
The Oroville Dam is to be soaked by a foot of rain by Tuesday, ramping up the pressure on engineers who are frantically trying to repair 'patch and pray' quick-fixes which led to its near-collapse last week.

Up to five inches of rain will land on the Northern California dam this weekend in the first storm which will also bring winds of up to 33mph.

Another 10-12 inches will land at the start of next week and bring even stronger winds which may thwart repair works.

Meteorologists said it is that storm which will be a concern to engineers using helicopters to try to secure the dam's emergency spillway which nearly gave way last week to the dam's full reservoir.

200,000 people were suddenly evacuated on Sunday when the California Department of Water Resources dramatically announced that an emergency spillway at the dam was an hour away from collapse.

Residents nervously returned home as the evacuation order was downgraded to a warning on Tuesday but they have been told to be ready to flee again at a moment's notice if the volatile situation turns on its head again.

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The enormous scale of the damage - and the required work to fix it - at California's Oroville Dam became plain this week as 125 emergency crews worked round the clock to patch up its eroded spillways

There is a gaping 40ft hole in the main concrete spillway (above last week) which engineers have been trying to repair with quick fixes for years

The water in Lake Feather, at the foot of the dam, flowed violently on Thursday as engineers battled rain and wind to continue repairing the site

'Wind looks like a concern,' Sacramento National Weather Service forecaster Eric Kurth told DailyMail.com on Thursday.

On Thursday morning, engineers were battling gusts of up to 33mph as they lined the erosion with rocks and boulders.

'It's pretty windy up there. There were reports of some trees coming down in the area too. With sustained winds of 28mph and gusts of 33mph, that would make things pretty difficult,' Kurth added.

At a press conference on Thursday afternoon, officials confirmed the reservoir's water level had dropped to 868ft - some 30ft less than the 901ft capacity it reached over the weekend.

They revealed plans to slow the release of water so they could begin clearing debris from the site and eventually restart a power plant next to the dam's main chute which remains closed.

They said they expect to find more erosion across the dam but that the situation is 'much, much, much' less dangerous than it was over the weekend.

On Thursday morning, engineers were battling gusts of up to 33mph as they continued to repair the eroded site

The winds remained at around 28mph for most of the morning on Thursday as light showers fell in the first time. Engineers in diggers persevered against the conditions

125 crews are working at the site with diggers, helicopters and lorries. The helicopters battled the strong winds well on Thursday (right) to bring boulders from the bottom of the dam to the top

There is a main staging area at the foot of the dam where boulders are being collected by helicopters to take to the eroded spillway

Strong winds brought some tree branches down to the road on Thursday morning as the first storms took hold

'The more water we move out, the threat levels lower. It's much, much, much lower than what it was on Sunday,' Acting Director of the California Department of Water Resources said.

Earlier it was revealed cracks in the main concrete spillway have been included in site reports since 2009 but crews have been resorting to quick-fix concrete solutions to try to stop them from getting worse.

The repairs that have been going on for years were labeled shoddy by Robert Bea, professor emeritus of civil and environmental engineering at University of California, Berkeley.

'It's 'obvious those repairs didn't work.' We don't have details on the repairs, but they put cement into the cracks and troweled it over. I call it "patch and pray.''

Inspectors with the state agency that both operates and checks the dam, the nation's tallest at 770 feet, went into the half-mile-long spillway in 2014 and 2015 and did not find any concerns.

'Conditions appeared to be normal,' the inspector wrote in reports from both years. The most recent report which deemed the dam safe was in August last year when a team of inspectors checked it from only from afar.

The inspection was ordered as California was enduring a five-year drought which meant that until last year, the spillways had gone largely unused.

The eroded emergency spillway to the right of the main concrete spillway was all but washed away over the weekend after water in the over-spilling reservoir behind it rushed over it for the first time in 49 years. Above, engineers try to repair it on Tuesday

The situation became drastic over the weekend when water overwhelmed the barrier and threatened to wash it away entirely. Above the site on Monday once water stopped flowing over it

An overhead view taken on Wednesday shows the huge swathe of damaged ground (left of the dam in red) which needs to be fixed

In 2005, the view of the dam was drastically different. The now bursting Feather River was more contained and the emergency spillway was in tact, having never been used before

Threat: The towns beneath the dam were given just an hour to evacuate on Sunday when officials feared the emergency spillway (towering above it to the left of the gushing water) would give way

Now: Emergency crews work to repair the site at the emergency spillway on Wednesday, lining it with boulders and rocks

Before: On Saturday, water flowed over the emergency spillway for the first time when the water levels in the lake rose. Above, the erosion can be seen to begin with parts of the network of roads which ran through it becoming submerged

The engineers have not stopped working since the weekend when the emergency spillway (what remains of it is pictured above) threatened to give way and send a 30ft wall of water rushing into the towns below

The roads beneath the emergency barrier were washed away when the water flowed over it and are now being repaired

125 crews are bringing 30 tonnes of rocks to the dam to patch up the holes (above) before bad weather at the weekend

When the emergency spillway was used for the first time over the weekend, it nearly gave way entirely to the rising lake water. The result was that huge swathes of the largely earthy emergency barrier were washed away, taking with it roads at the top of the dam (above)

The helicopters bringing materials to the site are fundamental to the speed of the repair operation but may be grounded by strong winds this weekend

The Department of Water Resources declined to answer specific questions about the repair work, saying engineers were focused on ensuring public safety.

On Monday, federal regulators told the department it must enlist a group of independent consultants both to assess what went wrong and to recommend long-term fixes.

Documents and interviews show that crews were patching cracks in 2009 and 2013. A water resources department spokesman said it was normal for maintenance crews to be troubleshooting cracks in the channel during dry summer months.

One resident of the region said he saw crews in the spillway at least once a year for the past several years.

'When they have four or five trucks down there, the only thing they have to do is fill cracks,' said Don Reighley, a retiree and fisherman who several times a week drives past the channel to launch his boat into the reservoir.

One of the state inspectors who went to Oroville Dam in August said authorities may never know exactly what destabilized the spillway.

A huge repair operation is underway with 125 crews working at the site 24/7. The damage is in the region of $100million

The water in the lake has been drained by 20ft since it reached capacity and spilled over the wall on Saturday. Engineers photograph on Wednesday

Engineers are using cranes, diggers and lorries to move material around the eroded site at all hours of the day before stormy weather at the weekend threatens to call off their efforts

Engineers are lining the crumbled emergency barrier with boulders to make it strong enough to hold if the lake water rises again

Officials are heaping praise on the teams of engineers who are now working flat out to make the dam secure enough before more rain this weekend

Lorries shuttle tonnes of boulders to the top of the Oroville Dam on Wednesday as the repairs continue

Race against time: Helicopters rush more material to the site on Monday night for engineers to use in repairs

A TIMELINE OF THE OROVILLE DAM DISASTER Tuesday, February 7: Authorities halt flow on the main spillway to investigate erosion Wednesday, February 8: They reveal plans to release water over damaged spillway to test its function Thursday, February 9: Test release of water adds to main spillway damage as expected but they plan to allow more through after heavy rain caused lake to rise Friday, February 10: More water is allowed to flow down the damaged spillway to avoid using the fragile emergency spillway Saturday, February 11: First flow of water is allowed to pass down emergency spillway and authorities say erosion on main spillway has slowed. They repeat there is no risk to the public Noon, Sunday, February 12 : At a press conference, officials say the dam and its spillways are stable and that the emergency dam will hold steady 4.45pm, Sunday, February 12: The Department for Water Resources tweets an emergency evacuation order warning the emergency spillway is about to fail Monday, February 13: Officials cannot say when evacuees will be able to return as they frantically work to repair the damaged main spillway Tuesday February 14: Evacuation order is lifted after engineers drain the lake by 12ft - enough they say to remove the immediate threat to residents Wednesday February 15: The National Guard is called in to help control the volatile situation as 200,000 people return home Advertisement

'Any type of evidence that might have been there is gone,' Eric Holland of the water resources department's dam safety division said. 'Everything has been washed away.'

Now, state agencies are pumping water out of the reservoir at a rate of 750,000 gallons per second - double the speed they would normally work at.

Up to five inches of rain will fall on the lake by Sunday - not enough to pose enough of a threat to fill the lake back up to its 902ft capacity at current forecasts.

Water is currently pouring in to the reservoir at a rate of 150,000 gallons per second. Five times more is being drained.

Strong gusts of wind are however a threat to the repair efforts which are relying on helicopters to bring rocks and boulders to the site to patch up the damage.

If the gusts, which are currently 33mph at their strongest at the dam, become too strong for engineers to continue working, the risk of danger will increase.

It means that 200,000 residents who have returned home since the evacuation order was lifted may be forced to flee again.

For now, they are being advised to have a plan in place to leave at a moment's notice.

'It's important for people to be prepared.

This is an opportunity for them to get things together so that if the risk level increases and there is a need for us to issue an evacuation order, they'll have the things they'll need and they'll be able to do that quickly and efficiently.

'This is still an emergency situation,' Butte County Sheriff Kory Honea said on Wednesday.

In the meantime, 150 National Guard troops have been sent to the area to help control the delicate situation and prevent it from returning to the chaos seen over the weekend.

President Trump has acknowledged the ongoing situation is an emergency and has granted Governor Jerry Brown's request for funding to meet the the situation's needs.

200,000 people fled their homes and took shelter in evacuation centers in neighboring regions last week.

They were rushed out of their communities immediately on Sunday after days of assurances from the state that the situation was under control.

The problems: The crisis was sparked when authorities stopped allowing water down the main spillway to investigate a large hole caused by erosion. Cracks on the main spillway had been filled in the past with concrete and troweled over. Right, the now-eroded emergency spillway can be seen in tact before engineers began pouring down it when the lake rose on Saturday

ANOTHER CALIFORNIA DAM THREATENS TO SPILL OVER FOR THE FIRST TIME IN 10 YEARS The Anderson Dam in Morgan Hill, around 25 miles from San Jose in Southern California, is also on the verge of spilling over. The reservoir, the largest in its county, has not been full since 2006 but is almost at capacity due to one of the wettest winters in the area for years. Lake Anderson was 99.3 percent full on Wednesday, almost a third higher than the 68 percent recommended by local governments to account for the risk of flooding if the reservoir is compromised by an earthquake. It will cause the same panic as Oroville, say officials, who insist the dam's spillways are secure. They are pumping water out of the dam to make room for oncoming rain this weekend. The Anderson Dam in Morgan Hill, around 25 miles from San Jose in Southern California, is also on the verge of spilling over. It is seen above in a file image at less than capacity Advertisement

It began last Tuesday when the California Department of Water Resources quietly revealed they had halted water flow on the main spillway to investigate a large hole caused by erosion.

They insisted there was no danger to the public or threat of flooding.

By Wednesday, authorities said they planned to release water of the spillway despite the erosion to test its function.

It caused more damage, which was expected, but they said they have to allow more down the chute due to rising water in the reservoir.

By Saturday, the reservoir's levels had risen enough to send water over the never-before-used emergency spillway.

Over 100,000 cubic meters (750,000 gallons) of water per second continues to gush through the Oroville,CA, dam spillway as workers rush with helicopters and rock trucks to repair its emergency spillway before more storms hit

Water is now gushing through the Feather River and pouring downstream towards the towns at the foot of the dam

In Bedrock, Oroville, a group of young residents watch as the Feather River continues to pour through the town. They were allowed to return home on Tuesday but have been told to be ready to leave again at a moment's notice

Oroville's residents returned nervously on Tuesday under reduced threat of flooding. They are willing the engineers to complete repairs sufficiently before the storms hit in full swing

Residents rushed to newly reopened stores on Wednesday to stock up on supplies that will last them if they have to flee again

It's not just Oroville: Flash flood warnings across Southern California ahead of biggest storm in six years Southern California will be soaked by the biggest storm it has seen in six years this weekend sparking flash flood warnings across the region. Six inches of rain will fall between by Saturday night, piling on to what has already been the wettest winters on record for the state. Los Angeles, Orange, Riverside, San Bernardino and Ventura are all at risk of flash floods when the downpours begin to move across the area late on Thursday night. The rain will begin softly, with less than an inch forecast before Friday when it will then grow stronger. There has been more rain in Los Angeles already since October than there was throughout the entire wet season (until April) last year It will peak on Saturday night, with 2 inches set to fall on Los Angeles alone from 10pm. 'This will likely go down in the record books as one of the wettest February days ever,' Crystal Egger, NBC's weather forecaster, said. The storm will move east then down into Mexico by Sunday morning. It will boost the Los Angeles's rain total since October from 16.25 inches to more than 20 and brings the risk of mudslides to two parts of the city - Glendora and Azusa. Snow will flurry in the mountains where winds will reach 70mph. At the storm's peak, the snow level will drop to rise to 8,000ft which adds to the risk of flooding in the towns below. This year has been one of the wettest winters on record for California after five years of crippling drought, The Weather Channel reports. The sudden downpours have filled reservoirs across the state to capacity, sparking catastrophe at one, The Oroville Dam in Northern California, which threatened to give way to erosion last week. Engineers are now draining it before storms hit again next week. The Anderson Dam at Morgan Hill, around 27 miles south of San Jose, is also threatening to overflow. The dam, which is the largest in Santa Clara County, was 99 percent full on Wednesday but water agencies say its spillways are equipped if it reaches its capacity. Northern California is on track to record its wettest winter ever. The central part of the state has had its second wettest and Southern California is on a par with 1968-1969, its wettest ever. Advertisement

The water department insisted there was still no threat to the public and repeated the claim on Sunday afternoon at 12pm.

Just four hours later, they issued an emergency evacuation order on its Twitter page, telling residents they had just an hour to get out of the area before the spillway gave way.

Residents later told how they fled in 'pure chaos', piling in to their packed up cars with last-minute supplies and thrown together belongings.

Some abandoned their pets as they fled for shelters in towns a few hours' drive away. On Tuesday, as they were allowed to return home, newly reopened supermarkets received an onslaught of anxious shoppers.

They piled in to Walmart in Oroville to stock up on supplies to last them long enough in case another evacuation order is given.