(1) No person may cause or contribute to concentrations of fluoride in or on forage which exceed the following standards:
(a) monthly average: 50 µg/g.
(b) grazing season average: 35 µg/g.
(2) The following sampling protocol must be applied:
(a) A sample plot must be located on an area which has forage being grazed by domestic livestock, or an area upon which forage is grown for use or commercial sale as a livestock feed. A sample plot must be located on a US geological survey map, or on an aerial photograph, for consistency of resampling. A written description of the plot location is acceptable, in the alternative, if the area can be verbally defined to the satisfaction of the department. Plot descriptions must be filed with the department on standard site identification forms provided by the department. The location of sample plots must be approved by the department.
(b) The sample plot must be a minimum of one acre in area. At locations where forage growth is sparse, the sample plot must be large enough to allow a sampling capability, which meets the provisions of sample number and size, as described in this protocol under (e). Location of the plot must be chosen according to the predicted location of maximum fluoride impact. This location must be determined through modeling, historical monitoring data or other scientifically supportable procedures acceptable to the department. In the event that the predicted location of maximum concentration lies in an area unsuitable for sampling, another nearby plot suitable for sampling must be chosen. Locations where grasses are less than three cm in height or locations less than 100 meters from dirt roads or at locations less than 30 meters from paved roads must not be sampled.
(c) Sampling of each plot must be performed at least twice per month. The sampling schedule, if twice per month, must provide a minimum of 12 days between sampling periods. Should additional sampling be conducted, sampling intervals must be spaced in accordance with the definition of monthly average to represent the entire monthly forage fluoride uptake. Grazing season sampling must commence and terminate on the appropriate month following the constraints in (a) and (f).
(d) Samples must be collected through the sample period by alternately using S, U, W, S, U, W, etc., shaped transects, which traverse the full sample plot. Samples must be collected at regularly spaced distances as one progresses along the transect. Regardless of the plot size, a minimum of 25 clippings per plot must be collected. Clippings collected at each plot must be placed into a single composite sample. Samples must not be washed or in any way treated to remove particulate material from the plant.
(e) Approximately equal-sized clippings of at least ten grams each must be cut from the forage in a given sample plot. The entire aerial portion above three-cm of the base of the plant must be collected, unless the splashline is clearly above the three-cm mark, in which case the vegetation must be cut slightly above the splashline. The clipping must include old and new leaves. Entire leaves must be collected and analyzed rather than only leaf tips or edges. An attempt must be made whenever possible to obtain plant tissue that is free of dew or other moisture.
(f) Only forage grasses must be sampled and only on sample plots on which livestock are actively grazing or sample plots on which forage is grown for use or commercial sale as livestock feed. In order to determine compliance with this rule, forage sampling must occur during months for which any livestock can obtain its minimum nutritional requirements by grazing the land. Sampling may not take place on forage grown for use or commercial sale as a livestock feed unless the sampling takes place during a month in which the forage is growing and the growth is expected to be harvested for use in livestock feeding.
(g) Plant tissue must be stored in the laboratory in labeled and ventilated kraft bags, or other acceptable containers, at temperatures of 2º-8ºC. The sample tissue must be air dried at a temperature of 80ºC (±5ºC) for 24 to 48 hours prior to grinding. The tissue shall be milled to pass a 40-mesh sieve.
(h) The composite sample must be thoroughly mixed prior to any chemical analysis. Replicate aliquots are to be taken using a sample splitter or any other unbiased technique, and analyzed chemically for fluoride using a method approved by the department.
(i) A five-gram replicate aliquot from each plot must be forwarded to the department for quality control purposes. Another aliquot of the collected plant material must be saved for a minimum of three years in labeled air-tight plastic containers in the event additional analyses are required.