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United States Office of Water EPA 842-S-92-006 - Environmental Protection (WH-556F} June 1992 Agency ":EPA Determination of Sludge Dumping Rates for the 106-Mile Site FINAL REPORT DETERMINATION OF SLUDGE DUMPING RATES FOR THE 106-MILE SITE March 15, 1989 U.S. ENVIRONMENTAL PROTECTION AGENCY Region II New York, New York and Office of Marine and Estuarlne Protection Washington, DC Prepared Under Contract No. 68-03-3319 FINAL REPORT DETERMINATION OF SLUDGE DUMPING RATES FOR THE 106 MILE SITE June 1992 U.S. ENVIRONMENTALPROTECTION AGENCY RegionII New York, New York and Office of Wetlands, Oceans and Watersheds Washington, D.C. TABLEOF CONTENTS EXECUTIVE SUNHARY ................... t 1. INTRODUCTION .................. 1-I 2. BACKGROUND INFORMATION ............. 2-1 2.1 REVIEWOF EXISTING DILUTION MODELS..... 2-1 2.2 CHARACTERIZATION SLUDGE OF TRANSPORT BARGES 2-4 2.2.1 Ba~Je Characte¢ist~cs , 2-4 2.2.2 Dump,rig Methods . . . : : . : : : : : ....... 2-7 2.3 NEARFIELD STUDIES OF SLUDGEPLUME BEHAVIOR ....... 2-13 3. DEVELOPMENTOF DUMPING RATE EQUATION .............. 3-1 3.1 SLUDGE PLUME DILUTION .................. 3-2 3.1.1 Wake-Induced Initial Nixing ............ 3-3 3.1.2 Oceanic Mixing ................... 3-7 3.2 DUMPING RATE EQUATION ................... 3-9 3.3 BARGE SPEED CONSIDERATIONS ................ 3-14 4. RECOMMENDED DUMPING BATES ................... 4-1 4,1 DUMPING RATES FOR INDIVIDUAL PERMIT APPLICANTS ...... 4-1 OF 4.2 NOMOGBAPH DUMPINGBATES FOR SPECIFICDILUTION REQUIREMENTS ..................... 4-6 5. STRATEGIES FOR MULTIPLE DUMPING ............. 5-I 5,1 BULK LOADING CONSIDERATIONS ............. 5-I AT RATE OF 15,500gpm 5.2 DUMPINGSTRATEGIES COURT-ORDERED 5-3 5.3 DUMPING STRATEGIES AT REDUCED RATES ......... 5-6 6. RECONNENDATIONS ...................... 6-1 7. REFERENCES ........................ 7-i LIST OFTABLES OF TABLE2.1 ASSESSMENT MODELS OF FORPREDICTION INITIAL MIXING OF SLUDGE AT DUHPED THE 106-NILE SITE ...... 2-3 OF TABLE2.2 SUMMARY VESSELS THATTRANSPORT SEWAGE SLUDGE TO THE lOB.-MILE SITE ................. ; 2-6 CAPACITY VESSELS TABLE2.3 SLUDGE OF THAT TRANSPORT SEWAGESLUDGE TO THE 106-MILE SITE ........... 2-8 DIHEHSIONS VESSELS TABLE2.4 PHYSICAL OF THATTRANSPORT SEWAGESLUDGE TO THE lOB-NILE SITE ........... 2-9 TABLE2.5 SLUDGEDISCHARGE AND METHODS MAXIMUM RATESFOR VESSELS SEWAGE THATTRANSPORT TO SLUDGE THE lO6-MILE SITE ................... 2-11 DILUTIONSANORATES DILUTIONFORSLUDGE TABLE2.6 OBSERVEO OF IN PLUMES SURVEYED SEPTEHBER 1987 AND 1988 .... 2-22 SLUDGE TABLE4.1 WHOLE RESULTS HETALCHARACTERIZATION FROM JERSEY THENINE NEt4 YORK-NEW AUTHORITIES. SEWERAGE 4-3 SLUDGE TABLE4.2 WHOLE FROM TOXICITY RESULTS THE NINE NEWYORK-NEI~ JERSEY SEWERAGE AUTHORITIES ..... 4-4 OF DUMPING TABLE4.3 COMPARISON SLUDGE RATESBASEDON TOXICITY AND TRACE METAL RESULTS ......... 4-5 SLUDGE TABLE4,4 RECOMMENDED BUMPING REQUIRED RATESVERSUS DILUTION ..................... 4-9 LIST OFFIGURES Pa__.9~ FIGURE1.1 DIAGRAIt OF ACTIVITIESASSOCIATED THE SCHEMATIC WITH AND OF REGULATION HONITORING SLUDGE RATES DUMPING FOR THE I06-MILE SITE ..................... 1-3 FIGURE2.1 OF DIAGRAM SLUDGE CONPARTNENTS OPERATED WITHINBARGES BY THENEW CITY DEPARTNENT ENVIRONMENTAL YORK OF PROTECTION ......................... 2-10 FIGURE2.2 OF TIME HISTORY SLUDGE EVENT DILUTIONWITHINPLUNE DB-3 AT THE 106-NILE SITE DURINGSEPTEMBER1987 ...... 2-16 FIGURE2.3 CORCEPTUAL OF PARCELS DIkGRH4 THEDILUTIONOF SLUDGE WITHIN PLUMESFORTWOCASES MIXIfiG CONDITIONS OF ...... 2-18 OF FIGURE2.4 TIRE HISTORY SLUDGE DILUTIONWITHINTHE COREOF SLUDGE PLUMES IN SURVEYED SEPTEMBER 1987 AND1988 ..... 2-20 MODEL SLUDGE FIGURE3.1 CONCEPTUAL OF PLUNEDILUTIONFROM OBSERVATIONSDURING PLUME EVENT DB-3 ............ 3-11 FIGURE3.2 PLOTOF VOLUMEDUMPING RATE(gal/min) VERSUS BARGE SPEED.THESHAOEDREGION EPA REPRESERTS OUMPIRG REGULATIONS ........................ 3-15 FIGURE3.3 PLOTOF VOLUME BARGE DUNPIflG RATE(gal/min) VERSUS SPEED.BARGEDUMPING FROM CHARACTERISTICS SEPTEMBER BY 1987 AND1988 AREREPRESENTED INDIVIDUAL POINTS..... 3-17 OF FIGURE4.1 ROI~RAPH SLUDGE OUHPIRG RATES (in g~,l/min) VERSUS REQUIRED SLUDGEDILUTION4-h AFTER AT DUMPING THE 106-NILE SITE ....................... 4-7 SIJ~RY EXECUTIVE The U.S. Environmental Protection Agency (EPA), under the Marine Protection,Research, Act and Sanctuaries of 1972,is responsible for regulating of the disposal sludgeat the 106-MileDeepwaterMunicipal Sludge Site (106-Mile 100 Site)locatedapproximately nmi offshore New York and New Jersey.EPA has developeda monitoringplan ( EPA , ig92a) for the 106- Mile Site whichensuresthat regulatory are requirements met, and that field are measurements made to supportsite management As decisions. part of the monitoring plan, a seriesof fieldmeasurement surveyshas been conducted to monitor the nearfieldbehavior and fate of sludgedumpedat the 106-Mile Site. Thesemeasurements a represent high-quality data set from which to of base analyses nearfield, short-termsludgeplomedilution and compliance with marinewaterqualitycriteria. EPA received for sludgedumpingpermitapplications continued use of the 106-Hile Site fromnine sewerage in authorities New York and flew Jersey, and is in the processof reviewing to the applications determine whetherthe proposed dumpingoperations As will complywith waterqualitycriteria. part of this reviewprocess, EPA must determinewhetherthe court-ordereddumping is rate of 15,500gal/min suitable for the 106-MileSite,or whetherdumping must be altered. rates and strategies This reportpresents analysesthat decislons’concerning dumpingof wild aid EPA in makingsoundmanagement the sewagesludgeat the 106-Mile Site.The study focuseson threemajor objectives: ¯ of Development an empirical equation optimum for calculating sludgedumping of rates,basedupon fieldobservations sludgeplume at behavior the 106-Mile Site. ¯ of permit Calculation sludgedumpingratesfor individual basedupon sludgecharacteristics. applicants, ¯ of strategies Development candidate for multipledumpingat the Site. I06-~ile activities The following as objectives: were conducted secondary i ¯ of An assessment whetherthe existing modelsof wasteplume dilutionare suitable of at for prediction sludgeplumedispersion the 106-MileSite. ¯ A preliminarysurveyof the physical and characteristics dumping proceduresfor the bargesthat dump sludgeat the 106-MileSite. of Analyses the physicaland chemical obtained measurements duringthe nearfield monitoring surveysin SeptemberI987 and 1988 indicatethat sludge plumesare not dispersed rapidlyduringsummerconditions; plumesare generally to confined the upper25 m of the water columnduringthe first4 h after dumping. of Dilutions sludgeparcelswithinthe core of the plumes were on the order of 4,000:14 h afterdumpingat ratesbetween12,000and 15,000gal/min. of Analyses tracemetalsand toxicity in data provided the dumping and permitapplications obtained of from analyses wholesludgesamples in obtained August1988 indicate at that sludgedilutions 4 h must be much greaterthan I0,000~Ifor many of the sewerageauthorities.These dilution are requirements based upon compliance with specific waterqualitycriteria 4 for metalsand toxicity h after sludgeis dumped.Metal-based and toxicity-based dilutionrequirements for differsignificantly each sewerage authority, are and largedifferences observed in among the nine authorities New York and New Jersey.To achievethese high dilutions, sludgedumping at ratesmust be reducedgreatlybecauseoceanicmixingprocesses, least duringsummer,are not sufficient for attaining this degreeof dilution over a periodof 4 h; wintermonitoring to surveyswill be necessary determine whetheroceanographic mixingprocesses are significantly more intenseduring winter. An empirical equation has been developed the for calcuTating optimum sludgedumpingrate for each permitapplicant, basedupon the field data from the September 1987 and 1988 monitoring surveys. The resultsindicate that dumpingratesshouldbe less than 1,000gal/minfor three of the permit applicants and less than 5,000 gal/minfor the remaining six applicantsto ensurecompliance 4 with water qualitycriteria h after dumping. is It recommended that additional nearfield data be acquired duringplume monitoring surveysin order to validate in the coefficients the empirical ii dumpingrate formula:however,the resultsfrom the September1987 and 1988 surveysare viewedas an excellentdata set from whichto base a conservative at modelof sludgeplumedilution the 106-Mile Site. iii 1. INTRODUCTION Protection The U.S. Environmental Agency(EPA),underthe Marine Research, Protection, Act and Sanctuaries of 1972 (MPRSA,PL 92-532) for responsible regulating of the disposal municipalsewagesludgein ocean to waters.As a resultof an April 11, 1985, decision deny petitions to the redesignate 12-MileSludgeSite offshore New York,EPA RegionIf halted in all sludgedisposal New York Bight.Effective JanuaryI, 1988, all in municipalities the New York and New Jerseyhave shiftedsewagesludge disposal to operations the IO6-Mile Deepwater Municipal SludgeSite (106-Mile Site). EPA has developeda monitoring plan ( EPA , 1992a) for the 106-Mile Site whichensuresthat regulatory are requirements met, and that field are measurements made to supportmanagement decisions concerning (I) site or (2) redesignation dedesignation, issuance, or continuation, revocation sludgedumpingpermits, and (3) continuation, or modification, termination the monitoring of programitself.The overallstrategy the monitoring plan, and its companion implementation plan ( EPA , 1992b),focuseson two areas of concern= of assessment compliance with permitconditions and assessmentof potential on impactsof sludgedisposal resources and other aspectsof the marineenvironment. As part of the 106-MileSite monitoring a plan,EPA has conducted series of fieldmeasuremeet surveysto monitorthe nearfield behaviorand fate of sewagesludgedumpedat the IO6-Mile Site ( EPA ]992c;1988a;1988b). Thesesurveys(in September 1987 and Marchand September 1988)provided accurate, high-resolution of I measurements physica and chemical properties withinsludgeplumesimmediately after dumping. The physicalmeasurements were used to determine the physical of characteristics the sludgeplumesand of the effects oceanographic on processes sludgeplumedilution and advection. The chemical measurements were used to determinerates of sludge dilution and to test compliance with marinewaterqualitycriteria. EPA received for dumpingpermitapplications continued use of the 106- Mile Site from nine sewerage in authorities New York and New Jersey,and is in the processof reviewing to the applications determine whetherthe proposed sludgedumpingoperations will complywith marinewater quality I-I As criteria. part of this reviewprocess, EPA must determine whetherthe court-mandatedsludgedumpingrate of 15,500gal/minis suitable for the 106- Mile Site,or whetherdumpingratesand strategies must be alteredto ensure with waterqualitycriteria compliance limiting (WQC)and toxicity-based permissible (LPCs).Thesemanagement concentrations decisionswill require of studiesfollowed regulatory analyses monitoring by as decisions in of illustrated Figure1.1;the four majorcomponents this schemeare described regulation/monitoring below. ¯ wherebysludgedumpingratesare established Regulation, and monitored routinely with waterqualitycriteria. for compliance ¯ DumpingOperations,whereinthe effectiverate of sludgedisposal is basedupon volumedumpingratesand bargespeed. ¯ whichis governed dumpingrates,barge SludgeDispersion, by and characteristics, oceanographic processes. dispersion ¯ Monitoring, and wherebyfieldmeasurements watersamplesare used with waterqualitycriteria to test compliance and recon~end of, changesto, or maintenance sludgedumpingrates. 1-111of Contract Work Assignment was initiated No. 68-03-3319 to provideEPA with technical on assistance variousoperational aspectsof the 106-MileSite sludgedumpingprogram,including of the evaluation appropriate sludgedumpingrates.This reportpresents the resultsof Task I of Work Assignment of 1-1ll. The majorobjectives this task include ¯ of An assessment whetherthe existing modelsof wasteplume dilutionare suitable of at for prediction sludgeplumedispersion Site. the 106-Mile ¯ A surveyof physical and for the characteristics dumpingprocedures Site. bargesthat dump sludgeat the 106-Mile ¯ of Development an empirical optimumsludge formulafor calculating of dumpingrates,baseduponfieldmeasurements sludgeplumesat the 106-MileSite. ¯ of permit Calculation sludgedumpingratesfor individual baseduponsludgecharacteristics. applicants, ¯ of strategies Development candidate for multipledumpingat the Site. lO6-Mile 1-2 OPERJ~TIONS DUMPING REGULATION DUMPINGRATE (gal/min) BARGE SPEEO L (kn) EFFECTIVE DUMPINGRATE fail pass (gal/ft) r ’i WATERQUALITY TESTS Barge I WAKE DILUTION WATERSAMPLE Configuration (0-5min) 1 COLLECTION 3 ~ I Oceanographic OCEANICDILUTION OCEANOGRAPHIC Conditions (0-4h MEASUREMENTS SLUDGEDISPERSION MONITORING FIGURE1.1 SCHEMATIC ASSOCIATED DIAGRAMOF ACTIVITIES WITH THE REGULATION OF AND MONITORING SLUDGEDUMPINGRATESFOR THE SITE. 106-MILE i-3 in This reportis structured sections that addressthe specific objectives given above.Section2 presents on information existing modelsof waste plumedilution, and of bargecharacteristics, fieldobservations sludge at plumebehavior the 106-Mile of Site.The derivation an empirical formula for calculatingoptimumsludgedumpingratesis givenin Section3. Section 4 presents recommendeddumpingratesfor individualpermitapplicants, in to addition a homograph of for quickdetermination optimumdumpingratesfor in a wide varietyof sludgedilutions receiving water.Section5 presentsa strategies numberof operational for dumping sludgeat the 106-MileSite. for Recommendations additional analyses and fieldstudiesare givenin are listedin Section7. Section6. References I-4 INFORHATION 2. BACKGROUND This section presents background information on three topics that pertain to ocean disposal of sewage sludge. Subsection 2.1 provides a brief review of existing models of waste plume dispersion; rationale is given for the use of field data over existing models when estimating sludge dilution. Subsection 2.2 describes the physical dimensions, sludge capacity, and dumping procedures of the barges that transport sludge to the 106-Mile Site. Field observations of sludge plume dilution from a rocent EPAc~uise to the lO6-Mile Site are discussed in Subsection 2.3. 2.1 OF REVIEW EXISTINGDILUTIONMODELS The oceandumpingregulations of requirecalculation the limiting permissible concentration(LPC)for wastesthat are to be dumpedin the of ocean.The LPC is the concentration a constituent, after allowancefor initial mixing,that does not exceed(I) applicable marineWQC and (2) toxicity threshold,definedas 0.01 of a concentration shownto be acutely toxic to appropriate,sensitive marineorganisms. The LPC is used to calculate the maximumallowable dumpingrate based on the initialmixingof the waste.Initialmixingis definedas the mixingthat occurswithin4 hoursof dumping. allowfor severalmethodsof calculating The oceandumpingregulations initial in are as follows: mixing.These methods, order of preference, 1. When fielddata on the proposeddumpingactivities are adequatefor of prediction initialdispersion of and dilution the waste,these data shall be used.If necessary,the field data shouldbe used in conjunction mathematical with an appropriate modelof wastemixing and dilution. 2. and dilution a wastesimilar When field data on the dispersion of to in characteristics that proposed for discharge are available, thesedata shallbe used in conjunction with an appropriate mathematical model. 3. theoretical When no fielddata are available, oceanicturbulent diffusion may of relationships be appliedto known characteristics the wasteand the disposalsite. 2-1 4. Whenno other means of estimation are feasible, a procedure for calculating in initialmixingis presented the regulations. The regulations thus emphasize these that when fielddata are available, of data shouldbe used in the estimation initialmixing.As a resultof the recentnearfieldmonitoring studiesat the IO6-MileSite ( EPA , 1992c; 1988a;1988b),high-quality fielddataare now available the for estimating initialmixingof sludgedumpedat the IO6-MileSite.The question that is remains what model,if any, shouldbe used with thesedata to estimatethe amountof initialmixing,and hence, the optimumratefor dumpingsludgeat the 106-MileSite. statethat the procedure for calculating Becausethe regulations initial in mixingwhichis specified Part 227 of the Code of FederalRegulations (CFR)shouldbe used only "whenno othermeansof estimationare feasible," for this "model"is not appropriate estimating the initialmixingof sewage sludgedumpedat the 106-Hile Site. Sincethe mid-lg7Os, modelshave been used to ten "stateof-the-art" predictinitialmixingof dumpedwastes(see Table 2.1).These modelshave ( been reviewed EPA 1986) to determinethe extentto which they had with fielddata,and to ascertain been validated for the typesof materials The whichthey are appropriate. following statementsare based upon the above-mentioned reviewof mixingmodels. in Of all the modelspresented Table2.1, none are presently capableof predicting of maximumconcentrations isolated parcelsof sludgein ocean water.These modelspredicteitheraverageor Gaussian-distributed of concentrations disposed in material receiving waters.With the exception of the Walkeret al. (1987)sewagesludgemodeland the Offshore Operators Committee (OOC)Mud Discharge et Model(Brandsma el., 1983),all of modelsare inappropriatefor,or wouldrequiremajorrevisions beforeuse in, estimatinginitial mixingof sewagesludgein oceanicwaters. The Walkeret al. modelwas developed for specifically analyses of at sewagesludgedisposal the IO6-Mile is Site, Its major application predictingfarfield dispersion of characteristics sewagesludge.The model predictsaverage, steady-state of concentrations sludgeconstituents over the farfield,but the resultsare basedupon an empiricalalgorithm(with inherenttnon-conservativeassumptions) solution. ratherthan a deterministic 2-2 TABLE2.1 OF FOR OF DIn4PED THE106-NILE SITE. ASSESSMENT MODELS PREDICTION INITIAL NIXING OF SLUDGE AT Authors Year Material Validation Appropriate for Initial Mixing and Divoky Brandsma 1976 material Dredged Fieldand lab No Brandsma, Sauer,and Ayers a 1983 muds and Drilling Fieldand lab Potentially water produced Christodoulou eta]. Ig74 sediments Suspended Some No Analysis Economic and ASA 1986 Spilledoil None No and Goldenblatt Dowers 1978 Dredgedmaterial Lab No Koh and Chang 1973 Dredgedmaterial Fieldand lab No Krishnappen 1983 Dredgedmaterial Lab and othermodels No et Lavelle al. 1981 sediments Suspended Field No Walker,Paul,and Bierman 1987 Sewagesludge None Doubtful Wu and Leung 1983 muds Drilling Othermodels No of aFinalversions produced waterand drilling in mud modelswill be available February 1989. The drillingmud modelwas fieldvalidated convective for the important descentphase(O’Reillyet.al,1988), and laboratoryvalidatedfor convectivedescentand dynamiccollapse phases(Brandsmaand Sauer,1983). Although the model cannot he validated by field measurements, the general concensus is that it overestimates long-term dilutions. The OOC Mud Discharge to Model,whichis beingexpanded includefluids withoutparticles, and farfield can predictthe nearfield of dispersion almostany type of discharged fluid,including sewagesludge,for most current regimes. The model contains the appropriatephasesof dispersion to of dynamics predictdilution dumpedmaterial; convectivedescent, dynamic collapse, and passivediffusion. The first two phasesthat are importantto initial mixinghave been laboratory and fieldvalidated for drilling fluid discharges. Although this model only considers dischargesfrom a fixed to point,it can easilybe modified predict dilutionsfro~ a movingbarge. to It also has the capability consider wake effectsand particle flocculation. Presently, the computer modelsthat are availablefor use in modeling dispersion and initialmixingof sewagesludgedumpedin the IO6-Mile Site are inapplicable. Thereare, however,candidate modelsas notedabovethat of have the potential beingused for sewagesludgedispersion determinations aftermodification At and/orverification. this time,the recentnearfield monitoring surveysat the 106-Mile for Site providethe best alternative evaluating initialmixing. OF BARGES 2.2 £HARACTERIZATIDN SLUbGETRAHSPORT presents preliminary Thissubsection a of surveyof the characteristics sewagesludgefrom New York and New Jersey bargesthat are usedto transport to the 106-Mile on Site.Information thesebargeswas obtained from files by the New York City Department maintained EPA RegionII, and by contacting of Environmental and Protection the varioustransportation companies below. identified 2.2.1 Barge Characteristics Sludgetransport by of vesselsare operated the New York CityDepartment Protection Environmental (NYCDEP) companies. and fourprivatetransport thesetransport Together, and NYCDEPhave permitsto use 23 barges companies 2-4 of and motor vesselsfor the transport sewagesludgeto the 106-Mile Site, Individual sludgedumpingpermitsare issuedfor each transportvesselby EPA RegionIf. Table2.2 lists the 23 vessels,their ownership,and the sewerageauthorities by serviced each vessel. Of the 23 sludgevessels, only 14 travelto the 106-Mile Site on a g regularbasis;the remaining are primarily used for sludgetransport and transfer withinthe variousNew York and New Jerseyharbors. The 14 barges that dump regularlyhave a collective carrying of capacity nearly46 million of of gallons sludgelthe totalcapacity the g standbybargesis 5.5 million gallons.Santoroand Fikslin(1987)indicate that the 9 New York and New Jerseysewerage authorities produced1.5 billiongallonsof sludgein 1985. If this volumeof sludgewere dumpedat the IO6-Mile Site by the 14 regular on carriers, average, to each wouldbe required make 32 tripsto the site. a NYCDEPowns and operates fleetof four identical bargesthat have a collective carrying of capacity 14 milliongallonsof sludge,whichis roughly of one-third the totalcarrying of capacity the 14 bargesthat regularly transportsludgeto the 106-Mile Site. 106-M|le Transport is of Associates a consortium threetransportation companiesthat carry sludgeto the 106-Mile Co., Site: WeeksStevedorings A & S Transportation Marine.Together, Co., and GeneralTransport/Standard these three companiesown and operate15 sludgebarges.Nine of these barges are regulardumpersat the 106-Mile Site, with a totalcarryingcapacityof 22.5 million gallonsof sludge,and roughlyhalf the carrying of capacity the entire23-barge fleet. National Seatrade Inc. owns one largesludgebarge and threesmaller vessels. ~, Only the largebarge,the Seatrader regularly transports sludge to the 106-Mile Site. The other vesselsare primarily used for sludge transport withinharbors, but in rare cases,these smallvesselsdo transport sludgeto the 106-Mile I Site. The Seatrader is the largestbargethat transports sludgeto the 106-Mile Site;its carrying is capacity 9.3 million of 20 gallons sludge,whichis approximately percentof the carrying capacity fleetthat regularly of the entire14-vessel dumpssludgeat the 106-Mile Site. 2-5 TABLE2,2 OF SBNHARY VESSELS SEWAGE THATTRANSPORT TO SLUDGE THE IO6oMILESITE.. SEWERAGE SERVICED EACH AUTHORITIES BY BARGE ARE OPERATOR INDICATED, BargeOperator Vessel Sewerage Authority New York City LemonCreek New York City Department of SpringsCreek Department of Environmental TibbettsBrook Environmental Protection UdallsCove Protection Co.l WeeksStevedoring Weeks701 New Jersey: Weeks702 Passaic Valley, Weeks703 Middlesex County, Weeks704 Bergen County, Linden-Roselle, RahwayValley, Essexand Union Counties. New York: Westchester County Co.1 A & S Transportation Dina Marie sameas Weeks Eileen KimberleyAnn Lisa Maria VeronicaEvelyn GeneralTransport/Standard Leo Frank sameas Weeks Marinel MorrisJ. Berman PrincessB. RebeccaK. SusanFrank Seatrade National Inc. OBI IV NassauCounty SeatraderI of Department SotocoII PublicWorks E-S7 authorities Westchester iTheseownersservesix New Jerseysewerage and Associates. Countyundera jointventurecalled106 Mile Transport 2-6 Table 2.3 presentsthe sludgecarrying capacity for each of the 23 vessels; to the 14 vesselsthat are regularcarriers the 106-Mile Site are listedseparately from those that are standbycarriers. The standby carriersare much smallerthan the regularcarriers.Table2.4 presentsthe dimensions each of the 23 vesselsin the fleet. physical of Sludgetransport unpowered vesselshave two generalbull categories: bargesor motor vessels.Unpoweredbargesare typically with a constructed pointedbow, a rectangular and cross-section, a flat bottom.Some (includingthe NYCDEPbarges)have a notchin the sternfor use by tugs when in pushingis necessary harborsand alongside piers.All unpoweredbarges of are constructed weldedsteel and are towed,usinga long (mI/4mile) towingcable,to the 106-Mile Site. Motor vesselsare basicallyself-powered sludgetankers. These diesel-poweredvesselsoperateunder theirown control,with nothingin tow. for Typicalconstruction any vesseltransporting liquidincludes internalcompartmentalization, to primarily preventinstability and A and plan for the New York City barges capsizing. cross-section compartment is shownin Figure2.1. 2.2.2 DumpingMethods The vesselsthat dump sludgeat the 106-MileSite use three different of methods dumping: gravity-inducedbottomdumping; or pumping; an.eductor of system.Regardless the dumpingmethod,the individual sludgecompartments on a vesselare equippedwith separatedischargelines,valves,or pumps so that dumpingratescan be controlled,eitherby on-boardpersonnelor, in the case of unmanned by on bargessuch as thoseoperated NYCDEP,by personnel the towingvessel(tug). Table2.5 lists the 14 vesselsthat regularly sludgeto the transport 106-MileSite and their individualdumpingprocedures. Bottomdumpingis the most commonmethod(11 barges), to compared 2 vesselsthat pump sludge,and I) A I vessel(the Seatrader that uses an eductor. briefdescription each dumpingmethodis givenbelow. 2-7 TABLE2.3 SLUDGE OF THATTRANSPORT CAPACITY VESSELS SLUDGE THE SEWAGE TO 106-MILESITE. RegularCarriers StandbyCarriers Barge Capacity Capacity Operator Vessel (ShortTons) Vessel (ShortTons) New York City LemonCreek 15,000 Department of SpringCreek 15,000 Environmental TibbettsBrook 15,000 Protection UdallsCove 15,000 Weeks Weeks701 6,400 Weeks703 4,000 Co. Weeks 702 Stevedorings 17,832 Weeks704 3,000 A&S Transpor- Eileen 18,132 Dina Marie 2,900 tationCo. Ann Kimberley 8,000 VeronicaEvelyn 2,900 Lisa 8,000 Maria 7,900 General Leo Frank 5,500 K. Rebecca 1,620 Transport/ MorrisJ. Berman )2,DO0 SusanFrank Standard-MarinePrincessB. 12,000 National Seatrader 1 38,528 OBI IV g96 Inc. Seatrade SotocoII 954.5 E-57 6,200 2-8 TABLE2.4 PHYSICAL OF SEWAGESLUDGETO THE I06-MILE DIMENSIONS VESSELSTHAT TRANSPORT SITE. Dimensions Loaded Sludge BargeOperator Vessel Type Length" Width Draft Compartments New York CityDepartment LemonCreek Barge 380’ 84’ 21’-6" 10 of EnvironmentalProtection SpringCreek 380’ 84’ 21’-6" 10 TibbettsBrook 380’ 84’ 21’-6" 10 UdallsCove 380’ 84’ 21’-6" 10 Co. WeeksStevedoring Weeks701 266’ 56’ II’ 8 Weeks702 400’ 80’ 25’ 10 Weeks703 290’ 53’ 16’-8" 8 Weeks704 78’ 43’ 13’-7" 8 Co. A&S Transportation Dina Marie 211’ 42’-9" 12’-6" 2 Eileen 390’ 78’ 27’ 10 KimberlyAnn 272’ 68’ 18’-4" 6 Lisa 272’ 68’ 14’-11" 6 Maria 300’ 64’ 18’-4" 12 VeronicaEvelyn 211’ 42’-9" 12’-6" 2 GeneralTransport/Standard Leo Frank 298’ 50’ 15’ 8 Marine MorrisJ. Berman 303’ 90’ 15’-10" 9 PrincessB. M/V 303’ 90’ 15’-10" 9 RebeccaK. Barge 260’ 46’-6" 11’ 6 SusanFrank M/V 260’ 46’-6’ 11’ 6 National Seatrade Inc. OBI IV M/V 180’ 38’ 12’-6" 16 SeatraderI Barge 430’ 105’ 35’-6" 6 SotocoII M/V 180’ 38’ 13’-6" 14 E-57 Barge 300’ 50’ 13’ 10 VALVE ~ $CUDG; ~RGE j J SLUDGE TANK J P1$ ¥A1-¥1~ e~S FOREPEAK 8AI.LAST C~ i /BOW ~ ~ / ~ ~ "~ 7 ~ ~,~ ~/THRUSTER SPACE ,,P, , )IP) liPI (P ~ 9 I ""~ I I .ISi, .Is, , 7 ~lS, 7 ~" f ¯ "ilS’/ |j~J i ?,,.s-’;,s.o- ,o ,B’B" ,o’o" ss’s" ’; ,,," l ’"s" ;’ I FP FIGURE2.1 OF DIAGRAH SLUDGE COt4RARTMENTSWITHIN BARGES BY OPERATED THE OF NEWYORKCITY DERARTHENT ENVIRONHENTAL PROTECTION: REAR VIE#OF PORT SIDE OF BARGE(UPPER); PLAN VIE# (LOWER). 2.5 TABLE SLUDGEDISCHARGEMETHODS HAXIHUMRATES AND THATTRANSPORT FORVESSELS SLUDGE SEWAGE TO THElOB-NILESITE. Average Estimated Capacity Discharge Discharge Maximum Barge Operator Vessel (Million Gallons) Method Duration (h) Discharge Rate At 15,500 gal/min (gal/min) NewYork City LemonCreek 3.513 Bottom Dump 4 150,0001 Department of Spring Creek 3.513 Bottom Dump 4 150,0001 Environmental Tibbetts Brook 3.513 Bottom Dump 4 150,0091 Protection Udalls Cove 3.513 Bottom Dump 4 150,0001 WeeksStevedoring Co. Weeks701 1.504 Bottom Dump 1.5 46,0002 Weeks702 4.190 Bottom Dump 4.5 139,5002 A&S Transportation Co. Eileen 4.200 Bottom Bump 4.5 31,0003 Ann Kimberly 2.000 BottomDump 2 31,0003 Lisa 2.000 BottomDump 2 31,0003 Maria 1.850 BottomDump 2 31,0003 GeneralTransport/ Leo Frank 1.290 BottomDump 1.5 31,9003 StandardMarine MorrisJ. Berman 2.820 PumpOut 3 3 31,OOO PrincessB. 2.820 PumpOut 3 31,0003 NationalSeatradeInc. SeatraderI 9.290 EductorSystem 12.5 13,500 IAttained all 20 valveswereopenedat once. if of 2Capable dischargingfullload in 30 minutes. 3Rateswithvalvesfullyopened. BottomDumpinq In bottom-dumping operations, sludge exits the bottom of the barge via dumpvalve openings that are installed in the bottom of each sludge compartment. Dumpvalves are hydraulically operated and may be throttled to vary sludge levels in each tank compartment. The sludge dumpvalves are approved by the U.S. Coast Guard for the specific category of service in which they are utilized. Although the valves can be closed somewhatmore than the position used to achieve dumping rates of 15,500 gal/min, extremely low dumping rates would most likely lead to clogging of the valves. For bottom-dumping barges, the maximumattainable discharge rate is a function of the available pressure head, the viscosities of sludge and seawater, and the configuration and diameter of the dumpvalve. The rate of discharge varies with the square root of the pressure head, according to the expression: following Q=CA (2gAh)½ where: Q = flow (ft3/sec) C = a constant A = 2) dischargearea (ft g = 32 gravity; ft/sec2 Ah= pressure (ft) head differential Pum B. Sludgeis pumpedout of the MorrisJ. Bermanand the Princess using variablespeed,submersible slurrypumps.Discharge rates can be controlled by varyingthe speedof the pumps.Pump discharge by ratesare affected the pressurehead in the individual but sludgecompartment, the effectof head on dischargeratesis muchless for pumpersthan bottom-dumping barges. Eductor System I The eductorsystemused on the Seatrader is unique.It operates on of the principle aspiration causedby a pressure differentialbetweentwo fluids.Seawater, servingas the motivating fluid,is pumpedinto the sludge compartment againstthe low head of the sludge.Seawaterand sludgeare 2-12 mixedto achievea 1:1 dilution the mixtureis expelled consequently as into the receivingwater beneaththe barge.This processdoes not requirea is slurrypump becauseonly cleanseawater pumpedinto the barge;the sludge mixtureexitsthe bargedue to the pressurewithinthe compartment. I The eductorsystemon the Seatrader was installedless than 2 years its and ago, and consequently, effectiveness maintenance requirements have It yet to be evaluated. is expected that the eductorsystemwill require less maintenance than standardsludgepumpingsystems, whichuse slurrypumps that are proneto mechanical failure. Table 2.5 also presentsthe averagetime for each bargeto discharge a a full load of sludge,assuming constantrate of 15,500gpm. With the of !, exception the Seatrader which requires 12.5 h to dump its load of 9 million gallons,the remainingbargesrequirebetweenI and 5 h for dumping. The maximumattainabledischarge in ratespresented Table2.5 are estimates basedon informationobtained barge operators. from individual Although the individualbargerepresentativesstatedthat the barges at discharge a maximumrate of 15,500gpm, they indicated that the bargesare at if capableof discharging much higherrates.For instance, the valves of were openedfor all 10 sludgecompartments a New York City barge,then the discharge ~, rate could reach 150,000gpm. Only the Seatrader which has an eductorsystem,has a maximumdischarge rate that is belowthe permissible dumpingrate of 15,500gpm. If dumpingratesare to be loweredby factorsof 10 or more (see Section 4), representativesfrom 106-Mile TransportAssociates indicate(C. Hunt personal communication) that severeengineering problemswill arise.One resultis that only one sludgecompartment will be dumpedat a time, which would pose seriousvesselstability Other considerations given problems. are in subsection5.3. 2.3 NEARFIELDSTUDIESOF SLUDGEPLUME BEHAVIOR presents summaryof recentfield observations This subsection a within sludgeplumesthat were dumpedat the 106-Mile Site. These observations a represent high-resolution of data set for analyses the nearfield, short- of term behavior sludgeplu~es.The resultswere obtainedduringEPA surveys 2-13 to the 106-MileSite in Septemberof lgB7 and 1988 ( EPA , 1992c~]9BBb). Although was on information acquired the physica] behaviorand transportof sludgeplumesduringthe nearfieldsurveyin March1988,the chemicaldata for from the surveywere insufficient accurate of determinations sludge dilution versustime. The primaryscientific of surveyswere to objectives the two September ¯ Tracka specificportionof a sludgeplumeto monitorits movement withinand outsideof the 106-MileSite. ¯ of Remainwith the plumefor at least4 h for collection water of samplesfor analyses chemical and biologicaltracersand total solids. suspended ¯ of Conductin situ measurements near-surface currentsand water to properties identify physicalfeaturesand processesthat may affectsludgeplumebehavior and transport. ¯ Acquire to watersamplesfor analysis determine actual of in concentrations sludgecomponents a plume.Resultsare to be used for testing with marinewaterqua]itycriteria compliance and calculatingratesof sludgedilution. ¯ Performall sampling for a numberof sludgeplumesto activities on acquirestatistics plumebehavior for differentbargesunder variousoceanographicconditions. ¯ Evaluate instrumentation sampling shipboard and for procedures in of theirsuitability monitoring sludgeplumes. to A majorfactorthat contributed the successof thesesurveyswas the instrumentationused for in situ samplingwithinthe sludgeplumes.In order to achieverapid,high-resolution of measurements physical waterproperties with the collection watersamples concurrently of for chemical a analyses, pumpingsystemwas integrated seawater witha CTD (conductivity- profiling temperature-depth) system.With the real-time samplingand display of to capabilities this system,it was possible locatethe mostconcentrated of parcels sludgewithinthe plumeand position unit at the the underwater maximum, depthof the turbidity of whichwas indicative the highest of concentrations sludge.Thus, the profilingactivities yieldedaccurate of ¯ easurements 2-14 ¯ as of Plumedepth and thickness a function time,from which plumecross-sectional dilution areazand plume-averaged can be estimated. ¯ of Concentrations chemical tracerswithin and biological samplesof plumewater,from whichsludgedilution can be estimated parcelsof sludgewithina for the most concentrated plume. a Figure2.2 presents time seriesplot of sludgedilutionderivedfrom data collected 3, duringplumeevent DB-3 on September 1987. Note that is dilution plottedon a logarithmic the scale to accommodate wide rangeof dilutions observedduringthe g-h survey.This figurepresents information on the plume-averageddilution as (soTidcircles) well as the dilution discrete parcelsof plume water(open symbols),derivedfrom analyses tracemetals. dilutions, Plume-averaged area of the derivedfrom the cross-sectionaT plumeand the averagedumpingrate per unit of plumelength,suggesta high rate of dilutionduringthe first 2 h afterdumping.Initialdilutions 5 (within min after dumping) 2,500:1; were approximately 30 dilutions min and 2 h afterdumpingwere on the orderof 10,000:I respectively. and 80,000~I, in As indicated Figure2.2, the plume-averaged were much dilutions greater derivedfrom chemical than dilutions of analyses water samples collected withinthe core of the plume.One may suspectthat the high plume- averaged dilutions the were a resultof overestimating widthof the plume, but the error associatedwith this estimateis less than 10 percent. During the first2 h afterdisposal, the plumesspreadlaterally, but they remained intact, turbidity such that horizontal profilesalong the plumetransects no exhibited significant patchesof "clean"receiving waterinsidethe distinctouter edges of the plume.Thus, these high plume-averaged dilutions of of were not a consequence "streaking" the plumeand of overestimation plumewidth. Detailed of analyses turbidity plume data withinthe individual transectshave revealed are that the highestsludgeconcentrations maintained withina concentrated a core which,on a volumebasis,represents small of by percentage the plume.As i11ustrated the open symbolsin Figure2.2, discreteparcelsof sludgefrom the core of the plume were much less dilute than the "average At plume"derivedfrom the plumedimensions. the various 2-15 100,000 o ~PLUME Z i/// _o ~o,oao ¯ 0 /I" 121 ~ REI’E t13 UEI,~I..S TRACE r~ 03 1,000 -~ - m o~ 0 Cu o--o Pb ~--~, ~ Zn n--~ I PLUMEEVENTDB-3 1987 SEPTEMBER I 0 1 2 3 4 5 6 7 8 TIME (hours) 2.2 FIGURE OF TINE HISTORY SLUDGE DILUTIONWITHINPLUNE EVENTDO-3 AT THE SEPTERBER IO6-HILE SITE DURING 1987. SOLIDCIRCLESREPRESENT AVERAGE OF DILUTION ENTIREPLUNE; OPEN SYNBOLSREPRESENT TRACE HETALS RESULTS ENOH RATER OISCRETE MITHIN THECORE THE PARCELS OF PLUHE. samplingtimesindicated, separate of analyses copper,lead,and zinc were on performed the samplescollected withinthe most concentratedportionof the plume.Dilutions by were calculated dividing the measuredconcentrations of of a tracemetal by the mean concentration that specific trace metal by withinsludgegenerated the Port Richmond treatment facility(Santoroand Fikslin,1987),whichwas the sourceof the sludgedumpedduringeventDB-3. The final report for the September1987 survey ( EPA Igg2c)provides detailed on information sludgedilution calculations. The solid linesconnecting the tracemetalresultsin Figure2.2 illustratethat (I) parceldilutions were much lower than plume-averaged dilutions, of (2) the rate of dilution concentrated parcelswas much less dilution than the rate of plume-averaged duringthe first4 h after the dump, and (3) the resultsfrom threetrace metalswere very similar.Within5 min after dumping, parceldilutions at were roughly1,000:1; 4.4 h, parcel dilutions were on the order of 4,500:1. The highersludgedilutions at indicated 3.4 and 4.3 h were obtained from waterparcelssituated outside the most concentrated portionof the sludgeplume,and consequently, they in are not appropriate estimating minimumdilution. BeyondS h afterdumpingfor event DB-3,the sludgeplume was broken into patchesof undetermined sizes.Using the real-time samplingsystem,it to was possible locaterelatively concentrated parcelsof sludgewater 5 between and 9 h afterdumping, but therewas no way to ensurethat a single parcelw~s being surveyedrepeatedly.Chemicalanalysesof the most concentratedportionof sludgewater located8.5 h after the dump a of of demonstrated parceldilution 77,000:1(Figure2.2).Attainment these dilutions an in required increase the rate of dilution over the rate that is demonstrated dilutionwas most likely between1 and 4 h. This accelerated to of attributed the break-up the plume;with the directed sampling capabilityduringthe survey,we are relativelyconfident that this sample portionof the plumethat existedat the was takenfrom the most concentrated time of the observation. a Figure2.3 presents conceptual diagram(with lineardilution axis) the threephasesof plume dilutionthat may have occurredduringeventDB-3: initial, mixing,gradualoceanicmixing,and accelerated wake-induced mixing after plume break-up.The solidline in this figurerepresentsa 2-17 10,000 - / MIXING AFTER / PLUME BREAK-UP / (Dbu) I Z i 0 F- / I d -- I D d LL~ / 0 5,000. / .< / Q- / MIXING(Do) co LLI / (.3 Q / d / (n / -- WEAKMIXING CONDITIONS .... ACTIVE MIXING CONDITIONS 0 I 0 4 8 TIME (hours) FIGURE 2.3 CONCEPTUAL OF PARCELS DIAGRAM THE DILUTION OF SLUDGE WITHIN PLUHESFOR TWO CASESOF NIXING CONDITIONS. case of weak mixingconditions hypothetical (e.g.,low winds,calm seas) duringplume eventDB-3. Plume break-up such as those encountered and accelerateddilutionapparently occurred after 4 h. The brokenllne in a Figure2.3 represents case of activemixing,wherebythe rate of oceanic mixingwould be greaterthan the rate duringweak mixingconditions. During activemixing,plumebreak-up may occurwell before4 h. All four of the plumesmonitored duringthe September1987 survey exhibited dilution characteristicssimilarto those representingweak mixing in conditions Figure2.3. Although the linearplumesbegan to breakup 2 or 3 h afterdumping, concentratedpatchesof plume waterremained relatively intactfor periodslongerthan 4 h. For example, Figure2.4 presents minimum of dilutions plumeDB-3,based upon field-measured copperconcentrations and by mean coppervaluesof sludgedescribed Santoroand Fikslin(1987).With dilutions on presented a linearaxis,it is evidentthat the rate of parcel dilution to from initialmixing(5 min afterdumping) 4 h was quiteconstant (~go0per h). The dilutionestimatesgivenin Figures2.2 and 2.4 providea realistic of representation the short-term of behavior plumeeventDB-3,but three factorscontributeerrorsto theseminimumdilutionestimates: (I) spatial samplingproblems; in uncertainties havingsampledthe maximumconcentration errorsduring withinthe plumeat a giventime,(2) laboratory/analytical processing of and analysis trace metalsamples, in and (3) uncertainties the in actualmetalsconcentration the sludgethat was dumped.Positioning but errorscannotbe quantified, missingthe maximumconcentration will resultin higherapparent dilutions than actually existwithinthe core of the plume.Laboratory in errorsare small (<104),but uncertainties sludge constituent are concentrations large.Constituent of concentrations the dumpedsludgewere not measured; dilutions were calculatedfrom published valuesof constituent in concentrations sludge.Santoroand Fikslin(1987) estimate in that mean copperconcentrations Port Richmond sludgeare 50.9 mg/L with a standard of deviation 364 of the mean. Thus, with .I standard deviation aboutthe mean,copperconcentrations couldrange from 32.6 to 69.2 mg/L for the Port Rich~ondfacility. in This variation copperconcentration in may also resultin a *36 percentuncertainty the rate of dilutionafter initialwake mixing(e.g.,900 .324 per hour). 2-19 20.000 0 DB-3 1987 SEPTEMBER ¯ DB-21 1988 SEPTEMBER ¯ DB-23 1988 SEPTEMBER 15,000 Z 0 E-- d I 0,000 LLJ > QC LLJ O3 ’~ o - ms.ooo ~¯~r-~-~" I ¯/¯ m o i t [ I I I I t I 1 2 ,5 4 5 6 7 8 9 10 TIME (hours) FIGURE2.4 SLUDGE TIME HISTORYOF OBSERVED DILUTION WITHIN THE COREOF SLUDGE PLUMES IN SURVEYED SEPTEI~ER1987 AND1988. DILUTIONSARE RASEDUPONCOPPER WITHZNWATER CONCENTRATIONS SAMPLES. To reducetheseerrorsduringthe September 1988 survey,sludgesamples were obtainedfrom the individualbargesthat transported sludgeto the site of duringthe survey.Trace metalsanalyses (I) the barge (sludge) samples and (2) watersamplescollected from the core of the plumesduringthe nearfield of of surveyyieldeddirectestimates the time rate of dilution the sludgeplumes. to In addition the dilution resultsfrom September1987, Figure2.4 presentsdilution from plumeeventsDB-21 and DB-23monitored information during the September1988 nearfieldsurvey ( EPA , 1988b). As discussed above,the 1988 resultswere derivedfrom the ratioof copperconcentrations in plume watersamplesto thosedetermined of from analyses I00~ sludge. This figureillustrates that both the rangeand the rate of changeof dilution were very similarfor plume eventsDB-3 and DB-21.Table 2.6 indicates that initialdilutions(~5 min afterdumping) were 1,018:1and dilutions 1,724~Ifor plumeeventsDB-3 and DB-21respectively; for both were near 4,000=I4h afterdumping.The resultsfrom plume event DB-21 also illustratethat the rate of core dilutionremained constant relatively for morethan 8h. The dilution a resultsfrom plumeeventDB-23 exhibited similarrate of dilutionduringthe periodfrom 1 to 4h afterdumping,but the extentof the dilutionwas roughlytwicethat of plume eventsDB-3 and DB-21.We suspect in of this offsetwas due to uncertainties the copperconcentration the sludgethat was dumpedin the portionof the plumesurveyed(the barge sampleswere collectedpriorto transitto the 106-MileSite and various of compartments sludgecouldhave had different chemicalcharacteristics). 2-21 TABLE2.6 DILUTZONS RATES D]LUTIONFORSLUDGE OBSERVED AND OF PLBNES IN 1987 AND1988. SURVEYED SEPTERBER Observed Dilutions Rate of D~lution (l/h) P1u~ Survey Date 5ain ]h 4h 7h t=lh to 4h t-Smtn to 4h ,~ DB-3 9-87 1,018 2,055 4,258 - 734 827 r~ r~ DB-21 9-88 1,724 2,629 3,717 5,303 363 508 DB-23 9-88 5,200 6,664 10,887 488 610a aEstimated value. 3. OF RATE DEVELOPHENTDUHP]NG EQUATION of is One of the primaryobjectives this work assignment to use existing (in information this case,field data ratherthan predictive models) determinethe rate at whichsludgeplumesare dilutedat the 106-Mile Site. of Fieldmeasurements short-term sludgedilution in are necessary orderto determinewhetherdumpingoperations are in compliance with EPA water quality criteria,but the resultscan also be used to developa conceptual dilution of modelthat will allowprediction optimumsludgedumpingrateswhich,in required the water qualitycriteria. turn,will achievethe dilutions by The of a process developing realistic model of sludgedilutionentailsa number of steps: I. of Utilization the fieldresultsfrom the nearfield studiesat the 106-MileSite to determinethe rate of changeof sludge concentrationwithinthe plumes,and hence,the ratesof sludge dilution. 2. of Identification the majorphysical responsible processes for sludgeplumedilution, by of followed formulation an empirical of modelfor dilution sludgeparcelsbasedupon the existingfield observations. 3. of Application the empirical model of sludgedilutionfor of prediction the rate at which sludgeshouldbe dumpedin order that satisfyEPA water qualitycriteria. to achievedilutions of 4. Identification the major sourcesof variability (e.g., " oceanographic barge dumpingcharacteristics, sludge conditions, and that characteristics) will affectsludgedilution yet cannot,at the presenttime,be quantified,giventhe limitedset of field observations. 5. of Recommendation additional that will fieldmeasurements facilitate of betterpredictions sludgedilution, and consequently, ratesfor dumpingof sewagesludgeat the 106-Mile more defensible Site. discussion The following the formulation the empirical addresses of modelof sludgedilutionand the assumptionsmade duringits development. PLUHE 3.1 SLUDGE DILUTION The field observations of sludge parcel dilution, which were presented in Subsection 2.3, indicate three phases of mixing during the first 8 h after dumping: (1) an initial period (from 0 to m5 minutes after dumping) turbulent, wake-induced mixing, (2) a gradual phase of relatively slow mixing primarily due to oceanographic processes, and (3) an accelerated mixing phase when the sludge plume is broken up and sludge parcels from the interior of the plume are actively mixed with clean receiving water. Dilution, D, at any time, T, after dumping can therefore be estimated from an whichcontains expression phasesof mixing: the threeobserved D = Di + dDo x + dDb x (i) o where D of = the dilution sludgeparcelsat any time,T, mixing afterinitialwake-induced Di = the dilutionachieved(at T~5 min) from initial, wake-inducedmixing dDo = the time rate of changeof sludgeparceldilution duringthe tlme from dumping(T=O)to the time at whichthe plumebreaksup (T=bu) T = time after dumping dDb = the time rate of changeof sludgeparcel dilution duringthe periodafterplumebreak-up(T-bu) The timeat whicha sludgeplumestartsto physicallybreakup is highly dependent conditions, upon oceanographic barge sludgecharacteristics, dumping and characteristics, otherphysical, chemical,and engineering factors. of Underextremeconditions high wavesand currentshear,plumes may breakup withinI to 2 h afterdumping,but duringweak mixing conditions,plumesmay remainrelativelyintactfor periodsof 4 h or longer. 3-2 of The fieldobservations plumesduringSeptember 1987 and 1988 were made duringrelatively and calm sea and mixingconditions, consequently, the on effectof plumebreak-up parceldilution was not substantial until many hours (>> 4 h) after dumping.Additional surveysof sludgeplume behavior to will be required developa statistical of estimate the time at which plumesbreakup, but basedupon the limitedfielddata, we can assumethat a significantnumberof sludgeplumeswill remainrelatively intactfor at least4 h. This type of plume behaviorwould be appropriatefor development of a modelthat predicts of the minimumdilution sludgeparcelsat any time afterdumping. If we are concerned behavior sludgeplumesand aboutthe conservative of dilutiononly up to 4 h afterdumping,then Eq.(1)reduces D Di + dDo x (2) This simplifiedexpressionrepresents behavior sludgeparcel the two-phase of dilution priorto plumebreak-up: at by dilution 4 h is achieved an initial phase of rapiddilution DiS by (to achievedilution , followed a slowerphase of oceanographicmixingand dilution. InitialMixing 3.1.1Wake-lnduced Mixingof sludgewithinthe wake of the barge is extensiveduringthe first few minutesafter dumping.Much of this mixing(and sludgedilution) to of is attributed the turbulence the receiving waterimmediately behindthe barge,but within5 to I0 minutesafterdumping, of the momentum the wake diminishes and otherfactorsgovernplumemixingand dilution. Duringthe periodof initial(0 to ~5 min) mixing,wake momentum may the most importantfactor,but thereare additional parameters/processes Initial, that affectmixingand dilution. dilutlon, wako-lndueed DI, is to of expected be a function the following parameters: 3-3 Di f { R, B, S, 7, Mw ] (3) where R dumpingrate:the amountof the effective sludgedumpedper unit of track(plume)length, in expressed unitsof gal/ft B (size,speed, the effectof bargecharacteristics draft,depthof dischargeport)and dumpingmethod (bottomdump,pump,or eductor) S sludgecharacteristics(specificgravity,solids content,abilit~to flocculate,densityrelativeto receivingwaterJ Z depth pycnocllne Mw due mixing(dispersion) to windsand waves of Determination the relative on effectsof theseparameters initial(0 to m5 min) sludgedilutionwouldrequirerapid,intensivefieldmeasurements of plumemixingover a wide rangeof dumpingrates,bargetypes,dumping methods,sludgetypes,stratification regimes, m~xing and oceanographic regimes.Becausethis research is activity well beyondthe scopeof the EPA we OceanDumpingprogram, will represent initial(0 to ~5 min),wake-induced as dilution a singleparameter, Di, in the reducedequation for sludge dilution(see Eq. 2). With the field resultsfrom the past nearfield monitoring it to surveys, is possible estimate initialdilution, Oi, 5 min afterdumping, but we cannotdetermine the relative of importance the individual in parameters Eq. (3). To facilitatefuturecomparisonsbetweeninitialdilutionratesfrom othermonitoringsurveys, and the variousengineering environmental conditionsencounteredduringplumeevent DB-21(Septemberlg~) are below. summarized R effectivedumpingrate was 22.85gal/ft,basedupon an average dumpingrateof 10,855gal/minat a bargespeedof 4.7 kn. B was bargeconfiguration that of the Princess~, which pumps sludgeout of its side;this bargehas a maxlmumdraft of 15 ft and a beam of go ft. S the sludge within the barge was from Passaic Valley; the specific gravity of the sludge (~1.004) was less than that of the receiving water (~1.023), which had water properties of ~22°C and =33 ppt. Z the seasonal pycnocline at the I06-Mile Site was strong and shallow, situated between roughly 25 and 40 m. Mw surface mixing conditions were mild, due to calm (<3 it) seas and winds less than 15 kn. As indicated in subsection 2.3, the initial dilution of sludge parcels B min after dumping for plume event DB-21 was estimated at 1,724:1 from analyses of trace metals data. Because the relative effects of the various parameters in the initial dilution equation (Eq. 3) are unknown, we can only speculate how the rate of initialdilution wouldchangeunder different dumpingand conditions: environmental Mw been more severe(i.e.,during Had the sea and wind conditions winterstormevents)initialdilution mighthave been significantly greaterdue to increased dispersion. Z The observedsludgeplumemight have settledsomewhat deeper,and dilutionsmighthave been greaterhad therebeen no seasonal pycnocline.Preliminaryresultsof the wintersurveyindicate, however,that sludgedumpedat ratesnear 15,000gal/mindoes not settledeeperthan about30 m in the first8 h followingdumping. S Other than from laboratorystudies, littleis knownabout the settling of characteristics the varioussludgesdumpedat the the site.Nevertheless, salinereceiving waterwill, duringall be seasons, much more densethan the sludgedumpedat the site, such that all plumeswill be relativelybuoyantand variationsin sludgesettling may characteristics have a second-order effectupon initial dilution. B The Princess_B,whichpumpssludgeout of one side of the vessel, may ~ somewhatdifferentinitial mixing characteristics than bargeswhich are bottomdumpers,but the availablefield results from bargesof differentconfigurationssuggestthat initial dilutionmay be relatively to insensitive dumpingmethod. In sun~nary, conditions the environmental ) uring (parameters and Z d w plume eventDB-21represent for sludgedilutions mild conditions (conditions that producelow dilutions).Becausethe objectof the presentanalysisis 3-5 of to derivea modelfor prediction worst-case (lowest) the field dilutions, for of data from eventDB-21are appropriate development the model. a For the purposeof developing conservative model,we will assumethat (I) all sludgeswill behavesimilarly duringthe firstfew minutesafter dumping, and (2) the rate of initialmixingis generallythe same for all bargeconfigurations. the With these assumptions, only parameter remaining that will appreciably affectthe wake-induceddilution,Di, is the effective is dumpingrate,R. We expectthat dilution inversely to proportional effectivedumpingrate,such that we obtainthe following for expression initialdilution: Di f (I/R) of The recentfieldobservations plumewidthwithinthe wake of barges indicate mixing,the sludge that,duringthe initialperiodof wake-induced plumeis confined mixingvolumecreatedby the barge withinthe turbulent wake. For the New York barges,the initialplumeis as wide as the barge B, wake,but for otherbargessuch as the Princess the plumeis a fraction of we the wake width.Therefore, may assumethat the initial(t=0) mixing volumebehinda bargehas an upperlimitequalto the volumeof the barge wake (roughly the bargewidthtimesthe draft),and to a first-order the approximation, averagedilution wouldbe inversely to proportional the volumeof material dumpedin the wake (the effectivedumpingrate, R). of (0 the absence short-term to 5-min)measurements behindthe various we barges, will considerthe initialmixingregimeas a linearsystemsuch that Di A/R where A a constantrelatlngdilution to effectivedumpingrate can dumpingrates This linearexpression then be used to predicteffective from observeddilutionsand knowndumpingrates: 3-6 [ R x Di ]obs = A = [ R x Di ] req or R req = [ R x Di ]obs (4) [ Di ] req where R req = the effectivedumping rate that will be to required achievea specific dilution Di req = the required initialdilution(at with water tm5 min) basedupon compliance at qualitycriteria 4 h and ’obs’ refersto observed and initialdilutions average ef~dumping rates from plume eventDB-21 will be used later,in conjunction This expression with Eq. (2), to obtain empiricalequationfor determiningdumpingrateswhichare basedupon (I) dilutions to required preventselected sludgeconstituents from exceeding at of waterqualitycriteria 4 h, (2) observations initialdilution, and (3) observedratesof oceanicmixingand sludgedilution. 3.1.2 OceanicMixing turbulent Afterthe initial(O to ~5 min) periodof wake-induced mixing, sludgeplumesare dilutedat slowerratesas a resultof buoyancyeffects, and sludgeflocculation settling, and oceanicdispersionprocesses.Under extreme near-surface wind and wave conditions, plumesmay be dispersedat ratesthat approachthe ratesachieved but duringwake-mixing, most of the is time,oceanicdispersion relatively slow. For the periodfollowingwake- induced to mixing,the factorsexpected controlthe rate of sludgedilution, dDo, are givenbelow: dDo f [ Di, S, Z, Hw, Mc ] (5) 3-7 where Di the extentof wake-induced initialdilution S sludgecharacteristicse.g., ( and flocculation settling) Z pycnoclinedepth Mw = dispersiondue to winds and waves Mc = dispersiondue to current shear 5 is Di, the initialdilution minutesafterdumping, an important (5 factorin the longer.term min to 4 h) dilution if phasebecause, the effective is dumpingrate is high and the dilution low, the core of the plume and of will be more concentrated achievement a specified (high)dilution will a require longerperiodof time. Sludgecharacteristics, pycnoclinedepth,and surfacemixingdue to as windsand waveswill affectsludgedilution described duringthe phaseof initialmixing.Dispersion to due to currentshear was not expected have a majoreffectupon dilution duringthe firstfew minutesafterdumping, becausethe turbulencedue to bargemomentu~ much greaterthan the is effectivemixingdue to currentshear.However, after the wake has lost its momentum, currentshear,if present,can effectivelyincreasedilution by lateral of of displacement portions the plume. DuringplumeeventDB-3 (September 1987),strungcurrentshearat the base of the surfacemixedlayereffectively increasedthe rate of dilution withinthe plume.Had the currentshear been weak or nonexistent (whichmay be the typicalcase exceptduringthe passageof warm-core eddies),the rate of plumedilution mighthave been less. Duringthe September1988 survey (plumeeventsOB-21and DB-23),therewas no significant currentshearat the in base of the mixed layer.As indicated Table 2.6, the rate of dilution less than observed from O to 4 h for DB-21and DB-23was significantly for DB-3,but we cannotbe sure this difference to was mainlyattributed the lack of current shear. To summarize, we although can identify the physicalfactors/processes that affectthe rate of sludgeplumedilution, dDo. afterthe periodof 3-8 initial, wake-induced mixing, we do not have sufficient field data to quantify the effects of each process in Eq. (5). Wewill therefore estimate the rate of dilution, dDo, from specific field data of representative sludge plumes. As discussed in subsection 2.3, the results from plume event DB-21 provide the most conservative (lowest) rate of dilution during the first 4 h following dumping: ~ SO0:l/h. This rate will he used in the following section. RATEEQUATION 3.2 DUMPING Derivation of an empirical equation for prediction of optimum dumping rates requires combination of Eqs. (2) and (4): D wqc IZ Di req + dDo x T (2) BE or Di req D wqc ~dDo x T t=4 ~) (2 t=O and Di req Robs x Di obs (4’) R req Eqs. (2’) and (4’) yields Combining R req Robs x Di obs I D wqc _ _ _ dDo x T t=4 t 0 (6) 3-9 where R req the requiredeffectivedumpingrateto 4 D achievea specified h dilution, wqc, that is basedupon waterqualitycriteria D wqc at the dilution 4 h thatis requiredby the waterqualitycriteria Robs, Di obs of fieldobservations plumeeventDB-21during 1988 September concepts The underlying and assumptions in inherent thisempirical dumpingrate equation in (Eq. 6) are illustrated Figure3.1. This figure schematically the observed represents time seriesof sludgeparceldilution from plumeeventDB-21(lowerline),as well as the required dilution(upper to D line)that wouldbe necessary achievea 4 h dilution, wqc,of 20,000:1. of is Note that this dilution 20,000:1 merelyan example; actualdilution for requirements each permitapplicant 4.1. are givenin subsection dilution This conceptual model(Eq. 6) is basedon two assumptions: ¯ The rate of oceanicdilutionfrom 0 to 4 b, dDo, for is equivalent the observedand requireddilutioncases. ¯ The requiredinitialdilution(at lm5 min), Di req, can by in - achieved a linearreduction the effective dumping rate,R. by Thus,if D wqc (at 4 h) can be specified waterqualitycriteria, then Eq. dumping (6) can be used to predictthe effective rate,R req, that would achieve the required at is dilution 4 h. A samplecalculation provided below. Usingthe resultsof plumeeventDB-21: Robs ~ 22.8 gal/ft(10,855gal/min÷ 4.7 kn ÷ 101.3 ft-h/min-nmi) 3-10 25,000 J Di wqc 20.000 Required Dilution jf "~’Slope = dDo Z 15,000 - dt F-- ./ 10.000 GJ I -Woke Dilution 5,000 III Observed Dilution I D / /=-i uu~ ~ Slope = dDo I / i obs I I I 0 1 2 3 4 TIME (hours) 3.1 HODEL FIGURE CONCEPTUAL OFSLUDGE PLUHEDILUTION FROM OBSERVATIONS (LOWER PLUME LINE)DURING EVENTDD-2I. OF IF A DILUTION 20,000 BY IS REQUIRED HATER CRITERIA 4 h+ THEN QUALITY AT THEREQUIRED IS BYTHE DILUTION REPRESENTED UPPER LINE. Di obs ~ 1,724 dDo ~ 500 per hour t=4 dDo x T t=O = 500 x 4 b 2,000 and, if the water quality criteria (e.g., for copper), require a dilution 20,000:1 at 4 b: D wqc 20,000 then, using Eqo (6) we obtain R req 22.8 x lf724 20,000 - 2,000 R req ~ 2.2 gal/ft for the effective to dumpingrate that wouldbe required meet waterquality criteria, baseduponthe fieldobservations from plumeeventDB-21. To determinethe voTumedumpingrate,in unitsof gallonsper minute, requires of multiplication the effectivedumpingrate by the averagebarge speedduringthe dumping operation: VDR = R req x K x 101.3 ft-h (7) where VDR the volumedumpingrate(gal/min) R req the required dumpingrate(gal/ft) effective K bargespeed(kn) B at DuringplumeeventDB-21,the bargePrincess was traveling 4.7 kn such that the volumedumpingrate shouldhave been VDR = 2.2 gal/ftx 4.7 kn x 101.3 1,047gal/min 3-12 to achieve a dilution of 20,000:1 at 4 h after dumping. Note that if the barge speed had been 3 kn, the volume dumping rate would have to be lowered to 668 gal/min (3/4.7 x 1,047). Combination of Eqs. (6) and (7) yields the complete expression determination of volume dumping rates from field observations of event DB-21 in September1988. VDR= 101.3 x K x R obs x Oi obs D wqc- dDo x T t=4 t=O and since V obs = Robs x K x 10].3 then VDR = V obs x D iobs D wqc - dDo x T t=4 (8) dt t=O of Substitution resultsfrom plumeeventDB-21 yields VDR = I0i855x 1,724 1.8714x 107 (gal/min) D wqc - 500 x 4 O wqc - 2,000 Section4 presents sludgedumpingratesthat are basedupon variousvaluesof Note that this equation O wqs in the above expression. assumesa barge speed to of 4.7 kn (equivalent that duringplumeevent DB-21).To determine the volumedumpingrate, VDRS at any barge speed,S, the rate for 4.7 kn (for by VDR) can simplybe multiplied the ratio of speeds: 3-13 = VDRS VDRx The following subsection demonstrates the importance of barge speed to the volume dumping rate (in gai/min)o SPEED 3.3 BARGE CONSIDERATIONS Whenconsidering sludge dumping rates, the most important point to is remember that plumedilution and compliance with waterqualitycriteria are more dependent upon the effectivedumpingrate (in gal/ft)than the volumedumpingrate (in gal/min). For a given volumedumpingrate,barges that travelrelatively fast (5 tO 8 kn) effectively dump much less sludge per unit tracklengththando bargesthat travelslower. Present for ErA regulations dumpingof sewagesludgeat the IO6-Mile Site specify(I) a maximumvolumedumpingrate,VDR, of 15,500gal/min,and (2) a minimumbarge speedof 3 kn. Compliance with these regulations by represented the shadedregionin Figure3.2. Underspecific of dumpingconditions 15,500gal/minand 3 kn, the effectivedumpingrate, R, is 51 gal/ft.Also shown in Figure3.2 is a line indicatingthe set of bargespeedsand volumedumpingrates(in gal/min) that satisfythe case of R = 51 gal/ft.The shadedregionillustrates that compliance (whichare basedupon volumedumping with ERA dumpingregulations ratesand bargespeeds)w|ll normally resultin effectivedumpingratesthat are well belowthe impliedmaximumrate of 51 gal/ft.For instance,if at bargesdump at 15,500gal/minwhiletraveling speeds>3 kn, the following dumping effective rates,R, result: At 6 kn and 15,500gal/min,R = 25.5 gal/ft At g kn and 15,500 gal/min,R = 17.0 gal/ft wereto achievean effective Thus,if the requirement dumpingrateof 51 gal/ft,the volumedumping as rates,V, couldbe increased follows: 3-14 20,000 R= 51 gal/ft 15,500 gal/min ¯ ~ 15,000- V LLI 10,000- o Z R= lo gal/ft 5,000 E3 0 0 3 6 9 12 BARGESPEED(knots) FIGURE 3.2 PLOT VOLUME OF DUHP][NG (GAL/NIH) RATE VERSUS SPEED,THE BARGE SHADED REGION EPA REPRESENTS BUI4P]NG SOLID REGULAT[OHS, LINES TWO OF REPRESENT VALUES THEEFFECTIVE RATE DUHP]NG IN UNITS OF GAL/FT. To achieve R = S1 gal/ft at 6 kn, V= 31,000 gal/min To achieve R = 51 gal/ft at 9 kn, V = 46,500 gal/min If EPAcontinues to regulate ocean dumping by specifying an upper limit on the volume dumping rate, regardless of barge speed (so long as it exceeds 3 knots), the effective dumping rate should at least be considered when setting criteria for ocean dumping violations. For instances, Figure 3.3 illustrates the volume dumping rates and barge speeds for the barges surveyed during the September 1987 and 1988 surveys at the lO6-Nile Site. Barges (events) DZ-1, DB-2, DB-3, OB-4, DB-21 and DB-23 were all dumping at rates below 15,500 gal/mtn, and at barge speeds greater than 3 kn, in accordance with permit requirements. Their effective dumping rates differed greatly, however, on account of large differences in barge speed. Event DB-3 had the lowest effective dumping rate (R m 15 gal/ft) because it had the highest barge speed; event DB-2 had the highest effective dumping rate (R ~ 29 gal/ft) of the four events, with volume dumping rates less than 15,500 gal/min. Nevertheless, the volume dumping rates for all of these barge eventscouldhave been increased substantially beyond15,500gal/minwhile an maintaining effective dumpingrate less than 51 gal/ft(the EPA requirement basedupon 15,500gal/min and 3 kn). Figure3.3 also illustrates that although plumeeventDB-I had a volume dumping rate in excessof 15,500gal/min, its effective dumpingrate (R~33 gal/ft)was still ]ess than the impliedEPA rate of 51 gal/ft.These examplesillustratethat,if sludgedumpingratesare to be basedupon water qualitycriteria,then dumpingratesshouldbe basedupon the effective dumpingrate;volumedumpingratescouldthen be specified for a givenbarge speed,or rangeof speeds(e.g.,4-6 kn). 3-16 20,000- R--75 gal/ft R-SO R--20 DB-I 15,500 gol/min .... DB-2 3 - .-~ 15,000 - DB-2 E De-~ DB-3 R-IO DB-21 ¯ I-- 10,000 ¯ .< 0:: 7 5,000, I E3 I R-2 3 6 9 12 SPEED BARGE (knots) FIGURE 3.3 PLOT OF VOLUME DUMPINGRATE(gal/mfn) VERSUS BARGE SPEED. VARIOUS CASESAREGIVEN FOR THE EFFECT]VEDIJHPING RATE,R,, (gaT/ft). BARGE DUMPINGCHARACTER[STZCSF’RONSEPTEMBER 1987 AND BY 1988 ARE REPRESEMTEO INDIVIDUAL POINTS. DUHPING 4. RECOHHENDED RATES The previous section presented an empirical equation (Eq. 8) for the estimating rate at whichsewagesludgeshouldbe dumpedin orderto meet toxicity and requirements waterquality at criteria the IO6-Mile Site. Althoughadditional will be necessary validate fieldmeasurements to this formulaundera varietyof oceanographicconditions,dumpingrates,and barge EPA configurations, is currently for facedwith time constraints sludge dumpingpermits, this preliminary and consequently, formulawill be used to set initialsludgedumpingratesfor the lOG-Mile Site.As additional field data becomeavailable monitoring from subsequent studiesat the IO6-Mile to in Site,modifications the variouscoefficients the dumpingrate equation shouldbe considered. In the following we dumpingrate equation subsections use the empirical to develop ¯ Specificdumpingratesfor each permitapplicant. ¯ A nomograph of to for selection dumpingratesaccording specific dilutionrequirements at that may be specified a laterdate. PERMITAPPLICANTS 4.1 DUMPINGRATESFOR INDIVIDUAL EPA RegionII has received for applications permitsto dump municipal sewagesludgeat the 106-Mile treatment Site from nine wastewater authorities in New York and New Jersey= PermitApplicants Abbreviation PassaicValleySewerage Commissioners PVSC MiddlesexCountyUtilities Authority MCUA BergenCountyUtilities Authority BCUA L]nden-RoselleSewerageAuthority LRSA RahwayValleySewerage Authority RVSA JointMeetingof Essexand UnionCounties JMEUC of New YorkCity Department EnvironmentalProtection NYCDEP of NassauCountyDepartment PublicWorks NCDPW Westchester of CountyDepartment Environment Facilities WCDEF 4-I Eachpermit application includes on information (1) the concentrations chemical constituents within the whole and sludge, {2) results wholeof sludge toxicity tests. of Withthe exception the NYCDEP, eachpermit application provides on information the sludge froma single treatment In facility. the case of NYCDEP, the however, pemitapplication provides dataon the maximum chemical or concentration mosttoxic toxicity test results obtained fromany one of twelve treatment facilities. Thus,high chemical from concentrations a single New YorkCityplant applyto all plants in designated the NYCDEP permitapplication. Tables 4.1 and 4.2 present metal and toxicity characterization data, from respectively, analyses on thatwereconducted whole sludge samples in obtained August 1988fromthe ninesewerage in authorities New Yorkand New Jersey. Analytical and of methods a comparison results withdata in provided the permit are in applications provided a separate report (Battelle, The Ig88f). two tables alsopresent of estimates the dilution be to thatwould required meetthe applicable or metal-based toxicity-based water quality criteria. in As indicated Table4.1,the highest metal-based dilutions are by for governed copper eightof the ninesewerage authorities; mercury-based dilutions exceed of those copper onlyfor the Bergen County Utilities Authority The (BCUA). metal-based dilutionsrangefrom4,140 for Nassau to County 80,000 for BCUA.The toxicity-based dilutions alsohavea wide of range values: from4,740for Middlesex to for County 166,700 Linden- Roselle. of Comparison Tables that 4.1 and 4.2 illustrates metal-based dilutions exceed toxicity-based for dilutions fiveof the ninesewage authorities studied. To relate the required dilutions in presented Tables 4.1 and 4.2 to actual sludge dumping we rates, haveusedthe empirical dumping rateequation (Eq.8) givenin the previous to the section calculate volume dumping rate (in gal/min) be to the thatwould required achieve specified dilutions 4 after and dumping thusmeetwater quality criteria. Table 4.3 presents volume dumping rates for eachsewerage authority based uponthe required dilutions in 4.1 given Tables and 4.2;dumping rates of 3, are alsogivenas a function bargespeed(e.g., 6, and 9 kn).These 4-2 TABLE4.1 WHOLESLUDGE gETALCHARACTERIZATION FRON RESULTS THE NINE NEW YORK-NEWJERSEY SEWERAGE APPLYING PERMITS AUTHORITIES FOR TO SEWAGE DISCHARGE AT SLUDGE THE106-MILE SITE. SAMPLES)/ERE IN COLLECTED AUGUST 1988. getal (mg/Lwhole sludge) Required Authority Cu Hg Diluttona 14eta1 PVSC 42.0 14,500 Cu HCUA 68.0 23,450 Cu BCUA 2.00 80,DUO Hg LRSA BO.O 27,5g0 Cu RVSA 16.0 5,520 Cu JMEUC 36 12,410 Cu NYCDEP 38.0 13,100 Cu NCDPW 12.0 4,140 Cu WCDEF 56.0 19,310 Cu PVSC = PassaicValleySewerage Commissioners. MCUA = MiddlesexCountyUtilities Authority. BCUA = BergenCountyUtilities Authority. LRSA = Linden-RoselleSewerageAuthority. RVSA = RahwayValleySewerage Authority. JMEUC = JointMeetingof Essexand UnionCounties. NYCDEP= of of Composite the New York City Department Environmental Protectionfacilities. of NCDPW = NassauCountyDepartment PublicWorks. WCDEF = Westchester of CountyDepartment EnvironmentalFacilities. basedon the metalrequiring aDilution the greatestamountof dilutionto meetwaterquality. 4-3 ’TABLE4.2 WHOLE SLUDGE’TOXICITY RESULTSFROMTHEKIRE NEWYORK-REWJERSEY SEWERAGE AUTHORITIESAPPLYING TO FORPERNITS DISCHARGE SEWAGE AT SLUDGE THE106-RILE SITE. SANPLES WERE IN COLLECTED AUGUST BASED 1988. THEP, AXII@.JNTOXICITY DILUTION SLUDGE FOR REQUIRED EACH ARE MUNICIPALITY LISTED. LCSO(~whole sludge) Toxicity Based le~nidia Nvsl"dopsis Required Authoritye ~ -~ Di|ui:loeb PVSC 0.49 0.17 58,800 MCUA 5.95 2,11 4,740 BCUA 1.55 2,10 6,450 LRSA 0.53 0.06 166,700 RVSA 1.49 0.88 II,360 JMEUC 1.92 1.68 5,950 NYCDEP 1.59 2.25 6,290 NCDPW 2.33 0.92 10,870 WCDEFW 0.91 1.17 10,990 are aAbbreviations definedin Table4,1. bThe species factorof 0.01 were used with the lowestLC50 and an application to determinethe requireddilution. 4-4 OF TABLE4.3 COMPARISON SLUDGE DUMPING RATES ON BASED TOXICITYANDTRACE NETALRESULTS. REQUIRED DILUTIONDATAWERE FROM DERIVED THE AUGUST1988 SLUDGE STUDY.DUI4PZNG CHARACTERIZATION RATES WERE ON BASED OBSERVED DILUTION RATESFRON 1988 THESEPTENBER SURVEY AT THE106-NILE SITE. Required Oump~n~nRate Recommended (gal/mfn)9 ¯ Authority a Dilution 3 kn Toxicity Basis PVSC 58,800 210 420 630 MCUA 4,740 4,359 8,719 13,078 BCUA 6,450 2,684 5,368 8,052 LRSA 166,700 85 171 256 RVSA 11,360 1,276 2,552 3,828 JHEUC 5,950 3,024 6,048 9,072 NYCDEP 6,290 2,784 5,568 8,352 NCDPW 10,870 1,347 2,694 4,041 WCDEF 10.990 1.329 2.658 3.987 MetalBasis PVSC 14,500 955 1,911 2,866 McuA 23,450 556 1,113 1,669 BCUA 80.000 153 306 459 LRSA 27,590 466 933 1,399 RVSA 5,520 3,393 6,786 10,179 OMEUC 12,410 1,147 2,295 3,442 NYCDEP 13,100 1,076 2,162 3,228 NCDPW 4,140 5,582 11,164 16,746 WCDEF 19,310 690 1,380 2,070 are in aAbbrev~atlons defined Table4.1. 4-5 results indicate that sludge dumping rates must be reduced greatly from the court-mandated rate of 15,500 gat/min in order that sludge concentrations 4 h after dumping are sufficiently low to meet EPAwater quality criteria. At a barge speed of 6 kn, recommended dumping rates for the nine permit applicants vary from 171 to 8,719gal/minbased upon toxicity requirements; 306 to 11,164gal/minbasedupon metals. The recommended dumpingrate for each permitapplicantis, therefore, dependent upon the speed of the barge (Table4.3).As demonstrated Section3, dilution requirementsdictatean effectivedumpingrate,but volumedumpingratesare basedupon the effective dumpingrate and the barge speed.Accordingly, to volumedumpingrates are directlyproportional barge at speed,such that bargestraveling 3 kn must dump at one-half the rate of a the rate of a barge with a speed of bargewith a speedof 6 kn, and one-third 9 kn. Thus,bargesthat travelrelatively fast (7 to 9 kn) could dump at to 3 timesthe dumpingrate of slow (3 kn) barges,and meet water quality The effectof barge speed on dumpingrate is, however, lesser criteria. a issuethan the actualrangeof recommendeddumpingrates that are givenin in Table 4.3. A major reduction dumpingrates from 15,500gal/minto near 1,OO0gal/minwouldrepresent in more than a 1S-folddecrease rates,and consequently, in more than a 15-foldincrease the time for a barge to dump its load at the 106-Mile repercussions this long Site. The logistical of dumping in time are discussed Section5. OF 4.2 NOMOGRAPN DUMPINGRATES FOR SPECIFICDILUTIONREQUIREMENTS The previoussubsectionpresented specific dumpingratesfor each of the nine permitapplicants. These rates were based upon whole sludgedata that were determinedfrom the characterization in study conducted August1988 ( EPA 1992d). We anticipatethat additional chemicalconstituent and toxicitydata will be acquired over the next few yearsfor the various sludgesdumpedat the IO6-Mile Site,and for this reason,a simplified or algorithm nomograph will be neededto determine optimumdumpingrates as a of function the required dilution. For this purpose, Figure4.1 illustrates betweenthe required the relationship dilution and the sludgedumpingrate, in expressed units of gal/mln. on The data are presented logarithmic scales 4-6 1,000,000 1,000 l I I 111 I~ I ; : : ; $ I II I I l : ~ t;~:li I I I I I I II 10 1 O0 1,000 10,000 100.000 DUMPING SLUDGE RATE(gal/min) FIGURE 4.1 OF NOHOGRAPH SLUDGE DUMPINGRATES(in gai/Bin) VERSUS REQUIRED SLUDGEDILUTIONS4-h AFTERDUMPIflG AT THE I06-NILE SITE. SEPARATECURVESARE GIVER FOR BARGE OF SPEEDS 3, 6, AND9 kn. CALCULATIONSBASED OF UPONFIELD OBSERVATIONS SLUDGE DILUTION DURINGSEPTEHBER1988. the to accommodate wide rangesof dilution and dumpingratesthat may be In encountered. accordance with Eq. (8), dumpingratesare inversely to proportional required dilution, in and increases bargespeed can effectivelyraisethe permissibledumpingrate for a givendilution requirement. to Becauseit is difficult extractvaluesfrom this graphic the in presentation, same data are presented Table4.4 for dilutions ranging from 5,000to 150,000,and bargespeedsof 3, 6 and g kn. 4-8 TABLE4.4 DUMPING RECOiqMENDEDSLUDGE RATES VERSUS REQUIREDDILUTION. VOLUME RATES DUI4PING (ga|Jm|n) AREfiIVEN FORTHREEBARGE SPEEOS. Effective Required Dumping Rate Volume DumpingRate (gal/min) Dilution (gal/ft) Barge Speed: 3 kn 6 kn 9 kn 5,000 11.4 3,982 7,g53 11,g45 10,000 2.5 1,493 2,985 4,47g 15,000 1.4 91g 1,838 2,757 20,000 0.98 664 1,328 1,992 25,000 0.75 520 1,039 1,559 30,000 0.61 426 853 1,279 40,000 0.44 314 628 942 50,000 0.34 249 498 747 75,000 0.22 163 327 490 I00,000 0.17 122 244 366 125,000 0.13 97 194 291 150,000 0.11 80 161 241 dumpingrate (gal/ft) achievethe required Note: The effective to dilution of is independent bargespeed. 4-9 FOR DUHPING 5. STRATEGIES HULTIPLE The previoussections the initial(4-h)dilution discrete addressed of parcelsof sewagesludgedumpedat the IO6-Mile Site. Dilution calculations and, therefore, dumpingrate formulaswere basedupon discrete parcels, ratherthan plume-average sludgeconcentrations, becausethe EPA regulations for ocean dumpingof municipal at wastesare directed waste parcelsrather of than spatialaveragesof entirewaste plumes.Consideration dumping strategies and wasteloadingat the site does, however,requireanalyses of on wholeplumesand calculations spatialscalesthat includethe entire dumpsite. we issuesand In this section, raisea numberof practical concerning considerations the presentand futuredumpingof sludgeat the IO6-MileSite.The followingsubsectionsaddressthe topicslistedbelow: ¯ Bulk loadingof sludgeat the IO6-MileSite ¯ Strategiesfor dumpingat presentratesof 15,500gpm ¯ for Considerations dumpingat greatlyreducedrates. 5.1 BULK LOADINGCONSIDERATIONS The volume(load)of sludgedumpedat the IO6-MileSite is estimated be roughly7.2 millionwet metrictons (1.7 billiongallons)annually, of 20,000m3 per day (Walkeret al.. 1987).The magnitude this dumping activity, coupledwith the presumed ecologicaleffectsof sludgeon the marinelife of the U.S. east coast,has fueledgreatconcernfor sludge dumpingat the IO6-Mile Site. To determine the true fate and effectsof sludgedumpingat the IO6-Mile Site will requirean extensive monitoring activityas outlinedin the IO6-MileSite monitoring plan ( EPA , Ig88a). This monitoring is on activity underway, but information the farfield fate and long-term effectsof sludgedumpingwill not be available for another year or two. of Prior to implementation the IO6-Mile Site monitoring plan,Walkeret a al. (1987)developed modelof the farfield transport and fate of sewage sludgedumpedat the lO6-Mile Site. Theirtransport model was based upon (I) 5-I of observations mean southwestward at currents the site,and (2) estimates sludgeloadingat the site,ratesof turbulent mixingwithinthe bargewake, and sludgediffusionratesover time scalesof days to months.This model provides of of estimates the mean transport sludge-derived dumped pollutants at the 106-MileSite.In addition, to the two- maps are provided illustrate dimensional of distribution sludgeconcentration (dilution) alongthe U.S. east coast.These steady-state model results, whichwere basedupon a dumping rate of 20,000m3 of sludgeper day, indicate that minimumdilutions (highest sludgeconcentrations) withinS0 km of the site wouldbe on the order of 1,000,000:1.Clearly, thesedilutions are 2 or 3 ordersof magnitude that were observed greaterthan the dilutions duringthe nearfield surveysof sludgeplumeswithinthe 106-Mile Site.Although the Walkeret al. modelmay representthe farfield,long-termfate of sludgedumpedat the 106-Mile actualnearfieid Site,it does not represent dilutions. of As a firststep towardanalyses sludgeloadingwithinthe 106-Mile (hoursto days),Table Site and on timesscalesof the dumpingoperations 5.1 presents of basiccalculations the site receiving volumeand the amount of sludgethat is now beingdumpedat the site. If the depthof the volumeduringsummeris takenas the depthof the seasonal receiving (20 of pycnocline m), and the dimensions the site are 7.2 km by 37.0 km, then the receivingvolumein summeris approximatelyI0.7 x 109 m3. Thus,one NYCDEPbarge load of sludge(12,500m3) mixedevenlythroughout the dumpsite of in summerwouldresultin an averagesludgedilution ~426,000:I. if Likewise, 10 bargesdumpedsludgeat the site duringa week-longperiod without (zeronet current), circulation the resultingsite-averageddilution in wouldbe ~42,600:I summer.Thesedilution estimates will certainlyvary of with the numberand size (sludgecapacity) the bargesthat would dumping but leads duringa periodof no circulation, this simplecalculation to the followingconclusion: ¯ If no circulation were to persistfor a week or so duringsummer months,and dumpingactivities of consisted at leastI bargeper day, then site-averaged sludgedilutions may be as low as 50,000:1. This condition represents the worst-case for sludge I~ because these site-averaged dilutionsare less than the mlnlmumrequired dilutlons for some of the sludgesbeingdumpedat the 106-Mile Site(see Tables4.1 and 4.2). 5-2 The nearfieldresultsfrom the winter1988 surveyat the 106-Mile Site ( EPA 1988a) indicatedthat, on time scales of less than one day, sludge may not settlein significantquantitiesbeyonda depthof roughly30 m. Althoughsludgemay penetratedeeperduringperiodsof activemixing(e.g., stormevents), pycnocline the data suggestthat the depth of the permanent of (~I00m) is an overestimate the actualdepthof the mixing(receiving) dumping. volumeduringthe firstfew days following on Therefore, time scalesof a few days,the receiving volumein wintermay not be significantly greater to than duringsummer(thuscontrary earliertheories basedsimply upon pycnocline depth). We suspectthat,due to significant currents that flushthe site on timesscalesof 2 to 20 hours,site-averaged sludgeloadingat the 106-Mile Site is not a problemfor most days of the year. Additionalsite-speciflc fielddata are neededfor meaningful on of statistics the frequency week-long stagnant flow periods,but we estimatethat such eventswouldnot occurmore than one or two timesduringthe S-month"summer"season. AT RATE OF 151500 qpm 5.2 DUMPINGSTRATEGIES COURT-ORDERED sludgeat the 106-Mile The presentcourtorderfor dumpingof municipal Site contains specifications: the following ¯ Dumpingratesmust not exceed15,500gpm. ¯ Bargesmust maintainspeedsof at least3 kn. ¯ Sludgemust be dumpedwithinthe 106-MileSite boundaries. ¯ An individualplumemust not crossnor come withinI/2 mile of itselfat any point. to Modifications the dumpingratesare beingconsidered (e.g.,this report), and the effectsof bargespeed on sludgedilutionmay also be the topicof futurestudiesrelatedto oceandumping. One of the most basic questions, "Alongwhat trackshouldsludgebe dumpedwithinthe site?",has, however, received littleattentioncomparedwith other issues.In this subsection we 5-3 propose a few strategies that may help to ensure that sludge dumping at the I06-Mile Site will meet EPA waterquality criteria. In Section3, an empirical equation (Eq. 8) was developed for prediction of sludgedumpingrates that will ensurethat waterqualitycriteriaare met 4 h after dumping.If, however,sludgeplumescross the site boundariesin will be less thanthosepredicted ( h and, less than 4 h, dilutions at therefore, if the dumplngrateswill be too high. Therefore, the dumping ratesderivedfrom £q. (8) are to be used,then (I) plumesmust not cross site boundaries within4 h afterdumping,and (2) a plumemust not cross another plumenor overlapitselfwithin4 h afterdumping. Ensuringthat sludgeplumesremainwithinthe site for at least4 h is a task,considering difficult currents that near-surface oftenattainspeedsof I kn or more duringperiodswhen eddiespass throughthe site.Present dumping regulationspermitdumpinganywhere withinthe site or alongits and boundaries, consequently, out sludgemay be transported of the site withinminutesor a few hoursafterdumping, dependingupon the positionof dumping and speedof the currents. and the direction Below,we presentcandidate for sludgedumpingduringthree strategies hypothetical flow regimes:weak flow,havingcurrentspeeds<0.25kn; moderate flow,with speedsbetween0.25and 1.5 kn; and strongflow,with speeds>1.5 kn. In reality, this rangeof currentspeedscan be obtained but from all currentdirections, we have basedthe presentanalyses upon the worst-case flow condition:east-westflow,directedacrossthe narrow(4.5 nmi; 7.4 km) widthof the dumpsite. WeakFlow (<0.25kn) ¯ Dumpingmust be prohibitedwithinI nmi of all site boundariesto ensurethat sludgedoes not crosssite boundaries before4 h after dumping. ¯ The trackof a bargemust not crossthe trackof a previousbarge withinthe site unlessat least4 h has elapsedbetweenthe two If dumpingoperations. the startof dumpingfor individual barges by couldbe separated 4 h, then bargescouldfollowthe same track withinthe site. ¯ If simultaneous then dumpingshouldbe dumpingis permitted, conductedalongparallel, lanesto ensurethat plumes north-south do not cross within4 h afterdumping.Three lanescould be 5-4 one established: alongthe centerof the site (along72°02.5’W); I of and two situated nmi from both the east and west boundaries the site (along72°01’Wand 72°04’W). Flow (0.25to 1.5 kn) Moderate ¯ or If flow is easterly westerly, then dumpingmust be directed alonga north-south trackthat coincides with the site boundaryon the upstream s!de of the site (e.g.,east boundary for westward flow).Thls w11l ensurethat plumesdo not leave the site within h of dumping. ¯ or If flow is northerly southerly, then dumpingshouldbe confined to the upstreamha]f of the slte (e.g.,south of 38°50’Nfor northerly flow)to ensurethat plumesdo not leavethe site within 4 h of dumping. ¯ for If a singledumpingtrackis established periodsof moderate flow,then dumpingoperations by must be separated at least4 h. StrongFlow(>1.5kn) ¯ Duringperiodsof strongeast-west flow, dumpingshouldbe prohibited in becausesludgeplumeswill cross the site boundaries is less than 3 h no matterwherethe material originally dumped. ¯ Duringperiodsof strongnorth-south flow, dumpingis permissible to but all dumpingshouldbe confined the upstream half of the site (e.g.,southof 38°50’Nfor northerly flow)to ensurethat plumes do not leavethe site within4 h of dumping. The" dumpingstrategies presentedabovewouldensurepropermanagement of at sludgedumpingoperations the IO6-Mile Site,but they will require(I) near-reel-time of at knowledge surfacecurrents the site, and (2) close coordination betweenEPA and the transportcompaniesthat tow sludgebarges to the 106-Mile Site. EPA currentlyplansto deploya surfacecurrent of mooringat the site in January1989 for telemetry near-real-time current data to EPA RegionII. This mooringwill providecontinuous informationon of the speedand direction the currents, whichcan be used to determine the optimum dumpingstrategy or (see weak,moderate, strongflow strategies given above).EPA could then post a radio bulletin, via the U.S. Coast Guard,that directs to to the transporters dump according a precoded or strategy lane designation. 5-5 to a It is important note that failureto implement dumpingstrategy resultin sludgeplumescrossing such as that givenabove will definitely the of boundaries the site within4 h of a dumpingoperation. The abovestrategiesare well suitedfor dumpingoperations roughly at I. 15,500gal/minand for all bargesexceptthe Seatrader To dump its load g [ of roughly milliongallonsof sludge,the Seatrader requires about12 h, of and an in-sitetrackline ~50 nmi at a towingspeedof 4 kn. A special dumping for this exceptionally plan wouldbe required largebarge. AT 5.3 DUMPINGSTRATEGIES REDUCEDRATES The previoussubsectionpresentedcandidate dumpingstrategiesthat for wouldbe appropriate sludgedumpingratesof roughly15,500gpm (e.g., presentrates).At this dumpingrate, the New York bargestake roughly4 to 5 h to dump their entireload of 3.3 milliongallonsof sludge.At towing speedsof 5 kn, sludgeplumesof New York bargesare roughlythe lengthof the dumpsite (20 nmi from 38°40’Nto 3g°OO’N).Only the Seatrader a lengthof the site. generates plumethat is 2 to 3 timesthe north-south standpoint, From an operational majorproblems ariseif dumpingrates in are reducedby factorsof 15 or more,as discussed Section4. For if it instance, a New Yorkbargewere to dump at 1,000gal/min, wouldrequire I about60 h to dump its entireload. If the Seatrader were to dump at it 1,0DOgal/min, wouldrequire6 days to dump its load of 9 million gallons.These long dumpingtimes are a problemfor severalreasons: ¯ Transport high due to costsfor each bargeload wouldbe extremely time awayfrom port. the extensive ¯ The contractedtugs may not have the fuel or watercapacityto of remainat sea for periods weeks. ¯ If the bargeshad to remainat the dumpsitefor long periods,then additional barges(maybe10 timesas many as currently used)would by be required the New York and New Jerseysewerage authorities to dump the amountof sludgegenerated. ¯ Low dumpingrateswouldresultin vesseltrafficproblems within the site because10 or morebargeswouldbe dumpingsimultaneously; this numberof vessels steamlng small insidethe relatively dumpsite a wouldbe represent navigational safetyproblem. 5-6 The issues presented above illustrate that sludge dumping at significantly reduced rates (say, 1,go0 gal/min) may be environmentally acceptable, but they could be operationally unfeasible for the 106-Mile Site. 5-7 ANO 6. SUN4ARY RECOI4HENOM[ONS This reportbrieflyreviewsour knowledge the nearfield, of short-term of behavior plumesof sewagesludgedumpedat the 106-Mile Site. Field of observations plumebehavior and dilution duringEPA surveysto the 106- 1987 and 1988 have been used to develop empirical Mile Site in September an equation the optimumratesof sludgedumpingthat satisfyEPA for predicting water qualitycriteria.Althoughdata from a singleplume eventhave been used to developthe dumpingrate formula, the observed conditionsand plume behavior may represent conditions worst-case for plumedilution (minimum dilution due to weak mixingconditionsduringa summerperiodwith a shallow seasonal As pycnocline). data becomeavailable from additional nearfield monitoring surveys, in the coefficients the proposed dumpingrate equation can be modified. From the limitedamountof plumeobservations acquiredduringthe recent monitoring we surveys, can predictthe following nearfield of behavior sludge dumpedat the 106-Mile Site: ¯ Duringsummer,sludgeis primarily to confined the surfacemixed layer(upper20 m) abovethe seasonal duringthe first pycnocline h afterdumping. ¯ Parcelsof concentratedsludgewithinthe centerof a plumeare dilutedat much slowerratesthan the averagedilutionfor the entireplume. ¯ The rate of sludgedilutionduringthe first5 min afterdumping withinthe bargewake is much greaterthan the rate of dilution from oceanographicmixingprocessesafterwake mixinghas ceased. ¯ 4 Sludgedilutions h afterdumpingmay be as low as 5000:1for individual plume-averaged sludgeparcels; at dilutions 4 h may be or 100,000=I greater. ¯ Plumebreak-up,whichinitiates of rapiddilution parcels,can occurbeforeor after4 h dependingupon initialplume and concentrations oceanographic mixingconditions. assessment sludgeplumebehavior The resultsof this preliminary of indicatethat sludgedumpingratesof 15,500gal/minare too high to achieve necessary meet water qualitycriteria. the 4 h dilutions to Dumpingrates 6-I should be less than 15,500 gal/min for all the permit applicants, based upon (1) sludge characteristics data and (2) observed mixing conditions at 106-Mile Site. The results have also left a number of unanswered questions that require further considerations before we fully understand the nearfield fate of sludge dumpedat the 106-Mile Site: ¯ How does the rate of sludgedilution vary with oceanographic mixingconditions, pycnoclinedepth,initialplumeconcentrations (dumping rate),and sludgecharacteristics? Were the environmental conditions encountered duringthe September 1987 and 1988 surveys for representative the site? ¯ Is wake-induced a of dilution linearfunction the effective dumpingrate (the amountof sludgedumpedper unit tracklength)? ¯ of Do the sludgeconcentrations parcelswithinplumes4 h after dumpinghave a Gaussian distributionsuch that statistical techniquescan be used to estimate of the percentage a plume that may violatewaterqualitycriteria? ¯ be Can plume break-up achieved earliersuch that the rate of sludge is dilution increased? If, after initialwake-induced mixing,a plumeis broaderand/ormore dilute,oceanicturbulent mixingwill disperse parcelsof sludgemore quickly. the concentrate ¯ and methodshave a significant Do bargeconfigurations discharge effecton initialdilution? ¯ Are instantaneous to dumpingratesroughlyequivalent average dumpingrates over the lengthof the plume?If not, water quality criteriamay be greatlyexceeded of alongportions the plume. ¯ Does sludgesettling and/orflocculationwithinthe bargeduring transitcreatesignificant in variations sludgecharacteristics If betweenthe top and bottomof the sludgecompartments? so, in largevariations sludgecharacteristics alongthe plumewould result. These questions for lead to recon~endations additionalanalyses of existingdata and additional duringfuturesurveysto the 106- measurements MileSite: ¯ valid studyof toxicity A statistically testsand laboratory of analyses chemical constituent concentrationsshouldbe conducted on sludgesamplesfrom each of the sewagetreatment to facilities determinewhetherdata from the permitapplications and/orSantoro of and Fikslin(1987)are representative mean sludge and characteristics rangesof variability. 6-2 ¯ Addi¢ional plume monitoring surveys should be conducted behind bargesdumping.at 151500 gal/mih to develop statistically defenstb|e estimates of the rates of sludge d]]utton during the first 4 h after dumping. The effects of barge configuration, dumping rate, sludge Gharacteristics, wcnocline depth, and oceanographic mixing conditions have yet to he quantified. ¯ If EPAis considering reductions in sludge dumping.rates to ensure compliance with water quality criteria, then nearfleld plume monitoring studies should be conducted behind barges dumping at reduced rated (e.g., 5,000 and 1,000 gal/min)o Analyses will indicate whether rates of plume dilution are highly dependent upon dumping rates, such that 4-h dilutions, and hence permissible dumping rates, may be higher than those predicted from nearfield studies at dumping rates of 15,500 gal/min. ¯ Pretreatment of sludge and modifications to barge dumping procedures should he considered as alternatives to major reductions in dumping rates, especially as greatly reduced dumping rates would pose major operational problems to barge operators and permit applicants. 6-3 7. REFERENCES Brandsma, M.G. and T.C. Sauer, Jr. 1983. 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