Observations/Finding

As requested, the site was visited by our AS Engineering and Consulting (ASEC) representative for the purpose of providing quality control inspection and testing services. Visual observation techniques were employed to verify compliance with project drawing/specifications, applicable codes, and materials submittals. The following observations were observed on site this day:

Upon arrival, it was observed that Graded Aggregate Base (GAB) was being delivered via tandem axle dump trucks for placement on Taxiway A3 and the A3 extension.

Representatives from ASEC, UES, Lead Edge Engineering, and C.W. Matthews Contracting Co. were present for a proof-roll performed with a loaded tandem axle dump truck in the Taxiway A4 area, extending from the duct bank to the edge of the connector (Station 35+00 to 36+00).

During proof-rolling, the subgrade was determined to be unacceptable, and the dump truck became mired adjacent to the duct bank. Organic material was observed at the subgrade surface. It was agreed that in an approximate 40-foot by 15-foot area parallel and adjacent to the duct bank, organic material would be removed to a depth of approximately 4 feet below the previously remediated elevation (approximately 6 feet below proposed finished asphalt grade) (see photos).

The UES representative recommended placement of geotextile fabric followed by recycled concrete rock (sourced on-site) up to subgrade elevation. This would be overlain with 12 inches of No. 4 stone and 12 inches of GAB.  No Geogrid was requested.

There was concern that additional buried organic material may exist within the Taxiway A4 and connector areas; however, due to budget and time constraints, further exploratory excavation was not performed.

An additional proof-roll was performed in the Taxiway A4 area between the duct bank and the previously installed storm drain. This area was also found to be unacceptable. For this section, the UES representative recommended placement of 12 inches of No. 4 stone followed by 12 inches of GAB, without the use of geotextile fabric or geogrid in order to reduce project costs.

It was observed that geogrid (installed with approximately 2-foot overlaps), along with geotextile fabric in the wetter areas, was placed within the connector between Taxiways A3 and A4. Placement of approximately 12 inches of No. 4 stone followed; however, this work was not completed across the entire connector on this date.

No. 4 stone placed throughout the project was compacted using a smooth drum vibratory roller (see photo) prior to placement of GAB. Following consolidation of the No. 4 stone in the connector area, geotextile fabric was placed, and GAB was subsequently installed above.

Placement of GAB on Taxiway A3 and the A3 extension was completed, with water applied to aid in compaction.

Additionally, an area measuring approximately 30 feet by 17 feet located between the duct bank and storm drain pipe was identified as having soft subgrade soil conditions. It was requested that this area be excavated an additional 12 inches and remediated accordingly.

No further observations were made.

Large recycled rock placed into approximately 4 foot deep excavation on top of Geofabric. 40 x 15 feet

#4s placed between A3 and A4 connector. Picture facing North.

Geofabric placed inside approximate 4 foot hole due to large organics. 40 foot x 15 foot

#4s being consolidated on connector between A3 & A4. Picture facing South

#4s being consolidatedat A3 & connector

Graded Aggregate Base placed and increasing moisture with water truck.

Geogrid being placed between A3 and A4 on connector

Geogrid bring placed between A3 & A4 on connector

Geogrid placed on connector between A3 &A4. Picture facing North.

#4s placed on additional remediation area undercut an extra 12 inches below other remedation.

Geogrid being used on this project

Excavation of Pit area with large organics.

Excavation of pit area.

Excavation of pit area with organics

Excavation of pit area (Large tree stump shown being removed)

Proof roll

Bury pit area before excavation.

#4s consolidated

Bury pit area before remediation.