How to Measure a Trench

Measure out the total length of your trench. If the trench is very short (less than 50 feet long) just use a tape measure by weighing the end of the tape down at one end of the trench and unfurling it until you get to the other end. Measure in sections for curved trenches. Do this by measuring one straight section, then the next section when it curves off, and so on. If your trench is very long or has a number of twists and turns, use a wheeled measuring pole. These are extendible shafts with a wheel and attached distance gauge at one end. Just set the gauge to zero and roll the wheel along the length of the trench to get your dimensions.

Calculate the width of the trench by taking a sample width at several evenly spaced points along its length. This will give you an average width and allow you to see how close it is to your target dimensions and where you need to widen the trench slightly. Remember that the bottom of a trench may not be as wide as the top, so follow the same process for the trench bottom and widen as needed.

Figure out the depth of your trench by using a plump bob and piece of 2x4 lumber. Lay the beam across the trench at several evenly spaced points that cover its whole length. From the part where the beam is over the middle of the trench, drop your plumb bob line and weight down until they touch the bottom. This will give you a dead vertical measurement of depth. use your finders to mark where the plumb bob's string is alongside the bottom of the beam and measure the distance from this point to the bottom of the weighted end with a measuring tape. Use the level to make sure the trench bottom is at least roughly level in the spots you're measuring depth.

Draw a rough diagram of your trench in a notepad and, as you measure out the various depths, lengths and widths, notate them on the diagram. It's easy to forget or confuse all the numbers you'll be dealing with, so write them down carefully in a way that clearly corresponds on the diagram to the proper points of the trenches dimensions.