During the implementation of Transmission Lines and Substations works, we have a major change in the landscape of the project's direct influence areas, especially during activities such as vegetation removal and earthworks that require a great deal of soil movement. Upon completion of the activities, the areas that no longer suffer direct interference must be recovered. These places are generally: construction sites, squares for the assembly of structures, squares for launching cables, new temporary accesses, and dump and soil loan areas. This recovery must take into account the vegetation that existed at the site before the interventions, but there are restrictions on the right of way of the Transmission Line and the surroundings of the substations. In these places, plant recomposition with tree species should not be carried out, so the plant cover usually used is grass. The recovery of these sites is extremely important for soil conservation, mainly to avoid the appearance of erosion processes that can cause a great impact on the project's direct and indirect influence areas. Interventions for the execution of a program or plan to recover degraded areas can be physical, chemical and/or biological. Physical measures include the direction of water, the structuring of the substrate, as well as other interventions related to soil conservation and erosion control, and can be used in situations where there is greater degradation or tendency to degradation of the soil and its structure . Chemical measures include soil correction and increase the availability of macro and micronutrients to plants, through the application of lime and fertilization, respectively. Biological measures, on the other hand, concern the enrichment of soil biota and the restoration or enrichment of vegetation cover. The combination of measures that associate physical, chemical and biotic elements tends to produce more satisfactory results from an environmental point of view. Therefore, to define the best strategy and effectiveness, different recovery actions must be considered for each of the impacted areas.
At Sendi, right after the end of the use of the impact areas, the execution of the Plan for the Recovery of Degraded Areas – PRAD begins. This plan is designed specifically for each work and sent for approval by the client. When the demobilization of any area begins, the site is first cleaned, and all waste is directed to duly licensed locations. Afterwards, the terrain is shaped to ensure the direction of rainwater, if necessary, contour lines are made to avoid morphodynamic processes. When we have the possibility to reserve the TOP SOIL (vegetable layer), which is removed at the time of earthmoving activities, this material is spread as a surface layer to ensure sufficient nutrients for the germination of the vegetable covering. When we do not have the possibility of using TOP SOIL and it is verified that it is a soil poor in nutrients, we do chemical fertilization and correction of the acidity. Then, sowing is done using the casting technique. The choice of quality seed is critical to the success of a well-executed PRAD. Sendi always opts for coated seeds that guarantee that germination only occurs when there is enough water in the soil for the development of the grass. This type of seed also helps against the predatory action of birds and ants that can influence a possible failure in the plant cover. In addition to being visually easier to identify if the seeds are well distributed throughout the area. In slope areas there are several possibilities for techniques for recovery and vegetation cover. One of the most used techniques is the planting of emerald grass in slabs, where slabs of grass are staked on the slopes and irrigation is carried out to aid in rooting and fixation on the slopes. There is also the possibility of digging the slope and planting grass and/or legume seeds manually. Another widely used form in recent years, which has been widely used in engineering, is hydroseeding. The technique consists of preparing an aqueous solution with nutrients and a mix of quality seeds, ensuring a more uniform lining of the slopes. Depending on the slope of these slopes, other complementary containment techniques must be used to ensure better effectiveness in the recovery.
The recovery of degraded areas is closely linked to the science of ecological restoration. Ecological restoration is the process of helping to restore an ecosystem that has been degraded, damaged or destroyed. An ecosystem is considered recovered – and restored – when it contains sufficient biotic and abiotic resources to continue its development without additional assistance or subsidies. Above all, the recovery of degraded areas is supported by the Federal Constitution of 1988, in its art. 225 which quotes:
Art. 225. Everyone has the right to an ecologically balanced environment, a good for common use by the people and essential to a healthy quality of life, imposing on the Public Power and the community the duty to defend and preserve it for those present and future generations.
§ 1 - In order to ensure the effectiveness of this right, it is incumbent upon the Government:
I - preserve and restore essential ecological processes and provide ecological management of species and ecosystems;
[...]
§ 2 - Anyone who explores mineral resources is obliged to recover the degraded environment, in accordance with a technical solution required by the competent public agency, in accordance with the law.
by Victor Bonassi
Environmental Engineer at Sendi