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, a 24-inch corrugated metal pipe was observed to have been placed from AH5 to AH1. The installation involved using an approximately 4-foot lift with a trench packer employed for compaction. A 3/8-inch probe rod was utilized to assess compaction, revealing a depression of 12 inches into the recently compacted section. Subsequently, a discussion was initiated with the storm drain personnel regarding the lift size, the high moisture content of the backfill, and the observed lack of compaction. Despite these concerns being raised, no corrective action was undertaken, and work on the next lift commenced.

Further installation involved the placement of reinforced concrete pipe (RCP) from AH2 to AH3. However, it was subsequently determined that the entire section of storm drain installed that day (AH1-AH3) was at an incorrect elevation due to an erroneous survey file. Consequently, all backfilling and piping were removed and reinstalled.

During the reinstallation process, an approximate 4-foot lift was consistently employed, with compaction achieved using a trench packer. As excavation progressed from AH3 to AH4, the presence of topsoil containing organics was discovered. A recommendation was made to the foreman to remove all topsoil. While the topsoil was cleared up to the point of storm drain placement, further investigation into potential implications was not carried out.

Recommendations:

1. Address concerns raised regarding backfill moisture content and compaction levels promptly to avoid potential issues with the integrity of the storm drain system.
2. Conduct thorough investigations into unexpected findings such as the presence of topsoil with organics to assess any potential impact on the project’s performance and longevity.
3. Implement proactive measures to mitigate risks associated with incorrect elevation and soil composition, such as regular quality checks and soil testing.

Overall, these recommendations aim to enhance the efficiency and quality of future storm drain installations, reducing the likelihood of rework and ensuring the longevity and reliability of the infrastructure.

AH2-AHAH# Topesoil covered

Storm drain AH3

AH3 topsoil exposed

Sanitation sewer 4.3-4.4

Topsoil with organics AH2-AH3

Topsoil removed AH2-AH3