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We study of the properties of a new class of circumgalactic medium absorbersidentified in the Lyman-$\alpha$ forest: "Strong, Blended Lyman-$\alpha$" (orSBLA) absorption systems. We study SBLAs at $2.4<z<3.1$ in SDSS-IV/eBOSSspectra by their strong extended Lyman-$\alpha$ absorption complexes covering138 km/s with an integrated $\log (N_{HI}/$cm$^{-2}) =16.04^{+0.05}_{-0.06}$and Doppler parameter $b=18.1^{+0.7}_{-0.4}$ km/s.  Clustering with the Lyman-$\alpha$ forest provides a large-scale structurebias of $b = 2.34\pm0.06$ and halo mass estimate of $M_h \approx 10^{12}{\rmh^{-1}M_{sol}}$ for our SBLA sample. We measure the ensemble mean columndensities of 22 metal features in the SBLA composite spectrum and find that nosingle-population multiphase model for them is viable. We therefore explore theunderlying SBLA population by forward modelling the SBLA absorptiondistribution. Based on covariance measurements and favoured populations we findthat $\approx 25$% of our SBLAs have stronger metals. Using silicon only wefind that our strong metal SBLAs trace gas with a $\log(n_H / $cm$^{-3}) >-2.45$ for $T=10^{3.5}$K and show gas clumping on $<255$ parsec scales. We fitmultiphase models to this strong sub-population and find a low ionization phasewith $n_H=1$cm$^{-3}$, $T=10^{3.5}$K and $[X/H]=0.8$, an intermediateionization phase with $\log(n_H / $cm$^{-3}) = -3.35$, $T=10^{3.5}$K and$[X/H]=-1.1$, and a poorly constrained higher ionization phase. We find thatthe low ionization phase traces cold, dense super-solar metallicity gas with aclumping scale of just 0.009 parsecs.

A Strong Blend in the Morning: Studying the Circumgalactic Medium Before Cosmic Noon with Strong, Blended Lyman-$\alpha$ Forest Systems