As we head into another weekend, the Old Fort Slide continues to move and create new & worrisome cracks. It has now entered the river channel, and an evacuation order was issued to include the islands in the river downstream of Site C.
“The main slide has already impacted one of the islands and recent changes and new information regarding the west slide indicates potential for increased mobilization and depth of failure,” reports Rhonda Mellafont, an engineering geologist with Westek.
The Peace River Regional District has issued a video warning – because of these new developments, pursuant to the Emergency Act as of today, 6am October 12th, anyone found entering the evacuation order zones may face imprisonment or fines. NO ENTRY WILL BE TOLERATED. The public safety risk is severe. The growing tension cracks and displacement clearly show significant instability and it is a deep-seated failure that is unpredictable.
The PRRD has posted some incredibly startling photographs taken between the initial slide and October 10th, which can be viewed at this PDF file here : Old-Fort-Slide-Pictures-Sept-30-to-Oct-10-2018
With the slide still on the move,what additional risk may develop for:
A) the communities downstream, and
B) Site C construction upstream,is unknown.
If the entire river becomes blocked either in a slow continuous fashion as is occurring now, or a sudden fast-moving slide event occurs, this could have serious consequences for both. ( FYI, the westernmost end of the back channel was supposed to be enhanced fish habitat as per project docs )
In addition, how much of the Old Fort Channel work here: 13-NB-7BCHydroPresentation was completed yet, if any? This would significantly impact this as well:
It highlights again the stark reality (insanity??) of building a dam in this kind of geologically unstable area, yet Andrew Watson – lead design of Site C – showed no concern in a radio segment on CBC yesterday: https://www.cbc.ca/player/play/1342405699546
Myself ? I’m still with Vern Ruskin in a call for an independent, outside safety review, and this is why.
Here are some photos taken within the last week and a half, of the diversion portals below the North Bank, and of the North Bank itself.
The first photo is of the upper bank and camp….now right on the edge.
Second is the outlet portal.
In the last two photo’s you can see orange streaks on the concrete shot coated terraces where iron rich water from the gravel seam inside, has leaked out and stained the concrete.
There remain significant unknowns with these tunnels under the north bank, ones that the Old Fort slide brings to the forefront. This should not be ignored.
From pages 104, 105 of the BCUC report here: 00699_A-8_Site-C-Inquiry_Deloitte-LLP-Independent-Report-No1-1
In the most recent Site C progress report ( Fiscal year 2019 report, page 9: https://www.sitecproject.com/news-and-information/progress-reports-to-the-bcuc ) , an issue was in fact, identified above Diversion Tunnel 2:
“On June 29, 2018, a small rock movement occurred on a localized area of bench -9, above and to the west of the diversion tunnel inlet portal number 2. A remediation plan is in place and work is well underway to resolve this issue. There were no workers in the area at the time of the incident. This small slope movement is not related to the tension cracks that occurred on the north bank in 2017. This current issue is related to a localized shear zone in bedrock material while the tension cracks were related to the overburden materials and slope conditions. Excavation of the inlet portal near tunnel number 1 is continuing, while remediation work proceeds above tunnel number 2. “
This is where I refer back to my featured image at the top of the post, taken from the PRRD photographs, clearly demonstrating what can happen at a shear zone as mentioned in the Site C excerpt report above:
A shear zone, is kind of like a fault in the earth, a line where the rocks or material on one side is under more tension or different tension than the other. As you see above, one side is static, or moving less than the other side which is moving quickly. So clearly these kind of issues do occur on the Site C project by their own reports and they are doing remediation. In some of the 2009 stage 2 engineering reports, the drill holes used don’t go down as far as the diversion tunnel depths and they had trouble drilling past the gravel that is at about 1550-1600 asl.
Watson also mentioned in his CBC segment that there are two other dams on the Peace that are just fine. What he left out is 1) both the WAC and Peace Canyon dams are of vastly different designs than the redesign of Site , and 2) that the areas they were built in, which still geologically similar, are more stable than the eastern portion of the valley where Site C is being placed.
These ongoing geotechnical issues are where the unknown risks and costs associated with resolving those risks remain…
In August, BC Hydro spokesperson Dave Conway told local media that the Crown corporation has not been searching for stronger bedrock at the dam site, where it has removed 11 million cubic metres of earth in an effort to resolve geotechnical issues that have added to the project’s escalating cost.
“We know what rock is here,” Conway said.
“The dam is going to rest on shales, and the powerhouse and spillway structures are going to be anchored into shale materials as well.”
Ruskin said it’s not uncommon to build dams on shale, even though it is weaker than other types of bedrock. But what concerns him is the combination of shale and the new L-shaped design structure that includes construction of a roller compacted concrete buttress that will serve as the foundation for the generating station and spillways.
“That has never been done before,” he said. “They are pioneering.”
Btw Watson, there is a slumped area just above the angled drop in the RCC conveyer you may want to keep an eye on…locals have noticed this recently.
I’ll have more updates in the comments as usual, and if you are just joining in, you can read