Production Water

Water used in contact with produce during growth
Irrigation, fertigation, foliar sprays, frost protection

Applies to water used with a direct water application method to covered produce

The second set of numerical criteria is for agricultural water that is directly applied to growing produce (other than sprouts). The criteria are based on two values, the geometric mean (GM) and the statistical threshold (STV). The GM of samples is 126 or less CFU of generic E. coli per 100 mL of water and the STV of samples is 410 CFU or less of generic E. coli in 100 mL of water.

• The GM is an average, and therefore represents what is called the central tendency of the water quality (essentially, the average amount of generic E. coli in a water source).
• STV reflects the amount of variability in the water quality (indicating E. coli levels when adverse conditions come into play—like rainfall or a high river stage that can wash waste into rivers and canals). Although this is an over simplification, it can be described as the level at which 90 percent of the samples are below the value.
  

Proposed Rule
https://www.federalregister.gov/documents/2017/09/13/2017-19434/standards-for-the-growing-harvesting-packing-and-holding-of-produce-for-human-consumption-extension

FDA Intends to Extend Compliance Dates for Agricultural Water Standards
https://www.fda.gov/Food/GuidanceRegulation/FSMA/ucm561844.htm

Agricultural Water for Production
https://gaps.cornell.edu/educational-materials/decision-trees/agricultural-water-production/