|
Title:
Introduction
Text: Sediment site investigation and cleanup can be challenging because of the evolving state of the science and environmental regulations. In the past, Remedial Investigations (RIs) of impacted sediment typically involved sampling strategies based on those used at terrestrial sites. However, the use of these methods is inappropriate due to the complexity of the aquatic environment. In addition, the evaluation of remedial alternatives in the Feasibility Study (FS) can be challenging because contaminated sediment remediation is a rapidly evolving field.
NAVFAC has recently developed a guidance document to help Remedial Project Managers (RPMs) in the completion of successful RI/FS efforts at sediment sites. The document is titled Implementation Guide for Assessing and Managing Contaminated Sediment at Navy Facilities.
This Web Data Sheet highlights the scope of the Guide and critical issues related to the RI/FS process at sediment sites. Click on the image to view the full text of the Guide [File is 20 MB].
|
|
Visual Description: Image of the sediment guide. Click on image to open guidance document.
|
|
Title:
Overview of Navy Policy (1 of 2)
Text: The Guide is intended to help RPMs avoid unfocused studies and to integrate data collection activities across all aspects of the RI/FS process. The Guide also complements the Chief of Naval Operations (CNO) Policy on Sediment Site Investigation and Response Action which was released in February 2002. The policy includes the following statements:
(1) All sources shall be identified to determine if the Navy is solely responsible for the contamination.
(2) All investigations shall primarily be linked to a specific Navy CERCLA/RCRA site.
(3) All sediment investigations and response actions shall be consistent with Navy policies on risk assessment and background chemical levels.
(4) Sediment cleanup goals shall be developed based on site-specific information and shall be risk-based.
(5) The Navy shall not clean up contamination from a non-Navy source where the Navy has not contributed to the risk in sediments. The Navy will not clean up a site before the source is contained. Any potential recontamination by non-Navy sources shall be documented.
(6) A monitoring plan with exit strategies shall be developed before collecting the first monitoring sample.
|
|
Visual Description: Photo of a Navy facility.
|
|
Title:
Overview of Navy Policy (2 of 2)
Text: As part of this policy, a NAVFAC Installation Restoration (IR) Sediments Framework was developed as shown here to serve as a guide to conducting site investigations and selecting response actions. The framework incorporates the principles of the Navy policy including source identification, future land use considerations, scientifically and technically defensible data collection, risk management, and remedial action evaluation when appropriate.
Click here to view the full text of the Policy on Sediment Site Investigation and Response Action.
|
|
Visual Description: Graphic of the installation restoration sediments framework developed under the Navy policy.
|
|
Title:
Scope of Sediment Guidance Document
Text: Critical sediment issues discussed in the Guide include:
- Comparison of terrestrial and aquatic site investigations;
- Addressing multiple contaminant sources (MCS) (Navy and non-Navy);
- Development of a detailed and accurate Conceptual Site Model (CSM);
- Collection of important geochemical and physical information for characterizing the source, fate, and transport of chemicals in sediment and supporting the evaluation of remedial alternatives;
- Selection and use of appropriate tests for ecological risk assessments (ERAs);
- Use of background and reference site data in risk assessments;
- Development of site-specific risk-based cleanup goals; and
- Evaluating remedial options for sediment and the associated risks and liabilities.
|
|
|
|
Title:
Aquatic versus Terrestrial Studies
Text: Sediment investigations are often more complex than terrestrial investigations for a variety of reasons as summarized in this table. Some challenges for sediment sites include the fact that sediment quality criteria are not fully promulgated, aquatic food webs often are complex or poorly understood, and risk-based threshold data are not available for many chemicals of potential concern (COPCs). In addition, sediment may require specialized methods for sampling, analysis, and remediation. Fate and transport mechanisms are also more complicated in aquatic environments.
|
|
Visual Description: Table showing focus of investigation comparisons for terrestrial site versus aquatic site.
|
|
Title:
Multiple Contaminant Sources (MCS)
Text: The most common release mechanisms encountered at Navy sites include discharges from outfalls, spills, or ships; surface water runoff; groundwater discharge; and erosion and transport of contaminated surface soils from onshore areas.
Because of the complex and dynamic hydrogeologic setting of many of these sites, it can be difficult to distinguish contributions from Navy versus non-Navy sources. Click here to view common Navy sediment COPC classes and potential sources.
|
|
Visual Description: Graphic of multiple contaminant sources. Contaminant source, runoff, fluid transport, groundwater flow, and contaminated sediment are illustrated.
|
|
Title:
Developing a Conceptual Site Model (CSM)
Text: The purpose of the CSM is to identify known or suspected contaminant sources, release and transport mechanisms, contaminated media, exposure routes, and receptors. This figure is an example of a preliminary CSM for a Navy sediment site that has been impacted by the release of chemicals from a stormwater outfall and a landfill adjacent to the shore.
A preliminary CSM should be developed for a sediment site during the RI phase and should be expanded and refined as additional site-specific information is collected. Refined CSMs should be developed for the ERA and human health risk assessment (HHRA). Further guidance on the development of CSMs is provided on the Navy's ecological and human health risk assessment Web sites.
|
|
Visual Description: Conceptual Site Model showing release mechanism, transport mechanism, exposure medium, exposure pathway, and receptor for outfall and landfill sources.
|
|
Title:
Contaminant Fate and Transport
Text: There are several processes affecting the fate and transport of contaminants in sediments.
Many persistent COPCs, particularly hydrophobic organic compounds, tend to adsorb to clay- and silt-size sediment particles as well as organic material. Therefore, the dominant transport mechanism for these contaminants is the movement of sediment particles.
Chemical and biological transformation processes will also influence fate and transport of sediment contaminants. The Guide discusses each of the mechanisms affecting fate and transport.
|
|
Visual Description: Graphic animation of contaminant fate and transport processes. Sedimentation, sediment-water interface, burial degradation and chemical reaction, and burial are shown.
|
|
Title:
Data Collection
Text: The Guide covers the key chemical and physio-chemical parameters that characterize a sediment site. It also provides an overview of study design and sediment sample collection methods. The sampling plan for a sediment investigation should address the data needs for all aspects of the RI/FS to the greatest degree possible in order to minimize mobilization costs and facilitate development of a focused, well-coordinated study. The data collected should provide sufficient information for site characterization, risk assessment, and the evaluation of remedial alternatives.
Another key reference is Methods for Collection, Storage, and Manipulation of Sediments for Chemical and Toxicological Analyses: Technical Manual (U.S. EPA, 2001). This document is referenced for details on the development of data quality objectives (DQOs), appropriate sample design (e.g., random or targeted), measurement quality objectives, and field investigation techniques. The field investigation techniques covered include vessel positioning; sediment sample collection, preservation, transport, and processing; collection of porewater samples; and quality assurance/quality control.
|
|
Visual Description: Photos of small gravity corer. Sand and silt substrates can be sampled to up to 1.5 m with small gravity corer devices. Penetration depths depend on substrate and core tube size. Core tube diameters vary from 2 cm to 6 cm, are generally metallic.
|
|
Title:
Risk Assessments
Text: NAVFAC uses a three-tiered approach for risk assessment as shown in this figure. The first tier consists of a very conservative, screening-level risk assessment intended to eliminate chemicals and areas that do not pose an unacceptable risk. This step focuses the investigation on those chemicals and areas that may pose an unacceptable risk. The Guide addresses technical issues specific to the evaluation of sediments such as physical and chemical properties of sediment that should be considered when performing a risk assessment for an aquatic site.
NAVFAC and U.S. Environmental Protection Agency (EPA) guidance should be reviewed and generally understood by the RPM before a risk assessment is initiated at any site. In addition, regular communication and involvement with the applicable regulatory agencies will facilitate the process of evaluating risks. This is especially important at sediment sites due to the multitude of additional state, national, and international regulations applicable to sediment management and the lack of promulgated sediment quality criteria.
|
|
Visual Description: Process flow diagram of a three-tiered approach for risk assessment: screening risk assessment, baseline ecological risk assessment, and evaluation of remedial alternatives.
|
|
Title:
Background (1 of 2)
Text: In accordance with Navy Policy (CNO, 2000), HHRAs should not be conducted on chemicals that are present at levels less than background chemical levels (i.e., anthropogenic or naturally occurring levels); therefore, sediment concentration data should be compared to available background concentrations.
All chemicals determined to be present below background levels should be eliminated from the Navy remedial evaluation process and those that exceed should be retained as COPCs. This is to ensure that the investigation is focused on those COPCs that are related to site activities such that incremental risks associated with Navy activities are quantified.
|
|
Visual Description: Map of Big Spruce Bay areas showing sediment sampling locations.
|
|
Title:
Background (2 of 2)
Text: Determining background in contaminated sediments poses a particularly important and complex problem as contaminants in the aquatic environment can be transported long distances from many potential sources. Therefore, it may be particularly difficult to identify contaminant sources and determine the scope of Navy cleanup responsibility. Background conditions may be accounted for in one of the following two ways:
Distinguishing COPCs from background chemicals
Determining background levels of COPCs
Techniques for statistical analysis of chemical data are fundamental components of the background analysis process. However, statistical analysis alone is not sufficient to fully understand and define the background conditions that exist at a particular site. Background chemicals that occur at a site, and the fate and transport of COPCs, depend on physical and anthropogenic characteristics of the site and the surrounding area. Site-specific factors such as physical and depositional processes must be considered during the background analysis.
Click here to view Navy Guidance on Background Analysis for Sediment.
|
|
|
|
Title:
Site-Specific Cleanup Goals
Text: According to a National Research Council (NRC) study:
"The mechanisms of the regulatory process in a given situation depend on where the sediments are located; where they will be placed; the nature and extent of the contamination; and whether the purpose of removing or manipulating the sediment is navigation dredging, environmental cleanup, site development, or waste management (NRC, 1997)."
As a result, stakeholders may focus on different COPCs, cleanup criteria, or goals that drive proposed actions in the sediment management process. Since there are no chemical-specific applicable or relevant and appropriate requirements (ARARs) for sediments at most sites, Navy Policy includes the following guidelines for the development of cleanup levels for sediment sites (CNO, 2002):
Risk-based sediment cleanup levels should be developed using site-specific information;
The cleanup levels must be risk-based and achievable;
Ecological screening values such as published benchmark values must not be used as cleanup levels;
Cleanup levels must not be lower than background levels.
|
|
Visual Description: Table: Further Guidance for Development of Remediation Goals for Sediment. Links to guidance documents are presented.
|
|
Title:
Evaluating Remedial Options
Text: Contaminated sediment remediation is a rapidly evolving field. The Guide provides an overview of remedial options including monitored natural recovery, in situ capping, and removal. The focus of the document is on major technical and management issues related to these remedial alternatives. References are also provided for more detailed technical information.
Other issues addressed in the Guide include planning considerations, determination of the volume of sediment requiring cleanup, remedial alternative selection, monitoring considerations, and management of sediments in areas requiring maintenance dredging.
|
|
Visual Description: Photo of sediment remediation site.
|
|
|
|
Title:
Contact
Text: For more information about the NAVFAC Sediment Guide, please contact:
PRTH_NFESCT2@navy.mil
|
|
|
|
|
