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In 1999, the U.S. Environmental Protection Agency (EPA) Region 9 requested the assistance of the U.S. Army Corps of Engineers (USACE) to perform a Remedial Investigation/Feasibility Study (RI/FS) follow-on study at the Site, focusing on the characterization of non-aqueous phase liquids (NAPL) source areas to support the selection of a final groundwater remedy. The USACE performed SPP with other project stakeholders, designing a technical approach for NAPL source area and release characterization that involved two investigation phases. This DWS approach was split between two mobilizations for several reasons, including: the costs could be borne over 2 fiscal years, legal requirements for access to off-site sampling locations required more than 6 months lead-time, and the additional time allowed project planners to refine the approach for additional release sampling in the slough adjacent to the Site. Field activities took place in the Summers of 1999 and 2000.
Highlights of applying the Triad Approach for this project include:
Based on the application of the DWS and PBMS, 31 planned borings were eliminated and 19 others were added for full delineation of NAPL contamination. Nine additional borings were completed to delineate a total petroleum hydrocarbon (TPH) source that had not been previously identified. Additionally, five microwells were installed beyond the 11 planned wells due to rapid installation times and cost savings realized from application of the DWS. The second phase of sampling was completed 30 days ahead of schedule.
Other highlights of the project include the SPP process as documented in the project management plans (see references below), and the mobile laboratory program implemented at the Site by the USACE.
| Site Name | McCormick and Baxter Creosoting Company |
| Location | Stockton, CA |
| Site Type |
Wood Treatment Facility/Creosoting Company |
| Site Regulatory ID |
CAD009106527 |
| Project Lead Organization | EPA |
| Project Lead Type |
EPA Lead |
| Regulatory Lead Program |
Superfund Remedial |
| Triad Project Status | Field Program Completed |
| Reuse Objective Identified |
Yes |
| Proposed Reuse: |
Commercial/Industrial |
The Site occupies approximately 32 acres and operated as wood treatment facility from 1942 until 1991. A variety of wood preservation processes were conducted during the Site's operational history involving creosote, pentachlorophenol (PCP), and metals. In addition to the chemicals used to preserve wood products, a number of carriers and solvents were used to aid in the preservation process. Carriers and solvents were mainly petroleum-based fuels including kerosene, diesel, butane, and ether. Wood was treated in pressurized retorts and allowed to dry at various locations across the Site. Waste oils were stored in unlined ponds and concrete tanks prior to disposal. The Site is bound by the Old Mormon Slough to the north, which connects to the Stockton Deepwater Channel on the San Joaquin River.
EPA added the Site to the National Priorities List (NPL) in October 1992 and later conducted a number of investigations at the Site, completing a Record of Decision (ROD) for sediments and soils, and an interim remedy for groundwater in March 1999. The follow-on investigation activities described in this profile were performed after EPA identified a need for further evaluation of remedies for NAPL and other source material at the Site to assist with selection of a final groundwater remedy.
Following the completion of the 2000 investigation, no new data gaps were identified; the pre-design characterization data collected during the 1999 and 2000 NAPL field investigations were considered sufficient to begin the evaluation of in situ thermal treatment technologies. This evaluation was documented in a final conceptual design report submitted to EPA in November 2001, which included ten percent engineering design and cost estimates for the installation, operation, maintenance, and post-operational stages of a combined steam injection and electrical heating remediation strategy. Costs were estimated for three design scenarios, with the coverage and number of injection and extraction wells increasing from Scenario 1 to Scenario 3. The life cycle cost of Scenario 1 (likely the cheapest option) was estimated at $83.2 million.
Due to the significant costs associated with the remedial strategy, five criteria were selected to prioritize areas of the Site for in situ thermal treatment. The criteria were developed with input from EPA, USACE, the California Department of Toxic Substance Control (DTSC), and the California Regional Water Quality Control Board (RWQCB). Criteria included: 1) relative amount of NAPL present; 2) proximity of NAPL to drinking water risk receptors; 3) certainty of the data indicating the presence of mobile NAPL; 4) potential for future changes in the land use and/or subsurface conditions that might facilitate the mobilization of currently immobile NAPL (e.g., increased pumping of drinking water downgradient of the Site); and 5) ease of access for follow-up remediation activities. On the basis of these criteria, the collaborative data sets were further applied to identify limited areas in the northwest and north central portion of the Site, adjacent to the Old Mormon Slough, as the highest priorities for thermal treatment. These areas were assessed to contain mobile and/or immobile NAPL at quantities and depths of greatest concern for surrounding receptors. An interim groundwater remedy was put in place using pump-and-treat technology. As of February 2007, a final groundwater remedy had not yet been selected for the Site.
EPA Region 9 identified a need for characterization and a feasibility study (FS) to evaluate NAPL source material present at the Site and develop a final remedial strategy. The overall objective of the two field investigations, conducted in 1999 and 2000, was to obtain sufficient information in limited mobilizations to develop a mature CSM. The CSM was intended to support the identification and costing of remedial alternatives for NAPL source areas and adjacent media with risks to receptors.
The DWS work plans used for the 1999 and 2000 investigations enabled the USACE to concentrate resources in areas requiring more rigorous characterization to develop a mature CSM for engineering purposes. The investigations produced a clear picture of the large extent of source materials present at the Site and the potentially significant costs associated with remediation.
NAPL at the Site and its effects on surrounding media were thoroughly characterized within two mobilizations using collaborative sets of on-site and off-site analytical data. The success of these collaborative data sets was possible due to the PBMS, which, through initial validation studies and detailed data review and quality assurance/quality control (QA/QC) throughout the investigation, allowed a full understanding of the applications and limitations of the different analytical methods used.
A primary goal of the project was to use EPA's Triad Approach and HRSC methods to increase data density, potentially driving down removal and treatment costs by more effectively defining the source areas requiring aggressive remediation techniques. Triad and HRSC allowed for accurate delineation of contamination, therefore, an accurate evaluation and costing of remedial alternatives was developed with a minimum number of mobilizations to outline a remedial strategy to the satisfaction of the project stakeholders.
SPP activities performed by the USACE identified the need to define a "box" in the Site subsurface requiring aggressive remediation from in situ thermal treatment technologies. HRSC sampling density employed with real-time results and collaborative analyses was proposed to achieve project goals within time and budget constraints. Site decision-makers accepted the USACE SPP approach and obtained buy-in from other stakeholders.
A preliminary CSM to support the "box" concept was developed based on historical information, and this CSM was matured in real-time using results from the Site Characterization and Analysis Penetrometer System (SCAPS) (CPT logs and LIF responses) during the 1999 and 2000 investigations. To a depth of 110 feet below ground surface (bgs), CPT and LIF results from the SCAPS provided a continuous, high-resolution profile of subsurface geology and NAPL throughout the Site. Rotosonic borings and monitoring wells provided supplemental data below the maximum achievable direct push depths of the SCAPS platform (155 feet), producing a detailed geologic and hydrogeologic CSM to approximately 200 feet bgs.
Overall project uncertainty was managed using multiple lines of evidence in conjunction with CPT and LIF logs (i.e., collaborative data sets). Sample cores were visually inspected for the presence of NAPL, and on-site TPH-Dx analyses provided confirmation of LIF results, further helping to refine the correlations between various NAPL products found in the subsurface and the associated wavelength signatures provide by the LIF.
The EPA Region 9 remedial project manager (RPM) was the principal decision maker for the Site. Other stakeholders with input to the Site decisions included the California DTSC, the California RWQCB, EPA Kerr Laboratory staff, and the USACE project team.
The USACE provided technical staff support for planning and conducting the investigations, in addition to the SCAPS platform. 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 (QA). EPA Region 9 provided on-site analyses using the Field Analytical Screening Program (FASP) mobile laboratory and off-site analyses at the Region 9 laboratory. Technical support was also provided by the EPA Office of Research and Development's (ORD's) Kerr Laboratory.
Results from the SCAPS LIF and CPT effort in conjunction with SCAPS soil sampling and installation of microwells allowed the project team to use real-time information to determine appropriate future sampling locations. This high-resolution, dynamic decision-making strategy assessed when the delineation of NAPL was complete in a particular direction or at a particular depth. Decisions were made in accordance with criteria established in the decision logic used to guide the investigation. Fixed-base laboratory analyses were used in combination with the field methods to limit costs, provide back-up for the on-site laboratory, and ensure completeness of the delineation efforts.
The DWS sampling plan outlined by the USACE included 10 initial SCAPS push locations chosen based on known or suspected areas of high contamination or where previous data gaps had been identified. During the 1999 investigation, an additional 96 push locations were completed based on real-time results from LIF and CPT along with collaborative results from the on-site mobile laboratory. A total of 75 SCAPS push locations were completed during the 2000 investigation. Logic for placement of these locations included additional data required for data gaps identified after the 1999 field effort, delineation of NAPL migration in the area north of the Old Mormon Slough, delineation of NAPL beyond the southern and eastern property boundaries, and delineation of NAPL in the area of a PCP mixing shed.
Detailed decision logic tools were developed to assist the field team in applying the analytical data to make decisions regarding the delineation program and determine future sampling locations based on real-time results. Refer to the case study, work plans, field investigation reports, and the Points of Contact (POCs) identified at the end of this Profile for further information concerning the decision logic and how real-time decision-making and communication occurred.
Field-based analytical technologies included LIF and CPT deployed from the SCAPS as continuous downhole sensors, total recoverable petroleum hydrocarbons (TRPH) performed in a mobile laboratory, and TPH-Dx performed in a mobile laboratory.
USACE used the downhole LIF sensor as a primary HRSC tool to characterize NAPL at the Site. The fluorescence data was used to provide approximate NAPL concentrations and identify types of petroleum classes (i.e., Diesel range TPH, heavier hydrocarbons such as creosote, and kerosene). The USACE had previously used LIF technology successfully at other sites. A preliminary pilot study, or DMA, was performed during the initial phase of the 1999 NAPL investigation as part of a PBMS approach to refine LIF application for the Site and provide a basis for interpreting the LIF responses. Multiple lines of evidence including visual core inspections and on-site laboratory analyses were used during the DMA and later during the field investigation to limit uncertainty associated with the LIF results. Field sampling methods and technologies included grab sampling with the SCAPS platform, rotosonic drilling, low flow groundwater sampling, and conventional "3 purge volume" groundwater sampling.
Decision-making with the SCAPS unit was based on assessing the presence or absence of NAPL using LIF intensity counts. LIF counts greater than 500 were considered indicative of the presence of NAPL, while LIF counts less than 300 were considered indicative of the absence of NAPL. LIF count results between 300 and 500 were considered questionable and were further evaluated using additional lines of evidence to conclude whether NAPL was present. Additional lines of evidence included visual core inspection (mobile product or a visible sheen) and significant positive results from on-site TPH-Dx analyses.
The LIF data were supported through extended diesel range TPH analyses (TPH-Dx) conducted on-site using EPA's FASP mobile laboratory and off-site using the EPA Region 9 laboratory. Methods applied at these laboratories were used to compare patterns to two distinct analytical standards (Florida TRPH standard and the XHc diesel fuel #2 composite standard). Using pattern matching of chromatograms from field samples compared to standards run in the off-site laboratories, the field team was able to identify five distinct fuel types during the 1999 investigation and one additional fuel type during the 2000 investigation.
The evolving analytical approach for the investigation demonstrated the importance of establishing contingencies as part of DWS-based investigations. Modification of analytical technologies to meet project needs under a PBMS is also considered an important aspect of the Triad Approach.
TQRS not prepared
The QA/QC program involved the analysis of standard QC samples (duplicates, spikes) and other method QC checks in the on-site analytical laboratory. Real-time analytical data were evaluated using collaborative results from the visual core inspections, SCAPS data, and on-site mobile laboratory results.
Other than standard spreadsheet, database, and statistical packages, decision support tools (DSTs) were not used as part of the 1999 and 2000 NAPL investigations.
July-September 1999. Phase I of the NAPL investigation.
June-August 2000. Phase II of the NAPL investigation
415-972-3177To update this profile, contact Cheryl T. Johnson at Johnson.Cheryl@epa.gov or (703) 603-9045.
