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Associate s Inc

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### 37579 3 

### GROUNDWATE R BASELIN E HUMA N HEALT H RIS K ASSESSMEN T CALIFORNI A GULC H SIT E LEADVILLE

, COLORAD O

Prepared For: Asarco, Inc. 495 East 51st Avenue Denver, Colorado 80216-2098
Prepared By: Golder Associates Inc. 200 Union Blvd., Suite 500 Lakewood, Colorado 80228

Jun e 199 6 943-281 9

OFFICE S I N AUSTRALIA

, CANADA

, GERMANY

, HUNGARY

, ITALY

, SWEDEN

, UNITE D KINGDOM

, UNITE D STATE SJun e

199 6 -i

- 943-281

9 TABL E O F CONTENT S
1 . 0 INTRODUCTIO

N 1 

### 1. 1 Objective s
......................................................................................... 1 1. 2 Scope............................................................................................... 2 2. 0 EXPOSUR E ASSESSMENT...................................................................... 2 2. 1 Potentia l Recepto r Population s
............................................................... . 3 2. 2 Conceptua l Sit e Model.........................................................................

. 6 

### 2. 3 Complet e Exposur e Pathways.................................................................

. 7 2. 4 Estimatin g Chemica l Intake s an d Exposur e Point Concentrations......................

.

7 2. 5 Exposur e Assumptions.........................................................................

. 8 3 . 0 RIS K CHARACTERIZATIO

N RESULTS......!.............................................. 9 4 . 0 UNCERTAINTIE

S AN D LIMITATION

S

.................................................. .

1 1 5. 0 CONCLUSIONS.................................................................................

. 1 2 6. 0 REFERENCES...................................................................................

. 1 4 LIS T O F TABLE S Tabl e 1 Leadvill e Groundwater

, Potentiall y Complet e Exposur e Pathway s Quantitativel y Evaluate d Tabl e 2 Genera l Assumption s fo r Bod y Weigh t Tabl e 3 Intak e Assumption s fo r Groundwate r Ingestio n Tabl e 4 Groundwate r

Carcinogeni c Risk s an d Noncarcinogenic Hazar d Inde x (H.I. ) Tabl e 5 Compariso n

o f Exposur e Poin t Concentration s (EPCs ) wit h Maximu m Contaminan t Level s (MCLs ) (mg/1 ) Tabl e 6 Summar y o f Uncertaint y Factor s i n th e Groundwate r Baselin e Ris k Assessmen t LIS

T O F FIGURE S Figur e 1 Conceptua l Sit e Model
, Groundwater

, Leadville

, Colorad o Figur e 2 Futur e Scenario

, Exposur e Poin t Locatio n LIS T O F APPENDICE S Appendi x A Huma n Healt h Ris k Evaluatio n Method s Golde r Associate sJun e

1996____________________-1-__________________943-281 9 

### 1. 0 INTRODUCTIO

N Th e followin g huma n healt h baselin e ris k assessmen t (RA ) fo r groundwate r ha s bee n 

### prepare d a s a supplemen t t o th e Hydrogeologi c Remedial Investigatio n (RJ ) Report (Asarco
, 1996a ) t o evaluat e potentia l healt h risk s relate d t o site-relate d metal s i n groundwater

. Al l potentia l exposure s fro m multipl e source s wil l b e evaluate d separatel y i n a sitewid e baselin e RA

. Thi s R A evaluates onl y the singl e source , contributio n fro m groundwater

. I t i s importan t 

### t o not e tha t th e exposur e parameter s use d i n thi s R A ma y chang e i n a sitewid e baselin e R A fo r th e Californi a Gulc h site

. Durin g th e cours e o f conductin g th e R A evaluation
, i t wa s determine d tha t th e hlgestio n o f fis h wa s th e onl y complet e o r significan t exposur e pathwa y fo r surfac e water at th e site

. Th e result s o f th e evaluatio n fo r huma n exposur e t o metal s i n fis h fillet s indicat e tha t th e noncarcinogeni c Hazar d Indexe s (His ) d o no t excee d th e EP A leve l o f concer n o f 1.0

. Estimate d carcinogeni c risk s d o no t exceed th e EP A acceptabl e ris k leve l o f 1 x 10 ^ fo r th e exposur e pathwa y evaluate d fo r an y receptors

. Additionally
, potentia l tota l cance r risk s fro m birt h t o ag e 3 0 wer e 2.29E-0 6 (averag e scenario ) an d 3.13E-05 (RM E scenario ) an d d o no t

excee d 1 x 10" 4 fo r exposur e b y fis h hlgestion

. Th e RM E scenari o i n thi s R A evaluatio n use d a combinatio n o f site-specifi c dat a and conservative assumption s that represen t the "high-end " exposur e an d mor e than likel y thi s overestimate s th e actua l tota l cance r ris k give n th e exposur e an d behavior pattern s assume d fo r thi s assessment evaluation

. 

### 1. 1 Objective s Th e primar y objectiv e o f thi s R A wa s t o evaluat e potentia l healt h risk s due t o exposur e t o groundwate r usin g recentl y collecte d groundwate r data

. Wher e possible
, the R A use s site

specifi c data

. Whe n site-specifi c dat a wer e lackin g o r incomplete
, conservativ e assumption s
wer e used

. Thi s approac h i s consisten t wit h the guidanc e issued b y the EP A Ris k Assessmen t 

### Counci l stressin g th e us e o f site-specifi c dat a t o evaluat e potentia l healt h risk s (EPA

, 1992a, Golde r Associate sJun e

1996__________________

_ -2

- 943-281

9 b)

. Thi s section follow s th e Ris k Assessmen t Council' s guidanc e fo r ris k characterization
, limitin g discussio n o f informatio n t o ris k assessment instea d o f includin g an y ris k 

### managemen t discussions

. The reasonabl e maximu m exposur e (RME ) scenari o i s designe d t o 

### b e a measur e o f "high-end " exposur e an d i s use d b y ris k manager s i n makin g remedial decision s tha t ar e protectiv e o f huma n health

. The averag e o r centra l tendenc y exposur e scenari o provide s necessar y informatio n t o mak e ris k managemen t decision s (EPA

, 1992c)

. Bot h th e RM E an d averag e exposur e scenario s hav e bee n include d i n thi s RA

. 

### 1. 2 Scop e Th e scop e o f thi s R A i s limite d t o th e evaluatio n o f potentia l healt h risk s associate d wit h groundwate r tha t ha s bee n affecte d b y minin g activities

. Th e approac h use d i s based o n EP A guidanc e for th e evaluatio n o f huma n healt h risk s a t Superfun d sites

. Specifically

, thi s R A i s consisten t wit h EP A guidanc e provide d i n th e followin g resources : Exposur e Factor s Handboo k (EPA

, 1989a)
, Ris k Assessmen t Guidanc e fo r Superfund

, Volum e I : Huma n Healt h Evaluatio n Manual (EPA

, 1989b)
, an d th e Integrate d Ris k Informatio n Syste m (IRIS ) (EPA

, 1992d)
, a compute r databas e containin g up-to-dat e healt h ris k an d EP A regulator y informatio n fo r numerou s chemicals

. EP A caution s tha t thes e source s ar e intende d onl y t o provid e guidanc e i n conductin g healt h ris k assessment s an d that considerabl e professiona l judgmen t mus t b e use d i n thei r applicatio n (EPA

, 1989b)

. 

### 2 . 0 EXPOSUR E ASSESSMEN

T The objectiv e o f the exposur e assessmen t i s t o identif y population s tha t ma y b e expose d t o site-relate d metal s i n groundwate r (potentia l receptors) ; the pathway s b y whic h exposure s
ma y occur ; th e rout e o f intak e an d intak e paramete r value s for ingestion ; an d th e frequency
, magnitude
, an d duratio n o f thes e potentia l huma n exposures

.

Golde r Associate s

### Jun e

1996___________________-3-_________________943-281 9 

### 2. 1 Potentia l Recepto r Population s Population s i n th e Leadvill e are a wer e evaluate d t o asses s th e likelihoo d an d exten t o f potentia l exposur e t o chemical s o f concer n (COCs ) i n groundwater

. Durin g th e Phas e I R I studies
, EP A identifie d 33 existin g well s tha t wer e drille d i n th e Californi a Gulc h alluvium

. Man y o f thes e well s hav e sinc e bee n abandone d due t o poo r wate r qualit y (EPA

, 1988)

. I n 1986 , EP A connected th e one remainin g househol d tha t use d 

### the alluvia l aquife r a s a drinkin g water sourc e t o the publi c wate r syste m (EPA

, 1988)

. Accordin g t o informatio n fro m th e Parkvill e Wate r District

, genera l area s serve d b y a publi c 

### wate r suppl y includ e Leadville

, Stringtown

, Silverheels

, an d Matchles s Estates (Parkvill e Wate r District

, 1993)

. Area s supplie d b y th e Parkvill e Wate r Distric t hav e wate r supplie d fro m th e Bi g Evan s Reservoir s an d th e Canterbur y Tunne l (Parkvill e Wate r District

, 1993)

. Turquois e Lak e Estates

, Fou r Season s Estates

, and Lak e For k Traile r Par k us e privat e well s
or communit y drinkin g wate r wells

. Turquois e Lak e an d Fou r Season s Estate s are locate d 

### upgradien t fro m an y source-relate d contamination

. Groundwate r a t th e Lak e For k Traile r Par k i s no t know n t o b e affecte d b y site-relate d metals

. Therefore
, thes e area s wer e no t quantitativel y evaluate d fo r potentia l risk s du e t o groundwate r ingestio n becaus e site-relate d contaminant s ar e no t know n t o b e present

. Ther e ar e no know n plan s t o us e additiona l groundwate r fo r a drinkin g water suppl y withi n th e Leadvill e are a an d ther e i s n o know n curren t exposure

. However
, a futur e residentia l groundwate r use r scenari o wa s considere d an d th e risk s o f consumin g groundwate r i n th e Stringtow n are a wer e quantified

. Eve n wit h thi s conservativ e approach
, i t i s highl y unlikel y tha t the wate r woul d b e o f potabl e qualit y considerin g the elevate d level s o f sulfate

. Therefore
, i t i s doubtfu l futur e residentia l receptors woul d consum e thi s groundwater

. Thi s aspec t o f groundwate r qualit y i s discusse d furthe r i n the Hydrogeologi c R I repor t (Asarco
, 1996a)

. Golde r Associate sJun e

1996____________________-4-__________________943-281 9 Whe n identifyin g a locatio n fo r a hypothetica l wel l t o us e a s a potentia l exposur e location
, certai n criteri a mus t b e considered

. Thes e includ e bu t ar e no t limite d to :

* • Th e hypothetica l groundwate r wel l shoul d b e locate d h i a positio n wher e i t 

### i s likel y t o b e affecte d b y upgradien t contaminatio n h i order t o represen t th e potentia l fo r ris k associate d wit h contaminate d groundwate r consumption

. I n addition
, appropriat e upgradien t groundwate r chemica l dat a mus t b e availabl e t o estimat e concentrations

. Risk-relate d interpretatio n o f upgradien t dat a mus t agree wit h hydrogeologica l an d geochemica l interpretations o f th e aquife r h i th e are a surroundin g th e hypothetica l wel l an d actua l monitorin g locations

. 

### * • Th e wel l shoul d b e screene d h i th e uppe r 1 0 t o 1 5 fee t o f th e alluvia l 

### aquife r i n order t o asses s ris k fro m near-surfac e potentia l contaminatio n source s suc h a s tailing s pile s an d surfac e water

. The potentia l o f th e 

### hypothetica l receptor s drinkin g fro m suc h a shallo w wel l i s questionabl e becaus e o f lac k o f potabl e qualit y (e.g.
, hig h sulfate ) an d possibl e poo r long-ter m yield

. Therefore
, us e o f thi s groundwate r a s a sourc e o f drinkin g wate r i s a highl y conservativ e assumption

. * Result s fro m a previou s investigatio n h i th e are a sugges t tha t concentration s o f potentia l contaminant s decreas e wit h dept h (EPA

, 1987a)

. Recen t investigation s indicat e tha t th e alluvia l aquife r ma y b e 

### 1,20 0 fee t thic k o r mor e h i th e areas
. Th e rational e fo r placin g a hypothetica l wel l i n th e Stringtow n are a t o asses s th e ris k o f consumin g potentiall y contaminate d groundwate r include : 

### Th e hypothetica l wel l woul d b e locate d downgradien t fro m severa l potentia l source s o f groundwate r contamination , includin g Colorad o Zinc

- Lead

, an d Apach e an d Orego n Gulc h tailings

. I n addition
, th e wel l woul d b e positione d nea r Californi a Gulch

, wher e the wel l coul d b e affecte d b y surfac e water contribution s t o groundwate r contamination

. Stringtow n are a residences ar e supplie d wit h treate d cit y water ; however
, for th e reason s presente d above
, a R A conducte d for th e Stringtow n are a ma y bes t represen t hypothetica l futur e groundwate r consumptio n fro m privat e wells

. Th e fiv e existin g privat e well s tha t ma y be use d fo r domesti c purpose s are als o i n th e Stringtow n area . Thus
, a hypothetica l futur e exposur e poin t i n Stringtow n wil l als o provid e a n estimat e o f ris k t o hypothetica l curren t groundwate r consumers
. Golder Associate sJun e

1996____________________-5-__________________943-281 9 

### Afte r locatin g th e exposur e point , EP A guidanc e specifie s tha t unflltere d groundwate r sampl e dat a shoul d b e use d (EPA

, 1989b)

. Unflltere d sampl e dat a wer e unavailabl e fo r th e groundwate r monitorin g well s upgradien t o f th e hypothetica l exposur e point

. However
, dat a fro m unflltere d sample s wer e availabl e fro m fou r mini-piezometer s an d si x spring s i n th e
area . Furthermore : Dat a fro m th e fou r mini-piezometers an d si x spring s probabl y provid e a realisti c representatio n o f metal s concentration s tha t migh t migrat e t o a downgradien t well

. Becaus e the mini-piezometer s an d spring s ar e spatiall y distribute d alon g Californi a Gulch

, concentration s measure d a t thes e location s shoul d represent th e dilutiona l effect s o f contaminan t transpor t fro m suspecte d sourc e areas
. 

### Groundwate r analytica l dat a fo r tota l metal s ar e availabl e fro m mini

piezometer s an d spring s locate d downgradien t fro m potentia l contaminatio n source s an d upgradien t fro m th e hypothetica l recepto r well

. Groundwate r chemistr y result s fro m the spring s and mini-piezometer s wer e use d t o estimat e groundwate r chemistr y a s a basi s fo r th e R A (Asarco
, 1996a)

. For the initia l comparison , concentration s o f arsenic , cadmium
, and zin c wer e chosen because arseni c i s th e onl y CO C wit h a n ora l slop e facto r an d 

### cadmium an d zin c ha d relativel y hig h exposur e poin t concentration s (EPCs)

. [Selectio n o f COC' s an d toxicit y value s ar e explaine d h i greate r detai l i n th e Hydrologi c RI Repor t (Asarco
, 1996a)]

. Becaus e th e concentration s o f thes e metal s i n mini-piezometer s and spring s appeare d simila r (i n term s o f magnitude)
, thes e dat a wer e combine d fo r statistica l 

### evaluatio n fo r th e ris k assessment

. Arsenic
, cadmium
, an d zin c level s i n unflltere d sample s (tota l metals ) fro m the mini-piezometer s and spring s wer e compare d wit h arsenic , cadmium
, an d zin c level s i n filtere d sample s (dissolve d metals ) fro m monitorin g well s downgradien t o f th e Apach e Tailing s Impoundment

. Thi s compariso n reveale d highe r concentration s i n th e mini-piezometer s an d springs

. Becaus e EP A guidanc e recommend s usin g tota l meta l concentration s whe n evaluatin g potentia l risk s due t o the ingestio n o f groundwate r (EPA

, 1989b)
, and because highe r meta l concentration s wer e foun d i n unflltere d samples
, sample s take n fro m th e mini-piezometer s an d spring s wer e use d i n thi s R A a s th e mor e conservativ e choice

.

Colde r Associate sJun e

1996____________________-6-__________________943-281 9 Population s withi n Leadvill e tha t ma y b e particularl y sensitiv e t o chemica l exposure s fro m the ingestio n o f groundwate r coul d includ e infant s and children
, the elderly
, pregnan t and nursin g women , and thos e wit h chroni c illnesses

. Sensitiv e recepto r location s ma y includ e 

### hospitals
, convalescent homes
, schools
, an d day-car e center s tha t use groundwate r a s th e 

### drinkin g wate r source
. I n orde r t o evaluat e sensitiv e recepto r population s fo r potentia l risk s pose d b y groundwate r consumption , th e R A ha s identifie d bot h childre n an d adult s a s th e sensitiv e population

. 

### 2. 2 Conceptua l Sit e Mode l A Conceptua l Sit e Mode l (CSM ) show s al l potentiall y complet e exposur e pathway s fo r a sourc e (Figur e 1)

. Thos e exposur e pathway s tha t ar e significan t ar e represente d wit h a soli d circle

. EP A guidanc e define s a n insignifican t pathwa y a s on e tha t ha s a n exposur e estimate d 

### t o b e tw o o r mor e order s o f magnitud e les s tha n b y other pathway s (t o th e sam e receptor)
, o r
one wit h a ver y smal l likelihoo d o f exposur e (EPA

, 1989b)

. 

### Exposur e pathway s associate d wit h othe r medi a ar e labele d a s "no t evaluated " o n th e CS M a s thes e media
, wit h the exceptio n o f garde n vegetabl e ingestion , hav e bee n considere d i n othe r ris k assessment s as par t o f separat e remedia l investigations

. Fo r example
, affecte d groundwate r possibl y dischargin g t o surfac e water wa s no t considered
, bu t i t wa s addresse d i n th e Surfac e Wate r R I Report (Asarco
, 1996b)

. Th e ingestio n o f garde n vegetable s potentiall y impacte d b y metal s i n groundwate r wil l b e considere d i n a sitewid e baselin e ris k 

### assessment

. Becaus e metal s ar e no t absorbed wel l acros s th e skin
, derma l contac t wit h groundwate r i s no t considere d significan t (EPA

, 1991a)

. Base d o n th e evaluatio n o f potentiall y complet e pathways
, th e huma n receptor s associate d wit h the exposur e poin t selecte d are :

> • Futur e Adul t Resident ; and
, Golde r Associate sJun e

1996____________________-7-__________________943-281 9

+ Futur e Chil d Resident

. Th e Futur e Adul t an d Chil d Resident s wer e selecte d t o represent hypothetica l receptor s wh o migh t routinel y inges t groundwate r afte r installin g a water-suppl y wel l h i Stringtown

. Th e hypothetica l exposur e poin t i s show n i n Figur e 2

. 

### 2. 3 Complet e Exposur e Pathway s 

### The fina l componen t o f a complet e exposur e pathwa y i s a n intak e rout e int o the body

. Tabl e 1 summarize s th e pathway s tha t wer e evaluate d i n th e RA

. A s show n h i th e CS M (Figur e 1)
, th e onl y complet e exposur e pathwa y considere d quantitativel y wa s th e ingestio n o f groundwater

. Thi s exposur e was evaluate d fo r bot h receptors

. 

### 2. 4 Estimatin g Chemica l Intake s and Exposur e Poin t Concentration s Th e nex t ste p h i th e exposur e assessment wa s t o quantif y th e magnitude
, frequency
, an d duratio n o f chemica l intake s b y recepto r populations

. Thi s ste p wa s conducte d i n two stages : 

### 1 ) estimatio n o f EPCs

, an d 2 ) estimatio n o f chemica l intak e fo r eac h exposur e pathwa y unde r consideration

. Chemica l intake s wer e calculate d usin g guidanc e h i Ris k Assessmen t Guidanc e fo r Superfun d (EPA

, 1989b ) an d Exposur e Factor s Handboo k (EPA

, 1989a)
, othe r E P A documents
, site-specifi c information
, an d professiona l judgmen t regardin g likel y exposur e conditions
, a s appropriate

. Chemica l intake s wer e estimate d usin g averag e an d RM E estimate s o f chemica l concentration s i n groundwater
, an d reasonabl e estimate s o f exposur e parameters suc h a s bod y weight
, ingestio n rates , and othe r assumption s regardin g frequenc y an d duratio n o f exposur e (Asarco
, 1996a)

. 

### EPC s use d t o calculat e potentia l risk s fro m th e ingestio n o f groundwate r wer e obtaine d b y calculatin g th e averag e an d th e 9 5 percen t uppe r confidenc e limit on th e arithmeti c mea n for
eac h chemica l o f concer n usin g availabl e analytica l dat a fro m recen t sit e investigation s (EPA

,
Colde r Associate sJun e

1996____________________-8-__________________943-281 9 1992e)

. Dat a collectio n an d analysi s ar e describe d i n th e Hydrogeologi c R I Report (Asarco
, 1996a)

. 

### 2. 5 Exposur e Assumption s 

### Th e assumption s use d t o estimat e potentia l intak e receive d throug h th e exposur e pathwa y
wer e base d on EP A guidance
, site-specifi c information
, an d professiona l judgment

. I t i s no t 

### possibl e t o estimat e th e exac t leve l o f exposur e fo r specifi c individual s du e t o uncertaintie s i n behavio r pattern s an d incomplet e knowledg e o f exposur e variabl e values

. A primar y objectiv e o f thi s R A wa s t o use site-specifi c dat a wher e possible

. Childre n wer e identifie d a s a sensitiv e recepto r populatio n i n Leadville

. Therefore
, exposur e variable s wer e calculate d tha t incorporate d yout h a s a factor

. Becaus e bod y weight s var y


### ove r time , time-weighte d averag e bod y weight s wer e calculate d fo r th e Futur e Adul t an d Chil d Resident t o mor e accuratel y reflec t the tempora l natur e o f exposur e and the dose s receive d b y eac h recepto r (Tabl e 2)

. Th e exposur e frequencie s use d wer e 35 0 an d 27 5 day s pe r yea r fo r th e RM E an d average exposur e scenario s respectively

. Whil e th e forme r exposur e frequenc y account s fo r onl y tw o week s awa y fro m th e hypothetica l residenc e (fo r example
, a vacation)
, th e latte r exposur e frequenc y accommodates fo r th e hypothetica l resident s t o b e hom e 7 5 percen t o f th e tim e (o r 2 5 percent o f th e tim e spen t awa y fro m home
, i.e. , 6 hour s pe r day)

. Th e groundwate r ingestio n rat e for th e Futur e Adul t Resident s wa s assume d t o b e 1. 4 an d 2. 0 liter s pe r da y fo r th e averag e an d RM E exposures , respectivel y (EPA

, 1989b)

. Thes e figure s ar e conservativ e because th e assumptio n wa s mad e tha t th e majorit y o f fluid s consume d o n a dail y basi s ar e fro m the ingestio n o f groundwater

. Groundwate r ingestio n rate s fo r th e Futur e Chil d Residen t wer e assume d t o b e 0. 5 an d 0. 6 liter s pe r da y fo r th e 

### average an d RM E exposures , respectively

. Thes e figure s represent th e dail y averag e intak e Golde r Associate s

### Jun e

1996___________________-9-_________________943-281 9



### o f wate r (0. 5 I/day ) fro m age s on e t o seven
. Th e RM E o f 0. 6 represent s th e intak e o f a chil d ag e si x t o seven
. Thes e intak e amount s ar e presente d i n th e EP A LEA D 0. 5 IEUB K Mode l 

### (EPA

, 1991a)

. Becaus e th e R A considere d childre n fro m birt h t o si x year s a s a sensitiv e receptor , an d becaus e th e nationa l media n an d uppe r boun d estimate s fo r residenc y ar e nin e an d thirt y years , respectivel y (EPA

, 1989b)
, i t wa s assume d tha t thi s recepto r woul d b e expose d fo r si x year s fo r bot h th e averag e an d RM E scenarios

. I n orde r t o b e mos t conservative , th e approac h wa s take n t o follo w on e perso n fo r th e residenc y period s describe d above

. Therefore
, i t wa s als o assume d tha t th e Adul t Residen t woul d b e expose d for 3 year s (age s 7 

### throug h 9 ) an d 2 4 year s (age s 7 throug h 30 ) fo r th e averag e an d RM E scenarios , 

### respectively

. Additio n o f thes e exposur e duration s fo r th e averag e scenari o equal s nin e year s ( 6 year s fo r childre n an d 3 year s fo r th e adult ) an d fo r th e RM E scenari o equal s 3 0 year s ( 6 

### year s fo r childre n and 2 4 year s fo r the adult)

. This recepto r i s referre d t o a s a Futur e Typica l Residen t wh o woul d b e expose d fo r thes e timeframes

. A s such
, the noncarcinogeni c hazard s
and carcinogeni c risk s for th e Futur e Chil d and Adul t Resident s wer e summe d t o represent thes e exposur e durations

. The equatio n an d specifi c variable s use d t o estimat e intak e o f chemical s vi a groundwate r ingestio n are summarized i n Tabl e 3

. Intak e facto r calculation s are documente d i n Appendi x A

. 

### 3 . 0 RIS K CHARACTERIZATIO

N RESULT S The ris k assessmen t i s base d o n the foli o whi g ris k characterizatio n factors

. 

### T h e potentia l fo r advers e noncarcinogeni c effect s resultin g fro m exposur e t o a chemica l o f concer n i s evaluate d b y comparin g th e average dail y intak e o f the chemica l (expresse d a s mg/kg-day ) t o a referenc e dos e expresse d a s mg/kg-day)

. Th e resultin g rati o i s calle d a hazar d quotient (H.Q. ) (EPA

, 1989b)

. Golde r

Associate sJun e

1996___________________-10-__________________943-281 9

* • Th e potentia l for noncarcinogeni c effect s i s characterize d b y comparin g 

### estimate d chemica l intake s wit h chemical-specific RfDs

. This measur e i s know n as th e hazar d inde x (H.I. ) fo r multipl e chemicals

. 

### A mor e detaile d explanatio n o f thes e factor s i s presente d i n Appendi x A

. Give n th e conservativ e assumption s use d i n thi s RA

, the combine d H.I. s o f the Futur e Adul t and Chil d Resident s resulte d i n a n H.I

. greate r than th e EP A leve l o f concer n o f on e (1.0)

. Thi s wa s don e b y summin g th e chroni c H.I. s acros s th e age s o f birt h t o 9 year s an d fro m birt h t o 3 0 

### year s fo r averag e an d RM E scenarios , respectively
, an d represent s th e Typica l Futur e Adul t Resident (Tabl e 4)

. Th e result s o f th e carcinogeni c risk s an d noncarcinogeni c hazard s ar e als o show n i n Tabl e 4 fo r bot h th e Futur e Adul t an d Chil d Residents

. Th e averag e exposur e fo r th e Typica l Futur e Adul t resulte d i n a chroni c H.I

. o f 3. 3 x 10 1

, an d fo r RM E assumptions , th e chroni c H.I

. wa s 4. 6 x 10 1

. Accordin g t o EP A guidance
, a limitatio n o f th e hazar d inde x approac h i s th e assumptio n o f dos e additivity

. Thi s assumptio n i s mos t properl y applie d t o CO C tha t induc e th e sam e effec t b y th e sam e mechanis m o f actio n (EP A 1989b)

. Th e applicatio n o f th e hazar d inde x equatio n t o severa l COC s tha t hav e no t 

### experimentall y demonstrate d the sam e critica l effec t o r mechanism o f actio n coul d overestimat e th e potentia l healt h effect s (EPA

, 1989b)

. T h e thre e COC s responsibl e fo r drivin g th e chroni c H.I

. abov e unit y (1.0 ) wer e arsenic, cadmium
, an d zin c for bot h averag e an d RM E scenarios

. Th e critical effect s use d t o deriv e
ora l RfD s fo r zinc , cadmium
, and arseni c ar e dissimila r enoug h (differen t target organ s and 

### endpoints ) tha t th e dos e additivit y assumptio n use d i n thi s R A overestimates noncarcinogeni c hazards

. However
, eve n whe n thes e COC s are use d individuall y t o estimat e noncarcinogeni c hazards
, th e H.Q. s calculate d fo r chroni c exposur e stil l excee d unit y fo r bot h scenarios

. Carcinogeni c ris k estimates exceede d th e EP A acceptabl e ris k leve l o f 1 x 1 0 fo r bot h receptor s wit h al l o f thi s ris k contribute d b y arseni c (arseni c wa s th e onl y CO C wit h a n ora l slop e factor)

. Tota l carcinogeni c ris k estimate d fo r th e Typica l Futur e Resident

, addin g

Golde r Associate sJun e

1996___________________-11-__________________943-281 9



### acros s th e age s fro m birt h t o 9 year s o f ag e (th e averag e scenario)
, wa s 2. 1 x 10 ^ an d fo r 

### age s fro m birt h t o 3 0 year s o f age , 1. 1 x 10" 3 

### (th e RM E scenario)

. T o put thes e noncarcinogeni c hazard s and carcinogeni c risk s int o perspective , EPC s fo r the COC s evaluate d wer e compare d t o MCL s o r SMCL s (Tabl e 5)

. Althoug h arseni c 

### contributes significantl y t o th e overal l H.I. s an d i s solel y responsibl e fo r th e cance r risks
, EPC s fo r arseni c d o not excee d the MC L (Tabl e 5)

. Nicke l an d cadmiu m EPC s excee d thei r respectiv e MCL s an d sulfat e (no t a COC ) EPC s ar e abov e the SMCL

. 

### 4 . 0 UNCERTAINTIE

S AN D LIMITATION

S The EP A guidanc e fo r ris k assessmen t provides a systemati c mean s fo r organizing , analyzing
, an d presentin g informatio n o n th e natur e an d magnitud e o f potentia l risk s t o public 

### healt h an d th e environmen t pose d b y chemica l exposures

. Despit e th e advance d stat e o f th e
curren t methodology
, uncertaintie s an d limitation s ar e inheren t i n th e ris k assessmen t 

### process

. The qualit y o f availabl e data
, incomplet e informatio n abou t existin g condition s an d futur e circumstances , a s wel l a s othe r factor s contribut e t o thes e uncertaintie s an d limitations

. Discusse d belo w i s genera l informatio n regardin g uncertaintie s an d limitation s o f th e ris k

assessmen t process

. Specifi c uncertaintie s are summarize d i n Tabl e 6

. Dat a use d i n th e R A wer e collecte d usin g th e Wor k Plan

. Th e dat a collecte d durin g thi s 

### progra m ar e subjec t t o uncertaint y associate d wit h samplin g an d analysis
, an d thi s ma y ac t t o
over - o r under-estimat e th e potentia l risks

. 

### Th e exposur e assessmen t wa s based o n site-specifi c dat a an d o n a serie s o f assumptions concernin g concentration s o f chemical s t o whic h human s ma y b e expose d (EPCs ) a s wel l a s 

### pattern s o f behavio r leadin g t o exposur e o r intak e o f chemical s (exposur e scenarios)

. The exposur e assessment relie d o n assumption s fo r potentia l huma n exposur e whe n site-specifi c analytica l dat a wer e incomplet e o r unavailable

. Assumption s use d wer e base d upon : Golde r Associate sJun e

1996___________________-12-__________________943-281 9


### * • Site-specifi c information ; * EP A Huma n Healt h Evaluatio n Manua l (EPA

, 1989b ) an d th e Exposur e 

### Factor s Handboo k (EPA

, 1989a) ; and
, * • Professiona l judgment

. I n general
, th e availabl e scientifi c informatio n i s insufficien t t o provid e a thoroug h 

### understandin g o f al l the potentia l toxi c propertie s o f chemical s t o whic h human s ar e 

### potentiall y exposed

. Consequently

, varyin g degree s o f uncertaint y surroun d th e assessment o f 

### advers e healt h effect s i n expose d populations

. I n thi s case , severa l chemical s (aluminum
, copper , manganese, an d titanium ) wer e eliminate d fro m consideratio n becaus e toxicit y value s
wer e no t available

. 

### Du e t o uncertaintie s i n eac h ste p o f th e R A process , uncertaintie s ar e ofte n magnifie d i n th e fina l ris k characterization

. Th e fina l quantitativ e estimates o f ris k ma y b e on e o r severa l order s o f magnitud e differen t fro m the potentia l ris k associate d wit h a given exposure

. I n a n 

### attemp t t o minimiz e th e consequence s o f uncertainty , EP A guidanc e typicall y relies on us e o f conservativ e estimates o f hazard s i n th e absenc e o f stron g scientifi c data

. Th e overal l resul t i s tha t ris k estimate s presente d i n thi s report ar e muc h mor e likel y t o overestimat e th e potentia l ris k tha n t o underestimat e it

. 

### Th e assessmen t ha s bee n prepare d i n a manne r consisten t wit h tha t generall y use d i n th e consultin g communit y an d agenc y guidanc e a t th e tim e i t wa s prepared

. 

### 5. 0 CONCLUSION S Base d o n th e curren t informatio n an d dat a use d fo r thi s RA

, th e followin g conclusion s ca n b e made : Ther e are n o know n curren t receptor s for th e exposur e pathwa y considere d (groundwate r ingestion)

. Thi s i s base d o n a recen t Golde r Associate sJun e

1996___________________-13-__________________943-281 9 demographic s surve y b y Dr

. Rober t Bornschei n o f th e Universit y o f Cincinnati' s Departmen t o f Environmenta l Healt h (Asarco
, 1992 ) an d a n EP A Recor d o f Decisio n (ROD ) (EPA

, 1988)

. Additionally
, th e Parkvill e Wate r District

, the municipa l supplie r o f water , indicate s tha t al l resident s o f th e town s o f Leadvill e an d Stringtow n ar e connected t o thei r wate r 

### syste m (Parkvill e Wate r District

, 1993)

. K Hypothetica l futur e receptor s (adul t an d chil d residents ) use d i n thi s R A consume d groundwate r wit h conservativ e EPCs

. Tha t is , th e arithmeti c mea n an d 95t h percen t UC L o n th e arithmeti c mea n use d i n th e averag e an d RM E scenario s wer e calculate d fro m dat a take n fro m mini



### piezometer s an d spring s locate d i n Californi a Gulch

. Dat a fro m unfiltere d sample s (i.e.
, tota l metals ) fro m mini-piezometer s an d spring s wer e use d


### a s a conservative substitut e fo r groundwate r monitorin g well s becaus e unfiltere d metal s analyses fo r groundwate r wer e unavailable

. I n addition
, th e sourc e are a concentration s o f metal s probabl y woul d b e unrealisticall y hig h t o expec t at the hypothetica l exposur e point

. The mini-piezomete r and sprin g concentratio n mor e realisticall y represen t lowe r concentration s tha t woul d resul t fro m advective an d dispersiv e transpor t o f th e metal s fro m the suspecte d sourc e areas
. * • Hypothetica l futur e receptor s use d i n thi s ris k assessment ha d risk s estimate d base d o n conservative exposur e assumptions

. Most assumption s followe d EP A defaul t value s tha t ar e use d whe n site-specifi c dat a ar e lackin g (EPA

, 1989b
, 1991b)

. Fo r th e average exposur e an d RM E scenario s i t wa s assume d tha t th e receptor s wer e ingestin g 1. 4 t o 2. 0 liter s o f wate r per day
, an d tha t adul t resident s consume d 10 0 percen t o f thei r dail y flui d intak e fro m th e tap

. Thi s consumptio n rat e wa s assume d t o occu r ove r nin e an d thirt y year s fo r th e averag e an d RM E scenarios , respectively

. * Risk s t o hypothetica l futur e receptors wer e estimate d based o n conservativ e exposur e assumptions

. Site-specifi c dat a wer e use d whe n available ; otherwis e EP A defaul t value s wer e use d (EPA

, 1989c , 1991b)

. For example
, the ingestio n o f 1. 4 and 2. 0 liter s o f water pe r da y assume s tha t th e adul t resident
, fo r th e averag e an d RM E exposur e scenario , consum e 10 0 percen t o f thei r dail y flui d intak e fro m th e tap

. Thi s consumptio n rat e wa s assume d t o occu r ove r nin e an d thirt y year s fo r th e average an d RM E scenarios , respectively

. 

### * • Currently

, ther e are n o risk s fro m th e consumptio n o f groundwate r fro m the alluvia l aquife r i n the Californi a Gulc h because no complet e exposur e pathwa y exists

. However
, i f groundwate r wa s consumed
, a s assumed fo r th e hypothetica l receptor s i n thi s RA

, bot h cance r an d non-cance r risk s woul d excee d regulator y levels

. Golde r Associate sJun e

1996___________________-14-__________________943-281 9 

### 6. 0 REFERENCE S ASARCO

. 1992d

. Metal s Samplin g an d Analysis Result s an d Demographics Results

. Prepare d b y Woodward-Clyd e Consultants

. Septembe r 15

. ASARCO

. 1996a

. Hydrogeologi c Remedia l Investigatio n Report

. Californi a Gulc h Site

, Leadville

, Colorado

. Prepare d b y Colde r Associates
, Denver

, fo r Asarco
, Inc

. May

. ASARCO

. 1996b

. Surfac e Wate r Remedial Investigatio n Report

. Prepare d b y Colde r Associates
, Denver

, fo r Asarco
, Inc

. May

. 

### Parkvill e Wate r District

. 1993

. Persona l communicatio n betwee n Kir n Broga n (WCC ) an d Sand y Maso n (PWD ) o n Februar y 11

. 

### U.S

. Environmental Protectio n Agenc y (EPA)

. 1987a

. Phas e I Remedial Investigatio n Report

, Californi a Gulch

, Leadville

, Colorado

. 53-8129.0/W63781.R1

.

Prepare d b y C H 2 M Hill
, Blac k & Veatch
, ICF

, PRC

, an d Ecolog y an d Environment

. May

. U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1988

. Recor d o f Decisio n (ROD)

, Ya k Tunne l Operabl e Unit
, Californi a Gulch Site

, Leadville

, Colorado

. Marc h 29

. 

### U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1989a

. Exposur e Factor s Handbook

. Exposur e Assessmen t Grou p Offic e o f Healt h an d Environmental Assessment

. Washington
, D.C

. EPA/600/8-89/043

. U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1989b

. Ris k Assessmen t Guidanc e fo r Superfund

. Volum e I : Huma n Healt h Evaluatio n Manual

. Interim final

. Offic e o f Emergenc y an d Remedia l Response

. Washington
, D.C

. EPA/540/1-89/002

. U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1989c

. Phas e n Remedial Investigatio n Technica l Memorandum
, Draft

, Californi a Gulch

, Leadville

, Colorado

. Vols

. I-VI

. 53-8129.0/DEN63786.R1

.

Prepare d b y CH 2 M Hill
, Blac k & Veatch
, ICF

, PRC

, an d Ecology an d Environment

. May

. U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1991a

. Preliminar y Huma n Healt h Baselin e Ris k Assessmen t fo r th e Californi a Gulch NP L Site

, Leadville

, Colorado

. Prepare d f o r th e U.S

. EP A Region VTfl
, Denver

, Colorad o b y Ro y F

. Weston
, Inc.
, Lakewood

, Colorado

. U.S

. Environmental Protectio n Agenc y (EPA)

. 1991b

. Huma n Healt h Evaluatio n Manual
, Supplementa l Guidance : "Standar d Defaul t Exposur e Factors"

. OSWE R Directiv e 9285.6-03

. Marc h 25

. Golde r

Associate sJun e

1996__________________-15-__________________943-281 9 U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1992a

. Guideline s fo r Exposur e Assessment

. 5 7 F R 22888-22938 , Ma y 29

. 

### U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1992b

. Mem o fro m F

. Henr y Habicht
, Deput y Administrator
, EPA

. Guidanc e o n Ris k Characterizatio n fo r Ris k Manager s 

### an d Ris k Assessors

. Februar y 26

. U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1992c

. Mem o fro m Henr y L

. Longest

, Director

, Offic e o f Emergenc y an d Remedia l Response

. Implementin g th e Deput y Administrator' s Ris k Characterizatio n Memorandum

. Ma y 26

. U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1992d

. Integrate d Ris k Informatio n Syste m (IRIS)

. On-lin e database

. U.S

. Environmenta l Protectio n Agenc y (EPA)

. 1992e

. Offic e o f Soli d Wast e an d Emergenc y Response

. Memorandum "Supplementa l Guidanc e t o RAGS : Calculatin g the concentratio n Term"

. Jun e 22

.

Golde r Associate s

### TABLE S

J M I

r

Gblde r

Associate s

# I I

TABL E 1 

### LEADVILL E GROUNDWATER POTENTIALL Y COMPLET E EXPOSUR E PATHWAY S QUANTITATIVEL

Y EVALUATE D 

### Potentiall y Expose d Recepto r 

### Scenari

o Potentiall

y Complet e Exposur e Pathway s Chil d Resident Future 2 Groundwate r

ingestio n


### Adul t Resident Future 3 

### Groundwate r

ingestio n



### This scenari o i s completel y hypothetical

.

Golde r

Associate sTABL E 2 

### GENERA L ASSUMPTION S FOR BOD Y WEIGH T Age Rang e 0- 3 3- 6 6- 9 9-1 2 12-1 5 15-1 8 18-3 0 Year s

i n Ag e Rang e 3 3 3 3 3 3 1 2 K g a

11. 6 17. 4 25. 0 36. 0 50. 6 61. 2 7 0 TIM E WEIGHTE D AVERAG E BOD Y WEIGHT S


### Chil d (1- 6 Adul t (7- 9 years) b year s an d 7-3 0 years) 0 

### Years

i n Ag e Rang e 

### 6 3/2 4 

### Bod

y Weigh t 1 6 25/5 7 

### Exposur e Factor s Handboo k (EP A 1989e)

. RAG S (EPA

, 1989f)

. Represent s th e 50t h percentil e bod y weight s fo r childre n age s 1 t o 6 year s (no t a tru e weighte d average)

. Averag e scenari o use d 7 t o 9 year s o f ag e an d RM E scenari o use d 7 t o 3 0 year s o f age .

Colde r Associate sTABL E 3 INTAK E ASSUMPTION S FO R GROUNDWATERINGESTIO N

Intak e Facto r = I R x E F x E D x F I BWxAT Paramete r Averag e Reasonabl e Maximu m I R = Ingestio n rate , L/da y Adul t (>6) 1. 4

2. 0 Chil d (0- 6 years) 2 0. 5

0. 6 E F = Exposur e frequency
, days/years

2 Adul t 27

5 35

0 Chil d 27

5 35

0 E D = Exposur e duration
, years 2 Futur e Adul t Residen t 3 2 4 Futur e Chil d Residen t 6 6 Futur e Typica l Residen t 9 3 0 F I = Fractio n ingeste d fro m contaminate d source

3 1. 0

1. 0 B W = Bod y weight
, kg 4 Adul t (weighte d average ) 2 5 5 7 Chil d (weighte d average ) 1 6 1 6 A T = Averagin g time , days 5 Noncarcinogen s Adul t 1,09 5

( 3 years ) 8,76 0 (2 4 years ) Chil d 2,19 0

( 6 years ) 2,19 0 ( 6 years ) Carcinogens 25,55 0

(70 years ) 25,55 0

(70 years )

1 EPA

, 1989f

. (Se e tex t fo r furthe r explanation
, Sectio n 6.2.5)

. 2 Se e text , Sectio n 6.2. 5 fo r explanation

. 3 A n F I o f 1. 0 represent s a conservativ e assumptio n abou t th e amoun t o f groundwate r tha t i s consumed

. Th e highe r th e FI
, th e greate r amoun t o f groundwate r i s consume d fro m th e contaminate d source
. A n F I
o f on e assume s al l wate r i s consume d fro m th e contaminate d source
. 4 EPA

, 1989e

. 5 Nin e year s ( 6 year s a s a chil d an d 3 year s a s a n adult ) an d 3 0 year s ( 6 year s a s a chil d an d 2 4 year s a s a n adult ) are year s spen t i n on e residenc e for th e nationa l media n an d uppe r boun d estimates , respectivel y (EPA

, 1989f)

. Averagin g tun e i s th e produc t o f thes e tim e period s an d day s pe r year .

Colde r Associate s

### TABL E 4 

### GROUNDWATER CARCINOGENI

C RISK S AN D NONCARCINOGENI

C HAZAR D INDE X (H.I.) Averag e Exposur e Reasonabl e Maximu m Exposur e Receptor/Pathwa y Cancer

Subchroni c Chroni c Ris k H.I

. H.I

. Cance r Subchroni c Chroni c Ris k H.I

. H.I

. Futur e Adul t Residen t Ingestio n o f Groundwate r l.OE-04

1.8E+0 1 2.1E+0 1 Futur e Chil d Residen t Ingestio n o f Groundwate r 1

. IE-0 4 9.9E+0 0 1.2E+0 1 Futur e Typica l Adul t Residen t Ingestio n o f Groundwate r 2

. IE-0 4 2.8E+0 1 3.3E+0 1 8.7E-0

4 1.8E+0 1 2.2E+0 1
2.3E-0 4 1.9E+0 1 2.4E+0 1 1.IE-0 3 4.6E+0 1 4.6E+0 1

Colde r Associate s

### TABLE S

COMPARISO N O F EXPOSUR E POIN T CONCENTRATION

S (EPCs ) WIT H MAXIMU M CONTAMINAN

T LEVEL S (MCLs ) (mg/1 ) 

### Chemica l Arseni c Cadmiu m Mercur y Nicke l 

### Silve r Sulfat e Zin c Average 1 3 

### 3.17E-0 2 9.45E-0 2 7.70E-0 5 

### 1.23E-0 1 1.34E-0 2 

### 1.38E+0 3 6.00E+0 1 EP C 

### RME

b 

### 4. 3 IE-0 2 1.30E-0 2 1.44E-0 3 

### 1.63E-0 1 1.58E-0 2 

### 3.46E+0 3 7.38E+0 1 MCL a 

### 5.00E-0 2 5.00E-0 3 2.00E-0 3 l.OOE-0 1 N A C 

### 2.50E+02 a d N A C

a 

### EP A 1992g

. Offic e o f Water

. Drinkin g Wate r Regulation s and Healt h Advisories

. b 

### Averag e

= Averag e Exposur e RM E = Reasonabl e Maximu m Exposur e 0 

### N A = No t Availabl e d 

### Secondar

y MCL ; base d o n odo r an d aesthetics

. BOL D Values represen t those exceedin g MCL

.

Colde r Associate s

### TABL E 6 SUMMAR Y O F UNCERTAINT Y FACTOR S I N TH E GROUNDWATER BASELIN E RIS K ASSESSMEN T Uncertaint y Facto r Effec t

o f Uncertaint y Commen

t Us e o f cance r potenc y factors

. Ma y overestimat e risks

. Critica l toxicit y value s derive d Ma y over - o r primaril y fro m anima l studies

. underestimat

e risks

. Critica l toxicit y value s derive d primaril y fro m hig h doses
, mos t exposures ar e a t lo w doses

. Critica l toxicit y values

. Ma

y over - o r underestimat e risks

. Ma y over - o r underestimat e risks

. No t al l chemical s a t th e sit e hav e Ma y underestimat e critica l toxicit y values

. risks

. Metal s analysi s fo r tota l metal s Ma y overestimat e risks
, only

. Effec t o f absorption

. Ma

y over - o r underestimat e risks

. Exposur e assumption s regardin g Ma y overestimat e risks
, the groundwate r ingestio n rate

. Exposure s assume d constan t ove r Ma y over - o r time

. underestimat e risks

. Exposur e poin t concentrations

. Ma y overestimat e risks

. Exposur e poin t concentrations

. Ma y overestimat e risks

. Exposur e poin t concentrations

. Ma y overestimat e risks

. Contrac t required detectio n limits

. Sampling

. Ma

y underestimat e risks

. Ma y overestimat e risks

. Potencie s

ar e uppe r 95t h percen t confidenc e limit s derive d fro m th e linearize d model

. Considere d unlikel y t o underestimat e tru e risk

. Extrapolatio n fro m anima l t o human s ma y induc e erro r du e t o difference s h i absorption
, pharmacokinetics
, targe t organs , enzymes , an d populatio n variability

. Assume s linea r a t low doses

. Tend s t o hav e conservativ e exposur e assumptions

. Not al l value s represen t the sam e degre e o f certainty

. Al l ar e subjec t t o change a s new evidenc e become s available

. Thes e chemica l are no t addresse d quantitatively

. Di d no t distinguis h betwee n valenc e o r speciation

. Assume d al l metal s wer e presen t a s tota l metal s vs
. dissolve d metals

. Th e assumptio n tha t absorptio n i s equivalen t acros s specie s i s implici t h i th e derivatio n o f th e critica l toxicit y values

. Absorptio n ma y actuall y var y wit h specie s an d ag e a s wel l a s othe r factor s suc h a s nutritiona l status

. Groundwate r intak e doe s no t accoun t fo r tim e spen t awa y fro m th e sourc e o r othe r fluid s ingested

. Doe s no t accoun t fo r environmenta l fate
, transport , o r transfe r whic h ma y alte r alluvia l groundwate r concentratio n o f metal s ove r tune

. Us e o f 95 % UC L i n calculatin g RM E ma y no t accuratel y represen t exposur e levels

. Use d th e arithmeti c mea n concentratio n an d 95 % UC L t o evaluat e average an d RM E exposures

. Ma y no t accuratel y represent exposur e levels

. Use o f unfiltere d groundwate r sample s ma y no t accuratel y represen t exposure s a s peopl e ma y neve r drin k thi s qualit y o f water

. Fo r som e chemicals
, thi s detectio n limi t i s abov e a concentratio n whic h migh t b e o f concern . Samplin g biase d towar d area s o f know n or suspecte d elevate d metal s concentrations

. Colde r Associate sTABL E 6 (Concluded ) Uncertaint y Facto r Effec t o f Uncertaint y Commen

t Exposur e scenario

. Ma

y overestimat e risks

. Ver y conservativ e approach b y assumin g tha t hypothetica l futur e exposur e coul d occur . Risks/dose s withi n a n exposur e Ma y over - o r Doe

s no t accoun t fo r synergis m o r antagonism

. rout e assume d t o b e additive

. underestimat

e risks

. Ris k characterization

. Ma

y overestimat e risks

. Combinin g conservativ e assumptions a t eac h ste p o f ris k assessmen t ma y lead t o highl y conservativ e ris k estimates

.

Colde r Associate s

### FIGURES

Golde r Associate sPOTENTIA L HUMA N EXPOSUR E PATHWAY S POTENTIA L HUMA N RECEPTO R PRIMAR Y SOURC E T

RELEAS E MECHANIS M 

### r EXPOSUR E MEDIU M 2 *

RELEAS E MECHANIS M 2 EXPOSUR E

MEDIU M EXPOSUR E

ROUT E FUTUR E RESIDENT S ADULT | CHIL D

SURFAC E WATE R RUN-OF F INGESTIO N DERMA L I I I I

•INGESTION

, DERMA L

* H INGESTIO N [ N E [ N E

LEGEN D
• COMPLET E AN D SIGNIFICAN

T PATHWA Y I INCOMPLET E PATHWA Y N E NO T EVALUATE D SOURCE : WOODWARD-CLYD E

CONSULTANTS

, DRAF T SURFAC E WATE R R l INFILTRATIO N ALLUVIAL

GROUNDWATE R

—

^

- COMMUNICATIO N WIT H SURFAC E WATE R BODIE S FIS H

—————— — (fc . INGESTIO N

| N E N E

CLIENT/PROJEC T 

### ASARC O HYDROGEOLOGI

C HUMA N HEALT H RIS K ASSESSMEN T Denver

, Colorad o TITL E 

### CONCEPTUA

L SIT E MODE L GROUNDWATE R LEADVLLE

, COLORAD O DRAW N R B CHECKE D A

R REVIEWE D BD

P DAT E JUN E 199 6 SCAL E N O SCAL E FIL E

NO

. 2819A06 0 J O B

NO

. 943-281 9 D W

G NO./REV.NO

. A06 0 FIG

.N 520,00 0

N 510,00 0

P- 8 8PR- 1 MINI-PIEZOMETE R SPRIN G MINI-PIEZOMETE R

- DAT A USED I N R A 

### EXPLANATIONS APPROXIMAT E LIMIT S O F TAILING S LEADVILL E MUNICIPA L WAST E FACILIT Y 0 100 0 200 0 400

0 TOPOGRAPHI

C CONTOU R INTERVA L = 25 SURFAC E WATE R DRAINAG E

- DOTTE D WHER E INTERMITTEN

T EXPOSUR E POIN T -.—-, .

AREA S I N WHIC H BEDROC K ( • • ) FORMATION S OUTCRO P O R Denver

, Colorad o CLIENT/PROJEC T 

### ASARC O HYDROGEOLOGI

C HUMA N TITll E 

### FUTUR E

SCENARI O 

### EXPOSUR E POIN T LOCATIO N DRAW N R B

DAT E JUN E 199 6 CHECKE D SCAL E -i»

_ 

### r =2.000 * J O B

NO

. 943-281 9 DWG

. NO./REV

. NO

.

### APPENDI X A RISKEVAL U

Golde r Associa l 

### METHOD S

### Appendi x A Jun e 1996___________________A-l

_________________ 943-281

9 APPENDI X A
- EXPLANATIO N O F RIS K ASSESSMEN T COMPUTE R OUTPU T (ASSES S PROGRAM ) ASSES S i s a compute r progra m designe d b y Woodward-Clyd e Consultant s t o calculat e noncarcinogeni c hazard s an d carcinogeni c risks

. ASSES S consider s al l exposur e pathway s evaluate d a t a site

. Al l informatio n neede d t o verif y calculation s i s provided

. Dat a ar e organize d an d reporte d i n categorie s liste d below :

* • Chemica l Lis t
* Receptor/Pathwa

y Summar y * • Pathwa y Summar y * Intak e Factor s * • Medi a Concentration s Number s i n ASSES S ar e writte n i n scientifi c notation

. The numbe r followin g the E i s a powe r o f 10 ; s o 1.61E-0 2 i s 0.0161

.
1 . 0 CHEMICA L LIS T 

### Thi s shee t list s th e EP A toxicit y value s fo r eac h chemical

. Whe n available
, value s ar e liste d fo r bot h ora l an d inhalatio n exposur e route s fo r eithe r subchroni c o r chroni c exposur e duration s (referenc e dose s o r RfDs ) o r fo r carcinogeni c ris k (slop e factor s o r SF)

. Thes e value s ar e obtaine d usin g th e hierarch y recommende d b y EPA' s Ris k Assessmen t Guidanc e fo r Superfun d site s (EP A 1989b
, 1991b)

. Th e firs t an d secon d source s i n thi s hierarch y ar e ( 1 ) IRI S (Integrate d Ris k Informatio n System)

, a n on-lin e compute r databas e o f chemica l ris k informatio n (EP A 1992d)
, an d (2 ) HEAS T (Healt h Effect s Assessmen t Summar y Tables ) (EP A 1992e)
, EP A table s whic h ar e periodicall y up-dated

. Toxicit y value s (RfDs an d SFs ) d o not yet exis t fo r man y chemicals

. For ris k assessment purposes , whe n thi s i s true , a

Colde r Associate sAppendi x A Jun e 1996___________________A-2__________________943-281 9 

### chemica l ma y b e discusse d qualitativel y i n th e tex t o f th e repor t bu t wil l no t b e reporte d quantitativel y i n ASSESS

. RfD s ma y b e derive d fo r eithe r subchroni c o r chroni c exposure s an d ar e use d t o calculat e subchroni c o r chroni c hazar d quotients , respectively

. A subchroni c Rf D ma y no t exis t fo r a particula r chemica l eve n thoug h a chroni c Rf D exists

.
2 . 0 RECEPTOR/PATHWA

Y SUMMAR Y Th e Recepto r Summar y shee t list s eac h recepto r an d th e potentia l healt h risk s associate d wit h chemica l exposur e fro m al l pathway s quantitated

. Th e potentia l advers e healt h risk s ar e divide d int o tw o exposur e scenarios : averag e exposur e and reasonabl e maximu m exposur e (RME)

. For eac h exposur e scenario , potentia l healt h impact s ar e segregate d int o tw o categories : cance r ris k an d a hazar d inde x for bot h subchroni c an d chroni c scenario

. Th e 

### value s show n o n thi s shee t sho w th e tota l carcinogeni c risk s an d noncarcinogeni c hazard s associate d wit h average an d RM E scenari o fo r eac h recepto r listed

. RfD s are use d wit h a leve l o f exposur e durin g a specifi c tim e perio d and expresse d a s a rati o
o r hazar d quotient

. Accordin g t o the EP A (EPA

, 1989b
, 1991b)
, generally
, the greate r the valu e o f the hazar d quotien t (o r hazar d index)
, the greate r the leve l o f concer n fo r healt h impacts

. Anothe r are a o f EP A guidanc e state s tha t becaus e H.I

. i s no t a probabilit y function
, a n increase d valu e doe s no t indicat e a degre e o f risk

. Th e hazar d inde x i s th e su m o f a numbe r o f hazar d quotient s for a particula r pathway

. A hazar d inde x o f on e mean s th e estimate d chemica l intak e equal s th e referenc e dose

. Whe n thi s occurs , a mor e detaile d evaluatio n o f th e sit e i s indicated

. Whe n th e H.I

. i s les s tha n one , furthe r evaluatio n i s generall y no t warranted
, an d th e exposur e i s expecte d t o b e saf e i f th e H.I

. i s equa l t o or les s than one .

Golde r Associate sAppendix A 

### Jun e 1996__________________A-3_________________943-281 9 A chemical' s slop e facto r i s multiplie d b y th e lifetim e dail y averag e intak e o f that chemica l i n
a certai n mediu m t o estimat e the incrementa l probabilit y (o r risk ) o f an individua l developin g
cance r durin g a lifetime

. Whe n a recepto r potentiall y i s expose d t o a variet y o f chemical s (i n
a give n medium ) possessin g slop e factors
, al l o f th e product s ar e summe d t o yiel d th e tota l

cance r ris k fo r thos e chemical s fo r tha t specifi c exposur e pathway

. Thi s ris k numbe r i s acceptabl e i f i t i s les s tha n IE- 4 o r 10" 4 o r 1 i n 10,000

. 

### Recepto r Detai l Report 

### Thi s repor t i s include d i n the Receptor/Pathwa y Summar y Shee t because i t detail s the carcinogeni c ris k an d th e noncarcinogeni c hazar d fo r eac h o f th e receptor' s exposur e 

### pathway(s ) fo r bot h the averag e and RM E exposur e scenarios

. Tota l carcinogeni c risk s and noncarcinogeni c hazard s fo r eac h recepto r ar e als o given

. Eac h recepto r ma y hav e a numbe r
o f exposur e pathways

. A n exposur e pathwa y i s a rout e tha t a chemica l ma y tak e t o reac h a populatio n o r receptor

. Eac h pathwa y i s categorize d a s on e o f th e following :

* • Inhalatio n *> Derma l contac t wit h solid s * • Derma l contac t wit h wate r * Ingestio n o f solid s * Ingestio n o f wate r 3 . 0 PATHWA Y SUMMAR Y Thi s shee t als o provide s th e sam e basi c informatio n a s th e Recepto r Detai l Repor t describe d above

. Th e differenc e betwee n th e tw o i s tha t th e Recepto r Detai l Report include s al l receptor s whil e th e Pathwa y Summar y Repor t i s receptor-specific
, providin g informatio n o n 

### onl y on e recepto r pe r page

. Golde r

Associate sAppendi x A Jun e 1996___________________A-4__________________943-281 9 

### Pathwa y Detai l Repor t Thes e sheet s compris e th e majorit y o f th e ASSES S report

. Fo r bot h averag e an d RM E exposur e scenarios , carcinogeni c ris k and noncarcinogeni c hazard s ar e liste d fo r eac h recepto r exposur e rout e an d chemical

. Tota l carcinogeni c risk s an d noncarcinogeni c hazard s
are als o provided

. Thi s repor t i s especiall y helpfu l i n determinin g whic h chemical(s ) i s (are ) drivin g the overal l risk s o r hazard s fo r a particula r exposur e route

. Other value s provide d i n thi s repor t includ e the concentratio n o f eac h chemica l i n the medium
, the intak e facto r for 

### tha t exposur e route, an d th e dail y intak e o f th e chemica l bein g evaluated

. This dail y intak e
o f a n individua l chemica l i s either multiplie d b y it s slop e facto r or divide d b y it s Rf D for a give n exposur e rout e (ora l o r inhalation)

. Unti l othe r informatio n i s availabl e fro m EPA

, ora l RfD s an d SF s ar e use d fo r assessin g th e potentia l healt h impact s o f derma l exposure

.
4 . 0 INTAK E FACTOR S Thes e sheet s represent , i n equatio n format
, th e method o f calculatin g th e intake factor s tha t appea r i n the pathwa y detail repor t explaine d above

. Eac h o f the parameters tha t goe s int o


### an intak e facto r equatio n i s define d for bot h the average and RM E scenarios

. Thes e parameter s are mor e full y describe d i n th e Exposur e Assessmen t section o f thi s report

.
5 . 0 MEDI A CONCENTRATION

S Thes e sheet s describ e th e chemica l concentration s for th e averag e an d RM E scenario s for a give n medium

. I n som e cases , a highe r concentratio n ma y b e use d t o evaluat e short-ter m risks

. Fo r example
, particulat e concentration s i n ai r ma y b e highe r durin g a shor t constructio n projec t tha n th e long-ter m (2 5 year ) averag e migh t be

. I n mos t cases , th e sam e 

### concentration s wil l b e use d fo r subchroni c an d chroni c scenario

. Thes e figure s ar e describe d i n the Dat a Summar y and Selectio n o f Chemical s o f Concern sectio n o f thi s report

.

Colde r Associate sChemica l

List : SURFAC

E WATE R Februar y 2 , 1 9 •' 18 :

Inhalatio n —————————————

— ——— — Non-Inhalatio n Slop e Subchroni c

Chroni c Slop e Subchroni c

Chroni c Facto r RF

D RF D Facto r

ftF D RF O Chemica l (mg/kg/day)- 1

mg/kg/da y mg/kg/da y (mg/kg/day)- 1

mg/kg/da y mg/kg/da y Arseni c - 1.50E+0 1

1.75E+0 0 3.00E-0 4

3.00E-C K Cadmiu m (food ) 1.00E-0 3 Chromiu n II I 2.00E-0 5 2.00E-0 6

1.00E+0 0

1.00E+0 0 Chromit m V I 4.10E+0 1 5.70E-0 6

5.70E-0 7

2.00E-0 2

5.00E-0 3 Coppe r 3.70E-0 2 3.70E-0 2 Mercury 8.60E-0 5 8.60E-0 5

3.00E-0 4

3.00E-0 4 Zin c 2.00E-0 1 3.00E-0 1Receptor/Pathwa y

Summary : SURFAC E WATE R Februar y 2 , 19 9 18: 1

Recepto r / Pathwa y ADUL T RECREATIONA L USE R

- - Inges t io n o f Fis h Averag e Exposur e Cance r Subchroni c Chroni c Ris k H.I

. H.I

. Reasonabl

e Maximu m Exposur e Cance r Subchroni c Chroni c Ris k H.I

. H.I

. 1.92E-0 6 3.30E-0 1 3.58E-0 1 2.70E-0 5 5.S5E-0 1 5.98E-0 1 1.92E-0 6 3.30E-0 1 3.58E-0 1 2.70E-0 5 5.55E-0 1 5.98E-0 1 CHIL D RECREATIONA L USE R

- - Inges t io n o f Fis h 3.74E-0 7 3.21E-0 2 3.48E-0 2 4.33E-0 6 3.56E-0 1 3.84E-0 1 3.74E-0 7 3.21E-0 2 3.48E-0 2 4.33E-0 6 •J.56E-0 1 3.8AE-0 1ADUL T RECREATIONA L

USE R Ingestio n o f Fis h Averag e Exposur e

1 | Carcinogeni c

Ris k i Chemica l Arseni c

i | Hazar d Inde x - - Subchroni c i Chemica l Arseni c Chromiu m V I Coppe r Mercur y Zin c

i | Hazar d Inde x - - Chroni c r Chemica l Arseni c Chromiu n V I Coppe r Mercur y Zin c 1

1 1 Chemica l Concentratio n (ing / kg ) 3.00E-0 2

l 1 1 Chemica l Concentratio n Cmg/kg ) 3.00E-0 2 2.80E-0 1 3.80E-0 1 7.00E-0 2 5.62E+0 0
I I I Chemica l Concentratio n (mg/kg ) 3.00E-0 2 2.80E-0 1 3.80E-0 1 7.00E-0 2 5.62E+0 0 Ingestio n Intak e Facto r C kg / kg / day ) 3.66E-0 5

Ingestio n Intak e Facto r (kg/kg/day ) 8.55E-0 4 8.55E-0 4 8.55E-0 4 8.55E-0 4 8.55E-0 4

Ingestio n Intak e Facto r (kg/kg/day ) 3.55E-0 4 8.55E-0 4 8.55E-0 4 8.55E-0 4 8.55E-0 4 Daily

Intak e <mg/kg/day) 1.10E-0 6

Dail y Intak e (mg/kg/day ) 2.56E-0 5 2.39E-0 4 3.25E-0 4 5.98E-0 5 4.80E-0 3

Dail y Intak e <mg/kg/day ) 2.56E-0 5 2.39E-0 4 3.25E-0 4 5.98E-0 5 4.80E-0 3 Slop e

Facto r (mg/kg/day)- 1 1.75E+0 0

Subchroni c R F O (mg/kg/day ) 3.00E-0 4 2.00E-0 2 3.70E-0 2 3.00E-0 4 2.00E-0 1

Chroni c R F D <mg/kg/day ) 3.00E-0 4 5.00E-0 3 3.70E-0 2 3.00E-0 4 3.00E-0 1 Carcinogeni c

Ris k 1.92E-0 6

Hazar d Quotien t 8.55E-0 2 1.20E-0 2 8.78E-0 3 1.99E-0 1 2.40E-0 2

Hazar d Quotien t S.55E-0 2 4.79E-0 2 8.78E-0 3 1.99E-0 1 1.60E-0 2 Tota l

Ris k 1.92E-0 6

Hazar d Inde x

3.30E-0 1

Hazar d Inde x

3.58E-0 1ADUL T RECREATIONAL

USE R Ingestio n o f Fis h Reasonabl e Maximu m Exposur e J | Carcinogeni c

Ris k i Chemica l Arseni c

i | Hazar d Inde x - - Subchroni c ! Chemica l Arseni c Chromiu m V I Coppe r Mercur y Zin c

i | Hazar d Inde x - - Chroni c i Chemica l Arseni c Chromiu m V I Coppe r Mercur y Zin c 1

1 1 Chemica l Concentratio n (rog/kg ) 4.00E-0 2

1 1 I Chemica l Concentratio n (mg/kg ) 4.00E-0 2 3.30E-0 1 4.20E-0 1 9.00E-0 2 6.42E+0 0
I I I Chemica l Concentratio n (mg/kg ) 4.00E-0 2 3.30E-0 1 4.20E-0 1 9

. 006-0 2 6.42E+0 0 Ingestio n Intak e Facto r (kg/kg/day ) 3.86E-0 4

Ingestio n Intak e Facto r C kg/kg/day ) 1.12E-0 3 1.12E-0 3 1.12E-0 3 1.12E-0 3 1.12E-0 3

Ingestio n Intak e Facto r (kg/kg/day ) 1.12E-0 3 1.12E-0 3 1.12E-0 3 1.12E-0 3 1.12E-0 3 Dail y

Intak e (mg/kg/day ) 1.54E-0 5

Dail y Intak e (mg/kg/day ) 4.50E-0 5 3.71E-0 4 4.72E-0 4 1.01E-0 4 7.22E-0 3

D a i l y Intak e (mg/kg/day ) 4.50E-0 5 3.71E-0 4 4.72E-0 4 1.01E-0 4 7.22E-0 3 Slop e

Facto r (mg/kg/day)

- 1 1.75E+0 0

Subchroni c R F D (mg/kg/day ) 3.00E-0 4 2.00E-0 2 3.70E-0 2 3.00E-0 4 2.00E-0 1

Chroni c R FO (mg/kg/day ) 3.00E-0 4 5.00E-0 3 3.70E-0 2 3.00E-0 4 3.00E-0 1 Carcinogeni c

Ris k 2.70E-0 5

Hazar d Quo t i en t 1.50E-0 1 1.86E-0 2 1.28E-0 2 3.37E-0 1 3.61E-0 2

Hazar d Quotien t 1.50E-0 1 7.42E-0 2 1.28E-0 2 3.37E-0 1 2.41E-0 2 Tota l

Ris k 2.70E-0 5

Hazar d Inde x

5.55E-0 1

Hazar d Inde x

5.98E-0 1CHIL D RECREATIONA L

USE R Ingestio n o f Fis h Averag e Exposur e

1 | Carcinogeni c

Ris k i Chemica l Arseni c

i | Hazar d Inde x - - Subchroni c i Chemica l Arseni c Chromiu m V I Coppe r Mercur y Z i n c

i | Hazar d Inde x - - Chroni c i Chemica l Arseni c Chromiu m V I Coppe r Mercur y Zin c 1

1 1 Chemica l Concentratio n (mg/kg ) 3.00E-0 2

l 1 1 Chemica l Concentratio n (mg/kg ) 3.00E-0 2 2.80E-0 1 3.80E-0 1 7.00E-0 2 5.62E+0 0

l I l Chemica l Concentratio n (mg/kg ) 3.00E-0 2 2.806-0 1 3.80E-0 1 7.00E-0 2 5.62E+0 0 Ingestio n Intak e Facto r (kg/kg/day ) 7.13E-0 6

Ingestio n Intak e Facto r (kg/kg/day ) 8.32E-0 5 8.32E-0 5 8.32E-0 5 8.32E-0 5 8.32E-0 5

Ingestio n Intak e Facto r (kg/kg/day ) 8.32E-0 5 8.32E-U 5 8.32E-0 5 8.32E-0 5 8.32E-0 5 O a i

l y Intak e (mg/kg/day ) 2.14E-0 7

Dail y Intak e (mg/kg/day ) 2.50E-0& 2.33E-0 5 3.16E-0 5 5.83E-J 6 4.68E-0 4

O a i l y Intak e (mg/kg/day ) 2.50E-0 6 2.33E-0 5 3.16E-0 5 5.83E-0 6 4.68E-0 4 Slop e

Facto r (mg/kg/day )
- 1 1.75E+0 0

Subchroni c R F D (mg/kg/day ) 3.00E-0 4 2.00E-0 2 3.70E-0 2 3.00E-0 4 2.00E-0 1

Chroni c R F D (mg/kg/day ) 3.00E-0 4 5.00E-0 3 3.70E-0 2 3.00E-0 4 3.00E-0 1 Carcinogeni c

Ris k 3.74E-0 7

Hazar d Quotien t 8.32E-0 3 1.17E-0 3 8.55E-0 4 1.94E-0 2 2.34E-0 3

Hazar d Quotien t 8.32E-0 3 4.66E-0 3 8.55E-0 4 1.94E-0 2 1.56E-0 3 Tota l

Ris k 3.74E-0 7

Hazar d Inde x

3.21E-0 2

Hazar d Inde x

3.48E-0 2CHIL D RECREATIONA L

USE R Ingestio n o f Fis h Reasonabl e Maximu m Exposur e

1 | Carcinogeni c

Ris k i Chemica l Arseni c

i | Hazar d Inde x - - Subchroni c i Chemica l Arseni c Chromiu m V ! Coppe r Mercur y Zin c

i | Hazar d Inde x - - Chroni c i Chemica l Arseni c Chromiu m V I Coppe r Mercur y Zin c l

1 i Chemica l Concentratio n (ing/kg ) 4.00E-0 2

1 1 I Chemica l Concentratio n <mg/kg ) 4.00E-0 2 3.30E-0 1 4.20E-0 1 9.00E-0 2 6.42E+0 0

l I i Chemica l Concentratio n (mg/kg ) 4.00E-0 2 3.30E-0 1 4.20E-0 1 9.00E-0 2 6.42E+0 0 Ingestio n Intak e Facto r (kg/kg/day ) 6.18E-0 5

Ingestio n Intak e Facto r {kg/kg/day ) 7.21E-0 4 7.21E-0 4 7.21E-0 4 7.21E-0 4 7.21E-0 4

Ingestio n Intak e Facto r (kg/kg/day ) 7.21E-0 4 7.21E-0 4 7.21E-0 4 7.21E-0 4 7.21E-0 4 O a i

l y Intak e (mg/kg/day ) 2.47E-0 6

Davl v intan e (mg/tcg/day ) 2.88E-0 5 2.38E-0 4 3.03E-Q 4 6.49E-0 5 4.63E-0 3

D a i l y Intak e (mg/kg/day ) 2.88E-0 5 2.38E-0 4 3.03E-0 4 6.49E-0 5 4.63E-0 3 Slop e

Facto r (mg/kg/day)

- 1 T.75E+0 0

Subchroni c R F D (mg/kg/day ) 3.00E-0 4 2.00E-0 2 3.70E-0 2 3.00E-0 4 2.00E-0 1

Chroni c R FD (mg/kg/day ) 3.00E-0 4 5.00E-0 3 3.70E-0 2 3.00E-0 4 3.00E-0 1 Carcinogeni c

Ris k 4.33E-0 6

Hazar d Quo t i en t 9.62E-0 2 1.19E-0 2 8.19E-0 3 2.16E-0 1 2.32E-0 2

Hazar d Quotien t 9.62E-0 2 4.76E-0 2 8.19E-0 3 2.16E-0 1 1.54E-0 2 Tota l

Ris k 4.33E-0 6

Hazar d Inde x

3.S6E-0 1

Hazar d Inde x

3.84E-0 1Intak e

Factor : SURFAC E WATE R
Description : Adul t Recreationa l Use r - Fis h Inges t io n Abbreviation : AUF G Pathwa y Type : Ingestio n o f Soi l

Intak e Facto r =
Parameters : (

I R x E F x E O x M E X F I x C F x S S ) ( B U x A T ) Carcinogeni c Abbreviatio n I R E F E D H E F I C F S S B W A T Descriptio n Ingestio n Rate(mg/day } Exposur e Freq.(dys/yr ) Exposur e Duration(yrs ) Matri x Effec t Fractio n Contaminate d Conversio n Facto r (kg/mg ) Site-specifi c Facto r Bod y Weigh t (kg ) Averagin g Tim e (dys ) A v e

15000 0 5 2 3 1 1 .00000 1 1 2 5 2555 0 R M E
15000 0 15 6 2 4 1 1 .00000 1 1 5 7 2555 0 Non

-

Carcinogeni c A v e 15000 0 5 2 3 1 1 .00000 1 1 2 5 109 5 R ME
15000 0 15 6 2 4 1 1 .00000 1 1 5 7 876 0 Intak e Facto r Calculations : Carcinogenic : Averag e Exposur e ( 1.50E+0 5 x 5.20E+0 1 x 3.00E+0 0 x 1 x 1 x 1.00E-0 6 x 1 3.66E-0 5 = (

2.50E+0 1 x 2.56E+0 4 > Carcinogenic : Reasonabl e Maximu m Exposur e ( 1.50E+0 5 x 1.56E+0 2 x 2.40E+0 1 x 1 x 1 x 1.00E-0 6 x 1 ) 3.86E-0 4 = (

5.70E+0 1 x 2.56E+0 4 ) Non-Carcinogenic :

Averag e Exposur e ( 1.50E+0 5 x 5.20E+0 1 x 3.00E+0 0 x 1 x 1 x 1.00E-0 6 x 1 ) 8.55E-0 4 = (

2.50E+0 1 x 1.10E+0 3 ) Non-Carcinogenic :

Reasonabl e Maximu m Exposur e ( 1.50E+0 5 x 1.56E+0 2 x 2.40E+0 1 x 1 x 1 x 1.00E-0 6 x 1 ) 1.12E-0 3 = Februar y 2 , 19 9 18: 1

( 5.70E+0 1 x 8.76E+0 3 )Intak e

Factor : SURFAC E WATE R Description : Chil d Recreationa l Use r - Fis h Ingestio n Abbreviation : CUF G Pathwa y Type : Ingestio n o f Soi l

Intak e Facto r = ( I R x E F x E D x M E x F I x C F x S S ) ( B U x A T ) Februar y 2 , 19 9 18: 1

Parameters : Carcinogeni c Abbreviatio n I R E F E O M E fl C F S S B U A T Descriptio n Ingestio n Rate(mg/day ) Exposur e Freq.(dys/yr ) Exposur e Duration(yrs ) Matri x Effec t Fractio n Contaminate d Conversio n Facto r (kg/mg ) Site-specifi c Facto r Bod y Weigh t (kg ) Averagin g Tim e Cdys ) A v e

8100 0 6 6 1 1 .00000 1 1 1 6 2555 0 R M E

8100 0 5 2 6 1 1 .00000 1 1 1 6 2555 0 Non

-

Carcinogeni c A v e 8100 0 6 6 1 T .00000 1 \ 1 6 219 0 R M E
8100 0 5 2 6 1 1 .00000 1 1 1 6 219 0 Intak e Facto r Calculations : Carcinogenic : Averag e Exposur e ( 8.10E+0 4 x 6.00E+0 0 x 6.00E+0 0 x 1 x 1 x 1.00E-0 6 x 1 7.13E-0 6 = C

1.60E+0 1 x 2.56E+O A ) Carcinogenic : Reasonabl e Haxirtiu m Exposur e ( 8.10E+0 4 K 5.20E+0 1 x 6.00E+0 0 x 1 x 1 x 1.006-0 6 x 1 ) 6.18E-0 5 = <

1.60E+0 1 x .2.56E+0 4 ) Non-Carcinogenic :

Averag e Exposur e ( 8.10E*0 4 x 6.00E+0 0 x 6.00E+0 0 x 1 x 1 x 1.00E-0 6 x 1 ) 8.32E-0 5 = (

1.60E+0 1 x 2.19E+0 3 ) Non-Carcinogenic :

Reasonabl e Maximu m Exposur e ( 8.10E+0 4 x 5.20E+0 1 x 6.00E+0 0 x 1 x 1 x 1.00E-0 6 x 1 ) 7.21E-0 4 = (

1.60E+0 1 x 2.19E+0 3 >Medi a

Chemica l Concentrations :

SURFAC

E WATER Februar y 2 ,
Medium : Fis h Abbreviation : FIS H Mediu m Type : Soi l Subchroni c Chronic/Carcinogeni c Chemica l Averag e

(mg/kg ) R.M.E

. (mg/kg ) Averag e

R.M.E

. (mg/kg ) (mci/kg ) Arseni c 3.00E-0 2 4.00E-0 2 3.00E-0 2 4.00E-02 Cadmiu m (food ) Chromiu m II I Chromiu m V I 2.80E-0 1 3.30E-0 1 2.80E-O f : 3.30E-0 1 Coppe r 3.80E-0 1 4.20E-0 1 3.80E-0 1 4.20E-0 1 Mercur y 7.00E-02 9.00E-02 7.QOE-0 2 9.00E-0 2 Zin c 5.62E+0 0 6.42E+0 0 5,62E+0 0 6.42E+0 0

### Appendi x A Jun e 1996__________________A-14________________943-281 9 Dat a Analysi s and Chemical s o f Concer n A n earl y ste p i n th e R A proces s wa s revie w o f chemica l dat a specifi c t o groundwate r a t th e 

### site

. Th e objectiv e o f dat a analysi s wa s t o identif y COC s relate d t o groundwater

. Dat a wer e compile d an d entere d int o a compute r database

. The analytica l dat a wer e obtained followin g th e protocol
, expresse d i n th e Wor k Pla n (Asarco
, 1991a)
, and wer e evaluate d t o identif y COCs

. Th e dat a wer e collecte d i n 199 1 and 1992

. A s describe d i n Sectio n 6.2-1 , unfiltere d metal s sample s collecte d fro m si x springs
an d fou r mini-piezometer s wer e use d t o estimat e EPCs

. COC s fo r groundwate r wer e selecte d fro m spring s an d mini-piezometer s locate d upgradien t

o f the hypothetica l exposur e point

. Chemical s tha t wer e neve r detecte d i n thes e sample s
wer e eliminate d an d include d antimony , beryllium
, chromium
, cyanide
, an d molybdenum

. EP A guidanc e recommend s tha t a detectio n frequenc y o f fiv e percent o r les s b e use d i n orde r t o exclud e chemical s o f potentia l concer n (EPA

, 1989f) ; bariu m was als o exclude d (fou r percent detectio n frequenc y or on e detec t ou t o f twenty-fou r records ) on thi s basis

. Iro n wa s exclude d based o n it s classificatio n a s a n essentia l nutrient (EPA

, 1989c)

. Metal s exclude d

a s COC s becaus e o f unavailabl e toxicit y value s wer e aluminum
, copper , manganese , and titanium

. Lea d wa s no t quantitativel y evaluate d i n thi s medium-specifi c RA

. Th e potentia l healt h impact s fro m the exposur e t o lea d wil l b e quantitate d i n a sitewide
, multi-media
, baselin e ris k


### assessment usin g th e mos t curren t EP A Integrate d Exposur e Uptake-Biokineti c (IEUBK ) lea d mode l available

. Th e us e o f thi s model account s fo r lead exposur e fro m man y source s an d predict s bloo d lea d level s wit h th e inpu t o f eithe r EP A defaul t values
, site-specifi c values
, o r
a combinatio n o f both

.

Colde r

Associate sAppendi x A Jun e 1996___________________A-15__________________943-281 9 T h e followin g si x metal s wer e quantitativel y evaluate d fo r potentia l noncarcinogeni c hazard s
an d carcinogeni c risks :

* • Arsenic ; * • Cadmium ; * Mercury ;



### + Nickel ; * • Silver ; and
,
+ Zinc. Th e resultin g analytica l result s fo r th e COC s ar e provide d i n Tabl e 6.3-1

. Al l dat a hav e bee n validate d and onl y reliabl e dat a or dat a wit h a "J " qualifie r wer e use d hi th e quantitativ e evaluatio n o f risk s fo r th e COCs

. Thi s qualifie r refer s t o dat a tha t ar e estimate d values but ar e stil l appropriat e t o us e i n quantitativ e ris k assessment (EPA

, 1989f
, 1990)

. Nondetec t dat a wer e reporte d at th e Contrac t Require d Detectio n Limi t (CRDL ) appropriatel y adjuste d fo r an y dilutions

. I n orde r t o quantif y analyt e averag e an d reasonabl e maximu m exposur e (RME ) concentrations , a valu e o f on e hal f th e CRD L wa s use d whe n th e 

### analyt e wa s reporte d a s no t bein g detected

. Th e arithmeti c mea n analyt e concentration s wer e use d t o represen t EPC s i n th e calculation s o f ris k fo r average exposur e an d th e 9 5 percen t uppe r confidenc e limi t on th e arithmeti c mea n analyt e concentration s wer e use d t o represen t EPC s i n the calculation s o f the RM E scenari o (EPA

, 1992d)

. Toxicit y Assessmen t The purpos e o f th e toxicit y assessmen t i s t o evaluat e th e toxicit y o f source-relate d COC s an d t o estimat e th e dose-respons e relationshi p fo r eac h o f thes e chemicals

. Th e informatio n

Colde r Associate sAppendi x A Jun e 1996___________________A-16_________________943-281 9 

### obtaine d i n th e toxicit y assessmen t i s combined wit h estimate d contaminan t intake s calculate d

a s par t o f the exposur e assessment t o estimat e the potentia l exces s lifetim e cance r risk s and 

### potentia l noncarcinogeni c healt h hazard s (EPA

, 1989f)

. Th e Referenc e Dos e (RfD ) an d Slop e Facto r (SF ) value s use d i n thi s R A wer e obtaine d fro m th e followin g sources :

+ EPA' s Integrate d Ris k Informatio n Syste m (IRIS ) (EPA

, 1992e ) on-lin e databas e syste m

> EPA' s Healt h Effect s Assessmen t Summar y Table s (EPA

, 1992f ) 

### The EP A ha s develope d variou s type s o f RfD s dependin g o n the exposur e rout e (ingestio n o r inhalation)
, th e critica l effect
, an d th e lengt h o f exposur e bein g evaluate d (chroni c o r subchronic)

. Th e EP A base s th e Rf D on th e mos t sensitiv e anima l specie s teste d (i.e.
, th e specie s tha t experiences advers e effect s a t th e lowes t dose)

. The EP A define s a chroni c Rf D a s an estimat e o f a dail y exposur e leve l tha t i s unlikel y t o resul t i n deleteriou s effect s durin g a lifetim e fo r th e huma n populatio n (7 0 years , accordin g t o EP A guidance)

. A chroni c Rf D i s use d t o evaluat e th e potentia l noncarcinogeni c hazard s associate d wit h long-ter m contaminan t exposure s ( 7 year s t o a lifetime)

. Subchroni c RfD s hav e bee n develope d t o characteriz e potentia l noncarcinogeni c hazard s associate d wit h short-ter m contaminan t exposures

. Th e EP A define s subchroni c exposur e a s period s rangin g fro m tw o week s t o seve n year s (EPA

, 1989f)

. Subchroni c RfD s generall y ten d t o b e on e order o f magnitud e highe r tha n chroni c RfD s becaus e o f th e shorte r exposur e 

### duration

. Althoug h not a COC

, sulfat e can contribut e an offensiv e odo r and tast e t o drinkin g water

. Despit e sulfat e currentl y not havin g a n MCL

, a secondar y MC L base d o n odo r an d aestheti c
Colde r Associate s

### Appendi x A Jun e 1996___________________A-17_________________943-281 9 qualit y doe s exist

. This secondar y MC L (SMCL ) i s fa r exceeded b y the EPC s (averag e and RME ) foun d i n th e mini-piezometer s an d th e springs considere d i n th e R A discusse d i n Sectio n 6.5.5

. Sulfate ha s bee n detecte d a t elevate d level s i n th e groundwate r sample d fro m th e spring s an d 

### mini-piezometer s use d i n thi s R A (averag e concentratio n o f 1,38 4 mg/1)

. Th e EP A ha s establishe d a SMC L fo r sulfat e o f 25 0 mg/1

. Again
, thi s SMC L i s base d o n aestheti c effect s (i.e.
, tast e and odor ) and i s not healt h base d (5 5 F R 143 , Jul y 25 , 1992)

. N o chroni c healt h effect s hav e bee n associate d wit h long-ter m exposur e t o elevate d level s o f sulfate
, however
, sulfat e ca n hav e advers e acut e effects

. Exposur e t o hig h level s o f sulfat e h i drinkin g wate r can lea d t o an osmoti c diarrhea

. Thi s effec t ease s an d disappear s a s th e perso n become s acclimate d t o th e hig h level s o f sulfate

. 

### Thi s effec t h i infant s ma y lea d t o dehydratio n an d i s a potentia l concern . EP A ha s no t establishe d an y health-base d maximu m contaminan t leve l MC L o r RfD s fo r sulfat e (5 7 F R 138 , Jul y 17 , 1992)

. However
, level s o f sulfat e a s measure d i n th e spring s and mini

piezometer s use d i n th e R A woul d mor e than likel y b e offensive

. I t i s doubtfu l that unfiltere d groundwate r o f sulfurou s odo r an d likel y discoloratio n woul d b e consumed

. 

### Chemical s wit h hig h SF s an d lo w RfD s exhibi t highe r toxicities

. Tabl e 6.4- 1 summarize s 

### toxicit y value s use d i n th e R A fo r th e selecte d COCs

. Ris k Characterizatio n Ris k characterizatio n i s th e fina l ste p o f th e R A process

. I n thi s step , th e toxicit y factor s (RfD s an d SFs ) fo r th e COC s ar e applie d i n conjunctio n wit h estimate d chemica l intake s t o predic t noncarcinogeni c an d carcinogeni c healt h risk s t o expose d individuals

.

Golde r Associate s

### Appendi x A Jun e 1996

_____________________ A-18

___________________ 943-281

9 Th e potentia l fo r noncarcinogeni c effect s i s characterize d b y comparin g estimate d chemica l 

### intake s wit h chemical-specifi c RfDs

. Thi s measur e i s know n a s th e hazar d quotien t (H.Q. ) fo r a singl e chemica l o r th e hazar d inde x (H.I. ) fo r multipl e chemicals

. Potentia l carcinogeni c effect s ar e characterized i n term s o f th e incrementa l o r exces s probabilit y tha t

a n individua l wil l develo p cance r i n hi s o r he r lifetim e du e t o th e modele d exposure

. Exces s
cance r ris k i s estimate d fro m th e projecte d lifetim e intake s and th e cance r slop e factor
, whic h represent s a n upper-boun d estimat e o f the dose-respons e relationship

. I n thi s RA

, subchroni c ( 2 week s t o 7 years ) H.I. s ar e th e appropriat e indicato r o f potentia l

non-cance r advers e effect s fo r th e averag e Chil d Resident exposur e ( 6 years)
, th e RM E Chil d Residen t exposur e ( 6 years)
, and the averag e Adul t Residen t ( 3 years)

. The chroni c H.I

. i s the appropriat e indicato r fo r the RM E Adul t Resident becaus e the exposur e duratio n i s 2 4 year s (whic h i s greate r than th e 7-yea r cutof f betwee n subchroni c an d chroni c timespans)

. However
, whe n th e chil d an d adul t scenario s ar e summe d t o represen t continuou s exposur e
o f one individua l ove r bot h age group s (e.g.
, birt h throug h 9 year s for averag e and birt h throug h 3 0 year s fo r RME)

, th e chroni c H.I. s ar e summe d a s th e appropriat e indicator s o f

non-cance r ris k fo r timespan s exceedin g 7 years
. Hazar d Inde x fo r Noncarcinogeni c Effect s Th e potentia l fo r adverse noncarcinogeni c effect s resultin g fro m exposur e t o a chemica l o f

concer n i s evaluate d b y comparin g th e averag e dail y intak e o f th e chemica l (expresse d a s mg/kg-day ) t o a referenc e dos e (expresse d a s mg/kg-day)

. The resultin g rati o i s calle d a H.Q

. (EP A 1989f)

. I t i s derive d i n th e followin g manner :

x T „ . ~ . . . Chemical Intak e (mg / kg

- day ) Noncance r Hazar d Quotien t = ——————————————

— Rf D (mg / kg

- day ) (6

_ 1

}

Colde r Associate sAppendi x A Jun e 199 6
___________________

A-1 9
_________________

943-281 9 Use o f th e Rf D assume s a leve l o f intak e (th e RfD ) belo w whic h i t i s unlikel y tha t eve n sensitiv e individual s wil l experienc e advers e healt h effect s ove r a lifetim e o f exposure

. I f th e 

### averag e dail y intak e exceed s th e Rf D (tha t is, i f th e H.Q

. exceed s 1.0)
, ther e ma y b e caus e fo r concer n fo r potentia l noncance r effects

. I t shoul d b e noted
, however
, tha t th e leve l o f

concer n doe s no t increas e linearl y a s th e Rf D i s approache d o r exceeded

. This i s becaus e al l RfD s ar e no t equall y accurat e an d ar e no t base d o n th e sam e severit y o f toxi c effects

. Thus
, th e slope s o f th e dose-respons e curv e i n exces s o f th e Rf D ca n var y widel y dependin g o n th e 

### substance

. Furthermore
, i t mus t b e emphasize d tha t th e H.Q

. doe s no t represen t a statistica l probabilit y o f a n effec t occurrin g (EPA

, 1989f)

. T o asses s th e overal l potentia l fo r advers e healt h effect s pose d b y exposur e t o multipl e chemicals
, th e H.Q

. s fo r eac h chemica l o f concer n associate d wit h a give n exposur e pathwa y


### ar e summed

. The resultin g sum i s referre d t o b y EP A a s the H.I

. The H.I

. approac h

assume s tha t multipl e subthreshol d exposure s t o severa l chemical s coul d resul t i n a n advers e healt h effect

. Th e H.I

. i s expresse d a s follows : H.I

. = Ej/RfD ! + E2/RFD 2 .. . + Ej/RfD j (6-2 ) where : 

### E j = Exposur e leve l (o r intake ) fo r toxican t i RfD j = Referenc e dos e fo r toxican t i Wher e a recepto r ma y b e subjec t t o multipl e exposur e pathway s (e.g.
, inhalatio n o f particulate s an d ingestio n o f soils)
, th e individua l H.I. s fro m al l relevant pathway s ar e summe d t o obtai n the total H.I

. for tha t receptor

. This R A ha s onl y one complet e exposur e pathway : th e ingestio n o f groundwater

. Fo r multipl e chemica l exposures , th e tota l H.I

. migh t excee d 1.0 , eve n i f no singl e chemica l intak e exceed s it s RfD

. I f the total H.I

. i s less 

### tha n 1 .0 , cumulativ e exposure s t o th e COC s a t th e sit e ar e judge d unlikel y t o resul t i n a n advers e effect

. I f the su m i s greate r than 1.0 , a mor e detaile d an d critica l evaluatio n o f the
Colde r Associate sAppendix A Jun e 1996___________________A-20_________________943-281 9 

### risk s i s require d t o ascertai n i f th e cumulativ e exposur e woul d i n fac t b e likel y t o har m expose d individual s (EP A 1989'f)

. Th e evaluatio n ma y includ e consideratio n o f specifi c targe t organ s affecte d an d mechanism s o f toxi c action o f the COCs

. T h e assumptio n o f additiv e effect s reflecte d in th e cumulativ e H.I

. i s mos t properl y applie d t o substance s tha t induc e th e sam e effec t b y th e sam e mechanis m (EPA

, 1989f)

. Consequently

, applicatio n o f th e equatio n t o a mixtur e o f substance s that are no t expecte d t o induce th e sam e typ e o f effect s coul d overestimat e th e potentia l fo r advers e healt h effects

. 

### Th e H.I

. provides a roug h measur e o f potentia l toxicity , bu t i t i s conservativ e an d dependen t

o n th e qualit y o f th e experimenta l evidence

. Sinc e th e H.I

. doe s no t defin e dose-respons e 

### relationships
, it s numerica l valu e canno t b e construe d a s a direc t estimat e o f ris k (EPA

, 1989f)
, bu t onl y a s a leve l o f concern . Carcinogenic Ris k 

### Carcinogeni c risk s ar e estimate d a s th e incrementa l probabilit y o f a n individua l developin g
cance r ove r a lifetim e a s a resul t o f exposur e t o a potentia l carcinogen

. Th e numerica l estimat e o f exces s lifetim e cance r ris k i s calculate d b y multiplyin g th e chemica l intak e average d ove r a lifetim e b y th e cance r slop e facto r (SF ) as follows : Ris k = Chemica l Intak e (mg/kg-day ) x S F (mg/kg-day)" 1 (6-3

) Th e EP A slop e factor s ar e 95t h percen t uppe r confidenc e limi t o f th e probabilit y o f respons e per uni t intak e o f chemica l ove r a lifetime

. Slop e factor s are base d on experimenta l anima l dat a an d epidemiologica l studies whe n available

. A linea r nonthreshol d mathematica l mode l 

### fo r low-dos e extrapolation
, th e linearize d multistag e model
, i s use d t o calculat e a numerica l slop e facto r value

. EP A state s tha t carcinogeni c risk s estimate d usin g thi s approac h are

Colde r Associate sAppendi x A Jun e 1996___________________A-21______________943-281 9 upper-boun d estimates

. Thi s mean s tha t th e actua l ris k i s likel y t o b e les s tha n th e predicte d 

### ris k (EPA

, 1989f)

. EP A guidanc e t o evaluat e cance r ris k fro m simultaneou s exposur e t o severa l carcinogen s assume s tha t incrementa l cance r risk s ar e additive

. Th e concep t tha t cance r risk s ar e additiv e i s base d o n a numbe r o f assumptions

. I f thes e assumption s ar e incorrect , over - o r under

estimatio n o f th e actua l ris k coul d resul t (EPA

, 1989f)

. Th e total cance r ris k i s estimate d b y 

### summin g the risk s estimate d fo r eac h chemica l o f concer n and fo r eac h pathway

. EP A polic y mus t b e considere d i n orde r t o interpre t th e significanc e o f th e cance r ris k estimates

. Curren t EP A guidanc e states tha t wher e th e cumulativ e sit e ris k t o a n individua l base d o n reasonabl e maximu m exposur e i s les s tha n 1 x 10" 4

, action i s generall y no t warrante d (EPA

, 1991b)

. A carcinogeni c ris k leve l o f 1 x 10" 4 wa s therefor e use d a s th e 

### appropriat e ris k leve l fo r evaluatio n o f potentia l exposures i n thi s RA

. Ris k Quantificatio n Th e potentia l fo r noncarcinogeni c healt h effect s du e t o a chemica l o f concern , expresse d a s a H.Q.

, i s calculate d usin g th e followin g format : [ ( Chemica l Intak e

) Dail y ] Rf D Concentratio n X Facto r = Intak e X (mg/kg-day ) = Hazar d (mg/y ) (y/kg

-

(mg/kg

-

Quotient day ) day

) Wher e y = specifi c amoun t (weigh t o r volume ) o f medium i n whic h th e chemica l i s measured ; the unit s o f whic h ar e mediu m dependent

. Fo r example
, a chemica l i n soi l ma y b e reporte d i n mg/k g an d i n wate r h i mg/liter

. 

### Averag e o r RM E concentration s o f eac h noncarcinogeni c chemica l o f concer n ar e multiplie d 

### b y th e pathway-specifi c intak e factor s t o yiel d an averag e or RM E dail y intake

. Th e dail y
Colde r Associate s

### Appendi x A Jun e 1996___________________A-22__________________943-281 9 intak e i s then divide d b y th e Rf D t o obtai n th e H.Q

. for averag e or reasonabl e maximu m 

### exposures

. Individua l H.Q. s are summe d for al l chemical s i n a n exposur e pathwa y t o provid e a pathway

specifi c H.I

. Pathway-specifi c indexe s ar e summe d t o obtai n th e tota l H.I

. fo r al l exposur e 

### pathway s applicabl e t o a give n receptor

. Fo r thi s RA

, onl y th e exposur e pathwa y o f ingestio n o f groundwate r wa s considered

. H.I. s fo r eac h recepto r an d pathwa y ar e summarize d i n Sectio n 6.5.2

. H.I. s ar e calculate d 

### fo r chroni c and subchroni c exposures fo r al l receptor s at the exposur e poin t selected

. Ris k calculation s ar e presente d i n Appendix H

. Th e potentia l fo r carcinogeni c effects
, expresse d a s exces s cance r risk
, ar e calculate d by : 

### [( Chemica l Lifetim e

) Lifetim e ] Slop e Facto r Exces s Concentratio n X Intak e = Dail y X (mg/kg-day)"

1 = Cance r 

### (mg/y ) Facto r

Intak e

Ris

k (y/kg-day ) (mg/kg



### day ) 

### Wher e y = specifi c amoun t (weigh t o r volume ) o f a medium i n whic h th e chemica l i s measured ; th e unit s o f whic h ar e medium dependent

. 

### Concentration s o f eac h potentia l carcinogen ar e multiplie d b y pathway : 

### specifi c intak e factor s t o yiel d a lifetim e dail y intake

. Th e dail y intak e i s the n multiplie d b y th e slop e facto r t o obtai n a numerica l estimat e o f exces s cance r risk

. The cance r risk s ar e the n summe d fo r al l o f th e chemical s evaluate d fo r eac h exposur e pathway

. T o determin e th e tota l carcinogeni c ris k t o a give n receptor , th e cancer risk s fo r
eac h exposur e pathwa y ar e summed

. However
, onl y the exposur e pathwa y o f groundwate r ingestio n wa s considere d i n thi s RA

. Carcinogeni c risk s fo r averag e an d RM E condition s ar e presente d i n Tabl e 6.5-1

. Cance r ris k calculation s ar e show n i n Appendi x H

.
Colde r Associate s

# ASARC O

GLOB E PLAN T Jun e 28 , 199 6 Ms

. Rebecc a Thoma s Remedial Projec t Manage r U.S

. EP A Region VII I 999 18t h Street

, Suit e 50 0 Denver

, Colorad o 80202-240 5 R E : GROUNDWATE R

BASELIN E HUMA N HEALT H RIS K ASSESSMEN T Dea r Rebecca : Enclose d pleas e fin d 4 copies o f Asarco' s Groundwate r Baselin e Huma n Healt h Ris k Assessmen t fo r th e Californi a Gulch Superfun d Site

, Leadville

, Colorado

. Pleas e not e tha t thi s documen t wa s previousl y include d a s Sectio n 6. 0 o f the Hydrogeologi c Remedia l Investigatio n (RI)

. I n respons e t o EP A comments , th e groundwate r ris k assessmen t sectio n wa s remove d fro m the Hydrogeologi c R I and therefor e i s transmitte d separatel y wit h thi s letter

. Sincerely

, Margare t (Poppy ) Stau b Sit e Manage r 4 copie s sen t

cc : Rus s Alien
, CDPH E Mauree n Yaskanin
, Golde r Assoc

. Scot t Ronzio

, Golde r Assoc

. Bo b Comer

, Asarc o

19\2819swri.lt r

ASARC O

Incorporated

. 49 5 Eas t 51s t Avenue

. Denver

. Colorad o 8021 6 209 8 Phon e (303 ) 296-590 0 FA X (303 ) 29 6 050 8