Api publ 352 1999 scan (american petroleum institute)

~ STD.API/PETRO PUB 352-ENGL 1999 m ~ 0732290 Ob2L84L T B b American Petroleum Institute L MANAGEMENT OF RESIDUAL MATERIALS: 1997 PETROLEUM REFININGPERFORMANCE `,,-`-`,,`,,`,`,,` - REGULATORY AND SCIENTIFIC AFFAIRS NUMBER 352 PUBLICATION SEPTEMBER 1999 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale ~ S T D * A P I / P E T R O PUB 352-ENGL 1777 M 0732270 ObZLBY2 712 `,,-`-`,,`,,`,`,,` - American Petroleum Institute American Petroleum Institute Environmental, Health, and Safety Mission and Guiding Princ'iples MISSION The members of the American Petroleum Institute are dedicated to continuous efforis to impmve the compatibility of our operations with the environment while economically developing energy resources and supplying high quality products and services to consumers We recognize our responsibility to work with the public, the government, and others $0 develop and to use natural 'resources in an envimnmentally sound manner while protecting the health and safety of our employees and the public To meet these responsibilities,API members pledge to manage our businesses according to thefollowing principles using sound science to prioritize risks und to implement cost-effective management practices: PRINCIPLES e To recognize and to respond to community concerns about our raw materials, products and operations o To operate our plants and facilities, and to handle our raw materials and products in a manner that protects the environment, and the safety and health of our employees and the public To make safety, health and environmental considerations a priority in our planning, and our development of new products and processes To advise promptly, appropriate officials, employees, customers and the public of information on significant industry-related safety, health and environmental hazards, and to recommend protective measures To counsel customers, ttansporters and others in the safe use, transportation and disposal of our raw materials, products and waste materials To economically develop and produce natural resources and to conserve those resources by using energy efficiently To extend knowledge by conducting or supporting research on the safety, health and environmental effects of our raw materials, products, processes and waste materials To commit to reduce overall emission and waste generation To work with others to resolve problems created by handling and disposal of hazardous substances from our operations To participate with government and others in creating responsible laws, regulations and standards to safeguard the community, workplace and environment e Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS To promote these principles and practices by sharing experiences and offering assistance to others who produce, handle, use, transport or dispose of similar raw materials, petroleum products and wastes Not for Resale STD.API/PETRO PUB 352-ENGL 1797 0732290 0b218Li3 859 Management of Residual Materials: 1997 Petroleum Refining Performance Regulatory and Scientific Affairs API PUBLICATION NUMBER 352 `,,-`-`,,`,,`,`,,` - PREPARED UNDER CONTRACT BY: ROBFERRY THETGB PARTNERSHIP HILLSBOROUGH, NORTH CAROLINA SEPTEMBER 1999 American Petroleum Institute Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale S T D = A P I / P E T R O PUB 352-ENGL 1999 = 0732290 Ob21844 775 FOREWORD API PUBLICATIONS NECESSARILY ADDRESS PROBLEMS OF A GENERAL NATURE WITH RESPECT TO PARTICULAR CIRCUMSTANCES, LOCAL, STATE, AND FEDERAL LAWS AND REGULATIONS SHOULD BE REVIEWED API IS NOT UNDERTAKING TO MEET THE DUTIES OF EMPLOYERS, MANWACTURERS, OR SUPPLIERS TO WARN AND PROPERLY TRAIN AND EQUIP THEIR EMPLOYEES, AND OTHERS EXPOSED, CONCERNING HEALTH AND SAFETY RISKS AND PRECAUTIONS, NOR UNDERTAKING THEIR OBLIGATIONS UNDER LOCAL, STATE, OR FEDERAL LAWS NOTHING CONTAINED IN ANY API PUBLICATION IS TO BE CONSTRUED AS GRANTING ANY RIGHT, BY IMPLICATION OR OTHERWISE, FOR THE MANUFACTURE, SALE, OR USE OF ANY METHOD, APPARATUS, OR PRODUCT COVERED BY LETTERS PATENT NEITHER SHOULD ANYTHING CONTAINED IN THE PUBLICATION BE CONSTRUED AS INSURING ANYONE AGAINST LIABILITY FOR INFRINGEMENT OF LEïTERS PATENT `,,-`-`,,`,,`,`,,` - All rights reserved No part of this work m y be reproduced, stored in a retrieval system or transmitted by m y means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher Contact the publishel; API Publishing Services, 1220 L Street, N.W, Washington D.C 20005 Copyright Q 1999 American Petroleum Institute ii Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale S T D - A P I I P E T R O PUB 352-ENGL 1979 0732290 Ob21BV5 b TABLE OF CONTENTS secbon lb@ ExeciveSummary e5-1 1.Methodol~y 1-1 1-1 Rationale for Survey Clariñcations 1-1 R e s i d d S t ~ m 1-1 ~ g ~ P r a c b c e s a n eclmiques dT 1-2 DataMysis 1-2 R .~ 2-1 Re~pon~eRate 2-1 W a s t e w a t e r ~ .g ~ 2-4 P o l l ~ ~ P rention ev 2-9 3.ResidualStreamPr0 3-1 API Separator Sludge 3-2 Biomass 3-6 contaminatedsoils 3-9 DAFFloat 3-13 FCCCatalyst 3-16 Hy&o.Catalyst 3-20 ûtherSpaitCatalysts 3-24 3-27 PrimarySludges 3-30 s1opoilEmulsions0lids 3-34 SpeaitCresylicCaustic 3-37 SpentNaphthenicCauStic 3-40 Spent Sulfidic Caustic 3-43 TankBott011~ 3-47 4.cOmbinedstreams 4-1 ListingofR~ se PadSdm&S 4-1 SpentCaustics 4-3 `,,-`-`,,`,,`,`,,` - OilyWastewaterResiduals Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale Appendix A ELECTRONIC SURVEY FORM A-1 Appdx B DESCRWITON OF STATISTICAL PROCEDURES B-1 Appendix c G1 PARTICIPATIONSUMMARY D-1 DATATABLES Appendix D LIST OF FIGURES oage Figure Sample S a e m fiom the Survey Form 1-2 Response Rate by Refinery Capacity 2-1 U.S Department ofEnergy's Petroleum Administration fir Defénse (PAD) Regions 2-1 ResponseRatebyPADRegion 2-1 Response Distribution by Complexity of Facility 2-2 ResponseDistributionbyAgeofFacility 2-2 Response Distribution by Average Weight Percent of Sulfur in the Cnide Run 2-2 Wastewater Treatment System Summary 2-5 Struches 2-6 Stomwater and Wastewater Hol- 10 Stormwater anci Wastewater Impoundment Acreage 2-6 11 Sources of Discharge Water 2-7 12 Nationwide Estimate afResidual Quatltltyper Year: 1987-1997 3-1 13 Nationwide Estimate of Residuals Distribution: 1996-1997 3-1 14 Nationwide Estimates of API Separator Sludge per Year:1987-1997 3-2 15 Nationwide Estimates of API Separator Sluáge by Management Practice: 1996-1997 3.2 16 Disüibuíion of API Separator Sludge by Management Technique: 1996-1997 3-3 17 API Separator Sludge Summary: 1997 3-4 18 Onsite Management Cost fbr API Separator Sludge: 1997 3-5 19 offsite Managemeut Cost fix API Separator Sludge: 1997 3-5 20 Total Management Cost for API Separator Sludge: 1997 3-5 21 Nationwide Estimates of Biomass per Year:1987-1997 3-6 `,,-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale S T D - A P I I P E T R O PUB 352-ENGL 1979 0732290 Ob2LBLi7 4TLi W 22 Nationwide Estimates of Biomass by Management Practice: 1996-1997 3-6 23 Distribution of Biomass by Management Technique: 1996-1997 3-7 24 BiomassSummary:1997 3-8 25 Nationwide Estimates of Contaminated Soils per Year:1987-1997 3-9 ted Soils by Mauagement Practice: 1996-1997 3-9 26 Nationwide Estimates of Conitannna 27 Distribution of Cantarainate4 Soils by m e m e n t Teclmique: 1996-1997 3-10 28 C-4 Soils Summary: 1997 3-11 29 Onsite Management Cost for Contaminat d Soils: 1997 3-12 30 offsite Management Cost for contaminated Soils: 1997 3-12 31 Total hkagement Cost for Contaminated Soils: 1997 3-12 32 Nationwide Estimates of DAF Float per Year:1987-1997 3-13 33 Nationwide Estimates of DAF Float by Management Practice: 1996-1997 3-13 `,,-`-`,,`,,`,`,,` - 34 Distribution of DAF Float by Management Technique: 19961997 3-14 35 DAFFioatSurmnary:1997 3-15 36 Nationwide Estimates of FCC Catalyst per Year: 1987-1997 3-16 37 Nationwide Estimates of FCC Catalyst by Management Practice: 1996-1997 3-16 38 Distribution of FCC Catalyst by Management Technique:1996-1997 3-17 39 FCCCatalystSummary:1997 3-18 40 Onsite Managaneait Cost for FCC Catalyst: 1997 3-19 41 E t e Management Cost for FCC Catalyst: 1997 3-19 42 Total Management Cost for FCC Catalyst: 1997 3-19 43 Nationwide Estimates of Hydro Catalyst per Year:1987-1997 3-20 44 Nationwide Estimates of Hydro Catalyst by Management Practice: 1996-1997 3-20 45 Distribution of Hydro Catalyst by Management Technique:1996-1997 3-21 46 Hydro Catalyst Summary: 1997 3-22 47 Onsite Management Cost for Hydro Cataiyst: 1997 3-23 48 offsite Management Cost for Hydro Catalyst: 1997 3-23 49 Total Management Cost fir Hydro Catalyst: 1997 3-23 50 Nationwide Esỵimates of Other Speut Catalysts per Year:1987-1997 3-24 51 Nationwide Estimates of Wer Spent Catalysts by Manag- Practice: 1996-1997 3-24 52 Distribimm of Other Speslt Catalysts by Management T e d m i ~ p 1996-1997 : 3-25 53 Oh~~SperitCatalystsS~mmary:1997 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale 3-26 54 Nationwide Estimates of Pond Sedimentsper Year: 1987-1997 55 Nationwide Estimates of Pond S w 3-27 s by Management Practice: 1996-1997 3-27 56 Distnbutim ofPond Sedh&s by Managemebit Technique: 1996-1997 3-28 `,,-`-`,,`,,`,`,,` - 57 PmdSechmentsSummav: 1997 3-29 58 Nationwide Estimates Of Primary Sludges per Year: 1987-1997 3-30 59 Nationwide Estimates ofPnmary Sludges by Management Practice: 1996-1997 3-30 60 Distnbuti~nOf Primary Sludges by Management Technique: 1996-1997 3-31 61 Primary Sludges Sunntiary: 1997 3-32 62 Onsite Managemesit Cost for l?nmary Sludges: 1997 3-33 63 f M e Management Cost for Primary Sludges: 1997 3-33 64 Total Management Cost fbr Prirnary Sludges: 1997 3-33 65 Nationwide E h t e s O f Slop Oil Ermilsim Solids per Year: 1987-1997 3-34 66 Nationwide Estimates of Slop oil Emulsion Solids by Management Practice: 19961997 3-34 67 Distributb Of Slop Oil Emulsion Solids by hhagement TeCaniiq~e:1996-1997 3-35 68 Slop Oil Ennilsim Solids Sirmma~~: 1997 3-36 69 Nationwide Estimates of Spent Cresyiic Causticper Year:1994-1997 3-37 70 Nationwide Estimates of Spent Cresyhc Caustic by Managemmt Practice: 1996-1997 3-37 71 Distribution of Speut Crayhc Caustic by Management Teclmique: 1996-1997 3-38 72 Spent Cresyhc Caustic Summary: 1997 3-39 73 Nationwide Eshates of Spent Naphthetic Causticper Year:1994- 1997 3-40 74 Nationwide Estimates of Spart Naphthenic Caustic by Managemeut Practice: 1996-1997 3-40 75 Distribution of Spent Naphther~icCaustic by Management Techique: 1996-1997 3-41 76 Spent NaphtheMc Caustic Summary: 1997 3-42 77 NatimWiCie Estimates 0fSpeSit Sulñdic Caustic per Year: 1994-1997 3-43 78 Nationwide Estimates of Spent Sulñdic Caustic by Management Practice: 1996-1997 3-43 79 Distribution of Spent Sulñdic Caustic by Management Technique:1996-1997 3-44 80 Spent Sulfidic Caustic S u m m y : 1997 3-45 81 Onsite Management Cost for Spent Sulñdic Caustic: 1997 3-46 82 OfEte Management Cost for Spent Sulñdic Caustic: 1997 3-46 83 Total Management Cost for Spent Sulñdic Caustic: 1997 3-46 84 Nationwide Estimates of Tank Bottoms per Year:1987-1997 3-47 85 Nationwide Estbates of Tank Bottoms by Management Practice: 1996-1997 3-47 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale STD.API/PETRO PUB 352-ENGL 9 0732290 Ob21847 277 86 DistIibda ofTank BOUODE by Management Technique: 1996- 1997 3-48 87 TankBottomsSumma~y: 1997 3-49 88 Nationwide Estimates of Oily Wastewater Residualsper Year: 1987-1997 4-1 89 Nationwide Esbmates of ûily Wastewater Residuals by Managanent Practice: 19961997 4-1 90 Disiribution of Oily Wastewater Residuals by Management Tedmique: 1996-1997 4-2 91 Nationwide Estimates of Spent Caustics per Year: 1987-1997 4-3 92 Nationwide Estimates of Spent Caustics by Management Practice: 1996-1997 4-3 93 Distribution of Spent Caustics by Managanent Technique: 1996-1997 4-4 LIST OF TABLES Table PW2 Number of Facilities in Each WDES Classification Reporting Each Stream 2-3 Percat of Faciiities in Each NPDES Classification Reporting Each Stream 2-3 Sources of Discharge Water as a Per& of Total 2-7 Water Quaiity Discharge Parameters (pounds per year) 2-7 Water Quaiity Discharge Parameters (pounds per million gallons of wastewater discharge) 2-8 Water Quaiity Parameters at J n t d a t e P d s (pounds per million @ons P~lluti~nPreventi~nActi~ities ofwastewater flow) 2-8 `,,-`-`,,`,,`,`,,` - 2-9 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale S T D * A P I / P E T R O PUB 352-ENGL 1777 0732290 DbZLB50 T99 = EXECUTNE SUMMARY ï h e 1997 API Reñ~ungResidual Survey c o l l e c t e d data on the m e r in which U.S petroleum rehenes manage their resiciuai materiais 'Ibis report summarizes the characteristicsofthe iàciiities that responded, and presents nationwidetrends in residual management practices ' h e nationwide estimates were detenmnedfim a regression analysis of the respondent data in terms of resictual cpant~tyin wet tonsby refinery capacity in barreis per stream day (bsd) 1997 Reñmng Residual Survey-Response Levei EstimatedU.S Total No.of Facilities 152 Refimng Capacity 16,086,100bsd ResidualQuantis 2,736,000wet tons Survev ReSpJll& 70 7,328,500bsd 1,179,000wet tons 'percent 46% 46% 43% The 1997 survey collected data cm the management of 14resimial streams and requested cost data on six of îhese streams By comparison to the quantities reported for 30 residual streams in the surveys prior to 1994,these 14 streams are believed to represent neariy 80% of the total quam@ofresiduals manageci at U.S reñneries As with previous surveys, data were mllectgd on the age, size, location, and type of reñnery, and on the d g u r a t i o n ofthe wastewater treatment system DIFFERENCE FROM PRIOR YEAR RESULTS ?his year's survey &ued to se& improvement in the ccmiskncy of reported data Prior to the 1997 survey,the managementtechniques had induded recychg to the cat cracker, which refixredto Toutmg a residuai to a catalytic crackmg unit (rqpxdiess of whether fluidizedbed or other type) Most of the &es for this technique were for FCC cadyst Telephone follow up reveaied that this response was gmerally meant to indicate catalyst eitherhavingbeencascadedto another c r a w unit or seatto anotherhiìityhr COntifiuBduse as catalyst By definitiq however, ifthe material was still muse for its ongmal purpose, it was not yet a residual Furthermore, entries for other residual stream to the cut cracker mar.ugement teclmique were generally foundto have belonged in a differ& recycie category It seemeú, ~IIE that S the I, quantity ofresiduals actually rqcledto a crackmg unit was very mail, andperhaps non- The cat cracker category was &erefixre deldeû fimthe 1997 survey Data fÒr prior years were adjusted by deleting qumt~tiesshow as FCC catalyst routed to a cat cracker, and moving ali other cpanhties reported under cat cracker to the other recycle management techique category - U x O c 'x-4.* &,, C.+'/ I l I l l I I l I 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 Year ES1 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale -.+-.- Recycle Treatment Disposal `,,-`-`,,`,,`,`,,` - Trends m Management Practices-Nationwide Estimates of Quantity per Year 5,000 nie 1997 survey addeda fornithat is d e d amnatidy when enines are made to the Reclaim/Reuse managemc?nttschmque 'Ihisc.alledfinmrequests~montheenduseofthereclaimedorreused material Sded the appropriate enduse category from this list The fwmthat is d e d by selecting a management practice also induds a qluestianonỵhetype of dewatmgoperationsused,ifany lllisquestionisrepeatsdforeach~techaiquelistedcmthe iinm As with most othernon-numericaíqueries, a pop up meau is providedto facilitatethe respanse the dewatering button pops \upClicking a menu d dewateringoperations `,,-`-`,,`,,`,`,,` - ehdp A-10 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale S T D - A P I I P E T R O PUB 352-ENGL 7 = 0732290 Ob21731 T1B The buüm under the dewakmg question calls a form with the dewakmg operations listed, as shown onthenext screen Clicking on any of the dewatering operations pops up a description of that operaiion ~ click it from the list below in the box (don't worry K your texi runs out of sight) ." - " - _ I Clickingontheb~withthenameofadewatenngoperationpopsupamaiuwitha~~onofthat operation The descriptions of the áewatering operations are listed below Drymg-Drymg with low heat, such as steam, is clasdíed as DewateIing Medium to high heat (eg., hot oii, electric drier, or rotary k h ) is classified as H eat Treatmat, rather than as Dewakmg Mechanical Thickening-This generallyinvolves a r o d tank with rating arms in the bottom that stir the sludge Liquid is drawn offthe top by flowing over a weir into a trough The sludge isn't treated, it just has some of its liquid removed FilterPress-ỵle sludge is pressed against a rigid, sievelike ñbr to &ze liquid out DeCanimg (Gravity S&thng) -The sludge is placed in a tank,roii &box, or other container fim which water is &awn off from the top Vacuum Fi€tration-"his is similar to a ñiter press, but flow of liquid throughthe fiber is assistedby mamtamq a negative pressure beyond the mer Gravity Fikratitm-Tñe sludge is placed in a cmỵajner (suchas a roii offbox chgned for this purpose) which aliows water to drain outthroujjh a screen orñlterinthebottorn CgQituge-'Ihis is kind of like putúng sludge in your washrng machine on the SPIN cyde The ñual f;orm of the survey is activatedby clicking Button SCost Data 'ibis h m is simiiar in appearanceto the Residual Streams form, but collIajIls streams rather than 14, as shown in the following screen A-11 `,,-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale ~~ ~~ STD=API/PETRO PUB 352-ENGL 1979 = 0732270 Ob21732 754 m The Cost Data form is similar to that for Residual bstream, but lists only six streams clicking the button caUs a form with boxes to enter cost data Ciidmg for either the gisite Mofhite co6t quesiian calls a form fw mỵmingthe cost data, shown mthene?ctscreen Separate cdumns are provided onsite & offsite costs A-12 `,,-`-`,,`,,`,`,,` - Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale Appendix B DESCRIPTION OF STATISTICAL PROCEDURES The 1997 API Reñmng Residual Survey used similar statistical analysis methods as used in previous years No changes were made in the procedures for generaúng the rqgession model, extrapolamg the respondeat data to nationwide estimates, or in estimating~ t i ~ ~quanbties ~ ~ i for the e individual residual streams This was done to maintah consistency in the reporhng methoás fim year to year DATA COLLECTION ?he 1995 survey was the firstto require elecb-onic submission of data while this impactedthe mechanics ofcompiling the data, it required no &ange in the proCsdures used to analyze the data The eietmmic formatwascontinuedwiththe1996and1997surveys It was observed that a certainamount ofthe variability m earher surveys was atbibutable to incunsimcy in the assumptions made by r e s p o n h Quar&tieshad varied depending upon whether a f d t y reported the amount ofresidmi a r e &watering, or only the sludge cake remainmg atter dewatering Furthermore, the assignmPnd:of categories by respondents had varied due to ddììsng intapretations ofthe meaning of Certain survey terms To promote wmktency, the 1995 survey mciudedexplicit inshwtims to report only the quauhty ofresidual remaining after dewaterjng, exciusive ofrecovered d or water Anuther step takm to hcilitate mmisteaicy was to add a pop up message box fbr each categoxy m the survey, amhiuhg a dehition ofthe label fbr that category 'Ihese guidance tools were enhanced in the 1996 and 1997 surveys Data wnỵinue to be collected on the same 15 residual streams as in the 1994 survey, but combmmg the two primary sludge categoriesfrom that survey resulted in 14 streams begmmng with the 1995 survey The 15 streams in the 1994 survey were dyhalfthe 30 streams indudedin d e r surveys, but those 15 streams r q d approximately 80% ofthetotal residual quantity &om the previous surveys ï h e 1994 report concludedthatthe data pa#emhad changed very little withthe fewer streams, and theregression model usedprevi~ywasretainedandhasconiinuedinusewithsubseqwntsurveys REGRESSION MODEL In order to generate an estimate ofthe total quarrtity of residuais managednatimwiáe,amodei &be developed for predictingthe quantity of residuals managed at the h d t i w which did not respond, based on the data received &om those r&eries that did respond The developof this niodel involves establishngthe relatiodnp ofsome known quantity to the unknown quanúty of resiáuak In each year of the API lùzhung Residual Survey?the known quantity ofíhroughput capacityhas been usedto predict the uuknown quanúty ofresiduais managed ỵ đ e model assumes a linear r e l a l i w behiveen throughput capacity andthe square root of the total @ty of resimials manageù, as shown in the foilowing equation $R Where: = b,+b,C R = estimate of total residuais managedby a fbcility (wet tons), bo= the y-intercept of the regression line, b, = the slope ofthe regression line,and C = the throughput capacity of the facility (bsd) B-1 Copyright American Petroleum Institute Provided by IHS under license with API No reproduction or networking permitted without license from IHS Not for Resale `,,-`-`,,`,,`,`,,` - nie value o f R is described as an esbmate ofthe total quanitity ofresiduais managed by a r & q , but in factis now taken as thetotal ofthose streams inchided mthe survey Given this revised deñniticm of R, &,ich was ñrst introduced in the 1994 survey, throughput capacity COZl$I1UeS to be an accepỵable predictor `,,-`-`,,`,,`,`,,` - the square root ofresidual quanti@ nie known d u e ofthrougúput capacity was taken as that published by the Oil & Gas Journal m the table7WorMuideRejneries-Gqmcitiesm of Jmnuay I , 1997 F“G THE MODEL TO THE 1997 DATA Data fiomfive ofthe 70 respondentsto the survey were either missing or inaccessible oníhe submitted cliskettes Data &omthe reanaimng 65 r e p d e n & wereplotted on a scale ofR”’ versus C and assessedforoutlim Alinearregressianwa~displayedonthescattergtaphafthedata~withp~ei boinids árawn on either sick ofthe regression A visual appraisal i