Ground Water Contamination by Toxic Substances - ACS Publications

29 Ground Water Contamination by Toxic Substances A California Assessment

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on August 25, 2015 | http://pubs.acs.org Publication Date: July 17, 1986 | doi: 10.1021/bk-1986-0315.ch029

David B. Cohen Pollutant Investigations Branch, State Water Resources Control Board, Sacramento, CA 95801

Overoptimistic risk perception, coupled with inadequate risk assessment, has led to underprotective risk management of toxic chemicals in ground water. In California, soil nematicides like DBCP are a particular concern. DBCP use was banned in 1977, yet it is s t i l l found in over 2500 wells. An estimated 700,000 people in 32 towns are either drinking water with measurable levels of DBCP or have had to seek alternative water supplies. Over 50 other pesticides including 1,2-D, EDB, and aldicarb have been found in California ground water from both point and nonpoint sources. Future risk management strategies must be based on a more conservative risk perception approach. California Water Resources Control Board's ground water "hot spots" program is an example of such an approach. In s e m i - a r i d C a l i f o r n i a , ground water i s a p r e c i o u s r e s o u r c e . D u r i n g t h e p a s t decade, t h e S t a t e Water Resources C o n t r o l Board, C a l i f o r n i a ' s e n v i r o n m e n t a l p r o t e c t i o n agency f o r water q u a l i t y , has l e a r n e d t h a t we have n o t done enough t o p r e v e n t t h e growing problem of t o x i c c h e m i c a l c o n t a m i n a t i o n o f our ground water. While both i n d u s t r i a l and a g r i c u l t u r a l c h e m i c a l s have been found i n C a l i f o r n i a ground w a t e r s , p e s t i c i d e s i n j e c t e d beneath the s o i l s u r f a c e t o c o n t r o l nematodes a r e a p a r t i c u l a r c o n c e r n . The n e m a t i c i d e 1,2-dibromo-3-chloropropane (DBCP), which was banned i n C a l i f o r n i a i n 1977, i s t h e most s e r i o u s example o f t h i s problem i n C a l i f o r n i a ( 1 - 2 ) . F i g u r e 1 shows t h e i n c r e a s e between 1979 and 1984 i n t h e number o f w e l l s found t o c o n t a i n measurable q u a n t i t i e s of DBCP. As o f A p r i l 1984, 2522 w e l l s c o n t a i n e d DBCP, w i t h over h a l f t h e s e w e l l s (1455) h a v i n g c o n c e n t r a t i o n s i n e x c e s s o f 1.0 part per b i l l i o n , the c u r r e n t C a l i f o r n i a "action l e v e l " . T a b l e I l i s t s over 50 o t h e r p e s t i c i d e s (from both p o i n t and n o n p o i n t s o u r c e s ) t h a t have been i d e n t i f i e d i n ground water from 28 o f C a l i f o r n i a ' s 58 c o u n t i e s . F i g u r e 2 shows t h e g e o g r a p h i c

0097-6156/ 86/ 0315-0499$08.75/0 © 1986 American Chemical Society

In Evaluation of Pesticides in Ground Water; Garner, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

500

EVALUATION O FPESTICIDES ING R O U N D WATER

2600 (2522)

2400

(2252)


LU >

2200

2000

Ο 1800

LU

1600

ο

(1455)

UJ

< Ζ

1400

(1292)

i < ο ο

1200

-

LL

1000

-

800

-

Ο CO CC LU

m 3 600

>1.0 p p b (Action Level)

400

-

200

-

'79

'80

'81

'83

'84

YEAR

F i g u r e 1. DBCP i n C a l i f o r n i a (May 1979 - A p r i l 1984) .

Ground Water

- Cumulative

Summary


29.

COHEN

501

Ground Water Contamination by Toxic Substances

Table I.

Pesticides Detected in California Ground Water


(Large Water Systems vs. Small Domestic Systems) No.Verified

Pesticide

N

Pesticide

o

*

Incidents

Aldicarb Aldrin

27 22

Dieldrin Dimethoate

Atrazine

2

Bentazon Benzaldehyde

1 1 4

Diphenamid Disulfoton DNBP

Chlordane Chlorpropham

1

Dacthal

4

DBCP DDD

2522 4 15

DDE DDT DEF

10 1 4

Delnav Diazinon Dichlone 1,2-Dichloropropane 1,3-Drchloropropene(cis) 1,3-Dichloropropene(tran8)

12 1 72 2 1

Verified Incidents

DNOC Dursban EDB Endosulfan

4 24 1 6 11 2 3 32 23 1

Pesticide

Omite Ordram Paraoxon P a r a t h i o n , ethyl P a r a t h i o n , methyl PCNB PCP Phorate Phthalates

Ethion Ethylene thiourea Furadan (carbofuran)

5

Sevin Simazlne

1 2

TCP Toxaphene

Heptachlor

4 3

Treflen Zytron

Endrin

Kelthane

(dicofol)

Lindane Malathion Methylene chloride Naled

18 5 4 7

No. Verified Incidents

2,4-D 2,4,5-T 2,4.5-TP TOTAL


2 3 1 4 1 1 38 2 4 3 9 6 5 1 4 10 4 3 2963

WATER


E V A L U A T I O N O F PESTICIDES IN G R O U N D

F i g u r e 2. V e r i f i e d I n c i d e n t s o f Ground Water C o n t a m i n a t i o n P e s t i c i d e s ( I n c l u d i n g DBC).


with

29.

COHEN


503

d i s t r i b u t i o n o f a l l v e r i f i e d i n c i d e n t s o f ground water c o n t a m i n a t i o n by p e s t i c i d e s ( i n c l u d i n g DBCP) as o f November 1984. T h i s paper f o c u s e s on C a l i f o r n i a ' s e x p e r i e n c e s w i t h p e s t i c i d e s i n ground water, p o t e n t i a l c a u s e s , and p o s s i b l e s o l u t i o n s .


C a l i f o r n i a ' s Water Q u a l i t y P r o t e c t i o n

Program

In 1969, C a l i f o r n i a adopted the P o r t e r - C o l o g n e A c t g i v i n g t h e S t a t e Water Resources C o n t r o l Board ( S t a t e Board) t h e a u t h o r i t y t o (1) a s s u r e t h a t a l l water d i v e r s i o n s be p u t t o a b e n e f i c i a l u s e , and (2) m a i n t a i n and enhance t h e q u a l i t y o f a l l waters o f t h e State. One major d i f f e r e n c e between f e d e r a l and s t a t e water q u a l i t y p r o t e c t i o n programs i n v o l v e s p r o t e c t i o n o f ground water. The 1972 F e d e r a l C l e a n Water A c t a d d r e s s e d s u r f a c e water q u a l i t y ( " f i s h a b l e and swimmable" by 1985), s p e c i f i c a l l y e x c l u d i n g n o n p o i n t s o u r c e a g r i c u l t u r a l r e t u r n f l o w s from r e g u l a t i o n . C a l i f o r n i a law p r o t e c t s a l l waters o f the S t a t e , i n c l u d i n g ground water and g i v e s the S t a t e Board a u t h o r i t y t o r e g u l a t e a l l s o u r c e s o f c o n t a m i n a t i o n including pesticides i n a g r i c u l t u r a l runoff. H i s t o r i c a l l y , such n o n p o i n t s o u r c e s have r a r e l y been r e g u l a t e d by t h e S t a t e and R e g i o n a l Boards because o f t h e d i f f i c u l t y i n t r a c i n g problem e v e n t s t o an unknown number o f d i f f u s e s o u r c e s . The S t a t e i s s u b d i v i d e d a l o n g d r a i n a g e b a s i n b o u n d a r i e s i n t o n i n e r e g i o n s , each w i t h i t s own R e g i o n a l Water Q u a l i t y C o n t r o l Board ( F i g u r e 3 ) . The r e g i o n a l b o a r d s have t h e a u t h o r i t y t o (1) i s s u e waste d i s c h a r g e r e q u i r e m e n t s , (2) m o n i t o r water q u a l i t y , (3) take enforcement a c t i o n s , and (4) adopt n a r r a t i v e o r n u m e r i c a l water q u a l i t y objectives i n t o basin plans. A t y p i c a l basin plan narrat i v e o b j e c t i v e s t a t e s t h a t "the d i s c h a r g e o f p e s t i c i d e s t o waters o f t h e r e g i o n o r a t l o c a t i o n s where the waste may s u b s e q u e n t l y r e a c h waters o f t h e r e g i o n i s p r o h i b i t e d " . In o r d e r t o p r o t e c t ground water, t h e S t a t e Board i n 1972 adopted r e g u l a t i o n s g o v e r n i n g hazardous waste d i s p o s a l t o l a n d . These r e g u l a t i o n s (Subchapter 15 o f the C a l i f o r n i a Water Code) c l a s s i f i e d both wastes and s i t e s . Wastes were c a t e g o r i z e d on t h e b a s i s o f t h e r e l a t i v e h a z a r d t o h e a l t h and t h e environment, w h i l e s i t e s were p r i o r i t i z e d a c c o r d i n g t o p o t e n t i a l f o r l e a c h i n g and ground water c o n t a m i n a t i o n . As t h r e a t s from b i o l o g i c a l p o l l u t a n t s i n s u r f a c e waters l e s s e n , the awareness o f t h r e a t s from t o x i c c h e m i c a l s i n c r e a s e s . Hardly a week goes by w i t h o u t a new r e p o r t o f t o x i c o r g a n i c c h e m i c a l s i n a community water s u p p l y o r o t h e r water r e s o u r c e . DBCP

(1,2-Dibromo-3-chloropropane)

The most w i d e s p r e a d p e s t i c i d e c o n t a m i n a t i o n o f ground water i n C a l i f o r n i a (and, p o s s i b l y , the n a t i o n ) has o c c u r r e d t h r o u g h use o f DBCP. The c h e m i c a l was f i r s t d i s c o v e r e d i n C a l i f o r n i a ground water i n 1979 by t h e C e n t r a l V a l l e y R e g i o n a l Board. Eight years a f t e r i t s use was banned, more DBCP-contaminated w e l l s a r e s t i l l b e i n g discovered. DBCP i n some w e l l waters was a t h i g h e r l e v e l s i n 1984 than when f i r s t d i s c o v e r e d i n 1979 ( F i g u r e 4 ) . Many o f t h e s e w e l l s have been shut down p e r m a n e n t l y , w h i l e o t h e r s a r e o n l y used on an emergency b a s i s o r when DBCP c o n c e n t r a t i o n s d e c r e a s e below 1 ppb.



E V A L U A T I O N O F PESTICIDES IN G R O U N D

F i g u r e 3.

R e g i o n a l Water Q u a l i t y C o n t r o l

Boards.


WATER


29.

COHEN


505

Of 8,190 C a l i f o r n i a w e l l s m o n i t o r e d by November 1984, 30.8 p e r c e n t were found t o c o n t a i n DBCP. F r e s n o County had the h i g h e s t p e r c e n t a g e (41.3 p e r c e n t ) and g r e a t e s t number (1,696) o f DBCP c o n t a m i n a t e d w e l l s . In some a r e a s o f F r e s n o County, over h a l f the p r i v a t e w e l l s sampled c o n t a i n e d DBCP above the DHS a c t i o n l e v e l o f I ppb. C a l i f o r n i a has spent over $10 m i l l i o n i n Fresno County a l o n e to r e h a b i l i t a t e DBCP-contaminated ground water s u p p l i e s . Many o f the worst p o l l u t i o n problems were found i n s m a l l or p r i v a t e r u r a l systems where a w e l l s e r v e s one or more homes. Table I I compares t h e degree o f DBCP-contamination f o r both l a r g e p u b l i c water systems (>200 c o n n e c t i o n s ) and s m a l l e r systems (5-200 c o n n e c t i o n s ) i n 11 C a l i f o r n i a c o u n t i e s . Large water systems had 14.6 p e r c e n t o f t h e i r w e l l s c o n t a m i n a t e d w i t h DBCP compared t o 33.6 p e r c e n t f o r s m a l l and d o m e s t i c water systems which f r e q u e n t l y pump from s h a l l o w e r , more v u l n e r a b l e a q u i f e r s . By comparison, a r e c e n t l y i n a u g u r a t e d s t a t e w i d e m o n i t o r i n g program f o r over 40 t o x i c c h e m i c a l s i n l a r g e community w e l l s (AB 1803) found t o x i c o r g a n i c c h e m i c a l s i n 82 o f 320 systems (25.6 p e r c e n t ) . (3) DBCP c o n c e n t r a t i o n s i n some F r e s n o County d o m e s t i c w e l l s sampled between 1979-1984 have f l u c t u a t e d s e a s o n a l l y by an o r d e r o f magnitude. F i g u r e 5 shows DBCP c o n c e n t r a t i o n s i n one w e l l f l u c t u a t e d between 3 t o 33 p a r t s per b i l l i o n w i t h i n s i x months d u r i n g 1981. Sample c o l l e c t i o n and a n a l y t i c a l methods were unchanged d u r i n g t h i s p e r i o d . A l t h o u g h the reasons f o r t h i s v a r i a b i l i t y a r e not y e t c l e a r l y u n d e r s t o o d , t h e s e examples demonstrate the need t o c o n t i n u e m o n i t o r i n g even a f t e r c o n c e n t r a t i o n s f a l l "below detection limits". Plumes o f DBCP c o n t a m i n a t e d ground water can move u n p r e d i c t a b l y through a q u i f e r s t o r e a c h p r e v i o u s l y u n c o n t a m i nated monitoring w e l l s . These r e t r o s p e c t i v e DBCP m o n i t o r i n g d a t a a r e p r e s e n t l y b e i n g t r a n s f e r r e d t o computer f i l e s . When t h i s work i s completed, a n a l y s i s o f s p a t i a l and temporal t r e n d s and p o s s i b l e c o r r e l a t i o n s w i t h s o i l and water p r e d i c t i v e f a c t o r s w i l l be attempted. C a l i f o r n i a i s f o r t u n a t e i n h a v i n g a mandatory use r e p o r t i n g system f o r r e s t r i c t e d p e s t i c i d e s . ( 4 ) Computer t a p e s c o n t a i n i n g the raw d a t a from t h i s program a r e t r a n s f e r r e d t o the U n i v e r s i t y of C a l i f o r n i a a t D a v i s , which has, w i t h S t a t e Board s u p p o r t , d e v e l o p e d a computer program f o r mapping p e s t i c i d e use i n f o r m a t i o n g e o g r a p h i c a l l y (by c o u n t y , r e g i o n , or the S t a t e ) and t e m p o r a l l y (by s e a s o n , y e a r , or c u m u l a t i v e y e a r s ) . F i g u r e 6, which shows r e p o r t e d C a l i f o r n i a use o f DBCP f o r 1972-1977, i s an example o f that c a p a b i l i t y . U n f o r t u n a t e l y , not a l l p e s t i c i d e use was r e q u i r e d t o be r e p o r t e d d u r i n g t h i s p e r i o d . DBCP was o n l y r e q u i r e d t o be r e p o r t e d s h o r t l y b e f o r e i t s use was banned i n 1977. The Department of Food and A g r i c u l t u r e has t h e r e f o r e e s t i m a t e d a c t u a l use t o be a p p r o x i m a t e l y t h r e e times r e p o r t e d use. The b e s t e s t i m a t e o f a c t u a l c u m u l a t i v e DBCP use between 1957 and 1977 i s i n e x c e s s o f 50 m i l l i o n pounds. D e s p i t e the i n c o m p l e t e n e s s o f p a s t p e s t i c i d e use r e p o r t s , t h i s p e s t i c i d e mapping c a p a b i l i t y i s an i m p o r t a n t t o o l i n f o c u s i n g S t a t e Board f i e l d m o n i t o r i n g e f f o r t s on a r e a s o f greatest potential risk. A p r o s p e c t i v e f i e l d s t u d y o f DBCP movement (both h o r i z o n t a l and v e r t i c a l ) through s o i l t o ground water has been proposed by r e s e a r c h e r s a t the U n i v e r s i t y o f C a l i f o r n i a , D a v i s . A particularly


EVALUATION O F PESTICIDES IN G R O U N D WATER


506

YEAR

F i g u r e 4.

DBCP C o n c e n t r a t i o n s

i n E s c a l o n M u n i c i p a l W e l l No. 3.

Table Π . Percent of Wells Contaminated with DBCP (Point and Nonpoint Source-1884) County

Large Systems

Small Systems

TOTAL

19.1

43.4

41.3

KERN

5.9

23.3

15.9

MADERA

2.7

22.9

20.7

MERCED

22.7

23.5

23.4

TULARE

10.4

29.4

23.8

SAN

19.9

19.4

19.6

16.2

19.9

18.5

2.7

9.1

FRESNO

JOAQUIN

STANISLAUS RIVERSIDE SAN

BERNADINO

SUTTER BUTTE TOTAL

5.0

-

35.8

44.4

52.4

-

33.3

33.3

14.6

33.6

30.8

35.8 100.0




-

Ο

Ι I

δ-

Ground Water Contamination by Toxic Substances - ACS Publications

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