In November 2002, the Corps of Engineers, as a part of the Brownfields Technology Support Center, was asked by the City of East Palo Alto to facilitate application of the Triad approach to a pesticide investigation planned for a disadvantaged neighborhood. Suspected or known contamination from the past use of pesticides had slowed the area's redevelopment, especially by non-profit and local resident developers such as those in this pilot, forcing developers to attempt financing the high cost of field investigation and cleanup, drive up the cost of housing, or leave potentially contaminated lots undeveloped. The City had noted that conventional investigation approaches were likely to be more costly than the developers could afford. In addition, there was a desire by both City officials and the residents in create need of more housing to speed the pace of redevelopment activities. The project began by organizing the project team and identifying the goals of all stakeholders. The project team was careful to ensure that a consensus was achieved on key investigation aspects such as contaminants of concern, action levels, the preliminary conceptual site model (CSM), and sampling approaches, before moving the project to the next level. Anticipated decisions and acceptable levels of uncertainty were discussed. This phase of the project included preparation of a systematic project planning memorandum, which detailed project goals and the preliminary CSM. Next, the Sampling and Analysis Plan was structured to gather sufficient soil data to conclude the investigation activities with a single field effort by applying real-time measurement technologies and dynamic work strategies. The field work occurred during the week of October 13, 2003 and it was determined that only pesticide application residues were present, not any hot spots. Over the next several months limited additional fixed laboratory data was obtained to answer several remaining regulatory concerns. By early 2004, the investigation was completed and the redevelopment poised to proceed.
|Site Name||791/805, 855 and 872 Runnymede Street and 875 O'Conner Street|
|Location||East Palo Alto, CA|
|Site Type||Agriculture Applications|
|Project Lead Organization||City of East Palo Alto|
|Project Lead Type||Municipal/Local Lead|
|Regulatory Lead Program||State Remedial|
|Triad Project Status||Field Program Completed|
|Reuse Objective Identified||Yes|
Beginning in the early 1900's the study area was used for commercial agricultural activities involving the use of pesticides. Steady development has occurred since the 1950's, and therefore the land use is now predominantly residential. Pesticides were found at other parcels in the neighborhood that were developed earlier. The homeowners were unable to finance environmental investigation, which lowered the property value and slowed development. City redevelopment officials used Brownfields resources to comprehensively investigate the sites. Off-the-shelf field analytical methods and standard laboratory methods were available for this project.
During the investigation 78 primary soil samples were analyzed by immunoassay and 21 split samples were analyzed with fixed laboratory methods. Both cyclodienes and DDT were detected by the immunoassay analysis. The immunoassay field analysis found that cyclodienes were widespread in the study area, detected in 64 samples at a maximum kit concentration of 1.76 milligrams per kilogram (mg/kg) total cyclodienes (the detection limit ranged from 0.01 to 0.05 mg/kg). It should be noted that the cyclodiene immunoassay results are biased high by approximately a factor of 20. There were only 9 detections of the DDT family with this semi-quantitative immunoassay method. All immunoassay DDT detections fell in the range of >0.2 to <1 mg/kg. Chemical specificity was provided by the laboratory analysis. Cyclodienes found in the soil included dieldrin, chlordane, endrin and heptachlor epoxide. Dieldrin was the most frequently detected cyclodiene with a maximum value of 0.09 mg/kg. The laboratory analysis detected DDE and DDT at maximum concentrations of 0.019 and 0.010 mg/kg, respectively. The only pesticide to exceed its action level (0.030 mg/kg) was dieldrin. Lead also exceeded its action level at one location. It was concluded that in most cases the pesticide levels in site soils did not pose a risk to future residents and that contaminants exceeding action levels could be addressed during future construction.
The objective was to determine the environmental condition of the properties to support residential redevelopment. Specific objectives included:
The Triad offered a cost effective approach to gather the information necessary to ensure that confident decisions could be made in a timely manner. Investigation costs and mobilizations were minimized. Redevelopment was facilitated.
No formal cost comparison was performed. It is estimated that months of time and thousands of dollars were saved.
Systematic project planning began with team formation. Coordination was accomplished with meetings, telephone conferences and e-mail. After initial project team discussions, the Corps prepared a systematic project planning memorandum to guide Triad implementation. This memo included a preliminary CSM that was based on information gleaned from existing reports from similar sites in the area. Uncertainty regarding the presence of hot spots and volumes of soil exceeding regulatory criteria was managed with a strategy of progressive sample evaluation based on the preliminary CSM. Field techniques were used to reduce sampling uncertainty, while laboratory analysis was used additionally to provide analyte specific results, to aid field data interpretation, and to manage field analytical uncertainty.
Decision logic grew out of the project decisions to be made. Sample analysis (initially with field methods) was used to first establish that no hot spots were present, and then to determine the extent of low-level pesticide application residues. The analysis proceeded sequentially beginning with near surface samples. Deeper samples were only analyzed if earlier analysis indicated the presence of a hot spot. The work plan allowed for the collection of additional samples to define the extent of hot spots. Spreadsheets were used to manage data in the field. Site meetings and telephone conferences were used to share information.
The project decision logic was incorporated into a flow chart included with the Sampling and Analysis Plan. The logic began with the premise, based on the CSM, that pesticide contamination would be present as hot spots and/or application residuals. The initial sampling grid was designed to ensure detection of all hot spots 50 feet in diameter or greater. The logic included provisions to delineate the vertical and horizontal extent of any hot spots discovered. Immunoassay was the primary analytical method used to address sampling uncertainty and to determine the pattern of contaminant distribution. Laboratory analysis was used to obtain chemical specificity, as a quality control check on the immunoassay analysis, to aid interpretation of the immunoassay data, and to gather data below the immunoassay detection limits. Sufficient samples were submitted for laboratory analysis to provide the fundamental decision unit - a residential building lot - with such data.
Following approval of the work plan, soil samples were collected from a pre-established grid. The initial sample collection was performed at multiple depths (using a back hoe) to ensure cost efficiency by reducing the number of equipment mobilizations. The deeper soil samples were held in reserve pending analysis of the near surface samples. Additional soil samples would have been collected if it were found necessary to delineate the extent of any hot spots. The soil samples were analyzed using two immunoassay methods. The immunoassay analysis was performed both in a field office and in the controlled conditions of the Region 9 laboratory. Laboratory methods included organochlorine pesticides (EPA 8081), lead (EPA 6010) and arsenic (EPA 6010).
Quality control measures included 3-point calibration curves with positive and negative controls run with each batch. Careful sampling and homogenization procedures were observed, and about 10% field duplicates (after homogenization) were run. Selected samples were split for comparison analysis in a fixed laboratory. All 18 field duplicate pairs showed good agreement with an average difference of approximately 20%. All sample detections fell within calibration range.
Cyclodiene immunoassay and laboratory analysis demonstrated good predictive relationships, despite a 20-fold positive bias noted for the immunoassay. The positive bias was expected with immunoassay analysis. Despite the positive bias, there were no false positive or false negative cyclodiene decision errors, and the summation of cyclodiene results normalized to dieldrin yielded a moderate correlation with laboratory results. The few detections for the DDT series field analysis also agreed well with the laboratory data with no false positive or false negative decision errors. There were insufficient detections for the DDT family to determine the magnitude of kit bias.
October 13 - 17, 2003
|Sampling and Analysis Plan (3.3 MB)|
|Systematic Planning Technical Memorandum (178 KB)|
To update this profile, contact Cheryl T. Johnson at Johnson.Cheryl@epa.gov or (703) 603-9045.