LEGEND - Brookhaven National Laboratory · detected in onsite monitoring wells include carbon...

CHAPTER 8: GROUNDWATER PROTECTION

1998 SITE ENVIRONMENTAL REPORT8-21

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1998 SITE ENVIRONMENTAL REPORT

Figure 8-10. Former Hazardous Waste Management Facility/Current Landfill Area -

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system initiated in June 1997 (extractionwells EW-3 through EW-8). This monitoringprogram characterizes the effects of thispumping on the contaminant plume, andwill provide data that are necessary formaking decisions on the future operations ofthe extraction wells.

♦ Monitor the offsite segment of the plume and“outpost” wells located to the south(downgradient) of the defined extent of theoffsite VOC plume to provide data on anypossible future downgradient migration ofthe plume. Outpost wells are also situated inthe southwestern portion of BNL, directlyupgradient of the Suffolk County WaterAuthority (SCWA) Parr Village Well Field onWilliam Floyd Parkway. These wells areused to verify groundwater quality south ofthe BNL apartment areas, and they wouldalso provide an early warning if contami-nants from BNL were to migrate toward theSCWA well field.Volatile Organic Compounds: The OU III

VOC “plume” is composed of multiple com-mingled plumes, some of which can be traceddirectly to their source areas. This commin-gling is partially due to the significant periodicchanges in groundwater flow patterns createdby historical and ongoing groundwaterpumping and recharge effects. Some identifiedsources that were evaluated during the OU IIIRI/FS include spill areas within the AGSComplex, former Building 96 area (a formervehicle maintenance and drum storage area)and Building 208, located within the Supplyand Materiel area. Figure 8-12 depicts the OUIII VOC contamination plume. (Please notethat the OU IV plume is also depicted onFigure 8-12.) The primary OU III VOCsdetected in onsite monitoring wells includecarbon tetrachloride, TCA, and PCE; carbontetrachloride is the primary VOC detected inoffsite wells. The OU III plume extends fromthe AGS Complex in the north-central part ofthe site southward approximately 5,180 meters(17,000 feet) to the vicinity of Flower Hill Drivein North Shirley. The plume is about 1,525meters (5,000 feet) wide at its maximum, asdefined by the 5 µg/L isoconcentration contouron Figure 8-12. The width of the high concen-tration portion of the plume (portions >50 µg/L) is approximately 550 meters (1,800 feet) atthe site boundary. The area defined by the 5µg/L isoconcentration line should not be

interpreted to mean that there is continuousVOC contamination from the western 5 µg/Lline eastward to the central core of the OU IIIplume. In actuality, the plume includes manyareas with <5 µg/L concentrations.

Portions of the plume displaying the highestVOC concentrations include the vicinity ofBuilding 96 (primarily PCE with lowerconcentrations of TCA), with TVOC concen-trations ranging from 1,000 to >18,000 µg/L)and continuing south to Carleton Drive withTVOC concentrations of >500 µg/L. In thevicinity of Well 000-130, located offsite onCarleton Drive, TVOC concentrations aregreater than 7,000 µg/L (consisting primarilyof carbon tetrachloride). As shown in Figure 8-13, this high level carbon tetrachloride con-tamination is located in the upper portion ofthe Magothy aquifer. Groundwater character-ization to define the extent of carbon tetrachlo-ride contamination in the Magothy aquiferand the installation of additional monitoringwells is planned for 2000.

An underground storage tank (UST), locatedin the vicinity of the corner of Rowland Streetand Rochester Street was excavated andremoved in April 1998. The UST had beenused at the former Chemistry DepartmentComplex in the 1950s, and contained carbontetrachloride. Monitoring Well 85-06 wasdestroyed as a result of this effort, and replacedby new well 85-98. Historically, samplescollected from Well 85-06 have shown low levelconcentrations of carbon tetrachloride (<20µg/L). However, sampling of the new well inJune 1998 revealed carbon tetrachloridecontamination approaching 100,000 µg/L. Itnow appears that the contamination wascaused by the inadvertent release of residualcarbon tetrachloride from the tank during theremoval process. Subsequent groundwatercharacterization efforts during the summer andfall of 1998 successfully characterized the extentof the carbon tetrachloride plume, andremediation of this area is planned for in 1999.A summary of the data from this groundwatercharacterization project can be found inSummary Report for the Carbon TetrachlorideInvestigation (BNL, 1999b).

Trend plots showing changes in VOC concen-trations over time are depicted for key OU IIImonitoring wells in Figure 8-14 and 8-15. Wellslocated in the vicinity of known source areas inthe central onsite portion of OU III have



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Isoconcentration ContourRepresenting Line of Equal TVOCConcentration in PPB (DashedWhere Inferred)

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Figure 8-12. OU III and OU IV VOC Plume Map N

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Figure 8-14. Time-vs.-VOC concentration trend plots for key wells in the OU III VOC Plume (centralarea): Well 65-06 located downgradient of the AGS area; Well 85-98 located downgradient of a carbontetrachloride spill area; Well 95-84 located in the former Building 96 area; and Well 96-07 locateddowngradient of the Supply and Materiel Building 208.

Figure 8-15. Time-vs.-VOC concentration trend plots for key wells in the OU VOC Plume (southernboundary and off-site areas): Well 121-10 located at the BNL southern boundary; Well 000-112 locatedoff-site near the Brookhaven Industrial Park; Well 000-130 located on Carleton Drive; and Well 800-43located near Flower Hill Drive near the leading edge of the OU III plume.

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shown significant increases in concentrationsduring 1998. For example, VOC concentrationsin Well 65-06 (primarily TCA), which islocated downgradient of the AGS researchcomplex, increased from typical concentrationsranging from 5 to 20 µg/L in 1997 and the firstthree-quarters of 1998 to >170 µg/L during thelast quarter of 1998. (Characterization of theextent of VOC contamination in the AGS areawill be augmented with data obtained fromnew Facility Monitoring Program wells to beinstalled in 1999.) Additionally, TCA concen-trations decreased in Supply and Materiel areamonitoring Well 96-07. Historically, TCAconcentrations have exceeded 100 µg/L.However, during 1998 concentrations droppedto <5 µg/L. Wells located near the southernboundary extraction system are displayingsignificantly decreasing concentration trends(in Wells 121-10, 122-19 and 122-22), which canbe attributed to the effect of the remediationsystem. The 1998 OU III Pump and TreatSystem Annual Report (BNL 1998a) providesdetailed evaluations of VOC concentrationtrends and recommendations for changes to thesystem operations.

8.1.2.3.1 HFBR TRITIUM PLUME

Following the January 1997 discovery oftritium in wells south of the HFBR, it wasdetermined that the HFBR’s spent fuel poolwas leaking tritiated water at a rate of approxi-mately six to nine gallons per day. (Note: Toprevent additional leakage, the HFBR’s spent-fuel pool was completely emptied by December1997.) As the result of an extensive groundwa-ter investigation, it was determined that thetritium plume remains completely onsite . Theextent of the tritium plume (as defined by the1,000-pCi/L contour) was found to extendfrom the HFBR to a location immediatelynorth of Weaver Drive on the BNL site, adistance of approximately 1,220 meters (4,000feet) (see Figure 8-16). The plume is approxi-mately 305 meters (1,000 feet) at its maximumwidth. However, the portion of the plume withconcentrations exceeding the DWS of 20,000pCi/L is approximately 60 meters (200 feet)wide. The area of the plume containing thehighest concentrations extends in a narrowband from the HFBR south to the vicinity ofRowland Street. Tritium is detected in theshallow Upper Glacial aquifer in the vicinity

of the HFBR and in the deep Upper Glacialaquifer just to the north of Weaver Drive.

During 1998, the HFBR tritium plume wasmonitored using 88 monitoring wells that weresampled on a quarterly basis. The highesttritium concentrations continue to be found inwells located directly downgradient of theHFBR. For example, Well 75-43, locatedapproximately 100 feet downgradient of theHFBR, displayed a tritium concentration of1,920,000 pCi/L (71,040 Bq/L) in December of1998 (see trend plots for key HFBR tritiumplume wells on Figure 8-16). Although severalwells located south of Brookhaven Avenue(e.g., Wells 85-67 and 095-48) showed increas-ing tritium concentrations throughout theyear, the majority of the HFBR tritium plumewells displayed decreasing or fluctuatingtritium concentration trends. The fluctuationin tritium concentrations for these wells islikely due to the effects of lateral movement ofthe plume resulting from periodic changes ingroundwater flow directions caused by onsitepumping and recharge effects. Additionalgroundwater characterization work, includingthe enhancement of the HFBR tritium-plumemonitoring well network, is planned for 1999.

8.1.2.3.2 WASTE CONCENTRATION FACILITY ANDBROOKHAVEN GRAPHITE RESEARCH REACTOR(BGRR)/PILE FAN SUMP AREAS

Groundwater quality in the areas surround-ing the WCF, former BGRR and its associatedPile Fan Sump has been affected by strontium-90 contamination. A groundwater characteriza-tion effort utilizing temporary wells wasundertaken in 1997 to better define the extentof strontium-90 contamination in the areas ofthe WCF, the BGRR, and the Pile Fan Sump.As a result of this investigation, strontium-90was found to occur at concentrations up to 432pCi/L (16 Bq/L) in the Pile Fan Sump area,and up to 53 pCi/L (2 Bq/L) in wells locateddowngradient of the BGRR. Strontium-90concentrations up to 146 pCi/L (5 Bq/L) havebeen detected in wells located downgradient ofthe WCF. The distribution of strontium-90contamination using the 1997 characterizationdata is shown on Figure 8-17. Current planscall for the installation of new monitoringwells in the spring of 1999 to allow for betterlong-term monitoring of the strontium-90plumes.



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