The U.S. Navy Public Works Center (PWC) Environmental Department, San Diego, California is home to the Navy west coast Site Characterization and Analysis Penetrometer System (SCAPS). SCAPS has been extensively used at Department of Defense (DoD) sites since 1995 to provide real-time, high-resolution data sets. The Triad Approach provided an ideal framework for optimizing the use of the Navy SCAPS during a volatile organic compound (VOC) source investigation at Installation Restoration (IR) Site 1114 at Marine Corps Base (MCB) Camp Pendleton, California. All three elements of Triad; systematic project planning (SPP), DWS, and use of real-time measurement tools, were implemented using a high-resolution site characterization (HRSC) approach to manage decision uncertainty and expedite the site management process. The investigation was conducted using the Navy SCAPS outfitted with a CPT, MIP and a DSITMS detector which allowed for real-time collection of over 690 feet of continuous lithologic information and VOC concentration data. These data were used collaboratively with 24-hour turnaround EPA Method 8260B VOC groundwater results from temporary direct-push technology (DPT) wells to support the conclusion that a limited source area was present. Implementation of the Triad-based, HRSC approach for this investigation provided an expedited high-density data set and a refined conceptual site model (CSM) in real-time that resulted in cost savings estimated at $2.5 M and reduced the site characterization and cleanup schedule by approximately 3 years. This project demonstrates how the Triad Approach can be applied to streamline site characterization and cleanup while appropriately managing decision uncertainty in support of defensible site decisions.
|Site Name||Marine Corps Base Camp Pendleton IR Site 1114|
|Site Type||Contaminated Aquifer - Contamination Source Unknown|
|Project Lead Organization||Navy Facilities Engineering Command, Southwest Division|
|Project Lead Type||U.S. Navy Lead|
|Regulatory Lead Program||State Remedial|
|Triad Project Status||Field Program Completed|
|Reuse Objective Identified||Yes|
|Proposed Reuse:||The Base Master Plan restricts site land-use to military training. The site is also overlain by protected endangered species habitat, and is therefore not subject to development. The site vicinity is part of a larger region reserved for habitat preservation.|
The subject site (IR Site 1114) is located within MCB Camp Pendleton, adjacent to the west and crossgradient of IR Site 9, a former waste stabilization pond. IR Site 9 is located in an area with minimal historic development restricted to dirt roads, the former waste stabilization pond, and a former grease disposal pit. The Record of Decision (ROD) for IR Site 9 documents the selection of monitored natural attenuation (MNA) as the remedy for groundwater, with effectiveness measured by long-term monitoring (LTM) of groundwater. The Five-Year Review conducted to assess groundwater conditions indicated that tetrachloroethene (PCE) concentrations measured in one monitoring well identified as 9W-07A increased steadily through time until exceeding drinking water standards. The inconsistency of these results with the MNA prediction resulted in additional soil and groundwater sampling, which ultimately ruled out IR Site 9 as the source of PCE in groundwater. The suspected off-site source of VOCs detected in monitoring well 9W-07A was addressed as new IR Site 1114 which is the subject of this investigation.
The only time restriction on this project was that fieldwork would not conflict with nesting seasons, which preclude work between August and February.
PCE was identified as the primary compound of concern (COC) at the site, because it was the only contaminant detected at concentrations exceeding groundwater maximum contaminant levels (MCLs). In the systematic project planning (SPP) meeting, the project team agreed that the MIP/DSITMS interface (one of the real-time measurement tools used during this investigation) would be calibrated to detect and quantify PCE, trichloroethene (TCE), and cis-1,2-dichloroethene (cis-1,2-DCE). If at any time during the investigation other VOCs were identified, including vinyl chloride (VC), a new calibration curve including the unexpected analyte(s) would be generated.
The greatest VOC concentration encountered was 1,000 micrograms per liter (µg/L) PCE identified by the MIP/DSITMS at one location within a 2-foot interval at the water table. PCE concentrations attenuated sharply with depth, decreasing an order of magnitude within 2 feet of the highest measured concentration. Target VOCs were not detected below 46.5 feet below ground surface (bgs). The vertical distribution of VOCs was further supported by the temporary DPT groundwater data set.
The location of the maximum PCE concentration was bounded laterally within approximately 200 feet, and vertically within 10 feet. PCE was vertically stratified, with greatest concentrations measured at, or near, the water table. PCE concentrations indicated a dilute source. Dense non-aqueous phase liquid (DNAPL) conditions and product-level concentrations were not encountered.
There are no complete pathways linking the PCE identified at IR Site 1114 to receptors. The depth of contamination is over 40 feet bgs. The site is overlain by protected endangered species habitat, and is therefore not subject to development. Finally, the site is located approximately 0.5 mile upgradient from the non-beneficial use boundary.
The integrated results of this investigation provided a robust CSM, and identified IR Site 1114 lithologic conditions, preferential pathways, and a limited VOC presence. Over 690 feet of continuous, high-resolution VOC data were collected using SCAPS-MIP/DSITMS, in addition to detailed lithologic data from CPT logs and groundwater quality data from temporary DPT wells. Based on these findings, a recommendation of no further action (NFA) was made. Regulatory agency partners tentatively concurred; however the California Department of Toxic Substances Control (DTSC) expressed concerns over potential risks associated with VOCs in soil gas if the Site was ever redeveloped. In June 2008, a soil gas sampling survey was conducted where several VOCs were detected in soil gas samples collected throughout the Site. The Site subsequently advanced to the Remedial Investigation (RI) phase.
To identify potential source area(s) of VOCs to groundwater and delineate the area where VOCs exceed MCLs in groundwater.
Implementation of the Triad-based, HRSC approach using the SCAPS/MIP on this project provided a high-density data set, a detailed CSM, and resulted in expedited site characterization and closure.
Cost avoidance estimated at $2.5 M was realized, and the site characterization and cleanup schedule was reduced by approximately 3 years.
A preliminary CSM for IR Site 1114 was developed based on data gathered during previous investigations at IR Site 9, and available historical information such as maps, aerial photographs, and previous facility operations. Available information on the lithology beneath IR Site 1114, although limited, indicated interbedded layers of silt, sandy silt, clay, and sand.
The preliminary CSM postulated that an upgradient release of PCE was migrating vertically from the source(s), most likely located in the upgradient developed area, until reaching a layer of less permeable sediments that would allow for lateral migration. Considering that PCE could potentially be present in DNAPL or in dissolved phase, it became clear that this initial CSM lacked the level of resolution needed to understand geologic heterogeneities that are known to strongly influence the distribution of contaminants in the subsurface. With this understanding and as part of the CSM optimization strategy, lithology was identified as a major uncertainty. The investigation was planned in four linked phases to occur in one field mobilization. The analytical strategy for each phase was designed to provide data in near real-time so decisions could be made in the field. The real-time measurement tools used during each phase are described in the DWS section. To facilitate collaboration among the parties involved, one agency point of contact was identified and given the authority to represent all other agencies. Data were posted to an established file transfer protocol (FTP) web site at the conclusion of each field day.
Agency partners and project team members included representatives of the San Diego Regional Water Quality Control Board (RWQCB), U.S. Environmental Protection Agency (EPA), DTSC, Navy Southwest Division (SWDIV), and the Navy PWC. Systematic planning meetings were key to set the stage for engaging stakeholders' participation and bringing consensus to project decisions, uncertainties, and the tools proposed to manage these uncertainties. Expertise was provided by geologists and chemists.
To accomplish project objectives in support of the decisions to be made, the investigation was designed to occur in four linked phases during one field mobilization.
Real-time decisions such as selection of screen intervals were based on the review of lithologic data to determine sand layers correlating to the screened interval of monitoring well 9W-07A and to identify other potential preferential migration pathways. Data from CPT logs were used to determine the optimum screened interval for adjacent temporary DPT wells. The field technical team incorporated the CPT (lithology) and the analytical data into an evolving CSM to determine the need for additional data points. As the investigation progressed, several MIP borings were added to address specific agency partner concerns. For example, one new location was added to address a potential data gap associated with the IR Site 9 Former Grease Pit. Other new locations were added at the request of project stakeholders to increase data density and CSM resolution.
TQRS not prepared
A number of quality assurance (QA) measures were implemented to monitor conformance with the established framework for making real-time decisions. While the quality control (QC) measurements for the EPA Method 8260B employed conventional fixed-base laboratory routines, the QC strategy for the MIP/DSITMS focused on managing uncertainties in the data that could directly impact field decisions. Instrument stability and reproducibility checks were performed daily by conducting instrument calibration and running calibration check standards and blanks throughout the day. The calibration curve was generated using test solutions of known concentrations (ranging from 250 to 2,000 parts per billion [ppb]) and clean sand. Calibration checks consisted of verification check standards within the calibration range concentrations as well as system blanks to monitor instrument stability and reproducibility over time. The frequency of the QC checks was adaptive in nature and a function of the analytical performance in the context of an evolving CSM. For example, an excessive number of unexpected non-detects would result in a higher frequency of calibration checks at lower concentrations to control analytical uncertainty within the lower range of the calibration curve. Comparison of data generated from the MIP/DSITMS with CPT logs and groundwater quality data from temporary DPT wells provided another QC check by combining knowledge of subsurface heterogeneity with potential instrument response variability. QC measures associated with samples analyzed by EPA Method 8260B included the analysis of laboratory control samples (LCS), matrix spike (MS), and matrix spike duplicates (MSDs), surrogate spikes, field duplicates, method blanks, and field blanks. QC sample results were evaluated in conjunction with sampling procedures and the evolving CSM to determine overall data quality and whether data usability goals had been met. The evaluation was documented in data quality review forms and integrated with the daily summary reports for posting on the project FTP site.
Overall data quality was determined based on the evaluation of both sampling and analytical variability. The elements affecting sampling variability such as matrix type, sample collection, handling, and overall adherence to standard operating procedures (SOP) were assessed qualitatively as part of the QA oversight for this project. Analytical uncertainty was evaluated based on the type of analytical tool used (MIP/DSITMS or GC/MS) and the review of associated QC parameters including system calibration. Potential data usability issues were evaluated in relation to the CSM to ensure that the data would support field decisions.
Initial systematic project planning proceeded from a preliminary CSM that predicted VOC concentrations in groundwater would increase towards the direction of the developed areas upgradient of well 9W-07A. The initial CSM also predicted that the dissolved contamination would be migrating along preferential pathways consisting of thin sandy layers, perhaps representing old stream channel deposits. In anticipation of a complex migration pattern, the project team planned to use the three-dimensional data-visualization modules in the Groundwater Modeling System software package to maintain and present the evolving CSM and the collaborative data sets. Data would be processed on board the SCAPS truck in near real-time, and posted on the ftp site each night.
However, as the investigation progressed and the vast majority of the contaminant data was non-detect, it became clear that computerized data visualization was not needed to support project decisions. The data management methods were adapted to simply and effectively meet the needs of the decisions. During the Phase II Groundwater Investigation, CPT printouts were used as base figures to design the screened intervals for the temporary DPT wells. The well design was documented by hand drawing and notating the CPT logs. The logs were then scanned each night and posted to the ftp site for review by the project team and regulators. During the Phase III Focused Source Area Investigation, MIP/DSITMS data (nearly all non-detect), was compared to the Phase II CPT logs, and the findings were documented and communicated to the project in the daily narrative report, posted to the ftp site at the conclusion of each field day.
|Five-Year Review Report for Marine Corps Base Camp Pendleton IR Site 9 (2.2 MB)|
|Marine Corps Base Camp Pendleton IR Site 9 Explanation of Significant Differences (423 KB)|
|Marine Corps Base Camp Pendleton IR Site 9 Groundwater Monitoring Report - Part 1 (18 MB)|
|Marine Corps Base Camp Pendleton IR Site 9 Groundwater Monitoring Report - Part 2 (19 MB)|
|Record of Decision for Operable Unit 1 - Site 9 and Group A No Action Sites (10 MB)|
To update this profile, contact Cheryl T. Johnson at Johnson.Cheryl@epa.gov or (703) 603-9045.