analy- sis methodology report. The report should be used as a vehicle for coordination and concurrence on selected sensitive receptors; pro- posed measurement program; assumptions; applicable federal, state, and local standards or criteria for impacts assessment; and the par- ticular computer model program to be used for predicting future noise levels at sensitive receptor sites.

If an adverse noise impact is expected, the methodology report should discuss available mitigation techniques and their acceptability for use. Agreement should be obtained on the performance success, or achieved attenuation, for specific measures. For example, all interest- ed parties should reach agreement that a particular noise barrier or wall will provide a particular noise reduction at particular heights, lengths, and composition of materials.

15.3 Describing the Existing Noise Environment

After consultation with appropriate officials and agencies to establish applicable standards and criteria, the expected impact area of the proposed project or action should be delineated. Sensitive receptors, such as schools, churches, parks, residential neighborhoods, hospi- tals, and libraries within the expected impact area, should be identi- fied. Noise measurements with industry-approved equipment are then taken at selected representative sensitive receptor sites. The number of measurements, duration of measurement, and time of day will be dictated by the particular methodology selected as appropriate based on characteristics of the proposed project or action. During ac- tual measurements, notations are made of any unusual occurrences which may distort a true representation of ambient noise levels, such as dogs barking, airplanes overhead, or excessive vehicle horns. Based on the selected descriptor, the measured sound levels are then converted to Leq, Ldn , CNEL, or peak pass-by values.

The Environmental Assessment or Draft Environmental Impact Statement should contain a map of sensitive receptor locations, a list of what the sensitive receptors are, and a table of existing noise mea- surements at each measurement site. A brief discussion of the exist- ing noise environment should describe the general characteristics, any major contributing sources, or other features important for the public to understand the general nature of the ambient noise environ- ment throughout the day.

For areas near transportation facilities, existing noise levels some- times can be determined without actual monitoring or measurement. The FHWA has noise prediction models which estimate average noise levels at fixed distances from the roadway centerline based on road- way geometrics, estimated traffic volumes for automobiles and medi- um- and heavy-duty trucks, vehicle speeds, and a designated noise drop-off rate. Shielding effects from topographical features, buildings, and other barriers are not accounted for in the model; it thus produces a conservative, worst-case estimate of traffic-generated noise levels.

The description of the existing noise environment in the environ- mental document may contain two values for existing noise levels: measured and modeled. The environmental analysis must consider and compare future noise levels of the no-action alternative with fu- ture noise levels of proposed build, or action, alternatives. Therefore, future existing noise levels are calculated with a computer model. For transportation projects, the measured noise levels and simultaneous- ly collected traffic counts are used to calibrate the noise model. The calibration compares the expected noise levels with the actual measured noise levels and thus permits correction to account for effects of topography and building shielding unique to a particular sensitive re- ceptor site. If the analysis does use both measured and modeled val- ues for existing and future existing noise levels, the reasons for the two values and the value for use as a baseline for determining future noise increases should be described in the environmental document in a straightforward, easy-to-comprehend manner through the use of ta- bles or graphs.

15.4 Predicting Noise Impacts

As with most areas of impact analysis, the first step in noise impact assessment is to reach a complete understanding of the specific char- acteristics, physical and operational, of the project or action being proposed. For transportation projects, such information will include physical parameters of the actual facility and traffic volume and flow characteristics. For stationary sources or construction activities, in- formation required will include type of equipment, hours of operation, and specific noise-producing attributes of various equipment.

As with air quality studies, future noise levels at particular sensi- tive receptor sites are predicted by using a computer model. There are some major differences in important considerations between air quali- ty and noise studies. For example, whereas the worst-case air quality impact will normally occur during peak-hour traffic conditions with maximum congestion, noise levels may actually be quite low during peak traffic hours. Because a major source of noise from vehicles is generated by tire movement on pavement, vehicles moving at slow speeds during congested conditions do not produce much noise com- pared with vehicles moving at higher speeds. The worst-case noise peak hour is thus normally considered to be when traffic is operating at level of service C, or moving at maximum volumes with little delay.

For this reason, future noise-level calculations often are dependent not on actual projected traffic volumes, but rather on the level of ser- vice C volume for the particular physical design features of the high- way. Particularly for highway projects on a new location, data input to the computer model relies on physical characteristics of the pro- posed highway (width, grade, etc.), details of projected traffic charac- teristics (volume, speed, percentage truck mix), and topographic or other buffering or intervening land features.

Use of level of service C volumes is based on the assumption that at some period during the day, the highway does actually operate at level of service C. For projects that propose widening or other alter- ation of an existing highway facility, it must be considered that the existing facility also most likely operates at level of service C at some time during the day. The evaluation of impact may therefore rely mostly on changes in physical characteristics and perhaps the dura- tion of level of service C conditions.

Another consideration that becomes more obviously important in noise studies as compared with air quality studies is the incorpora- tion of information on the possible removal of structures and other changes in land form that may affect sensitive receptors protected from noise impacts in before-project settings. For example, a row of houses immediately adjacent to an existing freeway may be destroyed as the freeway is widened. Not only is traffic physically closer to the next row of houses due to widening of the freeway, but also the buffer of the row of houses that previously shielded those second-row homes has now been removed.

Stationary sources are normally assessed for noise impacts by using industry data and literature review on the actual noise pro- duced by the employed equipment or noise source. Evaluation of con- struction-related noise also relies upon known information on the noise produced by various equipment and activities at individual stages of construction. For example, noise levels produced at 50 ft are about 84 to 85 dBA from backhoes and bulldozers, 91 to 92 dBA from graders, 80 to 88 dBA from compressors, 85 to 98 dBA from jackham- mers, and 96 to 107 dBA from pile drivers (U.S. Department of Transportation, FHWA, CADOT, and SBAG 1993; County Sanitation Districts of Los Angeles County 1994). Review of the construction schedule and associated duration of each type of noise-producing ac- tivity is used to determine the degree of noise impact on sensitive re-

ceptors. The analysis includes assumptions on noise levels from the equipment, the drop-off rate for distance, an atmospheric absorption coefficient, and distance to the receptor. Effects of shielding due to in- tervening ground topography or structures also may be considered.

In some cases, use of more than one descriptor may be appropriate to fully explore possible noise impacts. Analysis methodologies may need to include multiple modeling approaches. For example, projects that produce intermittent loud noises, such as trains, airplanes, and perhaps certain types of manufacturing or resource recovery activi- ties, may not be appropriately assessed by using an Leq descriptor or L eq standards and criteria. The Leq method would incorporate the in- termittent loud noise occurrences into an hourly average and thus may not truly represent the level of disturbance to nearby sensitive receptors. In these types of circumstances, the noise impact analyst should consider presenting both the Leq descriptor and perhaps re- sults of a peak occurrence analysis to determine effect.

The particular conditions of a proposed project may require a rather detailed analysis of effect of intervening features or physical parameters. For example, a noise source below or above a sensitive receptor would not produce the same noise levels as if the source were at the same elevation. The presence of structures or walls may redi- rect noise to receptors otherwise not expected to be affected.

Results of a noise analysis will be computed future dBA levels at se- lected sensitive receptor sites. These noise values are then compared with existing measured or modeled values, and with applicable stan- dards and criteria. The comparison should be between the various pro- posed action alternatives and the no-action alternative. Locations where the appropriate standards and criteria are exceeded require consideration of mitigation.

15.5 Ground-Borne Vibration and Noise

Certain types of projects have the potential to produce vibration waves through the ground as well as through air. Trains are the most common source of vibration impact, so rail projects will be used here as examples of criteria, impact assessment, and mitigation.

Ground-borne vibration and ground-borne noise are the same phe- nomenon up to the point of perception at the dwelling or building. Ground-borne vibration describes waves in the ground which can be measured by using vibration equipment mounted on sidewalks, foun- dations, or stakes in the ground, and which can be perceived as me- chanical motion. Ground-borne noise describes sound generated when the same waves in the ground reach room surfaces in buildings, caus- ing them to vibrate and radiate sound waves into the room.

Vibration surveys result in data in velocity levels, to compare with es- tablished criteria. Although studies about vibration and associated im- pacts are not extensive, it is generally thought that weighted vibration levels below 69 dB are generally imperceptible, or just perceptible, to the average person under nonnal conditions (U.S. DOT, UMTA, and City and County of Honolulu 1989). Criteria have been established for maxi- mum pass-by ground-borne vibration velocity levels for train operations for various land uses and for particular types of buildings. Similar crite- ria exist for ground-borne noise, measured in A-weighted decibels.

Because the magnitude of vibration transmitted from the source to receptor buildings depends largely on soil conditions within the inter- vening geologic strata, the analysis of potential impact is normally based on very site-specific characteristics. Specific characteristics of the proposed project and the receptor buildings also are extremely significant factors in the impact assessment. For example, a steel wheel and steel rail train will produce substantially more vibration than a rubber tire type of light-rail transit system. Specific significant differences can result from the type of track, type of vehicle, use of a rotary versus a linear induction motor, and location at ground level, above ground level, or below ground.

Another example may be the specific location of operational equip- ment, such as frog switches for train crossovers. A steel wheel and steel rail train crossing the gap inherent in switches will generate sig- nificantly higher vibration levels than operation on standard continu- ous trackwork. It is therefore necessary to locate such switches as far as possible from vibration-sensitive buildings, such as residences or hospitals, and preferably in industrial or undeveloped areas.

Many times, exact determination of possible ground-borne vibration and noise impacts will not be made during the environmental analysis phase of the project. The reasoning for this approach is that the level of detailed study required could not feasibly be conducted for all loca- tions of all possible considered alternatives. Therefore the detailed analysis of impacts and required mitigation is normally reserved until the preliminary engineering phase of the selected alternative.

There would be no reason to even consider vibration impact at the environmental study phase if results could not contribute to the deci- sion-making process. These studies do become useful, however, by making a more general analysis of potential impact during the envi- ronmental impact assessment phase. Using train operations again as an example, the comparative evaluation of alternatives can be devel- oped based on expected distance from the rail, or base of column for aerial systems, beyond which vibration impacts would likely not occur.

For example, a study may conclude that vibration levels from a steel wheel and steel rail system would be acceptable for residential structures beyond 35 to 40 ft, while the vibration levels from a beam- straddling monorail system would be acceptable beyond 15 to 20 ft and would be lower than or equal to those due to trucks and buses on local roads. This type of information, combined with variations among the alternatives in location alignment relative to location of sensitive buildings, can then permit an impact comparison among proposed considered alternatives.

15.6 Cumulative and Secondary Impacts

The assessment of cumulative impacts should consider other pro- posed projects within the same impact area. By use of existing mea- surements, existing noise sources will be included. Proposed future projects or actions, however, may need to be incorporated into the evaluation of cumulative impacts.

Secondary impacts are most easily identified by thoroughly review- ing all the ramifications of the proposed project or action. For exam- ple, if a factory will use raw material to be supplied by trucks or rail, the evaluation of secondary impacts should include the sensitive re- ceptors along the truck haul routes and the rail line. If a proposed project is a major employer, secondary impacts may occur due to in- creased traffic on local streets accessing the new facility. Construction equipment needs to be transported to and from a project site, and often soil or other materials will need to be hauled away. Again, the assessment of possible secondary impacts should include proposed haul routes. Detours of vehicular traffic will similarly expose recep- tors along detour routes to increased noise levels.

15.7 Mitigation

Mitigation of potentially adverse noise impacts can be accomplished through a variety of methods. Noise-producing equipment can be modified, such as with muffiers, to produce less noise. Railroad and transit noise can be reduced through changes in wheel or track de- sign. Noise barriers, or walls, are often used to shield sensitive recep- tors from highway noise. If there is sufficient space, earthen barriers may also be considered. At times, the project sponsors will make changes to the receptor rather than to the noise source, such as in- stalling air conditioning so that windows may remain closed at all times. Restricting time of day for noise-producing activities also can be used to ensure a minimized difference in noise levels.

Noise barrier design can be quite complicated and is again based on the use of computer models to determine the exact attenuation of noise levels obtained with varying wall heights, lengths, and materials.

It is acceptable for a project-sponsoring agency to set feasibility cri- teria for implementation of mitigation measures. For example, the criteria for determining whether to construct a noise wall to shield sensitive receptors from highway noise may include factors such as maximum attainable reduction in noise, number of residents or homes to benefit, and cost of the wall per benefited receptor. In some cases, it may be more feasible and cost-effective to purchase the home(s) and relocate the residents than to construct a noise barrier.

All proposed mitigation measures, such as walls, that visibly or oth- erwise directly affect a neighborhood, church, school, etc., should be developed with productive input from the affected receptor. Some neighborhoods, for example, may rather have the noise than a wall.

Ground-borne vibration and noise impacts mitigation is very indus- try- and site-specific. Examples of types of successful mitigation tech- niques for rail systems would include use of special frog switches, ballast mats or floating slab under the track, special bearing pads be- tween the track structure and support column, soft and resilient rail fasteners, or avoiding a rigid connection with adjacent buildings.

15.8 Contents of Environmental Document

If a detailed noise impact analysis is conducted, a separate supporting technical report should be prepared. The technical report contains de- tailed information on assumptions, methodologies, measurement equipment and survey, model calibrations, and results of impact and abatement analyses.

The Environmental AssessmentIFONSI or DraftlFinal Environmental Impact Statement should contain summary tables and discussions re- quired to understand the results of the analysis and lead to a better de- cision on selection of an alternative. Maps should show locations of sensitive receptors, measurement sites, modeling sites, and noise barri- ers, if proposed. Tables should indicate measured and modeled future existing noise levels and the calculated noise levels for each proposed ac- tion alternative. Tables should indicate the resultant noise levels before and after proposed mitigation implementation.

As with other areas of impact assessment, all coordination with re- gional and local agencies, and relevant community opinions derived through the public participation program, should be summarized and addressed.

Marriott, B. (1997). Environmental impact assessment: A practical guide. New York, NY: McGraw-Hill.

Booklet

1. Council on environmental quality, executive office of the president. (2007). A citizen’s guide to NEPA: Having your voice heard . Retrieved from http://energy.gov/sites/prod/files/nepapub/nepa_documents/RedDont/G-CEQ-

Public Participation 3 points possible
Content Criteria	Weight
The student discusses which two public participation steps are the most important in the NEPA process and why these two steps are vital to the NEPA procedure.	1
The student discusses in detail what steps could be taken to improve the process of public participation.	1
The student responds to at least two classmates’ initial posts.	0.5
Research Criteria
The student utilizes proper APA format, provides a post of at least 250 words, and answers with proper spelling and grammar.	0.5