One importan goal of the High Energy program of the LAGO project is to detect the high energy component of cosmic rays due to Gama Ray Bursts. Therefore, high altitude sites (over 4500 m.a.s.l) are chosen for installation of some detectors. The altitude allows the improvement of the sensitivity of the detectors otherwise reduced due to the strong absorption of extensive air showers initiated by gamma rays in the atmosphere.\\
In Peru, near the city of Huancayo ($12^\circ \ 2,7 ' \ S \ 75^\circ \ 2 0.4 ' \ W$), an array of three water Cherenkov detectors for the LAGO project is under construction. Here we describe the chosen location for this purpose and the detector development. Then, we show the development of a semi-analytical method for fast calibration and its comparison to CORSIKA/Geant4 simulations.