The intergalactic medium (IGM) is the region surrounding the circumgalactic medium (CGM) of galaxies and these environments mix at their boundaries. This diffuse gas also dominates the baryon budget in the low-z Universe, and the ΛCold Dark Matter (ΛCDM) paradigm predicts that a significant fraction of these baryons are in a diffuse and warm intergalactic medium (WHIM) most likely located in cosmic web filaments. In order to trace the WHIM we used a sample of 12 broad HI Lyα absorbers (BLAs) detected in the HST/COS spectrum of a single QSO whose sightline intersects several inter-cluster axes, to study the relation between BLAs and the large-scale structure of the Universe. Apart from BLAs we also detect metals related to CGM like CIV in these high-density regions. From the 12 BLAs in our sample, we obtained different observational parameters of the intervening gas along found that four are associated with a strong overdensity of galaxies while five are associated with tentative overdensities. The remaining three are located at redshifts where we do not identify any excess galaxies. Finally, we find a positive correlation between the inferred total hydrogen column density and the relative local excess of galaxies, consistent with the picture where warm-hot gas resides deep within the gravitational potential well of cosmic filaments.