Soils and Geological Resources (including Seismicity) Mitigation Measures
Mitigation measures to avoid or reduce impacts to soils and geological resources from an energy transmission project.
The following are examples of mitigation measures that could be applied to reduce soil and geologic impacts of a project depending on site- and project-specific conditions. Impacts to soils and geological resources are related to the project footprint (e.g., topographic disturbance; habitat destruction, erosion, and hydrological alterations), resource use (e.g., sand and gravel extraction), and construction procedures (e.g., blasting requirements). Many impacts can be reduced or avoided when considered during the siting and design of a project during the site evaluation phase.
Develop a final set of mitigation measures for any project in consultation with the appropriate federal resource management agencies and stakeholders. Conduct these consultations in the project development process and preferably prior to final project siting and design.
Siting and Design Mitigation Measures
Siting and design considerations that mitigate impacts include:
Identify unstable slopes and local factors that can cause slope instability (groundwater conditions, precipitation, seismic activity, slope angles, and geologic structure).
Place access roads to follow natural topography, and avoid or minimize side hill cuts. New roads should avoid going straight up grades in excess of 10%. Design roads with eventual reclamation in mind.
Design runoff control features to minimize soil erosion.
Minimize the amount of land disturbed as much as possible. Use existing roads, disturbance areas, and borrow pits and quarries. Minimize vegetation removal.
Construct drainage ditches only where necessary. Use appropriate structures at culvert outlets to prevent erosion.
General Mitigation Measures
General mitigation practices and principles that could apply to any or all phases of an energy transmission project include:
Clean and maintain catch basins, drainage ditches, and culverts regularly.
Inspect and maintain project facilities regularly, including access roads, to ensure erosion levels remain the same or less than current conditions.
Reclaim or apply protective covering on disturbed soils as quickly as possible.
Apply erosion controls, such as jute netting, silt fences, and check dams.
In areas of potential wind erosion, apply gravel to access road surfaces.
Use special construction techniques in areas of steep slopes, erodible soils, and stream crossings.
Maintain vegetative cover within the right-of-way (ROW) to prevent erosion and monitor periodically to assess erosion.
Project Phase-Specific Mitigation Measures
Mitigation measures specific to a particular phase of an energy transmission project include:
Construction
Save topsoil removed during construction and use to reclaim disturbed areas upon completion of construction activities.
Install appropriate roadway drainage to control and disperse runoff.
Avoid creating excessive slopes during excavation and blasting operations.
Dispose of excess excavation materials in approved areas to control erosion and minimize leaching of hazardous materials.
Conduct blasting to minimize the occurrence and velocity of flyrock (e.g., by use of blasting mats) and ground vibration to safe levels.
Decommissioning/Site Reclamation
Repeat mitigation measures used to minimize impacts to soils and geologic resources during construction during the decommissioning/site reclamation phase.
Use topsoil removed during the beginning of the project or during decommissioning activities to reclaim disturbed areas.
Reestablish the original grade and drainage pattern to the extent practicable.
Stabilize all areas of disturbed land using weed-free native shrubs, grasses, and forbs.
