That first photo is disturbing! Interestingly, the article makes no mention of using flexible dryer duct or mounting the fan backwards.
I do like the advice to carefully sand the edges of the suction point hole with sandpaper!

Valid point. I do duplicate samples, and they were within acceptable RPD. Thanks,

30K and 169K Samples were all taken from hose faucet on wellhead after running water for 10-15 minutes. Thanks

Samples were taken from faucet on wellhead after running water for 10-15 minutes. Thanks

Yes to all.

Not sure where or how (or if) this connects to the house, as this box is about 25 ft away from, and 15 ft lower than the back of the house!

Stay tuned: I am going to visit the property soon!

I too, have concerns about the way Standards are evolving. Until every structure is built exactly the same way on the same soil it is ridiculous to attempt to use Standards to micromanage every decision on every job. I have quite a high IQ, a Bachelor of Science degree, and 25 years of mitigation experience, and it is my opinion that the Standards are becoming so complex that a normal person can not possibly learn (and apply in the field) all the details and nuances. The Standards should not become the Idiots Guide to Mitigation, but should assume some degree of competence and professionalism on the part of those who agree to abide by them. They should be guidelines, not shackles.

Our processes have evolved over the years to where we use a 20-watt fan on 90% of the homes we mitigate that have crushed stone under them. Those with dirt or red clay often require a high-suction fan.

Same here in North Carolina. 10 ft 3" PVC has gone from $10 to $24/stick in the last 6 months.

Are you testing the PFE with all appliances discharging air to exterior? we have not. Are the heating and cooling units in the attic of the house? Unsure. I like to see -0.02 "WC or - 5Pa at all test holes. -.008 at weakest point. Was stronger with larger fan, but radon concentrations were also higher. What is the pressure difference between the basement living area and the exterior? Don't know. Is it possible there is a footing between the closet and the owners family room restricting flow? No. How is the owners family room and apartment living room stitched together? They are not, but bathroom and laundry are in middle of basement, and excellent PFE numbers are most likely due to plumbing penetration through the central footer. Have you tried flipping the fan and run a crm to see what radon levels do? Not yet, but it is under consideration. Are there any exterior structures, patios or steps that could be causing an issue? No.

UPDATE: Homeowner confirmed that exterior walls are filled (not hollow) concrete block, and the center wall is framed with 2x10s. Thanks,

No attached garage, carport, patio or porch. Thanks,

I have had some similar cases (with much lower numbers). Thanks,

It does. Thank you,

Oh, no! Sorry to hear this news: I always looked forward to seeing Jay at Symposium.

Thanks for the A/C info. Logically, I can not figure out why such a Unit would exhaust indoor air, as cooling would be much more effective when recirculating the indoor air. I do know for certain that the portable A/C unit was off during the last two tests. As for the second system: that has been suggested, but I have trouble justifying that when there are good negative sub-slab PFE readings in all rooms. When we had the Eagle Extreme fan on, the lowest PFE reading was -.015, and the radon test result was 4.6 pCiL. When we downsized to a Maverick, we still had -.008, and the retest was 4.4 pCi/L. Thanks,

Interesting. Thanks for sharing.

The front wall is below grade, and just a little bit of the side walls.

Possibly, but we occasionally do block-wall depressurization, and I am pretty sure I ruled that out and just didn't note it on my worksheet.