Sea-Tac Airport International Arrivals Facility PCB Remediation

The Problem:

With traffic growing by 41 percent over the last five years, Sea-Tac Airport is now the ninth busiest airport in the US. To meet its goal of increasing the number of international flights and destinations over the next 25 years, the Port of Seattle is building a new, 450,000 square-foot expanded International Arrivals Facility (IAF). This new facility will nearly double the international capable gates—increasing passenger capacity, increasing size and number of bag claim carousels, and ultimately reducing passenger connection time. During construction of the IAF, polychlorinated biphenyl (PCB)-contaminated soils were encountered at a former airline hangar maintenance building. This discovery initiated a remediation project within an active and congested construction site.

Photo Credit:  Port of Seattle

Photo Credit: Port of Seattle

How we helped:

Aspect and our teaming partner, DH Environmental, conducted environmental investigations and remediation in accordance with Toxic Substances Control Act PCB regulations. The Port used Aspect’s expertise in source identification and extent delineation, developing a conceptual site model, managing cleanup of PCB-contaminated soils, and navigating regulatory oversight by EPA and Ecology. Aspect also responded quickly to vapor intrusion concerns by evaluating vapor intrusion risk and designing a vapor barrier solution for potentially affected portions of the IAF. Groundwater downgradient from the source area was also evaluated to ensure the contaminants were not migrating via a groundwater pathway.

Milestones for the Port

No interruptions to the construction schedule or public usage occurred during the investigation and remediation activities. The IAF is on target to open in the last quarter of 2020 and welcome international travelers to the Seattle region.

PLIA's Revolving Loan and Grant Program

The Problem

With around 9,000 underground petroleum storage tanks (USTs) and systems across Washington state, petroleum leaks and cleanup is a big issue for business owners, homeowners, and regulators. The traditional leaking UST cleanup process is typically counted in years and often stymied by the lack of available regulatory staff to handle the large volume of sites efficiently. To help remedy this, the state’s Pollution Liability Agency’s (PLIA’s) created new programs in 2018 to speed up the cleanup process and restore leaking UST sites to productive use. One of these new initiatives is the Revolving Loan and Grant Program that provides financial assistance to owners and operators of underground storage tanks (UST) to:

  • Remove, replace, or upgrade aging fuel systems to prevent leaks

  • Cleanup historical or ongoing contamination caused by a UST release; or

  • Install new and convert existing fuel systems to dispense alternative fuels, including electric vehicle charge stations

To complete these goals, PLIA hired a team of technical consultants to perform Preliminary Planning Assessments (PPAs) at UST sites throughout Washington state.

Learn more about PPAs here and PLIA here.

PLIA Loan and Grant Program Flow Chart

PLIA Loan and Grant Program Flow Chart

How we helped:

As a prime consultant for PLIA, Aspect is performing PPAs for petroleum-contaminated USTs sites statewide. The scope of the PPAs include reviewing existing data and reports to identify data gaps, completing remedial investigations to fill in data gaps with respect to contamination and exposure pathways, and recommending a cleanup strategy to help site owners achieve regulatory closure. The final PPA Report is intended to satisfy the Washington State regulatory requirements for remedial investigations and feasibility studies and select a preferred final remedy for each site based on input from multiple stakeholders.

PPA Milestones:

With Aspect’s help, PLIA’s revolving loan and grant program is an effective and efficient government funding model to support owners and operators meet financial responsibility and environmental cleanup requirements for USTs.

PLIA Gas Station.jpg

The Oen Family’s Quilcene Site: A PLIA Success Story

Since 1928, Sandy and Linda Oen’s family have owned a service station and repair shop in Quilcene, WA. In 1997, they discovered a gasoline release at the site resulting from retail station operations and leaking USTs. Having been denied insurance coverage and any assistance from major oil companies, the Oen’s undertook the cleanup themselves. 

Between 1997 and 2004, investigation and cleanup activities included decommissioning of four USTs,  excavating over 90 tons of petroleum impacted soil, and bioremediation of residual soil impacts.  In the course of investigation and cleanup activities, the business was closed in 2001.

In 2006, the Oen’s sought regulatory closure of the cleanup and entered the Washington State Department of Ecology’s Voluntary Cleanup Program. Ecology determined that further action was necessary to complete the site characterization and select a final remedy. In 2012, the Oen’s resumed work with their environmental consultant to perform a site assessment to determine whether soil impacts were remediated, but the mounting costs of the investigation and cleanup activities stalled further progress.

In 2017, PLIA’s loan and grant program has allowed the Oen’s to work with Aspect to complete the remedial investigation and the results indicated that soil and groundwater at the site were in compliance with Washington State’s cleanup levels. Based on these findings, the site recently received a no further action determination from PLIA, thereby restoring the value to the property and bringing the site to closure for the Oen’s.

Mount Baker Gateway Affordable Housing Redevelopment - Seattle, WA

Over the past two years on behalf of Mt. Baker Housing Association, the Aspect team, along with legal partner Perkins Coie, has led a unique multi-property acquisition, cleanup action and redevelopment project in south Seattle. This project spans five properties and will result in the construction of two mixed-use buildings for 150 units of affordable housing, as well as commercial use. Located in an underserved part of south Seattle near the Mount Baker Light Rail Station, the site’s soil and groundwater are contaminated from releases from previous dry cleaners and gas stations.

Aspect has led this first-in-state brownfields project in concert with Washington State Department of Ecology (Ecology) through a Prospective Purchaser Consent Decree (PPCD) and Redevelopment Opportunity Zone (ROZ). The PPCD and ROZ combination allows State grant funds to be directed to non-profit housing developers. To establish cleanup cost estimates, Aspect completed a multi-phased site characterization program for both environmental and geotechnical engineering purposes. Dozens of explorations have been completed on unused property, within operating businesses, and on rights-of-ways. We have coordinated schedules and permits and we’ve interacted with legal counsel, regulatory agencies, and the design team. Our work is critical to understanding, and then managing, the risks that come with soft ground and fill soils, slopes, high groundwater table, and contaminated soil and groundwater.

Part of our outreach to the MBHA community has involved some of its youngest members. We have coordinated with the Resident Services Coordinator to engage school-age residents through the field work happening in their neighborhood. Kids have observed our groundwater monitoring rounds as Dave Cook and Senior Geologist Jessica Smith explain what is happening and what we are looking for. They will continue these visits as the project progresses to share results from the sample and what that data tells them about how the contaminants are behaving underground.

Environmental Investigations, Monitoring, and Remediation Services at King County Closed Landfills

Providing ongoing maintenance, and routine monitoring of groundwater, surface water, wastewater and landfill gas to satisfy post-closure requirements,  King County maintains custodial responsibilities for nine closed landfills (under WAC 173-304 and 173-351). At four of the closed landfills (Cedar Falls, Vashon Island, Enumclaw, and Duvall), Aspect provides hydrogeologic and engineering services to support the County in meeting reporting and compliance requirements of the Seattle-King County Department of Public Health, Ecology, and Puget Sound Clean Air Agency.  

We have helped develop landfill gas and groundwater monitoring networks; provided hydrogeologic characterization and site conceptual model development, monitoring, and aquifer testing; and contributed to engineering controls development.   Our hydrogeologic characterization has supported groundwater, gas, and surface water migration assessments; environmental assessments of groundwater, leachate and gas systems; and pre-design level assessments of environmental control systems. Engineering controls have included landfill gas system collection and treatment upgrades, design and monitoring of an evapotranspiration (Poplar) cover, and leachate collection improvements. 

Jefferson County Closed Landfill Groundwater Monitoring

To help Jefferson County streamline post-closure monitoring and reporting required by Jefferson County Public Health and Ecology (under WAC 173-304), Aspect developed a database to manage over 20 years of data to support statistical analyses on the groundwater quality data. The groundwater monitoring program includes groundwater sampling, water-level measurements, groundwater-flow direction and velocity, in addition to statistical data analysis. Our statistical analyses includes:  Time Series Plots, Sen’s Slope Estimator Plots and Mann-Kendall Tests, Box and Whisker Plots, and Mann-Whitney and Kruskal-Wallis Tests. The statistical methods efficiently evaluate if groundwater resources could be impacted by potential releases from the landfill.   

Port Angeles Landfill Engineering Services

Located on a steep bluff above the Strait of Juan de Fuca, Port Angeles’s 3-cell landfill was closed under three regulatory statutes (WAC 173-301, 173-304, and 173-351). Aspect  provides ongoing compliance and reporting to support all post-closure requirements. Analyzing geochemical data, we assess the groundwater and leachate monitoring program. We have addressed gas flare operations and maintenance, recommending strategies such as flow balancing and infrastructure improvements, and assisting with gas collection during relocation of a solid waste cell. We have also evaluated greenhouse gas emissions following EPA protocols. 

Georgetown Area RI/FS and Compliance Monitoring of Chlorinated Solvent Plume

A chlorinated solvent plume is impacting soil, groundwater, and soil vapor in Seattle’s Georgetown neighborhood. Aspect is working on behalf of Art Brass Plating to investigate and cleanup the plume. Our work includes completing the RI, initiating a source control air sparging/soil vapor extraction system, and leading public participation over an approximate six block area. We also monitor and mitigate against vapor intrusion potential in more than 20 neighboring buildings to protect against exposure while groundwater remediation progresses. We negotiated an Agreed Order with Ecology that enables facility-specific investigation and coordinated data sharing with the area potentially liable parties (PLPs). 

Gates Foundation Headquarters Redevelopment Integrated Remediation

In redeveloping a site adjacent to the Seattle Center grounds as the location of their new headquarters campus, the Bill and Melinda Gates Foundation negotiated a property transfer that obligated the Seattle Center to address groundwater remediation of the former vehicle maintenance site. Helping the Seattle Center meet the groundwater remediation obligations, Aspect led the groundwater assessment and remediation efforts with an emphasis on integrating cleanup into the redevelopment plans, designing a full-scale air sparging (AS) and soil vapor extraction (SVE) remediation system for phased installation. The first phase of AS/SVE was successfully installed in the pre-construction footprint and operated while the campus design and permitting process was completed. The second phase of the remedial system was installed within the active excavation footprint. By integrating the remediation system into the campus design, the second phase of the remedial action was designed to continue once the structure was completed.


The Bremerton Gasworks is a former manufactured gas plant located along the Port Washington Narrows in Bremerton. The Gasworks produced fuel gas from about 1930 until 1963. Byproducts of the gas manufacturing process have contaminated soil, groundwater and sediment at the site. Aspect is performing investigation and cleanup activities for Cascade Natural Gas Corporation, who has entered into an Administrative Settlement Agreement and Order on Consent with the US Environmental Protection Agency for the performance of a remedial investigation and feasibility study under CERCLA.

Technical and Litigation Support for Closed Pasco Landfill

To protect human health and the environment, and to limit long-term financial liabilities, Aspect provides technical and litigation support to a select group of Potentially Liable Parties (PLPs) at the Pasco Landfill Site. The Site is on the National Priorities List and is regulated by Ecology under MTCA.  Our technical support includes optimizing a 24-well, landfill-gas collection system to prevent potential groundwater impacts, and maintaining flare operations to destroy hundreds of pounds of VOCs per day. Our litigation support includes forensic assessments in anticipation of cost recovery actions by other PLPs, and negotiation with Ecology to develop an effective Cleanup Action Plan.

Ameron Industrial Stormwater General Permit (ISGP) Support

Aspect is assisting a concrete pole manufacturer complete stormwater infrastructure improvements to comply with their ISGP. The facility is on a Port of Everett brownfield undergoing MTCA cleanup. We developed, coordinated, and implemented a strategy to fast-track remediation of overlying contaminated soils to facilitate replacement of their storm drainage pipes. Our approach resulted in faster removal of 2,000 cubic yards of contaminated soil, improved ISGP compliance, better site drainage, and lower construction cost by separating the work from the RI/FS process. Our involvement in both the remediation and stormwater work allows adaptation of the project to changing conditions.

Transfer Station Underground Injection Control (UIC) Design and Permitting, Pasco, WA

Aspect assisted in upgrading the stormwater management system for a municipal waste transfer station in Pasco. We authored a SWPPP, evaluated and designed upgrades to the stormwater treatment and disposal system to enhance protection of groundwater, and permitted the existing and new drywells under the Washington State’s UIC regulations.

Auto Recycler Stormwater Treatment System Design, Renton, WA

Aspect designed an innovative media-filtration treatment system to complete a Level 3 Corrective Action at a 5-acre auto-recycling facility as a component of settling a Clean Water Act citizen suit.  Our design was aimed at treating low to moderate levels of copper and turbidity. The media bed consisted of oyster shells over a bioretention soil mix. The system was constructed by the client at low cost. The client has not triggered a Level 2 or 3 Corrective Action since installation of the system.

Duwamish Marine Terminal Industrial Stormwater General Permit Support

After providing expert support during settlement of a Clean Water Act citizen suit, Aspect designed an above-ground media-filtration stormwater treatment system for a 5-acre marine terminal and barge loading facility on the Duwamish River.  Our design included an innovative collection and conveyance system to avoid soil disturbance along the shoreline and reduce local permitting requirements. The client has not triggered a Level 2 or 3 Corrective Action since installation of the system in 2011.

One Site. Four Sources. One System.

The groundwater beneath an eight-acre shopping center exhibited chlorinated solvent impacts from four different source areas of varying ages. 

To sort out the complexities of multiple sources with multiple responsible parties, Aspect hydrogeologists distinguished the relative solvent contribution from each historical source and developed a site conceptual model that was used to reach an equitable cost-sharing agreement. At the same time, our remediation engineers pilot tested an in situ chemical oxidation system for groundwater treatment without disruption to the active retail facility.

The final remediation system treats all source areas through one air sparge and soil vapor extraction (AS/SVE) system consisting of 16 soil-vapor extraction wells and 47 air-sparging wells spread over an acre of the property.

Olympic Sculpture Park Site Remediation

Seattle Art Museum (SAM) with the City of Seattle formed a public development authority to obtain remedial action grant funding for the cleanup and redevelopment of an 8-acre former fuel facility on the downtown Seattle waterfront for use as a park. As environmental lead, Aspect helped the development team incorporate the requirements of the Cleanup Action Plan (CAP) into the park design, integrating remedial elements into the infrastructure requirements. Many of the larger costs for park construction were covered as remediation expenses under remedial action match funding, providing substantial cost savings for the redevelopment project.

Metal Fabricator Industrial Stormwater General Permit Support, Seattle, WA

A metal fabricator and electrical supplier was sued under the Clean Water Act for elevated concentrations in stormwater zinc just weeks before of a Level 3 Corrective Action deadline. Aspect quickly determined roofing was the primary source and negotiated installation of a roof downspout filter—meeting the deadline and greatly aiding settlement. After settlement, we assisted the client in coating the roof to avoid ongoing maintenance costs. The site now routinely meets all benchmarks.

Log Yard Industrial Stormwater General Permit Support (ISGP), Hoquiam, WA

Aspect assisted a small, partially paved log yard respond to a Clean Water Act citizen’s suit. After investigating the fecal coliform monitoring requirement, we determined that Ecology erred in requiring additional monitoring and successfully worked with Ecology to eliminate the requirement. As a component of settling the lawsuit, Aspect updated the SWPPP, performed employee training, recommended operational and structural BMPs, and participated in Consent Decree negotiations.