ASTM F2534-17(2022)

Standard Guide for Visually Estimating Oil Spill Thickness on Water

SIGNIFICANCE AND USE
3.1 Estimations of oil slick thickness are useful for:  
3.1.1 Estimating amount (volume) of oil in an area,  
3.1.2 Positioning oil spill countermeasures in optimal locations,  
3.1.3 Evaluating a spill situation,  
3.1.4 Estimating volume for legal or prosecution purposes, such as for an illegal discharge, and  
3.1.5 Developing spill control strategies.  
3.2 This guide is only applicable to thin sheens (sheen and rainbow sheen up to about 3 μm). Thick oil and water-in-oil emulsions do not show visual differences with respect to thickness (1, 2).3
SCOPE
1.1 This guide provides information and criteria for estimating the thickness of oil on water using only visual clues.  
1.2 This guide applies to oil-on-water and does not pertain to oil on land or other surfaces.  
1.3 This guide is generally applicable for all types of crude oils and most petroleum products, under a variety of marine or fresh water conditions.  
1.4 The thickness values obtained using this guide are at best estimates because the appearance of oil on water may be affected by a number of factors including oil type, sea state, visibility conditions, view angle, and weather.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 28-Feb-2022
• ICS: 13.060.01 - Water quality in general
• Technical Committee: F20 - Hazardous Substances and Oil Spill Response
• Drafting Committee: F20.16 - Surveillance and Tracking

Relations

• Refers: ASTM F1779-20 - Standard Practice for Reporting Visual Observations of Oil on Water from Aircraft
• Effective Date: 01-Feb-2020
• Refers: ASTM F1779-08(2014) - Standard Practice for Reporting Visual Observations of Oil on Water
• Effective Date: 01-Mar-2014
• Refers: ASTM F1779-08 - Standard Practice for Reporting Visual Observations of Oil on Water
• Effective Date: 15-Sep-2008
• Refers: ASTM F1779-97(2003) - Standard Practice for Reporting Visual Observations of Oil on Water
• Effective Date: 10-Feb-1997
• Refers: ASTM F1779-97 - Standard Practice for Reporting Visual Observations of Oil on Water
• Effective Date: 01-Jan-1997

Overview

ASTM F2534-17(2022): Standard Guide for Visually Estimating Oil Spill Thickness on Water provides guidance on estimating the thickness of oil slicks on water surfaces using visual observations. This standard is applicable for a wide variety of crude oils and most petroleum products under diverse marine or freshwater conditions. Estimating oil spill thickness visually is essential for informed oil spill response, environmental protection, and legal compliance.

This guide is designed specifically for oil-on-water scenarios and does not apply to oil spills on land or non-water surfaces. The standard focuses on thin sheens, particularly in the range of sheen and rainbow (up to about 3 micrometers), as visual clues become unreliable for thicker oil or water-in-oil emulsions.

Key Topics

• Visual Clues for Thickness Estimation
  The standard details how to use visible characteristics-such as color changes or the presence of rainbow sheens-to estimate the thickness of an oil spill on water.

• Applicability and Limitations
  Only applicable to thin sheens and rainbows (up to 3 μm); beyond this, visual differentiation becomes unreliable.

• Factors Affecting Estimation
  Visual estimation is influenced by various factors, including:

  • Type of oil
  • Sea state and waves
  • Visibility and weather conditions
  • Viewing angle
  • Water surface conditions

• Estimate Ranges and Uncertainties
  The guide emphasizes that all estimations are best possible approximations due to the variability in appearance caused by environmental and physical conditions.

Applications

Visual estimation of oil slick thickness on water is critical in many operational and regulatory scenarios, including:

• Volume Calculation for Spill Response
  Determines the approximate quantity of oil present to guide clean-up efforts and resource deployment.
• Countermeasure Placement
  Allows responders to position containment booms, skimmers, and dispersants optimally based on slick thickness.
• Situational Assessment
  Facilitates evaluation of oil spill extent and severity, supporting environmental impact assessments and reporting.
• Legal and Regulatory Compliance
  Visual estimates of oil slick thickness support documentation and prosecution in cases of illegal discharge or accidental release.
• Spill Control Strategy Development
  Provides essential data for developing and updating oil spill control and mitigation plans.

Related Standards

Experts and practitioners working with ASTM F2534-17(2022) may also need to reference the following standards:

• ASTM F1779: Practice for Reporting Visual Observations of Oil on Water from Aircraft
  Establishes procedures for consistent reporting during overflight monitoring.
• Bonn Agreement Oil Appearance Code: Widely used international reference for visually estimating oil layer thickness at sea.
• ITOPF Guidelines: Aerial Observation of Oil at Sea, guiding observers in classifying and estimating oil on water.
• Regional and International Oil Spill Reporting Standards: Such as those prescribed by the International Maritime Organization (IMO) and regional agreements.

Practical Value

Implementing the guidance in ASTM F2534-17(2022) ensures rapid, standardized, and cost-effective assessment of oil spill thickness, enabling:

• Swift and prioritized disaster response and mitigation
• Accurate estimation of environmental impact for remediation
• Improved legal documentation for regulatory proceedings

Keywords: oil spill thickness estimation, visually estimating oil on water, oil slick observation, oil spill response, visual clues for oil thickness, oil contamination assessment, oil slick thickness standards.

By adhering to this standard, professionals enhance the reliability of oil spill monitoring and contribute to environmental stewardship and regulatory compliance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F2534 − 17 (Reapproved 2022)
Standard Guide for
Visually Estimating Oil Spill Thickness on Water
This standard is issued under the fixed designation F2534; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Significance and Use
1.1 This guide provides information and criteria for estimat- 3.1 Estimations of oil slick thickness are useful for:
ing the thickness of oil on water using only visual clues. 3.1.1 Estimating amount (volume) of oil in an area,
3.1.2 Positioning oil spill countermeasures in optimal
1.2 This guide applies to oil-on-water and does not pertain
locations,
to oil on land or other surfaces.
3.1.3 Evaluating a spill situation,
1.3 This guide is generally applicable for all types of crude
3.1.4 Estimating volume for legal or prosecution purposes,
oils and most petroleum products, under a variety of marine or
such as for an illegal discharge, and
fresh water conditions.
3.1.5 Developing spill control strategies.
1.4 The thickness values obtained using this guide are at
3.2 This guide is only applicable to thin sheens (sheen and
best estimates because the appearance of oil on water may be
rainbow sheen up to about 3 µm). Thick oil and water-in-oil
affected by a number of factors including oil type, sea state,
emulsions do not show visual differences with respect to
visibility conditions, view angle, and weather.
thickness (1, 2).
1.5 The values stated in SI units are to be regarded as
4. Summary of Thickness Estimation Results
standard. No other units of measurement are included in this
standard. 4.1 Table1hasbeensummarizedfromavarietyofliterature
sources (see Appendix X1).
1.6 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.2 It should be noted that the only physical change in
responsibility of the user of this standard to establish appro-
appearance that is reliable is the onset of rainbow colors, at 0.5
priate safety, health, and environmental practices and deter-
to 3 µm thickness. All other appearances vary with weather,
mine the applicability of regulatory limitations prior to use.
visibility conditions, viewing angle, oil type, water conditions
1.7 This international standard was developed in accor-
and color, presence of waves, and the presence of other
dance with internationally recognized principles on standard-
material on the water surface. Therefore it is important to treat
ization established in the Decision on Principles for the
these as estimates and where possible give ranges of thick-
Development of International Standards, Guides and Recom-
nesses. If volume is to be calculated, it should also be given as
mendations issued by the World Trade Organization Technical
a range of values.
Barriers to Trade (TBT) Committee.
5. Summary
2. Referenced Documents
5.1 The change in visual appearance of an oil slick on water
2.1 ASTM Standards:
provides a means to estimate oil slick thickness. Only the
F1779 Practice for Reporting Visual Observations of Oil on
appearance of rainbow colors at 0.5 µm to 3 µm is a strong
Water from Aircraft
indication of slick thickness and only in the range noted. Other
appearances change with the variables noted and thus should
be used with caution.
This guide is under the jurisdiction of ASTM Committee F20 on Hazardous
Substances and Oil Spill Response and is the direct responsibility of Subcommittee
6. Keywords
F20.16 on Surveillance and Tracking.
Current edition approved March 1, 2022. Published March 2022. Originally
6.1 oil observations; oil thickness; oil thickness estimation;
approved in 2006. Last previous edition approved in 2017 as F2534 – 17. DOI:
oil visibility; slick thickness
10.1520/F2534-17R22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to the list of references at the end of
the ASTM website. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2534 − 17 (2022)
TABLE 1 Visibility Characteristics (Appearance)
Minimum Onset Thickness (µm)
Minimum
Observable
Dark
A
Silvery Rainbow Dark
Thickness
Rainbow
Average 0.08 0.1 0.5 3 > 3
Typical 0.05 to 0.2 0.1 to 0.3 0.2 to 3 > 3
Range
A
This color is sometimes called ‘oil-like,’ ‘dark colored,’ ‘brown,’ ‘black,’ or
‘metallic.’
APPENDIX
(Nonmandatory Information)
X1. SUMMARY AND BACKGROUND OF SLICK THICKNESS DATA
X1.1 Introduction X1.2.1.1 Horstein (1972) (5) reviewed theoretical ap-
proaches and used interference phenomenon to correlate the
X1.1.1 An important tool for working with oil spills has
threshold of rainbow colors to slick thickness. The appearance
been the relationship between appearance and thickness. Little
of rainbow colors is the result of constructive and destructive
research work has been done on the topic in recent times
interference of light waves reflected from the air-oil interface
because thickness charts were available for many years (Prac-
with those reflected from the oil-water interface (Fingas et al.,
tice F1779) (Fingas et al., 1999) (3). In fact, present thickness
1999) (3). The difference in optical path lengths for these two
charts actually date from 1930 (Congress, 1930) (4).Itwas
waves depends on the refractive index of the oil.The refractive
recognized before 1930 that slicks on water had somewhat
indices of given wavelengths results in different optical path
consistent appearances. A series of experiments were con-
lengths. This difference can be given as:
ducted in the 1930s and resulted in charts that are still used.
2 2 1/2
Only a few experiments have been done in recent years. This ∆L 5 2t~µ 2 sin I! (X1.1)
Appendix will summarize this development of slick appear-
where:
ance charts.
∆L = the difference in optical path length,
X1.1.2 The early work may not have accounted for several
t = the film thickness,
factors:
µ = the refractive index of the film, and
X1.1.2.1 Effect of Slick Heterogeneity—Oils, especially
I = the angle of light incidence.
heavier ones, do not form slicks of consistent thickness on the
X1.2.1.2 Horstein points out that if ∆L contains an even
water surface. Even visual examination shows a type of ‘fried
number of wavelengths, then maximum destructive interfer-
egg’vertical profile. This effect is, however, not as relevant on
ence will occur. Destructive interference occurs when light
largerslicksandwithlessviscousproducts.Manyslicksdonot
waves are in a phase alignment that they annul each other and
cover the entire area. The effect of surface tension is to pull
thus the resulting amplitude of light is less. Constructive
some oils together so that slicklets are formed rather than one
interference is the opposite. If ∆L contains an odd number of
uniform slick.
wavelengths, then maximum constructive interference will
X1.1.2.2 Effect of Evaporation—The early experiments ig-
occur.
nored the effect of evaporation on mass balance.
X1.2.1.3 Thenthemaximumdestructiveinterferencesoccur
X1.1.2.3 Effect of View Angle—View angle is critical to
at:
observing slicks on water, especially with respect to the sun.
λ 5∆L/x (X1.2)
How this affects appearance thresholds is not fully explored.
X1.1.2.4 Eff
...