2327 Soil bioengineering and biotechnical stabilization refer to a set of slope and soil treatment techniques where vegetation is used as the primary stabilizing element and for erosion control. The bioengineering techniques used at the Mirador Project are detailed below: • Manual revegetation involves planting stolons or cuttings of native plants. For slopes, Cyperus sp. is used because it adapts to different soil conditions and altitudinal zones; it occurs naturally throughout the project area, produces abundant seeds year-round, and has fibrous roots reaching depths of up to 1 m under high-moisture conditions. For waste dumps and deposition sites, bitter grass (Brachiaria sp.) and Cariamanga or elephant grass (Pennisetum purpureum) have been planted as fast-growing species to protect areas against erosion. However, efforts have also focused on planting forest species, maintaining them, and conducting continuous monitoring. • Hydroseeding involves using bags of mulch (organic fibers with stabilizers), fertilizer, water, and seeds (Brachiaria and Cyperus sp.). All components are mixed in a hydroseeder and sprayed hydraulically onto slopes. This method has been used for rehabilitating slopes along roads, access routes, dikes, and channels. Mulch requires approximately 5 hours to fully adhere to the slope and begins photodegradation after 7 days, while seeds begin germinating from day 18 onward. When feasible, hydroseeding is also applied to waste dumps, areas declared closed, and material deposition sites. In addition to geotechnical stability measures, environmental rehabilitation treatments were implemented through revegetation of slopes and areas undergoing closure using the techniques described above. Species with potential for ecological restoration were identified through nursery trials, determining that Cyperus luzulae and Cyperus odorata show high adaptability, achieving cover close to 73% within four weeks. S4 S12 S14 S15 Figure 4. Germination of Cyperus luzulae, chronological order by week: 4, 12, 14, and 15 in a divided seedbed with evaluation quadrants. Soil analyses indicated favorable conditions for these species in acidic soils with high nitrogen content, low phosphorus, and medium potassium content. Given soil characteristics, topographic conditions, and high precipitation, rehabilitation has been carried out both manually and by hydroseeding. However, over years of operation, hydroseeding has proven to be the most suitable system, demonstrating that it is a safe, efficient, and rapid method.
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