Due to environmental concerns, regulatory agencies are opposing, or in some cases, prohibiting the use of jetting for pile installation. Under the correct conditions jetting is an effective and economical method of pile installation. Currently, no rational criteria or specific guidelines are available to assess the environmental impact and to ensure the preservation of environmental sensitive areas during pile jetting. The NCDOT has experience with bridge projects where without jetting, pile foundations could not be used and the cost of construction escalated significantly.
The jetting process can be considered to affect the hydric soil layer within the pile installation profile. The ecological impact of the jetting installation method can be measured by the disturbance caused to the hydric layer in terms of zone of extent as well as thickness of the disturbed zone. Assessment techniques such as Habitat Evaluation Procedure (HEP) and Wetland Evaluation Technique (WET) can evaluate the impact of this hydric layer disturbance on aquatic and vegetative ecosystems.
The objective of this research is to characterize and define disturbance due to jetting as manifested by the zone of influence and volume of the debris area. This disturbance will be defined as a function of jetting pressure, flow rate, and site conditions including soil types with specific emphasis on hydric soils. Second, draft specifications will be developed with recommendations regarding jetting parameters to minimize disturbance as well as possible conjugate practice modification of the jetting procedure with such addition of vacuum and/or water extraction/circulation techniques
