When the emergency spillway showed signs of erosion, engineers feared a 30-foot-high section could fail, and about 188,000 people were ordered to evacuate their homes in the Feather River valley below the dam, 65 miles (105 km) north of Sacramento. Raj Gill, who manages a Shell gas station in the region, was torn between evacuating and staying open to serve a steady stream of customers. Technicians reduced the amount of water flowing down that spillway and the lake's level kept rising.

Almost 200,000 people remained holed up in Northern California shelters Tuesday while engineers rushed to fix a crumbling overflow channel and drain the rain-flooded reservoir of the national's tallest dam.

The Oroville Mercury Register reports (http://bit.ly/2kGTXzt ) that Lt. Gil Zarate says officers are beefing up patrols to dissuade crime amid empty homes and businesses. The packed parking lot of a 7-Eleven convenience store in nearby Live Oak was one of the few signs of life along the route, other than emergency personnel.

Stork continued, explaining how officials from the Department of Water Resources informally confirmed the Metropolitan Water District and water contractors who purchased Oroville water just wanted to avoid extra costs.

According to the Los Angeles Times, helicopters are depositing sacks of rocks into the hole created by the erosion, helped by dump trucks that are also patching up spots with rocks, and creating a slurry - a cementlike mixture - to plug everything in place.

He said that only when the situation is deemed safe, based on the evaluations of California's Department of Water Resources (DWR), federal and state authorities, will they be in a position to determine whether to lift the evacuation order, emphasising that the main objective of the measure is to safeguard the public.

Crews working around the clock atop the crippled Oroville Dam have made progress repairing the damaged spillway.

KQED has a nice slideshow shot over the weekend of both spillways in use, before the crisis began. The target is to lower the lake's water level by 15 metres, according to the California Department of Water Resources. Officials want the level to drop 50 feet to make room for storms expected later this week.

The Army Corps of Engineers has now capped the lake's capacity at 66 percent because of the heavy rains this season and the dam's inadequacies.

State authorities and engineers on Thursday began releasing water from the dam after noticing that large chunks of concrete were missing from a spillway.