y close by eye. The inexperi- enced person should always measure. CONVENTIONAL WASTE DISPOSAL SYSTEMS Figure 5.8 Measuring the slope of the trench bottom with a carpenter's level. Figure 5.8 shows one way of measuring the trench bottom to see if it is level. This method is to use a carpenter's level to sight on a pole moved along the trench bottom at about 10-ft intervals. Start at what appears to be the lowest spot and mark the pole at the sight height. Then shave the high spots until the mark on the pole drops down to the original sight height. When the same height is sighted on the pole from the carpenter's level, no matter where on the trench bot- tom the pole is placed, the bottom is level. The second method (Figure 5.9) uses what is known as an "Arkan- sas" level. Two lengths of clear plastic hose are attached to the ends of a garden hose, and the hose is filled with water so that the water level is visible through the clear hose at each end. Drive a stake into the trench bottom at one end of the trench and tie the clear hose to it. Mark the water level on the stake. Now you can drive and mark Figure 5.9 Measuring the slope of the trench bottom with an "Arkansas" level. ONSITE WASTEWATER DISPOSAL Figure 5.10 Backhoe bucket with side teeth to rough up sides of trench. another stake at the other end of the trench at the same level and run a string between the two marks. The distance between the string and the trench bottom should be the same everywhere if the trench bottom is level. If you don't want to set up a level string, you can simply wander over the trench bottom with the free end of the hose, measuring the distance from the water level to the trench bottom and adjusting the bottom depth as you go. The third method is to rent an optical level and target. Wherever there are indications that the bottom or sides of the trench have been smoothed off by the bucket, shovel blade, or shoe, these areas should be scraped with a rake to break up the soil and assure easy passage of the effluent. Remove the scrapi