April 12, 2010 

Ms. Allison Wiedeman 

Rural Branch Chief 

Office of Water 

US Environmental Protection Agency 

1200 Pennsylvania Avenue, NW 

Washington, DC 20460 

RE: Follow-up to February 24, 2010 Meeting Regarding National Pollutant 

Discharge Elimination System Permits for Pesticide Application To, On, 

or Near Waters of the United States 

Dear Ms. Wiedeman: 

Thank you for the opportunity to meet with you and your staff to discuss 

EPA’s current effort to develop a regulatory structure under the Clean Water 

Act (CWA) National Pollutant Discharge Elimination System Permit 

(NPDES) program for permitting pesticide application in, above, or adjacent 

to surface water. The utility members of the American Water Works 

Association, Association of California Water Agencies, and the Association of 

Metropolitan Water Agencies appreciate you and your staff’s recognition as to 

how critical aquatic pesticides are to maintaining effective water facility 

operations throughout the nation. As we discussed at the meeting, aquatic 

pesticides serve numerous crucial roles for our members. 

Aquatic pesticides are essential to assuring safe and aesthetically acceptable 

drinking water, enabling irrigation systems to effectively convey and deliver 

water to crops, and preventing the proliferation of aquatic plant and animal 

pest species. And while we all need to recognize that pesticides are one of the 

many tools we have available to control pests (plant and animal) and that we 

should always strive to use the tool that achieves pest management objectives 

with the least impact on the environment, we also need to recognize that 

aquatic pesticides are often the most efficient and cost-effective approach. 

Furthermore, when considering the bigger picture, there are many 

circumstances in which the proper use of pesticides can actually reduce the 

overall impacts to the environment while enhancing public health. 

While we support including water resource management pesticide 

applications within the general federal NPDES permit model, we believe the 
Ms. Allison Wiedeman 

April 12, 2010 

Page 2 

unique aspect of such applications needs to be recognized. After all, our 

members’ aquatic pesticide applications are specifically designed to be either 

directly applied to waterbodies or to infrastructure facilities that convey and 

or store water. Specific examples of aquatic pesticide uses by our members 

include control of disease carrying organisms, algae, floating, submersed, and 

emergent aquatic plants, mollusks and other invertebrates, and invasive 

plant and animal species. Such uses are fully considered by EPA’s Office of 

Pesticide Programs when determining whether a specific pesticide should be 

approved for such uses and if so, what additional restrictions should be 

imposed on such uses. It is essential that the general NPDES permit for 

pesticide use acknowledge that compliance with Federal Insecticide 

Fungicide and Rodenticide Act (FIFRA) label provisions will, in the vast 

majority of cases, satisfy the requirements of the permit. As you are aware, 

each FIFRA label is supported by an extensive body of research and expert 

assessment compiled by EPA. FIFRA labels, in general, effectively balance 

efficacious pesticide application with minimizing adverse impacts associated 

with pesticide residuals. 

We also believe that the new permit should recognize and support state and 

local efforts to regulate pesticide use to ensure environmental protection and 

human health and safety. With regards to this last point, as we discussed, it 

is critical that the general permit be crafted in a manner that accounts for 

the magnitude of variation across the country, in terms of geographic and 

demographic conditions and pest management challenges, and consequently, 

provides sufficient flexibility to allow for local solutions to address local 

circumstances. 

You and your staff posed several specific questions. Attachment A to this 

letter summarizes each question and includes an associated response. We 

appreciate the agency’s consideration of our concerns and recommendations. 

If there are any questions, please direct them to Steve Via, AWWA, at (202) 

326-6130, Mark Rentz, ACWA, (916) 441-4545, and Erica Brown, AMWA, 

(202) 331-2820. 

Best regards,

Thomas W. Curtis Mark S. Rentz Diane VanDe Hei 

Deputy Executive Director Director Executive Director 

AWWA Government Affairs ACWA Regulatory Affairs AMWA 
Ms. Allison Wiedeman 

April 12, 2010 

Page 3 

cc: Jack Faulk, EPA/OW/OWM 

Bill Jordan, EPA/OPPTS/OPP 

Mike Muse, EPA/OW/OGWDW 

 Mike Finn, EPA/OW/OGWDW 
Attachment A 

Question 1. What is the best way to express the application (e.g., area, 

volume, linear distance, etc) for our members’ applications? 

Water volume in acre-feet is the most common metric though it may be 

simpler to administer a permit program where key thresholds are expressed 

in surface area or linear distance. Water volume is the metric to which one 

most often returns when planning an aquatic pesticide application. You will 

find that this measure can be derived from a few simple measurements (e.g., 

the length, width, and average depth1 of the application area). There are 

instances, when application of herbicide occurs on the shoreline of a water 

body (e.g., a canal, ditch, pond, etc.) in these instances a simple linear 

measure could be used, recognizing that the nature of the permit presumes a 

volume of the adjacent waterbody is receiving the pesticide as well. 

By reflecting application in water volume treated, e.g., acre-feet, the user is 

able to represent either the static volume of a lake, pond or reservoir or 

flowing water volume in a canal or ditch. Water bodies can differ 

tremendously in size. For example, a canal for transferring water can be one 

mile or hundreds of miles long. Similarly, a canal might be 100 feet or just a 

few feet wide. Consequently, if a linear distance is used to simplify permit 

language and simplify implementation, it would be important to include 

flexibility to address situations where the assumed linkage between linear 

distance and affected volume is not sound. 

A final aspect of clearly communicating linear measurements in the context 

of this NPDES permit is that application is typically occurring on both banks 

of a linear waterbody (e.g., canal, ditch, etc.). So, for every mile of actual 

distance, the applied distance is 2 miles. Current practice is to discuss linear 

distance in terms of the length of bank to which pesticide is applied. EPA 

should be very clear when it is expressing the length of a water feature (e.g., 

a canal, stream, etc.) vs. when it is describing the length of bank to which 

pesticides are applied. 

 

 

1

 When the FIFRA label includes a target concentration, the effective volume can and should be limited to 

the volume where that target concentration exists, for instance, in the case of surface application of copper 

sulfate the often used depth is three feet. 
Question 2. What is an appropriate threshold for Notices of Intent? 

There are at least three significant nationwide assessments of the number of 

lakes in the United States. The first conducted Olsen et al. (2009)2 based on 

1999 data indicates that there are almost 270,800 lakes discernable from 

United States Geologic Survey (USGS) USGS Reach 3 data. A subsequent 

effort also published in December 2009, the National Lakes Assessment 

(NLA), was limited to lakes greater than 10 acres in size; it placed the 

national inventory of lakes at 49,546. Roughly 41% of the lakes reflected in 

the NLA are categorized as man-made. A third compilation was prepared in 

2009. This final compilation was prepared by the U.S. Army Corps of 

Engineers, the National Inventory of Dams (NID). NID indicates that there 

are almost 84,000 dams in the United States, implying that there are a 

similar number of constructed impoundments. We were not able to identify a 

similar national compilation of the miles of irrigation canals and ditches. 

The Army Corps of Engineers data is limited to man-made impoundments, 

but it is the only dataset that provides insight into who is managing these 

water resources nationally. Based on NID more than 18,000 lakes and 

reservoirs are managed by local government and utilities. NID also indicates 

that almost 15,000 lakes and reservoirs are managed for either drinking 

water or irrigation supplies. 

Our members’ experience indicates that the use of integrated pest 

management (IPM) is prevalent and that IPM includes the use of pesticides 

as needed. Accordingly, virtually every water system that relies on surface 

water supplies may at some time need to apply pesticides. Moreover the 

distribution of invasive species such as zebra mussels 

(http://www.invasivespeciesinfo.gov/aquatics/zebramussel.shtml ) and quagga 

mussels (http://www.invasivespeciesinfo.gov/aquatics/quagga.shtml ) 

continues to grow; wherever infestations of these species occur there is 

substantial likelihood that drinking water suppliers and irrigation districts 

will need to utilize pesticides to protect the functionality of their 

infrastructure. 

Because aquatic pesticide application in reservoirs is typically targeted at a 

portion of the water body, and for most applications effective concentrations 

are limited to only a portion of the water column, it seems appropriate to take 

these factors into account when setting the NOI for reservoir treatment. 

Based on the data in Reach 3, NLA, NID and our members’ experience, a 

reasonable NOI is 300 surface acres. This surface area is consistent with 

 

2

 Anthony R. Olsen, Blaine D. Snyder, Leanne L. Stahl, Jennifer L. Pitt. Environ Monit Assess (2009) 

150:91–100. Survey design for lakes and reservoirs in the United States to assess contaminants in fish 

tissue. 
typical assumptions used to treat surface water bodies with algaecides, which 

is a pesticide treatment common among many of our members. 

Irrigation systems vary tremendously in scope and scale both within any 

given irrigation activity and between irrigation regions. For example in 

California there is an extensive irrigation canal system where individual 

canals can measure 100 or more feet in width; as the volume of water gets 

closer to its point of application, the size of the conveyance systems reduces 

significantly. Table 1 provides an illustrative example. 

Table 1: Example Canal/Ditch Length of 50 miles 

(Resulting treated bank length of 100 miles) 

Average 

Width 

(feet) 

Surface 

(acres) 

Assumed 

Depth 

(feet) 

Static Volume 

(acre feet) 

5 30.3 1 30.3

10 60.6 3 363.6

50 303.0 10 3030.3

100 606.1 10 6060.6

If 300 acres represents a reasonable NOI for reservoir / lake applications of 

aquatic pesticides, then a comparable surface area could be used as a point of 

departure for calculating the NOI for irrigation systems. These systems 

could either calculate a surface area or volume of their water treated. By 

way of comparison if the average width and depth of the irrigation system 

were 10 feet and 3 feet respectively, then roughly 250 linear miles of canal 

would be the NOI. 

Question 3. What is the specific process for dealing with endangered species / 

critical habitat in California Aquatic Pesticide General Permit process? 

Endangered species are addressed both in California and in other states 

through direct interaction between the relevant state agencies and the 

permittee. This approach allows the responsible entity to incorporate 

measures to avoid harm to endangered species in their overall IPM process. 

Question 4. Are there data to illustrate that post-application pesticide 

residual levels are minimal? 

The FIFRA pesticide label typically includes appropriate pesticide application 

rates for the target pest species and application. The label often includes 

information on persistence of the pesticide in the environment. Every 

pesticide (i.e., herbicide, algaecide, surfactant, etc) has a different environmental 

persistence. For some pesticides this means that there will be no detectable 
residue, but for others a residue will exist for some time period. For those 

chemicals that have residue, the amount of residue will depend upon the 

application rate, time after application the chemical is tested, and other factors. 

A recently compiled dataset organized by Blankenship and Associates based on 

compliance with the California NPDES aquatic pesticide permit does provide 

some insight into the presence of pesticide residuals. This dataset represents 

data from 30 water systems and irrigation districts in central and northern 

California over a seven year period. The pesticides listed (glyphosate, 

nonylphenol, acrolein, and copper) are those applied by some or all of the 

contributing owner/operators. See Attachment B. 

Question 5. Is pesticide use declining over time? Is this drop linked to 

integrated pest management? 

A nearby case study of pesticide use decline over time is the use of copper 

algaecides to control algae blooms in the Occoquan Reservoir. The Occoquan 

Reservoir is located in northern Virginia and is managed by Fairfax Water. 

Over the past three decades, source water protection measures have been 

implemented to help mitigate the impacts of the increasing suburban 

development in the Occoquan watershed. These measures have included 

indirect potable reuse through advanced wastewater treatment and stringent 

phosphorus reduction requirements for storm water runoff. While not 

directly attributable to the pesticide use reduction, these measures have 

stabilized water quality in the Occoquan Reservoir. Further, Fairfax Water 

undertook several pro-active operational actions including: 

1. Evaluating the reservoir and its ecology to determine the key 

regions of the reservoir to which algaecide application should be 

used to be effective and develop the ability to recognize the onset 

of an algal bloom that will impair drinking water treatment, 

2. Installing continuous monitoring equipment within the reservoir 

to provide a more comprehensive view of water quality. 

3. Employing standard operating procedures that utilize ongoing 

monitoring to facilitate targeted and timely pesticide 

application. 

4. Making changes in the depth at which water is withdrawn from 

the reservoir to reduce the concentration of algae entering the 

water treatment plant. 

5. Maintaining and upgrading as needed an in-reservoir aeration 

system. 
6. Considering algae-related water quality issues in making 

improvements to drinking water treatment. The current plant 

disinfects using ozone which is a very effective oxidant and 

removes many algae-related taste and odor compounds. 

Because observed algae occurrence varies with flow conditions, growing 

season temperatures, and other factors, it is not possible to identify a single 

action that led to reduction in algaecide use. Despite an extensive suite of 

actions, algae blooms continue to occur at levels that sometimes necessitate 

use of targeted copper algaecide treatments. The timing and intensity of 

these blooms are highly variable. 

This case study is a good example of IPM reducing the amount of applied 

pesticide. By clearly identifying which algal species represent a challenge to 

treatment, and conditions when algal levels are such that other tools are 

inadequate to protect the drinking water supply, Fairfax Water has 

developed a suite of strategies that together address the system’s water 

treatment needs and minimize both the area and magnitude of pesticide 

application in the reservoir. However, it should be noted that 

implementation of IPM does not necessarily mean a concurrent reduction in 

pesticide use. 

Question 6. What are the key elements of defining the “entity in responsible 

charge”? 

As is typical practice in permitting under the Clean Water Act, the “entity in 

responsible charge” is charged with complying with regulatory requirements. 

In the case of the proposed NPDES general permit for pesticides, complying 

entails: 

1. Determining if an NOI must be submitted and if so making such 

submission, 

2. Assuring that provisions of the general permit are met including 

recordkeeping and reporting requirements, and 

3. Adherence to IPM-based strategy with respect to pesticide 

application. 

In almost all cases the “entity in responsible charge” will be the 

owner/operator of the waterbody being treated. This entity is very typically 

the one that understands site history and has firsthand knowledge of site 

characteristics. Accordingly, the familiarity that this entity has allows for 

the best and most appropriate decision on the use of pesticides. In the case of 

a community water system or irrigation district, it would be the utility itself. 

The utility could then either conduct the application itself or contract for 
application services as necessary, ensuring that appropriate contractual 

requirements are in place to assure compliance with the NPDES permit. It is 

possible that either because ownership of the water resource rests with 

another entity or due to the structure of the utility that the responsibilities 

associated with the NPDES would be delegated through a contractual 

arrangement. In order to have flexibility to deal with this limited subset of 

cases, the NPDES permit structure should be based on “entity in responsible 

charge.” 

Question 7. Nationally where are there irrigation districts? 

Irrigation districts are organized in numerous states to ensure a reliable 

water supply to agriculture, including the states of: Arizona, California, 

Colorado, Idaho, Kansa, Montana, North Dakota, Nebraska, New Mexico, 

Nevada, Oregon, South Dakota, Texas, Washington, and Wyoming. These 

states are all reflected in a compilation prepared by the U.S. Bureau of 

Reclamation (http://www.usbr.gov/rra/IDStatus/IDStatus.pdf). Many U.S. 

Bureau of Reclamation projects include an irrigation component (an 

alternative project specific website link is 

http://www.usbr.gov/projects/index.jsp. 

The National Water Resources Association may be better positioned to 

provide a complete national picture of where irrigation districts are organized 

and estimate the number of miles of associated irrigation canals and ditches. 

NWRA maintains a list of its members at 

http://www.nwra.org/member_links.php. There are also state level 

associations for irrigation districts like the Washington State Water 

Resources Association, http://www.wswra.org. 
Attachment B 
Revised: 3/23/2010

Source: Blankinship & Associates

Summary of Post-Application Detection of Pesti

Applied to Water to Control Aquatic Vegetatio

California: 2002-2009

877

811

285

3

97

22 49 

000 

0

100200300400500600700800900

1000

Glyphosate Nonylphenol Acrolein 

# of Samples

Total # of Samples Analyzed# of Detects > Water Quality Objective (WDownstream Sample Immediately After Ap# of Detects > WQO in Downstream SampApplication