Within each SCM is its test chamber: 33 feet long ... Basket-like cable trays span the ceiling, keeping cables, hoses and small pipes off the floor. Slotted, vertical struts line the walls ...

John Kiefner, a hydro-test expert who is helping PG&E conduct the inspections, acknowledged the method isn’t perfect. It can cause property damage if a pipe bursts and the water gushes out ...