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White Paper on Development of Community Water System Drinking Water Intake Percent Cropped Area Adjustment Factors for Use in Drinking Water Exposure Assessments; Notice of Availability

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Environmental Protection Agency (EPA).




The Environmental Protection Agency uses computer modeling to estimate human exposure to pesticides in drinking water. An input parameter for these exposure models is the percentage of a water supply's watershed area to which pesticides may be applied, a metric which EPA refers to as the “percent cropped area” (PCA). Recently, EPA has developed delineations of watersheds for surface water intakes of community water systems throughout the continental United States and has used this dataset to develop a corresponding dataset of watershed-specific PCAs. Development of this Community-Water System—Drinking Water Intake dataset is described in a draft white paper, which has been updated based on peer review comments. EPA is making this updated version available for public review and comment.


Comments must be received on or before July 8, 2014.


Submit your comments, identified by docket identification (ID) number EPA-HQ-OPP-2013-0442, by one of the following methods:

  • Federal eRulemaking Portal: Follow the online instructions for submitting comments. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute.
  • Mail: OPP Docket, Environmental Protection Agency Docket Center (EPA/DC), (28221T), 1200 Pennsylvania Ave. NW., Washington, DC 20460-0001.
  • Hand Delivery: To make special arrangements for hand delivery or delivery of boxed information, please follow the instructions at​dockets/​contacts.html. Additional instructions on commenting or visiting the docket, along with more information about dockets generally, is available at​dockets.
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Jim Carleton, Environmental Fate and Effects Division (4304T), Office of Pesticide Programs, Environmental Protection Agency, 1200 Pennsylvania Ave. NW., Washington, DC 20460-0001; telephone number: (703) 347-0335; fax number: (703) 347-8011; email address:

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I. General Information

A. Does this action apply to me?

You may be potentially affected by this action if you are required to conduct testing of chemical substances under the Toxic Substances Control Act (TSCA), the Federal Food, Drug, and Cosmetic Act (FFDCA), or the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Since other entities may also be interested, the Agency has not attempted to describe all the specific entities that may be affected by this action. If you have any questions regarding the applicability of this action to a particular entity, consult the person listed under FOR FURTHER INFORMATION CONTACT.

B. What should I consider as I prepare my comments for EPA?

1. Submitting CBI. Do not submit this information to EPA through or email. Clearly mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD-ROM that you mail to EPA, mark the outside of the disk or CD-ROM as CBI and then identify electronically within the disk or CD-ROM the specific information that is claimed as CBI. In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not Start Printed Page 26754contain the information claimed as CBI must be submitted for inclusion in the public docket. Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.

2. Tips for preparing your comments. When submitting comments, remember to:

i. Identify the document by docket ID number and other identifying information (subject heading, Federal Register date and page number).

ii. Follow directions. The Agency may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.

iii. Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.

iv. Describe any assumptions and provide any technical information and/or data that you used.

v. If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.

vi. Provide specific examples to illustrate your concerns and suggest alternatives.

vii. Explain your views as clearly as possible, avoiding the use of profanity or personal threats.

viii. Make sure to submit your comments by the comment period deadline identified.

C. How can I get copies of this document and other related information?

A copy of the draft white paper is available in the docket under docket ID number EPA-HQ-OPP-2013-0442.

II. Background

A. What action is the agency taking?

EPA uses PCA adjustment factors to modify modeled concentrations of pesticides in surface waters in accordance with land cover types (i.e., crops) associated with a pesticide's uses. PCA-adjusted concentrations are used as estimated drinking water concentrations in human health risk assessments. Previously, PCAs were generated for Hydrologic Unit Code 8 (HUC-8) regions (part of a hierarchical system for classifying and mapping drainage areas in the United States). In this current update, PCAs have been generated for watersheds delineated based on surface-source drinking water intakes (DWI) of community water systems (CWSs) across the United States

The new PCAs are an improvement over previously calculated PCAs in terms of their relevance to human health risk assessment because they were derived for known drinking water sources. Out of 6,550 DWI locations, which both met the selection criteria for watershed delineation and passed a Quality Assurance screen, 74% (4,840) had delineated watersheds that also passed a Quality Assurance screen. Summary values are presented in the draft white paper along with detailed descriptions of their development and suggested procedures for their routine use in pesticide risk assessment.

B. What is the agency's authority for taking this action?

The Agency's authority is FIFRA (7 U.S.C. 136-136y).

List of Subjects

Environmental protection, Community water systems, Drinking water exposure assessments, Health and safety, Percent cropped area, Pesticides and pests, Surface water intakes.

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Dated: May 1, 2014.

Donald J. Brady,

Director, Environmental Fate and Effects Division, Office of Pesticide Programs.

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[FR Doc. 2014-10693 Filed 5-8-14; 8:45 am]