staff report - nevada irrigation district€¦ · page 1 of 20 staff report for maintenance and...

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Staff Report for Maintenance and Resources Management Committee Meeting August 28, 2018

TO: Maintenance and Resources Management Committee

FROM: Brian Powell, Maintenance Manager

DATE: August 21, 2018

SUBJECT: Copper Residual Testing in Canal Sediment

MAINTENANCE DEPT RECOMMENDATION: Discussion of the Copper Residual Testing in Canal Sediment and PowerPoint Presentation to be given. BACKGROUND: Review attached report BUDGETARY IMPACT: No Budget Impact in this discussion at this time. Attachments (7):

1. Copper Residual Testing in Canal Sediment Report 2. Copper Residual Graph 3. BSK Associates Test Results 4. Copper Residual Samples Location Maps 5. Title 22 TTLC Limits 6. Aquatic Herbicide Product Labels

Nevada Irrigation District

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NID CANAL SYSTEM – COPPER RESIDUAL TESTING AND EVALUATION

Introduction

Nevada Irrigation District’s (NID or District) canal system has a multitude of uses and serves many different functions. The canals deliver water to the six water treatment plants throughout the District and to hundreds of local farmers to irrigate their crops. They also provide stock water for cattle, sheep and goat herds that reside in the Nevada and Placer county areas. In order to provide the water necessary for all of these uses, the canals need to be maintained and the water allowed to flow freely to NID customers.

A major issue that occurs throughout the canal system is the presence and growth of aquatic weeds in the flow line of the canals. Aquatic weeds restrict the flow of water, causing water to back up and potentially overtop the canal berm, which can result in property damage.

There are several methods that can be used to control or remove aquatic weeds from the canals, including manual, mechanical and chemical methods. NID uses all of these methods throughout its canal system, depending on location and time of year.

Approximately 30% of NID’s canal system is not accessible by vehicle, due to terrain or narrow canal berms. So, for these areas, the method for aquatic weed control or removal is either manual labor or aquatic herbicides. The remaining 70% of the canal system is accessible by vehicle (quad, side-by-side, truck or excavator), which allows for manual labor, aquatic herbicides and the use of equipment (backhoe or excavator) to control or remove aquatic weeds from the canals.

NID is always looking to provide the most cost effective, least damaging and safest methods to deliver water. Over the many decades of delivering water to its customers in Nevada and Placer counties, NID has developed a program of using aquatic herbicides, which provides the most cost effective method.

Concerns

NID has been applying aquatic herbicides to control aquatic weeds in its canals for over forty years and during this time, concerns have been raised about the type of aquatic herbicides being used. NID has tried many different types of aquatic herbicides and those that were found to be ineffective or came with handling concerns were discontinued.

NID has developed its aquatic herbicide program based on the laws and guidelines developed by various government agencies. NID only uses aquatic herbicides that have been approved by the U.S. Environmental Protection Agency, State of California and local agencies, and the application of the herbicides is based on the directions provided on each product label. The District also provides its customers with aquatic herbicide application dates, to allow customers the opportunity to shut down their raw water delivery box on specific dates.

Each of the aquatic herbicide labels state the handling level and approved uses for the product. NID currently uses four different aquatic herbicides: Cutrine Plus, Cutrine Ultra, Nautique and Captain (see Figures 1 through 4 for labels). Each of these products state

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the recommended use in still or flowing aquatic sites, including: (1) crop and non-crop irrigation and drainage systems (canals, ditches and laterals), (2) golf courses, (3) ornamental, swimming and fire ponds, and (4) fish, shrimp and other aquaculture.

Over the forty years the District has been using aquatic herbicides, there have not been any reports or claims of injury or illness, either from the public or District staff, due to the use of aquatic herbicides. While this is to be expected, given the District’s limited and conservative approach to aquatic herbicide use, it does speak to the fact that NID has followed the regulatory and manufacturer directions.

Testing

Over the last several months, and at the District’s cost, canal sediment “grab samples” were taken at many different locations throughout the canal system. These samples contained sediment from the bottom of the canals in order to test for copper residual that may be present. The theory is that the aquatic herbicides that contain a form of copper, which is effective in the elimination of aquatic weeds, will accumulate in canal sediments and may create a hazardous environment.

A total of ten sediment grab samples were taken between February and May 2018. Six samples were taken in canals that have been treated with aquatic herbicides for many years and four samples were taken in canals that are not treated with aquatic herbicides.

Of the six, three grab samples were taken on a 2.5-mile long section of the Lower Tarr Canal near Spenceville Road and Indian Springs Road (see Figure 5), and three more samples were taken at the end of the Tarr, Newtown and Livingston Canals (see Figures 6, 7 and 8). All of these locations are where aquatic herbicides have been used to control aquatic weed growth in the canal system.

The four additional samples were taken at locations along the DS Canal, Cement Hill Canal and two on the Cascade Canal, were no aquatic herbicides have been applied, to determine background levels of copper in the sediments (see Figure 9).

All of the samples taken were collected in areas of the canals that had not been cleaned during the 2017-2018 cleaning season or were in undisturbed sections of the canals, and should represent the highest concentration of copper residual for the canal system overall. During a regular cleaning process, vegetation in the canals is removed along with a small layer of soil and sediment.

Results

The ten canal sediment grab samples were sent to BSK Associates for analyses. BSK has been conducting water analyses for NID’s National Pollutant Discharge Elimination System (NPDES) permit for many years.

The results (see Figures 10 through 16) show that the concentrations of copper residual are within the normal range of copper concentration that is found in typical farm soil (2 ppm to 100 ppm). Also, there is no accumulation effect at the end of canal systems or at the reservoir from the flushing of storm water through the canals.

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To better understand the significance of copper in an agricultural setting, NID staff researched typical copper concentrations in agricultural soil used for crops, background copper levels in soil, and how copper affects plants. Based on this research, the typical range of copper residual in soil is between 2 ppm to 100 ppm. Copper is 1 of 17 essential elements in soil for proper growth of plants. The copper in the soil actually helps the plant grow and thrive. The amount of copper needed by any particular plant depends on both the type of crop and soil. For example, beets, lettuce and tomatoes require a higher concentration of copper, while alfalfa, corn and grains require less.1 Soil type also has an impact on the copper utilization by plants.2 An inverse relationship exists between organic matter and copper. The more organic material present in soil, results in less uptake of copper by the plants.

As a reference, the California Code of Regulations Title 22 has the Total Threshold Limit Concentration (TTLC) for Copper at 2,500 ppm (see Figure 16). TTLC limits are used to determine if a waste is hazardous. The canal sediment grab samples taken from NID’s canal system are magnitudes of order under the TTLC limits as set by the State of California.

Conclusion

The copper residual concentrations found in all of the grab samples from multiple canals within the District’s system are within the range of typical copper concentrations for soil that is beneficial for healthy plant growth, and they are magnitudes of order under the TTLC limits as set by the State of California for a hazardous waste.

The results of the testing demonstrate that the aquatic herbicides used by NID to control the growth of vegetation in its canal system are not dangerous products and have no detrimental effects. The four aquatic herbicide products used by NID are regulated and approved by the State of California and are safe to use in many different aquatic sites, including crop and non-crop irrigation and drainage systems (canals, ditches, and laterals) and ponds.

In conclusion, the sampling that was conducted demonstrates that the use of aquatic herbicides in NID’s canal system does not represent a level of risk and the products are approved for these uses. The use of these aquatic herbicides should not cause concern, due to the low level of copper residuals that are present in NID’s canal system and these residuals are consistent with levels in ordinary farming soils.

1 Soil and Applied Copper (copy and paste link into browser)

http://corn.agronomy.wisc.edu/Management/pdfs/a2527.pdf

2 Toxic Heavy Metals in Farm Soil (copy and paste link into browser)

http://smallfarms.oregonstate.edu/sfn/su10toxicmetals

http://corn.agronomy.wisc.edu/Management/pdfs/a2527.pdf

http://smallfarms.oregonstate.edu/sfn/su10toxicmetals

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Figure 1

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Figure 16

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