10/24/97 17:00 ®202 833 7057 1^1002/013 0000 O TCEWEINBERG GROUP INC, 1220 Nineteenth EX NW, Suite 300 Weshingtan,DC ZM36-2400 Phone 2D2.«3.»i/7 Fa* 202.833.7057 e-msil science' I 1 weinberggroup.com WASHINGTON BRUSSELS October 24, 1997 VIA E-MAIL Mr. Mark Leibrock Waste Management Inc. - Midwest Group Two Westbrook Corporate Center P.O. Box 7070 Westchester, IL 60154 Dear Mark: We have finalized the responses to the U.S. Environmental Protection Agency's \ USEPA) comments on the H.O.D. Landfill Baseline Risk Assessment (BRA). This final version has incorporated a response to paragraph one fl[ 1) of the October 2, 1997 EPA memo, as requested by the site RPM, Ron Murawski, on October 6, 1997. The overall conclusions of the risk assessment with respect to the need for remediation are unchanged. If you have any questions or comments on our responses, please feel free to call me. Very truly yours, Sarah A. Foster THE WEINBERG GROUP INC. SAF/skw Attachment
Transcript
10/24/97 17:00 ®202 833 7057 1^1002/013
0000 O
TCEWEINBERG GROUP INC,
1220 Nineteenth EX NW, Suite 300Weshingtan,DC ZM36-2400
Phone 2D2.«3.»i/7Fa* 202.833.7057
e-msil science' I1 weinberggroup.com
WASHINGTONBRUSSELSOctober 24, 1997
VIA E-MAILMr. Mark LeibrockWaste Management Inc. - Midwest GroupTwo Westbrook Corporate CenterP.O. Box 7070Westchester, IL 60154
Dear Mark:
We have finalized the responses to the U.S. Environmental Protection Agency's \ USEPA)comments on the H.O.D. Landfill Baseline Risk Assessment (BRA). This final version hasincorporated a response to paragraph one fl[ 1) of the October 2, 1997 EPA memo, asrequested by the site RPM, Ron Murawski, on October 6, 1997. The overall conclusions ofthe risk assessment with respect to the need for remediation are unchanged.
If you have any questions or comments on our responses, please feel free to call me.
Very truly yours,
Sarah A. FosterTHE WEINBERG GROUP INC.
SAF/skw
Attachment
RESPONSES TO AGENCY COMMENTS ON THEH.O.D. LANDFILL SITE BASELINE RISK ASSESSMENT RESPONSES
Comment p. E-6: Change "MCLG" to "MCL."
Response: Our original response referred to a thallium maximum contaminant level goal(MCLG) of 2 fJg/L. iliis should h _ v c been referred to as a maximum contaminant level(MCL)of2ug/L.
Comment p. 1-2: In addition to the statistical comparison to background, a toxicityscreen should be performed to select chemicals of potential concern (COPC) to ensure noCOPCs are omitted from evaluation.
Response: The screening process used in the Baseline Risk Assessment (BRA) to selectCOPCs was approved in 1994 by USEPA Region V. The history of USEPA's approvalof the HOD Landfill BRA approach is presented in the following documents:
Technical Workplan dated October 12, 1993USEPA Region V comments dated January 21, 1994Waste Management of Illinois, Inc.'s (WMII's) response to comments datedFebruary 24, 1994Additional USEPA Region V comments dated May 2, 1994Additional WMII's responses to comments dated May 18, 1994
The detailed methodology for summarizing site sampling data and selecting COPCs wasexplicitly provided in WMII's February 24, 1994 response to USEPA comments. Thisletter states that inorganic compounds would not be retained as COPCs if either: 1) theconcentrations in site samples were not significantly different than the concentrations inbackground samples, or 2) they were essential human nutrients. If these criteria were notmet, the inorganic compound was retained as a COPC. For example, if a statisticalcomparison to background could not be conducted (e.g., background data were notavailable or there were fewer than three samples from either site data or background data)and the inorganic was not an essential human nutrient, it was automatically selected as aCOPC. Further, all organic chemicals were conservatively selected as COPCs regardlessof their toxicity (i.e., even organics with very low toxicity were included as COPCs).This methodology was reviewed by USEPA Region V, and the Agency had no objectionsto or comments on this approach in their review comments dated May 2, 1994.
Although the selection of the COPC approach was approved by USEPA Region V in1994, discussions held with USEPA Region V on July 23, 1997 indicated the Agency'sinterest in examining potential risks for inorganic compounds that were detected in thesurficial sand and the deep sand and gravel aquifers but were not originally evaluated indetail in the BRA. These inorganic compounds were not evaluated because they werewithin background levels or are essential nutrients, or both, criteria that were accepted bythe Agency in 1994 for exclusion of a chemical as a COPC. In addition, EPA Region V
(EPA 1997) provided further input on October 2, 1997 regarding selection of essentialhuman nutrients as potential chemicals of concern. EPA (1997) evaluated the maximumdetected concentrations for the inorganic compounds not originally evaluated in the BRAfrom the surficial sand and deep sand and gravel aquifers (see Table 1). EPA Region Vconcluded that:
"the following chemicals should be considered as potential COCs in both,the Surficial and Deep Aquifers: calcium, iron and sodium. Thus, theseinorganic chemicals should be discussed in the Baseline Risk Assessment,or in a Supplement to the Baseline RA.The Nutritional Screen, for screening nutrients and essential elements aspotential COCs, is similar to the screen used for non-cancer chemicals.That is, any non-cancer chemical whose maximum concentration in amedia results in HQ 0.1, the chemical should be considered as a potentialCOC. The Nutritional Screen is similar in that, any nutrient or essentialelement whose maximum concentration in a media results in a Ratio > 0.1,the chemical should be considered as a potential COC.The Ratios for calcium, iron and sodium were 0.25, 0.16 and 0.38,respectively, in the Surficial aquifer, and were 0.2, 0.3 and 0.3,respectively, in the Deep aquifer.In addition, Magnesium at 55 ppm and 63 ppm in Surficial and Deepaquifers, respectively, results in a HQ 0.1, using an oral RfD of 9.7mg/kg/day. Thus, Magnesium also qualifies as a potential COC.1'
In response to these new comments by EPA Region V, risks were calculated for all theinorganic compounds that were not originally evaluated in detail in the BRA. A reviewof the BRA showed that 10 inorganic compounds were detected in the off-sitedowngradient surficial sand aquifer but were not included as COPCs. Five inorganiccompounds were detected in the off-site downgradient deep sand and gravel aquifer butwere not included as COPCs. Eight of the 10 compounds in the surficial sand aquifer hadconcentrations downgradient from the site that were not significantly different frombackground levels. An overview of the basis for not selecting these compounds asCOPCs may be found in Table 2-13 of the BRA,
Potential exposures to the additional inorganic compounds were evaluated using the sameconservative exposure assumptions applied in the BRA (i.e., ingestion of 2 L/day ofwater, 350 days/year for 30 years). Additionally, potential exposures were calculatedusing the single maximum detected concentration downgradient of the landfill. The useof the maximum concentration will overestimate potential exposures, but allows for arapid screening evaluation in response to this comment.
The calculated exposures were compared to USEPA health-based toxicity criteria(noncancer references doses or RfDs and cancer slope factors) where available. RfDsreflect the average daily dose below which noncancer effects arc not expected to occur,even among sensitive subpopulations. USEPA toxicity criteria were not available.
however, for four compounds that are essential human nutrients. In this analysis,therefore, potential exposures for these compounds were compared to recommendeddietary allowances (RDAs). RDAs are suggested levels of essential nutrients consideredadequate to meet the nutritional needs of healthy individuals. Intake of an essentialnutrient above the RDA does not mean that an adverse health effect may occur. In fact,ingestion of levels higher than the RDA for some nutrients can have beneficial effects.For example, the calcium RDA for an adult is ?00 mg/day, whereas in pregnant orlactating women the RDA is 1,200 mg/day. Further, even large doses of calcium showno toxic effects as the body rids itself of excesses by reducing absorption and increasingurinary excretion (Garrison and Somer 1995).
Different approaches were used to evaluate each inorganic compound, depending uponwhether USEPA toxicity criteria or RDAs were available. For compounds with USEPARfDs, hazard quotients were calculated as the ratio of exposure (in mg/kg/day) to theRfD. Hazard quotients less than one indicate that adverse health effects are not expectedfor that chemical whereas quotients greater than one indicate a potential for adverseeffects to occur under the assumed exposure conditions. Excess lifetime cancer riskswere calculated for arsenic, the only inorganic compound evaluated with a USEPA cancerslope factor, by multiplying the exposure (in mg/kg/day) by the slope factor. Targetcancer risk levels used by USEPA in evaluating Superfund sites range from one in onemillion (1x10" ) to one in ten thousand (1 x 10" ). For compounds with RDAs, theexposure (in mg/day) was divided by the RDA to produce a ratio. Ratios derived usingthe RDA indicate whether daily exposure to the compound would be lower or higher thanan adequate nutritional intake. These ratios are not hazard quotients, and do not indicatethe potential for adverse health effects.
Table 1 lists the inorganic compounds evaluated in this response, the USEPA toxicitycriteria and RDAs, and the calculated results (hazard quotients, excess lifetime cancerrisk and ratios of exposure to the RDA). As shown on this table, the hazard quotients areless than one for all of the inorganic chemicals in the surficial sand and deep sand/gravelaquifers, indicating that adverse health effects would be unlikely to occur for thesechemicals. This conclusion remains the same even if these hazard quotients arecombined with those for chemicals already evaluated in the BRA according to targetorgan or endpoint affected. The excess lifetime cancer risk assuming regular exposure tothe maximum arsenic concentration in the surficial sand aquifer for 30 years is 1x10" . Ifthis risk is considered in conjunction with that already calculated for the BRA, the total
_^l _
excess lifetime cancer risk would be 2x10 , due to arsenic and beryllium. This riskslightly exceeds USEPA's target risk range for Superfund sites; however, there is noactual current use of water from the off-site surficial sand aquifer and the maximumdetected arsenic concentration of 6.3 ug/L is well below its legally enforceable MCL of50 ug/L. Further, arsenic is not considered to be a site-related chemical based on acomparison of downgradient to background concentrations. In addition, the availablesampling data suggest that beryllium may not be site-related either. Beryllium wasselected as a COPC in the off-site downgradient surficial sand aquifer because nobackground dissolved groundwater data were available. It was only detected in 1 of 4
Tabla 1Evaluation ol Inorganic Chemicals hi Off-Site Downgradlent Grcundwatar in Reapoiue to USEPA Region V Comment
- Not ippficaWeBRA = BaseCra RdV AsseastnenrlEPA Region III = ERA Region III Rfsn Based Concentration Table March 17. 1997IRIS = Inlegraied Risk Information System. National Cento for Environ men la I AstetsnwntMA = Not available or not applicable.ND - Nal detected
a) Hazard quotient and cancer nek calculated using the same assuifipliorvs proscnted In ttie baBdine risV asstsimonLHazard Quolient = [(ConcwiUatioft(iiC^-) ' 2(L/day) * 350 (daji/yr) ' 30 (yr)*1E-3 (moyug))/ (70 (kg) * I0.95Q (daya»l / R'D (mo/kfl/day)Exceis lifeime cancer risk = [(CancenWation [ug/L) ' 2 (L/ila/)' 35D (day/yr>' 30 (yr)*5E-3 (mg/ug))/(70 (kg) ' 25,550 (day*))] ' Cancel slope factor (mgfta/dayH
b) The cadmium till) developed tor dnnting watw oxpostres was uted lo evaluate risks.L} Recontfner>dedDlelary_Allowances (RDA)obraioed tram Natkmal Research COUIKJ! (18B9). Recommandad Dialaiy Affowanoes.. KaUonal Acadniny Press. Waihington, DC 10th Edition.d) Rato = [CancenlratJon (uj/L) * 2 (L/day) *1E-3 (irg/ug
samples from off-site surficial sand aquifer at a concentration of 0.95 ng/L. Berylliumwas not, however, detected in the on-site surficial sand or deep sand and gravel aquifers,or in the off-site deep sand and gravel aquifer. It was detected in 1 of 34 regionalbackground samples (total not dissolved) at a concentration of 1 ug/L.
The ratios of exposure to RDA are all below one, indicating that daily ingestion of themaximum uetecte-1 oncentration of essential lutrients would be less than the levelsconsidered adequate to meet the nutritional needs of healthy individuals. This is notsurprising, as diet provides the primary source of these nutrients. The incrementaldifference between the RDAs and the intakes calculated here will not have adverse healthimplications.
In conclusion, the BRA is not substantially affected by evaluation of inorganic chemicalsoriginally removed as COPCs. Only the excess lifetime cancer risk for arsenic is of notebecause it is at the high end of USEPA's target risk range. However, as described above,in the previous response document (dated April 24, 1997) and in the BRA, arsenicconcentrations downgradient of the site were not significantly different from backgroundlevels, and the arsenic concentrations do not exceed USEPA's MCL.
Comment p. 2-1 and 2-2: In the absence of the sample quantitation limit for inorganics,one-half the contract-required detection limit (CRDL) should used. The use of one-halfthe CRDL versus one-half the instrument detection limit (IDL) can affect the distributionof the data and ultimately determine whether the 95% upper confidence limit (UCL) orthe maximum value is used.
Response: This comment only affects antimony in surface water because the maximumdetected concentration was used to evaluate all other inorganics in all media exceptberyllium in soil (which was detected in 5 of 5 samples). Antimony was detected in oneof six surface water samples with a maximum detected concentration of 20 ug/L. One-half the CRDL of 60 ug/L for antimony exceeds the maximum detected concentrationand, therefore, this result would be excluded in calculating a 95% UCL to prevent theaverage from being artificially biased high by detection limits.
Risks were, however, recalculated for antimony in surface water using the maximumdetected concentration of 20 ug/L, rather than the 95% UCL of 17 ug/L. The revisedhazard quotient for dermal contact with 20 ug/L antimony in surface water is 0.038, stillwell below a comparison level of 1. The resulting hazard index for dermal contact withsurface water by potential site trespassers would consequently increase from 0.03 to 0.04(based on rounding to one significant figure), indicating that adverse health effects areunlikely to occur under the assumed exposure conditions. This revised result, therefore,has no impact on the overall conclusions of the risk assessment.
Comment p. 2-1 and 2-2: The Region does not agree with the following statement"although the use of detection limits has limitations, it is more conservative than the useof quantitation limits."
Response: This sentence from the original response (dated April 24, 1997) was incorrectand should be deleted.
Comment p. 2-7: Please send the data used to generate the t-test results for arsenic andmagnesium in the off-site surficial groundwater.
Response: A copy of the data is presented in Attachment A.
References:
Garrison, R.H. and Somer, E. 1995. The Nutrition Desk Reference. Third Edition.New Canaan, CT: Keats Publishing.
U.S. Environmental Protection Agency (EPA) Region V. 1997. Memorandum fromAndrew Podowski, Technical Support Section, to Ron Murawski, RPM, regardingResponse to Waste Management's Fax of 8/19/97 for the HOD Landfill. October 2,1997.
ATTACHMENT A
-"50 93 PAGE 41
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