Expert Systems for Environmental Applications - ACS Publications

Chapter 15

The Defense Priority Model for Department of Defense Remedial Site Ranking

Downloaded by NATL UNIV OF SINGAPORE on May 5, 2018 | https://pubs.acs.org Publication Date: July 5, 1990 | doi: 10.1021/bk-1990-0431.ch015

Judith M. Hushon Roy F. Weston, Inc., 955 L'Enfant Plaza, S.W., Sixth Floor, Washington, DC 20024

The Defense Priority Model (DPM) i s designed to provide an estimate of the relative potential risk to human health and the environment from sites containing hazardous materials. The DPM evolved from a model called the Hazard Assessment Risk Model (HARM) developed by Oak Ridge National Laboratory from 1984-1986 for the A i r Force. The automation of DPM was done f i r s t i n KES(r) and then in Arity Prolog(r) for use on an IBM-PC/AT class machine. The computerized model has already become more sophisticated than the paper model and as development continues, it i s possible to take advantage of additional expert system features. This paper i s designed as a case study of DPM development and presents the reasons for the choice of expert system environment and its evolution, the current scope of the model, and planned additions that w i l l increase the functionality of model i n the future. The methodology used to evaluate this expert system i s also described. Work on what i s now the Defense P r i o r i t y Model was i n i t i a t e d i n 1984 when t h e U.S. A i r F o r c e r e c o g n i z e d t h e need f o r a d e f e n s i b l e methodology f o r r a n k i n g f o r c l e a n u p s i t e s c o n t a i n i n g hazardous w a s t e s . The o r i g i n a l work was conducted by Barnthouse and h i s c o l l e a g u e s a t Oak Ridge N a t i o n a l L a b o r a t o r y and r e s u l t e d i n the development o f t h e Hazard Assessment R i s k Model (HARM). (1,2) T h i s model was t h e n e v a l u a t e d u s i n g c o m p a r a t i v e t e s t i n g by a number o f r e v i e w e r s and t h e r e s u l t s l e d t o t h e i n c o r p o r a t i o n o f a number o f changes and t h e development o f HARM 11.(3) HARM I I c o n s i d e r e d t h e t o x i c i t y and q u a n t i t y o f t h e p o l l u t a n t s p r e s e n t , two exposure r o u t e s - s u r f a c e and ground w a t e r , and human and ecological receptors. To o b t a i n a s i g n i f i c a n t s c o r e , a s o u r c e , a pathway and a r e c e p t o r a l l h a d t o e x i s t s i n c e t h i s ensured t h a t exposure was a p o s s i b i l i t y . 0097-6156/90/0431-0206$06.00/0 © 1990 American Chemical Society

Hushon; Expert Systems for Environmental Applications ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

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Defense Priority Model

207


The A i r F o r c e d e t e r m i n e d t h a t the model needed t o be c o m p u t e r i z e d t o be m a x i m a l l y u s e f u l . They i n i t i a l l y c o n s i d e r e d u s i n g dBase o r L o t u s s o f t w a r e f o r i m p l e m e n t i n g the model, b u t t h e n d e c i d e d t h a t e x p e r t systems t e c h n o l o g y c o u l d p r o v i d e some d e f i n i t e advantages such as the a b i l i t y t o : ο

Incorporate

uncertainty

ο

Accommodate m i s s i n g

ο

Use a l t e r n a t i v e pathways required factor

ο

Manage f l o w t h r o u g h the program so t h a t o n l y q u e s t i o n s are asked o f the u s e r

ο

Include user

ο

I n c l u d e b o t h q u a n t i t a t i v e and q u a l i t a t i v e d a t a i n the scoring process.

expert

data t o obtain

an i n d i c a t i o n o f a

appropriate

knowledge and make t h i s a v a i l a b l e t o t h e

site

S e l e c t i o n o f the Programming Environment The A i r Force wanted the model t o be u s e a b l e by a l a r g e number o f g e o g r a p h i c a l l y d i v e r s e u s e r s so t h e IBM-PC/AT was s e l e c t e d as t h e l o g i c a l d e l i v e r y environment. A number o f e x p e r t system s h e l l s were then examined and K E S ( r ) by S o f t w a r e A&E was s e l e c t e d . U s i n g t h i s s o f t w a r e , a p r o t o t y p e o f the system was c o n s t r u c t e d and demonstrated. T h i s p r o t o t y p e modeled exposure from o n l y t h e s u r f a c e w a t e r exposure r o u t e s p l u s t h e accompanying h a z a r d and r e c e p t o r s c o r i n g . I t was p o s s i b l e t o c o m p i l e t h i s s i n g l e pathway, but when attempts were made t o add a second pathway s c o r i n g t o i n c l u d e ground w a t e r exposure, the program became too l a r g e t o c o m p i l e . KES a l s o p l a c e d severe l i m i t a t i o n s on s c r e e n management. A d e c i s i o n was t h e r e f o r e reached t h a t t h e code w o u l d be t r a n s l a t e d i n t o p r o l o g . A r i t y P r o l o g ( r ) was s e l e c t e d because i t i s the most complete and p o w e r f u l o f the PC-based p r o l o g c o m p i l e r s . The e f f o r t i n v o l v e d i n c h a n g i n g development environments was m i n i m i z e d somewhat by p r e p a r i n g d e f i n i t i o n s f o r t h e p r o l o g v e r s i o n t h a t r e c o g n i z e d the KES grammar and code p r e p a r e d t o d a t e . However, u s i n g a language r a t h e r t h a n a s h e l l meant t h a t a number o f program segments f o r s c r e e n management, f i l e a c c e s s , e t c . had t o be w r i t t e n w h i c h had p r e v i o u s l y been a c c o m p l i s h e d by KES. Development proceeded and i n the F a l l o f 1988, a v e r s i o n o f the code t h a t i n c l u d e d a l l o f the f e a t u r e s o f HARM I I was a v a i l a b l e f o r t e s t i n g (DPM v e r s i o n 1.0). A t t h i s t i m e , the name o f the model was a l s o changed t o the Defense P r i o r i t y Model (DPM) and i t was adopted by t h e O f f i c e o f t h e Deputy A s s i s t a n t S e c r e t a r y o f Defense (Environment) f o r u n i f o r m use by the armed s e r v i c e s t o rank s i t e s f o r r e m e d i a l a c t i o n i n F i s c a l year-1990 ( 4 ) .


E X P E R T SYSTEMS FOR ENVIRONMENTAL APPLICATIONS

208


Evaluation The comparative t e s t i n g o f t h e automated DPM v e r s i o n 1.0 was done by a team o f s c i e n t i s t s i n c l u d i n g two each o f l i f e scientists, g e o l o g i s t s , and e n v i r o n m e n t a l e n g i n e e r s . F i v e s i t e s a t each o f t h r e e m i l i t a r y i n s t a l l a t i o n s were s e l e c t e d and c o p i e s o f t h e a p p r o p r i a t e I n s t a l l a t i o n R e s t o r a t i o n Program (IRP) Phase I I r e p o r t s (Remedial I n v e s t i g a t i o n s / F e a s i b i l i t y S t u d i e s ) were made a v a i l a b l e t o t h e r e v i e w e r s a l o n g w i t h a copy o f t h e c u r r e n t u s e r ' s manual and a d i s k c o n t a i n i n g t h e code. Each s i t e was s c o r e d by two r e v i e w e r s r e p r e s e n t i n g d i f f e r e n t d i s c i p l i n e s . The e v a l u a t o r s were g i v e n a oneday c o u r s e i n DPM and h o t l i n e a s s i s t a n c e was p r o v i d e d d u r i n g t h e e v a l u a t i o n p e r i o d . The s c o r e s were then c o l l e c t e d and summary t a b l e s prepared. When d i f f e r e n c e s i n s c o r i n g were n o t e d between two e v a l u a t o r s , they were q u e s t i o n e d as t o why each had made h i s / h e r s e l e c t i o n . S e v e r a l sources o f d i f f e r e n c e s were i d e n t i f i e d : ο

One r e v i e w e r used h i s d i s c i p l i n a r y knowledge t o i n t e r p r e t the a v a i l a b l e d a t a and r e a c h a c o n c l u s i o n w h i l e t h e o t h e r d i d n o t have t h i s s p e c i a l knowledge.

ο

E r r o r s were made c o n v e r t i n g u n i t s .

ο

D e f i n i t i o n s were n o t as c l e a r as they might have been and d i f f e r e n t c o n c l u s i o n s were reached by two e v a l u a t o r s as t o how a v a r i a b l e s h o u l d be s c o r e d .

ο

Reviewers d i f f e r e d i n t h e i r r e a d i n g o f map d i s t a n c e s .

A d d i t i o n a l l y , t h e e v a l u a t o r s made s u g g e s t i o n s on how t o improve t h e f u n c t i o n a l i t y o f t h e program t o make i t more u s e r f r i e n d l y . The agreement among t h e i n i t i a l r e v i e w e r s was m o d e r a t e l y good, w i t h t h e s i t e s r a n k i n g i n t h e same o r d e r , b u t t h e i n d i v i d u a l s c o r e s v a r i e d by more than was f e l t t o be d e s i r a b l e . T h i s prompted a number of changes i n d e f i n i t i o n s and program s t r u c t u r e . F o r example, two s c o r e r s l o o k e d a t a s i t e map and one f e l t t h a t t h e d i s t a n c e t o a w e l l was 2.9 m i l e s (which gave a s c o r e o f 1) and t h e o t h e r f e l t t h a t t h e d i s t a n c e was 3 m i l e s (which was o u t s i d e t h e s c o r i n g boundary and was g i v e n a s c o r e o f 0 ) . As a r e s u l t , t h e d i s t a n c e from a t a r g e t t o a r e c e p t o r was m o d i f i e d t o i n c l u d e a m a t r i x o f p o p u l a t i o n s i z e by d i s t a n c e from t h e s i t e t o t h e w e l l . I n a d d i t i o n t o these changes, s e v e r a l a d d i t i o n a l major a d d i t i o n s were made t o t h e model a t t h e s u g g e s t i o n o f o u t s i d e r e v i e w e r s : ο

An a i r / s o i l pathway was added

ο

Some exposure d i s t a n c e s were extended by i n t r o d u c i n g m a t r i c e s f o r s c o r i n g so- t h a t t h e s c o r e was a f u n c t i o n o f the number o f people as w e l l as t h e d i s t a n c e from the s i t e

ο

Automatic look-up was added.

o f m e t e o r o l o g y d a t a f o r A i r Force bases


15.

HUSHON


209

The f i r s t a d d i t i o n was a major one w h i c h i n v o l v e d s i g n i f i c a n t r e s e a r c h t o determine how b e s t t o d e a l w i t h v o l a t i l e s and a i r / d u s t emissions. These a d d i t i o n s were f u l l y implemented i n the v e r s i o n o f DPM t h a t was r e l e a s e d f o r e v a l u a t i o n i n March 1989.


A d d i t i o n a l l y , a number o f new f e a t u r e s were i n c l u d e d i n t h e c o m p u t e r i z e d v e r s i o n t o make i t more f u n c t i o n a l ( 5 ) ; these i n c l u d e the a b i l i t y to: ο

Answer a q u e s t i o n one time even i f i t i s used i n s e v e r a l s e p a r a t e pathways and c a l c u l a t i o n s

ο

Record c e r t a i n t y o f i n p u t

ο

Automatically convert u n i t s

ο

Use a l t e r n a t e d a t a i f i n f o r m a t i o n are m i s s i n g

ο

Check range o f i n p u t d a t a , and

ο

Change responses and t o r a p i d l y r e c a l c u l a t e a f i n a l

data

score

The automated v e r s i o n can a l s o g e n e r a t e a r e p o r t t h a t i n c l u d e s , i n a d d i t i o n t o t h e s c o r e s , f u l l documentation o f the f i n a l s c o r e t h r o u g h comments and the c e r t a i n t y i n d i c a t i o n . A d d i t i o n a l l y , the automated v e r s i o n c o n t r o l s the u s e r ' s passage t h r o u g h the model and o n l y p r e s e n t s those r e q u e s t s f o r i n f o r m a t i o n t h a t are deemed n e c e s s a r y depending on p r e v i o u s l y s u p p l i e d answers. Overview o f the Model S t r u c t u r e DPM c o n s i d e r s the h a z a r d s a s s o c i a t e d w i t h source m a t e r i a l s , pathways t h a t may r e s u l t i n e x p o s u r e , and t h e presence o f p o t e n t i a l receptors.(6) There are t h r e e pathways i n DPM: ο

Surface water

ο

Ground w a t e r

ο

Air/Soil

( c o n s i d e r s v a p o r i z e d compounds and

dust).

DPM c o n s i d e r s b o t h human and e n v i r o n m e n t a l r e c e p t o r s , though the human r e c e p t o r s are more h i g h l y w e i g h t e d . The e n v i r o n m e n t a l r e c e p t o r s i n c l u d e b o t h a q u a t i c and t e r r e . s t r i a l p o p u l a t i o n s as a p p r o p r i a t e . F i g u r e 1 demonstrates how the v a r i o u s pathway s c o r e s are combined to y i e l d the s i x p a t h w a y / r e c e p t o r s c o r e s per s i t e . These s i x s c o r e s are t h e n combined u s i n g a r o o t mean square methodology t o o b t a i n a s i n g l e s i t e s c o r e (see F i g u r e 2 ) . A l l s c o r e s are n o r m a l i z e d so t h a t they range from 0 t o 100; t h i s s c o r e , by i t s e l f , has no meaning and s h o u l d not be compared t o the Hazard Ranking System (HRS) ranking number f o r i n c l u s i o n on the N a t i o n a l P r i o r i t y L i s t (NPL). Most s i t e s e v a l u a t e d t o date s c o r e d i n the 20 t o 30 range, but s i t e s have s c o r e d as h i g h as 89 and as l o w as 3 so a b r o a d range o f v a l u e s can be expected.(7)



Compute Receptor Score

Compute Hazard Score

Contamination Observed

No

Yes

Normalized Human Receptors Score Normalized Ecological Receptors Score

Human Receptors Score

Ecological Receptors Score

F i g u r e 1. How Pathway Scores a r e Computed

Normalized Ecological Hazard Score

Normalized Health Hazard Score

•

Pathway Score

Ecological Hazard Score

Health Hazard Score

Compute Pathway Score Based on Characteristics

Assign Pathway Score of 100 Pathway Human Health Score

Pathway Ecological Score

\ A



X5

Surlace Waler Human Health Score

Surface Water Ecological Score

F i g u r e 2.

Ground Water Ecological Score

How S i t e S c o r e s are Computed

Overall Site Score

X5

Ground Water Human Health Score

X5

Air/Soil Human Health Score


Air/Soil Ecological Score

E X P E R T SYSTEMS FOR

212

E N V I R O N M E N T A L APPLICATIONS


Pathways To b e t t e r u n d e r s t a n d what i s i n c l u d e d i n the pathway s c o r e s , i t i s n e c e s s a r y t o examine each pathway more c l o s e l y w i t h r e g a r d t o the types o f d a t a t h a t are i n c l u d e d . Each pathway s c o r e i s computed by s c o r i n g a number o f r e l a t e d f a c t o r s ; d i f f e r e n t f a c t o r s have d i f f e r e n t weights. The f a c t o r s c o r r e s p o n d t o i n d i v i d u a l measureable r e l a t e d v a r i a b l e s such as f l o o d i n g p o t e n t i a l and net p r e c i p i t a t i o n as components o f the s u r f a c e w a t e r pathway.. The approach used i s t o o b t a i n a s c o r e f o r each v a r i a b l e and t o m u l t i p l y t h i s s c o r e by a preestablished weight. The w e i g h t e d s c o r e s f o r a l l f a c t o r s i n a pathway are then added and d i v i d e d by the maximum p o s s i b l e s c o r e t o o b t a i n a n o r m a l i z e d v a l u e . F o r each o f the pathways, i f a c h e m i c a l r e l e a s e i s observed i n t h a t pathway, a maximum s c o r e i s a s s i g n e d . However, t h i s s c o r e can be m o d i f i e d by a w e i g h t i n g based on how w e l l the waste/hazard i s c o n t a i n e d . S u r f a c e Water Pathway. The s u r f a c e w a t e r pathway o f DPM r a t e s the p o t e n t i a l f o r contaminants from a waste s i t e t o e n t e r s u r f a c e w a t e r s v i a o v e r l a n d f l o w r o u t e s , o r from ground w a t e r d i s c h a r g e t o s u r f a c e w a t e r . I f p o l l u t a n t s are n o t d i r e c t l y observed i n s u r f a c e w a t e r , but are p r e s e n t i n sediments o r s o i l , t h e r e i s a p o t e n t i a l f o r s u r f a c e w a t e r c o n t a m i n a t i o n so i t i s n e c e s s a r y t o c o l l e c t i n f o r m a t i o n from w h i c h t h e i r l i k e l i h o o d t o r e a c h a r e c e p t o r can be e s t i m a t e d . The f o l l o w i n g v a r i a b l e s are s c o r e d t o p r o v i d e an i n d i c a t i o n o f t h i s exposure p o t e n t i a l : ο

d i s t a n c e to nearest surface water (scores are assigned to a m i l e )

ο

net p r e c i p i t a t i o n

ο

surface erosion particle size)

ο

rainfall

ο

surface permeability

ο

flooding potential (location within floodplain)

potential

(combination

of

slope

up

and

intensity

The most h e a v i l y w e i g h t e d f a c t o r i s f l o o d i n g p o t e n t i a l w i t h n e t p r e c i p i t a t i o n r e c e i v i n g the l e a s t w e i g h t . The containment o f the waste i s a l s o e s t i m a t e d by the s c o r e r based on guidance and becomes an i m p o r t a n t w e i g h t i n g f a c t o r . Containment i s a f u n c t i o n o f the type o f s i t e ( e.g., o l d l a n d f i l l , f i r e t r a i n i n g a r e a , lagoon) and the e f f i c i e n c y o f p r e s e n t p o l l u t i o n c o n t r o l measures. Ground Water Pathway. The ground w a t e r pathway ranks the p o t e n t i a l f o r p o l l u t a n t exposure t o o c c u r from contaminated ground w a t e r . If a c t u a l ground w a t e r c o n t a m i n a t i o n has n o t been d e t e c t e d , but t h e r e i s contamination i n s o i l or surface water, there i s a p o t e n t i a l f o r ground w a t e r c o n t a m i n a t i o n t o o c c u r i n the f u t u r e . The f o l l o w i n g f a c t o r s a r e s c o r e d t o o b t a i n a ground w a t e r pathway s c o r e :



15.

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213


ο

depth t o s e a s o n a l h i g h ground w a t e r

ο

p e r m e a b i l i t y o f the u n s a t u r a t e d zone

ο

i n f i l t r a t i o n p o t e n t i a l (measured from n e t p r e c i p i t a t i o n and the form o f the waste)

ο

p o t e n t i a l f o r d i s c r e t e f e a t u r e s i n the u n s a t u r a t e d zone t o " s h o r t c i r c u i t " the pathway t o the w a t e r t a b l e .

Waste containment e f f e c t i v e n e s s i s a l s o a w e i g h t i n g f a c t o r on the pathway s c o r e . Of the above f a c t o r s , the depth t o t h e s e a s o n a l h i g h w a t e r t a b l e i s the most h e a v i l y w e i g h t e d f a c t o r . A i r / S o i l Pathway. The o r i g i n a l HARM model d i d n o t have an a i r / s o i l pathway and thus c o u l d n o t account a d e q u a t e l y f o r exposure due t o v o l a t i z a t i o n o f o r g a n i c s from s o i l o r s u r f a c e w a t e r , o r f o r exposure t o c o n t a m i n a t e d d u s t . The f a c t o r s t h a t a r e c o n s i d e r e d i n s c o r i n g t h i s pathway a r e : 0

average temperature

ο

net p r e c i p i t a t i o n

ο

wind v e l o c i t y

ο

s o i l porosity

ο

days p e r y e a r w i t h s i g n i f i c a n t

ο

site

precipitation

activity.

A l l o f t h e s e f a c t o r s a r e w e i g h t e d e v e n l y . A f a c t o r f o r waste containment i s a l s o s e l e c t e d by the u s e r and employed t o m o d i f y the f i n a l score. Contaminant

Hazards

The contaminant h a z a r d component o f DPM s e p a r a t e l y r a t e s human h e a l t h and e c o l o g i c a l h a z a r d s o f i d e n t i f i e d o r s u s p e c t e d c o n t a m i n a n t s i n each o f t h e t h r e e pathways. Hazard s c o r e s a r e c a l c u l a t e d d i f f e r e n t l y depending on whether e n v i r o n m e n t a l c o n t a m i n a t i o n has been d e t e c t e d . F o r media i n w h i c h c o n t a m i n a t i o n has been d e t e c t e d , h e a l t h h a z a r d s c o r i n g i s based on the concept o f an a c c e p t a b l e d a i l y i n t a k e (ADI). The highest concentration regardless of the t o x i c i t y of the contaminants o b s e r v e d a t a s i t e i s used. The o b s e r v e d c o n c e n t r a t o n i s f i r s t c o n v e r t e d t o a d a i l y i n t a k e i n (ug/day) and t h e n d i v i d e d by the a p p r o p r i a t e benchmark c o n c e n t r a t i o n s ( p r o v i d e d i n the manual o r on the computer system) w h i c h a r e e s t i m a t e d ADI's. E c o l o g i c a l h a z a r d s c o r i n g f o r o b s e r v e d c o n t a m i n a n t s i s s i m i l a r , a l t h o u g h an e c o l o g i c a l benchmark i s used i n s t e a d . The sum o f the e c o l o g i c a l h a z a r d q u o t i e n t s ( c o n c e n t r a t i o n d i v i d e d by the benchmark) i s used f o r a l l d e t e c t e d contaminants.


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214

For media i n w h i c h c o n t a m i n a t i o n has n o t been d e t e c t e d , h e a l t h h a z a r d s c o r e s a r e a s s i g n e d based on t h e ADIs and b i o a c c u m u l a t i o n f a c t o r s o f contaminants known t o be p r e s e n t a t t h e s i t e b e i n g r a t e d . I n t h i s c a s e , t h e s c o r e i s based on t h e most t o x i c c o n t a m i n a n t . S c o r i n g i s s i m i l a r f o r a l l pathways, though t h e a p p r o p r i a t e benchmarks w i l l v a r y . F o r example, i f t h e pathway i s s u r f a c e o r ground water, aquatic benchmarks w i l l be used as w e l l as t e r r e s t r i a l benchmarks. F o r t h e a i r / s o i l pathway, however, o n l y t e r r e s t r i a l benchmarks a r e employed.


Receptors Scoring The r e c e p t o r s p o r t i o n o f t h e DPM methodology r a t e s t h e p o t e n t i a l f o r human and e c o l o g i c a l p o p u l a t i o n s t o be exposed t o c o n t a m i n a n t s from a waste s i t e . The p o t e n t i a l r e c e p t o r s a r e c o n s i d e r e d s e p a r a t e l y f o r each pathway and f o r human and e c o l o g i c a l t a r g e t s . Human R e c e p t o r s f o r S u r f a c e Water. The f o l l o w i n g f a c t o r s a r e s c o r e d t o o b t a i n a measure o f human exposure t o s u r f a c e w a t e r p o l l u t i o n : ο

size of population obtaining d r i n k i n g water from p o t e n t i a l l y a f f e c t e d downslope/downstream surface waters (up t o 5 m i l e r a d i u s )

ο

w a t e r use o f t h e n e a r e s t s u r f a c e w a t e r

ο

p o p u l a t i o n w i t h i n 1500 f e e t o f t h e s i t e

ο

distance t o the i n s t a l l a t i o n

ο

l a n d use and z o n i n g w i t h i n 2 m i l e s o f s i t e

boundary

The f i r s t two f a c t o r s l i s t e d above a r e w e i g h t e d most h e a v i l y . Human R e c e p t o r s f o r Ground Water. The f o l l o w i n g f a c t o r s a r e used as i n d i c a t o r s o f p o t e n t i a l human r e c e p t o r exposure t o contaminants suspected i n ground w a t e r : ο

e s t i m a t e d mean ground w a t e r t r a v e l time from waste l o c a t i o n t o n e a r e s t downgradient w a t e r s u p l y w e l l ( s )

ο

e s t i m a t e d mean ground w a t e r t r a v e l time from c u r r e n t waste s i t e t o any downgradient s u r f a c e w a t e r body t h a t s u p p l i e s w a t e r f o r domestic use o r f o r f o o d c h a i n a g r i c u l t u r e

ο

ground w a t e r use o f t h e uppermost

ο

s i z e o f p o p u l a t i o n p o t e n t i a l l y a t r i s k from ground w a t e r contamination

ο

p o p u l a t i o n w i t h i n 1000 f e e t o f t h e s i t e

ο

distance t o the nearest i n s t a l l a t i o n

aquifer

boundary


15.

HUSHON

215


Of t h e s e f a c t o r s , t h e e s t i m a t e d ground w a t e r t r a v e l time i s c o n s i d e r e d most i m p o r t a n t w i t h the w a t e r use o f t h e uppermost a q u i f e r b e i n g i m p o r t a n t as w e l l .


Human R e c e p t o r s f o r A i r / S o i l . The f o l l o w i n g f a c t o r s a r e used as measures o f t h e p o t e n t i a l f o r human exposure: ο

s i z e o f p o p u l a t i o n n e a r t h e s i t e (4 m i l e

ο

l a n d use i n v i c i n i t y o f t h e s i t e

ο

distance t o nearest

radius)

i n s t a l l a t i o n boundary

Land use has t h e most pronounced impact on t h e f i n a l s c o r e . E c o l o g i c a l R e c e p t o r s - A l l Pathways. Exposure o f p o t e n t i a l e c o l o g i c a l r e c e p t o r s i s d e t e r m i n e d by whether t h e r e a r e s e n s i t i v e environments ( i . e . , w e t l a n d s o r h a b i t a t s o f endangered s p e c i e s ) w i t h i n 2 m i l e s o f the s i t e and whether t h e r e a r e c r i t i c a l environments ( i . e . , l a n d s o r w a t e r s s p e c i f i c a l l y r e c o g n i z e d o r managed by f e d e r a l , s t a t e , o r l o c a l government a g e n c i e s o r p r i v a t e o r g a n i z a t i o n s as r a r e u n i q u e , u n u s u a l l y s e n s i t i v e , o r important n a t u r a l r e s o u r c e s ) . Combining Pathway Scores t o O b t a i n a F i n a l S i t e Score The scores f o r each pathway a r e o b t a i n e d by combining t h e i n f o r m a t i o n on t h e pathway and t h e h a z a r d s f o r h e a l t h and e c o l o g i c a l r e c e p t o r s . The r e s u l t a r e s i x subscores, one f o r each r e c e p t o r / p a t h w a y combination. These s c o r e s a r e t h e n combined u s i n g a r o o t mean square methodology w i t h t h e human h e a l t h s c o r e s w e i g h t e d f i v e times h e a v i e r than the e c o l o g i c a l scores. The f i n a l score i s t h e n n o r m a l i z e d by d i v i d i n g by t h e maximum p o s s i b l e s c o r e t o o b t a i n a s i t e score r a n g i n g from 0 t o 100. Future

Directions

I n November o f 1987, t h e DoD proposed t h e use o f t h e DPM f o r p r i o r i t i z i n g r e m e d i a l a c t i o n s and announced a p u b l i c comment p e r i o d i n t h e F e d e r a l R e g i s t e r ( 4 ) . Comments on the model were r e c e i v e d from the E n v i r o n m e n t a l P r o t e c t i o n Agency and t h r e e s t a t e s . These were c o n s i d e r e d and based on them, changes were made t o t h e model. F i s c a l Year 1990 was t h e f i r s t y e a r t h e model was a p p l i e d t o DoD installations. Over 120 Army, Navy, A i r F o r c e and Defense L o g i s t i c s Agency r e p r e s e n t a t i v e s were t r a i n e d i n o p e r a t i o n o f t h e automated model. Feedback i s a l s o b e i n g e l i c i t e d from them as t o how t h e model can be improved t o f a c i l i t a t e f u t u r e s c o r i n g . Some a r e a s t h a t have a l r e a d y been i d e n t i f i e d f o r improvement include: ο

L o g i c a l checking

o f r e l a t e d answers.

ο

A d d i t i o n o f m a t e r i a l s t o t h e c h e m i c a l s f i l e s t h a t have been i d e n t i f i e d a t IRP s i t e s b u t a r e c u r r e n t l y m i s s i n g . This i s e x p e c t e d t o i n c l u d e e x p l o s i v e s and r a d i o a c t i v e s as w e l l as i n d i v i d u a l compounds.


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ο

More a b i l i t y t o move around t h r o u g h the model,

ο

Computation o f an o v e r a l l c e r t a i n t y

score.

Work i s p r o g r e s s i n g on DPM and the F i s c a l Year 1990 a p p l i c a t i o n w i l l c r e a t e a l a r g e body o f d a t a on a c t u a l s i t e s . These d a t a w i l l be a n a l y z e d and improvements w i l l be made t o t h e model as a p p r o p r i a t e .


There i s a l s o a p l a n t o convene a group o f e x p e r t s t o v a l i d a t e the model. Acknowledgment Work on DPM was conducted under c o n t r a c t s w i t h t h e US A i r F o r c e ' s O c c u p a t i o n a l and E n v i r o n m e n t a l H e a l t h L a b o r a t o r y l o c a t e d a t Brooks AFB, TX. The T e c h n i c a l Program Managers f o r t h i s work were Capt. A r t K a m i n s k i and Mr. P h i l Hunter.

References 1.

Barnthouse, L.W., J.E. Breck, T.D. Jones,S.R. Kraemer, E.D.Smith and G.W. Suter I I , Development and demonstration of a hazard assessment rating methodology for Phase I I of the Installation Restoration Program. ORNL/TM-9857, Oak Ridge National Laboratory, Oak Ridge, TN, 1986.

2.

Barnthouse, L.W., J.E. Breck, G.W. Suter I I , T.D. Jones, C. Easterly, L. Glass, B.A. Owen and A.P. Watson, Relative toxicity estimates and bioaccumulation factors i n the Defense Priority Model, ORNL-6416, Oak Ridge National Laboratory, Oak Ridge, TN, 1986.

3.

Smith, E.D. and L.W. Barnthouse, User's Manual for the Defense Priority Model. ORNL-6411, Oak Ridge National Laboratory, Oak Ridge, TN, 1986.

4.

Federal Register. Vol. 52, No. 222, p. 44304-5, November 1987.

5.

Hushon, J.M., G.M. Mikroudis, and C. Subramanian, Automated Defense Priority Model User's Manual, Version 2.0, Roy F. Weston, Inc., Washington, DC, June 1989.

6.

Hushon, J.M., G.M. Mikroudis, and C. Subramanian, Defense Priority Model User's Manual, Version 2.0, Roy F. Weston, Inc., Washington, DC, June 1989.

7.

Hushon, J.M., G.M. Mikroudis, and N. Pandit, Final Report on Phase I of DPM, Roy F. Weston, Inc., Washington, DC, December 1988. RECEIVED April 20, 1990


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