Responses to Comments on Organic Detection Summary

Resampling was 179 days apart, required testing must be within 180 days, and EPA conducted only one split sample from well G25D, other three wells tested by the EPA had no original contamination. I believe at the last meeting I attended some comments had been made that the wells that showed the contamination had been temporary wells and had been sealed and could not be tested again. Maybe the EPA could not test G25M G25R and G26D.

Illinois EPA management determined that the wells chosen for split sampling should provide coverage of the overall facility, in addition to double-checking wells that had had organic detections. Sampling would therefore include, at a minimum, one upgradient well, one well downgradient of the Municipal Solid Waste Unit (MSWU), and one well downgradient of the Chemical Waste Unit (CWU).

G02D is an upgradient well for the entire facility. The organic compound acetone was reported in a sample from G02D in 2009. G25D is downgradient of the MSWU and organic compounds were reported in samples collected from it in 2nd quarter 2013. G24D is also downgradient of the MSWU and the organic compound benzene was reported in a sample collected from it in 1st quarter 2013. Lastly, G49D was chosen as a well downgradient of the CWU. Late in the preparation process for the sampling event, the list of selected wells was announced to PDC. PDC advised that G24D was unlikely to produce enough water for split sampling (due to variations in hydrogeology, not all wells produce the same amount of water). PDC suggested G16D as an alternative. It is relatively near G24D and would produce sufficient water for split sampling. Therefore, G16D was sampled instead of G24D.

Why would the regulations assert that the initial, 2nd quarter sampling was an anomaly based upon a resampling by the same entity that apparently mishandled the initial sampling. Why wouldn't it be just as likely that the re-sampling was done incorrectly?

The regulations can only assume that sampling is done correctly, not including random, non-repeated errors. To attempt to do otherwise would introduce unworkable complexity into already complex regulations. The Illinois EPA witnesses sampling on a spot-;check basis to verify that it is done correctly.

Moreover, Clinton Landfill has a sampling and analysis plan – a comprehensive set of procedures – that was reviewed and approved by the Illinois EPA. The purpose of the sampling and analysis plan is not only to propose procedures for Illinois EPA approval but also to provide a written, cookbook approach to conducting the sampling to ensure consistency between sampling technicians. While the fourth quarter 2013 event, which constituted the resampling event for 2nd quarter 2013, was not witnessed by the Illinois EPA, the 2nd quarter 2014 event was witnessed and PDC’s samplers’ techniques were found to be acceptable.

It seems odd that six separate samples would be compromised in this fashion – there would be a separate vial of liquid for each well, correct?

Sample bottles are typically prepared (cleaned, then later inoculated with a sample preservative chemical) in batches – as such, any occurrence that could contaminate one bottle could contaminate the entire batch, or a significant part of the batch. Even if contamination of the bottles did not happen during preparation, the bottles would tend to be kept together in storage at the laboratory, during transportation to the subject facility, during the sampling event, during transportation to the analytical laboratory, and during storage prior to analysis, and finally, they would almost certainly be analyzed on the same machine by the same chemist. There would be plenty of opportunity for multiple vials to be impacted by one source of contamination, and due to the nature of the bottle and the sensitivity of the analysis, volatile organic compound sample bottles can easily become contaminated. Therefore, if bottle contamination occurs, it would more likely happen to more than one bottle than just to one bottle.

PDC reports that samples other than those from Clinton Landfill #3 were similarly impacted during the 2nd quarter of 2013 – in other words, samples from landfills in other cities showed similar spurious contaminants. This lends support to the belief that the detections were not intrinsic to Clinton Landfill #3.

Also, are the "samples" that are shown to have an exceedence preserved? If not, why not.

Yes, they are preserved in a number of ways. These preservation methods are specified by USEPA guidance. First, sample bottles are designed to be chemically compatible with their intended analytes. For example, samples for organic analysis are collected in glass bottles instead of plastic ones, as plastic is a mixture of organic compounds and could therefore bias the sample. Second, bottles for most analytes are inoculated with a chemical preservative selected to enhance the availability of the intended analytes for detection and quantitation. Finally, collected samples are stored at a temperature just above freezing (specifically, 4°C ± 2°C). In accordance with that guidance, all samples collected at Clinton Landfill #3 are placed into a container made of a certain material (e.g., glass or plastic depending on the desired analytes) and then chilled to and maintained at the requisite temperature following collection. Most of those containers have a chemical preservative as specified by guidance.

It would be nice to have had the ability to re-test the actual samples that were associated with the reported exceedences to possibly show that the reported substances were in fact NOT present in those samples.

Sample bottles may or may not be retained following analysis, depending on laboratory policy and other factors. If all the sample volume is used in the analysis, the empty bottles would typically be disposed of afterward unless the laboratory had been instructed to retain them as physical evidence (such as for presentation in court).

If residual sample volume remains after analysis is complete, there still may not be sufficient volume to perform the analysis a second time. Sample bottles are typically sized to provide just enough volume for the desired analysis and laboratory quality control testing, plus a small residual. There may or may not be enough left over to rerun the sample. To collect copious excess volume on all samples, when the results of many or most analyses would not indicate a need for retesting, would not be economical or practical in light of the time and effort needed to collect and transport the sample, especially if the samples are shipped by commercial carrier.

Moreover, the approved methodologies employed by environmental laboratories specify that analysis must occur within a certain timeframe (called “holding time”) after collection. For volatile organic compounds, such as were the concern at Clinton Landfill #3, this holding time is typically seven days. Volatile organic compounds are called “volatile” because they readily evaporate out of the sample and once in vapor form, they readily transfuse out of the sample container and are lost, causing the sample result to underestimate the true original concentration. Therefore, the limited holding time is designed to ensure that the sample is analyzed before significant analyte loss occurs. If residual sample volume were tested beyond the approved holding time, the results would be considered questionable because the approved method was not followed (i.e., the sample was run too long after collection).

Due to the time required to transport the sample to the laboratory, run the analysis, and report the data to the project manager, and for the project manager to react to the report, a holding time as brief as seven days would almost always be exceeded. Typically, project managers would not ask for samples to be rerun outside holding times, as the data would not be defensible. It would be preferable to have more samples collected to ensure defensible results.

Who collected the samples that were split, Clinton Landfill's lab or Illinois EPA personnel? I am hoping it would be the IEPA that would have actually drawn, stored and transported the samples to reduce the chances that there was a false negative result associated with the same types of errors that are discussed earlier as an explanation for the false positive results.

Almost all of Clinton Landfill #3’s wells have positive-displacement (“bladder”) pumps installed in them. Bladder pumps are one of the few recommended means for collecting samples from groundwater monitoring wells for chemical analysis, especially when volatile organic compounds are constituents of concern.

In addition to the pump that is installed in the well, operation requires a source of compressed gas (air or nitrogen) and a control box to adjust flow rate. The Illinois EPA does not have such equipment and it is possible that controllers and pumps from different manufacturers are not intercompatible.

Removal of a pump from a monitoring well is not without risk. Removal could damage the pump or the well itself, and once out of the well the pump requires special handling and storage to prevent it from becoming contaminated.

Due to these factors, it was necessary for PDC to utilize and operate their dedicated pumps to produce groundwater from the wells. Based on accepted groundwater sampling methodology, it was determined that PDC was producing groundwater at an appropriate flow rate for sampling. The Illinois EPA then used its own bottles, collected groundwater from the pump discharge, and transported the samples to its own laboratory to be analyzed by Illinois EPA chemists. PDC technicians also collected their own sample portion and analyzed it in their own laboratory, since was their routine sampling event for 2nd quarter 2014. A comparison of Illinois EPA and PDC results is posted on the Illinois EPA’s Clinton Landfill portal.

Is this because it would be extremely unlikely that the substances of concern could have migrated out of the well or could have been diluted to a point of no detection between the time of the 2nd quarter sampling and the time of the 4th quarter sampling? Is it not possible the conflicting results are the result of the extent of the release of those substances rather than the result of an erroneous reading or contaminated sample?

A release of contaminants from a landfill into groundwater would be the result of a hole in the landfill liner allowing leachate to migrate into the groundwater. Once there is a hole, it is more likely to remain open, thereby allowing a continuous release of leachate, than to heal itself or close and reopen intermittently. Even if there were a temporary hole and temporary release of leachate, groundwater flow rates are generally so low that elevated concentrations of constituents would be expected to remain in an impacted well for a number of sampling events prior to dissipating below analytical detection limits.