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( V discharijes on page 17 shows that 0.7^ gpra will be discharged by a 1/^1-inch perforation at a head of 1.0 foot. Multiplying perforations by O.yil gpm/perforation results in a total flow of 35.5 gpm. While this value is slightly lower than the 37.5 gpm as determined from page 13, it is a more accurate figure. The table at the bottom of page 17 contains friction factors that can be used to calculate the friction loss in a perforated lateral. To use these ”F" factors, the friction loss is first calculated as if the entire flow were moving through the entire length of pipe. In the previous example, each lateral would have a flow of 35.5/3 = 11.8 gpm. The friction loss for 11.8 gpm should be calculated for 48 lineal feet of the pipe diameter under consideration. This total friction loss is then multiplied by an facoor which is 0.376 for a pipe having 16 outlets. The friction loss in the pipe with multiple outlets should not be greater than 20 percent of the average operating pressure, in this case 1.0 foot. Thus the maximum allowable friction loss would be 0.20 foot, and the difference in discharge between the first and last perforation along the perforated lateral will be less than 10 percent. By using the ”F” factors on page 17 and the friction loss for plastic pipe presented on page F-18, the maximum allov/able number of various size perforations that are allowed on various diameter laterals were calculated and are presented in the middle tabic on page 18. This table is suitable only for the perforations listed and similar tables can be developed for other perforation diameters. The first table on page 16 presents allowable loading rates of soils located under mounds. This table is fundamental tc designing mounds by the basal width concept, which is explained on pages 21 and 22. The downward percolation rate of original soil profiles in Minnesota have been measured on many slowly permeable soils. None of these original profiles have been found to have a vertical movement slower than 1 cm per day. This is a loading rate of 0.24 gpd/sq ft which is found in the second column of the table for a percolation rate range of 6l to 120 rapi. The design loading rate on the sand layer of the mound is 1.20 gpd/sq ft (which is the reciprocal of the soil sizing factor of 0.83 sq ft/gpd). Thus, if 1.20 gallons per day is the loading rate on a square foot of the clean sand, but the soil under the sand can absorb only 0.24 gallons per day per square foot, then 5.0 times as much basal area must be available as sand area in contact with the rock layer. Since only the side dikes are used in the determination of basal area, the term basal width is preferred. Very little liquid will move out into the end dikes of the mound. Page 18 presents multipliers which are used to determine upslope and downslope dike widths. This table will allow calculation of the values presented on page 5. The table on page 13 will also allow calculation of downslope dike width for rock bed widths narrower than 10 feet. In order to achieve sufficient basal width, it is occasionally necessary to use a narrower and longer rock layer. For the mound which was designed, a 10 x 50 foot rock layer was selected. On a slowly permeable soil, however, an 8-foot wide by 62.5-foot long rock layer would function better hydraulically. If this mound is located on an 8 percent slope, the -V-