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Final Report
Remediation of Soils along the Perimeter of the Sludge Drying Beds
Winston-Thomas Waste Water Treatment Plant
April 22, 1998
PSARA Technologies for CBS Corp.
1.0 INTRODUCTION
This document constitutes the final report for the remediation and post-excavation sampling of the Drying Bed Perimeter area at the Winston Thomas site in Bloomington, Indiana. Figure 1 illustrates the location of this work at the Winston Thomas site. The work described in this report was performed between May and July of 1998.
This report includes a descriptive narrative of work performed, along with associated figures, tables, and laboratory certificates of analysis. Additional records associated with this project, including air monitoring results, weekly progress reports, chain-of-custody documents, etc., are on file for review and future reference upon request.
2.0 BACKGROUND
The sludge drying beds at the Winston Thomas site were remediated during the fall of 1997. The scope of work for this remediation project is described in the Work Plan dated May 22, 1997, for the remediation of the digesters and drying beds. A final report describing this remediation effort was previously submitted to the consent decree parties.
During the sludge drying bed remediation project, 17 shallow (0 to 6 in.) soil samples were collected byCBS along the perimeter of the drying beds. These samples were collected to evaluate the possibility that sludge from the drying beds had overflowed from the beds during their operation and gradually been incorporated into the surrounding soils. The perimeter soil sample locations and initial sample results are presented in Figure 2. Seven perimeter sample locations (1, 2, 4, 12,14,15, and 16) were found to contain polychlorinated biphenyls (PCBs) above 25 parts per million (ppm), and two of these locations (1 and 16)were found to contain PCBs at concentrations exceeding 100 ppm. 6-in. lift of soil was immediately removed at these two locations and disposed of with the sludge material from the digesters. Figure 3 presents the approximate extent of these initial excavations.
Following receipt of these results and further discussions with the U.S. Environmental Protection Agency (USEPA) and the City of Bloomington, it was determined that further remediation in this area would be conducted in conjunction with the 1998 remediation of the remaining work areas at the Winston Thomas site.
3.0 SUMMARY OF PROJECT ACTIVITIES
A Field Sampling and Analysis Plan, dated May 6, 1998, was prepared to address the delineation and removal of soils along the perimeter of the sludge drying beds. This plan was reviewed and approved by the consent decree parties in May 1998 prior to the start of excavation activities at the site. Health and safety, air monitoring, and transportation and disposal were conducted in accordance with the work plan documents approved for the Trickling Filter Remediation Project.
The delineation sampling effort was conducted by PSARA Technologies, Inc., between May 13 and 30,1998. Figures 4, 5, and 6 present the results of the delineation for drying beds 1, 2, and 3, respectively. Sample numbers, dates, depth intervals for each sample, and analytical results are presented in Table 1.
Excavation activities were conducted in two phases. The perimeters of drying beds 2 and 3 were remediated between May 19 and 22, 1998. This work was time-critical due to the plan to place washed stone from the Trickling Filter Project in the area of drying bed 3. Excavation at the perimeter of drying bed 1 was also initiated at this time but was suspended when several consecutive days of wet weather made the drying bed impassable by trucks. This excavation work was completed in a second phase of excavation work between May 20 and July 17, 1998. All removal activities were performed by Blasland Bouck &Lee (BB&L) under the direction of CBS and in cooperation with the City of Bloomington. All material was removed and disposed of at a Toxic Substances Control Act (TSCA)-permitted landfill in Belleville, Michigan, operated by Environmental Quality.
In each grid, the delineation sampling was conducted vertically until a clean depth interval was identified. The excavation was performed by removing soils to at least the depth determined by the delineation effort. Following this removal, the excavation was inspected for visual evidence of residual sludge. If present, this additional material was removed prior to the performance of verification sampling.
Post-excavation verification sampling was performed consistent with the procedures described in the sampling plan. One sample was collected from the 0- to 6-in. depth interval in the approximate center of each excavated grid. These samples were analyzed for PCBs. If the laboratory result from a grid sample showed a PCB concentration in excess of 25 ppm, an additional 6-in.lift of soil was removed, and the grid was resampled. This procedure was continued until all of the delineated grids showed a PCB concentration of less than 25 ppm. Figures 7, 8, and 9 present the resultsof the final post-excavation verification samples for drying beds 1, 2, and 3, respectively. Sample numbers, dates, depth intervals for each sample, and analytical results are presented in Table 2.
During the execution of the perimeter of drying bed 1, a band of dark material was observed in the northside wall of the excavation. Initially, the excavation was extended northward to remove this material where encountered. Because the excavation abutted the south berm of the tertiary lagoon, however, only a very limited extension of the excavation was possible without endangering the berm stability.
Four samples were collected of the material in the excavation sidewall and analyzed for PCBs. The sample locations and results of this sampling are included in Figure 10. As the figure shows, there appears to be a layer of residual PCB sludge under the south berm at these locations. This material will be remediated as part of the tertiary lagoon remediation project. The work plan documents for the tertiary lagoon already address the delineation and remediation of PCB sludge under the south berm, and the remaining work will be accomplished as part of that project.
All excavated areas were backfilled with a minimum of 12 in. of clean backfill. Those excavation areas which encroached on site roads were backfilled with cleaned stone from the trickling filter area to facilitate their use throughout the remaining remediation projects. This action was approved by the City of Bloomington. The remaining excavations were backfilled with clean clay. The analytical results identified no PCBs in the clay backfill material used at the site. Plastic sheeting was placed between the backfill and the south berm to assist in separating the remediated area from the south berm excavation zone when that project is performed.
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