infographic from DC Water / SkanskaJayDee on freezing the ground - part of the 1st Street Tunnel project

Unearthed by Bloomingdame:

The north-south alleys west of 1st Street NW, north of Rhode Island Avenue NW, had "freezing pipes" installed.

DC Water First_Street_Tunnel_Infographic Freezing Ground 2015 12 by Scott Roberts