Why is my Radon level high even with passive ventilation in place?
Radon is serious business

But at least there's some cool science around it.   Ever wonder why volcanos exist? Why is the earth hot? Turns out it is radioactive decay.  When God created the earth He "aged" it 5 billion years, which destroyed all radioactive substances except uranium, which has such a long half-life that some still exists.   "Half-life" means the element spontaneously decays randomly - in 4.5 billion years, half your uranium-238 will decay into Thorium-230.  That decays much sooner into Radium-226 (which was discoved by Marie Curie in 1898, yes, a woman scientist then). That's all well and fine, these are all heavy metals that combine with other elements to make heavy molecules, and just stay in the earth.  The heat of decay becomes volcanos.  

However, Radium-226 decays into Radon-222.  Problem.  Radon is also a noble gas, to enter a whole 'nother branch of science.  The noble gas you know best is helium: it's like air, but lighter than air.  Noble gases  are complete by themselves, they don't want to combine with any other elements - which is why they are gases. 

The problem is radon doesn't want to stay in the earth.  It is lighter than earth, so it tries to go straight up, and heads for places like basements.   However, unlike helium it is heavier than air, so it likes to collect in low places.  

Radon is highly unstable (short half-life), which means it is highly radioactive. It will soon decay into Polonium-218, famous for being used to kill Russian dissidents.  Noble gases are harmless, but if radon decays while it's in your lungs, two things happen.  First, it emits alpha radiation which lungs are vulnerable to.  Second, it turns into polonium-218 which is not a gas, it's a heavy metal, so it falls to the bottom of your lungs instead of being exhaled. So the bottom of your lungs take damage from the polonium both from the heavy metal toxins and from the radiation when it decays. Not good.

This is a natural process. Nuclear technology had nothing to do with it.  

This damage is cumulative. Every decay is a "dice roll" - 99.9% of hits, the DNA damage is detected and the cell self-destructs. But that is done by the 17p and 11q chromosomes, if that takes a hit, the error may replicate endlessly.  That's what cancer is. 

The upshot is, do whatever you need to get that stuff outta there.  No more sleeping in the basement - not even tonight - and get some windows open throughout the house to keep fresh air rolling through.

Given the large number of pipes, I gather this is a "passive system" - they are hoping convection or gravity would carry the radon away.  That was probably a good bet, but not every good bet wins.  This one didn't.  The next step is to use small fans to force the air to circulate.  I wouldn't wing-ding this, this is one of the extremely rare cases where I say at least consult with a professional.  

If you're into DIY, ask them how much work you can do yourself, like get power wired to the right places in the right way, e.g. On the generator board but not on a circuit that might trip, e.g. The table saw circuit or AFCI/GFCI.

Dueling safety systems are a problem, like a low-water trip on a fire pump.  Save the pump, lose the hospital. You don't want a GFCI saving you from a ground fault by shutting down the radon system.