A number of flat concrete pads, some with metal threaded rods sticking out of them, which seemed to delineate an area 30m west northwest - east southeast on a level area on the southwest side of the Grwyne Fawr river just below the reservoir. The area was overgrown with grass and nettles when recorded in September 2007. It seems likely that this is the remains of a building connected with the construction of the reservoir, along with NPRNs 267137 and 267138. According to Rev DA Tipper in his 1975 book Stones and Steam in the Black Mountains, page 45, there were several buildings on this spot including a locomotive shed, a fitters shop, a joiners, and electricians and the blacksmiths. J.J.Hall, Trysor, 27 September 2007