CA: Storm Water Sampling – A Quick Review Just in Case!

Deanne Meyer, Ph.D. Department of Animal Science, University of California, Davis

Deanne Meyer, Ph.D., Livestock Waste Management Specialist Department of Animal Science, University of California, Davis

Now that the rainy season is upon us, it’s wise to review your Emergency Manure Management Plan and those unusual (wet weather) sampling times. Review your Emergency Manure Preparedness Plan to be sure you have updated contact information for farm staff to inform you of any emergency and for you to report the emergency to the appropriate agencies.  Also be sure that the location/contact information for specialized equipment and services (backhoe, large tractors, graders, excavators, manure haulers, etc.) is current. An investment of 20 minutes today (when chaos is at a minimum) can save you much anxiety and frustration should an accidental discharge of manure occur.  Thinking through your options is much easier when things are calm and you’re not faced with an emergency.

The normal sampling (liquid manure quarterly, solid manure twice a year, forage at each harvest for each field, well water, soil in 20% of fields) is routine by now. However, with winter rains comes the potential for runoff and special sampling needs.  A brief review of sampling requirements for off-site discharges: Sampling of storm water discharges requires different sampling containers and preservatives and collection of much information.  You may want to have your environmental consultant’s number available should you find yourself needing these samples collected.


Sampling and record keeping requirements of liquid manure or storm water discharges from the dairy proper or the cropland are detailed on pages 46 in Table 3 of the Monitoring and Reporting Program (beginning on page 42 of the file at this link): .

What needs to be sampled?

✓ liquid manure discharged from the production or land application area

✓ Storm water discharges to surface water from the production area

✓ Storm water discharges to surface water from each land application area (first storm event of the rainy season and during the peak storm season (typically February) from one-third of the fields

✓ Tailwater discharges to surface water from one-third of the land application areas if an irrigation occurred less than 60 days after application of manure


Storm water samples are taken from field when the storm produces runoff for at least one hour or a minimum of three hours in a 12-hour period. For Central Valley dairies, Tab 8 of your Water Quality Reference binder has documents for discharge monitoring should you need them.  May the rains come with regularity and intensity!