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Department of Pesticide Regulation Environmental Monitoring Branch 1001 I Street, P.O. Box 4015 Sacramento, California 95812
September 2017
STUDY #300: PROTOCOL FOR GROUNDWATER MONITORING OF DCPA AND ITS DEGRADATES (MTP AND TPA)
I. INTRODUCTION
The Pesticide Contamination Prevention Act (PCPA) is defined in Sections 13141-13152 of the California Food and Agricultural Code (FAC). Currently, Section 13149 mandates that when a pesticide active ingredient or other specified ingredient or degradation product of a pesticide is detected and confirmed in groundwater and the contamination is found to be due to legal agricultural use, then the California Department of Pesticide Regulation (DPR) is required to conduct a formal review (Detection Response Process) to determine if use of the pesticide should continue and, if so, under what conditions.
Chlorthal-dimethyl (DCPA or Dacthal) is the active ingredient of a number of herbicide products with historic or current use in California. DCPA has two major degradation products: monomethyl tetrachloroterephthalate (MTP) and 2,3,5,6-tetrachloroterephthalic acid (TPA). DPR conducted groundwater sampling studies between 1990 and 1997 in different areas of the state where DCPA had been legally used, looking specifically for DCPA, MTP, and TPA. None of the laboratory analyses of the collected samples from those studies yielded a confirmed detection of DCPA or MTP. However, the laboratory analyses did confirm detections of TPA in samples collected in several counties.
The PCPA was originally enacted in 1985 under Assembly Bill 2021 and was significantly revised in 2014 under Senate Bill 1117. Under the 1985 version of the PCPA (i.e., that includes the period from 1990 to 1997 when DPRs DCPA sampling studies were conducted), an active ingredient was entered into the Detection Response Process when one of its degradation products was found in groundwater only when the measured levels of that degradation product were determined to be high enough to pose a threat to public health. Although confirmed detections of TPA were found between 1990 and 1997, the DPR Medical Toxicology Branch reviewed the toxicological data for TPA submitted by the registrant at the time and concluded that the levels found in groundwater did not pose a threat to public health (CDPR, 1991). Consequently, it was recommended then to not enter DCPA into the Detection Response Process (CDPR, 1992). A health reference level (HRL) of 70 g/L was subsequently calculated for both DCPA and TPA by the United States Environmental Protection Agency (USEPA) (USEPA, 2008) and adopted
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by DPR for its monitoring of these constituents in groundwater (CDPR, 2012). Since 1997, several agencies have reported detected levels of TPA in water wells located throughout the state but the measured TPA concentrations were all well below the established HRL.
The revision of the PCPA in 2014 lifted the requirement to demonstrate a threat to public health of degradation products found in groundwater. Consequently, an active ingredient is now entered into the Detection Response Process simply when its degradation product is found in groundwater and determined to have originated from legal agricultural use. Given the recent changes to the PCPA and the previous detections of TPA throughout the state, DCPA will be entered into the Decision Response Process. Current groundwater concentrations of DCPA, MTP, and TPA in areas of the state where DCPA use has been relatively high will be needed to inform the Detection Response Process in its determination of whether current use of DCPA pollutes, or threatens to pollute, groundwater in California.
II. OBJECTIVE
The purpose of this study is to assess current concentrations of DCPA, MTP, and TPA in groundwater samples collected in regions where recent agricultural use of DCPA has been relatively high and where detections of TPA have been found in previous studies. Assessment of current concentrations of DCPA, MTP, and TPA will be used to inform the Detection Response Process.
III. PERSONNEL
Well sampling will be conducted by the Environmental Monitoring Branch of DPR under the general direction of Joy Dias. Project personnel include:
Project Leader: Nels Ruud Field Coordinator: Craig Nordmark Senior Scientist: Murray Clayton Laboratory Liaison: Sue Peoples Analytical Chemistry: Center for Analytical Chemistry, California Department of Food
and Agriculture (CDFA)
Please direct questions regarding this study to Nels Ruud at (916) 324-4167, e-mail: .
IV. AGRICULTURAL USE OF DCPA
The DPR Pesticide Use Report database contains reported agricultural use of DCPA (in pounds) on a township-range-section basis from 1990 to present (CDPR, 2015a). Total annual use of DCPA in California from 1990 to 2014 is shown on Figure 1. Annual use declined steadily during the 1990s from a high of 849,074 pounds (lbs) in 1992 to a low of 133,688 lbs in 2000
mailto:[email protected]
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(Figure 1). Annual use from 2001 to 2014 leveled off somewhat with an average rate of 192,771 lbs per year. Total use during 2014 was 172,054 lbs.
Annual DCPA use by county from 2000 to 2010 is given in Table 1. The top users of DCPA were Monterey and Imperial counties with average annual usages of 75,526 and 45,731 lbs, respectively. Lesser amounts of DCPA (
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public water supply wells in Monterey County (CDPR, 2015b). Although these detections have not been confirmed by DPR using its monitoring standards, their reported occurrence provides useful information in planning the sampling for this study.
VI. GROUNDWATER SAMPLING IN THE SALINAS VALLEY
Monterey County has the highest current and historic use of DCPA among all counties in the state (Table 1). DCPA use in Monterey County occurs primarily in the Salinas Valley, where five confirmed detections of TPA have been found (see Figure 2 and Table 3). Therefore, initial groundwater sampling in this study for DCPA, MTP, and TPA will be planned in the Salinas Valley approximately between the cities of Salinas and King City where use has historically been the highest (Figure 2). After sampling has been conducted in the Salinas Valley and the follow-up laboratory analyses of the samples has been completed, additional sampling may be planned in other counties with relatively high DCPA use (i.e., Imperial, Fresno, Ventura, Riverside, San Luis Obispo, and Santa Barbara).
The Salinas Valley Groundwater Basin is the source of groundwater for the urban, rural-domestic, and agricultural water users in the Salinas Valley. The Salinas Valley Groundwater Basin is divided into eight sub-basins. Sections between Salinas and King City with the highest DCPA use in Monterey County are located in four of the eight sub-basins: 1) Pressure Sub-basin (sometimes referred to as the 180/400-Foot Aquifer Sub-basin) (CDWR, 2004a), 2) Eastside Sub-basin (CDWR, 2004b), 3) Forebay Sub-basin (CDWR, 2004c), and 4) Upper Valley Sub-basin (CDWR, 2004d) (see Figure 2 for locations of sub-basin boundaries). The four sub-basins are not hydraulically isolated from one another but instead exchange horizontal groundwater flows across their common boundaries. The four sub-basins are distinguished from one another by differences in hydrostratigraphy, water levels, and groundwater recharge characteristics.
In this section, we describe an approach for selecting potential sampling sites in the four sub-basins as a function of local hydrogeology, locations of wells with previous confirmed detections, and sections with relatively high DCPA use.
Pressure Sub-basin
The Pressure Sub-basin (Figure 2) is conceptualized as consisting of three semi-confined to confined aquifer units: 180-foot aquifer, 400-foot aquifer, and deep aquifer. The three aquifers are so-named with respect to the approximate depths beneath the ground surface at which they occur. The 180-foot aquifer is overlain by a confining layer called the Salinas Valley Aquitard (SVA). Vertical recharge from irrigation return flows, rainfall, and seepage from the Salinas River is known to create a perched water table condition above the SVA in areas of the Pressure Sub-basin. Horizontal recharge into the Pressure Sub-basin from the southeastern (upgradient) direction occurs across its boundary with the Forebay Sub-basin. Horizontal recharge from the northwestern (downgradient) direction occurs as seawater intrusion from the Monterey Bay. Although the SVA is generally thought to be relatively continuous across the Pressure Sub-basin,
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some amount of groundwater from the perched water table is likely recharging the 180-foot aquifer via vertical leakage through the SVA (Fogg et al., 1999).
Wells in the Pressure Sub-basin between Salinas and Gonzales that have been previously sampled by various agencies have completed depths from 50 to 700 feet beneath the ground surface (ft bgs) (CDPR, 2015b). Wells that are considered shallow in the Pressure Sub-basin are screened in the perched aquifer with completed depths in a range of about 50 to 200 feet bgs. Wells that are considered deep are screened in the 180-foot, 400-foot, and Deep aquifers and have top-of-screen locations generally greater than 200 feet bgs. For this study, sampling in the Pressure Sub-basin should be conducted in wells with completed depths less than 200 ft bgs.
An ordering of the township-range-sections in the Salinas Valley from the highest to lowest total DCPA use (i.e., minimum of 6,000 lbs per section) from 2000 to 2010 and the sub-basins in which they are respectively located is given in Table 4. The section (M16S04E10) with the highest total DCPA use in the Salinas Valley (18,569 lbs), for example, is located in the Pressure Sub-basin (Table 4). The regional direction of groundwater flow in the Pressure Sub-basin is northwest along the valley axis and northeast into the Eastside Sub-basin. For this study, sampling should be conducted in shallow wells located within, north, or east of the high use sections in the Pressure Sub-basin identified in Table 4 and displayed on Figure 2.
Three wells with confirmed detections of TPA are located in the Pressure Sub-basin (Figure 2). Re-sampling of those three wells will also be attempted for this study.
Eastside Sub-basin
The SVA present in the Pressure Sub-basin is thought to diminish in thickness at or near the boundary separating the Pressure and Eastside sub-basins (Figure 2). Groundwater in the Eastside Sub-basin is not otherwise subjected to confined conditions and the sub-basin is therefore conceptualized as an unconfined to semi-confined aquifer. Vertical recharge in the Eastside Sub-basin is only from irrigation return flows and rainfall since the Salinas River does not intersect that sub-basin. Horizontal recharge into the Eastside Sub-basin from the western direction occurs across its boundary with the Pressure Sub-basin; from the southeastern direction across its boundary with the Forebay Sub-basin; and from the northwestern direction as seawater intrusion from the Monterey Bay (CDWR, 2004b).
Pumping along the eastern side of Salinas has created a significant groundwater depression in that region of the Eastside Sub-basin (MCWRA, 2015). In general, groundwater levels in the Eastside Sub-basin are lower than those in the adjacent Pressure Sub-basin and upgradient Forebay Sub-basin. For example, during the 2014 Water Year (WY) the average depth to groundwater (DGW) for eleven monitoring wells in the Eastside Sub-basin ranged from about 125 feet bgs in February 2014 to 158 feet bgs in August 2014 (MCWRA, 2015). By comparison, the average DGW for five monitoring wells in the 180-foot Aquifer in the Pressure Sub-basin ranged from about 45 feet bgs in February 2014 to 65 feet bgs in August 2014. The average
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DGW in the Eastside Aquifer in November 2014 was about 139 feet bgs in comparison to about 130 feet bgs in November 2013. Given a lack of perched water conditions in the Eastside Sub-basin and the significant pumping impacts on groundwater levels east of Salinas, sampling in this study should be conducted in wells with completed depths of 300 feet bgs or less.
Sections in the Eastside Sub-basin with the highest total DCPA use from 2000 to 2010 are listed in Table 4 and displayed on Figure 2. The regional direction of groundwater flow in the Eastside Sub-basin is northwest along the valley axis towards the groundwater depression east of Salinas. For this study, sampling should be conducted in the shallowest wells located within or northwest of the high use sections in the Eastside Sub-basin identified in Table 4 and displayed on Figure 2.
One well with a confirmed detection of TPA is located in the Eastside Sub-basin (Figure 2). Re-sampling of that well will also be attempted in this study.
Forebay Sub-basin
The Forebay Sub-basin (Figure 2) is conceptualized as an unconfined to semi-confined aquifer. Vertical recharge in the Forebay Sub-basin is from irrigation return flows, rainfall, and seepage from the Salinas River. Horizontal recharge into the Forebay Sub-basin occurs from the upgradient Upper Valley Sub-basin and horizontal discharge occurs from the Forebay Sub-basin into the downgradient Pressure and Eastside sub-basins. Wells in the Forebay Sub-basin generally tend to be shallower (
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downgradient Forebay Sub-basin (CDWR, 2004d). During the 2014 WY, the average DGW for nine monitoring wells in the Upper Valley Sub-basin ranged from about 46 feet bgs in February 2014 to 55 feet bgs in September 2014 (MCWRA, 2015). The average DGW in the Upper Valley Aquifer in November 2014 was about 58 feet bgs compared to about 46 feet bgs in November 2013. For this study, sampling in the Upper Valley Sub-basin should be conducted in wells with completed depths of 200 feet bgs or less.
Sections in the Upper Valley Sub-basin with the highest total DCPA use from 2000 to 2010 are listed in Table 4 and displayed on Figure 2. In general, total DCPA use from 2000 to 2010 in the Upper Valley Sub-basin between King City and the boundary with the downgradient Forebay Sub-basin is low to moderate and southeast of King City is low. For this study, sampling should be conducted in the shallowest wells located within or northwest of the high use sections in the Upper Valley Sub-basin identified in Table 4 and displayed on Figure 2.
No wells with previous confirmed detections of TPA are located in the Upper Valley Sub-basin for re-sampling.
VII. SAMPLING AND ANALYTICAL METHODS
Wells for sampling will be chosen in the areas described in the previous section following the guidelines described in the standard operating procedure (SOP) Number FSWA006.02 (Nordmark and Wong, 2013). Domestic wells are preferred for sampling since they tend to be shallower than municipal and agricultural wells and are more accessible. Samples will be collected from the wells using the methods described in SOP Number FSWA001.01 (Nordmark and Herrig, 2011). Quality assurance samples will be collected in the field following the guidelines described in SOP QAQC001.00 (Segawa, 1995).
Chemical analysis will be performed by the CDFA Center for Analytical Chemistry. CDFA will analyze for DCPA, MTP, and TPA using method EMON-SM-05-040 (CDFA, 2016). The method detection limits for DCPA, MTP, and TPA are 0.00629, 0.0155, and 0.0313 g/L, respectively (Table 5). The DPR reporting limit for all three chemicals is 0.05 g/L (Table 5). Analytical laboratory quality control will be conducted following the guidelines described in SOP QAQC001.00 (Segawa, 1995).
VIII. DATA ANALYSIS
Results obtained from the CDFA Center for Analytical Chemistry will be used to assess current levels of DCPA, MTP, and TPA in the sampled aquifers in the Salinas Valley in order to inform the Detection Response Process. A report of the results will be prepared. A letter report describing the results will be provided to participating property owners.
http:QAQC001.00http:QAQC001.00http:FSWA001.01http:FSWA006.02
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IX. TIMETABLE
January through June 2017: Conduct sampling August 2017: Obtain and review analytical results from CDFA laboratory September 2017: Review laboratory results and determine if additional sampling in other counties is necessary.
December 2017: Prepare report of findings. Communication
o Provide notice to the County Agricultural Commissioner, DPR Enforcement Branch Regional Office, and the local Farm Bureau two weeks prior to initiating monitoring in a county. Additional notice will be provided if there is a six-month lapse in monitoring within a county.
o Provide results to property owners within 30 days of receipt. o Provide results to state and local agencies when sampling is concluded and results have been reviewed and approved by the project team.
X. BUDGET
Budget Component Units Expense per Unit Total Component Cost Primary sample analysis
50 $840 $42,000
Backup sample analysis
25 $840 $21,000
Control sample analysis
25 $840 $21,000
Travel 45 $130 $5,850 Person Years 1 $100,000 $100,000 Total $189,850
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IX. References
CDFA. 1992. Report EH 92-01: Survey of Chlorthal-Dimethyl Residues in Well Water of Seven California Counties. Available at: http://www.cdpr.ca.gov/docs/emon/pubs/ehapreps/eh9201.pdf (verified June 30, 2015) California Department of Pesticide Regulation, Sacramento, California.
CDFA. 2016. EMON-SM-05-040. Analysis of Dacthal, Dacthal Monoacid, and Dacthal Diacid in Well Water using Gas Chromatography/MSD. California Department of Pesticide Regulation, Sacramento, California.
CDPR. 1991. Memorandum from Larry Nelson to Ron Oshima: Toxicological significance of a degradation product of Dacthal (chlorthal-dimethyl). Dated: October 11, 1991. California Department of Pesticide Regulation, Sacramento, California.
CDPR. 1992. Memorandum to John Sanders from Kean Goh: Z060: Determination whether residues of a degradation product of chlorthal-dimethyl pose a threat to public health, and whether residues of the active ingredient, chlorthal-dimethyl, were also present in ground water in Los Angeles County. Dated: August 28, 1992. California Department of Pesticide Regulation, Sacramento, California.
CDPR. 2012. Memorandum from Jay Schreider to Lisa Ross: Toxicological Significance of Degradation Product of Dacthal. Dated: January 31, 2012. California Department of Pesticide Regulation, Sacramento, California.
CDPR. 2015a. Pesticide Use Reporting. Available at: http://www.cdpr.ca.gov/docs/pur/purmain.htm (verified June 30, 2015) California Department of Pesticide Regulation, Sacramento, California.
CDPR. 2015b. Well Inventory Database. Available at: http://www.cdpr.ca.gov/docs/emon/grndwtr/wellinv/wirmain.htm (verified June 30, 2015) California Department of Pesticide Regulation, Sacramento, California.
CDWR. 2004a. Salinas Valley Groundwater Basin, 180/400 Foot Aquifer Subbasin. Californias Groundwater Bulletin 118.
CDWR. 2004b. Salinas Valley Groundwater Basin, Eastside Aquifer Subbasin. Californias Groundwater Bulletin 118.
CDWR. 2004c. Salinas Valley Groundwater Basin, Forebay Aquifer Subbasin. Californias Groundwater Bulletin 118.
CDWR. 2004d. Salinas Valley Groundwater Basin, Upper Valley Aquifer Subbasin. Californias Groundwater Bulletin 118.
http://www.cdpr.ca.gov/docs/emon/pubs/ehapreps/eh9201.pdfhttp://www.cdpr.ca.gov/docs/pur/purmain.htmhttp://www.cdpr.ca.gov/docs/pur/purmain.htmhttp://www.cdpr.ca.gov/docs/emon/grndwtr/wellinv/wirmain.htm
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Fogg, G.E., LaBolle, E.M., and G.S. Weissmann, 1999. Groundwater Vulnerability Assessment: Hydrogeologic Perspective and Example from Salinas Valley, California. In book: Application of GIS, Remote Sensing, Geostatistical, and Solute Transport Modeling to the Assessment of Non-point Source Pollution in the Vadose Zone, AGU Monograph Series 108, Publisher: AGU, pp.45-61
MCWRA, 2015. Monterey County Water Resources Agency Groundwater Level Monitoring Program. Available at: http://www.mcwra.co.monterey.ca.us/groundwater_level_monitoring/groundwater_level _monitoring_overview.php (verified June 30, 2015)
Nordmark, C. and J. M. Herrig, 2011. SOP FSWA001.02. Obtaining and Preserving Well Water Samples. Available at: http://www.cdpr.ca.gov/docs/emon/pubs/sops/fswa00102.pdf (verified June 30, 2015) California Department of Pesticide Regulation, Sacramento, California.
Nordmark, C. and M. Wong, 2013. SOP FSWA006.02. Planning, Conducting, and Documenting Small-Scale Ground Water Monitoring Studies. Available at: http://www.cdpr.ca.gov/docs/emon/pubs/sops/fswa00602.pdf (verified July 13, 2015) California Department of Pesticide Regulation, Sacramento, California.
Segawa, R. 1995. SOP QAQC001.00. Chemistry Laboratory Quality Control. Available at: http://www.cdpr.ca.gov/docs/emon/pubs/sops/qaqc001.pdf (verified June 30, 2015) California Department of Pesticide Regulation, Sacramento, California.
USEPA. 2008. Regulatory Determinations Support document for Selected Contaminants from the Second Drinking Water Contaminant Candidate list (CCL 2), Chapter 4: DCPA Mono- and Di-Acid Degradates. EPA Report 815-R-08-012.
http://www.cdpr.ca.gov/docs/emon/pubs/sops/fswa00102.pdfhttp://www.cdpr.ca.gov/docs/emon/pubs/sops/fswa00602.pdfhttp://www.cdpr.ca.gov/docs/emon/pubs/sops/qaqc001.pdfhttp:QAQC001.00http:FSWA006.02http:FSWA001.02http://www.mcwra.co.monterey.ca.us/groundwater_level_monitoring/groundwater_level
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Table 1. Annual DCPA use (pounds) by county from 2000 to 2010 (CDPR, 2015a).
County 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Total Average Monterey 77,704 78,985 74,270 77,743 94,815 73,347 75,683 77,692 74,900 66,731 58,921 830,790 75,526 Imperial 17,056 38,811 48,616 60,166 53,111 64,055 58,885 54,303 36,743 27,709 43,584 503,039 45,731 Ventura 8,267 12,358 22,475 27,094 16,828 15,139 9,185 5,000 6,294 6,629 8,578 137,847 12,532 Fresno 2,820 1,660 7,763 2,072 2,154 23,328 29,252 7,000 3,731 20,999 10,978 111,757 10,160 Riverside 9,610 9,160 8,225 11,586 9,852 9,308 24,279 19,433 16,039 5,523 2,225 125,239 11,385
Santa Barbara 4,888 11,658 11,132 10,312 16,013 12,396 10,464 7,401 8,607 4,799 4,497 102,167 9,288 San Luis Obispo 1,187 6,424 6,510 10,273 7,154 6,977 8,173 5,958 3,902 4,255 5,092 65,904 5,991 San Benito 5,540 5,254 7,011 7,890 7,341 6,794 8,298 5,046 5,059 3,463 5,699 67,394 6,127
San Bernardino 824 3,325 8,259 9,704 3,774 3,920 4,984 6,120 5,704 8,151 5,036 59,802 5,437 Kern 2,400 1,920 732 756 324 1,853 4,612 7,871 7,084 4,920 3,681 36,153 3,287
Santa Clara 148 1,498 3,012 2,355 4,667 5,191 3,543 4,358 3,083 1,511 1,549 30,915 2,810 Stanislaus 3 521 738 569 1,578 3,886 1,827 2,215 1,548 3,512 1,036 17,431 1,585 San Joaquin 0 180 374 1,730 159 889 1,488 1,726 2,145 768 951 10,409 946 Los Angeles 948 1,440 1,157 184 137 44 1,023 144 9 40 25 5,150 468
Tulare 221 74 209 1,711 953 703 278 4,148 593 Merced 27 12 659 405 843 1,947 389
Santa Cruz 410 182 366 336 372 110 241 179 78 5 11 2,290 208 Shasta 420 626 407 585 2,037 509 Yolo 64 104 84 317 209 91 133 108 117 330 55 1,611 146
Siskiyou 330 330 330 Madera 223 3 1,013 392 1,630 408 Colusa 1,310 34 133 8 1,485 371 Kings 166 647 544 1,357 452 Modoc 0 0
Sacramento 24 390 24 60 25 523 105 Glenn 420 420 420 Sonoma 18 15 23 23 26 34 38 38 36 249 28 San Diego 23 21 9 38 91 23 Sutter 147 147 147
Contra Costa 0 35 16 15 23 89 18 San Mateo 35 12 16 11 11 6 5 95 14 Orange 3 1 0 12 1 2 1 20 3 Solano 18 18 18 Butte 18 18 18 Placer 0 1 2 2 2 1 8 1
Calaveras 6 1 7 3
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Table 2. Total DCPA use (pounds) by crop from 2000 to 2010 (CDPR, 2015a).
Crop DCPA Use (pounds)
BROCCOLI 967,953 ONION (DRY, SPANISH, WHITE, YELLOW, RED, ETC.) 469,723 CAULIFLOWER 152,078 CABBAGE 89,986 BROCCOLI RAAB (RAPA, ITALIAN TURNIP, RAPINI) 69,877 CHINESE CABBAGE (NAPPA, WON BOK, CELERY CABBAGE) 56,554 ONIONS (GREEN) 51,744 BOK CHOY (WONG BOK) 41,187 RADISH 38,166 NOUTDR GRWN CUT FLWRS OR GREENS 32,235 ORNAMENTAL TURF (ALL OR UNSPEC) 32,197 PEPPERS (FRUITING VEGETABLE), (BELL,CHILI, ETC.) 22,273 GAI LON 18,465 KALE 13,999 TURNIP, GENERAL 8,177 MUSTARD, GENERAL 7,073 COLLARDS 5,693 CHINESE GREENS, CHINESE LEAFY VEGETABLES 5,461 GARLIC 5,264 LEEK 4,726 RAPE (ALL OR UNSPEC) 3,613 BRUSSELS SPROUTS 3,105 NOUTDR CONTAINER/FLD GRWN PLANTS 3,087 KOHLRABI 2,553 LEAFY VEGETABLES (ALL OR UNSPEC) 1,811 PEPPERS (CHILI TYPE) (FLAVORING AND SPICE CROP) 1,551 TOMATOES, FOR PROCESSING/CANNING 1,307 NOUTDR GRWN TRNSPLNT/PRPGTV MTRL 1,160 GAI CHOY (LOOSE LEAF) 1,004 WATERMELONS 998 CANTALOUPE 942 BEANS, SUCCULENT (OTHER THAN LIMA) 830 CHINESE RADISH/DAIKON (LOBOK, JAPANESE RADISH) 599 LETTUCE, HEAD (ALL OR UNSPEC) 498 STRAWBERRY (ALL OR UNSPEC) 496 RIGHTS OF WAY 492 UNCULTIVATED AGRICULTURAL AREAS (ALL OR UNSPEC) 483 EGGPLANT (ORIENTAL EGGPLANT) 432 SOIL APPLICATION, PREPLANTOUTDOOR (SEEDBEDS,ETC.) 425 LANDSCAPE MAINTENANCE 416 MELONS 364 CUCUMBER (PICKLING, CHINESE, ETC.) 351 SQUASH (ALL OR UNSPEC) 326 SHALLOT, ONIONS (SHALLOT) 321 SQUASH (SUMMER) 300 CHERRY 300 LETTUCE, LEAF (ALL OR UNSPEC) 257 NGRNHS GRWN PLANTS IN CONTAINERS 227 COTTON, GENERAL 166 OATS, GENERAL 158 RESEARCH COMMODITY 152 COLE CROPS (ALL OR UNSPEC) 138 GARBANZOS (INCLUDING CHICK PEAS) 102 TOMATO 91 NGRNHS GRWN CUT FLWRS OR GREENS 84 PIMENTO (PIMIENTO TYPE PEPPER) 66 BEANS (ALL OR UNSPEC) 56 PEAS, GENERAL 48 UNCULTIVATED NONAG AREAS (ALL OR UNSPEC) 44 VERTEBRATE PEST CONTROL 32 BEETS, GENERAL 32 YAMS, TRUE (LISBON & WHITE YAM) 30 GRAPES, WINE 30 CILANTRO (CHINESE PARSLEY, CORIANDER LEAVES) 21 STRUCTURAL PEST CONTROL 18 SPINACH 15 FLAVORING AND SPICE CROPS (ALL OR UNSPEC) 8 CHIVE (SIBERICUM) 8 DILL 5 MINT (ALL OR UNSPEC) 5 PECAN 4 CHICORY (ALL OR UNSPEC) 3 CORN, HUMAN CONSUMPTION 3 VEGETABLES (ALL OR UNSPEC) 1 NGRNHS GRWN TRNSPLNT/PRPGTV MTRL 1 ENDIVE (ESCAROLE) 1
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Table 3. Summary of previous confirmed detections of TPA by CDPR (CDPR, 2015b).
County Sampling Date Range
Reporting Year
Unique Wells
Sampled
Confirmed TPA
Detections Los Angeles 5/9/1990 1991 1 1 Santa Clara 5/9/1990 1991 1 1 Los Angeles 7/10/1990 1991 5 2 Santa Clara 7/11/19907/12/1990 1991 7 5 Monterey 8/6/19908/8/1990 1991 15 5 Fresno 8/13/19908/23/1990 1991 15 2 San Luis Obispo 8/14/1990 1991 3 1 Santa Barbara 8/14/19908/16/1990 1991 7 4 Kern 8/21/19908/22/1990 1991 10 5 Los Angeles 8/21/1990 1991 4 0 Tulare 8/21/19908/22/1990 1991 6 0 Monterey 7/8/19917/11/1991 1992 2 0 San Luis Obispo 5/19/19925/20/1992 1993 6 1 Colusa 4/19/19944/28/1994 1994 8 0 Fresno 4/19/19946/9/1994 1995 147 2 Tulare 5/11/19946/8/1994 1995 31 0 Madera 7/16/19961/16/1997 1997 6 3
Total 274 32
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Table 4. Total DCPA use (pounds) from 2000 to 2010 by townshiprangesection number in Monterey County (CDPR, 2015a)
TownshipRangeSection DCPA Use (lbs)
Subbasin Location
27M16S04E10 18,569 Pressure 27M16S05E06 15,612 Eastside 27M18S06E02 15,551 Forebay 27M15S04E15 15,124 Eastside 27M15S04E32 14,698 Pressure 27M15S04E26 11,771 Eastside 27M19S07E17 10,772 Forebay 27M16S04E14 10,001 Pressure 27M18S06E33 9,605 Forebay 27M17S05E26 9,554 Forebay 27M19S07E22 9,512 Upper Valley 27M17S06E31 9,465 Forebay 27M19S07E13 9,458 Upper Valley 27M15S03E15 9,315 Pressure 27M16S05E28 9,233 Eastside 27M18S06E27 8,924 Forebay 27M16S05E21 8,530 Eastside 27M14S03E31 8,515 Pressure 27M17S05E36 8,385 Forebay 27M15S04E36 8,375 Eastside 27M15S04E21 8,110 Eastside 27M15S04E20 8,002 Eastside 27M15S03E10 7,813 Pressure 27M19S07E12 7,404 Upper Valley 27M18S06E04 7,382 Forebay 27M18S07E19 7,361 Forebay 27M18S06E23 7,025 Forebay 27M14S03E19 7,022 Pressure 27M17S05E09 6,997 Forebay 27M15S04E28 6,899 Eastside 27M21S09E24 6,640 Upper Valley 27M19S07E03 6,406 Forebay 27M19S07E04 6,285 Forebay 27M19S07E25 6,264 Upper Valley 27M15S04E08 6,165 Eastside 27M19S07E10 6,097 Forebay 27M16S05E32 6,015 Pressure
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Table 5. Method detection and reporting limits for DCPA, MTP, and TPA (CDFA, 2016).
Chemical Method Detection Limit (ug/L)
Reporting Limit (ug/L)
DCPA 0.00629 0.05 MTP 0.0155 0.05 TPA 0.0313 0.05
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Figure 1. Annual DCPA use in California from 1990 to 2014 (CDPR, 2015a).
0
100,000
200,000
300,000
400,000
500,000
600,000
700,000
800,000
900,000
DCPA Use
(pou
nds)
Year
Annual DCPA Use in California
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San Benito County
M16S10E
M15S08E M15S09E
M14S10E
M16S07E
6E
M13S10E
M12S08E
M16S08E
6E
M12S07E M12S10E
E
6E
6E
M17S07E
M15S07E
M13S07E
M15S10E
M13S08E
E
M13S09E
M14S08E
M12S09E
M14S07E M14S09E
M16S09E M16S11
Figure 2. Total DCPA use (lbs per section) from 2000 to 2010 and locations of confirmed and unconfirmed detections of TPA in Salinas Valley area of Monterey County(CDPR, 2015a; 2015b).
!A
!A
!A
!A!A
!A
!A
!A
!A
!A
!A
!A
!A!A !A!A!A
!A
!A!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
!A
Chualar Spence
Monterey County
Salinas
Gonzales
Soledad
Greenfield
King City
Eastside Sub-basin
Pressure Sub-basin
Forebay Sub-basin
Upper Valley Sub-basin
M17S10E
M18S05E
M17S05EM17S02E
M15S0
M21S06E
M18S04E
M12S05E
M14S0M14S03E
M18S03E
M17S06M17S03E
M15S03E
M18S10E
M22S06E
M15S05E
M12S03E
M15S04E
M13S05EM13S04E
M21S09E
M12S0
M18S09E
M21S08E
M13S03E
M19S08E
M20S04E
M16S05E
M19S06E
M22S09E
M20S10E
M15S02E
M12S02E
M17S04E
M21S10E
M14S02E
M13S0
M20S09E
M19S10EM19S09E
M18S07E
M16S04E
M21S04E
M12S04E
M22S05E M22S08E
M20S08E
M17S09E
M16S06
M22S07E
M19S07E
M22S10E
M18S08EM18S06E
M19S05E
M17S08E
M20S05E
M18S02E
M21S07E
M19S03E
M13S02E
M21S05E
M19S04E
M20S03E
M19S02E
M22S04E
M23S05E M23S06E M23S07E M23S08E
M21S03E
M23S09E M23S10E
M20S02E
M11S10EM11S09EM11S08EM11S07EM11S06EM11S05EM11S04EM11S03EM11S02E
M14S05E
M14S04E
M16S03E
M20S07E
M16S02E
M20S06E
M22S11E
M21S11E
M20S11E
M19S11E
M18S11E
M17S11E
E
M23S11E
M11S01E
M23S04E
M22S03E
M13S01E
Monterey County !A Confirmed Detections of TPA !A Unconfirmed Detections of TPA
Sub-basins of Salinas Valley Groundwater BasinDCPA Use (2000 to 2010)(lbs per section)
20,000
-
S14S10E
S16S11ES16S10E
S15S11E
S14S11E
S17S10E
S15S10E
S17S11E
S16S09E
S15S09E
17S09E
14S09E
Figure 3. Total DCPA use (lbs per section) from 2000 to 2010 and locations of confirmed detections of TPA in Imperial County (CDPR, 2015a).
Brawley
El Centro
Salton Sea
Imperial County
Imperial
Calexico
SALTONS
S13S13E S13S15E S13S14E S13S16E
S13S10E
S10S16E
S11S16E
S16S12E
S12S16E
S10S14E S10S15E
S11S10E
S09S16E S09S15E
S13S11E
S09S14E
S11S15E S11S14E
S09S13E
S13S12E
S12S15E
S15S12E
S12S14E
S16S15E
S14S12E
S12S10E
S16S14E S16S16E
S15S14E
S16S13E
S15S13E
S14S15E
S15S15E S15S16E
S14S13E S14S16E S14S14E
S12S13E S12S11E
S09S12E
S17S12E
S08S12E S08S13E
S13S17E
S08S11E S08S14E
S10S10E
S17S13E
S09S17E
S08S15E
S10S17E
S08S16E
S14S17E
S11S17E
S10S13E
S17S14E
S15S17E
S12S17E
S16S17E
S12S09E
S08S17E
S17S15E
S11S09E S11S13E
S17S16E
S12S12E
S09S11E
S17S17E
S10S09E
S
S
S13S09E
S11S11E
S09S09E
S08S10E
S09S10E
S18S09E
S10S11E
S10S12E
Imperial CountyDCPA Use (2000 to 2010)(lbs per section)
20,000
-
S02S24W
Figure 4. Total DCPA use (lbs per section) from 2000 to 2010 and locations of confirmed detections of TPA in Ventura County (CDPR, 2015a).
Santa Paula
Ventura
Oxnard Camarillo
Ventura County S05N22W S05N23W S05N20W S05N21W S05N19W
S02N22W
S05N18W S05N24W
S04N23W S04N19W S04N22W
S03N22W
S04N20W
S03N20W
S01N20W
S03N19W
S01S18W
S04N18W
S03N23W
S01N19W
S02N19W
S01N18W
S03N21W
S02N18W S02N20W
S03N18W
S04N24W S04N21W
S01S19W
S01N21W
S02N21W
S05N17W
S01N22W
S04N17W
S01S20W
S03N17W
S02N17W
S01N17W
S01S17W
S06N23W
S03N24W
S06N22W S06N18W S06N21W S06N20W S06N19W S06N24W
S05N25W
S04N25W
S06N17W
S02N23W
S06N25W
S01S21W
S02S18W S02S19W
S03N25W
S01N23W
S01S22W
S02S17W
S02N24W
Ventura CountyDCPA Use (2000 to 2010)(lbs per section)
20,000
-
!A!A!A
M21S21EM22S21E
19E M20S22E
M19S21E
19E M18S22E
M23S21E
M18S21E
19E
M20S21E
M21S20E
M20S20E
M19S22E
M23S22E
M21S22E
M18S20E
M22S22E
9E
M23S20E9E
M22S20E
M19S20E
9E
M23S23E
M21S23E
M22S23E
M18S23E
M20S23
M19S23
M24S22EM24S21E9E M24S20E M24S23E
Figure 5. Total DCPA use (lbs per section) from 2000 to 2010 and locations of confirmed detections of TPA in Fresno County (CDPR, 2015a; 2015b).
!A !A
!A
!A
San Joaquin
Mendota Fresno
Huron
Fresno County
M19S14E
M20S14E
M23S16E
M22S16E
M20S17E
M17S12E M17S17E
M19S17E
M18S17E
M11S21E M11S17E
M18S12E
M21S15E
M19S15E
M14S16E
M22S13E
M11S20E M11S12E
M15S16E
M20S18E
M21S14E
M11S18E M11S22E
M10S22E
M12S12E
M11S14E M11S15E
M16S16E
M22S14E
M18S15E
M11S13E M11S19E
M17S15E
M20S
M17S21E
M11S16E
M10S14E
M15S15E
M13S16E
M10S17E
M23S14E
M18S
M16S15E
M19S18E
M17S14E
M19S
M23S15E
M20S12E
M13S15E
M14S15E
M18S18E
M13S14E
M14S17E
M17S18E
M12S17E
M14S14E
M12S15E
M16S17E M16S21E M16S22E
M17S22E
M21S12E
M16S20E
M15S17E M15S19E M15S21E
M13S17E
M12S13E
M23S18E
M21S18E
M13S18E
M14S20E
M15S20E
M10S15E
M13S13E
M16S19E
M21S1
M15S13E
M12S14E
M15S14E
M20S15E
M10S18E
M12S16E
M17S19E
M21S16E
M10S20E
M22S18E
M13S22E
M16S18E
M14S21E
M15S18E
M10S16E
M23S1 M23S13E
M18S14E
M15S22E
M14S19E
M10S13E
M13S21E
M16S14E
M21S17E
M12S21E M12S22E M12S20E
M20S16E
M14S18E
M12S18E
M13S19E
M10S19E
M13S20E
M16S13E
M13S12E
M14S22E
M22S1
M14S13E
M23S17E
M17S20E
M10S12E
M22S17E
M12S19E
M10S21E
M23S12E
M14S12E
M19S16E
M18S16E
M17S16E
M22S15E
M15S12E
M20S13E
M21S13E
M22S12E
M16S12E
M19S13E
M17S13E
M18S13E
M09S18E M09S17E M09S20E M09S19E M09S16E M09S22E M09S14E M09S21E M09S15E
M19S12E
M09S13E M09S12E
M17S23E
E
E
M13S23E
M15S23E
M14S23E
M16S23E
M10S23E
M12S23E
M11S23E
M09S23E M09S11E
M24S12E M24S16E M24S13E M24S14E M24S15E M24S17E M24S18E M24S1
M10S11E
M11S11E
M12S11E
M17S11E
M14S11E
M15S11E
M13S11E
M16S11E
M18S11E
Fresno County !A Confirmed Detections of TPA DCPA Use (2000 to 2010)
(lbs per section)20,000
-
ea
S09S03E
S11S01E S11S02E
S07S03E
S12S01E S12S02E S12S03E
S0
S10S02E
S07S01E S07S02E
S10S01E
S08S01E
S11S03E01W
S09S01E
S08S02E
S09S02E
S08S03E
01W
S
S0
1W
S
S10S03E
1W
1W
W S07
S13S03ES13S02ES13S01E01W
Figure 6. Total DCPA use (lbs per section) from 2000 to 2010 and locations of confirmed detections of TPA in Riverside County (CDPR, 2015a).
Salton S
Riverside County
Coachella
Temecula
Hemet
Rancho Mirage
San Bernardino County
San Diego County SALTONS
S11S05E
S12S07E
S11S08E
S12S06E
S10S05E
S07S06E
S12S05E
S09S07E S09S05E
S11S09E
S03S02E S03S01E
S08S06E
S10S08E
S03S08E
S02S08E
S09S08E
S11S07E S11S06E
S01S05E
S12S04E
S01S08E
S03S03E
S06S02E
S10S09E
S02N04E
S02S09E
9S04E
S04S07E
S05S07E
S02S07E
S05S06E
S01S06E
S04S06E
S02N05E
S05S05E
S09S06E
S06S07E
S04S04E
S07S02W
S06S03E
S05S08E
S11S02W
S01S09E
S03S04E
S05S03E
S03S06E
S06S08E
S12S09E
S04S05E
S03S05E
S01N05E
S02S02E
S12S08E
S05S01E
S03S07E
S04S08E
S02S01E
S06S06E
S07S08E
S04S09E
S01S03E
S03S09E
S01N09E
S06S05E S06S09E
S07S07E
S02N06E S02N09E
S01N03E S01N02E
S01S02E
S01N08E S01N07E
S02S04E
S01N06E
S05S09E
S06S01E
S01S07E
S08S05E
S02S03E
S04S03E
S05S02E
S02N01E S02N07E
S02S05E
S10S07E
S02N02E
S11S
S01N01E
S02S06E
S02N08E S02N03E
S06S04E
S05S04E
S01S01E
S10S02W
S12S02W
S04S02E
S01S04E
S07S05E
S09S02W
S04S01E
S12S
S10S06E
S01N01W
10S04E
S08S07E
S04S02W
8S04E
S06S02W
S10S0
S08S08E
S02S01W
11S04E
S04S01W
S03S02W
S05S01W
S01N04E
S03S01W
S02N01W
S06S01W
S01S02W
S05S02W
S02S02W
S01S01W
S08S0
S07S09E
S09S0
S01N02W
S02N02W
S07S01 S04E
S08S02W
S13S09E S13S07E S13S08E
S09S09E
S02N10E
S01N10E
S13S06E S13S05E
S01S10E
S13S04E S13S S13S02W
S03N02W S03N01W S03N01E S03N02E S03N03E
S13S03W
S03N04E S03N05E
S02S10E
S12S03W
S11S03W
S04S10E
S03S10E
S05S10E
S10S03W
S09S03W
S06S10E
S07S03W
S08S03W
S07S10E
S08S09E
S03N06E S03N07E S03N08E
S09S10E
S03N09E
Riverside CountyDCPA Use (2000 to 2010)(lbs per section)
20,000
-
S
Figure 7. Total DCPA use (lbs per section) from 2000 to 2010 and locations of confirmed detections of TPA in San Luis Obispo and Santa Barbara counties (CDPR, 2015a; 2015b).
!A
!A
!A
!A!A !A
San Luis Obispo County
Santa Barbara County
Lompoc
Arroyo Grande
San Luis Obispo
Santa Maria
M30S15E M30S16E M30S14E
M32S16E
M30S11E M30S12E
M31S13E M31S17E
M30S17E M30S13E
M32S13E
M31S12E M31S16E
S11N35W
S08N35W
S10N34W
S11N34W S11N33W
M32S14E
S08N34W
M32S15E
S09N34W S09N33W
S10N35W S10N33W
S08N33W
S07N34W S07N33W
S06N31W
M31S14E
S09N35W
S11N32W
S06N34W S06N33W
S09N31W
M31S11E
S07N31W
S09N32W
S11N31W
S07N32W
S10N31W
M31S15E
S08N31W
S06N32W
M29S15E
S06N35W
S08N32W
M32S17E
S07N35W
S10N32W
M29S17E M29S16E M29S14E M29S11E M29S12E M29S13E
S05N34W S05N33W S05N31W S05N32W
M32S18E
10N36W
S12N32W S12N31W S12N33W
M31S10E
M32S12E
S12N34W S12N35W
S05N35W
M31S18E
M30S18E
S11N30W
S09N30W
M29S18E
S10N30W
S07N30W
S08N30W
S06N30W
M30S10E
S06N36W
S11N36W
M29S10E
S12N30W
S08N36W
S09N36W
M32S11E
S12N36W
S07N36W
San Luis Obispo CountySanta Barbara County !A Confirmed Detections of TPA DCPA Use (2000 to 2010)
(lbs per section)20,000
-
Figure 8. Locations of previous confirmed detections of TPA in California from samplingconducted between 1990 and 1997 (CDPR, 2015b).
!H!H!H
!H
!H!H!H !H
!H
!H!H!H!H
!H!H!H
!H !H!H!H
!H
!H !H
!H
!H!H!H
!H!H!H!H!H
Kern
InyoFresno
Tulare
Mono
Monterey
Los Angeles
MaderaMerced
Kings
Ventura
Tuolumne
San Luis Obispo
Santa Barbara
MariposaStanislaus
Solano
Orange
Calaveras Napa
Alameda
Alpine
San Bernardino
San Benito
San Joaquin
Santa Clara
Amador Yolo Sacramento
Contra Costa
San Diego
San Mateo
Santa Cruz
Marin
El Dorado
San Francisco
!H Confirmed Detections of TPA County Boundaries
Tables_Figures_finalized.pdfTables_finalTable1_finalTable2_finalTable3_finalTable4_finalTable5
Figures_1_8_finalFig1_CA_DCPA_use_finalFig2_Monterey_DCPA_use_finalFig3_Imperial_DCPA_use_finalFig4_Ventura_DCPA_use_finalFig5_Fresno_DCPA_use_finalFig6_Riverside_DCPA_use_finalFig7_SLO_SB_DCPA_use_finalFig8_confirmed_detects_final