Technical Review Comments on "Conduit Investigation Summary for the Southeast Landfill Area," Lemon Lane Landfill, Bloomington, Indiana

September 14, 2000

Tetra Tech EM Inc. (Tetra Tech), with assistance front its subcontractors, Triad Environmental Consultants and Earth Tech, reviewed the "Conduit Investigation Summary for the Southeast Landfill Area'' prepareci by CBS Corporation (CBS) for use in a meeting with the regulatory authorities held on July 6, 2000. Included as an attachment to the summary is a report prepared by GECOH Exploration (GECOH) titled "RIM investigation in the South Side of the Lemon Lane Landfill, Bloomington, Indiana." The Summary includes(1) conclusions regarding the nature of contaminant distribution and migration and (2) recommended steps to obtain additional data on contaminant distribution and migration. The following review comments on the summary focus on the conclusion and recommendation sections 6.0 and 7.0, respectively and include suggestions for additional investigation.

In general, review of the conclusions and recommendations would have been facilitated by the regulatory authorities having access to all the relevant data generated during the investigation. Several hiring logs and various geophysical data have not been submitted, making the data set incomplete. Therefore, regular data package submittals should be established to ensure timely and complete review of data.

Comments on Conclusion Section 6.0

1. PCBs have entered the bedrock at the site primarily in the southeast corner of the landfill. Most likely they entered here because there was concentrated PCB dumping and thin soils.

2. There are two major east-west oriented fracture zones in the southern portion of the landfill. These have significant conduit development along them. These active fractures/conduits are identifiable with resistivity surveys.

Comment: The fracture zones in the south portion of the landfill have been identified only by means of resistivity surveys and analysis of aerial photographs. Richard Parizek's report titled "Fracture Trace and Lineament Analysis of the Lemon Lane Landfill" (September 7, 1999) states that the features should be field-checked. Specifically, the Parizek report recommends test drillnig at a suspected fracture trace intersection at the southwest portion of the landfill and at a location near the northwest corner of Valhalla Cemetery. The GECOH report also indicates a need for test drilling at the location of geophysical anomalies. However, no drilling program has been performed to field-check the linear features identified in the summary as "active fractures/conduits." CBS should perform test drilling in the east- and west-oriented fracture zones to delineate the conduit development along them.

3. There are likely north-south oriented fracture zones that help route water from the more northern east-west fractrue zone to the southern zone. These have not been adequately identified because not enough east-west oriented resistivity lines have been run in the southern protion of the landfill.

Comment: The presence of north- and south-oriented fracture zones can be inferred from the regional geology. Resistivity surveys may be able to locate such zones, but only drilling or excavation should allow the geophysical anomalies to be defined. The role that these fracture zones may play in migration of Groundwater through the karst system can only be adequately determined by performing tracer tests between established monitoring points. CBS should perform tracer tests to determine the continuity of the north- and south-oriented fracture zones.

4. The southeast area conduits under the landfill appear to be the wetted by storm water from the east and or north. The southernmost fracture zone just south of the landfill is also wetted by runoff from the railroad tracks.

Comment: Inferences based on geographic proximity and local knowledge of geology are useful, but the exact and direction of Groundwater flow cannot be determined based on geophysical surveys, aerial photo analysis of aerial photographs, or even drilling operations. Tracer tests are needed to determine the origin and direction of Groundwater flow. CBS should conduct tracer tests to determine the Groundwater flow direction in the southeast area conduits under the landfill.

5. There are standing water levels in many of these conduits and DNAPL pools of PCBs in some. These standing waters and some PCBS may be flushed out as storm water surges through the conduits. These conduits also are partially clay filled in some locations.

Comment: Although there is direct physical evidence of the presence of Groundwater, clay, and PCBs in the borings drilled to date, the degree of connection between the southeast area conduits and others that run through tile karst system has not been established. CBS should investigate the degree of connection between the conduits identified to date.

Comment: Inferences based on geophysical surveys or analysis of aerial photographs cannot adequately determine Groundwater flow direction. Only pumping and tracer tests can determine the degree of integration and the direction of Groundwater flow between the suspected fracture zones. CBS should investigate the south fracture zone using pumping or tracer tests.

7. Based on the response to rain events and the amount of product in LF-6, this sump area alone could account for the high PCB spike seen at the spring during big stroms. However, there may be a couple of other locations where similar sumps exist.

Comment: Identifying locations such as sumps where high concentrations of PCBs exist is critical to any remediation of Groundwater or removal of free product. Only an extensive drilling or excavation program could locate such sumps. CBS should conduct additional drilling to locate the sumps in the southern portion of the landfill.

Comment: If a number of such sumps exist, which is likely, excavation will not be a practical remediation alternative. However, if one or more sumps can be reached by means of excavation, the knowledge gained of the conduit geometry and the nature of the contamination could be valuable. CBS should access the epikarst sump at the LF-6 location by means of excavation and determine its degree of connection with other sumps in its vicinity.

In general, the conclusions offered by CBS in the summary form an interesting draft conceptual site model based on the data gathered so far. It is necessary, however, to obtain more concrete data before any firm conclusions can be formulated regarding Groundwater flow directions and the interconnection of various suspected fracture zones and conduits. The geophysical data gathered to date indicate solution features, and these data should be used to help guide future drilling operations. However, no conclusive evidence exists that the RIM technology is providing reliable data. CBS should confirm the effectiveness of this geophysical technique if it is to be used to define particular site conditions.

Comments on Rccommendation Section 7.0

1. The proposed boring program should be expanded to include locations along the entire south side of the landfill, including areas already identified by Richard Parities and GECOH as likely fracture zones as well as any probable fracture zones identified by continued RIM surveys. The number of borings should be sufficient to confirm the geophysical findings and to provide monitoring points for Groundwater studies. Additional boring locations may be indicated by soil sample analytical results obtained during ongoing site remediation. Also, borings should be drilled in the northeast portion of the landfill where other potential fracture zones have been identified. Coring of borings is recommended because downhole videotaping has often failed to provide the resolution needed for detailed logging. Finally, borings should be drilled to support falsification testing of geophysical data. These test borings should be drilled where the RIM data indicate lack of karst conduit development in the bedrock. Only by demonstrathig that the RIM technology can truly distinguish between competent bedrock and solution-channel development can confidence in the technique be improved.

2. Any borings drilled at or near the landfill that encounter karst solution features. whether dry or wet, should be completed with piezometers. These piezometers should then be monitored during and after rain events to support contaminant migration studies.

3. Although pumping tests may be useful in demonstrating hydraulic connections between various solution features, only tracer tests can conclusively define Groundwater flow direction. Tracer tests should be conducted to confirml the conceptual model of Groundwater flow presented in Section 6.0 of the summary. Small-scale tracer tests may be needed before completion of the boring program to help select the locations of borings. More extensive tracer tests may be conducted once all piezometers have been installed.