GPR QA.pdf

Questions and Answers: Ground Penetrating Radar (GPR)

1. How thick is the pavement in the area of interest? Varies between 12-16” average

2. Was the void they found directly under the pavement? And how deep was the void? Yes, void was approx. 8’x8’

3. Just the taxiways main ramp are being scanned correct? Do you have approximate dimensions of the 1M square feet? Yes, see attached distance map (3,068’x337’)

4. What is the estimated slab thickness of the area needing to be scanned? Varies between 12”-

16” average

5. What are the minimum dimensions of the potential void(s) to be detected? 1ft3

6. What is the maximum depth of possible detection? 10’

7. What is the estimated start date of the period of performance for this effort? ASAP

8. What is the anticipated length of period of performance for this effort? Completed by 30 April

9. What is the minimum size (lateral extent and depth) void you are concerned about. This would affect our proposed line spacing’s and related cost? 1ft3

10. What is the thickness of the concrete runway? Varies between 12”-16” average

11. What is the spacing of steel reinforcement in the concrete? Varies on location, some slabs have keyways. Note: there are also tie

12. What is the soil type beneath the runway (e.g sand, gravel, clay, or silt)? Refer to attached geotech report (Mostly lean clays, some fat clays especially on South end)

13. What is the depth to water table? Per a groundwater monitoring well in the same general area, the water table is around the 5.5’ mark

14. What are the available working hours and can the work be completed on weekends? Our duty hours are 0700-1600 and weekend work can be accommodated

15. Can you provide a map showing the locations of areas to be investigated for voids? Yes, Attached

16. Can you provide drawings of ramp with slabs including the slab length and width as well as the ramp length and width? Yes, see attached maps, pads vary from 20’x30’ to 20’x20’

17. What was the dimensions of the void that was discovered, i.e. diameter or length, width and depth? Approximately 8’x8’ void was found directly under slab

18. What was the top depth and bottom depth of void, i.e. depth below ground level? Directly under 12” slab to 8’ deep

19. Do you have any previous geotechnical reports available that show the type of soils underneath the ramp, i.e. deep boring logs? If these geotechnical reports are available, can we get a copy?

Yes, I have attached current geotech reports done on Golf taxiway, which connects to the main ramp and should provide data comparable to main ramp makeup of soils.

20. Do you have any Falling Weight Deflectometer data available from this area? If this data is available, can we get a copy of the raw data files? We do not have this data.

21. Do you have any CAD drawings available for the ramp, that we can use to show the void locations: Yes, see attached CAD file

22. Can you provide typical cross section drawings of the pavement of the ramp that shows all layers of pavement section above subgrade as well as the type and thickness of each pavement layer? Yes, refer to the APE (Airfield Pavement Evaluation) report, attached.