5 replies to this topic

[maestro]

Day after two new videos posted, city placed concrete over sinkholes in "ADA ramp".   Sinkholes will continue under heavy concrete and water running beneath, but you won't see them.   No warning, no patrolling.   Just loose rocks (why it was made federal "Conservation Zone/limited access."

 

"ADA ramp" is either on Private Property with No Easement (according to park/rec director's July 2016 Report to council).   

Or it's on federal piles of loose rocks.

Either way, rocks collapsed as Youngdahl Geotechnical Report told city.

Mandatory CA Building Permit was never sought.   Federal 404 Permit was never sought.

 

Who is policing for Engineering Compliance?   Legal Compliance?  

 

Comment:   who is looking out for safety of the vulnerable.........

 

 

 

[Carl G]

Can you tell if there is a hole under the surface, or if this is simply the ground settling, or if caused by the heavy rains of late and its runoff? My house is built on rock piles, so could the same thing happen here?

[The Average Joe]

That is not settling . That is obviously inadequate erosion control during the last several rains.  That said, concrete generally has a 400 psi strength in tension and 4000 in compression (give or take) You would be hard pressed to overload an 18 inch span of 4 inch concrete unless you drove a vehicle or forklift over it. Normal foot traffic shouldn't be a cause for worry. That said, I'm sure they will mitigate the problem, and once the vegetation is restored, the runoff scenario experienced here will not be an issue either. 

 

"Rock piles" surrounded by dirt are not going to "collapse."  River rock weighs about 2700 pounds per yard. Let's do some simple math.   We're going to ballpark the area for this ramp. Let's use conservative numbers. For 6 x 8 section of ramp (48 square feet), let's assume a 6 foot deep "rock pile" underneath (it's probably much larger in width, but we'll ignore that).  That means there is 288 cubic feet of rock pile (we'll ignore the dirt between rocks even though that would add to the weight). A cubic yard is 27 cubic feet, so that is 10.67 cubic yards at 2700 pounds. That is 28,809 pounds.  You are adding approximately 1500 pounds of concrete on top of that or about 5%.  The rock is in compression. Rock can have compressive strength of 7-21000 psi. Let's use 10k. Obviously, compression is not going to be a problem. The tension of the materials between rocks will be the issue.  As long as that material is not eroded away (as in this case) there should be zero issue as the minimal downward force applied by the concrete and people will not be near enough to apply enough lateral force to cause the "rock piles" to shift.

 

I appreciate your concern, but it is terribly misplaced.

[The Average Joe]

Can you tell if there is a hole under the surface, or if this is simply the ground settling, or if caused by the heavy rains of late and its runoff? My house is built on rock piles, so could the same thing happen here?

 Rock piles will not cause any issue by shifting. Where would they "shift" to? Your only issue will be IF the material around the rocks was inadequately prepared. Or if you were on a hillside that was inadequately prepared. This was a big problem in Rocklin (with a name like that, who would have guessed). Builders were not compacting the soil well enough, and the foundations were settling with all the attending issues that can cause. I think they mitigated that by requiring a 50% deeper compaction if I remember right.

 

If you notice stress cracks in stucco, cracks around doors or windows (weak points) or large cracks in your concrete, your house may be settling. All houses do to some degree. Ever walked into an old house and felt like the floor was sloping? It was. The piers under the home settle over the years. Older wood framed and wood siding were far more forgiving that today's houses which are very rigid by comparison because of the concrete foundations, and all the strapping, bolting and sheathing required of new homes (mostly for earthquake compliance). The plywood shear panels alone add a lot of stiffness to homes, and that is a good thing.

 

Bottom line, I wouldn't even worry about it unless you see obvious signs of settling, or are on a hillside that is close to the angle of repose for what lies beneath your foundation.

[maestro]

Sac Bee last night Jan 28

tbizjak@sacbee.com

Gas company crews have fixed 34 leaks that sprung up this week in several Folsom neighborhoods, but are maintaining patrols in the area this weekend in case more troubles arise, gas officials said Saturday evening.

Pacific Gas & Electric Co. representatives said they are still investigating the cause of the cluster of leaks, and are on alert in case more leaks happen.

 

Constructing on loose rock piles is known hazard.    Folsom riverside rocks stability?   They are  CERTIFIED dangerous.   That's why fed land on south bank is Conservation Zone.   Federal engineers as well as reputable Geotechnical Engineers addressed the dangers of the American River banks & slopes.   Drought killed trees that helped stabilize loose rocks.   City tore down many for 'ADA' trail.

 

First hand documentation includes dozens of incidents on dredge rock piles:  sinkholes, collapses, infrastructure breaks, foundation collapse, and subsidence.    No engineer could stop city's growth onto marshes, rock piles, vulnerable slopes.

 

PG&E chose to put 'pig' sensors in parts of city, assuming other parts were "safe."    Dozens of leaks shows otherwise.    Hopefully this is not next San Bruno, but how much gas can freely leak from pipes installed in loose rocks?    Shouldn't gas engineers need to develop a monitoring program.   

 

Sinking area city refused to repair until school district intervened.   Sewer junction below the wet spot (still wet Jan. 2017).

 

[The Average Joe]

Okay. That is NOT  a sinkhole. At first, it appeared to be inadequate substrate preparation, but you point out that you have a marked water line right where the issue is. That line has obviously been leaking for years. You have an EROSION issue due to water. If it has been wet since 07, that should have been your first clue.

 

How much gas can leak from pipe installed in loose rocks? 

 

None. The pipelines are not installed directly on the rocks (as that would be dumb). They either "jacket" the pipeline, or they put a non-rock (often sand) backfill in the trench before the pipe is laid. They then backfill with screened dirt (if rocky), clean dirt, or trust the jacket if applied.

 

For one type of installation, check this out. Notice the sand,