Santa Ana Region -


Orange County North Basin Regional Groundwater Plume

Upcoming Orange County North Basin Community Meeting:

Fullerton Public Library, 353 W. Commonwealth Avenue, Fullerton, CA 92832
Wednesday, November 14, 2018

6:00 pm - 6:30 pm Open House
6:30 pm - 7:00 pm Community Meeting
7:00 pm - 8:00 pm Informal Discussions

The purpose of the meeting is to discuss site activities; promote meaningful community involvement; share information about the National Priority Listing (NPL), Superfund Alternative Approach, and interim Remedial Investigation (RI); explain site cleanup activities; learn about the public health assessment activities that will be conducted; and hear the community’s health and exposure concerns related to the site.


The EPA and Orange County Water District (OCWD) will be discussing:

  • What is Superfund, National Priority Listing (NPL), and Superfund Alternative Approach
  • Ongoing remedial investigation and site cleanup activities

The CDPH will be discussing:

  • What is CDPH’s role in this community
  • What is a Public Health Assessment
  • How you can participate in the public health assessment process


  • USEPA will publish an ad with this information in local newspapers such as the OC Register, the Fullerton Observer, the Anaheim Independent, Unidos en el Sur de California (OC Edition), Ngoui Vet Daily News, and either the Korea Daily OR Korea Times.

You can find more information at EPA’s webpage ( and the CDPH webpage (
   If you have any questions, please contact:


Nancy Villaseñor, MS | Health Educator
California Department of Public Health | Center for Healthy Communities
Environmental Health Investigations Branch
Site Assessment Section

p: (510) 620-5845

a: 850 Marina Bay Pkwy, Bldg P, 3rd Floor, Richmond, CA 94804 


Information on Proposed National Priority Listing

On January 18, 2017, the United States Environmental Protection Agency (USEPA) opened a Comment Period for the proposed addition of the Orange County North Basin (OCNB) to the National Priority List (NPL). The Site, located in Northern Orange County, is a comingled groundwater plume of chlorinated solvents and other contaminants covering more than 5 square miles, primarily beneath the cities of Anaheim and Fullerton, California.

As of March 8, 2018, EPA gave all interested parties an additional 60 days to submit comments related to OCNB proposed NPL addition. The public comment period ended on May 18, 2018.
As of August 13, 2018, EPA is providing a notice of data availability for documentation supporting the proposal of the Orange County North Basin Site.  This notice provides an opportunity to comment on the additional reference documentation only. The comment period closed on September 12, 2018.

Ongoing Investigations and Cleanup Activities

In 2014, the State of California referred the OCNB Site to the USEPA to prevent further migration of contamination into the groundwater, which is the primary drinking water source for Orange County. In 2016, the USEPA became the lead agency for the OCNB commingled plume project.

Under USEPA oversight, the Orange County Water District (OCWD), is currently conducting an interim remedial investigation and feasibility study (RI/FS) to address groundwater contamination in the OCNB. As of April 2018, 13 monitoring wells have been constructed and sampled and an additional 8 monitoring wells are planned for construction. The data collected as part of this study will provide the USEPA with the information needed to develop an initial remedy that will prevent further vertical and horizontal migration.

While USEPA is taking the lead in overseeing the investigation of the regional groundwater contamination, the Santa Ana Regional Water Quality Control Board (Regional Board) and the California Department of Toxic Substances Control are lead agencies in overseeing the investigation and cleanup of contamination at individual industrial properties suspected of having contributed to the regional groundwater contamination.

USEPA Project Contacts

USEPA Community Involvement Coordinator:
Carlin Hafiz
(213) 244-1814

USEPA Remedial Project Managers:
Kathleen Aisling
(213) 244-1823
Wayne Praskins
(415) 972-3181

Additional Contacts:

Orange County Water District
Dave Mark, Project Manager

Santa Ana Regional Water Quality Control Board
Maile Gee, Site Cleanup Case Manager
(951) 782-4379

This page contains links to websites and documents pertaining to the proposed project.

Interested parties are invited to subscribe to the Regional Board's E-Mail Notification System.
Links to Documents and Websites

  • To access the USEPA OCNB NPL Website – Click Here
  • To view the recently updated USEPA Factsheet, please go to USEPA Factsheet.
  • To view USEPA NPL documents for OCNB, please go to Site Documents & Data
  • For information on how to submit comments, please go to - Submit Comments to USEPA
  • For the OCWD OCNB Website - Click Here
  • To view Regional Board cases related to OCNB in GeoTracker - Click Here
  • View an slide show overview of OCNB presented at the Association for Environmental Health and Sciences Foundation 2018 Conference - Click here



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