Observations/Finding

On the above date, an AS ENGINEERING AND CONSULTING, LLC (ASEC) representative visited the site at the contractor’s request to observe proofrolling and evaluate the stability of the subgrade and sub-base stone in various roadway sections. Two separate trips were made to the site on this day.

During the initial visit, proofrolling of the in-place sub-base stone was observed. Moderate to severe movement was noted under traffic. Depth checks of in-place base stone were performed, with measured thicknesses ranging from approximately 3 inches to 6 inches. All areas observed exhibited wet underlying subgrade soils.

Recommendations were provided to the contractor to clip and remove the in-place sub-base stone where soil contamination was present and to undercut wet subgrade soils to a suitable, stable bearing condition. The contractor was advised to replace removed materials with suitable base stone free of soil contamination. The contractor indicated that he believed the removed base stone could be reused without contamination concerns; the writer advised against reusing contaminated stone.

A second trip was made later in the day to observe the exposed subgrade soils following removal of the base stone and clipping of wet areas. Subgrade conditions were evaluated by probing with a rounded-end steel rod and by observing proofrolling with a loaded tandem-axle dump truck carrying approximately 18 tons of stone. The subgrade soils appeared stable with no apparent movement. Depth checks into the subgrade ranged from approximately 9 inches to 14 inches. Based on these observations, the subgrade was approved for placement of new base stone, with a reminder not to reuse contaminated stone as such material may move once moisture is introduced during base stone placement and compaction.

The repair area observed and approved consisted of the east half of the roadway on Hawthorne Grove Lane between Laurel Bend Terrace and Reserve Crest Drive.

Additionally, proofrolling of the sub-base stone along approximately 500 feet of Reserve Crest Drive was observed. The first approximate 200 feet from the Hawthorne Grove Lane intersection appeared stable, with about 8 inches of base stone in place. The next approximate 200 feet exhibited grade issues requiring regrading. The remaining roadway on Hawthorne Grove Lane, south of Laurel Bend Terrace to the existing asphalt pavement, was also observed. The sub-base stone in this area had isolated locations exhibiting slight movement due to soil contamination.

Proof rolling of sub base on Hawthorne having slight to severe movement under traffic.Also inplace base stone depths ranging from 3" to six ".

Re observe sub grade after removal of base stone and clip wet sub grades on Hawthorne with depth checks ranging from 9" to 14" requiring 9".