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Expedited Site Characterization of Mixed Chlorinated Solvents and Petroleum Dense Non-Aqueous Phase Liquid (DNAPL) Using Multiple Investigative Techniques in Conjunction with Mobile and Fixed Labs at Fort Lewis Logistics Center, Fort Lewis, WA

Triad Elements Used

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Table of Contents

  1. Site Information
  2. Project Information
  3. Triad Approach Information
  4. Supporting Information



In 1997, Fort Lewis Public Works requested the assistance of the U.S. Army Corps of Engineers (USACE) to perform a Remedial Investigation at the Site, focusing on determining if significant dense non-aqueous phase liquid (DNAPL) was present within the East Gate Disposal Yard (EGDY) and acting as a long term source for an approximately 18,000 foot long groundwater plume of trichloroethene (TCE) that had previously been delineated. The EGDY is an area encompassing approximately 35 acres in which debris and mixed solvent/hydrocarbon wastes were buried in scattered trenches. The USACE performed systematic planning, culminating in the development of a technical approach for NAPL source area and release characterization. The first phase of the site characterization occurred in 1998-1999. The dynamic field investigation approach was split between two mobilizations approximately mid-way through the investigation to allow for an Engineering Evaluation/Cost Analysis (EE/CA) conducted in 2000 to determine what remedial actions, if any, would be taken in the source area. Results of the EE/CA led to selection of drum excavation/removal and thermal remediation to remediate the source area. Drum excavation was conducted in 2001 between investigation phases. The second investigation phase occurred in 2001-2002 and incorporated data from the drum removal and the first phase to refine the CSM and collect additional data necessary to support thermal remediation. A contract for thermal remediation was awarded in early Fall of 2002.

Highlights of applying the Triad Approach for this project chiefly concern the application of dynamic work strategies (DWS) and field-based analytical technologies, and include:

  1. Design of a high-resolution, DWS sampling and analysis program to increase data density and limit decision uncertainty in real-time. Field crews and the project manager were able to review data as it was produced in the field and then use that knowledge to update the CSM and determine appropriate future sampling locations necessary to complete project objectives.
  2. The CSM of the source area was continuously updated during all phases of the investigation and remediation to provide decision makers with the necessary information to determine where and how to collect more data and when characterization was complete.

Based on the application of the adaptive sampling strategy and real time updates of the CSM, data of sufficient density and quality were collected in Phase I of the site characterization to determine the location of all disposal trenches and identify the general location of three primary DNAPL hot spots ("Areas 1, 2, and 3"). Disposal trenches were excavated and an estimated 40,000 pounds of TCE in DNAPL were removed. The second phase of the site investigation was focused to rapidly and efficiently collect the necessary data to support the thermal remediation contract award.

1. Site Information

Site Name Fort Lewis Logistics Center, East Gate Disposal Yard (EGDY)
Location Tillicum, WA
Site Type  Disposal Pit
Site Regulatory ID  WA7210090067
Project Lead Organization Fort Lewis Public Works
Project Lead Type  U.S. Army Lead
Regulatory Lead Program  Superfund Remedial
Triad Project Status Field Program Completed
Reuse Objective Identified  Yes
Proposed Reuse:  Industrial with Land Use Controls

Background Information About Site 

The Site occupies approximately 35 acres and operated as an industrial landfill from approximately 1946 until the mid-1970s. Spent petroleum hydrocarbons contaminated with chlorinated solvents (primarily from vehicle maintenance work) were poured into open trenches as free liquids and also disposed in these trenches as drummed waste. Construction debris and other miscellaneous industrial and military scrap materials were also disposed in the trenches.

In 1985 the EPA confirmed groundwater contaminated with TCE under the city of Tillicum. In 1986, TCE was confirmed to be originating from the EGDY. A remedial investigation/feasibility study (RI/FS) was conducted in 1986-1988. In 1990, a Record of Decision (ROD) was signed, and pump and treat was selected as the preferred remedy for the upper aquifer and also for the lower aquifer as necessary. The pump and treat system for the upper aquifer began operations in 1995. The source area investigation began in 1999 and was completed in 2002 with an EE/CA and drum removal remedial activity occurring between two investigation phases.

Fort Lewis Public Works set a goal of completing source area remediation by 2007. Thermal remediation was active at the site when this profile was written and was scheduled to be completed by 2007.

Contaminant(s) of Concern 

Contaminated Media 

Project Results and Outcomes 

The first phase of the source area investigation identified the locations of metallic debris-filled trenches using an electromagnetic survey. Other, non-metal containing trenches were identified from historical aerial photos. This set the boundaries of the disposal site, which were previously unknown due to lack of records or site controls (such as perimeter fences), and indicated that the site was much larger (i.e., 35 acres) than the originally identified 13 fenced acres. High-resolution site characterization (HRSC)using multi-level direct push groundwater sampling with on-site gas chromatography (GC) analyses led to rapid identification of three major hot spots of groundwater contamination where DNAPL was likely present and acting as a continuing long-term source of groundwater contamination. Exploratory trenching with a backhoe revealed the presence of intact DNAPL-filled drums with up to 75% TCE.

The results of the Phase I investigation were used to develop an EE/CA that determined that aggressive source removal was the best long term strategy for reducing risk and costs of operation of a pump and treat system in excess of 100 years. Thermal remediation of the three DNAPL hot spots was chosen as the remedial technology for source removal. A disposal trench excavation/drum removal action was also conducted which resulted in recovery of an estimated 40,000 pounds of TCE in DNAPL from drums and incidental contaminated soils.

The Phase II investigation was planned to collect data sufficient to allow contracting for services to design a thermal treatment system. Plans and specifications for the thermal remediation contract were developed during the site investigation and removal action to ensure data were collected that were adequate to support the design. A contract for design, construction, and operation of a thermal treatment system was awarded within six months of completion of the Phase II investigation. Further application of the Triad Approach during the thermal treatment program is described in another Triad profile.

2. Project Information

Project Objectives/Decisions 

Fort Lewis Public Works identified a need, based on an Explanation of Significant Differences (ESD) to the site ROD, for characterization to determine the presence of DNAPL, perform an EE/CA to determine remedial actions, and obtain sufficient information using limited sampling mobilizations to develop a mature CSM and support the design of remedial actions for the source area.

Remedial Phase

Site Investigation (Includes RI/FS or Similar Detailed Investigation Work)

Triad Project Benefits 

Flexibility allowed changes in investigation and remediation strategy to occur simultaneously resulting in efficient use of time and money. Real-time, high-resolution data and decision-making by highly qualified staff assured high quality and complete data were collected to support the intended uses of the data.

Cost and Time Savings 

The work was accomplished with minimal mobilizations, because the necessary quantity and quality of data were collected in each phase. Reduced mobilizations results in less time needed to plan and fund additional phases.

Cost savings are estimated at 40-50% based on avoiding the likely need to nearly double the number of sampling points required for the Triad Approach if a standard grid was implemented with no adaptive ability to optimize sampling locations based on near real-time data. The time savings is estimated at 1-2 years based on avoiding the need to develop and approve plans for additional field mobilizations and implement contracting for additional mobilizations.

3. Triad Approach Information

Systematic Project Planning 

Systematic project planning was conducted for both phases of the investigation. A CSM was generated at the beginning of the first phase as a basis for identifying data gaps to be filled during the site investigation. The CSM was updated continuously during each phase of the investigation. The CSM consisted of geologic cross-sections, maps of known contaminant distribution, locations of known disposal trenches and hydrogeologic data on groundwater flow. Uncertainty at the beginning of the first phase of investigation was high. The total aerial extent of trenching activities was roughly known from historical aerial photos, but many trenches were not well documented in the spotty aerial photographic record. An electromagnetic geophysical survey was conducted to reduce the uncertainty of trench locations by identifying buried metallic debris.

Because the disposal area was large (i.e., 35 acres) and the locations of DNAPL were unknown due to a lack of groundwater sampling data, groundwater samples were collected using a direct push rig to collect discrete groundwater samples from multiple depths in the portion of the aquifer suspected to be contaminated with DNAPL. Uncertainties in selecting locations to collect water samples were reduced by having an on-site lab to provide rapid turn around of water quality data. This rapid data turn around allowed optimal placement of subsequent water sampling locations until the locations of high concentrations of TCE indicative of DNAPL had been delineated. On-site laboratory data quality was sufficient to determine order of magnitude variations in TCE concentration from sample to sample. Exploratory trenches were excavated to eliminate the uncertainty of whether or not non-leaking and leaking drums of DNAPL were still present in the vadose zone. It was confirmed with fewer trenches than originally planned that many drums of TCE contaminated hydrocarbons were present in many of the old disposal trenches identified with the Electromagnetic geophysical survey.

The CSM was updated using data from the first phase of investigation and the drum excavation/removal action and was used as the guide to planning the second phase of the investigation. The primary data quality objective (DQO) for the second phase of investigation was to obtain the data necessary to design a thermal remediation system. High-resolution definition of the vertical and horizontal extent of DNAPL in the subsurface was critical to establish a volume of space to be treated to contract specified performance criteria. This goal was achieved by fielding several different sub-surface exploration technologies to determine which technology would provide adequate data for the least cost. Rotosonic drilling combined with NAPL observation techniques (i.e., sheen test, UV fluorescence, hydrophobic dye tests, photoionization detector (PID), and visual) and fixed-base laboratory soil analyses with 72 hour turn around time were selected as the primary technique for delineating the extent of NAPL in the course sand, gravel and cobble sediments present at the site. Uncertainties related to defining chlorinated versus non-chlorinated NAPL were minimized by selecting NAPL contaminated soil for analysis at the fixed-base laboratory for total petroleum hydrocarbon (TPH) and volatile organic compound (VOC) analysis. Multi-port monitoring wells were installed at key locations throughout the source area to characterize the vertical distribution of TCE in shallow and deep portions of the aquifer where direct push technologies could not reach. Many shallow piezometers were installed with direct push techniques to help develop a higher resolution map of the groundwater piezometric surface, producing a better understanding of the complicated groundwater flow regime at the site.

Collaboration between contractors, USACE field and office staff and Fort Lewis Public Works was managed successfully by sharing data through an internet-based data and document management site. The rapid availability of information allowed decision makers in the field and in the office to continuously optimize the investigative strategy.

Project Team Description 

The Fort Lewis Public Works project manager was the principal decision maker for the Site. Other stakeholders with input to the site decisions included the USACE project team, the USGS, Pacific Northwest Laboratory — Battelle, EPA Region 10, and the EPA Office of Research and Development's (ORD's) Kerr Laboratory in Ada, Oklahoma.

The USACE provided technical staff support for planning and conducting the investigations, plus contracting to mobilize technical support from Architect-Engineering service firms, laboratories and drilling contractors. USACE's staff provided the principal project management support as well as technical leadership in geosciences, risk assessment, engineering, field sampling and data collection, analytical chemistry, and quality assurance.

Dynamic Work Strategies 

In both phases of the site investigation, data were collected using one specific tool at a time. Data from each tool were reviewed as data became available and near real-time decisions were made as to how much additional data to collect, from where to collect additional data, and when to terminate/initiate data collection activities. These decisions were made by a core team of decision makers with representatives from each stakeholder organization. Data were typically processed and the CSM updated by USACE office personnel. These CSM updates were provided to all decision makers routinely. Team decisions were typically made during teleconferences as not all participants were located within commuting distance to a central location.

Examples of how dynamic work was conducted in the field include:

Decision Logic 

The DQOs developed for the investigation were continuously reviewed during the investigation and compared to the updated CSM to determine how and where to collect more data and when to stop collecting data once the DQOs were met. A suite of investigation tools (e.g., direct push groundwater sampling, rotosonic core drilling, geophysics, excavation) were provided to allow flexibility in selecting or rejecting investigation techniques based on the success of these techniques at meeting the DQOs.

The decision logic flow diagrams are located in the Phase 1 and Phase 2 Management Plans that are linked at the end of this profile.

Real-Time Measurement Technologies 

Real time measurement technologies included:

Technology Category(s) for Sampling and Analysis 

Specific Technology(s)/Model Used (e.g., SCAPs) 

Technology Vendor(s)

The SCAPS platform is currently only available through the USACE, however, there are some commercial vendors using similar LIF technologies.

Attached Technology Quick Reference Sheet (TQRS) Form 

TQRS pending

Data Quality Assessment 

The QA/QC program involved the analysis of standard QC samples (duplicates, spikes) and other method QC checks (PE) in the on-site analytical laboratory. Real-time analytical data were evaluated using information gained from a combination of investigative techniques and compiled in the continuously updated CSM. The varied data sets from these techniques managed different forms of uncertainty, collaborating to produce a weight-of-evidence CSM that supported decision-making at a level of confidence acceptable to the project stakeholders.

Data Management Approach and Tools 

Data management tools included spreadsheet, database, statistical packages, contouring software and a web-enabled data and document sharing repository. Decision support tools (DSTs) were not used as part of the investigations.

4. Supporting Information

Key Triad Project Milestones 

Dates of Operation - Field Work

October 1998 to April 1999. Phase I of the NAPL investigation

January 2001 to July 2001. Trenching/drum removal remedial action

June 2001 to April 2002. Phase II of the NAPL investigation

Source(s) of Information

Electronic Documentation of Supporting/Related Information

PDF Fort Lewis EGDY Phase II Final Management Plan (28 MB)
PDF Fort Lewis Final EE/CA Executive Summary (78 KB)
PDF Fort Lewis Final Phase I Technical Memorandum (17 MB)
PDF Fort Lewis Phase II Remedial Investigation - Field Investigation Report (17 MB)

Point(s) of Contact 

Richard Smith
U.S. Army Corps of Engineers, Seattle District
4735 East Marginal Way South
Seattle, Washington  98134
Telephone icon 206-764-3309

Last Update:  05/25/2005

To update this profile, contact Cheryl T. Johnson at or (703) 603-9045.