Ag Water 1.3

This document provides a comprehensive overview of the Produce Safety Rule (PSR) requirements concerning microbial water quality management for growers. The PSR mandates that growers establish a Microbial Water Quality Profile (MWQP) for each untreated surface agricultural water source used during the production of covered produce, excluding sprouts. The initial MWQP must be based on a minimum of 20 water samples collected over a period of 2 to 4 years, with sampling conducted as close to harvest as feasible. The profile relies on measuring generic E. coli levels, adhering to the EPA Method 1603 or an equivalent scientifically validated method that demonstrates comparable accuracy, precision, and sensitivity.

The purpose of the Ag Water app is to support growers in navigating these regulatory requirements through practical tools. It facilitates calculations of geometric mean (GM) and statistical threshold value (STV) to assess if water meets established criteria for pre-harvest application. Additionally, the app offers guidance on water management decisions if results indicate non-compliance, and evaluates current sampling data to estimate the risk of microbial contamination based on environmental and weather conditions.

Definitions relevant to this context include:

• Agricultural water: Refers to water intended to contact the harvestable portion of produce or food-contact surfaces.
• Geometric mean (GM): Represents the average microbial load in the water source; the PSR sets a threshold of ≤126 E. coli CFU per 100 ml.
• Statistical threshold value (STV): Indicates variability in E. coli levels; the PSR requirement is ≤410 CFU per 100 ml.
• Colony forming units (CFU): An estimate of viable bacteria concentration in the water sample.

Additional information regarding agricultural water regulations under the Produce Safety Rule can be accessed here: FDA FSMA Guidance.

The Microbial Water Quality Profile tool enables users to determine their MWQP by analyzing at least 20 representative water samples. These samples should be collected over several years, with geometric mean and STV calculations derived from this data serving as benchmarks against regulatory criteria. Once established, annual updates incorporating minimum five new samples refine these metrics in a rolling fashion—combining new data with previous measurements—to ensure ongoing compliance and water safety.

The Current Water Sampling Conditions feature assesses prevailing environmental factors and weather data alongside user-inputted parameters to estimate microbial contamination risks. This provides practitioners with real-time insights into potential hazards affecting their water sources.