Water Resources Mitigation Measures

Mitigation measures to avoid or reduce water resource impacts from an energy transmission project.

The following are examples of mitigation measures that could be applied to reduce water resource impacts of a project depending on site- and project-specific conditions. Impacts to water resources are related to the project footprint (e.g., land disturbance; erosion; and hydrological alterations), number of water bodies crossed or impacted by project-related activities, resource use (e.g., water extraction), and likelihood of water resource contamination. 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 and avoid unstable slopes and local factors that can cause slope instability (groundwater conditions, precipitation, seismic activity, slope angles, and geologic structure).
• Research local hydrogeology. Identify areas of groundwater discharge and recharge and their potential relationships with surface water bodies and groundwater quality. Avoid creating hydrological conduits between two aquifers.
• Construct drainage ditches only where necessary.. Use appropriate structures at culvert outlets to prevent erosion.
• Do not alter existing drainage systems, especially in sensitive areas such as erodible soils or steep slopes.
• Use special construction techniques in areas of steep slopes, erodible soils, and stream crossings. Cross water bodies at right angles to the channel and/or at points of minimum impact. Natural drainage patterns should not be altered or restricted.
• Minimize the amount of land disturbed as much as possible. Use existing roads, borrow pits, and quarries.
• Develop a stormwater management plan to ensure compliance with regulations and prevent off-site migration of contaminated stormwater or increased soil erosion.
• Identify water body crossings prior to construction to minimize the span over or trenching within them and to avoid the more environmentally sensitive portions of the water bodies.
• For most stream crossings, locate transmission line support structures as close as possible to the edge of the stream buffer to allow for taller vegetation, thus minimizing trimming requirements and potential thermal warming of normally shaded water bodies.

General Mitigation Measures

General mitigation practices and principles that could apply to any or all phases of an energy transmission project include:

• Use only nonpersistent, immobile herbicides.
• Refuel in a designated fueling area that includes a temporary berm to limit the spread of any spill.
• Maintain appropriate erosion control along permanent access roads.
• Clean and maintain catch basins, drainage ditches, and culverts regularly.
• Restore the banks of water bodies to their natural condition.
• Use existing bridges or fords to access the right-of-way.
• Reclaim or apply protective covering on disturbed soils as quickly as possible.
• Apply erosion controls, such as jute netting, silt fences, and check dams.

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 it to reclaim disturbed areas upon completion of construction activities.
• Avoid creating excessive slopes during excavation and blasting operations.
• For in-stream construction, use isolation techniques such as berming or diversion to limit the exposure of disturbed substrates to moving water.
• Consider trenchless technology for pipeline crossings of streams (e.g., suspension crossings or directional drilling).
• Closely monitor construction near aquifer recharge areas to reduce potential contamination of the aquifer.
• Obtain borrow material from authorized and permitted sites.
• Dispose of excess excavation materials in approved areas to control erosion and minimize leaching of hazardous materials.
• Where access roads would cross a dry wash, restrict the road gradient to 0% to avoid diverting surface waters from the channel.

Operation and Maintenance

• Ensure that vegetative cover is maintained within the right-of-way and regularly monitor for indications of erosion.
• Maintain equipment and vehicles to minimize the risk of accidental fuel spillage.

Decommissioning/Site Reclamation

• Repeat mitigation measures used to minimize impacts to water resources during construction during the decommissioning/site reclamation phase.