Vacuum excavation is essentially a method of breaking up ground material and then suctioning it to clear the area exposing a target utility. Although the technology used is high-pressure, there risk of damaging the buried utility lines and pipes are eliminated. This method is highly efficient and disturbs the least amount of soil. It is also accepted as the safest digging method, earning the name "soft dig".
Soil conditions play a major factor in determining the amount of test holes we are able to complete within a day as well as the rate of completion of the test holes. Some conditions that can affect the productivity of the job include wet clay, shale, saturated soil, rocks, and boulders.
Digging remotely past 75 to 80 feet will affect the suction of the vacuum hose and will slow down the job.
Groundwater erodes away the soil and could cause the surrounding area near the test hole to collapse. This could undermine the soil below grade level, which can create a collapsing hazard and a fall hazard. The backfilling process will also be affected because a sinkhole could form due to the lack of strength and solid material of the soil.
The air knife or air spade is one of the two main tools we use for excavation. It uses compressed air to break up the soil and loosen it for the vacuum hose to suck up into the debris tank. The recommended digging pressures that can be used for the air knife are 150 to 250 psi.
This is typically a flexible 6 inch vacuum hose that is mounted to the tank and then clamped together at the end where the dig tube is. The dig tube is the part that is lowered into the test hole to suck up the dirt loosened by the air knife. The primary dig tube is typically 5 to 6 feet long and can be lengthened through metal extension tubes that come in 3, 4, 5, and 6 feet respectfully.
The jackhammer we use is typically 65 pounds. It uses compressed air around 95 to 100 psi.
The air tamper we use also operates around 95 to 100 psi. When backfilling the excavated we compact the soil at 1 foot increments starting at the reachable depth we can safely get to.
The hydro lance is metallic and has a handle with a trigger that is used to perform hydro excavation. It has extensions to increase the depth we can excavate to. It also has a multitude of nozzles and tips to use for the excavation that help with certain types of soil conditions.
The core drill is used for work done in the road and sidewalks. It can also be used to help keep a test hole clean so it does not crack surrounding asphalt. This is esspecially useful in areas where the surrounding asphalt could be old, breaking, or cracking apart. It is usually a 12 inch core bit so that we can fit the dig tube and the air knife in the hole at the same time.