Sen came back down the cold stair with the valve plan rolled under her arm.
It was old. Linen-backed paper, brown at the edges, with the guild’s mark in one corner and a date older than the Compact. She unrolled it on the bench beside the oiled tools and weighted its corners with shims from the stack, and Mara and Eshel and Caldris gathered round it. Eshel was on the Cinder link, on Mara’s slate, propped against the bench so he could see.
The plan showed the basin.
A great irregular shape, drawn in blue wash, cut into the rock below the fourth level of the terraces. Larger than the pump hall. Larger, Mara thought, than the Low Brace’s whole yard and the lane and the water tower together. Its depth was marked in fathoms along one edge.
“The deep reserve,” Sen said. “The city’s drinking water. Every tap on Meridian. Held in one basin, fed from the catchments, drawn up through the mains.” She put a finger on the basin’s edge. “Here’s the jacket’s return pipe.” She traced it: a red line, running from the well’s jacket up beside the cold stair, along the rock, past the basin’s wall. “And here’s the valve.”
