### 1 

## Summary Report Pesticide Monitoring in the Walla Walla Basin

2005-2007 Results

September 28, 2007

Kevin Masterson Agency Toxics Coordinator Oregon Department of Environmen tal Quality, Laboratory Division

I. INTRODUCTION

The Walla Walla River sub-basin in northeastern Oregon is largely an ag ricultural area, with tree fruits such as apples and cherries comprising a significant proportion of the ag ricultural land in the watershed. The other major agricultural crops in the area incl ude wheat, peas and winegrapes. A segment of the Walla Walla River is on the Department’s 303(d) list of impaired waters due to elevated temperatures during the summer months. Based on knowledge of the use of orga nophosphate insecticides for tree fruit crops and the adverse impacts of low levels of such chemicals on aquatic life, the Department, the Walla Walla Basin Watershed Council, Oregon State Un iversity (OSU) Extensi on Service and the Blue Mountain Horticultural Society ini tiated a Pesticide Stewardship Part nership (PSP) in the Walla Walla sub-basin in 2005. The objective of th e PSP project is to conduct monito ring of streams within the area, and then use the results of the monitoring as a catalys t for collaborative efforts by local stakeholders to reduce pesticide concentrations in streams where detec tions have been identified. This is a report on the results of pesticide analysis of water samples co llected in the Walla Walla sub-basin from 2005 to 2007

II. MONITORING M ETHODS AND LOCATIONS

Water samples were collected from March through the first half of June, when the majority of insecticide applications occur. The timing and frequency of sampling each year was based on information about when specific types of insecticid e applications were occu rring in the Walla Walla Valley. For instance, applica tions of chlorpyrifos (the “dormant” sp ray) in fruit orchards typically occur during the last three weeks of Marc h, while azinphos-methyl applications (for pos t-bloom codling moth control) usually occur at the end of May and beginni ng of June. However, the exact timing of pesticide applications is dependent on several variables, including the insect growth cycle, crop phenology and prevaling weather conditions.

When monitoring began in 2005, two smaller Little Walla Walla River tribut ary sites were included along with several main stem Walla Walla River sites. These tributaries are also known as

“distributaries” because the flow is controlled at a diversion point in Milton-Fr eewater. In response to the pesticide detections observed at these tribut ary sites in 2005, two additional Little Walla Walla tributary locations were added to the sampling program in 2006 to better assess the extent and magnitude of pesticide detection in these smaller streams.

Water samples were collected from Walla Walla basin streams at the locations described below in Table 1 and depicted visually in Fig. 1. Water samples we re analyzed for organophosphate insecticides and triazine herbicides according to US EPA Method 8141B (Table 2).

### 2 Table 1. Sampling locations.

Station Upstream Land Use

South Fork Wall Walla River at Harris County

Park 

### National Forest (reference site)

Walla Walla River at Day Road South 

### Agriculture – fruit orchards & berries

Walla Walla River at Gove School Bridge 

### Mixed urban and agriculture

Walla Walla River at Pepper Bridge 

### Agriculture – mixed crops

Little Walla Walla River Main Stem at The Frog 

### Urban

East Little Walla Walla River, North of

Stateline Road 

### Agriculture – fruit orchards

West Prong Little Walla Walla River, North of

Stateline Road 

### Agriculture – fruit orchards

Little Walla Walla River, West

Branch/Crockett 1 

### Agriculture – fruit orchards

Little Walla Walla River, Midwest Prong 1 

### Agriculture – fruit orchards

Table 2. Pesticide analysis using USEPA Method 8141B.

Insecticides Herbicides Insecticide Metabolites

Azinphos-methyl Atr azine Azinphos-methyl oxon Chlorpyrifos Simazine Chlorpyrifos oxon

Diazinon Imidan oxon

Dimethoate Malathion oxon

Fenvalerate-Esfenvalerate

Imidan

Malathion Methyl parathion Pyriproxyfen

1 Sampling locations added in 2006

### 3 Figure 1. Map of Pesticide Monitoring Sites in the Walla Walla Watershed near Milton-Freewater

[ELECTRONIC MAP GOES HERE]

### 4 SUMMARY OF RESULTS

Watershed-Wide Results

Between 2005 and 2007, pesticide residues were detected at five of the nine sampling sites included in the monitoring project. However, since inception of the project, no pesticide detections have been observed (at or above the 0.025 μg/l me thod detection limit) at any of th e Walla Walla River main stem sampling locations. In addition, only one pesticide detection was found at the Little Walla Walla River main stem site (“The Frog”) within the City of Mi lton-Freewater. Nearly all of the pesticide detections over the three years of monitoring were found in the tributaries of the Little Walla Walla River. Multiple detections were found in all four of the tributary sampli ng locations, but none were found in

2007 at the East Little Walla Walla Rive r, North of Stateline Road site.

Chlorpyrifos, diazinon, and azinphosmethyl were detected in all three year s, and most of the detections of chlorpyrifos and azinphosmethyl exceeded state water quality standards. Dimethoate, another organophosphate insecticide, was detected less freque ntly, while the herbicide simazine was detected once. However, in 2007, detections occurr ed at only three of the nine sites.

The median concentrations of all pesticide detecti ons throughout the watershed are presented in Figure 2 and the maximum concentrations are in Figure 3 be low. Limited conclusions can be drawn from a comparison between the 2005 results for all sites in the watershed with those from 2006 and 2007 because of the two new tributary sites that were adde d in 2006. These sites were chosen because of the high likelihood of detecting pesticides. However, th e figures do illustrate significant reductions in both

the median and maximum concentrations of chlorpyrifos between 2006 and 2007. The median

concentration in the watershed decreased by 67% between 2006 and 2007, while the maximum concentration dropped by 94%. In addition, th e maximum diazinon detection decreased by 97%

between 2006 and 2007. The 2007 median concentration for diazinon depicted in Figure 2 represents only one data point, as there was only one diazin on detection in 2007 compared with ten in 2006.

Dimethoate was also not detected in 2007 at any of the sites.

All detections of azinphos-methyl ex ceed the state water quality standa rd, as the method detection limit for this pesticide is above the water quality st andard. The watershed-wi de median and maximum azinphos-methyl concentrations observed in 2007 were le ss than the corollary con centrations in both the 2006 and 2005. However, the number of sampling events conducted during the la te May and early June time frame (the application period for azinphosmet hyl) in 2007 were about one-half the number of sampling events during the same period in the previ ous two years. A larger set of samples may make for a more useful comparison.

Figure 4 shows the detection frequency for pesticid es in the watershed. Detection frequency is expressed as a ratio of the number of detections to the total number of samples collected. Detection frequencies for most pesticides dropped between 2006 and 2007. The ch lorpyrifos detection frequency is slightly higher in 2007 than in 2006. However, th is is attributable to th e larger number of sampling events in 2006 during the latter part of spring when chlorpyrifos detect ions have not been observed. A

review of detections found in Marc h of both years (the month when n early all chlorpyrifos detections have been found) reveals that ther e were 5 fewer chlorpyrifos detec tions in March 2007 than in March 2006. The number of March sampling ev ents in 2006 and 2007 were the same.

### 5 Figure 2. Median Pesticide Concentrations of a ll Detections for Walla Walla Sub-basin 2005-2007

Walla Walla Subbasin: 2005-07 Me dian Pesticide Concentrations

0.00 0.10 0.20 0.30 0.40 0.50

Azi n

p h

osmet h

yl Chlo r p

y

r i fo

s Diaz i non Dimetho a te SimazineMedian (ug/L) 2005 median

2006 median

2007 median

WQS Azinphosmethyl (0.01 ug/l)

Chronic WQS Chlorpyrifos (0.041 ug/l)

Acute WQS Chlorpyrifos (0.083 ug/l)



### Figure 3. Maximum Pesticide Concentrations for All Walla Walla Sites 2005-2007

Walla Walla Subbasin: Maximum Pesticide Concentrations

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00

Az

in

p hosm e t h

y l Chlorpyrifos

Di azi n

on Dime t h

o

a t e

Si m

a zineMaximum (ug/L) 2005 maximum

2006 maximum

2007 maximum

### 6 Figure 4 – Pesticide Detection Frequencie s in the Walla Walla Subbasin

Walla Walla Subbasin: 2005-2007 P esticide Detection Frequencies

0 0.05 0.1 0.15 0.2

Azinphosmethyl Chlorpyrifos Diazinon Dimethoate 2005 Detection Frequency
2006 Detection Frequency
2007 Detection Frequency



### Site-Specific Results

A more detailed analysis of two tributary sites where pesticides ha ve been consistently detected provides some useful insights. One of the sites (West Prong Little Walla Walla River, North of Stateline Road) has been sampled each of the past three years, while the other (Little Walla Walla River, West Branch/Crockett) was added in 2006. Tables 3 and 4 provide a chlorpyrifos and diazinon data comparison between the monitoring year s for both of these sites. [Note : The other site where multiple detections have been found, the Midwest Prong site, is not included in this anal ysis because insufficient flow resulted in sporadic samp le collections in 2006 and 2007]

Table 3. Chlorpyrifos and Diazinon Concentrations a nd Detections: West Prong Little Walla Walla River, North of Stateline Road

Number of Detections Median
Concentrations Maximum
Concentrations

2005 2006 2007 2005 2006 2007 2005 2006 2007 Chlorpyrifos 6 6 3 0.112 0.245 0.067 0.49 0.54 0.091

Diazinon 2 3 0 0.073 0.092 ND 0.122 0.15 ND

### 7 Table 4 Chloryrifos and Diazinon Concentrations and De tections: Little Walla Walla River, West

Branch/Crockett

Number of Detections Median
Concentrations Maximum
Concentrations

2006 2007 2006 2007 2006 2007 Chlorpyrifos 5 4 1.100 0.245 7.4 0.46
Diazinon 5 0 0.390 ND 6.2 ND



### The most noteworthy findings from this data ar e the significant reductions in median and maximum concentrations between 2006 and 2007, and the drop in the number of diazinon detections. The median

and maximum concentrations at the Stateline Road site decreased by 73% and 83% respectively between 2006 and 2007, and there was a 78% reduction in median concentrations and a 94% reduction at the

West Branch/Crockett site. The 2007 median concentration at the Stateline Road site was also 40% lower than the 2005 median. In addition, diazinon was detected eight times at the two sites in 2006, yet

no detections were found in 2007.

Figures 5 and 6 below provide a gr aphic illustration of the median concentrations of all pesticide

detections observed at the Stateline Road and West Branch/Crockett sites. The water quality standards for chlorpyrifos and azinphosmethyl are also depicted. The median concentration for detections at the Stateline Road site fell below the acute water quality standard for chlorpyrifos in 2007, but it remains above the chronic water quality standard. The median concentrations of dete ctions found at the West

Branch/Crockett site exceeded th e state water quality standards fo r azinphosmethyl and chlorpyrifos during all three years of monitoring. However, the significant decrease in chlorpyrifos concentrations

observed in 2007 resulted in a much less substantial exceedance of the standards than occurred in 2006.

There were no azinphosmethyl detecti ons at the Stateline Road site in 2007, compared with five detections in 2006. However, the aforementioned caveat regarding the relatively small number of late season sampling events should be co nsidered when assessing these results. There was little difference

between the 2006 and 2007 median concentration of azi nphos-methyl at the West Branch/Crockett site.

### 8 Figure 5 Median pesticide concentra tions of detections observed at West Prong Little Walla Walla River, North of Stateline Road, 2005-2007



### Median Pesticide Concentrations: West Prong Little WW River, N. Stateline Rd.

0.00 0.05 0.10 0.15 0.20 0.25 0.30

Az

in

p ho s

m

e t h

y l Chlorpyrifos Diazinon

D imet h

oat e SimazineMedian (ug/L) 2005 median

2006 median

2007 median WQS Azinphosmethyl (0.01 ug/l) Chronic WQS Chlorpyrifos (0.041 Acute WQS Chlorpyrifos (0.083 ug/l)



### Figure 6 Median Pesticide concentrati ons of detections observed at Little Walla Walla River, West Branch/Crockett, 2006-2007



### Median Pesticide Concentrations: Little WW River, West Branch/Crockett

0.00 0.20 0.40 0.60 0.80 1.00 1.20

A

zin p ho s met h

y l

Ch lor p

y

r i f

o

s Diaz i non Dime t h

o

a t e Simazi n

eMedian (ug/L) 2006 median

2007 median

WQS Azinphosmethyl (0.01 ug/l)

Chronic WQS Chlorpyrifos (0.041 ug/l)

Acute WQS Chlorpyrifos (0.083 ug/l)

### 9 IV. CONCLUSIONS

The pesticide monitoring from 2007 produced a numb er of encouraging resu lts related to improved water quality in the Walla Walla Sub-basin. Re ductions in median and maximum chlorpyrifos

concentrations and the decrease in the number of diazinon detections we re substantial. Dimethoate and simazine were detected multiple times in 2006 (and di methoate was detected in 2005), but neither were detected at any site in 2007. In addition, no detections of azinphosmet hyl were detected at any of the sampling locations in 2007, where consistent pestic ide detections had been observed since monitoring began in 2005. Also, no detections of any pesticides were found at one tributary location (East Little Walla Walla River, North of Stateline Road) wher e they had been detected in both 2005 and 2006

The Department and the Walla Walla Basin Wate rshed Council met with growers from the Blue Mountain Horticultural Society and OSU Extension Service in July 2007 to learn about what – if any – changes in application practices occu rred earlier in the year. A signifi cant level of applicator education was provided, including a spray calibra tion workshop in February as well as individualized training. Some of the growers also completely disconti nued the use of organophosphate insecticides, and switched to less toxic pesticides and mineral oil. Furthermore, buffer zones between orchards and waterways were also were also created on propertie s, which had open ditches. OSU Extension Service will be developing a report documenting these best management practices and other pest management practices in the area. Funds ar e available to continue pesticid e monitoring in 2008, and all of the stakeholders are optimistic about the potential for further improvements in stream quality.

Acknowledgements

This project was funded by a 319 grant from the Environmental Protection Agency.

### 10 APPENDIX A – SAMPLE COLLECTION DATES

2005

March 10 April 4 May 31 March 14 May 2 June 1 March 16 May 13 June 3 March 17 May 17 March 21 May 20 March 28 May 23 March 30 May 24 March 31 May 26

2006

March 22 (1) May 18 June 6 March 22 (2) May 23 June 8 March 28 May 25 (1) March 29 May 25 (2) March 30 May 31 April 11 June 1 April 12 June 5

2007

March 19 May 15 June14 March 21 May 23 March 22 May 24

March 26

March 2911APPENDIX B – PESTICIDE DETECTION DATAWalla Walla Pesticide Stewardship Partnership2005 and 2006 Pesticide DetectionsCase Sample date YearBottleNo.Site AnalyteConc.(ug/L)Reportinglimit (ug/L)200502403/10/200520052675West Prong Little WW River, North of Stateline Rd.Diazinon0.1220.026200502403/10/200520052675West Prong Little WW River, North of Stateline Rd.Dimethoate0.0440.026200502443/14/200520052626East Little WW River, North of Stateline Rd.Chlorpyrifos0.0260.025200502443/14/200520052627West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.0330.025200502603/16/200520052629East Little WW River, North of Stateline Rd.Chlorpyrifos0.0260.026200502603/16/200520052663West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.490.026200502643/17/200520052657West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.380.025200502793/21/200520052632West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.160.025200503103/28/200520052624West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.0630.024200503103/28/200520052624West Prong Little WW River, North of Stateline Rd.Diazinon0.0240.024200502183/30/200520052687West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.0440.025200505425/26/200520054156West Prong Little WW River, North of Stateline Rd.Azinphosmethyl0.0540.02620060224 3/22/2006 2006 5023 Little WW River, WestBranch/Crockett Chlorpyrifos 7.4 0.02520060225 3/22/2006 2006 5028 Little WW River, West Branch/Crockett Chlorpyrifos 1 0.02520060224 3/22/2006 2006 5022 Little WW River,Midwest Prong Chlorpyrifos 3.8 0.02520060225 3/22/2006 2006 5029 Little WW River,Midwest Prong Chlorpyrifos 1.1 0.02520060224 3/22/2006 2006 5024 West Prong Little WW River,North of Stateline Rd.Chlorpyrifos 0.54 0.02520060225 3/22/2006 2006 5030 West Prong Little WW River,North of Stateline Rd.Chlorpyrifos 0.34 0.02520060224 3/22/2006 2006 5023 Little WW River,West Branch/Crockett Diazinon 6.2 0.02520060225 3/22/2006 2006 5028 Little WW River,West Branch/Crockett Diazinon 0.56 0.02520060224 3/22/2006 2006 5022 Little WW River, Midwest Prong Diazinon 0.027 0.02520060225 3/22/2006 2006 5029 Little WW River, Midwest Prong Diazinon 2.1 0.02520060225 3/22/2006 2006 5030 West Prong Little WW River, North of Stateline Rd. Diazinon 0.15 0.02520060235 3/28/2006 2006 5037 Little WW River, WestBranch/Crockett Chlorpyrifos 0.075 0.02520060235 3/28/2006 2006 5041 Little WW Riverat the Frog Chlorpyrifos 0.05 0.02520060235 3/28/2006 2006 5038 West Prong Little WW River,North of Stateline Rd.Chlorpyrifos 0.07 0.02520060235 3/28/2006 2006 5037 Little WW River,West Branch/Crockett Diazinon 0.069 0.02520060237 3/29/2006 2006 5044 Little WW River, WestBranch/Crockett Chlorpyrifos 1.7 0.02520060237 3/29/2006 2006 5045 West Prong Little WW River,North of Stateline Rd.Chlorpyrifos 0.26 0.02520060237 3/29/2006 2006 5044 Little WW River,West Branch/Crockett Diazinon 0.39 0.02520060237 3/29/2006 2006 5045 West Prong Little WW River, North of Stateline Rd. Diazinon 0.092 0.0251220060237 3/29/2006 2006 5044 Little WW River, West Branch/CrockettDimethoate 0.52 0.02520060237 3/29/2006 2006 5045 West Prong Little WW River, North of StatelineRd. Dimethoate 0.027 0.02520060242 3/30/2006 2006 5052 Little WW River, WestBranch/Crockett Chlorpyrifos 1.1 0.02520060242 3/30/2006 2006 5053 West Prong Little WW River,North of Stateline Rd.Chlorpyrifos 0.23 0.02520060242 3/30/2006 2006 5052 Little WW River,West Branch/Crockett Diazinon 0.041 0.02520060242 3/30/2006 2006 5053 West Prong Little WW River, North of Stateline Rd. Diazinon 0.068 0.02520060242 3/30/2006 2006 5052 Little WW River, West Branch/CrockettDimethoate 0.034 0.02520060279 4/11/2006 2006 5092 West Prong Little WW River,North of Stateline Rd.Chlorpyrifos 0.03 0.02520060421 5/18/2006 2006 5144 Little WW River, Midwest Prong Simazine 0.041 0.02520060421 5/18/2006 2006 5146 West Prong Little WW River, North of Stateline Rd. Simazine 0.039 0.02520060450 5/25/2006 2006 5165 Little WW River, WestBranch/Crockett Azinphosmethyl 0.11 0.02520060445 5/25/2006 2006 5142 Little WW River, WestBranch/Crockett Azinphosmethyl 0.072 0.02520060450 5/25/2006 2006 5167 Little WW River,Midwest Prong Azinphosmethyl 0.99 0.02720060450 5/25/2006 2006 5153 West Prong Little WW River,North of Stateline Rd.Azinphosmethyl 0.064 0.02520060445 5/25/2006 2006 5149 West Prong Little WW River,North of Stateline Rd.Azinphosmethyl 0.029 0.02620060459 5/31/2006 2006 6107 Little WW River, WestBranch/Crockett Azinphosmethyl 0.119 0.02520060459 5/31/2006 2006 6108 Little WW River,Midwest Prong Azinphosmethyl 0.116 0.02520060459 5/31/2006 2006 6109 West Prong Little WW River,North of Stateline Rd.Azinphosmethyl 0.029 0.02620060463 6/1/2006 2006 6116 Little WW River, WestBranch/Crockett Azinphosmethyl 0.097 0.02620060463 6/1/2006 2006 6117 Little WW River,Midwest Prong Azinphosmethyl 0.105 0.02820060463 6/1/2006 2006 6118 West Prong Little WW River,North of Stateline Rd.Azinphosmethyl 0.026 0.02620060463 6/1/2006 2006 6116 Little WW River, West Branch/Crockett Simazine 0.028 0.02620060479 6/5/2006 2006 6228 West Prong Little WW River,North of Stateline Rd.Azinphosmethyl 0.031 0.02520060479 6/5/2006 2006 6222 Little WW River,Midwest Prong Azinphosmethyl 0.035 0.02620060479 6/5/2006 2006 6227 Little WW River, WestBranch/Crockett Azinphosmethyl 0.026 0.025200702363/21/200720076342Little WW River, West Branch/CrockettChlorpyrifos0.160.026200702453/22/200720077010West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.0670.025200702453/22/200720076338Little WW River, West Branch/CrockettChlorpyrifos0.460.025200702533/26/200720077013West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.0910.026200702533/26/200720077012Little WW River, West Branch/CrockettChlorpyrifos0.330.026200702633/29/200720077024West Prong Little WW River, North of Stateline Rd.Chlorpyrifos0.0630.025200702633/29/200720077022Little WW River, West Branch/CrockettChlorpyrifos0.130.026200702633/29/200720077021Little WW River, Midwest ProngChlorpyrifos0.340.026200702633/29/200720077021Little WW River, Midwest ProngDiazinon0.160.026200704865/23/200720077037Little WW River, West Branch/CrockettAzinphosmethyl0.190.026200704935/24/200720077046Little WW River, West Branch/CrockettAzinphosmethyl0.0320.025200704935/24/200720077045Little WW River, Midwest ProngAzinphosmethyl0.0280.025