A Review and Assessment of the Results of Water 

Monitoring for Herbicide Residues 

 For the Years 1991 to 1999 

USFS Region Five 

David Bakke 

Regional Pesticide-Use Specialist 

February, 2001 
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Abstract

Water quality monitoring has long been associated with herbicide use in Region 5 of the 

Forest Service. The 1989 R5 Vegetation Management for Reforestation FEIS Record of 

Decision requires the consideration of water quality monitoring. This has led to 

monitoring surface and ground water on several operational herbicide projects since 

1991. 

There have been eight Forest reports on glyphosate monitoring, and five reports on 

triclopyr monitoring. Results from these reports indicate that glyphosate and triclopyr are 

rarely detected in surface water. This result is expected from the respective herbicide 

characteristics. Detections have been associated with use within riparian areas or not 

following established Best Management Practices. There have been nine reports on 

hexazinone surface water monitoring and eight on ground water monitoring. Hexazinone 

has been detected numerous times in both surface and ground water, which is also 

expected, based on the herbicide characteristics. If label direction and Best Management 

Practices are followed, detected amounts of hexazinone are very low. Projects utilizing 

hexazinone should be carefully designed to reduce the chances of unintentional direct 

introduction of hexazinone into surface water. 

Many of the herbicide water monitoring projects in R5 have not consistently used 

adequate quality controls. The accuracy of the data must be considered in that light. 

 
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I. Introduction

In February 1989, the Record of Decision (ROD) was signed for the Final Environmental 

Impact Statement on Vegetation Management for Reforestation (R5 FEIS). This ROD 

allowed the local land manager to utilize all available tools, including herbicides, for the 

management of competing vegetation in conifer plantations in Region 5. Included in the 

ROD (page 12) was the requirement that each project involving the use of herbicides in 

proximity to water conduct monitoring of water quality, as defined in the project’s site 

specific environmental analysis. This was a reiteration of the water monitoring described 

in the R5 FEIS, on page 2-32, in which the monitoring was intended to “identify patterns 

of herbicide persistence and mobility at sensitive sites”. Monitoring can also include 

implementation monitoring, to determine whether mitigations that are supposed to be 

implemented actually are completed. 

Since the R5 FEIS was signed, several Forests have initiated herbicide treatments that 

have resulted in water monitoring. Since 1991, about 113,000 acres have been treated 

with herbicides to aid in reforestation; these acres have occurred on well over 30 separate 

projects. There have been three herbicides that have been monitored: glyphosate; 

triclopyr; and hexazinone. The documentation of this monitoring has been recorded in 

various formats and at varying frequencies since the first monitoring was conducted in 

the Region after 1989, on the Eldorado NF, in 1991. Considerable effort and financial 

resources have been expended to collect these monitoring data, and develop these reports. 

This review is intended to pull together the various reports completed over the past 10 

years, and compare the results with the assumptions in the R5 FEIS as well as to develop 

conclusions or recommendations that can be passed on to project managers. 

II. Assumptions in the R5 FEIS 

The R5 FEIS assumes, for the purposes of analyzing effects to human health and wildlife 

(including fish and other aquatic organisms), that certain amounts of any applied 

herbicide will drift to nearby watercourses. The amount considered in the R5 FEIS as the 

realistic water contamination rate is 10 parts per billion (ppb) per 1-pound active 

ingredient (lb ai) applied (pg F-84). The 10 ppb rate is a conservative rounding-up of 7 

ppb, calculated by assuming that 1% of any applied herbicide would move to the other 

side of a 50-foot unsprayed buffer strip as a result of a 5 mph crosswind. The resulting 

water concentration is based on this errant herbicide being deposited into a 6” deep creek 

(page F-84). 

 

Table 4-11 in the R5 FEIS (page 4-49), shows ‘realistic’ and ‘worst case’ concentrations 

in water based on the drift assumptions and using the mid-range (realistic) rate of use 

(from Table F-27, page F-93), or the label maximum rate (worst case) as well as a 1.21 

multiplier to represent mixing and overlap errors. [There is an error in this table, for the 

realistic concentration of hexazinone; the mid-range application rate is 2.25 lbs/ac for 

hexazinone, which should equate to 0.022 parts per million (ppm), instead the value in 

Table F-27 shows 0.011 ppm.] The values for glyphosate from Table F-27 are 2.75 lbs 

and 5 lbs for mid-range and for label maximum; the values for triclopyr are 4 lbs and 8 
Page 4 

lbs; and for hexazinone are 2.25 lbs and 3 lbs. This results in concentrations for 

glyphosate (from Table 4-11) of 0.028 and 0.061 ppm for realistic and worst case. For 

triclopyr, they are 0.040 and 0.097 ppm, and for hexazinone (corrected) they are 0.022 

and 0.036 ppm. 

Table 4-2 in the R5 FEIS (page 4-8) shows the results of water quality monitoring in the 

period 1974 to 1984. During this period, glyphosate and hexazinone were sampled, but 

triclopyr was not. Of 50 glyphosate samples, only 1 had detected residues, and that was 

below 10 ppb. Of 29 hexazinone samples, only 1 had detectable residues, and that was at 

2 ppb. Of the total water monitoring conducted during this period (1,237 samples, most 

of which involved 2,4-D), 90% of samples had no detections, 9.7% had detections at or 

below 10 ppb, and 0.3% of samples had levels up to 40 ppb (R5 FEIS, pages 4-8 and 4-

11). 

The R5 FEIS expects that storm runoff may result in brief increases in herbicide 

concentrations but that because such increases are transitory and because the R5 FEIS 

assumes relatively little herbicide exposure contributed by drinking water (as opposed to 

other sources of exposure), “runoff is unlikely to significantly contribute to human 

exposure and it is not considered in this analysis” (page F-87). This is referring to 

surface runoff, not subsurface movement. On page 4-10, the R5 FEIS states, 

“Contaminated sediment, leached soil water, and surface water have not been shown to 

produce significant concentrations of herbicides.... Accidental direct application and drift 

are the most likely ways detectable amounts of herbicides could enter forest streams.” 

The R5 FEIS (Table 4-3, page 4-9) assumes that glyphosate has a half-life in the 

environment, in both soil and water, of less than 3 months. Triclopyr is assumed to have 

a half-life of less than 3 months in soil, and only 7 days in water. Hexazinone has a halflife up to 12 months in soil and 8 months in water. 
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III. Summaries of Monitoring Reports – 1991 to 1999

The following summaries are taken from the available written reports as of December 

2000, as well as some personal communications on results not yet incorporated in final 

reports. A reference number follows each study title; refer to the References (Section V) 

for the complete identification of these reports. This section is broken into four 

subsections: hexazinone ground water results; hexazinone surface water results; 

glyphosate surface water results; and triclopyr surface water results. In this section, if 

field quality control (spike and blank samples) was implemented, it is noted. 

A. Hexazinone Ground Water Results 

Sierra NF Study (Reference 8)

Background – Stand 728-505. Lewis Creek Watershed, Mariposa RD. 4400’ elevation. 

Holland Soil. 3 lbs/acre hexazinone applied March 15, 1994. Formal study with 

lysimeters installed, catchment basin to measure hexazinone movement into ‘vadose 

zone’ (above water table, unsaturated soils) as well as surface flow. Test plot at edge of 

25’ buffer along Class 4 streamcourse. Lysimeters set up at edge of buffer, 10’ and 20’ 

into buffer at 2, 4, and 6 feet deep. Surface water runoff was collected 15 feet into buffer. 

By April 29, 1994 (about 6 weeks after treatment), dead target vegetation in treated plot 

indicates that hexazinone has moved into soil. Laboratory analysis limit of detection 

(LOD) = 0.10 ppb in water. 

Results: 

- Non-detection (ND) on April 5 (20 days after treatment (dat)) and April 15 

(30 dat). 

- May 2 (47 dat), picked up hexazinone at both 2 and 4 feet depth and at edge 

and 10’ into buffer, 0.5 – 2.1 ppb. 

- May 2 picked up hexazinone at 6 feet depth and 20 feet into buffer, from ND 

to 0.2 ppb. 

- May 26 (71 dat), ND at 6’ depth; 0.2 – 1 ppb at 2 and 4 foot depth. 

- June 9 (85 dat), 0.2 – 0.5 ppb at 2 and 4 foot depth at edge and 10 foot in, 1 

detect at 6 feet depth, 20 feet into buffer (0.10 ppb). 

Conclusions – This study used soil lysimeters that measured hexazinone at soil depths of 

2-6 feet, which is within the rooting zone of target vegetation. This study is different 

than the other groundwater results involving 10 to 45-foot deep monitoring wells, which 

focused on measuring water in shallow groundwater, but outside the rooting zone. 

“Subsurface water transported hexazinone vertically and laterally in the soil profile.” 

Movement is at least 20 feet horizontally and 6 feet vertically. Highest level detected in 

groundwater - 2 ppb. Didn’t measure water concentrations in surface water, so cannot 

compare with R5 FEIS assumption, but very low concentrations in subsurface water and 

surface runoff would indicate any amount contributed to surface water would be very 

low. 
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Eldorado NF Amador RD Study (Reference 4)

Background – Unit 123-44, 6200’ elevation. Application October 12, 1993, rate and 

formulation unknown (but likely Pronone, at 2-3 lbs ai/ac), 50-foot buffer on creek. 

Chosen as likely unit to see hexazinone movement subsurface because: 1) 

volcanic/granitic contact zone; 2) close to a perennial creek; 3) close to a meadow: 4) 

presence of water-loving vegetation. Soils are DG or andesitic lahar, sandy loams. Three 

shallow groundwater wells established: #1, 20 feet from creek, 17 feet deep; #2, 30 feet 

from creek, 21 feet deep; #3 in the treated unit, 100 feet from creek, 28 feet deep. 

Quality control (QC) included spikes/blanks. LOD = 0.2 ppb. 

Results: 

Samples were taken once a month through June 1994, then December 1994 and February 

1995. 

- Well #1 had 3 positives 0.5 – 0.96 ppb, first detection 5 months after treatment, 

last one in December 1994 (about 14 months after treatment). 

- Well #2 had 1 positive 0.29 ppb (March 1994, 5 months after treatment) 

- Well #3 had 1 positive 0.2 ppb (March 1994, 5 months after treatment) 

- No detections in wells in February 1995 (last sample, 16 months after treatment) 

- The stream didn’t show any positives (the hydrologist assumed dilution resulted 

in ND) 

Conclusions – “...hexazinone did enter the groundwater and traveled a distance of at 

least 50 feet...” “Hexazinone has the ability to enter shallow aquifers and be transported 

through the saturated zone. The study also shows that hexazinone can persist on site for 

over a year [14 months].” Highest level detected in groundwater - 0.96 ppb. Hexazinone 

leached at least 28 feet deep. No detections in surface water, so within assumptions of 

R5 FEIS. Low concentrations in subsurface water would indicate any amount 

contributed to surface water would be very small. 

Stanislaus NF – Paper (Reference 11)

Background – Hunter and Duckwall Creeks, 3000 – 5000 foot elevation. Two wells 

established as part of this project; located near surface water monitoring point HU30. 

Wells established March 8, 1996: 10 feet and 25 feet deep. Unit treated March 17, 1996, 

with 3 lbs/acre hexazinone (Pronone) aerially applied. Buffers were 100 feet if stream 

has flowing water, otherwise no buffer. 

Results: 

- ND on day wells established (pre-treatment) 

- ND on April 18, 1996 (30 dat) 

Conclusions – Very limited sample size, little to be concluded. 

 
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Stanislaus NF – Hamm-Hasloe (Reference 12)

Background – Moore Creek, Big Creek, Deer Lick Creek and Jordan Creek. Project 

involved 817 acres of ground-based hexazinone (Pronone) application in March 1996 

(rate not shown). Buffers – 50 feet if water is in channel, otherwise 10 feet. Two wells 

established, one in Moore Creek and one in Big Creek watershed. Big Creek well 

(MW26-12) at 3200-foot elevation established October 19, 1994 and 30 feet deep. 

Moore Creek well (MW26-21) at 3000-foot elevation, established March 3, 1995 and 15 

feet deep. LOD = 0.1 ppb. 

Results: 

- Pretreatment samples on March 11 showed ND in both wells. 

- Big Creek well showed ND on May 8 (about 60 dat) and June 6, 1996 (about 90 

dat). 

- Moore Creek well showed 0.18 ppb on April 18 (about 30 dat), and ND on June 

6, 1996 (90 dat). 

Conclusions – Consistent with other studies, with very low levels (0.18 ppb) or nondetect in relatively shallow wells. Hexazinone leached between 15 and 30 feet deep. 

Low concentrations in subsurface water would indicate any amount contributed to 

surface water would be very small. 

Stanislaus NF – Ruby (Reference 14)

Background - Rose Creek Watershed. Treatments in 1997-98-99. In 1997, 3 lbs 

hexazinone (Pronone) applied aerially on 1167 acres, 220 acres by ground. 100-foot 

buffer for aerial, 50-foot buffer for ground. QC – blanks, no spikes. Private lands had 

previously been treated. Two wells established in March 1997 to monitor 1997 

application, RU1 (32 feet deep) and RL1 (22 feet deep). LOD = 0.1 ppb. 

Results: 

- Baseline sample taken in March 1997 (about 2 weeks after treatment) from RU1 

showed ND; pretreatment sample taken from RL1 had 0.31 ppb but hydrologist 

determined it to be a result of the contamination of sample, since no precipitation 

had occurred after treatment. 

- Samples taken in each well May, June 1997 and May 1998; all ND. 

 

Conclusions – After 14 months, no detectable levels of hexazinone at this depth. 

Consistent with other studies, with very low levels or non-detect in relatively shallow 

wells. 

Stanislaus NF – Domingo (Reference 10)

Background - San Domingo Creek watershed, Calaveras County. 3000-foot elevation. 

440 acres treated with hexazinone (Velpar L) by ground application, March 1995. 
Page 8 

Buffers 80-100 feet on San Domingo Creek, 50 feet on tributaries. LOD = 0.1 ppb. QC 

– blanks/spikes. One ground water well (SD-36) established at base of unit 35, 17 feet 

deep. Noted that well dries out quickly between storms and in summer. 

Results: 

- ND during pretreatment sample 

- Detections on May 3 (0.2 ppb) and May 9, 1995 (0.21 ppb) (about 2 months after 

application) 

Conclusion – Consistent with other studies, with very low levels or non-detect in 

relatively shallow wells. Low concentrations in subsurface water would indicate any 

amount contributed to surface water would be very small. 

Sierra NF – Mariposa (Reference 7)

Background – Miami Creek watershed, 4000 foot elevation. Chosen as likely unit to see 

hexazinone movement subsurface because: 1) shallow aquifer yielding flow to nearby 

perennial creek; 2) aquifer likely to flow rapidly due to slope steepness; 3) access to 

wellheads. Soils are DG. 2 wells established in Unit 103 (37 feet deep and 17 feet deep); 

2 wells in Unit 115 (45 feet deep and 10 feet deep), all established March 31, 1993. 2.6 

lbs/acre hex applied in unit 103 on March 10, 1993; 1.6 lbs/acre hex applied in unit 115 

on March 23, 1993. LOD = 0.1 ppb. 

Results: 

- 3 of 4 wells sampled March 31, 1993 (one well was dry) (21 dat, 8 dat) – all ND 

Conclusion – Geologist had determined that enough rainfall had occurred to move hex 

into ground water (unit 103 had 5.7” rain, unit 115 had 4.5” rain between treatment and 

sample). Geologist assumed only days needed to do so, which, based on other studies 

may not have been correct, especially for sample taken 8 dat. In any case, consistent 

with other studies, with very low levels or non-detect in relatively shallow wells. 

Eldorado NF – Peddler Hill (Reference 2)

Background – Peddler Hill Springbox located about 450 feet downhill from unit treated 

November 1991 with hexazinone by ground (rate and formulation unknown (but likely 

Pronone, at 2-3 lbs ai/ac)). LOD = 1 ppb. 

Results: 

- first post-treatment sample was May 20, 1992 (6 months after treatment), showed 

1.7 ppb 

- Samples taken June 22, June 29, and June 8, 1992 showed ND 

- Sample taken July 13, 1992 showed 1.4 ppb 

- Samples taken July 21, July 27, and December 21, 1992 showed ND 

- No further results published. 
Page 9 

Conclusion - Consistent with other studies, with very low levels or non-detect in a spring. 

Low concentrations in subsurface water would indicate any amount contributed to 

surface water would be very small. Movement up to 450 feet in groundwater. 

 
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B. Hexazinone Surface Water Results 

Eldorado NF – 1991 (Reference 2)

Background – Hexazinone (Pronone 10G) applied via ground-based methods in various 

units on the Eldorado NF in October and November of 1991, at rates of 2-3 lbs ai/acre. 

Buffers: Class 1, domestic – 200 feet; class 2, 3 – 100 feet; class 4 – 50 feet. LOD = 1 

ppb. 

Results: 

- 1 of 29 sites had a detection as a result of a storm (3.5 – 5” rain) within days of 

application (treated October 25, sampled October 26). Detected 1.8 ppb. 

- 6 of 36 sites had detections from spring snowmelt runoff, with rates ranging from 

1.3 to 2.8 ppb. 

- 0 of 14 sites had detections in fall, 1992 (about 1 year after treatment) 

Conclusions – Results were below assumption in the R5 FEIS. Overland flow as result of 

storms can contribute to surface water contamination. 

Eldorado NF – 1992 (Reference 3)

Background - Hexazinone (Pronone 10G) applied via ground-based methods in various 

units on the Eldorado NF in late October and early November of 1992, at rates of 2-3 lbs 

ai/acre. Buffers varied by district: class 2, 3 – 100 feet (Class 2 - 200’ Georgetown); 

class 4 – 50 feet. QC – blanks and spikes. LOD = 1 ppb. 

Results: 

- 0 of 12 sites had detections as a result of first storm within 1-1.5 months of 

treatment 

- 8 of 25 sites had detections from spring snowmelt, ranging from 1.3 to 19 ppb 

(one sample was >10 ppb). 

- 3 of the 8 sites with spring snowmelt detections dropped to ND by August, 1993. 

5 of these 8 had detections 1 year later, ranging from 1.1 to 15 ppb. 

- 3 of the 5 with detections after 1 year have been continuously showing low levels 

of detection, with no apparent seasonal trends, for 24 months after treatment (at 

levels mostly below 4 ppb) [NOTE – based on personal communication with 

Cheryl Mulder, Eldorado hydrologist, monitoring through Spring of 1997 has 

shown very low (0.74 – 1 ppb) but continuing detections.] 

Conclusions – Levels detected were below assumption in the R5 FEIS. However, 

persistence has been longer than anticipated, but absence of QC in later samples and 

levels near LOD should be considered. Groundwater is likely source of continuing 

contamination but hexazinone groundwater studies have not detected similar lengthy 

persistence times. 
Page 11 

Sierra NF Study (Reference 8)

Background - Stand 728-505. Lewis Creek Watershed, Mariposa RD. 4400’ elevation. 

Holland Soil. 3 lbs/acre hexazinone (Velpar L) applied March 15, 1994. Formal study 

with lysimeters installed, catchment basin to measure movement into ‘vadose zone’ 

(above water table, unsaturated soils) as well as surface flow. Test plot at edge of 25’ 

buffer along Class 4 streamcourse. Surface water runoff was collected 15 feet into 

buffer. LOD = 0.10 ppb in water, 10 ppb in soil. By April 29, 1994 (about 6 weeks after 

treatment), dead target vegetation in treated plot indicates that hexazinone has moved into 

soil. 

Results: 

- Surface water runoff indicates overland flow, with detections during the period 

from March into May (2 months after treatment) at levels of 0.11 to 1.0 ppb, 

fifteen feet into buffer. 

- Surface soil collected in buffer on May 3rd also had detections, indicating surface 

movement of hexazinone out of unit (11 to 15 ppb five feet into buffer, ND to 13 

ppb ten feet into the buffer). 

- By June 3, surface soil showed ND in buffer. 

- In contrast, surface soil in the unit showed 900 ppb on April 1; 600 ppb on May 3 

and 360 ppb on June 3, 1994. 

Conclusions – Results were below assumption in the R5 FEIS. Normal rainfall and 

snowmelt patterns can move hexazinone, in solution, over soil surface with runoff. 

Distance traveled in this case was at least 15 feet (no further distances measured), but at 

very low levels. [NOTE – Continuing Phase II study is in progress.] 

Stanislaus NF – Paper (Reference 11)

Background - Hunter and Duckwall Creeks, 3000 – 5000 foot elevation. Nested 

monitoring design: 3 subwatersheds (1 in Duckwall, 2 in Hunter) with high proportion of 

area treated, plus various points along collector creeks. Included one point (HU 50) that 

monitored water flowing from private land that was described as a 375 acre subwatershed 

that was 100% treated in November 1994 with aerial application of 30 lbs Pronone 

10G/acre (3 lbs/ac hexazinone). Unit treated March 17, 1996, with 3-lbs/acre 

hexazinone aerially applied. Buffers 100 feet if water is flowing in stream, otherwise no 

buffer. Day of application samples also taken at three points. Samples taken with both 

automated samplers and grab samples. LOD = 0.1 ppb. 

Results: 

- Private land monitoring (HU 50) showed detections of 4.8 to 14 ppb from March 

1996 to June 1996, which is 16-18 months after treatment. 

- Day of treatment samples at all three sites showed detections, ranging from 6.5 

ppb in Hunter subwatershed with 98% treated (HU 15) to 0.7 ppb in another 

subwatershed (HU 30), while mainstem of Hunter Creek showed 1.3-1.8 ppb (HU 

10), although this point is below private land monitored at HU 50. 
Page 12 

- Pre-treatment samples at HU 10 and HU 20, on the Hunter Creek mainstem, 

showed 1.2 and 1.9 ppb, and are also receiving water from private land. 

- Subwatershed HU 15 continued showing detections, peaking at 43 ppb during a 

storm event (March 28, 1996, 11 dat), dropping below 10 ppb after. Last reading 

June 5, 1996 (about 80 dat) showed < 1 ppb. 

- Subwatershed HU 30 continued showing detections, peaking at 36 ppb during a 

storm event (April 16, 1996, about 30 dat). Last reading on June 5, 1996, < 1 

ppb. 

- Subwatershed DU 5 began showing detections within 10-14 days after treatment, 

showing 6.8 ppb on March 28. Detections were consistent, but lower, through 

April. Last sample on June 5, 1996 showed ND. 

- HU 20 and HU 10, on mainstem Hunter Creek, showed detections, all below 5 

ppb between treatment and June 5, 1996, except for storm peaks (16 ppb on April 

16 at HU 20, and 28 ppb on March 28 and 6.5 ppb on April 18 at HU 10). DU 10 

on mainstem of Duckwall Creek showed a peak of 15 ppb on March 28, otherwise 

all detections below 5 ppb, with ND on June 5. 

Conclusions – Water from private lands showing detection after 16-18 months is in line 

with other results showing detections for up to 2 years. Day of application detections in 

HU 15 and HU 30 indicate applications to surface water, which is not consistent with 

Best Management Practices (BMPs). Day of application detection in HU 10 is partially 

or wholly due to private land treatment, although some contribution from the Paper 

project could be possible, depending upon the timing of sample and water travel time. 

Peak levels above 36 ppb are in excess of R5 FEIS worst-case estimate of detection, but 

the estimate was based on drift, not direct application. Storm peak flows were consistent 

throughout both watersheds with pulses of hexazinone (notably March 28 and April 16-

18), however whether this is due to subsurface leaching, overland surface flow, or 

deposition into dry drainages that subsequently ran water is unknown. 

Stanislaus NF - Hamm-Hasloe (Reference 12, 13)

Background - Moore Creek, Big Creek, Deer Lick Creek and Jordan Creek. Project 

involved 817 acres of ground-based hexazinone application in March 1996, with 3 

lbs/acre hexazinone ground applied. Buffers – 50 feet if water is flowing in channel, 

otherwise 10 feet. Nested monitoring design: 5 subwatersheds (all in Moore Creek 

drainage) with high proportion of area treated, plus various points along collector creeks. 

LOD = 0.1 ppb. 

Results: 

- Subwatershed MO-T1 (90% treated) had two samples taken in May 1996, with 

0.79 ppb to ND. [NOTE – Reference 13 indicates detections during storm flows 

in November 1996 through early January 1997 of 59 to 150 ppb.] 

- Subwatershed MO-T2 (40 acres, 100% treated, except buffers) had several high 

peaks during storms: April 1, 1996 – 140 ppb; April 18, 1996 – 52 ppb; May 16, 

1996 – 600 ppb. Readings on May 16, after peak of 600 ppb, dropped to 6.9 ppb 

by end of day. Baseflow readings in June 96 showed ND or < 1 ppb. [NOTE – 
Page 13 

Reference 13 indicates detections during storm flows in November 1996 through 

early January 1997 (10 months after treatment) of 76 to 110 ppb.] 

- Subwatersheds MO-T4 (353 acres, 38% treated), MO-T5 (8% treated), and MOT6 (29% treated) showed detections that were 5.2 ppb or less between the 

treatment date and June 1996. MO-T4 was fairly heavily monitored: 19 of 26 

samples in 2 months after treatment showed detects between 0.1 and 5.2 ppb; base 

flow readings dropped below 1 ppb. 

- The main channel of Moore Creek, below all these subwatersheds had 9 of 23 

samples with detections during the 2 months after treatment, ranging from 0.2 to 

2.7 ppb. During day that subwatershed MO-T2 peaked at 600 ppb, this main 

channel peaked at 1.2 ppb. 

- Other drainages monitored showed very low (< 1 ppb) or ND for all samples. 

Conclusions – Analysis in Hamm Hasloe EIS, using the PRZM model, predicted 

maximum detections of 700 ppb at peak stormflow, with 1-10 ppb at baseflow (Hamm 

Hasloe FEIS, page 4-130), although the water monitoring write-up mentions expected 

rates of less than 100 ppb at stormflow. As a result of high readings in subwatershed 

MO-T2, a review was conducted, which determined that the results were due to areas of 

shallow soil that shouldn’t have been treated, steep slopes that facilitated movement of 

herbicide, and likely misapplication, due to poor footing and steep slopes. Day of 

application monitoring was not done, so cannot determine whether misapplication 

actually occurred. Hydrologists on both Stanislaus and Eldorado think that there may be 

a predictor of hexazinone in water flowing from a subwatershed based on the percentage 

of the watershed treated and the size of the watershed. Same day comparisons of results 

show the effects of dilution on concentration of hexazinone: MO-T2 peaks at 42 ppb on 

March 28 and 140 ppb on April 1; station MO-M1 on the mainstem of Moore Creek (4 

miles downstream) records peaks of 0.1 ppb and 2.7 ppb on these same days. 

Stanislaus NF – Ruby (Reference 14)

Background - Rose Creek Watershed. Treatments in 1997-98-99. In 1997, 3 lbs 

hexazinone applied aerially on 1167 acres, 220 acres by ground; in 1998, 245 acres was 

treated by ground; in 1999, 591 acres was treated aerially. Monitoring design included 

three points that monitored water flowing from private land that had been previously 

treated with hexazinone (extent or timing not described). Other monitoring sites were at 

various points on mainstem of Rose Creek. Day of application samples were taken at two 

points (one in 1997, one in 1999). QC – blanks only, no spikes. 100-foot buffer for 

aerial, 50-foot buffer for ground. LOD = 0.1 ppb. 

Results: 

- Private land monitoring (RC-15, RC-30, RC-40) showed ND or very low levels of 

detection (< 1 ppb). The report doesn’t indicate when the private land was 

treated. RC-15 had 5 samples between March 1997 and November 1997, all ND. 

RC-30 had 10 detects out of 16 samples taken between March 10, 1997 and 

March 12, 1999, last detect was October 1, 1998 (19 months after sampling 

began). RC-40 had 3 detects out of 13 samples taken between March 10, 1997 
Page 14 

and March 12, 1999, last detect was June 22, 1998 (15 months after sampling 

began). 

- Monitoring during application showed a detect at RC-12 on March 17, 1999 at 15 

ppb. From March 23 to July 7, 1999, 4 more samples were taken, showing a peak 

of 5.2 ppb, with summer baseflows at ND or < 1 ppb. 

- Monitoring during application at RC-10 (the mainstem of Rose Creek) during the 

1997 application (March 18, 1997) had 3 of 5 samples with detects, the highest at 

3.1 ppb. The same point was monitored during the 1999 application, with 4 

samples, all detects, with a peak of 32 ppb. Subsequent sampling at this point 

showed fast and sharp decline (March 23 – 2.2 ppb, April 1 – 1.2 ppb, May 20 – 

0.31 ppb, July 7, 1999 – ND). 

Conclusions – Day of application detections would indicate misapplication of hexazinone 

to surface water, as private land contributions appear not to be a factor. This was cause 

for investigation of project after 1999 application, which did determine that contractor 

did not maintain buffers and that Pronone was applied to surface water. The subsequent 

decline in detections would indicate that this pulse of hexazinone was rapidly removed 

from the system. Private land contributions indicate a persistence of at least 19 months, 

assuming that private land was treated prior to the beginning of sampling. 

Stanislaus NF – Domingo (Reference 10)

Background - San Domingo Creek watershed, Calaveras County. 3000 foot elevation. 

440 acres treated with hexazinone (Velpar L) by ground application, March 1995. 

Buffers 80-100 feet on San Domingo Creek, 50 feet on tributaries. Nested monitoring 

design: one 35 acre subwatershed (SD 20) with 100% of area treated except buffers; and 

various points along mainstem of San Domingo Creek. LOD = 0.1 ppb. QC – 

blanks/spikes. 

Results: 

- The subwatershed SD-20 had 10 of 15 samples with detects, ranging from 0.2 to 

1.6 ppb, with first detect 2-3 weeks after treatment (April 6, 1995). The last 

sample taken was about 1 year after treatment, and showed 0.3 ppb. 

- SD –10, the point on the mainstem immediately below all spraying, showed 

detections for 4 of 11 samples from mid-April to mid-May 1995 and then dropped 

to ND in baseflow through March 18, 1996. 

- The other two sample points were downstream, and had very few samples taken, 

but showed levels at the limit of detection (0.1 – 0.11 ppb) in May of 1995. 

Conclusions – The project EA had anticipated 30-50 ppb. The first storm had shown ND, 

detections began with second storm, and levels increased with 3rd, 4th storms, and then 

dropped off. Indicates that subsurface moisture was likely driving hexazinone through 

system. No samples taken day of application, but low levels in subsequent samples from 

SD-20 would indicate a proper application. Results were below realistic water 

contamination assumption in the R5 FEIS. 
Page 15 

Lassen NF – Lost Fire (Reference 5)

Background – March of 1992, 200 acres treated with hexazinone (Pronone) in Proctor 

Creek watershed. During the fall of 1992, an additional 2,200 acres was treated. 

Results: 

- Monitoring of 200-acre application in May 1992 involved two points and one 

sample in each; both showed ND. 

- Monitoring of the 2,200-acre application in March 1993 at two stations showed 

one with a detection, at 1.6 ppb. Subsequent monitoring in May 1993 at 4 

locations showed ND at all. 

Conclusion – Very small sample size, but results consistent with other monitoring. 

Results were below realistic water contamination assumption in the R5 FEIS. 

Sierra NF – Mariposa (Reference 6)

Background – Miami Creek watershed, 4000-foot elevation. 2.6 lbs/acre hexazinone 

applied in Unit 103 on March 10, 1993; 1.6 lbs/acre hex applied in Unit 115 on March 

23, 1993. QC – Blanks/spikes. LOD = 0.1 ppb. 

Results: 

- Pretreatment monitoring at 4 points below Unit 115 – ND in 4 samples. 

- During first storm after treatment (March 29), samples taken at same 4 points, all 

ND. 

Conclusion – Unknown whether sufficient rainfall occurred in this storm to move the 

hexazinone into soil solution. Monitoring occurred less than 1 week after treatment. 

 
Page 16 

C. Glyphosate Surface Water Results 

Sierra NF – Mariposa (Reference 6)

Background – Application of glyphosate during June and July 1992. Miami Creek 

watershed. QC – blanks/spikes. Unknown buffer width. 

Results: 

- Pretreatment samples show ND (2 samples) 

- Day of treatment sample (July 10, 1992) on unit 728-501 shows ND. 

- Samples collected following storms in July (sampled July 12) and October 

(sampled October 27) show ND (4 samples) 

- Sediment samples collected after October storm also show ND. 

Conclusions – No detections in any samples. 

Eldorado NF – 1991 Program (Reference 2)

Background – Glyphosate applied in various units around the Eldorado in June-August of 

1991. Buffers, class 1 – 200’; class 2,3 – 100’; class 4 – 50’. Rates applied from 1.1 to 

2.1 lbs/acre. LOD = 14 or 25 ppb, depending upon the lab used. Pretreatment samples, 

48-hour post-treatment samples and samples after the first storm within 90 days were 

collected. 

Results: 

- 16 pretreatment samples - all ND. 

- 7 48-hour post-treatment samples - all ND 

- 16 first storm samples - all ND (taken October 26, 1991) 

- Sediment samples (pretreatment (18 samples) and after first storm (18 samples)) 

all ND. 

Conclusions – There was some concern that glyphosate would be transported to streams 

through drift or overland flow and settle in streambed sediments. There is no evidence 

that this is the case. No detections in any samples. Results may be below realistic water 

contamination assumption in the R5 FEIS (11 to 21 ppb), but LOD may be higher than 

these assumed levels (information about treatment rates per unit above each sampling 

station are not in the reference). 

Eldorado NF – 1992 Program (Reference 3)

Background – Glyphosate, 2 lbs/ac, applied in various units around the Eldorado in MayAugust of 1992, and May-June 1993 on Georgetown RD. Buffers varied by District: 

class 2 – 200’ on Georgetown RD, 100’ on Placerville RD, 50’ on Pacific RD; class 3 – 

100 feet (50’ Pacific RD); class 4 – 50 feet (25’ Pacific RD). Pretreatment samples, 48 

hour post-treatment samples (Georgetown RD only) and samples after the first storm 

within 90 days were collected. LOD = 14 or 25 ppb, depending upon the lab used. 
Page 17 

Results: 

- 17 pretreatment samples - all ND. 

- 3 48-hour post-treatment samples - all ND 

- 7 first storm samples - all ND (taken June 1992, May 1993) 

- Sediment samples after first storm (5 samples) had one detection (88 ppb), 

although this was ascribed to either contamination of sample or private land 

contribution. 

- [NOTE: communication with Eldorado hydrologist Cheryl Mulder indicates that 

1993 - 1998 results show ND for glyphosate.] 

Conclusions - No detections in any samples. Results may be below realistic water 

contamination assumption in the R5 FEIS, but LOD may be higher than assumed levels 

in R5 FEIS. 

Stanislaus NF – Domingo (Reference 10)

Background – glyphosate applied in March – May 1995. Buffers 20 feet on all streams. 

LOD = 9 ppb. QC = blanks/spikes. 

Results: 

- 8 post-treatment water samples, all stormflow - all ND. 

- 1 post-treatment sediment sample – ND 

Conclusions - No detections in any samples. Results are likely to be below realistic water 

contamination assumption in the R5 FEIS, but exact rate of application not known 

(assumed greater than 1 lb/ac ai. 

Stanislaus NF – Hamm-Hasloe (Reference 12)

Background – glyphosate applied in March 1995 (rate not specified). Buffers 10 feet. 

LOD not specified in report. 

Results: 

- 4 pre-treatment water and sediment samples – all ND 

- 25 post-treatment storm flow water samples (April 13 – May 13, 1995, and March 

28 – April 1, 1996) – all ND 

- 11 post-treatment storm flow sediment samples – all ND 

Conclusions - No detections in any samples. Results may be below realistic water 

contamination assumption in the R5 FEIS, but LOD and rate applied not specified in the 

report. It appears that very small buffers can effectively prevent glyphosate movement 

into streams, although wind speed and direction during this application are not known. 

Stanislaus NF – Groveland 1992 (Reference 9)
Page 18 

Background – Glyphosate applied June 1992 (rate not specified). Buffers 15 feet. LOD 

= 24 ppb (water) and 50 ppb (sediment). QC = limited use of spiked samples. 

Results: 

- No detections in any post-treatment water samples (samples from June through 

December, 1992) (17 samples). 

- No detections in any post-treatment sediment samples (10 samples). 

Conclusions - No detections in any samples. Results may be below realistic water 

contamination assumption in the R5 FEIS, but exact rates applied are not specified in the 

report, therefore the LOD may be higher than assumed levels in R5 FEIS. 

Stanislaus NF – Rogge-Ackerson (Reference 15)

Background – Application of glyphosate in June 2000 (rate not specified). Buffers 10 

feet where water is present. QC – blanks. LOD not specified. 

Results: 

- 11 day of application water samples – all ND 

- First storm after application, within 90 days (2 samples) – ND 

Conclusions - No detections in any samples. Results may be below realistic water 

contamination assumption in the R5 FEIS, but LOD and rate of application not specified. 

Angeles NF (Reference 1)

Background – Not a reforestation project, but a noxious weed control project. 

Glyphosate applied to noxious weed Arundo donax adjacent to and within riparian areas 

in the summer of 1995. 13 acres treated with 80 lbs glyphosate (6 lbs/ac), with <1 acre 

actually aquatic (in-channel) application. LOD = 6 ppb. 

Results: 

- Sample taken 1⁄4 mile downstream (1 sample) – ND 

- [NOTE – memo from Forest Pesticide Coordinator, Joe Gonzales, on 5/25/00 

indicates monitoring at San Francisquito Canyon in 1996, after 10 acres treated 

with 4 lbs/ac glyphosate – ND.] 

- [NOTE – personal communication 12/13/00 with Joe Gonzales, he indicated that 

in 1997, in San Francisquito Canyon, there was one detect of 12 samples, showing 

15 ppb.] 

Conclusions – Appears that riparian application of glyphosate runs small risk of 

detectable concentrations in adjacent water (1 of 13 samples). Don’t know the exact rate 

of application in subsequent applications, but likely greater than 1.5 lbs/acre, so results 

are likely below assumption in R5 FEIS (even though treatments occurred up to and in 

the stream channel). 
Page 19 

D. Triclopyr Surface Water Results 

Eldorado NF – 1991 Program (Reference 2)

Background – Triclopyr applied in various units around the Eldorado in August of 1991. 

Buffers, class 1 – 200’; class 2,3 – 100’; class 4 – 50’. Rate applied 1 lb/acre. LOD = 1 

ppb. Pretreatment samples, 48-hour post-treatment samples and samples after the first 

storm within 90 days were collected. 

Results: 

- 6 pretreatment samples – all ND 

- 5 48-hour post-treatment samples – all ND 

- 6 samples after first storm (samples collected October 26, 1991) – 5 had ND, 1 

had 82 ppb (Station 55J91) 

- 55J91 remeasured on December 11, 1991 - ND 

Conclusions – The detection at 55J91 was determined to be the result of not establishing 

a buffer along the ephemeral portion of the headwater of a drainage. When the storm 

occurred, this portion of the drainage likely ran water. No detections in other samples. 

With the exception of the one detection, the results are below realistic water 

contamination assumption in the R5 FEIS. 

Eldorado NF – 1992 Program (Reference 3)

Background - Triclopyr, 1 lb/ac, applied in various units around the Eldorado in JuneAugust of 1992, and May-June 1993 on Georgetown RD. Buffers (class 2 varied by 

District): class 2 – 200’ on Georgetown RD, 100’ on Placerville and Pacific RDs; class 3 

– 100 feet; class 4 – 50 feet. Pretreatment samples, and samples after the first storm 

within 90 days were collected. LOD = 0.1 and 1 ppb. QC – spikes and blanks. 

Results: 

- 11 pretreatment samples – all ND 

- 1 sample after first storm – ND 

Conclusions – Very small sample size, as only one monitoring point had precipitation 

within 90 days, which was a spring storm after an application in May 1993. 

Stanislaus NF – Domingo (Reference 10)

Background – Triclopyr applied in the spring (April-May) of 1995 (report noted that on 

many days, the applications were interrupted with rain). Buffers – 20 feet. QC – blanks 

and spikes. LOD 0.4 ppb. 

Results: 

- 8 post-treatment water samples (May through mid-June), mostly stormflow 

sampling – all ND 
Page 20 

- 1 sediment samples – ND 

Conclusions – No detections in samples. Although application rate is not specified, it is 

likely that with the low LOD, results are below realistic water contamination assumption 

in the R5 FEIS. 

Stanislaus NF – Hamm-Hasloe (References 12 and 13)

Background – Triclopyr applied in summer of 1996 on 413 acres in tank mix with 

glyphosate (rate not specified). Buffers 10 feet. LOD not specified. 

Results: 

- MO-T9 (Tributary to Moore Creek, near Smith Ridge), shows following postspray detections: June 4, 1996 – ND; June 26 – 0.6 ppb; October 25 – ND; 

November 17-18 – 0.6-2.4 ppb (4 samples); December 10 – 0.6-0.8 ppb; 

December 11 – ND; December 30 – 0.47 ppb. The detections in June, October 

and November are indicated as being during stormflows. 

- NM-T1 (Tributary of NF Merced, near Jackass Mountain), shows following 

detections: December 5, 1996 – 0.63 ppb; December 10 – 0.6-0.7 ppb; December 

11 – ND 

Conclusions – Buffers may have been insufficient to keep triclopyr out of streamcourses, 

although detected amounts are below R5 FEIS realistic water contamination assumptions 

(assuming 1 lb ai/acre applied and a LOD < 1ppb). 

Stanislaus NF – Groveland 1992 (Reference 9)

Background – Triclopyr applied June 1992. Buffers 15 feet. LOD = 0.1 ppb (water) and 

1 ppb (sediment). 

Results: 

- Five stations monitored for triclopyr; pretreatment samples – ND 

- One station (54O) showed a detection after storm in December 1992, at 1 ppb. 

No other detections in any post-treatment water samples (6 samples from June 

through December, 1992). 

Conclusions - Buffers may have been insufficient to keep triclopyr out of streamcourses, 

although detected amounts are below R5 FEIS realistic water contamination assumptions 

(assuming 1 lb ai/acre applied). 

 
Page 21 

IV. Conclusions and Recommendations

As a foreword to this section, it must be noted that the inconsistent use of quality control 

practices involving the use of known blank and spiked samples makes some conclusions 

difficult to support. This has been recognized as a problem by the hydrologists in the 

Region and is more a logistical problem to be solved than one of understanding the need 

for such quality control practices. 

Overall, one can conclude from this monitoring that when Best Management Practices 

are correctly implemented, monitoring results indicate that the R5 FEIS realistic water 

contamination levels of 10 ppb per pound active ingredient applied are easily met and can 

be considered very conservative in any effects analysis. In most of the monitoring that is 

documented here, the majority of samples were either clear of detectable levels of 

herbicides, or were at very low levels. The exceptions will be discussed below. Table 1 

shows the number of samples collected, and the levels of detections for each herbicide. 

This table can be compared with Table 4-2 (page 4-8) in the R5 FEIS. 

Table 1 – Water quality monitoring of Region 5 herbicide projects, 1991 – 2000 

1

 No control or pretreatment samples have been included in this table. 

2

 ppb = parts per billion 

3

 Where limit of detection (LOD) may be higher than a reported concentration, the 

maximum has been listed as “less than” (<) the LOD. This is the case with glyphosate. 

Hexazinone 

Hexazinone has been extensively monitored in Region 5 since 1991. As expected by its 

chemical nature, hexazinone goes into soil solution quickly and then some percentage 

moves through soil profiles into shallow ground water, or moves overland in surface 

water flow, and is subsequently found in surface water in streams. From Table 1, out of 

the total hexazinone samples, roughly half showed no detections. 

Once detected, the levels of hexazinone in groundwater are very low (see Figure 1). The 

highest level detected was 2.1 ppb (reference 8) in very shallow lysimeter holes (2 feet 

deep). 95% of detections are at levels very near limits of detection (<1 ppb). Lag time 

and amount of positive detections with depth vary considerably. Once hexazinone is in 

shallow groundwater, lateral movement can be extensive (example, Peddler Hill 

springbox was about 450 feet downhill from treated unit). It appears from the surface 

water data that groundwater can continue to feed hexazinone into surface water over a 

long period of time, regardless of implementation of BMPs to directly protect surface 

Herbicide Total 

Samples 1

With No 

Detectable 

Residues 

0-10 

ppb 2

11-

30 

ppb 

31-

50 

ppb 

51-

100 

ppb 

101-

600 

ppb 

Maximum 

observed 

concentration 3

Glyphosate 104 103 1 < 25 ppb 

Triclopyr 43 30 12 1 82 ppb 

Hexazinone 

 Surface 

 Ground 

580 

103 

245 

78 

301 

25 

16 4 8 6 600 ppb 

2.1 ppb 
Page 22 

water. The FEIS did not consider this source to be a substantial component of surface 

water contamination. Ground water monitoring however has not shown long persistence, 

although sampling for this purpose is limited in these reports. 

Surface water monitoring of hexazinone over long periods shows very low levels of 

detected hexazinone, well below the expected 10 ppb/lb ai applied (often below 1-2 ppb 

total)(Figure 2), so regardless of source, the R5 FEIS assumptions of levels of 

contamination are very conservative. Based on the surface water sampling, 90% of all 

hexazinone detections are below 7 ppb; 95% are below 15 ppb. Assuming that the 

average application rate is between 2 and 3 pounds per acre active ingredient, then 97% 

of the time, amounts of hexazinone were either below limits of detection or at levels 

below what the R5 FEIS assumed (20-30 ppb) for this rate of application. As a method 

of comparison, the current EPA Health Advisory level (HA) is 400 ppb (the highest 

concentration of hexazinone in drinking water considered safe for us to drink on a daily 

basis). In lab testing, some species of algae have seen growth effects at levels of 

hexazinone of 3 ppb, although any effects to aquatic insects and fish are not expected 

until levels greatly exceed 1 ppm (1,000 ppb). 

Figure 1. 

Cumulative Frequency Graph

Hexazinone in Groundwater, n=103

0.7

0.75

0.8

0.85

0.9

0.95

1

0.01 0.1 1 10

concentration (ppb)

cumulative frequency

Figure 2. 
Page 23 

Cumulative Frequency Graph

Hexazinone in Surface water, n=580

0.4

0.5

0.6

0.7

0.8

0.9

1

0.1 1 10 100 1000

concentration (ppb)

cumulative frequency

400 ppb, current 

EPA HA

3 ppb, effects seen in 

one species of algae

Persistence of hexazinone in the environment may be longer than anticipated in the R5 

FEIS (which assumed a half-life of 1 – 12 months), with fairly consistent results 

indicating at least an 18 – 24 month timeframe when hexazinone can be detected, and two 

studies indicating the potential for even longer timeframes. The Eldorado results (C. 

Mulder, Personal Communication) would indicate persistence times of up to 4.5 years, 

and preliminary results from the Stanislaus (S.Apperson, personal communication) would 

indicate in one case, persistence in surface water of up to 4 years. None of the ground 

water monitoring results indicate such long persistence. 

There is some thinking that the percentage of a subwatershed that is treated with 

hexazinone may be tied to levels of hexazinone detected in downstream water. However, 

in the cases where this has been observed (References 11, 12), the untreated buffers that 

were in place along streams may have been inadequate to prevent overland flow into 

drainages. This conclusion is supported by the results of one monitoring study 

(Reference 10) where a small subwatershed with 100% of the area outside of buffers, did 

not show high levels of downstream hexazinone, but also had wider buffers (i.e., 50 feet 

vs 10 feet or 0 feet on ephemerals) as compared to the two other studies. Whatever the 

cause of the high rates from these subwatersheds, it does appear that high subwatershed 

levels of hexazinone are quickly diluted downstream. It also appears that these small 

subwatersheds, if they have high levels of hexazinone detected in the first wet season, can 

have high pulses of hexazinone the following year (Reference 12). 

Erroneous applications directly to surface water result in high spikes in hexazinone 

concentration that quickly subside. This is in agreement with the discussion in the R5 

FEIS (page 4-10). 
Page 24 

Outside of an accidental misapplication of herbicides to water, it appears that treating a 

high percentage of a small subwatershed, in combination with placing buffers only on 

streams running water, represents the higher risk over the longer term of introducing 

hexazinone at levels above assumed levels in the R5 FEIS. In small subwatersheds (<100 

acres), consideration of this observed effect should result in heightened awareness of the 

need for a more effective buffer system. 

It would seem advisable to continue to monitor hexazinone in surface water, including 

day of application sampling for new projects. The groundwater monitoring may be better 

focused on resampling of existing wells to see if persistence of hexazinone for periods 

greater than 2 years can be determined. It is also recommended that any water 

monitoring program be consistent in its use of known blank samples and spiked samples. 

Any resampling of the streams with long histories of detection should be accompanied by 

a comprehensive quality control sampling scheme. 

 

Glyphosate 

All sampling was done after ground-based applications. There were no detections in 

water or sediments in any samples taken after reforestation projects (that were not 

ascribed to sample contamination). The one type of project with a detection of 

glyphosate involved treatment of noxious weeds within the riparian zone. Even here, 

only one of twelve samples had a detection, and that was at a low level (15 ppb), below 

any level of concern for human health or aquatic resources (SERA, 1996a). 

Recently, the amount of post-treatment sampling done for glyphosate has dropped 

considerably as most sampling protocols call for sampling only if a storm occurs within 

90 days of application and causes a rise in stream levels. With glyphosate generally 

applied in late spring to late summer, this condition rarely occurs. Based on monitoring 

to date, glyphosate applications, as generally practiced in reforestation projects, will not 

result in stream sediment or water contamination. 

It would seem that the monitoring of ground-based applications of glyphosate outside of 

riparian areas, and absent any project-specific unique circumstances or concerns, should 

be discontinued, especially on the Westside of the Sierra Nevada range. If any aerial 

applications of glyphosate occur, they should be monitored, including day of application 

monitoring, since there are no monitoring data on this combination of herbicide and 

application method. Implementation monitoring of BMPs should continue to be done on 

all projects. 

Triclopyr 

All sampling was done after ground-based applications. The few positive detections in 

non-accidental or erroneous applications in water monitoring are all at low levels (highest 

2.4 ppb). These levels are below the R5 FEIS realistic levels of water contamination, and 
Page 25 

are below any aquatic levels of concern (SERA 1996b, EPA, 1998). The use of untreated 

buffers of some minimal size on ephemeral drainages (ten feet is the smallest 

implemented buffer involved in these projects) is needed to avoid levels of triclopyr in 

water that exceed the R5 FEIS expectations. The detection that resulted in the highest 

level of triclopyr (82 ppb) was the result of an absence of an untreated buffer on an 

ephemeral stream. It would appear from these monitoring data that untreated streamside 

buffers of greater than 15 feet in width reduce risk of water contamination to near zero, 

although it should be noted that the 82 ppb transient level does not represent a substantial 

risk of harm to humans or the environment. 

It would seem that the water quality monitoring of ground-based applications of triclopyr 

outside of riparian areas, and absent any project-specific unique circumstances or 

concerns, should be discontinued, especially on the westside of the Sierra Nevada range. 

If any aerial applications of triclopyr occur, they should be monitored, including day of 

application monitoring, since there are no monitoring data on this combination of 

herbicide and application method. 

Implementation monitoring of BMPs should continue to be done on all projects. 
Page 26 

V. References

The following are the actual water monitoring studies summarized and numerically 

referenced in this report. General references follow. 

1. USFS, Angeles NF. 1996. Untitled. Correspondence from Joe Gonzales, ANF 

Pesticide-Use Coordinator to John Borrecco, Regional Pestiicde-Use Coordinator, with 

copies of water quality testing results for glyphosate. February 1996. 12 pp. 

2. USFS, Eldorado NF. 1993. Water Monitoring Report, 1991 Herbicide 

Application Projects, Eldorado National Forest. Joan Carlson, Hal Fiore. September 

1993. 33pp. 

3. USFS, Eldorado NF. 1995. Water Monitoring Report, 1992 Herbicide 

Application Projects, Eldorado National Forest. Hal Fiore. January 1995. 32pp. 

4. USFS, Eldorado NF. 2000. Hexazinone Detection in Groundwater Study – 

Amador Ranger District, Eldorado national Forest. Anne Boyd. February 2000. 10 pp. 

5. USFS, Lassen NF. 1993. Lost Fire Forest Recovery – Water Monitoring Results 

to Date. Letter from Tom Simonson to Lassen Forest Supervisor, file code 2470, with 

attachments. August 1993. 

6. USFS, Sierra NF. Undated. Monitoring Documentation – Site Preparation and 

Release. Earle Franks, Forest Hydrologist. 3 pp. 

7. USFS, Sierra NF. 1993. Groundwater Monitoring Results for the March, 1993 

Application of Hexazinone on the Mariposa Release Project, Mariposa RD, Sierra NF. 

April 1993. 53 pp. 

8. USFS, Sierra NF. 1994. Phase I Results of Intensive Monitoring to Detect OffSite Migration of Hexazinone from Vegetation Management Sites, Mariposa Ranger 

District, Sierra NF. Jerome Degraff, Brent Roath, Earle Franks. June 1994. 

9. USFS, Stanislaus NF. 1993. Water Quality Monitoring Report – 1992 Groveland 

Conifer Release Project. Michael Parenti, District Hydrologist. April 1993. 

10. USFS, Stanislaus NF. 1996a. Water Quality Monitoring – Herbicide Application 

– Domingo Reforestation Project. Jim Frazier, Jerome DeGraff. June 1996. 

11. USFS, Stanislaus NF. 1996b. Water Quality Monitoring – Herbicide Application 

– Paper Reforestation Project – Interim Report Number 1. Steve Apperson, Jerome 

DeGraff. July 1996. 

12. USFS, Stanislaus NF. 1996c. Surface Water, Ground Water, and Soil 

Monitoring Report – Herbicide Application – Hamm-Hasloe Reforestation Project – 
Page 27 

Interim Report Number 1. Todd Ellsworth, Doris Grinn, Jim Frazier, Jerome DeGraff. 

October 1996. 

13. USFS, Stanislaus NF. 1997. Groveland Conifer Release & Hamm-Hasloe 

Herbicide Monitoring Results – Summer/Fall 1996. Jim Frazier. February 1997. 2 pp. 

14. USFS, Stanislaus NF. 2000a. Water Quality Monitoring – Herbicide Application 

– Ruby Reforestation Project – Interim Report Number 1. Sharon Grant, Jerome 

DeGraff. January 2000. 

15. USFS, Stanislaus NF. 2000b. Water Quality Monitoring – Herbicide 

Applications – Rogge-Ackerson Reforestation – Wilson Loop Project Area. Sharon 

Grant, Steve Apperson. October 2000. 7 pp. 

General References: 

Apperson, Steve. Stanislaus NF Hydrologist. Personal Communication. January 2001. 

Gonzales, Joe. Angeles NF Pesticide Use Coordinator. Personal Communication. 

December 2000. 

Mulder, Cheryl. Eldorado NF Hydrologist. Personal Communication. July 2000. 

Syracuse Environmental Research Associates, Inc. 1996a. Selected Commercial 

Formulations of Glyphosate – Accord, Rodeo, and Roundup. Risk assessment. Final 

Report. March 20, 1996. 

 

Syracuse Environmental Research Associates, Inc. 1996b. Selected Commercial 

Formulations of Triclopyr – Garlon 3A and Garlon 4 – Risk Assessment. Final Report. 

March 31, 1996. 

Syracuse Environmental Research Associates, Inc. 1997. Selected Commercial 

Formulations of Hexazinone – Human Health and Ecological Risk Assessment. Final 

Report. March 4, 1997. 

USDA Forest Service, 1989. Final Environmental Impact Statement, Vegetation 

Management for Reforestation. Four Volumes. 

US EPA, 1998. Reregistration Eligibility Decision (RED) – Triclopyr. EPA 738-R-98-

011. October 1998. 269 pages.