Nogales Ground Water Monitoring

1. Purpose and Objectives: The purpose is to determine the extent and possible origin of volatile organic compounds (VOC) in the transboundary aquifer under the Nogales Wash in ambos Nogales, which could pose a potential public health threat. Objectives include the construction of monitoring wells and implementation of a quarterly monitoring program to quantify VOC and other contaminant levels, assist in ground water contaminant source identification and control, and establish a baseline for VOC levels in the transboundary aquifer.

2. Funding: EPA has provided $200,000 to USIBWC and $65,000 to Arizona Department of Environmental Quality (ADEQ) to implement this project. EPA is also funding a position at ADEQ in part to provide technical support on this project.

3. Partners: ADEQ will be the leading organization responsible for carrying out the project in the U.S. and USIBWC will serve as a primary partner. Mexican partners include MxIBWC and CNA.

4. Description: Past studies of ground water quality in the Nogales, AZ, area have indicated the presence of VOCs and trihalomethanes in the transboundary aquifer under the Nogales Wash. The problem seems to exist on both sides of the border, but the problem has not been satisfactorily studied on a binational level. Thus, the project will consist of the construction and monitoring of equal numbers of wells on each side of the border. Samples will taken and analyzed on a quarterly basis. All samples taken will be split for separate analysis by the U.S. and Mexico.

5. Status: Construction of wells on U.S. side were begun in January, 1996 and were completed in April, 1996. Samples have been taken and are currently being analyzed. Preparation for construction of wells in Mexico are currently underway.

6. Methodology: The project consists of the construction and monitoring of wells on each side of the border. The wells on the U.S. side have been drilled and developed. Well construction equipment has been purchased and transferred to Mexico for their use. After all the wells are constructed, samples will be taken by a national team and analyzed on a quarterly basis for a period of one year. Sampling in the U.S. was initiated in July 1996. All samples will be split for separate analysis by the U.S. and Mexico. IBWC arranged OSHA training in April 1996 for the Mexican members of the sampling team; the training was necessary for their participation in the sampling activities in the U.S.

7. U.S. Contacts: Doug Eberhardt, EPA Region 9, (415) 744-1280 Bill Ruth, USIBWC, (915) 534-6690 Mario Castenada, ADEQ, (602) 207-4409