March 18, 2002

Thank you for your letter of January 12, 2002, expressing your concerns about operation of the Illinois Central Spring (ICS) water treatment facility. I would like to take this opportunity to respond to your comments.

You state in your letter that you feel the facility is not operating successfully as a PCB remediation facility, based on your perceived deficiencies in design and monitoring. The plant was constructed in 1999 under the Environmental Protection Agency's (EPA) removal authority to address the problem of polychlorinated biphenyl (PCB) contaminated water emerging from ICS. The purpose of the plant is to reduce the risk of human exposure to PCBs through reduction in the PCB content of water emerging from ICS. As such, the sampling plan for the plant is designed to verify that the plant effluent has been treated to an acceptable level for PCBs prior to discharge. Based on the effluent sampling conducted to date, the plant is operating successfully as a PCB remediation facility.

The 25-year storm event is merely a design event, used to engineer the correct sizes for pumps, the sump, and other components. The facility is still in the pilot stage of operation, and data gathering activities are still ongoing. Further evaluation of the facility will take place at a later date, as the status of the facility changes from a removal to a remedial action. Additional storage capacity, thickener capacity, or other modifications may be added if determined to be necessary.

You express concern that the main channel of ICS is not covered. After rain events, overflow springs emerge from the hillside north of the railroad tracks and flow toward the main channel of ICS. It was determined during design that we should capture as much of the water that flows from these additional springs as possible. The inlet pipe is situated in such a way that allows the most efficient capture of water while being as close to the main spring outlet as possible. It would be extremely difficult, if not impossible, to cover the springs to the extent that we would ensure that no part of the inlet flow is exposed to the air. Your questions regarding Henry's Law constant, vaporization, and sampling issues have been reviewed. Indiana Department of Environmental Management (IDEM) and U.S. EPA staff have made the following observations:

1) To determine the potential for PCB exposure in air inside the facility, the U.S. EPA conducted air sampling for PCBs on July 4, 2001, and October 24, 2001. The sampling was conducted under worst-case scenario conditions, with all venting closed, the plant operating at maximum capacity (1000 gallons per minute [gpm]), and the sampling pumps placed directly over the tops of the sludge thickener tanks, the clarifier, and the opening in the floor of the spring receiving sump (SRS). The daily average flow during the October 24, 2001, storm was 2,682 gpm. Peak flow during the July 4, 2001 storm was approximately 1,217 gpm. We do not have daily average flows calculated for the period before the IDEM contract was executed, which was August 1, 2001. Under low flow conditions, approximately 90&per; of the time, the PCB concentrations in the spring are lower, and likely to produce lower PCB results in air.

PCB levels recorded in air during the storms are as follows:

These samples do not represent the typical exposure of an operator during a normal work day, but if we assume the highest level measured in the facility is a typical exposure, the level would still be below the Occupational Safety and Health Administration (OSHA) permissible exposure level (PEL) of 1,000 ug/m³ for Aroclor 1248. We plan to conduct further personnel sampling to determine actual exposure to PCBs in the breathing zone. The results will be reviewed, and changes in operations of the plant facility will be implemented if it is determined there is an unacceptable risk to worker safety. We also may implement site perimeter air monitoring, based upon the review of the facility monitoring. Based on the data we have reviewed to date, we believe volatilization from the plant does not pose a risk to human health or the environment.

2) Henry's Law describes the theoretical behavior of ideal substances at equilibrium. To be precise it is, in the nomenclature of Levine (1988):

P_i = Ki xi, where P_i is the vapor pressure of solute i,
X_i is the concentration of solute i, and
K_i is the Henry's Law constant for solute i in units compatible with Pi and xi.

The most surprising thing about this "law" is that, as long as you do not have additional phases (such as sediment or a nonaqueous phase liquid) to complicate things, it actually describes the behavior of PCBs in water and air under equilibrium conditions. The turbulence that is experienced in the plant may allow equilibrium conditions to be attained at the plant. However, this situation would apply only at the air-water interface. The air at other locations, such as in the breathing zone, within the plant, and outside the plant, is affected by dispersion and dilution.

Molecular weight for Aroclor 1242 = 266.5 g/mol = 2.665 x 10⁸ ug/mol
Therefore, 50 ug/L / 2.665 x l0⁸ug/mol = 1.876 x 10^-7 mol/L = 1.876 x 10^-4 mol/m³ as 10³ L = m³
Using Henry's Law, vapor pressure= 5.2 x 10^-4 atm-m³ /mol x 1.876 x 10^-4 mol/m³= 9.756 x 10^-8 atm x (1 x 10⁶) = 0.09756 ppm (or 0.09756 x [1 x 10^-6mol/mol])
0.09756 (1 x 10^-3 mol/mol) x (266.5 g/mol / 24,450 mL/mol) x (1 mg/ lx10^-3g) x (1 mL/lxlO^-3 L)= 1.1 x 10^-3 mg/L= 1.1 mg/m³
Therefore, the maximum observed PCB concentrations in air within the treatment facility are a factor of 25 less than the theoretical predictions under equilibrium conditions at the plant (1.1 mg/m³ / 0.044 mg/m³).

Acceptable general public exposure levels to PCBs are typically set an order of magnitude or two below the OSHA PEL. In Region 5, the precedent for public exposure to PCBs is from the Grand Calumet River site, where the maximum acceptable level is 1,000 ng/m³. In addition, the general public does not frequent the treatment building, either inside it or near it on the outside. Therefore, one must calculate an additional dispersion factor that considers the mixing of the plant interior air with outside air and diffusion of the mixed air as it travels to the fence line. These dispersion factors are usually several orders of magnitude. As noted above, there is a dispersion factor of 25 inside the spring receiving sump room. Typically, indoor air concentrations inside the treatment plant are much less, implying higher dispersion values because the PCB concentrations detected have been much lower than the sump room. Additionally, outdoor PCB air concentrations will likely be much lower as dispersion factors will be greater. Therefore, the expected levels of PCBs from this source to the general public would be much less than 0.044 mg/m³.

Solubility and vapor pressure are independent parameters. See Chapter 3 on vapor pressure and Chapter 7 on water solubility in Boethling and Mackay (2000) for more details. Therefore, finding a correlation between them would be due to random chance, depending primarily on which chemicals one chose to use for the correlation. If the selected chemicals all have similar properties (such as volatile and semivolatile organic chemicals with no significant ionization properties; a group which includes organochlorine solvents, PCBs, polynuclear aromatic hydrocarbons, and most organochlorine pesticides) then some apparent spurious correlation is rather likely.

Finally, some useful data for Aroclor 1242 at 25°C (ATSDR 2000) that is being treated at the ICS plant:
Molecular Weight: 266.5 g/mol
Boiling Point: 325 to 360°C
Water Solubility: About 240 ug/L (three studies were listed-two others stated solubilities of 340 and 100 Ug/L, respectively.)
Henry's Law Constant: 5.2 x 10^-3 atm-m³/mol
Vapor Pressure: 4.06 x 10^-4 mm Hg

Generally, water emerging from ICS has been measured at a temperature ranging from 12.88°C to 13.2°C. As temperature decreases, both solubility and vapor pressure will decrease, as well as the Henry's Law Constant.

3) System performance monitoring at the ICS facility is conducted on a regular basis. Please see Attachment 1 for details of the sampling and analysis program. Influent and effluent samples are taken on a weekly basis when flow is over 100 8pm to ensure adequate treatment. Storm sampling occurs when flows are in excess of 500 8pm. These parameters can be revised if it is determined to be necessary. Additional parameters can be added to ensure plant optimization.

The automatic sampler in use at the facility is utilized to ensure storm samples are not missed if they occur during the night or weekend hours. The sample carousel is refrigerated to a temperature of 4°C, to minimize potential volatilization from the open container. The samples are removed from the sampler carousel as soon as possible, and are sent to the laboratory promptly for analysis. IDEM's contractor will take manual samples (using a hand dipper) to correlate with the storm flow samples taken by the auto sampler, to ensure data accuracy.

The mass balance approach for determining PCB removal efficiency at the plant would be very difficult to implement. The concept of mass balance is to measure the amount of contaminant going into the treatment train and determine how much is removed at each stage. The input mass of PCB into the system is dependent on flow volume and PCB concentration in the flow. Specifically, the influent quality is significantly impacted by environmental factors such as rain events. In addition, to do a mass balance on the ICS plant, one has to collect representative samples of all inputs to and outputs from the ICS plant. At the ICS plant, (1) the input point would be influent to the clarifier and (2) the ultimate outputs would be solids captured in the thickener, spent carbon, treated effluent, potential PCB sinks such as filter media (sand and coal), disposable micron-filter bags, and ambient air above the open treatment units. A good mass balance requires that all inputs and outputs be samples for a well-defined control volume, which is not practical at the ICS plant. Even in a hypothetical situation, when many media and sampling locations are involved, the cumulative sampling and analysis error defeats the purpose of setting a meaningful and realistic goal for mass balance. For this reason, PCB mass balance is not considered a required element for this project.

At this time, there are no plans for performing mass balance calculations. At some point in the future, samples between the various components of the treatment train (clarifier, multi-media filters, etc.) may be collected for plant optimization purposes. Sludge sampling is done only for disposal purposes. Please see Attachment 1 for details regarding the sludge sampling program. The sludge is contained in a roll-offbox, which is kept covered at all times when not in use. Volatilization from the sludge in the roll-off is likely to be minimal.

The ICS facility was designed to remove PCBs from spring water, and, based on the data gathered to date, is effectively achieving this objective. IDEM and EPA will continue to review and evaluate possible expansions or upgrades to the facility as necessary, as we work to convert the plant from a pilot facility to a long-term remedy.

References

Levine, Ira N. 1988. Physical Chemistry. Third Edition. New York. McGraw-Hill Book Company.

Lewis, Gilbert N., and Merle Randall. 1961. Thermodynamics. Second Edition, revised by Kenneth S. Pitzer and Leo Brewer. New York. McGraw-Hill Book Company.

Boethling, Robert S., and Donald Mackay. 2000. Handbook of Property Estimation Methods for Chemicals. Boca Raton, Florida. Lewis Publishers.

Agency for Toxic Substances and Disease Registry (ATSDR). 2000. Toxicological Prof le for PoIychIorinated Biphenyls (PCBs). November.

Panshin, Sandra Y.and Ronald A. Hites. 1994. Atmospheric Concentrations of Polychlorinated Biphenyls at Bloomington, Indiana Environmental Science and Technology, vol. 28, no.l2, pages 2008-2013, December.

I hope this letter answers your questions adequately. If you wish to discuss this matter further, you may contact me at (317) 233-2823.