1977-05-06 Septic System Design and Soil Testing

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V_ The minimum center to center distance be- tween adjacent trenches shall be 8.5 feet. The proposed drainfield location is shown in Figure 2. These delineations are to be adjusted in the field to conform to actual contours of the naturae ground. The contours shown on the figures are approximate. The drop box detail is shown in Figure 3. Trench details showing materials and in- stallation are shown in Figure 4. Esti- mated quantity of washed gravel or crushed rock for pipe bedding is 82 cubic yards. Estimated quantity of loamy sand is 61 cubic yards. Figure 1 through 4 are, by refer- ence, Trade part of these specifications. Construction of the drainfield system shall not proceed unless the, moisture content of the clay soil at 1 to 4 feet deep is lower than the plastic limit of the soil. Con- struction equipment wheels or tracks shall not be allowed to come into contact with the bottom of the excavation during construc- tion. After the trenches have been dug and before placement of the loamy sand and filter rock, the sides and the bottom of the trenches shall be scaribied with a rake. The loamy sand layer shown in the cross-sec- tion drawing on Figure 4 may be thicker than sig: inches but must be less than 12 inches. DETERMINATION OF PLASTIC LI11IT - Plastic limit is the soil moisture content above which manipulation of the soil will cause compaction and puddling. If a frag- ment of soil can be easily rolled into a wire 1/8 inch in diameter, the moisture content is above the plastic limit. If the soil is dry enou.Th to be friable and falls apart when rol,ing it into a wire, the moisture content is below the plastic limit and the soil may be manipulated.