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
Frequently Asked Questions
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.
CDM Smith
Background
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.
| Climate Change Vulnerability | Adaptive Measures to Increase Resilience | Measures to Assess Adaptive Capacity |
|---|---|---|
| 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 | Shoreline reinforcements 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 |
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.
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.
Moving Forward
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
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.
References
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.
Research Corner
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Colorado State University
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