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r { CALIFORNIA ]REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION Fact Sheet No. 6 For Dairies Evaluating Proposed Waste Holding Pond Sites Introduction The California Code of Regulations (Title 27, Subdivision 1, Chapter 7, Subchapter 2, Article 1, Section 22562d) requires that holding ponds utilized for animal wastes be lined with, or underlain by, soils which contain at least 10 percent clay and not more than 10 percent gravel or be lined with artificial materials of equivalent impermeability. In addition, the Tulare Basin Water Quality Control Plan and some county ordinances require a 5-foot separation between the bottom of a holding pond and the highest anticipated groundwater elevation. The following information is provided to assist dairy owners who want to construct a dairy waste holding pond and need to document that the pond meets the legal requirements. Initial Assessments of Soils at Proposed Holding Pond Sites An initial evaluation of soils at proposed holding pond locations can be made by using soil borings before the start of pond construction (see Fact Sheet No. 5 for Dairies). The borings can also provide information on expected depth to groundwater. Cuttings or cores from the borings can be examined by a geologist or soil scientist to assess soil type. If desired, soil samples from borings can be submitted for laboratory analysis to evaluate clay and gravel content. For some proposed pond locations, observations or available information (such as a county soil survey) may indicate that soil will not meet the required clay and gravel limits. In such instances, no samples of native V f soil are collected, and the pond is constructed with a liner of imported soil that meets the required clay } content. Samples of the completed liner should be collected and analyzed as described below to document that the required values are inet, Visual and Tactile Assessments of Soils in Pond Excavations In most instances, clay and gravel content in the sides and bottom of holding ponds is evaluated by collecItili" samples from the pond excavation. The number and location of samples depends on site specific conditions as determined by visual and tactile assessment. The visual assessment documents soil appearance that indicates different soil types are present in the excavation. Tactile assessment'refers to an evaluation of the soil "feel" when it is dry and wet. Such assessments when conducted by a trained or experienced person (i.e., a "qualified person") can indicate.the presence of significant amounts of sand and clay. The results of the visual and tactile assessments should be documented as discussed below. It is normal to find horizontal layers of soil with different properties- In most instances, the different layers have different appearances (color or structure) and/or a different "feel". A written description of the visual assessment and tactile assessment (i.e., feel of soil in the different layers) should be prepared. The written description should be supplemented by drawings as appropriate (see attai hed example), The drawing can be i done by hand or computer. Photographs may also be used to document the visual assessment. Each t. significant layer should be assessed, and the description should focus on observations related to clay and gravel content. At least one composite sample of soil from each significant layer should be collected and `ibed below. analyzed as desct 1< s ;