March 8, 2002

RE: Response to February 27, 2002 Correspondence [PCB releases at springs]

The United States Environmental Protection Agency (U.S. EPA) is in receipt of your letter, dated February 27, 2002 regarding your concerns with calculating the polychlorinated biphenyls (PCBs) mass released from the springs at Neal's Landfill. You also discuss an issue with the granulated activated carbon (GAC) at the Illinois Central Spring Water Treatment Plant which is associated with the Lemon Lane Landfill.

With respect to your comments in paragraphs two and three, generally relating to the development of predictive relations for PCB content of spring water, the U.S. EPA is well aware of the PCB "flushing" that occurs at both the Neal's Landfill and Lemon Lane sites during storm events. During storms, PCBs appear to be discharged from storage in the epikarst as slugs. At the Lemon Lane Landfill, the Illinois Central Spring (ICS) monitoring during 2001 has shown that these slugs may exceed peak concentrations of 500 microgram/liter (ug/l). Both Viacom and the U.S. EPA have spent, and continue to spend, considerable resources in assessing the nature of these PCB slug flows. The U.S. EPA is attempting to develop predictive relationships to allow us to estimate PCB concentrations using something other than the simple linear regression PCB-flow model we have applied to the Neal's Landfill data. To generate data to make this predictive relationship at Lemon Lane, we are focusing sampling resources during storms and at times when the PCB concentration peaks appear. Uses of the data may include:

1. 1. Long term ground water monitoring
2. Calculation of PCB discharge quantities
3. Engineering design for plant expansion

1. Spring Flow Monitoring
2. General Water Quality Monitoring
3. PCB Sampling and Analysis

It is also apparent from Figure 3 that the arrival of the PCB peak for all storm events precedes the conductivity minimum by 1 to 5 hours. Most commonly, the PCB peak occurs 1 to 2 hours before the conductivity minimum. Because the landfill is located near the headwaters of the Illinois Central Groundwater basin, and the PCBs must be flushed from the epikarst down to the phreatic zone prior to transport through the conduit system, the arrival of the PCBs is relatively late and only a short time prior to the maximum reflex of short-residence time ground water from the conduit system (the conductivity minimum). At Neal's Landfill, a completely different pattern is apparent.

Clearly, generating complete PCB chemographs for every storm is impractical. To obtain estimates of peak PCB concentration for a storm using a minimum number of samples it is necessary to be able to predict when the peak PCB concentration will arrive at ICS. The historic data presented above suggests that sampling slightly before the conductivity minimum is a reliable strategy for determining the peak PCB concentration.

Figure 4 shows the relationship between ICS peak flow rate and delta-t_spc for 13 storms during April to September 2001. These data were obtained from analysis of the ICS Flowink database. The relationship is similar to that shown for the older 1995-1999 data (Figure 3), and further refines the delta-t_spc and peak discharge relationship. I might add that Viacom has developed a similar power function relationship based on average flow rather than peak flow.

Either Figure 4, or more appropriately, the continuously recorded Specific Conductance data may be use to select sample times to monitor the maximum PCB concentration. We have made an effort to sample most storms in this manner since late October 2001, and are beginning to develop a good post-remediation storm flow dataset. One of the things that will probably complicate the development of a PCB predictive equation is that intense storms appear to generate higher PCB peaks than equivalent sustained rainfall events. But, it is not clear whether this necessarily amounts to a higher PCB mass. As you suggest, one of the techniques that may be most useful is to analyze both the flow hydrograph and PCB chemograph data to derive a total mass discharge from a storm, or a portion of a storm encompassing the PCB peak. Viacom has been using this technique to compare a few post-remediation storms at Neal Landfill, as we discuss below. It is U.S. EPA's view that in the long term this technique will offer a good strategy for long-term ground water monitoring of both Neal's and Lemon Lane Landfills. But, the approach requires a considerable amount of data, time and expense.

We return to the concern you raised regarding the use of a simple recession limb PCB-flow model for estimating Neal Landfill discharges. EPA recognizes that spikes in PCB concentrations occur very early on the rising limb of a typical storm hydrograph at Conard's Branch. Our sampling during 2001 suggests that the initial flows from the various Overflow springs of the Northwest Spring System, may indeed have the highest PCB concentrations.

Figure A-22 shows PCB and flow data at Conard's Branch during a storm event on February 25, 2001. This storm event had comparable flow estimates by both Viacom and the EPA, and hourly PCB samples over a 48-hour period. It is one of the best post-remediation storm events monitored at Conard's Branch. We have chosen this storm for examination because a large amount of PCB data were gathered, the rising limb of the storm hydrograph was sampled, and a particularly prominent, and unusually high, PCB peak of 12 ug/1 occurred on the rising limb. The PCB peak, represented by a single hourly sample at Conard's Branch occurs in conjunction with a conductivity peak. The conductivity peak occurs after surface water runoff in the Conard's Branch channel ceases, and prior to the arrival of the surge of storm flow through the conduit system. This situation has been observed during other sampling events, and may represent long-residence-time groundwater containing elevated PCB levels that is flushed from the karst drainage system by storm water very early in a storm event. PCBs appear at maximum concentration very early in a storm event due to the extreme downstream position of the landfill within the ground water basin.

In the recent of the draft Neal Landfill Long Term Ground Water Monitoring Plan (the Final Long-Term Groundwater Monitoring Plan should be released in a few weeks), Viacom presented cumulative PCB mass curves for a few monitored storm events, including the February 25, 2001 event. The U.S. EPA believes this type of analysis has merit in assessing long-term trends in PCB storm discharges. The Long Term Ground Water Monitoring Plan, Figure 28 indicates that the total PCB mass released during the monitored period of the February 25 storm event, discussed above, was about 19 grams. The U.S. EPA independently performed a calculation using the same flow and PCB data and derived a mass release estimate of 18.1 grams. This analysis used the "summing of the quadrangles approach" you reference in your letter.

Using the recession limb PCB flow regression we have updated for the revised Neal Landfill Current Status Report, the PCB mass release for this storm is calculated at 11.7 grams, or about 65% of the value calculated using the summing procedure. The difference, clearly, is that flow regression model does not consider the prominent, though short term PCB spike on the rising limb. We thus regard the mass release estimates using PCB - flow regression as conservative, but not unreasonable, given the relative lack of more definitive data at this point in time to make a more informed PCB mass release model. Only a few post-remediation storm monitoring events have been conducted at Neal Landfill to date, and rising limb storm data are not available for some of these. In the future as more data are collected we anticipate moving toward an analysis as you have suggested, and as we are developing for Illinois Central Spring. In the interim we believe the simple flow regression analysis provides a reasonable, conservative estimate of PCB mass discharged.

The tone of your correspondence appears to question the U.S. EPA and it's consultants Tetra Tech and Earth Tech's competence. The U.S. EPA and the other parties to the Consent Decree have been putting considerable time and effort into understanding the complex hydrogeology and the U.S. EPA is making considerable progress. The U.S. EPA would like to make it clear to you that in addition to our continuing analysis of PCB mass released at Neal's Landfill, with the help of the United States Geological Survey (USGS), flow analysis at Neal's Landfill has been improved. The USGS has assisted the U.S. EPA in gathering flow data for the overflow springs at Neal's Landfill and Viacom has installed a new weir in Conard's Branch for more accurate flow measurements. Viacom has also hired an Indiana University Professor and they have completed a storm event treatability study to evaluate possible treatment options at Neal's Landfill. The final treatability report should be released in a few months and other treatability studies may be scheduled. The U.S. EPA has also funded the sampling of fish tissue in Conard's Branch and Richland Creek and the U.S. EPA is in the process of evaluating the risk to both human health and the environment. Finally, the U.S. EPA will be releasing shortly the updated Neal's Landfill Status Report which summarizes the water, sediment and fish tissue data for the project.

In your final paragraph you infer that poor data may be at fault for performance failure of the GAC units at the Illinois Central Spring water treatment plant. You further criticize the Illinois Central Spring water treatment plant by stating that the "having to add new tanks and components to a system that was supposed to handle 25 year storm events, yet which cannot manage base flow treatment needs without discharging untreated water, as is occurring, indicates a poor understanding of the problem and a poor management of public resources." After discussing this issue with the Indiana Department of Environmental Management (IDEM), which is operating the ICS water treatment plant, you appear to be misinformed and have made an inaccurate conclusion. Also somewhat surprising is your lack of understanding of the pilot plant approach both the U.S. EPA and IDEM are using, especially considering the numerous public discussions by the U.S. EPA and in personal discussions you have had with IDEM staff.

The U.S. EPA with full support of all the governmental parties decided in 1998 that building a water treatment plant with expansion capabilities under U.S. EPA's removal authority was appropriate. Illinois Central Spring had been releasing PCBs unabated for many years and Viacom refused to address the release of PCBs. Enough information was available to build a pilot plant under the U.S. EPA's removal authority and provisions to modify and expand the water treatment plant was taken into consideration in the design. Our knowledge of ICS is improving as we gather more PCB storm and flow data, but to wait until our complete understanding of ICS occurs to build a final water treatment plant would have resulted in nothing being done to address the release of PCBs for many years. It was extremely critical to have the water treatment plant operating during the remediation of the Lemon Lane Landfill.

The U.S. EPA would suggest that you contact Ms. Jessica Huxhold Fliss of IDEM for specific details of plant operation, but it is our understanding that given the rainfall events in December 2001 the system worked very well within its design parameters and in every case exceeded its design capacities. In December, multiple back to back storm events occurred and given the large volumes of water produced, the GAC units required backwashing to prevent damage to the units. This is not a failure of the GAC units but is operational issue associated with a pilot plant. Operational issues along with evaluating additional storage and process equipment for the final water treatment plant remedy is occurring. In addition, the public will have an opportunity to comment on any future remedy proposals.

Finally, the U.S. EPA disagrees with your statement regarding our lack of understanding of the problem and poor management of public resources. The U.S. EPA with the help of it's consultants have made tremendous progress in understanding the hydrogeology at the Bloomington sites and we take seriously the management of the limited public resources.

Sincerely,

Thomas Alcamo
Chemical Engineer
US EPA Region 5
77 West Jackson Blvd.
Chicago, IL 60604-3590