Post Harvest Water

Water used during or after harvest
Cannot eliminate every food safety risk in the field

Postharvest water has the potential to spread contamination widely
Rinsing/washing
Commodity movement 
(i.e., dump tanks/flumes)
Cooling
Ice making
Postharvest fungicide and wax
Handwashing
Cleaning and sanitizing
Untreated surface water may not be used for these purposes

No detectable generic E. coli are allowed for certain uses of agricultural water in which it is reasonably likely that potentially dangerous microbes, if present, would be transferred to produce through direct or indirect contact. Examples include water used for washing hands during and after harvest, water used on food-contact surfaces, water used to directly contact produce (including to make ice) during or after harvest, and water used for sprout irrigation. The rule establishes that such water use must be immediately discontinued and corrective actions taken before re-use for any of these purposes if generic E. coli is detected. The rule prohibits use of untreated surface water for any of these purposes.

Equivalent Testing Methodology for Agricultural Water
https://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm575251.htm

Postharvest Water
https://gaps.cornell.edu/educational-materials/decision-trees/postharvest-water/

Eliminate Fecal Coliforms from Your Vegetable and Fruit Safety Vocabulary
http://postharvest.ucdavis.edu/files/269366.pdf