Observations/Finding

As requested, a representative from AS Engineering and Consulting (ASEC) visited the site to provide quality control inspection and testing services. Visual observation techniques were employed to verify compliance with project drawings/specifications, applicable codes, and material submittals. The following observations were made during the site visit:

Observations:

The observed area is located on the slope behind Lots #975 through #979 of the Nature Walk Subdivision Phase 6A. Based on our field observations, we believe the failure observed on the slope did not appear to be due to the quality of the material, but rather due to inadequate compaction along the face of the slope. It appears the material placed on the slope face absorbed moisture (due to the pervious nature of the inadequately compacted material) from recent rainfall and subsequently shifted toward the toe of the slope.

Recommendations for Slope Construction:

1. Erosion Control Measures (BMPs):
   Erosion control measures should be implemented as required by applicable local regulations.
2. Site Preparation:
   • Clear all vegetation, including trees, grass, brush, roots, and stumps, from wooded and grassy areas.
   • Strip topsoil. (Note: Based on visual observations, a moderate amount of accumulated topsoil is expected.)
   • If encountered, remove buried structures, underground utilities, and any debris from failure areas.
3. Fill Placement and Compaction:
   • All embankment fill should be compacted uniformly to at least 95% of the soil’s maximum dry density, as determined by the Standard Proctor compaction test (ASTM D-698).
   • Compaction is particularly difficult along slope faces. To address this, construct slopes beyond their design limits and then cut them back, ensuring the exposed slope face is well compacted.
   • New fill embankments placed over existing grade should be benched to allow for compaction in horizontal layers. This ties the new fill into the existing grade and helps prevent slippage or slope stability failures at the interface.
4. Slope Protection:
   • Establish vegetation or apply mulch on slope faces as soon as practical after grading to provide erosion protection.
   • Divert rainwater runoff away from the crest of slopes to prevent erosion and saturation.
5. Monitoring and Oversight:
   • All slope construction should be monitored by the Geotechnical Engineer or their designated representative.
   • Field density test reports for the embankments should be reviewed carefully by the Engineer to ensure proper compaction and slope stability.

We appreciate the opportunity to support your project. If you have any questions regarding this report or need further assistance, please do not hesitate to contact us.