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Fact Sheet No. 6 /For Dairies i Page 2 Collection .of Soil Samples Representative samples of soil in pond excavations should be collected and submitted for analysis of clay and 1711�' gravel content. As previously noted, the number of samples will depend on the observed conditions in the pond excavation. If the pond excavation has homogenous soils in the sidewalls and bottom (an unusual ` condition), only one composite sample' may be adequate if the clay content is significantly gn y greater than 10%. More often, several'individual or composite samples are submitted in order to document uniformity rw and to assess each soil layer that appears to be different. Each composite sample may be composed of soil collected from several (3 to 10) locations within the excavation as long as the soil in each location appears ? to be essentially the same. Diagrams should be used to show the locations of the samples that were used to create each composite (see attached example). If the clay content is expected to be relatively low, more individual samples should be collected to assess spatial variability and minimum clay content in different 1t locations. When imported soil is used to create a pond liner, a composite sample of the constructed liner should be collected and analyzed. Any damage done to the liner as a result of sample collection should be repaired. If the liner does not cover the entire excavation (i.e., bottom and sidewalls), one or more composite samples of the exposed native material should also be collected. Again, diagrams should be used to show the locations of the samples that were used to create each composite. Analysis of Soil Samples The soil samples collected from the pond excavation should be submitted to a commercial laboratory for soil r particle size analysis. When using a laboratory for the first time; it is desirable to review their qualifications and quality assurance/quality control (QA/QC) procedures. Although the focus is on clay and gravel content, the laboratory should be requested to also report the percentages of silt and sand in the sample; there will be little or no additional cost for such reporting. Most laboratories will also provide QA/QC 3. a information at no additional cost when reporting analytical results. Groundwater Assessments t In locations where the county of regional board requires a 5-foot separation between the base of a holding pond and highest anticipated groundwater, documentation should be provided showing that the proposed pond location meets the criteria. Information on the depth to groundwater and historical fluctuations in groundwater elevations may be obtained from soil borings, wells, and/or from historical information provided by county or local agencies. Presentation of Results A report should be prepared presenting a summary of the visual and tactile soil assessments, a description of the soil sampling and compositing procedures, the reported analytical results, and relevant information on groundwater. Figures should be used to describe the observed soil conditions in the excavation and to identify f the sample collection sites. Photographs may be used to supplement the figures. Reported analytical results should be summarized in tables and the laboratory reports should be included as an appendix. Groundwater information should be summarized relative to the pond construction. Relevant groundwater data should be included as an appendix. R +' A composite soil sample is obtained by thoroughly mixing equal quantities (by weight or volume)of soil from two or . more locations. For example, five I-pound samples may be mixed in a 5-gatlon pail, and a single I-pound composite [ ( sample removed and sent for analysis. For holding pond site evaluations,composite samples are used only when the soil in each location appears to be essentially the same based on visual and tactile assessment. Composite samples should not be created from soil samples that have different appearances or feel. . f }i IL