Applied NAPL Science Review
Benefits of Including Climate Change Considerations in a Sediment NAPL Remedy
Editor: Lisa Reyenga, PE
ANSR Scientific Advisory Board
J. Michael Hawthorne, PG, Board Chairman, GEI Consultants, Inc.
Andrew J. Kirkman, PE, BP Corporation North America
Robert Frank, RG, Jacobs
Paul Cho, PG, CA Regional Water Quality Control Board-LA
Randy St. Germain, Dakota Technologies, Inc.
Dr. Terrence Johnson, USEPA
Brent Stafford, Shell Oil Co.
Douglas Blue, Ph.D., Imperial Oil Environmental & Property Solutions (Retired)
Natasha Sihota, Ph.D., Chevron
Kyle Waldron, Marathon Petroleum
Danny D. Reible, Professor at Texas Tech University
Reeti Doshi, National Grid
Applied NAPL Science Review (ANSR) is a scientific ejournal that provides insight into the science behind the characterization and remediation of Non-Aqueous Phase Liquids (NAPLs) using plain English. We welcome feedback, suggestions for future topics, questions, and recommended links to NAPL resources. All submittals should be sent to the editor.
DISCLAIMER: This article was prepared by the author(s) in their personal capacity. The opinions expressed in this article are the author’s own and do not necessarily reflect the views of Applied NAPL Science Review (ANSR) or of the ANSR Review Board members.
Benefits of Including Climate Change Considerations in a Sediment NAPL Remedy
Breanna Moak, Melissa Harclerode, Sean Sheldrake, Cannon Silver
For sediment NAPL corrective action to be both effective and adaptive to climate change impacts, resiliency plans that address vulnerabilities for both the site and the remedy are essential. Many state and federal regulatory programs either require or recommend an evaluation of resiliency as an important component of evaluating long-term effectiveness and remedy permanence to protect human health and the environment.
According to a 2019 Government Accountability Office (GAO) Report, climate change may result in higher frequency, and more extreme weather events that could damage remedies and lead to contaminate releases that pose risks to human and environmental health (GAO 2019). NAPL sediment remediation sites are typically in aquatic environments that are vulnerable to climate events. These environments can be subject to sea level rise, wave action, erosional and depositional forces, flooding, and stormwater flow. This may result in higher likelihoods of remedy failures if climate vulnerability and resiliency measures are not considered. NAPL sediment sites may rely on in-place containment remedies, creating potential releases of NAPL both during initial remedy implementation, and over the long term, if the remedy is adversely impacted by climate change driven extreme weather events. This makes identification of climate related vulnerabilities and the consideration of resiliency measures all the more critical in remedy effectiveness, integrity, and sustainability (triple bottom line).
Without consideration of these impacts (e.g., sea level rise, storm surge and ocean acidification), there can be adverse effects on contaminant toxicity (e.g., change in temperature or chemistry conditions transforming contaminant speciation), contaminant fate and transport, exposure and uptake rates to contaminants, and effective site operations and maintenance (O&M) (Maco et al 2018). Climate vulnerability assessment tools and climate resiliency best practices have gained traction in the environmental remediation industry, and information and guidance have come from state and federal entities and from professional organizations (ITRC 2021).
Climate change adaptation planning should include identifying climate change vulnerabilities at the site and the proposed remedies and the development and implementation of a climate resiliency plan. This can be best accomplished using a three-stage process (Figure 1). Table 1 describes how this three-stage process can guide resiliency planning in sediment remediation projects.
Figure 1. Three-stage Climate Change Adaptation Management Process, image courtesy of
EPA Climate Resilience Technical Fact Sheet for Contaminated Sediment Site (EPA 2019)
Adaptive Measures to Increase Resilience
Measures to Assess
Scour of sediment cap or underlying sediment
Designing armor layers for caps and shorelines and prioritization of removal instead of capping
Develop a robust conceptual site model (CSM) and cap model under future conditions
Suspension and displacement of in situ media and contaminated sediments
Diversion of stormwaters and associated sediments utilizing green infrastructure
Designing backfill layers to prevent displacement and higher prioritization of dredging/excavation
Develop a robust CSM under future conditions
Desiccation of submerged sediment caps
Using materials that can withstand weather extremes
Periodic precipitation and storm surge monitoring
Submergence of contaminated soils or mobilization of these soils to the water body
Acquire and protect undeveloped landscapes adjacent to the site
Periodic precipitation and storm surge monitoring
Increased contaminant flux through contaminated soils and sediment from upland groundwater table fluctuations
Design for potential future contaminant flux changes (both magnitude and location)
Periodic precipitation and storm surge monitoring
Contaminant monitoring following severe weather events
Sensitivity analyses on a range of contaminant fluxes based on extreme weather events
Widely varying wave (wind and vessel) action elevations and locations
Design shoreline reinforcements to account for potential future increase in wave action at new elevations
Wave action, shoreline, and storm surge monitoring both periodically and following severe weather events
Changes in the freshwater-saltwater boundary
Protect and restore coastal habitats and marshes adjacent to site
Develop a robust CSM under future sea level rise conditions
Periodic sea level monitoring
Changes in benthic habitat footprint due to sea level and/or wave action changes
Design to account for potential future benthic habitat changes
Develop a robust CSM under future sea level rise and wave action conditions
Periodic biological community monitoring
Table 1: Example Vulnerabilities, Resilience, and Adaptation Strategies for Sediment Sites
Applications of Resiliency Evaluations for Remediation Sites
Two sediment sites will be used as case studies to show how climate vulnerability assessments and resiliency evaluations are utilized at various phases in the remedial lifecycle. Though none of these were performed at sites with NAPL impacts, the findings could be applied to NAPL sediment sites.
Case Study: Confidential Coastal Washington Site
The site for this project was contaminated with heavy metals along a waterway in coastal Washington State. The selected remedy was a permeable reactive barrier (PRB) to prevent the mobilization of heavy metals into the waterway and the surrounding environment. A site-specific vulnerability assessment was conducted after remedy selection to identify climate
related vulnerabilities present at the site, during PRB install, and during PRB O&M. The vulnerability assessment was used to inform changes to the remedy design and O&M practices to increase resiliency.
This project followed the State of Washington Department of Ecology’s Adaption Strategies for Resilient Cleanup Remedies Guidance (Ecology 2017). Three tools were used to assess the climate vulnerabilities at the site: the National Oceanic and Atmospheric Administration’s (NOAA) Sea Level Rise Coastal Viewer Tool; the Federal Emergency Management Agency’s (FEMA) Flood Zone Mapping; and the University of Washington (UW) Impacts Group Sea Level Rise Viewer Tool. A generic representation of the NOAA tool’s visualization of various levels of sea level rise on a given site is shown in Figure 2. The FEMA tool provided insight into the current floodplain, the low-lying areas near the site that could contribute to nuisance flooding, and the locations of high tide flooding. The UW tool allowed for a look at different climate change scenarios and projected the likelihood of occurrence of sea level rise surrounding the site.
Figure 2. Example NOAA Sea Level Rise Viewer Comparing 3-feet and 6-feet of Sea Level Rise, image courtesy of CDM Smith
The vulnerability assessment concluded that there would be a low likelihood of climate change impacts on the site during implementation and in the near future. However, there are possible future impacts on the remedy due to sea level rise, therefore a resiliency evaluation was required. The resiliency evaluation concluded that no design changes would be required, although site climate change vulnerability monitoring and periodic reviews would be essential in understanding the development of potential future vulnerabilities. For example, if high tide flooding or sea level rise were immediate concerns to the mobilization of heavy metals at the site, then the design would have required adaptation to prevent this risk. Because this is not a short-term risk, monitoring and using updated climate models will be essential to determine if sea level rise is occurring at a faster rate and will impact the site.
Case Study: Confidential Client, USA
The location of this site is adjacent to a reservoir and includes contaminated sediment in portions of three creek waterbodies. Climate resiliency at this site was evaluated and incorporated during the remedy design, optimization, and performance monitoring phase (part of the O&M process). The remedy for this site consisted of capping and institutional controls. Significant flooding during the removal action caused the shoreline reinforcement to fail into one creek waterbody, prompting an optimization to reinforce the cap armoring and to perform shoreline stabilization measures.
The vulnerability assessment performed during optimization determined that alternative remedies to capping were also vulnerable to climate change impacts. These included above ground treatment components that were vulnerable to extreme temperatures and increased wind intensity, electrical power that was susceptible to interruptions, and the stabilization of contaminants into an inert material that could impact floodplain hydraulics and storage capacity.
Climate change vulnerability monitoring was also incorporated into the remedy O&M to record the frequency and location of onsite flooding events, evaluate trends in surface water flow velocity and water levels over time, and to periodically define storm conditions that may impact cap integrity and shoreline stabilization. Acoustic doppler profilers and staff gauges were installed to monitor real time creek velocity and water levels over time, as shown in Figure 3.
This riverine site highlights how vulnerability assessments can be applied to existing remedy components and be updated based on O&M vulnerability monitoring at NAPL sediment sides. This site also highlights how resiliency evaluations aid in the selection of remedy components that reduce the likelihood of remedy failure at NAPL sediment sites.
Figure 3. Climate Change Vulnerability Monitoring Station, image courtesy of CDM Smith
The case studies described above highlight successful climate vulnerability assessments and resiliency evaluations. Through these projects knowledge was gained, such as:
- Early, proactive consideration at the CSM development stage and alternative selection stages can mitigate loss of opportunities.
- Collecting accurate and relevant site data for vulnerability assessments.
- Utilizing climate models that consider variable climate change impact scenarios is advantageous.
- Assessing other site vulnerabilities such as heat island impacts, impacts of upland wildfires, proximity to impermeable surfaces, biodiversity, and nearby use provides a more comprehensive evaluation.
- Integration of strategies that contribute to the reduction of climate change impacts, such as reforestation or the use of renewable energy and green infrastructure.
- Improving stakeholder communications helps define shared resiliency goals, metrics, and tools.
A Word of Caution
When designing with resiliency in mind, there is a risk of under or over designing, which can lead to remedy failure, inefficient use of resources, and schedule delays. This occurs when climate projection models and data sets are misused, or when the likelihood of design storms or sea level rise is not understood. These issues can be addressed by having a full understanding of the model assumptions and uncertainties, sensitivity analyses, and employing the use of multiple models.
Disclaimer: The views expressed in this article are those of the authors and do not necessarily represent the views or the policies of the U.S. Environmental Protection Agency. These views have not been subject to the Agency’s review, and therefore do not necessarily reflect the views of the Agency. As such, no official endorsement should be inferred.
“Adaptation Strategies for Resilient Cleanup Remedies,” Nov-2017. [Online]. Available: https://apps.ecology.wa.gov/publications/documents/1709052.pdf.
Barbara Maco, P. Bardos, F. Coulon, E. Erickson-Mulanax, L. J. Hansen, M. Harclerode, D. Hou, E. Mielbrecht, H. M. Wainwright, T. Yasutaka, and W. D. Wick, “Resilient Remediation: Addressing Extreme Weather and Climate Change, Creating Community Value,” Remediation Journal, vol. 29, no. 1, pp. 7–18, 2018.
“Climate Resilience Technical Fact Sheet: Contaminated Sediment Sites,” Environmental Protection Agency, Oct-2019. [Online]. Available: https://www.epa.gov/superfund/climate-resilience-technical-fact-sheet-contaminated-sediment-sites.
“Integrating Resilience and Sustainability into the Remedial Project Life Cycle,” Sustainable Resilient Remediation. Apr-2021 [Online]. Available: https://srr-1.itrcweb.org/integrating-resilience-and-sustainability-into-the-remedial-project-life-cycle/#6_1_2.
“SUPERFUND: EPA Should Take Additional Actions to Manage Risks from Climate Change.” GAO-20-73. Washington, D.C.: US Government Accountability Office. https://www.gao.gov/products/GAO-20-73.
Master of Science
Colorado State University
Sediments impacted with petroleum hydrocarbons (oil) may sheen due to ebullition-driven transport or sediment disturbance. The goal of this project was to develop a screening method that can be deployed on a small autonomous watercraft that will provide a reliable indication of sheening potential of embedded oil in shallow sediments. Different potential probes and methods were explored to penetrate sediments and determine sheening potential. Preliminary probe identification focused on development of a standardized laboratory column to test different probes and penetration methods to determine which probe has the highest probability to generate a sheen. Column tests were performed that consisted of different combinations of five crude oil types and a control (no oil embedded), seven probe candidates, two types of oil deposits, two targeted sheen levels, and with or without embedded air. Based on the data collected, a direct push rod with water injection had the greatest potential to generate a sheen.
In coming newsletters, look for more articles on NAPL movement in sediment in 2022. Moving forward we are planning articles on surfactant injection case studies, bioremediation, and natural source zone depletion. Let us know if you have article ideas or would like to see articles on other topics.
The ASTM Standard Guide for NAPL Mobility and Migration in Sediments – Evaluating Ebullition and Associated NAPL/Contaminant Transport (E3300-21) is now available!
The ASTM Standard Guide for NAPL Mobility and Migration in Sediments – Evaluation Metrics (E3282-21) is now available!
The ASTM Standard Guide for NAPL Mobility and Migration in Sediments – Screening Process to Categorize Samples for Laboratory NAPL Mobility Testing (E3281-21) is now available!
The ASTM Standard Guide for NAPL Mobility and Migration in Sediment – Sample Collection, Field Screening, and Sample Handling (E3268-20) is now available!
The ASTM Standard Guide for NAPL Mobility and Migration in Sediment – Conceptual Models for Emplacement and Advection (E3248-20) is now available!
API has published the “API LNAPL Transmissivity Workbook Training Video” to assist with baildown test interpretation and identification of frequently encountered problems.
Check them all and join us on the ANSR LinkedIn page for discussion or to share your own tips and tricks!
Upcoming ITRC Training – Learn More Here.
- April 7: Harmful Cyanobacterial Blooms (HCBs) Strategies for Preventing and Managing
- April 19: Incremental Sampling Methodology (ISM-2) Update – Q&A Panel Discussion
- May 3: Bioavailability of Contaminants in Soil: Considerations for Human Health Risk Assessment
- May 5: Integrated DNAPL Site Characterization
- May 10: Long-term Contaminant Management Using Institutional Controls
- May 17: 1,4-Dioxane: Science, Characterization & Analysis, and Remediation
- June 2: Vapor Intrusion Mitigation Session 1: Conceptual Site Model for Vapor Intrusion
Mitigation, Public Outreach, Rapid Response, Remediation & Long-term
Contaminant Management Using Institutional Controls
- June 14: Vapor Intrusion Mitigation Session 2: Active Mitigation, Passive Mitigation,
Installation/ OM&M/Exit Strategy
Upcoming IPEC Training – Learn More Here.
- April 7: Environmental Compliance Assurance
- April 7: Produced/Flow-Back Water Recycling/Storage/Evaporation Ponds
- Global EnviroSummit, April 4-6, 2022 in Charlotte, NC.
- Battelle’s 2022 Chlorinated Conference. May 22-26, 2022 in Palm Springs, CA.
- 27th National Tanks Conference, September 13-15, 2022 in Pittsburgh, PA.
- MGP Conference, September 28-30, 2022 in Rosemont, IL.
- RemTECH & Emerging Contaminants Summit, October 4-6, 2022 in Westminster, CO
- AEHS 38th Annual International Conference on Soils, Sediments, Water, and Energy, October 17-22, 2022.
- 24th Railroad Environmental Conference, 2-3 November, 2022.
Upcoming Conference Abstract Deadlines
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