Calculate Geometric Mean and Statistical Threshold Value

Several tools were developed to make it easy to calculate the GM and STV and to determine if your water meets the criteria for appropriate application to produce before harvest. The tools were also designed to assist you with making water management decisions if your water does not meet the criteria in the Produce Safety Rule.

Untreated Surface Water:
Download the Excel Tool (Western Center for Food Safety, Version 4.0, June 10, 2016)

Get the Ag Water App (University of Arizona Coop. Ext.)

Access the Online Calculator (University of Arizona Coop. Ext.)

Untreated Ground Water:
Download the Excel Tool (Western Center for Food Safety, Version 3.0, June 10, 2016)

Framework Documents

Agricultural Water and Soil Amendment Framework Documents

The Western Center for Food Safety was asked by the U.S. Food and Drug Administration to facilitate the development of research protocols for scientific studies that evaluate the persistence of foodborne pathogens in the environment and on the edible portions of fresh produce following:

    • application of potentially contaminated untreated soil amendments of animal origin to land used to grow fresh produce or,
    • application of potentially contaminated agricultural water applied to the edible portion of the crop.

The Agricultural Water and Soil Amendment framework documents were developed by two committees through a series of webinars, e-mail communication, and a workshop that was held in Davis, CA in October 2011. Additional academic, government and industry food safety experts reviewed the draft documents prior to submission to the Journal of Food Protection.

Water Framework Documents
Manure Framework Documents

Online Media



Harris, L.J. and T.V. Suslow. 2014. Food safety tips for your edible home garden (major revisions). UC Foodsafety, University of California, Davis. Download


Partyka, M. L. Growers need to develop water safety management plan. Good Fruit Grower Magazine.

Partyka, M. L. FSMA water sampling 101: Tips for sampling piped water. Good Fruit Grower Magazine.

Bond, R.F. FSMA water sampling 101: Tips for sampling irrigation canal water. Good Fruit Grower Magazine.

Partyka, M. L.  FSMA water sampling 101: Irrigation pond site assessment. Good Fruit Grower Magazine.