Fix My Logic - Boring Log Question

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aviv

August 10, 2026 06:53

Question from the PA practice exam:

I'm confused as to why Boring areas #3 and #4 are the best choice -- I chose Boring 10. Could someone please explain why my logic is wrong and B3 and B4 are correct? See my logic below the images:

1. The question states 2 levels of underground parking: Estimating min. 10' per level, we need a water table (WT) more than 20' below grade

          -I eliminated: B1 & B2 (WTs < 10' from grade), and B3 (WT < 15' from grade). B4's    

           WT is borderline suspicious but I don't eliminate it yet

2. Avoid bedrock: Options with bedrock within 20' from grade are out

          -I eliminated: B5, B6, B7, B8

3. Avoid dewatering: I assume silty and clay-ey sands will need more dewatering than well-graded sand (please correct me if I'm wrong), so I thought to eliminate options with silty sand +/-20' below grade (for the underground parking)

          -I eliminated: B9

3. Decide between B4 and B10: B4 is closer to the street but the WT level looks too suspicious 

          -I chose B10

I can maybe see why B4 would be "correct" since it's closer to the street but the WT seriously threw me off. Thanks for any insight!

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  abruno168 August 10, 2026 19:15

  Another part of the question to consider is the footprint of the building and extent of earthwork to prepare the ground for the building footprint and underground parking. The elevation changes/property line adjacency around B10 would create more work due to needing to level out that area for the proposed development, and would include other borings you've eliminated for the stated criteria of the question.

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  aviv August 14, 2026 08:12

  That's a good point, thanks abruno168!

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  Ralph Hale August 19, 2026 16:44

  Aviv, 
  
  You've missed a key detail - B10 has no road access and would not place the first floor of the housing near street level - the 224' contour that is downhill from B10 is 6' above the 218' contour that is the lowest elevation on the site with direct access to the street running diagonally at the left side of the parcel.  
  
  The way to answer this question is to first eliminate the parts of the site that don't meet the descriptive elements of the program (here, it's direct street access for parking, first floor at street level) then pick the location(s) that meet the remaining prescriptive criteria (no bedrock or groundwater close to the surface for the underground parking).  Sometimes it'll be better to work the other way around (prescriptive elements first), but you've always got to ensure both the prescriptive and descriptive criteria are met by your answer choice!
  
  Best,
  Ralph, the Amber Book Team

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