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Low-Head Hydropower Decommissioning/Site Reclamation Impacts

Decommissioning and site reclamation activities that may cause environmental impacts include facility removal, land recontouring, and revegetation.

Typical activities during the low-head hydropower facility decommissioning and site reclamation phase include facility removal; breaking up of concrete pads, foundations, intake and tailrace structures, and dams; removal of access roads that are not maintained for other uses; recontouring the land surface; and revegetation. Potential impacts from these activities are presented below according to the type of affected resource.

The following potential impacts may result from low-head hydropower facility decommissioning and site reclamation.

Acoustics (Noise)

Sources of noise during decommissioning would be similar to those during construction, and would include equipment (rollers, bulldozers, and diesel engines); breaking up of concrete pads, foundations, intake and tailrace structures, and dams; and vehicular traffic. Whether the noise levels exceed U.S. Environmental Protection Agency (EPA) guidelines or local ordinances would depend on the distance to the nearest residence. If near a residential area, noise levels could exceed the EPA guidelines, but would be intermittent and occur for a limited time.

Air Quality (including Global Climate Change and Carbon Footprint)

Emissions from decommissioning activities include vehicle tailpipe emissions; diesel emissions from large equipment and generators; and fugitive dust from many sources such as land clearing, structure removal, backfilling, dumping, restoration of disturbed areas (e.g., grading, seeding, planting), and truck and equipment traffic. Permitting would be required (as during construction), and therefore these emissions would not likely exceed air quality standards or impact climate change.

Cultural Resources

Decommissioning activities would be unlikely to impact cultural resources because these resources would have been removed professionally prior to construction, or would have been already disturbed or destroyed by prior activities. Collection of artifacts could be a problem if access roads were left in place and the area was not monitored.

Visual impacts of the project area would be mitigated if the site were restored to its preconstruction state. However, despite the physical removal of the development, the impact of a scarred landscape on an area considered sacred to Native Americans would likely remain.

Ecological Resources

Impacts to biological resources from decommissioning activities would be similar in nature to impacts from construction, but of a reduced magnitude. There would be temporary increases in noise and visual disturbance associated with the removal of the project facilities and site reclamation. Negligible to no reduction in wildlife habitat would be expected, and injury and mortality rates of vegetation and wildlife would be much lower than they would be during construction. Removal of the project components would eliminate impacts associated with wildlife interactions with facility structures and from habitat fragmentation. Following site reclamation, the ecological resources at the project site could eventually return to pre-project conditions, depending on the end use selected for the project area. One exception would be the removal of an impoundment. Significant effort would be needed to reclaim these lands. Grasses and forbs may initially be more plentiful during early years of reclamation than existed prior to project development. This could increase forage for some wildlife species. Reclamation of forest or sagebrush habitats could take decades or longer.

Environmental Justice

If significant impacts occurred in any resource areas, and these impacts disproportionately affected minority or low-income populations, then there could be an environmental justice impact. Issues that could be of concern during decommissioning are noise, fugitive dust, and visual impacts from the project site, as well as possible restoration of fish and wildlife populations that could benefit subsistence users.

Hazardous Materials and Waste Management

Substantial amounts of solid and industrial waste would be generated during the decommissioning and dismantling of the facility. Much of the solid material (e.g., concrete and masonry, steel, power cable, pipelines) could be recycled and sold as scrap or used in road building or bank restabilization projects; the remaining nonhazardous waste would be sent to permitted disposal facilities.

Industrial wastes (lubricating oils, hydraulic fluids, heat transfer fluids, dielectric fluids, coolants, solvents, and cleaning agents) would be treated similarly to maintenance wastes during operation (put in containers, characterized and labeled, possibly stored briefly, and transported by a licensed hauler to an appropriate permitted off-site disposal facility). Impacts could result if these wastes were not properly handled and were released to the environment.

Human Health and Safety

Potential impacts to worker and public health and safety during the decommissioning would be similar to those from any construction-type project with earthmoving, crushing, large equipment use, and transportation of overweight and oversized materials. In addition, health and safety issues include working in potential weather extremes and possible contact with natural hazards, such as uneven terrain and dangerous plants, animals, or insects.

Land Use

Upon decommissioning, land use impacts resulting from construction and operation of a low-head hydropower facility would be largely reversed. No permanent land use impacts would occur during this phase. If the head pond or impoundment is left in place upon decommissioning, it could provide a new water source for livestock or a new recreation facility.

Paleontological Resources

Decommissioning activities have little potential to impact paleontological resources, because these resources would have been removed professionally prior to construction, or would have been disturbed already or destroyed by prior activities. Fossil collection could be a problem if access roads were left in place and the area was no longer periodically monitored.


Direct impacts would include the creation of new jobs for workers during decommissioning activities, and the associated income and taxes paid. Indirect impacts would occur from associated economic development and would include things such as jobs at businesses that support the decommissioning workforce or that provide project materials, and associated income and taxes. Decommissioning activities would not be expected to affect property values. In the long term, the loss of jobs and revenue after decommissioning is completed could adversely impact the local and regional economies.

Soils and Geologic Resources

Activities during the decommissioning phase that would impact soils and geologic resources include removal of access and on-site roads, buildings, and other structures; and heavy vehicle traffic. Surface disturbance, heavy equipment traffic, and changes to surface runoff patterns can cause soil erosion. Impacts of soil erosion include soil nutrient loss and reduced water quality in nearby surface water bodies. Upon completion of decommissioning, disturbed areas would be contoured and revegetated to minimize the potential for soil erosion. Impacts to geologic resources would not be expected.


Short-term increases in the use of local roadways would occur during the decommissioning period. Heavy equipment would remain at the site until reclamation is completed. Overweight and oversized loads could cause temporary disruptions to local traffic.

Visual Resources

During decommissioning, visual resource impacts would be similar to those from construction. Impacts could occur from road redevelopment, removal of buried structures and equipment, intermittent or phased activity persisting over extended periods of time, and the presence of idle or dismantled equipment, if allowed to remain on the site.

Restoring a decommissioned site to pre-project conditions would entail recontouring, grading, scarifying, seeding and planting, and, perhaps, stabilizing disturbed surfaces. Newly disturbed soils and land previously occupied by an impoundment would create visual contrasts that would persist at least several seasons before revegetation would begin to disguise past activity. Restoration to pre-project conditions may take much longer. Invasive species may colonize newly and recently reclaimed areas. Nonnative plants that are not locally adapted could produce contrasts of color, form, texture, and line.

Water Resources (Surface Water and Groundwater)

Water Use

Water required to support decommissioning and reclamation activities is likely to be obtained from nearby surface water bodies or aquifers, depending on availability, but could be trucked in from off-site. It would be used for fugitive dust control for road traffic, dismantling of buildings, and for consumptive use by the decommissioning/site reclamation crew.

Water Quality

Water quality could be affected by activities that cause soil erosion, weathering of newly exposed soils leading to leaching and oxidation that could release chemicals into the water, discharges of waste or sanitary water, presence of dissolved salts from untreated groundwater used to control fugitive dust, and pesticide applications. Upon completion of decommissioning, disturbed areas would be contoured and revegetated to minimize the potential for soil erosion and water-quality-related impacts.

Flow Alteration

The river system would be returned to the natural state that existed before construction of the hydropower facility unless an impoundment is maintained. Surface and groundwater flow systems would be little affected by withdrawals made for water use, wastewater and stormwater discharges, and the diversion of surface water flow for access road reclamation.