Methods for determining groundwater under the influence of surface water, and BMPs for mitigating distribution system contamination

This proposal addresses a critical knowledge gap in microbial issues in fresh produce irrigation sources and distribution systems. Aligned with the Center for Produce Safety's focus, our project collaborates with growers in Arizona, California, Florida, and Georgia to identify groundwater wells that may be under the influence of surface water. The research and Extension team will use innovative microbiological sampling techniques coupled with historical records review to assess groundwater source vulnerability. In the second phase, the research and Extension team will evaluate interventions like pipe flushing, shock chlorination, and water treatment to establish effective mitigation measures for acute and chronic irrigation pipe distribution system contamination. Success will be measured by industry adoption of our recommended sampling strategies and Best Management Practices for remediation of distribution system contamination.

This proposal addresses a critical knowledge gap concerning the identification and resolution of microbial issues in irrigation sources (surface/ground water) and distribution systems, offering practical solutions for the fresh produce industry. Focused on areas 1(b) (wells or groundwater sources) and 1(c) (acute or chronic water system contamination) from the Center for Produce Safety, our project aims to generate new insights and effective strategies. In collaboration with local growers in Arizona, California, Florida, and Georgia, the first phase of this project involves identifying groundwater wells under the influence of surface water, using innovative sampling techniques (e.g., 100 L sample volumes) and assessing both traditional and non-traditional parameters, including generic Escherichia coli, Total Coliform bacteria, bacteriophage, protozoa, and Microscopic Particulate Analysis. This comprehensive monitoring, coupled with records review, will guide the industry on suitable sampling methods to detect surface water influence on groundwater. The second phase of this project entails constructing irrigation distribution system pipe-loops in three locations to assess the impact of atmospheric and water quality conditions on water quality degradation. Upon biofilm establishment, interventions—pipe flushing, pipe shocking using sodium hypochlorite, and routine water treatment—will be evaluated for efficacy. Project success will be measured by the development and adoption of a recommended sampling strategy by the fresh produce industry for assessing surface water impact on groundwater sources and implementing effective mitigation measures (Best Management Practices) for distribution system contamination.

Objective 1: Identify up to ten groundwater wells that are suspected as being under the influence of surface water in four produce growing regions (including AZ, CA, FL, and GA), and evaluate wells using various alternative water sampling methodologies. 

Objective 2: Use water quality data collected in year 1 and intensive review of grower records to identify trends, correlations, and recommended monitoring strategies for industry to use to effectively evaluate surface water and ground water connectivity. 

Objective 3: Use model irrigation system pipe-loop distribution systems to evaluate industry Best management Practices (BMPs) for mitigation of acute/chronic distribution system contamination.

This project is ongoing. A final report will be provided when the project is finished.