AUBURN, Calf. June 20, 2024 – Placer County Water Agency (PCWA) Directors and members of the public received a status update on the ongoing repairs at the Spaulding facilities from Eric Van Deuren, Sr. Director Power Generation Project Execution for PG&E. His report contained new information, including the root cause for the failed discharge horns in the powerhouse, additional issues with support columns and more.
Van Deuren began by explaining why the return to service date for the Spaulding Powerhouse #1 have changed so many times, stating “I think that the key thing to recognize is this is not a normal plan project. This is emergent work, and a pretty significant amount of emergent work if you look at that. So when we first put out what we thought was a date, it was a very rough schedule. No design complete at that time, right. Just an idea of what it is we thought we had to do to complete this. The contractor we brought on board to do the work did not have a design in front of them. So they couldn’t plan out their schedule to do the work as well. So, as we’ve gone through this process, as the design has matured and as we sort of understood the challenges to work in a very confined and constricted environment. That’s when we’ve seen some risks that are there, from the fact that we didn’t have a very mature scope of work at the time we started this, start to come to light. The schedule that was put out and has been put out every time since is what we call a critical path schedule. I don’t know how familiar the board is with critical path, but there is no contingency or as a project manager, we’ll call it float in the schedule. It’s essentially, everything goes right this is how soon we can have it completed. So, as we continue to go forward in this latest push that has happened in the schedule, to the end of July, is a result of just the production time that it’s taking to put in the new line.”
Root cause of the discharge horns failure – a 2011 repair
He also addressed the rebuilding of the discharge horns – both horns have failed – and one is being repaired now, with the second horn slated for repair in the fall/winter season.
“Essentially, the discharge liners on the PRV’s [pressure relief valves], which are the bypass valves around the turbine, were pretty badly damaged from a repair that happened from a similar damage incident back in 2011. That was done rather quick, and we’re sort of paying the result for that, I guess you could say, for the fact that that didn’t hold up beyond the ten years. So at this point, we’re putting in a much more robust design. Our goal here is to put us in the best position that we don’t run into this again in the future. The discharge liners, or the discharge horns that they’re called, that come out from the PRV’s very small space, ten foot or so diameter, that runs up, down and next down to even a smaller space.
FERC documents re the 2011 PRV failure
A report submitted by PG&E to the Federal Energy Regulatory Commission (FERC) in November of 2011 detailed the cause of the PRV failures at the time:
“Inspections and preliminary evaluations by PG&E and its engineering consultants concluded that the original overlapping riveted joints for the rolled steel plate segments, typical early 1900s construction, was problematic and main contributor to the cause of damages. These overlapping riveted joints protruded into the flow path of the high velocity PRV discharge. Cavitations and impact from the discharge likely initiated damages and dislodgement of the existing steel liner at the lapped joints and caused subsequent scouring and erosion of the underlying concrete.”
According to the report, the repairs were completed rapidly:
Spaulding One Powerhouse was taken out of service since discovery of the additional problems in September 2011. The damages were inspected by PG&E and its consultants to assess the problem and to formulate solutions and repair. Grouting was performed on October 15 & 16, 2011 to stabilize the damaged concrete and reduce leakage for the planned repair.
Both PRV steel liners will be replaced with new stainless steel liners with butt welded joints to provide better hydraulics and reduced cavitations potential. Damaged concrete in the existing concrete block and the adjoining tailrace wall will be repaired and grouted. Voids between the new steel liner and the existing concrete will be filled with grout. The new steel liner will be secured to the concrete block with anchors.
The new steel liners are being designed and fabricated. Repairs to the existing concrete are being performed. Installation of the new liners will begin in late November and expected to be completed in mid-December 2011.
PG&E incident report to FERC dated October 31, 2011
In January 2012, PG&E reported to FERC the repairs had been completed, “This letter is to notify you that all repairs were completed and the Unit was returned to service with no restrictions on December 18, 2011 at 23:57 hours. The unit has been operating normally since that time.”
Back to the present – Welding activities on track
“We’re at about 60%, 59% as of earlier today, of welds complete. And we’re on track to have all of the construction, not only the welding, but everything else to pull out of the site from a construction perspective by July 17. So that’s what’s in our schedule today,” Van Deuren explained. After the construction is complete, the tunnel feeding the powerhouse has to be filled, the construction debris and dust removed before testing and startup activities can occur.
Hydraulic study still not complete
One of the requests made by NID repeatedly, both in correspondence and during public meetings, is a copy of the hydrological engineering study confirming the single horn can actually carry the 400 cubic feet per second (cfs) PG&E predicts.
“The discharge horns that were designed, and although we believe it’s a very robust design, the design engineer who performed that work hasn’t had the ability to complete hydraulic and really what is a final element design check on that to tell us how robust it is to use this bypass flow.”
Van Deuren stated they have been doing that (using the discharge horns) for many, many years on that particular device. “Given that we need to have the unit back in order to pass flows downstream. We’re looking at having that back by [July] 30. That’s our date right now, we’ve shared that already at this point in time.”
Damage on more support columns discovered
During NID’s June 12 meeting, PG&E’s spokesperson Brandon Sanders said, “The repair of the structural columns and the substructure of Spaulding 1 Powerhouse, that work is also on track and no emerging issues or new concerns with that work is on schedule and proceeding according to plan.” A little later on, after a question by Director Heck, Sanders stated, “I would have been told if there were concerns with the other columns. We’re down in the space, two shifts since it started, so if there was a concern at this point it would have been identified by now.”
Today, Van Deuren shared that, “there was additional damage to some support columns for the generator deck that was found when we went down in there into the tail race area. So that work is mostly complete. We’ve got the concrete board, we have one item left to install, the steel columns that would go on top of the concrete. This design will prevent what occurred in the past, but that is not critical path. So that work, we’re very confident, does not have an impact on the overall schedule.”
South Yuba Pipe repairs proceeding apace
The South Yuba Pipe at Spaulding Powerhouse #2 delivers water down to Scotts Flat normally. The pipe was damaged and 240 ft were destroyed by a rockslide in early February.
“We have made really good progress on it. This is another challenging work, right? Very steep slopes. We got the bench cleared this week, we put one third of the footings in. We’ve got the concrete poured in, and we are on track for an August 24 completion date. So, what that does is it allows us then to put water down into Scotts Flat.”
PCWA to conserve 20% of water by reorificing
Reorificing, or replacing the boards that connect customer ditches to irrigation ditches with boards having a smaller hole or orifice, is PCWA’s solution to conserve 20% of water volume. “We found that this has less impact than, for example, the rotating outages,” said Matt Young, PCWA’s Director of Customer Services. The reorificing only affects customers who normally receive more than one miner’s inch of water. Smaller water users are being asked to voluntarily conserve as well.
As of today, PCWA ag water customers have conserved 133 miner’s inches, or about 1,000 acre ft.
“This is not a water supply or drought issue, we have ample water in storage, it’s an infrastructure issue at one of PG&E’s facilities. In times like these, it’s important that we all pitch in to help each other out until this is issue is resolved.” said Robert Dugan, PCWA Board Chair.
NID cancels rotating canal outages
As PCWA’s meeting was going on, NID posted a release with good news for their ag water customers:
NID is canceling the canal outages that were scheduled to begin today, June 20. After analysis of the ever-changing water shortage situation and adjusting water management practices, the District is able to provide enough water in the DS Canal to ensure water deliveries.
“The NID operations team has been able to work their magic and we are able to postpone the canal outages on the Scott’s Flat side,” said General Manager Jennifer Hanson. “We are running more flow tests to see how hard we can push the system to determine if we can also make it through the peak in July.”
On June 12, NID’s Board of Directors approved temporary, rotating canal outages on several canals to save water during a time when, effectively, no water supplies are flowing into the NID system while repair work continues on failed infrastructure owned by Pacific Gas & Electric (PG&E) at Lake Spaulding. PG&E recently announced an additional month delay in repairs at the Spaulding 1 Powerhouse. That delay put NID in a precarious position to deliver water to customers.
The issue was, and is, the capacity in the DS Canal, a major NID artery. Natural runoff flows are diminishing, and the delay in the return to service of the South Yuba Canal means the District must rely solely on the DS Canal for water deliveries. The canal was not designed to carry the entire load of the Nevada County water supply, and was anticipated to run out of capacity towards the end of June.
The District’s operations team has done daily analysis to find a way to continue deliveries facing a water shortage. Several factors have been included in the analysis: successful customer conservation, the recent weather pattern and alterations in water management.
Now, NID is increasing the head pressure going into the DS Canal by filling the Lower Scott’s Reservoir to its maximum elevation to deliver more water.
NID update
Follow our ongoing reporting on the Spaulding repairs here: https://yubanet.com/spaulding