WESTON WAYWEST CHESTER, PA 19380PHONE: 215-69Z-3030TELEX: 83-5348

MANAGERS \ S OESIGNE«S/CONSUlTAMr&

3 August 1993

Ms. Lisa MarinoU.S. Environmental Protection AgencyDE/MD Remedial Section (3HW42)Region ffl841 Chestnut BuildingPhiladelphia, PA 19107

W.O. No.01631-016-002

Dear Ms. Marino:

On behalf of Sussex County, I am submitting the enclosed Sussex County ReviewComments on EPA's Preliminary Human Health Risk Calculations and Findings forSussex County Landfill No. 5 (dated 15 June 1993). These risk calculationsreceived by Sussex County on 1 July 1993.

Should you have any questions, please contact us.

Very truly yours,

ROY R WESTON, INC.

Thomas A. Drew, P,G,Project ManagerGeosciences Department

TAD/rfh

Enclosure (as stated)

cc: Michael Izzo, P.E. - Sussex Co.Robert Wood, RE. - Sussex Co.George Weiner, Esq. - McCutchen, Doyle, Brown, and EnersenJamie Hackney - DNRECEva Timmer - WESTONChuck Dobroski - WESTON

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SUSSEX COUNTY REVIEW COMMENTSEPA'S PRELIMINARY HUMAN HEALTH RISK CALCULATIONS

AND FINDINGSSUSSEX COUNTY LANDFILL NO. 5 (LAUREL LANDFILL)

This document presents Sussex County's comments on the preliminary human health riskcalculations and findings for the Laurel Landfill Site, which were prepared by U.S. EPARegion III and documented in the attached agency memorandum dated 15 June 1993.The attached document was received by Sussex County on July I, 1993,

This preliminary risk assessment document notes the agency's conclusion that the onlypotential exposure pathway of any significance is the groundwater route, an opinion weshare with the agency based on our knowledge and understanding of site conditions andan evaluation of the RI analytical data. Notwithstanding the County's concerns on thefuture and current use scenarios, as specified in the paragraphs that follow, the riskcalculations showed that even in the conservative baseline conditions, exposure to areagroundwater did not pose an excess cancer risk beyond EPA's 10"" to 10'6 range ofgenerally acceptable risk.

With respect to the current use scenario, the Joseph well was selected as the sole receptorof contaminants via the groundwater pathway, apparently since contaminant levels at theother residential wells downgradient of Laurel Landfill were negligible. As you know,however, Sussex County has some time ago installed a treatment system on the Josephwell to prevent any exposure to contaminants that may appear in that well. Consequently,there is some question whether the Joseph well should be considered a current receptorof groundwater contaminants in the context of a risk assessment, and it cannot beconsidered in connection with any future use scenario.

We interpret from the Preliminary Risk Assessment that the RI groundwaier quality datafrom the listed monitoring wells form the basis for evaluating potential risk under EPA'sproposed future groundwater use scenario. It is questionable whether future groundwateruse in the site vicinity is a reasonable consideration given constraints/Iimitalions presentlyemployed by both the DNREC and Sussex County relative to future groundwater usageand development in the area surrounding the Laurel Landfill. Under a Memorandum ofUnderstanding (MOU) with the DNREC, Sussex County previously establishedgroundwater management zones around the landfill to control and restrict futuregroundwater usage, and the installation of a central water supply system is scheduled fornext year. This MOU program is currently being implemented by the DNREC andSussex County. Subsequent to the steps outlined above, notices were added to the deedsfor all property in the groundwater management zones, confirming the existence of theMOU and its related restrictions on groundwater usage. Furthermore, the Sussex CountyCouncil has adopted a formal resolution precluding any future property developmentwithin the management area without first evaluating possible adverse impacts of the site

SUS5EX-W1EVIEW.RFD 1 2 August 1993

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on that ust, Collectively the above mentioned actions undertaken by Sussex County andthe DNREC greatly diminish, if not eliminate altogether, the possibility of futuredevelopment and future groundwater use in the area around the Laurel Landfill.

When assessing existing supply wells as potential future receptors, recognition should begiven to the apparent stability hi downgradient groundwater quality conditions, asidentified from the trend analysis of historical site data (see attached document dated 18January 1993), This apparent stability in water quality conditions is further supported bythe more recent analytical data generated from the RI sampling events. Considering theaforementioned, and the in-place mechanisms to preclude future ground-water use in thesite vicinity, it is not unreasonable to propose a future groundwater use that does notshow any human receptors of area groundwater.

An additional point of concern is the language that is used in the assessment wheninterpreting the results of the non-carcinogenic hazard index and carcinogenic risk. It isfrequently stated in the preliminary human health risk assessment that if a hazard indexvalue exceeds one that "adverse health effects may be expected to occur". This is amisleading statement that can lead a reader to believe that adverse health effects are likelyif a hazard index of one is exceeded. In order to prevent this misinterpretation of thehazard index, the language should be changed to indicate that if a hazard index of one isexceeded this simply means that there may be a concern for potential health effects. Inaddition, the assessment refers to carcinogenic risk to children" when in fact the risk isnot to a child but to an individual over a lifetime due to exposure as a child.

As discussed in the preliminary human health risk assessment, the hazard index (whichexceeds one) is driven primarily by benzene through the inhalation exposure route.Benzene contributes 97-98% of the total hazard index based on the monitoring well data,and 96-98% of the total hazard index based on the residential well data. As you knowthere are currently no EPA-verified inhalation reference doses (RfDs) or referenceconcentrations (RfCs) for benzene available in either the Integrated Risk InformationSystem (IRIS) or the Health Effects Assessment Summary Tables (HEAST). As outlinedin EPA's Risk Assessment Guidance for Superfund (Part A, Human Health EvaluationManual), these are the preferred sources of toxicity information when conductingSuperfund risk assessments. If a health criterion is not available from these sources orany other EPA documents, then a request to develop a health criterion can be made toEPA's Environmental Criteria and Assessment Office (ECAO). Based on our discussionswith EPA Region 111 personnel, we have been informed that the benzene inhalation RfDused in the human health risk assessment was based on a RfC developed by the ECAO.We received the supporting documentation for the ECAO derivation of the benzene RfCon July 19, 1993.

As a brief summary, the ECAO report, dated December 15, 1992, begins by noting thatthe development of a RfC for benzene was last discussed by the RfD/RfC Work Groupin July of 1989, and that there had been some difference of opinion between EPA offices

SUSSEX-SNtEVffiWJRFD 2

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as to an acceptable RfC. The report went on to summarize the results of several benzeneinhalation studies involving human and animal populations. The provisional RfC derivedby ECAO was based on a no-observed-effect-level (NOEL) for hematological effects inindividuals occupationally exposed to benzene. The principal study relied upon wasconducted by Collins, et al. in 1991. In this study, workers were exposed to an 8-hourtime-weighted average (TWA) of 0.01 to 1.40 ppm benzene over a 10-year period. Themean TWA exposure was 0.045 pprn, according to a personal communication with Dr.Collins, which was not further documented. The report also noted that chronic exposureof humans to benzene vapor in the work place has resulted in hematological and/orhematopoietic effects at concentrations of 30-218 ppm (Aksoy et al., 1971; Fishbeck etal., 1978). Also, in animals, the most sensitive endpoint for long-term exposure tobenzene vapor is toxicity to hematopoietic progenitor cells. The lowest-observed-adverse-effect-level (LOAEL) identified for this effect was 5 ppm in mice exposed to benzene inutero. An associated NOAEL for this effect in mice has not been established.

The ECAO report concluded by presenting a provisional RfC of 2 x 10"4 mg/m3. The RfCwas calculated by adjusting the NOEL of 0.045 ppm for intermittent exposure, anddividing by an uncertainty factor of 300. The uncertainty factor of 300 includes a factorof 10 for intraspecies variability, 10 for database deficiencies including the lack of amultigeneration reproduction study, and 3 for a less than chronic exposure period in theoccupational population. In closing, ECAO recounted the reason why its level ofconfidence in the principal Collins study and database was only "medium", the sameranking it gave to its confidence in the provisional RfC. It is also important to note thatthe memo asks that the reader "[pllease note that these assessments have not been throughthe Agency review process and therefore do not represent Agency verified riskassessments."

Based on our review of the ECAO benzene RfC derivation, we have noted a number ofuncertainties and limitations in using this RfC in a risk assessment, as outlined below:

There is a wide gap between the NOEL used to derive the RfC, andobserved adverse effects in humans and animals. Adverse effects are firstobserved in humans at exposure concentrations (30 ppm) approximately670 times higher than the NOEL (0.045 ppm) used to derive the RfC. Inaddition, effects in animals are first observed at exposure concentrations(5 ppm) approximately 1 10 times higher than the NOEL. Currently thereis insufficient information to determine the actual benzene concentrationat which effects would first begin to occur. There is also insufficientinformation with which to lessen the gap between the NOEL and currentlyobserved adverse effect levels.

Uncertainty in the RfC is compounded by the application of an uncertaintyfactor of 300 in deriving the RfD. Where uncertainty exists, EPA errs onthe side of conservatism by adjusting the RfC lower, through the

2A«gi»llW3

application of a series of uncertainty factors. Here, this resulted in animprobably small RfD of 0.0000571 mg per kg of bodyweight per day.

Confidence in the principal Collins study and benzene database used toderive the RfC was "medium".

It is important to point out that 10.3 was the largest benzene hazard index calculated forLaurel Landfill. Thus, only a 10-fold reduction in the benzene RfD would reduce thehazard index below a level of concern. A factor of 10 is relatively small compared withthe magnitude of the total uncertainty incorporated into the RfC (2 to 3 orders ofmagnitude). If more information was available for benzene (e.g., the thresholdconcentration at which effects first begin to occur, intraspecies variability informationetc.), the resulting adjustments in the RfD would more than likely result in a reductionrather than an increase in the benzene hazard index calculated for this site. It is alsoimportant to note that there have been no effects observed in animals or humans at thebenzene doses calculated in this risk assessment

Thus, it is evident that there are critical uncertainties in the benzene RfD which is drivingthe hazard index in this risk assessment. EPA's risk assessment guidance calls for a "fulland Open discussion of uncertainties in the body of each EPA risk assessment, includingprominent display of critical uncertainties in the risk characterization....The riskassessment process calls for identifying and highlighting significant risk conclusions andrelated uncertainties partly to assure full communication among risk assessors and partlyto assure that decision-makers are fully informed. Issues are identified by acknowledgingnoteworthy qualitative and quantitative factors that make a difference in the overallassessment of hazard and risk, and hence in the ultimate regulatory decision." (Memofrom Henry Habicht, Deputy Administrator, to Assistant and Regional Administrators,February 26,1992). .Thus, we expect that the significant uncertainties associated with thebenzene RfD used in the preliminary risk calculations will precipitate the revaluation ofthis RfD by the EPA and result in a more realistic RfD being utilized in the final riskassessment

SUSSEX-9*EVH5W,RED 4 2 Augtut 1993

UNITED STATES ENVIRONMENTAL PROTECTION AGENCYREGION •

841 Chestnut BufcfingPhaadeiphta Pennsylvania 10107

SUBJECT: Sussex County Landfill DATE 6-15-93Risk Assessment - Preliminary Findings

FROM: Reginald F. Harris, senior ToxicologistTechnical Support Section (3HW13)

TO: Lisa Marino, RPMDelaware/Maryland section (3HW25)

The preliminary risk calculations for the Sussex County Landfillhave been completed. Risk calculations were performed inaccordance with Agency guidance. Risk calculations were performedfor both residential and monitoring well sampling results. Therisks due to ingestion of groundwater and the inhalation ofvolatile compounds during showering and bathing have beencalculated for adults in a residential exposure scenario. Risksdue to the exposure of children by ingestion of groundwater,inhalation of volatile constituents during showering and bathing,and dermal contact during bathing have been calculated for exposurethrough a residential use scenario. Due to the limited size of thedata set, and in accordance with the RAGS guidance document, themaximum concentrations of each contaminant were used for riskassessment purposes since their 95th% upper confidence limit valuesall exceeded the maximum concentration.

After preliminary screening and evaluation, it was decided that theonly exposure pathway of significance at the Sussex County LandfillNumber 5 was the groundwater route. Risks were then estimated forthe exposure of residents to the contaminants identified as b«ingpresent in selected on-site monitoring wells at the site. Theexposure point concentrations derived for this risk assessment w«r«based upon the maximum contaminant concentrations of the selectedcontaminants of concern based upon the analytical results formonitoring wells LD-01, LS-07R, and LS-16. Risk estimates providadin this risk assessment represent both current and future usescenarios for site residents.

The contaminants identified as contaminants of concern ingroundwater at this site based on monitoring well results are vinylchloride, benzene, trichloroethylene, 1,2-dichloropropan«,tetrachloroethylene, and 1,4-dichlorobenzene.

MONITORING WELL RESULTS

The combined increased cancer risks calculated forresidential exposure through ingestion of groundwater and

inhalation of volatile organic compounds during showering andbathing are 5.05E-05 and 2.47E-05 respectively. The total combinedincreased carcinogenic risk for adult residential exposure is7.S2E-OS. Vinyl chloride contributes 82.7% of the totalcarcinogenic risk in this scenario. The total combined increasedcarcinogenic risk of 7.52E-05 for adult residential exposure fallswithin the Agency's carcinogenic risk range of i.QE-06 to l.OE-04.

The combined increased cancer risk calculated for the residentialexposure of children to the contaminants in groundwater iscalculated as 4.7IE-05 for the ingestion of groundwater, 5.38E-06for the inhalation of volatile contaminants during showering andbathing, and 1.42E-07 for dermal contact during bathing. The totalcombined increased carcinogenic risk for children has beencalculated as 5.26E-05. With vinyl chloride contributing 86.7% ofthe total risk. The total combined increased cancer riskcalculated for children fall within the Agency's risk range.

Noncarcinogenic risk is evaluated as a function e>£ Hazard Index.If a Hazard Index value exceeds l.QE-f-00, adverse health effects maybe expected to occur. In the adult residential exposure scenarioa Hazard Index value of 3.85E-02 was calculated for the ingestionof groundwater, and a Hazard Index of 9.80E+00 .was derived forinhalation during showering and bathing. The total combinednoncarcinogenic Hazard Index calculated for this scenario is9.84E+00, which indicates that adverse health effects may beexpected to occur if this groundwater were to be used by adultreceptors. It should be noted that these potential adverse healtheffects would be expected to occur due to inhalation exposureduring showering and bathing based upon the Hazard Index value of9.80E+OQ calculated for that route of exposure. Benzene isresponsible for 98.2% of the total noncarcinogenic risk in theadult residential exposure scenario. Inhalation of volatileorganics during showering and bathing contributes 99.6% of thetotal combined noncarcinogenic risk.

In the residential exposure scenario for children a Hazard Indexvalue of 1.79E-01 was calculated for the ingestion of groundwater.A Haaard Index of 1.05E+01 was derived for inhalation duringshowering and bathing, and a Hazard Index value of 6.01E-04 wascalculated for dermal contact during bathing. The total combinednoncarcinogenic Hazard Index calculated for this scenario is1.06E+OL, which indicates that adverse health effects may beexpected to occur if this groundwater were to be used by children.Based upon the Hazard Index value of 1.05E+01 calculated for theinhalation of volatile compounds during showering and bathing bychildren, that route of exposure would be expected to elicitadverse noncarcinogenic health effects upon exposure of receptors.Benzene is responsible for 97.2% of the total noncarcinogenic riskfor children. Inhalation of volatile organics during showering andbathing contributes 99.1% of the total combined noncarcinogenicrisk.

RESIDENTIAL WELL RESULTS

Data for the residential wells in the vicinity of the site wasreviewed and it was determined that only Residential Well GW-2showed significant contamination* Due to the limited amount ofdata collected for the risk assessment, maximum contaminant valueswere used for risk calculation as in the case of the monitoringwells. Contaminants of concern in Residential Well GW-2 are vinylchloride, trichloroethylene, benzene, tetrachloroethylene, 1/2-dichloropropano, and 1,4-dichlorobenzene.

Based upon the data from Residential Well GW-2, the combinedincreased cancer risks calculated for adult residential exposurethrough ingestion of groundwater was calculated as 4.73E-Q5. Theincreased cancer risk calculated for the inhalation of volatileorganic compounds during showering and bathing for adults wascalculated as 2.07E-Q54 The total combined increased carcinogenicrisk for adult residential exposure is 6.80E-OS, Vinyl chloridecontributes 91.3% of the total carcinogenic risk in this scenario.The total combined increased carcinogenic risk of 6.80E-05 foradult residential exposure falls within the Agency's carcinogenicrisk range of l.OE-06 to l.QE-04.

The combined increased cancer risk calculated for the residentialexposure of children to the contaminants in groundwater iscalculated as 4.42E-05 for the ingestion of groundwater, 4«53£-06for the inhalation of volatile contaminants during showering andbathing, and 1.27E-07 for dermal contact during bathing. The totalcombined increased carcinogenic risk for children has beencalculated as 4.88E-OS. With vinyl chloride contributing 93.4% ofthe total risk. The total combined increased cancer riskcalculated for children fall within the Agency's risk range.

Noncarcinogenic risk is evaluated as a function of Hazard Index.If a Hazard Index value exceeds l.OE+00, adverse health effects maybe expected to occur. In the adult residential exposure scenarioa Hazard Index value of 2.14E-02 was calculated for the ingestionof groundwater, and a Hazard Index of 4.38E+00 was derived forinhalation during showering and bathing. The total combinednoncarcinogenic Hazard Index calculated for thi* scenario is4.40E+00, which indicates that adverse health effects may beexpected to occur if this groundwater were to be used by adultreceptors. It should be noted that these potential adverse healtheffects would be expected to occur due to inhalation exposureduring showering and bathing based upon the Hazard Index value of4.40E+00 calculated for that route of exposure. Benzene isresponsible for 97.7% of the total noncarcinogenic risk in theadult residential exposure scenario. Inhalation of volatileorganics during showering and bathing contributes 99.5% of thetotal combined noncarcinogenic risk.

In the residential exposure scenario for children a Hazard Indexvalue of 9.98E-02 was calculated for the ingestion of groundwater.

A Hazard Index of 4.68E+00 was derived for inhalation duringshowering and bathing, and a Hazard Index value of 2.30E-04 wascalculated for dermal contact during bathing. The total combinednoncarcinogenic Hazard Index calculated for this scenario is4.78E+00, which indicates that adverse health effects may beexpected to occur if this groundwater were to be used by children.Based upon the Hazard Index value of 4.68E+00 calculated for theinhalation of volatile compounds during showering and bathing bychildren, that route of exposure would be expected to elicitadverse noncarcinogenic health effects upon exposure of receptors*Benzene is responsible for 96.0% of the total noncarcinogenic riskfor children. Inhalation of volatile organics during showering andbathing contributes 97,9% of thetotal combined noncarcinogenic risk.

cc: Eric JohnsonBernice pasquiniBob Davis

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1.47E+02 2.89E-03 LD9E+01 1.056*03 L01E*01 L3SE+01 L«5E*00 4.93E+01L47«»02 2.89E-03 1.09E+01 1.056+03 L01E+01 1.35E+01 4.1iE-01 L42£*01

IfMter ft ChroatoweM, continued)(Canc*r> <Non-canc«r)

' UfetiM chronic Uptwr toundIntake tntakt Lifetime Kaianl Index

•U/kg/d Cancer litfc (!nt«ka/*ft»

O.DCE+W———o.OOE*00 "0,OOE*00 O.OOE-MM O.OOE+00 0,00i*00

S.82E-05 1.3*6-04 L75E-05 O.OOE+00L28E-OS L49C-04 3.84£-06

2.39E-05 5.57E-05 O.OOE+QO 3.99E-044.9«E-06 S.81E-OS 0.006*00 4.07E-04

9.796-05 2.28E-04 0.006*00 2.2SE-022.06E-OS 2.40E-04 O.OOC+00 2.40E-022.36C-04 5.52E-04 6.886-06 9.6«*00S.OSE'OS 5.90t-04 L47E-06 L03E+Q1

4.39E-OS 1.02E-04 2.63E-07 1.TIE'029.016-06 LOSE-04 5.40E-08 L75E-02J.19E-05 5.11E«05 Q.OOE+00 4.49£-024.506-06 5.25£-05 O.QOC+00 4.606'OZ4.97E-05 L16E-04 O.OOE+00 1.02E-031.0SE-05 L22E-04 O.OOE+00 I.OTE.QJ

2.63E-05 4.736-05 4.126-01 4.736-034.10C-06 4.79E-OS 8.336-09 4.796-03

9.02E-05 2.116-04 0.006*09 3.69E-021.86E-OS 2.176-04 0.006*00 3.806-02

2.34C-Q5 5.50E-05 O.OOE+00 1.92E-044.916-06 5.73£*05 O.OOE+00 2.00E-Q44.7SE-03 1.11E-02 O.OOE+00 5.54E-039.90E-04 1.16E-02 O.OOE+00 S.7tt-03

O.OOE+00O.OOE+OO

O.OOE+00O.OOE+00o.ooe+ooo.ooe*ooO.OOE+00O.OOC+00

8.036-05 1.876-04 O.OOE«00 8.1K-04L62E-OS L89E-04 O.OOE+00 8.26E-04

O.OOE+00O.OOE+00O.OOC+OQO.OOE+00

AWLT RISK AOULT Ml2.47S-05 9.MC+00

CHILD RISK CHILD Ml5.361*06 1.05E+01

DERMAL INTAKE (XMING KATHtNG <F<wter t ChroitMiaki, 1986)Averaa* Octanol: (Cancer) (Non-cancer)•ethwet*r Water Lffetlae Chronfc Upptr

Concentration Part. Ctxff. Intake Intafca lifetfaw Hazard Index<w«/lJ (Kow) aa/kf/d a«/kg/d Cancer ftitk (Intake/KfO)

O.OOE+00 6.906*02 0.006*00 O.OOE+00 O.OOE+OO 0.006+00

3.006*OO1.006*00 Z.16E+00 1.436-07 L67E-Q6 O.OOE+00 8.33C-06

2.006+002.00E+00 1.3SE+00 6.0aE-08 7.09E-07 1.166-07 O.OOE+00

4.00€*004.00E+00 O.OOE+00 Q.OOE+00 O.OOE*00 O.OOE+00

Looe+ooL006+OQ 1.796*00 3.94E-08 4.60E-07 O.OOC+00 4.40E-06

4.00E+004.0DE+00 7.00E-01 6,176-08 7.20VOT 0.006*00 7.20E-05

9.00C+009.006+00 2.126*00 4.20E-07 4.90E-06 1.22E-OB O.OOE+00

2.00C+002.00E+00 2.381+00 L05E-07 L22E-06 L15i»09 2.04€*04LOOE+OOLOOE+OO 2.006+00 4,416-08 5M4E-07 3.006-09 O.OOE+00E.ooe+oo2.00e*00 2.736*00 1.206-07 1.4QE-06 O.OOE+00 7.0ZE-06LOOE+OO1.00E+00 2.60E+QO 5.73€-06 6.686-07 2.W-09 6.68C-05

4.006+004.006+00 2.846+00 2.SOC-07 2.92E>06 O.OOE+00 L46E-041.006+001.006+00 3.1SE+OQ 6.94E-OS 8.10E-07 O.OOE+00 9.106-06

2.01E+022.016+02 3.26E+00 Lt4£*05 1.686-04 O.OOE+00 8.42E-05

LOOC+00LOOE+OO O.OOE+00 O.OOE+00 O.OOE+00 O.OOE+00LOOE+OOLOOE+OO 0.006+00 O.OOE+00 O.OOE+OO O.OOE+00

3.00E+003.006+00 O.OOE+00 O.OOE+00 O.OOE+00 O.OOE+00a.ooE+oo8.QQ6+00 Q.OOE+00 O.OOE+00 O.OOE+00 O.OQE+004,006*004.006*00 3.60E+00 3.17E-Q7 3.706-06 7,616-09 O.OOE+00

LOOE+OOLOOE+OO O.OCf+00 0.046+00 O.OOE+00 O.OOE+00LOOE+OOLOOE+OO o.ooe+oo O.OOE+OO O.OOE+OO o.ooe+oo

CHILD HSK CHILD HIL42C-07 6.01E-04

«IS<5 COJW1KEO ACROSSEMICAI* AND EXPOSURE KWtES

TotalUpper lound TotalTifetfa* Hazard IndexCancer Rftk Untake/*fD)

- —— OTBOE+W ——O.OOE+00

O.OOE+00o.ooe+oo6.216-05*.56E'QS

O.OOE+000.006+00

O.OOE+000.006+00

O.OOE+00O.OOE+009.9SE-06

S.22E-073.96E-07

?:S«:o?fc" O.OOE+OQk O.OOE+00* «.52E-07

O.OOE+00o.oot+ooO.OOE+000.006+00O.OOE+00O.OOE+00O.OOE+00O.OOE+00O.OOE+00O.OOE+00O.OOE+000.006+00

O.OOE+00O.OOE+00

L13C-06L06E-06

O.OOE+00O.OOE+00O.OOE+00O.OOE+00

AOULT RISK ADULT^ 7.516-03

WILD RISK CHILD

O.OOE+OO0.006+00

4.111-041.93E-03O.OOE+OQO.OOE+00

5.4fli-032.M6-02

«.«3E-041.696-083.38E-02

9.66E+001.03E+012.62E-026.036-024.49C-024.60C-021.29E-032.36E-03

7.47E-03L76E-02

4.24C-026.38E-02

4.66E-04L49E-03

A.S06-03L»7£-OZO.OOE+00O.OOE+OQO.OOE+OOO.OOE+00O.OOE+00O.OOE+00

O.OOE+OQO.OOE+00

8.19E-048,266-04

O.OOE+OO0.006*006.8SE-043-20E-03II9.84E+00

•tL06E*01

RIBCt COtajlMCO AttOJSCMEM1CALS AND EXPOSURE ROUTE*

ToUtUpper Sound TotalLffetfM Hazard indexCancar Rfak (Intake/RfD)

———OOE+ttJ————OOE+W"0.006+00 O.OOE+00

O.OOE+00 4.111*04O.OOE+00 L93E-036.216-05 O.OOE+004.56E-05 0.006+00O.OOE+00 S.UE-03e.DOe+OQ 2.S6E-OZO.QOE+00 6.63E-04O.OOE+00 L69E-03O.OOE+OQ 3.386-02O.OOE+00 7.52E-029.956-06 9.66E+004.341-06 L03E+01

S.22E-07 2.62E-022.96E-07 6.036-027.KK-07 4.4W-027.486-07 4.606-020.006+00 1.296-Q3O.OOi+00 2.36E-036.52E-07 7.47E-035.81E-07 L76E-02O.OOC+OQ 4.24E-02ft.OOE+00 6.3«E-02O.OOE+00 4.666-040,006+00 L49E-03O.OOE+OQ 8.30E-030.006+00 L8TE-020.006+00 Q.OOE+00O.OOE+00 O.OOE+00o.ooe+oo O.OOE+OOO.OOE+00 O.OOE+000.006+00 O.OOE+OOO.OOE+00 O.QOE+00O.OOE+00 O.OOE+000.006+00 O.OOE+00L1K-06 S.19E-04Lfl6E>06 8.26E-04O.OOE+00 Q.OOE+00O.OOE+00 O.OOE+OflO.OOE+00 &.8SE-MO.OOe+00 3.20E-Q3

ADULT RISK AOULT HI7.51E-05 9.84E+00

CHILD RISK CHILD HI5.26E-OS L06E+01

J\R'3QL>552

DERMAL INTAKE DURING IATHIHG (FCrttar 4 ChroatOUtkt, 1986)Avtrae* octanel: (Cancer) <Movcanc*r)tathwater Water Ltfatfatt Chronic Upper lound

:onc«ntratf«n f»rt. C<«ff. Intak* Intake Lifetiew Maiard Index(uo/lt (Kow) a«/ka/d fl«/ka/d Cancer «1»k Clntakc/ftfD)

O.QQE+00 6,906+02 O.OOE+00 0.006+00 0.006*00 O.OOE+00

2.00E+00Z.OOE+00 1.38E+00 6.08E-08 7.096-07 L16E-07 O.OOE+00O.OOE+00O.OOE+002.00E+002.00E+00 L79E+00 7.896-08 9.20E-Q7 O.OOE+00 9.20E-06O.OOE+000.006+00 2.16E+00 O.OOE+00 O.OOE+00 O.OOE+00 O.QOE+00

LOOE+OOLOOE+OO 2.38E+00 5.24C-08 6. IK-07 5.776-10 LOX-04

4.006+004.006+00 2.12E+00 1.876-07 2.18E-06 5.42E-09 O.OOE+003.00E-013.00E-01 2.60E+00 L72E-OB 2.006*07 8.94E-10 2.00£>OSO.OOE+00O.OOE+00 L846+00 O.OOE+00 O.OOE+00 O.OOE+00 O.OOE+005.006+005.0QE+00 7.0QC-Q1 7.71E-08 9.00C-07 O.OQE+00 9.006-057.00E-02r.OOf-02 4.80E-01 7.40E-10 8.64E-09 O.OOE+00 4.32E-07

LOOE+OOLOOE+OO 2.00E+00 4.41E-08 5.14E-07 3.00E-09 0,006+00

1.006-01LOOE-01 2.T3E+OQ 6.01E-09 7.026*08 O.OOE+00 3.516-070,006*00O.OOE+00 2.84E+00 O.OOE+00 0.006+00 O.OOE+00 O.OOE+006 OOE-016.006*01 3.156+00 4.166-08 4.86E-07 O.OOE+00 4.86E-063 OOE+003.'006+00 3.Z6E+00 2.1SE-07 2.51E-06 0.006*00 L26E-06Z.OOE-012.00E-01 3.606*00 LHE-OB 1.85E-07 0.006+00 Z.Q6E*06O.OOE+00O.OOE+00 3.606*00 O.OOE+00 O.OOE+00 O.OOE+00 0,006+00

8.006-018.006-01 3.60E+00 6.34E-Q8 7.406-07 L52E-09 O.OOE+002.006+002.006*00

CHILD RISK CM110 mlL2TE-07 2.30E-04

fttSICS CCMftlNED ACROSSCHEMICALS AND EXPOSURE ROUTES

TotalUopar taunt Total• UfetiM Hazard indexCareer Riak <lntaka/RfO)

"~ O.OOE+00 0.006*00O.OOE+00 O.OOE+00

6.216-05 O.OOE+004.566-05 O.OOe+00o.ooe+oo O.OOE+OOO.OOE+00 O.QOE+00

0.006+00 1.33E-030,OOE+00 3.386-03O.OOE+00 O.OOE+000.006+00 O.OOE+00

2.61E-07 1.316-02L4«E-07 S.OZE-024.42E-Q6 4.306+001.93E-06 4.59E+00

L966-07 2.24E-03L74E-07 5.29E-OJo.ooe+oo O.OOE+OOO.OOE+00 0.006+000.006+00 4.23E-020.006+00 9.40E-02

0.00€+00 2.95E-04O.OOE+00 6.576-047.V8E-07 4.496-027.486-07 4.60E-02

0.006+00 6.46E-OS0.006*00 1.1*6-04

O.OOE+00 O.OOE+000.006+00 0.006+00O.OOE+00 2.80E-04O.OOE+00 8.926-04O.Q06+OQ L24E-04O.OOE+00 2.79E-04

O.OOE+00 2.20E-04O.OOE+00 4.46E-04O.OOE+00 O.OOE+000.006+00 0,006+00

2.2SE-07 1.64E-042.12E-07 1.656-04O.OOE+00 LSTf'OJO.OOE+00 6.396-03

AOUiT RISK ADULT MI6.806-05 4.406*00

CHILD RISK CHILD HI4.&E-05 4.78E+00 *

*

1 WESTON WAYWEST CHESTER. PA 19380-H99PHONE: 21 5-692-3030

Is January 1993

Ms. Stephanie DehnhardU.S. Environmental Protection AgencyDE/MD Remedial Section (3HW25)Region HI841 Chestnut BuildingPhiladelphia, PA 19107

W.O. No. 01631-016-002

Re: Sussex County Landfill No. 5RI/FS Program

Dear Ms. Dehnhard:

In response to your request, this letter presents additional information on the historicalgroundwater quality conditions at Sussex County Landfill No. 5 (Laurel Landfill),specifically with respect to trends and fluctuations in analyte concentrations ingroundwater downgradient of this landfill. As we have discussed, the largest historical •database on groundwater quality conditions downgradient of the Laurel Landfill has beengenerated from the numerous sampling events performed at monitor well LD-1. This wellwas installed directly downgradient of the landfill in 1979. The historical inorganic andorganic analytical data for monitor well LD-1 are appended to the RI/FS Work Plan forthis site. In general, they indicate the presence of contaminants at low levels that havestabilized and, in some cases, declined in recent years.

To illustrate historical changes in groundwater quality downgradient of the landfill, totaldissolved solids (IDS) results from groundwater sampling of LD-1 during the periodJanuary 1980 to October 1990 were plotted against time, as presented in Figure 1. Thesegroundwater quality monitoring data show a gradual increase in total dissolved solids atLD-1 in the early 1980s with a general "plateauing" of TDS concentrations during themost recent sampling events. In general, the TDS data obtained from the LD-1groundwater samples suggest that groundwater quality conditions downgradient of thelandfill have stabilized in recent years. Review of the volatile organic results from LD-1samples collected in the period December 1984 to June 1992 show nominal fluctuations

analyte concentrations, with the most significant change being a very marked declinethe toluene concentration since 1984 (see selected volatile organic results in Table 1).

Overall, the analytical data generated from the groundwater sampling of LD- 1 support theconcept regarding the apparent stability in recent years of downgradient groundwaterquality conditions that were never seriously degraded. With time, analyte concentrationsin groundwater downgradient of the Laurel Landfill should tend to decrease from thelevels observed in the recent sampling events.

Ms. Stephanie DehnhardU.S. E.P.A. -2- 18 January 1993

If you have any additional comments or questions on this subject, please do not hesitateto contact me.

Very truly yours,

ROY R WESTON, INC

Thomas A. Drew, P.O.Project ManagerGeosciences Department

TAD/rfh

Enclosurescc: Reginald Harris - EPA

Michael Lzzo - Sussex CountyPatricia Deptula - Sussex CountyRobot Wood - Sussex CountyDave Cairns -WESTONCharles Dobroski - WESTON

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