The ground surface was improved by two methods. Being unable to dig the ground, both methods were limited to just improving the ground surface. One was the method of forming three layers on the ground surface in order to prevent weeds from growing on the surface (Fig. 5). This method would keep weeds from growing even if seeds and earth were blown and scattered on the ground by the wind from the surrounding area.
By making the three-layer ground surface exhibit its permeable nature to quickly absorb water as soon as it rains, the method keeps weeds from rooting and growing. This also has the benefit of keeping water from pooling on the ground surface. On a sunny day, this method also has the advantage of curbing the temperature rise through vaporization heat and reducing power generation loss owing to high temperatures. Ground surface improvement by this method was used in the perimeter of the site.
The other method was used in the area where solar panels were arrayed. Crushed stones were spread over the earth cover (Fig. 6). This method was also aimed at inhibiting the growth of weeds; however, compared with the three-layer ground surface in the perimeter, it is relatively easier for weeds to root and grow.
Having been exposed to severe weather for years, the ground surface in the site was no longer flat and had grown uneven in some areas. It was also overgrown with weeds.
When constructing the mega-solar plant, the constructor reclaimed the site so the uneven surface could be leveled, measuring the depth of earth cover on the ground surface by area to maintain an optimum depth. At the same time, the constructor temporarily removed earth on the ground surface to remove overgrown weeds, separated the weeds from the earth, returned the earth and disposed of the weeds outside the site.