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CALIFORNIA REGIONAL WATER QUALITY CONTROL$UARD <br /> CENTRAL VALLEY REGION <br /> ti Fact Sheet No. 5 For Dairies <br /> Soil And Groundwater Assessments For Dairies <br /> =.a Introduction <br /> The California Water Code requires that animal wastes be managed to protect water quality. To lielp achieve <br /> protection, regulations established pursuant to the Water Code (reference California Code of Regulations, <br /> Title 27, Subdivision 1, Chapter 7, Subchapter 2, Article 1, Section 22562d) require that holding ponds <br /> t utilized for animal wastes be lined with, or underlain by, soils which contain at least 10 percent clay and not <br /> more than 10 percent gravel or be lined with artificial materials of equivalent impermeability. In addition, <br /> the Tulare Basin Water Quality Control Plan and some county ordinances require a 5-foot separation <br /> between the bottom of a holding pond and the highest anticipated groundwater elevation. <br /> Title 27 also requires that manured areas (including corrals) be managed to minimize infiltration of water <br /> into underlying soils. Consequently, corrals and manure storage areas are usually designed and managed to <br /> reduce the potential for standing water ("ponding"). There are no state regulations that specify soil charac- <br /> teristics for corrals or manure storage areas. However, soils with low levels of clay and without underlying <br /> restrictive layers (such as a hardpan) are likely to allow significant infiltration. Studies conducted at dairies <br /> ' by the Central Valley Regional Water Quality Control Board have identified impacts to groundwater from <br /> corrals and manure storage areas. <br /> The following information is provided to assist dairy owners who want to obtain soil and groundwater <br /> z information related to environmental issues at existing or proposed dairy sites. Obtaining site-specific <br /> ! information is useful in developing recon-tmcndatioils for dairy design and operation. The following are not <br /> requirements, but can serve as a guide for discussions with consultants who conduct environmental <br /> assessments <br /> l <br /> Assessments of Holding Pond Sites <br /> Clay and gravel content in the sides and bottom of holding ponds is best evaluated by collecting samples from <br /> a 1 the pond excavation. However, an'initial evaluation of soils can be made by using soil borings before the <br /> start of pond construction. The borings can also provide information on expected depth to groundwater. <br /> {.; Cuttings or cores from the borings can be examined in the field by a geologist or soil sciciltist to assess soil <br /> type and soil variability at the site. If desired, soil samples from borings can be submitted for laboratory <br /> analysis to evaluate clay content and/or nitrogen levels. Borings can be also be used to evaluate several <br /> potential pond locations and the site with the "best soils" for a pond can be identified. <br /> Assessments of Corrals <br /> Soil borings in existing or proposed corrals can provide information on soil conditions including the presence <br /> , a of conditions that will restrict percolation. Analysis of soil samples from the borings can provide <br /> information on nitrogen levels under the corrals. Subsequent soil sampling and analysis can identify any <br /> charms in nitrogen levels to help assess the potential for corrals to impact groundwater. <br /> x <br /> ij <br />