DWR investigates “erosion of concrete” at Oroville Dam spillway, and water officials severely cut back on water releases from Lake Oroville to the Feather River.

Erosion gets worse Wednesday, but engineers said they are pleased with the test results because increased erosion is expected.

A constant onslaught of rain doesn’t help the situation at the spillway. Water officials work to assess the damage and a possible solution for the continued erosion as the hole gets significantly bigger since it was first noticed, in part because of the increased outflow from the lake.

Lake Oroville reaches 99 percent capacity, as of 5 p.m., with only 3.5 feet left to fill. DWR announces that it will make a slight reduction to the releases to prevent the spillway erosion from getting worse on the north side. DWR does not anticipate the emergency spillway to be used, but tells the public they should not be surprised if it does.

Water begins flowing over the emergency spillway this morning after rain and inflows to Lake Oroville filled up the reservoir. It's the first time the emergency spillway has been used in the dam's 50-year history.

By 4 p.m., more than 180,000 people are ordered to evacuate as officials spot severe erosion on the emergency spillway. Officials warn the emergency spillway was in danger of failing and could send a 30-foot wall of water into communities along the Feather River basin.

Water levels at Lake Oroville drop below capacity, and water stops flowing over the potentially hazardous emergency spillway.Helicopters begin dropping packages into the erosion scar in the emergency spillway to fortify the weir and prevent a future disaster.

The mandatory evacuation orders that were in place for two nights are reduced to evacuation warnings near Lake Oroville. Butte County Sheriff Kory Honea said the decision was made to reduce the evacuation orders because the situation at Lake Oroville had improved.

Water releases at Lake Oroville via the damaged spillway are completely shut off after water officials began ramping down the outflows several hours before. Water outflows are expected to remain shut off for five to seven days.

DWR officials project thecost to fix the damaged spillway would be more than $275 million, as they puh for a deadline of Nov. 1 for both spillways to be repaired and operational. Nov. 1 is the traditional start of the rainy season.

A Butte County farm files a $15 million claim with the state’s Department of General Services, claiming it has sustained damages exceeding $15 million “as a result of dam and gates spillway failure at the Oroville Facility.” They claim the loss of cleanup and remediation, production and acreage costs along the Feather River., including 27 acres and walnut-producing trees that would have produced about 189,000 pounds.

An independent team of national dam safety experts releases a report that bad design and construction, as well as an inadequate state oversight led to the spillway collapse. The report adds that the state probably could have detected the problems if dam managers had reviewed the original flaws in the half-century-old dam using modern engineering standards.

KCRA gets an up-close look at the construction on the main and emergency spillways at Oroville Dam. Seven-hundred contractors are working 24 hours a day, 7 days a week.

DWR officials report that the costs to repair the Oroville Dam spillway are nearly double what was originally projected and will top $500 million. The original cost was estimated at $275 million.

DWR officials say a "milestone" is reached as Phase 1 of the spillway construction is completed by DWR’s self-imposed deadline of Nov. 1, less than nine months after the large hole eroded in the structure of the 3,000-foot-long spillway.

DWR officials say that small cracks that have appeared in the brand new concrete spillway at Oroville Dam are expected and do not pose a threat, adding that steps taken to build a more durable spillway caused the cracks.

The city of Oroville files a lawsuit against the state over the spillway emergency, arguing the crisis was caused by decades of mismanagement, a culture of cronyism and a priority for low-cost dam repairs over quality maintenance for the crisis. Oroville’s case seeks unspecified monetary damages to reimburse the city for the costs of the evacuation, lost revenue from sales taxes and tourism, and other expenses.