Significance and Use

The approach presented in this guide is a practical and streamlined process for determining the appropriateness of remediation by natural attenuation and implementing remediation by natural attenuation at a given petroleum release site. This information can be used to evaluate remediation by natural attenuation along with other remedial options for each site.

In general, remediation by natural attenuation may be used in the following instances:

As the sole remedial action at sites where immediate threats to human health, safety and the environment do not exist or have been mitigated, and constituents of concern are unlikely to impact a receptor;

As a subsequent phase of remediation after another remedial action has sufficiently reduced concentrations/mass in the source area so that plume impacts on receptors are unlikely; or

As a part of a multi-component remediation plan.

This guide is intended to be used by environmental consultants, industry, and state and federal regulators involved in response actions at petroleum release sites. Activities described in this guide should be performed by a person appropriately trained to conduct the corrective action process.

The implementation of remediation by natural attenuation requires that the user exercise the same care and professional judgement as with any other remedial alternative by:

Ensuring that site characterization activities focus on collecting information required to evaluate and implement remediation by natural attenuation;

Evaluating information to understand natural attenuation processes present at the site;

Determining whether remediation by natural attenuation is the most appropriate and cost-effective remedial alternative with a reasonable probability of achieving remedial goals; and

Monitoring remedial progress.

Application and implementation of remediation by natural attenuation is intended to be compatible with Guide E1739 or other risk-based corrective action programs.

This guide does not address specific technical details of remediation by natural attenuation implementation such as site characterization (see Guide E1912 ), sampling, data interpretation, or quantifying rates. For additional discussion and guidance concerning these technical issues for remediation by natural attenuation see Appendix X1 through Appendix X7.

This guide does not specifically address considerations and concerns associated with natural attenuation of non-petroleum constituents, such as chlorinated solvents. Care must be taken to ensure that degradation by-products will not cause harm to human health or the environment. In addition, if constituents are present which do not readily attenuate, such as methyl-t-butyl ether (MTBE), remediation by natural attenuation may not be a suitable remedial alternative or may need to be supplemented with other remedial technologies.

This guide is intended to be consistent with Guide E1599 and U.S. EPA guidance for implementation of remediation by natural attenuation (U.S. EPA, 1995, Chapter 9).

1. Scope

1.1 This is a guide for determining the appropriateness of remediation by natural attenuation and implementing remediation by natural attenuation at a given petroleum release site, either as a stand alone remedial action or in combination with other remedial actions.

1.2 Natural attenuation is a potential remediation alternative for containment and reduction of the mass and concentration of petroleum hydrocarbons in the environment to protect human health and the environment. Remediation by natural attenuation depends upon natural processes such as biodegradation, dispersion, dilution, volatilization, hydrolysis, and sorption to attenuate petroleum constituents of concern to achieve remedial goals.

Note 1Remedial goals must be established through another process as determined by the appropriate regulatory agency.

1.3 In general, remediation by natural attenuation should not be considered a presumptive remedy. A determination of whether remediation by natural attenuation is appropriate for an individual petroleum release site, relative to site-specific remedial goals, requires site characterization, assessment of potential risks, evaluation of the need for source area control, and evaluation of potential effectiveness similar to other remedial action technologies. Application and implementation of remediation by natural attenuation requires demonstration of remedial progress and attainment of remedial goals by use of converging lines of evidence obtained through monitoring and evaluation of resulting data. When properly applied to a site, remediation by natural attenuation is a process for risk management and achieving remedial goals. Monitoring should be conducted until it has been demonstrated that natural attenuation will continue and eventually meet remedial goals.

1.3.1 The primary line of evidence for remediation by natural attenuation is provided by observed reductions in plume geometry and observed reductions in concentrations of the constituents of concern at the site.

1.3.2 Secondary lines of evidence for remediation by natural attenuation are provided by geochemical indicators of naturally occurring degradation and estimates of attenuation rates.

1.3.3 Additional optional lines of evidence can be provided by microbiological information and further analysis of primary and secondary lines of evidence such as through solute transport modeling or estimates of assimilative capacity.

1.4 The emphasis in this guide is on the use of remediation by natural attenuation for petroleum hydrocarbon constituents where ground water is impacted. Though soil and ground water impacts are often linked, this guide does not address natural attenuation in soils separate from ground water or in situations where soils containing constituents of concern exist without an associated ground water impact. Even if natural attenuation is selected as the remedial action for ground water, additional remedial action may be necessary to address other completed exposure pathways at the site.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

D888 Test Methods for Dissolved Oxygen in Water

D1125 Test Methods for Electrical Conductivity and Resistivity of Water

D1293 Test Methods for pH of Water

D1452 Practice for Soil Exploration and Sampling by Auger Borings

D1498 Test Method for Oxidation-Reduction Potential of Water

D1586 Test Method for Penetration Test (SPT) and Split-Barrel Sampling of Soils

D4043 Guide for Selection of Aquifer Test Method in Determining Hydraulic Properties by Well Techniques

D4044 Test Method for (Field Procedure) for Instantaneous Change in Head (Slug) Tests for Determining Hydraulic Properties of Aquifers

D4050 Test Method for (Field Procedure) for Withdrawal and Injection Well Tests for Determining Hydraulic Properties of Aquifer Systems

D4104 Test Method (Analytical Procedure) for Determining Transmissivity of Nonleaky Confined Aquifers by Overdamped Well Response to Instantaneous Change in Head (Slug Tests)

D4105 Test Method for (Analytical Procedure) for Determining Transmissivity and Storage Coefficient of Nonleaky Confined Aquifers by the Modified Theis Nonequilibrium Method

D4106 Test Method for (Analytical Procedure) for Determining Transmissivity and Storage Coefficient of Nonleaky Confined Aquifers by the Theis Nonequilibrium Method

D4372 Specification for Flame-Resistant Materials Used in Camping Tentage

D4448 Guide for Sampling Ground-Water Monitoring Wells

D4658 Test Method for Sulfide Ion in Water

D4700 Guide for Soil Sampling from the Vadose Zone

D4750 Test Method for Determining Subsurface Liquid Levels in a Borehole or Monitoring Well (Observation Well)

D5092 Practice for Design and Installation of Ground Water Monitoring Wells

D5269 Test Method for Determining Transmissivity of Nonleaky Confined Aquifers by the Theis Recovery Method

D5270 Test Method for Determining Transmissivity and Storage Coefficient of Bounded, Nonleaky, Confined Aquifers

D5434 Guide for Field Logging of Subsurface Explorations of Soil and Rock

D5473 Test Method for (Analytical Procedure for) Analyzing the Effects of Partial Penetration of Control Well and Determining the Horizontal and Vertical Hydraulic Conductivity in a Nonleaky Confined Aquifer

E1599 Guide for Corrective Action for Petroleum Releases

E1689 Guide for Developing Conceptual Site Models for Contaminated Sites

E1739 Guide for Risk-Based Corrective Action Applied at Petroleum Release Sites

E1912 Guide for Accelerated Site Characterization for Confirmed or Suspected Petroleum Releases

Keywords

attenuation; bioremediation; ground water; intrinsic remediation; natural attenuation; passive remediation; remediation; remedial action; Attenuation; Bioremediation; Ground-water monitoring/sampling; Natural attenuation; Passive remediation; Petroleum release sites; Remedial action process/sites;

ICS Code

ICS Number Code 13.060.10 (Water of natural resources)

DOI: 10.1520/E1943-98R10

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ASTM E1943