Considerations for Exposing Utilities Using Vacuum Excavation

Abstract

Vacuum excavation systems are frequently used to expose utilities and verify the utility location when any excavation is required. The need for exposure could be to repair the exposed utility, or to know the location of the utility so it is not damaged during the excavation. The process generally consists of spraying high-pressure water at the suspected utility location and using a vacuum hose to remove the slurry into a holding tank. The process is continuous, and progressively expands as the excavation moves deeper and wider until the utility is located. Some utility owners are concerned high-pressure water will damage their product resulting in an interruption of service to their customers or injury to the vacuum operator. This concern led to testing to gain more information about the effects of specific Ditch Witch® vacuum systems on in-ground utility products. Ultimately, the desire of utility owners is to have a comprehensive set of operating parameters that, if followed by the vacuum system operators, will not damage in-ground utilities. There are many parameters that can impact the amount of damage produced by pressurized water on a material. The parameters considered in this test were water pressure, water flow rate, water temperature, water stream geometry – which is determined by nozzle type, distance of the nozzle from the product, and time that the product was exposed to the pressurized stream of water. This paper discusses testing performed by the Ditch Witch factory with the intent to determine which parameters of a vacuum system have the greatest influence on damage to material in-ground. Data from this test does support general operational guidelines for vacuum excavation systems as stated in the conclusions of this report.

Techniques