August 19, 1992Mr. Russell K i l l e b r e wW o o d w a r d - C l y d e c onsu l tant sP.O. BOX 66317Baton Rouge, Louisiana 70896Dear Mr. K i l l e b r e w :Enclosed are the comments of the Environmental Pro t e c t i on Agency(EPA) Region 6 on the d r a f t Remedial I n v e s t i g a t i o n (RI) and RiskAssessment for the Dutchtown Oil Treatment site in Dutchtown,Louis iana. O v e r a l l , the RI and Risk Asse s sment were wel l wri t t enand in accordance with EPA guidance .If you have any questions on the enclosed EPA comments, p l e a s e donot h e s i ta t e to contact me* A l s o enclosed is the EPA Region 6c l a r i f i c a t i o n concerning the d i f f e r e n c e between Central Tendencyand the Reasonabl e Maximum Exposure Parameter s .If you wish to discuss the comments in person, I wi l l be in BatonRouge on S e p t e m b e r 2, 1 9 9 2 , for another meet ing and w i l l bea v a i l a b l e to meet with you on the Dutchtown RI and Risk Asse s smenton the morning of S e p t e m b e r 3, 1992. Dr. Jon Rauscher is al soa v a i l a b l e f or a S e p t e m b e r 3 , 1 9 9 2 , m e e t i n g , i f needed.S i n c e r e l y yours,

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(LA-Cathy D. G i l m o r eRemedia l P r o j e c t M a n a g e rA R / L A S e c t i o n ( 6 H - E A )Enclo sure scc: Ms. Barbara AndersonBlack and V e a t c h W a s t e S c i e n c e and T e c h n o l o g y

M r . T o m S t a f f o r dL o u i s i a n a Department o f Environmenta l Q u a l i t yMr. F r a n k CraigGarder© and W y n n eMr. Bob H o l d e nLiskow and Lewi sMr* Rick A d d i s o nP a r n e l l , Rain, and H a r r e l l

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R E V I E W C O M M E N T SD U T C H T O R S O I L T R E A T M E N T S I T E

D R A F T R E M E D I A L I N V E S T I G A T I O N REPORTG E N E R A L C O M M E N T S1. The presence of inorganics in the s u r f a c e and s u b s u r f a c e soilneeds to eva luat ed more t h o r o u g h l y . The presence ofinorganics in the background s a m p l e s is to be e xp e c t ed .However, the background concentrations should be d e f i n e d andused when eva lua t ing the presence of inorganics at the site.T h i s w i l l a l l o w f o r d e t e r m i n i n g i f e l evated l ev e l s o finorganic s are present and if the e l evated l e v e l s can bein t e rpr e t ed a s e f f e c t s f r o m t h e f a c i l i t y o p e r a t i o n s .2 . The r e su l t s o f the e x p e d i t e d re sponse action (ERA) conductedat the site need to be incorporat ed into the R e m e d i a J .I n v e s t i g a t i o n ( R I ) report i n greater d e t a i l . T h e remedialac t ions c o m p l e t e d d u r i n g the ERA r e s u l t i n g in the removal ofsource areas have a great dea l of i n f l u e n c e on the e x i s t i n gnature and extent of c on taminat i on at the s i t e , and thep o t e n t i a l f o r m i g r a t i o n o f contaminant s f r o m th e s i te.S P E C I F I C C O M M E N T S1. section 1.2.1, S i t e H i s t o r y , E x p e d i t e d Response A c t i o n

The q u a n t i t i e s of wastewater r epor t ed to have been treatedons i t e and d i s c h a r g e d , as s ta t ed in th i s s e c t ion, contradi c tthe volumes that were r epor t ed in the "Dutchtown ERA F i n a lS i t e P r o d u c t i o n R e p o r t , N o v e m b e r 15, 1990 - October 4, 1991".P l e a s e amend the RI or e x p l a i n the reason for th i s d i f f e r e n c ein r e p o r t e d volumes of was tewater t r e a t e d .A l s o , p l e a s e p r o v i d e a b r i e f d e s c r i p t i o n o f th e soil treatmentproce s s e s used d u r i n g the ERA in th i s section.As a l l u d e d to in Sec t i on 1.1 of the RI repor t , p l ea s esummarize t h e b e n e f i t s o f p e r f o r m i n g t h e R I / F S concurrent lywith the ERA in th i s s ec t ion.T h i s s e c t ion on page 5 should a l s o s t a t e that v i s i b l ycontaminated ground water was observed s e e p i n g into theh o l d i n g pond d u r i n g axcavat ion and v e r i f i c a t i o n s a m p l i n g .T h i s section shou ld also ind i ca t e that the ERA work p l a n wasm o d i f i e d to inc lude the i n s t a l l a t i o n of a f r e n c h drain toserve a« an interim measure a d d r e s s i n g th© contaminated groundw a f c & r observed to b& s e ep ing into the waste p i t *

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S e c t i o n 1.2.3, S i t e De s c r ip t i onThe f i r s t p a r a g r a p h o f th i s section should a l s o r e f er enceF i g u r e 2. In a d d i t i o n , the text should note, e x p l a i n , or becorrected such that the 0*07 acre smal l waste pit is the sameas the "oil pit" i d e n t i f i e d on F i g u r e 2. Using both names isc o n f u s i n g .A d d i t i o n a l i n f o r m a t i o n concerning the p e r m e a b i l i t y o f th e c l a ycap should be in c luded . The text should s p e c i f y whether thep e r m e a b i l i t y of the cap was v e r i f i e d a f t e r construct ion orwhether the p e r m e a b i l i t y is only a d e s i g n cri teria based upongeotechnical laboratory tests.S e c t i o n 2.1, F i e l d I n v e s t i g a t i o n sThe text a l s o needs to s ta t e that the s u b s u r f a c e i n v e s t i g a t i o nwas a l so conducted to de t ermine the hor i zon ta l extent ofc on tamina t i on at the s i te.T h e R I / F S work p l a n s ta t e s that t h e s i te c h a r a c t e r i z a t i o n taskal so i n c l u d e s i d e n t i f y i n g t h e contaminant s o f concern. T h i sshould be added to the d e s c r i p t i o n of the s i techarac t e r i za t i on task.The term ground water monitoring in the s ix th b u l l e t under theseries of i n v e s t i g a t i o n s should be changed to ground waters a m p l i n g because s a m p l e s were not c o l l e c t e d at e s t a b l i s h e din t erva l s f r o m the new or e x i s t i n g m o n i t o r i n g w e l l s at thes i te .S e c t i o n 2.1.1, T o p o g r a p h i c SurveyP l e a s e i n c l u d e the year that the t o p o g r a p h i c survey wasconducted at the site.The text should s ta t e in the las t sentence of p a r a g r a p h 2 thatthe s i te f e a t u r e s m a p p e d dur ing the t o p o g r a p h i c survey areindicat ive of the site b e f o r e any of the e x p e d i t e d responseact ion was i m p l e m e n t e d .s e c t ion 2 , 1 . 2 , Contaminant Sourc e I n v e s t i g a t i o nThe p a r a g r a p h on the waste oil pit i n d i c a t e s that the wasteoil pit is l o ca t ed a l o n g the northwes t ern edge of the s i t e ,H o w e v a r , ac cording to the f i g u r e s in the RX and the f i e l dover s igh t , the pit is a c t u a l l y l o ca t ed at the west central0dg© of the site. T h i s p a r a g r a p h should ba m o d i f i e dac cord ing ly .The d i s cu s s i on of the wasta pit should inc lude a more thoroughe x p l a n a t i o n of the visual contamination present in the waste

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oi l p i t during the ERA. The text should s p e c i f i c a l l y inc ludethat visual contaminat ion was present in the pit to 9 f e e tbelow ground s u r f a c e and that ground x^ater was observeds e e p i n g into the pit on several occasions.Under tankage , p l e a s e s ta te what was done with the contents ofthe drums and tanks during the ERA.A summary of the ERA re su l t s should be pre s ent ed in the RIreport because the r e su l t s serve as a d d i t i o n a l s uppor t of theRI data .

6. S e c t i o n 2.1.3, M e t e o r o l o g i c a l I n v e s t i g a t i o nP l e a s e s ta t e the year that the me t e oro l og i ca1 survey wasc o m p l e t e d .

7. S e c t i o n 2.1.4, s u r f a c e W a t e r / S e d i m e n t i n v e s t i g a t i o n sP l e a s e s p e c i f y the parameter s r e f e r r e d to as "conventionals".The text i n d i c a t e s that a d r a i n a g e d i t c h e x i s t s west of thep r o p e r t y p a r a l l e l to I n t e r s t a t e 10, and that another d i t chruns a l o n g the eastern edge of the s i te a d j a c e n t to the W a t t sp r o p e r t y . H o w e v e r , the I n t e r s t a t e i s l o ca t ed east of the siteand the W a t t s p r o p e r t y i s l o ca t ed west of the site. T h i sp a r a g r a p h should be changed a c c o r d i n g l y .The r e p o r t i n g l i m i t for lead was pre s en t ed as 2.5 u g . l .should b e pre s ent ed a s J . 5 u g / 1 . I t

Because many t y p e s of soil s a m p l e s are pr e s en t ed on F i g u r e 3,p l e a s e s ta t e how these s a m p l e s can be d i s t i n g u i s h e d on thef i g u r e . The d i s c u s s i o n should a l s o s t a t e th e number o fs a m p l e s c o l l e c t e d and whether these s a m p l e s were c o l l e c t e db e f o r e or a f t e r the c l a y cap was i n s t a l l e d .8. S e c t i o n 2 . 1 , 6 , S o i l ana V a d o s e Zone I n v e s t i g a t i o n s

The text should e x p l a i n the reason why the s u b s u r f a c e boringsB-113, B-120, and B-121 were t erminated b e f o r e encounteringthe water t ab l e .The t«xt shou ld s tate the average d e p t h o f the s h a l l o wboringe.The BPA f i e l d oversight contractor recorded that the boringthrough the h o l d i n g pond was terminated at 28 f e e t becausevi s ib l e contaminat ion was s t i l l present in the ho l e at thatd e p t h and it was f ear ed that advancing the boring f u r t h e rwould cause th© contaminat ion t o spread. F l e a s © e x p l a i n f u l l ythe r a t i o n a l e for th© dec i s ion to tarminata the boring through

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the h o l d i n g pond at 28 f e e t .

9. S e c t i o n 2.1.7.2, W e l l I n s t a l l a t i o nP l e a s e i d e n t i f y the l o c a t i o n s o f the three e x p l o r a t o r y boringsassociated with each de ep we l l i n s t a l l e d at the site*The text should s tate that the p i e z ome t e r s were i n s t a l l e d toa p p r o x i m a t e l y the same d e p t h as the s h a l l o w w e l l s at the site.

10. E l e c t i o n 2.1.7.3^ Ground W a t e r S a m p l i n gThe text should s ta t e that the d e v e l o p m e n t water was capturedand c on ta iner i z ed .

11 S e c t i o n 2.1.8 and 2.1.E c o l o g i c a l I n v e s t i g a t i o n s Human P o p u l a t i o n surveys and

The textconduc t ed . should s ta t e when these i n v e s t i g a t i o n s were.

12. S e c t i o n 2.3, F i e l d Documentat ionThe las t p a r a g r a p h s ta t e s that the do cumenta t i on i s pre s en t edin the a p p e n d i c e s . For the ease of the reader, it would beh e l p f u l to s ta t e where the r e f e r e n c e d i n f o r m a t i o n can bef o u n d .

13. sec t ion 3.4.1.2, Y o u n g e r D e l t a i c D e p o s i t sP l e a s e d i s cu s s the da ta that i n d i c a t e that the younger d e l t a i cd e p o s i t s are not pre sent in the Dutchtovn s i t e v i c in i ty .

1 4 . s ec t ion 3 , S . I . 2 * Ground W a t e r tig©The text does not s ta t e that in the immed ia t e v i c i n i t y of thes i t e that the s urround ing p o p u l a t i o n e x c l u s i v e l y uses p r i v a t eground water w e l l s f or r e s i d e n t i a l use.

1 5 . S e c t i o n 3 , 5 . 2 , S i t e H y d r o g e o l o g yBecause the terms p e r m e a b i l i t y and h y d r a u l i c c o n d u c t i v i t y aresynonymous as used in th i s r e p o r t , the uni t s for both shouldbe c ons i s t en t . In the t e x t , p e r m e a b i l i t y has a unit ofe & n t i m e t a r s per second wh i l e h y d r a u l i c c o n d u c t i v i t y has a unitot f ® e t per minute.The text shou ld describe th© u p p e r and lowsr permeabl e uni t saa b e l o n g i n g to the point bar s ed iment s a q u i f e r system whichwas d i s cu s s ed in S e c t i o n 3.5.1.

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A d i s cu s s i on de s cr i b ing th e p o s s i b l e e f f e c t s o f t o p o g r a p h i ccontrol s on p r e c i p i t a t i o n i n f i l t r a t i o n needs to be included inthe eva lua t i on of ground water f l o w in the upper p ermeab l eunit which is di scus sed in p a r a g r a p h 3.The third sentence in the third p a r a g r a p h s ta t e s that groundwater f l o w in the u p p e r p ermeab l e unit is rad ia l f r o m tht>h o l d i n g pond* T h i s d e s c r i p t i o n a p p e a r s to be correct for pre»ERA condi t ions . P l e a s e s tate thi s in the text .The units for h y d r a u l i c gradient should al so be inc luded inthe t ex t .The text s tate s that the vertical gradient i s uncertain. T h i sconclusion should be q u a l i f i e d as based on p r e s e n t l y a v a i l a b l eda ta .P a r a g r a p h 2 on p a g e 37 s ta t e s that the p e r m e a b l e uni t s whichare monitored ons i t e do not b e l o n g to any of the regionalg e o l o g i c or h y d r o g e o l o g i c unit s . Based on i n f o r m a t i o npre s ent ed in the r e p o r t , it a p p e a r s that the p e rmeab l e unit si m m e d i a t e l y u n d e r l y i n g the Dutchtown s i te are po int barsediment o f the younger d e l t a i c d e p o s i t s . E x p l a i n the.r a t i o n a l e for d e t e r m i n i n g that the p ermeab l e units do notb e l ong to any of the regional g e o l o g i c or h y d r o g e o l o g i c units .

16. S e c t i o n 4.5, AirThe f i r s t sentence s ta te s that "since the sources f r o m thesite have been removed, ,*.". T h i s wording is too conclusivef o r a Remedial I n v e s t i g a t i o n ( R I ) repor t . T h e c lause could b etrue and the RI report s hou ld be used to s u p p o r t thes ta tement .

17* S e c t i o n 5.3.1, Eva lua t i on Parame t er sT h i s section should in c lud e a d i s cu s s i on d e s c r i b i n g why theparameter s benzene, e t h y l b e n z e n e , and styrene were s e l e c t edf o r m o d e l i n g .

18. S e c t i o n 5 . 3 . 2 , M o d e l i n g T e c h n i q u e s and R e s u l t sThe s tatement in the text that the model p r e s e n t s aconservative view is not e n t i r e l y correct for the f o l l o w i n greasons:* The vertical p e r m e a b i l i t i e s were estimated f r o ml a b o r a t o r y teats which have been shown in some casas tobe one to two orders of magni tude lower than actual f i e l dp s o i a a b i l i t i a s . Laboratory p e rmeab i l i t i e s do not r e f l e c tin-situ p e r m e a b i l i t i e s because the values do notnecmssar i ly in c lud e an adj ustment f or f l o w a long

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f r a c t u r e s which o f t e n d e v e l o p in c lays .* The p o r o s i t y used in the s e epage ve loc i ty c a l c u l a t i o n sshould be e f f e c t i v e , no t actual poro s i ty . The a f f e c t i v ep o r o s i t y of a clay is g e n e r a l l y much less than the actualp o r o s i t y .* The l o n g i t u d i n a l d i s p e r s i v i t y values used in the modela p p e a r quite low. The s e n s i t i v i t y o f th i s parametershould be ta s t ed by using a larger value, such as 10f e a t .* The h a l f - l i f e values used in the model have an ex tr eme lylarge i n f l u e n c e on the model r e su l t s . However , thesenumbers a l so have a great deal of uncer ta inty as sociatedw i t h them. Severa l model runs should be c o m p l e t e d us ingd i f f e r e n t h a l f - l i f e value s t o d emons tra t e t h e s e n s i t i v i t yof t h e model t o th i s p a r a m e t e r , I n c r e a s i n g th e h a l f - l i f eof the compounds by an order of magni tud e , which isp o s s i b l e given the uncer ta in ty of e s t i m a t i n g thi sparameter , may have a large i n f l u e n c e on th© r e su l t s .Because an a n a l y t i c a l model is being used for the s i m u l a t i o n s ,it is not a time consuming proces s to run a d d i t i o n a lscenarios. P l e a s e run the m o d e l s to i n c l u d e a s e n s i t i v i t ya n a l y s i s to d emons t ra t e the s e n s i t i v i t y of the mode l to thevarious parameter s ©numerated above. A range of values shouldbe pre s en t ed in the conc lus ion sec t ion, i n c l u d i n g a d i s cu s s i onof the uncer ta in ty of each parame t er . M o d e l i n g at any l e v e l ,e s p e c i a l l y a n a l y t i c a l m o d e l i n g , has a large degree o fu n c e r t a i n t y as sociated with it that s h o u l d be q u a n t i f i e d tothe gr ea t e s t extent p o s s i b l e .

19 . S e c t i o n 7.2.1, Data L i m i t a t i o n s and Recommendat ions f or F u t u r eW o r kP r o d u c t i o n h i s t o r y and a n a l y t i c a l r e su l t s f o r th e f r e n c h d r a i nshould be a v a i l a b l e f or the f i n a l Rl report . T h i s i n f o r m a t i o nand how it may a f f e c t the pre sent i n t e r p r e t a t i o n s ofcontaminant extent near the waste pit should be i n c l u d e d inthe f i n a l RI repor t .

2 0 . S e c t i o n 7 . 2 , 2 , Recommended Remed ia l A c t i o n O b j e c t i v e sC o n t a m i n a n t s i d e n t i f i e d onsite ar@ s t i l l consideredcontaminants of concern even though the concentrations arewith in a c c e p t a b l e h e a l t h - r i s k l ev e l s . Furthermore , M C L s f o rs thylbenzena and benzene (0 .7 and 0.005 m g / 1 , r e s p e c t i v e l y )were excaaded in well M W - 1 4 . The d i s cu s s ion on thecontaminants of concern needs to b© revised to r e f l e c t thesepoints.

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21. T a b l e 4*7S p e c i f i c c onduc t iv i ty , pH, and t emperature o f th e ground waters a m p l e s should be added to T a b l e 4-7.

2 2 * F i g u r e I SThe e thylb enzene concentration in the soil s a m p l e c o l l e c t e d atboring B-13Q was 1200 u g / g . T h e r e f o r e , an i soconcentrat ioncontour of 1000 u g / g needs to be inc luded on the f i g u r e .Due to the l im i t ed s u b s u r f a c e soil s a m p l i n g in the area of theh o l d i n g p o n d , the e x t r a p o l a t i o n of the l e v e l s o f contaminantconcentrations in th i s area needs to i l l u s t r a t e d on F i g u r e 15.Because of l im i t ed data r e s u l t s , the concentrat ion ofcontaminants in thi s area may be greater than 100 x i g / g .

23. F i g u r e 17It i s not c lear whether " T o t a l Organic C o n s t i t u e n t s " i n c l u d e sthe s e m i v o l a t i l e r e su l t s . The f i g u r e should be reconstructedusing both s e m i v o l a t i l e and v o l a t i l e r e s u l t s , or i f the f i g u r ehas a l r e a d y been constructed based on both v o l a t i l e ands a m i v o l a t i l e r e s u l t s , the f i g u r e should be r e t i t l e d .

24. A p p e n d i x BThe d e p t h s at which water was encountered are not i n c l u d e d onthe l o g s for borings B-122, B-123, B-126, B-127, and B-128.If a v a i l a b l e , inc lude thi s i n f o r m a t i o n on the boring log s orgive an e x p l a n a t i o n as to why it does not ex i s t .E x p l a i n why bor ings B-113, B-120, and B-121 were t e rminat edb e f o r e encountering the water t a b l e .For c l a r i t y , the l o g s for borings B - E X P L - 3 , B - E X P L - 2 , and B~E X P L - 1 need to i n d i c a t e that the borings were a l s o for M W - 1 8 ,M W - 1 9 , a n d M W - 2 0 , r e s p e c t i v e l y .

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R E V I E W C O M M E N T SD t J T C H T O W N O I L T R E A T M E N T S I T S

D R A F T R I S K A S S E S S M E N TGeneral comments1. Ground W a t e r P a t h w a y : The exposure pathway f r o m ground waterto human re c ep tor s is l i s t e d as i n c o m p l e t e ( F i g u r e 18, S i t eConceptual M o d e l ) * However, thi s exposure pathway i saddressed quanti tat ive ly through the ground water mode l ing.The risk assessment should either use the ground waterm o d e l i n g data to characterize risk f r o m ground water exposure( i n g e s t i o n and i n h a l a t i o n ) or prov ide more d e t a i l s on why theground water pa thway is i n c o m p l e t e as described in C h a p t e r 5.0Contaminant F a t e and T r a n s p o r t .2. Environmental Evaluat ion: The Environmental Eva lua t i on shouldprovide a d i s cu s s i on of cap maintenance to prevent v eg e ta t i on( e . g . , tree r o o t s ) and b u r r o w i n g / d i g g i n g animal s f r o md i s r u p t i n g the i n t e g r i t y o f the c lay cap. The cap i n t e g r i t yassures that the environmental pa thways are i n c o m p l e t e . Theground water to s u r f a c e water pa thway should be d i s cu s s ed . Ina d d i t i o n , the Environmental Eva lua t i on should p r o v i d e a S i t eC o n c e p t u a l M o d e l s im i lar to F i g u r e 18 (or by m o d i f y i n g F i g u r e18) .S p e c i f i c Comments1. S e c t i o n s 6*1 and 6 .2 , I n t r o d u c t i o n and scope and O b j e c t i v e s

In a d d i t i o n to current use and no act ion c o n d i t i o n s , theba s e l ine risk assessment should cons ider f u t u r e land usec o n d i t i o n s . Discu s s ions of f u t u r e c o n d i t i o n s should be morec l e a r l y d e f i n e d .2. S e c t i o n 6 * 4 * 1 , Source s of Chemical Data

The e l i m i n a t i o n of ch emica l s that do not exceed backgroundconcentrat ions has been a source of c o n f l i c t at several s i te s( e . g . , G u l f C o a s t , D . L . M u d ) . T h e "treatment" o f backgroundchemical s i s ambiguous in the RAGS guidanc e . The ra t ional fore l i m i n a t i n g ch emica l s should be s tated on a chemical s p e c i f i cbasis.3. S e c t i o n 6 .5 .2 .2 , P o t e n t i a l Recep tor P o p u l a t i o n s

^feis p a r a g r a p h s ta t e s that the f u t u r e land use is lUc^ ly to befor indu s t r ia l purpose s . T h i s stat@ment is inconsistent withSec t i on 3,6 (Demography and tand U s m ) which s tates that thesite is surrounded by r e s i d en t ia l and commercial land withsome pa s ture and S e c t i o n 6.5.1 ( S i t e D e s c r i p t i o n ) which

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mentions the prox imi ty of the r e s id en t ia l area,c l a r i f y . Please

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Sect ion 6 * 5 . 2 . 5 , integration of Exposure Pathway Components:The S i t e Conceptual Exposure ModelThe site conceptual exposure model is shown in F i g u r e 18instead of F i g u r e 17. T h i s paragraph notes that the twoprimary sources of contaminants are the sha l l ow ground waterand the sur face and subsurface soils* However, F i g u r e 18( S i t e Conceptual M o d e l ) indicates that the exposure pathwayf r o m ground water to human receptors is l i s t ed as incomplete.T h i s exposure pathway is addressed quant i ta t ive ly through theground water mode l ing . A discussion on the p r a c t i c a l i t y ofusing the shal low aqu i f e r s as a drinking water source shouldbe included ( e . g . , the i n s u f f i c i e n t y i e l d ) .S e c t i o n 6 . 5 * 3 , Exposure Point Concentrat ionsThe last sentence of the last ^ p a r a g r a p h should read that theuse of the .upper, c o n f i d e n c e l imit of the arithmetic mean asrecommended by the guidance document is a conservativeapproach ( U S E P A 1 9 9 2 a ) .S e c t i o n 6.5.4.1, Q u a n t i f y i n g Average and Reasonable MaximumExposure sThe average exposure should be e s t imat ed using the 95% u p p e rc o n f i d e n c e l i m i t on the a r i t h m e t i c mean of the measuredchemical concentrations. The average and reasonable maximumexposure (RME) should use the same concentration term (US EPA1 9 9 2 a ) .Sect ion 6*5 .4 .3 ,A s s u m p t i o n s Exposure A s s u m p t i o n s , S p e c i f i c Exposure

What is th& j u s t i f i c a t i o n or basis for the assumption that aperson is exposed 8 h o u r s / d a y and 275 d a y s / y e a r in the averagecase and 16 h o u r s / d a y and 350 d a y s / y e a r in the RME case? Areasonable as sumption would be to assume 24 h o u r s / d a y and 350d a y s / y e a r for both cases*The average and RME soil i n g & s t i o n rates for ch i ldren shouldbe 200 m g / d a y (US EPA 1989a). A soil inge s t ion rate forch i ldren of 200 m g / d a y r epre s en t s an average case. An u p p e rbound soil inge s t i on rate for ch i ldr en would be Suo m g / d a y (USEPA 1989b) . Tha average and RME soil inge s t ion rates fora d u l t s should be 100 m g / d a y (US EPA 1 9 8 9 a ) . P l e a s t e reviseaccordingly.

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What is the basis for the assumption that th© f r a c t i o n of soilcontaminated is 10% and 20% for the average and RME eases,

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r e sp e c t i v e ly? A reasonable a s s u m p t i o n would be to assume thef r a c t i o n of soil contaminated to be 100% for both cases.What is the basis for the a s sumpt i on that 10% and 20% of thebody surface would be exposed for the average and RME cases,r e s p e c t i v e l y ? P l e a s e c l a r i f y *The toxic i ty values (reference doses and oral s l o p e f a c t o r s )used in risk assessment are based upon admini s t e r ed dose.T h e r e f o r e , "matrix e f f e c t " for oral inge s t i on should not beaccounted s e p a r a t e l y in the risk c a l c u l a t i o n s . The riskc a l c u l a t i o n s should be p e r f o r m e d using 100% b i o a v a i l a b i l i t y .The soil l o a d i n g on skin (adherence f a c t o r ) should be 0.2rag/ cm 2 and 1 m g / c m 2 for the average and RME cases, r e s p e c t i v e l y( U S E P A I 9 9 2 b ) , P l e a s e revise a c c o r d i n g l y *T o x i c i t y values (re f e r enc e concentrations and inha la t i on s l o p ef a c t o r s ) used in risk assessment u s u a l l y are based uponi n h a l a t i o n s t u d i e s a n d a d j u s t e d f o r do s ime try ( U S E P A 1 9 9 0 ) .Clearance should not be accounted for s e p a r a t e l y in the riskc a l c u l a t i o n s . T h e correction f o r lung d e p o s i t i o n a n d c i l i a r yclearance should be e l i m i n a t e d .S e c t i o n 6 .6 .3 , T o x i c i t y A s s e s s m e n t f o r C o m p o u n d s withCarc inogen i c E f f e c t sPleas e d e l e t e last sentence of the last p a r a g r a p h in thissection.S e c t i o n 6.6.4, Lead T o x i c i t y , R e s u l t sPage 89 , T h i r d P a r a g r a p h : P l e a s e p r o v i d e a d e p i c t i o n o f th ed i s t r i b u t i o n o f c h i l d r e n ' s b lood lead a n d p r o p o r t i o n o f t h ep o p u l a t i o n which exceeds a blood lead concentrat ion of 10/ i g / d l .S e c t i o n 6 . 6 . 4 , Lead T o x i c i t y , P r e d i c t e d Average Blood L e v e l sThe mean b lood lead l e v e l s mentioned in the text are f r o m 1975to 1980. A more recent re ference on mean blood lead l eve l s isd e s i r a b l e due to the reduction of lead sources since the l a t e1 9 7 0 ' s .

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R e f e r e n c e s :U S E P A . 1989a. I n t e r i m F i n a l G u i d a n c e f o r S o i l I n g e s t i o n H a t e s .OSWER Directive 9850.4.U S E P A . 1 9 f l 9 b , Exposure F a c t o r s H a n d b o o k , E P A / 6 0 0 / 8 - 8 9 / 0 4 3 .

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US E P A . 1990. I n t e r i m methods for d eve l opment o f inha la t i onr e f e r enc e concentrations. B P A / 6 0 0 / 8 - 9 0 / 0 6 6 A .US E P A . 1992a. S u p p l e m e n t a l Guidance t o RAGS: C a l c u l a t i n g th eConcentra t ion Term. P u b l i c a t i o n 9285 ,7-081 .US E P A . 1992b. Dermal Expo sure A s s e s s m e n t : P r i n c i p l e s andA p p l i c a t i o n s , E P A / 6 0 0 / 8 - 9 1 / 0 1 1 B .

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