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.

1.5 This guide does not address enhanced bioremediation or enhanced attenuation.

1.6 Also, while much of what is discussed is relevant to other organic chemicals or constituents of concern, these situations will involve additional considerations not addressed in this guide.

1.7 The guide is organized as follows:

1.7.1 Section 2 lists referenced documents.

1.7.2 Section 3 defines terminology used in this guide.

1.7.3 Section 4 describes the significance and use of this guide.

1.7.4 Section 5 provides an overview of the use of natural attenuation as a remedial action alternative, including;

1.7.4.1 Advantages of remediation by natural attenuation as a remedial alternative;

1.7.4.2 Limitations of remediation by natural attenuation as a remedial alternative; and

1.7.4.3 Using multiple lines of evidence to demonstrate the appropriateness of remediation by natural remediation.

1.7.5 Section 6 describes the decision process for appropriate application and implementation of remediation by natural attenuation including;

1.7.5.1 Initial response, site characterization, selection of chemicals of concern, and establishment of remedial goals;

1.7.5.2 Evaluation of plume status;

1.7.5.3 Collection and evaluation of additional data;

1.7.5.4 Comparing remediation by natural attenuation performance to remedial goals;

1.7.5.5 Comparing remediation by natural attenuation to other remedial options;

1.7.5.6 Implementation of a continued monitoring program;

1.7.5.7 Evaluation of progress of remediation by natural attenuation; and

1.7.5.8 No further action.

1.7.6 Section 7 lists keywords relevant to this guide.

1.7.7 Appendix X1 describes natural attenuation processes;

1.7.8 Appendix X2 describes site characterization requirements for evaluating remediation by natural attenuation;

1.7.9 Appendix X3 describes considerations for designing and implementing monitoring for remediation by natural attenuation;

1.7.10 Appendix X4 describes sampling considerations and analytical methods for determining indicator parameters for remediation by natural attenuation;

1.7.11 Appendix X5 describes the interpretation of different lines of evidence as indicators of natural attenuation;

1.7.12 Appendix X6 describes methods for evaluation and quantification of natural attenuation rates; and

1.7.13 Appendix X7 describes example problems illustrating the application and implementation of remediation by natural attenuation.

1.8 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 and health practices and determine the applicability of any regulatory limitations prior to use.

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/E1943-98R04

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