EPA-430/9-76-003
TECHNICAL REPORT
DIRECT ENVIRONMENTAL FACTORS
AT MUNICIPAL WASTEWATER
TREATMENT WORKS
Evaluation and Control of Site Aesthetics,
Air Pollutants, Noise and Other Operation
and Construction Factors
January 1976
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Program Operations
Washington, D.C. 20460
MCD-20
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EPA REVIEW NOTICE
This report has been reviewed by the Environmental
Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily
reflect the views and policies of the Environmental
Protection Agency, nor does mention of trade names
or commercial products constitute endorsement or
recommendation for use.
DISTRIBUTION
Single copies of this report are available to the public
by submitting a written request to:
General Services Administration (8 FY)
Centralized Mailing Lists Services
Building 41
Denver Federal Center
Denver, Colorado 80225
Please indicate the title of the publication and the
MCD number.
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EPA-430/9-76-003
TECHNICAL REPORT
DIRECT ENVIRONMENTAL FACTORS
AT MUNICIPAL WASTEWATER
TREATMENT WORKS
Evaluation and Control of Site Aesthetics,
Air Pollutants, Noise and Other Operation
and Construction Factors
By
R. Ernest Leffel
Contract No. 68-01-0324
January 1976
Prepared For
Environmental Protection Agency
Office of Water Program Operations
Washington, D.C. 20460
MCD-20
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PREFACE
With the impetus given to water quality improvement under PL 92—500 through
the municipal construction grants program, the design and construction of many
new wastewater treatment plants have commenced. At the same time, the public
has become accustomed to better environmental planning of such structures. In
the past, environmental factors have created public doubts and uneasiness about
nearby municipal treatment works. These adverse environmental factors can and
must be prevented or controlled, to minimize objection to wastewater treatment
works in the neighborhood.
This report, although not EPA policy, does contain a good summary of evaluation
and control measures designed to arrive at environmentally sound projects. Environ-
mental factors considered in the report include odors, noise, site planning,
architecture, lighting, aesthetics, subsurface conditions, construction nuisances, and
treatment during construction.
Designers and review authorities must exert special effort to ensure projects are
environmentally sound. In a few cases, this may result in higher capital and operat-
ing costs. Generally, however, costs are lower over the planning period because
there is no need for expensive alterations to correct nuisance problems. The
Cost-Effectiveness Analysis Guidelines (40 CFR 35, Appendix A, Federal Register,
September 10, 1973) details how to incorporate non-monetary factors, such as
social and environmental factors, into cost-effectiveness analysis.
The level of detail required in a facility plan to deal with direct environmental effects
will vary according to the circumstances, and the size, nature, and location of the un-
dertaking. Local municipalities and consultants should discuss the extent of planning
required with officials of the State and EPA.
11
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TABLE OF CONTENTS
Chapter Page No.
1 INTRODUCTION 1
1.1 Purpose of Publication 1
1.2 Goals 1
1.3 Scope 2
1.4 Reference Legislation 2
1.5 Related EPA Publications 2
2 PLANNING AND SITE DESIGN 3
2.1 Planning Studies and Investigations 3
2.2 Site Design 5
2.2.1 Introduction 5
2.2.2 General Considerations 6
2.2.3 Site Design Examples 7
2.3 Specific Site Design Considerations 14
2.3.1 Process Construction Considerations
Affecting Site Development 14
2.3.2 Building Orientation 16
2.3.3 Shoreline and Wetlands Planning 16
2.3.4 Flood Plain Avoidance 19
2.3.5 Recreation and Education 19
2.3.6 Wildlife Habitats and Historic Sites 19
2.3.7 Landscaping 20
2.3.8 Lighting 20
2.3.9 Security 21
2.3.10 Building Aesthetics 21
2.3.11 Future Development 21
2.3.12 Site Traffic 22
3 AIRBORNE POLLUTANTS 23
3.1 General Information 23
3.2 Odors 24
3.2.1 Units of Expression 24
in
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TABLE OF CONTENTS (Continued)
Chapter Page No:
3.2.2 Odor Potential at Wastewater
Treatment Facilities 25
3.2.3 Characteristics of Odors 26
3.2.4 Hydrogen Sulfide 27
3.2.5 Standards or Acceptable Levels 29
3.2.6 Odor Detection and Measurement 30
3.2.7 Odor Analysis Methodology 31
3.2.8 Odor Control Measures 31
3.2.9 Odor Intensity Determinations 37
3.2.10 Sample Calculations 38
3.3 Aerosols and Particulates 45
3.4 Gases 47
3.5 References 48
4 NOISE 53
4.1 General Background 53
4.2 Units of Expression and Measurement 54
4.3 Typical Noise Levels 57
4.4 Acceptable and Standard Noise Levels 57
4.4.1 Allowable Exposure to Impact
or Impulsive Noise 57
4.4.2 Impulse Noises 61
4.4.3 Community Noise Criteria 61
4.4.4 Machinery Noise 64
4,4.5 Interior Noise 64
4.4.6 Exterior Noise 64
4.5 Noise Control Methods 66
4.5.1 Source Control 66
4.5.2 Piping Systems 66
4.5.3 Mechanical Aerators 67
4.5.4 Compressors, Fans, and Blowers 67
4.5.5 Vacuum Filter Pumps and Blowers 67
4.5.6 Pumps 67
4.5.7 Incinerators 67
4.5.8 HVAC 67
4.5.9 Architectural Noise Control 67
4.5.10 Construction Noise Control 68
4.5.11 Operational Noise Control 70
4.6 Acoustical Computations 70
4.6.1 Addition of Decibels 71
4.6.2 Sound Power Level/Pressure
Level Conversions 71
4.6.3 Reduction of Sound Pressure
Level With Distance Outdoors 73
iv
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TABLE OF CONTENTS (Continued)
Chapter Page No.
4.6.4 Conversion of Octave Band Sound
Pressure Levels to A-Scale
Sound Pressure Levels 74
4.6.5 Calculation of Effective Sound
Isolation of Composite
Barrier Construction 74
4.6.6 Calculation of Sound Insulation
From an Enclosed Room to Outside 80
4.6.7 Calculation of Noise Output From
Plant Equipment 81
4.6.8 Calculation of Total Noise Levels
at Typical Locations on Periphery
of Wastewater Treatment Works
Property From All Significant
Sources 82
4.7 References 87
5 SITE PREPARATION, CONSTRUCTION, AND
OPERATION PROBLEMS 89
5.1 Flooding and Drainage 89
5.2 Site Preparation 90
5.3 Disposal of Clearing Debris
and Construction Wastes 91
5.4 Excavation and Backfill 92
5.5 Pile Driving, Blasting, and
Earthquake Problems 93
5.6 Dredging 93
5.7 Erosion and Siltation 94
5.8 Restoration of Easements
After Construction 97
5.9 Wastewater Treatment During
Treatment Plant Modification 98
5.10 Sludge, Process Sidestreams,
and Onsite Disposal 99
5.11 Groundwater Pollution 100
5.12 References 101
Appendix A Reference Legislation 103
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LIST OF FIGURES
Fig. No. Page No.
2-1 Wastewater Treatment Works
Formulation and Development 4
2-2 Urban Site 8
2-3 Socially Sensitive Suburban Site 10
2-4 Ecologically Sensitive Suburban Site 12
2-5 Shoreline Planning 17
3-1 Gaussian Distributions 39
3-2 Gaussian Distribution Curve 39
3-3 Ordinate Values of the Gaussian Distribution 40
3-4 Area Under Gaussian Distribution Curve 40
3-5 Horizontal Dispersion Coefficients 41
3-6 Vertical Dispersion Coefficients 42
3-7 The Product of ay a2 44
4-1 Frequency-Response Characteristics 56
4-2 Peak Permissible Sound Pressure Levels 63
4-3 Construction Equipment Noise Ranges 65
4-4 Sound Level Conversion Chart 76
4-5 Effective Transmission Loss of
Composite Acoustic Barriers 77
4-6 Transmission of Noise Through Walls and Floors 78
4-7 Environmental Noise Levels for Residential, Hospital,
and Educational Activity 83
4-8 Plan for Example 4-6 84
VI
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LIST OF TABLES
Table No. Page No.
3-1 Odorous Vapors Found at Wastewater Facilities 28
3-2 Possible Odor Prevention and Control Methods 36
3-3 Key to Stability Categories 37
4-1 Equivalent Sound Levels 58
4-2 Estimated Percentage of Urban Population
Residing in Areas With Various Day/Night Noise Levels 58
4-3 Average Single Number Sound Levels 59
4-4 Yearly Average Equivalent Sound Levels
Identified as Requisite To Protect Public Health
and Welfare With Adequate Margin of Safety 60
4-5 Typical Values of Peak Sound Pressure Levels
for Impulse Noise 62
4-6 Noise Exposure Levels 62
4-7 Basic Information on Construction Equipment 69
4-8 Addition of Decibels 72
4-9 C Values for Omnidirectional Noise Sources 72
4-10 Relation Between Octave Band Center Frequency
and A-Scale Frequency 75
4-11 Airborne Sound Transmission Loss Values for
Some Common Building Constructions
Derived From Field Measurements 79
Vll
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1. INTRODUCTION
1.1 PURPOSE OF PUBLICATION
The purpose of this report is to provide the methodology and reference information for federal
guidelines and for designers of publicly owned wastewater treatment works. To assist in
obtaining maximum flexibility and economy in the design, construction, operation, and
maintenance of wastewater treatment works, while ensuring the required level of environ-
mental compatibility, relevant considerations are presented. Wastewater treatment works
include treatment plants, pumping stations, separation structures, interceptors, force mains,
certain collection systems, and outfalls.
1.2 GOALS
Wastewater treatment works must not be the ugly duckling in the community but rather the
good neighbor. In the past, odors, unsightliness, dust, and erosion have created public doubts
and uneasiness about nearby municipal treatment works. These adverse environmental factors
can and must be prevented or controlled, to minimize objections to wastewater treatment
works in the neighborhood. In the final analysis, the design engineer must ask: "Would I be
willing to live near this plant?" It is not acceptable to create new environmental problems
while solving water quality problems.
Incorporation of environmental considerations in the design, construction, operation, and
maintenance of wastewater treatment works should ultimately result in the least cost to the
total fiscal and environmental resources. Capital and operating dollar costs may not be lower,
but such considerations of natural environmental resources should lead to overall savings in
total resources. Works that are designed, constructed, and operated with consideration of the
social and ecological aspects of the environment can both encourage and facilitate the
development and improvement of nearby lands in conformity with comprehensive plans for
the area.
In assessing impacts on an environmental factor, the design engineer must (a) check whether
the impacted environmental factor is important and (b) determine whether the effects on the
environmental factor are significant. Detailed assessments should be largely confined to
important factors which might be significantly affected by a plan of action.
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1.3 SCOPE
It is recognized that there are many broader issues relating to the overall environmental
impacts of wastewater treatment works. Although this document is concerned mostly with
direct environmental factors, some of the broader environmental issues are identified, together
with references where additional information may be found.
The environmental compatibility considerations discussed in this report are limited to those
direct factors affected by the design, construction, operation, and maintenance of wastewater
treatment works. Possibly significant effects, both beneficial and adverse, of the works on each
aspect of the environment should be evaluated in the project conception stage and in the
facilities planning stage (when a formal assessment is required) and reevaluated in the design
stage, always keeping in mind the possible impact caused by construction of the works and
by the operation and maintenance of the completed works.
The Environmental Protection Agency (EPA) requires that assessments of the possible
impacts on significant aspects of the environment accompany all plans for wastewater treat-
ment works submitted to the EPA for federal assistance.
1.4 REFERENCE LEGISLATION
Legislation with respect to environmental factors at wastewater treatment works is discussed
in Appendix A.
1.5 RELATED EPA PUBLICATIONS
1. Federal Water Pollution Control Act Amendments of 1972.(P L 92-500).
2. Design, Operation and Maintenance of Wastewater Treatment Facilities (September 1970).
3. Procedures for Providing Grants to State and Designated Areawide Planning
Agencies (40 CFR Subchapter B. Part 35, November 28, 1975).
4. Policies and Procedures for the State Continuing Planning Process (40 CFR
Part 130, November 28, 1975)
5. Preparation of Water Quality Management Plans(40 CFR Part 131,November 28, 1975).
6. Preparation of Environmental Impact Statements (40 CFR Part 1500, 1 August 1973).
7. Preparation of Environmental Impact Statements (40 CFR Part 6, April 14, 1975)
8. Areawide Waste Treatment Management Planning Areas and Responsible Planning
Agencies (38 CFR Part 103, 30 May 1973, and 38 CFR Part 126, 14 September 1973).
9. Cost-Effectiveness Analysis Guidelines (40 CFR Part 35, 10 September 1973).
10. Guidance for Preparing a Facility Plan (U.S. EPA, May 1975).
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2. PLANNING AND SITE DESIGN
2.1 PLANNING STUDIES AND INVESTIGATIONS
The engineer should be concerned with minimizing possibly adverse environmental effects,
and maximizing beneficial effects, of the wastewater works project on the region. Fig. 2-1
illustrates general items in the life cycle of wastewater treatment works. During the formula-
tion and development stage of such a project, there must be a close relation between the
design engineer and government, public, and industry representatives. Areawide comprehen-
sive plans, with criteria and guidelines for wastewater works planning, should have been
prepared by regional, basin, and state authorities and be available for use by the engineer.
The reader is referred to sections 201, 208, and 303 of PL 92-500 for more detailed informa-
tion on such facilities planning.
Much of the difficulty in locating wastewater works has resulted from inadequate considera-
tion of aesthetics in the design, construction, and operation of these works. Odors and noises,
although not dangerous to health or safety, can be very unpleasant. Intrusive or badly focused
light fixtures can be a source of irritation. Unattractive buildings and grounds can create
adverse public reactions, as can poorly maintained works. The designer and operator must
reduce these disturbing conditions, if not eliminate them entirely. In the past, the possibility
of gas explosions, exposure to wastewater from ruptured tanks, overflows of wastewater,
chlorine and oxygen hazards, and the danger of open tanks or ponds has biased the public
against siting these facilities near a developed community.
Other factors to be considered in evaluating environmental impact are: the degree to which
short-term uses can be made of the environment while maintaining its long-term productivity;
the period for which the proposed works should be designed, to handle wastewater needs
effectively; the beneficial and adverse effects on land development in the area, both within
and without the treatment works; and any irreversible modification of resources caused by
the proposed project, including utilization of potentially valuable land, water resources, and
possible depreciation of adjacent property values.
Because of the increasing complexity of the planning and design process, based on the
necessity of considering social, ecological, and aesthetic factors (as well as the more conven-
tional engineering requirements), government authorities should obtain the advice of qualified
public representatives in those areas in which the public will be directly affected, such as
initial site selection, environmental inventory, planning, and review. Identification of the
effects (both monetary and resource) on the environment in terms which the public can
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FIG. 2-1. WASTEWATER TREATMENT WORKS FORMULATION
AND DEVELOPMENT
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comprehend and evaluate will result in valid reactions to the proposals and will improve
the probability of the project's success.
The planning process should start with an environmental survey of the site, adjacent lands,
municipality, and region, to identify those factors which could be important in preventing
or minimizing significant adverse effects. The engineer may require the assistance of profes-
sionals in one or more of the environmental disciplines, to provide expert advice about the
importance of specific site characteristics.
Once the survey is completed, permissible levels or amounts of aerosols, odors, noise, light-
ing, or other possible problems resulting from wastewater works can be determined for that
particular area. Land use, environmental, and wastewater design requirements can then be
integrated, and possible alternatives investigated for feasibility. Finally, an environmentally
compatible solution can be recommended, after a detailed engineering study of the feasible
alternatives.
With regard to the effects of the proposed works on the environment, the planning phase
should also include an evaluation of the possible effects during each step of the proposed
project, such as:
1. the effect of preempting land for the works
2. the effect of effluent discharges
3. the effect of possible diversion of existing wastewater flow
4. the effect of flooding, plant malfunctions, and emergency
situations
5. the effect of proposed sludge treatment and disposal
6. the possible effect of noise, aerosols, and odors
7. the effects of construction, operation, and maintenance of
the facilities.
Appendix A provides a useful reference for Federal laws and executive orders which
should be considered in the planning phase.
2.2 SITE DESIGN
2.2.1 Introduction
Selection of the wastewater treatment facility site should be based on careful consideration
of the region's land use and development patterns, as well as engineering constraints of the
existing and proposed wastewater system. Site selection is covered in other EPA documents;
however, the basic principles of site analysis and design described here can be used to make
a general assessment of site suitability.
Because municipal wastewater treatment facilities are the end points of sewer systems, they
are generally located at a lower elevation and near a body of water, or irrigable land, capable
of accepting their treated effluent.
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Unfortunately, it is usually in those areas where a facility is most needed that its site is most
likely to be subject to the constraints of neighboring development. It is a consequence of
urban geography, politics, and economics that, as an area's development necessitates the
building of a wastewater treatment facility, this same development more severely restricts the
design of the site. This chapter will address how the nature of these constraints can be dis-
covered and addressed in site planning and design.
The designer should become familiar with the proposed site and its neighborhood. Because
a wastewater facility is an essential social service, its design should maximize its contribution
to the area's social resources and minimize any detrimental effects. The wastewater facility
must be well engineered, but onsite planning and development which improve the facility's
operation, aid its acceptance in the neighborhood, and minimize its effects on sensitive
natural features are also required.
Characteristics of the site and its neighborhood must be inventoried, to identify any features
which might make some aspect of site development incompatible with its environs. Factors
influencing site design are both natural and social. For example, it would be important to
know both that a specific section of the site is subject to spring flooding and that one of its
borders is shared with a residential community. Both facts indicate that sections of the site
should be avoided or be given special treatment. It cannot be emphasized too strongly that
natural and social factors influence design. Obviously, an area subject to flooding requires
special design treatment, if it must be used, to safeguard facility access and operation during
flood. Similarly, a section close to relatively incompatible land use (such as residences)
requires a special design effort and perhaps development expense to render the facility
acceptable.
Matters to be investigated include, but are not limited to: topography, drainage, surface
water, groundwater, soil types, bedrock, vegetation, prevailing winds, temperature ranges,
precipitation, seasonal solar angles, wildlife habitats, ecosystems, regional and local land use,
transportation, zoning, archaeological and historical features, and special natural features.
2.2.2 General Considerations
A successful wastewater facility site design makes use of the existing and developed features
of the site to satisfy the demands of the treatment facility and its neighbors and to minimize
any conflict of interest. It is the designer's responsibility to take the information gathered in
the site inventory, together with the requirements of process and plant operation, and produce
a site and facility layout satisfactory to all parties. Design is not the simple result of analysis
of site constraints. Assessment of the site's character does not establish what should be done
but only what would be affected if something were done. The designer must clarify goals for
the site design, to facilitate public decisions as to which site features are to be respected,
enhanced, altered, or destroyed in pursuit of those goals.
Specific principles to be followed in the design of wastewater facilities are given in a later
section of this chapter. Before reviewing such matters, three examples of site inventory and
design will be discussed, to illustrate how site constraint and assessment information may be
gathered and how it informs and influences, but does not dictate, site design decisions. From
the examples, three basic strategies for site planning and design can be abstracted: (a)
advantageous use of existing site conditions to solve problems of facility functioning and
environmental compatibility, (b) disposition and design of the necessary facility elements
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to minimize or avoid environmental compatibility problems, and (c) addition of design
elements not necessary to facility function to solve environmental compatibility problems.
The choice and mix of strategies to solve site design problems will depend on the particular
problems of each site and the skills of the designers. A fourth strategy not discussed here
(because it is more closely related to process engineering than site analysis) is studying
feasible alternative treatment processes to select the one best suited to achieve both the
required effluent quality and environmental compatibility.
2.2.3 Site Design Examples
The following examples illustrate three cases in which site inventories were used to assist
site design. These cases (one urban and two suburban semirural sites) show how principal
environmental problems can change according to the site's location and character. In the
urban area, the principal concerns are maintenance of limited urban recreational and open
space and separation of the facility from its sensitive neighbors. In the suburban cases, the
principal problems are siting the facility in a socially sensitive environment in one case and
in an ecologically sensitive area in the other.
It must be remembered that these examples are meant only to be illustrative of the design
process and are neither complete nor definitive.
Although the analyses and site planning drawings are reproduced here in black and white,
they need not be executed monochromatically. The specific examples illustrate graphic
techniques which would be useful for client presentation and indicate a rather high level of
graphic competence. In this way public discussions and decisions concerning the treatment
facility can benefit from the engineer's and designer's expertise.
The drawings and accompanying commentaries show how the inventory of existing site
characteristics, design goals, and site design solutions can be documented. In the urban case,
the inventory of existing conditions, design goals, and site design solutions are reduced to
single drawings. The socially sensitive suburban case presents both initial and final site plans.
The final example comprises six drawings presenting existing conditions, two of design
choices, and one final site design.
URBAN SITE. In this hypothetical urban case, the inventory of existing conditions (Fig. 2-2a)
illustrates existing land uses and traffic patterns. The site, located in a densely developed
urban setting, also contains a large undeveloped open area. The inventory allows the designer
to establish specific goals in the site development (Fig. 2-2b). Based on discussions between
the engineer and client, it has been decided to (a) preserve the character of the park; (b)
design the street edges to respond to the residential neighborhood, historical monument, and
heavy traffic; (c) preserve the marsh as an ecologically important feature; and (d) maintain
the river's edge for recreation. A location for vehicular access to the site and the general area
for facility development have been found. The final site design (Fig. 2-2c) illustrates a layout
responsive to the identified site planning goals. The facility has been developed away from
the residential edge, and existing trees and new landscaping have been used as buffers.
Because the facility has been located nearer the river, the use of the river's edge as a recrea-
tion area has been accomplished by building a garden walk and esplanade. On this, tight
urban site, the facility would have to be placed near either the residential front or the river.
In either case, facility development would require special treatment of this narrow edge.
Once the important design goals are established, the designer should consider all solutions
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EXISTING
CONDITIONS
LEGEND
RIVER—Sailing, fishing, limited
sunbathing
OPEN LAND—Several abandoned
bldgs. and dump
PARK—Mature trees, some sitting areas
MARSH—Used by water fowl in spring
and fall
RESIDENTIAL
Single family
Multi family
High rise
PUBLIC BLDG.
Institutional
Educational
BUSINESS
Commercial
Light Industry
Historically significant
Views of site and from site
»•»• Heavy car and truck traffic
— Heavy car traffic
— Moderate car traffic
Light car traffic
Pedestrian
FIG. 2-2B.
DESIGN GOALS
FIG. 2-2C.
SITE DESIGN
SOLUTION
KEY SITE PLANNING FACTORS
LEGEND
S Preserve and enhance character of park
II Design edge of street for residential
' neighborhood
- Preserve marsh
| Design shoreline for river recreation
• Design street edge for heavy traffic
• Potential public access
Most suitable vehicular access
Respect historic site
1 Approximate site of wastewater
treatment plant
FINAL SITE PLAN
LEGEND
I. Site entry
2. Visitor and staff parking
3. Truck yard
4. Process building
5. Administration
6. Maintenance facilities
7. Primary sedimentation basin
8. Earth mound using materials from
excavation
9. Gravity thickeners
10. Mechanical aeration basin
11. Landscape visual barrier
12. Final clarifiers
13'. Chlorine contact tank
14. Bicycle and walking path
15. Marsh
16. Fence
17. Influent
18. Effluent
19. Mechanical bar screens
20. Aerated grit chambers
21. Memorial
22. Garden wall and esplanade seating
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which meet the requirements, even if an additional design element is necessitated. In very
tight urban sites, like this hypothetical one, such extra elements are to be expected as part of
the development cost.
SOCIALLY SENSITIVE SUBURBAN SITE. The inventory of existing conditions for this suburban
site (Fig. 2-3a and b) shows the site as a large undeveloped tract between two suburban
streets lined with single-family houses. Fig. 2-3c indicates the prevailing winds and seasonal
solar angles—general information which should be ascertained for any wastewater treatment
facility. Prevailing wind information allows the designer to place odor and aerosol processes
downwind of inhabited areas. Solar angles are used to design the facility buildings for mini-
mum energy consumption for heating, ventilating, and air conditioning. Also, in northern
climates, truck areas would be placed where snow melting could be aided by the sun.
For this particular case, the principal site constraint is the existence of residential neighbors.
Development of the site must produce a socially acceptable facility within the heavily vege-
tated zone.
The design analysis (Fig. 2-3 d) shows the wastewater treatment facility located in the center
of the tract, with buffer zones between it and the residential areas. The specific area chosen
for development is a relatively level sector above flood level. The designer has also combined
site access with the influent line, so that minimal construction can be undertaken, with as
little destruction of the existing vegetation as possible. The site design schematic (Fig. 2-3e)
indicates the preliminary layout of process elements and buildings on the site. Truck and
driving areas have been kept on the sunny side of major structures, to aid snow melting.
Ample space for future process expansion is also indicated. The final site plan (Fig. 2-3f)
shows the site and orientation of the initial construction. Also, the design intention of using
vegetation as a visual buffer for the residential areas is emphasized by boundaries of vegeta-
tion around the facility.
In this case, site analysis and design have identified the major compatibility problem as that
of screening the facility from visually sensitive neighbors. In this regard, the designer made
use of the existing site vegetation and the site size and boundaries. In addition, the entry
road is so located that truck and automobile traffic can be easily separated at the entrance to
the plant.
ECOLOGICALLY SENSITIVE SUBURBAN SITE. In this hypothetical case, the very large parcel of
land, somewhat haphazardly bounded, presents combined problems of incompatibility. The
principal constraint is the serious ecological problem associated with development of the
site. Extensive analyses of natural conditions in the area (shown in part in Fig. 2-4b, c, d,
and e) indicated that most of the site would be unsuitable for development because of
severe slopes, erodible soils, flood plain and drainage pattern encroachment, and sensitive
vegetation. The first problem of site planning is thus finding an area of adequate size for
development which is relatively insensitive ecologically. The second problem is that the site
requires visual buffer planning, similar to the previous example.
Based on the site inventory (Fig. 2-4a through e), a parcel of land which would be safe for
development—presenting no insuperable problems of erodible soils, flood plain encroach-
ment, valuable vegetation, and special wildlife habitats—has been found. Fig. 2-4f shows
this same parcel hidden from the view of most of the residential neighbors. The designer has
thus managed to solve both problems by choosing the larger area. A site design drawing
could be eliminated, because the principal and secondary design goals have been achieved.
-------
FIG. 2-3A.
EXISTING
CONDITIONS-
TOPOGRAPHY
FIG. 2-3B.
EXISTING
CONDITIONS-
VEGETATION
FIG. 2-3C.
EXISTING
CONDITIONS-
SOLAR ANGLES
AND WINDS
10
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FIG. 2-3D.
SITE FACTORS
ANALYSIS
FIG. 2-3E.
SITE DESIGN
SCHEMATIC
FIG. 2-3F.
FINAL SITE PLAN
11
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FIG. 2-4A.
EXISTING
CONDITIONS-
SITE BOUNDARIES
FIG. 2-4B.
EXISTING
CONDITIONS
CONTOURS
FIG. 2-4C.
EXISTING
CONDITIONS
SLOPES
SLffi
E
: . ..
SI-SB PC
%-sorc
\2
-------
FIG. 2-4D.
EXISTING
CONDITIONS-
SUPERFICIAL
GEOLOGY
'
.
wan
FIG. 2-4E.
EXISTING
CONDITIONS
VEGETATION
FIG. 2-4F.
EXISTING
CONDITIONS
VIEWS
li
13
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Fig. 2-4g and h illustrates schematic choices which the designer must make in the final site
plan. Alignment of the influent line and service water can follow many routes. The designer
must refer to the earlier site inventory drawings, to ascertain the impact of each choice on
the sensitive site areas.
The final site design (Fig. 2-4i) illustrates how the designer has managed to fit the large
areas required for treatment processes within the portion of the site suitable for such develop-
ment. In this hypothetical southern climate, snow melting is not a problem; thus truck and
parking areas can be arranged to allow separation of visitor and employee parking. Visitors
would be shielded from truck and process areas and led to a special administrative building
entry. Facility personnel would park close to the service building.
2.3 SPECIFIC SITE DESIGN CONSIDERATIONS
2.3.1 Process Construction Considerations Affecting Site Development
SITE TOPOGRAPHY AND GEOLOGY. For sites which are sloped, a site plan which will facilitate
gravity flows in the process should be considered. Reduction of pumping requirements by
such a hydraulic strategy can save both capital and operating costs, as well as conserve
energy. Existing slopes should be respected in construction planning, to limit erosion and
siltation. Similarly, if particularly good soils for fill or excavation exist on the site, the plan
should attempt to use these resources, to minimize construction costs.
COMPACT SITE PLANNING. A relatively compact site plan can minimize piping requirements
and thereby reduce pumping energy and costs. Particular attention should be paid to the
distances over which materials like sludge must be conveyed. A compact plan will also limit
the extent of site development—a desirable feature in tight urban areas where open land may
be at a premium or in sensitive rural sites where intrusion in ecologically sensitive areas is to
be avoided. As part of compact planning, manned areas and work stations should be grouped
to allow centralization of process equipment and personnel facilities in a single major build-
ing and thus reduce total staff size and optimize plant supervision and operation functions.
ODOR AND AEROSOL SOURCES. Known potential odor and aerosol sources in treatment process
areas can be partially controlled, if they are located downwind (according to the prevailing
wind pattern) from near neighbors or public spaces on the site. Such process elements could
be located near each other or be covered. In conjunction with the topographic and wind
information, odor producers should not be sited in valleys or other areas where natural air
movements cannot produce sufficient air changes to dissipate odors rapidly (see chapter 3).
NOISE SOURCES. Noise in the facility buildings and on the site should be controlled, to pre-
vent discomfort to plant personnel and nuisance to neighbors. Process and auxiliary equip-
ment, such as pumps, ejectors, generators, and vacuum assemblies, which can produce
disturbing sound levels should be isolated from personnel areas and work stations wherever
feasible. Noise levels from such machinery should be investigated for compliance with U.S.
EPA and OSHA requirements for wastewater facility employee exposure to noise. In facility
buildings, noise sources can be segregated from quieter areas by acoustic barriers, and
offending noise levels can be attenuated by sound absorbing materials. Transmission of
sounds from process equipment offsite should also be controlled. Road alignments on the
site should be designed to eliminate steep grades, so that noises from truck braking and
14
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FIG. 2-4G.
PLANNING
FACTOR—SEWER
ALIGNMENTS
H8EWEK S
ISTE IE* VIA
I «4 VIA
K1AS LINK COT
TO ISTE fl'M VIA
NEW OHT
TO ISTE «4 VIA
NEW K.O.W
FIG. 2-4H.
PLANNING
FACTOR—WATER
ALIGNMENTS
FIG. 2-41.
FINALSITE
DESIGN
LEGEND
I. Influent
2. Entry road
3. Grit screenings building
4. Grit chambers
5. Visitors car park
6. Administration
7. Solids handling
8. Service facilities
9. Primary sedimentation
10. Primary pump gallery and access
structure
11. Primary tunnel
12. Aeration basins
13. Trucking yard
14. Gravity thickeners
15. Final clarifiers
16. W.A.S. pump gallery and access
structure
17. Tunnel
18. Employee car park
19. Chlorine building
20. Chlorine contact basins
21. Effluent
15
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shifting can be avoided. Facility sound sources should not produce noise levels offsite which
regularly or greatly exceed ambient sound levels. The simplest method for sound attenuation
is reduction at the source (for every doubling of distance, sound pressure levels decrease by
approximately 6 decibels). However, a facility cannot always be located well away from
noise-sensitive neighbors. In such cases, onsite sound sources should be acoustically isolated.
Noise sources in buildings can be placed inside sound barriers and absorptive enclosures.
Noise sources outside buildings can be controlled by placing partial acoustic barriers, such as
embankments, very dense plantings, and the facility buildings themselves, between these
sources and the sensitive neighbors. Construction noise can be screened in a similar manner.
If possible, construction equipment producing low noise levels should be chosen (see
chapter 4).
MAINTENANCE AND ACCESS REQUIREMENTS. The site plan must allow normal and emergency
maintenance to be carried out in the facility buildings and on the site.
Access roads or paths should always be included in the site planning, and their size and
bearing capacity for all maintenance or emergency tasks, including fire righting, should be
considered.
2.3.2 Building Orientation
The climate of the area should be considered in building orientation and design. To control
heating, ventilating, and air conditioning costs, major building faces should be oriented to
minimize heat loss in the cold season and heat gain in the warm season through openings,
windows, skylights, etc. The building enclosure should be carefully designed to avoid
excessive energy use for the building's internal climate.
In northern climates, buildings should not shade trucking and parking areas, thereby exac-
erbating the problems of winter snow and ice clearance. Similarly, landscape planting should
take into account shade from buildings. Neither buildings nor landscaping should shade open
bodies of wastewater undergoing treatment but should, if possible, prevent wind cooling
action.
Buildings should be located to serve as barriers to undesired views of the facility. For instance,
the designer may locate the facility so that it limits the neighbors' view of the facility and
presents an acceptable public face.
2.3.3 Shoreline and Wetlands Planning
The shoreline of the body of water usually associated with wastewater facilities should be
respected in site planning. The shore is a critical zone in the earth's natural system—the
place where land, air, and water meet. It is also a prime recreational zone, and thus site
planning of a wastewater facility should consider means by which shorelines within the site
boundaries can be reserved for public use. Fig. 2-5a and b illustrates how an adequate public
way along a shore drive can be maintained. Preservation of the shoreline is especially impor-
tant in urban areas where little open public access to the shore is likely to exist. Because
construction at the shoreline could result in erosion of the banks, siltation of the waterway,
and destruction of valuable ecological niches, methods should be specified where necessary,
to prevent such damage. Facilities impacting the Coastal Zone must be in conformance
with the Coastal Zone Management Act (Appendix A), and appropriate State officies
and the appropriate office of the Department of Commerce should be contacted during
environmental review.
16
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Q
O
CO
UJ
5
POLLUTION CONTROL
FACILITY
APPROACH TO FENCE
VISUAL SCREENING
PARK FURNITURE-
BENCHES, LIGHTS,
WASTE RECEPT.& TREES
SEWER RIGHT-OF-WAY
RECREATIONAL USE WHERE POSSIBLE
EMERGENCY VEHICLES
PAVED SURFACE
SHORE TREES & SHRUBS
EROSION CONTROL
SHALLOW SPAWNING AREA
WET ROOT PLANTS
LAND ANIMAL WATER SUPPLY
ALTERNATE WETTING & DRYING OF LAND
| FIG. 2-5A. SHORELINE PLANNING "|
17
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o
CO
cc
III
I
BERM (POSSIBLY FROM
EXCAVATION MATERIAL)
LANDSCAPING-DESIGNED
FOR:
1.VISUAL APPEARANCE
2.MAINTENANCE
3.PLANT FUNCTION
4.CLIMATE & SOILS
PAVED SURFACE FOR
EMERGENCY VEHICLES,
BICYCLES, MAINTENANCE
PARK FURNITURE-BENCHES,
LIGHTS, WASTE RECEPTACLES
DECORATIVE LANDSCAPING
SEWER RIGHT-OF-WAY
WALKING SURFACE
SHORE TREES & SHRUBS
EROSION CONTROL
SHRUBS TO INHIBIT
APPROACH TO FENCE
SHALLOW SPAWNING AREA
WET ROOT PLANTS
LAND ANIMAL WATER SUPPLY
ALTERNATE WETTING & DRYING OF LAND
FENCE
POLLUTION CONTROL
FACILITY
| FIG. 2-5B. SHORELINE PLANNING |
18
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Wetlands are another unique and valuable resource and must be protected from alteration
of the quantity or quality of the natural water flow. If facility construction and operation
might produce such an effect, the appropriate offices of the Department of the Interior,
Department of Commerce, and the U.S. Army Corps of Engineers should be contacted to
determine the probable impact on the pertinent fish and wildlife resources and land use of
the wetlands. Administrator's Decision Statement =f=£4 (Appendix A) describes EPA wetlands
policy.
2.3.4 Flood Plain Avoidance
Flood plain boundaries of a site should always be determined prior to site design. If possible,
siting within a flood plain should be avoided. Building in the flood plain necessitates raising
the facility entry above flood level and safeguarding facility elements against flood damage,
flotation effects, and process interruption. Also, for every cubic foot of flood plain volume
occupied, flood levels are raised correspondingly. Thus flood effects are worsened by flood
plain encroachment. Any facility siting must be in conformance with Executive Order 11296
and the Flood Disaster Protection Act (see Appendix A).
2.3.5 Recreation and Education
The Wild and Scenic Rivers Act (see Appendix A) defines three classifications for selected
rivers: wild, scenic, and recreational. Water resources projects, such as treatment facilities,
may be prohibited where a direct and adverse effect would result on the values for which
such rivers were established. Facility planners should avoid where possible siting on one of
these designated waterways. Designation and classification of rivers may be obtained from
the Bureau of Outdoor Recreation (Interior) or the National Forest Service (Agriculture).
Only those portions of the site necessary for facility operation should be dedicated to the
wastewater facility itself. Other portions of the site should be reserved for other public uses,
particularly recreation (for example, along waterways). The facility buildings themselves
should be designed to provide opportunities for public education concerning the wastewater
facility, its operation, and its role as a public utility.
A public entrance to the facility site which will lead clearly to a public entry to the main
facility building should be provided. At this entry point, an appropriate educational display
can be located or a tour of the facility can begin. If public education is to be part of the
facility function, then educational displays should be designed to be clear, accurate, and
informative. If frequent tours of the facility are to be accommodated, then safe, complete,
and easily followed paths through the facility should be included in the site and building
designs.
2.3.6 Wildlife Habitats and Historic Sites
The Endangered Species Act (Appendix A) provides for the conservation of threatened or
endangered flora and fauna.lt is important that endangered species and their critical habitats
adjacent to or directly affected by the proposed site be identified.
Project sites must be evaluated for the presence of archaeological, historical, or other cultural
properties included on or eligible for inclusion in the National Register of Historic Places. This
is required by the National Historic Preservation Act of 1966 and Executive Order 11 593
19
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(Appendix A). If such properties are identified and will be adversely affected by the project,
the procedures of the Advisory Council on Historical Preservation (Appendix A) must be
followed and means developed to mitigate the adverse impacts. The State Historic Preser-
vation Officer should be consulted during this process.
2.3.7 Landscaping
Existing site vegetation should be assessed. If it can remain undisturbed throughout con-
struction, it should be safeguarded, because its destruction will only require later planting
to return the area to an acceptable condition.
Existing or newly planted vegetation can be used as a visual screen for process elements and
buildings. Of course, the value of the screen must be assessed for all seasons and throughout
the natural history of the planting. Planting should be considered for control of slope erosion
and water runoff, and to emphasize architectural or site forms, so that it can frame attractive
objects as well as hide unattractive ones. In considering major planting for any purpose,
views to, from, and on the site must be carefully studied. Planting can be designed to shade
processes, buildings, paths, and truck yards in summer and still allow effective use of winter
light. If landscaping elements are to be used, the local soil, climatological, and biological
conditions should be carefully investigated by a competent landscape architect or nursery-
man, before investment is made in fragile vegetative materials. Materials requiring little or
no maintenance are to be preferred over those requiring a higher degree of care. Planting
near open basins should be designed so that leaves and needles do not fall or cannot be easily
blown by the wind into process waters.
References such as the U.S. Department of Interior's publication Plants/People and Environ-
mental Quality by G.O. Robinette may be consulted on landscape and planting design.
2.3.8 Lighting
Design standards and techniques are well established for both interior and exterior lighting
systems, to provide adequate light for safe operation, efficiency, and security. These are
briefly described below.
INTERIOR LIGHTING. Architectural and engineering reference texts provide adequate design
standards for the interior lighting required for a good working environment. Illuminating
Engineering Society Lighting Handbook is a basic reference.
EXTERIOR LIGHTING. Exterior lighting should be based on analysis of ambient light levels in
the area. Possibly adverse impacts of the proposed lighting on the area should be assessed,
including consideration of annoyance, loss of privacy, and resulting decline in property values.
SAFETY LIGHTING. Redirecting lights necessary for safe operation without diminishing light on
the work area is desirable, if there might be an adverse impact on adjacent areas. Corrections
may be accomplished by spotlighting specific areas. Shielding the lighting will also result in
a lower light level outside the working area.
SECURITY LIGHTING. High light levels which permit ready visual observation for security
purposes are rarely necessary.
AESTHETICS. Lighting may be used to highlight structural and landscape features.
20
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CONSTRUCTION LIGHTING. Construction lighting may be classified as that necessary for con-
struction operations and that needed for security during construction. Care should be taken
to eliminate light spillover onto adjacent land, if such spillover would adversely affect land
use. Spillover effects should be based on ambient light levels and land use in the adjacent
areas. Light from moving vehicles may be blocked by temporary barriers. Security lighting,
to permit surveillance of parked equipment, can be minimized by parking equipment in a
limited remote area or by parking equipment in areas already lighted.
If security lighting during construction will intrude on adjacent residential areas or on other
areas which might be detrimentally affected, the designer may specify that these be lighted in
a manner to eliminate or reduce nuisances. Specifications should include direction of lighting,
height of light, and intensity.
2.3.9 Security
A wastewater facility can attract children, with its tanks of water and unfamiliar processes.
It is also an essential public service which must be safeguarded against vandalism and dam-
age. For these reasons, access to the facility should be controlled. Fences and other barriers
should enclose the facility in a way unoffensive to the public eye. If the facility is near an
important public way or close to a sensitive neighbor, then a specially designed barrier—
garden wall or landscaped buffer with hidden fence, for example—should be provided.
Security considerations need only apply to the immediate area bordering the facility, not to
the entire site. If possible, walls of process elements and buildings themselves should enclose
the facility, minimizing fencing requirements. If process and building walls form part of the
security boundary, their materials should be chosen to resist whatever forms of vandalism
can be expected at the site.
2.3.10 Building Aesthetics
As important public structures of high utilitarian and monetary value, wastewater facility
buildings deserve forthright and careful architectural treatment. Because they are planned
for long-term public service, their design, materials, and construction should show them to
be permanent additions to the community. If the building is not to be screened from view,
the public face of the structure should be designed to express the building's public utility
capacity and to reflect society's pride in its works.
Building design should not hinder process function but should order the workings of plant
personnel, process equipment, and visitors. Such quality of design is not easily achieved, and
competent architectural designers should be employed whenever possible.
In residential neighborhoods, the scale of the wastewater facility should closely match that
of other public facilities nearby. Siting and views of the wastewater treatment facility should
be studied fully, so that it can be reduced in apparent scale as much as possible. A reduced
visual scale and minimal functional presentation is a good strategy for building design in
sensitive areas.
2.3.11 Future Development
Site design must include provision for future expansion of the facility, if that will be required.
A good site design for future development requires more than simple designation of adequate
21
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area for expansion. Expansion areas should be chosen so that future construction can occur
without interruption of existing facility processes. In other words, neither construction nor
its access should interfere with regular plant operation. Locating future expansion areas for
different elements near each other can facilitate expansion construction. Flexibility should
also be allowed in plans for expansion.
Future changes in process equipment and processes themselves cannot be predicted with
certainty; thus the site plan should not be rigidly adapted to one particular process and in-
capable of future alteration without excessive construction and operation penalties. Areas
designated for future expansion need not be reserved behind the facility fence. Because
expansion may not occur for many years, and may not occur in the manner originally
planned, reserved areas may be temporarily dedicated to other public uses such as public
open spaces or recreation.
2.3.12 Site Traffic
Trucks and service traffic should be separated from operation and employee traffic early and
easily upon site entry. Visitors should be directed to an appropriate building entry. Employee
and visitor traffic in truck yard areas should be limited, wherever feasible. Truck traffic should
also be clearly routed.
Truck turning and backing areas should be sized for the largest vehicle expected. Pedestrian
traffic onsite should not have to cross the truck yard or process areas to enter buildings.
22
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3. AIRBORNE POLLUTANTS
3.1 GENERAL INFORMATION
Airborne pollutants from a wastewater treatment facility, if sufficiently concentrated or
intense, can make the facility environmentally incompatible with neighboring land uses.
The purpose of this chapter is to familiarize the designer with the characteristics of possible
airborne pollutants, to provide measurement techniques for determining the pollutant's
strength, to discuss acceptable pollutant levels, to summarize control technology and the
locations where each technology can be used, and to illustrate design calculations with
examples. There are many areas and processes in wastewater facilities which can be potential
sources of airborne pollutants, if such pollution is not prevented by satisfactory design, con-
struction, operation, and maintenance. Airborne pollutants include: odors; noxious, toxic,
or asphyxiating gases; particulates from sludge incinerators and construction operations; and
aerosols from trickling filters, aeration basins, cooling towers, stripping towers, ventilation
systems, and construction operations.
Recently, aerosols have been shown to be deserving of attention. Pathogens present in
aerosols must be considered a potential source of disease and infection, because aerosols have
been found to include E. coli, A. aerogenes, and pathogenic enteric organisms (1, 2,
3, 4, 5,). No evidence, however, has been found that aerosols have affected the
health of either wastewater facility workers or others.
Controls for particulates and gases from incinerators are well established (6)(7). EPA has
developed criteria and standards for permissible levels of pollutants in stack emissions (8).
These standards established limits on particulate discharge and opacity.
Gases which can cause air pollution are emitted from many locations in treatment works,
including: wastewater, sludge, and liquid sidestream processing; wastewater collection, pump-
ing, and transmission; and disposal operations. Some of these gases are explosive, toxic,
asphyxiating, and/or flammable. Dangerous gases are discussed in reference (9).
23
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3.2 ODORS
3.2.1 Units of Expression
Units of expression used in odor discussions are defined as follows (14):
1. acuity—keenness of the sense organs in detecting qualita-
tive or quantitative differences among stimuli
2. adequate stimulus—one which normally elicits a response
with a particular sense concern
3. anosmia—total or partial lack of sensitivity to odor stimuli
4. attitude—acquired predisposition to respond in a consis-
tent way toward a given class of objects; a persistent state
of readiness to react to a certain object or class of objects,
not as they are, but as they are conceived to be
5. attribute—any quality or characteristic descriptive of stim-
ulus
6. contrast—presentation of two different stimuli which re-
sults in emphasizing their contrary characteristics; may be
of two types: (a) simultaneous or (b) successive
7. detection threshold—minimum physical intensity detec-
tion by a subject if subject is not required to identify the
stimulus but just detect the existence of the stimulus
8. difference threshold—physical difference between two
stimuli which can be correctly judged as subjectively dif-
ferent beyond chance expectation
9. intensity—quantitative attribute of stimuli roughly cor-
related with strength of stimuli; odor intensity is a sensa-
tion, not a concentration, and is measured on a psycho-
logical reaction scale
10. masking—in odor applications, situation in which one
quality within a mixture dominates or overrides another
quality or other qualities present, thus changing the qual-
ity or intensity
11. odor—perception of smell referring to the experience, or
that which is smelled referring to the stimulus (odorant is
preferred for this latter usage)
12. odor counteraction—nonchemical odor phenomenon in
which two individually discernible odors yield, upon mix-
24
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ture, a third odor which is weaker in intensity than either
of the original two odors
13. odor unit—quantity of odorous substance or combination
of substances which, when completely dispersed in 1 cubic
foot of odor-free air, is detectable by a median number of
observers in a panel of eight or more persons (12)
14. odorant—substance which stimulates olfactory receptors
15. odor panel—group of individuals who may be selected
on the basis of sensitivity to stimuli, reliability, or whose
perceptions are judged to be representative of some larger
population; used to obtain information concerning the
subjective attributes of physical stimuli
16. subjective—pertaining to experience which can be ob-
served and reported only by the person involved; that is,
mental phenomena usually verbally reported
17. threshold odor—minimum physical intensity of stimulus
which elicits a response 50 percent of the time.
3.2.2 Odor Potential at Wastewater Treatment Facilities
A 1974 telephone survey of 500 wastewater collection and treatment system superintendents
indicated that about 40 percent of the systems had received complaints about odor and about
34 percent had instituted measures to control odors (13).
Any organic material containing sulfur and/or nitrogen in domestic wastewater can, in the
absence of an oxygen source, undergo incomplete oxidation, resulting in the emissions of
byproducts which may be malodorous. For this reason, a major effort must be given to the
prevention of odorant production and to the control of odors which can be generated acci-
dentally, by the careful design and operation of wastewater treatment works.
The degree of obnoxiousness of malodorous gases depends not only on the concentration of
the odor and on the person exposed to the odor but also on the intensity of the odor. Most
people are particularly sensitive, and have greater acuity, to unfamiliar odors. Olfactory
sensitivity varies from person to person. The olfactory senses of persons continually exposed
to an odor become anosmic or insensitive to that odor with time; therefore, odor nuisance
determinations are highly subjective. In fact, gases such as H2S rapidly affect the olfactory
senses to such an extent that, after a few minutes' exposure to even low concentrations, a
person can no longer detect the H2S. Environmental engineers, or plant operators, regularly
associated with the operation of a wastewater treatment plant and who may be at least
partially anosmic to the plant's odors should not be the ones who judge whether or not their
treatment plant has an odor problem.
Odors that can be identified as having come from domestic waste are particularly objection-
able to most people. Even fresh wastewater and digested sludge have odors which, although
25
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not objectionable to environmental engineers or treatment plant operators, are often unac-
ceptable to the general public. Potential sources of wastewater odors include:
1. fresh, septic, or incompletely treated wastewater
2. raw or incompletely stabilized sludge
3. raw or incompletely treated liquid process sidestreams
4. screenings, grit, and skimmings containing septic or putres-
cible matter
5. oil, grease, fats, and soaps from industry, homes, and street
runoff
6. gaseous emissions from treatment processes, manholes,
wells, pumping stations, leaking containers, turbulent flow
areas, and outfall areas
7. chlorinated water containing phenols
8. dredged or excavated material containing odor producing
substances
9. incompletely oxidized hydrocarbon fuels with high sulfur
content.
There are innumerable odors in airborne gases and vapors resulting from various concentra-
tions and intensities of each odorous constituent. As these odorous gases and vapors travel
downwind, they often are neutralized (by counteraction) or to some extent intensified by
reaction with other gases, vapors, or particulate matter.
3.2.3 Characteristics of Odors
Inorganic gases and organic vapors result from biological activity. The more common inor-
ganic gases associated with domestic wastewater treatment facilities include hydrogen sulfide
(H2S), sulfur dioxide (SO2), ammonia (NH3), carbon dioxide (CO2), methane (CH4),
nitrogen (N2), oxygen (O2), and hydrogen (H2). Only hydrogen sulfide, sulfur dioxide,
and ammonia are malodorous.
The most frequently emitted odors found in the studies of some 300 wastewater treatment
works (14) were: methylmercaptans, methylsulfides, and amines, followed by indole, skatole,
hydrogen sulfide, and, to a lesser extent, sulfur dioxide, phenolics, and chlorine compounds.
Some organic acids, aldehydes, and ketones may also be odorous either individually or in
combination with other compounds. The mild, musty odor often found near treated sludge
is caused by algae, fungi, and molds continuing the organic decomposition processes.
The concentration of an odorant is measured in milligrams per liter (mg/1) or micrograms
per liter (^g/1); the intensity is a measure of the stimulation of the olfactory senses. Odor
intensity or strength does not vary proportionally with the concentration of the odorant. The
26
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intensity of an odor at a concentration of 100 may be only twice as great as its intensity at a
concentration of 10 (15). The intensity of an odor may be decreased by the same ratio
whether the concentration is reduced from 50 mg/1 to 25 mg/1 or from 10 mg/1 to 5 mg/1.
Complete oxidation of odorants usually results in complete eradication of odor. Incomplete
oxidation may result in an increase in odor. For example, butanol has a mild odor and, upon
complete oxidation, is changed to odorless CO2 and H2O. However, if it is incompletely
oxidized, it is successively changed to butyraldehyde and then butyric acid, both of which
have strong odors.
To prevent odors when organic compounds are decomposed, the oxidation-reduction potential
(ORP) of the wastewater or sludge must be maintained sufficiently high for complete oxida-
tion, to avoid the formation of partially oxidized products such as H2S, NH3, mercaptans,
skatoles, indoles, etc. Common oxidizing agents, in decreasing order of their half-ORP
(ORP/2) in volts, are ozone (2.07), hydrogen peroxide (1.77), permanganate (1.70),
chlorine (1.36), oxygen (1.23), iodine (1.20), bromine (1.07), nitrate (0.94), sulfate
(0.17), and hydrogen (0.00). For the ORP to remain sufficiently high to avoid incom-
plete oxidation of organic compounds containing sulfur, oxidizing agents must be added if
the amount of oxidizing agents normally present in wastewater—oxygen (O2) or nitrate
(NO3)—is not adequate. Other oxidizing agents, such as chlorine, ozone, pure oxygen,
hydrogen peroxide, and oxides of nitrogen, also raise the ORP when added to wastewater.
In sufficient concentrations, these agents can cause completely odor-free oxidation.
Warm wastewater, under anaerobic conditions with a low ORP and a pH of about 6 to 8,
will produce odors that have been characterized by different people as rancid, fecal, cabbage-
like, skunklike, etc., depending on the predominant odorant. Some of the characteristics of
the more common odorants found near wastewater or sludge are presented in Table 3.1.
3.2.4 Hydrogen Sulfide
Sulfur (ORP/2 = 0.14) is present in human excreta, and sulfates are found in most water
supplies. Therefore, sufficient sulfur is normally available in domestic wastewater, in the form
of inorganic sulfides or organic sulfides (e.g., mercaptans, thioethers, and disulfides), for the
production of odorous gases or vapors by anaerobic and facultative bacteria.
Hydrogen sulfide (H2S) is the most commonly known malodorous gas emanating from
domestic wastewater collection and treatment facilities. H2S is highly soluble (2,800 mg/1 at
30° C to 5,650 mg/1 at 5° C) in normal domestic wastewater. In addition to its rotten-egg
odor, H2S can cause highly corrosive conditions and is an extremely toxic substance. The
walls and crowns of sewers or closed tanks often have droplets of attached spray or con-
densation on the surface. Water (such as condensed water vapor in the form of dew or drop-
lets) saturated with H2S as a result of bacterial action forms sulfuric acid, which is very
corrosive to lead-based paint, concrete, metals, and other materials. The toxicity of H2S is
on the same order of magnitude as hydrocyanic acid (HCN). Death appears to have resulted
from an H2S concentration of 0.03 percent in the air (18). The maximum permissible 8-hour
H2S concentration is about 0.001 ml/1 (10). H2S is treacherous, because the ability of a
person to sense it is quickly lost. If the person ignores the first notice, the senses will no
longer give warning and the person may be killed (18).
27
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TABLE 3-1. ODOROUS VAPORS FOUND AT WASTEWATER FACILITIES'
Substance (Odor Description) Formula
Odor Normal Boiling
Molecular Threshold, Point, °C at
Weight /jLg/l 760 mm Hg
Ammonia (sharp and pungent) NH3
Ethyl mercaptan (decayed
cabbage and garlic)
Hydrogen sulfide (rotten eggs)
Indole (excreta)
Methyl mercaptan (decayed
cabbage and onions)
Skatole (fecal, pungent, and
irritating)
Dimethyl amine
Methyl amine
Dimethyl sulfide
Chlorophenol (medicinal)
Chlorine (pungent, irritating)
Allyl mercaptan (garlic)
Diphenyl sulfide (unpleasant)
n-butyl mercaptan (skunk)
Ozone (slightly pungent,
irritating) O3
*See references (7,15,16,17).
KUS
C8H6NH
CH3SH
(CHs)oNH
CH3NH2
(CH3)2S
ClC(iH5O
C12
CH,:CH-CHo-SH
(CflHB)2S
CH3-CH:CH-CH2-SH
17.03
62.1
34.1
117.1
48.1
48
37
0.2
1.1
1.1
-33
23
-62
254
131.2
45.08
31.06
62.13
128.56
70.91
74.15
186.28
90.19
9.0
4.7
21.0
2.5
0.18
10
0.05
0.05
0.03
266
7
-7
37
214
-34
67
296
98
-111.3
28
-------
If wastewater is kept in a force main or siphon for more than a few minutes, sulfides may be
formed, particularly if the temperatures are high. The possible buildup in a filled pipe can
be estimated roughly, using the following formula (19):
- n (1 + O.Old)
— U-
where
ACB = sulfide concentration increase, mg/1
t = detention time, min
CEBOD = effective BOD = 1.07(T-20) (BOD5),mg/l
T = temperature, °C
d = pipe diameter, in.
At a pH of about 9, hydrogen sulfide dissolved in water is over 99 percent in the form of the
nonodorous sulfide ion (HS~) but only 1 percent at a pH of about 5. If the pH is above 8,
there is little trouble from H2S gas.
H2S is most commonly produced by reduction of the sulfate ion (SO42~) by anaerobic sulfate-
reducing organisms. These bacteria thrive at low oxidation-reduction potentials (ORPs of
-0.20 to -0.30 V), pH of about 6 to 9, and temperatures near 30° C. The ORP of fresh
wastewater is usually too high for the first one or two days for significant production of H2S.
However, anaerobic slime growths and sludge deposits which accumulate in sewer lines
usually have lower ORPs than the wastewater, making them more conducive to H2S pro-
duction. H2S may thus be produced even though the wastewater contains up to about
0.3 mg/1 of O2 and the ORP is not sufficiently low to support sulfate-reducing organisms.
If nitrates or dissolved oxygen is present and well distributed, the ORP will be too high for
H2S production by sulfate reducers.
For more details on methods to prevent and control hydrogen sulfide, see references (4, 15,
18, 20-23, 25-32). References (15) and (18) are particularly valuable.
3.2.5 Standards or Acceptable Levels
Standards, or acceptable levels, of odors from wastewater treatment plants normally have not
been set, because any odor traceable to such works is deemed excessive. For this reason, it
has been the practice to surround wastewater treatment plants with open ground or natural
barriers such as forests, rivers, major highways, etc. However, treatment facilities built in
open country may in time be surrounded by populated areas whose residents undoubtedly
will insist on freedom from detectable odors from the facilities. As a result, wastewater treat-
ment facilities should be designed and built so that, if odors become detectable outside the
plant site, alleviation will be easily attained.
Designing for odor control requires that the engineer assess the effect of the odor on adjacent
land use, as well as on the workers at the facility. Significant criteria are frequency and
intensity of occurrence related to the population affected. For example, the effect of an odor
on a residential area will be substantially different from the effect on some heavy industrial
area where some odor is already present. In certain cases, costs of providing odor control will
be minimal, because safety requirements dictate effective venting of units, and only odor
elimination equipment installations will be required to process the odorous gas.
29
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3.2.6 Odor Detection and Measurement
Absolute identification of all ingredients of an odor is not necessary. To date, no instrument
can better measure odors than the human nose, because odor is a physiological response to a
complex grouping of airborne compounds. In fact, no known mechanical device can quan-
titatively measure the intensity of combined odors. The concentration of the primary compo-
nents of some odorous compounds, such as hydrogen sulfide or sulfur dioxide, can be
monitored. However, because of variations in composition of the ingredients of the gas, it is
very difficult to correlate intensity findings from the individual odor concentrations. Odor
measurement for odor abatement purposes can be made more easily and accurately at the
source, because the characteristics of the odorous vapors and gases often change with move-
ment downwind, by diffusion and by combination with other gases or vapors.
Each attempt to measure a strong odor may cause some olfactory fatigue and loss of acuity in
the tester, thus reducing the accuracy of subsequent trials. Continued testing is more accurate
if the nose is intermittently subjected to only diluted odors. For this reason, strength or
intensity of an odor is best established by determining the number of dilutions with odor-free
air required to reduce the odor from a sample to a barely detectable level. The dilution should
be prepared by other than the odor testers, or some time should elapse after most of the
necessary dilution has been completed before the final threshold determination is made.
The sensitivity of the olfactory senses varies considerably from person to person, and the
interpretation of odors is very subjective. It is thus necessary to have several persons who are
known to be sensitive to all expected types of odors make the tests. It has been found that
persons with discriminating food tastes are also usually more sensitive to odors (7). The
detectability of odors will increase with increases in temperature and humidity at the time of
testing. Some odors, such as the earthy odor of polysulfides formed when H2S is treated with
chlorine, are only released when wastewater is heated.
The odor unit is the amount of odor necessary to contaminate 1 cubic foot of odor-free air
to the detection threshold level; i.e., the odor is detectable by a median number of observers
in an odor panel. For example, if it takes 9 cubic feet of an air sample to reduce the odor
to the threshold "level, the air sample contains 10 odor units per cubic foot. Total odor units
emitted are equal to the odor units per cubic foot times the cross-sectional area in square
feet of the odor emission times the velocity of emission in feet per minute.
Four methods, based on human perception of odors, are normally used for measuring odor
concentrations (7):
1. Odor-free air and odor-containing air are mixed in a con-
tainer, and samples of the mixture are injected into the
tester's nose.
2. Odor-free air and odor-containing air are mixed in a con-
tainer, and the tester inhales from the container.
3. Odor-free air and odor-containing air are mixed in a duct
from which a flow of the mixture is discharged to a nose-
piece, headpiece, hood, or chamber for sniffing by the
tester.
30
-------
4. Odor-free air and odor-containing air are mixed in a mea-
surable dilution, utilizing the energy exerted in the process
of inhalation.
The major differences in these methods have to do with preventing odorous vapors from being
deposited on the equipment or in the nostrils of the testers, thus interfering with subsequent
tests.
For detailed descriptions of the odor testing methods, see references (7. 32, 34). Discussions
of selection of odor panel members and the procedures to be followed are contained in
references (7, 21, 33, 34, 35).
3.2.7 Odor Analysis Methodology
References (33, 36, 37, 38) contain descriptions of methods used to qualitatively and quan-
titatively analyze odorous gases. However, because two or more of these odorants may com-
bine to produce either a weaker or stronger odorant, the quantitative measurement of the
component odorants in an odorous gas or vapor is of little value.
For this reason, methods of measuring strength of odors must rely on the olfactory nerves of
odor panels described in the previous section. These measurements can be correlated with
the quantitative findings of gas chromatography.
Table 3-1 lists the threshold concentrations of the more common odorants found at domestic
wastewater treatment plants.
3.2.8 Odor Control Measures
Odor control measures should take into account the following: (a) completely aerobic oxida-
tion of organic matter prevents the formation of odorous compounds of sulfur and nitrogen;
(b) slime buildup on conduit and tank walls, and sludge or organic waste deposits, will
almost always produce some H2S and other odorants; and (c) H2S and other odorants will
be released from wastewater at points of turbulence, particularly where freefall occurs.
Dague (15) listed the various factors which should be considered in the control of wastewater
odors: (a) all normal people can smell; (b) some substances are odorous, others are not;
(c) we can smell at a distance; (d) substances of different chemical constitution may have
similar odors; (e) substances of similar constitution usually have similar odors (however,
isomers or even stereoisomers may have different odors); (f) substances of high molecular
weight are usually not odorous and often nonvolatile or insoluble; (g) the quality as well
as the strength of an odor may change on dilution; (h) the sense of smell is rapidly fatigued;
(i) fatigue for one odor will not affect the perception of other dissimilar odors but may
interfere with the perception of similar odors; (j) two or more odorous substances may cancel
each other out (on the other hand, two or more mildly odorous substances may add together
to form a very odorous substance); and (k) odors travel downwind.
Measures which have been successful in the prevention or control of odors generated at waste-
water facilities are described in the following paragraphs.
31
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OXIDATION/DISINFECTION. This is usually accomplished with such chemicals as chlorine, ozone,
hydrogen peroxide, and sodium permanganate.
Chlorination. Chlorine gas and hypochlorite solutions have been successfully used to stop the
action of odorant producing bacteria and to oxidize odorants such as H2S and mercaptans
(12, 18, 40), by injecting chlorine or hypochlorite into wastewater or by passing collected
odorous air through a chlorine solution in a tank. It takes about 5 g (2.1 to 8.87 g) of
chlorine to 1 g of H2S to inhibit odor production (39) and often as much as 10 to 15 g to
convert all the sulfur to sulfates, because of the other more easily oxidizable compounds
present (18). If C12 dosages are down to about 2.1 g/g of H2S, hydrochloric acid is formed;
if C12 dosages are up to about 8.4 g/g of H2S, both hydrochloric and sulfuric acids are
formed. Each of these is very corrosive. In many locations, to prevent damage to downstream
ecological systems, it may be necessary to dechlorinate and remove those chlorinated com-
pounds which are toxic before the treated wastewater is discharged. Some odors are not re-
moved by chlorination. If the odorous compound concentration is above the design concen-
tration, other odorous compounds may be formed. Chlorine supresses bacterial activity even
in a combined form, but most bacterial populations, including the coliform population, will
often be regenerated shortly after the chlorine residual disappears (54). For more information
on odor control with chlorine, see reference (18). Chlorine application is discussed in
reference (53).
Ozonation. Ozone is used to oxidize odorants in air, collected from above wastewater pro-
cesses, before discharge to the atmosphere (40)(41). Ozonation of wastewater has not been
practiced to a great extent in the past; however, recent developments, including the possible
dangers of chlorine compounds and the reduced costs of newer ozonators, make the use of
ozone in place of chlorine feasible for both odor control and disinfection, particularly if the
wastewater must also be dechlorinated. Active research is being sponsored by the EPA, to
develop better design criteria for the safe use of ozone. Oxidation of airborne odorants with
ozone may present a hazard if ozone remains in the treated air in concentrations above
0.2 mg/m;i of air at the time of discharge (42). Further information on odor control with
ozone is contained in reference (51). Ozone application is discussed in reference (53).
Hydrogen Peroxide. Hydrogen peroxide is another oxidant used to destroy sulfate-reducing
bacteria in sewers and to oxidize any sulfides present (31)(32). In recent years, hydrogen
peroxide has been used in place of prechlorination, to prevent hydrogen sulfide buildup in
transmission lines and pumping stations and to prevent hydrogen sulfide problems in wet
wells (18). It is usually necessary to first condition (oxidize slimes and organic deposits on
walls) the pipes and tanks in which the wastewater is to be treated by one or more dosages
of 50 nig/1 for 4 to 8 hours. Following one or more of these massive treatments, dosages can
be lowered to 5 to 10 mg/1 to prevent H2S formation. Between 1 and 2 Ib of H^O^ are
needed per pound of H2S after the slug dosages (39). H2O2, like ozone, raises the dissolved
oxygen content of the wastewater in addition to killing sulfate-reducers and reducing odors.
H2OL> is competitive in price with chlorine for control of H2S (39).
Sodium Permanganate. Sodium permanganate, like ozone and H2O2, is a significantly more
active oxidizing agent than chlorine. However, it is generally not competitive with respect to
cost with other oxidizing agents (12, 22, 40). In some cases, the manganese content of the
water may be increased to a troublesome level.
RAISING THE ORP. To prevent the production of odorants by sulfate reducers and other anaer-
obes, air, nitrates, and pure oxygen have also been added to wastewater to raise the ORP.
32
-------
Air. Wastewater is commonly aerated by mechanical aerators, diffusers, a free fall which
causes turbulence, and U-tube aeration. The addition of air to prevent anaerobic conditions
in wastewaters will prevent the production of odorants. The addition of air to anaerobic
wastewater may strip out odorants and thus cause odor problems if not adequately controlled,
particularly at drops or falls in septic wastewater streams. Sufficient air must be dissolved
and confined sufficiently long for oxidation of sulfides to be accomplished. U-tubes with air
addition by aspirators have proved to be an effective and odor-free method of adding air to
wastewater lines. A detailed description of aeration methods is presented in reference (18).
Oxygen. If a main has little rise, making air injection relatively feasible, pure oxygen may be
used as an alternative for sulfide control in force mains and siphons, if the oxygen can be
kept in solution (18).
Nitrate. This chemical has been satisfactorily added to wastewater to reduce and temporarily
control odors. Nitrate may serve to prevent sulfide buildup by preventing sulfate reduction,
because nitrate-reducing bacteria can use nitrate to oxidize sulfide, if oxygen is not
available (18).
pH CONTROL. If sulfide odors predominate, it is possible to reduce or eliminate hydrogen sul-
fide by raising the pH. At pH above 9, H2S is not present, but biological treatment processes
will be substantially impeded (6). Caustic soda or quicklime used to raise the pH of waste-
water in sewers to 13 will inactivate the slime on sewer walls for about 1 week (18). Because
sulfide producers can adjust to pH over 10.5, the pH should not be held above 9 for more
than 30 minutes.
ABSORPTION/SCRUBBING. Odor removal by reactive scrubbing can be an effective method of
odor control, particularly if followed by activated carbon or ozonation, depending on the
odorous components of the gas. Potential scrubbing reagents are KMnO4, NaCIO, C12, C1O2,
and NaHSOs. However, a single scrubbing reagent can seldom remove all odorous com-
pounds effectively (12). The efficiency of odor removal can often be improved by increasing
the pH of the scrubbing solution (12). The resulting solution, however, must be amenable to
treatment in a wastewater treatment plant or pretreated to make it so. Scrubbers are best
suited for treating large volumes of air containing relatively low concentrations of odorous
contaminants. Possible advantages of scrubbers include: capability of installation in a low
building, because conventional scrubbing towers are not needed; gravity flow of solution;
quiet operation; and reasonable cost, because this equipment is mass-produced. Possible
disadvantages include: necessity for auxiliary processes such as adsorption or filtration, cor-
rosion of equipment, and maintenance of minimum concentration of reagent. See reference
(51) for further information on scrubbing. Low concentrations of odorants may be removed
by bubbling the polluted air through activated sludge or water with a high dissolved oxygen
content.
ADSORPTION. Adsorption with activated carbon can be an effective and economical odor con-
trol method for emissions from wastewater treatment facilities containing a low concentra-
tion of odorous compounds (12). The odorous gases and vapors must be collected, as for
ozonation, and then passed through the adsorbent beds of activated carbon. Adsorbent beds
should be continuously monitored, because the activated carbon may have a low capacity for
some odorants and, without regeneration, a short adsorbent life with respect to those odorants
(12)(23). In Sacramento, where a large treatment plant became closely surrounded by a
better-than-average residential area, it was found that sodium hypochlorite scrubbers followed
33
-------
by carbon adsorption units successfully removed all odors (43). Further information on odor
control using activated carbon is contained in reference (51).
Adsorption-absorption using soil beds has proved to be an effective way of treating odorous
gases collected at pumping stations (15, 44, 45). A carbon filter was included in one installa-
tion for backup but was not needed during the first year of operation (44). Warm, moist,
loamy soils are necessary for effective odor removal in soil beds.
INCINERATION—CATALYTIC AND DIRECT FLAME. Fumes from wastewater treatment works can
be deodorized using direct flame. Incineration at an adequate temperature for a sufficient
time oxidizes organic compounds to odorless water and carbon dioxide and relatively odor-
less oxides of nitrogen and sulfur. At temperatures below 1,400° F, partial oxidation may
result, with the production of highly odorous gases. To accomplish complete oxidation,
3 seconds at 1,400° F is sufficient detention time (15). To ensure that all parts of the burning
chamber have temperatures above 1,400° F, it is well to have the control thermostat set to
operate between 1,550° and 1,600° F. Above 1,750° F, dangerous oxides of nitrogen may
be formed and cause air pollution. Incineration can be effective in controlling highly con-
centrated odors in low volumes of air (12)(22). In some cases, if particulate matter is present,
incineration should be preceded by condensers or dust collectors (12)(22). Catalytic oxida-
tion operates at temperatures from 1,000° to 1,300° F. The lower cost for fuel is offset by
the catalyst replacement cost, particularly if the odorous gas is corrosive to the" catalyst.
Advantages of direct flame incineration with respect to catalytic oxidation are lower mainte-
nance costs, less downtime, and better odor destruction. Advantages of catalytic oxidation are
lower temperatures, lower operating costs, lighter construction, and better removal of par-
ticulates and aerosols. Steam plumes from incinerators can be controlled using condensers or
afterburners. Emission standards for wastewater treatment incinerators are contained in
reference (52).
DESIGN MEASURES. Prevention of odor nuisance conditions should be considered in the design
of any conduit or basin which will contain wastewater or sludge. Some important design
elements and operational practices to consider include:
1. Locate the facility on a well ventilated site to prevent
odor accumulation, not in a hollow or where it will be
surrounded by trees.
2. Provide for sufficient mixing, to ensure scouring velocities
over the entire floor of aeration basins and to prevent
sludge accumulation in corners where velocities are too
low.
3. Enclose locations of turbulent flow, where odorants or
aerosols might escape from anaerobic wastewater or
sludge, to prevent escape of odorants and to collect them
for oxidation before discharge to the atmosphere. Such
locations may include headworks, primary clarifiers,
trickling filters, sludge thickeners, sludge dewatering
tanks, and sludge holding tanks.
34
-------
4. Provide high pressure connections for hoses, for use in
the daily flushing of walls and corners to prevent any ac-
cumulation of slime or sludge.
5. Provide adequate slopes in all conduits, whether open or
closed, to ensure scouring velocities once a day.
6. Provide for mechanical cleaning of all closed conduits, if
slopes are not sufficient to ensure daily scouring velocities.
7. Provide for U-tube aeration of anaerobic wastewater in
manholes upstream of pumping stations or treatment fa-
cilities, or a means of adding hydrogen peroxide, chlorine,
or hypochlorite, if the sulfide problem is too much for
simple aeration, to prevent escape of odors at the pump-
ing station or treatment facility head works.
8. Provide aeration in distribution channels, to maintain
aerobic conditions as well as to ensure homogeneity of the
organic material in the wastewater.
9. Provide for returning a portion of the waste activated l^--^'
sludge to the headworks, to assist in reducing odors.
10. Provide for pneumatic or other enclosed transfer of
screenings or other odorous compounds to the disposal
point.
11. Provide a vacuum cleaner truck for cleaning grease traps,
screening boxes, scum boxes, and catch basins and carry-
ing their odorous contents in an enclosed tank to the dis-
posal point.
12. Provide an adequate section in the facility operation and
maintenance manual on odor control. This should in-
clude procedures: for daily flushing to remove slime and
sludge accumulations, for checking for sufficient condi-
tioning of sludge before its discharge to open drying
beds or use as fertilizer on lawns, for cleaning all sludge
discharge pipes and areas immediately after use, for pre- ,
venting overuse of treated wastewater for irrigation, and ' "
for using sulfuric acid or caustic soda for removing slime
or lime encrustations.
13. Provide requirements in the sewer ordinance for removal,
or for reduction to a treatable level, of all industrial waste
compounds which might cause odor problems at a prop-
erly operated wastewater facility.
Suggested measures to be considered during design, to prevent odor and control or reduce
the possibility of odor nuisances, are presented in Table 3.2.
35
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TABLE 3-2. POSSIBLE ODOR PREVENTION AND CONTROL METHODS
PREVENTION
Enforcement of good sewer ordinance
Regular inspection and maintenance
Hydrogen peroxide
Chlorine
Alkalinizing agents
Lime*
Sodium hydroxide
Maintain O2 source in wastewater
Forced ventilation
Discharge waste activated sludge to unit inlet
Dilution with aerated wastewater
Aeration
Oxygenation
Sodium nitrate
Zinc sulfate
Prevent sludge aging and deposits
More frequent solids withdrawal
Complete mixing in tanks
Sufficient velocity in flows
Smooth transitions in structures
Regular cleaning
Miscellaneous
Equalization of flow
Pretreat at previous units
Reduce loading on unit
Raise temperature to over 1,600 F
Give special treatment before return
CONTROL
Enclose and vent
Structure
Dome
Floating cover
Separate room in building
Add chemicals to odorous wastewater
Hydrogen peroxide
Ozone
Chlorine
Activated carbon
Zinc sulfate
Sodium nitrate
Treat vented gases before discharge* *
Ozonation
Combustion at over 1,600°F
Wet scrubbing
Catalytic oxidation
Vent through activated sludge tank
Activated carbon adsorption
Treated wood chip adsorption
Filter through soil bed
Disinfect effluent
Pretreat influent
avity Sewers
O
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
>rce Mains
u.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
mping Stations
CL
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
eatment Plant Headworks
I-
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
rit Handling and Disposal
a
X
X
X
X
X
X
reenings Handling & Disposal
co
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
^ualization Tank
ill
X
X
X
X
X
X
X
X
X
X
X
X
X
Y
imary Clarifier
Q.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Y
otation Units
U_
X
X
X
X
X
X
:um Handling and Disposal
CO
X
X
X
X
X
X
X
X
X
X
Y
X
X
X
udge Holding
CO
X
X
X
X
X
X
X
X
X
X
X
Y
X
X
X
udge Thickening
CO
X
X
X
X
X
X
X
X
X
x
Y
x
X
X
X
udge Digestion
CO
X
X
X
X
X
X
Y
udge Dewatering
CO
X
X
X
X
X
X
X
Y
X
Y
X
X
X
udge Incineration
CO
X
X
X
x
x
Y
X
rocess Sidestream
Q.
X
X
X
X
X
X
X
X
X
X
X
X
X
eration Tanks
<
X
X
X
X
X
X
X
X
X
X
rickling Filters
h-
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
tabilization Ponds
CO
X
X
X
X
X
A
econdary Clarifier
CO
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X,
X
X
X
ranular Media Filters
O
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Dlishing With Screens
CL
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
eptage Manhole
CO
X
X
X
X
X
X
X
X
X
X
X
X
X
X
x
Y
X
X
X
X
X
c
o
o
en
K
=a
t
0)
m
ra
c
>
Q
0)
01
•c
CO
X
X
X
X
X
X
X
X
X
Y
X
X
X
X
onditioned Sludge Storage
O
X
X
X
X
X
X
X
X
x
x
x
x
x
X
awns Irrigated w/Wastewater
-I
X
X
X
X
X
X
ffluent Structure
III
X
X
X
X
X
X
X
X
X
X
x
X
X
X
X
X
* Lime should not be used where sludge is incinerated.
**Piping, vents, diffusers, etc., must be corrosion resistant.
36
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3.2.9 Odor Intensity Determinations
The transmission of any detectable odor to an inhabited location may be detrimental to the
value of that location. Determination of possible odor transmission from wastewater treat-
ment facilities is usually limited to studies of those conditions conducive to the transmission
of the maximum odor concentrations expected under adverse conditions.
Turbulence of air movement increases dispersion, decreases odor concentrations, and de-
creases the probability of odor nuisances. Three factors lead to increases in turbulence:
vertical temperature profile, surface topography, and wind velocity.
If the temperature decreases with height (a temperature lapse) at a rate lower than adiabatic,
which is defined as about 5.4° F per 1,000 ft (about 1° C per 100 m), vertical air movements.
are damped or reduced and an inversion exists. If the lapse rate is more than adiabatic (more
than 5.4° F per 1,000 ft), vertical air movement is increased.
Ground roughness increases from flat unforested farmland to suburban low-rise construction
areas to urban multistoried areas (the rougher the ground, the more turbulence). Turbulence
also increases with ruggedness of terrain. In flat country, for instance, turbulence caused by
rural conditions might reach about 250 ft (76 m). In suburban areas, this height could
increase to 350 or 400 ft (107 or 122 m), while in the high-rise part of central cities the
height could increase to 500 ft (152 m) or more. In hilly or mountainous country, the
heights of increased turbulence would tend to be even greater than over flat land.
Air turbulence increases with an increase in wind velocity, variations in velocity from
average, and variations in wind direction. In general, an increase in wind flow or its gustiness
in comparison with the average gradient wind velocity creates a corresponding increase in
turbulence.
Six classes of stability categories established by the EPA (35j are given in Table 3.3. Class A
is the most unstable, class F the most stable. Night refers to the period from 1 hour before
sunset to 1 hour after sunrise. Note that the neutral class, D, can be assumed for overcast
conditions during day or night, regardless of wind speed.
TABLE 3-3. KEY TO STABILITY CATEGORIES
Surface \Vind
Speed (at 10m)
m/sec
<2
2-3
3-5
5-6
>6
Day
Incoming Solar Radiation
Strong
A
A-B
B
C
C
Moderate
A-B
B
B-C
C-D
D
Slight
B
C
C
D
D
Night
Thinly Overcast
or >4/8 Low
Cloud
E
D
D
D
<3/8
Cloud
F
E
D
D
The following material on dispersion is largely based on Turner's workbook on atmospheric
dispersion estimates (46). The concentration x of odorous gases or aerosols from a continuous
37
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ground level point source resulting from atmospheric dispersion (if the plume spread is
considered to have a Gaussian distribution, as shown on Figs. 3-3, 3-4, 3-5, and 3-6) along
the centerline of a plume at ground level with no effective plume rise and minimum tur-
bulence (from surface topography or gusty winds), utilizing Turner's diffusion equations
(46), can be expressed:
= Q
X Trovers (Eq. 3-1)
where
x = concentration, in odor units per cubic meter x km downwind
u = wind speed, in meters per second
o> — standard lateral deviation (wind with Gaussian distribution) of odor particles
across the plume, in meters (see Fig. 3-1 )
(7z = standard vertical deviation (wind with Gaussian distribution) of odor particles
across the plume, in meters (see Fig. 3-2)
0 = average emission rate of odor-causing vapor, in odor units per cubic meter
Eq. 3-1 can be used to determine whether an odor of known strength from a source might
be detected and in what amount at a specific location downwind of the source.
Similarly, the concentration of odorous gases or aerosols in odor units per cubic meter at a
point downwind during inversion conditions (for limitations, see reference [35] ) from a
continuous ground level area source, utilizing Turner's diffusion Eq. 3-1, can be expressed:
where x = concentration at points x, y
x, y = downwind and horizontal crosswind coordinates, respectively, in meters
ov, o"z = standard lateral and vertical deviations of wind (see Figs. 3-5 and 3-6),
in meters
exp ("a") = e(or2.7183) raised to the "a" power ; for this example, e is raised to
'/2(y/o>)2
Eq. 3-2 would be used after the cross-section of a plume near the source had been tested to
determine the odor concentration Q at a theoretical point source.
In either case, odor tests would be required to determine the threshold odor concentration.
On a calm, cloudless day in rural areas, inversion conditions start near the ground at sunset
and grow in intensity and depth during the night, reaching a maximum near sunrise. The
inversion then starts decreasing at the ground level so that, by about 9:00 AM, there would
only be an inversion layer somewhere between 500 to 1,000 ft (about 150 to 300 m). Under
similar wind conditions, the atmosphere is more stable on clear summer nights.
3.2.10 Sample Calculations
POINT ODOR SOURCE. Sometimes, odors are collected in a treatment plant structure and vented
through a stack above the roof. This would be considered a point odor source. In the case
of an existing plant, it is not difficult to measure the flow of gas from the stack and, by
regular sampling, determine the maximum strength of the odor to be expected. For new plant
38
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Gaussian
Distribution
Curves
Plane
Cross Section
Limits
, ~y, z)
U,-y,o)
FIG. 3-1. GAUSSIAN DISTRIBUTIONS
p or
FIG. 3-2. GAUSSIAN DISTRIBUTION CURVE
39
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I.U
9
8
7
6
5
O.I
9
8
7
6
0.01
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2_0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
X-X
FIG. 3-3. ORDINATE VALUES OF THE GAUSSIAN DISTRIBUTION
45
4.0
0.01 O.I 0.9 I 2 9 10 20 30 40 90 60 70 80 90 99 98 99 99.8 99.99
exp(-0.5p2)dp
FIG. 3-4. AREA UNDER GAUSSIAN DISTRIBUTION CURVE
40
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10,000.
1,000
0>
100
10
O.I
10
DISTANCE DOWNWIND, km
FIG. 3-5. HORIZONTAL DISPERSION COEFFICIENTS
41
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1,00
10
B,-'
.••
10
I.O
O.I
DISTANCE DOWNWIND, km.
FIG. 3-6. VERTICAL DISPERSION COEFFICIENTS
42
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design, until better data are available, it is best to test an existing similar plant to determine
odor strengths. If there are more than one stack, the normal expansion of the plume down-
wind will cause overlapping of the plumes and some combining of their odorants at a certain
distance from their sources.
In the design and siting of a wastewater stabilization lagoon, it must first be determined if
any odor emissions during periods of thermal turnover, overloading, after high algae growth,
or when the ice cover which caused anaerobic conditions breaks up would cause an odor
nuisance to adjacent residents. The odors are sometimes concentrated at 'the outfall, which
is thus similar to a point odor source. This is particularly true if there is considerable turbu-
lence in the treated effluent before it enters a receiving stream. Odor units emitted from
several ponds under worst conditions and threshold odors can be determined by an odor
panel for each pond. The threshold odor concentration of the most common odorants emitted
from domestic wastewater varies from about 20 to 0.05 ^g/1 (with H2S having a value of
about 1 /xg/1). Because of the unknown constituents of odors from wastewater, it is not
practical for the designer to determine the concentration in micrograms per liter of the
combination of odorants. For purposes of dispersion calculations, the odor units of an
unknown odorant may be assumed equal to concentration in micrograms per liter.
For example, given that 1,000 odor units per cubic meter of air are emitted per cubic meter
of wastewater discharged at the outfall. The maximum allowable threshold odorant concen-
tration is 1 odor unit per cubic meter, and the stability conditions most apt to cause a
problem occur with a wind velocity of 3 m/sec (7 mph). How far downwind would a
threshold odor be detectable?
Based on Eq. 3-1:
- Q _ 1,000
_ 1ft,
- 106
Utilizing Fig. 3-7, it can be found from curve F that, when overs = 106, the maximum
distance downwind that the odor could be detected would be about 1,200 ft (400 m). A
safety factor should be used by the designer, depending on the effect of stronger than
expected maximum odors.
AREA ODOR SOURCES. Odors may rise from areas such as trickling niters, sludge beds, waste-
water or sludge lagoons, wastewater or sludge processing tanks, etc., rather than point
sources. Odor rise depends on vertical air temperature profile; movement of the odor hori-
zontally depends on wind. The most probable conditions for odor problems is at the end of
a long hot holiday weekend in the summer when maintenance is at a minimum. Because the
most stable conditions must exist for detectable odors to be transmitted the maximum dis-
tance, tests made on existing wastewater facilities should be made on a clear but humid
night or early morning while the night inversion conditions still continue and a mild, steady
breeze is blowing. Under such conditions, a cross-section immediately downwind of the
facilities can be sampled to define the variations in odor concentration across the plume.
Under inversion conditions, the odors normally do not rise into the breeze at as high a rate
as they do under temperature lapse conditions. Therefore, tests should ideally be run under
both temperature lapse and inversion atmospheric thermal conditions.
CASE STUDY. A comprehensive study of possible odor problems arising from area sources and
the possible resulting effects on neighboring urban and suburban developments is contained
43
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DISTANCE DOWNWIND, km
FIG. 3-7. THE PRODUCT OF Qya2
44
-------
in reference (31). This study was based on odors detected from an inadequately maintained,
overloaded plant. It was assumed that the new plant, if also poorly maintained, would emit
the same concentration of odors per unit area of facility as the existing plant. Another
approach would have been to determine the maximum probable odor intensities which might
be expected from an operating plant designed and operated similarly to the new facility. The
study of odor distribution includes locating threshold odor concentrations by distance down-
wind of the source. The magnitude of the source was computed using the diffusion theory to
produce the observed concentration at the observed location under the stability and wind
conditions existing during the test.
The existing nine aeration tanks (40 ft each in diameter) had a total area of 11,300 ft2,
which the authors assumed to be the equivalent of one 106-ft-diameter tank. The source
width then becomes 106 ft (32.4 m). The effective source strength is that concentration
which is just sufficient to produce a threshold odor at some critical point downwind.
Threshold odors were detected 1.9 miles (3 km) downwind one day and 1.4 miles (2.3 km)
another day from the plant by making cross-traverses of the plume at successively greater
distances from the source. Wind speed, solar radiation, and the temperature lapse rates were
measured during sampling. Types B and E stability conditions, respectively, prevailed during
the two tests conducted.
Utilizing the curves reproduced on Figs. 3-1 to 3-4, the effective source concentrations were
found to be 156 odor units per cubic foot for the test conducted under E stability conditions
and 800 odor units per cubic foot for the test conducted under B stability conditions.
From the two examples, it can be seen that major odor nuisances result when conditions at
the wastewater surface cause vapor to rise and carry large concentrations of odorants into the
wind. This study concluded that the superadiabatic conditions in the locality could produce
an odor source over five times as strong as inversion conditions. From this it is easily deduced
that atmospheric conditions are very important and quite difficult to predict. Therefore, the
safety factor to be used in determining the distance an odorant will travel should be from
2 to 5, depending on the sensitivity of the neighboring population to wastewater facility odors.
3.3 AEROSOLS AND PARTICULATES
Aerosols are defined as suspensions of approximately microscopic, solid or liquid, particles
dispersed in the atmosphere. Aerosols from treatment works are usually 5 to 10 microns or
less in size.
Particulates are, in general, considered to be liquid or solid particles of any size dispersed in
the air. Aerosols and particulates may be organic, inorganic, or a combination of both.
Foams, mists, dusts, smog, fumes, and smoke are among the different forms of aerosols and
particulates. Liquid aerosols are generated at wastewater treatment works when bubbles of
air from wastewater or liquid sludge burst and discharge tiny droplets into the atmosphere.
All aeration, ventilation, evaporation (cooling towers), spray irrigation, and stripping activ-
ities involving wastewater or sludge are potential sources of aerosols. Activated sludge, trick-
ling filter, and aeration units—particularly those handling raw wastewater—are probably
the major potential sources of pollutional aerosols. However, with the increasing demands
for reuse of wastewater, cooling towers and scrubbing units might become a major source of
45
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air pollution. Treated (but not disinfected) wastewater is sometimes used in these towers for
evaporational cooling or for stripping out volatile organics and inorganics. Pathogens and
toxic or injurious organic and inorganic pollutants in the wastewater may be aerosolized.
According to research studies of aerosols from wastewater treatment works, viable coliforms
have been found up to 0.8 mile from sources (3, 4, 47, 48, 49). E. coli has an extremely short
life span in aerosol form. However, coliform bacteria of the genus Klebsiella, all species of
which are known pathogens, form a capsule which apparently protects this organism from
desiccation while in flight (50). Results of specific tests for Klebsiella have not been found.
While certain calculations (1) have shown that Klebsiella inhalation is possible at the
downwind edge of an aeration basin, no evidence has been found that aerosols have
affected the health of either wastwater works operators or other persons.
Sludge incinerators should be designed in accordance with state and local policies and regula-
tions. EPA has developed performance standards (8) for wastewater treatment plant sludge
incinerators. These standards require that no air pollutant discharge be made which is:
1. in excess of 0.030 grain (weight measure of pollutant) per
standard cubic foot of gas
2. of 10 percent opacity or greater, unless the presence of un-
combined water is the only reason for failure to meet this
requirement.
Further restrictions may be placed on municipal plants processing industrial wastewaters, to
prevent release of specific metals, toxic organics, or radioactive substances in the flue gases.
The sludge incinerator should be designed and located with regard to prevailing wind direc-
tion. Aerosols and particulates can often be removed from stack emissions by either scrubbing
or electrostatic precipitation. Other control measures include the use of afterburners, collec-
tors, and filtration. Some heavy metals and SO2 have been found in emissions from inciner-
ators, and care must be taken to ensure that their control is adequate.
Aerosols may also be caused by construction operations. Examples of these and methods for
their control are given below:
Clearing, grubbing, and stripping. Control dust by water
sprinkling and chemical treatment such as use of calcium
chloride. Seeding may be effective. Light petroleum or bitu-
minous surface treatment may be used.
Excavation, stockpiling earth, and embankment placement.
Control dust by water sprinkling and chemical treatment.
Seeding may be effective. Light petroleum or bituminous sur-
face treatment may be used.
Blasting, quarry drilling, and rock crushing. Use coverings or
enclosures, and restrict operations to low wind conditions.
46
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Cement and aggregate handling operations at mixing plants.
Enclose operations and restrict to the most suitable location
given land use and prevailing wind.
Cement or lime in soil stabilization operations. Select equip-
ment to contain dust within dispersing hopper and also to dis-
pense cement or lime with minimum dust.
Haul road construction and maintenance. Control dust by
water sprinkling and chemical treatment.
Sandblasting and gunite operations. Conduct operations in en-
closed space, properly vented, to trap aerosols. Enclosure may
be by temporary barriers.
Smoke from heaters during winter operations and from asphalt
plant heaters. Select better fuels and heaters to ensure higher
than 1,400° F temperature and essentially complete oxidation.
Paint spraying operations. Control hazards by proper venting
of work spaces. Reduce aerosols by use of proper application
techniques and properly maintained equipment. Specify alter-
native coatings or applications.
Smoke from burning cleared growth and scrap material. Use
pit incineration to limit escape of particulates, especially if
burning is permitted for debris disposal.
3.4 GASES
Explosive, toxic, noxious, lachrymose, and asphyxiating gases found at wastewater works
include chlorine, methane, ammonia, hydrogen sulfide, carbon monoxide, and oxides of
nitrogen, sulfur, and phosphorus. If there is a possibility that such a gas can escape from
the works, or into work areas, in dangerous or nuisance concentrations, the knowledge might
affect the use and development of adjacent land and the operation of the works. Therefore,
it is of the utmost importance that all precautions be taken to prevent the escape of such
gases in hazardous or nuisance concentrations. Such gases are usually a greater detriment
within wastewater structures than in adjacent areas.
Of the gases (including those above) collected from wastewater works structures by ventila-
tion systems, some could be unsafe or adversely affect the environment if discharged directly
to the atmosphere. Consideration should be given to monitoring such ventilation discharges
for objectionable gases. Consideration should also be given to providing standby means for
neutralizing, stabilizing, or destroying gases which might have significant effects on the
environment.
47
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Permanent or standby controls for gases or aerosols include:
1. passage through incineration or high temperature boilers
whose flues are equipped with fly ash controls
2. passage through chambers or towers where oxidizing agents
such as ozone, permanganate, or hypochlorite are intro-
duced
3. passage through activated carbon columns
4. passage through chambers, scrubbers, or towers where
masking or neutralizing chemicals are added, depending
on the gases present in significant amounts.
Additional design, operation, and maintenance criteria for control of gases at wastewater
works are presented in WPCF Manual No. 1, Safety in Wastewater Works (9).
3.5 REFERENCES
1. Sorber, C.A. and Outer, K.J., "Health and Hygiene Aspects of Spray Irrigation," Amer-
ican Journal of Public Health, Vol. 65, No. 1 (January 1965).
2. Adams, A.P. and Spendlove, J.C., "Coliform Aerosols Emitted by Sewage Treatment
Plants," Science, Vol. 169 (September 1970).
3. Ledbetter, J.O., "Air Pollution From Wastewater Treatment," Water and Sewage Works,
113 (2):43-45 (February 1966).
4. Ledbetter, J.O. and Bandall, C.W., "Bacterial Emissions From Activated Sludge Units,"
Industrial Medicine and Surgery, pp 130-133 (February 1965).
5. Thibodeaux, L.J. and Carter, N.J., Coliform Emissions From Air/Water Contractors:
A Preliminary Attempt To Establish Maximum Concentrations, Paper Presented at 65th
Annual Meeting, American Institute of Chemical Engineers (November 1972).
6. Danielson, J.A., Air Pollution Engineering Manual, National Center for Air Pollution
Control, Cincinnati, Ohio, U.S. Government Printing Office, Washington, D.C. (1967).
7. Stern, A.C. (ed.), Air Pollution, Vols. I, II, III, Second Edition, Academic Press, New
York (1968).
8. Background Information for Proposed New Source Performance Standards, U.S. EPA
Office of Air Programs, Research Triangle Park, North Carolina (June 1972).
9. Safety in Wastewater Works, WPCF Manual of Practice No. 1 (1975).
48
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11. Sensory Evaluation of Materials and Products, ASTM Standard E253-67 T (1974).
12. Bethea, R.M., Murphy, B.N., and Carey, D.R., "Odor Controls for Rendering Plants,"
Environmental Science and Technology (June 1973).
13., Poltorak, R.L., Odor Pollution and Control of Sewage Treatment Facilities, Calgon
Corporation, Pittsburgh (April 1974).
13. Post, N., "Counteraction of Sewage Odors," Sewage and Industrial Wastes, Vol. 28, No.
2, pp 221-225 (February 1956).
15. Dague, R.R., "Fundamentals of Odor Control," Journal WPCF, Vol. 44, No. 4, pp
583-594 (April 1972).
16. Atmospheres for Analyses of Gas and Vapors, 1974 Annual ASTM Standards, Part 26,
01605-60 (1973).
17. Dean, J.A., Langes Handbook of Chemistry, McGraw-Hill, New York (1973).
18. Process Design Manual for Sulfide Control in Sanitary Sewerage Systems, U.S. EPA
Office of Technology Transfer (October 1974).
19. Design and Construction of Sanitary and Storm Sewers, ASCE Manual of Practice No.
37,p 125 (1969).
20. Bhatla, M.N., "Control of Odors at an Activated Sludge Plant," Journal WPCF, Vol. 47,
No. 2 (February 1975).
21. Rains, B.A. and DePrimo, M.J., Odors Emitted From Raw and Digested Sewage Sludge,
Prepared for U.S. EPA Office of Research and Development, EPA-670/2-73-098
(December 1973).
22. Osag, T.R. and Crane, G.B., Control of Odors From Inedibles-Rendering Plants, Pre-
pared for U.S. EPA Office of Air and Wastes Management (July 1974).
23. Newfeld, R.N., "Wastewater Treatment Plant Odors: A Continuing Enigma," Public
Works (March 1975).
24. Jones, F.W., "What Are Offensive Odors About a Sewage Works?" Sewage Works
Journal, Vol. 4, No. 1., pp 60-71 (January 1932).
25. Kremer, J.G., Odor Control Methods, Experimentation and Application, County Sanita-
tion Districts of Los Angeles County, California (No Date).
26. Cohn, M.M., "Sewage Works Odors and Their Control," Sewage Works Journal, Vol. 1,
No. 5, pp 568-577 (October 1929).
27. Beardsly, C.W., "Removal of Sewer Odors by Scrubbing With Alkaline Solution,"
Sewage and Industrial Wastes, Vol. 30, No. 2, pp 220-225 (February 1958).
49
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28. Pomeroy, R. and Bowlus, F.D., "Progress Report of Sulfide Control Research," Sewage
Works Journal, Vol. 18, No. 24, pp 597-640 (July 1946).
29. Schneider, W.A., "Sewer Maintenance Practice in Los Angeles," Sewage and Industrial
Wastes, Vol. 26, No. 2, pp 222-229 (February 1954).
30. Sawyer, C.N. and Kahn, P.A., "Temperature Requirements for Odor Destruction in
Sludge incineration," Journal WPCF, Vol. 32, No. 12, pp 1274-1278 (December 1960).
31 Shepherd, J.A. and Shreve, B.C., Jr., Odor Control With Hydrogen Peroxide, WPCF
Deeds and Data (April 1973).
32. Keller, P.J. and Cole, C.A., "H2O2 Controls Bulking," Water and Wastes Engineering
(September 1973).
33. Standard Methods for the Examination of Water and Wastewater, APHA, AWWA,
WPCF, American Public Health Association, Washington, D.C. (1971).
34. Manual on Sensory Testing Methods, ASTM Special Technical Publication No. 434
(1968).
35. Measurement of Odor in Atmospheres, ASTM D1391-57 (Reapproved 1967).
36. Handbook for Analytical Quality Control in Water and Wastewater Laboratories, U.S.
EPA NERC Analytical Quality Control Laboratory for U.S. EPA Office of Technology
Transfer (June 1972).
37. Sampling Atmospheres for Analyses of Gases and Vapors, ASTM D1605-60 (Reap-
proved 1973), Part 26 of Annual Book of ASTM Standards (1974).
38. General Gas Chromatography Procedures, ASTM E260-73, Part 42 of Annual Book of
ASTM Standards (1973).
39. Shepherd, J.A. and Hobbs, M.F., "Control of Hydrogen Sulfide With Hydrogen Per-
oxide," Water and Sewage Works (August 1973).
40. Santry, I.W., Jr., "Hydrogen Sulfide Odor Control Measures," Journal WPCF, Vol. 38,
No. 3, pp 459-463 (March 1966).
41. Unangst, P.C. and Nebel, C.A., "Ozone Treatment of Sewage Plant Odors," Water and
Sewage Works, Reference No. 1971, Vol. 118, pp R-42,43 (31 August 1971).
42. Sax, I.L., Dangerous Properties of Industrial Materials, Reinhold, New York (1963).
43. Herr, E. and Poltorak, R.L., "Program Goal—No Plant Odors," Water and Sewage
Works (October 1974).
44. Stone, R., Newton, L.C., and Rowlands, J., "Wastewater Pumping Station Designed To
Avoid Odor Problems," Public Works (January 1975).
50
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45. Carlson, D.A. and Leiser, C.P., "Soil Beds for Control of Sewage Odors," Journal
WPCF, Vol. 38, No. 5, pp 829-840 (May 1966).
46. Turner, B.C., Workbook of Atmospheric Dispersion Estimates, U.S. EPA Office of Air
Programs, NTIS PB 191482 (1970).
47. Adams, A.P. and Spendlove, J.C., "Coliform Aerosols Emitted by Sewage Treatment
Plants," Science, Vol. 169, pp 1218-1220 (18 September 1970).
48. Nelson, R.Y. and Ledbetter, J.O., "Atmospheric Emissions From Oxidation Ponds,"
Journal of the Air Pollution Control Federation, Vol. 14, No. 2, pp 50-52 (February
1964).
49. Pomeroy, R.D., "Sanitary Sewer Design for Hydrogen Sulfide Control," Public Works,
pp 93-96 (October 1970).
50. Randall, C.W. and Ledbetter, J.O., "Bacterial Air Pollution From Activated Sludge
Units," Am. Ind. Hyg. Assoc. /., 27:506-519 (1966).
51. Cross, F.L., Air Pollution Odor Control Primer, Technomic Publishing Co., Inc., West-
port, Connecticut (1973).
52. Standards of Performance for New Stationary Sources, Federal Register, Vol. 39, No. 47,
Part II, Subchapter C—Air Programs (8 March 1974).
53. Design Manual for Small Wastewater Treatment Plants, U.S. EPA Office of Technology
Transfer (At Press).
54. Silvey, J.K.G., Abshire, R.L., and Nunez, W.J. Ill, "Bacteriology of Chlorinated and
Unchlorinated Wastewater Effluents," Journal WPCF, Vol. 46, No. 9 (September 1974).
51
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4. NOISE
4.1 GENERAL BACKGROUND
Wastewater facilities must be designed, constructed, operated, and maintained in such a
manner that they do not produce excessive noise which would be an irritant to nearby
inhabitants or a hazard to plant workers. Noise prevention and control measures are discussed
in this chapter, as are noise level criteria. Noise analyses and examples of calculations of noise
transmission are presented at the end of the chapter.
The purpose of this chapter is to enable the designer to make preliminary estimates of the
reactions of the community and works' personnel to noise generated by wastewater treatment
facilities and to quantify the amount of noise reduction required to meet level standards. If
indicated by the preliminary studies, specialists in noise engineering should be consulted.
Excessive noise may adversely affect personnel in interior and exterior areas of the facility as
well as the surrounding community. Noise effects on people may be classified into auditory,
general psychological and sociological, and physiological effects (l)(2). Auditory effects
include ear damage, with resulting temporary or permanent hearing loss, and masking effects,
such as interference with speech communication, inability to hear warning signals, etc.
Psychological and sociological effects may include sleep loss, annoyance, disruption of
activities, lowering of performance, mental stress, and anxiety. Physiological effects include
such responses as tautness of skin and abnormal sensations in the extremities.
Evaluation of noise levels in a community is a complex problem, involving individual
perception of how an objectionably noisy environment is defined. Definition of these
perceptions is difficult and involves measurements of ambient noise levels in the area. People
respond in a complex way to the sum of stimuli present in their environment. They may react
differently to an identical sound under different circumstances but similarly to sounds which
are dissimilar.
Maximum noise levels for working areas are defined by regulations authori/ed under the
federal 1970 Occupational Safety and Health Act (OSH A) and by its predecessor, the Walsh-
Healey Act (3)(4). Acceptable levels for adequate speech communication in the working
environment are available (5). Community noise levels have been researched, and information
exists on desirable noise levels (6, 7, 2). Both maximum and d-ejfirable noise levels for working
spaces as well as community noise levels are presented in the following sections.
53
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4.2 UNITS OF EXPRESSION AND MEASUREMENT
Noise control techniques are determined by comparing noise source measurements (sound
pressure level, source direction, sound direction, sound power, etc.) with a specified design
goal or criterion for acceptable noise levels at a listener's position. Sound pressure is sensed by
a microphone and amplified in a sound level meter for frequency analysis or display on a
decibel meter (8).
Decibels are logarithmic units for measuring the relative levels of various acoustical quantities
(9) on a scale beginning with 0 for faintest audible sound and reaching 130, the approximate
threshold of pain.
Sound power levels should not be confused with sound pressure levels, which are also
expressed in decibels. Sound power level is related logarithmically to the total acoustic power
radiated by a source. Sound pressure level specifies the acoustic disturbance produced at a
point. Sound pressure level depends on the distance from the source, losses in the intervening
air, room effects (if indoors), etc. Sound power level is analogous to the heat production of a
furnace; sound pressure level is analogous to the temperature produced at a given point in the
house.
Noise has four important attributes (10):
1. Sound pressure level and directivity characteristics.
Sound pressure level LP = 10 Iog(p2/p2ai)
where
p = root-mean-square sound pressure in pascals
(Pa) or newtons per square meter (N/rrT)
Pai = reference pressure at 2 X 10~5 Pa or 20 juPa*
2. Intensity (sound power level), measured in decibels.
Intensity Li = 10 log(I/Iai)
where
I = watts passing in a specified direction through
a unit area
Ird = 1 picowatt** (pW)
NOTE: Manufacturers' data sometimes include sound power levels but seldom sound
pressure level.
*1 micropascal (juPa) = 10'' pascal (Pa) = 10 '' newton per square meter.
**1 picowatt (pW) = 10~': watt (W).
54
-------
3. Duration and number of times a noise occurs. Intermittent sound (a noise whose sound
pressure level equals the ambient level for about 1 second twice or more during the
observation period [77]) and impulsive sound (a noise characterized by brief excursions
of a sound pressure of about 1 second which significantly exceeds the ambient sound [//])
are usually more disruptive than continuous noise.
4. Frequency (the number of oscillations per second of a sine wave of sound expressed in
hertz* [Hz]). The human ear is more sensitive to high frequency sounds than low ones.
Noise nuisance can occur over all or part of the audible range.
The threshold of hearing at 1 kilohertz (1 kHz or 103 Hz) for a young listener with acute
hearing, measured under laboratory conditions, was determined to be at a sound pressure of 20
micropascals (20 /uPa). This value was then selected as the reference pressure for sound
pressure level.
Because the human ear does not respond uniformly to all sound frequencies, and in view of the
fact that single-number descriptions of noise levels are often more convenient, decibel
measurements are made using frequency weighting scales. The sound level meter (SLM)
contains a weighting network which gives greater importance to sounds in a certain frequency
range. A typical sound level meter contains four different response weighting networks.
designated A, B, C, and D (International Electrotechnical Commission [IEC] Recommen-
dations 123 and 179 and American National Standards Institute Standard SI.4-1971).
Fig. 4-1 shows the four weighting curves. The rationale for the weighting network is based on
the fact that the apparent loudness attributed to sound varies with the sound pressure and its
special content—the frequencies of the components of the sound. This effect is taken into
account to some extent using the weighting networks. The A-. B-, and C-weighted scales
discriminate against normal low, medium, or high frequencies, respectively (dBA, dBB, dBC)
(12). The D-weighted scale was developed for jet aircraft noise measurements. The A-weighted
scale is commonly used in field measurements to better detect the higher frequencies to which
the human ear is more sensitive. Weighted noise levels are increasingly used in codes and
standards, because of the generally excellent correlation with observed human response to the
many types of industrial and community noises.
The A-weighted sound level is measured directly with an A-weighting sound meter. There is a
high degree of correlation among the A-weighted measurements of speech interference.
loudness, and NC or PNC (see below) levels. A-weighted levels may be used to statistically
describe varying noise levels; e.g., Lm>, Lso, Ln>, etc., would describe noise levels exceeded 90
percent, 50 percent, and 10 percent of the time, respectively.
Several rating procedures have been found useful for gaging human response to noise (5):
1. Noise criteria (NC) or preferred noise criteria (PNC) rating
curves. This method combines speech interference and
loudness procedures to specify simultaneously the max-
imum permissible loudness level for a given space. The
curves are used in rating noises in buildings (including air
conditioning)—primarily in the design of offices such as
those within treatment plants.
*l hertz (Hz) = frequency measured in occurrences per second.
55
-------
+15
+ 10
+ 5
LJ
CD
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(/)
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to
UJ
CE
UJ
<
_l
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-20
-25
-30
-35
-40
-45
-50
20
FREQUENCY RESPONSES
FOR SLM WEIGHTING CHARACTERISTICS
50 100 200 500 1000 2000
FREQUENCY - HERTZ
5000 10,000 20POO
FIG. 4-1. FREQUENCY-RESPONSE CHARACTERISTICS
56
-------
2. Equivalent A-weighted sound pressure level (in decibels
relative to 20 ^PA) computed over any continuous 8-hour
period identified with typical occupational exposure.
Equivalent sound level Lcq (8) is the time weighted, root-
mean-square, A-weighted sound pressure which, in a given
situation, has the same sound energy as does a time-varying
sound. Because the magnitude of sound is of the utmost
importance as far as cumulative noise effects are concerned,
the long time average sound level is considered the best
measure of the magnitude of environmental noise levels
which cause damage to hearing (2).
3. Equivalent A-weighted sound pressure level (in decihels
relative to p. PA ) computed over a 24-hour period. L^ (24) is
related to the cumulative noise exposure experienced by an
individual irrespective of where, or under what cir-
cumstances, the exposure is received (2).
4. A-weighted average sound pressure level (in decibels
relative to 20/j.PA) during a 24-hour period, with a 10-dB
weighting applied to nighttime sound levels. Lj represents
the equivalent sound pressure level for the 15-hour daytime
period from 7:00 AM to 10:00 PM, and L,, represents the
equivalent sound pressure level for the 9-hour nighttime
period. The combined day night weighted measure is
represented by L^n(2).
Computation of equivalent sound is presented in reference (2) and example 4-4.
4.3 TYPICAL NOISE LEVELS
Various organizations, including the EPA, have developed data on ambient and typical noise
levels in the locations most frequented by people (Tables 4-1, 4-2, and 4-3).
4.4 ACCEPTABLE AND STANDARD NOISE LEVELS
Equivalent sound levels of different activities found by the EPA to be the maximum allowable
while maintaining public health are listed in Table 4-4.
4.4.1 Allowable Exposure to Impact or Impulsive Noise
Occupational exposure to impact or impulsive noise, as ruled by OSH A, must not exceed 140
dB of peak sound pressure (16). It has been indicated by others that an increase of impulse
durations above 1 microsecond, frequencies of about 3 kH/. or sound pressure levels above 130
dB will increase the probability of auditory damage (2).
Peak sound pressure levels should be measured with an instrument having a rise time of 50
microseconds or less (for square waves), which can calculate and display sound pressure le\els
57
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TABLE 4-1. EQUIVALENT SOUND LEVELS
Interior
Lee,,* db
Small store (one to five clerks)
Large store (more than five clerks)
Small office (one to two desks)
Medium office (three to ten desks)
Large office (more than ten desks)
Miscellaneous business
Residences
Typical movement of people—no TV or radio
Speech at 10 ft, normal voice
TV listening at 10 ft, no other activity
Stereo music
60
65
58
63
67
63
40-45
55
55-60
50-70
* Measurements were taken over durations typical of the operation of these facilities.
TABLE 4-2. ESTIMATED PERCENTAGE OF URBAN POPULATION
(134 MILLION) RESIDING IN AREAS WITH VARIOUS DAY/NIGHT
NOISE LEVELS{2)
Description
Quiet suburban residential
Normal suburban residential
Urban residential
Noisy urban residential
Very noisy urban residential
Typical
Range L
-------
TABLE 4-3. AVERAGE SINGLE NUMBER SOUND LEVELS, dBA
(5, 13, 14, 15)
Interior noises
Bedroom at night
Quiet residence
Residence with radio
Small office or store
Large store
Large office
Electric typewriter at 10 ft
Factory office
Automobile
Factory
School cafeteria
Railroad car
Garbage disposal
Airplane cabin
30-40
39-48
47-59
47-59
5L-63
57-68
62-67
60-73
64-78
65-93
76-85
77-88
78-83
88-98
Noises 3 ft from source
Whispering
Quiet ventilating outlet
Quiet talking
Noisy ventilating outlet
Business machine
Lathe
Shouting
Power saw
Power mower
Farm tractor
Power wood planer
Pneumatic riveter
30-35
41-47
59-66
60-75
71-86
73-83
74-80
93-101
94-102
94-103
97-108
110-120
Outside noises
Leaves rustling
Bird call
Quiet residential street
1 50 to 200 ft from dense traffic
Edge of highway with dense traffic
Car at 65 mph at 25 ft
Propeller plane at 1.000 ft
Pneumatic drill at 50 ft
Noisy street
Under elevated train
Jet plane at 1,000 ft
Jet takeoff at 200 ft
50-hp siren at 100 ft
10-15
40-45
40-52
55-70
70-85
75-80
75-84
80-85
84-94
88-97
100-105
120-125
130-135
59
-------
TABLE 4-4 YEARLY AVERAGE* EQUIVALENT SOUND LEVELS
IDENTIFIED AS REQUISITE TO PROTECT PUBLIC HEALTH AND
WELFARE WITH ADEQUATE MARGIN OF SAFETY (2)
(Based solely on health and welfare. Do not include considerations of Cost or Technology)
-* ^
•~
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Outdoor
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Residential, outside
space and farm buildings
Residential, no outside
space
Commercial
Inside transportation
Industrial
Hospitals
Educational
Recreational areas
Farm land and general
unpopulated land
Ldn
Leq(24)
Ldn
Leq(24)
Leq(24)
Leq(24)
T 4
Leq(24)
Ldn
Leq(24)
Leq(24)
Leq(24)
Leq(24)
Leq(24)
45
45
70
2
2
2
45
45
70
(2)
70
45 55
45
70
55
V
70
70
70
70
70
703
2
703
45 55
45 55
703
2
70
70
70
70
70
70
703
703
55
55
703
703
Based on lowest level.
Because different types of activities appear to be associated with different levels, identification of a maxi-
mum level for activity interference may be difficult, except in those circumstances where speech communication
is a critical activity. Noise levels as a function of distance which allows satisfactory communication are presented
in reference (2).
3Based only on hearing loss.
"An Leq(g) of 75 dB may be identified in these situations, as long as the exposure over the remaining 16 hours per
day is low enough to result in a negligible contribution to the 24-hour average; i.e. no greater than an Lcq of
60 dB.
*Refers to energy rather than arithmetic averages.
NOTE: The exposure period which results in hearing loss at the identified level is 40 years.
The levels cannot be construed as standards since they are based solely on health and welfare.
60
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within 1 dB of true peak (11). Typical peak sound pressure levels for impulse noises are given in
Table 4-5.
Potential hearing impairment, which is a direct effect of noise, is of primary importance to a
person who must work adjacent to the source of the noise. Workers should not he subjected to
noise exposure levels exceeding those listed in Table 4-6.
The document Information on Levels of Noise That Are Requisite To Protect Public Health
and Welfare With an Adequate Margin of Safety, prepared by the EPA Office of Noise
Abatement, indicates that noise levels should be lowered to protect against the effects of
occupational exposure. Accordingly, EPA has undertaken a critical evaluation of this subject
and recommended the noise exposure levels listed in Table 4-6.
If the daily noise exposure comprises two or more periods of noise of different levels, their
combined effect should be considered rather than the individual effect. Exposure to different
levels for various periods of time is computed according to the formula:
F = T,/Li + T:/L2. . . + T,,/Ln
where
F = equivalent noise exposure factor
T = period of noise exposure at any essentially
constant level
L = duration of permissible noise exposure at
constant level (from Table 4-6)
If the value of F is greater than unity, the mixed exposure must be considered to exceed the
permissible exposure (16).
4.4.2 Impulse Noises
The impulse noise limit to prevent more than a 5-dB permanent hearing loss at 4,000 H/ after
years of daily exposure is a peak sound pressure level (SPL) of 145 dB (2). However, for a
duration of 25 microseconds or less, a peak level of 167 dB SPL would produce the same effect,
as is shown in Fig. 4-2 (based on a study made by the NAS-NRC Committee on Hearing and
Bio-Acoustics [CHABA]).
Fig. 4-2 shows a set of modified CHABA limits for daily exposure to impulse noises having B-
duration (representing the duration of an impulsive sound, including the oscillatory noise
decay time period) in the range 25 microseconds to 1 second (2). (Parameter: number (N) of
impulses per daily exposure; criterion: noise induced permanent threshold shift (N1PTS) not
to exceed 5 dB at 4 kHz in more than 10 percent of the people.)
4.4.3 Community Noise Criteria
Description of community noise must take into account varying nuisance problems
throughout a representative 24-hour period as well as seasonal fluctuations, if any. Noise is less
tolerated at night in residential areas. Figure 4-7 can be used to judge the acceptability
61
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TABLE 4-5. TYPICAL VALUES OF PEAK SOUND PRESSURE LEVELS
FOR IMPULSE NOISE (2)
SPL Example
190+ Within blast zone of exploding bomb
160-180 Within crew area of heavy artillery
piece or naval gun when shooting
140-170 At shooter's ear when firing hand gun
125-160 At child's ear when detonating toy cap or
firecracker
120-140 Metal to metal impacts in many indus-
trial processes (e.g., drop forging, metal
beating) adjacent to listener
110-130* On construction site during pile driving
adjacent to listener
"These figures represent general ranges of SPL. The designer must ob-
tain specific values from the manufacturer.
NOTE: All SPLs in db re 20 ,uPa.
TABLE 4-6. NOISE EXPOSURE LEVELS*
Duration, hours/day
8
4
2
1
0.50
0.25 or less
Maximum
Sound Level,
dBA Slow Response
85
88
91
94
97
100
Recommended
Sound Level,
dBA Slow Response
75
78
81
84
87
90
^Personal protective equipment should be supplied and used whenever reduction to the levels in column
3 of above table is not feasihlp
62
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1 MAX. PERMISSIBLE '
SOUND PRESSURE LEVEL
MODIFIED CHABA LIMITS
PARAMETER NUMBER OF
IMPULSES PER DAY.
105
0.025 0.05 O.I 0.2 0.5 I 2 5 10 20 50 100 200 500 1000
B- DURATION (ms)
* CHABA- COMMITTEE ON HEARING AND BIO-ACOUSTICS
FIG. 4-2. PEAK PERMISSIBLE SOUND PRESSURE LEVELS (2)
63
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of community noise levels generated by a wastewater facility. State and local standards
should also be consulted. In addition to Figure 4-7, consideration of the. existing en-
vironmental noise level should also be used to determine neighborhood tolerance for
new intensive noise sources. If the noise is 0 to 3 dBA higher, little or no impact may
be expected; if 3 to 15 dBA higher, moderate impact may be expected; and if 15+ dBA
higher, severe impact may be expected. For typical environmental noise levels, see
Tables'4-1 and 4-3.
Information on Levels of Environmental Noise Requisite To Protect Public Health and
Welfare With an Adequate Margin of Safety contains data on noise in industrial and traffic
areas related to sleep interference, work efficiency, and social activities (2).
4.4.4 Machinery Noise
Machinery noise measurement standards have been established, and the more important
include:
Test for the Measurement of the Airborne Noise Emitted by Rotating Electrical Machinery,
ISO Recommendation R1680, American National Standards Institute (ANSI), 1970 (18).
Test Procedure for Airborne Noise Measurements on Rotating Electrical Machinery, IEEE
No. 85 (11).
4.4.5 Interior Noise
Interior noise measurement standards have been established, and the more important include:
Field and Laboratory Measurements of Airborne and Impact Sound Transmission, ISO
Recommendation R140, ANSI, 1960 (20).
Acoustics: Assessment of Occupational Noise Exposure for Hearing Conservation
Purposes, ISO Recommendation R1999, ANSI, 1971 (21).
For normal interior noise levels, refer to Tables 4-1 and 4-3.
4.4.6 Exterior Noise
Standards for measurement of noise from construction equipment have been established, and
the more important include:
Measurement of Sound Level at Operator Station for Agriculture and Construction
Equipment, SA1 Recommended Practice J919a, 1971.
Sound Levels for Engine Powered Equipment, SAE Standard J9526, 1969.
Ranges of noise levels in various urban areas are presented in Tables 4-2 and 4-3. Fig. 4-3
illustrates schematically construction equipment noise ranges.
64
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NOISE LEV
60 7
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IMPACT
EQUIPMENT
C£
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COMPACTERS (ROLLERS)
FRONT LOADERS
BACKHOES
TRACTORS
SCRAPERS, GRADERS
PAVERS
TRUCKS
CONCRETE MIXERS
CONCRETE PUMPS
CRANES (MOVABLE)
CRANES (DERRICK)
PUMPS
GENERATORS
COMPRESSORS
PNEUMATIC WRENCHES
JACK HAMMERS & DRILLS
PILE DRIVERS (PEAKS)
VIBRATOR
SAWS
«•
EL (dbA) AT 50 FT
n an an
—
—
—
1
in Tin
NOTE: Based on limited available data samples.
FIG. 4-3. CONSTRUCTION EQUIPMENT NOISE RANGES (17)
65
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4.5 NOISE CONTROL METHODS
Designers of wastewater treatment works should consider the inclusion of noise control
measures—including source control of machinery noise, special architectural treatment to
absorb sound and isolate noisy equipment, buffer zones within the plant between noisy and
quiet areas, and site planning and buffer zones-—to minimize impact of the plant on
community noise levels. These measures should take into account both interior noise and
community noise criteria, as discussed above.
The American Society of Heating, Refrigeration and Air Condition ing Engineers (AS HRAE.
345 East 47th Street, New York, NY 10017) publishes a handbook of fundamentals at 3-year
intervals. Sound Control Fundamentals, chapter 6 in the 1972 edition, is a good design
reference.
4.5.1 Source Control
Normally, noise can be most efficiently controlled at the source. A designer can control
machinery noise by specifying the least noisy equipment consistent with performance. To meet
acceptable acoustical levels, the designer should specify allowable sound power levels (or
sound pressure levels at a specified distance) for the equipment, submission of laboratory
and/or field measurements for approval, and field conformance tests.
The following techniques, singly or in combination (10)(21), may be used to reduce machinery
noise:
Segregation of noisiest elements in groups
Vibration damping
Vibration isolation
Sound absorbing line of enclosures
Sound attenuation at exhaust observation booth in auditory damage risk areas
Partial protective booths (open in rear)
Plenum treatment
Pipe lagging
Partial barrier
Lined ducts
Muffler
Reduction of high velocity air.
Gears can be a source of noise, unless the equipment is properly designed or the gear housing is
placed in a sound-absorbing enclosure.
4.5.2 Piping Systems
Piping systems transmit noise through the fluid as well as along the pipe wall. To control noise,
use flexible hangers and resilient connectors, do not connect drainpipes from vibrating
equipment rigidly to building drains (22), and use wrappings and duct linings where
appropriate (5).
Valve noise may be appreciable at pressure reducing valve stations. Control measures include
commercial mufflers, enclosure, use of a diffractor to reduce turbulent flow (22), reducing the
throttling velocity, and adjusting the orifice diameter and valve trim (23).
66
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4.5.3 Mechanical Aerators
Noise from mechanical aerators consists of at least two components: noise from the equipment
itself and splash noise. Pure tone whine could also occur from a noisy bearing. Because
mechanical aerators are located in the open, they may be a potential noise nuisance to the
community. Equipment selection should be based on an assessment of the community and the
impact aerator noise will have on it. Control measures include proper maintenance to
eliminate bearing noise; acoustically lined enclosure, or physical barrier surrounding the
motor itself.
4.5.4 Compressors, Fans, and Blowers
Because of the intense, high pitched noise generated by this equipment, isolation in separate,
acoustically insulated spaces is advisable. Mufflers may be placed on exhausts and/ or intakes
to control external noise. A plenum chamber may also be used to reduce external noise.
4.5.5 Vacuum Filter Pumps and Blowers
Noise from this source can best be controlled by isolating the pump in a separate room or on
another floor from the filter equipment. Resilient pads and flexible piping connections will
reduce transfer of vibration to the structure and piping system.
4.5.6 Pumps
Large pumps may generate noise exceeding the OSHA permissible noise limits. Control
measures include sound absorbing enclosures and baffles.
4.5.7 Incinerators
Air inlet and exhaust noise from induced draft fan systems may be controlled by a plenum
chamber or packaged attenuators.
4.5.8 HVAC
General control measures apply for most heating, ventilating, and air conditioning (HVAC)
equipment. Ducts should be designed to reduce fan noise transmission as well as secondary
noise generated by downstream air valves and other devices. Fresh air intake and exhaust
grilles at the building exterior must be designed to avoid excessive noise transmission to the
neighboring community. Pressurized oxygen generator units used in oxygen activated sludge
treatment systems may require enclosure to reduce noise levels.
4.5.9 Architectural Noise Control
Architectural noise control is accomplished primarily by absorption and isolation. Interior
noise levels in occupied spaces should not be allowed to exceed levels listed in Table 4-6. The
more desirable 70-dBA design level will allow the speech and telephone communication
necessary for safe operation. There are methods for determining noise levels in interior spaces,
if machinery noise output is available from the manufacturer (24) (25). If machinery noise
output information is lacking, the designer may estimate likely noise levels, identify potentially
noisy equipment based on experience, and design appropriate noise control measures.
67
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NOISE CONTROL BY ABSORPTION. Absorption techniques can only minimize reflected noise
(i.e.. noise in the reverberant field of a room). Noise levels near equipment, usually within
several feet, cannot be reduced by boundary surface treatment, because these levels are
established by the sound emanating directly from the machinery.
Ceilings and walls may be lined with absorptive material, or absorptive baffles may be used if
piping, ductwork, etc., precludes continuous application of acoustical treatment.
NOISE CONTROL BY ISOLATION. Noisy equipment can be isolated by impervious baffles or
enclosures. Relatively heavy constructions such as sand-filled, concrete block walls are
effective noise suppressants. Double door sound lock entryways may be used. Machinery can
be isolated from the structure by special mountings and, in certain cases, by separate
foundation pads.
4.5.10 Construction Noise Control
Noise during construction has an impact on the surrounding population. One study (17)
estimates that 30 million Americans will find themselves living or working near a construction
site each year.
Construction equipment, with built-in noise controls as well as operational management, may
sufficiently control noise output to meet environmental noise requirements in most cases.
Noise may be measured at the borders of the construction site, to determine limits of maximum
flexibility of operation onsite, while meeting noise standards offsite.
Design considerations to reduce equipment noise include: exhaust mufflers, intake silencers,
engine enclosures, proper cooling system, and fan design. Table 4-7 lists basic information on
sound levels associated with various types of construction equipment. Because these levels are
average, actual noise levels will vary somewhat from those indicated. In particular, noise levels
may be higher than those in the table for products within each category having a higher than
average capacity. Level 1 in the table indicates current quiet products; level 2 lists equipment
which can be quieted by the use of best demonstrated technology. Other techniques to be
considered include: replacing individual operations and techniques by less noisy ones (e.g.,
using welding instead of riveting, mixing concrete offsite instead of onsite, and employing
prefabricated structures instead of building them onsite) and selecting the quietest alternative
items of equipment (e.g., electric instead of diesel-powered equipment, hydraulic tools instead
of pneumatic impact tools).
Earth-moving equipment noises are associated predominantly with exhaust and inlet noise.
Other sources include mechanical and hydraulic transmission and actuation systems and
cooling fans. These usually result in noise levels at a 50-ft range of about 73 to96dBA(see Fig.
4-2). Mufflers offer the greatest potential for noise abatement. If possible, locate haul roads
behind natural earth berms or embankments.
Most of the noise from materials handling equipment, such as cranes, concrete mixers, and
concrete pumps, is generated by the engine. The greatest potential abatement is via engine
quieting.
Where necessary, stationary equipment, such as pumps, generators, and compressors, can be
quieted by mufflers and enclosures.
68
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TABLE 4-7. BASIC INFORMATION ON CONSTRUCTION EQUIPMENT
(1972)
Present
Equipment
Types
Air compressor
Backhoe
Concrete mixer
Concrete pump
Concrete vibrator
Crane, derrick
Crane, mobile
Dozer
Generator
Grader
Jackhammer
Loader
Paver
Pile driver
Pneumatic tool
Pump
Rock drill
Roller
Saw
Scraper
Shovel
Truck
Sound
Level*
81
85
85
82
76
88
83
87
78
85
88
84
89
101
85
76
98
80
78
88
82
88
Average
Unit
Price
$ 8,500
18,000
25,000
50,000
2,000
110,000
50,000
28,000
1,000
22,000
800
20,000
42,000
33,000
300
430
35,000
1 1 ,000
100
70,000
7 1 ,000
18,000
Quiet Products
Level 1
Sound
Level*
71
80
83
80
70
80
80
83
71
80
80
80
80
90
75
71
90
75
70
83
80
83
Average
Unit
Price
$ 9,500
18,500
25,400
50,650
2,060
1 1 1 ,000
5 1 ,000
28,800
1,100
22,600
850
20,600
43,000
33,500
320
450
36,000
11,330
110
71,500
72,000
18,250
Best Technology
Level 2
Sound
Level*
65
76
75
75
66
76
76
78
65
76
75
76
76
80
65
65
80
70
65
78
76
75
Average
Unit
Price
$ 12,000
19,800
27,500
55,000
2,200
113,000
53,000
30,800
1,400
24,200
950
22,000
44,200
37,000
400
580
39,000
12,100
150
75,000
74,000
19,500
Units
Produced
per Year**
12,000
18,000
7,000
500
6,000
2,200
4,300
18,000
70,000
7,000
(20,000)***
30,000
800
350
(100,000)
50,000
(1,000)
6,000
(500,000)
5,000
3,000
75,000
*Sound level refers to average level during operation in dBA at 50 ft.
**Estimated from Department of Commerce published data and industry sources (sales may include other industries).
***Parentheses enclose preliminary estimate.
Source: BBN Report No. 2887, 27 November 1974, Regulation of Construction Activity Noise (Table SI).
-------
Impact tools include pile drivers, pavement breakers, jackhammers, and rock drills. Pile driver
noise emanates predominately from the hammer hitting the pile (vibratory or sonic drivers
eliminate this source). If necessary, holes may be drilled to bedrock and reinforced concrete
piles may be poured in place to lower unsatisfactory pile driver noise levels. Noise from
pneumatic jackhammers, pavement breakers, and rock drills comes from the exhaust and from
the bit against the work. Exhaust can be muffled. A jacket will reduce internal tool noise.
4.5.11 Operational Noise Control
The following techniques could be utilized to reduce operational noise:
Using low noise emission equipment
Scheduling equipment operations to keep average noise levels
low (e.g., scheduling the noisiest operation to coincide with
times of highest ambient levels, keeping noise levels relatively
uniform in time and turning off idling equipment, restricting
working hours)
Increasing the number of machines at work at any one time to
reduce the duration of noise exposure (this will increase the
noise level during that time of operation)
Making use of speed limits to control noise from vehicles
Keeping noisy equipment operations as far as possible from
site boundaries
Providing enclosures or sound shield skins for stationary
items of equipment and barriers around particularly noisy
areas on the site or around the entire site
Maintaining noise control devices.
The techniques for computing noise levels adjacent to the works are presented later in this
chapter.
Noise control measures will be effective only as long as control devices are properly
maintained. Mufflers need to be replaced before breakdown. Engine compartment enclosures
and insulation may warp or bend. Large enclosures surrounding work areas may be breached
and holed during operations and should be promptly repaired.
4.6 ACOUSTICAL COMPUTATIONS
Although special training and experience may occasionally be required, many of the noise
problems encountered in wastewater treatment works design, construction, and operation arc
readily solvable. Reference (5) is particularly useful in this regard. In addition, the basic
computations described in the following paragraphs are frequently encountered in deter-
mining the extent of acoustical problems present as well as in developing solutions.
70
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4.6.1 Addition of Decibels
Often, the total contribution of more than one sound source must be considered. Because
decibels are logarithmic units, their summation is not algebraic. Table 4-8 illustrates a
simplified method for adding decibels.
4.6.2 Sound Power Level/ Pressure Level Conversions
As stated earlier, sound power is a measure of the total acoustic power radiated by a source
independent of its acoustic environment. Sound power level is the source power, expressed in
decibels, relative to the reference power quantity 1 pW.* Ideally, specifications for the
allowable noise output of equipment should be written in terms of sound power levels over the
audible frequency range, usually in octave bands of frequency. Many manufacturers have
sound power level data available for their equipment. Sound pressure levels (LP) are those
actually measured by a noise meter in a particular acoustical environment and are expressed in
decibels relative to a standard reference pressure of 20
The following represents an approximate method for converting sound power level data to
sound pressure levels in outdoor situations (i.e., no nearby reflections except the ground or
roof surfaces on which the source is located).
(LP) avg = Lw - C
where
Lw = sound power level of the source in dB re 1 pW
(Lp)avg = average sound pressure level in dB re 20 juPa in
specified frequency band
C = correction term in dB depending on type of source;
for an omnidirectional source outdoors, assuming
hemispherical spreading of sound, C is a function of
the distance d in feet from the source given by:
C = 10 log(2rrd2) - 5
The correction term C, for an omnidirectional noise source outdoors, is to be used to estimate
sound pressure levels for distances of less than 100 ft (for typical wastewater treatment works
noise sources, conversions of sound power levels to sound pressure levels should be made to
some convenient distance from the source; e.g., 25 or 50 ft [see Table 4-9]). Further reduction in
sound pressure levels beyond that specified distance would be computed by the procedure
described in the section Reduction of Sound Pressure Level With Distance Outdoors.
*1 pW is the reference power used in this report and is the currently accepted power reference. When dealing
with sound power levels, the reference must always be stated. Some acoustics literature uses 0.1 pW reference
power. Sound power levels in dB re 0.1 pW may be converted to dB re 1 pW by reducing the numerical value by
10; e.g., HO dB re 0.1 pW equals 100 dB re 1 pW (pW = 10 ~12 watt = 1 picowatt).
71
-------
TABLE 4-8. ADDITION OF DECIBELS
Difference Between Decibels To Be Added to
Two Decibel Quantities Higher Value To Yield Sum
0 to 1 dB 3
2 or 3 dB 2
4 to 8 dB 1
9 dB or more 0
62 dB
TABLE 4-9. C VALUES FOR OMNIDIRECTIONAL
NOISE SOURCES*
Distance to Acoustic
Center of Source, ft
5
10
15
20
25
30
35
40
45
50
55
60
70
80
90
100
C in dB for U
re 1 pW
12
18
22
24
26
28
29
30
31
32
33
34
35
36
37
38
*C=101og(27rdV5
72
-------
Example 4-1
Given the sound power level of 1 10 dB re 1 pW in the octave
band center frequency of 1 kHz (from manufacturer's data).
Determine the average sound pressure level at 1 kHz and 25 ft
from the geometric center of the source:
Lp L\v — \~
= 110-26
= 84 dB re 20
Similar computations of average sound pressure levels may be made at other frequency bands
of interest. The values in individual octave bands may be added to yield overall sound pressure
levels by the procedure described earlier in this section and in Table 4-8. Alternatively, the
individual values may be corrected by appropriate frequency weighting values and then sum-
med to yield an A-weighted sound level in dBA (See section 4.6.4).
Many noise sources, such as motor exhausts, are not omnidirectional — they radiate sound
energy more efficiently in certain directions from the source. Thus the directional
characteristics as well as the sound power of the source must be known to perform sound
power level to sound pressure level conversions. The directivity index in a given direction from
a sound source is the difference in decibels between (a) the sound pressure level produced by the
source in that direction and (b) the space average sound pressure level of that source, measured
at the same distance. Data on directivity for various mechanical equipment noise sources are
usually available from the manufacturer, along with the equipment sound power level data, or
may be estimated using the procedures of references (26)(27).
In rooms, sound energy is not dissipated with distance because of the effect of room boundaries
in establishing relatively constant reverberant field sound pressure levels, usually within
several feet from the source. The correction terms for indoor conditions will vary with the
average absorptivity of the room surfaces (see references 26 and 27).
4.6.3 Reduction of Sound Pressure Level With Distance Outdoors
When the sound pressure level at a specified distance (d i ) from a noise source is known, a first
approximation of the sound pressure level at a greater distance (d:) from the source can be
made by subtracting a distance correction term from the known sound pressure level. For a
simple omnidirectional source outdoors, the distance correction term is given by 20 log(di / d:).
More complete engineering calculations would include additional losses from air absorption,
atmospheric attenuation, line of sight obstructions between the source and receiver, and other
effects.
Example 4-2
The sound pressure level 50 ft from a noise source is 70 dB re
20 juPa. What is the sound pressure level 100 ft from the
source?
73
-------
Distance correction term:
20 log( 100/50) = 20 log 2 = 6 dB
at 100 ft
LP = 70 - 6 = 64 dB re 20
4.6.4 Conversion of Octave Band Sound Pressure Levels to A-Scale
Sound Pressure Levels
Sound levels, as measured with a simple sound level meter using A-scale frequency weighting
network, are often used in noise ordinances and codes, because they correlate well with human
reaction to many types of sounds. Table 4-10 can be used to convert octave band sound
pressure levels to A-weighted sound pressure levels when the latter cannot be measured
directly (see also Fig. 4-4 and example 4-5).
4.6.5 Calculation of Effective Sound Isolation of Composite
Barrier Construction (Interior Noise)
When a building exterior wall is made up of more than one component with different sound
transmission loss (TL) characteristics, the effective sound transmission loss of the composite
construction may be calculated using Figs. 4-5 and 4-6 and Table 4-11. The following
parameters are used in Fig. 4-5:
Ti = TL of basic acoustic barrier (wall)
T: = TL of secondary barrier element (window,
door, crack, hole, or other sound leaks)
located in basic acoustic barrier.
K = Percentage of total barrier areas of second-
ary element with respect to basic barrier.
D = Difference in TL of basic and composite
barriers — Ti - To
74
-------
TABLE 4-10. RELATION BETWEEN
OCTAVE BAND CENTER FREQUENCY
AND A-SCALE FREQUENCY (5)
Octave Band SPL Relative Response in dB re
Center Frequency, 20 fj.Pa for A-Scale SPL
Hz Frequency Weighting Network
31.5 ~39.4
63 -26.2
125 -16.1
250 -8.6
500 -3.2
1,000 0
2,000 +1.2
4,000 +1.0
8,000 -1.1
16,000 -6.6
75
-------
140
LU
>
UJ
u
tr
Z3
V)
V)
LU
OC
a.
o
CO
Q
Z
CD
LU
t-
o
o
130
120
CO
_J
LU
CD
UJ
o
no
100
90
30
\
\
\
\
\
\
UJ
>
125 UJ
_J
120 Q
I 15
CO
105 ul
100
95 LU
90 o
UJ
I I 'I
00 200 500 1000 2000 4000 8000
BAND CENTER FREQUENCY - HERTZ
FIG. 4-4. SOUND LEVEL CONVERSION CHART
76
-------
4 5 6 7 8 9 10
0 IN DECIBELS
15 20 30 40 5060
FIG. 4-5. EFFECTIVE TRANSMISSION LOSS (TL)
OF COMPOSITE ACOUSTIC BARRIERS (14)
77
-------
WEIGHT IN KG PER SQUARE METER
CD
O
- 35
CO
CO
O
CO
CO
CO
2
(C
r3 CINDER
BLOCK
4 CONCRETE SLAB
RESILIENTLY SUSP
CEILING
4 CONCRETE SLAB
CONV. SUSP CEILING
I
METAL LATH
PLASTER"
4 CONCRETE
SLAB
1/2 GYPSUM WALLBOARD
4 CINDER BLOCK
MHARDWOOD
FLOOR
METAL LATH
PLASTER
2x4 WOOD STUDS
DOOR, AIRTIGHT
2 1/2" HEAVY WOOD
GYPSUM WALLBOARD
1/2
„ I
1/4 PLYWOOD
4 CINDER BLOCK
I x 3 WOOD STUDS
I 3/4 SOLID OAK
DOOR, 3/16 ' WOOD PANELS
30
25
20
15 -
10
3 45678910 20 30 40 50 60 70 8090 100
WEIGHT IN POUNDS PER SQUARE FOOT
FIG. 4-6. TRANSMISSION OF NOISE THROUGH
WALLS AND FLOORS (27)
78
-------
TABLE 4-11. AIRBORNE SOUND TRANSMISSION LOSS VALUES FOR
SOME COMMON BUILDING CONSTRUCTIONS DERIVED FROM FIELD
MEASUREMENTS (16)
Building Construction
Transmission Loss (db) at Listed Frequencies, Hz
125 250 500 1,000 2,000 4,000
Single Wall
2-in. solid gypsum perlite-aggregate plaster (10 Ib/sq ft)
2-in. solid gypsum sand-aggregate plaster (18 Ib/sq ft)
4-in. hollow-core gypsum block 5/8-in. sand-aggregate plaster
both sides (25 Ib/sq ft)
6-in. hollow-core cinder block painted both sides (33 Ib/sq ft)
6-in. hollow-core cinder block, 5/8-in. sand-aggregate plaster both
sides (43 Ib/sq ft)
4-1/2-in. solid brick, plastered both sides (45 Ib/sq ft)
7-in. stone-aggregate concrete, plastered both sides (90 Ib/sq ft)
2X4 wood studs, 1/2-in. gypsum board both sides (6 Ib/sq ft)
2X4 wood studs, 1/2 in. sand-aggregate plaster on 3/8-in. gypsum
lath both sides (16 Ib/sq ft)
2-1 / 2-in. wire studs, 5 / 8-in. sand-aggregate plaster on metal lath both
sides (19 Ib/sq ft)
2-1/2 in. wire studs, 1/2-in. sand-aggregate plaster on 3/8-in.
gypsum lath both sides (12 Ib/sq ft)
Double Wall
Two separated rows of 3/4-in. furring channels 2-3/4-in. on center,
5/8-in. sand-aggregate plaster on metal both sides (4-3/4-in. total
thickness) (17 Ib/sq ft)
2-1/2-in. wire studs, 1/2-in. sand-aggregate plaster on 3/8-in. gypsum
lath on 1/2-in. resilient metal clips both sides (12 Ib/sq ft)
Staggered 3-1/4-in. wire studs, 1/2-in. sand-aggregate plaster on
3/8-in. gypsum lath both sides (5-3/4-in. total thickness) (13 Ib/sq
ft)
4-in. hollow-core gypsum block, 5/8-in. sand-aggregate plaster one
side, 1/2-in. sand-aggregate plaster on 3/8-in. gypsum lath on
7/8-in. resilient metal clips second side (26 Ib/sq ft)
Two wythes of plastered 3-in. dense concrete, 3-in. airspace between
(bridging in airspace and at edges) (85 Ib/sq ft)
Two wythes of plastered 4-1/2-in. solid brick, 2-in. airspace between
(sound-absorbing material in airspace—bridging at edges only)
(90 Ib/sq ft)
Two wythes of plastered 4-1/2-in. solid brick, 12-in. airspace between
(wythes completely isolated) (90 Ib/sq ft)
Floor, Ceiling
Typical residential floor-ceiling wood finish; and subfloors on wood
joists, gypsum lath and plaster below (about 15 Ib/sq ft)
Concrete floor slab, 1/2-in. plaster finish coat below (about 45 Ib/sq
ft)
Wood floating floor of finish; and subfloors on 2 X 2 sleepers on
3/4-in. glass fiber blanket on concrete structural slab, 1/2-in.
plaster finish coat below (about 50 Ib/sq ft)
28
31
30
29
36
34
44
20
27
26
26
25
38
43
57
30
32
31
31
33
35
42
30
25
24
32
29
33
33
36
38
40
52
36
31
37
41
33 43
40 51
50 52
70 83
34
38
39
40
45
51
58
41
44
31
45
48
54
61
93
38 48 55 61
40
45
42
46
50
57
66
43
34
37
38
34 39 44 49 48
49
57
73
24 32 40 48 51
43 40 44 53 56
59
48
53
46
52
56
60
70
42
50
50
52
29 35 44 43 46 55
30 37 43 48 43 60
60
54
65
78
54
58
55
Door
1-3/8-in. hollow-core wood door, normally hung
1-3/8-in. solid wood door, normally hung
1-3/8-in. solid wood door, fully gasketed
Specially constructed 2-5/8-in. wood door, full double gasketing
Two specially constructed 2-5/8-in. wood doors, each with full
double gasketing, 12-in. airspace between, each door hung on
independent wythe of double wall
5
10
16
20
31
11
13
18
23
47
13
17
21
29
43
13
18
20
23
48
13
17
24
31
57
12
15
26
37
66
2
2
2
2
2
*1. Beranek, L.L., (ed.). Noise Reduction, chap. 13. McGraw-Hill Book Company, Inc., New York (1960).
2. Bolt Beranek and Newman Inc., unpublished data.
79
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Example 4-3
Given one window with TL = 20 dB inserted in a wall with TL
= 40 dB. The window occupies 5 percent of the wall. What is
the effective TL of the composite barrier?
T, - T2 = 40 dB - 20 dB = 20 dB
K = 5 percent
from the chart
D = 7dB
To = T, - D = 40 - 7 = 33 dB
The composite wall will then act like a homogeneous wall
having a TL = 33 dB.
4.6.6 Calculation of Sound Insulation From an Enclosed Room to Outside
When the sound pressure level in a room is known, the exterior sound pressure level may be
estimated for the frequency bands of interest from the expression:
Lp outside = Lp inside - TL - 6
where
Lp outside = average sound pressure level just outside struc-
ture in question (in dB re 20 /uPa)
TL = sound transmission loss of enclosing construc-
tion in dB (use procedure shown in Example 4-3
if construction is made up of more than one com-
ponent) ,
Example 4-4
The average sound pressure level inside a filtrate building is
75 dB re 20 ^Pa in the 1-kHz octave band. The exterior con-
struction of the filtrate building has a sound transmission
loss of 30 dB at 1 kHz. What sound pressure levels would be
expected at 1 kHz outside the building?
LP3 outside = 75-30-6
= 39 dB re 20
80
-------
Example 4-5
Compute the equivalent A-scale sound level, given the octave
band sound pressure level below:
Octave Band
Center
Frequency, Hz
63
125
250
500
1,000
2,000
4,000
8,000
Octave Band
Sound Pressure
Level,
dB re 20 /uPa
80
75
70
65
60
55
50
45
Relation
A-Scale
Response, dB
-26.2
-16.1
-8.6
-3.2
0
+1.2
+1.0
-1.1
Weighted
Octave Band
Sound Pressure
Level,
dB re 20 ,uPa
53.8
58.9
61.4
61.8
60.0
56.2
51.0
46.1
Sum of weighted octave band levels = 67 dBA.
4.6.7 Calculation of Noise Output From Plant Equipment
Generally, noise from fully enclosed, indoor equipment will not be significant. However, noise
transmission through building walls should be checked, using control procedures described
previously. Most significant wastewater treatment works noise will emanate from exterior
mechanical aerators or from diffused air blowers housed indoors but with exposed inlets. The
designer should obtain pertinent sound power and sound pressure level data from the
manufacturer. For example, if blowers are to have only their inlets exposed, specific
information on noise generated at the inlet should be obtained as well as overall noise
generation data.
81
-------
Noise from various equipment on the site should be summed using the methods described
above. The noise level from an array of identical sources can be considered to emanate from
the geometric center of the individual sources (e.g., a bank of mechanical aerators). If several
sources are scattered throughout the site, they should be evaluated independently (e.g.,
separated banks of mechanical aerators, blowers, and other identifiable sources at the site).
4.6.8 Exterior Noise: Calculation of Total Noise Levels at Typical Locations on
Periphery of Wastewater Treatment Works Property From All Significant
Sources
This step is necessary, even if the land surrounding the wastewater treatment works is
undeveloped, because future encroachment by residential and commercial construction may
be possible. If noise levels are excessive at the periphery, it may be desirable to reduce noise
emission from the equipment, acquire additional land, or zone for use compatible with high
noise levels. In addition, noise levels at particular locations beyond the periphery of the
facilities (e.g., at the nearest residences) should be estimated.
Finally, the estimated total noise generated by the treatment works should be compared with
applicable codes or ordinances and EPA criteria The following examples and calculations
are given as an aid to the design engineer.
Evaluation Method 1. Determine existing environmental (from all sources) noise
levels at the site of adjacent land use:
1. By direct measurement and determination of Ldn
2. By use of Table 4-3 to determine an assumed existing noise level Ldn
3. Use the lower of the findings (1) or (2).
Determine probable reaction of adjacent land owners by comparing the estimated total noise
from the wastewater treatment works at the site with existing noise levels at the site. If the noise
from the wastewater treatment works is 0 to 3 dBA higher, little or no impact may be expected;
if 3 to 15 dBA higher, moderate impact may be expected; if 15+ dBA or higher, severe impact
may be expected.
Evaluation Method 2. Compare the estimated total noise levels from the wastewater
treatment works with Figure 4-7 or existing State and Local Standards (whichever are
more stringent).
Example 4-6
Determine the relative impact on residence A as a result of the
noise emanating from the treatment works. Given: locations as
shown on Fig. 4-8.
NOISE SOURCES
Mechanical aerators Each aerator produces 82 dBA, 10 ft
from its geometric center (cal-
culated from manufacturer's in-
82
-------
Figure 4-7. Environmental Noise Levels for Residential, Hospital,and Educational Activity
Environmental Noise Level
Associated with an Action
(exterior environment
Qualitative Considerations Applicable to
Individual Actions
Levels have unacceptable public health and
welfare impacts
Significant adverse noise impacts exist:
allowable only in unusual cases where lower
levels are clearly demonstrated not to be
possible
Adverse noise impacts exist: lowest noise
level possible should be strived for
65
55
Levels are generally acceptable: no noise
impact is generally associated with these
levels
*Some structures do not contain relevant exterior activity space and therefore, in these cases, special
determination of the acceptability of the interior environment should be made.
83
-------
MECHANICAL
AERATORS No
MECHANICAL
AERATORS No. 2
FIG. 4-8. PLAN FOR EXAMPLE 4-6
84
-------
Blower unit
Filter building
formation); aerator bank No. 1, six
aerators at 82 dBA, aerator bank
No. 2, four aerators at 82 dBA
70 dBA at 50 ft (from man-
ufacturer's data)
60 dBA at wall exterior, estimated
from interior sound pressure levels
and transmission loss through struc-
ture (assume source to be at center of
building, 60-dBA noise level at ex-
terior wall 50 ft from center)
MECHANICAL AERATOR BANK NO. 1. Convert given sound
pressure levels (dBA) for individual aerators to a total sound
level for the entire bank at an arbitrary point (point A) beyond
the outer boundary of the bank (say, point A = 100 ft from the
geometric center of the bank). The aggregate sound level at
point A is then:
Aerators 1 & 3:
Reduction
Aerator 2:
Aerators 4 & 6:
d = [(75)2 + (137.5)2]'/2= 157 ft
= 20 log 157/10 = 24 dBA
LP = 82 - 24 = 58 dBA
d = 137.5 ft, LP = 82-23 = 59 dBA
d = [(75)2 + (62.5)2]I/2 = 98,LP = 82-2
= 62 dBA
d = 62.5 ft, LP = 82 - 16 = 66 dBA
Distance correction: 20 log (300 + 100)/100 = 12 dBA
LP at residence A = 70 - 12 = 58 dBA
85
-------
MECHANICAL AERATOR BANKNO.2. Sound pressure level at
point B is:
Aerators 1 & 2:
d = [(137.5)2 + (37.5)2]1/2
= 143 ft, LP = 82 - 23 = 59 dBA
Aerators 3 & 4: d = [(62.5)2 + (37.5)2]1/2
= 73, LP = 82- 17 = 65 dBA
69 dBA at point B
Distance correction 20 log(l,000/100) = 20 dBA
LP at residence A 69 - 20 = 49 dBA
BLOWER. Distance correction
20 log [(200)2 + (600)2]'/2/50 = 22 dBA
L at residence A 70 - 22 = 48 dBA
FILTRATE BUILDING. Distance correc-
tion: 20 log [(200)2 + (600)2]1/2/50 = 22 dBA
at residence A
60 dBA - 22 =38 dBA
The total noise level at residence A from the wastewater
works will be:
59 dBA
Determine probable impact on residential area as determined
for nearest residence, house A. From Table 4-3, assume
average nighttime suburban:
50 Ldn = approximately 40 dBA nighttime
From method 1: 59 — 40 = 19 dB difference, severe impact is
expected to result. From method 2, the total noise level at
86
-------
house A equals 59 dBA. Enter Figure 4-7 to determine that
adverse noise impacts exist: lowest noise level possible
should be strive d for.
The result of this analysis is that sound reduction of one or more pieces of equipment is
necessary. This preliminary analysis should be repeated for subsequent designs or alternative
equipment selections. If the results of the final analysis still indicate adverse noise impact on
the adjacent residential area, a comprehensive noise analysis should be undertaken to
determine adequate noise abatement measures. The latter may include site layout changes to
provide greater separation between the noisiest wastewater treatment works sources, provision
of line-of-site barrier walls on earth berms at the property line, and noise attenuation of specific
sources.
4.7 REFERENCES
1. Effects of Noise on People, U.S. Environmental Protection Agency, NTID 300.7,
Government Printing Office 5500-0050, Washington, D.C., 1971.
2. Information on Levels of Environmental Noise Requisite To Protect Public Health and
Welfare With an Adequate Margin of Safety, EPA 550/9-74-004, March 1974.
3. Occupational Noise Exposure, Occupational Safety and Health Administration, Federal
Register, Vol. 36, No. 105, 1910.95, 29 May 1971.
4. Errata Published in Federal Register, Vol. 34, No. 96, 15 July 1969, Walsh-Healey Public
Contracts Act; Federal Register, Vol. 34, No. 96, Rule 50-204.10, 20 May 1969.
5. Beranek, L.L., Noise and Vibration Control, McGraw-Hill Book Company, New York,
1971.
6. Community Noise, U.S. Environmental Protection Agency, NTID 300.3, Government
Printing Office 5500-0041, Washington, D.C., 1971.
7. Noise Assessment Guidelines, U.S. Department of Housing and Urban Development,
Government Printing Office 2300-1194, Washington, D.C., 1971.
8. Gately, W.S., "Industrial Noise Control," Mechanical Engineering, April 1971.
9. Fundamentals of Noise: Measurement, Rating Schemes and Standards, National Bureau
of Standards, NTID 300-15, U.S. Government Printing Office, Washington, D.C., 1972.
10. Beranek, L.L., "Industrial Noise Control," Chemical Engineering, 27 April 1970.
87
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11. American National Standards Methods for the Measurement of Sound Pressure Levels,
American National Standards Institute, New York, 14 July 1971.
12. Highway Noise: A Design Guide for Highway Engineers, Highway Research Board,
Report'l 17, Washington, D.C., 1971.
13. Peterson, Arnold P.O., and Gross, Jr., Ervin E., Handbook of Noise Measurement,
General Radio Company, Concord, Massachusetts, 1972.
14. Newman, R.B. and Cavanaugh, W.J., Acoustics, Time Saver Standards, 4th Edition,
McGraw-Hill, 1966.
15. Heer, J.E.; Hagerty, D.J.; and Paroni, J.L., "Noise in the Urban Environment," Public
Works, October 1971.
16. Occupational Noise Exposure, Occupational Safety and Health Administration Rules
and Regulations 1926.52, Federal Register, 16 December 1972.
17. Noise From Construction Equipment and Operation, Building Equipment and Home
Appliances, U.S. Environmental Protection Agency, NT1D 300.1, Government Printing
Office 5500-0044, Washington, D.C., December 1971.
18. Test for Measurement of the Airborne Noise Emitted by Rotating Electrical Machinery,
ISO Recommendation R 1680, ANSI, 1970.
19. Field and Laboratory Measurements of Airborne and Impact Sound Transmission, ISO
Recommendation R 140, ANSI, 1960.
20. Acoustics: Assessment of Occupational Noise Exposure for Hearing Conservation
Purposes, ISO Recommendation R1999, ANSI, 1971.
21. Seebold, J.G., Process Plant Noise Control at the Design Engineering Stage,Transactions
of the American Society of Mechanical Engineers, Paper No. 70-Pet-ll, 1970.
22. Yergas, L.F., Sound, Noise and Vibration Control, Van Nostrand Reinhold Company,
New York, 1969.
23. Noise From Industrial Plants, U.S. Environmental Protection Agency, NTID 300.2,
Government Printing Office 5500-0042, Washington, D.C., 1971.
24. Power Plant Acoustics, U.S. Army, TM 5-805-9, Headquarters, Department of the Army
Washington, D.C., 1970.
25. U.S. Army, Noise Control for Mechanical Equipment, TM, Headquarters, Department
of the Army, Washington, D.C., 1970.
26. Public Buildings Service Guide Specifications, PBS: 4-0110 General Services Administra-
tion, Amendment 2, August 1972.
27. Harris, C., Handbook of Noise Control, McGraw-Hill Book Co., New York, 1957.
88
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5. SITE PREPARATION, CONSTRUCTION,
AND OPERATION PROBLEMS
This chapter addresses the many problems associated with site development and facility
construction.
5.1 FLOODING AND DRAINAGE
The engineer must always consider problems which might result from flooding of the site or
from flood runoff. EPA reliability guidelines specify the amount of protection against floods
to be provided for wastewater treatment facilities (1). Onsite flooding can be caused by in-
adequate flood protection measures; inadequate provisions for stormwater drainage from the
site; or inadequate provisions for overflows of wastewater resulting from failure of equip-
ment, stoppages of flow, or stormwater entering the wastewater system. Flood runoff from
wastewater works sites might pollute both downstream land uses and waters receiving the
runoff. To prevent interruption of operations by collection and treatment of such flooding,
adequately protected standby facilities and equipment should be provided.
For flood plain analysis, refer to Flood Hazard Evaluation Guidelines published by the
United States Water Resources Council, May 1972 (2). Detailed evaluation criteria are
included in this reference.
It is generally accepted in the courts that land cannot be modified in any way which will
result in flooding, erosion, or additional damage to adjacent lands. Wastewater works are
often constructed at low elevations or flood plains to take advantage of wastewater collection
by gravity. In such cases, the design must allow floods to pass without significant restriction.
Great care must be taken to ensure that existing natural drainage is not impaired and that
runoff will not be impeded and result in flooding. This is particularly true in the design and
construction of interceptors which cross natural drainage channels or shallow aquifers.
If the construction of a pond to store flood waters above a drainage culvert is possible, the
culvert should be designed to restrict flows for maximum utilization of the available storage.
Flood runoff increases when the surface of an open area become more impervious because of
construction of roads, parking areas, and structures. To prevent downstream flooding, down-
stream drainage channels must be sized to take the increased load or detention must be pro-
vided at the wastewater works site. Depressed parking areas which can store flood peaks and
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discharge the excess after rains have stopped are common practice. In other cases detention
basins have been constructed by digging a 10- to 12-ft-deep basin, lining it, and filling it with
crushed stone and gravel. Excess stormwater enters the rock-filled basin through a sedimenta-
tion basin and is pumped out after the storm has passed. Parking lots or other structures can
be built on top of such detention basins.
5.2 SITE PREPARATION
Site clearing, grading, and excavating may generate such nuisances as dust, noise, erosion,
and debris. Construction nuisances may be minimized by proper planning of construction
operations. Working hours may be limited to reduce nuisances in the early morning and at
night. Construction equipment must be selected for minimum noise and exhaust emissions.
Weight and loading of vehicles should be kept below that causing damage to roadways, as
determined by the governmental agency responsible for roadways. Construction operations
should take into account adjacent land use. Permissible impact magnitudes will vary in
importance according to the type of use.
Effective traffic control procedures might include provision to limit the length of an open
trench. Stockpiling of excavated material could be limited to offsite locations only.
Construction sites, and particularly long rights-of-way, may include historical and archeo-
logical areas and remains. These cultural properties must be identified and protected in
accordance with federal and state preservation programs. Impacts of federally assisted con-
struction projects on cultural properties should be evaluated under procedures established
by the Advisory Council on Historic Preservation (36 CFR 800). Cultural properties should
be identified early in the project's planning stages, to avoid later construction delays which
may result from mitigation activities to save affected properties.
If an archeological site is discovered during the construction process, project specifications
could require that construction be halted to permit expert evaluation. For example, specifica-
tions could include a procedure to be followed in obtaining expert opinion, such as naming
the expert to be employed, length of time construction may be halted without additional
compensation to the contractor, and compensation to be paid for halting construction. In
some cases it may be necessary to shift construction operations to another area of the project,
to permit archeological excavation, or to relocate some portion of the proposed works.
It is desirable—and usually very important—to limit clearing to minimize erosion, reduce the
visual impact of denuded landscape, preserve wildlife habitat, and (often) reduce total costs.
An effective method of controlling clearing is to limit construction in an easement or right-
of-way to a specified area or width not necessarily as large or wide as the easement or right-
of-way. The required width for efficient construction depends on soil, depth of excavation,
groundwater level, type of material utilized, method of construction, and equipment to be
used. Because machine operators, who actually do the clearing, may not be informed of
areas which must remain undisturbed, an effective control measure such as fencing or staking
the area available for construction should be used. The method of construction may be
specified to include use of particular types of equipment which reduce damage. For example,
rubber-tired rather than tracked vehicles might be specified, to minimize damage to roads
and sidewalks.
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Trees may be protected by wrapping the trunks in protective covering and fencing them off.
The root system may be safeguarded by limiting excavation and backfill within the dripline.
If an impervious fill or surfacing covers 25 percent or more of the area under the branches
of a tree, a tree well protecting the tree trunk and provision of a satisfactory method for
irrigating the roots under the impervious fill or surfacing must be provided. Small trees may
be removed with the root systems intact, burlapped, and set aside under carefully maintained
conditions for use elsewhere on the site.
5.3 DISPOSAL OF CLEARING DEBRIS AND
CONSTRUCTION WASTES
Disposal of material from construction operations is an increasing problem. Disposal sites,
particularly in urban areas, are limited, and burning restrictions have created an increased
demand for such sites.
Because of the complexity of the problem, detailed requirements for disposal of clearing and
construction wastes should be included in contract documents. Such a plan might include
expected types and quantities of waste, methods of transport, and methods of disposal,
including identification of sites.
Construction wastes include:
wastes from equipment (fuel, oil, and grease)
wastewater from core drilling and foundation grouting opera-
tions
wastes from concrete operations
aggregate washwater and screenings
cement and concrete spillage
concrete lift pump cleanup
spillage and waste of curing compounds
cleanup and washing of mixers and batch trucks
wastes from roads, camps, shops, and storage areas
sanitary and other wastes
spillage of fuels, grease, oil, etc.
wastewater from equipment washing
wastes from asphalt operations
spillage of bituminous materials
aggregate washwater and screenings
pesticides.
Wastes should be transported in vehicles designed to prevent spillage. If odors are a problem,
the vehicle should be entirely closed (the exterior of vehicles should be kept clean to prevent
odor problems). The contractor could be required to maintain a vehicle cleaning station,
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with steam or high pressure water available. Overloading of vehicles is certain to result in
spillage.
Vegetative debris may be landfilled, chipped and spread on bare earth, or burned in a pit
incinerator or refuse incinerator, depending on state and local regulations. Wood chippings
can often be stored and used later as a mulch on newly seeded areas or to protect bare slopes.
Stumps or other organic material should not be buried where construction is expected in the
near future, because the surface will settle as the material decays. In burying waste, leachate
problems, groundwater pollution, and future settlement must be considered. Land disposal
of problem material, such as organic overburden and muck, requires adequate compaction
and covering with suitable soil.
The two basic principles in designing against landfill leachate pollution are: prevent water
from entering the landfill, and prevent leachate from reaching the groundwater. Methods
commonly used to prevent water from entering the landfill include: (a) intercept all runoff
and bypass it around the area, and (b) place an impervious soil, or membrane, cover over
the landfill and adequately slope and drain the surfaces of the landfill to prevent water from
ponding. Construction techniques commonly used to prevent leachate from reaching the
groundwater include preparation of the site by: (a) underlining the entire site with an
impervious clay layer or a membrane and/or placing a systems of drains and/or gravel
adequately sloped to drain leachate to a sump where it can be pumped to a treatment facility;
and/or (b) designing the low point of the landfill no less than 4 ft above the water table.
The landfill material should be baled before placing, or maximum compaction obtained after
placing, to minimize the rate of leachate formation, the decomposition of organic material,
and the rate of percolation through the fill. For additional requirements, see reference (3).
5.4 EXCAVATION AND BACKFILL
Excavation should be done with the least disturbance to ground cover and tree root systems.
Excavated material should be stockpiled in such a way that it will not be a source of silt or
pollution in stormwater runoff or be a source of dust in the air. Diking, chemical treatment,
reseeding, and/or covering with tarpaulins may be desirable.
Excavation in stream, ocean, or lake bottoms should be controlled, to minimize damage to
fish spawning areas and shellfish beds. For example, clamshell or orange peel buckets could
be specified instead of dragline buckets. Blasting should be done according to accepted
safety practices and should also be limited to daytime working hours when such noise is
more acceptable. Excavations where the walls of the opening are not sufficiently supported
can cause subsidence of adjacent land and damage to structures. Excavation and fill slopes of
ponds and lagoons require protection against wave action as well as against erosion and must
be amenable to efficient removal of scum, debris, or weed accumulation. Experts in soil
mechanics and geology should assist in the design of the shoring or piling used to adequately
support the walls of an excavation.
Subsidence of land and structures can be caused by lowering of the water table. Granular
material is often placed on the bottom of excavations or trenches, to keep the working sur-
face dry and to drain infiltrating groundwater or stormwater to a sump where the water is
pumped out, thus possibly lowering the water table adjacent to the excavation. In other cases,
well point systems are used to lower the water table below the excavation to keep the site
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dry. Adjacent soils should be examined by soils experts (if there is a question), to ensure
that permanent drainage in areas where groundwater is near the surface is designed to pre-
vent subsidence of the soil and possibly of structures resting on that soil. In older urban
areas, structures may have been built on wooden piling which has been kept continuously
wet by high groundwater. If the water table is lowered, the piling may become weakened,
resulting in settlement damage to structures.
Material used for backfill must be carefully selected, and methods used for placement must
be designed to ensure satisfactory compaction. Organic matter such as wood shoring or
stumps must be removed from any backfill. The construction contractor should be required
to return and repair, within 1 year, any surface irregularities or other damage caused by
faulty excavation or faulty backfill.
5.5 PILE DRIVING, BLASTING, AND
EARTHQUAKE PROBLEMS
Potential vibration or shock waves must be considered in the design of wastewater works,
to protect them from earthquakes or to prevent damage to adjacent structures from construc-
tion procedures such as pile driving or blasting. All wastewater works must be designed to
remain watertight and meet local building design regulations, including those relating to
possible earthquakes. Pile drivers and explosives also cause noise and shock waves. The
designer must specify construction methods, after consultation with competent geologists if
necessary, which would minimize detrimental effects.
Selection of the correct type of piling or foundation support to meet site conditions (such as
concrete poured into driven pipe or drilled holes) or of pile driving equipment (such as sonic
pile drivers) can reduce or eliminate such problems, although at a higher construction cost.
All safety codes applicable to the use of explosives must be rigidly complied with, if damages
are to be minimized. If pile driving or explosives must be used in a particular situation, the
detrimental effects on the environment must be considered in the environmental assessment.
5.6 DREDGING
Before commencing dredging operations, the dredged material should be sampled to ascer-
tain the proper method of disposal. Toxic or odorous substances in the dredged material will
require special disposal techniques. Dikes around spoil and settling areas, overflow weirs,
and outfall channels should be designed to prevent escape of dredged materials. Use of a
clamshell bucket rather than a hydraulic dredge will decrease the water content of the
dredged material and minimize the escape of silt in drainage from the spoil area. Also,
bottom dump scows, which drop the spoil in a large mass, are preferred. Fish spawning
areas and shellfish beds must be protected from siltation.
Dredging operations should be monitored for toxic substances and the escape of material
from the spoil area. Contact the U.S. Army Corps of Engineers to determine permit
requirements.
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5.7 EROSION AND SILTATION
Erosion not only creates unsightly conditions but also leads to water pollution and muddy
areas and is a source of dust. Inorganic silts in runoff water entering watercourses reduce the
numbers and types of organisms normally present in the receiving stream. Silt can blanket
the bottom, screen out light, change heat radiation, destroy living spaces, and create unfavor-
able conditions by covering organic materials. Silt may smother fish eggs, shellfish, and other
bottom organisms and may interfere with fish feeding. Information on erosion and sediment
control is contained in EPA guidelines (5).
General recommendatons for sediment control on wastewater facility sites include (7)(11):
Plan development to fit drainage patterns, topography, and
soils of the construction site.
Avoid removal of trees and surface vegetation wherever
feasible.
Minimize exposed land area and duration of exposure.
Divert runoff around exposed areas to stabilized outlets.
Provide temporary cover on areas of critical erosion hazards,
and establish permanent cover as soon as possible.
Construct impoundments to trap sediment and reduce runoff
peaks before flow leaves the construction area.
Meyer (6) describes a method for predicting soil loss from erosion. The amount of erosion is
determined in large measure by soil type, degree of slope, and shape of the transition at the
top and bottom of the slope.
Fording of streams, another source of erosion, should be carried out by bridging the streams,
sheeting, using conveying equipment, or constructing a stabilized roadbed into and through
fords.
Borrow pit operations should be controlled to prevent escape of sediments. The excavated
area should be restored by proper grading, replacement of topsoil and vegetation, and revet-
ment of steeper slopes. Revegetation (7)(8) is one of the best erosion control measures avail-
able. Vegetation selected must, of course, be hardy for the specific site. Mulch (8)(9) may be
used to control runoff from bare slopes after seeding until the grass or other vegetation is
well started or as a long term erosion preventive. Netting may be required over mulch. A
mulch of wood chips or crushed stone is sometimes used as a permanent slope control
against erosion. Burlap or plastic is sometimes used in place of mulch as a temporary
measure.
Suggested procedures to improve chances of re vegetation include:
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Spoil areas should be graded. If revegetation must be delayed,
areas should be temporarily covered with tarpaulins, burlap,
or mulch.
Dikes or ditches to control runoff may be required.
Several inches of the original or imported topsoil over scalped
soil is usually necessary, if seeding is to be effective.
Development of adequate soil fertility, which denuded soils
often do not have, is essential. Irrigation with treated waste-
water often provides sufficient nutrients for good growth of
vegetation, and conditioned disinfected sludge is a good soil
conditioner.
Shallow tillage of areas immediately prior to seeding will break
the crust, aid revegetation, and improve infiltration.
A seed mixture containing both slow and fast growing varieties
proved satisfactory for the site conditions is desirable. Fast
growng temporary varieties (such as rye) will protect slower
growing permanent varieties (such as blue grass or fescue).
Mulching of seeded or planted areas is most important for
speeding revegetation of denuded land.
Supplemental controlled irrigation is often required until
growth is well underway.
Temporary erosion or runoff control measures such as impoundments, dikes, or ditches
should be coordinated with the final project design. These temporary measures should be
planned to minimize the additional earthwork necessary for final design.
Prior to the start of work, construction specifications should require that the contractor sub-
mit to the owner, for review and approval, proposed plans for clearing, excavating, grading,
and constructing haul roads and borrow pits. Also needed are a plan for disposal of waste
materials, for erosion control methods, for drainage during construction, and a land
restoration schedule.
Wischmeier (10) describes an erodibility model using parameters obtained from routine
laboratory determinations and standard soil profile descriptions. A nomograph is also pre-
sented. The parameters used are: percentage silt plus very fine sand, percentage sand greater
than 0.10 millimeter, organic matter content, structure, and permeability. Wischmeier
indicates that this technique can be used to plan sediment control measures such as deter-
mining the proper depth of cut to avoid highly erodible soil layers and the proper shape of
the slope.
Erosion and runoff control measures are well known (7, 11, 12, 13, 14). In summary, the
following methods for erosion or runoff control are recommended for consideration:
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Bare slopes should receive cross-slope scarification prior to
mulching and revegetation. Contour plowing and/or terracing
may also be effective for some plantings.
Slope shaping (7)(10) is an erosion control technique to re-
duce erosion rates and sediment yields. A concave slope will
yield less sediment, because the steepest part of the slope
occurs where flow is least. If a concave slope is not practical,
a complex slope (convex upper and concave lower) will re-
duce sediment yield.
Permanent mulching, crushed rock, paving, or revegetation
can be used to protect raw slopes.
Interceptor dikes and diversions using soil ridges or furrows
may be constructed to carry runoff around the slope. Consid-
eration should be given to revetting or lining such dikes or
ditches (or providing check dams), if the ditches are expected
to be permanent.
Waterways may be sodded or lined with gravel, stone, con-
crete, or asphalt.
Sediment traps made of hay bales or brush with wire fencing
can be placed in steep natural channels to form a series of
check dams.
In some cases, underground conduits are best for carrying
trapped runoff from the site.
Before dredging operations which might lead to problems with
runoff from the disposal area are begun, the dredged material
should be sampled to ascertain the proper method of dis-
posal. Toxic or odorous substances in the dredged material
will require special disposal techniques. Approval for method
of disposal of dredged material is to be obtained from the per-
tinent EPA regional administrator on a case-by-case basis.
Care should be taken during design and construction to mini-
mize the amount of restoration work required.
Clearing and grubbing should be used in lieu of herbicides,
if it is necessary to remove vegetation. Good drainage should
be maintained on the site to eliminate stagnant pools, rather
than using insecticides to prevent breeding of insects. Care
must be taken not to significantly damage important ecological
systems by faulty use of pesticides, if it is deemed necessary
to use pesticides.
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5.8 RESTORATION OF EASEMENTS AFTER CONSTRUCTION
To minimize costs of restoration of easements, measures to be taken during construction
must be included in the specifications. It is often possible during restoration of easements and
rights-of-way to improve the utility and attractiveness of a site, compared with its condition
before construction, at little if any increase in cost. This is particularly advisable for property
which has been adversely affected during construction.
Proposed changes in the restoration of easements to other than the original condition must
be shown on the construction plans and be approved by the owner of the property on which
the easement is located. Vegetation which will be hardy under conditions existing at the
restored site, and which will permit quick and easy access for maintenance of the wastewater
works, should be placed according to good landscaping principles.
Subjects which should be considered for inclusion in the construction specifications include:
normal excavation backfilling
allowable trench widths
allowable working widths
rock and boulder excavation
pumping and drainage
storage of excavated material
compaction procedure
boulder and stone fill
tree protection
disposal of rock and waste excavated material
trench surface restoration
recommendations of agricultural agent
topsoil
fertilizer and soil conditioners
reseeding and revegetation
mulching
riprap and other protective surfacings.
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5.9 WASTEWATER TREATMENT DURING TREATMENT
PLANT MODIFICATION
All new works and expansions to existing works must be designed for further expansion (1).
During a works upgrading or expansion, the interruption of normal operation must be mini-
mized and will be subject to the approval of the EPA regional administrator (1). If existing
effluent quality must be maintained, it may be necessary to provide temporary treatment.
Details on process design for temporary treatment works, if required, should be included in
contract drawings and specifications. Contract documents should include provision for opera-
tion and maintenance of such temporary works.
Maintaining existing treatment levels during all periods of construction may not be feasible.
Design standards for temporary facilities may be developed after the effect of effluent on
stream water quality is determined. The importance of any detrimental effects to the environ-
ment must be evaluated before temporary works are designed. Losses to shell fishermen (22),
because of reduced disinfection efficiency, can be estimated. Loss of commercial fishing and
loss of man-days of recreational fishing can be estimated from decline in DO (determined
from accepted dissolved oxygen sag computations). Loss of swimming and boating time can
be determined by relating effects of the effluent against appropriate water quality standards.
Should water quality standards be violated, loss of swimming and boating will result. Loss of
the value of recreation man-days can be balanced against cost of disinfection, color removal,
turbidity removal, etc. Effluent standards, for use in the design and operation of any
temporary treatment works, must be approved by the EPA regional administrator.
Disinfection of effluent is required to eliminate pathogens. High rate sedimentation may be
carried out using coagulants in the remaining settling tanks while some tanks are out of
service because of construction, or temporary settling basins may be constructed. Sludge
handling might involve pumping to existing sludge facilities or holding in a temporary storage
pit dosed with appropriate chemicals. Temporary tanks could be earthen berms with plastic
liners. Multiple independent tanks may be needed to permit taking a tank out of service for
sludge removal.
Temporary chemical treatment often involves high operating cost for chemicals; however,
the capital cost of mixing equipment will be low. Lime, alum, and ferric chloride may be
used as coagulants, but the cost of materials handling and the increased sludge volumes often
make polymers a better alternative. A cost analysis of the two approaches is required.
Microscreens or high rate screens may be used in lieu of, or to augment, clarifiers. Physical
treatment, including activated carbon, may be used to remove soluble organic material.
Holding and stabilization ponds may be constructed of earthen berms with plastic liners.
Generally, temporary stabilization pond treatment may include: (a) aeration followed by
disinfection of effluent, (b) aeration with the addition of chemical coagulants followed by
settling and disinfection, or (c) facultative ponds followed by slow sand niters and disinfection.
It may be advantageous to use equipment intended for final construction during the
temporary treatment phase. For example, chlorinators and mechanical aerators might be used
for temporary treatment prior to final installation. Existing treatment processes might be
converted for temporary treatment. For example, primary tanks might be used as aeration
basins by adding floating mechanical aerators.
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Package plants which will satisfy local requirements could be used for temporary treatment
but require careful operation to obtain desired effluent quality.
The lack of process flexibility makes it desirable to monitor the temporary process, to avoid
upset and loss of efficiency. Because of the lack of flexibility and the need for rapid assess-
ment of treatment efficiency, the chemical oxygen demand (COD) or total organic carbon
(TOC) test is preferred to the BOD test. The TOC test can be performed rapidly and can
be automated.
5.10 SLUDGE, PROCESS SIDESTREAMS,
AND ONSITE DISPOSAL
Inadequately treated or raw sludge is invariably a source of odor. Guidelines for
the treatment of sludge and resulting process sidestreams are presented in the EPA
technology transfer publication Sludge Treatment and Disposal (15). Process design
information is provided in an EPA technology transfer process design manual on sludge
treatment and disposal (21). Liquid sidestreams resulting from thickening, dewatering, or
other sludge treatment processes are often potential sources of odor or require special treat-
ment before being returned to the normal wastewater treatment flow, to prevent reduction in
treatment efficiency. The final disposal of sludge is another major problem, because of
possible runoff and groundwater pollution, damage to agricultural soils, and air pollution.
Waste solids may be transported from the treatment facility to the disposal area as primary
or secondary sludge (digested or not), sludge incinerator ash, or residue from heat treatment
or wet air oxidation processes. Sludge may be piped, trucked, barged, or shipped by rail
(4, 17, 18). Shipping sludge by rail may be feasible. Chicago has used a train to haul sludge
from the city to outlying areas (18)(19). Pipeline transport eliminates the odor problem along
the route and, if economically feasible, offers an alternative to truck haul of raw or digested
sludge or filter cake. However, a pipeline system often requires a storage lagoon at the
disposal site, and open lagoons are themselves a potential source of odor.
Truck haul of waste solids is common. Generally, residue from sludge incineration and wet
air oxidation processes does not generate objectionable odor. Blowing dry ash may cause a
problem; these loads should be dampened or covered. Methods and equipment to prevent
spillage and drainage from trucks hauling liquid sludge should be provided.
Thickened, conditioned, or dewatered sludge cake may be a source of odors. If it is necessary
to haul the cake through populated areas, the truck body should have airtight closure. Truck
bodies used for hauling both sludge ash and filter cake should have a one-piece, pan-type
body to prevent leakage, because gasket fittings cannot be relied on to remain tight. Tank
trucks and portable liquid transport containers may be used to haul raw digested sludge.
Sludge Ioad4ng areas should be designed to contain odors, by enclosing sludge handling
equipment such as conveyor systems. Such equipment must still be accessible for lubrication,
cleaning, and general maintenance.
Discharge of sludge from the treated sludge hopper to the vehicle should be through an
enclosed flexible chute. Tank cars may be loaded using pressure fittings, venting the empty
tank to an odor disposal unit. Loading sites should be designed to eliminate areas where
sludge can collect and should have high pressure water hose or steam cleaning apparatus
available.
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Frequent cleaning of equipment is essential. Overloading, with consequent spillage, should
be avoided. Adequate standby vehicles and equipment should be provided.
Before discharge to treatment processes, if it is difficult to control the formation of aerosols,
disinfection should be provided if there is a possibility that the aerosols or their residues
will come in contact with humans. State and federal regulations regarding disinfection of
wastewater and sludge must be followed and standby equipment provided for emergencies, if
significant danger to the health of others might result from failure of the initial disinfection
process.
Some chlorinated organics in low concentrations are toxic to aquatic biota and humans. This
must be considered in selecting the disinfection method and/or agent to be used.
Consideration should be given to the possibility of hazardous conditions which might arise
if the containers used to transport gaseous disinfecting agents were damaged during transpor-
tation or use.
Consideration must be given to disinfection of treated wastewaters which will be used for
spray irrigation, particularly if there is any possibility that runoff can carry pollutants or
pathogens from the site to neighboring land or public bodies of water. Disposal of undisin-
fected wastewater or sludge on site is a potential danger to wastewater works operation and
maintenance personnel who must walk through the irrigated areas to perform their work.
Special boots and protective clothing should be made available for workers who must enter
or work in such areas.
5.11 GROUNDWATER POLLUTION
Groundwater is a very valuable resource—once contaminated, it is very slow to recover.
Because of the many unknowns, design measures to protect groundwater must be conserva-
tive. If there is any chance of groundwater pollution, a soils testing program should be
established, monitor wells should be installed, and a regular water sampling and testing
program should be instituted. Groundwater must be adequately protected from any degrada-
tion in use or pollution. If inadequately treated wastewater or sludge is placed on or in the
soil, there is a possibility of groundwater pollution.
Wastewater pipelines or structures can be dangerous sources of pollution, if adequate provi-
sions are not made by the designer to ensure that such pipelines or structures will be reason-
ably leakproof. Granular bedding under structure foundations or pipes can also act as a drain
and carry wastewater leakage into aquifer recharge areas.
Investigation of soils and aquifers along rights-of-way should be conducted, so that the pipe-
line and foundations can be designed to prevent wastewater leakage into aquifers. Care must
be taken in designing land application operations and plant operation and maintenance pro-
cedures, to ensure that dangerous amounts of pollutants such as nitrogen, sodium, heavy
metals, pesticides, or pathogens will not be carried into the groundwater by surface water
percolating through the soil. In general, the control methods are similar to those used to
prevent landfill leachate pollution of groundwater described in section 5.3. Other control
methods include disinfection and/or special treatment before land application. The Environ-
mental Protection Agency has developed standards to protect groundwater used for raw source
drinking water supply (23). All land application operations must insure that these standards
are maintained.
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Other adverse effects may result if nutrients or pollutants are adsorbed temporarily on fine
grained soil particles and later released to the groundwater. The adsorptive capacity of some
soils for some heavy metals and organic compounds is small, and after this capacity is
reached such soils no longer remove these pollutants from the water.
Procedures are set forth in references (20)(21) to assist in evaluating systems for land applica-
cation of treated municipal wastewater. Reference (21) contains an evaluation checklist and
is concerned with facilities plans, design plans and specifications, and operation and mainte-
nance manuals for land application systems.
5.12 REFERENCES
1. Design Criteria for Mechanical, Electric, and Fluid System and Component Reliability,
EPA-430-99-74-001 (1973).
2. United States Water Resources Council—Flood Hazard Evaluation Guidelines for
Federal Executive Agencies, Washington, D.C. (1972).
3. Sanitary Landfill Guidelines, EPA (6 April 1972).
4. MacKenthun, Kenneth M., The Practice of Water Pollution Biology, Division of Tech-
nical Support, Federal Water Pollution Control Administration, U.S. Department of the
Interior, U.S. Government Printing Office, Washington, D.C. (1969).
5. U.S. Environmental Protection Agency, Guidelines for Erosion and Sediment Control
Planning and Implementation, EPA-R2-72-015, U.S. Government Printing Office,
Washington, D.C. (August 1972).
6. Meyer, L. Donald and Kramer, Larry A., "Erosion Equations Predict Land Slope
Development," Agricultural Engineering, Vol. 50, No. 9 (September 1969).
7. Meyer, L. D., Reducing Sediment Pollution by Erosion Control on Construction Sites,
Paper Presented at Seventh American Water Resources Conference, Washington, D.C.
(October 1971 ).
8. Meyer, L. D., et al., "Erosion Runoff and Revegetation of Denuded Construction Sites."
Transactions of the American Society of Agricultural Engineers, Vol. 14, No. 1, St.
Joseph. Michigan (1971).
9. Meyer, L. D., et al., "Mulch Rates for Erosion Control on Steep Slopes," Soil Science
Society of America Proceedings, Vol. 34. No. 6. Madison. Wisconsin (November/
December 1970).
10. Wisclimeier, W. H., et al., "A Soil Erodibility Nomograph for Farmland and Construc-
tion Sites," Journal of Soil and Water Conservation (September/October 1971).
1 1. Environmental Protection Agency, Office of Water Program Operations, Control of
Erosion and Sediment Deposition From Construction of Highways and Land Develop-
ment, U.S. Government Printing Office. Washington, D.C. (1971 ).
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12. U.S. Department of the Interior, Federal Water Quality Administration, Urban Soil
Erosion and Sediment Control, U.S. Government Printing Office, Washington, D.C.
( 1970).
13. Lotspeich, Frederick B., Environmental Guidelines for Road Construction in Alaska,
Environmental Protection Agency, Alaska Water Laboratory, College, Alaska, No. 1610,
G01 08/71 (August 1971).
14. Dalton, F. E., et al., "Land Reclamation—A Complete Solution to the Sludge and Solids
Disposal Problems," Journal WPCF, Vol. 40, No. 5 (May 1968).
15. U.S. Environmental Protection Agency, Technology Transfer, Process Design Manual for
Sludge Treatment and Disposal. (October, 1974).
16. Taynes, Bertram C., "Economic Transport of Digested Sludge Slurries," Journal WPCF,
Vol. 42, No. 7 (July 1970).
17. Sparr, Anton E., "Pumping Sludge Long Distances," Journal WPCF, Vol. 43, No. 10
(October 1971).
18. Triebel, W., "Experiences With the Disposal of Sewage Sludge in Agriculture," Korresp.
Awass., No. 10 (1966).
19. Freytag, B., "Hygienic Aspects of the Utilization of Sewage and Sewage Sludge in Agri-
culture," Schr Reihe Kuratoriums Kulturbaum, No. 16 (1967).
20. Pound, C.E., and Crites, R.W., Wastewater Treatment and Reuse by Land Application—
Volume II, U.S. EPA Office of Research and Development, EPA-660/2-73-0066
(August 1973).
21. Evaluation of Land Application Systems, EPA-430/9-75-001 (1975).
22. U.S. Environmental Protection Agency, Office of Water Program Operations, Protection
of Shellfish Waters (July, 1974).
23. National Interim Primary Drinking Water Regulations, (40 CFR 141, Federal Register,
Dec. 23, 1975).
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APPENDIX A: Reference Legislation
FEDERAL LAWS AND EXECUTIVE ORDERS WHICH AFFECT THE CONSTRUCTION
GRANTS PROCESS AS ADMINISTERED BY THE ENVIRONMENTAL PROTECTION AGENCY
I. LAWS AND ORDERS OF MAJOR DIRECT SIGNIFICANCE
A. Environmental Impact
1. The Archaeological and Historic Preservation Act of 1974 (16 U.S.C. 469a-l et seq.);
2. The Clean Air Act (42 U.S.C. 1857b-l et seq.);
3. The Coastal Zone Management Act of 1972 (16 U.S.C. 1451 et seq.);
4. The Endangered Species Act of 1973 (16 U.S.C. 1531 et seq.);
5. The Federal Water Pollution Control Act, as amended (33 U.S.C. 1251 et seq.);
6. The Fish and Wildlife Coordination Act of 1958 (16 U.S.C. 661 et seq.);
7. The Flood Disaster Protection Act of 1973 (12 U.S.C. 24.1709-1, 42 U.S.C. 4001 et seq.);
8. The Marine Protection Research and Sanctuaries Act of 1972 (16 U.S.C. 1431 et seq.
33 U.S.C. 1401 et seq.);
9. The National Environmental Policy Act of 1969 (42 U.S.C. 4231 et seq.);
10. The National Historic Preservation Act of 1966 (16 U.S.C. 470 et seq.); Executive Order
11593 ("Protection and Enhancement of the Cultural Environment," May 13, 1971); and 36 CFR
Part 800 ("Procedures For the Protection of Historic and Cultural Property, January 25, 1974);
11. The Rivers and Harbors Act of 1899 (33 U.S.C. 401 et seq.) particularly 403 requiring
Corps of Engineers permit for dredge and fill activity);
12. The Safe Drinking Water Act of 1974 (16 U.S.C. 1424e);
13. The Solid Waste Disposal Act (42 U.S.C. 3259);
14. The Water Resources Planning Act of 1965 (42 U.S.C. 1962d), all as amended;
15. The Wild and Scenic Rivers Act of 1968 (16 U.S.C. 1274 et seq.);
16. Executive Order 11296 ("Evaluation of Flood Hazard in Locating Federally Owned
or Financed Buildings, Roads, and Other Facilities, and in Disposing of Federal Lands and
Properties," August 10, 1966);
17. Federal Insecticide, Fungicide, and Rodenticide Act as amended (7 U.S.C. 136 et seq.);
18. The Noise Control Act of 1972 (42 U.S.C. 4901 et seq., 49 U.S.C. 1431);
19. Administrator Decision Statement #4, "EPA Policy to Protect the Nation's Wetlands,"
February 21, 1973.
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B. Other Impact
1. The Civil Rights Act of 1964 (particularly Title VI and excluding enforcement and
compliance) (42 U.S.C. 2000e et seq.) and Executive Orders issued thereunder ;
2. The Davis-Bacon Act (excluding enforcement and compliance) (40 U.S.C. 276a);
3. The Intergovernmental Cooperation Act of 1968 (40 U.S.C. 531 et seq., 42 U.S.C.
4201 et seq.);
4. The Uniform Relocation Assistance and Real Property Acquisition Policies Act of
1970 (42 U.S.C. 1415, 2473, 3307, 4601 et seq., 49 U.S.C. 1606);
5. Executive Order 11246, with regard to equal employment opportunities;
6. The Contract Work Hours and Safety Standards Act (40 U.S.C. 327 et seq.);
7. The Copeland (Anti-Kickback Act) (40 U.S.C. 276b, 41 U.S.C. 51 et seq.);
8. The Hatch Act (5 U.S.C. 1501 et seq.);
9. Executive Order 11738, prohibiting utilization of facilities on EPA List of
Violating Facilities.
II. ACTS WHICH PROVIDE ADDITIONAL FUNDING
1. Appalachian Regional Development Act (Allows matching of EPA grants with
ARC funds);
2. Consolidated Farm and Rural Development Act (Makes grants and loans available
from the Farmers Home Administration for small towns to raise funds for their matching
share of EPA assisted projects);
3. The Demonstration Cities and Metropolitan Development Act and Intergovernmental
Cooperation Act of 1966 (42 U.S.C. 3311, 3374);
4. Housing and Urban Development Act of 1974 (Community development block grants
may be used to match EPA's 75% grant, but only for collector and interceptor sewers);
5. Public Works and Economic Development Act of 1965, as amended (Allows Economic
Development Administration to match EPA grants).
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