use to be served. Keep in mind that this is a design flow, and is large enough to allow for an occasional visit from relatives or an all-night poker game. Trench and bed design is an important step; sufficient absorption area must be present to accept all the effluent pumped to the mound. The medium to coarse sand specified for use in the mound (0.25 to 1 mm diameter grains) will accept no more than 1.2 gal per day per ft2 of bottom area. Therefore, if this sand is used, the neces- sary bottom area would be found by dividing the design flow by 1.2 gal per day per ft2 (gpd/ft2), the application rate. Recent studies have shown that with some mounds using fill finer than this, ponding within the beds and trenches can occur. Therefore, consider the application rates in Table 6.2 for fine sand, loamy sand, sandy loam, etc., as being absolute maxima. Example For a three-bedroom house, the bottom area would be: 3 bedrooms X 2 people per bedroom X 75 gpd per person 375 ft2 1.2 gpd/ft2 If sandy loam is used in the mound, the application rate would be at best only half of that acceptable for sand, and the bottom area CONVENTIONAL SYSTEM MODIFICATIONS would have to be at least twice as large. This could more than double the required size of the whole mound. When the necessary absorption area is known, its dimensions can be established. Trench width can be from about 18 in. to about 5 ft. There should be no more than three parallel trenches in one mound, and each trench should extend no more than 50 ft from the distribu- tion system manifold. The maximum reasonable trench bottom area for a single mound is about 1500 ft2, which could serve a maximum of 24 people. The maximum width for beds is about 15 ft and the maximum length, as with the trench, is 100 ft. So a bed could con- tain up to 1500 ft2 and serve up to 24 people as well. If you own a large hotel, you should use multiple mounds rather than one huge mound. Selecting a trench width establishes how long each trench must be and how many trenches are needed. If you need 