AWWA B100-16 pdf download.Granular Filter Material
1. Silica gravel shall consist of coarse aggregate in which a high propor- tion of the particles are round or equidimensional in shape. It shall possess suf- fcient strength and hardness to resist degradation during handling and use, be substantially free of deleterious materials, and exceed the minimum specifc gravity requirement.
2. Silica gravel shall have a saturated-surface dry specifc gravity of not less than 2.5, unless a higher minimum specifc gravity requirement is specifed to meet a design requirement for a particular layer or flter.
3. Not more than 25 percent by dry weight of the particles shall have more than one fractured face (see Sec. 5.3.2).
4. Not more than two percent by dry weight of the particles shall be fat and elongated to the extent that the longest axis of a circumscribing rectangular prism exceeds fve times the shortest axis (see Sec. 5.3.2).
5. Te silica gravel shall be visibly free of clay, shale, or organic impurities.
Note: Testing for clay, shale, or organic impurities is normally not necessary. However, if deleterious materials are noticeable, the gravel shall be within the fol- lowing limits: (1) a maximum of 1 percent minus No. 200 (0.074 mm) material by washing, as determined by ASTM C117; and (2) a maximum of 0.5 percent coal, lignite, and other organic impurities, such as roots or twigs, as determined by ASTM C123 for lightweight pieces in aggregate using a liquid with a 2.0 specifc gravity.
4.1.2.3 Gravel size. Filter-media support gravel shall be provided in the particle size ranges as required in the purchase documents. For each required size range of gravel, not more than 8 percent by dry weight shall be fner than the low- est designated size limit, and a minimum of 92 percent by dry weight shall be fner than the highest designated size limit.
4.1.2.4 Acid solubility. Acid solubility shall not exceed fve percent for sizes smaller than No. 8 (2.36 mm), 17.5 percent for sizes larger than No. 8 (2.36 mm) but smaller than 1.0 in. (25.4 mm), and 25 percent for sizes 1.0 in. (25.4 mm) and larger. If gravels contain materials larger and smaller than the specifed size and if the total sample does not meet the specifed solubility limit for the smaller material, the gravel shall be separated into two portions, and the acid solubility of each portion must meet the appropriate designated percent solubility.AWWA B100-16 pdf download.